INFLUENCE OF NUTRITION AND BODY CONDITION ON PITUITARY, OVARIAN, AND THYROID FUNCTION OF NONLACTATING BEEF COWS',* R. J. Rasby3, R. P. Wettemann4, R. D. Geisert5, Oklahoma Agricultural Experiment Station, Stillwater 74078-0425 ABSTRACT
Nonpregnant Hereford cows (n = 70) were used to determine the effect of nutrient intake and body condition on reproductive and thyroid function. Body condition scores (BCS; 1 = emaciated, 9 = obese) of cows averaged 5.0 f .2 on July 1, and cows were fed for 4 mo either to lose weight and BCS (thin, n = 22). to maintain weight and BCS or to gain weight and BCS (fat; n = 24). After November 1, cows (moderate; n = a), received a complete ration to maintain weight and BCS. Cows were slaughtered in December (six thin, eight moderate, and eight fat cows) or the subsequent March (16 cows (PGF) per group). Before slaughter, cows were given two injections of prostaglandh FzOL 11 d apart. Six days after the second PGF injection, cows were simultaneously treated with 100 pg of gonadotropin releasing hormone (GnRH, i.m) and 100 pg of thyrotropin releasing hormone iv.) and serum samples were obtained. The BCS of cows at slaughter (8 d after PGQ averaged 3.4, 5.3, and 7.1 (P e .01) and carcass energy content averaged 243,432, and 714 Mcal (P < .01) for thin, moderate, and fat cows, respectively. Wet ovarian (P < .00l) and corpora lutea (P < .01) weights were heavier for fat cows. Content of LH in the pituitary gland and concentrations of thyroxine (T4) in serum after GdUVIXH were not influenced by nutrient intake or BCS. However, thin cows had greater concentrations (P < .05) of LH in serum after GnRIWRH than did moderate or fat cows. We conclude that nutrient intake and body energy reserves of beef cows influenced ovarian function and LH in serum after treatment with GnRH. Key Words: Beef Cows, Nutrition, Body Condition, Anestrus, LH, Thyroxine J. Aub. Sci. 1991. 69:2073-2080
Introduction 'Journal article 5824 of thc A@c. Exp. Sta, m e interval from parturition to first e m s Oklahoma state Univ., stillwater. is influenced by age of cow (Wiltbank, 1970; %'he authors gratefully acknowledge G. D. Niswender, Colorado State Univ., Fort Collins for the LH antisera; L. Bellows and short, 19781, suckling frecruency E. Richat, Jr., Albany Med. College, Albany, NY for rhe bv calves Wettemann et al.. 1978; Carruthers
Nebraska, Lincoln 6858~-0908. 4Reprint requests: .' Deptq Oklahoma State Univ., Stillwater 740784425. -5 sei. mpt., 0 state uniV., swwam 740784423. %sat add re^^: ~ e p of t ~ n i mand . Range sci.. S. Dakota State Univ., Bmkings 57007. Received July 11, 1990. Accepted November 16, 1990.
condition of the cow (Lishman et al., 1979; Dunn and Kaltenbach, 1980; Sek et al., 1988). The mechanisms by which these factors independently or collectively affect the length of anestrus in beef cows is unclear. Cattle fed less than maintenance amounts of energy had greater (Gombe and Hansel, 1973).
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J. J. Wagnep and K. S. Lusby5
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RASBY ET AL.
Materlals and Methods
Multiparous, nonpregnant Hereford cows (n = 72), previously described by Wagner et al. (1988), were randomly assigned to one of three feeding regimens to alter weight and body condition. Two cows eventually were removed from the study because of sickness. Thirty-five cows were slaughtered in each of 2 yr. Experimental protocol was initiated on July 1 of each year. From July 1 to November 1, cows were fed either to lose weight and body condition (thin; n = ll/yr), to maintain weight and body condition (moderate; n = 12/yr), or to gain weight and body condition (fat; n = 12/ yr). It was anticipated that, by November 1,
BCS (Wagner et al., 1988) would be 6 or greater, 5, and 4 or less for fat, moderate, and thin cows, respectively. After November 1, cows were weighed and BCS was determined weekly. Each cow was individually fed a complete ration to maintain weight and BCS. Cows were slaughtered in December (a total of six thin, eight moderate, and eight fat cows, respectively) or the subsequent March (16 cows per group) each year. This allowed evaluation of cows after they had been maintained at a BCS for 1 or 4 mo. Before slaughter, two i.m. injections of 25 mg of prostaglandin F a (PGF)' were given 11 d apart to all cows to synchronize estrus. Blood samples were collected by venipuncture on the days of the first and second PGF injection and 6 d after the second injection of PGF. Blood samples (20 ml) were mixed in tubes containing 12.5 mg of oxalic acid, immediately cooled on ice to 4'C, and centrifuged (5,000 x g for 15 min). Plasma was decanted and stored at -20'C until it was assayed for concentration of progesterone (Lusby et al., 1981). Intra- and interassay CV were 6.0 and 7.2%. respectively. Five days after the second PGF injection, a cannula (polyvinyl; 2.08-mm 0.d) was inserted into an external jugular vein of each cow, and cows were confined to individual stalls (1.2 m x 2.1 m) at 20 f 3'C. On the next day, cows were simultaueously treated with GnRH (100 pg i n ; chloride form, batch #2, NJDDK) and thyrotropin releasing hormone8 (TRH;100 pg, i.v.). Commencing at O600, serum samples (20 ml) were obtained every 15 min for 30 min before treatment. After treatment, samples were obtained every 15 min for the first 2 h, every 30 min for the next 4 h, and then every 2 h until 12 h after treatment. Samples were allowed to clot (24 h), and serum was separated by centrifugation (4,000 x g) and stored at -2VC until LH and thyroxine (T4) were quantified. Concentrations of LH (Hallford et al., 1979) were assayed in pretreatment samples and samples obtained every 15 min for the first 6 h after treatment with GnRH.. Antisera (3225) against bovine LH was used at a dilution of 1: 100,000. Bovine LH (NE€-LH-B9) was used as the standard Radiolabeled ligand was prepared using LEX-1374A-ovine LH and lzI. Intra- and interassay CV (n = 16 assays) for the LH assay were 4.7 and 12.2%, respectively.
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similar (Hill et al., 1970; Dunn et al., 1974; Spitzer et aL, 1978), or decreased (Apgar et al., 1975) concentrations of LH in serum compared with cows fed adequate amounts of energy. Restricting energy intake resulted in greater concentrations of L.H in serum after GnRH in heifers (Beal et al., 1978) and cows (Whisnant et al., 1985). Inconsistencies among experiments suggest that energy reserves of cows may influence pituitary function. Hypophyseal LH was correlated with body condition score (BCS)in cows at parturition and at 30 d postpartum (Connor et al., 1990). In addition, the onset of nutritionally induced anestrus in beef cows is associated with decreases in body energy reserves and the frequency of LH pulses (Richards et al., 1989). Increased pulsatile release of LH is a prerequisite for initiating estrous cycles in postpartum beef cows (Rawlings et al., 1980; Wettemann, 1980; Lamming et al., 1981; Riley et al., 1981; Humphrey et al., 1983). Content of thyroid stimulating hormone (TSH)in the pituitaries of ewes is inversely related to LH content (Lmw et al., 1964) and may account for the anestrus exhibited in cows fed thyroprotein (Wagner and Hansel, 1969) and in triiodothyronine-treated sheep (Howland et al., 1966). Objectives of this experiment were to determine the influence of nutrient intake, body condition, and time maintained at a particular body condition on pituitary, ovarian, and thyroid function of beef cows.
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NUTRITION AND BOVINE REPRODUCTM;! FUNCTION TABLE 1. LEAST SQUARES MEANS FOR BODY CONDlTION, WEIGHT, AND CARCASS ENERGY CONTENT OF COWS WITH THIN, MODERATB, OR FAT BODY CONDITIONS'
ctitelia
Thin
Body condition Moderate
Concentrations of T4 (Pratt et al., 1986) were quantified in samples obtained every 30 min for the first 6 h and at 8, 10, and 12 h after treatment. Intra- and interassay CV (n = 11 assays) for the T4 assays were 5.4 and 6.8%, respectively. pituitary glands were removed and weighed within 45 min of exsanguination. The posterior lobe was dissected from the anterior lobe, and weight of the anterior lobe of the pituitary was determined. Anterior pituitaries were immediately frozen on dry ice and stored at -2o'C until assayed for LH content by RIA. The anterior pituitary was prepared for assay of LH as described by Rasby et al. (1990). Pituitary LH content was quantified in a single RIA in which the intra-assay CV was 2.5%. Corpora lutea (CL) were removed from ovaries and total wet ovarian and CL weights were determined. In addition, the ovaries were minced, blotted on paper, and weighed to determine follicular fluid weights. Dry ovarian weights were determined after desiccation at 90°C for 54 h. One-half of the carcass was obtained at slaughter. Soft carcass tissues were separated from the bone, and energy content and percentage of fat of the soft tissues were determined (Wagner et al., 1988). Analyses of variance were used to analyze cow, carcass, pituitary, and ovarian characteristics. Analyses of variance of endocrine responses were split-plot designs in which cows were nested within treatment, year, and season slaughtered (Gill and Hafs, 1971). Repeated measurements over time were taken on cows, and time sampled was the subplot. The effect of year and interactions with year were not significant for any traits and were omitted from the model. Full-model analyses
SE
6.9d 1.ld
.1
.1
48od
8
483d 714d 21.6d
6
8 .7
of LH and T4 after GnRH and TRH treatments indicated nonsignificant season slaughtered x treatment, season slaughtered x time sample, and season slaughtered x treatment x time sampled interactions. Therefore, the r e d u d model included season slaughtered, treatment, cow (season slaughtered x treatment), and time sampled. If a significant treatment x time sampled interaction existed, response curves for hormone concentrations were characterized by time trends that were analyzed by regression (SAS, 1988). Tests of homogeneity of regressions were used to determine differences in time trends for endocrine responses among cows with thin, moderate, or fat body condition (Snedecor and Cochran, 1968). Resultsand Dlscusslon
From July 1 to November 1, thin cows lost approximately 60 kg and 2 BCS units, moderate cows maintained weight and BCS, and fat cows gained about 80 kg and 2 BCS units. Between November 1 and slaughter, cows on all treatments maintained BCS (Table 1). Body condition score at slaughter for thin cows (3.4)was less (P c .001) than that for moderate (5.3) and fat (7.1) cows. Cows in all groups maintained weight (Table 1) from November 1 until slaughter; at slaughter, thin, moderate, and fat cows weighed 341,394,and 483 kg (P c .001), respectively. Energy content and percentage of fat in soft tissue of carcasses were greatest (P< .OOl) for fat cows and less for moderate and thin cows (Table 1). Analyses of LH response to GnRH included only cows that exhibited luteal activity as indicated by the presence of a CL at slaughter or plasma progesterone equal to or greater than 1 n g / d at the time of the first or second PGF injection or at the time or treatment with
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Condition score on November 1 3.9 5.3c 3.4b 5.3c Condition score at slau@ter 339b 3WC Weight on November 1, kg 341b 3WC Weight at slaughter, kg 243b 432' Carcass energy content, Mcal 7.0b 12.T FaZ 5% BThese data were derived from another stady (Wagner et at., 1988). ~.C*~WXUM not having a common superscript letter differ (P < .OOI).
pooled
Fat
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RASBY ET AL. TABLE 2. LEAST SQUARES MEANS FOR OVARIAN AND PITUITARY CHARACTERISTICS OF COWS WITH THIN, MODERATE, OR FAT BODY CONDlTION
~~
Body condition
Moderate
Fat
Wet ovarian wt, g Dryovarianwt,g corpus luteum wt, g Pituitarywfg Autcrior pihutary wt, g Concentration of pituitary LH,pgbg Total pituitary LH,mg
12.1. l.8@ 1.0lC 2.33 1.96 159 3.05
14.7'
20.6b 2.43d 1 .93d 2.54 2.03 1.79 3.66
C.d~-
2.09 2 . d
2.40 1.92 1.44 2.78
pooled SE 1.3 .19 .25 .06
.06 .14 23
not having a common supemaipt letter m e r (P < .OOI). not having a common superscript letter m e r (P < .IO).
GnRH and TRH. Eighteen (81.8%) thin, 24
(100%) moderate, and 23 (95.8%) fat cows (P < .025)had luteal activity, and data from these cows were used in the analyses. Percentage of fat in the carcasses of the four thin cows that did not exhibit luteal activity averaged 4.1%, compared with 7.4% (P < .05)for thin cows with luteal activity. In an experiment with similar cows, anestrus occurred when BCS of ncmlactating, cyclic beef cows averaged 3.5 (Richards et al., 1989). Total pituitary gland and anterior pituitary weights did not differ among treatments (Table 2). Likewise, concentrations and total pituitary LH content were similar (P > .lo) for thin, moderate, and fat cows. Pituitary and anterior pituitary weights were similar to those observed in cyclic beef cows and heifers (Beal et al., 1978) and dairy cows (Carruthers et al., 1980). Pituitary LH umtent of cows in this experiment was similar to that in pituitaries of cows slaughtered when BCS (1 = extremely thin, 5 = extremely fat) averaged 4.4 f .2,3.1 f .l, and .1.6 f .3 (Moss et al., 1982). Our results suggest that nutrition and BCS do not influence pituitary weights in ncmlactating cows and they agree with previous results (Beal et al., 1978). However, it has been demonstrated that energy intake (Beal et al., 1978) and BCS (Moss et al., 1982) of beef cows can affect pituitary LH content. In these studies cows in poor body condition with restricted energy intake had reduced pituitary LH. Cows in the previous experheats were losing weight and body condition until the time the pituitary was removed. Cows in the present experiment maintained weight for 1 to 4 mo before slaughter, which may have influenced pituitary LH content.
Season that the cows were slaughtered (March vs December) influenced pituitary weights and pituitary LH content. Regardless of nutrient intake and BCS, cows slaughtered in March had heavier (P< .02)total pituitaries and anterior pituitaries and had more (P c .02) LH in the pituitary than did cows slaughtered in December (Table 3). It has been demonstrated that there is a seasonal influence on LH secretion in ovariectomized cows, and serum LH concentrations in those cows are greater in spring than in fall (Day et al., 1986). In addition, cows in this experiment that were slaughtered in December maintained weight and body condition for about 1 mo before slaughter, whereas, cows slaughtered in March maintained weight and BCS for about 4 mo before slaughter. The length of time that a cow maintains weight and BCS may influence pituitary characteristics. Cows maintaining weight and BCS had greater basal LH and greater GnRH-induced LH release than cows losing weight and BCS mutter and Randel, 1984). Reducing energy substrate at the cellular level does result in decreased pituitary function. Rat pituitaries in medium treated with metabolic inhibitors that alter glycolysis and oxidative phosphorylation released less LH than control pituitaries when stimulated with GnRH (Sen et al., 1979). Fat cows had heavier (P < .001) wet ovarian weights than did moderate or thin cows (Table 2). Dry ovarian weights for fat cows tended to be heavier (P c .lo)than those for thin cows (Table 2). Corpora lutea weights were less for thin cows than for moderate and fat cows. In agreement with previous studies, cows that were fed limited amounts of energy had
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criteria
Thin
"ITON
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AND B O W REPRODUCTIVE FUNCTION
TABLE 3. LEAST SQUARES h 4 " S FOR PITUITARY cHARAcrERISTIc.5 FOR COWS WITH THLN, MODERATE, OR FAT BODY CONDITION IN DECEMBER AND MARCH
TABLE 4. LEAST SQUARES MEANS FOR FOLLJCULAR PLUID WEIGHT (g) POR COWS WITH THIN, MODERATE, OR PAT BODY CONDITION IN DECEMBER AND MARCH Month slaughtered
pooled
Criteria
December March
SE
Body condition
December
March
pituitarywt.g
2.32' 1.88'
2.53b 2.Mb
.06
1.72 3.61b
.14 28
Thin Modcrate Fat Pooled SE
1.83" 2.66"b 3.6SbC .28
2.42 1.84 25 1 .38
Anteri0rpituitarywt.g Concentrationof pituitary LH, Fdw3 1.49 TotalpituitaryLH,mg 2.72'
.06
~
~bMeansnot having a common superscript letter d i e r
not haviog a common soperscript letter differ (P < .01).
reduced ovarian weights (Gombe and Hansel, 1973; Bed et al., 1978). Thin cows had lighter wet and dry ovarian and CL weights, suggesting that nutrients available to maintain ovarian cell structure and integrity may differ in thin cows. When cows were fed diets that contained less than the required amounts of protein and energy to maintain BW, concentrations of glucose in plasma were decreased (Rasby et al., 1982) and concentrations of nonesterified fatty acids in plasma were increased (Garmendia et al., 1984). Blood glucose is the primary energy substrate used at the cellular level and reduced concentrations may influence ovarian and CL weights. Secretion of pituitary gonadotropins necessary to maintain ovarian and CL function may be reduced in thin cows. Although, total pituitary LH content of thin,moderate, and fat cows in our experiment were similar, secretion of GnRH may have been reduced, which could result in reduced secretion of LH. The amount of GnRH in the infundibular stalk-media eminence of beef cows is negatively correlated with BCS (Wettemann et al., 1989). Regardless of nutrient intake and BCS, CL from cows slaughtered in March were heavier (2.03 g; P < .01) than CL from cows slaughtered in December (1.26 g). Rtuitary LH content was greater (P < .02) in cows slaughtered in March than in cows slaughtered in December and may influence ovarian luteal cell function in cows slaughtered in March, causing heavier CL. Analysis of follicular fluid weight indicated a treatment x season slaughtered interaction. Thin cows had the least and fat cows had the greatest amount of follicular fluid (P < .01; Table 4) in December. Follicular fluid weights
of moderate cows were intermediate and did not differ from those for thin and fat cows. However, in March, follicular fluid weight did not differ among treatment group. Thin cows slaughtered in December lost weight and body condition from July 1 to November 1, then maintained weight and BCS for about 1 mo before slaughter. Thin cows slaughtered in March maintained weight and BCS for about 4 mo before slaughter. Losses of weight and BCS followed by a short period of maintaining weight and BCS may alter the hypothalamo-pituitary-ovarianaxis. Thin cows slaughtered in March may have adjusted to a lighter BW and less body energy stores, resulting in increased hypothalamic and pituitary gonadotropin secretion and increased follicular development. Concentrations of T4 in serum before TRJ3 treatment tended to be reduced (P < .12) in thin cows (64ng/ml) compared with moderate (72 ng/ml) and fat (73 ng/ml) cows. Reduced thyroid activity decreases ruminal motility and rate of passage but increases digestibility (Kennedy et al., 1977). Thin cows may use feed more efficiently, minimizing the effect of nutrient intake on pituitary and ovarian characteristics. This supports the conclusion that less feed was required for maintenance of cows in thin vs moderate body condition (Wagner et al., 1988). Concentrations of T4 in serum of cows in thin, moderate, or fat body condition were best described by a third-order polynomial regression equation. Time trends for concentrations of T4 were similar (P > .lo) for thin,moderate, and fat cows. At the time of TRH treatment, concentrations of T 4 averaged 69.4 f .9 ng/ml for all cows (Figure 1). Concentrations of T4 in serum increased to 91.7 f 1.3 ngml by 5 h
~ b * C ~ e in a ncolumns ~
(P < .02).
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Monthslaughtered
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RASBY ET AL.. 0.
94 -
0
. '
.
0
.
-c - - - - - -
-. 0
A
40
g
35-
C
A
5
0
120
240 360 480 Minutes Post Treatment
600
720
Figure 1. Least squares regressions and least squares means for concentrations of thpxine in serum of cows in thin (-, A), moderate (-, r). or fat ..., 0) body condition.
after TRH and were similar to those observed after TRH treatment of steers (Pratt et al., 1986) and cows (Vanjonack et al., 1974). Our results suggest that thyroid function, as indicated by T4 release after TRH, is similar in thin, moderate, and fat cows. Even though BCS among groups differed, environmental conditions in this experiment were not adverse. Cows were allowed a 1-d adaptation period in stalls in a temperaturecontrolled mom before TRH treatment. This adjustment period may have minimized any differences in thyroid response to TRH treatment. Concentrations of LH in serum of cows in thin, moderate, and fat body condition after GnRH were best described by a fourth-order polynomial regression equation. Time trends for LH concentrations in serum of thin, moderate, and fat cows were not parallel (Pc .025). Before GnRH treatment, concentrations of LH in serum were similar for all treatments and averaged 2.2 f .6 ndml (Figure 2). At 105 min after treatment, concentrations of LH in serum averaged 41 f 3, 32 f 4, and 34 f 4 ngf ml for thin,moderate, and fat cows, respective ly. By 360 min after GnRH treatment, concentrations of LH in serum averaged 4 f 1 ndml for all groups. Our results are similar to those of Whisnant et al. (1985) and Killen et al. (1989) and indicate greater release of LH after treatment with GnRH in cows or heifers fed restricted amounts of energy. Thin cows release more LH when treated with GnRH than do cows in a moderate or fat body condition; therefore, pituitary stores of
10
0 30 60 90 120 150 180 210 240 270 300 330 360 Minutes Post Treatment
Figure 2. Least squares regressions and least squares
means for concenlrations of luteinizing hormone in serum of cows in thin (-, A),modcrate (-, r), or fat (..., 0 ) body condition.
releasable LH in thin cows may be greater than those in moderate and fat cows. The releasable pool of LH in the rat changes during the estrous cycle, but total pituitary LH does not change Wckering and Fink, 1979). Our results indicate that pituitary LH content is similar among cows in different body conditions. We suggest that greater concentrations of LH after treatment with GnRH in thin cows is a result of a greater releasable LH pool. We conclude that nutrient intake and BCS do not influence total pituitary weight, anterior pituitary weight, pituitary LH content, or thyroxine after TRH treatment. However, nutrition and BCS influence ovarian and CL weights and the release of LH from the pituitary gland. Therefore, effects of BCS on reproductive efficiency seem to be mediated through secretion of LH. lmpllcatlons
Thin body condition of beef cows is associated with reduced secretion of luteinizing hormone, reduced ovarian and corpora lutea weights, and the cessation or lack of initiation of estrous cycles. Reproductive failure is a major cost to cattle producers. Body condition of cows should be monitored to evaluate feeding programs and to reduce reproductive inefficiencies. Literature Cited Apgar, J., D. Aspros, I. E.Hixon, R. R Saatman and W. Hansel. 1975. Effect of restricted feed intake on the
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m
NWIRlTION AND BOVINE REPRODUCTIVE FUNCTION
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Kennedy, P. M., B. A. Young and R. J. christopherson. 1977. Stndies on the Aationphip between thyroid fnnction, cold acclimationand retention time of digesta in sheep. J. Anim. Sci. 491084. men,J. EL, D.W. Fomst, F. M. Byers, G. T. Schellingand C.R. Low. 1989. Gonadotrop&releasing hormominduced luteinizing hormone release in beifers: Effect of nutrition during gestation. I. Anim. Sci. 67:4%. Lamming.G. E., D. C. Watha and A. R. Peters. 1981. Endocrine patterns of the postpartum cow. J. Reprod. Fertil. (Suppl.) 30955. Lishmaq A. W.. S . W . Allison, R. L. Fogwell, R. L. Butcher and E. K. InsLetp. 1979. Follicnlar development and functionof i n d u d corpora lutea in undded postpartum anestrousbeef cows. J. Anim. Sci. 482367. Low,G. N., T. Enrsnas, A. Mouton and W. H m L 1964. Evidencefor a thyrotropiceffect of diethylstilbestrolin sheep via a hypotheticalpituitary mechanism. S. M r . J. Agric. Sci. 7797. Lusby, K. S.. R. P. WeUemann and E. I. Turmau 1981. Effects of early weaning calves from first-calf heifers on calf and heifer perfomauce. J. Anim.Sci. 53: 1193. Moss. G. E.,J. R Parfet, M. A, Diekman, R P. h e n a g e r andK. S.Hendrix. 1982. Pituitary luteinizinghormone (LH), follicle stimulating hormone 0, semm progesterone (P) and hyp0-c gonadotropinreleasing hormone (GnRH) in beef cows in varied body condition I. Anim. Sci. 55(Suppl. 1):374 (Abstr.). Pickcring, A.J.M.C. and G. Fhk. 1979. Variation in size of the readily relasable pool of luteinizing hormone dmjng the oestrous cycle of the rat. J. Endocrinol. 8 3 53. ha,B. R and R P. Wetternarm. 1986. The effect of envjrommtal temperature on comemations of thyroxine and triiodothyronb after thyrotropinreleasing hormone in s t e m . J. Anim. Sci 621346. Rasby,R.J., R. P.Wettemann, R D. Geisert, L. E.Rice and C. R Wallace. 1990. Nutrition, body condition and reproduction in beef cows: Fetal and placental development, and estrogens and progesterone in plasma. I. Anim. Sci. 684267. Rasby, R J., R. P. Wemmanu, K.S. Lusby, B. R. Pratt and (Abstr.). E.I. 'Lhrmaa 1982. Influem of prepartam nutrition Garmendia, J. C., R.P.Wettcmann and K.S. Lusby. 1984. on plasma glucose, protein and esterified fatty acids in Effect of prepartum nutrition on plasma constituents range cows.J. Anim. Sci. 55(Suppl. 1):380 (Abstr.). and reproductive performance of range beef cows. J. Rawliugs, N. C., L. Weir, B. Todd J. Maoris and J. H. Hyland. 1980. Some endocrine changes associated Anim. Sci. 59(Suppl. 1):325 (Absbr.). Gill, J. L. and H. D. Hafs. 1971. Analysis of repeated with the post-pintnm period of the suckling beef cow. measurements of animals. I. Anim. Sci. 33:331. I. Repmd. F e d . m301. Gombe, S. and W. Hansel. 1973. Piasma luteinizing Richards, M.W., R. P. Wettemannand H.M Schoenemann. 1989. Nutritional aoesfrus in beef cows: Body weight hormone (LH) and progesterone levels in heifers on change, body condition,luteinizing hormone in semm restricted energy intalres. J. Anim. Sci. 37728. Hallford,D.M.,E. J.Turman,R.P. WenemannandC.E. and ovarian activity. J. Anim. Sci. 67:1520. . Pope. 1979. Endocrine and reproductive response of Riley, G. M,A. R. Petem and G. E. J ~ J 1981. Induction of pulsatile LH release, FSH release arid beef cows to PMSG. J. Anim. Sci. 491030. Hill, J. R., Jr., D.R. Lamod, D. M. Hcnricks, J. F.Dickey ovulationinpost-partumacyclicbeefcows by repeated and G. D. Niswender. 1970. The effects of undenmtrismall doses of &RH. J. Reprod. Fertil. 63:559. tion on ovarian function and fertility in beef heifers. Rutter, L. M.and R D. Randel. 1984. Postpartum nutrient Biol. Reprod. 2:78. intakeand body conditio^ Effect on pituitary function Howland, B. E., R A. Bellows, A. L. Pope and L. E. Casida. and onset of e m in beef cattle. J. Anim. Sci. 58:265. 1966. Ovarian activity in ewes treated with @ncose SAS. 1988. SASJSTAT User's Guide (6.03 Ed.). SAS Inst. and triiodothyronb. J. Anim. Sci. 25:836. Inc., Cay, NC. Humphrey, W. D., C. C. Kaltenbach, T. G. Dunn, D. R. Selk, G. E., R P. Wettanann,K.S. Lusby,J. W. Oltjen, S .L. Kwitnilc and G.D. Niswender, 1983. Characterization Mobley, R. J. Rasby and J. C. Gamenda . 1988. Of hormonalp m in the beef COW daring p~stpmRelationships among weight change, body condition tum anestrus. J. Anim. Sci. 56445. and reproduction performance of range beef cows. J. sensitivity of the bovine corpus luteum to LH in vitro. J. Anim. Sci. 41:1120. Bed, W. E.,R.E.Short, R.B. Stai-er, R. A. Bellows, C. C. Kaltenbach and T. G. Dum. 1978. Iuflucnce of dietary energy mtake on bovine pituitary and luteal function. J. Anim. Sci. 46A81. Bellows, R A. and R E. Shon 1978. Effects of precalving feed level on birth weight, calving dSculty and subsequent fertility. J. Anim. Sci. 46:1522. Carruthers,T.D..E.MConvey,J. S.Kesner,H.D.Hafsand K. W. Cheng. 1980. The hypothalamo-pituitary gonadotrophic axis of sackled and nonsuckled daily cow p o s t p m J. Anim. Sci. 5 1 9 9 . Cmthers, T. D. and H. D.MS. 1980. Suckling and fourtimesdailymilking:Influenceonovulation,estrosund semm luteinizing harmom, g l m c o i d s and prolactin in postpartum Holsteins. J. Anim. Sci. 50919. Connor. H. C., P. L. Houghton, R P. Lemnager, P. V. htalven, J. R. M e t and G. E.Moss. 1990. Effect of dietary energy, body condition and calf ranoval on pituitary gonadotropins, gondotroph-releasing hormone (GnRH) and hypothalamic opioids in beef cattle. Domest Anim. Endocrinol. 7403. Corah, L. R., T. G. Dunn and C. C. Kaltenbach. 1975. Influenceof prepartum nutrition on the reproductive performawe of beef females and the performawe of their progeny. J. Anim. Sci. 41:819. Day, M.L., K.hakawa, P. L. Penuel, D. D.Zalesky, A. C. Clutta, R. J. Kittok and J. E.Kinder. 1986. Idhence of season and estradiol on secretion of lutciniziag hormone in ovariectomized cows. Biol. Reprod. 35: 549. Dunn, T. G., J. E. Ingab, D. R Zimmemulnand J. N. Wiltbank. 1%9. Reproductive performance of %year-old Herdord and Angus heifers as influenced by PE- and post-calving energy intake. J. Anim. Sci. 29719. Dunn, T. G. and C. C. Kaltenbach. 1980. Nutrition and the postpartum intend of the ewe. sow and cow. J. Anim. Sci. 51(Suppl. 2):29. Duun, T. G., J. Rone. C. C. Kaltenbach,L. A. van der Walt, M.L.Riley and A. M Akbar. 1974.Hormone changes duringunderfeedingof beef cows.J. Anim.Sci. 39:206
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Anim. Sci. 633153. Sen, K.K., S. Azbar and K.M.J. Menon. 1979. Evidace for the involvement of an energy-depndent process in
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gonadotropin-releasing hormone-stimulated luteink+ ing hormone release by rat anterior pituitary. Endoainology. 1051158. Snedecor, G. W. and W. G. cochran. 1968. Statistical Methods (6th Ed.). Iowa State Univ. Press, Ames. Spitzer, J. C., G.D.Niswdex, Ct. F. Seidel, Jr. and J. N. Wiltbad. 1978. Fatilization and blood levels of progesterone and LH in beef heifers on a restricted energy diet. J. Anim. Sci. M1071. Van.nack, W. J., M.W.Felz, L.Hahn and H. D. Johoson. 1974. 'Izlyrotropin-releashg hormone 0 dfects on bovine plasma thyroxine. Roc. Soc. Exp. Biol. Med. 145~925. Wagner, J. J., K.S. Lusby,J. W. Oltjen, J. Rakestnrw, R.P. Wettemannand L.E.Walters. 1988. Carcass composition in mature Hereford cows: Estimation and effect on daily metabolizablee w g y requirementduring Winter. J. Anim. Sci. 66503.
Wagner, W. C. and W. Hansel. 1969. Reproductive physiology of the post partom cow. I. clinical and histological f h d h g s J. Reprod. pcrtil. 18:493. Wettanann, R. P. 1980. Postparbrm endoaine function of cattle., sheep and swine. J. Anim Sci. Sl(Supp1. 2):2. Wetkmam,RP.,R J.Rmby,P.G.Harms,K. S.Lusbyand J. J. Wagner. 1989. LHRH in the i n f u n d i i stalkmedian eminence is related to percentage body fat in cows. J. Anim. Sci 67(SuppL 2):57 (Abstr.). Wemuam, R.P.,E.J. 'hman, R.D.Wyatt and R.Totusek 1978. Influence of suckling intensity on reproductive performance of range cows. J. Anim. Sci. 47342. Whisnaut. C. S., T. E. Kiser, F.N. Thompsonand J. B.Hall. 1985. Effect of nutrition on the LH response to calf removal aud GnRH. Theriogemlogy 24565. Wiltbank, J. N. 1970. Research needs in beef cattle reproduction. J. Anim. Sci. 31:755. WiltbanL,J. N.,W. W. Rowden, J. E.Ingalls. K. E.Gregory and R. M.Koch. 1%2. Effect of energy level on reproductive phenomena of mature Hereford cows. J. Anim. Sci. 21:219.
Nonpregnant Hereford cows (n = 70) were used to determine the effect of nutrient intake and body condition on reproductive and thyroid function. Body condition scores (BCS; 1 = emaciated, 9 = obese) of cows averaged 5.0 f .2 on July 1, and cows were fed for 4 mo either to lose weight and BCS (thin, n = 22). to maintain weight and BCS or to gain weight and BCS (fat; n = 24). After November 1, cows (moderate; n = a), received a complete ration to maintain weight and BCS. Cows were slaughtered in December (six thin, eight moderate, and eight fat cows) or the subsequent March (16 cows (PGF) per group). Before slaughter, cows were given two injections of prostaglandh FzOL 11 d apart. Six days after the second PGF injection, cows were simultaneously treated with 100 pg of gonadotropin releasing hormone (GnRH, i.m) and 100 pg of thyrotropin releasing hormone iv.) and serum samples were obtained. The BCS of cows at slaughter (8 d after PGQ averaged 3.4, 5.3, and 7.1 (P e .01) and carcass energy content averaged 243,432, and 714 Mcal (P < .01) for thin, moderate, and fat cows, respectively. Wet ovarian (P < .00l) and corpora lutea (P < .01) weights were heavier for fat cows. Content of LH in the pituitary gland and concentrations of thyroxine (T4) in serum after GdUVIXH were not influenced by nutrient intake or BCS. However, thin cows had greater concentrations (P < .05) of LH in serum after GnRIWRH than did moderate or fat cows. We conclude that nutrient intake and body energy reserves of beef cows influenced ovarian function and LH in serum after treatment with GnRH. Key Words: Beef Cows, Nutrition, Body Condition, Anestrus, LH, Thyroxine J. Aub. Sci. 1991. 69:2073-2080
Introduction 'Journal article 5824 of thc A@c. Exp. Sta, m e interval from parturition to first e m s Oklahoma state Univ., stillwater. is influenced by age of cow (Wiltbank, 1970; %'he authors gratefully acknowledge G. D. Niswender, Colorado State Univ., Fort Collins for the LH antisera; L. Bellows and short, 19781, suckling frecruency E. Richat, Jr., Albany Med. College, Albany, NY for rhe bv calves Wettemann et al.. 1978; Carruthers
Nebraska, Lincoln 6858~-0908. 4Reprint requests: .' Deptq Oklahoma State Univ., Stillwater 740784425. -5 sei. mpt., 0 state uniV., swwam 740784423. %sat add re^^: ~ e p of t ~ n i mand . Range sci.. S. Dakota State Univ., Bmkings 57007. Received July 11, 1990. Accepted November 16, 1990.
condition of the cow (Lishman et al., 1979; Dunn and Kaltenbach, 1980; Sek et al., 1988). The mechanisms by which these factors independently or collectively affect the length of anestrus in beef cows is unclear. Cattle fed less than maintenance amounts of energy had greater (Gombe and Hansel, 1973).
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J. J. Wagnep and K. S. Lusby5
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RASBY ET AL.
Materlals and Methods
Multiparous, nonpregnant Hereford cows (n = 72), previously described by Wagner et al. (1988), were randomly assigned to one of three feeding regimens to alter weight and body condition. Two cows eventually were removed from the study because of sickness. Thirty-five cows were slaughtered in each of 2 yr. Experimental protocol was initiated on July 1 of each year. From July 1 to November 1, cows were fed either to lose weight and body condition (thin; n = ll/yr), to maintain weight and body condition (moderate; n = 12/yr), or to gain weight and body condition (fat; n = 12/ yr). It was anticipated that, by November 1,
BCS (Wagner et al., 1988) would be 6 or greater, 5, and 4 or less for fat, moderate, and thin cows, respectively. After November 1, cows were weighed and BCS was determined weekly. Each cow was individually fed a complete ration to maintain weight and BCS. Cows were slaughtered in December (a total of six thin, eight moderate, and eight fat cows, respectively) or the subsequent March (16 cows per group) each year. This allowed evaluation of cows after they had been maintained at a BCS for 1 or 4 mo. Before slaughter, two i.m. injections of 25 mg of prostaglandin F a (PGF)' were given 11 d apart to all cows to synchronize estrus. Blood samples were collected by venipuncture on the days of the first and second PGF injection and 6 d after the second injection of PGF. Blood samples (20 ml) were mixed in tubes containing 12.5 mg of oxalic acid, immediately cooled on ice to 4'C, and centrifuged (5,000 x g for 15 min). Plasma was decanted and stored at -20'C until it was assayed for concentration of progesterone (Lusby et al., 1981). Intra- and interassay CV were 6.0 and 7.2%. respectively. Five days after the second PGF injection, a cannula (polyvinyl; 2.08-mm 0.d) was inserted into an external jugular vein of each cow, and cows were confined to individual stalls (1.2 m x 2.1 m) at 20 f 3'C. On the next day, cows were simultaueously treated with GnRH (100 pg i n ; chloride form, batch #2, NJDDK) and thyrotropin releasing hormone8 (TRH;100 pg, i.v.). Commencing at O600, serum samples (20 ml) were obtained every 15 min for 30 min before treatment. After treatment, samples were obtained every 15 min for the first 2 h, every 30 min for the next 4 h, and then every 2 h until 12 h after treatment. Samples were allowed to clot (24 h), and serum was separated by centrifugation (4,000 x g) and stored at -2VC until LH and thyroxine (T4) were quantified. Concentrations of LH (Hallford et al., 1979) were assayed in pretreatment samples and samples obtained every 15 min for the first 6 h after treatment with GnRH.. Antisera (3225) against bovine LH was used at a dilution of 1: 100,000. Bovine LH (NE€-LH-B9) was used as the standard Radiolabeled ligand was prepared using LEX-1374A-ovine LH and lzI. Intra- and interassay CV (n = 16 assays) for the LH assay were 4.7 and 12.2%, respectively.
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similar (Hill et al., 1970; Dunn et al., 1974; Spitzer et aL, 1978), or decreased (Apgar et al., 1975) concentrations of LH in serum compared with cows fed adequate amounts of energy. Restricting energy intake resulted in greater concentrations of L.H in serum after GnRH in heifers (Beal et al., 1978) and cows (Whisnant et al., 1985). Inconsistencies among experiments suggest that energy reserves of cows may influence pituitary function. Hypophyseal LH was correlated with body condition score (BCS)in cows at parturition and at 30 d postpartum (Connor et al., 1990). In addition, the onset of nutritionally induced anestrus in beef cows is associated with decreases in body energy reserves and the frequency of LH pulses (Richards et al., 1989). Increased pulsatile release of LH is a prerequisite for initiating estrous cycles in postpartum beef cows (Rawlings et al., 1980; Wettemann, 1980; Lamming et al., 1981; Riley et al., 1981; Humphrey et al., 1983). Content of thyroid stimulating hormone (TSH)in the pituitaries of ewes is inversely related to LH content (Lmw et al., 1964) and may account for the anestrus exhibited in cows fed thyroprotein (Wagner and Hansel, 1969) and in triiodothyronine-treated sheep (Howland et al., 1966). Objectives of this experiment were to determine the influence of nutrient intake, body condition, and time maintained at a particular body condition on pituitary, ovarian, and thyroid function of beef cows.
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NUTRITION AND BOVINE REPRODUCTM;! FUNCTION TABLE 1. LEAST SQUARES MEANS FOR BODY CONDlTION, WEIGHT, AND CARCASS ENERGY CONTENT OF COWS WITH THIN, MODERATB, OR FAT BODY CONDITIONS'
ctitelia
Thin
Body condition Moderate
Concentrations of T4 (Pratt et al., 1986) were quantified in samples obtained every 30 min for the first 6 h and at 8, 10, and 12 h after treatment. Intra- and interassay CV (n = 11 assays) for the T4 assays were 5.4 and 6.8%, respectively. pituitary glands were removed and weighed within 45 min of exsanguination. The posterior lobe was dissected from the anterior lobe, and weight of the anterior lobe of the pituitary was determined. Anterior pituitaries were immediately frozen on dry ice and stored at -2o'C until assayed for LH content by RIA. The anterior pituitary was prepared for assay of LH as described by Rasby et al. (1990). Pituitary LH content was quantified in a single RIA in which the intra-assay CV was 2.5%. Corpora lutea (CL) were removed from ovaries and total wet ovarian and CL weights were determined. In addition, the ovaries were minced, blotted on paper, and weighed to determine follicular fluid weights. Dry ovarian weights were determined after desiccation at 90°C for 54 h. One-half of the carcass was obtained at slaughter. Soft carcass tissues were separated from the bone, and energy content and percentage of fat of the soft tissues were determined (Wagner et al., 1988). Analyses of variance were used to analyze cow, carcass, pituitary, and ovarian characteristics. Analyses of variance of endocrine responses were split-plot designs in which cows were nested within treatment, year, and season slaughtered (Gill and Hafs, 1971). Repeated measurements over time were taken on cows, and time sampled was the subplot. The effect of year and interactions with year were not significant for any traits and were omitted from the model. Full-model analyses
SE
6.9d 1.ld
.1
.1
48od
8
483d 714d 21.6d
6
8 .7
of LH and T4 after GnRH and TRH treatments indicated nonsignificant season slaughtered x treatment, season slaughtered x time sample, and season slaughtered x treatment x time sampled interactions. Therefore, the r e d u d model included season slaughtered, treatment, cow (season slaughtered x treatment), and time sampled. If a significant treatment x time sampled interaction existed, response curves for hormone concentrations were characterized by time trends that were analyzed by regression (SAS, 1988). Tests of homogeneity of regressions were used to determine differences in time trends for endocrine responses among cows with thin, moderate, or fat body condition (Snedecor and Cochran, 1968). Resultsand Dlscusslon
From July 1 to November 1, thin cows lost approximately 60 kg and 2 BCS units, moderate cows maintained weight and BCS, and fat cows gained about 80 kg and 2 BCS units. Between November 1 and slaughter, cows on all treatments maintained BCS (Table 1). Body condition score at slaughter for thin cows (3.4)was less (P c .001) than that for moderate (5.3) and fat (7.1) cows. Cows in all groups maintained weight (Table 1) from November 1 until slaughter; at slaughter, thin, moderate, and fat cows weighed 341,394,and 483 kg (P c .001), respectively. Energy content and percentage of fat in soft tissue of carcasses were greatest (P< .OOl) for fat cows and less for moderate and thin cows (Table 1). Analyses of LH response to GnRH included only cows that exhibited luteal activity as indicated by the presence of a CL at slaughter or plasma progesterone equal to or greater than 1 n g / d at the time of the first or second PGF injection or at the time or treatment with
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Condition score on November 1 3.9 5.3c 3.4b 5.3c Condition score at slau@ter 339b 3WC Weight on November 1, kg 341b 3WC Weight at slaughter, kg 243b 432' Carcass energy content, Mcal 7.0b 12.T FaZ 5% BThese data were derived from another stady (Wagner et at., 1988). ~.C*~WXUM not having a common superscript letter differ (P < .OOI).
pooled
Fat
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RASBY ET AL. TABLE 2. LEAST SQUARES MEANS FOR OVARIAN AND PITUITARY CHARACTERISTICS OF COWS WITH THIN, MODERATE, OR FAT BODY CONDlTION
~~
Body condition
Moderate
Fat
Wet ovarian wt, g Dryovarianwt,g corpus luteum wt, g Pituitarywfg Autcrior pihutary wt, g Concentration of pituitary LH,pgbg Total pituitary LH,mg
12.1. l.8@ 1.0lC 2.33 1.96 159 3.05
14.7'
20.6b 2.43d 1 .93d 2.54 2.03 1.79 3.66
C.d~-
2.09 2 . d
2.40 1.92 1.44 2.78
pooled SE 1.3 .19 .25 .06
.06 .14 23
not having a common supemaipt letter m e r (P < .OOI). not having a common superscript letter m e r (P < .IO).
GnRH and TRH. Eighteen (81.8%) thin, 24
(100%) moderate, and 23 (95.8%) fat cows (P < .025)had luteal activity, and data from these cows were used in the analyses. Percentage of fat in the carcasses of the four thin cows that did not exhibit luteal activity averaged 4.1%, compared with 7.4% (P < .05)for thin cows with luteal activity. In an experiment with similar cows, anestrus occurred when BCS of ncmlactating, cyclic beef cows averaged 3.5 (Richards et al., 1989). Total pituitary gland and anterior pituitary weights did not differ among treatments (Table 2). Likewise, concentrations and total pituitary LH content were similar (P > .lo) for thin, moderate, and fat cows. Pituitary and anterior pituitary weights were similar to those observed in cyclic beef cows and heifers (Beal et al., 1978) and dairy cows (Carruthers et al., 1980). Pituitary LH umtent of cows in this experiment was similar to that in pituitaries of cows slaughtered when BCS (1 = extremely thin, 5 = extremely fat) averaged 4.4 f .2,3.1 f .l, and .1.6 f .3 (Moss et al., 1982). Our results suggest that nutrition and BCS do not influence pituitary weights in ncmlactating cows and they agree with previous results (Beal et al., 1978). However, it has been demonstrated that energy intake (Beal et al., 1978) and BCS (Moss et al., 1982) of beef cows can affect pituitary LH content. In these studies cows in poor body condition with restricted energy intake had reduced pituitary LH. Cows in the previous experheats were losing weight and body condition until the time the pituitary was removed. Cows in the present experiment maintained weight for 1 to 4 mo before slaughter, which may have influenced pituitary LH content.
Season that the cows were slaughtered (March vs December) influenced pituitary weights and pituitary LH content. Regardless of nutrient intake and BCS, cows slaughtered in March had heavier (P< .02)total pituitaries and anterior pituitaries and had more (P c .02) LH in the pituitary than did cows slaughtered in December (Table 3). It has been demonstrated that there is a seasonal influence on LH secretion in ovariectomized cows, and serum LH concentrations in those cows are greater in spring than in fall (Day et al., 1986). In addition, cows in this experiment that were slaughtered in December maintained weight and body condition for about 1 mo before slaughter, whereas, cows slaughtered in March maintained weight and BCS for about 4 mo before slaughter. The length of time that a cow maintains weight and BCS may influence pituitary characteristics. Cows maintaining weight and BCS had greater basal LH and greater GnRH-induced LH release than cows losing weight and BCS mutter and Randel, 1984). Reducing energy substrate at the cellular level does result in decreased pituitary function. Rat pituitaries in medium treated with metabolic inhibitors that alter glycolysis and oxidative phosphorylation released less LH than control pituitaries when stimulated with GnRH (Sen et al., 1979). Fat cows had heavier (P < .001) wet ovarian weights than did moderate or thin cows (Table 2). Dry ovarian weights for fat cows tended to be heavier (P c .lo)than those for thin cows (Table 2). Corpora lutea weights were less for thin cows than for moderate and fat cows. In agreement with previous studies, cows that were fed limited amounts of energy had
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criteria
Thin
"ITON
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AND B O W REPRODUCTIVE FUNCTION
TABLE 3. LEAST SQUARES h 4 " S FOR PITUITARY cHARAcrERISTIc.5 FOR COWS WITH THLN, MODERATE, OR FAT BODY CONDITION IN DECEMBER AND MARCH
TABLE 4. LEAST SQUARES MEANS FOR FOLLJCULAR PLUID WEIGHT (g) POR COWS WITH THIN, MODERATE, OR PAT BODY CONDITION IN DECEMBER AND MARCH Month slaughtered
pooled
Criteria
December March
SE
Body condition
December
March
pituitarywt.g
2.32' 1.88'
2.53b 2.Mb
.06
1.72 3.61b
.14 28
Thin Modcrate Fat Pooled SE
1.83" 2.66"b 3.6SbC .28
2.42 1.84 25 1 .38
Anteri0rpituitarywt.g Concentrationof pituitary LH, Fdw3 1.49 TotalpituitaryLH,mg 2.72'
.06
~
~bMeansnot having a common superscript letter d i e r
not haviog a common soperscript letter differ (P < .01).
reduced ovarian weights (Gombe and Hansel, 1973; Bed et al., 1978). Thin cows had lighter wet and dry ovarian and CL weights, suggesting that nutrients available to maintain ovarian cell structure and integrity may differ in thin cows. When cows were fed diets that contained less than the required amounts of protein and energy to maintain BW, concentrations of glucose in plasma were decreased (Rasby et al., 1982) and concentrations of nonesterified fatty acids in plasma were increased (Garmendia et al., 1984). Blood glucose is the primary energy substrate used at the cellular level and reduced concentrations may influence ovarian and CL weights. Secretion of pituitary gonadotropins necessary to maintain ovarian and CL function may be reduced in thin cows. Although, total pituitary LH content of thin,moderate, and fat cows in our experiment were similar, secretion of GnRH may have been reduced, which could result in reduced secretion of LH. The amount of GnRH in the infundibular stalk-media eminence of beef cows is negatively correlated with BCS (Wettemann et al., 1989). Regardless of nutrient intake and BCS, CL from cows slaughtered in March were heavier (2.03 g; P < .01) than CL from cows slaughtered in December (1.26 g). Rtuitary LH content was greater (P < .02) in cows slaughtered in March than in cows slaughtered in December and may influence ovarian luteal cell function in cows slaughtered in March, causing heavier CL. Analysis of follicular fluid weight indicated a treatment x season slaughtered interaction. Thin cows had the least and fat cows had the greatest amount of follicular fluid (P < .01; Table 4) in December. Follicular fluid weights
of moderate cows were intermediate and did not differ from those for thin and fat cows. However, in March, follicular fluid weight did not differ among treatment group. Thin cows slaughtered in December lost weight and body condition from July 1 to November 1, then maintained weight and BCS for about 1 mo before slaughter. Thin cows slaughtered in March maintained weight and BCS for about 4 mo before slaughter. Losses of weight and BCS followed by a short period of maintaining weight and BCS may alter the hypothalamo-pituitary-ovarianaxis. Thin cows slaughtered in March may have adjusted to a lighter BW and less body energy stores, resulting in increased hypothalamic and pituitary gonadotropin secretion and increased follicular development. Concentrations of T4 in serum before TRJ3 treatment tended to be reduced (P < .12) in thin cows (64ng/ml) compared with moderate (72 ng/ml) and fat (73 ng/ml) cows. Reduced thyroid activity decreases ruminal motility and rate of passage but increases digestibility (Kennedy et al., 1977). Thin cows may use feed more efficiently, minimizing the effect of nutrient intake on pituitary and ovarian characteristics. This supports the conclusion that less feed was required for maintenance of cows in thin vs moderate body condition (Wagner et al., 1988). Concentrations of T4 in serum of cows in thin, moderate, or fat body condition were best described by a third-order polynomial regression equation. Time trends for concentrations of T4 were similar (P > .lo) for thin,moderate, and fat cows. At the time of TRH treatment, concentrations of T 4 averaged 69.4 f .9 ng/ml for all cows (Figure 1). Concentrations of T4 in serum increased to 91.7 f 1.3 ngml by 5 h
~ b * C ~ e in a ncolumns ~
(P < .02).
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Monthslaughtered
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RASBY ET AL.. 0.
94 -
0
. '
.
0
.
-c - - - - - -
-. 0
A
40
g
35-
C
A
5
0
120
240 360 480 Minutes Post Treatment
600
720
Figure 1. Least squares regressions and least squares means for concentrations of thpxine in serum of cows in thin (-, A), moderate (-, r). or fat ..., 0) body condition.
after TRH and were similar to those observed after TRH treatment of steers (Pratt et al., 1986) and cows (Vanjonack et al., 1974). Our results suggest that thyroid function, as indicated by T4 release after TRH, is similar in thin, moderate, and fat cows. Even though BCS among groups differed, environmental conditions in this experiment were not adverse. Cows were allowed a 1-d adaptation period in stalls in a temperaturecontrolled mom before TRH treatment. This adjustment period may have minimized any differences in thyroid response to TRH treatment. Concentrations of LH in serum of cows in thin, moderate, and fat body condition after GnRH were best described by a fourth-order polynomial regression equation. Time trends for LH concentrations in serum of thin, moderate, and fat cows were not parallel (Pc .025). Before GnRH treatment, concentrations of LH in serum were similar for all treatments and averaged 2.2 f .6 ndml (Figure 2). At 105 min after treatment, concentrations of LH in serum averaged 41 f 3, 32 f 4, and 34 f 4 ngf ml for thin,moderate, and fat cows, respective ly. By 360 min after GnRH treatment, concentrations of LH in serum averaged 4 f 1 ndml for all groups. Our results are similar to those of Whisnant et al. (1985) and Killen et al. (1989) and indicate greater release of LH after treatment with GnRH in cows or heifers fed restricted amounts of energy. Thin cows release more LH when treated with GnRH than do cows in a moderate or fat body condition; therefore, pituitary stores of
10
0 30 60 90 120 150 180 210 240 270 300 330 360 Minutes Post Treatment
Figure 2. Least squares regressions and least squares
means for concenlrations of luteinizing hormone in serum of cows in thin (-, A),modcrate (-, r), or fat (..., 0 ) body condition.
releasable LH in thin cows may be greater than those in moderate and fat cows. The releasable pool of LH in the rat changes during the estrous cycle, but total pituitary LH does not change Wckering and Fink, 1979). Our results indicate that pituitary LH content is similar among cows in different body conditions. We suggest that greater concentrations of LH after treatment with GnRH in thin cows is a result of a greater releasable LH pool. We conclude that nutrient intake and BCS do not influence total pituitary weight, anterior pituitary weight, pituitary LH content, or thyroxine after TRH treatment. However, nutrition and BCS influence ovarian and CL weights and the release of LH from the pituitary gland. Therefore, effects of BCS on reproductive efficiency seem to be mediated through secretion of LH. lmpllcatlons
Thin body condition of beef cows is associated with reduced secretion of luteinizing hormone, reduced ovarian and corpora lutea weights, and the cessation or lack of initiation of estrous cycles. Reproductive failure is a major cost to cattle producers. Body condition of cows should be monitored to evaluate feeding programs and to reduce reproductive inefficiencies. Literature Cited Apgar, J., D. Aspros, I. E.Hixon, R. R Saatman and W. Hansel. 1975. Effect of restricted feed intake on the
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m
NWIRlTION AND BOVINE REPRODUCTIVE FUNCTION
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Kennedy, P. M., B. A. Young and R. J. christopherson. 1977. Stndies on the Aationphip between thyroid fnnction, cold acclimationand retention time of digesta in sheep. J. Anim. Sci. 491084. men,J. EL, D.W. Fomst, F. M. Byers, G. T. Schellingand C.R. Low. 1989. Gonadotrop&releasing hormominduced luteinizing hormone release in beifers: Effect of nutrition during gestation. I. Anim. Sci. 67:4%. Lamming.G. E., D. C. Watha and A. R. Peters. 1981. Endocrine patterns of the postpartum cow. J. Reprod. Fertil. (Suppl.) 30955. Lishmaq A. W.. S . W . Allison, R. L. Fogwell, R. L. Butcher and E. K. InsLetp. 1979. Follicnlar development and functionof i n d u d corpora lutea in undded postpartum anestrousbeef cows. J. Anim. Sci. 482367. Low,G. N., T. Enrsnas, A. Mouton and W. H m L 1964. Evidencefor a thyrotropiceffect of diethylstilbestrolin sheep via a hypotheticalpituitary mechanism. S. M r . J. Agric. Sci. 7797. Lusby, K. S.. R. P. WeUemann and E. I. Turmau 1981. Effects of early weaning calves from first-calf heifers on calf and heifer perfomauce. J. Anim.Sci. 53: 1193. Moss. G. E.,J. R Parfet, M. A, Diekman, R P. h e n a g e r andK. S.Hendrix. 1982. Pituitary luteinizinghormone (LH), follicle stimulating hormone 0, semm progesterone (P) and hyp0-c gonadotropinreleasing hormone (GnRH) in beef cows in varied body condition I. Anim. Sci. 55(Suppl. 1):374 (Abstr.). Pickcring, A.J.M.C. and G. Fhk. 1979. Variation in size of the readily relasable pool of luteinizing hormone dmjng the oestrous cycle of the rat. J. Endocrinol. 8 3 53. ha,B. R and R P. Wetternarm. 1986. The effect of envjrommtal temperature on comemations of thyroxine and triiodothyronb after thyrotropinreleasing hormone in s t e m . J. Anim. Sci 621346. Rasby,R.J., R. P.Wettemann, R D. Geisert, L. E.Rice and C. R Wallace. 1990. Nutrition, body condition and reproduction in beef cows: Fetal and placental development, and estrogens and progesterone in plasma. I. Anim. Sci. 684267. Rasby, R J., R. P. Wemmanu, K.S. Lusby, B. R. Pratt and (Abstr.). E.I. 'Lhrmaa 1982. Influem of prepartam nutrition Garmendia, J. C., R.P.Wettcmann and K.S. Lusby. 1984. on plasma glucose, protein and esterified fatty acids in Effect of prepartum nutrition on plasma constituents range cows.J. Anim. Sci. 55(Suppl. 1):380 (Abstr.). and reproductive performance of range beef cows. J. Rawliugs, N. C., L. Weir, B. Todd J. Maoris and J. H. Hyland. 1980. Some endocrine changes associated Anim. Sci. 59(Suppl. 1):325 (Absbr.). Gill, J. L. and H. D. Hafs. 1971. Analysis of repeated with the post-pintnm period of the suckling beef cow. measurements of animals. I. Anim. Sci. 33:331. I. Repmd. F e d . m301. Gombe, S. and W. Hansel. 1973. Piasma luteinizing Richards, M.W., R. P. Wettemannand H.M Schoenemann. 1989. Nutritional aoesfrus in beef cows: Body weight hormone (LH) and progesterone levels in heifers on change, body condition,luteinizing hormone in semm restricted energy intalres. J. Anim. Sci. 37728. Hallford,D.M.,E. J.Turman,R.P. WenemannandC.E. and ovarian activity. J. Anim. Sci. 67:1520. . Pope. 1979. Endocrine and reproductive response of Riley, G. M,A. R. Petem and G. E. J ~ J 1981. Induction of pulsatile LH release, FSH release arid beef cows to PMSG. J. Anim. Sci. 491030. Hill, J. R., Jr., D.R. Lamod, D. M. Hcnricks, J. F.Dickey ovulationinpost-partumacyclicbeefcows by repeated and G. D. Niswender. 1970. The effects of undenmtrismall doses of &RH. J. Reprod. Fertil. 63:559. tion on ovarian function and fertility in beef heifers. Rutter, L. M.and R D. Randel. 1984. Postpartum nutrient Biol. Reprod. 2:78. intakeand body conditio^ Effect on pituitary function Howland, B. E., R A. Bellows, A. L. Pope and L. E. Casida. and onset of e m in beef cattle. J. Anim. Sci. 58:265. 1966. Ovarian activity in ewes treated with @ncose SAS. 1988. SASJSTAT User's Guide (6.03 Ed.). SAS Inst. and triiodothyronb. J. Anim. Sci. 25:836. Inc., Cay, NC. Humphrey, W. D., C. C. Kaltenbach, T. G. Dunn, D. R. Selk, G. E., R P. Wettanann,K.S. Lusby,J. W. Oltjen, S .L. Kwitnilc and G.D. Niswender, 1983. Characterization Mobley, R. J. Rasby and J. C. Gamenda . 1988. Of hormonalp m in the beef COW daring p~stpmRelationships among weight change, body condition tum anestrus. J. Anim. Sci. 56445. and reproduction performance of range beef cows. J. sensitivity of the bovine corpus luteum to LH in vitro. J. Anim. Sci. 41:1120. Bed, W. E.,R.E.Short, R.B. Stai-er, R. A. Bellows, C. C. Kaltenbach and T. G. Dum. 1978. Iuflucnce of dietary energy mtake on bovine pituitary and luteal function. J. Anim. Sci. 46A81. Bellows, R A. and R E. Shon 1978. Effects of precalving feed level on birth weight, calving dSculty and subsequent fertility. J. Anim. Sci. 46:1522. Carruthers,T.D..E.MConvey,J. S.Kesner,H.D.Hafsand K. W. Cheng. 1980. The hypothalamo-pituitary gonadotrophic axis of sackled and nonsuckled daily cow p o s t p m J. Anim. Sci. 5 1 9 9 . Cmthers, T. D. and H. D.MS. 1980. Suckling and fourtimesdailymilking:Influenceonovulation,estrosund semm luteinizing harmom, g l m c o i d s and prolactin in postpartum Holsteins. J. Anim. Sci. 50919. Connor. H. C., P. L. Houghton, R P. Lemnager, P. V. htalven, J. R. M e t and G. E.Moss. 1990. Effect of dietary energy, body condition and calf ranoval on pituitary gonadotropins, gondotroph-releasing hormone (GnRH) and hypothalamic opioids in beef cattle. Domest Anim. Endocrinol. 7403. Corah, L. R., T. G. Dunn and C. C. Kaltenbach. 1975. Influenceof prepartum nutrition on the reproductive performawe of beef females and the performawe of their progeny. J. Anim. Sci. 41:819. Day, M.L., K.hakawa, P. L. Penuel, D. D.Zalesky, A. C. Clutta, R. J. Kittok and J. E.Kinder. 1986. Idhence of season and estradiol on secretion of lutciniziag hormone in ovariectomized cows. Biol. Reprod. 35: 549. Dunn, T. G., J. E. Ingab, D. R Zimmemulnand J. N. Wiltbank. 1%9. Reproductive performance of %year-old Herdord and Angus heifers as influenced by PE- and post-calving energy intake. J. Anim. Sci. 29719. Dunn, T. G. and C. C. Kaltenbach. 1980. Nutrition and the postpartum intend of the ewe. sow and cow. J. Anim. Sci. 51(Suppl. 2):29. Duun, T. G., J. Rone. C. C. Kaltenbach,L. A. van der Walt, M.L.Riley and A. M Akbar. 1974.Hormone changes duringunderfeedingof beef cows.J. Anim.Sci. 39:206
2080
RASBY ET AL.
Anim. Sci. 633153. Sen, K.K., S. Azbar and K.M.J. Menon. 1979. Evidace for the involvement of an energy-depndent process in
Downloaded from https://academic.oup.com/jas/article-abstract/69/5/2073/4705376 by guest on 13 September 2018
gonadotropin-releasing hormone-stimulated luteink+ ing hormone release by rat anterior pituitary. Endoainology. 1051158. Snedecor, G. W. and W. G. cochran. 1968. Statistical Methods (6th Ed.). Iowa State Univ. Press, Ames. Spitzer, J. C., G.D.Niswdex, Ct. F. Seidel, Jr. and J. N. Wiltbad. 1978. Fatilization and blood levels of progesterone and LH in beef heifers on a restricted energy diet. J. Anim. Sci. M1071. Van.nack, W. J., M.W.Felz, L.Hahn and H. D. Johoson. 1974. 'Izlyrotropin-releashg hormone 0 dfects on bovine plasma thyroxine. Roc. Soc. Exp. Biol. Med. 145~925. Wagner, J. J., K.S. Lusby,J. W. Oltjen, J. Rakestnrw, R.P. Wettemannand L.E.Walters. 1988. Carcass composition in mature Hereford cows: Estimation and effect on daily metabolizablee w g y requirementduring Winter. J. Anim. Sci. 66503.
Wagner, W. C. and W. Hansel. 1969. Reproductive physiology of the post partom cow. I. clinical and histological f h d h g s J. Reprod. pcrtil. 18:493. Wettanann, R. P. 1980. Postparbrm endoaine function of cattle., sheep and swine. J. Anim Sci. Sl(Supp1. 2):2. Wetkmam,RP.,R J.Rmby,P.G.Harms,K. S.Lusbyand J. J. Wagner. 1989. LHRH in the i n f u n d i i stalkmedian eminence is related to percentage body fat in cows. J. Anim. Sci 67(SuppL 2):57 (Abstr.). Wemuam, R.P.,E.J. 'hman, R.D.Wyatt and R.Totusek 1978. Influence of suckling intensity on reproductive performance of range cows. J. Anim. Sci. 47342. Whisnaut. C. S., T. E. Kiser, F.N. Thompsonand J. B.Hall. 1985. Effect of nutrition on the LH response to calf removal aud GnRH. Theriogemlogy 24565. Wiltbank, J. N. 1970. Research needs in beef cattle reproduction. J. Anim. Sci. 31:755. WiltbanL,J. N.,W. W. Rowden, J. E.Ingalls. K. E.Gregory and R. M.Koch. 1%2. Effect of energy level on reproductive phenomena of mature Hereford cows. J. Anim. Sci. 21:219.
