Responses by Lactating Cows in Commercial Dairy Herds to Recombinant Bovine Somatotropin J. W. THOMAS Department of Animal Science Michigan State University East Lansing 48824 R. A. ERDMAN Animal Science Department University of Maryland College Park 20742 D. M. GALTON Department of Animal Science Cornell University Ithaca, NY 14853 R. C. LAMB and M. J. ARAMBEL Animal, Dairy, and Veterinary Science Department Utah State University Logan 84322 J. D. OLSON Department of Clinical and Population Sciences University of Minnesota St. Paul K. S. MADSEN. W. A. SAMUELS, C. J. PEEL, and G. A. GREEN

Monsanto Agriculture Company St. Louis, MO 63167 ABSTRACT

4.2; FCM 6.0 vs. 4.7 kg/d cow). Temporarily, concentration of milk fat increased

Cows (890) in 15 US herds were assigned randomly in equal numbers to control or bST injections (500 mg in a prolonged-release form every 14 d for 12 wk) within three stages of lactation (57 to 100, 101 to 140, and 141 to 189 d postpartum) and two parity groups (primiparous and multiparous). Yield and milk composition were monitored 1 d/wk for 16 wk including 2 wk pretreatment and 2 wk posttreatment. Increases in milk and FCM due to bST injections were less at 57 to 100 d than at 101 to 189 d postpartum (milk 3.6 vs. 5.5; FCM 3.9 vs. 6.1 kg/d per cow), and increases in milk and FCM were more for multiparous than for primiparous cows (milk 5.5 vs.

and protein decreased; later, concentrations for control and injected cows were similar. Postinjection milk fat concentration decreased, but milk protein concentration increased temporarily. The net increase in milk (and FCM) varied significantly among herds from 2.9 to 7.6 kg/d per cow (mean, 4.9 kg). Responses in FCM were similar over a wide range of pretreatment yields. A great variety of feed ingredients were fed as total mixed rations, and nutrient concentrations varied greatly. The SCC were similar before, during, and after treatment, but increase in FCM of injected cows exhibited a negative correlation with pretreatment SCC. Changes in body condition score of sometribove-injected cows varied among herds ( 2 5 to -.45) and averaged -.02 compared with .07 for controls. There

Received April 19, 1990. Accepted A u p t 3, 1990. 1991 J Dairy Sci 74945-964

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THOMAS ET AL.

was no pattern in incidence of mastitis during sometribove injections. (Key words: somatotropin, lactating cows, commercial dairies)

Abbreviation key: BCS = body condition score, CON = control group, SOM = sometribove-injected group. INTRODUCTION

The concept of enhancing milk yield by administration of naturally occurring hormones was demonstrated over 50 yr ago by injecting cows with a pituitary extract (2). A large variation in response was noted. These early observations were amplified by several subsequent investigations (5,13,20). The limited supply of pituitary glands and the timeconsuming prep aration, purification, and cost of extracted material limited the use of pituitary glands as a source of bST. The development of recombinantly derived bST, its availability, and the comparable increases in milk yield from this material have led to numerous trials and publications (3, 4, 10, 16, 18, 20). Increases in milk yield to bST have been variable (3 to 10 kg) and dosedependent (6, 9, 17, 24). Any effects on health or reproduction of cows given bST have been nil or small and similar to that of cows with comparable yields of milk (4, 6, 9, 17,24). Increased feed intake after bST administration occurs several weeks after increase in milk yield (3, 12, 16, 24). Gross efficiency of milk production was increased by bST administration with some reported decreases in body condition scores and body fat content (3, 4, 12, 22, 24). Most studies to date have been in relatively controlled experiments in university or company research herds. If bST is to be used throughout the dairy cow population, there is a need to measure quantitatively any milk and health-related responses in commercial dairy herds under various environmental conditions. Trials using commercial or farm herds have been limited (6). Increase in milk yield of 2.5 to 5.0 kg/d per cow was reported with no adverse effects on herd health or reproduction. The present study was planned to measure the effects of bST on milk yield and composition as well as on health in commercial dairy herds in the United States. Journal of Dairy Science Vol. 74, No. 3, 1991

MATERIALS AND METHODS

Fifteen commercial dairy herds in six states were selected and screened for satisfactory cow availability and milk yield, management and feeding practices, absence of restrictions on milk sales, and ease of weekly monitoring for milk yield and obtaining samples. Characteristics of these herds and values for other criteria used in screening herds are in Table 1. All cows were healthy and on a satisfactory vaccination and herd health program. Each cow was examined visually before being placed on the trial. Cows with low body condition score or any noticeable health problems were eliminated during the screening process. Cows were housed in free stall arrangements and milked in herringbone milking parlors. Cows were fed total mixed rations; three herds had an arrangement for supplemental grain feeding to designated cows. The selected cows were allotted randomly to one of two treatment groups: either cows were injected with bST in a liquid, prolonged-release form (sometribove, Monsanto A.gricultural Co., St. Louis, MO), (SOM), or not injected, control cows (CON),within stage of lactation (57 to 100, 101 to 140, and 141 to 189 DIM), and parity (primiparous or multiparous lactations two to eight). A criterion for herd selection was that there be at least four milking multiparous and four primiparous cows in each of the three DIM categories prior to treatment allocation. However, of the 15 herds, 6 herds had too few primiparous cows to fill one of the parity-DIM categories (Table 2). Numbers of cows in each herd and their distribution according to parity and DIM are in Table 2. A total of 870 cows finished the 16-wk trial, 20 cows did not finish. One-third of the cows were primiparous and two-thirds were multiparous; approximately one-third of the cows were in each of the three DIM stages. The 16-wk experiment was divided into three periods: a 2-wk pretreatment period, a 12-wk treatment period, and a 2-wk posttreatment period. The 12-wk treatment period was divided into six 2-wk periods for evaluating certain production responses and into three 4-wk periods for feed sampling and analysis. Treatment consisted of six injections of 500 mg of sometribove at 2-wk intervals beginning on d 1 of the treatment period when cows were 57 to 189 DIM. The posttreatment period began 14

SOMATOTROPIN IN FARM HERDS

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d after the last sometribove injection. Injections were performed by one of the authors or a aualified assistant and were given subcutane &sly in the postscapular region on alternate sides of the body every 2 wk utilizing a 16-gauge, 2.5cm needle. Cows in herds 1 and 2 were injected in the ischiorectal fossa (tailhead) area. The sometribove injections were performed at the same hour of each day in selflocking stanchions, in the milking parlor, or in chutes designed for this pupose, depending on the preferred situation for each herd. On the same day of each of the 16 wk, milk weights for each milking in a 24-h period were recorded using portable meters (Surge Tru-Test Meters; Babson Bros., Inc., Naperville, L)or in-line milk meters. Milk samples were obtained for concentrations of milk fat, protein, and SCC. These analyses were performed at regional DHI milk testing laboratories. Milk sampling coincided with d 3 and 10 posthjection. For herds 14 and 15, weather made the monitoring of milk data impossible during wk 15 and 16, respectively, so data for the posttreatment period are incomplete for these two herds and not considered in most analyses. At weekly intervals, feed ingredients and TMR samples were obtained and composited according to the following five periods: the 2-wk pretreatment period, the first, second, and third 4-wk subperiods of the 12-wk treatment period; and the 2-wk posttreatment period. Samples were analyzed at commercial feed testing laboratories using standard procedures. At one location (herds 14 and 15). feed samples were not obtained during the pre- and posttreatment periods. Samples from herds 10, 11, and 12 were composited only twice during the treatment period. In some other locations, only the TMR, and not individual ingredients, were analyzed during the posttreatment period. Body condition scores (BCS, 1 = very thin to 5 = very fat) (15) on every cow were recorded at each injection time and at the end of the treatment period. Records of treatments for reproductive aberrations, breedings, pregnancy examinations, incidence of mastitis treatments, and other health disorders and management alterations were recorded daily and transcribed onto standard forms throughout the study. Data for the 12-wk treatment period and the 2-wk posttreatment were analyzed for treatment effect and interactions of treatment effects with Journal of Dairy Scimce Vol. 74, No. 3. 1991

parity and DIM; the 2-wk pretreatment average of each variable was used as a covariate. The statistical model was:

where: Yfiy = 12 wk average (milk, FCM, or milk composition or constituent yield), M = mean, Hh = herd, Pi = parity, Sj = DIM or stage of lactation, PSij = parity x DIM, Tk = treatment, THu = treatment x herd, TP& = treatment x parity, TSjk = treatment x DIM, TPSijk = treatment x parity x DIM, P-w = 2-wk pretreatment average (expressed as deviation from parity-DIM mean), and Egw = error. Herd was considered a random effect, and when the treatment x herd interaction was statistically signifcant (P c .05), it was used as the error term for treatment effect. Pretreatment averages also were analyzed with this model, as were body condition scores and changes in scores during the treatment period, but with no covariate (P-y term). This design is similar to that reported by Aguilar et al. (1). Typical analysis with probabilities associated with the null hypothesis for some variables are in Tables 3 and 4. All analyses were performed with SAS procedures (23). Regression analyses were performed to relate FCM response to several variables. Unless otherwise noted, statistical significance was P c .05. RESULTS AND DISCUSSION Mllk Yleld

During the pretreatment period, the yield of milk or 3.5% FCM were approximately equal for the CON and SOM groups (Table 5 ) in 14

of the 15 herds. The one exception was herd 2,

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SOMATOTROPIN IN FARM HERDS

TABLE 4. Values for ANOVA for milk yield (Lpjd per cow) and change in FCM (kg/d per cow). Treatment Variable Pretreatment covariate4 Herd Pari+ DIM Treatment (trt)6 Herd x trt Parity x m DIMxtrt DIM x parity DIM x parity x M Error W S ) Model

R2

df 1 14 1 2 1 14 1 2

2 2 826 40

...

Change in ECM'

ss'

P2

ss

P2

13353 10272 1761 2980

.OOO1

4065

.OOO1 .0057 .0048 .o006 .ooOl .7122

1172 1137 1048 19 4857 378 77 191 2 13 8207 11713 .59

.OOO1 .OOOl .ooO1 .3948 .OOO1 .o006 .0055 .ooO1 9239 .5162

307 79 149 1053 7 8116 37187 .82

.OOO1 .OOO1

.OOO1

(MS = 9.8)

.OOOl

...

(Ms

= 9.9)

.ooO1

...

sum

of squares. 2P = Robability that null hypothesis is correct. 3change in FCM is difference in FCM between preecatment and treatment. %or certain variables. the values during the pretreatment period were used as a covariate for treatment and posttreatment paiods. Spist lactation or second to eighth lactation. 6Control versus sometriboveinjected cows.

in which CON cows produced more than SOM cows. Results for cows in these herds were as expected in that during this 2-wk pretreatment period the multiparous cows produced more milk and FCM than did the primiparous cows for both CON and SOM groups (Table 5). Cows in both groups in the earlier stages of lactation produced more milk than those in later stages of lactation ("able 5). Cows in parity 1 did not show as much difference due to DIM as those in parity 2 because of established differences in persistency. The cows exhibited normal lactational trends prior to bST injections. The bST-injected cows in all 15 herds produced more milk than CON cows (P c .01 to P c .OOOl) during the 12-wk treatment period (Tables 3 and 5). The calculated difference in milk amounted to 4.9 kg more milk and 5.3 kg more FCM due to bST injections. This calculated difference in response among the 15 herds ranged from 2.9 (11%) to 7.6 (29%) kg/d of milk. The large variation among herds for yield and other variables always was significant (P c .OO01, Tables 3 and 4). During the treatment period, the difference in milk or FCM (data not shown) between SOM and CON cows was greater for multiparous than for primiparous cows (5.5 vs. 4.2 kg milk/d or 6.0 vs. 4.7

kg FCWd). Among DIM stages, differences between CON and SOM cows were greatest for cows in DIM stage 2 (101 to 140 DIM, Tables 3 and 5 ) and least for cows in DIM stage 1 in both primiparous and multiparous cows. Our data indicating greater response for multiparous than for primiparous cows is more extensive and definitive than reported by others (4, 6, 12, 22). The relation between parity and DIM should be considered and defined when quantitatively measuring the variable response to bST. This term was noticeably significant before, during, and after treatment (Tables 3 and 4). Trends in mean daily FCM yield over the 16 wk are shown in Figure 1. During the entire 12-wk injection period, yield for the SOM cows remained above that during the pretreatment period, and the difference between the two groups remained approximately constant. Milk yield on d 10 postinjection exceeded that on d 3 postinjection. An undulating response due to bST injections at 14-d intervals was observed previously (4), but in this experiment the undulations became less extensive as time on bST increased (Figure 1). Yields of milk and FCM were practically identical (P > .lo) between CON and SOM cows during pretreatJournal of Dahy Science Vol. 74, No. 3, 1991

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-2

0

2

4

6

8

10

12

14

Week of Study

Figure 1. Average daily 3.5% FCM for the 15 herds during the 16-wk trial for control (dashed line) and bST (sometribve)-injected(solid line) cows. Injections given at wk 0, 2, 4, 6. 8, and 10.

ment and at wk 16 (after bST injections), indicating that milk yields returned to expected amounts after cessation of bST injections. As expected, both CON and SOM multiparous cows produced greater amounts of milk (and FCMJ than did primiparous cows during the treatment and pretreatment periods (Tables 3 and 5). Daily milk yield consistently decreased as DIM increased for multiparous cows, but only slightly for primiparous cows, reflecting difference in persistency of production between multiparous and primiparous cows. Although cows in DIM stage 1 had greater milk and FCM yields than those in stages 2 or 3, their increase in milk or FCM due to bST was less. Because of the small response in cows with less than 100 DIM, any prospective user of bST may decide not to initiate bST treatment until cows exceed 100 DIM. During the treatment period, 92% of primiparous cows injected with sometribove produced more FCM per day than during the pretreatment period compared with only 37% of the control cows. These percentages varied among herds. In nine herds, 100% of the primiparous cows given sometribove produced more FCM per day during treatment than during pretreatment, but one herd produced only 70%. The size of the primiparous cows may influence their response and may be responsible for this Journal of Dairy Science Vol. 74, No. 3, 1991

large herd variation. For multiparous COWS injected with bST, 77% produced more FCM per day during treatment than during pretreatment compared with 14% of control cows; herd averages varied from 57 to 94% for bST-injected cows. Herd averages for actual change in FCM (FCM during treatment minus FCM during pretreatment) in bST-injected cows ranged from .7 to 5.6 kgld among the 15 herds (average = 3.34 f .17). The change for control cows ranged from -.l to 4 . 8 kg FCM/d per cow among the 15 herds (average = -1.98 kg f .17). The change for individual bST-injected cows ranged from 14 kg FCM/d to -10.4; both extremes occurred in the same herd. All herds had at least one bST-injected cow for which FCM decreased. Variation in response among cows and herds has not been given in previous publications except that of Asimov and Krouze (2). This type of information would be of value to prospective users of bST. Using individual cow’s change in FCM (FCM during treatment minus FCM during pretreatment) as a measure of response, we have related response to pretreatment yield in Figure 2. The slopes of the regression lines for the two equations representing CON and SOM cows were similar (P > .lo) and parallel. This indicates that the difference in the change in milk yield from pretreatment to treatment between CON and SOM cows was independent of previous milk yield. For instance, the regression equations indicate that a cow yielding 40 kg milk prior to bST injections would have a change of .86 kg during the next 12 wk when injected with bST or 4 . 2 if kept as a control: a difference of 5.1 kg. For a 20-kg pretreatment yield, the difference would be 5.3 kg (6.02 to .72). These regression lines indicate that the average increase in FCM after bST injections was similar for cows yielding 17 to 48 kg FCM/d per cow (5.4to 5.1 kg). Similar regressions and correlation coefficients have been calculated for CON and SOM cows from four clinical trials in the US and four clinical trials in Europe (16, 18) confirming the similarity of increases in milk for low and high yielding cows. The similar negative correlation and regression coefficients indicate that CON and SOM cows have similar rates of decline as lactation progresses. This trend also was noted in Figure 1.

953

SOMATOTROPIN IN FARM HERDS

TABLE 5. Milk yield (lcgjd) for control (CON)and M T (sometribove)-injected cows (SOM) in 15 herds during pretreatment, treatment, and posttreatment periods (least squares means).

Herd no. 1 2 3 4 5

6 7 8 9 10 11 12 13 14 15 Avg.

SE Parity 12 Parity 22 DIM l 3 DIM z3 DIM 33 Parity I-DIM 1 Parity 1-DIM 2 Parity I-DIM 3 Parity 2-DIM 1 Parity 2-DIM 2 Pari6 2-DIM 3

CON 29.3 365 24.6 31.3 28.7 27.6 24.1 26.8 33.5 35.6 32.0 31.2 22.9 25.3 24.9 28.9 28 26.2y 31.7 31.9y 28.7 26.3 27.7 25.8 25.1 36.1y 31.6 27.5

Pretreatment DiffCrSOM ence

30.3 33.W.l 24.6 30.9 27.7 28.6 25.7 25.9 32.2 33.8 33.7 30.7 24.1 25.2 23.7 28.7 .28 26.1y 31.3 31.N 29.0 26.0 26.6 26.7 24.9 35.4 31.4 27.0

1.0 -35 .O

-.4 -1.0 1.0 1.6 -9 -1.3 -1.8 1.7 -5 12 -.l

-1.2

-2

... -.I -.4 -.9 .3 -.3 -1.1 .9 -.2 -.7 -.2 -.5

Treatment

Damence

CON

SOM

28.8 31.4 21.3 295 27.8 26.7 25.1 24.8 29.9 31.5 30.0 30.0 21.4 25.7 23.5 27.2

33.0*** 4.2 36.8*** 5.3 27.4*** 6.1 34.3*** 4.9 33.3*** 5.6 30.5*** 3.8 30.4*** 5.4 29.1*** 4.3 34.2*** 4.3 39.1*** 7.6 36.5*** 6.5 33.9”** 3.9 25.9*** 4.6 28.6** 2.9 27.4*** 3.9 32.01** 4.9 .. .25 30.1***y4.2 33.9*** 5.5 33.9***y 3.6 32.7*** 5.9 29.5*** 5.1 30.6*** 3.2 30.7*** 5.2 29.01** 4.2 37.3***y 4.0 34.6*** 6.6 29.9*** 6.0

.25

25.9y 28.4 30.3y 26.8 24.4 27.4 25.6 24.8 33.3y 28.0 23.9

Posttreatment

CON

SOM

Difference

27.3 28.2 19.2 27.6 25.4 23.5 23.5 22.4 29.3 28.6 26.0 19.7

28.8 31.5*** 22.3** 28.0 27.4** 23.9 27.6*** 24.1 27.9 33.3*** 30.7** 27.1 22.0f

1.4 3.3 3.1 .4 2.0 .4 4.1 1.7 1.5 3.9 2.1 1.2 2.3

25.2 26 25.3 25.0 28.8y 24.8 21.9 27.1y 25.3 23.6 30.6y 24.3 20.1

27.3*** .25 27.2*** 27.4*** 29.7y 27.8*** 24.3*** 28.1 27.5** 25.9* 31.3y 28.1*** 22.7***

2.1

26.4

... ...

. . . . . . . . . . . . ...

1.8 2.4 .9 3.0 2.5 1.0 2.2 2.3 .7 3.8 2.6

‘Significance for CON vs. SOM on same row: t P < .lQ *P < .OS; **P .01; ***P < .OOOl; YP < .05 for values in that column for that subset term, i.e., parity, DIM, or their interaction 2Parity 1 = F i t lactatio~Parity 2 = second through eighth lactation. 3DIM 1 = 57 to 100 DIM; DIM 2 = 101 to 140 DIM; DIM 3 = 141 to 189 DIM.

During the posttreatment period, which was 3 and 4 wk after the last bST injection, the injected cows produced 2.1 kg more milk p a ble 5) and 1.7 kg more FCM (data not shown) than the CON cows (P < .OOOl). For the 13 herds that had yield data during the posttreatment period, the SOM cows outproduced CON cows by .4 to 4.1 kg milk (P> .1 to P < .OOOl). In 6 of the 13 herds, the probability of this difference was P < .01. For both parities, three DIM stages and six parity-DIM subsets, the cows that had received bST produced more milk (Table 5 ) and FCM (P > .1 to .OOOl) than did CON cows during the 2-wk posttreatment period. When yields during posttreatment and pretreatment were compared,

cows given bST had a smaller decrease (P < .Ol) in FCM or milk (Table 5; 28.7 to 27.3Q8.9 to 25.2) than controls. The decrease was least for SOM cows in 12 of the 13 herds and least, but variable, among DIM and parity subsets. These findings indicate that bST as given in this experiment can result in increased milk yield 16 to 17 d after the last injection. Data in Figure 1 indicates that by 23 to 24 d after the last injection, milk yield was similar for the two groups. The rate at which milk yield returned to normal after cessation of a series of bST injections varied among herds and among cows. Some herd managers noted, and records verified this observation, that a few COWS had a Journal of Dairy Science Vol. 74, No. 3, 1991

THOMAS ET AL.

954

Sometribove

Control

lr=-.381

'6 1

.. -

1 10

6 20

16

h 26

I

30

36

40

46

Pretreatment FCM (kgkow)

1

,

1

60

10

16

,

I

20

26

30

36

40

46

l

60

Pretreatment FCM (kg/cow)

Figure 2. Relation between pretrearment FCM yield and change in FCM yield calculated as FCM during a 12-wk period of bST (sometribove) injections (or control) minus yield in a 2-wk pretreatment period. Cows were in 15 farm herds in the US. Control cows: y = 5.72 - .Ux; r = -.W, SE of prediction = 2.88. Sometribove cows: y = 11.26 .26x; r = -.38; where x = pretreatment FCM yield in kgld per cow.

large decrease in milk yield from wk 14 to 16. The range was from a decrease of 21 kg a d per cow to an increase of .5 kg and may represent the stimulation due to bST at that stage of lactation. This large range in decreased yield following bST withdrawal is consistent with the large range in increased yield after initiating bST injections. A marked decrease after withdrawal of bST may be useful in dryoff management of the SOM cows near the end of their lactation. Milk Composltlon

During pretreatment, CON cows and those to be given bST had similar concentrations of fat and protein in their milk (Tables 6 and 7). In only 2 of the 15 herds did the milk fat test for SOM cows exceed that for CON cows (P c .05)during pretreatment (Table 6). Multiparous cows tended to have a greater milk fat concentration than did primiparous ones during both pretreatment and treatment. Milk fat concentration tended to increase as DIM increased during treatment and posttreatment, but this trend was not consistent during pretreatment period (Table 6). The average milk fat test during treatment was similar to that during pretreatment. HowevJournal of Dairy Science Vol. 74, No. 3, 1991

er, the milk fat concentration was greater for bST-injected cows than for CON cows (3.67 vs. 3.59%. P e .OOOl). In only 5 of 15 herds did this difference exceed .14 percentage units or P e .05 (Table 6). Both multiparous and primiparous cows given bST had a greater milk fat concentration (P e .01) than CON cows (Table 6). The SOM cows over 100 DIM had a greater (P< .Ol) milk fat concentration than did similar CON cows; this was not so (P > .OS) for cows with less than 100 DIM. Reasons for differential responses to bST in milk fat concentration among herds, trials, and cows are not readily apparent but have been related to relative energy balance or to time on bST (17, 18). Reported changes in milk fat concentration have been variable (2, 3, 4, 10, 24). Examination of milk fat concentration over time for each herd and statistical comparisons of CON to SOM cows during each of the six 1 4 d injection periods indicated that milk fat concentration of bST-injected cows exceeded that of CON cows during only the first 2 to 4 injection periods. Any differences during the latter portion of the treatment period were not significant (P > .lo). The average for all herds in Figure 3 indicates that fat test for bSTinjected cows was noticeably above that of CON cows only during the first 7 wk of the

955

SOMATOTROPIN IN FARM HERDS

12-wk treatment period. A similar response was reported previously (22). The average increase in milk fat concentration was transient and probably related to energy balance. During pretreatment, milk protein concentration was similar for CON cows and those to receive bST for all 15 herds, both parities, and the three DIM stages (Table 7). However, during the treatment period, milk protein concentration was less for SOM than for CON cows (3.14 vs. 3.21%. P < .O001). Milk protein content for SOM cows was at least .05 percentage units less than that for CON cows in 10 of the 15 herds (P < .05 to P < .001). For each parity or parity-DIM subset, the CON cows had the greatest milk protein con-

centration (P < .01 to P < .OOl). Previous reports have indicated that changes in milk protein content due to bST were nil (3, 6, 12, 20,24), increased (1,4,22), or decreased (7, 10 18). Average milk protein concentration during the 16-wk trial shown in Figure 3 indicates that bST-injected cows had noticeably lower milk protein content than CON cows only during the first 7 wk of bST injections. This transient decrease was noted in graphs of most of the individual herds and statistical comparisons of the 2-wk subperiods during bST injections. The transient decrease in milk protein concentration contrasts with the transient increase in milk fat. In this study, milk protein concentration usually was greater for cows in parity group 2 than

TABLE 6. Milk fat concentration for control (CON) or bST (somehibve)-injected cows (SOW in 15 herds during pretreatment, treatment, and posttreatment periods (least squares means). Prerreatment Herd no.

CON

SOM

1 2 3 4 5 6 7 8 9 10 11 12 13 14

3.80 3.66 3.84 3.41 3.87 3.69 3.82 3.01 3.63 3.73 3.32 3.37 3.99 3.76 3.31 3.61 .03 3.58 3.65 356 3.67 3.61 3.56 3.64 3.54 3.56 3.70 3.68

3.69 3.68 3.83 3.33 3.92 3.85 3.64 3.34** 3.58 3.75 3.29 3.51 4.24 3.77 3.7w 3.68t .03 3.64 3.71 3.65 3.64 3.74* 3.64 3.57 3.72 3.65 3.71 3.76

15

Avg.

SE Parity 12 Parity 22 DIM l3 DIM Z3 DIM 33 Parity I-DIM 1 Parity 1-DIM 2 Parity 1-DIM 3 Parity 2-DIM 1 Paritv 2-DIM 2 Pari6 2-DlM 3

Difference -.11 .02 -.01

-.os .W .16 -.18 .34 -.05

.02 -.03 .14 .26 .01 .39 .06

... .06

.06 .08

-.03 .13 .08

-.w

.I8 .09 .01 .Os

Treatment

Posttreatment

Difference

CON

SOM

3.60 3.48 3.69 3.47 3.67 3.70 3.44 3.19 3.27 3.77 3.34 3.33 4.36 3.67 3.80 3.59 .02 3.57 3.61 3.52 3.61 3.63 3.52 3.57 3.60 353 3.64 3.66

.01 3.61 3.58 .10 3.82.~~ .13 3.61* .14 0 3.67 3.67 -.03 3.49 .06 3.36, .17 3.49** .22 .ll 3.88t 3.37 .03 3.49* .I6 0 4.36 3.82t .I5 3.86 .06 3.67*** .09

.M 3.66** 3.68+** 3.59t 3.69** 3.74** 3.60 3.66t 3.72* 3.57 3.73* 3.75*

...

.10 .08 .06 .09 .ll .08 .08 .I3 .05

.09 .09

CON

SOM

3.42 3.43 3.73 3.44 3.68 3.68 3.38 3.49 3.39 3.76 3.35 3.52 4.58

3.31 3.38 3.71 3.43 3.49. 3.54 3.27 3.51 3.34 3.79 3.197 3.327 4.29*

..

.

4.18 3.64 .02 3.65y 3.64 3.53 3.64 3.76 3.57 3.59 3.79 3.50 3.69 3.73

%gniticance for CON VS.SOM on same line: t~ < -10,*P < .M; **P < .01; ***P < .OOOI;YP column for that subset, Le., parity, DIM, or their interaction. 2Parity 1 = first lactation; Parity 2 = second through eighth lactation

...

3.94 3.54*** .02 3.48*** 3.59 3.41* 3.57 3.63* 3.34* 3.53 3.57* 3.48 3.61 3.69

Difference -.11 -.05

-.02 -.01 -.I9 -.14 -.lo .02 -.05

.03 -.I6 -20 -29

...

-.23 -.I1

...

-.17 -.05

-.I2 -.07 -.13 -.22

-.M -.22 -.02 -.08

-.W < .OS for values in that

3DIM 1 = 57 to 100 DIM; DIM 2 = 101 to 140 DIM; DIM 3 = 141 to 189 DIM. Journal of Dairy Science Vol. 74, No. 3, 1991

THOMAS ET AL. 3 6-

Body C o n d i t i o n S c o r e

3.0-

2.6-

3 6-

Milk Protein

(Z)

3.0

2.64.0-

M i l k Fot

(Z)

3.5-

3.0'

I

1


.lo). Yields of milk fat and proteins were greater for SOM than CON cows for every herd, parity, and DIM during the bST-injection period (P < .05 to P < .OO01, data not shown). The treatment averages for fat were .96 f .007 kg f d d per cow for CON cows compared with 1.17 f .007 for bST-injected cows (P < .OOOl). Corresponding averages for protein were .86 f .005 compared with 1.00 f .005 kg protein/d per cow (P c .OOOl), respectively. The use of bST consistently increased the yield of milk fat and milk protein even though its effect on concentration was variable because amount of milk was consistently increased. During posttreatment, yield of fat tended to be greater (P c .lo) by the SOM cows (.05 kgld per cow). Milk protein yield was greater (.08kg/d per cow, P c .OO01).

957

SOMATOTROPIN IN FARM HERDS

TABLE 7. Milk p t e b concentration for control (CON)or bST (sometribove)-injected cows (SOW in 15 herds during pretreatment, Ireatmest, and posttreahment periods (least squares means). Treatment

Pretreatment Herd no.

1 2 3 4 5

6 7 8 9 10 11 12 13 14 15 Avg.

SE Parity 12 Parity 22 DIM 13 DIM z3 DIM 33 Parity 1-DIM 1 Parity 1-DIM 2 Parity 1-DIM 3 Parity 2-DIM 1 Parity 2DIM 2 Parity 2-DIM 3

CON

SOM

3.24 3.16 3.39 3.18 3.18 3.20 3.07 3.32 3.00 3.15 2.99 2.98 3.22 2.83 3.22 3.14 .01 3.14 3.14 3.w 3.15 3.23 3.07 3.15 320 3.01y 3.15 3.26

3.17 3.19 3.38 3.17 3.25 3.24 3.02 3.33 3.08 3.20 2.98 2.87t 3.23 2.86 3.21 3.15 .01 3.14 3.15 3.w 3.16 323 3.06 3.15 3.20 3.03Y 3.17 3.27

Differewe

-.07 .03 -.01 -.01 .07 .OS

-.os

.01 .08 .07 -.01 -.lo .01 .03 -.01 .01

... 0 .01 .01 .01 0

-.01 0 -.01 .02

.Cn 0

CON

SOM

3.14 3.17 3.31 3.15 3.24 324 3.14 325 3.14 321 3.06 3.99 3.37 3.26 3.42 3.21

3.10tl' 3.16 3.24** 3.08* 3.w 3.16** 3.03*** 3.28 3.OS* 3.12*** 3.02t 3.98 3.21*** 3.14** 3.34, 3.14***

32@' 322 3.19 3.22 3.27 3.14 3.22 323 3.12y 322 3.31

3.13***Y 3.15*** 3.07***Y 3.16*** 3.20"** 3.08** 3.16*** 3.17** 3.07**y 3.16*** 3.23***

.m

.005

Difference

-.W -.01

-.W -.a7

-.os -.08 -.11 .03

-.06 -.09 -.04 -.01 -.16 -.12 -.07 -.07

...

-.06 -.06 -.06

-.06 -.07 -.07 -.06

-.06 -.04

-.06

-.07

Posttreatment DifferCON SOM ence 3.19 320 3.30 3.11 3.21 3.21 3.17 3.29 3.25 3.22 3.11 3.19 3.51

3.23 .04 3.29* .09 3.38* .08 3.18 .06 3.22 .01 3.22 .01 3.16 0 3.41** .13 3.26 0 3.35*** .13 .05 3.15 3.23 .04 3.58 .08

3.50 3.25 .01 3.23y 327 3.18y 326 3.30 3.18 3.24 3.26 3.17y 3.29 3.35

;.bit

...

3.31*** .01 328**Y 3.33*** 321b 3.32** 3.39*** 3.21 3.W 3.34* 3.22*y 3.33t 3.44***

... .ll

.06

... .06 .06

.04 .OS

.OS .03 .06 .OS

.05

.W .08

'Significance of CON vs. SOM on same line for that period: t P < .1& *P < .05; **P < .01; ***P < .OOOl; YP < .OS for in that column for that subset of parity, DIM, or their intmctioa 2~arity1 = first lactation; parity 2 = second throug~~ e i m lactation. k I M 1 = 57 to 100 DIM; DIM 2 = 101 to 140 D W DIM 3 = 141 to 189 DIM.

values

Mastitis The SCC were similar (P > .l) for CON and SOM cows during each of the three periods except for herd 2 during pretreatment and posttreatment (Table 8). Statistical probabilities of results were similar when expressed as observed numbers or when transposed to the natural lag basis. Multiparous cows had a greater SCC than primiparous cows during all three periods (273 vs. 203 x Id/&). No consistent trends were noted for DIM groups. These results, showing variable influence (or none) of bST on SCC among herds, agree with reports of others (1, 17). The number of cows that received a mammary infusion of an antibiotic for clinical

mastitis and the number of days of treatment were similar €or both p u p s during pretreatment (chi-square test, P = .69). During 12 wk of bST injections, 28 CON cows (6.4%) and 41 SOM cows (9.4%)were infused with antibiotic for mastitis (Table 9, chi-square test, P = .097). During posmatment, the respective numbers were 4 vs. 13 (chi-square test, P = .03). A method that more accurately reflects economic value of milk loss is to compare incidence of clinical mastitis calculated as the number of cow-days of treatment divided by the number of cow-days in the period. During treatment, SOM cows were treated on .36% of the cow-days compared with .16% for CON cows (chi-square test, P = .027). During posttreatJournal of Dairy Science Vol. 74, No. 3, 1991

958

THOMAS ET AL.

TABLE 8. Somatic cell count for control (CON) and bST (sometribove)-hjected cows (SOW h 15 herds during prelreatment, treatment, and posttreatment periods (least squares means). Pretreatment

Treatment

Posmeatment

Herd no.

CON

SOM

CON

SOM

CON

SOM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

130 95 140 98 145 473 139 113 140 204 123 399 576 463 188 228 24

164 275+*l 79 89 115 320 159 53 171 188 186 231 694 126** 393 216 24

190 166 73 60 133 318 224 207 139 320 119 213 655 285 301 227 13

297 223 66 105 128 315 289 123 135 261 224 231 624 168 397 239 14

191 242 60 60 184 567 263 174 156 314

266

Avg.

SE

305 645

337 18 87 261 362 542" 84 193 388 206 396 624

413 262 22

317 292 23

%

...

...

lsignificance of CON vs. SOM: tp < .IO;*P < .OS; **P < .01.

TABLE 9.Number of cows given antibiotic infusions for mastitis and d a y s antibiotic administered in the 15 herds during the treatment period for control (CON) and bST (sometib0ve)-injected cows (SOM). ~

~

Infusions during treatment period CON

No. of cows

on trial Herd no. 1

2 3 4 5 6 7 8 9 10 11 12 13 14 15 Total Avg.

CON

SOM

37 37 34 30 39 25 25 25 27 37 35 24 18 24 17 434

39 38 38 30 40 25 24 25 26 38 35 25 19 20 15 437

...

...

SOM

Percent- PercentNo. of cows1

1 0 3 0 4 5

1 2 1 2 0 5 0 1 3 28

...

age of cow-d4

No. of cows'

2.7 0 8.8 0 10.3 20.0 4.0 8.0 3.7 5.o 0 21.0 0 4.0 18.0

;10 0 .11 0 .31 .90 .14 .10 .13

5 0 1 0 10 3 2 2 1 3 3

...

...

6.4

.16

No.

age

3

of cow2

3.0 0 1 .o 0 25 32 3.0 1 .o 3.0 1.5 0 1 .o 0 4.0 1.3 24.5 2.2

.10

0 .25 0 20 23

4 1 2 4 41

...

No.

5.0 0 4.0 0 3.5 3.0 3.5 4.0 1.o

1.7 2.0 1.3 1 .o 3.5 5.3 38.8 2.98

Percent- Percentage age of

13.0 0 2.6 0 25.0 12.0 8.O 8.O 3.8 8.O 9.0 16.0 5.o 10.0 27.0

.70 0 .13 0 1.04 .5 1

.35 .38 .os .16 20 20 .06 .42 1.68

...

...

9.4

.36

'Number of cows that were given mammary infusions of antibiotics duriog that period. 2Avemge number of days that a treated cow was given antibiotic for mastitis. 3Percentagt of cows in a p u p (CON or SOW that received antibiotic infusions for mastitis during that period. h n t a g e of total cow-days (number of cows in a group x number of days in that period) that cows were given antibiotic infusions (cow-days infused divided by total cow-days x 100). Journal of Dairy Science Vol. 74, No. 3, 1991

959

SOMATOTROPIN IN FARM HERDS

TABLE 10. Initial,f d ,and change in body condition scores of control (CON) or W T (sometribove)-injectedcows in 15 herds (least squares means).

Initial Herd no.

1 2 3 4 5

6 7 8 9 10 11 12 13 14 15 Avg.

BE Parity 12 Parity 22 DIM l3 DIM 23 DIM 33 Parity 1-DIM 1 Parity 1-DIM 2 Parity 1-DIM 3 Parity 2-DIM 1 Parity 2-DIM 2 Pari& 2-DIM 3

CON

SOM

CON

2.67 2.68 2.47 2.26 2.28 2.26 2.92 2.90 2.93 3.35 3.30 3.01 2.94 3.10 3.11 2.8 1 .02 2.82 2.80 2.731 2.8 1 2.90 2.76 2.86 2.85 2.70 2.76 2.94

2.64 2.74 2.48 2.32 2.31 2.13 2.91 2.91 2.55 3.38 3.32 3.00 2.95 3.09 3.12 2.82 .02 2.80 2.84 2.77 2.81 2.87 2.76 2.79 2.86 2.79 2.83 2.89

259 3.12 2.67 2.57 2.61 2.58 2.93 2.88 2.99 3.08 2.96 3.05 2.92 3.07 321 2.88 .01 2.86 2.90 2.84 2.87 2.95 2.86 2.87 2.86 2.81 2.86 3.03

'Sipticme for CON vs. SOM t~ < .I@ *P < .05; **P < .OI;***P

Final SOM

2.48**1 2.89*** 2.62 2.56 256 2.43* 2.86 2.85 2.88t 2.997 2.87t 2.93t 2.84t 3.22t 3.01** 2.80*** .01 2.77***y 2.83*** 2.76** 2.80*** 2.84*** 2.767 2.76. 2.79 2.75? 2.85 2.90***

CON -.09

.44 .2 1 .31 .33 .32 .02

-.m

.M -.27 -.33 .04

-.m -.m .10 .07 .01

.w

change SOM -.16 .IS*** .I4 23 .25 .30 -.05 -.06 -.07 -.39* -.45t -.07 -.11 .13 -.11**

-.m*** .01 -.03*

.IO

- m***

.ll

- m***

.06 .05 .IO .01 .01 .ll .ll .09

-.01* -.03* .Do

-.m -.07

- w*** .01* .01*

.0001;YPe . ~ for f values in tbat c o ~ m of

that subset.

2Pdty 1 = fist lactation; Parity 2 = second to eighth lactation. 3DIM 1 = 57 to 100 D W DIM 2 = 101 to 140 DIM and DIM 3 = 141 to 189 DIM.

ment, this value for SOM cows was .43% compared with .13% for the CON cows (chisquare test, P = .038). The percentage of cows treated for mastitis increased in the bST-injected cows during the treatment and posttreatment periods compared with CON cows or compared with SOM cows during pretreatment. In six herds, there was either no change or a decrease in the incidence of mastitis for SOM cows compared with CON cows, whereas in seven herds the mastitis incidence was greatest for the bST-injected cows. Two herds had a questionable increase for bST-injected cows. The numbers of somatic cells in milk are considered a guide to mastitis incidence; however, there were no differences in SCC between the two treatment groups. These SCC data do not

support the differences in use of therapy for mastitis in this trial. Other reports have noted no change in the incidence of mastitis due to bST administration (6, 9, 16). Increased incidence of observed mastitis among bST-injected cows on a few of the farms may be attributable to factors associated with increased milk yield, environment, or management factors and not to direct effects of bST on mammary gland health (11, 21). Body Condition Score

Body condition scores were similar for CON and SOM cows when injections were initiated, but after six M T injections the average BCS was less (P e .001) for SOM cows (2.80 vs. Journal of Dairy Science Vol. 74, No. 3, 1991

THOMAS ET AL.

960

>oooooooooooo++oooooooooo+oooooo

~ m m ~ ~ ~ 0 + ~ 0 0 0 0 N0" w w w n * 0 o o o o o o o o o o o c

cI

eo:

U

E!

3 'u

8

X

Journal of Dairy Science Vol. 74, No. 3, 1991

SOMATOTROPIN IN PARM HERDS

-

balance, which is sometimes temporarily negative after initiation of bST treatment (4,18,24). In none of the 15 herds did BCS decrease to the extent reported by others (5,20,24). Evidently cows in the herds of the 15 dairy producers had sufficient feed available and the desire to consume feed such that BCS did not decrease as it had in university herds given bST (1, 5, 18, 20, 23). Good feed management likely will prevent the large decrease in BCS that has been noted previously.

2ol . 15

10-

Y Is,

m

F 6

5-

01

(0

c

.-0

I

-5-10-

8

2

-15-

6

-20

961

-30 -35

I

40

I

80

EO

100

120

140

180

180

200

Rations Fed

Days in Milk

Cows in these 15 herds were fed a large variety of ingredients in their rations typical of their geographic area. Ration ingredients and their proportions are shown in Table 11. Twelve herds had more than one production group of cows (Table 1). Most ingredients were fed as a TMR, but in 8 herds some hay was fed separately. Three herds had a feeder to dispense a concentrate mix to specified cows. 2.88,Table 10). However, in only 4 of the 15 The nutrient concentrations of the rations fed herds (1, 2, 6, and 15) was the final BCS to the groups of cows in the 15 herds are significantly less for the SOM than for the presented in Table 12. The TMR varied from CON cows. During treatment, CON cows had 40 to 69% DM, 15 to 21% CP, 1.50 to 1.68 an average increase in BCS of .07 units, Mcal NE& DM, 15 to 30% ADF, .45 to whereas SOM cows decreased by .02units (P < 1.19% Ca, and .31 to .56% P.Range in nutrient .001). In only three herds (two decreased, one concentrations was larger than expected or increased) was this change significant. The desirable. Some of the nutrient concentrations ability to detect a change in BCS of .1 by any diverged from generally recommended concendairy producer is doubtful. trations (14)for the cow groups being fed the For initial, final, and change in BCS by far mixed rations. For instance, the herd with the the largest source of variance in the ANOVA largest response (10) was fed rations with less was herd (Table 3) even though treatment sig- DM and Ca and with more ADF and P than nificance was P < .OOO1 for final BCS and BCS usually recommended. Good responses were change. As DIM increased, initial and final noted in other herds that had nutrient concenBCS increased (P c .OOOl). This trend was trations differing from general recommendagreater for cows in parity group 2 than in parity tions (Le., herd 5 with 15% ADn. Feed consumption was not measured in these herds and P U P 1. Previous reports have indicated that BCS may be more related to response and general temporarily decreased after bST administration. milk production than are ration ingredients .or After 84 (24), 120 (4),or 35 d (20), BCS of composition. cows given bST or bovine growth hormone decreased about .4. At the end of 252 d of Varlables Related to Response treatment, BCS, BW, but not estimated body fat content, were similar to that of control The herd term contributed the greatest animals (23). In the present trial, after 12 wk of amount of variance for milk yield during somebST injections, BCS had decreased by less than tribove injections or the change in FCM from .l.This is much less than reported by others for pretreatment to treatment (Table 4). a similar time period (1, 4, 20, 24). Body Increase in FCM (FCM during treatment condition scores have been related to energy period minus FCM during pretreatment period)

Figure 4. Relationship between days in milk (DIM)and change in daily milk from the. 2-wk pretreatment period to the 12-wk treatment period for control (dashed line, o p circle) and bST (sommive)-injected (solid line) cows in 15 herds. Regression equations were y = -1.32 - .016x + .M1005x2,R2 = .004 for control cows; and y = -6.80 + .15x - .0006x2 for sometribove cows. R2 = .05.

Journal of Dairy Science Vol. 74, No. 3, 1991

962

THOMAS ET

Journal of Dairy Science Vol. 74, No. 3, 1991

a.

963

soMAToTRopIN IN FARM HERDS

after bST injections was .0003 kg/d for each lo00 kg increase in rolling herd average. The regression equation was y = 2.67 + .0003x;r2 = .04,and SE of estimate = 3.08 (y = increase in FCM, kg/d and x = rolling herd average). Slope was not significantly different from zero with this data set on a between-herd basis. Rolling herd average is a measure of productive ability of that herd, plus all other management and environmental factors, and was only slightly related to response to bST. The trend was similar when individual cow response was regressed on rolling herd average. The SCC during pretreatment period exhibited a small, negative correlation with change in FCM for SOM cows. The regression equation was y = 5.417 - .515x; 1;! = .02;SE of estimate = 3.63 (y = change in FCM, kg/d and x = natural log of SCC). The slope of this line was significantly different from zero (P < .003). There was no evidence of a relationship between pretreatment SCC and change in FCM for CON cows. The relationship between change in FCM (as defined above) and DIM was curvilinear and convex for bST-injected cows but virtually linear for CON cows (Figure 4). The FCM response was maximum at 125 d for SOM cows but minimum at about 170 d for CON cows, with the greatest difference between the two groups at 100 to 140 DIM. The relationship between response and DIM has not previously been measured. The large variation for change in FCM among all cows is readily observed in Figure 4. The five herds milked three times per day had an average increase in FCM of 5.7 kg, whereas the 10 herds milked twice per day increased 5.0 kg. Their respective rolling herd averages were 9132 and 8046 kg milk/yr per COW.

Stepwise regression techniques were used to develop a multiple regression equation predicting change in FCM for both CON and SOM cows. The independent variables examined were pretreatment FCM yield (XI); pretreatment SCC (X2 = natural log of SCC); initial BCS (X3); parity (1 for primi arous and 0 for multiparous); DIM and D . The resulting equation for controls was y = 14.5 - .26X1 1.57X3 + 1.66 parity - .067 DIM + .o0018 DIh.12, R2 = .43. The respective standard partial correlation coefficients were -.41, -.16, .23, -.11, and .08. For the bST-injected cows, the

ap

equation was y = 7.13 - 25x1 - .54X2 + .lo DIM - .00042 DIM2 with R2 = .33, and respective standard partial correlation coefficients -.41, -.17, .15, and -.15. For controls, the regression coefficients all were significant1 different from zero (P< .OS) except for D For bST-injected cows, all coefficients were significantly different from zero (P < .01). In both groups, pretreatment yield was the most important variable accounting for 17% of the variation; and there was no significant difference between the slopes. For each of the other variables, however, comparison of the two equations indicates differences in their relationship to change in FCM. For SCC, parity, and BCS, a significant effect was observed in the equation for one group but not for the other. For DIM and D M , a statistically significant difference (P < .001) was noted between their coefficients for the CON and SOM equations. For the prospective user of bST, these findings suggest that a more satisfactory response will be associated with cows with low SCC, for cows initially injected 100 to 140 d postpartum, cows beyond their first lactation, and cows with good BCS. Further research and data are needed, however, to confirm and to quantify accurately these and other relationships. The 437 cows in 15 US herds given bST in a prolonged-release formulation at six biweekly intervals had an average increase of 5.3 kg F W d with large individual and herd variations. The response was similar at pretreatment yields from 17 to 50 kgjd per cow. Increase in yield was maximum at 125 d postpartum and somewhat greater for multiparous than primiparous cows. Any changes in milk composition or body condition were nil or small. Relationships between response and previous yield, SCC, DIM, herd, body condition, and parity were significant but explained only a small portion of the variation noted.

nJ

REFERENCES 1 Aguilar, A. A., D. C. Jordan. J. D. Olson, C. Bailey, and G. Hartnell. 1988. A short-term study evaluating the galactopoietic effects of the administration of somatotropin in high producing dairy cows milked three. times per day. J. Dairy Sci. 71(Suppl. 1):208.(Abstr.)

2 Asimov. G. J., and N. K. Krouze. 1937. The lactogenic preparations from the anterior pituitary and the increase of milk yield in cows. J. Dairy Sci. 20289. 3Bauman, D. E., P. J. Eppard, M. J. DeGeeter, and G. M. Lanza. 1985. Responses of high producing dairy cows to long-term treatment with pituitary somatotroJournal of Dairy Science Vol. 74, No. 3, 1991

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pin or recombinant somatotropin. 1. Dairy Sci. 68: 1352. 4 B a a m a n , D . E . , D . L . H a r d , B . A . Crooker, M S. wrtridge, K. Garrick, L. D. S a d e s , H.N. Erb, S. E. FrandSon.G. F.Hartnell, and R. L.Hbk. 1989. Longterm evaluation of a prolonged-release formulation of n-methionyl bovine somatotropin in lactating dairy cows. J. Dairy Sci. 72642. SBauman, D. E.. and S. N. Mcclltcheon. 1985. The effects of growth bomrone and prolactin on metabolism. Page 436 in Roc. 6th Int. Symp. Ruminant Physiol.: control of digestion and metabolism in nlminants. L. P. Milligan, W. L. Growm, and A. Dobson, ed. Reston Publ. Co., Inc., Rcston, VA. 6Cbalupa, W.,A. Kutches, D. Swager, T. Lehenbauer, B. Vecchiarelli, R. Shaver, and E. Robb. 1988. Respom of cows in a commercial dairy to somatofm pin. J. Dairy Sci. 7l(Suppl. 1):210.(Abstr.) J. Dairy Sci. 72(Suppl. 1):327.(Abstr.) 7Davis. S. R, R. J. Collier, J. P. McNamara, H. H. Head, and W.Sussman. 1988. Effects of thyroxine and growth hormone treatment of dairy cows on milk yield, cardiac output, and mammary blood flow.J. Anim. Sci. 66:70. 8 Emery, R. S. 1988. Milk fat depression and the M u ence of diet on milk composition. in Metabolic diseases of ruminant livestock Vet. Clin. North Am.Food Anim. Pract. 4289. 9Eppard, P. J., D. E. Bauman, C. P. Curtis. and H.N. Erb. 1987. Effect of 188-day treatment with somatotropin on health and reproductive paformawe of lactating dairy cows. J. Dairy Sci. 70582. lOEppard, P. J., D. E. Baaman, and S. N. Mccutcheon. 1985. Effect of dose of bovine growth hormone on lactation of dairy cows. J. Dairy S u . 68:llW. 11 Heyneman, R, C. Bweaich, M. Van Hoegaerden, and G. b t m . 1989. Influence of recombinant mtbionyl bovine somatotropin (rbST) on blood nentrophil respiratory bunst activity in healthy cows. J. Dairy Sci. 72(Suppl. 1):349.(Alwtr.) 12 H u ~ J., T.,S. Willman. K. Marrnu, and C. B. Thwer. 1988. Effect of IK)I11ctcibovc (SB),USAN (recombinant metbionyl bovine somatotropin) injected in lactating cows at 144 i n t w a l s on milk yields, milk composition, and health. J. Dairy Sci. 71(Suppl. 1): 2@7.(Abstr.)

13 Machlin, L.J. 1973. Effect of growth hormone on milk

J o d of Dairy Science VoL 74, No. 3. 1991

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production and feed utilization in dairy cows. J. Dairy Sci. 56575. 14Natiod Research Council. 1978. Nutrient requiremeats of cattle. 6th rev. d. Natl. Acad. Sci., Washington, Dc. lSPatton, R A., H.F. Bucholtz, M.K. Schmidt, and F. M.Hall. 1988. Body condition scoring-a management tool. Dep. Anim. Sci., Michigan State Univ., East Lansing. 16 Ped. C. J., and D. E. Baumaa 1987. Somatotropinand lactation. J. Dairy Sci. 70474. 17C. J., P. J. Eppard, and D. L. Hard. 1989. Evaluation of Sometribove (methionyl bovine somatropin) in toxicology and clinical trials in Europe and the United States. Page 107 in Biotechnology in growth regulation. R B. Heap.C. G. Prosser, and G. E. Lamming,ed. Buttem&. London, Engl. 18Ped, C. J., T. J. Pronk, D. E. Baaman, and R. C. Gorewit. 1983. Effect of exogenous growth hormone in early and late lactational pedormance of dairy cows. J. Dairy Sci. 665'6. 19Peel. C. J., D. L. Hard, K. S. Madsen, and G. de Kerchove, 1989. Bovine somatotropin: mechanism of action and experimental results from different world amas. Page 9 in Monsanto Tech Symp., Syracuse, NY. Z O W , C. J., L. D. Sandles, K. J. Quelcb, and A. C. Herington. 1985. m e effects of long-term administration of bovine growth hormone on the lactaiional performance of identical-twin cows. Anim. Rod. 41:135. 21 Roets, E.,C. Bwenich, and G. Vandeputte-Van Messom, 1989. Influence of recombinant bovine somatotropin on wktalbumh in blood and milk of cattle with E. coli mastitis. J. Dairy Sci. 72(Suppl. 1): 16.(Abstr.) 22Samuels, W.A., D. L.Hard, R L.€Iink.P. K.Olson. W. J. Cole, a d G. F. Harlnell. 1988. Long term evaluation of sometribovc, U S A N (recombinant methionyl bovine somatotropin) treatment in a prolonged release system for lactating cows. I. Dairy Sci. l(Supp1. 1):209.(Abtr.) 23SAS User's Guide: Statistics. 1982. Version 5.18. SAS Inst., Inc., Cary, NC. 24 Soderholm, C. G., D. E. Otterby, J. G. Liun, P.R Ehle, J. E. Wheaton, W. P. Hansen, and R. J. Amexstad. 1988. Effects of recombinant bovine somatotropin on milk prodaction. body composition, and physiological parameters. J. Dairy Sci. 71:355.

Responses by lactating cows in commercial dairy herds to recombinant bovine somatotropin.

Cows (890) in 15 US herds were assigned randomly in equal numbers to control or bST injections (500 mg in a prolonged-release form every 14 d for 12 w...
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