GROWTIt AND FEED EFFICIENCY AND THEIR RELATIONSHIP T O P U B E R A L T R A I T S O F C H A R O L A I S B U L L S 1'2
The Pennsylvania State University 4, University Park 16802 Summary
.05) ejaculate fructose concentrations and lower ( P < .05) initial sperm motility, unTwenty-two purebred Charolais bulls were stained (live) sperm and post-thaw motility fed concentrate ad libitum from weaning than less rapid gaining bulls. through 550 days of age. Puberty, defined as Bulls which attained puberty at a relatively the age at which the first ejaculate containing a late age showed a higher rate of postyearling minimum of 50 X l 0 6 sperm with at least 10% growth during the 285-day test than bulls showing progressive motility was collected by which attained puberty at a very early age. The artificial vagina, was attained at a mean age of correlation (-.47, P < .05) between age at 41 + 1 weeks and a mean body weight of 396 -+ puberty and postyearling within bull ADG 13 kilograms. One bull was removed from decline which was responsible for this relationexperiment after 365 days of age because of ship accounted for only 22% of the variation in chronic bloat, three bulls lacked data for feed the rate of decrease in postyearling growth rate. consumption and six bulls had not attained 2 Ranges in postyearling ADG (.85 to 1.71 kg) years of age when the data were analyzed. and feed efficiency (7.94 to 12.20 kg) suggest Mean body weights of 356 -+ 10,520 -+ 11, that sufficient variation exists to warrant 744 +- 14 and 859 -+ 20 kg were recorded at performance testing for these traits. The 265, 365, 550 days and 2 years of age, concept of postyearling performance testing respectively. Average daily gain (ADG) and feed should be applicable especially to terminal cross efficiency during a 285-day test (265 to 550 beef sire selection programs. days of age) averaged 1.35 + .03 and 8.09 + .16 kilograms. Introduction Puberal weight per day of age was not significantly related to age at attainment o f Efforts to increase efficiency of beef puberty. Although based on a single puberal production have utilized various selection ejaculation, rapid gaining bulls had higher (P < criteria including growth rate and feed efficiency. In order to identify genetically superior ~Authorized for publication as Paper No. 4702 in the Journal Series of The Pennsylvania Agricultural sires for these traits as quickly as possible, beef Experiment Station, University Park, on May 21, progeny testing programs ideally should com1974. mence at puberty (Martig and Almquist, 1969). 2Stipported in part by Atlantic Breeders Coopera- Thus it is important to determine the tive, Lancaster, Pa., Northeastern Breeders Association and Sire Power, Inc., Tunkhannock, Pa., and the relationship between beef production traits and American-lnternational Charolais Association, Itous- puberal characteristics in beef bulls. ton, Texas. Age, body weight, body measurements and 3Appreciation is expressed to Dr. L. L. Wilson, Mr. seminal characteristics at attainment of puberty M. Holsopple, Mrs. A. Keene, Mrs. H. Homan and Mrs. in bulls vary greatly among and within breeds T. Shirk for their assistance. This paper is a portion of (Bellows et al., 1964; Wolf et al., 1965; the M.S. thesis of the senior author. Dairy Breeding Research Center, Department of Almquist and Barber, 1974). Except for reports Dairy Science. from this center on Angus and Hereford (Wolf 288 J O U R N A L O F A N I M A L S C I E N C E , vol. 4 0 , n o . 2, 1 9 7 5
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K. A. Barber and J. O. Almquist 3
289
PUBERAL TRAITS OF CHAROLAIS BULLS
Experimental Procedure Growth and feed efficiency were studied using data obtained from 22 purebred Charolais bulls. These bulls were unrelated, except that two sires were each represented by two sons. One bull was co-twin with a heifer. Nineteen bulls had been creep-fed. Calves were dehorned and treated for internal parasites prior to starting a gain test. The bulls were individually housed in either 3.0 • 4.3 m box stalls a_djoining 3.0 • 12.2 m exercise paddocks or 3.4 X 2.4 m box stalls and exercised Singly in an adjacent 11.3 X 12.2 m lot. A 285-day gain test (265 to 550 days of age) for 22 bulls was divided into gain periods of 100 days (265 to 365 days of age) and 185 days (365 to 550 days of age). Recorded weight values were determined by averaging three consecutive daily weighings centered on 265, 365 and 550 days of age. Postyearling changes in average daily gain and feed efficiency (kg feed/kg gain) were based on the difference between means for the preyearling (100-day) and postyearling (185-day) periods. Postyearling within-bull change in average daily gain and feed efficiency was calculated by the following method:
WithinbuU change
preyearling performance postyearling performance preyearling performance
The bulls were individually fed concentrate and mixed alfalfa-timothy, hay, s-c IRN 1-00-336 twice daily and a record of feed consumption was maintained throughout the gain test. The concentrate portion of the ration consisted of 48% corn, yel-
low, grain, rolled IRN 4-14-017; 28% oats, grain, rolled IRN 4-03-307; 15% wheat, bran IILN 4-11-741; 7% soybean, seeds, solv extd grnd, mx 7% fiber IRN 5-04-604;soybean meal, 1% limestone, grnd, mn 33% Ca, IRN 6-02-632; and 1% salt. Total protein and TDN content of feed samples collected during the experiment were estimated from proximate analyses and N.R.C. (1970) tabular data. On a dry matter basis the concentrate and hay contained, respectively, 15.8 and 10.5% crude protein and 84.6 and 56.0% TDN. Before the gain test, concentrate was gradually increased and hay was supplied at the rate of .75 kg/lO0 kg body weight. During the test, concentrate was fed ad libitum, while hay was restricted to 1.8 to 3.2 kg per head daily. If a bull consumed less than approximately 1.0 kg of hay daily for a week, the amount of concentrate fed was reduced temporarily until hay consumption increased to at least 1.0 kg daily. This was done to minimize possible digestive disturbances brought on by excessive consumption of concentrate. After the gain test was completed, hay was increased to 1.0 kg/100 kg body weight and concentrate was reduced to provide nutrients for growth and maintenance (N.R.C., 1970). Bulls were individually weighed at 7-day intervals. Body measurements consisting of body length, width and depth (Wilson et al., 1971), as well as heart girth circumference and height at withers, were recorded at 28-day intervals beginning at 24 weeks of age. Body volume (length x width x depth) was calculated. These body measurements also were recorded at 2 6 5 , 3 6 5 , 5 5 0 days and 2 years of age. Recorded values for these measurements were means for two technicians working independently. In situ measurements of the greatest circumference and width of the testes-scrotum at 1 and 2 years of age were means of measurements obtained by three technicians. Puberal traits for these bulls were reported by Almquist and Barber (1974) except that data were excluded from the present study for the two bulls with bilateral testicular hypoplasia. Puberty was defined as the age at which the first ejaculate containing a minimum of 50 x 106 sperm with at least 10% showing progressive motility was collected by artificial vagina. At attainment of puberty and based on
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et al., 1965) and Charolais bulls (Almquist and Barber, 1974) that there was no significant correlation between age or body weight at puberty and preyearling average daily gain on test, there is scant information on the relationship between growth and puberty. This study was designed to determine body and skeletal growth rates and feed efficiency ratios for Charolais bulls and to establish the relationships of these characteristics to age, body weight, body measurements and seminal traits at attainment of puberty.
290
BARBER AND ALMQUIST TABLE 1. LEAST SQUARES MEANS (-+SE)FOR GROWTH TRAITS OF CHAROLAIS BULLS Item
Age
365 days N=22
550 days Nffi21
2 years N=15
356+ - 10
520-+ 11
744+ 14
859-+ 20
113+ - 1a 156-+ 2a 133-+ l b 39-+ .4b 55-+ .5 b 2 9 1 -+ 8 b
122-+ 1 179-+ 1 148-+ 1 b 46+- .4b 62-+ .5 b 417-+ 9 b
132-+ 1 204+ 2 164+ - 1 52 + .4 69+- .6 592+ - 11
138+- 1 214+ 2 173+- 2 57 + .6 72-+ .7 710 + 19
. .. ...
33.4-+ .5 11.8-+ .2
... ...
37.8-+ .7 13.4+ .3
aN = 21. bN = 19.
their puberal age and b o d y weight, the bulls were paired and randomly assigned to a weekly semen collection frequency o f either one or six ejaculates. Weekly semen collections were maintained until the bulls reached 2 years o f age. Least squares methods (Harvey, 1960), including ejaculation frequency in the model as a continuous independent variable, were used to calculate partial correlations among and between growth and puberal traits. Coefficients o f variation and regression coefficients (Snedecor and Cochran, 1967) were calculated. TABLE 2. LEAST SQUARES MEANS (-+sE) FOR AVERAGE DAILY GAIN, FEED EFFICIENCY AND POSTYEARLING CHANGES IN THESE TRAITS FOR CHAROLAIS BULLS Item
Average daily gain
285-day test, kg 1.35+.03 a Preyearling ( 100-day period), kg 1.63+.03 Postyearling (185-day period), kg 1.20+.04 Postyearling change, kg --.43+.04 Within bull change, % 26+2 aMean -+ SE for 21 bulls. bMean -+ SE for 18 bulls. ekg feed/kg'gain.
Feed efficiency c 8.09-+.16 b 6.13+.12 9.58+.25 +3.45+.20 56+_3
Results
Least squares means and standard errors for b o d y weights and measurements and testesscrotum measurements are listed in table 1. Means and standard errors for average daily gain and feed efficiency are presented in table 2 and for puberal traits in table 3. Coefficients o f variation (CV) for age-constant traits ranged from 9 to 14% for b o d y weights, 3 to 12% for body measurements and were 7% for all testes-scrotum measurements. Less variation was observed for average daffy gain and feed efficiency (10 and 8% CV) during the 285-day test than for postyearling changes in average daily gain and f e e d efficiency (42 and 25% CV). F o r age at puberty, the CV was 11%. Variation in puberal b o d y weight, b o d y measurements and testes-scrotum measurements was similar to that observed for age-constant traits. Characteristics of the puberal ejaculate, however, varied widely with CV ranging from 29 to 126%. Ejaculation frequency had no significant effect on b o d y weights or measurements, testes-scrotum measurements, average daffy gain or feed efficiency except for a solitary (P < .05) effect on b o d y width at 550 days o f age. Mean b o d y width was 51.6 cm for the low and 53.3 cm for the high ejaculation frequency group. One bull was removed from gain test at 489 days o f age because o f chronic bloat and data
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Body weight, kg Body measurements Wither height, cm Heart girth c i r c u m . , c m Length, cm Width, cm Depth, cm Volume, 104cm a Testes-scrotum Circum., cm Width, cm
265 days N=22
PUBERAL TRAITS OF CHAROLAIS BULLS
291
T A B L E 3. L E A S T S Q U A R E S M E A N S ( + S E ) F O R P U B E R A L T R A I T S O F C H A R O L A I S B U L L S (IN = 2 2 )
Item
Mean •
Age puberty attained, weeks a Physical traits at puberty B o d y measurements
41
396 1.37 116 163 135 40 57 311
-+ 13 + .04 +
1
-+ + + + +
2 1 9
28.8 + 10.3 +
Traits o f first ejaculate S e m e n volume, ml
2.7
Progressive motility, %
28
Sperm c o n c e n t r a t i o n , 1 0 6 / m l
.4 .1
-+
.3
• 3 -+ 33
122 222
•
Fructose, rag/100 mid
75 49 41 764
• 19 + 4 -+ 3 • 91
Post-thaw m o t i l i t y , %e
13
Total sperm, 10 v Total motile sperm, 106 Live sperm, %c A b n o r m a l sperm, %c
aFirst ejaculate containing a minimum motility. b N = 19. CN = 20. dN = 21. e A t t e r storage for 3 w e e k s a t - - 1 9 6 C.
.5 .6
•
42
3
o f 5 0 X 1 0 ~ t o t a l s p e r m w i t h a t l e a s t 1 0 % showing progressive
obtained after 365 days of age were excluded from analyses. Three bulls lacked feed consumption data and six bulls had not attained 2 years of age when these data were analyzed. Relationships Among Growth Traits. Correlations among and between body weights and measurements (range zero to .99) were generally high and significant through 550 days of age. However, 265- and 365-day weights and measurements were less reliable than 550-day weight and measurements for predicting weight and body measurements at 2 years of age. Average daffy ga/n (ADG) was correlated (-.75, P < .01) with feed efficiency during the 285-day test. Preyearling and postyearling ADG were correlated with preyearling and postyearling feed efficiency (-.65 and -.81, P < .01). Although postyearling average daffy gain accounted for 92% of the total variation in 285-day ADG, the correlation between preyearling and postyearling gain was .49 (P < .05). There was a significant ( P < .01)
correlation of .62 between preyeading and postyearling feed efficiency. Body weights and the majority of body measurements recorded at 550 days and 2 years of age were significantly correlated with average daily gain but not with feed efficiency during the 285-day test. On the contrary, on-test body weights and measurements recorded at 265 days of age generally were correlated with feed efficiency but not average daily gain. Testes-scrotum measurements were not correlated significantly with body weights. However, 365-day testes-scrotum circumference and width were correlated .65 and .61 (P < .01), respectively, with 365-day body width, .49 and .45 (P < .05) with. 550-day width and -.064 and -.64 (P < .05) with 2-year body length. Correlations between 365-day and 2-year testes-scrotum measurements were .70 and .70 ( P < .01) for circumference and width, respectively. Relationships Among Puberal Traits. Cor-
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Weight, kg Weight per day o f age, kg Wither height, em Heart girth circum., cm Length, cm b Width, crab Depth, cmb Volume, 104cm 3b Testes-scrotum Circum., cm Width, em
-+ 1
292
BARBER AND ALMQUIST All body measurements at puberty were positively and significantly correlated with body weights at 265,365 and 550 days of age. At 2 years of age, only wither height and body depth at puberty retained this significant relationship with body weight. Volume of the puberal ejaculate was correlated .44 (P < .05), .67 and .66 (P < .01) with 550-day width and 2-year scrotal circumference and width, respectively. Fructose concentration in the puberal ejaculate was correlated .50 and .49 ( P < .05) with body weight at 265 and 365 days of age. Significant correlations between' fructose concentration and several of the body measurements at the above ages support these results. Body weight at 365 days of age was correlated (-.42 to -.50; P < .05) with quality traits of the puberal ejaculate consisting of initial progressive motility, live (unstained) sperm and post-thaw motility. Significant correlations were obtained between these quality traits and some of the body measurements recorded at 365 days of age. Similar relationships were observed at 265 days of age for initial progressive motility and post-thaw motility and at 550 days of age for live sperm and post-thaw motility. Testes-scrotum measurements at puberty were significantly correlated with 365-day heart girth circumference, body width and scrotal circumference. Other correlations between testes-scrotum measurements at puberty and growth and feed efficiency traits were not significant. Discussion
Economics of beef production might be improved by feeding rapid and efficient gaining cattle to heavier weights than are presently acceptable. Under such conditions it is not known if contravening reproductive phenomena such as late puberty and low fertility would be associated with selection for improved rate of gain and/or feed efficiency. Since puberty marks the initiation of capacity to participate in the reproductive process, relationships involving puberal characteristics and growth and feed efficiency were studied. Results of the present study with 22 Charolais bulls support the postulation that b,dls which attain puberty at an early age show
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relations involving puberal traits (table 4) suggested that age was significantly correlated with body weight and most individual body measurements but age was not significantly correlated (-.04) with weight per day of age (WPDA) at attainment of puberty. Differences in growth rate from birth to puberty expressed by WPDA were correlated ( P < .05) with fructose concentration (.47), initial percentage of progressively motile sperm (-.47) and percentage of live sperm (-.45) in the puberal ejaculate. Weight per day of age at puberty accounted for 52% of the variation in body weight at puberty while age at puberty accounted for an additional 45%. Neither body weight, age, individual body measurements nor testes-scrotum measurements at puberty were significantly correlated with any of the puberal ejaculate traits. Testes-scrotum circumference and width were significantly correlated with age and body weight at puberty and the majority of individual body measurements, but not WPDA. Relationships between Puberal and Growth Traits. Partial correlations between puberal and growth traits are presented in tables 5, 6 and 7. Correlations between age at puberty and body weights and between age at puberty and skeletal or testes-scrotum measurements were low and not significant. A negative effect of puberal age (-.47, P < .05) was observed on the within bull rate of postyearling decline in average daily gain during the 285-day test and is expressed by the linear regression equation Ye = 71.53 + (-1 .IO)X. This general relationship is illustrated in figure 1 by the test mean growth curves for the four youngest (33 to 37 weeks of age) and four oldest (44 to 53 weeks of age) bulls at attainment of puberty. There were significant (P < .01)correlations of .60, .61 and .67 between body weight at puberty and at 265,365 and 550 days of age, respectively, but not between body weight at puberty and 2-year weight. Weight per day of age at puberty was correlated ( P < .01) with body weight at 265, 365 and 550 days of age (.97, .96 and .78, respectively). Puberal WPDA also was correlated significantly with all body measurements at 265, 365 and 550 days of age. Correlations between WPDA at puberty and 2-year body weight and measurements were not significant.
PUBERAL TRAITS OF CHAROLAIS BULLS
293
0
I I
I
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[.-, .
The Pennsylvania State University 4, University Park 16802 Summary
.05) ejaculate fructose concentrations and lower ( P < .05) initial sperm motility, unTwenty-two purebred Charolais bulls were stained (live) sperm and post-thaw motility fed concentrate ad libitum from weaning than less rapid gaining bulls. through 550 days of age. Puberty, defined as Bulls which attained puberty at a relatively the age at which the first ejaculate containing a late age showed a higher rate of postyearling minimum of 50 X l 0 6 sperm with at least 10% growth during the 285-day test than bulls showing progressive motility was collected by which attained puberty at a very early age. The artificial vagina, was attained at a mean age of correlation (-.47, P < .05) between age at 41 + 1 weeks and a mean body weight of 396 -+ puberty and postyearling within bull ADG 13 kilograms. One bull was removed from decline which was responsible for this relationexperiment after 365 days of age because of ship accounted for only 22% of the variation in chronic bloat, three bulls lacked data for feed the rate of decrease in postyearling growth rate. consumption and six bulls had not attained 2 Ranges in postyearling ADG (.85 to 1.71 kg) years of age when the data were analyzed. and feed efficiency (7.94 to 12.20 kg) suggest Mean body weights of 356 -+ 10,520 -+ 11, that sufficient variation exists to warrant 744 +- 14 and 859 -+ 20 kg were recorded at performance testing for these traits. The 265, 365, 550 days and 2 years of age, concept of postyearling performance testing respectively. Average daily gain (ADG) and feed should be applicable especially to terminal cross efficiency during a 285-day test (265 to 550 beef sire selection programs. days of age) averaged 1.35 + .03 and 8.09 + .16 kilograms. Introduction Puberal weight per day of age was not significantly related to age at attainment o f Efforts to increase efficiency of beef puberty. Although based on a single puberal production have utilized various selection ejaculation, rapid gaining bulls had higher (P < criteria including growth rate and feed efficiency. In order to identify genetically superior ~Authorized for publication as Paper No. 4702 in the Journal Series of The Pennsylvania Agricultural sires for these traits as quickly as possible, beef Experiment Station, University Park, on May 21, progeny testing programs ideally should com1974. mence at puberty (Martig and Almquist, 1969). 2Stipported in part by Atlantic Breeders Coopera- Thus it is important to determine the tive, Lancaster, Pa., Northeastern Breeders Association and Sire Power, Inc., Tunkhannock, Pa., and the relationship between beef production traits and American-lnternational Charolais Association, Itous- puberal characteristics in beef bulls. ton, Texas. Age, body weight, body measurements and 3Appreciation is expressed to Dr. L. L. Wilson, Mr. seminal characteristics at attainment of puberty M. Holsopple, Mrs. A. Keene, Mrs. H. Homan and Mrs. in bulls vary greatly among and within breeds T. Shirk for their assistance. This paper is a portion of (Bellows et al., 1964; Wolf et al., 1965; the M.S. thesis of the senior author. Dairy Breeding Research Center, Department of Almquist and Barber, 1974). Except for reports Dairy Science. from this center on Angus and Hereford (Wolf 288 J O U R N A L O F A N I M A L S C I E N C E , vol. 4 0 , n o . 2, 1 9 7 5
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K. A. Barber and J. O. Almquist 3
289
PUBERAL TRAITS OF CHAROLAIS BULLS
Experimental Procedure Growth and feed efficiency were studied using data obtained from 22 purebred Charolais bulls. These bulls were unrelated, except that two sires were each represented by two sons. One bull was co-twin with a heifer. Nineteen bulls had been creep-fed. Calves were dehorned and treated for internal parasites prior to starting a gain test. The bulls were individually housed in either 3.0 • 4.3 m box stalls a_djoining 3.0 • 12.2 m exercise paddocks or 3.4 X 2.4 m box stalls and exercised Singly in an adjacent 11.3 X 12.2 m lot. A 285-day gain test (265 to 550 days of age) for 22 bulls was divided into gain periods of 100 days (265 to 365 days of age) and 185 days (365 to 550 days of age). Recorded weight values were determined by averaging three consecutive daily weighings centered on 265, 365 and 550 days of age. Postyearling changes in average daily gain and feed efficiency (kg feed/kg gain) were based on the difference between means for the preyearling (100-day) and postyearling (185-day) periods. Postyearling within-bull change in average daily gain and feed efficiency was calculated by the following method:
WithinbuU change
preyearling performance postyearling performance preyearling performance
The bulls were individually fed concentrate and mixed alfalfa-timothy, hay, s-c IRN 1-00-336 twice daily and a record of feed consumption was maintained throughout the gain test. The concentrate portion of the ration consisted of 48% corn, yel-
low, grain, rolled IRN 4-14-017; 28% oats, grain, rolled IRN 4-03-307; 15% wheat, bran IILN 4-11-741; 7% soybean, seeds, solv extd grnd, mx 7% fiber IRN 5-04-604;soybean meal, 1% limestone, grnd, mn 33% Ca, IRN 6-02-632; and 1% salt. Total protein and TDN content of feed samples collected during the experiment were estimated from proximate analyses and N.R.C. (1970) tabular data. On a dry matter basis the concentrate and hay contained, respectively, 15.8 and 10.5% crude protein and 84.6 and 56.0% TDN. Before the gain test, concentrate was gradually increased and hay was supplied at the rate of .75 kg/lO0 kg body weight. During the test, concentrate was fed ad libitum, while hay was restricted to 1.8 to 3.2 kg per head daily. If a bull consumed less than approximately 1.0 kg of hay daily for a week, the amount of concentrate fed was reduced temporarily until hay consumption increased to at least 1.0 kg daily. This was done to minimize possible digestive disturbances brought on by excessive consumption of concentrate. After the gain test was completed, hay was increased to 1.0 kg/100 kg body weight and concentrate was reduced to provide nutrients for growth and maintenance (N.R.C., 1970). Bulls were individually weighed at 7-day intervals. Body measurements consisting of body length, width and depth (Wilson et al., 1971), as well as heart girth circumference and height at withers, were recorded at 28-day intervals beginning at 24 weeks of age. Body volume (length x width x depth) was calculated. These body measurements also were recorded at 2 6 5 , 3 6 5 , 5 5 0 days and 2 years of age. Recorded values for these measurements were means for two technicians working independently. In situ measurements of the greatest circumference and width of the testes-scrotum at 1 and 2 years of age were means of measurements obtained by three technicians. Puberal traits for these bulls were reported by Almquist and Barber (1974) except that data were excluded from the present study for the two bulls with bilateral testicular hypoplasia. Puberty was defined as the age at which the first ejaculate containing a minimum of 50 x 106 sperm with at least 10% showing progressive motility was collected by artificial vagina. At attainment of puberty and based on
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et al., 1965) and Charolais bulls (Almquist and Barber, 1974) that there was no significant correlation between age or body weight at puberty and preyearling average daily gain on test, there is scant information on the relationship between growth and puberty. This study was designed to determine body and skeletal growth rates and feed efficiency ratios for Charolais bulls and to establish the relationships of these characteristics to age, body weight, body measurements and seminal traits at attainment of puberty.
290
BARBER AND ALMQUIST TABLE 1. LEAST SQUARES MEANS (-+SE)FOR GROWTH TRAITS OF CHAROLAIS BULLS Item
Age
365 days N=22
550 days Nffi21
2 years N=15
356+ - 10
520-+ 11
744+ 14
859-+ 20
113+ - 1a 156-+ 2a 133-+ l b 39-+ .4b 55-+ .5 b 2 9 1 -+ 8 b
122-+ 1 179-+ 1 148-+ 1 b 46+- .4b 62-+ .5 b 417-+ 9 b
132-+ 1 204+ 2 164+ - 1 52 + .4 69+- .6 592+ - 11
138+- 1 214+ 2 173+- 2 57 + .6 72-+ .7 710 + 19
. .. ...
33.4-+ .5 11.8-+ .2
... ...
37.8-+ .7 13.4+ .3
aN = 21. bN = 19.
their puberal age and b o d y weight, the bulls were paired and randomly assigned to a weekly semen collection frequency o f either one or six ejaculates. Weekly semen collections were maintained until the bulls reached 2 years o f age. Least squares methods (Harvey, 1960), including ejaculation frequency in the model as a continuous independent variable, were used to calculate partial correlations among and between growth and puberal traits. Coefficients o f variation and regression coefficients (Snedecor and Cochran, 1967) were calculated. TABLE 2. LEAST SQUARES MEANS (-+sE) FOR AVERAGE DAILY GAIN, FEED EFFICIENCY AND POSTYEARLING CHANGES IN THESE TRAITS FOR CHAROLAIS BULLS Item
Average daily gain
285-day test, kg 1.35+.03 a Preyearling ( 100-day period), kg 1.63+.03 Postyearling (185-day period), kg 1.20+.04 Postyearling change, kg --.43+.04 Within bull change, % 26+2 aMean -+ SE for 21 bulls. bMean -+ SE for 18 bulls. ekg feed/kg'gain.
Feed efficiency c 8.09-+.16 b 6.13+.12 9.58+.25 +3.45+.20 56+_3
Results
Least squares means and standard errors for b o d y weights and measurements and testesscrotum measurements are listed in table 1. Means and standard errors for average daily gain and feed efficiency are presented in table 2 and for puberal traits in table 3. Coefficients o f variation (CV) for age-constant traits ranged from 9 to 14% for b o d y weights, 3 to 12% for body measurements and were 7% for all testes-scrotum measurements. Less variation was observed for average daffy gain and feed efficiency (10 and 8% CV) during the 285-day test than for postyearling changes in average daily gain and f e e d efficiency (42 and 25% CV). F o r age at puberty, the CV was 11%. Variation in puberal b o d y weight, b o d y measurements and testes-scrotum measurements was similar to that observed for age-constant traits. Characteristics of the puberal ejaculate, however, varied widely with CV ranging from 29 to 126%. Ejaculation frequency had no significant effect on b o d y weights or measurements, testes-scrotum measurements, average daffy gain or feed efficiency except for a solitary (P < .05) effect on b o d y width at 550 days o f age. Mean b o d y width was 51.6 cm for the low and 53.3 cm for the high ejaculation frequency group. One bull was removed from gain test at 489 days o f age because o f chronic bloat and data
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Body weight, kg Body measurements Wither height, cm Heart girth c i r c u m . , c m Length, cm Width, cm Depth, cm Volume, 104cm a Testes-scrotum Circum., cm Width, cm
265 days N=22
PUBERAL TRAITS OF CHAROLAIS BULLS
291
T A B L E 3. L E A S T S Q U A R E S M E A N S ( + S E ) F O R P U B E R A L T R A I T S O F C H A R O L A I S B U L L S (IN = 2 2 )
Item
Mean •
Age puberty attained, weeks a Physical traits at puberty B o d y measurements
41
396 1.37 116 163 135 40 57 311
-+ 13 + .04 +
1
-+ + + + +
2 1 9
28.8 + 10.3 +
Traits o f first ejaculate S e m e n volume, ml
2.7
Progressive motility, %
28
Sperm c o n c e n t r a t i o n , 1 0 6 / m l
.4 .1
-+
.3
• 3 -+ 33
122 222
•
Fructose, rag/100 mid
75 49 41 764
• 19 + 4 -+ 3 • 91
Post-thaw m o t i l i t y , %e
13
Total sperm, 10 v Total motile sperm, 106 Live sperm, %c A b n o r m a l sperm, %c
aFirst ejaculate containing a minimum motility. b N = 19. CN = 20. dN = 21. e A t t e r storage for 3 w e e k s a t - - 1 9 6 C.
.5 .6
•
42
3
o f 5 0 X 1 0 ~ t o t a l s p e r m w i t h a t l e a s t 1 0 % showing progressive
obtained after 365 days of age were excluded from analyses. Three bulls lacked feed consumption data and six bulls had not attained 2 years of age when these data were analyzed. Relationships Among Growth Traits. Correlations among and between body weights and measurements (range zero to .99) were generally high and significant through 550 days of age. However, 265- and 365-day weights and measurements were less reliable than 550-day weight and measurements for predicting weight and body measurements at 2 years of age. Average daffy ga/n (ADG) was correlated (-.75, P < .01) with feed efficiency during the 285-day test. Preyearling and postyearling ADG were correlated with preyearling and postyearling feed efficiency (-.65 and -.81, P < .01). Although postyearling average daffy gain accounted for 92% of the total variation in 285-day ADG, the correlation between preyearling and postyearling gain was .49 (P < .05). There was a significant ( P < .01)
correlation of .62 between preyeading and postyearling feed efficiency. Body weights and the majority of body measurements recorded at 550 days and 2 years of age were significantly correlated with average daily gain but not with feed efficiency during the 285-day test. On the contrary, on-test body weights and measurements recorded at 265 days of age generally were correlated with feed efficiency but not average daily gain. Testes-scrotum measurements were not correlated significantly with body weights. However, 365-day testes-scrotum circumference and width were correlated .65 and .61 (P < .01), respectively, with 365-day body width, .49 and .45 (P < .05) with. 550-day width and -.064 and -.64 (P < .05) with 2-year body length. Correlations between 365-day and 2-year testes-scrotum measurements were .70 and .70 ( P < .01) for circumference and width, respectively. Relationships Among Puberal Traits. Cor-
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Weight, kg Weight per day o f age, kg Wither height, em Heart girth circum., cm Length, cm b Width, crab Depth, cmb Volume, 104cm 3b Testes-scrotum Circum., cm Width, em
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BARBER AND ALMQUIST All body measurements at puberty were positively and significantly correlated with body weights at 265,365 and 550 days of age. At 2 years of age, only wither height and body depth at puberty retained this significant relationship with body weight. Volume of the puberal ejaculate was correlated .44 (P < .05), .67 and .66 (P < .01) with 550-day width and 2-year scrotal circumference and width, respectively. Fructose concentration in the puberal ejaculate was correlated .50 and .49 ( P < .05) with body weight at 265 and 365 days of age. Significant correlations between' fructose concentration and several of the body measurements at the above ages support these results. Body weight at 365 days of age was correlated (-.42 to -.50; P < .05) with quality traits of the puberal ejaculate consisting of initial progressive motility, live (unstained) sperm and post-thaw motility. Significant correlations were obtained between these quality traits and some of the body measurements recorded at 365 days of age. Similar relationships were observed at 265 days of age for initial progressive motility and post-thaw motility and at 550 days of age for live sperm and post-thaw motility. Testes-scrotum measurements at puberty were significantly correlated with 365-day heart girth circumference, body width and scrotal circumference. Other correlations between testes-scrotum measurements at puberty and growth and feed efficiency traits were not significant. Discussion
Economics of beef production might be improved by feeding rapid and efficient gaining cattle to heavier weights than are presently acceptable. Under such conditions it is not known if contravening reproductive phenomena such as late puberty and low fertility would be associated with selection for improved rate of gain and/or feed efficiency. Since puberty marks the initiation of capacity to participate in the reproductive process, relationships involving puberal characteristics and growth and feed efficiency were studied. Results of the present study with 22 Charolais bulls support the postulation that b,dls which attain puberty at an early age show
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relations involving puberal traits (table 4) suggested that age was significantly correlated with body weight and most individual body measurements but age was not significantly correlated (-.04) with weight per day of age (WPDA) at attainment of puberty. Differences in growth rate from birth to puberty expressed by WPDA were correlated ( P < .05) with fructose concentration (.47), initial percentage of progressively motile sperm (-.47) and percentage of live sperm (-.45) in the puberal ejaculate. Weight per day of age at puberty accounted for 52% of the variation in body weight at puberty while age at puberty accounted for an additional 45%. Neither body weight, age, individual body measurements nor testes-scrotum measurements at puberty were significantly correlated with any of the puberal ejaculate traits. Testes-scrotum circumference and width were significantly correlated with age and body weight at puberty and the majority of individual body measurements, but not WPDA. Relationships between Puberal and Growth Traits. Partial correlations between puberal and growth traits are presented in tables 5, 6 and 7. Correlations between age at puberty and body weights and between age at puberty and skeletal or testes-scrotum measurements were low and not significant. A negative effect of puberal age (-.47, P < .05) was observed on the within bull rate of postyearling decline in average daily gain during the 285-day test and is expressed by the linear regression equation Ye = 71.53 + (-1 .IO)X. This general relationship is illustrated in figure 1 by the test mean growth curves for the four youngest (33 to 37 weeks of age) and four oldest (44 to 53 weeks of age) bulls at attainment of puberty. There were significant (P < .01)correlations of .60, .61 and .67 between body weight at puberty and at 265,365 and 550 days of age, respectively, but not between body weight at puberty and 2-year weight. Weight per day of age at puberty was correlated ( P < .01) with body weight at 265, 365 and 550 days of age (.97, .96 and .78, respectively). Puberal WPDA also was correlated significantly with all body measurements at 265, 365 and 550 days of age. Correlations between WPDA at puberty and 2-year body weight and measurements were not significant.
PUBERAL TRAITS OF CHAROLAIS BULLS
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