Relationship of Milk Production, Milk Expected ...

Relationship of milk production, milk expected progeny difference, and calf weaning weight in angus and simmental cow-calf pairs T. T. Marston, D. D. Simms, R. R. Schalles, K. O. Zoellner, L. C. Martin and G. M. Fink J ANIM SCI 1992, 70:3304-3310.

The online version of this article, along with updated information and services, is located on the World Wide Web at: http://jas.fass.org/content/70/11/3304

www.asas.org

Downloaded from jas.fass.org by guest on July 10, 2011

Relationship of Milk Production, Milk Expected Progeny Difference, and Calf Weaning Wei ht in Angus and Simmental Cow-Calf Pairs

K

T. T. Marston2, D. D. Simms, R. R. Schalles, K. 0. Zoellner, L. C. Martin, and G. M. Fink

Department of Animal Science and Industry, Kansas State University, Manhattan 66502

ABSTRACT: Milk EPD, used to predict the milk production potential of a parent's daughters, have been reported by all major cattle breed associa tions. Our objectives were to determine the relationship of milk EPD of a dam to actual milk production (both fluid and components) and offspring weaning weight. Angus (AN; n = 1141 and Simmental (SM; n = 821 cows were machinemilked at approximately 60, 104, and 196 d postpartum after overnight calf removal. In addition, one herd of AN was also milked a t approximately 35 and 145 d postpartum. A lactation curve was fitted to these measurements to estimate total milk production during lactation. Simple correlations between 205-d total milk yields (TMY) and adjusted 205-d calf weaning weight CWW) were .30 (P < .0011 and .47 (P e .001) for AN and SM, respectively. Furthermore, milk EPD was positively correlated to adjusted WW (r = .38 P < .001;

= .39, P e .0011 and TMY Or = .32, P < .001; r = .44, P e .001) for AN and SM cows, respectively. A 1-kg change in TMY changed WW by .014 k .006 kg (P e .0011 in AN and by .032 f .009kg ( P < .001)

r

in SM. A 1-kg change in milk EPD resulted in a 4.85 f 1.14 kg change in WW UD < .001) in A N and a 3.74 ~t 1.73 kg P c .05) change in SM. Corresponding changes in TMY were 42.1 f 16.6 kg (P < .01) and 69.3 f 16.0 kg (P c .001) for A N and SM, respectively. Correlations between percentage of milk fat, protein, lactose, or total solids and adjusted W W were not significant. However, correlations between amount of milk components and adjusted WW were significant (P e .0001). These data indicate that milk EPD, in fact, do predict milk production differences. Furthermore, milk EPD seem to be conservative in their estimates of genetic differences.

Key Words: Beef Cattle, Lactation, Weaning Weight, Milk Yield, Expected Progeny Differences

J. Anim. Sci. 1992. 70:3304-3310

Introduction Because a calf's weaning weight is influenced by the milk production of its dam (Neville, 1962; Melton et al., 1967; Rutledge et al., 1971; Notter et al., 1978; Reynolds et al., 1978; Boggs et al., 19801, the ability to change the genetic potential of a ~

~

'Contribution No. 92-188-5 of the Kansas Agric. Exp. Sta. Appreciation is expressed to the Am.Simmental Assoc. and the Am. A n g u s Assoc. for partial funding for this project. 2Present address: Dept. of Anim.Sci., Oklahoma State Univ., Stillwater 74078. Received October 25, 1991. Accepted June 25, 1992.

herd for milk production could benefit cow/calf producers. Milk EPD have been developed to account for the genetic differences in milking ability of beef cattle (Benyshek et al., 1988).If milk EPD adequately predict milk production potential, prodricers could use them to change the milking ability of their herds and to assist in matching production levels to the environment. Using sires with various milk EPD results in offspring with various levels of milk production (Marshall and Freking, 1988; Diaz et al., 1992). However, the relationship between a cow's milk EPD and her actual milk production has not been delineated. Our objective was to find the relationship between the milk EPD of the dam, actual milk production, and the offspring's weaning weight.

3304 Downloaded from jas.fass.org by guest on July 10, 2011

MILK EXPECTED PROGENY DIFFERENCES

3305

Table 1. Lactation curve parameters, milk production, expected progeny difference, and calf performance for Angus Herd ~

Item

A1

A2

A3

All Angus

No. of cows Milk curve parameter and milk estimates

60

42

44

146

a k Days to peak milk yield Total milk yield, kg/205-d lactation Peak milk yield, kg/d Cow and calf data Milk EPD, kg' Calf weaning EPD, kga Birth wt, kg Weaning age, d Weaning wt, kg Adjusted weaning wt, kgb Calf average daily gain, kg Age group

.53 .10 76 1,263 8.5 7.3 7.3 34.0 222 244 239 .e4 2

f .03 f .003 f 2.3 f 43 f .3 f .2 f .2 f .5 f 2 f 3.6

f 3.4 f .01

.51 .10 85 1,556 10.7 .4 12.0 40.3 202 254 259 1.08 2 to

f .ll f ,005 f 11.4 f 43 f .5 f .4

f .3 f .7 f 2

f 4.5 f 4.1 f .02

> 10

.65 .07 105 1,617 10.1 1.3 8.8 40.7 196 260 288 1.13 3 to

f

.06

f .003 f 4.4 f 77

f

.6

f

.3

.56 .09 88 1,454 9.6

*

f f f

>

f 3.8 f 37 f .3

3.5 f 9.1 f 37.9 f 209 f 252 f 254 f 1.03 f 2 to10

k .5 f

f .04 f .002

.6 3 4.8 7.0 .03 10

.3

.3 .4 2 2.5 3.0 .01

'Supplied by American Angus Association, St. Joseph, MO bCalf weaning weights adjusted to a common age (205 dl.

Experimental Procedure

milk EPD ranged from -5.1 to 10.5 kg E = 3.5, S D = 3.81, whereas SM milk EPD ranged from -5.5 to Data were collected from two herds of purebred 6.4 kg E = 1.2, SD = 2.31. Weaning weight records Angus (AN)and three herds of Simmental (SM) generated during this study were not used in cows in 1988 and(or1 1989. One hundred fortysix calculating the EPD of the cows milked. lactations from 114 AN and 94 lactations from 82 Cow Management. The herds are described in SM were estimated by 899 individual machine Tables 1 and 2. They differed by location, calving milkings. Cows calved in a 65-d period within their season, management, breed, and year. Cows were respective herds. Calving occurred between Februgrouped by age using Beef Improvement Federaary 26 and April 15 in the spring or between tion Uniform Guidelines IBIF, 1986). Herd A1 included 60 primiparous 2-yr-oldheifers August 20 and October 10 in the fall. Herds were used that had a wide range in milk EPD. Angus that calved in August through October of 1988. Table 2. Lactation curve parameters, milk production, expected progeny difference, and calf performance for Simmental Herd Item

s1

s2

No. of cows 25 11 Milk curve parameter and milk estimates .34 f .06 .33 f .05 a k . i i f .ooa .oe f .oo4 Days to peak milk yield 69 f 6 88 f 12 Total milk yield, kg/205-d lactation 1,848 f 80 1,668 f 85 Peak milk yield, kg/d 12.4 f .6 11.7 f .7 Cow and calf data .4 f .7 Cow Milk EPD,kg' 2.4 f .5 Calf weaning EPD, kga 4.4 f 1.0 1.0 f .5 Birth wt, kg 43.9 f 1.2 38.3 f .6 Weaning age, d 180 f 6 187 f 3 Weaning wt, kg 261 f 6.2 252 f 8.4 Adjusted weaning wt, kgb 314 f 5.8 312 f 15.5 Calf average daily gain, kg 1.27 f .02 1.18 f .04 4 to10 3 to10 Age group 'Supplied by American Simmental Association, Bozeman, MT. bCalf weaning weights adjusted to a common age (205 d).

.51 .OB 84 1,419 9.1

.e 2.9 38.6 194 257 291 1.12 2

s3

s4

All Simmental

33

25

94

f .04 f ,003

f 64 f 52

f .3 f .3 f .7 f .8

2 f 4.8 f 5.8 f .02 f


.31 .10 75 2,027 13.4

.02 .002 f 3 f 104 f .7 f f

.9 f 2.9 f 46.3 f 195 f 295 f 337 f 1.27 f 3 to10

.5

.8 1.3 2 6.3 8.6 .03

.41 .09 80 1,724 11.4

f .02 f ,002 f 3.7 f 47

1.2 f 3.1 f 41.9 f 191 f 272 f 311 f 1.21 f 2 to10

.3 .2 .4 .6 2 3.4 4.2 .01

3306

MARSTON ET AL.

When maintained in drylot, they were given ad libitum access to alfalfa hay and were group-fed 2.27 kg * animal-' d-I of dry-rolled grain sorghum. Between the fourth and fifth milking, they were removed from the drylot and allowed to graze winter wheat pasture as one group. A n g u s herds A2 and A3 represented 54 cows in the same location in 1988 and 1989, respectively, and calved in March and April. Various age groups were represented, and several of the cows were milked in consecutive lactations. Management was similar for both years with supplemental alfalfa hay and dry-rolled grain sorghum from the beginning of calving to May 1, then native (predominantly bluestern) pastures. Throughout the trial, ad libitum access to trace mineralized salt was provided. Simmental cows in herds S1, S2, and S4 were managed alike, calving during February, March, and April on dormant native (predominantly bluestem) pastures. Supplemental alfalfa hay and dry-rolled grain sorghum were consumed on a n ad libitum basis until May 1. Then cows were moved to native grass pastures, similar to AN herds A2 and A3. Ad libitum access to trace mineralized salt was provided. Herds S1 and S 4 were essentially the same cows but milked in consecutive years (1988 and 1989). Herd S3 consisted of primiparous 2-yr-old heifers that calved in September and October. They grazed dormant native grass (buffalo grass, bluestem, and gramma) pastures from calving to weaning and were provided with ad libitum access to sudangrass hay and 2.27 kg.animal-l.d-l of dry-rolled grain sorghum. Calf Management. All calves suckled their dams at will from birth to weaning, except during the day before and the day of milk production estimation. During separation periods, ad libitum access to water was supplied. No supplemental feed was provided for any of the spring-born AN or SM calves. Fall-born calves in herd S3 received a highenergy creep feed from December 1, 1988, until weaning, and fall-born calves in herd A1 had access to the alfalfa hay fed to their dams. Springborn AN and SM calves from herds A2,S1, and S2 were weighed only at birth and weaning. All other calves were weighed a t birth, weaning, and a t each milk production estimation. Weaning weights (WW) were adjusted to 205 d of age. Age of dam adjustments were not included because they were confounded with milk production. All male calves were left intact, and no growth stimulants were used. Milking Procedure and Data Collection. Cows were machine-milked a t an average of 60, 108, and 194 d postpartum for all herds. Herd A1 had additional milkings at 35 and 145 d postcalving. The day before milking, pairs were gathered

between 1500 and 1800. Then calves were isolated from their dams until approximately 2200, when pairs were reunited and calves were allowed to nurse their dams a d libitum, but for < 45 min. Cows and calves were then separated until milking was completed. Milking started at 0700 and was completed by 1200, with a mean time of calf separation time of 10.7 (SD = 1.8) h for AN and 11.3 (SD = 2.1) h for SM. For milking, cows were restrained in a chute and injected (i.m.1 with 40 IU of oxytocin; milking started immediately. Milking machines consisted of a portable vacuum pump connected to a Bowman@claw. During milking (mean time = 9.31 f .14 min for AN and 9.50 f .23 min for SM), udders were massaged. When milk flow ceased from all quarters, machines were removed and udders were hand-stripped of residual milk. All cows were weighed, given a body condition score (BCS; 1 = emaciated, 9 = obese; Whitman, 19751, and then reunited with their calves. At each milking, milk from the machine was combined with that from hand stripping and weighed. After mixing, samples were taken, preserved with 2-bromo-2-nitropropane-1,3-diol, and delivered to the Kansas Dairy Herd Improvement Association for milk component analysis. Fat, total solids, protein, and lactose percentages were determined by infrared analyses (Infrared Dairy Product Analyzer, Berroin Instr. Group, North Hollywood, CAI as described by Akers and Thompson (1987). Somatic cell counts were determined using a Fossomatic 215 (Foss Electric, Hillerod, Denmark). Estimation of Lactation Yield. To determine the rate of milk production during the period from initiation to termination of milking on each day, the data (n = 899) were pooled and analyzed with the regression model M = p + b [M (12 - CSII, where M is the amount of milk weighed and CS is the hour of calf separation. From this analysis, it was determined that milk production changed a t a rate of 4.17% per hour during the period that milking took place. Therefore, daily milk yields tY(n)l were adjusted to 24-h production by the formula Y, = [M + M x (12 - CSI x .04171 x 2. Individual animal daily milk yields were used to estimate parameters for the lactation curve defined by the empirical equation (Jenkins and Ferrell, 1984) Y, = n/aekn, where Yn is the daily milk yield of the nth week postpartum, and a and k define the shape of the lactation curve. Total milk yield RMY) was obtained by integrating the lactation curves to 205 d. Parameters were estimated by expressing the equation in logarithms: log,[Y(n)/nl = (log,l/a) - kn and regressing the value log,[Y,/nl on n for individual animals (as proposed by Jenkins and Ferrell, 1984).If the R2for


MILK EXPECTED PROGENY DIFFERENCES

a cow was c .75, she was removed (AN

SM = 22) from the analysis. Total yields of milk components were calculated using the same protocol with adjustment for levels of somatic cell count using coefficients for dairy cattle [Kansas Dairy Herd Improvement Association, personal communication). However, because the low somatic cell counts observed in this study resulted in high correlations between unadjusted and adjusted yields (r = Bl), unadjusted yields were used in all analyses. Statistical AnaZysis. Data were analyzed by breed. The data for TMY were analyzed using a least squares procedure GAS, 19851 to fit a linear regression with unequal subclass numbers. Nonsignificant interactions (P > .20) were eliminated, leaving the model Yijklm = HERDi + SEXj + AGEGRPk + PlBWl+ PzMILK EPDm + e i j u , where Yijklm is TMY, HERDi is the ith herd, SEXj is the jth sex, AGEGRPk is the kth age group of the dam, PlBWl is the regression of TMY on birth weightl, PzMILK EPDm is the regression of TMY on milk EPD,, and eijklm is the sampling error. A similar model was used to analyze the data for adjusted calf weaning weight: Y i j k h = HERDi + PlBWj + PzTMY 1 + PsWeaning EPDm + e i j b , where Yijklm is the adjusted WW, HERDi is the ith herd, P1BWj is the regression of WW on BWj, PzTMYl is the regression of WW on TMY1, PsWeaning EPDm is the regression of WW on calf weaning EPDm, and eijklm is the sampling error. The term PzTMYl was replaced with PzMILK EPDl to determine the relationship of adjusted WW to milk EPD. In addition to using linear regression coefficients to measure the relationships between the variables TMY, WW, and milk EPD, Pearson product-moment correlations were computed using herd as a classification variable to define the groups of observations. Because the chi-square test for homogeneity of the within-herd covariance matrix was significant (P < .OOOl), the within-herd covariance matrix was used for calculating the Pearson correlation coefficients. The repeatability of milk production between consecutive lactations was estimated using intraclass correlation with 51 cows that had milking records from both 1988 and = 19,

1989.

Results and Discussion Condition and Body Weight of Cows. Both breeds tended to increase in BCS and weight during lactation. Cow weights averaged 554.0 f 2.5 and 558.4 rt 4.8 kg, whereas BCS averaged 5.73 f .03 and 5.21 f .O2for AN and SM, respectively, during lactation.

3307

Angus BCS depended on herd, days postpartum, and TMY (P c .01) but not on age group. Simmental BCS did not depend on days postpartum but were influenced by herd, age group, and TMY ( P c .011. Both AN and SM BCS tended to decrease as TMY increased. Angus cow weight was influenced by herd, days postpartum, TMY, and age group (P c .(Ill, and cows that produced more milk tended to be lighter. Simmental cow weight was not influenced by days postpartum or TMY but was influenced by herd and age group (P c .01). Milk Traits by Breed. Least squares means and standard errors for lactation curve parameters, TMY estimates, peak daily milk yield, days to peak yield, milk EPD of the cow, weaning weight EPD of the calf, and calf growth are presented in Tables 1 and 2. The form of the lactation curve equation forced milk production to follow a nonlinear rise until peak lactation Wkl, then to decline from peak lactation until weaning. Differences in daily milk production between breeds and cows within breeds were maximum during peak lactation and declined in magnitude as lactation persisted, in agreement with results of Belcher and Frahm (1979). Least squares means for TMY were 1,454 f 38.4 and 1,724 f 47.1 kg per lactation for AN and SM, respectively. Milk yield a t peak lactation was 9.8 f .3 kg/d for AN and 11.4 rt .3 kg/d for SM. Peak milk production was reached at 67 f 1.8 and 80 rt 3.7 d for AN and SM, respectively. Days to peak lactation were greater than those reported by Totusek et al. (19731 and Jenkins and Ferrell(19841, but they were similar to those reported by Clutter and Nielsen (1987). Movement of spring-calving cows to summer pastures preceded the mean days to peak lactation. Milk from AN cows averaged 3.59 f .05% fat, 3.38 f . O 2 % protein, 4.95 f .01% lactose, and 12.58 f .05% total solids, whereas milk from SM cows averaged 3.82 f .05% fat, 3.17 f .02% protein, 4.85 f .02% lactose, and 12.33 f .05% total solids. Those levels are similar to results reported by Jeffery and Berg (19711, Belcher and Frahm (19791, and Beal et al. (19901, but concentrations of fat and protein were lower than those reported by Masilo et al. (1992). Least squares mean percentages of milk constituents during lactation are displayed in Table 3. For both breeds, percentage of fat decreased as lactation persisted (P c .Oil, protein increased from mid- to late lactation (P c .011, and lactose rose throughout lactation (P c .011. Total solids decreased as lactation persisted (P < .01) for AN but not for SM. For milk of AN, least squares mean somatic cell count gradually decreased as lactation continued, but for milk of SM it declined only between early and mid-lactation.


MARSTON ET AL.

3308

Table 3. Least squares means and standard errors for milk components at three stages of lactation for Angus and Simmental cows Days postpartum Component

60

Days postpartum

106

194

106

60

Angus Fat, YO Protein, oh Lactose, % Solids, Q/o scca, 1,000 counts

4.30 3.49 4.89 13.38 233

f f f f

.15= .05y .03= .13x

f 51'

3.63 3.40 4.96 12.73 213

f f f f

194

Simmental .08y .04y .02y

.07y

f 66'

3.17 3.63 5.04 12.36 146

f f k

f

f 39'

.08'

.OB' .02' .08'

3.87 3.12 4.72 12.47 252

f f f f

.13y .04y .0gx .13

f 68y

3.62 3.16 4.82 12.34 125

Thirtythree AN and 18 SM were milked in successive lactations. Most of these cows were in their third and fourth or later lactations (31 of 511. Eight animals were in their first and second lactations and 12 were in their second and third lactations. The repeatability of TMY was .76 (n = 51; P < .OOOl). Beal et al. (19901 reported similar .021 using machine-milked results (r = .73;P cows approaching maturity, whereas Butcher and Freeman (19681 reported lower values for early lactations with Holstein cows. Mallenckrodt et al. (19901 reported a TMY repeatability of .64 for Polled Herefords and -49for SM using the weighsuckle-weigh procedure. The consistency of milk production between successive lactations in our study suggests that the genetic potential for milk production can be estimated by measuring a single lactation. Factors that Influence Milk Production. Milk EPD of AN and SM cows influenced (P < .01)TMY, whereas herd (P < ,031 and cow age (P < ,021 affected the SM, but not the AN TMY. A 1-kg change in dam's milk EPD resulted in a direct change of 42.1 16.6 kg in estimated TMY for AN and 69.3 k 16.0 kg TMY for SM (Table 41. Calf birth weight was related to TMY in AN (P < .031 but not in SM. Calf sex had little relationship to TMY for either breed. The AN dams of heifer calves tended to produce more TMY (81.9 f 69.2

*

.04y

.03y .llz

f 21'

&Somatic cell count. x.y*zValues in the same row within a breed with different superscripts are significantly different

3.55 3.27 4.96 12.35

.09'

f f f f

106

*

Simmental

f 16.0*** 60.3 42.1 f 16.6'* .014 f .006*** .032 f .009*** 4.85 f 1.14"' 3.74 f 1.73'

&Adjusted to 205 d.

*P