RELATIONSHIPS AMONG UDDER SHAPE, UDDER CAPACITY, COW LONGEVITY AND CALF WEIGHTS ~

RELATIONSHIPS AMONG UDDER SHAPE, UDDER CAPACITY, COW LONGEVITY AND CALF WEIGHTS ~ R. S. Kersey DeNise 2, D. E. Ray 2, A. M. Lane 2, V. L. Rundle 3 and M. Torabi 2 University of Arizona Tucson 85721 ABSTRACT and udder shape were scored on 3- to 10-yr-old cows from a large Hereford herd. was scored from 1 (small) and 5 (large) and udder shape was scored from 1 (balanced, udder level with ground) to 5 (unbalanced, funnel-shaped udder). Data were analyzed within age of cow for udder capacity scores from 1 to 4 and for udder shape scores from 1 to 3 because of the limited number of observations in other categories. Year of birth of cow was a significant source of variation in both udder capacity and udder shape. Days in lactation (ranging from 81 -+ 23 d in 3-yr-old cows to 71 +- 25 d in 4-yr-old cows) was an important source of variation for udder capacity; as lactation progressed udder capacity score declined. Body condition of the cow was an important source of variation for udder capacity in 3- and 4-yr-old cows; cows with more external body condition had larger udder capacity scores. The heritability estimates of udder capacity and udder shape for 3-yr-old cows were.12 -+.14 and.15 -+.16, respectively; the repeatability estimates of scores over years were.14 +-.02 and.16 +-.03, respectively. Residual correlations between udder capacity and udder shape were low, ranging from -.10 in 3-yr-old cows to.10 in 6-yr-old cows. Neither udder characteristic affected the number of years a cow remained in the herd, but cows with unbalanced udders had more udder defects. The regressions of early weight of the calf and weaning weight of the calf on udder capacity score were significant within each age of cow. Regressions of early weights ranged from 4.3 -+ 1.3 to 8.1 -+ 1.4 kg/capacity unit; regressions of weaning weight ranged from 6.1 +- 1.7 to 9.4 -+ 1.8 kg/capacity unit. However, little of the variation in weights at either age was explained by udder capacity. (Key Words: Udders, Heritability, Beef Cattle, Preweaning Weight, Weaning Weight, Longevity.) Introduction One of the most important influences on calf production is the milk yield of the cow (Neville, 1962; Christian et al., 1965; Rutledge et al., 1971). Actual amount of milk that a calf receives may also be dependent on size and shape of the teats (Frisch, 1982). Many of the breed associations, including the American Hereford Association, have designed a scoring system to evaluate the total mammary system; but little information is available to evaluate the usefulness of these scoring systems in a beef production system. The dairy industry has used descriptive type scores for many years to evaluate udder confor- 1 Published as paper no. 4321, Journal Series, Arizona Agr. Exp. Sta., Tucson. 2 Dept. of Anim. Sci. 3 Dept. of Anim. Sci., University of Nebraska, Lincoln 68583--0712. Received November 24, 1986. Accepted March 31, 1987. mation and has found a positive relationship between udder size and milk production (White and Vinson, 1975). Doornbos et al. (1981) reported favorable relationships between subjective udder score at 130 to 150 d postpartum and actual milk production and gain of calves (residual correlations of.46 and.32) in a herd of Hereford cattle. Several studies of dairy cattle have reported relationships among mastitis and udder conformation (Young et al., 1960; Seykora and McDaniel, 1985), and longevity and udder conformation (White and Vinson, 1975; Honnette et al., 1980a,b). In general, pendulous udders that were low to the ground were prone to mastitis; high, wide and firmly attached udders with appropriate teat size and placement were favorably correlated to longevity. The purpose of this study was to estimate the genetic and environmental effects on udder capacity and udder shape in beef cattle, and to evaluate the relationships among udder characteristics, cow longevity and calf weights. 366 J. Anim. Sci. 1987.65:366-372

UDDER CHARACTERISTICS OF RANGE BEEF COWS 367 Materials and Methods Data were collected from 1967 through 1975 from a purebred Hereford herd in eastcentral Arizona, owned by the San Carlos Apache Indian Tribe. Cows were assigned randomly within age group to single-sire breeding pastures of approximately 30 cows in January of each year. Forage availability was relatively constant among pastures in a given year, but forage conditions varied considerably between years. Cows were not supplemented; but during the years of 1970 to 1972, 3-yr-old cows were assigned to treatments of early weaning vs supplementation in single-sire breeding pastures. Cows that produced calves in the early-weaned group were removed from the subsequent analysis of weaning weights. The breeding season extended from May 1 to August 1;replacement heifers entered the herd at 2 yr of age. Cows and calves were weighed in late May of each year and cows were evaluated for udder characteristics. The average days in lactation at this scoring date over all years was 75 d. Cows were evaluated subjectively on udder capacity, udder shape and udder soundness by the same single evaluator throughout the experiment. WaS scored from 1 (small) to 5 (large), but cows with a score of 5 were deleted from the analysis because of the limited number of observations. was scored from 1 (balanced, even-quartered udder) to 5 (unbalanced, funnel-shaped udder), but only data of cows with scores of 1 to 3 were analyzed because of the limited number of cows that scored above 3. In addition to scoring, udder problems such as mastitis, large teats, and non-functional quarters were noted. Cows and calves were grouped as a single herd following the breeding season on a deferred pasture. In October, cows and calves were gathered, weighed and calves were weaned. Cows were routinely culled at 10 yr of age. The other major reason for culling was any physical unsoundness that could impair productivity. The latter category would include problems relating to locomotion and ability to consume range forage, cancer eye and udder unsoundnesses affecting more than one quarter. Data were analyzed by least-squares procedures as described by Harvey (1975). Each characteristic was evaluated separately within age of cow, from 3 through 6 yr of age. Each cow age group was evaluated separately to prevent correlated errors across ages and to minimize the effects of selection. Data from cows of 7 to 10 yr were not analyzed because of the limited number of cows within each age group. Udder traits were analyzed individually because not all cows evaluated had both udder capacity and udder shape scores. and udder shape were analyzed in a model that included year of birth of cow, sire of the cow nested within year, sex of calf, and covariates for days in lactation and body condition of cow at evaluation. Body condition of the cow was a subjective measure of fat cover and ranged from 5 (poor condition) to 14 (extremely fat), with a score of 12 considered optimum. Cow body condition was included to remove differences in feed quality and quantity between the pastures. Only cows with live calves in May were used in the analysis. Residual correlations between udder capacity and udder shape scores were calculated from the same model from a subset of cows with both scores. Heritability estimates for both scores were calculated from the intraclass correlation of paternal half-sibs. To evaluate the repeatability of udder capacity and udder shape scores over years, cows with at least three records between 3 and 10 yr of age were analyzed with a model that included year of birth, cow within year, sex of calf, and covariates for days in lactation and body condition of cow. For each age of cow category, longevity was the age of last record during a cow's productive life. Data were analyzed with a model that included year of birth of the cow, sire nested within year and a covariate for either udder capacity or udder shape. The interaction of udder capacity udder shape was tested and was not an important source of variation in longevity at any age. Udder defects were tabulated by age of cow using all available information. Mean udder capacity and.udder shape scores of cows with udder defects were calculated. The effects of udder capacity and udder shape on calf May and weaning weights were analyzed separately by udder characteristic. The model included year of birth of the calf, sire nested within year, sex and covariates for age and either udder capacity or udder shape. The interaction of udder capacity by udder shape was not significant; therefore, each udder characteristic was evaluated in separate analyses to maximize the number of observations. Results and Discussion The factors affecting udder capacity and udder shape are presented in table 1. Year of birth of the cow was a significant source of

368 DENISE ET AL. TABLE 1. MEAN SQUARES OF FACTORS AFFECTING UDDER CAPACITY AND UDDER SHAPE IN 3- TO 6-YR-OLD COWS 3 4 Item df Mean square df Mean square df Year of birth 6 4.8** 7 2.5** 8 Sire/year 76.5 70.6** 45 Sex of calf 1.3 1.4 1 Covariates Days of lactation 1 3.1"* 1 8.9** 1 Body condition of cow 1 11.6"* 1 5.3** 1 Remainder 378.4 333.4 229 Year of birth 5 2.8" * 6 5.5"* 7 Sire/year 59.4 55.4 38 Sex of calf 1.1 1.1 1 Covariates Days in lactation 1.1 1.1 1 Body condition of cow 1.1 1 3.6"* 1 Remainder 294.3 267.3 190 5 6 Mean square df Mean square 1.2"* 4 2.7**.3 ~ 28.4.6 1.8 1.3" 1 1.7".9 1.1.3 139.4 1.6"* 7 1.4".4 31.5.3 1.3 1.1 1.1.1 1.6.3 157.4 *P<.05. **P<.01. variation for both udder capacity and udder shape at all ages. For udder capacity, no relationship was evident among year constants for cows of a given age group scored in subsequent years; thus, carryover effects did not appear important. However, trends were similar across all age groups for cows scored in the same year. This suggests that extraneous environmental variation affected udder capacity scores in all age of cow groups similarly. No trends were evident in the year constants from the analyses of udder shape. Sex of the calf was not a significant source of variation in udder capacity or udder shape, but cows with bull calves consistently had higher udder capacity scores. Days in lactation was a significant source of variation for udder capacity at all ages. Partial regressions were -.004 +.001, -.007 +.001, -.003 +.002 and -.005 +.002 capacity units/d for 3-, 4-, 5- and 6-yr-old cows, respectively; mean days in lactation were 82 -+ 25, 72 +- 25, 74 -+ 24 and 75 -+ 25 d, respectively. Thus, cows calving earlier in the season tended to have smaller capacity scores. While the effects of days in lactation on udder capacity score was small (R 2 values ranged from.02 to.07), the effect of days in lactation on udder capacity was consistent across all age groups. Body condition scores significantly influenced udder capacity in 3- and 4-yr-old cows. Partial regressions of capacity score on body condition scores were.20 +.04 and.13 +.03 capacity units/condition unit for 3- and 4-yrold cows; mean body condition scores were 9.2 +.9 and 9.1 + 1.0 condition units, respectively. In younger cows, higher body condition of the cow at evaluation was associated with greater udder capacity. Residual correlations between udder capacity and shape from a reduced data set were -.10, -.09, -.004 and.10 in 3- to 6-yr old cows. Although all the correlations were low, younger cows with larger capacity scores tended to have more desirably balanced udders. In older cows, udder capacity was positively correlated with unbalanced udders. When udder capacity and udder shape were evaluated as repeated observations on a cow over years, year of birth of the cow and cow nested within year were significant sources of variation in both analyses (table 2). Year of

UDDER CHARACTERISTICS OF RANGE BEEF COWS 369 TABLE 2. MEAN SQUARES OF FACTORS AFFECTING UDDER CAPACITY AND UDDER SHAPE AS A REPEATED OBSERVATION ON A COW Item df Mean square df Mean square Year of birth 10 Cow/year 479 Sex of calf 1 Covariates Days in lactation 1 Body condition of cow 1 Remainder 1,520 **P<.01. 7.4" *.7** 3.9** 3.1"*.3.4 9 7.3** 390.8** 1.1 1.9 1.1 1,163.4 birth of the cow measures the cumulative environmental effects to which cows born in the same year were subjected. These effects can probably be attributed to differences in forage quality and quantity from year to year. Sex of the calf and days in lactation were significant sources of variation for udder capacity. Cows with bull calves had greater capacity scores; and as the number of days in lactation increased, udder capacity score decreased (mean days in lactation = 74 + 26 d and regression of udder capacity score on days in lactation = -.002 +.001 capacity units/d). The heritability estimates for udder capacity and udder shape from data of 3-yr-old cows and the estimate of repeatability of both udder capacity and udder shape using all available data are presented in table 3. The heritability estimates indicated that little of the variation in udder capacity and udder shape was attributed to additive effects of genes. Most of the variation in both estimates must have been due to temporary environmental effects unaccounted for by the model. The mean squares from the analyses of longevity are presented in table 4. Year of birth of the cow was a significant source of variation in longevity for 3- and 4-yr-old cows. Udder capacity and udder shape were not important in determining the number of years that a cow remained in this herd. The mean ages of last recorded data for 3-, 4-, 5- and 6-yr-old cows were 6.8 + 2.3, 7.2 + 2.0, 7.6 + 1.4 and 8.3 -+ 1.5 for udder capacity; and 6.7 + 2.3, 7.1 + 2.1, 7.6 + 1.6 and 8.3 + 1.5 for udder shape, respectively. and udder shape did not affect the average herdlife within the range of values analyzed. There was, however, no way to measure the economic impact of retaining cows with poor or defective udders from these data. Certainly the heritability estimates of.12 and.15 for udder capacity and udder shape indicated that progress from selection for these udder characteristics under range conditions would be slow. The incidence of udders with problems by age of cow and the mean udder capacity and udder shape scores of cows with problems are TABLE 3. HERITABILITY ESTIMATES OF 3-YR-OLD COWS AND REPEATABILITY ESTIMATES OF UDDER CAPACITY AND UDDER SHAPE Item Heritability analyses Mean 2.7 -+.03 1.9 _+.04 No. of observations 460 362 h 2.12 +-.14.15 +-.16 k 5.5 5.5 Repeatability analyses Mean 2.9.02 2.1 -+.03 No. of observations 2,013 1,566 r e.14 -+.02.16 -+.03 k 4.1 3.9

370 DENISE ET AL. TABLE 4. MEAN SQUARES OF FACTORS AFFECTING LONGEVITY BY AGE OF COW 3 4 5 6 Item df Mean square df Mean square df Mean square df Mean square Year of birth 6 15.2" 7 9.8* 8 4.0 8 2.7 Sire/year 77 6.0 72 3.8 47 3.9* 38 2.5 Covariate 1 2.6 1 7.2 1 4.2 1 1.3 Remainder 388 5.1 348 4.2 241 2.7 202 2.3 Year of birth 5 15.9" 6 10.8" 7 6.6 7 2.0 Sire/year 60 6.1 56 3.8 40 3.3 34 2.4 Covariate 1.5 1 5.0 1.8 1 2.0 Remainder 303 4.8 277 4.1 202 2.7 171 2.3 *P<.05. listed in table 5. All cows with udder data were included in this analysis, regardless of calving status. Cause and effect relationships were impossible to ascertain, but there appeared to be no relationship between udder capacity and the incidence of udder defects. However, cows with tendencies toward unbalanced udders appear to have greater udder problems. Young et al. (1960) found that the distance between the ground and the udder of dairy cows was negatively correlated to the incidence of mastitis. The incidence of udder defects was low in each age group (from 1.3% in 3- and 4-yr-old cows to 5.8% in 6-yr-old cows). The number of observations, least-squares means of May weights and ages of calves are presented in table 6. In addition, mean udder capacity and udder shape scores and the regressions of May weights on udder characteristic scores and R 2 values are included. was a significant source of variation in weight of calves, averaging from 71 to 81 d of age. The regression of weight on udder capacity score ranged from 4.3 to 8.1 kg/capacity unit; but the R 2 values ranged from.02 to.09, indicating that little of the variation in May weights could TABLE 5. INCIDENCE OF UDDER DEFECTS BY AGE OF COW AND COMPARISONS OF MEAN UDDER CAPACITY AND UDDER SHAPE SCORES Defect 3 4 5 6 Mastitis, %.3.0.3 1.3 Non-functional or spoiled quarters, %.5.8 2.9 2.4 Large teats, %.2.3 1.0 1.1 Unknown unsoundness, %.3.2.3 1.1 Total defects, % 1.3 1.3 4.4 5.8 Mean udder capacity score of cows with defects 2.5 2.3 2.3 3.1 Deviation from overall mean -.2 --.6 -.6 0 Mean udder shape score of cows with defects 2.4 3.3 3.6 3.5 Deviation from overall mean.5 1.2 1.6 1.4

UDDER CHARACTERISTICS OF RANGE BEEF COWS 371 TABLE 6. LEAST-SQUARES MEANS, NUMBER OF OBSERVATIONS, REGRESSION COEFFICIENTS AND STANDARD ERRORS AND R 2 VALUES OF MAY WEIGHTS OF CALVES ON UDDER CAPACITY AND UDDER SHAPE OF 3- TO 6-YR-OLD COWS Item 3 4 5 6 analyses No. of observations 503 467 297 259 Mean Maywt, kg 84 1 85 1 90 1 92 1 Mean May age, d 81 23 71 25 72 -+ 27 75 23 Mean 2.6.6 2.9.7 3.0 -+.6 3.0.6 Regression 6.4.9** 6.4 1.0"* 4.3 -+ 1.3"* 8.1 1.4"* R 2.05.05.02.09 analyses No. of observations 405 391 234 226 Mean Maywt, kg 84 -+ 1 86 1 90 1 92 1 Mean May age, d 82 24 71 -+ 26 72 -+ 25 75 23 Mean 1.8 -+.6 2.1.6 2.1.6 2.2 -+.6 Regression --1.3 1.1 --2.3 + 1.2.9 -+ 1.6 --1.9 1.7 R 2.002.005.001.004 **Regression significant (P<.O1). be accounted for by the udder capacity score of the cow. was not an important source of variation in early weights of calves. was also a significant source of variation in weaning weights of calves (table 7). Regression values ranged from 6.1 to 9.4 kg/capacity unit. But, as in the analysis of the May weights, the R 2 values (range of.03 to.07) indicated that a little of the variation in weaning weight could be attributed to differences in udder capacity scores of the cows. In studies that related actual milk production to TABLE 7. LEAST-SQUARES MEANS, NUMBER OF OBSERVATIONS, REGRESSION COEFFICIENTS AND STANDARD ERRORS AND R ~ VALUES OF WEANING WEIGHTS OF CALVES ON UDDER CAPACITY AND UDDER SHAPE OF 3- TO 6-YR-OLD COWS Item 3 4 5 6 analyses No. of observations 280 280 332 Mean weaning wt, kg 184 2 182 _+ 1 Mean weaning age, d 238 24 219 -+ 26 Mean 2.7.6 2.9.7 Regression 9.4 + 1.8"* 6.1 1.7"* R 2.07.03 analyses No. of observations 275 318 Mean weaningwt, kg 183 2 183 1 Mean weaning age, d 237 24 219 26 Mean 1.9.6 2.2.6 Regression --.1 2.0 --3.1 1.8 R 2 0.007 251 203 185 2 185 2 218 25 219 23 3.0.6 3.1.6 8.5 2.2** 8.0- + 2.6**.05.04 226 191 185 1 187 2 217 25 220 23 2.1.5 2.3 -+.6 3.9 _+ 2.7.9- + 2.8.009 0 **Regression significant (P<.O1).

372 DENISE ET AL. weights of calves, 60 to 77% of the differences in weight of the calves at different ages could be accounted for by differences in milk production of the cow (Drewry et al., 1959; Neville, 1962). Subjective udder capacity score, assigned at 70 to 80 d in lactation, appeared to be a poor predictor of weights of calves at 70 to 80 d of age or at weaning. In addition, subjective udder shape score, assigned at 70 to 80 d in lactation, was not related to calf weights at any age when values of 1 to 3 were analyzed. These data showed no relationship between any of the subjective udder scores assigned and the number of years a cow remained in the herd. Literature Cited Christian, L. L., E. R. Hauser and A. B. Chapman. 1965. Association of preweaning and postweaning traits with weaning weight in cattle. J. Anim. Sci. 24:642. Doornbos, D. E., D. C. Anderson and D. D. Kress. 1981. Milk production, udder size and calf growth in beef cattle. Proc. West. Sec. Amer. Soc. Anim. Sci. 32:317. Drewry, K. C., C. J. Brown and R. S. Honea. 1959. Relationships among factors associated with mothering ability in beef cattle. J. Anim. Sci. 18:938. Frisch, J. E. 1982. The use of teat size measurements or calf weaning weight as an aid to selection against teat defects in cattle. Anim. Prod. 35:127. Harvey, W. R. 1975. Least-squares analyses of data with unequal subclass numbers. ARS H4 USDA, Washington, D.C. Honnette, J. E., W. E. Vinson, J. M. White and R. H. Kliewer. 1980a. Contributions of descriptively coded type traits to longevity of Holstein cows. J. Dairy Sci. 63:807. Honnette, J. E., W. E. Vinson, J. M. White and R. H. Kliewer. 1980b. Prediction of herdlife and lifetime production from first lactation production and individual type traits in Holstein cows. J. Dairy Sci. 63:816. Neville, Jr.,,W. E. 1962. Influence of dam's milk production and other factors on 120- and 240- day weight of Hereford calves. J. Anim. Sci. 21:315. Rutledge, J. J., O. W. Robison, W. T. Ahlschwede and J. E. Legates. 1971. Milk yield and its influence on 205-day weight of beef calves. J. Anim. Sci. 33:563. Seykora, A. J. and B. T. McDaniel. 1985. Heritabilities of teat traits and their relationships with milk yield, somatic cell count and percent two-minute milk. J. Dairy Sci. 68:2670. White, J. M. and W. E. Vinson. 1975. Relationships among udder characteristics, milk yield, and non-yield traits. J. Dairy Sci. 58:729. Young, C. W., J. E. Legates and J. G. Lecce. 1960. Genetic and phenotypic relationships between clinical mastitis, laboratory criteria and udder height. J. Dairy Sci. 43:54.