| Weaning Weights of Hereford Calves as Affected by Inbreeding, Sex, and Age |  |  |
| Written by Burgess, J. B., Nellie L. Landblom, and H. H. Stonaker | | Friday, 01 January 1954 19:51 | Journal: J Anim Sci 1954 13: 843-851 Abstract: A set of descriptive constants was developed, whereby the variations in weaning weight caused by inbreeding, age and sex could be estimated in a herd of Hereford beef cattle. These constants were developed to increase effectiveness of selection for weaning weights among calves to be considered for replacements and their dams. The variables considered were years, age of dam, sex of calf, inbreeding of calf and dam, and age of calf at weaning; all were significant in their effect at the 0.05 or 0.01 level. Effect in pounds as deviations from the average weaning weight were: - Years: 1946, +6.; 1947, –24; 1948, –2; 1949, +2; 1950, –1; 1951, +20.
- Age of dam: 2 years, –15; 3 to 5 years; +5; 6 to 8, +21; 9 and over, –10.
- Sex: steer, –6; bull, +14; heifer, –8.
- Per one percent inbreeding of calf: –1.75.
- Per one percent inbreeding of dam: –1.15.
- Per increase in age of calf of one day: +1.67.
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| Heritability of Weaning Grade in Range Beef Cattle | | |
| Written by Rollins, W. C. and K. A. Wagnon | | Sunday, 01 January 1956 21:27 | Journal: J Anim Sci 1956 15: 529-536. Abstract: The heritability of weaning grade has been estimated in two experimental range herds, A and B, of similar breeding that were managed alike except that in Herd A cows were supplemented during the fall and winter when the range was nutritively deficient while the cows in Herd B were not supplemented. On the basis of paternal half sib relationships heritability estimates were made within each of three generations for each herd. The estimates for Herd A were consistently higher than those for Herd B. However, the herd difference in the estimates was not statistically significant. The average value of the heritability estimated for the two herds was 36%.
On the basis of selection experiments extending over two generations heritability of weaning grade in Herd A was estimated to be 42% and in Herd B 29%. Within years there was a correlation of .42 between weaning grade and weaning weight. The square of this correlation is .18, thus 18% of the variance in weaning grades within years was due to variation in weaning weight. Sex, herd and pasture differences in weaning grade were adequately explained on the basis of this correlation. For full text click here |
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| Estimation of Genetic and Environmental Factors Affecting Weaning Weights of Creep-Fed Cattle | | |
| Written by Hamann, H. K., S. Wearden, and W. H. Smith | | Tuesday, 01 January 1963 12:24 | Journal: J Anim Sci 1963 22: 316-319 Abstract: Data from 1,861 creep-fed calves raised during 1957, 1958, and 1959 were analyzed. Assuming that each weaning weight could be expressed as a linear combination of a sex effect, an age of dam effect, and an age of calf effect, least squares analyses were performed on an among- and within-year basis. Each source of variation was highly significant, so factors were obtained to adjust the weights of heifers to correspond to those of steers, and to adjust for age of dam to a mature equivalent. Sex of calf and age of dam constants were much larger than those previously published for noncreep-fed calves.
Searle's simplified method, involving a multiplicative factor based on subclass means was also used to obtain adjustments on a within-year basis. Comparing the reduction in sums of squares by the two methods, measures of relative efficiency of 99.2, 97.9, and 99.1% were found for Searle's method for 1957, 1958, and 1959 respectively. Since ease of computation is added to the apparently high relative efficiency of Searle's method, it appears to be useful for individual herds on a within-year basis. A paternal half-sib correlation of 0.12 was obtained by pooling the 458, 405, and 471 paternal half-sib records obtained in the 3 respective years. When this was compared with a coefficient based on 771 maternal half-sib records, the difference between paternal and maternal half-sib correlations was found to be nonsignificant. The estimate of heritability based on paternal half-sib records was 0.47. The 332 full-sib records obtained during 1958 and 1959 yielded an intraclass correlation of 0.37; after the maternal effect was deleted, a heritability estimate of 0.49 was computed. For full text click here |
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| Association of Preweaning and Postweaning Traits with Weaning Weight in Cattle | | |
| Written by Christian, L. L., E. R. Hauser, and A. B. Chapman | | Friday, 01 January 1965 12:20 | Journal: J Anim Sci 1965 24: 652-659. Abstract: Analysis of the effects of milk and butterfat production and weaning weight of the dam and birth weight, amount of creep feed, and sex of calf on weaning weight and gain to weaning of 88 offspring of 52 cows that were 2, 3 and 4 years of age indicated that these factors combined account for a highly significant portion of the total variation. The independent effects of birth weight, creep-feed consumption, sex of calf and butterfat production of the dam were significant. Whereas all measures of milk and butterfat production were significantly correlated with weaning weight and gain to weaning, only butterfat production from 0 to 60 days postpartum had a significant effect when other sources of variation were constant.
Estimates of the dam's milk production appeared to be independent of the birth weight of her calf, suggesting that the total milk produced was not affected by capacity of the calf to consume it.
A significant negative correlation was found between the weaning weight of the dam and her butterfat production to 60 days of age. The negative correlations between weaning weight and other measures of milk production approached significance. These results suggest a negative genetic or environmental correlation, or both, between weaning performance of the dam and the maternal environment she provides for her calf. If this correlation is genetic, selecting heifers superior in weaning weight would result in increased genetic value for growth response, but decreased milk production. Average daily gain during the later stages of the postweaning feeding period and the proportion of trimmed valuable cuts in the carcass were found to increase significantly with increased weaning weight. The external fat thickness over the 12th rib and carcass and quality grade were not associated significantly with weaning weight. For full text click here |
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