Journal of Animal Science

Patterson, D., J.;Corah, L., R.;Brethour, J., R.;Higgins, J., J.;Kiracofe, G., H.;Stevenson, J., S.

doi: 10.2527/1992.7071994xpmid: 1644671

Abstract Records of age at puberty (AAP) and duration of the postpartum interval to estrus (PPI) for heifers calving first at 2 yr of age were used to determine the relationship between the two reproductive traits. The study from which these records were obtained was designed in a 2 × 2 × 2 factorial arrangement of treatments. Angus × Hereford (AH; n = 148) and Brahman × Hereford (BH; n = 148) heifers were allotted within breed after weaning by weight into light (LW) and heavy (HW) weight blocks. Heifers were assigned by age to different levels of energy (low or high) in diets calculated to reach a target weight of 55% (LE) or 65% (HE) of their projected mature weight by the onset of the breeding period. Data were analyzed within breed and included only records for which both AAP and PPI were available. Pearson correlation coefficients for AAP to PPI were r = −.12 (P = .20) and r = .05 (P = .71) for AH and BH, respectively. Eliminating animals that experienced dystocia from the analyses yielded correlations of r = −.27 (P = .02) and r = .06 (P = .65) for AH (n = 69) and BH (n = 51), respectively. When energy level, weight block, and energy level × weight block were included in the model for PPI, analyses of variance indicated that PPI among AH heifers was influenced most by the weight at which heifers began the trial after weaning (P = .01) but not by energy level (P = .23) or the interaction of energy level × weight block (P = .48).(ABSTRACT TRUNCATED AT 250 WORDS) This content is only available as a PDF. Author notes 2 Present address: Dept. of Anim. Sci., Univ. of Kentucky, Lexington 40546-0215. Copyright © 1992 by American Society of Animal Science

Kennedy, B., W.;Quinton,, M.;, van Arendonk, J.A.M.

doi: 10.2527/1992.7072000xpmid: 1644672

Abstract Studies involving the effects of single genes on quantitative traits may involve closed populations, selection may be practiced, and the quantitative trait of concern may also be influenced by background genes that are inherited in a polygenic manner. It is shown analytically that analysis of such data by ordinary least squares, the usual method of analysis, can lead to finding an excess of spurious significant effects of single genes, when no effect exists, for both randomly and directionally selected populations and can lead to bias in estimates of single-gene effects when selection has been practiced. The bias depends on heritability of the polygenic effects on the trait, selection intensity, mode of inheritance, magnitude of gene effect, gene frequency, and data structure. It is argued that when genotypes of individuals can be identified for all individuals with observations on the trait, use of mixed-model procedures under an animal model treating single-gene effects as fixed effects can provide unbiased estimates of single-gene effects and exact tests of associated hypotheses for pedigreed populations, even when selection is practiced. Results are illustrated through computer simulation. This content is only available as a PDF. Copyright © 1992 by American Society of Animal Science

Muggli-Cockett, N., E.;Cundiff, L., V.;Gregory, K., E.

doi: 10.2527/1992.7072013xpmid: 1644673

Abstract The prevalence of bovine respiratory disease (BRD) was assessed in a population of 10,142 beef calves representing nine pure breeds and three composite populations born in 1983 through 1988. Twenty-four percent of the calves experienced at least one episode of respiratory disease during the 1st yr of life; frequencies over the six birth years ranged from 14 to 38%. The timing of respiratory disease outbreaks differed among birth years; in 4 of the 6 yr, more illness occurred in the pasture before weaning than in the feedlot after weaning. Frequencies of BRD during preweaning and postweaning periods were analyzed separately. Pure breeds and composite populations within a single preweaning location differed in frequency of illness during the preweaning period. However, not all possible breed comparisons could be made because preweaning location differed for the breed groups, and preweaning location had a significant effect on the frequency of respiratory disease in the preweaning period. The preweaning location effect did not carry through to the postweaning period. Pinzgauers had the highest BRD frequency within the feedlot (24.6%). The heritability estimates of BRD during the preweaning and postweaning periods did not differ significantly from 0 (.10 ± .02 and .06 ± .07, respectively). Although it is likely that response to selection for resistance to BRD would be slight using the animal's history of BRD as the selection criterion, including information on relatives or additional immune traits may improve the accuracy of an estimated breeding value for BRD resistance. This content is only available as a PDF. Author notes 1 The authors thank Darrell Light for data analysis, Gordon Hays, Dave Powell, Wade Smith, and Robert Bennett for animal operations support, and Jackie Byrkit and Barbara Stuart for manuscript preparation. Copyright © 1992 by American Society of Animal Science

Young, L., D.

doi: 10.2527/1992.7072020xpmid: 1644674

Abstract Meishan, Fengjing, Minzhu, and Duroc boars were mated by AI to crossbred gilts to compare the sire breeds for effects on productivity of their mates and performance of their progeny. Gilts were derived from a four-way cross of Chester White, Landrace, Large White, and Yorkshire. At weaning, litters sired by Meishan boars averaged 1.69 and 1.32 more pigs than those sired by Duroc and Minzhu boars, respectively (P < .05). Pigs sired by Meishan and Fengjing boars averaged 1.2 to 1.8 more nipples than pigs sired by Duroc and Minzhu boars (P < .05). Minzhu-sired pigs had a lower (P < .05) survival rate to 14 and 28 d of age than did those sired by Meishan, Fengjing, and Duroc. Fengjing-sired pigs were heavier than Minzhu-sired pigs at birth and heavier than Minzhu- and Duroc-sired pigs at 14, 28, and 56 d of age (P < .05). At 70 d of age, Meishan-sired pigs were heaviest, followed in order by Fengjing-, Duroc-, and Minzhu-sired pigs. At 98 d of age, Meishan-sired pigs were significantly heavier than all other breed groups and Duroc-sired pigs were significantly heavier than Minzhu-sired pigs. At 126 and 154 d of age, Duroc-sired pigs were heaviest, followed in order by Meishan-, Fengjing-, and Minzhu-sired pigs; all differences were significant. Average backfat thickness of gilts at 99.7 kg was least for Duroc-sired gilts and highest for Meishan-sired gilts. Sire breed groups did not differ significantly in feed efficiency from 70 to 98 d of age. Duroc-sired pigs were the most efficient (P < .05) from 98 to 126 and 126 to 154 d of age. Results indicate that use of these Chinese breeds in crossbreeding programs will decrease performance traits. This decrease would have to be offset by increases in reproductive efficiency of Chinese sows, use of repartitioning agents, or other management techniques if Chinese pigs are to improve overall production efficiency of a crossbreeding program. This content is only available as a PDF. Author notes 1 Appreciation is expressed to Brad Freking for data analysis. 2 Roman L. Hruska U.S. Meat Anim. Res. Center, P.O. Box 166. 3 Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply approval to the exclusion of other products that may be suitable. Copyright © 1992 by American Society of Animal Science

Young, L., D.

doi: 10.2527/1992.7072030xpmid: 1644675

Abstract Duroc, Meishan, Fengjing, and Minzhu boars were mated to crossbred gilts during two breeding seasons. From each sire breed group each season, six pens of approximately eight barrows each were slaughtered. A pen of pigs from each sire breed group was slaughtered at 7-d intervals from 168 to 203 d of age each season. Breed of sire effects were significant for all age-adjusted carcass traits except carcass length, fat thickness at the last rib, color score, and firmness score. At 184 d of age, Duroc crosses had the heaviest (P < .05) slaughter and carcass weights; Minzhu crosses were lighter (P < .05) than Meishan crosses but not lighter than Fengjing crosses. Differences among age-constant traits reflect differences in BW. After adjustment to a constant carcass weight of 78 kg, the three Chinese breeds had very similar carcass characteristics. Carcasses sired by Durocs had significantly less backfat and larger longissimus muscle area than carcasses sired by the Chinese breeds. Weight of each trimmed wholesale lean cut and their total weight were significantly higher for Duroc crosses than for Chinese crosses. Breed of sire means did not differ significantly for belly weight, but Duroc crosses had less (P < .05) weight of leaf fat. Relative to Chinese crosses, longissimus muscles from Duroc crosses had more marbling (P < .05). Sire breed groups did not differ significantly for color or firmness score. Pigs sired by Meishan, Fengjing, and Minzhu produced carcasses with significantly less lean content at a carcass weight of 78 kg than did pigs sired by Duroc. This content is only available as a PDF. Author notes 1 Appreciation is expressed to Brad Freking for data analysis. 2 Roman L. Hruska U.S. Meat Anim. Res. Center, P.O. Box 166. 3 Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply approval to the exclusion of other products that may be suitable. Copyright © 1992 by American Society of Animal Science

Sorensen, D., A.;Johansson,, K.

doi: 10.2527/1992.7072038xpmid: 1644676

Abstract Analytic results obtained using simple models show that estimates of selection response of univariate experiments using animal models are completely dependent on the heritability used as prior when fixed effects are nested within generations, and both on the prior and on the true heritability parameter when fixed effects overlap across generations. Univariate animal model estimators of correlated changes of a trait not selected directly are usually biased. The absolute value of the estimate of the correlated response is smaller than the true value when the traits are only genetically correlated and larger than the expected value of zero when they are only environmentally correlated. The validity of the results derived from the analysis of simple models is confirmed using computer simulations, which illustrate the magnitude of the bias. It is emphasized that use of univariate animal models to estimate response in breeding programs whose breeding objectives include several correlated traits may lead to erroneous conclusions. This content is only available as a PDF. Copyright © 1992 by American Society of Animal Science

Hagger,, C.

doi: 10.2527/1992.7072045xpmid: 1644677

Abstract Two generations of selection on restricted BLUP breeding values were applied in an experiment with laying hens. Selection had been on phenotype of income minus feed cost (IFC) between 21 and 40 wk of age in the previous five generations. The restriction of no genetic change in egg weight was included in the EBV for power-transformed IFC (i.e., IFCt, with t-values of 3.7 and 3.6 in the two generations, respectively). The experiment consisted of two selection lines plus a randomly bred control of 20 male and 80 female breeders each. Observations on 8,844 survivors to 40 wk were available. Relative to the base population average, the restriction reduced genetic gain in IFC from 4.1 and 3.9% to 2.0 and 2.2% per generation in the two selection lines, respectively. Average EBV for egg weight remained nearly constant after a strong increase in the previous five generations. Rates of genetic gain for egg number, body weight, and feed conversion (feed/egg mass) were not affected significantly. In the seventh generation, a genetic gain in feed conversion of 10.3% relative to the phenotypic mean of the base population was obtained. This content is only available as a PDF. Author notes 1 The author is grateful to G. Stranzinger for his support, to D. Steiger-Stafl and C. Marguerat for their expert technical assistance, and to M. Bishop for his help on style and English usage in an earlier version of the manuscript. Copyright © 1992 by American Society of Animal Science

Faust, M., A.;Robison, O., W.;Tess, M., W.

doi: 10.2527/1992.7072053xpmid: 1644678

Abstract A stochastic life-cycle swine production model was used to study the effect of female replacement rates in the dam-daughter pathway for a tiered breeding structure on genetic change and returns to the breeder. Genetic, environmental, and economic parameters were used to simulate characteristics of individual pigs in a system producing F1 female replacements. Evaluated were maximum culling ages for nucleus and multiplier tier sows. System combinations included one- and five-parity alternatives for both levels and 10-parity options for the multiplier tier. Yearly changes and average phenotypic levels were computed for performance and economic measures. Generally, at the nucleus level, responses to 10 yr of selection for sow and pig performance in five-parity herds were 70 to 85% of response in one-parity herds. Similarly, the highest selection responses in multiplier herds were from systems with one-parity nucleus tiers. Responses in these were typically > 115% of the response for systems with the smallest yearly change, namely, the five-parity nucleus and five-and 10-parity multiplier levels. In contrast, the most profitable multiplier tiers (10-parity) had the lowest replacement costs. Within a multiplier culling strategy, rapid genetic change was desirable. Differences between systems that culled after five or 10 parities were smaller than differences between five- and one-parity multiplier options. To recover production costs, systems with the lowest returns required 140% of market hog value for gilts available to commercial tiers, whereas more economically efficient systems required no premium. This content is only available as a PDF. Author notes 3 Present address: Dept. of Anim. Sci., 4 Kildee Hall, Iowa State Univ., Ames 50011. Copyright © 1992 by American Society of Animal Science

Odenya, W., O.;Elzo, M., A.;Manrique,, C.;McDowell, L., R.;Wakeman, D., L.

doi: 10.2527/1992.7072065xpmid: 1644679

Abstract Amounts of serum calcium, phosphorus, and magnesium at weaning (WCa, WP, and WMg, respectively) and weaning weights (WW) were obtained from 380 Angus (A), Brahman (B), and A × B calves of various expected A and B fractions reared at the Pine Acres Research Station of the University of Florida, Citra from 1989 to 1990. Calves were produced by mating A, .75A, .25B, .5A .5B, .25A .75B, B, and Brangus (.625A .375B) sires to dams of the same expected breed fractions, except for .25A .75B dams. Best linear unbiased estimates (BLUE) of genetic effects, expressed as regression coefficients, were 1) −15.07 ± 13.65 mg of WCa, −11.21 ± 12.07 mg of WP, −1.23 ± 2.99 mg of WMg, and .66 ± 1.18 kg of WW for the difference between A and B additive direct; 2) 9.79 ± 6.94 mg of WCa, −5.72 ± 6.14 mg of WP, 1.64 ± 1.52 mg of WMg, and .52 ± .60 kg of WW for the difference between A and B additive maternal; 3) 242.21 ± 51.56 mg of WCa, 66.67 ± 45.62 mg of WP, 52.16 ± 11.27 mg of WMg, and 22.61 ± 4.44 kg of WW for A × B nonadditive direct; and 4) 373.63 ± 38.44 mg of WCa, 93.96 ± 34.02 mg of WP, 69.90 ± 8.41 mg of WMg, and 36.83 ± 3.31 kg of WW for A × B nonadditive maternal. Nonadditive (A × B) effects were the main factors affecting total (sum of additive plus nonadditive) genetic effects in this multibreed population. Total genetic effects were used to rank breed group of sire × breed group of dam combinations.(ABSTRACT TRUNCATED AT 250 WORDS) This content is only available as a PDF. Author notes 1 Journal Series no. R-01725. The authors thank J. G. Wasdin, W. P. Dixon, and the personnel at the Pine Acres Res. Sta. for their contribution to this research, and D. D. Hargrove and T. A. Olson for comments on this paper. Copyright © 1992 by American Society of Animal Science

Odenya, W., O.;Elzo, M., A.;Manrique,, C.;McDowell, L., R.;Wakeman, D., L.

doi: 10.2527/1992.7072072xpmid: 1644680

Abstract Heritabilities of and genetic, environmental, and phenotypic correlations among serum amounts of calcium, phosphorus, and magnesium and weight at weaning (WCa, WP, WMg, and WW, respectively) were estimated for an Angus (A)-Brahman(B) multibreed herd located at the Pine Acres Research Station of the University of Florida, Citra. Records were obtained from 380 calves produced by mating A, .75A .25B, .5A .5B, .25A .75B, B, and Brangus sires across dams of the same breed groups, except for .25A .75B, during 1989 and 1990. Restricted maximum likelihood procedures were used to compute variance and covariance components. Estimates of heritability were .39 (WCa), .40 (WP), .36 (WMg), and .35 (WW). Estimates of genetic, environmental, and phenotypic correlations were .66, .55, .57 (WCa, WP), .70, .71, .70 (WCa, WMg), 1.00, .86, .88 (WCa, WW), .50, .51, .51 (WP, WMg), .78, .60, .63 (WP, WW), and .86, .73, .75 (WMg, WW). These correlations indicate that serum Ca, P, and Mg could be used in multiple-trait genetic evaluation procedures to help identify animals that require low amounts of these macrominerals for preweaning growth. This may prove advantageous in mineral-deficient regions. This content is only available as a PDF. Author notes 1 Journal Series no. R-01754. The authors thank J. G. Wasdin, W. P. Dixon, and the personnel at the Pine Acres Research Station for their contribution to this research and D. D. Hargrove and T. A. Olson for comments on this paper. Copyright © 1992 by American Society of Animal Science