Post-weaning Gain Research Articles

Interval mapping of growth in divergent swine cross.

A genomic scan of 18 swine autosomal chromosomes was constructed with 119 polymorphic microsatellite (ms) markers to identify quantitative trait loci (QTL) for 11 growth traits in the University of Illinois Meishan x Yorkshire Swine Resource Family. A significant QTL effect was found for post-weaning average daily gain (ADG) between 5.5 and 56 kg of body weight that mapped between markers SW373 and SW1301 near the telomere of Chromosome (Chr) 1 q (SSC1). This QTL effect had a nominal (pointwise) p-value of 0.000007, a genome wide p-value of 0.012, and accounted for 26% of the F2 phenotypic variance. The same chromosome region also had significant effects on ADG between birth and 56 kg body weight (p-value =. 000227), and on ADG between 35 and 56 kg (p-value =.00077). These observations suggest that a significant QTL for post-weaning growth resides on SSC1.

Genetic parameters for growth traits in Suffolk and Polypay sheep

Genetic parameters for growth traits in Suffolk and Polypay sheep were estimated using U.S. National Sheep Improvement Program data. Records on 12,814 Suffolks from 65 flocks and 9,028 Polypays from 39 flocks were used. Heritability ( h 2) estimates for weaning weights (WW) at 30, 60, 90, and 120 d in Suffolks were 0.16, 0.14, 0.21, and 0.55, respectively; h 2 for WW at 30, 60, and 90 d in Polypay were 0.07, 0.08, and 0.07. For postweaning gain (PWG), h 2 for models with and without maternal effects were 0.14 and 0.21, respectively, in Suffolk and 0.13 and 0.22, respectively, in Polypay. Maternal effects (additive+permanent environmental) accounted for 16 to 23% of variation in WW through 90 d of age but for 6% or less of the variation in 120-d WW and PWG. Correlations between WW at different ages were uniformly high. Postweaning gain had significant additive genetic correlations with WW at 30 d (1.00) and 60 d (0.69) in Suffolks but was not significantly correlated with 60 d WW in Polypay (0.41). Residual correlations between WW and PWG were small and not significant. Evidence for a modest antagonistic relationship between additive direct and maternal effects on WW was observed in both breeds.

Factors Affecting Body Weight, Scrotal Circumference Hip Height and their Relationships with Birth Weighl Preweaning and Postweaning Gains in Young Bulls

Morsy, N.H.A., Hassan, H.A., Makarechian, M. and El-Feel, F.M.R. 1998. Factors affecting body weight, scrotal circumference, hip height and their relationships with birth weight, preweaning and postweaning gains in young bulls. J. Appl. Anim. Res., 13: 81–92. Records of 125 bulls from two synthetic breed groups; Beef Synthetic (SYX, n = 64) and Dairy Synthetic (DSX, n = 61) fed two levels of energy (high concentrate, 85% grain or low concentrate, 55% grain) throughout 140-d feedlot test period were used in this study. The records were analysed by stepwise regression analysis to study the relative influence of birth weight (BW), preweaning daily gain (PWG) und postweaning daily gain (POG) on final body weight (WT), scrotal circumference (SC) and hip height (HHT) at the end of feedlot test. In addition the effects of the level of energy and breed group on the above relationships were investigated The data were analyzed by the general linear model to study the fixed effects of energy level, breed group and their interactions on final WT, SC and HHT. The results indicated that POG had the maximum associations with final WT and SC, while PWG had the highest association with HHT. The combination of PWG and POG provided the best prediction equations for final WT and SC. BW had the lowest associations with SC, HHT and final WT. The level of energy did not affect the regression coefficients of final WT, SC and HHT on BW, PWG and POG. The effects of breed group on the regression coefficients were not significant except for the regression of HHT on PWG. The level of energy in feedlot diet was a significant (P<0.01) source of variation for the growth measurements of WT, SC, HHT and their changes in feedlot test. Breed group did not have any significant influence on the growth measurements. The results indicated that in general final feedlot weight and testicular size could be predicted fairly accurately from the growth measurements of bulls from birth to yearling regardless of the level of energy and breed group effects on these relationships.

Additive and nonadditive genetic variability for growth traits in the Turipaná Romosinuano-Zebu multibreed herd.

Intrabreed additive genetic, environmental, and phenotypic variances and covariances for Romosinuano (R) and Zebu (Z), as well as interbreed nonadditive genetic variances and covariances (sire x breed-group-of-dam interactions), for birth weight (BWT), weaning weight (WW), and postweaning gain (GW) were computed using a Romosinuano-Zebu multibreed data set from the Turipaná Experiment Station in Colombia. Covariances were estimated with a sire-maternal grandsire model, using a multibreed REML procedure. The computing algorithm was a generalized expectation-maximization (GEM) algorithm. This algorithm yields no asymptotic standard errors as part of its computations. Because of the small size of the data set (2,546 calves), these REML covariance estimates should be viewed with caution. Estimates of intrabreed heritabilities were similar to the ratios of interbreed nonadditive to phenotypic variances (interactibilities) for direct and maternal effects of the growth traits evaluated in this study. Intrabreed heritability estimates for BWT, WW, and GW direct genetic effects were .16, .09, and .14, for R and .24, .10, and .14 for Z. Corresponding heritability values for maternal effects were .18, .09, and .23 for R and .14, .13, and .07 for Z. Interactibility estimates were .21, .05, and .12, for direct and .26, .04, and .11, for maternal BWT, WW, and GW. Negative correlations between additive maternal weaning weight and direct and maternal postweaning gain, as well as between environmental weaning weight and postweaning gain, suggested that there was compensatory postweaning gain in this herd. Estimates of genetic variation and predictions of expected progeny differences showed that Romosinuano animals competed well against Zebu and RZ crossbred animals under the tropical environmental conditions at Turipaná.

Plasma Cholecystokinin-8 in Pigs With Divergent Genetic Potential for Feed Intake and Growth

Plasma cholecystokinin-8 (CCK-8) was studied in pigs with divergent genetic potential for feed intake. Differences in feed intake resulted from selection for either fast (line F) or slow (line S) postweaning gain. The hypothesis was that the relatively lesser feed intake in S versus F may be attributable, in part, to greater circulating concentrations of the putative satiety hormone CCK-8. In Experiment 1, barrows from F ( n = 23) and S ( n = 19) were used to determine changes in CCK-8 associated with ad libitum feed consumption. Blood samples were collected after overnight feed deprivation, then periodically during a 2-hr feeding period. Averaged across sampling times, concentration of CCK-8 tended to be greater (P = 0.07) in S (6.70 pmol/l) than in F (5.06 pmol/l). Concentration of CCK-8 per unit of feed consumed (CCK-8/cumulative feed intake) was greater (P < 0.01) in S than in F during the first 30 min of the feeding period. In Experiment 2, plasma concentrations were determined for nine pairs (F, S) of the same barrows allowed an amount of feed equal to the previous ad libitum intake of the S barrow in the pair. Averaged across times, the difference between CCK-8 concentrations of S (11.65 pmol/l) and F (7.94 pmol/l) barrows was not significant (P = 0.18). A greater concentration of CCK-8 per unit of feed consumed in S than in F supports the hypothesis that satiety effects of CCK-8 may play a role in genetic differences between the lines for feed intake.

Estimation of the dominance variance for postweaning gain in the U.S. Limousin population.

The objective of this study was to estimate the dominance variance for postweaning gain in Limousin cattle. Data included 215,326 records of postweaning gain from 205 to 365 d, provided by the North American Limousin Foundation. Parental dominance subclasses were formed and related using the method of Hoeschele and VanRaden. Variance components were estimated using Method R based on six samples of 50%. Fixed effects in the model included contemporary group and covariates for inbreeding and breed composition (percentage Limousin). Heterozygosity was negatively correlated with breed composition (< -.99) and was therefore not included in the model. Two types of contemporary groups used as original groups from the National Cattle Evaluation were partially based on breed composition. Original contemporary groups that were too homogeneous for breed composition were replaced by herd-year-sex classes. Two models were used with the two data sets. Model 1 contained the fixed effects described above and an additive genetic effect. Model 2 included a dominance effect in addition to the effects contained in Model 1. In total, four combinations of contemporary group x model were used. Dominance variance was computed as being four times the estimated parental subclass variance. Estimates for inbreeding depression and breed composition (percentage Limousin) were all small and not greatly affected by inclusion of dominance effects or changes in contemporary groups. Estimates of the additive variance (expressed as percentage of the phenotypic variance) were only slightly affected, with values between 20 and 21%. Dominance estimates were highly affected when passing from original (10%) and to alternative contemporary groups (18%). Such large values may indicate that dominance is important for postweaning gain. Results showed the advantage of an individual dominance approach based on sire-dam combinations; therefore, expected gains through the use of specific combination ability as a part of the mating selection criteria for growth might be high.

Heterosis losses resulting from incorrect matings in a three-breed rotational crossbreeding system in pigs.

Losses in individual heterosis were estimated using performance records from 11,700 pigs, 959 litters, and 377 pens of pigs from a three-breed rotational crossbreeding system. Three types of rotational crossbred sows were produced using the Duroc, Landrace, and Yorkshire breeds. Twenty-nine Duroc, 27 Landrace, and 25 Yorkshire boars were mated to 275 sows to produce pigs with theoretical levels of breed heterozygosity of 85.7, 71.4, or 42.9% depending on the genetic composition of the sows and boars. Orthogonal polynomials for unequally spaced levels were used to partition sum of squares for individual heterozygosity into linear and quadratic responses. There was a linear decline in 56-d litter weight (-.222 kg; P < .01) for each 1% decrease in heterozygosity. Responses for pig weight at 56 d (-.02 kg; P < .001) and age at 105 kg (.12 d; P < .001) were linear for each 1% decrease in heterozygosity. Likewise, post-weaning average daily gain ( -.0004 kg/d; P < .05) and feed conversion (-.0001; P < .01) responses were linear for each 1% decrease in heterozygosity. There were linear responses for survival rates of pigs born alive to 21 d (-.089%; P < .01), alive from 21 to 56 d (-.025%; P < .05), alive from 56 d and to 105 kg (-.042%; P < .05), and from birth to 105 kg (excluding stillborn pigs) (-.129%; P < .001) for every 1% decline in heterozygosity from 85.7 to 42.9%, respectively. Quadratic responses were not important for any of the traits examined (P > .05). Decreased productivity, resulting from decreased heterozygosity, can be expected when three-breed rotational crossbred sows are mated to boars from the wrong breed.

Genetic parameters for lamb weight at different ages and wool production in Baluchi sheep

AbstractThe Baluchi breed is the most common native breed of Iran adapted to harsh environments in the eastern parts of the country. The data used in the present study, collected from two research flocks at the Abbasabad sheep breeding station in north-east Iran, included 20 534 animals descended from 363 sires, 5992 dams, 282 maternal grandsires, and 2865 maternal granddams during the period 1966 to 1989. The traits recorded were: birth weight (BW), weaning weight (WW), weight at 6 months (W6), weight at 12 months (YW), pre-weaning gain (WG), post-weaning gain (PWG), lamb fleece weight (LFW), ewe fleece weight sheared before first joining (FW1) and adult ewe fleece weight (FW). Genetic parameters, estimated with restricted maximum likelihood and a two-trait animal model, were similar in the two flocks. Direct heritabilities for the various body weight traits were moderate and varied between 0·13 and 0·32, while the maternal heritabilities were low and varied between 0·01 and 0·12. Direct and maternal genetic correlations between WW and weights at later ages were moderate to high (0·59 to 0·96). Direct heritabilities of weight gain measures varied between 0·12 and 0·19, while no significant maternal influence on either of these weight gain measures could be detected. The estimates of direct genetic correlation between WG and PWG were positive and varied between 0·54 and 0·74, while negative maternal genetic correlation (0·17 on average) between WG and PWG was detected. For LFW, direct heritability was low and no maternal heritability could be shown. For FW1, both direct and maternal genetic influences were demonstrated (0·07 to 0·26). Direct genetic correlation between LFW and FW1 was very low and close to zero, while maternal genetic correlation was positive and relatively high (0·72 on average). The relative contributions to phenotypic variance from variance components due to common environmental effects ranged from 0·01 to 0·15 for all traits. The repeatability of FW was low (0·03 to 0·12).

Sex‐specific genetic parameters for weaning and post‐weaning gain in Swedish beef cattle under field conditions

Sex‐specific variance components for weaning gain (WG) and post‐weaning gain (PWG) in Swedish beef breeds were estimated by restricted maximum likelihood. The WG model allowed for an animal effect, both genetic and environmental maternal effects, and a genetic covariance between direct and maternal effects. There were differences between breeds as well as between sexeswithin breed in the relative mangitude of the heritability of directeffects (0.10–0.32), maternal heritability (0.05–0.31), and maternal environmental effects (0.03–0.30) for WG. The direct‐maternal genetic correlation was moderately negative, on average −0.4. The genetic correlation between direct effects observed on males and females were in most cases moderately to highly positive, on average 0.7, but varied for the larger breeds between 0.6 and 0.9. The correlations between sexes for maternal effects, both genetic and environmental, were in all cases highly positive (0.7–1.0). Post‐weaning gain was analysed under a model with animal effects being the only random effect. There were some differences between breeds and sexes within breed for direct heritability (0.05–0.36). The genetic correlations between direct effects observed on males and females ranged between 0.4 and 1.0. It was suggested to apply a uniform multi‐trait evaluation system for all breeds, with sex‐ and breed‐specific parameters.

Genetic parameter estimates for growth and fleece characteristics in Targhee sheep.

Weaning weights at 60 (WW60) and 120 d (WW120), 60- to 120-d postweaning gains (PWG) for lambs weaned at 60 d, 120- to 365-d postweaning gains (YG) for lambs weaned at 120 d, fleece weights (FWT), and fiber diameters (FD) from 20 Targhee flocks were used to estimate parameters required for multiple-trait genetic evaluation. Flocks from western states (n = 10) recorded primarily WW60 (n = 1,762), WW120 (n = 5,961), YG (n = 2,388), FWT (n = 2,824), and FD (n = 2,000). Eastern flocks primarily recorded WW60 (n = 1,754) and PWG (n = 1,237). Heritability estimates were .01 for WW60 (.00 for western flocks and .07 for eastern flocks), .10 for WW120, .33 for PWG, .20 for YG, .41 for FWT, and .58 for FD. Additive maternal and maternal permanent environmental effects as a proportion of phenotypic variance were .10 and .09, respectively, for WW60 and .05 and .08 for WW120. In western flocks, maternal additive and permanent environmental effects on WW60 and WW120 were highly correlated (> .81), whereas WW120 and YG had a small positive additive genetic correlation (.19) but a negative residual correlation (-.34). Fleece weight had a genetic correlation of .50 with WW120 and YG. Supplemental analyses suggested that the observed genetic relationship between fleece weight and weaning weight arose primarily from a genetic association between additive direct genetic effects on fleece weight and additive maternal effects on weaning weight. Fiber diameter was nearly independent of body weights but had an undesirable additive correlation of .51 with FWT. In eastern flocks, WW60 and PWG had an additive correlation of .71 and a residual correlation of .15.

Effect of age and pattern of gain on induction of puberty with a progestin in beef heifers.

Crossbred heifers (n = 75) fed for rapid (R; .82 kg/d) or slow-then-rapid (SR; .41 kg/d for 90 d then .82 kg/d) postweaning gain were used to examine the effects of age or pattern of gain on induction of puberty by a progestin. At 9.5, 11.0, and 12.5 mo of age, 12 prepuberal heifers from each growth treatment received progestin (a 6-mg Norgestomet implant for 10 d) or control treatments. Induction of puberty, LH secretory profiles, and ovarian follicular characteristics were assessed in Norgestomet-treated and control heifers. Body weights of R heifers were greater (P < .01) than those of SR heifers at all ages. At 12.5 mo, more Norgestomet-treated heifers exhibited a puberal estrus within 5 d after implant removal compared with controls (82% vs 9%, respectively), but Norgestomet did not induce puberty at 9.5 or 11 mo of age (progestin x age, P < .05) in heifers of either gain pattern. Norgestomet increased (P < .01) LH pulse frequency at all ages, whereas Norgestomet increased only mean LH concentrations at 12.5 mo of age (progestin x age, P < .03). Norgestomet treatment altered (P < .01) ovarian follicular characteristics at all ages. Gain pattern did not affect (P > .1) LH secretory profiles, ovarian characteristics, or induction of puberty by Norgestomet. We conclude that progestins induce puberty by hastening the normal cascade of endocrine and ovarian events associated with spontaneous puberty. Furthermore, age, but not pattern of gain, seems to be the critical factor influencing the efficacy of progestins to induce puberty in heifers.

Variation Within and Between Groups of Genetically Identical Nuclear Transfer Brangus Bulls and Steers for Growth Measures Taken Over Time

A study was conducted to determine the variability within and among groups of beef cattle produced through nuclear transfer (NT) for postweaning growth of various body measurements. Four groups of male, Brangus, second-generation NT calves (four to six per group) were used in this project. At weaning (6 to 7 mo) two randomly selected animals in each group were surgically castrated and subsequently maintained under simulated feedlot conditions. The remaining bulls were maintained under standard 140-d postweaning gain test conditions. Beginning at weaning, BW, linear measurements of hip height (HH), body length (BL), rump length (RL), rump width (RW), shoulder width (SW), round mass (RNMS), metacarpal length and circumference (MCL and MCC), metatarsal length and circumference (MTL and MTC), and ultrasonic measurements ofbackfat thickness (BFT), Longissimus muscle area (LMA), Longissimus muscle depth (LMD), body wall thickness (BWT), rump fat thickness (RFT), and rump muscle depth (RMD) were obtained on each animal at 28-d intervals, until 16 to 17 mo of age. Both linear and quadratic models were used to determine the changes in these traits over time; however, the linear models appeared to best describe growth in both sexes. Linear regression coefficients were obtained for each trait by animal, and these were analyzed partitioning sex, genotype, and genotype x sex as sources of variation. The interaction effect of genotype by sex was not significant (P>0.10) for any of the measures and was dropped from the model. Genotype was significant (P<0.01) for measures of BW, HH, BL, RW, SW, RNMS, MCC, BFT, and BWT, whereas sex was significant (P>0.01)for BW, BL, MCC, BFT, and RFT. Over all traits, the percentage of variation attributable to genotype ranged from 19.8 to 96.2%. When traits lacking significance of the genotype effect were omitted, genotype accounted for 86.7 to 96.2% of the total variation.

Effect of preweaning feeding of pasteurized and nonpasteurized milk on postweaning weight gain of heifer calves on a Californian dairy

The effect of preweaning feeding of pasteurized colostrum and pasteurized waste milk on postweaning performance of dairy heifers on a dairy in the Central Valley of California was investigated as an extension of a clinical trial examining the effect of preweaning growth and morbidity on performance at weaning. Of the 150 heifer calves originally enrolled in the field trial, 115 calves (59 treatment, 56 controls) were followed to about 6 months of age, during which time their weights were measured. After weights were adjusted for several potential risk factors and effect modifiers, calves fed pasteurized colostrum and pasteurized waste milk were 3.7 kg heavier at 180 days of age than those fed nonpasteurized colostrum and nonpasteurized milk.

Increased postweaning gain of beef heifers enhances fertility and milk production.

Four hundred fifty-two (452) weanling heifer calves (192 +/- 23 kg) were used to determine the effect of postweaning weight gain on subsequent reproductive performance and lactation. Heifers grazed stockpiled tall fescue pastures and were fed a high (H) or low (L) amount of ground corn supplement (3.68 and 2.99 kg/[animal.d], respectively) during a postweaning treatment period of 136 d. Postweaning gain of heifers receiving L and H was .43 and .62 kg/d, respectively. These treatments resulted in a range of postweaning gain from .07 to 1.17 kg/d. Heifers receiving H were 26 kg heavier (P < .01), had .15 cm more fat thickness (P < .01), 5% greater pelvic area (P < .01), and tended (P = .08) to have greater hip height than heifers receiving L at yearling. More heifers in the H group were pubertal before the start of the breeding season (70.9 vs 61.3%) (P < .05). No significant differences were found in pregnancy rate or first-service calving rate between treatment groups. Mean milk production was 10% greater for H- than for L-fed heifers (P < .01) and resulted in heavier calves at 54, 104, and 153 d of age (P < .05). Regression analysis revealed that as weaning weight and postweaning gain increased, so did the probability for reaching puberty before the breeding season. Increasing weaning weight also increased the probability of calving to the first AI service. As heifer weaning weight and postweaning gain increased, subsequent milk production also increased. Increasing postweaning weight gain of lightweight heifers from .07 to 1.17 kg/d increased both reproductive and lactation performance.

Genetic parameter estimation of postweaning gain, feed intake, and feed efficiency for Hereford and Angus bulls fed two different diets

Postweaning gain performance and individual feed intake on 271 Hereford and 263 Angus bulls were recorded during three 168-d test periods from 1984 to 1986. Each breed was composed of two lines and within each breed bulls were fed either a high-energy (HD) or a medium-energy (MD) diet. Energy intake was partitioned into energy for maintenance and growth based on predicted individual animal requirements. Estimates of heritability were obtained using Restricted Maximum Likelihood with an individual animal model including fixed effects of year, diet, and covariates of initial weight and backfat change by breed and with line effects for overall data. Bulls fed the HD grew faster and had higher metabolizable energy intake per day (MEI), residual feed consumption (RFC), and gross and net feed efficiency (FE and NFE) (P < .001) than those fed the MD. Estimates of heritability for Hereford and Angus bulls, respectively, were .46 and .16 for 200-d weaning weight (WWT), .16 and .43 for average daily gain (ADG), .19 and .31 for intake per day (MEI), .43 and .45 for yearling weight (YWT), .07 and .23 for RFC, .08 and .35 for FE, and .14 and .28 for NFE. Genetic and phenotypic correlations between MEI and ADG, MEI and YWT, ADG and YWT, ADG and FE, YWT and FE, and FE and NFE were moderately to highly positive for both breeds. Negative genetic and phenotypic correlations between NFE and ADG show partial correlations of FE with ADG after accounting for energy requirement for maintenance. Residual feed consumption was negatively associated with YWT, FE, and NFE, indicating a possible genetic improvement.

Performance and genetic trends in purebred Simmental for regions of the United States.

A study was conducted to determine whether differences in regional performance could be attributed to different selection goals among Simmental breeders. Using data obtained from the spring 1993 National Simmental Cattle Evaluation, breeders were identified by region of the country as defined by the American Simmental Association: South Central (SC), North Central (NC), West (W), and East (E). Animals included in the analysis were at least 87.5% Simmental and from breeders who recorded data every year from 1978 to 1991. The number of breeders and animals from each region were 154 and 62,830 in the SC, 260 and 139,053 in the NC, 102 and 57,434 in the W, and 143 and 39,786 in the E. Phenotypic, genetic, and environmental trends were estimated in each region for birth weight (BWT), weaning weight (WWT), and postweaning gain (PWG). The growth genetic trends were increasing at similar rates in the regions over time. For maternal milk (MMK), breeders in the NC and W decreased maternal breeding value slightly compared to SC and E breeders. For BWT, the average environmental trends ranged from .0 kg/yr in the SC to .11 kg/yr in the NC. The regional WWT environmental trend ranged from 1.4 to 2.2 kg/yr. The environmental trends for PWG varied from -3.1 kg/yr in the SC to .3 kg/yr in the W. Selected parents had higher estimated breeding values than their birth year averages each year for BWT, WWT, and PWG. The average maternal breeding values for selected parents were essentially zero compared with their birth year averages.(ABSTRACT TRUNCATED AT 250 WORDS)

Post-weaning gain of calves from first-cross and reciprocal back-cross cows

Data on post-weaning gains and final test weights are reported for 2010 Limousin-sired steer and heifer calves from cows of 15 different F1 cross and back-cross breed types incorporating Charolais, Simmental, Hereford, Angus and Shorthorn breeding. Calves representing all 15 dam breed types were born and weaned under semi-intensive management at Brandon, Manitoba, then finished there on a self-fed all-concentrate diet. A subset representing eight dam breed crosses was born and weaned under extensive range management at Manyberries, Alberta, then fed at Lacombe, Alberta, on a lower energy diet of silage and concentrate mixed and fed to appetite in bunks. A comparison of common breed types revealed that the Brandon calves were lighter at weaning but gained more rapidly in the post-weaning test than the Manyberries/Lacombe calves. Under the Lacombe feeding regime, there were no significant differences in rate of gain on the feedlot test, but progeny of breed types containing some Simmental breeding generally reached a higher final weight than progeny of Hereford × Angus cows because of differences in weight at the beginning of the test. Under the higher energy feeding regime at Brandon, progeny of breed types containing Charolais or Simmental generally gained faster and attained higher final weights than progeny of Hereford × Angus cows. Progeny of Charolais × British and Simmental × British F1 cross cows generally performed as well as, or better than, the progeny of either backcross. Key words: Beef cattle, post-weaning gain, crossbred dam, back-cross dam, European cross

Evaluation of line and breed of cytoplasm effects on performance of purebred Brangus cattle.

Substantial differences between reciprocally crossed Bos taurus x Bos indicus calves for birth, weaning, and yearling weights have been reported. To determine whether cytoplasmic inheritance is responsible for a portion of these differences, field records for birth and weaning weight (n = 7,353) and postweaning average daily gain (n = 2,746) from registered Brangus calves were analyzed. An animal model that included maternal effects was fit for each trait. Breed of cytoplasmic origin was fit as a fixed effect and coded as Angus, Brahman, or unknown. Cytoplasmic line within each breed of origin was treated as a random effect. Variance components for random effects were estimated using derivative-free REML procedures. Line of cytoplasm accounted for less than .002% of the phenotypic variance in all three traits. Estimates for cytoplasmic breed of origin effects were small in magnitude, and contrasts tested (Angus vs Brahman and Angus vs Unknown) were not significant (P > .10). Estimates of heritability of direct (maternal) effects were .36 (.20), .41 (.27), and .21 (.08) for birth weight, weaning weight, and postweaning average daily gain, respectively. Estimates of genetic correlations between direct and maternal effects ranged from -.27 for postweaning average daily gain to -.58 for birth weight. No evidence for breed or line within breed of cytoplasmic origin effects was detected in these data.

Additive genetic groups for animals evaluated in more than one breed association national cattle evaluation.

Additive genetic groups were included in the 1993 Red Angus Association of America national cattle evaluation for phantom parents of individuals who were registered with the American Angus Association (AAA). Genetic groups were formed for each component in two multiple-trait evaluations in which all animal effects were fit. Additive direct effects were included for birth weight, weaning weight (WW), and milk (MILK). In a second analysis the additive direct effect of 160-d postweaning gain was analyzed with WW and MILK. Of the 387,665 animals, 50,838 had at least one phantom parent assigned to one of five genetic groups fit as fixed effects for each additive component. Of these 50,838 animals, 1,324 were identified as registered with the AAA. An average of 906 animals per component had an AAA EPD available. Animals with a known AAA EPD were designated into one of three groups of equal numbers based on AAA EPD for each component (1 = low, 2 = medium, 3 = high). Animals in the fourth genetic group were those registered with the AAA but with no EPD available for the component. The fifth genetic group included all other animals with phantom parents. Grouping on AAA EPD allowed for EPD on animals out of parent(s) registered with the AAA to be more closely aligned to the AAA EPD because they were regressed from the group solution instead of zero. Grouping based on EPD from another NCE should be considered in the production of multibreed EPD.

Cumulative selection and genetic change for weaning or yearling weight or for yearling weight plus muscle score in Hereford cattle.

Selection in three lines of Hereford cattle for 1) weaning weight (WWL), 2) yearling weight (YWL), and 3) an index of yearling weight and muscle score (IXL) was studied. Remnant foundation cows and semen from seven foundation sires were used to establish an unselected control line for the last 11 yr of the experiment. Performance data collected over a 23-yr period on birth weight (BWT), weaning weight (WWT), postweaning gain (PWG), yearling weight (YWT), muscle score (MSC), and an index (IDX) giving equal weight to standard deviations of yearling weight and muscle score were analyzed. Generation interval of midparents was about 4.16 yr in each selected line. Sire and dam selection differentials, in standard deviation units per generation, for primary criteria were, respectively, 1.59 and .33 for WWT in WWL, 1.75 and .25 for YWT in YWL, and 1.42 and .25 for IDX in IXL. Components of direct and maternal genetic variances, direct-maternal covariance, and dam permanent environmental variance were estimated by REML. The average annual response of males and females in actual units for each trait in WWL, YWL, and IXL was, respectively, BWT, .22, .24, and .27 kg; WWT, .98, .63, and 1.26 kg; YWT, 2.43, 2.64, and 3.44 kg; and MSC, .053, .009, and .104 scores. Average selection responses in BWT, WWT, YWT, MSC, and IDX per unit of primary criteria in each selection line (all in standard deviation units) were .22, .20, .31, .10, and .24 for WWT in WWL; .23, .12, .32, .04, and .21 for YWT in YWL; and .27, .22, .40, .20, and .36 for IDX in IXL. Responses in bold type are realized heritability and others are correlated responses. Realized genetic correlations were .78 for WWT and YWT, .87 for WWT and IDX, and .86 for YWT and IDX. Responses for all traits in IXL were greater than in other selected lines.