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Crossbred steers (n = 136) were used to assess breed differences in growth performance, carcass characteristics, fatty acid composition (total lipids and phospholipids), and palatability attributes of longissimus muscle. A multiple regression model was applied to crossbreeding data to estimate genetic differences between Simmental and Red Angus at the same level of backfat finish (10 mm). Simmental spent 71 more (P [is less than] 0.001) days on feed to acquire the same degree of backfat thickness as Red Angus, had heavier (P [is less than] 0.001) slaughter weights, larger (P = 0.002) longissimus muscle area, and increased (P = 0.023) lean yield. Average daily gain did not differ (P = 0.297) between breeds. Simmental were less (P = 0.012) efficient in converting feed to gain than Red Angus. Generally, there were few breed differences in palatability attributes for longissimus and semitendinosus muscles, with the exception of increased (P [is less than] 0.05) beef flavor scores for Simmental beef vs Red Angus beef across both muscles. For total lipids, concentrations of myristoleic acid (14:1), palmitoleic acid (16:1), and vaccenic acid (18:1n-7), along with n-6 to n-3 fatty acid (n-6:n-3) ratio, were greater (P [is less than] 0.05) in Simmental than Red Angus. In contrast, concentrations of margaric acid (17:0), eicosapentaenoic acid (20:5n-3), and total n-3 polyunsaturated fatty acids (n-3 PUFA) were greater (P [is less than] 0.05) in Red Angus than Simmental. For phospholipids, Simmental had lower (P [is less than] 0.05) amounts of 20:5n-3, docosahexaenoic acid (22:6n-3), and n-3 PUFA, with a greater (P = 0.017) n-6:n-3 ratio. Activity of [[Delta].sup.9]-desaturase enzyme in the conversion of palmitic acid (16:0) to 16:1 was greater (P = 0.001) in total lipids from Simmental as compared with Red Angus. A genetic basis for fatty acid differences is suggested, although the biological and practical significance needs to be demonstrated. Key Words: Beef Cattle, Breeds, Carcass Composition, Fatty Acids, Longissimus Dorsi, Palatability

Summary: An assumption in aquaculture of Atlantic salmon is that male and female growth within families is perfectly genetically correlated. That is, families would rank identically if based on male growth only or female growth only. Also, growth in freshwater and sea water is assumed to be highly correlated between males and females within families. However, structural analysis of the DNA of Atlantic salmon has found that the linkage maps of females differ significantly from that of males. Genetic variability for any trait measured on females could be greater or lesser than on males. Thus, male and female growth might be considered as separate traits giving rise to families ranking differently depending on gender. A multiple trait family model for weight and length at 3 years of age in Atlantic salmon according to gender was applied to data on North American Atlantic salmon obtained from the Oak Bay Hatchery in New Brunswick, Canada. Genetic correlations between male and female growth in both freshwater and sea water were estimated by Bayesian methods. The estimates support the possible existence of gender dimorphism in North American Atlantic salmon for growth traits. [ABSTRACT FROM AUTHOR]

Abstract: Our objective was to detect single nucleotide polymorphisms (SNPs) associated with resistance to the salmon louse in the Saint John River aquacultural population of North American Atlantic salmon using estimated breeding values (EBVs) and 6K genotypes from the parent‐generation and lice count phenotypes from the challenged, but ungenotyped, offspring‐generation. In 2011 and 2012, we challenged recent smolts with approximately 100 copepodids each. Fish were euthanized once the lice reached the chalimus stages and lice count, sex, tank and salt water weight were recorded. We used a multiple trait model to estimate breeding values for the parent‐generation using their own fresh water weights and the salt water weights and lice counts of the offspring‐generation. Salmon lice count heritability for untransformed and transformed data was 0.17 and 0.29 respectively. Two different genome‐wide association study methods were compared: (i) forward multiple linear regression and (ii) a mixed linear model using principal components to correct for population stratification as implemented in the egscore function of GenABEL. The two methods detected different SNPs located on different chromosomes. The multiple regression method incorporated 70 SNPs found on chromosomes 2, 7, 9, 12, 14, 15, 21, 22, 1p/23, 24. Many SNPs entered into the forward multiple regression are likely to be false positives from not correcting for the observed population stratification and cryptic relatedness. In contrast, the mixed linear model identified only two SNPs, one on chromosome 1p/23 (6.9%) and one on chromosome 1q (6.1%) consistent with louse‐resistance being a quantitative trait. [ABSTRACT FROM AUTHOR]

Variance components were estimated for 2 body size traits of Atlantic cod at 2 time points. Wild-caught founders from 3 regions off eastern North America were spawned and their progeny were reared at 2 locations in 2 consecutive years. Full-sib families (n = 148) were kept separate until individuals achieved a size large enough to be tagged. At that time (220 d of age), BW and length of 47,637 offspring from 90 sires and 89 dams were recorded. The juveniles were then transferred to sea cages at 3 sites, where they grew further for more than a year. A second set of measurements was collected on 11,839 fish (634 d of age). Dispersion parameters were estimated using REML in bivariate analyses. Models included fixed degree-days (covariate), year x location subclasses, and genetic groups composed of connected families within region of origin. Random factors were animal (additive genetic effects), considering known relationships among the fish; dam (maternal effects); and family (effects common to full-sibs). At tagging, heritability estimates were small to moderate (0.15 and 0.24 for BW and length, respectively; SE = 0.14), similar to or somewhat larger than the proportions of variation ascribed to dams and families (11 to 16%). Later, heritability estimates were greater (0.27 ± 0.08 and 0.31 ± 0.09 for BW and length, respectively), whereas darn and family variance proportions were very small (3 to 4%). Omitting maternal or family components substantially increased the values obtained for heritability at both time points. At the later point, failure to account for maternal effects inflated heritability estimates by about 24% for both traits; ignoring family effects had double the impact. These effects persisted even though endogenous feeding lasts only a couple of weeks in this species and the fish had been pooled since tagging. Discarding data from parents that were completely confounded with their mates decreased heritability estimates slightly (by 0.04, for both traits) at the second point, with no loss of precision despite 15% fewer records and 34% fewer parents; the improved design seemed to have more fully disentangled the additive genetic effects. Estimates of genetic correlations between traits and between time points were very large (>0.89). The results imply that genetic variation exists for body size of cod at both stages. Poor data structure and inadequate models can potentially lead to overstatement of heritability, and thus also of the predicted selection response. [ABSTRACT FROM AUTHOR]

Presents a study which evaluated the influence of three production systems (intensive, extensive, and intermediate) on litter size, lamb growth, and carcass characteristics in sheep. Materials and methods; Results and discussion; Implications.

Several features of data structure were studied to determine their effects on variance of prediction error and accuracy of evaluation. Assigning 50 sires with progeny to a portion of 10, 25, or 50 contemporary groups according to a sire model with and without additive genetic relationships, or assigning 50 individuals with their own record to one of 2, 5, or 10 contemporary groups according to an animal model, established the designs. Additive genetic relationships were based on stimulated pedigree files. Low, medium, and high heritabilities (.10, .25, and .40, respectively) were considered. The inverse of coefficient matrices gave variances of prediction error. Populations derived from the sire model (n = 8,100) consisted solely of progeny-tested individuals. For them, number of progeny had a quadratic (P < .001) association with variance of prediction error (R2 = 56 to 82%), which selection index theory underestimated when there were < 100 progeny. Number of direct connections (sires of contemporaries of progeny) together with progeny numbers explained variance of prediction error (R2 = 76 to 90%) better than either variable alone. With no direct connections, variance of prediction error was maximum unless a relative with at least one direct connection itself existed. Populations derived from the animal model (n = 900) consisted of animals with designs representing a progeny test, performance test, or a combination of both (34, 41, and 25% of the total, respectively). For performance-tested animals (without progeny), number of genetic connections was not highly correlated with variance of prediction error (r = -.10, across h2), but relatives prevented zero accuracies when contemporary groups consisted of one animal. Even when animals had no relatives, more than five members per contemporary group gave little additional increase in accuracy. For other than a progeny test, designs were complex, being described by many variables that were confounded.

Variance components were estimated for lamb weight at birth, 50 d, and 100 d of age. Data from the Canadian flock recording program for lambs born in 1977 to 1991 for Hampshires (n = 6,395) and Polled Dorsets (n = 29,204) and 1982 to 1991 for Romanovs (n = 3,432) were studied. Observed weights were pre-adjusted for the effects of age of dam, sex of lamb, birth-rearing type, month or quarter of year of birth, parity-lambing interval, and age of dam at first lambing, using estimates derived from a fixed effects model including contemporary groups plus these factors. Pre-adjusting for nuisance variables reduced the number of equations in the model for variance component estimation. A single-trait animal model with derivative-free restricted maximum-likelihood procedures was used. Random effects were additive direct and maternal genetic, litter (common environmental), and error. An alternate model excluded maternal genetic effects. Estimates of litter variance as a proportion of phenotypic variance were of moderate size (.12 to .43) and consistent across breeds and models. The mean correlation between direct and maternal genetic effects, across traits and breeds, weighted by the number of animals, was -.40 (SE = .15). The maternal genetic variance or direct-maternal genetic covariance component, or both, was different from zero (P < .05) for all traits in Hampshires and Polled Dorsets, suggesting that maternal effects were important for weight of lambs even at 100 d of age. Estimates of direct heritability ranged from .05 to .45, varying across traits, breeds, and models.(ABSTRACT TRUNCATED AT 250 WORDS)