Maternal age and maternal environment affect stress reactivity and measures of social behaviour in laying hens

Maternal effects can shape the phenotypes of offspring, but the extent to which a layer breeder’s experience can affect commercial laying hens remains unclear. We aimed to investigate the effects of maternal age and maternal environment on laying hens' behaviour and stress response. In our first experiment (E1), commercial hybrid hens were reared either in aviary or barren brooding cages, then housed in aviary, conventional cages or furnished (enriched) cages, thus forming different maternal housing treatments. Hens from each treatment were inseminated at three ages, and measures of response to manual restraint and social stress were assessed in offspring. In experiment 2 (E2), maternal age effects on offspring's stress response were further investigated using fertile eggs from commercial breeder flocks at three ages. In E1, maternal age affected struggling and corticosterone during manual restraint, feather pecking and pulling and comb wounds. Additionally, maternal rearing and housing in aviary systems showed positive effects on measures of behaviour and stress response in offspring. Effects of maternal age were not replicated in E2, possibly due to methodological differences or higher tolerance to maternal effects in commercial breeders. Overall, we recommend researchers start reporting parent stock's age to increase our understanding of the subject.

Avian Leukosis Virus in Hatchable Eggs of Commercial and Free-Range Chickens

Avian leukosis is caused by various avian retroviruses which induce a variety of benign and malignant neoplasm in chickens with subsequent economic losses to the poultry industry. A survey of avian leukosis in hatchable eggs of apparently healthy chickens was carried out in an attempt to determine the prevalence of avian leukosis virus (ALV) in exotic breeders and free-range indigenous chickens in Oyo state. A total of 188 (76 exotic breeders and 112 free-range chickens) albumen of hatchable eggs were obtained from 3 different commercial breeder farms and 12 free-range indigenous chicken farms. Eggs were tested by an antigen capture enzyme-linked immunosorbent assay (ELISA) technique. Eleven out of the 76 albumen obtained from eggs of exotic breeders tested positive to ALV antigen which represents 14.5% while 37 of the 112 albumen from free-range indigenous eggs were confirmed as positive representing 33%. Overall prevalence rate of 25% was recorded for all eggs sampled with the highest prevalence of ALV antigen detected in free-range indigenous chickens than the exotic chickens. The results emphasizes the control of the Avian Leukosis transmission by including both exotic and free-range indigenous birds as wells as the use of ALV free eggs in hatcheries

Inbred lab mice are not isogenic: genetic variation within inbred strains used to infer the mutation rate per nucleotide site

For over a century, inbred mice have been used in many areas of genetics research to gain insight into the genetic variation underlying traits of interest. The generalizability of any genetic research study in inbred mice is dependent upon all individual mice being genetically identical, which in turn is dependent on the breeding designs of companies that supply inbred mice to researchers. Here, we compare whole-genome sequences from individuals of four commonly used inbred strains that were procured from either the colony nucleus or from a production colony (which can be as many as ten generations removed from the nucleus) of a large commercial breeder, in order to investigate the extent and nature of genetic variation within and between individuals. We found that individuals within strains are not isogenic, and there are differences in the levels of genetic variation that are explained by differences in the genetic distance from the colony nucleus. In addition, we employ a novel approach to mutation rate estimation based on the observed genetic variation and the expected site frequency spectrum at equilibrium, given a fully inbred breeding design. We find that it provides a reasonable per nucleotide mutation rate estimate when mice come from the colony nucleus (~7.9 × 10−9 in C3H/HeN), but substantially inflated estimates when mice come from production colonies.

Valuing DNA marker tested bulls for commercial beef production

This paper quantifies the benefits of using a sire genotyped for a single recessive gene in a commercial beef herd. A modified gene-flow method was used to account for changing allele frequency over time. The benefits to a commercial breeder of using a genotyped sire were highest when initial allele frequency was moderate and when the sire was used in a self-replacing herd that had increased allele frequency over time. An example of the thyroglobulin gene affecting marbling in beef cattle was used. The value to a self-replacing herd of a sire homozygous for the favourable allele of the thyroglobulin gene was shown to be up to $338 more than of an ungenotyped sire, in a population where the initial gene frequency was 0.3 and the genotype accounted for 0.5 standard deviations of phenotypic variation.