Comparison of reproductive performance of AI- and natural service-sired beef females under commercial management.

The objective of this study was to assess differences in reproductive performance of natural service and artificial insemination () sired beef females based on pregnancy outcomes, age at first calving, and calving interval. Data were sourced from 8,938 cows sired by AI bulls and 3,320 cows sired by natural service bulls between 2010 and 2017. All cows were in a commercial Angus herd with 17 management units located throughout Virginia and represented spring and fall calving seasons.

Comparison of models for missing pedigree in single-step genomic prediction.

Pedigree information is often missing for some animals in a breeding program. Unknown-parent groups (UPGs) are assigned to the missing parents to avoid biased genetic evaluations. Although the use of UPGs is well established for the pedigree model, it is unclear how UPGs are integrated into the inverse of the unified relationship matrix (H-inverse) required for single-step genomic best linear unbiased prediction.

Evaluating the relationship between fecal egg count, FAMACHA score, and weight in dewormed and non-dewormed Katahdin rams during a parasite challenge.

The objective of this study was to evaluate and to estimate the relationship between fecal egg counts (FECs) and FAMACHA score and the body weight of growing Katahdin rams during a parasite challenge. One of the largest factors negatively influencing reproduction and economics in the sheep industry is gastrointestinal nematode (GIN) parasites. Due to anthelmintic resistance of these parasites, animals are selected for parasite resistance using FEC and FAMACHA scores.

Direct and correlated responses to selection for autumn lambing in sheep.

Background: Seasonal reproduction limits productivity, flexibility, and profitability in commercial sheep production. Hormonal and (or) photoperiodic manipulation can be used to control estrous cycles in sheep and reduce limitations that are imposed by the seasonal anestrous but are often impractical or incompatible with the extensive management systems preferred for ruminant livestock. Thus, the current study investigated the use of selection to improve realized fertility (i.