Assessment of skeletal muscle dynamics and milk production across a 300-day lactation in multiparous dairy cattle.

The objective of this study was to evaluate changes in longissimus dorsi muscle depth (LDD) across lactation (0 to 300 DIM) and identify the impact of low versus high muscle reserves immediately after parturition on body weight and body reserve changes as well as production variables across a 300-d lactation. Forty multiparous cows were classified as high muscle (HM; LDD > 5.0 cm; n = 18) or low muscle (LM; LDD ≤ 5.

Estimation of genetic parameters and genome-wide association study for enzootic bovine leukosis resistance in Canadian Holstein cattle.

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis (leukosis) frequently observed in North American dairy herds. Infection with BLV can lead to persistent lymphocytosis and tumors, and is associated with decreased production, immunity and fertility. With no available treatment or vaccine, reducing the prevalence of leukosis through management and culling has not yet been successful.

A comprehensive characterization of longevity and culling reasons in Canadian Holstein cattle based on various systematic factors.

The decision of premature culling cows directly impacts the profitability of dairy farms. A comprehensive characterization of the primary causes of culling reasons would greatly improve both management and selection objectives in dairy cattle breeding programs. Therefore, this study aimed to analyze the temporal frequencies of 34 culling reasons in Canadian Holstein cows.

Genetic Analysis of Methane Emission Traits in Holstein Dairy Cattle.

Genetic selection can be a feasible method to help mitigate enteric methane emissions from dairy cattle, as methane emission-related traits are heritable and genetic gains are persistent and cumulative over time. The objective of this study was to estimate heritability of methane emission phenotypes and the genetic and phenotypic correlations between them in Holstein cattle. We used 1765 individual records of methane emission obtained from 330 Holstein cattle from two Canadian herds.

Random-effect meta-analysis of genetic parameter estimates for carcass and meat quality traits in beef cattle.

Considerable variability of genetic parameter estimates is observed among different studies for the same trait, which is associated with the distinct effects included in the statistical model, population breed, and sample sizes. The random-effect meta-analysis summarizes genetic parameters considering the heterogeneity among studies. Therefore, the aim of this study was to perform a random-effect meta-analysis of heritability and genetic correlation estimates for carcass and meat quality traits in beef cattle.

Genetic parameters for milk yield and quality traits of Brazilian Holstein cows as a function of temperature and humidity index.

Measurements of milk yield (MY), somatic cell score (SCS), percentage of fat (FP), protein (PP), lactose (LP), casein (CP) and percentage of palmitic (C16:0), stearic (C18:0), oleic (C18:1), total saturated (SFA), unsaturated (UFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids in milk from 5,224 Holstein cows were evaluated as a function of a temperature and humidity index (THI). Legendre orthogonal polynomials from second to seventh order were tested. The best fit order for MY, PP and C18:0 was the third, whereas the second for all other traits.

Identification of novel mRNA isoforms associated with meat tenderness using RNA sequencing data in beef cattle.

The Warner-Bratzler shear force (WBSF) and myofibrillar fragmentation index (MFI) are complementary methodologies used to measure beef tenderness. Longissimus thoracis samples from the 20 most extreme bulls (out of 80 bulls set) for WBSF (tender (n = 10) and tough (n = 10)) and MFI (high (n = 10) and low (n = 10)) traits were collected to perform transcriptomic analysis using RNA-Sequencing. All analysis were performed through CLC Genomics Workbench.

Impact of including information from bulls and their daughters in the training population of multiple-step genomic evaluations in dairy cattle: A simulation study.

The objective of this study was to investigate the impact of accounting for parent average (PA) and genotyped daughters' average (GDA) on the estimation of deregressed estimated breeding values (dEBVs) used as pseudo-phenotypes in multiple-step genomic evaluations. Genomic estimated breeding values (GEBVs) were predicted, in eight different simulated scenarios, using dEBVs calculated based on four methods. These methods included PA and GDA in the dEBV (VR) or only GDA (VRpa) and excluded both PA and GDA from the dEBV with either all information or only information from PA and GDA (JA and NEW, respectively).