Colostrum yield (CY, L) and concentration of immunoglobulin G (IgG, g/L) are important phenotypes to monitor in dairy farms because of their association with the risk of failure of the passive transfer of immunity in the newborn calf. This can occur when the CY of the parturient cow is insufficient or when the IgG concentration is low. Given that both of these traits are heritable, the present study aimed to investigate their genetic determinism by identifying significant genomic regions. A genome-wide association study coupled with an exploratory functional enrichment analysis was carried out to provide preliminary biological context of the detected signals for the ‘colostrability’ defined as the cow’s ability to secrete enough volume (≥ 4 L) of good-quality colostrum (≥ 50 g IgG/L) at calving. Data comprised 960 genotyped Italian Holstein cows with CY recorded within 6 h of calving, together with colostral IgG and total immunoglobulin concentrations. The significant SNPs associated with CY were scattered across BTA3, 5, 10, 11, 21, and 22, with 23 genes on BTA22 either harbouring or flanking significant signals. Apart from some genes already known, part of the significant regions have unclear function. Signals were detected on BTA1, 6, 7, 11, 19, 21, and 25 for IgG concentration, and on BTA6, 7, 11, 21, 23, and 25 for total immunoglobulin concentration. The functional enrichment analysis provided preliminary support for possible involvement of secretory, immune-signalling, and epithelial receptor-related processes. This study confirms the polygenic nature of cows’ ‘colostrability’ being regulated by different genomic regions distributed across the genome. However, exploration of the genomic determinism of CY and immunoglobulin concentration requires larger, independent, and harmonized data, ideally standardized and highly comparable. These findings, although relevant for improving calf health, represent only part of a more complex picture when the goal is selective breeding toward calf health. In addition to dam-related data, including colostrum traits, future studies should integrate calf-related phenotypes associated with failure of passive transfer of immunity, such as intestinal IgG absorption capacity, gut permeability, early-life survival, and health outcomes.
A. Costa, Massimo De Marchi, J. Vegni et al.· Genetics Selection Evolution· 0 citations
Multiple birth (MB) is associated with adverse effects on cow fertility and calf survival, thereby contributing to economic losses for dairy farmers; however, it is not currently included in routine genetic evaluations or selection indices in cattle worldwide. This study aimed to (i) estimate the h2 and repeatability of MB, (ii) assess its genetic and phenotypic associations with calving performance, postpartum health, fertility, and milk production traits, and (iii) quantify its impact on these traits in Austrian Holstein population. After data editing, the analyses used 678,877 records belonging to 262,192 cows across 2,350 dairy farms spanning the period from 2000 to 2024. The h2 and repeatability of MB were estimated using both single-trait linear and threshold repeatability animal models, whereas genetic and environmental correlations between MB and the other traits were estimated using bivariate models within a Bayesian framework implemented via Gibbs sampling. The effects of MB on functional and production traits were quantified using linear and logistic mixed regression models, according to the specific trait. The h2 of MB was low (linear model: 0.017, threshold model: 0.076) as well as repeatability (linear model: 0.044, threshold model: 0.217). Estimated genetic correlations of MB with 305-d milk, protein, and fat yields were weak (∼0.10). Multiple birth was weakly genetically correlated with maternal gestation length (-0.195), maternal calving ease (0.095), and maternal stillbirth (0.150). The interval from calving to first service, the interval from first to last service, the non-return rate at 56 d after first service, days open, and calving interval were all weakly genetically associated with MB. Fertility disorders showed the strongest genetic correlation with MB (0.308), whereas cystic ovaries showed a weak genetic correlation (0.068). Multiple birth was associated with shorter gestation length (-5 d), higher risk of stillbirth and fertility disorders, longer calving interval (16 d), and lower 305-d milk (-67 kg) and fat yield (-7 kg) compared with singleton birth. The phenotypic trend indicated that MB increased slightly from 3.01 to 3.34% between 2000 and 2024, whereas the genetic trend remained largely stable throughout the study period, suggesting that past selection decisions had little or no effect on the genetic merit for MB. Overall, the findings of the present study indicate that selection aimed at reducing or stabilizing MB would not substantially impair milk production traits and may provide indirect benefits for fertility and health traits in the long term.
J. Katende, A. Costa, M. Santinello et al.· Journal of Dairy Science· 0 citations
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