Characterization of functional traits with focus on udder health in heifers with divergent paternally inherited haplotypes on BTA18

Abstract

Background: A major challenge in modern medicine and animal husbandry is the issue of antimicrobial resistance. One approach to solving this potential medical hazard is the selection of farm animals with less susceptibility to infectious diseases. Recent advances in functional genome analysis and quantitative genetics have opened the horizon to apply genetic marker information for efficiently identifying animals with preferential predisposition regarding health traits. The current study characterizes functional traits with a focus on udder health in dairy heifers. The animals were selected for having inherited alternative paternal haplotypes for a genomic region on Bos taurus chromosome (BTA) 18 genetically associated with divergent susceptibility to longevity and animal health, particularly mastitis.

Results: In the first weeks of lactation, the q heifers which had inherited the unfavorable (q) paternal haplotype displayed a significantly higher number of udder quarters with very low somatic cell count (< 10,000 cells / ml) compared to their paternal half-sib sisters with the favorable (Q) paternal haplotype. This might result in impaired mammary gland sentinel function towards invading pathogens. Furthermore, across the course of the first lactation, there was indication that q half-sib heifers showed higher somatic cell counts, a surrogate trait for udder health, in whole milkings compared to their paternal half-sib sisters with the favorable (Q) paternal haplotype. Moreover, heifers with the haplotype Q had a higher feed intake and higher milk yield compared to those with the q haplotype. Results of this study indicate that differences in milk production and calculated energy balance per se are not the main drivers of the genetically determined differences between the BTA18 Q and q groups of heifers.

Conclusions: The paternally inherited haplotype from a targeted BTA18 genomic region affect somatic cell count in udder quarters during the early postpartum period and might also contribute to further aspects of animal's health and performance traits due to indirect effects on feed intake and metabolism.

Keywords: BTA18; Bovine mastitis; Clinical performance; Genetic selection; Somatic cell score (SCS).

Fig. 1

Average weekly somatic cell score (SCS) with standard error across observation period for the Q and q group in the FBN cohort

Fig. 2

Average weekly somatic cell score (SCS) with standard error across observation period for the Q and q group in the TiHo cohort

Fig. 3

Proportion of udder quarters with extremely low somatic cell count in the Q and q groups for the FBN (week 2 to 6 p.p., difference between Q and q group P < 0.05) and TiHo cohort (week 5 p.p., difference between Q and q group P < 0.01)

Fig. 4

Average daily feed intake within week with standard error across observation period for the Q and q group in the FBN cohort

Fig. 5

Average daily energy-corrected milk (ECM) with standard error across observation period for the Q and q group in the FBN cohort