Breed- and trait-specific associations define the genetic architecture of calving performance traits in cattle

Reducing the incidence of both the degree of assistance required at calving, as well as the extent of perinatal mortality (PM) has both economic and societal benefits. The existence of heritable genetic variability in both traits signifies the presence of underlying genomic variability. The objective of the present study was to locate regions of the genome, and by extension putative genes and mutations, that are likely to be underpinning the genetic variability in direct calving difficulty (DCD), maternal calving difficulty (MCD), and PM. Imputed whole-genome single-nucleotide polymorphism (SNP) data on up to 8,304 Angus (AA), 17,175 Charolais (CH), 16,794 Limousin (LM), and 18,474 Holstein-Friesian (HF) sires representing 5,866,712 calving events from descendants were used. Several putative quantitative trait loci (QTL) regions associated with calving performance both within and across dairy and beef breeds were identified, although the majority were both breed- and trait-specific. QTL surrounding and encompassing the myostatin (MSTN) gene were associated (P < 5 × 10−8) with DCD and PM in both the CH and LM populations. The well-known Q204X mutation was the fifth strongest association with DCD in the CH population and accounted for 5.09% of the genetic variance in DCD. In contrast, none of the 259 segregating variants in MSTN were associated (P > × 10−6) with DCD in the LM population but a genomic region 617 kb downstream of MSTN was associated (P < 5 × 10−8). The genetic architecture for DCD differed in the HF population relative to the CH and LM, where two QTL encompassing ZNF613 on Bos taurus autosome (BTA)18 and PLAG1 on BTA14 were identified in the former. Pleiotropic SNP associated with all three calving performance traits were also identified in the three beef breeds; 5 SNP were pleiotropic in AA, 116 in LM, and 882 in CH but no SNP was associated with more than one trait within the HF population. The majority of these pleiotropic SNP were on BTA2 surrounding MSTN and were associated with both DCD and PM. Multiple previously reported, but also novel QTL, associated with calving performance were detected in this large study. These also included QTL regions harboring SNP with the same direction of allele substitution effect for both DCD and MCD thus contributing to a more effective simultaneous selection for both traits.

Economic values of traits for Slovakian Pied cattle under different marketing strategies

Economic values of 15 production and functional traits for Slovakian Pied cattle were calculated under different marketing strategies. The traits were as follows: birth weight of calves, daily gain of calves in fattening, mature weight of cows, weight of calves at 120, 210 (weaning weight) and 365 days (yearling weight) of age, dressing percentage, mean class for fleshiness and fat covering, conception rate of heifers and cows, losses of calves at calving and from 48 hours to weaning, lifetime of cows and mean class for calving performance. A purebred cow-calf pasture system producing its own female and male replacement was assumed for all strategies. The following marketing strategies for surplus weaned female and male calves were taken into account: (A) export of all surplus calves, (B) intensive fattening of all surplus calves, (C) rearing and selling of all surplus non-pregnant (1) or pregnant (2) breeding heifers and fattening or export of surplus male calves. All calculations were carried out with the computer program Ecoweight. The relative economic importance of traits was calculated multiplying the economic values by the genetic standard deviations of the traits. The lifetime of cows was the most important trait when applying export or fattening of all calves or when selling pregnant breeding heifers, whereas the yearling weight was even more important for the strategy with selling non-pregnant heifers. The second most important trait was weaning weight in strategy A, yearling weight in strategy B and lifetime of cows in marketing strategy C. Carcass conformation traits had the lowest economic importance in all calculations.