Associations of the NCAPG I442M and GDF8 Q204X loci on feed efficiency at the onset of puberty in a beef x dairy cattle resource population

Abstract Text: Recent studies highlighted the NCAPG/LCORL region as well as the GDF8 gene encoding myostatin being associated with genetic modulation of growth in several mammalian species. Specifically, the NCAPG I442M locus had been associated with pre- and postnatal growth in cattle. Furthermore, it had been demonstrated that the highest effect of this genetic variant is expressed at the onset of puberty, which is suggested as the inflection point of the growth curve. Feed costs account for a large proportion of total costs for production in livestock. Thus, including information about feed efficiency in selection decisions would improve the profitability of livestock production. The aim of our study was to evaluate, if the NCAPG I442M or GDF8 Q204X loci had an effect on feed intake and/or feed efficiency at the onset of puberty in cattle. Our study included 176 F₂ bulls from a Charolais x German Holstein resource population generated by multiple ovulation and embryo transfer to virgin heifers that were kept under standardized environmental conditions. After an initial period of four months on a milk replacer diet, the animals were fed ad libitum with concentrate (11.3 MJ ME/kg dry matter, comprising a mixture of barley, molasses chips, soybean extraction meal, molasses, minerals and a vitamin premix) and hay (9.0 MJ ME/kg dry matter). Feed intake was measured daily and body weight was recorded in monthly intervals. For this study, daily dry matter intake, feed conversion ratio and residual feed intake were investigated between day 183 and day 283 of age. Residual feed intake was calculated from daily dry matter intake, metabolic mid weight and average daily gain. The alleles at the loci NCAPG I442M and GDF8 Q204X were tested for association with daily dry matter intake, feed conversion ratio and residual feed intake. The model fitted year of birth and season as fixed effects, the additive effect of the NCAPG 442M or GDF8 204X allele, and an infinitesimal polygenic animal effect. The analysis revealed that the NCAPG I442M locus was significantly associated with daily feed intake (P = 0.03), feed conversion ratio (P = 0.00012) and residual feed intake (P = 0.00001). In contrast, the GDF8Q204X locus showed only significant effects on feed conversion ratio (P = 0.04) and residual feed intake (P = 0.0005). Our data indicated that NCAPG I442M is associated with genetic modulation of growth as well as feed efficiency in cattle

Keywords: Feed efficiency, cattle, NCAPG