Relationship between polymorphisms in the prolactin promoter and cytochrome P450 genes and post-weaning performance by steers weaned from wild-type or non-toxic endophyte-infected tall fescue pastures

Grazing endophyte-infected tall fescue (E+) negatively impacts cattle feed intake and growth negatively (Crawford et al., 1989). However, the interaction between environmental factors and animal genetics may influence important cattle growth measurements before and after the weaning process (Phillips et al, 2001). For example, polymorphisms (mutations) in the prolactin and cytochrome P450 genes were related to cattle productivity and profitability (Rosenkrans, 2007), and may interact with ergot alkaloids produced by the endophyte in toxic tall fescue which affect animal performance. Furthermore, selection of cattle with greater carcass composition, such as heavier carcass weight, is important for both producers and consumers (Zhao et al., 2004). Therefore, the objective of this study was to determine the relationship among single nucleotide polymorphisms (SNP) in prolactin promoter and cytochrome P450 genes and post-weaning performance and carcass measurements from steers weaned from toxic wild type (E+) or non-toxic (NE+) endophyte-infected tall fescue.