Variation in the genome region coding for PLAG1 has well-documented associations with skeletal growth and age at puberty in cattle. However, the influence of PLAG1 on other economically important traits such as cow stayability has not yet been explored. Here we investigate the effect of PLAG1 variation on early and later in life female fertility, as well as size and growth, in a well-phenotyped Australian Brahman herd. Yearly pregnancy and productivity records were collected from 2,839 genotyped Brahman cows and used to generate fertility, growth, and weight phenotypes. A variant on chromosome 14 in PLAG1 (NC_037341.1:g.23338890G>T, rs109815800) was previously determined to be a putative causative mutation associated with variation in cattle stature. The imputed PLAG1 genotype at this variant was isolated for each animal and the effect of PLAG1 genotype on each trait was estimated using linear modeling. Regardless of how heifer fertility was measured, there was a significant (P < 0.05) and desirable relationship between the additive effects of PLAG1 genotype and successful heifer fertility. Heifers with two copies of the alternate allele (TT) conceived earlier and had higher pregnancy and calving rates. However, the effects of PLAG1 genotype on fertility began to diminish as cows aged and did not significantly influence stayability at later ages. While there was no effect of genotype on growth, PLAG1 had a negative effect on mature cow weight (P < 0.01), where females with two copies of the alternate allele (TT) were significantly smaller than those with either one or none. Selection emphasis on improved Brahman heifer fertility will likely increase the frequency of the T allele of rs109815800, which may also increase herd profitability and long-term sustainability through improved reproductive efficiency and reduced mature cow size.
Keywords: PLAG1; Brahman; heifer fertility; stayability.
PLAG1 is a gene with allelic variation that has well-documented associations with stature and age at puberty in cattle. Here we extend knowledge of the effect of the PLAG1 alleles to later in life female fertility, as well as size and growth, in Australian Brahmans. Records were collected from 2,839 genotyped Brahman cows and used to generate fertility, growth, and weight phenotypes. A variant on chromosome 14 in PLAG1 (rs109815800) was previously determined to be highly associated with variation in cattle stature. The allele combination (the genotype) at this position was isolated for each animal and the effect of PLAG1 genotype on each trait was estimated using linear modeling. Regardless of how heifer fertility was measured, there was a significant and desirable relationship between PLAG1 genotype and successful heifer fertility. However, the effects of allele combination on fertility began to diminish as cows aged and did not significantly influence stayability at later ages. While there was no effect of genotype on growth, PLAG1 had a negative effect on mature cow weight. Selection emphasis on improved Brahman heifer fertility will likely increase the frequency of the desirable PLAG1 allele, which may have additional benefits on herd profitability and long-term sustainability.
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