Quantitative trait loci for male reproductive traits in beef cattle.

The objective of the present study was to detect quantitative trait loci (QTL) for male reproductive traits in a half-sib family from a Bos indicus (Brahman) x Bos taurus (Hereford) sire. The sire was mated with MARC III (1/4 Hereford, 1/4 Angus, 1/4 Red Poll and 1/4 Pinzgauer) cows. Testicular traits were measured from 126 male offspring born in 1996 and castrated at 8.5 months. Traits analysed were concentration of follicle stimulating hormone in peripheral blood at castration (FSH), paired testicular weight (PTW) and paired testicular volume (PTV) adjusted for age of dam, calculated age at puberty (AGE), and body weight at castration (BYW). A putative QTL was observed for FSH on chromosome 5. The maximum F-statistic was detected at 70 cM from the beginning of the linkage group. Animals inheriting the Hereford allele had a 2.47-ng/ml higher concentration of FSH than those inheriting the Brahman allele. Evidence also suggests the existence of a putative QTL on chromosome 29 for PTW, PTV, AGE and BYW. The maximum F-statistic was detected at cM 44 from the beginning of the linkage group for PTW, PTV and AGE, and at cM 52 for BYW. Animals that inherited the Brahman allele at this chromosomal region had a 45-g heavier PTW, a 42-cm(3) greater PTV, a 39-day younger AGE and a 22.8-kg heavier BYW, compared with those inheriting the Hereford allele. This is the first report of QTL for male reproductive traits in cattle.