Two papers were published last week by Dr Perry from QSML using Santa Gertrudis bulls in Queensland in the international reproduction journal; Theriogenology with her PhD student Matt Callaghan. We have previously shown that feeding high energy rations to bulls prior to sale reduces sperm quality. These recent papers are among those where we are looking at management practices that will enable bulls to meet sale specifications without the use of these deleterious practices. These two papers show the importance of protein supplementation of first-calf heifers to the growth, carcass traits and reproductive development of their bull progeny to sale age.
Protein supplementation of grazing primiparous beef heifers during lactation improves milk production and liveweight gain of the heifer. This is associated with increased weight gain of the bull progeny and increased circulating levels of growth hormone (IGF-1) and leptin. Such levels have previously been associated with reduced age at puberty. Interestingly this enhanced calf hood nutrition, via supplementation of the heifer, led to increased carcass muscling (EMA) to 22 months of age.
Protein supplementation of primiparous heifers during lactation initiates increased calfhood testosterone concentrations of bull progeny which was associated with increased testicular development, scrotal circumference, sperm motility and sperm morphology. This was associated with earlier age of sexual maturity in these bull progeny.
If you’re interested in some of our other studies please head over to our Research page.