A better than average diet for bull calves could make them superior herd sires.
“We could get bulls with larger testes and more sperm by just feeding them really well,” said Dr. John Kastelic of the University of Calgary’s faculty of veterinary medicine.
The effect of nutrition on bull calves is a research project by Alysha Dance, a PhD candidate at the university.
Preliminary results were presented at the veterinary school’s annual beef conference held in Calgary June 19-20.
Results suggest that producers might consider creep feeding potential sires before they reach puberty.
“Bull calves on a high nutrition diet during calfhood had more reproductive hormone that drives testosterone and consequently larger testicular development and earlier puberty by one month,” said Dance.
Angus breeder Cecelie Fleming of Granum, Alta., said the industry does not want fat bulls.
“In the seedstock industry, we see bulls that have been fed too well and it becomes a problem with overfeeding,” she said.
Kastelic said they did not see fat deposits in the scrotum.
As well, this kind of feeding regime is most effective before the bulls reach 30 weeks of age, at which time they go on a regular ration.
“After weaning is the wrong time to be overfeeding bulls,” he said.
“Prior to 30 weeks, what you feed them is hugely important. After 30 weeks we want them on a good maintenance diet. If we get them too fat, we have huge issues with laminitis and other problems.”
The study worked with three groups of bull calves, which were on low, medium and high planes of nutrition. The high level diet was 130 percent more than what the National Research Council’s nutritional guidelines suggest for bulls of this age.
The high nutrition group grew larger than the other two groups. They were heavier with larger scrotal circumference and larger testes than the others. Blood tests also showed more growth hormones.
They entered puberty sooner with a 45 day difference between those receiving the high nutrition and low diets. Semen was collected, and re-searchers found no difference in the amount of embryos produced from the semen produced by any of the bulls.
The research program will next raise another set of bulls that will be castrated so that their testes can be studied.