Anyone keeping bull calves for breeding stock needs to pay attention to proper nutrition early in the calf’s life, says an Agriculture Canada researcher in Lethbridge.
John Kastelic says research at the centre shows calves on a higher protein and energy ration in the first six months of life have larger scrotal circumference and higher sperm counts than calves on a lower protein and energy diet. And the key period for the higher ration is within the first 25 weeks of life. If calves are fed a lower protein and energy ration in the first six months, and then switched to a higher protein and energy ration later, they don’t catch up.
In the study, Kastelic says they placed groups of both Angus and Angus/Charolais cross bull calves onto three different feeding programs. All calves were weaned at six weeks of age for the study. One (control) group received 100 per cent of the recommended nutrition for protein and energy, another group was fed a ration 30 per cent higher in protein and energy and a third group was fed 30 per cent less protein and energy. All calves received the same vitamin and mineral package.
At the end of the study, those calves on the 130 per cent ration reached puberty one month earlier than the low-ration group, and perhaps more importantly scrotal circumference was 20 to 30 per cent larger and they produced 20 to 30 per cent more sperm.
Kastelic says the basic recommended ration was mostly barley silage and barley grain. The ration for the high-ration group had less silage, more grain and a canola meal supplement. The low-ration group had mostly silage and a small amount of grain.
Kastelic says calves on the low-ration diet, when switched to a higher protein and energy diet after 25 weeks never did catch up to the group that had the higher protein and energy diet from the start. He says they caught in weight in body size, but they didn’t have the same scrotal circumference or sperm production.
So a higher protein and energy ration in the first six months of life for bulls kept for breeding stock is critical. He says the ration can simply be provided as creep feed. He did have a couple of caveats — a 30 per cent higher ration was beneficial during the first six months, but don’t overfeed bull calves after weaning. They should go back to a good recommended base ration. Excessive feeding after weaning is not better, as overfeeding after weaning can decrease semen quality.
And he also cautioned not to put heifer calves on this higher protein and energy ration because they become too fat and the extra fat actually will suppress their milk production later on. Bull and heifer calves should be fed separately. †