Body protein proves key to pig production
MODERN genotype gilts must build up body protein rather than fat reserves to secure oestrus response, ovulation rates and embryo yields, says SAC pig specialist Sandra Edwards
Breeding pigs to utilise protein for lean meat production has replaced the former dependency on building up fat reserves to ensure reproductive performance, says Dr Edwards.
"Older gilts will come on heat faster, but the modern gilt must build up body protein to perform. They appear to be sensitive to a deficit in body protein and delay heat until reserves have been built up," she suggests.
Trials at SAC compared gilts fed a low protein 0.3g/MJ DE diet and gilts fed a high protein 0.9g/MJ DE diet to determine the effect on reproductive performance. Gilts from each group were injected with gonadotrophin to induce heat at either 160 days or 180-days-old.
For gilts induced at 160-days-old, those on the low protein diet ovulated an average of 17 eggs against 24 eggs for gilts on the high protein diet. Similarly, for gilts induced at 180 days old, those on the low protein diet ovulated an average of 14 eggs a heat compared with 19 eggs for gilts on the high protein diet.
"These ovulation rates determine the number of piglets a litter. Although the low protein diet was extreme, it shows the effect that low body protein could be having on production," she adds.
Gilts need higher levels of protein at a younger age and should be fed a diet of at least an average 0.6g/MJ DE throughout the rearing phase. Dr Edwards suggests protein levels may be increased to 0.8-0.9g/MJ DE in the three-week pre-service phase as a form of steaming up young gilts.
"Age didnt appear to have any significant effect on ovulation rate, however, in younger gilts it tends to be higher."
SACs Sandra Edwards: Gilts need higher levels of protein at a younger age.