A regional study involving 443 litters
from 182 sows was conducted at 5 cooperating experiment
stations to determine the effects of an i.m. injection
of vitamin A at weaning and breeding on subsequent
litter size of sows. The results of this
regional project demonstrated that injection of high
doses of vitamin A in young sows at weaning and breeding
improves the subsequent number of pigs born and
weaned per litter, indicating that vitamin A requirements
for maximal performance may vary with age.