In both genotypes, performance differences by supplementation level were greater at the beginning of the study than at the end--which is in keeping with previous research showing that vitamin requirements are greater in younger pigs.
Stahly says he was surprised more by the magnitude of the response to increased vitamin supplementation than by the response itself. He notes that the study should encourage a reconsideration of optimum B vitamin supplementation in the swine industry for two reasons.
"First, it's been suggested that stressed pigs and other pigs with slower growth benefit most from increased vitamin supplementation. Yet the pigs used in the study were very clean, rapidly growing pigs, and they still responded positively in both gain and feed efficiency. We did not include 'challenged' pigs in the study, so we can't say how their responses would compare with healthy pigs' responses." Second, he says the study invites a reassessment of the interaction between lean growth genetics and B vitamin requirements. The difference in the optimum supplementation levels for the two genotypes was especially noteworthy because it has often been assumed that dietary needs for some vitamins increase as dietary energy or feed consumption increases.
"For example, because the high lean--growth pigs actually consumed less total dietary energy, some people might expect their riboflavin requirement to be less than the moderate lean--growth group's. But it took considerably greater supplementation for the higher lean--growth pigs to reach their genetic potential."
In another study, Ramsey et al., (1995) compared the responses in live performance and carcass traits when pigs with high lean growth potential received two dietary levels of vitamin and mineral supplementation. (Table 1.)
