The summer slump in conception rates is a fact of life in most swine operations. But current research suggests that vitamin C can help alleviate the detrimental effects of heat stress on semen quality by meeting the increased needs of boars and replacing tissue losses of this nutrient.
In two research studies, boars had higher numbers of sperm per ejaculation and also fewer abnormal sperm during the spring, summer, and fall months when they were supplemented with 300 mg of dietary vitamin C per head daily (Figure 1). Other studies have found higher conception rates in sows when boars were supplemented with vitamin C (Figure 2).
The increase in sperm quality with supplemental vitamin C makes sense, since the testes normally contain a relatively high concentration of vitamin C. Semen quality in humans, turkeys, and broilers has also shown an improvement with ascorbic acid supplementation. Human research at the University of California/Berkeley suggests that increased concentrations of vitamin C in semen helps protect the sex cells from oxidative damage.
University of Kentucky researcher Dr. Merlin Lindemann recommends vitamin C for boar rations, particularly in hot weather, based on his review of the research.
To offset the poor stability of ascorbic acid, a stabilized vitamin C product should be used when adding vitamin C to swine rations.