Vitamin A at weaning and breeding increases litter size

 A study was conducted by five cooperating experimental stations in the USA to determine the effects of an intramuscular injection of vitamin A at weaning and breeding on subsequent litter size of sows.  Sows were assigned to one of three treatments given at weaning and again at breeding: 1) a placebo injection (2 mL of corn oil), 2) injection with 250,000 IU of vitamin A, and 3) i.m. injection with 500,000 IU of vitamin A. A common vitamin-mineral premix that supplied 11,000 IU of vitamin A/kg of diet (as-fed) was used by all stations. As would be expected, station effects were noted for many response measures. Analysis of the data also showed interactions between station, treatment and parity.

 For sows of parity 1 and 2, litter sizes increased from treatments 1 to 3, respectively, for total pigs born (10.15, 12.14, and 13.18), live born (9.70, 11.14, and 12.16) and weaned (8.92, 10.12, and 10.60) piglets. However, for sows of parity 3 to 6, litter sizes were not affected by the treatment with 11.82, 11.71, and 11.46 total born pigs respectively, 10.82, 10.64, and 10.23 live born, and 8.65, 9.01, 8.79 weaned piglets. Piglet birth weight decreased due to vitamin A treatment in parity 1 and 2 sows and was likely due to the differences observed in litter size. 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.

 WHJ comment: Many years ago it was quite common to give an injection of Vitamins A, D and E at weaning, although the response was often not clear on commercial farms. This trial work shows that the response to Vitamin A is quite large in young females but that there is not much benefit for older sows. The industry is becoming more aware that gilts and second litter sows need higher levels of certain nutrients, which sometimes cannot be supplied through the normal diet. While further work in this whole area is required Vitamin A injection, as shown in the trial, can be considered by producers as a technique for improving litter size in young females.

 Reference:  M. D. Lindemann, J. H. Brendemuhl, L. I. Chiba, C. S. Darroch, C. R. Dove, M. J. Estienne and A. F. Harper (2008). A regional evaluation of injections of high levels of vitamin A on reproductive performance of sows.  J. Anim Sci. 86:333-338. doi:10.2527/jas.2007-0153