Amino Acid Case Study - (Growth In Pigs)SUMMARY Effect of injections of high levels of vitamin A on reproductive performance of sows. Darroch, C. S., L. I. Chiba, M. D. Lindemann, A. F. Harper, and E. T. Kornegay, S-145 Committee on Nutritional Systems for Swine to Increase Reproductive Efficiency. A cooperative regional study involving 417 litters was conducted at four experiment stations (Alabama, Kentucky, Tennessee and Virginia) to determine the effect of an intramuscular injection of 250,000 IU or 500,000 IU of vitamin A, or a placebo at weaning and breeding on reproductive performance of sows. Gilts and sows were allotted to one of three treatments and data was collected over three reproductive cycles. Sows were fed 1.82 kg/day (2.27 kg/day during December, January, and February) during the breeding period and before farrowing. Feed was consumed on an ad libitum basis during lactation. Corn-soybean meal based diets were formulated to contain 0.60% and 0.90% lysine for breeding-gestation and lactation, respectively. Data for response criteria were analyzed using GLM procedures of SAS. The model included parity, treatment, station and treatment x station interaction. Parity was used as a covariant. There were 10.7, 10.8, and 10.4 ± 0.41 pigs born alive per litter (P = 0.78) for sows given 250,000 IU vitamin A, 500,000 IU vitamin A and the placebo, respectively. The effect of vitamin A injections on litter size was more apparent for the number of pigs weaned per litter, when compared to the placebo group (9.3 vs 8.6 ± .21; P = 0.09). Vitamin A did not affect the days to return to estrus (5 ± 0.15; P = 0.15) after weaning at 25.6 ± 0.38 days of lactation. Average piglet weights were affected (P < 0.001) by station and correlated to station differences (P < 0.001) in lactational sow feed intake. There were significant main effects of treatment and station on sow body weights at breeding, farrowing and weaning; but there was no clear relationship to the apparent increase in litter size following the injection of vitamin A. Although treatment x station interactions were not significant for any reproductive variable tested in this trial, differences in initial body weights of sows allotted to treatments, and differences in performance of sows at each station may have contributed to variation in body weights. The results indicate that the injection of high doses of vitamin A in sows at weaning and breeding improves reproductive performance by increasing the number of pigs weaned per litter. |
