A regional evaluation of injections of high levels of vitamin A on reproductive performance of sows

¹ S-145 Regional Research Committee on Nutrition and Management of Swine for Increased Reproduction Efficiency

^* To whom correspondence should be addressed. E-mail: mdlind1{at}uky.edu.

	Abstract

A regional study involving 411 litters from 182 sows was conducted at 5 cooperating experiment stations (AL, GA, KY, TN, and VA) to determine the effects of an i.m. injection of vitamin A at weaning and breeding on subsequent litter size of sows. Sows were assigned to 1 of 3 treatments given at weaning and again at breeding: 1) a placebo i.m. injection (2 mL corn oil), 2) i.m. injection with 250,000 IU of vitamin A (1 mL of vitamin A palmitate in oil), and 3) i.m. injection with 500,000 IU of vitamin A (2 mL of vitamin A palmitate in oil). Corn-soybean meal diets in gestation were formulated to contain 13% CP and 0.60% total lysine. Lactation diets were formulated to contain 17% CP and 0.90% lysine. A common vitamin/mineral premix that supplied 11,000 IU of vitamin A/kg diet was used by all stations. As expected, station effects were noted for many response measures. Analysis of data also revealed both treatment x station and treatment x parity interactions for litter size responses. The treatment x parity interactions were stronger and when the litter size response was separated into early parity sows (Parity 1 and 2) and late parity sows (Parity 3 to 6), the station x treatment interactions were no longer present in either subgroup. For sows of Parity 1 and 2, litter sizes were increased linearly (P 0.003) for Treatment 1 to 3, respectively, for the total (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). For sows of Parity 3 to 6, litter sizes were not affected for Treatment 1 to 3, respectively, for the total (11.82, 11.71, and 11.46), live born (10.82, 10.64, and 10.23), and weaned (8.65, 9.01, 8.79). Piglet weights were affected (P < 0.001) by station and associated with station differences (P < 0.05) in lactation length. Piglet weight decreased due to injection treatment in Parity 1 and 2 sows (linear, P 0.026) 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.

Key Words: injection, litter size, reproductive performance, sows, vitamin A