Effect of space allowance during rearing and selection criteria on performance of gilts over three parities in a commercial swine production system.

A total of 1,257 gilts were used to determine the effect of space allowance during rearing and age at puberty on total pigs produced and removal rate over 3 parities. There were 2 treatments. In treatment 1, gilts were given a space allowance of 1.13 m(2)/gilt (15 gilts per pen), and in treatment 2, gilts were given 0.77 m(2)/gilt (22 gilts per pen). Gilts (38 kg and 75 d of age) were individually weighed upon entry and before leaving the rearing site. They were scanned for backfat thickness and loin depth and had their feet and legs scored for structure, movement, and toe evenness before leaving the rearing site. Commencing at approximately 140 d of age, gilts were exposed to a vasectomized boar once daily with age of puberty recorded for all gilts attaining puberty before leaving the rearing site. Gilts were then moved to a specialized gilt breeding farm. When confirmed pregnant, they were moved to 1 of 9 sow farms at random, where gilts remained until removal from that herd. Space allowance in rearing had no effect (P > 0.29) on growth rate in rearing, backfat thickness and loin depth, total pigs produced, or removal rate. A greater percentage of gilts attained puberty (P = 0.02) and attained puberty at a younger age (P < 0.01) when given the greater space allowance in rearing. Gilts given the lower space allowance in rearing had more (P = 0.04) cracks on their rear hooves. Gilts attaining puberty at a younger age (<185 d) had a greater growth rate in rearing, greater backfat thickness at 200 d of age, and produced more (P < 0.05) pigs over parities 1 to 3. Gilts in the fastest growth-rate group in rearing (>860 g/d) had greater (P < 0.05) total born in parity 1, but total pigs produced to the end of parity 3 was not different (P = 0.47). Contrary to expectation, a fast growth rate in rearing did not negatively affect removal rate. Gilts served between 240 to 260 d of age produced more (P < 0.01) pigs by the end of parity 3 than those served at >260 d of age, whereas a greater (P < 0.01) percentage of gilts served at >280 d of age were removed by the end of parity 3. In conclusion, space allowance in rearing did not affect total pigs produced or removal rate; however, gilts that attained puberty at a younger age produced more pigs over parities 1 to 3.