LIFETIME PRODUCTIVITY IN GILTS PREVIOUSLY SELECTED FOR DECREASED AGE AT PUBERTY

A study was conducted to evaluate the effect of decreasing age of puberty on lifetime productivity in sows. Two lines of gilts from the Nebraska Gene Pool population were used in this study: a line that had been selected for decreased age at puberty (AP) and a line in which selection had been random (RS). The study was conducted in two parts. In part one, 75 gilts were mated at second oestrus and the productivity measured over five parities. A second experiment utilizing 68 gilts was conducted to provide further data for comparing litter size at parity 1, and also to compare ovulation rates in the two lines at second oestrus. Results showed that litter size was similar in both lines across parities. After five parities the percentage of sows farrowing relative to parity 1 was 58.8% for the AP line but only 39.4% for the RS line (P=0.17). Litter birth weight, litter size and weight at 21 days, number weaned, and lactation food consumption were similar for both lines. Lactation weight loss was not significantly different between the two lines (60.0(s.c. 5.9) v. 52.7 (s.e. 5.0) kg, for RS and AP gilts, respectively) but was consisted with the slightly longer weaning to remating intervals in the RS line (7.8(s.e. 0.7) v. 6.6 (s.e. 0.7) days, P=0.22). Ovulation rate at second oestrus did not differ between the two lines (14.1(s.e.0.9) v. 14.3(s.e. 0.5), for RS and AP gilts, respectively). The regression of mean accumulative productivity on time was in favour of the AP line (P=0.05). These results suggest that reproductive performance is not impaired in gilts which have been selected to reach puberty at earlier ages, and productivity at a specific age may be enhanced.