AGE AND WEIGHT AT FIRST SERVICE OF THE GILT TO IMPROVE HER LIFETIME PERFORMANCE
Keywords:
Body Weight, Age at Service, Gilt, Reproductive PerformanceAbstract
Swine farms show greater reproductive efficiency due to improvements in ovulation rate and litter size; however, they require a constant supply of replacement gilts because of the persistently high culling rates (40 to 50%) of sows in the breeding herd. It is recommended that gilts be selected from third-parity litters, with birth weights above 1.2 kg, achieving growth rates of 600 g/day at 140 days of age and 650 to 750 g/day at the time of first service. From 140 days of age onward, stimulation with a mature boar should begin for 15 to 20 minutes in the morning and afternoon to induce puberty between 150 and 180 days of age. Gilts should be first serviced when they reach a body weight of 135 to 150 kg, with at least 13 mm of backfat thickness (BFT), generally at the second or third estrus, around 210 to 240 days of age. Servicing gilts at a body weight between 135 and 150 kg allows them to reach approximately 180 kg at first farrowing and to have a short weaning-to-estrus interval (WEI) of 3 to 6 days, with sufficient body reserves (15–18 mm BFT) to achieve a high ovulation rate, sustain pregnancy, and produce a large litter at the second farrowing. Gilts that are too old (>250 days) and overweight at first service are at increased risk of premature culling. Premature culling is mainly due to reproductive failures and locomotor problems, although an increase in mortality rate has also been recently reported. Sows with extended reproductive longevity are often characterized by producing large litters in their first two parities. To determine the economically optimal parity at culling, the cumulative number of piglets born and weaned during the sow’s productive life in the breeding herd and the future productive potential of a replacement gilt should be considered. For a gilt to be economically profitable, she needs to achieve three to four parities, with at least 12 piglets weaned per litter.
