Altrenogest Supplementation during Early Pregnancy Improves Reproductive Outcome in Pigs

SIMPLE SUMMARY: Over the last decades, sows’ genetic selection was aimed at increasing litter size to improve profitability in the swine industry. However, large litter size has been associated with low birth weight, increased stillbirth rate and high perinatal mortality, which are traits linked to compromised welfare in modern pig production. These side effects related to large litter size are, in part, associated with early conceptuses and placental development. The action of progesterone is essential during early pregnancy stimulating the uterine tissue to produce and secrete nutrients, growth factors, ions, cytokines and other substances that together support a proper early embryo development and placentation, which in turn may result in greater litter traits at birth. The present study demonstrated that altrenogest (progesterone analogue) supplementation during early pregnancy (from day 6 to 12 of pregnancy) may contribute to profitability and welfare in pig production systems since it increased the number of total piglets born and born alive and decreased the stillbirth rate and the number of low birth weight (<800 g) piglets. ABSTRACT: Progesterone plays an important role in initial conceptus development and in a successful pregnancy, but results related to progesterone or its analogues (altrenogest) supplementation in early pregnancy of pigs are conflicting. The present study evaluated the effects of altrenogest supplementation in sows during days 6 and 12 of pregnancy on reproductive performance. On day 6 of pregnancy, 301 females were allocated at random to one of the following treatments: CON (Control: non-supplemented females, n = 163) or ALT (females daily supplemented with 20 mg of altrenogest, orally, from day 6 to 12 of pregnancy, n = 138). Ovulation was considered as occurred at 48 h after the first estrus detection to standardize the first day of pregnancy. The supplementation increased the number of total piglets born (ALT: 17.3 ± 0.4; CON: 16.6 ± 0.4), piglets born alive (ALT: 15.6 ± 0.4; CON: 14.8 ± 0.3), and placenta weight (ALT: 4.2 ± 0.1; CON: 3.8 ± 0.1) and decreased the stillbirth rate (ALT: 5.9 ± 0.6; CON: 7.6 ± 0.6) and the number of piglets born weighing less than 800 g (ALT: 6.6 ± 0.6; CON: 8.0 ± 0.6), without impairment on farrowing rate. These results demonstrated that altrenogest supplementation on swine females between days 6 and 12 of pregnancy may be used to improve reproductive performance.