Control of parturition in hyperprolific sows by using altrenogest and double administrations of PGF2α

The aim of the present study was to develop a protocol to reduce the variation in gestation length and synchronise the onset of parturition in sows by using altrenogest in combination with double administrations of prostaglandin F2alpha (PGF2α). In total, 188 Landrace x Yorkshire crossbred sows with parity numbers 3.1 ± 1.6 were included in the experiment. The sows were classified into two groups: CONTROL (n = 94) and TREATMENT (n = 94). CONTROL sows were allowed to farrow naturally, and TREATMENT sows were orally administered 20 mg/day of altrenogest starting when they entered the farrowing house (107.0 ± 2.0 days) until 113 (TREAT-113, n = 18), 114 (TREAT-114, n = 29) and 115 (TREAT-115, n = 47) days of gestation. The altrenogest-treated sows were administered PGF2α twice 6 h apart at 24 h after the withdrawal of altrenogest. The litters were randomly selected (25 and 26 litters from CONTROL and TREATMENT groups, respectively) to determine individual body weight at birth and at 24 h after birth. Gestation length of sows that farrowed naturally averaged 115.1 days (range 111-118), whereas gestation length of altrenogest-treated sows averaged 115.1-116.3 days (range 114-118). The colostrum yield of sows averaged 4.25 ± 1.19 kg and was not affected by the treatment (P > 0.05). Colostrum IgG in the CONTROL group was higher than in the TREAT-114 and TREAT-115 groups (P < 0.05) but did not differ significantly compared to the TREAT-113 group. The proportion of sows that farrowed during working hours (0700-1700 h) in the TREAT-113 group (72.3%) tended to be higher than in the CONTROL (46.4%, P = 0.053). The interval from the last altrenogest treatment until farrowing in the TREAT-113 group was longer than in the TREAT-114 and TREAT-115 groups (62.8, 40.7 and 34.6 h, respectively, P < 0.05). Similarly, the intervals from the first PGF2α administration to the onset of parturition in the TREAT-113 group (38.8 ± 3.8 h) was longer than TREAT-114 (21.9 ± 3.5 h, P = 0.002) and TREAT-115 (25.5 ± 3.7 h, P = 0.016) groups. However, the incidence of stillbirths in the TREAT-113, TREAT-114 and TREAT-115 groups was higher than in the CONTROL (16.4, 17.2, 11.8 and 5.8%, respectively, P < 0.05). In conclusion, altrenogest supplementation in combination with double administrations of PGF2α can reduce the variation in gestation length and synchronise the onset of parturition in sows. However, its side effects on the incidence of stillbirths should be considered.