Estratégias para o controle do ciclo estral e da lactação em fêmeas suínas

Abstract

The objective of this dissertation was to study the use of hormonal protocols as strategies for controlling the estrus cycle in swine females. The first study evaluated the efficiency of a protocol for artificial induction of lactation (AIL) in cyclic females (n= 5). The treatment consisted of 10 mg estradiol cipionate (EC), 12 days after the last day of estrus (D12); 10 mg CE and 300 mg progesterone (P4) at D26; and two 2 mL doses of a prostaglandin F2α (PGF) analogue, at a 12-hour interval, 10 days later. Milk secretion occurred 24 hours after the first PGF treatment. At D12, the serum P4 concentration was lower than those observed subsequently (P < 0.05), but estradiol serum concentrations did not differ (P > 0.05). The fat concentration in the milk was unaltered during the first three days of the induced lactation (P > 0.05) but increased from the fourth day on (P < 0.05). The protein concentration in the milk did not differ throughout the lactation (P > 0.05). Subsequently, the same AIL protocol was administered to four gilts, which each received four piglets to nurse. The tested protocol induced lactation in cyclic non pregnant females, allowing the suckling of nursed piglets. The second study evaluated the efficiency of cloprostenol, a PGF analogue, administered at two distinct periods after a protocol with human chorionic gonadotrophin (hCG), to synchronize the estrus cycle of gilts. Starting at the day of their third estrus (D0), 18 gilts were allocated to three treatments (n = 6 each). Gilts in PG25 received two doses of 1,500 IU hCG, at D12 and D15, plus two doses of 250 µg PGF at D25. Gilts in PG30, received the same hCG treatment but PGF was administered at D30. Control gilts were untreated. In PG25 and PG30, the period between the hCG treatment and the expression of the fourth estrus did not differ (P > 0.05). However, the period between PGF treatment and the expression of the fourth estrus was shorter in PG30 than in PG25 (P = 0.0003). After the PGF treatment, serum levels of P4 remained unaltered in PG25, at the three evaluated periods (P > 0.05), but such levels were reduced after two days n PG30, and even lower after five days (P = 0,011). The treatment with PGF 30 days after hCG, tested in the second study, was efficient on controlling the estrus cycle of gilts by prolonging the luteal phase.