9 EFFECT OF FLUSHING WITH PROTEIN SOURCES OF DIFFERENT DEGRADABILITY ON OVULATION NUMBER IN Santa Inês EWES

Abstract

Flushing provides sheep a diet dense in nutrients before the breeding season to increase the ovulation rate and is usually accompanied by increase in body weight (BW) and body condition score (BCS). Although the effect of flushing with high-energy diets is documented, the influence of flushing with high-protein diets on ovulation rate and on plasma urea nitrogen (PUN) is not well established. The aim of this study was to evaluate the ovulation rate of Santa Ines ewes subjected to flushing with protein sources with different ruminal degradability. Forty-eight ewes were assigned to 2 treatments in a randomized block design, based on initial BCS (2.25 to 2.5; 2.75; and 3.0 to 3.25; scale 1 = thin and 5 = fat). The treatments consisted of 2 isonitrogenous (12% crude protein) and isocaloric (3.9 Mcal of metabolizable energy per day) diets, but with different proportions of rumen-degradable protein; one with soybean meal (SM, n = 24) and the other with corn gluten meal and cottonseed meal (CG + CM, n = 24), provided for 28 d before ovulation. The BW and BCS were evaluated weekly. Estrus synchronization was initiated on Day 17 after beginning the treatment diets. An intravaginal sponge with 60 mg of medroxyprogesterone acetate (MAP-60®, Tecnopec, São Paulo, Brazil) was used for 11 d, and an injection of 300 IU of eCG (Novormon®, Syntex SA, Buenos Aires, Argentina) and 50 μg of cloprostenol (Prolise®, ARSA S.R.L., Buenos Aires, Argentina) was given 9 d after beginning the protocol. Estrus was monitored twice daily. The ovulation rate was evaluated by transrectal ultrasonography and was characterized by the disappearance of dominant follicles in the ovaries. Blood samples for determination of PUN were collected on Days 7, 14, 21, and 28 after the start of flushing. Quantitative data were subjected to ANOVA and the rate of estrus detection was analyzed by chi-square test. Treatment differences were considered significant if P < 0.05. The sheep consumed the equivalent to 1.60 times the metabolizable energy requirement for maintenance and 1.86 times the requirement of protein for maintenance. Estrus detection rate (95.83 v. 83.33%), BW (3.14 ± 0.55 v. 2.94 ± 0.61 kg) and BCS (0.04 ± 0.05 v. 0.10 ± 0.06) gain before ovulation, BW (54.46 ± 1.31 v. 53.36 ± 1.44 kg) and BCS (2.78 ± 0.05 v. 2.85 ± 0.05) on the 28th experimental day, PUN (17.25 ± 0.60 v. 16.23 ± 0.66 mg dL-1), ovulation rate (2.25 ± 0.16 v. 2.24 ± 0.18) and ovulatory follicle diameter (6.61 ± 0.17 v. 6.72 ± 0.19 mm) did not differ (P > 0.05) between ewes feed SM or CG + CM, respectively. Flushing with protein sources with different ruminal degradability did not alter the ovulation rate or the ovulatory follicle diameter in Santa Ines ewes. Funded by FAPEMIG, CNPq, TECNOPEC.