69 AGE AT PUBERTY AND REPRODUCTIVE DEVELOPMENT OF LAMBS FED SUNFLOWER CAKE

Abstract

The objective of this study was to evaluate the effects of lipid inclusion, represented by sunflower cake (SC), on the performance, age at puberty, ovarian follicular development, and metabolic panel of prepubertal lambs. Thirty-five crossbred Santa Ines lambs were used [initial body weight (BW) 21.5 ± 1.6 kg and age 138 ± 3 days]. Four SC inclusions were tested: 0% SC, n = 9; 15% SC, n = 9; 30% SC, n = 9; and 45% SC, n = 8, within the dry matter of the diet. The diets were offered to the lambs until they reached 43.6 ± 0.8 kg; after reaching this BW they were slaughtered. Dry matter intake and performance were analysed. The number of follicles, the diameter of the larger follicle, and the total cholesterol serum concentration were evaluated one day before slaughtering. The serum progesterone concentration was analysed every 6 days after the animals reached 30 kg. Puberty was determined when the progesterone concentration reached = 1 ng mL–1 for the first time. The animals were randomly confined in individual pens. To study the significant variable and its effects on the treatments, regression analysis was performed. The number of follicles visualised in the ovary through ultrasound and after slaughtering was analysed by Proc Genmod. Spearman correlation coefficient of the number of follicles obtained through the in vivo ultrasound technique and by the count of follicles in the ovary postmortem. SAS software was used (SAS Institute Inc., Cary, NC, USA). Daily dry matter intake (1.3 ± 0.5, 1.4 ± 0.5, 1.3 ± 0.5, and 1.3 ± 0.6 kg) and weight gain (0.19 ± 0.02, 0.23 ± 0.02, 0.19 ± 0.02, and 0.18 ± 0.02 kg) in the treatments of 0, 15, 30, and 45% of SC, respectively, presented no significant differences (P > 0.05). Total cholesterol serum concentration linearly increased (y = 73.1784 + 0.7206x), (R2 = 0.8477; P < 0.001) with the SC inclusion. The number of follicles <3 mm was not correlated with pre- and post-slaughtering (r = –0.097; P > 0.05), whereas the number of follicles = 3 mm of diameter was correlated (r = 0.56; P < 0.001). The number of follicles = 3 mm (2.4 ± 0.1, 2.3 ± 0.1, 2.4 ± 0.1, and 2.2 ± 0.1), >5 mm (0.5 ± 0.3, 0.7 ± 0.3, 0.8 ± 0.2, and 0.6 ± 0.3), and the diameter of the largest follicle (0.45 ± 0.03, 0.45 ± 0.04, 0.43 ± 0.03, and 0.40 ± 0.04 cm) verified through ultrasound, age at puberty (204 ± 11, 211 ± 13, 211 ± 13, 196 ± 11, 218 ± 11 days), and the weight at puberty (33.5 ± 1.5, 33.5 ± 1.7, 32.2 ± 1.5, and 33.5 ± 1.5 kg) in the treatments 0, 15, 30, and 45% SC, respectively, did not differ (P > 0.05), although the progesterone concentration presented a linear increase (y = 1.4783 + 0.02826x; P < 0.10). The number of follicles <3 mm observed postmortem was influenced (y = 3.0687 + 0.0288*x – 0.0006*x2; P < 0.001) by the levels of SC inclusion (i.e. a higher number of follicles were observed with the SC inclusion until 23.4% SC); follicles > 3 mm (0.91 ± 0.2, 0.91 ± 0.2, 0.97 ± 0.2, and 0.88 ± 0.2) did not differ (P > 0.05). In conclusion, the use of SC in the lamb’s diet positively affected the progesterone concentration and the development of follicles <3 mm of diameter, which presented an optimal level at 23.4% SC inclusion.