The objectives of the present study were to determine how varying frequency of LH pulses as controlled by varying treatments with progesterone (P 4 ) in cattle would affect: (1) concentration of steroid hormones and activity of insulin-like growth factor binding proteins (IGFBPs) in the ovarian follicular fluid and blood plasma, and (2) duration of persistence of largest ovarian follicles. There ଝ Published as paper no. 12594, Journal Ser. Nebraska Agr. Res. Div.; Research supported by USDA NRI 90-37240-5714. The mention of trade names is necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. This article is a U.S. government work, and is not subject to copyright in the United States.188 F.N. Kojima et al. / Animal Reproduction Science 77 (2003) 187-211 were four treatment groups (n = 7 per group) and a control group (n = 5) of mature, non-lactating beef cows. Treatments were: (1) two progesterone releasing intravaginal devices (PRIDs) for 16 days (2PRID); (2) a half PRID for 16 days (0.5PRID); (3) two PRIDs for 8 days, then a half PRID for 8 days (2-0.5PRID); or (4) a half PRID for 8 days, then two PRIDs for 8 days (0.5-2PRID). Treatment was initiated on the fifth day of the estrous cycle, which was designated as Day 0, and continued for 16 days. All P 4 -treated females were administered prostaglandin F 2␣ on Day 0 and 1 to regress their corpora lutea. Frequency of LH pulses was greater during treatment with the smaller dose of P 4 compared with treatment with the larger dose of P 4 and the control group. Ovarian follicles were classified into five categories based on ultrasonographic observations: growing (G); atretic (A); growing dominant (GD); growing persistent (GP); or atretic persistent (AP). At ovariectomy on Day 16, the largest and second largest follicles collected were re-classified into five categories based on follicular concentration of steroids. Classification of the largest follicle collected on Day 16 was influenced by treatment (P < 0.005), with the 2PRID group having A follicles, the 2-0.5PRID group GP follicles, the 0.5-2PRID group AP follicles, and the 0.5PRID group GD and GP follicles. Concentrations of 17-estradiol (E 2 ) were greatest in GD and GP follicles (P < 0.05). There was less (P < 0.05) activity of IGFBP-2 in GD follicles and less (P < 0.05) activity of IGFBP-3 in GD and GP follicles than other follicles. Activity of IGFBP-4 and -5 was greater (P < 0.05) in A and AP follicles than G, GD, and GP follicles. Maintenance of a frequent release of LH pulses over a 16-day period did not result in maintenance of persistent follicles throughout this period indicating that duration of dominance of these follicles is finite even when there is frequent release of LH pulses. Follicular atresia is associated with greater activity of IGFBP-2, -4, -5, and greater concentrations of P 4 in f...
The objective of the study was to evaluate the reproductive efficiency and antioxidant status of ewes supplemented with two levels of vitamin C during oestrous synchronization and early gestation. Sixty-three ewes were allocated to three treatments, namely T0: control group; T1: 3 g vitamin C coated with ethylcellulose (Rovimix C ® , powder); and T2: 6 g vitamin C coated with ethylcellulose. The ewes received the dietary supplementation during an oestrus synchronization period and lasted until 18 days after breeding. The occurrences of oestrus, gestation, fecundity and prolificacy were measured. Blood samples were collected at various stages to determine antioxidant capacity and oxidative state, and progesterone, glucose and insulin concentrations. Percentage occurrence of oestrus and gestation was analysed using the Chi-Square test, prolificacy and fecundity by GENMOD, and blood tests by the PROC MIXED procedure. It was recorded that the concentration of vitamin C in plasma increased with the supplementation of 3 g and 6 g vitamin C. The antioxidant capacity was higher in T1 than in T0 and T2. Lipid oxidation, and glucose, insulin and progesterone concentrations were not affected. It is concluded that supplementation of 3 g vitamin C during oestrous synchronization and early gestation does not modify the reproductive responses of the ewes. However, the concentration of this vitamin in the blood increased and improved the antioxidant capacity of the animals.
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