Effect of body weight, body condition score and metabolic hormone on reproductive performance of suckled Nelore cows exposed to TAI

Abstract

In beef cows, body conditional score (BCS) is associated with cyclicity reestablishment (WILTBANK, 1962; BOND, 1970) and pregnancy rate at fixed time artificial insemination (FTAI) (MENEGHETTI, 2008; SÁ FILHO et al., 2009). The monitoring of BCS may achieve strategies that improve reproductive performance of breeding season. Aiming understand the influence of body conditional and metabolic and reproductive hormones in Nellore cow's reproductive efficiency at timed artificial insemination (TAI), will be developed in this experiment: evaluation of 1400 suckled Nellore cows (primiparous and multiparous) evaluating the body condition score (BCS), body weight (BW) and reproductive and metabolic hormones in three times: around calving period, at TAI (D11) and at resynchronization (D41). The Nellore cows will be synchronized with estradiol plus progesterone based protocol: that consists in insertion of an intravaginal device containing 1.9 g of progesterone (CIDR®, Zoetis, Guarulhos- SP, Brazil) plus administration of 2 mg of estradiol benzoate (i.m.; 2 ml Gonadiol®, Zoetis) on day zero; an injection of 12,5 mg of dinoprost tromethamine (i.m.; 2,5 ml Lutalyse®, Zoetis) on day 7; on day 9 at device withdrawal plus estradiol cipionate administration (0,5 mg i.m., 0,25 ml ECP®, Zoetis) plus 300 IU of equine chorionic gonadotropin (i.m.; 1,5 ml Novormon®, Zoetis). Timed Artificial insemination will be done 48-54 h after progesterone device withdrawal. All the cows will be examined for pregnancy status by transrectal ultrassonography on day 30 after FTAI. Will be collected blood samples in around 20% of cows, maintened for 24 hours 4°C, then samples will be centrifuged at 3000 x g for 15 minutes at 4° C; plasma aliquots for the assay analysis of IGF-I, leptin and NEFA. The data will be analyzed by the software SAS®. Binominal variables (pregnancy rate on day 30 after FTAI; pregnancy rate on end breeding season) will be analyzed using PROC GLIMMIX, variable continuous (BCS, BW and Leptin, IGF-I and NEFA blood concentration) will be analyzed using PROC MIXED. (AU)