Two experiments evaluated the effects of copper (Cu) and zinc (Zn) injection on body weight (BW), body condition score (BCS), pregnancy rate, ovarian traits, and antioxidant and inflammatory responses of beef heifers. In Exp. 1, 29 heifers were assigned to having saline or CuZn (a solution containing 15 and 50 mg/mL of Cu and Zn) subcutaneously injected (5 mL/heifer) 9 days before artificial insemination. Exp. 2 was conducted to increase the statistical power to evaluate pregnancy rate, and 283 heifers were assigned to either the saline or CuZn group. In Exp. 1, CuZn heifers tended (p ≤ 0.10) to gain more BW and to have greater corpus luteum size and plasma concentration of glutathione peroxidase. No effects of treatment were detected (p ≥ 0.18) for BCS; estrus score; serum concentration of Cu, Zn, and cortisol; and plasma concentration of haptoglobin, ceruloplasmin, and superoxide dismutase. In Exp. 2, CuZn heifers had greater (p < 0.01) BW and serum Cu. The CuZn heifers with low BCS had greater (p ≤ 0.05) estrus scores and tended (p = 0.10) to have greater pregnancy rates. Thus, injecting CuZn may be an effective strategy to enhance growth, reproductive performance, and antioxidant responses in heifers, especially when their BCS is below 5.

The objective was to evaluate the pregnancy rate and pregnancy loss of precocious Nellore heifers submitted to one or two previous cyclicity inductions to TAI (timed artificial insemination). A total of 572 Nellore nulliparous aged 12 to 14 months-old were used, divided into two treatments: on D-50, T1- one cyclicity induction (n = 313): 1 ml of 0.9% NaCl and T2- two cyclicity induction (n = 259): 1 ml of injectable progesterone. From that date, the two groups received the same management as follows: On D-26, oral supply of 2.28 g/head/day (MGA^® PREMIX) for twelve days and on D-12, IM application 0.6 mg of estradiol cypionate (E.C.P.^®) in all. Subsequently carried out the TAI protocol and pregnancy diagnosis was performed on D41 and pregnancy confirmed on D101. The uterus and ovary were evaluated in D-50, D-26, and D0. There was no difference in pregnancy rate and pregnancy loss (P > 0.05), besides in T2, better grades of uterine and ovarian scores were observed between the beginning of cyclicity induction and D0 (P < 0.05). The two-induction group had better uterus and ovary scores, which did not interfere with pregnancy and pregnancy loss rates.