Microminerais injetáveis na reprodução de vacas de corte

Abstract

The objective with this study was to evaluate the application effects of a trace mineral mixture (Zn, Cu, Mn e Se), at the moment of fixed-time artificial insemination (FTAI), on pregnancy rates, body temperature, ovarian structures dynamics, and conseptus measurements variations and changes on body weight and body condition score in beef cows. In the first chapter a literature review was carried out addressing general features of reproductive physiology, emphasizing trace minerals importance on animal organism, the described results and the use potential of injectable trace mineral mixtures over reproductive and performance characteristics of beef cows. In the second chapter, two experiments were carried (Exp. 1 and Exp. 2) out to evaluated the effects of a single injectable trace minerals (ITM) dose (6mL/animal) at the time of insemination (AI) on pregnancy rates, body temperature (TºC), dynamics of ovarian structures, conceptus measurements changes, body weight (BW) and BCS of beef cows handled on tropical pastures. The Exp. 1, was conduced on threee commercial farms, where were evaluated 445 cows with approximately 400 kg BW and BCS between 3 and 6 (1-9 scale), kept on pastures and receiving ad libitum powdered mineral mixture. They were synchronized in a fixed time artificial insemination (FTAI) protocol of 11 days (d; d -11 to d 0), ramdomly divided within two treatments of a single injection of a saline solution (Salina; 6 mL/animal) or ITM (6 mL/animal) both applied on d 0. The pregnancy diagnoses waere performed on d 30, being pregnancy rate the only variable evaluated in this study.In Exp. 2, 20 multiparous cows, BCS (1-9) = 4.8 ± 0.41 and BW = 414.7 ± 43.8 kg, managed in pastures and receiving ad libitum powder mineral mixtures were used. The study lasted 71d and comprised the period from 11 d before AI (d -11) to AI (d 0) until 60 d after (d 60). Animals were divided sliced based on BCC and BW into two treatments: 1) injection of a saline solution (Salina; 6 mL/animal) or MMI (6 mL/animal), both applied on d0. Cows were synchronized by an FTAI protocol as described in exp. 1, inseminated on d0 and the pregnancy diagnosis was performed on d 30. Ovarian structures were evaluated on d 0 (dominant follicle diameter) and on d 7, 14 and 21 (corpus luteum diameter), and blood samples were taken on d 1, 3, 7, 14, 21 and 30 for progesterone (P4) evaluation. In Exp. 1, MMI application exhibited the trend to reducing pregnancy rates (P=0.07)in cows with a better BCS, with no significant effects on overall pregnancy rate or on cows with lower BCS (P>0.05). In Exp. 2, MMI did not change (P>0.05) ultrasound measurements of dominant follicle diameter, corpus luteum and conceptus measurements, as well as presented no effect (P>0.05) on BW, BW variation, BCS and BCS variation and pregnancy rate, however, MMI showedan increase (P<0.05) in rectal TºC in supplemented animals. Thus, MMI application did not chage ultrasound, BCS and BW measurements, however, increased rectal TºC and tended to reduce pregnancy rate in supplemented animals.