Vitamina A injetável em vacas de corte

Abstract

FURTADO, F, H, G. Injectable supplementation of vitamin A at the beginning of fixed-time artificial insemination in beef cows. 2022. 48f. Tese - Faculdade de Medicina Veterinária e Zootecnia, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, 2022. Objectives: Chapter 1) to carry out a literature review on the effects of vitamin A and β- carotene supplementation on the reproductive performance of cows. Chapter 2) to evaluate the effects of vitamin A supplementation on plasma progesterone concentration, dominant follicle size, diameter and volume, corpus luteum and pregnancy rate in Nelore beef cows on pastures. Material and methods: The experiment was divided into 2 stages: Stage 1) 18 multiparous Nellore cows with body condition score between 4 and 6 and dominant follicle greater than 7.0 mm were used at the beginning of the experiment. Cows had estrus synchronized with an 11- day protocol, with 3 passages. Step 2) 365 Nelore cows with body scores between 2 and 6 were used. The animals belonged to 3 different farms. Cows had estrus synchronized with an 11-day protocol, with 4 passages. The animals of the two stages were divided into 2 groups: Cont. (10 mL per animal of saline solution applied intramuscularly); VitA (10 mL of injectable vitamin A supplement - Hipovita A®, IBASA, Brazil - per animal administered intramuscularly). Results: Chapter 1) Vitamin A and/or β-carotene supplementation in cows deficient in these nutrients increased corpus luteum size and progesterone concentration, resulting in a higher pregnancy rate; Chapter 2) Step 1: Treatment with Vitamin A did not influence the size of the dominant follicle (p=0.16), the corpus luteum volume (p=0.90), the plasma concentration of progesterone (p=0. 44), nor in the pregnancy rate (p=0.13). The CL diameter in the Vit A group showed smaller measurements than the Cont group (VitA= 16.2 mm ± 1.10; Cont.= 18.7 mm ± 1.10; p= 0.03) 21 days after the insemination. The Vit A group showed a tendency to increase rectal temperature 21 days after insemination (VitA= 39.9ºC ± 0.19; Cont.= 39.4 ± 0.19; p= 0.10). Stage 2: There was no significant difference in the general pregnancy rate between the groups, however, when the animals were analyzed according to their body score, a tendency towards a reduction in the pregnancy rate of animals with body scores between 5 and 6 was observed. Vit A group (VitA= 35.90% ± 7.02; Cont.= 51.90% ± 7.02; p= 0.10). Conclusion: Chapter 1) Supplementation with Vitamin A and/or β-carotene improves the reproductive parameters of cows, especially in cases of deficiency of these nutrients (< 300 µg/dl of β- carotene and < 25 µg/dl of vitamin A); Chapter 2) Injectable vitamin A supplementation reduced the diameter of the corpus luteum and increased the rectal temperature of Nelore cows 21 days after insemination. The pregnancy rate of cows with a score between 5 and 6 that received vitamin A supplementation showed a tendency to decrease.Keywords: Antioxidant; carotenoids; fertility; oxidative stress; reproduction