RESUMOA subnutrição é o principal fator que afeta o nível de produção em um sistema extensivo de criação de bovinos de corte com conseqüências diretas nos índices reprodutivos. O presente trabalho teve por objetivo avaliar a influência da condição corporal (CC) quando avaliada no diagnóstico de gestação, sobre a taxa de prenhez e o momento da concepção na estação reprodutiva de vacas de corte, nas diferentes categorias. Foram utilizadas para este trabalho 435 fêmeas, sendo vacas solteiras, vacas com cria ao pé e novilhas. A taxa de prenhez, sem considerar a categoria, nos animais com CC = de 3 foi de 81,8% (304/373), sendo que a taxa de prenhez nos animais com CC < 3 foi de 17,7% (11/62) (p<0,001). Considerando apenas as vacas com cria ao pé, a taxa de prenhez nas vacas com CC < 3 foi de 17,7% (11/62), enquanto que para as vacas com CC = 3 foi de 68,6 % (94/ 137) (p<0,001). Considerando apenas as vacas gestando com cria ao pé, com CC < 3, 90,9 % (10/11) estavam no primeiro terço de gestação e apenas 1 de 11 vacas (9,1%) se encontrava no segundo terço de gestação (p<0,01). Os resultados deste estudo sugerem uma influência da CC sobre a taxa de prenhez nas diferentes categorias e sobre o momento da concepção nas vacas com cria ao pé.Descritores: condição corporal, taxa de prenhez, intervalo parto-concepção, bovinos de corte. ABSTRACTThe undernutrition is the main factor that affect the production level in a extension beef cattle system production which influences directly in the reproductive efficiency. The aim of this work was to evaluate the influence of body condition score (BCS) evaluated at pregnancy diagnosis in the pregnancy rate and moment of conception in the breeding period of beef cows of different categories. For this work 435 females were used, including heifers, non-lactating cows and lactating cows. The pregnancy rate, considering all categories, for the animals with BCS = 3.0 was 81.8% (304/373) and 17.7% (11/62) for animals with BCS < 3.0 (p<0.001).When we consider only the lactating cows, the pregnancy rate for cows with BCS < 3.0 was 17.7% (11/62), while it was 68.6% (94/137) for cows with BCS = 3.0 (p<0.001). For the pregnant lactating cows, with BCS < 3.0, 90.0% were in the second third of gestation (p<0.01). The results of this work suggest an influence of the BCS on the pregnancy rate of different categories and on the conception moment in the lactating cows. Dionello N.J.L. 2007. Efeito da condição corporal avaliada no diagnóstico de gestação sobre o momento da concepção... Acta Scientiae Veterinariae. 35: 303-307.
The objective was to determine the effect of the level of progesterone (P4) during the ovulatory wave on fertility. Low v. high progesterone concentrations which were expected to result in high v. low LH pulse-frequency were compared. Lactating, postpartum beef cows (n = 69) at random stages of the estrous cycle were given cloprostenol (PGF; Schering-Plough Animal Health, Pointe-Claire, QC, Canada) twice at an 11-day interval to synchronize ovulation (Day 0 = day of 2nd PGF). Cows were given 1.5 mg estradiol benzoate on Day 10 (7 days after expected ovulation). On Day 10, the Low-P4 group was given PGF and an intravaginal CueMate (Bioniche Animal Health, Belleville, ON, Canada) containing one P4 pod (expected to achieve a P4 plasma level of 1 ng mL–1). The High-P4 group also received a CueMate with one pod on Day 10, but no PGF was administered (i.e., cows were allowed to retain their CL for 4 days after expected emergence of the estradiol-induced wave). On Day 18, CueMates were removed and PGF was administered to both groups. Fifty-four to 56 h later, all animals received 12.5 mg of Lutropin-V (Bioniche) IM and were timed AI (TAI). Dominant follicle diameter was measured on Day 18 and at the time of AI. Pregnancy diagnosis was done by ultrasonography 27 days after AI to compare fertility between groups. Follicle diameter data were analyzed by Student's t-test and pregnancy rate data were compared by the chi-square test. The dominant follicle in the Low-P4 group was larger (P < 0.05) than in the high-P4 group on the day of the CueMate removal (Day 18) and on the day of the TAI (11.8 � 0.4 and 13.7 � 0.5 v. 13.3 � 0.6 and 15.3 � 0.6 in the High-P4 and Low-P4 groups, respectively). Pregnancy rate was similar (P = 0.16) between the groups (High-P4: 55.6% (20/36) and Low-P4: 44.4% (16/33)); however, a larger study is in progress to confirm these results. To conclude, Low-P4 resulted in a larger dominant follicle without any apparent effect on pregnancy rate. The project was funded by Saskatchewan ADF and NSERC. L. Pfeifer is funded through a CAPES scholarship. We acknowledge Schering-Plough and Bioniche for donation of pharmaceuticals.
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