Evaluation of the effect of muscular injection of progesterone on days 2-5 following insemination on pregnancy rate in dairy cows

Effect of progesterone, human chorionic gonadotropin and progesterone + human chorionic gonadotropin treatment on conception rates in repeat breeder cows

The aim of this study was to investigate the effects of hormonal support on the pregnancy rate in repeat breeder cows. Prostaglandin F2α + Ovsynch oestrus synchronization protocol was applied to the cows. Following the fixed time insemination (day 0), the cows were divided into 4 groups. In Group 1 (n = 42), progesterone releasing intravaginal device (PRID) was placed vaginally at 84 h and removed on the 9th day after the artificial insemination. In Group 2 (n = 40), the cows were administered human chorionic gonadotropin (hCG) on the 7th day. Group 3 (n = 45) was applied a combination of progesterone and hCG. Group 4 (n = 42) was not given any treatment. Blood samples were collected from all cows 4 times on days 3.5, 7, 12, and 18 to evaluate progesterone concentrations. The pregnancy rates were 40.47%, 37.50%, 44.44%, and 30.95% in Group 1, 2, 3, and 4, respectively (P > 0.05). In addition, in cows with progesterone concentrations <2 ng/ml on day 3.5, the pregnancy rates were found to be lower than in the cows with progesterone concentrations >2 ng/ml in Group 4 (P < 0.05). Progesterone supplementation in cows with progesterone concentrations < 2 ng/ml appeared to increase pregnancy rates (P < 0.05) in Groups 1 and 3. As a result, post-insemination hormonal applications in the repeat breeder cows did not increase the pregnancy rate. However, it was concluded that determination of progesterone concentrations on day 3.5 following artificial insemination and then hormonal support in the cows with low concentrations would increased the pregnancy rate.

Efficacy of progesterone supplementation during early pregnancy in cows: A meta-analysis

Progesterone is a critical hormone during early pregnancy in the cow. As a result, a number of studies have investigated the effects of progesterone supplementation on pregnancy rates. In this study, a meta-analysis using a univariate binary random effects model was carried out on 84 specific treatments reported in 53 publications involving control (n = 9905) and progesterone-treated (n = 9135) cows. Although the results of individual studies showed wide variations (-40% to +50% point changes), progesterone treatment resulted in an overall increase in pregnancy rate odds ratio (OR = 1.12; P < 0.01). Improvements in pregnancy rate were only observed in cows treated at natural estrus (OR = 1.41, P < 0.01) and not following synchronization of estrus or ovulation. Although treatment between Days 3 to 7 postinsemination was beneficial (OR = 1.15; P < 0.01), treatment earlier or later than this was not. Progesterone supplementation was beneficial in cows of lower fertility (<45% control pregnancy rate) but not in cows with higher fertility. These results indicated that the benefit of progesterone supplementation on fertility of cows required exogenous progesterone supplementation to start between Day 3 to 7 and the appropriate reproductive status (i.e., lower fertility, natural estrus) of the treated cows.

Administração de acetato de melengestrol após inseminação artificial em tempo fixo em vacas Nelore lactantes

Objetivou-se com este estudo avaliar o efeito do fornecimento de Acetato de Melengestrol (MGA®Premix) após IATF (inseminação artificial em tempo fixo), sobre a taxa de concepção em vacas paridas da raça Nelore. Experimento I, avaliou-se o efeito do fornecimento de 2,28g de MGA/ vaca/ dia, do dia 13 (D13) ao dia 18 (D18) após a IATF. As vacas foram divididas em dois grupos, sendo o Grupo I (n=83, controle) que foi realizado apenas IATF e Grupo II (n=104, tratado) que foi fornecido o MGA após a IATF. Experimento II, avaliou-se o efeito do fornecimento de 2,28g de MGA/ vaca/ dia, do dia cinco (D5) ao dia 10 (D10) após a IATF. As vacas foram divididas em dois grupos, sendo o Grupo I (n=94, controle) que foi realizado apenas IATF e Grupo II (n=100, tratado) que foi fornecido o MGA após a IATF. O diagnóstico de gestação foi realizado 45 dias após a IATF em ambos os experimentos. As taxas de concepção foram comparadas pelo teste de Qui-quadrado. No Experimento I, as taxas de concepção foram de 42,16% para o grupo controle e 50,0% para o grupo tratado. No Experimento II, a taxa de concepção do grupo controle (47,87%) foi significativamente maior do que o grupo tratado (28,0%). Conclui-se que o fornecimento de MGA®Premix, administrado do D13 ao D18 após a IATF não afetou a taxa concepção. Entretanto, quando fornecido do D5 ao D10, reduziu a taxa de concepção em vacas Nelore paridas.