Abstract

ROQUE-VELAZQUEZ, Carlos I.; MONTALDO-VALDENEGRO, Hugo H.; GUTIERREZ-AGUILAR, Carlos G.  and  HERNANDEZ-CERON, Joel. Effect of a single injection of progesterone five days after insemination on dairy cow fertility. Agrociencia [online]. 2016, vol.50, n.3, pp.287-296. ISSN 2521-9766.

A positive association was found between progesterone concentrations on days 5 and 7 of the estrous cycle and embryo survival. Addition of progesterone between days 5 and 9 post-insemination favored embryo development and the same treatment had no effect when applied between days 12 and 16. This study tested whether a single injection of progesterone 5 d after insemination increases conception rate (CR) in dairy cows. For the experiment, 855 cows with different number of inseminations and parturitions were used. The cows were assigned randomly to one of two treatments 5 d after insemination: P4 (n=427) received an intramuscular injection of 500 mg progesterone; control (n=428) did not receive progesterone. Pregnancy was diagnosed by transrectal palpation between days 40 and 50 post-insemination. The concentrations of progesterone were determined by radioimmunoassay in six cows of each group during 7 days as of day five post-insemination. CR was compared using logistic regression analysis. The independent variables were treatment, days in milk (<90, 90 to 150 and >150 d), number of parturitions (primiparous compared with multiparous), type of Puerperium (normal compared with pathological), body condition score <2.5 or >2.5) and type of estrus (natural, Ovsynch and PGF2 α). Progesterone concentrations were compared by a linear model for repeated measurements. CR (р = 0.39) for cows of group P4 (32 %) was similar to that of control cows (29%). No effect of interaction (p>0.10) of treatment with other independent variables was detected. Group P4 cows had higher concentrations (p<0.05) of progesterone 48 һ after treatment. The progesterone injection 5 d after insemination does not improve CR in dairy cows.

Keywords : Fertility; progesterone; dairy cows.

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