Large dairy herds reproduction management under Moroccan conditions. III. Heat resumption and post-natural insemination anoestrus

Abstract

This study aims at determining both the accuracy and the rate of heat detection together with the so-called post insemination anoestrus incidence in four Moroccan dairy herds under natural or semi-hand mating insemination, 369 females (cows and heifers) were involved from 4 large dairy units in which a herd fertility survey took place on a weekly basis. Heat detection was performed several times a day by the herdsman. Blood was sampled for plasma progesterone (P) determination on the oestrus and the mating day, on day 12 later as well as on day 21 after mating, Accuracy (A) was defined as the ratio of correct oestrus on detected oestrus during the mating days. Heat detection rate (R) was defined as the ratio of oestrus detected on oestrus expected, according to the P values 21 days after mating when the females were confirmed to be cycling. Post-insemination incidence was the complementary ratio to the latter. In the Moroccan dairy unit conditions, A = 91 p. 100, and R = 49 p. 100, the post-insemination anoestrus incidence was there­ fore just over 50 per cent. The distribution of the non-in-heat but mated females (9 per cent) allows two roughly equal sub populations to be distinguished: those mated in mid-luteal phase and those with a 1-2 day overlapping between the follicular phase and the oestrus. Finally, the high incidence of post-insemination anoestrus demonstrates the inadequacy of heat detection for pregnancy diagnosis even under natural or semi-hand mating conditions. To conclude, the heat detection accuracy (A) was satisfactory but not the heat detection rate (R), thus preventing any significant improvement in the efficiency of the reproduction management in these herds.