Factors influencing pregnancy rate and late embryonic loss in dairy cattle.

This trial was conducted on three Hungarian dairy farms between March 2003 and April 2004. The aims of this study were to examine the effect of milk production and milk contents, the day after calving (DAC) and the sire for the pregnancy rate (PR) and late embryonic loss (LEL) in dairies. Five thousand three hundred and eighty insemination was carried out in this period. Pregnancies (n = 1969) were detected by BioPryn test from 3919 blood samples between 30-36 days post insemination (PI). Retention of pregnancy was determined by rectal palpation on Day 60. LEL has been determined by the optical density (OD) of blood samples/cutoff ratio and the serum progesterone (P4) concentration 30-36 days PI. According to serum progesterone concentration the authors predicted a presumed or possible embryonic loss or maintenance of the pregnancy. The efficiency of the artificial inseminations (AI) was significantly lower 60 days within post-partum. Significant positive correlation was found between the result of early and late PR and DAC and the milk protein/fat ratio. Significant negative correlation was detected between the early and late PR the milk protein and fat content. A later stage (60 days PI) of pregnancy the milk production has a negative effect for retaining of pregnancy. More data would be necessary to state that sires can influence the reproduction ability of their progenies. This is a really important issue, because the AI bulls have a great impact on the herds and the one-way selection may cause decreased fertility on breed level as well.