Effect of body condition on reproductive efficiency of lactating dairy cows receiving a timed insemination

Body condition may influence pregnancy rates to a timed insemination (Ovsynck/TAI) protocol and affect the economical performance of dairy farms. The objectives were to compare pregnancy rates using the Ovsynch/TAI protocol for the first service of lactating dairy cows with body condition scores < 2.5 (scale: 1 to 5, low BCS group) versus greater than or equal to 2.5 (control group) and to estimate the economic impact of the effect of body condition on reproductive performance. At 63+/-3 d post partum, cows were assigned to 2 experimental groups (low BCS = 81; control = 126), and were treated with GnRN at d 0 and with PGF(2 alpha) 7 d later. At 48 h after PGF(2 alpha), cows received an injection of GnRH and were inseminated 16 h later. Pregnancy rates to the Ovsynch/TAI protocol were lower for the low BCS group than for the control group at 27 d (18.1 +/- 6.1 % < 33.8 +/- 4.5 %; P<0.02) and at 45 d (11.1 +/- 5.4 % < 25.6 +/- 4.1 %; P<0.02) after insemination. Economic analysis indicated that reducing the percentage of the herd in low body condition increases net revenues per cow per year. Body condition influenced pregnancy rates to the Ovsynch/TAI protocol. (C) 2000 by Elsevier Science Inc.