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 (Ovsyn ck/TAI) protocol and affect the economical performance of dairy farms. The objectives were to compare pregnancy rates using the Ovsynch/TAI protocol f or 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 (cont rol group) and to estimate the economic impact of the effect of body condit ion on reproductive performance. At 63+/-3 d post partum, cows were assigne d 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. Preg nancy rates to the Ovsynch/TAI protocol were lower for the low BCS group th an 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. E conomic analysis indicated that reducing the percentage of the herd in low body condition increases net revenues per cow per year. Body condition infl uenced pregnancy rates to the Ovsynch/TAI protocol. (C) 2000 by Elsevier Sc ience Inc.