ABSTRACT:
Protocols to artificially induce cows and heifers into lactation are effective and commercially available in Brazil. However, these protocols demand long hormonal treatments, which is debatable since little research has been done in the subject. To further understand artificial induction to lactation (AIL) protocols, we conducted two experiments. In experiment 1, our objective was to better characterize steroidal profile during an AIL protocol and assess the estradiol (E2) and progesterone (P4) serum profiles of Jersey cows (n=6) subjected to a conventional protocol. In experiment 2, we aimed to compare milk production and serum E2 concentrations of Holstein heifers induced into lactation by the standard AIL protocol (15 injections of E2 and 8 P4 injections) and by a short protocol in which the number of E2 injections and, consequently, the overall dosage of E2, were reduced (8 injections of E2 and 8 P4 injections). We hypothesized that a short AIL protocol (8 days) would be as efficient as the long standard protocol of 15 days. Our hypothesis was confirmed, since we demonstrated that a shorter protocol was able to induce lactation in Holstein heifers without hindering milk production.
Key words:
artificial induction to lactation; dairy cow; estradiol benzoate; injectable progesterone; intravaginal device.
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