Possibilities to shorten the duration of voluntary waiting period at dairy cows

Abstract

In order to achieve a 12-13 months interval between carvings, at dairy cows, is necessary that the cow becomes pregnant in a short interval from calving. For reducing the duration of voluntary waiting period (open days) we administered 500mcg Cloprostenol (PgF2α analog) in the 46^th day after calving. Females that did not manifested heats after first PgF_2α administration, received a second dose after 14 days (60 days from calving). Females that manifested heats were inseminated twice. The conception rate was calculated in respect to the number of females that did not return in heats after AI (Artificial Insemination). At experimental lot, from the 17 females at which PgF_2α was administered at 46 days after calving, 12 manifested heats (70.58%). The other five that did not manifested heats; a second dose of PgF_2α was administered after 14 days. Four of the females treated with a second dose of PgF_2α, manifested heats (80%). At the control lot, from the 6 females, two (33.3%) manifested heats in interval 45-50 days from calving, and another two (33.33%) in the interval 60-65 days from calving. The conception rate, at females from experimental lot, that manifested heats after the first PgF_2α dose, it was 58.33%, and at the females that manifested heats after the second dose the conception rate was 75%. At females from control lot the conception rate was 50%. At females from experimental lot, treated with PgF_2α, the conception rate is higher compared with the females from control lot.