The objective of this study was to evaluate the effect of a PGF2α-analogue (PGF) on ovulation and pregnancy rates after timed artificial insemination (TAI) in cattle. In experiment 1, crossbred dual-purpose heifers, in a crossover design (3 × 3), were given an intravaginal progesterone-releasing insert (controlled internal drug release [CIDR]) plus 1 mg estradiol benzoate (EB) intramuscularly (im) and 250 μg of a PGF-analogue im on Day 0. The CIDR inserts were removed 5 days after follicular wave emergence, and the heifers were randomly divided into three treatment groups to receive the following treatments: (1) 1 mg of EB im (EB group, n = 13); (2) 500 μg of PGF im (PG group, n = 13); or (3) saline (control group, n = 13), 24 hours after CIDR removal. Ovulation occurred earlier in EB (69.81 ± 3.23 hours) and PG groups (73.09 ± 3.23 hours) compared with control (83.07 ± 4.6 hours; P = 0.01) after CIDR removal. In experiment 2, pubertal beef heifers (n = 444), 12 to 14 months of age were used. On Day 0, the heifers were given a CIDR insert plus 2 mg EB im. On Day 9, the CIDR was removed and the heifers were given 500 μg of PGF im. Heifers were randomly assigned into one of three treatment groups: (1) 1 mg of EB (EB group; n = 145); (2) 500 μg of PGF (PG group; n = 149), both 24 hours after CIDR removal; or (3) 600 μg of estradiol cypionate (ECP group; n = 150) at CIDR removal. Timed artificial insemination occurred 48 hours after CIDR removal in the ECP group and 54 hours in the PG and EB groups. The percentage of heifers ovulating was higher in the PG group compared with the other groups (P = 0.08). However, the pregnancy rates did not differ among groups (47.6%, 45%, and 46.6%, for EB, PG, and ECP, respectively; P = 0.9). In experiment 3, 224 lactating beef cows, 40 to 50 days postpartum with 2.5 to 3.5 of body condition score were treated similarly as described in experiment 2, except for the ECP group, which was excluded. The treatments were as follows: 1 mg EB (EB group; n = 117) or 500 μg PGF (PG group; n = 107), 24 hours after CIDR removal. The calves were temporarily separated from their dams from Days 9 to 11. No difference was detected on the pregnancy rate between the EB and PG groups (58.1% vs. 47.6%, respectively; P = 0.11). Taken together, the combined results suggested that PGF2α could be successfully used to induce and synchronize ovulation in cattle undergoing TAI, with similar pregnancy rates when compared with other ovulatory stimuli (ECP and EB).
The aim of this study was to confirm the possible consequences of prepartum lameness on subsequent lactation among Holstein cows. In this research, 27 multiparous cows, were monitored from the 30th to 63rd day, relative to calving. Thirty days prior to parturition, the animals were segregated into two groups based on the locomotion score (LS), where LS 1 is attributed to animals without claudication, LS 2 to those with suspected lameness and LS 3, 4 and 5 to those with mild, moderate and severe lameness, respectively; in the lame cows group (LC) (n=15), the animals displayed LS ≥ 3, whereas in the non-lame cows group (NLC) (n=12) they showed LS 1. Milk production, body condition score (BCS) and blood concentration levels of β-hydroxybutyrate (BHB), urea, phosphorus, calcium aspartate aminotransferase (AST), gamma glutamyl transferase (GGT) and total plasma proteins (PPT) were evaluated. Milk production (17.675 ± 0.31 L of milk/day) and blood calcium concentration (7.42 ± 0.12 mg/dL) were lower in the lame cows in comparison to those without lameness (22.27 ± 0.42 L of milk/day and 9.63 ± 0.13 mg/dL). Besides, the lame cows showed higher BCS loss during the early postpartum period. The metabolites AST, GGT, PPT, urea, BHB and phosphorus revealed no difference between the groups during the period evaluated. The lameness evident in cows during prepartum exerted major negative effects on the milk production and calcemia, making the LS evaluation during these period an important tool in the early diagnosis of losses for future lactation.
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