Two experiments were designed to evaluate the effect of different treatments for the synchronization of ovulation on pregnancy rates following fixed-time AI (FTAI) of lactating dairy cows. In Experiment 1, 394 Holstein cows that were 61.7 � 13.6 days postpartum (range 35 to 94 days), with a milk yield of 30.7 � 6.8 liters per day (range 12.0 to 52.4 liters) and a body condition score (BCS) between 2.5 to 3.5 out of 5, were used. Cows were blocked by days postpartum and milk yield and randomly assigned to one of four treatment groups. Cows in P4+EB treatment groups received an intravaginal DIB device (1 g P4; Syntex, Argentina) and 2 mg of estradiol benzoate (EB; Syntex) i.m. on Day 0. On Day 8, DIB devices were removed, and cows received PGF (150 �g D+cloprostenol: Ciclase; Syntex), and were subdivided to receive 400 IU eCG (Novormon 5000, Syntex) i.m. or no further treatment at that time. On Day 9, all cows received 1 mg of EB and were FTAI 60 h after DIB removal. Cows in P4-Synch groups received a DIB device and 50 �g of GnRH (Lecirelina, Gonasyn; Syntex) i.m. on Day 0. On Day 7, DIB devices were removed; cows received PGF and were divided to receive 400 IU eCG i.m. or no further treatment. On Day 9, all cows received a second GnRH treatment and were FTAI 60 h after DIB removal. Blood samples were taken on Days -10 and 0 to determine plasma P4 concentrations; 93% of the cows had >1 ng/mL P4 in at least one sample. In Experiment 2, 200 lactating cows from the same farm were treated with the P4+EB+eCG and P4-Synch without eCG treatments with either a DIB or a CIDR-B (1.9 g P4; Pfizer Animal Health, Groton, CT, USA) in a 2 � 2 factorial design. Cows were examined by rectal palpation 50 days after FTAI to determine pregnancy status, and data were analyzed by chi-square Mantel-Haenszel test. There was an EB/GnRH by eCG interaction (P < 0.05) which was attributed to a higher pregnancy rate in the P4+EB+eCG group (44/98; 44.9%) than in the P4+EB without eCG group (30/100; 30.0%) and P4-Synch+eCG group (30/98; 30.6%); the P4-Synch without eCG group had an intermediate pregnancy rate that did not differ from the other treatment groups (37/98; 38.8%). In Experiment 2, no significant differences (P = 0.40) in pregnancy rates were detected between cows treated with DIB (51/100; 51.0%) or CIDR-B (42/100; 42.0%), and there was no difference (P = 0.18) between P4+EB+eCG (52/100; 52.0%) and P4-Synch without eCG (41/100; 41.0%) treated groups. Results suggest that the addition of eCG will improve pregnancy rates following FTAI in lactating dairy cows treated with EB but not in those treated with GnRH at the time of insertion and after removal of a P4 releasing device. Although treatment with P4+EB+eCG resulted in numerically higher pregnancy rates, results were not different from those obtained in the GnRH-based treatment, without the addition of eCG.
We have previously shown that the addition of eCG improved pregnancy rates following fixed-time artificial insemination (FTAI) in lactating dairy cows treated with estradiol benzoate (EB) and progesterone releasing devices (Veneranda et al. 2006 Reprod. Fertil. Dev. 18, 118). An experiment was designed to compare pregnancy rates in lactating dairy cows treated with progesterone-releasing devices and EB plus eCG with different gonadotropin-releasing hormone (GnRH)-based protocols. Five-hundred lactating dairy cows between 30 and 51 days postpartum (when prostaglandin F (PGF) treatments were given in the Pre-Synch groups), with a milk yield of 29.5 � 7.0 kg per day (range 13.0 to 46.0 kg) and a body condition score (BCS) between 2.5 to 3.5 out of 5 were used. Cows were blocked by days postpartum and randomly assigned to five treatment groups. Cows in the Pre-Synch group received PGF 28 and 14 days prior to the insertion of a DIB device (1 g progesterone, Syntex SA, Buenos Aires, Argentina) and the administration of 50 µg of Lecirelin (GnRH, Ovusin, Syntex SA) IM (Day 0). On Day 7, DIB were removed and cows received PGF (0.5 mg cloprostenol, Ciclase, Syntex SA). On Day 9, cows received a second GnRH treatment and were FTAI 16 h later (60 h after device removal). Cows in the Modified Pre-Synch group were treated similarly except that they received a DIB for 7 days prior to the second PGF injection and no DIB at the time of the first GnRH. Cows in the P4-Synch group were treated as those in the Pre-synch group but did not receive the two doses of PGF 28 and 14 days earlier. Cows in the P4 + EB + eCG groups received a DIB for 8 days, 2 mg of EB at DIB insertion (Day 0), and PGF and 400 IU eCG (Novormon, Syntex SA) IM at DIB removal (Day 8); they were subdivided to receive 1 mg of EB on Day 9 (P4 + EB + eCG + EB group) or GnRH on Day 10 (P4 + EB + eCG + GnRH group). Cows in these latter two groups were also FTAI 60 h after device removal. Pregnancy was determined by rectal palpation 50 days after FTAI and data were analyzed by logistic regression. Pregnancy rates were not affected by BCS, days postpartum, or milk yield (P > 0.5). However, there was a significant group effect due to a higher (P < 0.05) pregnancy rate in the P4 + EB + eCG + EB (49%) and P4 + EB + eCG + GnRH (44%) treatment groups than in those in the Modified Pre-Synch group (30%). Pregnancy rate in the P4-Synch group (39%) was lower (P < 0.05) than those in the P4 + EB + eCG + EB group but not different from the others. Finally, pregnancy rate in Pre-Synch group (41%) was intermediate and not different from the other treatment groups. Results of these experiments suggest that treatments with progesterone-releasing devices, EB, and eCG result in pregnancy rates that are comparable to or better than those obtained in GnRH-based protocols in lactating dairy cows. Further studies are needed to investigate whether eCG could increase pregnancy rates in cows treated with GnRH and progesterone-releasing devices. The authors thank Syntex SA for providing the hormones used in the study.
The objectives of this study were to evaluate the reproductive and productive performance of dairy cows with and without puerperal metritis and to evaluate the effectiveness of using a long-acting antibiotic (200 mg mL–1 ceftiofur, Excede, Pfizer Animal Health, New York, NY, USA). Dairy cows in one dairy farm calving from July 2009 to January 2010 were examined between 3 and 14 days postpartum and classified based on vaginal discharge into 3 groups: cows with normal discharge (control); cows with purulent or red-brown vaginal discharge without foul smell, and cows with purulent or red-brown vaginal discharge with foul smell (Sheldon et al. 2006 Theriogenology 65, 1516–1530). Cows in the first 2 groups were not treated, whereas those in the third group were randomly allocated to receive 1 mL/30 kg of body weight of Excede subcutaneously behind the ear or remain untreated. From the 640 cows examined, 372 (58.2%) had normal discharge, 86 (13.4%) had a discharge without foul smell and 182 (28.4%) had a discharge with foul smell. Kaplan-Meier survival curves were obtained to compare pregnancy rates across days postpartum, and differences between curves were tested with the log rank statistic. Proportional hazards regression with PROC PHREG Cox of SAS were done to estimate the risk of pregnancy in terms of treatment, parity (first parity or ≥2 parities), type of delivery (normal or assisted), and milk production. Finally, lactation curves were modeled using SAS PROC NLMIXED to estimate the cumulative milk production at 305 days. Survival curves differed between cows in the control group and those with foul-smell discharge that were not treated (P < 0.01) and between untreated versus treated cows (P < 0.01) in the latter group. Survival curves of cows with discharge but without foul smell were intermediate and did not differ from those in the control group (P = 0.2) and those with foul smell discharge and treated (P = 0.1), but tended to be different from those with foul smell discharge and not treated (P = 0.056). The postpartum interval to achieve a 25% pregnancy rate was 72 days for cows in the control group, 73 days for cows with foul smell and treated, 83 days for cows with discharge without foul smell, and 95 days for those with foul smell and not treated. The chance of pregnancy in cows in the control group was 1.98 times higher (95% CI = 1.33, 3.08) and in cows with foul smell and treated was 2.16 times higher (95% CI = 1.37, 3.50) than those with foul smell and not treated. Finally, the chance of pregnancy in cows with discharge but without a foul smell tended to be higher (P = 0.08) than those with foul smell that were not treated, but did not differ with the other 2 groups. Parity, type of delivery, and production level did not affect pregnancy rates. Cumulative 305-day milk production was higher (P < 0.01) in control cows than those with vaginal discharge, regardless of smell and regardless of treatment. It is concluded that puerperal metritis affects the reproductive and productive performance of dairy cows, and the treatment with Excede was effective in reducing the adverse effects on reproductive performance.
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