Presynchronization treatments associated with the Ovsynch protocol and its modifications have been used to improve reproductive performance in lactating dairy cows. Use of a PG-3-G protocol is indicated to increase the number of cows in the most ideal stage of the oestrous cycle (Days 5-9) at first gonadotropin-releasing hormone (GnRH) injection of the Ovsynch protocol. The objective of this study was to compare fertility of lactating dairy cows submitted to Ovsynch-P, preceded by PG-3-G protocol or not. A total of 86 Holstein cows [body condition score of 2.6±0.2 (1-to-5 scale), 3 and 10 years old, mean milk yield of 28.1±7.9kg per day, and 118±56 days postpartum period] maintained in a semi-intensive system were blocked by parity and date of calving and randomly assigned to groups: control (n=44) and PG-3-G (n=42). On Day -10 cows in the PG-3-G group received an injection of 500µg of sodium cloprostenol IM (Estron, Agener União, Brazil), and on Day -7 they received 0.05mg of Lecirelin IM (GnRH, Gestran, Agener União). On Day 0, all cows had the first dose of Ovsynch GnRH injection and a 1-g progesterone intravaginal implant (P4, Primer, Agener União). On Day 7, a dose of sodium cloprostenol was administered to induce corpus luteum (CL) luteolysis, and the P4 implant was removed. Forty-eight hours later, cows were injected with the second dose of GnRH and inseminated 12 to 18h later. The presence of CL and ovulatory follicle (OF) diameter were determined by transrectal ultrasonography (Aquila, Pie Medical, Maastricht, the Netherlands) on Days 0, 7, and 9, and gestation diagnosis was done on Day 30 after AI. Statistical analysis was performed using ANOVA, chi-square, Mann-Whitney, and Pearson correlation tests in SPSS 18 (Armonk, NY, USA), considering P=0.05 significant and a tendency when P>0.05 but P=0.10. Incidence of CL on Day 0 tended to be more frequent (P=0.1) in the PG-3-G group (78.6%) compared with the control (59%), but CL presence on Day 7 did not differ (P=0.98) between the groups (35 and 34%, respectively). Based on the odds ratio, PG-3-G cows were 2.16 times more likely to have a CL on Day 0. The mean diameter of OF on Day 9 was smaller (P<0.05) in PG-3-G cows (12.6mm) than in control cows (15.3mm), and a negative correlation was detected (r=−0.29) between the presence of CL on Day 0 and the diameter of OF on Day 9 (P=0.05). Pregnancies per AI tended (P=0.08) to be higher in PG-3-G cows (52%) than in control cows (34%). In summary, cows submitted to presynchronization with the PG-3-G protocol presented higher frequency of CL on Day 0 and tended to have a higher pregnancies per AI compared with control cows.
Beef heifers that conceive early during their first breeding season calve earlier, wean heavier calves, and tend to continue doing so throughout the rest of their reproductive lives. Otherwise, under extensively managed systems in Southern Brazil, only a variable proportion of 2-year-old beef heifers reach puberty before the start of the breeding season. The aim of this study was to evaluate a protocol to induce puberty in peripubertal beef heifers using injectable progesterone (P4) and oestradiol cypionate (EC) to improve pregnancy per AI (P/AI) in fixed-time AI (FTAI) programs. A total of 311 Angus heifers, 24±3 months of age, 3.1±0.3 body condition score (1=emaciated; 5=obese), and 328±41kg of body weight (BW), were examined before FTAI protocol (Day −24) by transrectal ultrasonography to determine reproductive tract score (RTS; 1=prepubertal; 5=pubertal). Prepubertal heifers (RTS 1; 12.8%, 40/311) were excluded from the study. Heifers with RTS=2 (n=271) were assigned to 2 groups: P4 (RTS 2 or 3, n=100) and cyclic (RTS 4 and 5, n=171). Peripubertal heifers were treated on Day −24 with 150mg of injectable P4 IM (Sincrogest® injectable, Ourofino Animal Health, Cravinhos, Brazil) and on Day −12 received 1mg of EC IM (Sincro CP®, Ourofino Animal Health). Cyclic heifers received no hormonal treatment before FTAI protocol. On Day 0, heifers in the P4 group were evaluated again to determine RTS, body condition score, and BW. Induction of puberty was defined by the presence of a follicle >8.5mm (RTS=4) or a corpus luteum (RTS=5). All heifers received an FTAI protocol consisting of 2mg of oestradiol benzoate IM (Sincrodiol®, Ourofino Animal Health) and an intravaginal progesterone implant (1 g; Sincrogest®, Ourofino Animal Health). On Day 8, heifers had implants removed and were injected with 1mg of EC and 500µg of sodium cloprostenol IM (Sincrocio®, Ourofino Animal Health). After 48h, all heifers received an FTAI. Thirty days after AI, the diagnosis of gestation was performed by ultrasonography. Statistics included chi-square and linear regression with coefficients analysed as independent variables, considering a significant P-value of 0.05. On Day 0, percentages of RTS 5, 4, and 3 in the P4 heifers were 37, 27, and 36%, respectively, resulting in 64% of puberty induction. The P/AI was similar (P=0.14) in P4-treated and cyclic heifers (59v. 50.3%, respectively). The regression analysis presented a linear and positive effect of BW on P/AI (P<0.001) in cyclic heifers and a positive influence of BW on RTS (P=0.05) and RTS on P/AI (P=0.008) in P4-treated heifers. The application of RTS system associated with P4 treatment of peripubertal heifers before FTAI protocol improved ovarian activity and might have contributed to higher P/AI, comparable with that achieved in cyclic heifers.
Foot-and-mouth disease represents an important barrier to the international commerce of animal products, potentially associated with significant economic losses. The systematic vaccination of bovines and buffaloes was fundamental for the eradication of this disease; however, the use of vaccines can lead to reactions at the application site. The objectives of this study were to evaluate the effects of the vaccination protocol to the production of dairy cows and to observe the occurrence of vaccinal reactions in the animals. At one property located in the municipality of Salvador do Sul, Rio Grande do Sul, 270 dairy cows were vaccinated against foot-and-mouth disease in May 2019. The vaccine was administered via a subcutaneous application using disposable syringes and needles for each animal. Inspection of the animals was performed before and 20 days after the vaccination to verify the presence of reactions to the vaccine. The study’s sample was set by convenience, including 203 lactating animals with or without bovine somatotropin (BST) administration during the data collection period, which was limited to 20 days before and 20 days after the vaccination. Milk production data was obtained through SmartDairy® HerdMetrix™ software, tabulated in electronic spreadsheets using Microsoft Excel® and processed using the program SAS®, considering a 5% significance level for mixed model statistical analysis. A total of 160 animals (78.82%) presented local lesions at the application site, even when the recommended vaccination practices were followed, suggesting that the high reaction power was provoked by the vaccinal components. In regards to milk production, a statistically significant (p<0.05) decrease of 0.30kg of milk per animal/day was observed in the average daily production in the 20 days post-vaccination. These results demonstrate the local and systemic effects caused by the foot-and-mouth disease vaccine, evidenced by reduced levels of milk production and the occurrence of vaccine reactions, implying significant economic losses.
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