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| Author(s): |
Adomar Laurindo Neto
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Pirassununga. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) |
| Defense date: | 2022-10-10 |
| Examining board members: |
Guilherme Pugliesi;
Michele Ricieri Bastos;
José Nélio de Sousa Sales
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| Advisor: | Guilherme Pugliesi |
| Abstract | |
We tested in dairy lactating cows the hypotheses: 1) that starting the resynchronization (Resynch) of ovulation for timed-artificial insemination (TAI) 17 days after TAI (Super-Early Resynch) improves the reproductive efficiency compared to the traditional resynch starting at day 31 after TAI; and 2) the treatment with 1 mg estradiol benzoate (EB) at beginning of Super-early Resynch does not compromise a pre-existing pregnancy and reduce the false positive (FP) rate of Doppler-based pregnancy diagnosis. Dairy cows from two commercial farms, and with a body condition score between 2 and 4 (scale: 1-5), and after 52 days of voluntary wait period, were submitted to an EB/P4 (progesterone)-based protocol for the first TAI post-partum (D0). On D17, cows were randomly assigned to three experimental groups (n=150/group): Control (C); Super-early Resynch (SE) and Super-early Resynch + 1mg EB (SE+EB). In the diagnosis of conventional pregnancy (31 days after each TAI), non pregnant cows (NP) of group C were submitted to the same hormonal protocol performed in the reproductive management of the farm, being repeated to perform three TAIs (D0, D42 and D84) in the interval of 84 days. In both Super-early Resynch groups, all cows received a first-use P4 intravaginal device (CIDR®, Zoetis, Brazil) associated (SE+EB) or not (SE) to 1mg EB (1 mL, i.m., Gonadiol®, Zoetis) 17 days after each TAI, being repeated until closing four TAIs in 84 days. On D24, D52 and D80 cows were evaluated by Doppler ultrasound to determine corpus luteum (CL) blood perfusion and those where luteolysis was detected were considered NP and received 25 mg tromethamine dinoprost (5 mL, i.m., Lutalyse®, Zoetis). On D26, the P4 devices were removed and were administered 1 mg estradiol cypionate (0.5 mL, i.m., ECP®, Zoetis) and 25 mg of tromethamine dinoprost in NP cows. On D28 a second TAI was performed (interval of 28 days between TAIs). Both type of resynch (Conventional or Super-early Resynch) were repeated until D84, which allowed a maximal of 3 TAIs in the C group and 4 TAIs in the SP and SP+EB groups. Confirmatory diagnosis of pregnancy was performed on days 31 and 66 after the first, second, third and fourth TAIs. Data were evaluated by ANOVA, Fisher’s exact test or logistic regression of SAS. The pregnancy rate (PR) at first TAI did not differ (P>0.1) among the C (44%), SP (47%) and SP+BE (47%) groups. Cows submitted to Super-early Resynch had a greater (P<0.05) follicular diameter (mm) at TAI (17.5±0.2) when compared to the C group (15.7±0.2). Considering Second, third and forth TAIs, the PR at resynch’s did not differ (P>0.1) among the C (29.6% [42/142]), SP (30.3% [44/145]) and SP+BE (30.2% [48/159]) groups; however, cumulative PR within the 84 days of experimental period was greater (P=0.05) in cows submitted to Super-early Resynch (79.3% [238/300]) compared to the C group (72% [108/150]). Furthermore, the rate of FP results between the D24 and confirmatory pregnancy diagnosis on D31 was lesser (P<0.05) in the SP+BE group (18% [23/128]) than in the SP (30% [48/160]). Finally, profitability, net present value (NPV), internal rate of return (IRR) and Payback were calculated for each scenario as indicators of economic viability. Under the conditions analyzed, it was observed that the scenario with the best economic performance was Super-early Resynchronization (Profitability of R$ 94,891.35; NPV R$ 63,172.81; IRR 76.32% per year and payback of 7 weeks), compared to Conventional (Profitability of R$ 94,756.06; NPV R$ 49,416.51; IRR 51.36% and payback of 11 weeks). In conclusion, the Super-early Resynchronization increases the PR during the first 84 days after the voluntary wait period in dairy cows. The use of 1mg EB associated with a P4 device on D17 after TAI is preferable to increase the effectiveness of the Super-early Resynch protocol, as it is not harmful to the previous pregnancy, and reduces the proportion of NP cows with functional CL at 24 days after previous TAI. (AU) | |
| FAPESP's process: | 20/05878-8 - Impacts of anticipating ovulation resynchronization by early detection of non-pregnant dairy cows with doppler ultrasound |
| Grantee: | Adomar Laurindo Neto |
| Support Opportunities: | Scholarships in Brazil - Master |