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Recombinant glycoprotein with eCG-like activity did not increase the incidence of multiple ovulation in beef cattle in a 5-day CoSynch protocol
Rodriguez, A.; Maresca, S...
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Objectives: The objective was to compare the effect of a glycoprotein with eCG-like activity on the incidence of multiple ovulation in Bos taurus beef cattle synchronized with a 5-d CoSynch plus progesterone protocol.
Material & Methods: Angus heifers of 22-month-old and suckled cows were submitted at random to either a 5-d progesterone CoSynch with reCG (reCG; n=140) or a 5-d progesterone CoSynch without reCG (Control; n=141). The body weight (BW; mean±SD) and body condition score (BCS, scale 1-9) of 22-month-old heifers of Herd 1 (n=95) and Herd 2 (n=97) were 377±21 Kg and 382±30 Kg, and 5.2±0.4 and 6.3±0.5 respectively, while suckled cows in Herd 3 (n=89) had 460±46 Kg and 5.2±0.5 units of BCS. The day of TAI was considered as Day 0 of the experiment. On Day -8, BCS was recorded and presence, number and location of CL (cyclicity) was de- termined based on ultrasonography. On the same day, all animals received 100 μg of GnRH analog (Gonadoreline acetate, 2 mL, im, Prolusyn®, Syntex) and a 1.0 g of progesterone intravaginal device (DIB®, Syntex). Ovulation in response to initial injection of GnRH was evaluated by the number and location of CL on Day -3 in relation to Day -8 based on ultraso- nography. Also, on Day -3, all animals received 0.500 mg of sodium closprostenol (2 mL, im, Ciclase®, Zoetis) at device removal and were assigned randomly to receive 300 IU (1.5 mL, im, reCG, Syntex) in heifers and 400 IU (2 mL, im, reCG, PCT/EP2019/073277, Syntex) in cows of reCG or remain as untreated controls. On Day -2 animals received a second dose of closprostenol and finally on Day 0 (72 h after DIB removal), received 100 μg of gonadoreline acetate concurrent with TAI. On Day 7, the number of ovulations (single = 1; multiple ≥ 2) in response to synchronization of ovulation protocol was determined by ultrasonography.
Data was analyzed using SAS (Statistical Analysis System). Optimal BCS was considered in heifers ≥6 and in cows ≥5. Baseline comparisons were es- tablished evaluating the distribution of cows in both treatment groups using a Chi-square test (Proc Freq, SAS system®). The effect of treatment group (reCG vs. control), herd (1, 2 and 3), BCS (<optimum vs. ≥optimum), cyclicity (anestrus vs. cyclic) and ovulation in response to initial injection of GnRH (yes vs. no) on incidence of multiple ovulation was evaluated by
univariate analysis with Chi-square test (Proc Freq, SAS sys- tem®). In addition, the effect of treatment adjusted by the rest of the variables and interactions on the incidence of multiple ovulation was evaluated by multiple logistic regression models (Proc Logistic, SAS system®) using the backward elimination procedure.
Results: There was no difference in the distribution of cows by herd (P=0.58) and cyclicity (P=0.96) between treatment groups. At the beginning of the experiment (Day -8), 85, 84 and 89 % of heifers and suckled cows from herd 1, 2 and 3, respectively, were cyclic. The percentage of heifers and suckled cows that ovulated in response to initial injection of GnRH was 38 and 55%, respectively. Two suckled cows did not ovulate in response to second injection of GnRH. A 7.2% (20/279) of animals had multiple ovulation in response to synchronization of ovulation protocol. In the univariate anal- ysis, the incidence of multiple ovulation was not affected by treatment group [6.5% (9/139) and 7.9% (11/140) in reCG and control group, respectively; (P=0.65)]. There was also not affected by herd (P=0.90), BCS (P=0.33), cyclicity (P=0.59) and ovulation in response to initial injection of GnRH (P=0.76). In the multivariable analysis, the incidence of multiple ovulation was also not affected by treatment group (P=0.81).
Conclusions: In conclusion, the addition of reCG in a 5-d CoSynch plus progesterone protocol did not affect the inci- dence of multiple ovulation in Bos taurus beef cattle.
Keywords: reCG, 5-day CoSynch, Multiple ovulation.
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Affiliation of the authors at the time of publication
Instituto Nacional de Tecnología Agropecuaria, Estación Experimental Agropecuaria Cuenca del Salado, Argentina;
Instituto Nacional de Tecnología Agropecuaria, Estación Experimental Agropecuaria Anguil, Argentina;
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Veterinarias Universidad Nacional de La Pampa, Argentina;
Facultad de Ciencias Veterinarias Universidad Nacional de La Pampa, General Pico, La Pampa, Argentina;
Syntex S.A., Buenos Aires, Argentina;
Laboratorio de Endocrinología y Metabolismo Animal, Facultad de Veterinaria, Universidad de la República, Montevideo, Uruguay.
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