Abstract The objective was to determine the effect of some factors on pregnancy rate of fixed-time embryo transfer (FTET), in cows and heifers kept under Mexican tropical conditions. Recipients females (n=405) grazing in pastures were selected according to breed group (Zebu and crosses), parity (nulliparous and multiparous), body condition score (BCS) and the presence of a corpus luteum (CL). The females were synchronized on day 0 using a progesterone vaginal device and 2 mg estradiol benzoate (EB), two groups were established. Group 1 (conventional protocol) were animals in which the progesterone device was removed on day 7. At this time, also received an injection of 50 mg cloprostenol sodium and 1 mg estradiol cypionate. Animals also received 300 IU (heifers) or 360 IU (cows) of eCG. Group 2 (J-Synch protocol) were animals in which the progesterone device was removed on day 6. Cloprotenol and eCG injections were applied as in Group 1. Additionally, on day 9, animals of group 2 received 0.01 mg buserelin acetate. Embryo transfer of in vivo or in vitro was done on day 16 and pregnancy diagnosis was realized by ultrasonography on days 23 and 53 after FTET. Statistical analyses were carried out using Chi-square tests and logistic regression. Pregnancy rate varied between farms (P<0.05). The highest pregnancy rate was for multiparous cows (66%). The recipient utilization rate was better in the J-Synch protocol (85%), and in vivo embryos (75%) had higher pregnancy rate. The diameter of the follicle and the CL had no effect on pregnancy rate (P>0.05). However, the logistic regression determined that the only significant factor on pregnancy rate was the type of embryo. In conclusion, pregnancy rate in FTET females was higher for in vivo embryos than for in vitro embryos in cows evaluated under humid tropical conditions in Mexico.

The aim of this study was to evaluate the productivity and profitability of two commercial sources of progesterone therapy as part of a hormonal induction treatment in a heifer dual purpose herd. A second objective was to determine the productivity and profitability of a recombinant bovine somatotropin (ST) application during induced lactation. Forty four Holstein heifers x Zebu crosses were used. Four treatments and two control groups were evaluated. For economic analysis all components of total cost (TC) of the companies were considered, further there was a simulation which was designed for three natural lactations after the hormonal induction, based on two scenarios in which different body weights were considered as different periods. Artificial induction of lactation yielded a 100% success rate in the four groups of animals with no statistical differences between them (P > 0.05). The best cost-benefit ratio (CBR) was recorded by CIDR treatment without ST. Although the four treatments showed economic viability, those without ST had a better ratio (B / C) than those supplemented with ST. As for the net present value (NPV), the benefits updated showed that the profits were higher when ST was not applied and, mainly, in the CIDR treatment. The internal rate of return (IRR) reveals that most of the treatments have a yield above 20%.

Los objetivos del presente trabajo fueron: 1) evaluar la productividad y rentabilidad de dos fuentes comerciales de progesterona como integrantes de un tratamiento lactoinductor en vaquillas de reemplazo de un hato de doble propósito y 2) determinar la productividad y rentabilidad de la aplicación de somatotropina bovina recombinante (ST) durante la lactación inducida. Se usaron 44 novillonas producto de cruzas Holstein x Cebú. Se evaluaron cuatro tratamientos y se manejaron dos grupos testigo. Para el análisis económico se consideraron todos los componentes del costo total (CT) de las empresas, adicionalmente se realizó una simulación en la que se proyectó para tres lactaciones naturales posteriores a la lactoinducción, basadas en dos escenarios en los que se consideraron diferentes pesos corporales como diferentes periodos. En los cuatro grupos de animales lactoinducidos, el 100% de las vaquillas respondió al tratamiento sin diferencias estadísticas entre ellas (P > 0.05). La mejor relación beneficio-costos (RBC) la registró el tratamiento CIDR sin ST. Si bien los cuatro tratamientos presentaron viabilidad económica, los tratamientos sin ST presentaron mejor relación (beneficio/costo) que aquellos tratamientos que sí fueron complementados con ST. En cuanto al valor actual neto (VAN), los beneficios actualizados de todos los años muestran que las utilidades que generaron los tratamientos fueron superiores cuando no se aplicó ST y, principalmente, en el tratamiento con CIDR. La tasa interna de rentabilidad (TIR) revela que la mayoría de los tratamientos tienen una rentabilidad arriba del 20%.