141 EFFECT OF ENVIRONMENTAL TEMPERATURE ON EMBRYO PRODUCTION AND CONCEPTION RATES IN BEEF AND DAIRY CATTLE

Abstract

The aim of this study was to evaluate the effect of environmental temperature at the time of embryo collection and transfer on embryo quality and conception rates after transfer of fresh and frozen embryos. Purebred dairy (Holstein, Czech spotted cattle, n = 174) and beef (Charolais, Blonde d’Aquitaine, Piedmontese, Hereford, Limousin and Simmental; n = 72) donors were collected during 2005 to 2007. Donor cows received one application of PGF_2α and superstimulation was initiated 9 to 11 days following estrus with pFSH (Folltropin-V; Bioniche Animal Health, Belleville, ON, Canada) given twice daily for 4 days. Prostaglandin_2α was given on Day 3 of the superstimulation treatment. Donors were inseminated 3 times, with 1 unit of semen on Days 5 and 6 of treatment. Embryo recovery was carried out on Day 7 after insemination. The recipients were synchronized with PGF_2α and embryos were transferred on Day 7 after estrus. The effect of temperature at the time of 246 embryo recoveries and 1338 transfers (fresh and frozen embryos) was analyzed using the GLM, assuming quasi-poisson and quasi-binomial error distribution by R software (www.r-project.org). We evaluated the total number of ova/embryos collected, embryo quality, and conception rates after transfer at the environmental temperatures shown below. Temperatures were divided into the following ranges: A) from –5 to 5°C; B) from 6 to 15°C; C) from 16 to 20°C; and D) over 20°C. The average temperature values were obtained from the Czech hydrometeorological institute and corresponded to the following seasons: winter (range A and B); spring (range B and C); summer (range C and D); fall (range C and B). Dairy cows were managed intensively in barns whereas beef cows were managed in barns during the winter and on pasture from April until October. In beef donors the mean number of total ova/embryos collected and transferable embryos were 9.1 ± 7.9 and 4.2 ± 4.5, respectively and no significant effect of temperature was detected (P > 0.05). In dairy donors the mean number of total ova/embryos collected and transferable embryos were 7.9 ± 6.0 and 4.9 ± 4.5, respectively and no significant effect of temperature was detected (P = 0.27). Conception rate was greatest (P < 0.001) in temperature range D (63.64%) compared with the other temperature ranges (A = 27.66%; B = 43.65%; C = 43.21%;) in beef cows and in the range C (65.31%) than in the other temperature ranges (A = 34.7%; B = 52.67%; D = 56.25%) in dairy cows. It was concluded that temperature at the time of embryo collection did not affect embryo production and quality. However, environmental temperature did have a significant effect on conception rates in both beef and dairy recipients. Nutritional status may also have contributed to the increased conception in beef cattle during warmer temperatures. However, the optimal period for conception in dairy cows was in temperature range from 16 to 20°C, because of the potential adverse effect of heat stress in high-yielding cows.

Supported by MEYS CR MSM 2678846201, LA 330; NAZV 1B44034.