Effect of Heat Stress on Early Embryonic Development in the Beef Cow

Abstract

Hereford and Hereford X Angus cows (n = 31) were utilized to determine the effects of heat stress on early embryonic development and survival. After acclimation to handling, cows were cannulated via the jugular vein on d 7 and assigned to either a control (C) chamber environment of 22 C, 35% relative humidity (RH) or one of two heat stress treatments. Ambient temperature was maintained at 37 C for 12 h followed by a decrease to 33 C for the remainder of the day in both treatment groups. Relative humidity was maintained at 27% in treatment 1 (TRT 1) and 38% in treatment 2 (TRT 2). On d 8 to 16, daily measurements of respiration rate (RES), rectal temperature (REC) and water intake were taken along with samples of blood, which were analyzed for hematocrit (HEM) and plasma concentration of protein (PP), progesterone (P4), estradiol-17 beta (E2), thyroxine (T4) and glucose (GLU). The uterus was recovered and flushed with saline on d 17 to recover the conceptus and uterine contents. Conceptus (if present) and corpus luteum (CL) wet weight were determined. Cows subjected to TRT 2 had increased RES and REC (P less than .01), while HEM was decreased (P less than .05) compared with C cows. Plasma T4 concentration was decreased (P less than .10) in TRT 2 compared with TRT 1 and cows, while P4 concentration were not significantly different. Corpora lutea wet weights were reduced (P less than .10) in heat-stressed cows vs C cows.(ABSTRACT TRUNCATED AT 250 WORDS)

Possibility of Diagnosing Uterine Function in Cows

“…Many researchers have demonstrated that lower conception rates may arise from changes in nutritional requirements due to the demand for increased milk production (Butler 1998, Butler 2000, Leroy et al 2008 and such external factors as heat stress (Liang et al 2013, Megahed et al 2008, Sakatani et al 2012 in dairy cows. In addition, a similar occurrence was reported in beef cattle (Biggers et al 1987, Burke et al 2001.…”

Nutritional effects on oocyte and embryo development in mammals: implications for reproductive efficiency and environmental sustainability

“…Heat-stressed heifers had a higher incidence of abnormal and retarded embryos with degenerative blastomeres, even though rectal temperature was only elevated (to 41.18C) during the 8 h of exposure to 428C. Increasing the temperature to which beef cattle were exposed to 378C for 12 h and 338C for 12 h between days 7 and 16 of pregnancy did not alter pregnancy rates, but resulted in reduced total conceptus mass compared with cows at 228C (Biggers et al 1987), suggesting that some embryo mortality occurred in heat-stressed cows. Interestingly, although increased humidity during this period altered metabolic and respiratory traits, it had no effect on conceptus mass or pregnancy rates.…”

Environmental effects on pregnancy rate in beef cattle1

“…This decrease in fertility is potentially caused by elevated body temperatures that influence ovarian function, expression of estrus, oocyte health, and embryonic development (Biggers et al, 1987;Lucy, 2002). Dunlap and Vincent (1971) reported 0% conception in beef cows that had an average body temperature of 40°C or above, whereas Biggers et al (1987) reported pregnancy rates of 82, 67, and 55% for cows with body temperatures of 38.9, 39.2, and 39.8°C, respectively.…”