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United States Department of Agriculture

Agricultural Research Service

Title: Differences in Sensitivity to Heat-Shock Between Preimplantation Embryos from Heat-Tolerant (Brahman and Romosinuano) and Heat-Sensitive(angus)breeds

item Hernandez-Ceron, J. - UNIVERSITY OF MEXICO
item Chase, Chadwick

Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: January 1, 2004
Publication Date: February 1, 2004
Citation: Hernandez-Ceron, J., Chase, C.C., Hansen, P.J. Differences in sensitivity to heat-shock between preimplantation embryos from heat-tolerant (brahman and romosinuano) and heat-sensitive(angus)breeds. Journal of Animal Science: Vol. 81, Suppl. 1 / Journal of Dairy Science Vol. 86, Suppl. 1.

Technical Abstract: Certain heat-tolerant breeds of cattle have acquired mechanisms to protect cells against damage from high temperature. Exposure of embryos to 41 C reduced development more for Holstein and Angus (An) embryos than for Brahman (Br) embryos. The Romosinuano (Ro) is a Bos taurus from Colombia. Like Br, Ro is a tropically-adapted breed. It is not known, however, whether this breed, distinct in origin from Br, has evolved to possess cellular adaptations to heat shock. A study was performed to test whether Br and Ro embryos survive heat-shock better than An embryos. Cows (n=14 An, 17 Br, and 15 Ro) were slaughtered in groups of 2-3 per breed (5-6 replicates). For each replicate, ovaries were pooled within breed and oocytes harvested and fertilized with semen from a pair of bulls of the same breed. A different pair of bulls was used for each replicate. At d 4 after fertilization, embryos (at least 8 cells) were randomly assigned to control (38.5 C) or heat shock (41 C for 6 h) treatments. Development to blastocyst was determined on d 8. The proportion of oocytes that cleaved at d 4 tended to be highest for Ro (54, 50, and 70% for An, Br, and Ro). The proportion of cleaved embryos that were at least 8 cells at d 4 was lowest for Br (76, 55, and 77% for An, Br, and Ro). Heat shock caused a reduction in the proportion of embryos that became blastocysts at d 8. At 38.5 C, there were no significant differences in development among breeds. Among embryos exposed to 41 C, however, development was lower for An than for Br and Ro. Furthermore, there was a trend for an An vs (BR + Ro) x temperature interaction because heat shock reduced development more for An (30.3% at 38.5 C vs 4.9% at 41 C) than for Br 25.1 vs 13.6%) and Ro (28.3 vs 17.5%). There were no effects on cell number of d 8 blastocysts. Results demonstrate that embryos from thermotolerant breeds (Br and Ro) are more resistant to elevated temperature than embryos from a thermosensitive breed (An). Thus, the process of adaptation of Br and Ro breeds to hot environments resulted in both cases in selection of genes controlling thermotolerance at the cellular level.

Last Modified: 4/15/2014
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