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2 results

  • 9 - Hybrid Dehydrations: Thermal Stress and Exercise

  • Neil E. Rowland, University of Florida
  • Book:
    Thirst and Body Fluid Regulation
    Published online:
    09 December 2021
    Print publication:
    16 December 2021, pp 164-186

  • Summary

    Thermolytic responses are required in either high ambient temperatures, when conductive heat loss is low, or during states of increased heat production such as during exercise. Most of the thermolytic responses involve fluid loss, including panting (i.e., tachypnea) and evaporative cooling from skin moistened by sweating or saliva spreading. The relative contribution of these mechanisms is species dependent. In all cases, the principal systemic change produced by the fluid loss is hyperosmolarity, although hypovolemia can also be considerable. Humans and animals usually do not drink sufficient water to replace the lost fluid, resulting in a state of hypohydration. This can be partially mitigated by repeated exposure (i.e., adapation) or by providing electrolytes to drink. Sustained hypohydration and/or elevated core temperature produces loss of physical performance and, in the extreme, can be lethal. Available evidence siuggests that the OVLT and/or MnPO play important roles in detection of heat stress and execution of the thermolytic responses.

  • Effect of water sprinkling during the hot-dry summer season on semen quality of Holstein bulls in Saudi Arabia

  • M. S. Salah, F. D. El-Nouty, M. R. Al-Hajri
  • Journal:
    Animal Production / Volume 55 / Issue 1 / August 1992
    Published online by Cambridge University Press:
    02 September 2010, pp. 59-63
    Print publication:
    August 1992

  • Ten Holstein bulls, 4 to 5 years old were used to study the effect of cooling the bulls on their semen quality. Five bulls were sprinkled with water for 15 min five times a day throughout a 6-week period of the summer season (hot-dry) in Saudi Arabia, and the other five bulls acted as the control and were not sprinkled with water. Semen quality was improved significantly during the cooling period. This improvement was evident from the significant increase in sperm motility (P < 0·01) and decrease in the percentage of both dead and morphologically abnormal (primary and secondary) spermatozoa per ejaculate of cooled bulls (P < 0·01). The effect of cooling was more marked through the last 3 weeks than during the first 3 weeks of the experimental period. Ejaculate volume, sperm concentration and hence total sperm counts did not differ significantly between the cooled and the non-cooled bulls. Concerning the type of abnormal spermatozoa, the overall secondary abnormality was higher than the primary in both the cooled and the control groups, with higher values for the control (P < 0·01). Only the mid piece showed higher primary defects than the secondary. The pyriform heads, the coiled mid pieces and tails and the bent tails were the main sources of variations (P < 0·01) in the incidence of sperm abnormality between the cooled and the non-cooled bulls. Cooling the bulls during the heat stress period also lowered their rectal temperature and increased blood haemoglobin level without affecting the packed cell volume