Effect of summer climatic conditions on different heat tolerance indicators in primiparous Friesian and Jersey cows

Abstract

The effect of climatic conditions during summer on different heat tolerance indicators was determined in Friesian and Jersey cows which were kept in open camps with no protection against solar radiation. A complete diet (15.0% CP and 10.8 MJ ME/kg) was fed daily on an ad libitum basis in fence-line feeding troughs. Heart rates, respiration rates and rectal temperatures of five primiparous Friesian and five primiparous Jersey cows, which were accustomed to handling, were measured at two-hourly intervals from 07:00 to 19:00 over 15 days during which high (≥ 27.1°C ) maximum temperatures were expected. Rectal temperatures of Friesian cows were higher (P ≤ 0.05) than those of the Jersey cows from 11:00 to 19:00, with the greatest difference (0.55°C) recorded at 15:00. The respiration rate of Friesian cows was higher (P ≤ 0.05) than that of Jersey cows at 15:00, 17:00 and 19:00, with the greatest difference (15.4 inhalations per minute) recorded at 15:00. The heart rate of the Friesian group was higher (P ≤ 0.05) than that of the Jersey cows at 15:00 and 17:00. Heart rate was not influenced by increasing ambient temperatures to the same extent as rectal temperature and respiration rate. Results suggest that Jersey cows display a higher heat tolerance than Friesian cows, and that Jerseys should be more widely used in the warmer regions of South Africa.

Die invloed van klimaattoestande gedurende die somer op verskillende warmteverdraagsaamheidsaanwysers is by Fries- en Jerseykoeie wat in oop kampe sonder enige beskutting teen sonstraling aangehou is, bepaal. 'n Volledige dieet (15.0% RP en 10.8 MJ ME/kg) is daagliks op 'n ad libitum-basis aan koeie in voerkrippe langs die grensdraad voorsien. Die rektale temperatuur, asemhalingstempo en hartklop van vyf eerste- laktasie Fries- en vyf eerste-laktasie Jerseykoeie wat aan hantering gewoond was, is oor 'n tydperk van 15 dae met verwagte hoë maksimum temperature (≥ 27.1°C ), elke twee ure vanaf 07:00 tot 19:00 bepaal. Die rektale temperatuur van Frieskoeie was vanaf 11:00 tot 19:00 hoër (P ≤ 0.05) as by Jerseykoeie. Die grootste verskil (0.55°C) tussen die twee rasse het om 15:00 voorgekom. Die asemhalingstempo van Frieskoeie was om 15:00, 17:00 en 19:00 hoër (P ≤ 0.05) as by Jerseykoeie. Die grootste verskil (15.4 asemhalings per minuut) het om 15:00 voorgekom. Die hartklop van Frieskoeie was eweneens om 17:00 en 19:00 hoër (P ≤ 0.05) as dié van Jerseykoeie. Die hartklop van beide rasse is nie tot dieselfde mate as rektale temperatuur en asemhalingstempo deur toenemende omgewingstemperature beïnvloed nie. Resultate bevestig die hoër hitteverdraagsaamheid van Jerseykoeie wat daarop dui dat hierdie ras meer in die warmer dele van Suid-Afrika gebruik kan word.

Keywords: Friesian and Jersey cows, heart rate, heat, Mediterranean climate, rectal temperatures, respiration rate.