Impact of heat stress on milk production performance of cattle in the suburban area of Ngaoundere, Cameroon

This study aims to assess the impact of heat stress on milk production of cattle under sudano-guinean climate in the suburban area of the city of Ngaoundere (Cameroon). It was carried out on 98 cattle of different breeds and sexes in order to determine their stress situation by measuring the level of cortisol in their blood plasma and by calculating the temperature-humidity index (THI). It was seen that, about half of the cattle (49.0%) are under stress according to their cortisol level (higher than 11.7 ng/ml). Gudali (75.9%) and Holstein (41. 7%) were more stressed than Montbeliard (38.2%) and cross breeds (34.8%). Females (54.3%) were more stressed than males (23.5%). Gudali and Montbeliard cattle were more susceptible to heat stress with a higher THI mean (70.4) than Holstein (69.5) and crossbreeds (68.9). There was a significant difference in THI among breeds whereas no difference in THI between sexes was observed. Stressed cows have lower daily milk production (7.81 L) than unstressed cows (19.9 L). Meanwhile, milk production decreases as THI increased.