The interest of a mountain dairy cow breed to cope with Mediterranean summer heat stress
2016
Bellagi, R | Pomiès, D | Martin, B | Najar, T
The Tarentaise cow, a rustic breed from the northern part of the French Alps, is well adapted to the mountain harsh conditions, in particular during the summer season due to its ability to use efficiently the highland pastures. The Tunisian farmers also consider that the Tarentaise cows are well adapted to the Mediterranean cli- mate. The aim of this work was to quantify the effect of summer heat stress on milk yield and quality of Tarentaise cows in comparison to Holstein cows. A dataset was collected for 441 Tarentaise and 560 Holstein cows reared in 21 farms in Tunisia from 2009 to 2014. This data comprising 16,400 monthly individual records of milk yield, fat, protein, urea and somatic cell count was merged with meteorological data from 5 public stations relative to the 21 farms. The temperature-humidity index (THI) calculated as a combination of ambient temperature (Ta) and relative humidity (RH) was used to characterize heat stress. Tarentaise and Holstein cows produced 11.4 and 14.8 kg per d of milk respectively. When THI increased from an average value of 53.7 in winter to 75.4 in summer, the Holstein and Tarentaise cows decreased their production by 0.93 and 0.15 kg per d respectively. Milk fat, protein and urea content decreased similarly in both breeds (-0.22 g per kg, -0.14 g per kg and -14 mg per L respectively) and milk somatic cell count increased for Holstein cows (+352,000 per mL) while it decreased slightly for Tarentaise cows (-160,000 per mL). The Tarentaise cows seem to be more resistant to heat stress than Holstein cows, especially when THI is over 78
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