EFFECT OF HEAT STRESS ON MILK YIELD AND MILK COMPOSITION TRAITS OF HOLSTEIN-FRIESIAN COWS IN KANO STATE

Abstract

This study was conducted to evaluate the effect of temperature-humidity index on milk traits of pure HolsteinFriesian cows in Kano State. Twenty mid-lactating Holstein-Friesian cows (three years of age with a mean weight of 1200kg) were used for this experiment. The cows were raised intensively in a covered free stall barn (3m2 per cow) with straw bedding. Metrological data, both inside and outside, of the barn including temperature (maximum and minimum) from both digital and analogue (dry and wet bulb) thermometers and relative humidity were collected. Three composite samples of milk from the cows were taken per month (on the 15th day of each month) and were analysed for protein, fat and somatic cells. Meteorological data were analysed to identify the most appropriate temperature-humidity index (THI) to measure heat stress in this study. Data were analysed using Analysis of Variance (ANOVA) and correlation procedures in the Statistical package SAS (2013). Comparison of the Means was done using Duncan Multiple range tests of the same statistical package. The minimum temperature for the period of the experiment had the lowest value (23.08±0.620C) in the month of December in Early dry season while the highest value (33.64±0.830C) was recorded in the April of the Late dry season. The differences in the THI for the two periods resulted in significant different (P < 0.05) in milk yield and milk composition traits. It was concluded that, heat stress affect milk production, milk composition of Holstein-Friesians cows reared in Kano State environment.