EFFECT OF SEASON ON THE MILK QUANTITY AND QUALITY OF CROSSBRED DAIRY COWS AT DISTRICT GOVERNMENT DAIRY FARM, SYLHET

Abstract

The present study was conducted to investigate the seasonal effect on milk quantity and quality in crossbred dairy cows. For this purpose, milk samples were collected from bulk milk tank of District govt. dairy farms, Sylhet and their qualities were measured with physico-chemical and microbiological test. The season has a significant effect (p<0.05) on the milk yield, milk quality and physical properties of the milk. The highest milk production was obtained during the rainy season 3354.00 kg followed by summer 3116.70 kg while the lowest average milk production was obtained in winter 2925.50kg. The chemical composition of bulk tank milk was the lowest in summer 4.27% fat, 3.20% protein, 4.46% lactose and 8.55% SNF and in rainy 3.96% fat, 3.24% protein, 4.49% lactose and 8.53% SNF respectively and the highest in winter 5.30% fat, 3.18% protein, 4.46% lactose and 8.59% SNF. The highest milk fat percentage was found in winter 5.30%. The minimum value for fat percentage was observed in rainy 3.96%. Protein percentage ranged from a minimum value of 3.18% observed in winter and the maximum value 3.24% observed in rainy season. The freezing point of the milk varied within a small range from one season to another season. The highest value for freezing point was observed during rainy -0.54 o C obtained during the winter season. The highest density of milk was recorded in summer 28.89% while the lowest was observed in winter 27.73%. Generally, the season had a significant influence on the density and freezing point of the milk (p<0.05). The temperature of the milk varied widely from one season to another season. The highest value for temperature was observed during rainy 28.77 C while the lowest value was -0.51 o C while the lowest value was 25.80 o C obtained during the winter. The salt percentage of the milk varied within a small range from one season to another season. The highest average for salt was observed during summer and rainy 0.66% while the lowest value was 0.65% obtained during the winter. During the winter season the average SPC bacteria count was lower compared with the other season, 38.02 ×10 o cfu/ml. The highest value was obtained in rainy season 40.50×10 5 cfu/ml in winter, 4.91×10 5 cfu/ml. Coliform bacteria count was on average 4.5×10 5 5 cfu/ml in rainy season. There was no significant differences compared to the value found during the other season. From this study it was found that season had a significant effect on the milk quantity and quality, except for protein, lactose, SNF, SPC and coliforms count. cfu/ml in summer and 5.46×10 5