Influence of Cow Age and Genotype on Milk Yield and Nutritional Composition in Dairy Cows in Khulna Region

Abstract

The present study aimed to compare the producing ability of crossbred dairy cattle along with lactation length, milk composition and physico-chemical properties in farm conditions as influenced by genotype and age. The study intended to discover the best cross bred genotype and the best age group to improve milk productivity and milk quality in field condition. Three crossbreds (Local × Friesian, Local × Jersey and Local × Sahiwal) and three age groups of the cows (young - 3-4 years, middle age - 5-6 years and older - ≥ 7 years) were considered. Milk production, lactation length data were gathered from dairy farms and milk samples were analyzed for composition and physico-chemical properties. The results indicated that genotype significantly (p <0.001) affected the milk yield of the morning, evening and total daily periods. The highest total milk yield (14.73 ± 0.23 kg/cow/day) was recorded in Local × Friesian cows, followed by Local × Jersey cows (13.80 ± 0.34 kg/cow/day) and the lowest milk yield (9.44 ± 0.53 kg/cow/day) was obtained in Local × Sahiwal cows. Lactation length was also greatly influenced (p<0.01) by genotype. Local × Friesian cows produced lactation duration of 274.75 ± 4.16 days which was the longest, followed by Local × Jersey cows (259.35 ± 5.44 days) and the shortest was in Local × Sahiwal cows (237.42 ± 9.88 days). Milk yield traits were significantly influenced by age (p <0.001). The effect of age on total daily milk yield was most pronounced with the highest yield for the middle-aged cows (5–6 years, 17.60 ± 0.20 kg/cow/day) followed by the young cows (14.78 ± 0.24 kg/cow/day) and the lowest yield for the older cows (10.74 ± 0.19 kg/cow/day ≥7 years). But no significant difference was found between the different ages in terms of lactation length (p>0.05). Lactation length was not significantly different among the age groups, ranging from 263.24 to 269.22 days. The genotype had a significant effect on total solids, fat content and protein content (p<0.001) as determined by the milk composition analysis. Milk from local × Sahiwal cows had the highest content of total solids (13.18 ± 0.12%), fat (4.30 ± 0.07%) and protein (3.61 ± 0.03%) while milk of local × Friesian cows had the least value for these attributes. The content of SNF, lactose, and ash were not significantly different between the genotypes (p>0.05). Regarding age, older cows produced milk with significantly higher total solids (13.22 ± 0.11%), fat (4.30 ± 0.07%), and protein (3.63 ± 0.03%) than young and middle-aged cows (p<0.001). The contents of SNF, lactose, and ash were not significantly affected by age, however. Physico-chemical parameters were evaluated, and genotype did not significantly affect these characters. Only milk pH value differed significantly (p<0.05) among parameters studied with the Local × Sahiwal cows having the highest value of milk pH (6.66 ± 0.03). There was no significant difference in density, salt content, freezing point and electrical conductivity between genotypes. Similarly, no significant difference (p>0.05) was observed for density, salt percentage, freezing point, pH or electrical conductivity, suggesting that these properties did not vary significantly as a function of age. To conclude, genotype and age had significant effect on milk yield and milk composition, and limited effect on physico-chemical properties. In terms of milk quantity and lactation duration, Local × Friesian cows were found better while Local × Sahiwal cows were better in terms of milk compositional quality. Maximum milk production was achieved with middle aged cows and higher level of solids, fat and protein was achieved with the older cows.

• Supervision