Changes in Milk Components During Lactation in Holstein Cows Fed a Uniform Ration

Abstract

This study was conducted to describe changes in milk components between weeks 2 and 32 of lactation in 30 Holstein cows calving in October in an intensive dairy farm with a capacity of 400 lactating cows in Adana province. Cows were housed in a free-stall barn and fed a uniform ration consisting of soybean meal, alfalfa hay, wheat straw, common vetch hay, corn silage, and a dairy concentrate containing 19% crude protein and 2750 kcal/kg ME. Milk samples collected from the morning milking at 2-week intervals were analyzed for total solids, solids-not-fat, fat, protein, and lactose. Data were evaluated in SPSS using a repeated-measures approach. Based on weekly means, total solids ranged from 11.48 to 13.17%, solids-not-fat from 8.57 to 9.05%, fat from 2.65 to 4.35%, protein from 3.07 to 3.33%, and lactose from 4.71 to 4.89%. Mean levels were 12.15, 8.90, 3.19, 3.22, and 4.79%, respectively. Lactation week had a significant effect on milk components (P < 0.05). More pronounced fluctuations were observed in fat and total solids, whereas protein, solids-not-fat, and lactose showed relatively limited variation. The findings indicate that the milk component profile may change across lactation weeks even under a uniform ration. Therefore, routine monitoring of milk components may be a useful tool in herd management.