IMPACT OF FEED ON MILK PRODUCTION AND COMPOSITION IN DAIRY CATTLE

Abstract

The objective of the study was to examine the responses of lactating dairy cows’ milk yield and milk composition to different dietary treatments. Sixty cows were allocated to three groups: a standard corn–soybean–based control group (n = 20), a high-protein diet group containing canola meal and undegradable protein supplementation of the rumen (n = 22), or a high fiber-based forage/bypass fat-supplemented group (n = 18). The daily milk yield and milk composition (milk fat, protein, lactose concentration, and milk urea nitrogen-MUN) were measured and analyzed by one-way analysis of variance in SPSS. There was a significant difference in milk yield among the dietary treatments (F (2,57) = 12.31, p <0.001), and cows receiving the high-protein diet had higher milk yield (34.9 ± 3.9 kg/day) compared to both the control (30.2 ± 4.2 kg/day) and the high-fiber diets (30.6 ± 3.7 kg/day). Milk fat percentage was significantly higher in cows receiving the high-fiber diet (4.18 ± 0.17%) than in those fed the control (3.66 ± 0.18%) or high-protein diets (3.60 ± 0.19%) (F (2,57) = 48.6, p < 0.001). Milk protein percentage was greatest in the high-protein group (3.53 ± 0.16%), followed by the control (3.20 ± 0.13%) and high-fiber diets (3.05 ± 0.11%) (F (2,57) = 32.4, p < 0.001). Milk lactose percentage did not differ significantly among treatments (p > 0.05). In contrast, MUN levels were significantly elevated in cows fed the high-protein diet (16.2 ± 1.5 mg/dL) compared with the control (11.1 ± 1.2 mg/dL) and high-fiber diets (8.9 ± 1.0 mg/dL) (F (2,57) = 89.7, p < 0.001). These findings indicate that dietary protein and fiber composition markedly influence milk yield, milk components, and nitrogen utilization efficiency in dairy cattle.