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Effect of dietary fat source on milk production and milk composition in early lactation cows in a continuous trial design
This study was designed to look at two dietary fat sources (MEGALAC and Palmit 80) when fed at amounts to deliver fatty acids at ~ 0.22 kg/d. Twenty four multiparous dairy cows in early lactation (average DIM = 68) were used to compare the temporal relationship of DMI, milk production, milk composition, body weight and BCS. Cows were fed individually via Calan headgates. Data from wk 1 to 2 was averaged and used as a covariate period and cows were fed Megalac as the only source of supplemental fatty acids. During wk 3 to 12, 12 cows were fed the Megalac diet at 1.15 % DM, and 12 cows were fed the Palmit 80 diet at 0.93% DM. Milk production was obtained 2x/d and once/wk an AM-PM composite of milk was obtained from each cow and analyzed for composition. Data were analyzed with Proc Mixed of SAS with repeated measurements using a model that included treatment, week, treatment x week. There was no treatment x week interaction (P > 0.1). The covariant played a significant role in the adjustment (P < 0.05). In this study, there was no significant difference between sources of supplemental fat on milk production 39.2 vs. 40.0 kg, DMI 29.2 vs. 29.1 kg, milk fat % 4.3 vs. 4.3%, milk protein % 2.91 vs. 2.98% (P < 0.09), milk fat yield 1.65 vs. 1.74 kg, BCS 2.81 vs 2.80, BW 668 vs. 677 kg or BW change 11.7 vs. 9.5 kg (Megalc vs. palmit 80, P > 0.1). Milk protein yield was greater 1.13 vs 1.19 kg (P = 0.002) when cows consumed Palmit 80. A previously reported trial of similar design (J. Dairy Sci. 96 (Suppl.E):Abstr. W29) showed higher production by cows fed MEGALAC vs. Palmit 80. In that trial, cows were earlier in DIM at the start of the study. A hypothesis is that cows at different stages of lactation use individual fatty acids differently due to metabolic status.
Keywords: milk fat, dietary fat, fatty acids