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Dietary factors that induce milk fat depression in dairy cows consuming dried distillers grains with solubles
Research has shown that dairy diets may contain up to 30% corn dried distillers grains with solubles (DDGS, interestingly, field experiences commonly report that milk fat depression (MFD), a disorder characterized by a sharp reduction in milk fat concentration and yield without affecting other productive traits, when feeding DDGS. The research described herein focused on the effects of feeding DDGS on MFD in dairy cows. Experiment 1 evaluated the effects of feeding high levels of corn oil and starch in diets containing 20% DDGS. The inclusion of corn oil or starch did not affect milk production but resulted in MFD; the combination of these two factors had additive negative effects that exacerbated the MFD response. Ruminal pH was similar across treatments. The results showed a shift in the ratio of acetate to propionate and suggest altered metabolism of unsaturated fatty acids that resulted in diet-induced MFD. Experiment 2 evaluated the effects of feeding reduced-fat DDGS (RFDDGS) as an alternative to lessen the risk of MFD and determine its effects on bacterial community structure. Milk yield was not affected by treatment. Feeding a control diet and RFDDG and resulted in greater concentration and yield of fat compared with DDGS. Proportions of Firmicutes decreased 9 h postfeeding and increased to the initial level by 23 h, conversely Bacteroidetes increased 9 h postfeeding. These results indicate that diurnal variation in bacterial community composition as well as diet-induced structural changes may affect animal performance. Experiment 3 examined the effects of feeding short and long particles of grass hay in combination with corn oil on milk production and composition. The smaller particle size reduced rumination time and increased ruminal rate of passage. There were no effects on dry matter intake and milk production. Milk composition was negatively affected in cows consuming fine particles in combination with corn oil as they exhibited MFD; this response was partially reversed by long particles. These results underscore the importance of providing dairy cows with adequate physically effective fiber in diets formulated to contain high levels of oil.
Ramirez Ramirez, Hugo Alonso, "Dietary factors that induce milk fat depression in dairy cows consuming dried distillers grains with solubles" (2014). ETD collection for University of Nebraska - Lincoln. AAI3610075.