Interactions of unsaturated fat or coconut oil with Rumensin on milk fat production might be mediated through inhibition of specific protozoal genera
Advisor:Firkins, Jeffrey L.
Contributors:Karnati, S. K. R.
Ribeiro, C. V. D. M.
Oelker, E. R.
Drow, C. M.
Homerosky, E. R.
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Series/Report no.:Interdisciplinary Ph.D. Program in Nutrition - OSUN. Graduate student poster competition, 2007
Feeding animal-vegetable (AV) fat or medium chain FA to dairy cows can decrease rumen protozoal count. In contrast, AV fat with Rumensin (R) can promote milk fat depression (MFD), whereas diets supplemented with coconut oil (CO; rich in medium chain FA) + R were not expected to cause MFD. In a 6x6 Latin square design, 6 rumen-cannulated cows were fed with +/-R (260 mg/d) and either: control (no fat), 5% AV, or 5% CO. The log10 of concentrations of total protozoa (cells/ml) were not different from control (5.97) vs. AV (5.95) but decreased by 93% with CO (4.79). Isotricha and Entodinium decreased by 99 and 97% by CO, whereas Epidinium was unchanged. In contrast, Epidinium were 67% lower for the main effect of +R and decreased 92% when AV was supplemented with R. Total VFA concentration was not affected by diet, but the A:P ratio decreased for CO (1.85) vs. control (2.95) or AV (2.58). The low A:P ratio was associated with a decreased total tract digestibility of NDF for CO (35.5%) vs. control (53.3%) and AV (46.5), with no difference in OM digestibility (averaging 67.9%). DMI was 5 kg/d lower with CO (15.3 kg/d). Milk production was lower with +R (31.6 kg/d) and CO (30.3 kg/d) than AV (33.0 kg/d). MFD occurred with AV+R and CO: 1.08, 1.01, 0.71, 1.05, 0.87, and 0.74 kg/d for control, AV, CO, control+R, AV+R, and CO+R, respectively. Further analyses should elucidate the role of protozoal concentration and genera on bacterial ruminal biohydrogenation.
Related Item:Animal Sciences
USDA/NRICGP Grant 2003–35206-12872
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