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Evaluating the effects of feeding whole cottonseed on primiparous and multiparous lactating dairy cows.

R. Pierce

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06-23-2020

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Abstract:

T133
Evaluating the effects of feeding whole cottonseed on primiparous and multiparous lactating dairy cows.
R. Pierce*, R. Bomberger, K. Harvatine. The Pennsylvania State University University Park, PA.

Milk fat is a valuable milk component and around 60% of milk fatty acids (FA) originate from dietary fat. Oilseeds are an economical source of oil compared with dry fat supplements, but contain unsaturated FA that increase risk for diet-induced milk fat depression. Cottonseed is expected to have a slower ruminal release rate of unsaturated FA and decrease diet-induced MFD. The hypothesis of the experiment was that increasing whole cottonseed in the diet would increase milk fat yield in high producing cows by providing additional dietary fat without induction of milk fat depression. Four primiparous and 8 multiparous lactating Holsteins were arranged in a 4 � 4 Latin square design with 21 d periods. Treatments were 0, 3.3, 6.6, and 9.9% whole cottonseed. Dietary NDF and protein were maintained by substitution for cottonseed hulls and soybean meal. Data were analyzed using the random effect of cow and period and fixed effect of treatment and preplanned contrasts tested the linear and quadratic effect of increasing cottonseed level. Milk yield was not modified by treatment. There was a treatment by parity interaction for milk fat percent and yield with no effect of cottonseed in multiparous cows, but milk fat percent and yield were quadractically decreased in primiparous cows. Importantly, multiparous cows were 4.05% and primparous cows were 3.53% milk fat when fed the control diet. Milk FA profile indicated that cottonseed increased trans-10 C18:1 in primparous, but not multiparous cows. Milk fat increased at the highest level of cottonseed in primiparous cows due to an increase in yield of preformed FA. In conclusion, cottonseed maintained milk and milk component yield when fed at up to 9.9% of the diet to multiparous cows, but the primparous cows in the current trial were more susceptible to diet-induced milk fat depression.

Keywords: milk fat, cottonseed, milk fat depression.