Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Animal, Dairy, and Veterinary Sciences

Committee Chair(s)

Ronald L. Boman


Ronald L. Boman


Don Sisson


Forty high producing early to mid lactation Holstein cows were blocked according to stage of lactation and previous two-week milk yield (experiment 1) . Eight ruminally and duodenally cannulated nonlactating Holstein cows were used for experiment 2. The objective was to determine the effects of the ration's high fat content (11.53%) when rumen degradable or rumen undegradable protein is fed with or without added niacin. Cows received one of five treatments: 1) basal ration (TMR); 2) basal ration with added rumen undegradable fat (RUF) (1.6 kg); soybean meal (SBM) (1.73 kg), and niacin (12 g); 3) same as treatment 2, without niacin; 4) same as treatment 2 but replacing the soybean meal with undegradable protein (UIP) (1.9 kg ) ; and 5) same as treatment 4, without niacin. Rations and water were offered ad-libitum for 10 weeks. Intake for experiment 2 was limited to 18 kg TMR, 0 .76 kg RUF, 0 .88 kg SBM or UIP, and 6 g niacin. All cows in experiment 2 received the five treatments by the end of five collection periods separated by 21 d adaption. RUF increased dry matter intake (22.95 vs. 23 . 72 kg/d ) and mean body weight (607 vs. 637 kg ) , but decreased milk protein, lactose and SNF (proportion and yield); and 4% FCM without affecting daily milk yield. RUF, SBM, and N did not affect milk production. Milk protein percentage, protein yield, lactose percentage, SNF percentage, and yield were decreased by UIP supplementation. Niacin had a negative effect on milk fat percentage and yield, and milk protein percentage when fed with RUF and UIP . Supplements did not affect milk protein components. RUF increased plasma glucose (56.8 vs. 63.5). RUF addition increased AD and ND digestibility while decreased fatty acid digestibility. UIP improved ND digestibility in the lactation trial. For experiment 2, UIP increased rumen propionate percentage, thus reducing acetate to propionate ratio. Niacin increased total VFA production (128.6 vs. 114.3 umol/ml) . RUF, UIP, and niacin increased total bacterial population. RUF reduced cellulolytic bacteria in rumen fluid. Nutrient rate of passage and digestibility were unaffected by treatments except for dry matter and RUF digestibility that were reduced by RUF supplementation.



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