| Popis: |
Our research examined the responses of palmitic, stearic and oleic fatty acids on neutral detergent fiber (NDF) digestibility and rumen fermentation and the impact of a palmitic acid-enriched supplement on animal performance. In the first research chapter, we evaluated the effect of purified palmitic, stearic, and oleic fatty acids on NDF digestibility and rumen fermentation. Palmitic acid increased NDF digestibility and total production of volatile fatty acids (VFA) compared with oleic acid. Bacterial fatty acid composition was altered by palmitic acid, increasing anteiso-C15:0, C18:2n6 and C18:3n3 fatty acids compared with oleic acid. Compared with control, total protein expression in chemiluminescence units (C.U.) of the fatty acid synthase and acetyl CoA carboxylase enzyme was decreased by the combination of palmitic, stearic, and oleic fatty acids. No treatment effect was observed for ammonia and cellulase activity. In conclusion, palmitic acid compared with oleic acid can be utilized in ruminant diets to improve NDF digestibility and total VFA production, providing more energy and nutrients for the host animal. Furthermore, palmitic, stearic and oleic acid decreased total protein expression of the fatty acid synthase and acetyl CoA carboxylase enzyme compared with control indicating that palmitic, stearic and oleic acid can be utilized by the bacteria and inhibit the ACC and FAS enzymes in the fatty acid synthesis pathway. In the second research chapter, we determined the impact of a palmitic acid-enriched supplement on production responses and nitrogen metabolism of Jersey and Holstein cows. Compared with control, palmitic acid increased milk fat yield, NDF and dry matter digestibility and tended to increase 3.5% fat-corrected milk and energy-corrected milk. Compared with Holstein cows, Jersey cows had greater intake as percentage of body weight and tended to have greater milk fat yield, but had lower milk production, and milk lactose yield. There was a breed effect on body weight change as Holstein cows gained 0.385 kg/d during the experiment while Jersey cows gained 0.145 kg/d. Jersey cows had lower nitrogen intake, blood urea nitrogen, urine total nitrogen and urine total nitrogen as a percent of nitrogen intake. Feeding a palmitic acid-enriched supplement increased milk fat yield as well as dry matter and fiber digestibility in both Holstein and Jersey cows. Palmitic acid did not have any major effects on nitrogen metabolism. Overall, our results indicate that palmitic acid can improve fiber digestion, rumen fermentation, and animal performance. |
