The Effects Of Omega 3 Fatty Acids On Milk Fat Synthesis And Composition In Dairy Cows PDF Download

Dietary fat is an important component on the diets of lactating dairy cattle. Concentration of dietary fat can be increase by feeding oilseeds or enriched fat supplements which allows cattle to partition energy differently which can lead to increases in milk fat concentration, milk fat yield, or milk yield. One common oilseed fed to dairy cattle is cottonseed, as it is high in fiber but also relatively high in fat compared to other common feedstuffs. Fat supplements are very high in fat (>95%) but are more expensive so dairy producers often strike a balance and may feed both fat supplements and oilseeds to dairy cattle. The first objective of this thesis was to investigate the effects of cottonseed on milk production in dairy cattle. Previous research feeding cottonseed fed inclusion rates of cottonseed in excess of 15% of dry matter intake (DMI), but cattle were producing less milk and consuming less so therefore, the actual mass of the cottonseed consumed may not be as high as contemporary dairy cattle. This thesis fed cottonseed at up to 9.9% of DMI and found that cottonseed inclusion into the diets of multiparous cattle did not affect milk yield or milk composition but led to a decrease in DMI indicating that it could be safely fed to mature cows. In primiparous cattle, cottonseed inclusion induced milk fat-depression, indicating that the level of unsaturated fatty acids in the diet was greater than the biohydrogenation potential of the ruminal microbes of these animals. The second part of this thesis was to examine the effects of increased concentrations of an unsaturated fatty acid (cis-9 C18:1; oleic acid) in a prilled fat supplement on the milk production and milk composition in dairy cows. Previous research suggests that oleic acid may increase digestibility of dietary fatty acids and consequently increase the amount of preformed fat for milk fat synthesis. This experiment indicated that fat supplementation in multiparous cows may decrease milk yield and DMI but was no effect of increased levels of oleic acid on other production components in dairy cattle. Further investigation of the data collected for each half of the thesis is required to determine the effects on the respective methods of fat supplementation on fatty acid digestibility in lactating dairy cattle.