Fat and Rumen Undegradable Protein for Grazing Cows: Effect on Composition of Milk and Quality of Cheese.
详细信息
文摘
The effect of supplementing cows on pasture with a partial total mixed ration pTMR) containing different fat and protein sources on milk yield, fatty acid profiles, protein content, cheese yield, cheese textural and sensorial properties and the economic feasibility were investigated. Twenty-seven multiparous cows were allowed to graze on alfalfa pasture and were supplemented with pTMR containing: 1) dried distillers grains with solubles DDGS), 2) soybean meal ESB), or 3) fishmeal FM). The pTMR were fed to supply 50% of estimated energy requirements. There were no dietary effects on milk yield. The concentration of fat and protein in milk was greatest for FM and DDGS compared to ESB supplemented cows. The Brown Swiss cows had greater true protein and casein when fed DDGS compared with FM. Holstein cows produced greater true protein and casein concentrations when fed FM followed by DDGS and ESB. Milk from cows fed DDGS and FM had greater concentrations of C12:0, C14:0 and C16:0 in milk fat compared with ESB. The concentration of C18:0 in milk was least in milk from cows supplemented with FM followed by DDGS and ESB. The least concentrations of long chain polyunsaturated fatty acids were observed in milk from cows supplemented with FM. Dietary treatments did not affect the concentrations of conjugated linoleic acid in milk. The dietary treatments had no effect on the estimated and actual cheese yields Cheese from cows supplemented with FM had greater concentrations of saturated and monounsaturated fatty acids and lesser concentrations of unsaturated and polyunsaturated fatty acids. The typical effects of age on texture and melt profiles were observed, however, there were no dietary effects on textural attributes, sensorial and melt profiles. Based on average prices for DDGS, FM and ESB over the study period, 2008--2010, gross and net profit were greatest in cows supplemented with DDGS followed by cows on ESB and FM. This study indicates that supplementing cows on pasture with fat and ruminally undegradable protein could increase the concentrations of fat, protein, and casein in milk without compromising yield, other components, cheese yield, cheese chemical composition and cheese textural and sensorial properties. It is economically feasible to increase the healthful fatty acids through dairy cow dietary manipulation, especially when relatively lesser expensive dietary supplements such as DDGS are used.