Browsing by Subject "fatty acids"

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    Effects Of Genetic Selection On Composition And Biosynthesis Of Milk Fats In Early Lactation Of Holstein Cows
    (2016-08) DING, FENG
    Genetic selection in dairy cattle has greatly improved the milk yield in the past decades. Contemporary Holsteins (CH) that were selected and maintained by the University of Minnesota produced more than 4,500 kg milk in 305 days than its counterpart unselected Holsteins (UH), which has stable milk yield since 1964. However, the influences of genetic selection on the chemical composition of cow milk were not well characterized. In this study, cows from UH and CH genotypes (CH) (n = 12/genotype) were co-housed and fed the same diet ad libitum 5 weeks prepartum. Weekly milk samples were obtained from the milking on each Tuesday night in the first 9 weeks of lactation. Analysis of macronutrients in milk indicated that CH and UH had comparable levels of lactose (4.75% vs. 4.69%, P=0.08). However, CH had a slight lower level of proteins (2.98% vs. 3.13%, P<0.05) and much higher level of fats than UH (4.33% vs. 3.55%, P<0.01). Lipidomic analysis through high-resolution liquid chromatography-mass spectrometry (LC-MS) analysis, multivariate data analysis (MDA), and MSMS fragmentation further revealed that the TAG profiles of UH and CH milk differed greatly in early weeks of lactation, but became more comparable by week 9. Hierarchical clustering analysis (HCA) of TAGs markers indicated that CH milk were more enriched with preformed fatty acids (FAs) while UH milk had higher abundance of FAs originated from de novo synthesis. This conclusion was further confirmed by quantitative analysis of FAs and organic acid precursors. Overall, these observations suggested that genetic selection increased the contribution of preformed FAs from blood lipids to the biosynthesis of milk TAGs, especially in the early phase of lactation.
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    Forage quality of two cover crop grazing systems and meat quality of organic beef from crossbred dairy steers finished on forages
    (2017-09) Phillips, Hannah
    This study analyzed the yield, forage quality, and mineral composition of organic winter rye and winter wheat in grazing systems, and analyzed the meat quality, fatty acids, and consumer acceptability of beef from Holstein and crossbred organic dairy steers finished on winter rye and winter wheat pastures. Steers (n = 30) were assigned to one of three replicate breed groups at birth: (1) Holstein (n = 10), (2) crossbreeds comprised of Montbéliarde, Viking Red, and Holstein (n = 10), and (3) crossbreeds comprised of Normande, Jersey, and Viking Red (n = 10). Breed groups were randomly assigned to graze either winter rye or winter wheat during their finishing phase. The results suggest that winter rye and winter wheat cover crops are viable options for grazing cattle, and suggest beef from crossbred dairy steers leads to an improved fatty acid profile and greater consumer acceptability compared to Holstein steers.