THE EVALUATION OF DIETARY BETAINE, PRE AND PROBIOTICS, TRANSITIONAL SUBSTRATES, AND B-MERCAPTOACETATE ON PHYSIOLOGICAL, METABOLIC, HORMONAL AND PRODUCTION RESPONSES IN LACTATING HOLSTEIN COWS SUBJECTED TO THERMAL STRESS.

摘要: This dissertation evaluated nutritional approaches such as the addition of betaine, prebiotics, probiotics, transitional metabolic substrates, and βmercaptoacetate (MAA; a compound which inhibits β-oxidation) to diet lactating dairy cows determine their impact on physiological, metabolic, hormonal production responses during thermal stress. The first objective was evaluate use an organic osmolyte, betaine reduce heat stress (HS). Cows were fed either 0 (control; CON), 57 mg/kg BW (mid) or 114 (high; HI) body weight (BW) subjected thermoneutral (TN) HS conditions. There increase in milk yield TN with HI over controls (P< 0.01), but advantage lost HS. Plasma glucose increased dose compared control (P < 0.01) did plasma insulin = 0.01). Betaine HS, not improve response. Objective two probiotic direct microbial (DFM), Calsporin (Bacillus subtilus C-3102) decrease effects cows. We hypothesized that feeding prior would pathogenic strains bacteria, maintain commensal microbes, ruminal anaerobic fermentation resulting improved (MY). Milk numerically (1.26 kg, P 0.11) reduced under (-2.67 protein content decreased 0.05). DFM tended somatic cell count (SCC) across periods 0.07). affect