| Summary: | 碩士 === 國立中興大學 === 動物科學系所 === 103 === Taiwan is located in subtropical regions, hot and humid climate is not suitable for the growth of dairy Holstein cattle in temperate regions, when the weather falls into summer. The dramatically change in summer that may affect dairy cows feeding behavior, prompting negative energy balance and cause many metabolic diseases such as ketosis, fatty liver, acidosis, displacement of abomasum happened. The purpose of this study was to evaluate the feasibility of glycerol as energy source in dairy Holstein cows by measuring the changes of blood biochemical value, production performance, rumen traits, milk fatty acid composition and body condition in transition period and lactation period. In experiment 1, four Holstein transitional cows were used according to completely randomized design, in which two dietary treatments were comprised with control and glycerol supplementation, the later one was control diet supplemented with 300g/d glycerol given daily from 21d before to 30 d after calving. The result showed that glycerol treatment was not different from control (P > 0.05) in dry matter intake but significantly （P < 0.05）lowered milk fat content (%) and plasma contents of β-hydroxybutyrate (11.5 mg/dL vs.8.67mg/dL)、nonesterfied fatty acid (338 μEq/L vs. 273 μEq/L) and higher milk yield（P < 0.05）but significantly increased the plasma serum glucose （50.6 mg/dL vs. 55.9 mg/dL）、cholesterol （77.1 mg/dL vs. 79.6 mg/dL）and triglyceride（15.7 mg/dL vs. 17.5 mg/dL）concentration。 In experiment 2, five Holstein cows were used according to single change-over design, in which three dietary treatments comprise with control、control plus glycerol (300g/d) and commercial product of glycerol (300g/d) treatment for 24 week to evaluate the effects on the blood biochemical value, milk production, production performance, ruminal metabolite, milk fatty acid composition, body weight and body condition in lactating period. The result showed that supplementation 300 g/d glycerol or commercial glycerol on dairy cows were significantly lower rumen pH value （Control and CG. vs. Glycerol，6.45 and 6.40 vs 6.29。P < 0.001）、lower acete ratio （Control and CG vs. Glycerol，56.5 % and 52.3 % vs. 51.29 %。P < 0.001）and increase the propionate concentration（P < 0.01）in lactating period, but there was not difference from the control in body weight, milk composition and body condition score （P > 0.05）. In milk fatty acid comcposition, there was part of fatty acid changed when supplementation of glycerol in dietary like In conclusion, dietary supplementation of glycerol was no effect the dry matter intake but increased the propionate in rumen and it could rapidly supply extra energy source. It’s possible to decrease the incidence of metabolic disorders with glycerol supplementration.
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