Effects of Season, Lactation and Milk Production on Milk Composition and Physicochemical Properties of High Productive Holstein Cow

Autor: Kuang-Yu Hung, 洪光宇
Rok vydání: 2008
Druh dokumentu: 學位論文 ; thesis
Popis: 96
Student ID: N9214013 Title of Thesis: Effects of season, lactation and milk production on milk composition and physicochemical properties of high productive Holstein cow Total Page: 71 Name of Institute: Department of Animal Science, National Pingtung University of Science and Technology Graduate Date: June, 2008 Degree Conferred: Master Name of Student: Kuang-Yu Hung Adviser: Mei-Jen Lin, Ph. D. The Contents of Abstract in This Thesis: The aim of dairy industry is to pursue the highest production, the best milk quality and the lowest production cost to acquire the highest economic benefit. Holstein cow’s milk yield decreased at the temperature between 21~ 27℃ and decreased significantly at the temperature above 27℃. The annual average temperature in Taiwan is 28℃. The production and market demand of the milk in hot and cold season is unbalanced, which is high market demand but low yield in hot season, and low demand but high yield in cold season. In 2004, milk price of hot season (Jun. ~ Sep.) was about NT$22.73 / kg, warm season (Apr., May; Oct., Nov.) NT$20.73 / kg, and cold season (Dec. ~ Mar.) NT$13.74 / kg in Taiwan, respectively. The purpose of this study was to understand the variation in milk composition and physicochemical properties of individual Holstein’s milk at various productivities, lactation stages, and seasons. The relationships among ethanol stability (EtOH%), milk composition and physicochemical properties were also investigated. The experiments were carried out from April 2005 to June 2006 at Guan-Tian dairy farm and from January to June 2006 at Liu-Ying dairy farm. Dairy cattles in high-yield area at 25 ~ 87 months of age, 1 ~ 5 parity, 14 ~ 297 days of lactation were randomly selected the total of 47 dairy cattle were used at Guan-Tian station and 10 were used at Liu-Ying station, respectively. At the day of sampling Dairy Herd Improvement (Dairy Herd Improvement, DHI) monthly milk samples, 200 ml of the same individual milk samples were taken. The physicochemical properties of milk, including pH, titratable acidity (TA), ethanol stability (EtOH%), total calcium concentration, and ionic calcium concentration (iCa) were carried out in 24 hours. Milk analysis of DHI include fat, protein, lactose, solids not fat, urea nitrogen and citrate contents and somatic cell counts. The data were statistically analyzed according to the milk yields (low milk production, less than 20 kg; Average milk production, 21 ~ 30 kg; high milk production, 31 ~ 40 kg; and special milk production, more than 41 kg), stages of lactation (early-lactation, within 60-days; early-mid-lactation, 61 ~ 100 days; late-mid-lactation, 101~200 days; and late-lactation, longer than 201 days), four seasons and industrial seasons (hot season, Jun. ~ Sept.; warm season, Apr, May, Oct, Nov, and coll season, Dec. ~ Mar.). Results showed that 4% fat corrected yield of special milk production was higher than others. Total solids, milk fat and protein contents in milk of low milk production were higher than special milk production. Lactose content in milk of high milk production and special milk production were higher than low milk production. The 4% fat corrected yield of early-lactation and early-mid-lactation were higher than late-lactation. Protein content of late-lactation milk was the highest. Titratable acidity of late-lactation milk was lower than early-lactation and late-mid-lactation milk. Total calcium concentration of early-lactation milk was the highest. The 4% fat corrected yield of winter and spring milk were higher than summer. Lactose content of winter milk was higher than spring and summer milk. Milk citrate content of summer milk was the lowest. Titratable acidity of spring milk was lower than summer and autumn milk. The pH value of spring milk was higher than summer and autumn milk. Ionic calcium concentration of autumn milk was the highest. Total calcium concentration of winter milk was higher than spring milk. The 4% fat corrected yield, lactose and citrate contents of cold-industrial-season milk were higher than warm-industrial-season and hot-industrial-season milk. The EtOH% of warm-industrial-season milk was the highest. The pH value of hot-industrial-season milk was the lowest. The iCa was negatively correlated to EtOH%, protein content, milk urea nitrogen content and lactating month, but positively correlated to titratable acidity and total calcium concentration. EtOH% was negatively correlated to somatic cell counts, fat, total calcium concentration, titratable acidity and ionic calcium concentration, but positively correlated to urea nitrogen content, lactose content and pH value. To sum up, the early-mid-lactation and late-mid-lactation had higher milk quality during lactation period. The EtOH% was the lowest and iCa was the highest in milk in Autumn, the EtOH% was the best in milk in warm-industrial-season. There was a negative correlation between iCa and EtOH%.
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