體细胞数（SCC）為目前生乳品質之指標之一，並反應牛隻乳房健康狀况。具乳房炎之牛隻其體細胞數會顯著增加。本研究目的為探討荷蘭牛乳之體细胞數及季節對其乳品質之影響。由2016年12月至2017年6月自台灣屏東某牛場採集樣品。分析項目為體細胞數、蛋白質、脂肪、乳糖、pH值、滴定酸度、游離性鈣離子、酒精安定性及總生菌數。試驗一依據不同範圍體細胞數將乳樣分為三組，第一組為體細胞數低於200×103/mL；第二組為體細胞數介於200×103〜500×103/mL之間；第三組為體細胞數介於500×103〜750×103/mL之間。試驗二於同一頭牛隻中，分別採集健康乳房之乳樣（體細胞低於400×103/mL）與具乳房炎之乳樣，並比較乳房炎對乳品質之影響。統計分析系统（9.3版，SAS）使用一般線性模式（GLM）進行數據分析。再以鄧肯氏新多次變域法比較各處理組平均值間差異顯著性。試驗一結果顯示，總乳體細胞數BMSCC數會影響牧場中總乳之乳品質。當BMSCC含量較高時其脂肪、蛋白質、游離性鈣離子、pH值及總生菌數皆顯著較高，而乳糖及酒精安定性則顯著較低。於不同季節中乳之脂肪、乳糖及游離性鈣離子皆具顯著差異，體細胞數則是夏季乳顯著高於冬季乳。試驗二結果顯示，具乳房炎之乳樣其脂肪、蛋白質、pH值、總生菌數、乳糖，及游離性鈣離子含量顯著較高，而滴定酸度及酒精安定性顯著較低。總合上述，牛隻之體細胞數等級能作為牧場乳品質之指標，包括其脂肪、蛋白质、乳糖、pH值、游離性鈣離子、酒精安定性及總生菌數。

The somatic cell count (SCC) is presently used as an indicator of raw milk quality and reflected the udder health status of the herd. During mastitis, SCC in milk drastically increases, which is associated with changes of milk quality. The aim of this study were to investigate the effect of bulk milk somatic cell count on milk quality of Holstein-Friesian cows, to evaluate a seasonal factor that influences bulk milk somatic cell count and milk quality, to investigate the effect of individual somatic cell count on milk quality of Holstein-Friesian cows, and to understand a relationship between bulk milk somatic cell count and milk quality. Milk Samples were collected from dairy farms at Pingtung, Taiwan during December 2016 to June 2017. All samples were analyzed for protein, fat, lactose percentage, pH, titratable acidity, ionic calcium, ethanol stability, and total bacterial count (TBC). In experiment I, milk samples from bulk tank in dairy farms were allotted into 3 groups according to total SCC, including group 1 with SCC below 200×103 cells/mL, group 2 with SCC ranged from 200×103 to 500×103 cells/mL, and group 3 with SCC ranged from 500×103 to 750×103 cells/mL respectively. In experiment II, milk samples from individual cows were collected from the healthy quarter (below 400×103 cells/mL) and infected quarter of the same cow for comparing influence of mastitis on milk quality. Statistical Analysis System (version 9.3, SAS) was used to perform data analysis using the general wlinear model (GLM). Duncan multiple range test was used for comparison of mean of treatments. Correlation coefficient was also established to investigate the relationships between parameters. The somatic cell count of bulk milk (BMSCC) influenced the milk quality in the dairy farm. The bulk milk with higher BMSCC showed higher fat, protein percentage, ionic calcium content, pH, and TBC (p < 0.01), and lower lactose percentage and ethanol stability (p < 0.01). Total bulk milk somatic cell count between summer and winter season were significantly different (p < 0.05). Differences among seasonal milk fat, lactose percentage, and ionic calcium contents were siginificant (p < 0.05). The highest bulk milk somatic cell counts were observed in summer season. The milk samples from infected quarter showed higher fat, protein percentage, ionic calcium content, pH, and TBC (p < 0.05), and lower lactose percentage, titrable acidity and ethanol stability (p < 0.05). Therefore, bulk milk somatic cell count level in the dairy farm showed a good indication for evaluating milk quality, including fat, protein, lactose, pH, ionic calcium, ethanol stability and total bacterial count.

摘 要 I
Abstract III
Acknowledgement V
Table of Contents VI
Figure and Table Contents IX
1. Introduction 1
2. Litelature review 3
2.1 Somatic cell count 3
2.2 The immune function of somatic cells in the udder 3
2.3 Bulk Milk Somatic Cell Count 5
2.4 Standart of somatic cell count in Indonesia and Taiwan 7
2.5 Mastitis 9
2.5.1 Subclinical and clinical mastitis 10
2.5.2 Bacterial causes mastitis 10
2.6 Impact of SCC on milk yield 11
2.7 Impact of SCC on milk composition 14
2.7.1 Impact of SCC on lactose and mineral 15
2.7.2 Impact of SCC on fat content 16
2.7.3 Impact of SCC on protein content 17
2.8 Impact of SCC on proteolysis and lipolysis 17
2.9 Impact of mastitis on milk product. 19
2.10Variations of ionic calcium in cow milk 19
2.11Factors affecting somatic cell count 20
2.11.1 Season 20
2.11.2 Milk fractions during milking 21
2.11.3 Stage of lactation 24
2.11.4 Age and Parity 25
3. Materials and methods 28
3.1 Materials 28
3.2 Methods 28
3.2.1 Somatic cell count 31
3.2.2 Milk composition 31
3.2.3 Titratable Acidity and pH 32
3.2.4 Total bacterial count 33
3.2.5 Ethanol stability 33
3.2.6 Ionic calcium concentration 33
3.2.7 Sensory evaluation 35
3.3 Characteristic of individual dairy cows 36
3.4 Characteristic of seasons environment 36
3.5 Statistical Analysis 37
4. Result and discussion 38
4.1 Effect of bulk milk somatic cell count on milk quality 38
4.1.1 Effect of bulk milk somatic cell count on milk composition 38
4.1.2 Effect of bulk milk somatic cell count on physical properties 42
4.1.3 Effect of bulk milk somatic cell count on microbial properties 46
4.1.4 Effect of bulk milk somatic cell count on pasteurized milk 47
4.2 Bulk milk somatic cell count in different season 49
4.2.1 The effect of season on milk yield of bulk milk 50
4.2.2 The effect of season on milk composition of bulk milk 50
4.2.3 The effect of season on physical and chemical properties of bulk milk 52
4.2.4 Effect of season on mircobial properties of bulk milk 53
4.3 Relationship between BMSCC and milk quality of cow 54
4.3.1 Correlation for relationship between BMSCC and milk composition 54
4.3.2 Correlation for relationship between SCC and physical and chemical properties of bulk milk 55
4.4 Effect of individual somatic cell count on milk quality 56
4.4.1 Effect of individual somatic cell count on milk composition 56
4.4.2 Effect of individual somatic cell count on Physical and chemical properties 58
4.4.3 Effect of individual somatic cell count on Microbial properties 60
5. Conclusion 61
References 62
Appendix 1. Sensory evaluation ballot for descriptive and acceptance test 68
Appendix 2. Mean sensory attribute score of pasteurized milk in different somatic cell count level evaluated by 30 panelist. 69
Biosketch of Author 70

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