Milk yield and composition in dairy cows with post-partum disorders

ABSTRACT This study aimed to determine the impact of different post-partum disorders on milk yield and composition. One hundred and fifteen Holstein cows from a commercial dairy farm located in the state of Rio Grande do Sul in southern Brazil were monitored up to 62 days post-partum. During this period, body condition score evaluation and animal clinical examination were conducted. Percentages of fat, protein, and lactose, as well as somatic cells score, were determined in milk samples. The AST activity and concentrations of NEFA, calcium, and BHBA, were analyzed in blood samples. The occurrence of clinical disorders was identified in 30 (26%) cows. Subclinical disorders were identified in 64 (56%) cows. Only 21 (18%) cows did not suffer any kind of disorder within the studied period. In this study, no significant differences were found in milk production, protein, and somatic cell count in clinical, subclinical, and healthy cows. Milk fat and the fat: protein quotient (F:P) were higher in cows with clinical disorders and the 6 to 21 days in milk, and lactose were lower in cows with clinical disorders and the 22 to 42 days in milk (P<0.05).

摘要 本研究旨在探究不同产后疾病对奶牛产奶量及乳成分的影响。研究选取巴西南部南里奥格兰德州某商业化奶牛场的115头荷斯坦（Holstein）奶牛，对其开展产后62天的跟踪监测。监测期间，对所有奶牛进行体况评分评定与临床检查；采集乳样并检测其中脂肪、蛋白质、乳糖的百分比含量以及体细胞评分（somatic cells score）；采集血样并检测天冬氨酸氨基转移酶（AST）活性，以及非酯化脂肪酸（NEFA）、钙与β-羟丁酸（BHBA）的浓度。研究期间，30头（占比26%）奶牛出现临床疾病，64头（占比56%）奶牛出现亚临床疾病，仅21头（占比18%）奶牛未发生任何类型的疾病。结果显示，临床患病、亚临床患病与健康奶牛的产奶量、蛋白质含量及体细胞计数均无显著差异。临床患病奶牛在泌乳6~21天时的乳脂肪含量及脂蛋比（F:P）显著高于健康奶牛，而在泌乳22~42天时的乳糖含量则显著低于健康奶牛（P<0.05）。