这项研究的目的是量化一些环境(个体牛群,羊群生产力,挤奶系统和季节)和动物因素[个体动物,品种,牛奶中的天数(DIM)和奇偶校验]对单个牛乳上体细胞计数(LSCC)和差异体细胞计数(DSCC)的log-10转化的变异性。从分布在223个牛群中的12,849头荷斯坦-弗里斯和9,275头西门塔尔牛中提取了总计159,360头与牛奶产量和成分有关的测试日记录。牧群分为高生产力和低生产力,根据奶牛产生的平均每日牛奶净能量输出(DMEO)定义。数据包括每日产奶量(DYM;kg/d),牛奶脂肪,蛋白质,乳糖,SCC和DSCC,和关于牛群的信息(即,生产力,挤奶系统)。计算牛奶中总体细胞和差异体细胞的日产量,然后进行log-10转化,获取DLSCC和DLDSCC,分别。使用混合模型分析数据,包括个体群的影响,动物,动物内重复测量是随机的,和羊群生产力,挤奶系统,季节,品种,DIM,奇偶校验,DIM×奇偶校验,品种×季节,DIM×挤奶系统和奇偶校验×挤奶系统作为固定因素。具有高DMEO的牛群的特征是LSCC和DSCC含量较低,和更高的DLSCC和DLDSCC,与低DMEO牛群相比。挤奶系统与体细胞特征之间的关联表明,使用自动挤奶系统将无法对奶牛进行快速干预,与其他挤奶系统相比,所有体细胞性状的含量更高。季节是变异的重要来源,夏季牛奶中的高LSCC和DSCC含量证明了这一点。奶牛品种有很大的影响,荷斯坦-弗里斯有更大的LSCC,DSCC,DLSCC和DLDSCC与Simmental进行比较。关于DIM,LSCC的变异性主要与DSCC有关,显示从产牛到哺乳结束的增加,并表明在泌乳末期奶牛中慢性乳腺炎的发生率更高。所有的体细胞性状都随着奇偶校验数的增加而增加,可能是因为年龄较大的奶牛对乳房内感染的易感性增加。
The aim of this study was to quantify some environmental (individual herds, herd productivity, milking system, and season) and animal factors [individual animals, breed, days in milk (DIM) and parity] on the variability of the log-10 transformation of somatic cell count (LSCC) and differential somatic cell count (DSCC) on individual bovine milk. A total of 159,360 test-day records related to milk production and composition were extracted from 12,849 Holstein-Friesian and 9,275 Simmental cows distributed across 223 herds. Herds were classified into high and low productivity, defined according to the average daily milk net energy output (DMEO) yielded by the cows. Data included daily milk yield (DYM; kg/d), milk fat, protein, lactose, SCC, and DSCC, and information on herds (i.e., productivity, milking system). The daily production of total and differential somatic cells in milk was calculated and then log-10 transformed, obtaining DLSCC and DLDSCC, respectively. Data were analyzed using a mixed model including the effects of individual herd, animal, repeated measurements intra animal as random, and herd productivity, milking system, season, breed, DIM, parity, DIM × parity, breed × season, DIM × milking system and parity × milking system as fixed factors. Herds with a high DMEO were characterized by a lower content of LSCC and DSCC, and higher DLSCC and DLDSCC, compared to the low DMEO herds. The association between milking system and somatic cell traits suggested that the use of the automatic milking systems would not allow for a rapid intervention on the cow, as evidenced by the higher content of all somatic cell traits compared to the other milking systems. Season was an important source of variation, as evidenced by high LSCC and DSCC content in milk during summer. Breed of cow had a large influence, with Holstein-Friesian having greater LSCC, DSCC, DLSCC, and DLDSCC compared to Simmental. With regard to DIM, the variability of LSCC was mostly related to that of DSCC, showing an increase from calving to the end of lactation, and suggesting the higher occurrence of chronic mastitis in cows toward the end of lactation. All the somatic cell traits increased across number of parities, possibly because older cows may have increased susceptibility to intramammary infections.
This study investigated factors affecting the variability of somatic cell traits in bovine milk. Animal had greater influence on somatic cell score (SCS) and differential somatic cell count (DSCC) compared to herd factors. Herds producing high average of daily milk energy were characterized by lower SCS and DSCC compared to the low average daily milk energy herds. The SCS and DSCC were higher in Holstein-Friesian than in Simmental, and during summer with respect to the other seasons. Older cows at the end of lactation showed the highest content of somatic cell traits. These results are helpful for the management of somatic cell traits at herd and animal levels.