Relationship between California Mastitis Test Scores and Somatic Cell Counts in Different Crossbred Dairy Cattle Genotypes
Abstract
The objective of this study was to evaluate relationship between California Mastitis Test scores (CMT) and Somatic Cell Counts indifferent crossbred dairy cattle genotypes. A total of 152 milk samples were screened for mastitis using the California Mastitis Test (CMT) kit. Somatic Cell Count (SCC) in milk samples were analysed directly using microscopic method. Based on the analysis of CMT score, the study found out that 55.92 % of udder quarters were negative while 43.99 % were positive for subclinical mastitis. The Least Square Difference (LSD) for pairwise comparison between CMT scores and lactation stage were significantly different between First and second lactation at 0.25±0.11; second and third at 0.27±0.0118 at P≤ 0.05. The means of SCC among the breeds were significantly different at P≤0.05; Ayshires and Friesians (68,055±18.82 cells/ml); Ayshire and Guernsey (71,976±23.844 cells/ml); Friesians and Jerseys (64.863±21.429 cells/ml); and Guernsey and Jersey (68.78±25.952 cells/ml). In conclusion, this study provides baseline information in the area of selection for mastitis resistant breeds of dairy cattle. This study also strongly recommends the use of this technique in screening for somatic cell counts in udder quarters of crossbred dairy cattle.
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Introduction
Good management practices especially on udder health are fundamental for quality and profitability of dairy production (Sadeghi & Amer, 2015; Gupta et al,. 2016). Somatic Cell Counts (SCC) are an important primary indicator of milk hygiene (Jingar et al., 2017). They are also linked to the level of profitability of dairy enterprises (Hadrich et al,.2015; Holland et al., 2015; Jadhav et al., 2016). These cells include; macrophages, polymorphonuclear neutrophils, lymphocytes, and epithelial cells, which resulted from infections of udder quarters. The number of cells are usually reported in milk per millilitre (Division, 2018), and are used internationally to scrutinize/screen milk quality and udder health status in the dairy herds (Li et al., 2014). The SCC above 310,000 cells/ml is the recommended value as a monitor of udder health status (Jadhav et al., 2018). However, the threshold level for assessing and monitoring in dairy herds is often 2.0 x 105 cells/ml and below (Division, 2018). Somatic Cells playa critical role in the immune response of infected udder quarters of cows (Li et al., 2014; Azmi et al., 2017; Iraguhaet al., 2017). The increased somatic cell counts in the milk as a resultof udder tissues’ inflammation, which subsequently affects the quality and quantity of milk produced (Division, 2018; Malik et al., 2018). The presence of somatic cells in milk is attributed due to an infection of the mammary glands, which eventually results in mastitic condition of the udder quarters (Balaji et al., 2016). Subclinical mastitis does not show visible clinical symptoms, but can results in severe economic losses from discarded milk, the sudden death of cattle, cost of veterinary services, the decline in quality and milk produced (Sadeghi & Amer, 2015; Hadrich et al.,2018).
The low heritability of mastitis makes it unfavourable for selection of mastitis resistance breeds of dairy cattle in conventional breeding (Boas et al., 2017). The heritability for milk production traits is usually moderate to high. Therefore, the low SCC could be employed in selection for mastitis resistance in crossbred dairy cattle in an attempt to reduce mastitis incidences the smallholder dairy farmers.
The clinical mastitis is genetically correlated to SCC. The correlation varies from 0.64 to 0.77. Udder health and SCC significantly affect the quality of milk produced by dairy cows (Bhutto et al., 2012). The objective of the present study was to assess the relationship between California Mastitis Test scores (CMT) and Somatic Cell Counts indifferent crossbred dairy cattle genotypes.
Conclusion
The study found out that CMT and SCS were significantly associated across all the udder quarters of these crossbred dairy cattle. Therefore, they can be used to predict amount of Somatic Cells presence in milk. It was also found out that an increase in age of crossbred cow results in a proportionate increase in California mastitis Test scores. The amount of somatic cell counts varies from one breed to another, and they were significant associated among the four genotypes of crossbred dairy cattle.