Determination of milk production losses and variations of fat and protein percentages according to different levels of somatic cell count in Valle del Belice dairy sheep

The somatic cell count (SCC) of milk is widely used to monitor udder health and the milk quality and because of its positive genetic correlation with mastitis this trait was included in breeding schemes of dairy sheep. The aim of this study was to estimate the loss in milk yield (MY) and related composition resulting from different levels of somatic cell count in Valle del Belice dairy sheep. Data were collected between 2006 and 2016 in 15 flocks following an A4 recording scheme. Somatic cell count (SCC), fat and protein percentage (F% and P%) were determined using mid-infrared spectroscopy. To evaluate loss in test day MY, F% and P%, five different classes of SCC were arbitrarily defined: SCC1 ≤ 500 × 103, 500 × 103< SCC2 ≤ 1000 × 103, 1000 × 103< SCC3 ≤ 1500 × 103, 1500 × 103< SCC4 ≤ 2000 × 103and SCC5 > 2000 × 103. To estimate the loss of milk production and quality a linear model, with test day milk production traits as dependent variable, was used. Furthermore, the effect of order of parity and season of lambing were investigated to study the effects on milk production traits. Least squares means were computed for milk production traits and the differences between means were determined by Fischer's least significant difference. The estimated losses in MY according to the level of used SCC were approximately 16% whereas there was an increase of 0.06% and 0.29% for fat and protein percentage, respectively. Apart from environmental factors and management, this study confirms that high levels of somatic cell count in sheep milk are associated with milk yield losses and changes in milk composition. Results suggest that it is necessary to implement a program aimed to reduce the milk somatic cell count in ewes' milk, with the aim of improving the quality of ewes' milk and dairy products.