Composition and colour indices of sheep's bulk-tank milk are influenced by production practices

Over the past few years, there has been a great development of the sheep dairy sector in Spain and a wide variability in the production outcomes of farms, although most of the farms have similar environmental and economic constraints. Milk quality evaluation is important not only for cheese production, but also for other dairy products. Therefore, the aim was to evaluate the effect of some factors on bulk-tank milk characteristics of Manchega sheep, with special attention to casein and urea contents and colour indices. Factors of variation such as season, annual milk yield of ewe (AMYE), the enrolment (or not) in a breeding programme (BPM) and the feeding strategy of farms have been considered. The study included 77 farms distributed along La Mancha region, in Spain. Data about production practices and feeding strategy were also collected from these farms. A total of 308 analytical determinations of milk characteristics including fat, protein, total solids, casein, lactose, protein/total solids, casein/fat, pH, urea content, colour indices and somatic cell count were analysed by automated methods. The results of the present work indicate that season was the source of variation with the greatest effect on chemical characteristics of bulk-tank milk, except for casein/fat ratio for which the difference was smaller. The feeding strategy effects on characteristics of milk have also been confirmed Moreover, it has been demonstrated that the feeding strategies are applied more coherently according to their productive characteristics in farms with small and medium size than in farms with the largest herd size.