Winter and spring variation in milk yield and milk mineral composition on pasture in the south-eastern cape

Discipline: Composition; 

Previous studies indicate that the mineral content of milk may be influenced by genotype and season on pasture, even when feed supplements are standardized. Mineral contents are important as minerals contribute significantly to the health attributes of milk. In South Africa, this has not been investigated and therefore researchers at Fort Hare University did such a study, using their pasture-based system, the pasture being perennial and annual ryegrass intersown with a clover cultivar.

The investigation was done with 20 Friesian, 20 Jersey and 20 Friesian × Jersey crossbred cows. As lactation number and stage of lactation could also affect the results, only cows in the early stage of their fourth lactation in winter and spring were used. The results showed that milk yield was highest in Friesian cows at 29.9 L per day, followed by crossbreds at 25.5 L per day and lowest with Jerseys at 20.8 L per day, suggesting additivity and not heterosis. More milk was produced in spring (27.1 L per day) than in winter (23.9 L per day). Seasonal effects were also observed in mineral concentrations of milk, with winter having higher values for aluminium, boron, copper, iron, magnesium, manganese, zinc and sodium while phosphorus was higher in spring.  Interesting, crossbred cows yielded higher concentrations of calcium, phosphorus and magnesium than the purebreds, suggesting heterosis. These minerals are interlinked in physiological function and indirectly associated with protein synthesis. Crossbreeding has been shown to affect milk protein, especially casein positively, and the higher concentrations of these minerals in Holstein × Jersey crossbreds suggest this as well. Crossbreeding amongst its other advantages, therefore, may also have a positive effect on milk quality.

Referance

Nantapo, C.T.W. & Munchenje, V., 2013. Winter and spring variation in daily milk yield and mineral composition of Jersey, Friesian cows and their crosses under a pasture-based dairy system. S. Afr J. Anim. Sci. 43 (Issue 5, Supplement 1), S17-S21.