Winter and spring variation in daily milk yield and mineral composition of Jersey, Friesian cows and their crosses under a pasture-based dairy system
This study was conducted to determine the effects of genotype and season on daily milk yield (DMY) and mineral composition of pasture-based dairy cows. This was done by collecting data from 20 Friesian, 20 Jersey and 20 Friesian × Jersey crossbred cows in the early stage of their 4th parity in winter and spring, respectively. Automated milk meters were used to measure the DMY. Mineral composition was determined by using the Inductively Coupled Plasma Optical Emission Spectrometric (ICP-OES) method. The data collected from milk yield and mineral composition were analysed using the general linear model of SAS. The results showed that milk yield was highest from Friesian cows both in spring and winter seasons while Jersey cows had the lowest yield. Seasonal effects were also observed in mineral concentrations, with winter having higher values for aluminium, boron, copper, iron, magnesium, manganese, zinc and sodium while phosphorus was higher in spring. Crossbred cows yielded higher concentrations of calcium, phosphorus and magnesium. It was therefore concluded that both milk yield and mineral compositions are affected by genotype and season.
Keywords: Genotype, seasonal effects, mineral content, novel health milk products