Effect of toasting field beans and of grass-clover: Maize silage ratio on milk production, milk composition and sensory quality of milk

Summary

The effect of toasting field beans and of grass-clover: maize silage ratio on milk production, milk composition and sensory quality of the milk was investigated in a 2*2 factorial experiment. Toasting of field beans resulted in lower contents in milk of both fat (44.2 versus 46.1 g/kg, P = 0.02) and protein (33.5 versus 34.2 g/kg, P = 0.008), whereas milk production and urea and somatic cell contents were unaffected compared with untreated field beans. Increasing the proportion of maize silage (from 2 to 5 kg DM/cow/day) in the ration decreased the content of urea in milk (P=0.002), whereas milk production and fat and protein contents were unaffected. Milk from cows fed the high proportion of maize silage had a lower (P=0.04) content of the long chain fatty acids (³ C18). Furthermore, milk from cows fed the high proportion of maize silage had a lower (13-26%) content of luteine (P=0.03), 13-cis-β-carotene (P=0.04) and β-carotene (P=0.05). Toasting of field beans compared with untreated field beans did not affect milk content of carotenoids and had only small effects on fatty acids composition. The sensory profiles of the four milk samples were quite similar characterized by a fatty mouthfeel and creamy flavour, though for the attributes sour feed odour and maize odour there was a significant difference between treatments. In conclusion, toasting field beans did not improve milk production, and toasted field beans in combination with a high proportion of maize in the feed resulted in milk with negative sensory characteristics. Increasing the proportion of maize silage at the expense of grass-clover silage did not affect milk production, but decreased the milk content of long-chain fatty acids, as well as the content of carotenes.