Transfer of total phenols from a grapeseed-supplemented diet to dairy sheep and goat milk, and effects on performance and milk quality1

Polyphenols are known to affect digestion of ruminants, whereas there is little information about their metabolic effects. In a 2 × 2-factorial experiment the effects of supplementing a phenolic grapeseed extract were compared in 11 East Friesian dairy sheep and 9 Saanen goats. The concentrate supplemented with 7.4 g/100 g DM grapeseed extract had contents of 3.5 g additional phenols/100 g DM and was compared with a low phenolic control concentrate. Performance, total phenols in blood, milk, urine and feces, antioxidant capacity of the blood, and saliva properties were examined. The experiment lasted for 11 wk from parturition to late lactation, with an initial adaptation phase of 1 wk. Milk yield was measured daily after weaning at about 7 wk after parturition. Blood, milk, saliva, feces and urine were sampled 4, 3, 2, 2 and 2 times per animal, respectively. The phenolic diet increased phenol concentrations in blood (+10% and 17% in wk 5 and wk 11, respectively) and in milk (+32% in wk 5) on some of the sampling weeks. There were no clear species differences in phenol concentrations in blood plasma, milk, urine and feces. However, at the end of the experiment the supplemented goats had a higher (48%) urinary phenol concentrations than the non-supplemented goats. A weak relationship (P < 0.05) was found between phenol intake and phenol excretion with milk for sheep but not goats. The phenolic diet did not influence blood antioxidant capacity and tannin binding capacity of the saliva. The saliva of the goats had a higher tannin binding capacity than sheep saliva. The effects of the extract on milk yield were inconsistent between sheep and goats. In general, goats had higher feed and nutrient intakes, were heavier, and yielded more milk. Additionally, milk protein and lactose contents were lower and milk urea content was higher in goats than sheep. In conclusion, supplementing grapeseed extract to sheep and goats elevated phenol concentrations in milk and blood to a certain extent, but most of the phenols were lost via urine. The study gave another indication that goats seem to have developed coping mechanisms like a higher salivary tannin binding capacity, mechanisms which are less pronounced in sheep.