Effect of concentrate type on rumen fermentation and milk production of cows at pasture

The experiment was conducted with 15 Autumn-calving Holstein–Friesian cows, three of which were fitted with rumen cannula, that were allowed to access a perennial timothy and meadow fescue sward between 10 June and 12 August 1996. The control treatment (C) consisted of pasture alone. For the other two treatments, cows were fed 4 kg per day of either a concentrate supplement consisting of barley (B) or a treatment (M) containing (g/kg) barley (200), oats (200), wheat bran (220), wheat (110), wheat syrup (60) and molassed sugar beet pulp (200). The experiment was carried out as a replicated (n=5) 3×3 Latin square design. The grazing area was divided into 15 paddocks and cows were grazed on a 1 to 2-day rotation. There was no treatment effect on rumen pH but the molar proportion of acetic acid in rumen fluid was higher (p<0.05) in cows grazing pasture alone (C). Ammonia N concentration was lower for M than B (p<0.01). Concentrate supplementation increased milk yield (p<0.001), the extent of which was greater for M than B (2.6 versus 1.3 kg per day; p<0.05). Protein yields increased (p<0.001) due to treatments B (51 g per day) and M (115 g per day). These results indicate that barley is a less suitable concentrate supplement than a mixture, formulated from a range of ingredients since energy corrected milk yield (ECM 20.5 versus 19.2 kg per day), protein (729 versus 665 g per day) and lactose (1000 versus 933 g per day) yields were greater (p<0.01) in treatment M than B.