Feeding High Proportions of Barley Grain Stimulates an Inflammatory Response in Dairy Cows

The objective of this study was to evaluate effects of feeding increasing proportions of barley grain on acute phase response in lactating dairy cows. Eight cannulated primiparous (60 to 140 d in milk) Holstein dairy cows were assigned to 4 diets in a 4 × 4 Latin square experimental design. The experimental period lasted for 21 d, with 11 d of adaptation and 10 d of measurements. Cows were fed the following diets: 1) no barley grain in the diet, 2) 15% barley grain, 3) 30% barley grain, and 4) 45% barley grain, as well as barley and alfalfa silage and alfalfa hay at 85, 70, 55, and 40% [dry matter (DM) basis]. All cows were supplemented with a 15% concentrate mix. Blood and rumen fluid samples were collected on d 1, 3, 5, 7, and 10 of the measurement period, and pH and endotoxin content were measured in rumen samples. Concentrations of serum amyloid A, lipopolysaccharide-binding protein, haptoglobin, and C-reactive protein in plasma were measured by ELISA. Feeding high proportions of barley grain at 0, 15, 30, and 45% of DM was associated with lower feed intake (32.6, 32.9, 27.34, and 25.18 kg/d ± 1.30, respectively), lower ruminal pH (6.8, 6.7, 6.7, and 6.5 ± 0.03, respectively), and higher DM intake (13.33, 15.28, 14.68, and 16.04 ± 0.63 kg/d, respectively) and milk production (27.2, 28.2, 29.0, and 31.0 ± 1.2 kg/d, respectively). Ruminal endotoxin increased in cows receiving 30 and 45% barley grain (5,021, and 8,870 ± 393 ng/mL, respectively) compared with those fed no grain or 15% barley grain (654 and 790 ± 393 ng/mL, respectively). Plasma concentrations of serum amyloid A, lipopolysaccharide-binding protein, and C-reactive protein increased in cows given higher (30 and 45%) proportions of grain. Plasma haptoglobin was not affected by treatments. In conclusion, feeding dairy cows high proportions (30 and 45% DM basis) of barley grain was associated with lower feed intake and rumen pH, increased endotoxin in the rumen fluid, and stimulation of an inflammatory response.