Nitrate and/or oils supplementation to diets with different roughage: concentrate ratios on in vitro some rumen parameters and protozoa population

Abstract This study aimed to determine the effect of nitrate and/or oils supplementation alone or in combination to diets with different roughage: concentrate ratios on in vitro methane (CH4) production, volatile fatty acid (VFA) and ammonia (NH3) concentrations, pH, and protozoa population. The experimental treatments comprised iso-nitrogenous total mixed rations based on forage with roughage to concentrate ratio of 40R:60C (High concentrate) or 60R:40C (High roughage) supplemented with 2 sources of nitrogen (sodium nitrate (NO3-: 45.94 g/kg DM) or urea (16.45 g/kg DM for control group) and 3 oil sources ((feed-derived oil (FDO: with no oil addition), hazelnut oil (HO: 36.58 g/kg DM) or soybean oil (SO: 36.58 g/kg DM)). For this purpose, 2 x 2 x 3 factorial design in 12 groups were used. The treatments were as follows: 40R:60C + Urea (Control) + FDO, 40R:60C + NO3- + FDO, 40R:60C + Urea (Control) + HO, 40R:60C + Urea (Control) + SO, 40R:60C + NO3- + HO, 40R:60C + NO3- + SO, 60R:40C + Urea (Control) + FDO, 60R:40C + NO3- + FDO, 60R:40C + Urea (Control) + HO, 60R:40C + Urea (Control) + SO, 60R:40C + NO3- + HO, 60R:60C + NO3- + SO. Then, the effect of nitrate, oils (O), roughage:concentrate ratio, and the combined effect of nitrate and oil associated with roughage:concentrate on in vitro methane production, VFA and NH3 concentrations, pH, and protozoa population were evaluated. In this study, while NO3-, O, 40R:60C x NO3-, 40R:60C x O, 40R:60C x NO3- x O, 60R:40C x NO3- 60R:40C x O, 60R:40C x NO3- x O (p<0.01) decreased in vitro CH4, protozoa population, ammonia (NH3) concentration, acetic acid, total VFA, acetic acid: propionic acid ratio and pH, they increased butyric acid and propionic acid concentrations. Furthermore, in vitro CH4 production (12.44 vs 9.09 ml), NH3 (8.23 vs 7.37 mmol/l), propionic acid (19.14 vs 17.93 mmol/l), butyric acid (15.50 vs 14.50 mmol/l), total VFA (86.46 vs 85.66 mmol/l), protozoa population (32.16 vs 26.96 x104 ml.) were high in the 40R:60C treatment (high concentrate). Although, 40R:60C x NO3- x SO, 60R:40C x NO3- x SO, and SO decreased more acetic acid concentration, protozoa population, and thus in vitro CH4 production than other groups.