Effect of ammonia treatment and carbohydrate supplementation of barley straw on rumen liquid characteristics and substrate degradation by sheep

Effects of medium-chain fatty acids (MCFAs) on in vitro rumen fermentation, methane production, and nutrient digestibility under low- and high-concentrate diets

This experiment was conducted to investigate the effects of different dosages and types of medium-chain fatty acids (MCFAs) on rumen fermentation in vitro under low- and high-concentrate diets. For this purpose, two in vitro experiments (Exp.) were conducted. In Exp. 1, the concentrate-roughage ratio of the fermentation substrate [total mixed rations (TMR), dry matter (DM) basis] was 30:70 (low-concentrate diet), while in Exp. 2, it was 70:30 (high-concentrate diet). Three types of MCFAs with octanoic acid (C₈ ), capric acid (C₁₀ ), and lauric acid (C₁₂ ) were added accounting for 1.5%, 6%, 9%, and 15% of the in vitro fermentation substrate weight (200 mg or 1 g, DM basis) based on control group, respectively. The results showed that the addition of MCFAs all could significantly reduce methane (CH₄ ) production and the number of rumen protozoa, methanogens, and methanobrevibacter under the two diets with the dosages increased (p < 0.05). In addition, MCFAs had a certain degree of improvement on rumen fermentation and influenced in vitro digestibility under low- and high-concentrate diets, and their effects were related to the dosages and types of MCFAs. This study provided a theoretical basis for the selection of types and dosages of MCFAs in ruminants production.

Effect of supplementation with different proportions of barley grain or citrus pulp on the digestive utilization of ammonia-treated straw by sheep

The effect of carbohydrate supplementation on rumen utilization of ammonia-treated straw was studied in four rumen-cannulated ewes (42•0 (s.e. 2•80) kg live weight) in a Latin-square design. Diets were a 50: 50 mixture of ammoniated barley straw and a concentrate made up with different ratios of barley grain and citrus pulp, namely M1 (100: 0), M2 (66: 33), M3 (33: 66) and M4 (0: 100). Concentrates also included soya-bean meal and urea to make diets isonitrogenous. Diets were given in one meal in the morning at 0•8 kg/day. There were no significant differences among treatments in daily weighted means of rumen pH and concentration of volatile fatty acids. Acetate, propionate and butyrate molar proportions were not different among treatments, but proportions of isobutyrate (P < 0•05) and isovalerate (P < 0•10) were higher for M1 and M2. Ammonia concentration immediately before feeding was lower (P < 0•05) for M3 and M4 (72•1 and 51•3 mg/l) than for M1 and M2 (97•0 and 107•9 mg/ l). Total rumen bacterial concentration was higher (P < 0•05) with the highest barley proportion, whereas enzymatic activity against structural carbohydrates of particle-associated bacteria did not differ significantly among treatments. Digestibility of neutral-detergent fibre increased (P < 0•05) with the increase in the proportion of citrus pulp in the concentrate (0•647, 0•674, 0•684 and 0•693 for M1, M2, M3 and M4; s.e. = 0•0086). Urinary excretion of purine derivatives decreased linearly (P < 0•05) as the proportion of citrus pulp in the diet increased, while faecal excretion of purine bases was not significantly affected by dietary treatments.

Effects of substitution of barley with citrus pulp on diet digestibility and intake and production of lactating ewes offered mixed diets based on ammonia-treated barley straw

Twenty-eight lactating ewes (mean 48 (s.e. 0·37) kg live weight) were used from days 12 to 52 after lambing to evaluate the effects on digestibility and production performance of replacing barley grain with citrus pulp in diets based on ammonia-treated barley straw. Concentrates included 0·82 to 0·83 of different barley to citrus pulp proportions: 100: 0 (T1); 66: 33 (T2); 33: 66 (T3) and 0: 100 (T4), 0·115 of soya-bean meal, and urea to make diets isonitrogenous. Ewes were adapted to a common diet for 11 days after lambing, and then were given 850 g/day of each experimental concentrate together with 850 g/day of chopped barley straw for 14 days and milk production and lamb growth were recorded. During the following 14 days ewes received the same amount of concentrate but the straw was offered ad libitum and straw intake was recorded as well as milk production and lamb growth. After completing both periods, four ewes per treatment were used for total collections of faeces and urine. Apparent digestibility of organic matter and neutral-detergent fibre increased linearly (P < 0·05) with increasing levels of citrus pulp although no differences were found in the digestible organic matter content of dry matter of diets because of differences in ash content. Urinary excretion of allantoin and purine derivatives per unit of digestible organic matter intake tended to decrease with increasing inclusion of citrus pulp (proportionately by 0·15), suggesting a decrease in microbial protein synthesis, though this effect was not significant (P > 0·05). Faecal excretion of purine bases also decreased (P < 0·05) as citrus pulp inclusion increased. No treatment effect (P > 0·05) on ewe live weight, milk composition or serum glucose and 3–OH butyrate was observed when a 1: 1 straw to concentrate ratio was given, but milk production and lamb daily gain decreased linearly (P < 0·05) with increased proportions of citrus pulp in the concentrate. Similar responses were detected when straw was given ad libitum and differences among treatments in terms of straw intake were not identified. It is concluded that a lower microbial protein flow might explain in part the reduction in milk production observed when barley was replaced with citrus pulp.

Effects of dietary potential Acid production value on productivity in dairy cows

This study was conducted to estimate the potential acid production value (PAPV) of major diets and to determine the relationship between dietary PAPV and dairy production traits. Estimation of PAPV of major cattle feeds was based on an in vitro technique, which determined the degree of Ca dissociation from CaCO₃. Data on feeds and production traits were collected on 744 multiparous lactating Holstein dairy cows from five different farms. Grains had high PAPV with variable protein sources and by-products. High PAPV feedstuffs had a higher total gas production and lower pH compared to those with low PAPV. Dietary PAPV had a positive correlation with intake of dry matter, NDF, ADF, milk yield and milk solid production but a negative correlation with milk protein and milk fat concentration. Current results indicate that dietary PAPV can be utilized in predicting dairy production traits.

Differences in microbial fermentation of barley straw induced by its treatment with anhydrous ammonia

The effect of ammonia treatment of straw on both the rumen environment and the extent of its microbial fermentation was studied. Four rumen cannulated sheep were randomly given 700 g/day of untreated straw plus urea (US), ammonia-treated straw (TS) and alfalfa hay (AH) in a change-over design with three periods. Rumen pH was lower and ammonia-nitrogen and total volatile fatty acid (VFA) concentrations were higher (P < 0·001) with AH than with US or TS. With the straw diets, TS promoted a lower pH than US (P < 0·05), but differences were less than 0·3 units and the mean pH was never below 6·5. There were no differences between the straw diets in ammonia-nitrogen or VFA concentration (P > 0·05). When untreated barley straw (BS) and treated straw (TS) were incubated in situ disappearance of dry matter (dDM) at 12, 24 and 48 h (P < 0·01) and neutral-detergent fibre (dNDF) at 48 h (P < 0·001) were higher with TS. In vitro incubation showed a higher gas production with TS only after 36 h (P < 0·05) whereas gas from BS fermentation was higher up to 14 h (P < 0·05). Among diets, dDM, dNDF and gas production with US were numerically higher than with TS or AH throughout, although few significant differences were observed, except for a higher dDM at 12 (P < 0·01) and 24 (P < 0·10) h and a higher dNDF at 12 h (P < 0·10). Particle-associated enzymes were extracted from BS and TS incubated in the rumen for 4, 8, 22 and 24 h. Results ofxylanase and cellulase activities support those of straw incubation, with a drop between 4 and 8 h in TS diet. The concentration of residual phenolics per unit of incubated straws after 12 and 24 h show that phenolics release to the media was higher with the TS diet. Daily changes of phenolic concentration into rumen liquid was also higher with TS than with US (P < 0·001). The increased release of straw phenolics by ammoniation reduced the potential for rumen degradation of straw, mainly in the first hours of the fermentation period.

Ruminal fermentation and degradation patterns, protozoa population and urinary purine derivatives excretion in goats and wethers fed diets based on olive leaves1

Olives leaves, accrued during the processing of olive harvests for oil extraction, are poor in N, rich in crude fat and ADF (1.19, 8.03 and 28.2 g/100 g of DM, respectively), and relatively low in condensed tannins (11.1 mg/g of DM). Three experiments were conducted in a 2 x 3 (two animal species: goats vs. wethers; and three experimental diets: olive leaves without or with polyethylene glycol supply and olive leaves supplemented with barley and faba beans) factorial design to evaluate ruminal degradation and passage kinetics (Exp. 1), fermentation pattern and protozoa population (Exp. 2), and urinary purine derivatives excretion (Exp. 3). Polyethylene glycol was supplied to evaluate the effects of condensed tannins contained in olive leaves. Ruminal degradability of CP was low in both goats and wethers, although goats showed higher (P < 0.05) values than wethers. Supplementation of olive leaves with barley and faba beans increased (P < 0.001) ruminal degradability of DM and CP. Both goats and wethers fed olive leaves showed similarly low particulate fractional passage rates (0.021 and 0.023/h, respectively). Ingestion of olive leaves promoted low NH3-N and VFA concentrations, which reflect poor microbial activity. These concentrations, especially that of VFA, increased when barley and faba beans were added. Ingestion of olive leaves affected ruminal protozoa: Entodiniomorphida showed low concentrations and Holotricha completely disappeared. When animals received a diet based on olive leaves, barley, and faba beans, Holotricha appeared in the ruminal liquor and Entodiniomorphida increased (P < 0.001). In goats and wethers fed olive leaves alone, urinary allantoin excretion was very low (163 and 164 micromol/kg BW0.75 in goats and wethers, respectively), and moderate values (352 and 389 micromol/kg BW0.75 in goats and wethers, respectively) were observed when a diet of olive leaves, barley, and faba beans was fed. The polyethylene glycol supply did not have an effect in goats or in wethers, indicating the lack of an effect of condensed tannins in olive leaves. Ingestion of olive leaves promotes a low microbial activity, although its supplementation with readily degraded carbohydrates and protein improves microbial activity and, as a consequence, increases its ruminal degradation. In general, for most of the measured variables, there were no animal species x diet interactions. Thus, goats and wethers had similar ruminal activities when fed diets based on olive leaves.