Nutritive value of thermoammoniated and steam-treated maize stover. I. Intake,digestibility and nitrogen retention

Chopped maize stover, ammoniated at ambient and elevated temperatures or steamed, was evaluated with eight wether lambs in a 4 × 4 double Latin square design. Treatments were: (i) control, 60% H₂O, ensiled for at least 40 days; (ii) 3% NH₃, 60% H₂O for 30 days at 21°C; (iii) 3% NH₃, 60% H₂O for 12 h at 90°C; (iv) steamed at 16.2 kg/cm² and 213°C for 4 min. Ammoniated materials were aerated prior to feeding. All rations were equally supplemented with molasses and soya bean meal while urea was added to treatments (i) and (iv) to increase the crude protein content to at least 12%. Ammoniation at ambient and elevated temperatures increased (P < 0.05) organic matter intake by 30 and 39%, respectively. No difference in intake occurred between the control and steam-treated stovers. However, apparent digestibility of dry matter, organic matter, neutral detergent fibre, acid detergent fibre and cellulose increased (P < 0.05) with all treated stovers. Thermoammoniation produced the greatest (P < 0.05) improvements in digestibility. Improvements in nitrogen retention were slight and non-significant with ammoniated stovers.Thermoammoniation of maize stover with 3% NH₃ and 60% H₂O for 12 h at 90°C increased the extent of digestion over ambient ammoniation and steam treatment, and is a rapid and effective method of improving the feeding value of low quality roughages.     

The feeding value of ammoniated flax straw,wheat straw and wheat chaff for beef cattle

Two experiments were conducted to assess the feeding value of ammoniated and untreated flax straw, wheat straw and wheat chaff in comparison to a mixed bromegrass/alfalfa hay. Anhydrous ammonia was applied to the crop residues at the rate of 35 kg t⁻¹ dry matter. In the first experiment, the effect of ammoniation on crude protein, acid detergent fibre (ADF), neutral detergent fibre (NDF) and acid detergent lignin (ADL), digestible organic matter in vitro and in vivo (DOM%), ADF and NDF digestibility of the crop residues was determined. In the second experiment, ammoniated flax straw, ammoniated wheat straw, ammoniated and untreated wheat chaff, each supplemented with barley, were compared to bromegrass/alfalfa hay as feed sources for wintering beef cows.Ammoniation increased the crude protein content of the crop residues ∼2-fold. Wheat straw DOM in vitro and in vivo was not increased by ammoniation. Ammoniation increased the DOM in vitro of wheat chaff from 36.3 to 46% and flax straw from 35.2 to 46.3%. The DOM in vivo increased from 53.3 to 63.4% (P < 0.05) for wheat chaff and from 33.9 to 58.4% (P < 0.05) for flax straw following ammoniation. Digestibility of ADF increased from 9.9 to 43.9% (P < 0.05) and of NDF from −0.6 to 37.9% (P < 0.05) in flax straw with ammoniation. Non-significant increases in ADF and NDF digestibility were observed for all other crop residues. Lignin content was not changed in the crop residues by ammoniation.In the winter feeding trial, young cows gained more weight than older cows (P < 0.05). Average daily gains of cows were greatest for hay followed by ammoniated flax straw, ammoniated chaff, untreated chaff and ammoniated wheat straw rations (P < 0.05). Increases in backfat in the younger cows was greatest with hay and ammoniated flax straw, followed by ammoniated chaff and ammoniated wheat straw (P < 0.05). Untreated chaff caused no increase in backfat thickness.Ammoniated flax straw (3.2 kg day⁻¹) given with barley (5.6 kg day⁻¹), is similar in feeding value to medium quality bromegrass/alfalfa hay. Furthermore, wheat chaff and ammoniated wheat chaff show good potential as alternatives to hay in winter feeding.     

Grass maturity effects on cattle fed silage-based diets. 1. Organic matter digestion,rumen fermentation and nitrogen utilization

Four silages were harvested at approximately one-week intervals from the same timothymeadow fescue sward. Advanced maturity of the herbage was evidenced by increased neutral detergent fibre [409, 497, 579 and 623 g in 1 kg dry matter (DM)] and decreased nitrogen (N; 29.9, using four ruminally and duodenally cannulated young cattle in a 4 × 4 Latin square experiment. On DM basis (g kg⁻¹), the diet comprised grass silage (700), rolled barley (240) and rapeseed meal (60) and it was given at a rate of 70 g DM (kg live weight)^−0.75 per day.Organic matter digestibility decreased in a curvilinear manner (P_{LINEAR (L)} < 0.001, P_{CUBIC (C)} < 0.01) the values being 0.821, 0.816, 0.758 and 0.747 for the diets based on the four silages in the order of harvest date. Rumen pH increased linearly (P_L < 0.05) and ammonia N concentration decreased curvilinearly (P_L < 0.01, P_C < 0.05) as the grass matured. The molar proportion of acetate in the rumen VFA increased (P_L < 0.001) and the proportion of butyrate decreased (P_L < 0.001) with increased grass maturity. The silage harvest date did not affect the proportion of propionate. The changes in rumen fermentation pattern were associated with a decrease (P_L < 0.05) in rumen protozoal number with increasing maturity of grass.N intake decreased significantly (P_L < 0.001, P_C < 0.01) with the maturity of grass from 167.5 to 118.0 g per day, but duodenal non-ammonia N decreased only from 111.3 to 97.3 g per day indicating greater N losses from the rumen with early-cut silages. The efficiency of microbial protein synthesis in the rumen was not affected by the maturity of grass ensiled. Apparent digestibility of N decreased (P_L < 0.001, P_C < 0.01) and the degradability of N in the rumen decreased (P_L < 0.05) as the grass matured.     

Different sources of ammonia for improving the nutritive value of low quality roughages

The study was undertaken to investigate the effectiveness of anhydrous NH₃, aqueous NH₄OH and urea + urease as sources of ammonia for treating maize stover, rice and wheat straws at graded treatment rates of 0, 25 and 50 g NH₃/kg DM of roughage and at two moisture levels of 20 and 40% in all combinations in improving dry matter digestibility in vitro (IVDMD), organic matter digestibility in vitro (IVOMD) and crude protein (CP) contents when allowed to react for 15 or 30 days.Rate of ammonia was the most important factor in enhancing IVDMD, IVOMD and CP. Moisture level and days of reaction had a less important influence on the parameters measured. While anhydrous NH₃ was most effective in improving IVDMD and IVOMD of maize stover, aqueous NH₄OH had a similar effect in increasing IVDMD and IVOMD of rice and wheat straws and urea + urease was the least effective but promising. Highest responses in IVDMD and IVOMD were obtained with rice straw, followed by wheat straw and, lastly, maize stover.In a second experiment maize stover which was treated with aqueous NH₄OH at 0, 25 and 50 g NH₃/kg DM at two moisture levels of 20 and 40% was given to Black Headed Persian rams. Digestibility of DM and OM and voluntary feed intake were improved significantly (P < 0.01) by ammonia treatment and there was also a significant (P < 0.01) response to increasing moisture levels.     

Feed digestion,rumen fermentation and blood biochemical constituents in Malpura rams fed a complete feed-block diet with the inclusion of tree leaves

This experiment assayed the influence of the inclusion of dried Azardirachta indica, Albizzia lebbek or Ailanthus excelsa leaves in pearl millet stover-based complete feed block diets on feed intake, nutrient utilization, rumen fermentation characteristics, ciliate protozoa population and blood biochemical constituents in adult Malpura sheep. Complete feed blocks were formulated to have roughage-to-concentrate ratio of 70:30. Pearl millet stover (PMS) was used as basal roughage; 30 parts of pearl millet stover was replaced with dried leaves either of Azardirachta indica (NL), Albizzia lebbek (SL) or Ailanthus excelsa (AL). Twelve hogget Malpura rams, divided into four equal groups, were offered one of the four dietary treatments. A feeding-cum-metabolic trial was conducted to assess nutrient utilization. Rumen liquor samples were collected at 0, 3, 6, 12, 18 and 24 h post-feeding to assess rumen fermentation pattern and ciliate protozoa population. Inclusion of dried leaves in PMS-based diets improved CP and DCP content. Dietary DCP was low (P < 0.01) in PMS (8.52%) compared to tree leaves (9.77–11.59%) diets. AL and NL diets had higher (P < 0.05) DCP than the SL diet. The inclusion of tree leaves did not influence organic matter, crude protein or cellulose digestibility, but depressed dry matter, NDF, ADF and energy digestibility. DE content was also lower in tree leave diets. Inclusion of tree leaves improved CP and DCP intake, but DE intake and nitrogen utilization did not change. The pH of rumen liquor (SRL) was low (6.99, P < 0.05), but total nitrogen (52.9 mg/dl SRL) and NH₃-nitrogen (9.34 mg/dl SRL) concentrations were higher (P < 0.01) in the AL diet. TVFA concentrations and ciliate protozoa population were similar on the four diets. Animals in the four groups had the desired concentration of rumen metabolites required for fibrous diets. Complete feed-block feeding provided a constant nutrient supply to rumen microbes that optimise rumen fermentation. Blood biochemical constituents did not change due to the inclusion of tree leaves. Therefore, tree leaves can be included with roughage-based feeding to improve the protein nutrition status of ruminants. Further studies are required to assess the negative influence of tree leaves on digestibility.     

Grass maturity effects on cattle fed silage-based diets. 2. Cell wall digestibility,digestion and passage kinetics

Four silages were harvested at approximately 1-week intervals from the same timothy-meadow fescue sward and studied in a 4 × 4 Latin square experiment with four ruminally and duodenally cannulated young cattle. The diets comprised silage and concentrate (7:3 dry matter (DM) basis) and were fed at a rate of 70 g DM kg^−0.75 liveweight in two equal meals per day.Neutral detergent fibre (NDF) digestibility was 0.757, 0.765, 0.692 and 0.686 on diets based on the four silages in order of harvest date. Increasing maturity of grass ensiled showed linear (P_L < 0.001) and cubic (P_C < 0.01) trends. NDF was separated into digestible (DNDF) and indigestible (INDF) fractions, which differed clearly in their rate of passage from the rumen (on average 0.0141 vs. 0.0258 h⁻¹). The rate of digestion (k_d) of DNDF was on average 0.076 h⁻¹ when derived from the rumen evacuations but only 0.036 h⁻¹ when calculated from the disappearance from nylon bags incubated in the rumen. Both methods detected decreased k_d of NDF with increasing maturity of grass ensiled.Rate of passage from the rumen increased with increasing maturity of grass both when determined for NDF with rumen evacuation technique and from the faecal excretion of ytterbium calculated with a two-pool model. Mean retention time (MRT) in the non-escapable pool of particles increased (P_L < 0.01) with increasing grass maturity, the opposite being true for the escapable pool (P_L < 0.05), resulting in no change in the total ruminal MRT. Pool sizes of ruminal DM P_L < 0.01) and NDF (P_L < 0.001) increased with increasing maturity of grass. Ruminal NDF digestibility was calculated by different methods. When digestion kinetic parameters were derived from rumen evacuations and two-pool models used for passage kinetics, estimated digestibilities were very close to the observed ones.     

Quantitative evaluation of ruminal methane and carbon dioxide formation from formate through C-13 stable isotope analysis in a batch culture system

Methane produced from formate is one of the important methanogensis pathways in the rumen. However, quantitative information of CH₄ production from formate has been rarely reported. The aim of this study was to characterize the conversion rate (CR) of formic acid into CH₄ and CO₂ by rumen microorganisms. Ground lucerne hay was incubated with buffered ruminal fluid for 6, 12, 24 and 48 h. Before the incubation, ¹³C-labeled H¹³COOH was also supplied into the incubation bottle at a dose of 0, 1.5, 2.2 or 2.9 mg/g of DM substrate. There were no interactions (P>0.05) between dose and incubation time for all variables evaluated. When expressed as an absolute amount (ml in gas sample) or a relative CR (%), both ¹³CH₄ and ¹³CO₂ production quadratically increased (P<0.01) with the addition of H¹³COOH. The total ¹³C (¹³CH₄ and ¹³CO₂) CR was also quadratically increased (P<0.01) when H¹³COOH was added. Moreover, formate addition linearly decreased (P<0.031) the concentrations of NH₃-N, total and individual volatile fatty acids (acetate, propionate and butyrate), and quadratically decreased (P<0.014) the populations of protozoa, total methanogens, Methanosphaera stadtmanae, Methanobrevibacter ruminantium M1, Methanobrevibacter smithii and Methanosarcina barkeri. In summary, formate affects ruminal fermentation and methanogenesis, as well as the rumen microbiome, in particular microorganisms which are directly or indirectly involved in ruminal methanogenesis. This study provides quantitative verification for the rapid dissimilation of formate into CH₄ and CO₂ by rumen microorganisms.     

Improving live weight gain of crossbred Limousin bulls with cassava peel silage

There is a growing demand for beef products across developing countries. Formulating rations to include locally available waste products has the potential to increase the live weight gain (LWG) of cattle and improve the livelihoods of smallholder farmers; however, upper limit inclusion levels of cassava peel products require investigation. An experiment evaluated the effect of using cassava peel silage (CPS) at the DM inclusion levels of 30, 40, 50, 60 and 70% (with the remainder protein meals and maize stover in the diet) on the LWG of crossbred Limousin × Ongole bulls (269 ± 48.8 kg). Thirty bulls, approximately two years of age, were allocated in a completely randomised block design with six blocks based on initial live weight (LW) and five treatments based on level of CPS. The combination of CPS (with 2% urea of the CPS) and protein meals significantly affected LWG with the highest values obtained at levels of 30 and 50% inclusion of CPS (1.16–1.35 kg/day) (P < 0.05). Polynomial analysis of LWG data revealed the optimal LWG is theoretically achieved at 37% CPS with a LWG of 1.31 kg/day; however, LWG was similar from 30 to 50% inclusion levels and then declined. There was little significant difference at CPS inclusion levels of 30–60%, for DM intake (DMI) which ranged from 2.3 to 2.6% LW, organic matter (OM) digestibility (77.8–81.6%), feed conversion ratio (FCR) (6.56–7.56 kg DM/kg LWG) and feed cost of gain (Indonesia rupiah (IDR)/kg LW 18 612 – 21 398). At a high (70%) level of CPS inclusion, these values were markedly changed when compared to the 30% inclusion level of CPS. Feed treatments did not affect rumen pH, NH₃-N, concentration or molar percentage of volatile fatty acids or protozoal population (P < 0.05). Rumen pH measured three hours after morning feed ranged from 6.7 to 6.8 and NH₃-N ranged from 14.1 to 19.3 mg NH₃-N/dl. It was concluded that inclusion of CPS up to 60% mixed with protein meals and urea and 20% maize stover maximised LWG and profitability of the production system.     

Rumen fermentation patterns and nutrient digestion in lambs fed cottonseed meal supplemental diets

Twenty crossbred 3–4-month-old male lambs of uniform body weight were used to assess the effect of raw and processed cottonseed (Gossypium) meals (CSM) on nutrient utilisation and rumen fermentation patterns. Lambs were assigned to five dietary treatments in a completely randomised design and fed isonitrogenous and isocaloric concentrate mixtures containing 30% deoiled groundnut cake (DGNC) (control), 40% of either raw, 45 min cooked, 1% calcium hydroxide (Ca(OH)₂) or iron (1 part free gossypol (FG):0.3 parts iron) treated CSM. The concentrate mixtures were fed to meet 80% of crude protein requirements (NRC, 1985) with ad libitum access to chopped maize hay (Zea mays). A metabolic trial of 6 days duration was conducted after 135 days of feeding, and rumen liquor was collected for 2 days at its end. Incorporation of 40% raw CSM resulted in reductions (P<0.01) in the digestibility of dry matter and organic matter in comparison to control fed lambs. Cooking and Ca(OH)₂ treatment of CSM improved digestibilities of these nutrients, to levels comparable to those in control fed lambs. The ether extract (P<0.05) and energy (P<0.01) digestibilities in lambs fed Ca(OH)₂ treated CSM were higher compared to those lambs fed raw CSM diets. Acid detergent fibre and cellulose digestibilities were lower (P<0.05) on cooked and iron treated CSM fed lambs. Retention of nitrogen and energy did not differ among diets. The digestible and metabolisable energy content of the Ca(OH)₂ treated CSM incorporated diet was higher (P<0.01) than the other CSM containing diets, but similar to DGNC containing ration. Rumen pH and total volatile fatty acid concentration was similar among diets, but NH₃–N was lower (P<0.05) on the cooked CSM diets versus the control. Feeding of lambs with raw CSM amounting to 17.9% of total dry matter intake (i.e. 303 mg FG intake per day) adversely affected utilisation of nutrients and rumen fermentation. This depression was alleviated to the greatest extent by 45 min cooking and 1% calcium hydroxide treatment. Iron treatment of CSM had little overall benefit.     

The effect of stage of maturity on yield and quality of maize grain and stover

Stage of maturity at the time of harvest is considered as one of the factors influencing the nutritive value of crop residues. Thus this study was carried out to assess the effect of harvesting maize at different stages of grain maturity on yield and quality of maize grain and stover. The maize crop was harvested at grain moisture content of 28–30, 20–23 and 10–12%, which were designated as Stages I, II and III, respectively. Grain yield, standardised to 12.5% moisture content, showed an increasing trend, whereas cob, stover, total crop residue and total biomass dry matter (DM) yield showed a decreasing trend with increasing stage of maturity (p>0.05). The declining trend in stover yield with increased stage of maturity was due mainly to leaf loss. There was a significant decrease (p<0.05) in crop residue–grain ratio and leaf–stem ratio and a significant increase in the harvest index and hectolitre weight of the grain as the grain moisture content decreased from about 30 to 10%. Maize stover harvested at Stage I had significantly higher (p<0.05) ash content than those harvested at Stages II and III. The crude protein (CP) content was significantly lower, whereas the neutral detergent fibre and cellulose contents were higher (p<0.05) in Stage III than in Stages I and II. There was a decreasing trend in in sacco DM degradability with increasing stage of maturity. The washing loss, potential degradability and effective DM degradability at 0.03 h⁻¹ rumen outflow rate were higher (p<0.05) in Stage I than in Stages II and III. The volume of gas produced after 3, 6, 12, 24, 48 and 72 h of incubation was higher (p<0.05) in Stage I than in Stages II and III. The a value (the intercept of the gas production curve) and the gas production potential (a+b) were higher (p<0.05) in Stage I than in Stage III. Reduction in the nutritive value of stover with increasing stage of maturity was characterised by reduction in CP contents and increasing concentration of fibrous constituents. These were reflections of changes in the morphological composition of stover and losses of nutrients within the morphological fractions with increasing stage of maturity.     

Effect of ammonia and urea treatments on digestibility and nitrogen content of dehydrated lucerne

Dehydrated lucerne of low (L: 0.53), normal (N: 0.55) and high (H: 0.73) in vivo dry matter (DM) digestibility were treated with ammonia or urea to study the effects on in situ and pepsin-cellulase DM digestibilities, water solubility and nitrogen content (Experiments 1, 2, 4) and on cell wall composition and degradability (Experiment 3). (1) N lucerne was treated with 30 g NH₃ kg⁻¹ DM for 1 to 12 weeks at 30°C and 2 to 6 days at 80°C; (2) L, N and H lucerne were treated with increasing ammonia levels: 15 to 100 g kg⁻¹ DM for 3 weeks at 30°C and 4 days at 80°C; (3) L, N and H lucerne were treated with 60 g NH₃ kg⁻¹ DM for 3 weeks at 30°C and 4 days at 80°C; (4) L, N and H lucerne were treated with 60 g urea kg⁻¹ DM without addition of urease for 3 and 6 weeks at 30°C. All treatments were carried out at 40% humidity.In situ and pepsin-cellulase DM digestibilities increased significantly (P < 0.05) with the duration of treatment (up to 3 weeks at 30°C and 4 days at 80°C) and with the level of ammonia (P < 0.01) (up to 30 g kg⁻¹ DM). The greatest improvements (similar at both temperatures) were for L, N and H of 7.3, 7.2 and 3.9 points for in situ and of 10.6, 11.3 and 6.3 points for cellulase digestibilities, respectively. Water solubility also increased with duration of treatment and level of ammonia (P < 0.01) and was greater at 80°C than at 30°C. Urea treatment significantly improved (P < 0.01) digestibilities and water solubility but the doubling of treatment duration had no influence. The degree of ureolysis was only 50 to 60%. Ammonia and urea treatments considerably increased (P < 0.01) nitrogen content.Treatment with 60 g NH₃ kg⁻¹ DM induced a decrease in ethanol insoluble residue content, which was significant (P < 0.01 for L and N, P < 0.05 for H) at 80°C but not at 30°C, and was greater for L and N than for H (about 12 and 5 points, respectively). This decrease was essentially due to solubilisation of hemicelluloses (− 15%) and uronic acids (− 26%). Thus, at 30°C, the chemical solubility of the cell wall was lower than at 80°C for the same total increase in microbial degradation. This result indicates that other phenomena are involved, such as an increase in cell wall porosity and consequently improved accessibility of cell wall polysaccharides to glycolytic enzymes.     

Effects of Bacillus subtilis natto on milk production,rumen fermentation and ruminal microbiome of dairy cows

Two experiments were conducted to evaluate the effects of Bacillus subtilis natto, which was initially isolated from fermented soybeans on milk production, rumen fermentation and ruminal microbiome in dairy cows. In Experiment 1, 36 early lactation Chinese Holstein dairy cows (56 ± 23 days in milk) were randomly assigned to three groups: Control, cows were fed total mixed ration (TMR); BSNLOW, TMR plus 0.5 × 10¹¹ colony-forming units (cfu) of B. subtilis natto/cow per day; and BSNHIGH, TMR plus 1.0 × 10¹¹ cfu of B. subtilis natto/cow per day. During the 70-day treatment period, daily milk production and daily milk composition were determined in individual cows. The results showed that supplementing dairy cows with 0.5 × 10¹¹ and 1.0 × 10¹¹ cfu of B. subtilis natto linearly increased (P < 0.01) milk production (25.2 and 26.4 kg/day v. 23.0 kg/day), 4% fat-corrected milk (27.3 and 28.1 kg/day v. 24.2 kg/day), energy-corrected milk (27.3 and 28.2 kg/day v. 24.2 kg/day), as well as milk fat (1.01 and 1.03 kg/day v. 0.88 kg/day), protein (0.77 and 0.82 kg/day v. 0.69 kg/day) and lactose yield (1.16 and 1.22 kg/day v. 1.06 kg/day) but decreased milk somatic cell counts (SCC) by 3.4% to 5.5% (P < 0.01) in BSNLOW and BSNHIGH treatments compared with Control. In Experiment 2, four rumen-cannulated dairy cows were fed the basal diet from 1 to 7 days (pre-trial period) and rumen samples were collected on days 6 and 7; the same cows then were fed 1.0 × 10¹¹ cfu/day B. subtilis natto from days 8 to 21 (trial period) and rumen samples were collected on days 20 and 21. B. subtilis natto was discontinued from days 22 to 28 (post-trial period) and rumen samples were collected on days 27 and 28. Compared with the pre- and post-periods, ruminal pH decreased by 2.7% to 3.0% during the trial period (P < 0.01), whereas ammonia nitrogen (NH₃-N), total volatile fatty acids and molar proportion of propionate (P < 0.01) and valerate (P < 0.05) increased. Molar proportion of acetate decreased and the acetate to propionate ratio was lower (P < 0.01) during the trial period. However, no differences for 24-h in sacco dry matter digestibility were detected among different periods (treatments) though NDF digestibility was reduced in the trial and post-trial periods (P < 0.01). Compared with pre-trial period, total ruminal bacteria, proteolytic and amylolytic bacteria in rumen enumerated by culture methods increased by 15.0%, 16.2% and 11.7%, respectively (P < 0.01) but protozoa decreased to 5.35 log₁₀ cfu/ml (P < 0.01) during the trial period. These results demonstrate that B. subtilis natto improves milk production and milk components yield, decreases SCC and promotes the growth of total ruminal bacteria, proteolytic and amylolytic bacteria, which indicate that B. subtilis natto has potential to be applied as a probiotic for dairy cows.     

Formulating rations with cassava meal to promote high live weight gain in crossbred Limousin bulls

Formulating rations with high energy and protein feeds such as cassava and locally sourced protein meals is an important strategy to increase live weight gain (LWG) of crossbred bulls in Indonesia. Current systems of production for Indonesian smallholders fatten bulls using cut and carry. Formulating a diet for an optimal combination of available feeds will increase production and potential profitability for smallholders. An experiment was conducted to evaluate the effect of using cassava meal in the diet at levels of 70C, 60C, 50C, 40C and 30C% (with most of the remainder being the protein meals) on the LWG of Limousin × Ongole bulls so as to determine the optimum combination of cassava meal and protein meals for LWG. Thirty bulls were allocated in a completely randomized block design with 6 blocks based on initial live weight (LW) and 5 treatments based on level of cassava meal. The combination of cassava meal (with 2% urea) and protein meals significantly affected LWG with the highest (1.35 kg/day) recorded at 40C (40% cassava meal, 40% protein meals and 20% maize stover). The LWG and nutrient intake increased curvilinearly with decreasing cassava meal and increasing protein meals (P < 0.05). Measured cassava meal inclusion in the final ration as a consequence of the changes in intake was 60, 56, 47, 37 and 28% for the designated 70C, 60C, 50C, 40C and 30C treatments, respectively. Dry matter intake reached 96 g/kg^0.75 per day or equal to 2.24% LW at this 40% level of inclusion. At the 70C treatment with 60% cassava meal and 9% protein meals, DM digestibility (69.1%) was lowest and that value increased as the proportion of cassava meal decreased and was highest at the 40C treatment (75.8%). Feed treatments significantly affected rumen pH, ammonia N (NH₃N) and volatile fatty acid concentrations (P < 0.05). There was no significant effect on protozoal population (P > 0.05). Rumen pH ranged from 6.3 to 6.9. It was concluded that a combination of 40% dried cassava meal and 40% protein meals with roughage (20%) maximized intake and LWG and beyond that level of cassava meal inclusion, LWG and intake decreased markedly.     

A comparative study of four rumen buffering agents on productive performance,rumen fermentation and meat quality in growing lambs fed a total mixed ration

Controlling rumen fermentation using buffering agents could contribute to enhancing ruminant productivity and performance. This study was realized to investigate the effect of dietary supplementation of AcidBuf, sodium bicarbonate, calseapowder and WMC seaweed (Utva Lactuca extra) on the animal performance, volatile fatty acids, rumen pH, rumen histology and carcass characteristics of growing male Awassi lambs. A total of 60 lambs was divided into five groups. One group served as a control and fed only on a concentrate diet without any buffering, whereas the other four groups were fed the concentrate diet supplemented with 0.4% AcidBuf (Buf1), 0.4% AcidBuf plus sodium bicarbonate, 50 : 50 (Buf2), 0.4% calseapowder (Buf3) or 0.4% WMC Seaweed (Buf4) for 98 days. The feed conversion ratio was (P<0.05) improved in Buf2 compared to the control and other treatment groups. The propionic acid decreased, whereas butyric acid was increased in the treatment groups (P<0.05) compared to the control. The pH of the rumen fluid and the length of submucosa were (P<0.05) higher in Buf4 and Buf1, respectively, compared to the control. Hot and cold carcass weights were (P<0.05) higher in Buf4 compared to Buf1. Lean meat percentage and rib eye area were (P<0.05) higher in Buf4; while the fat percentage was (P<0.05) lower in Buf2 and Buf4 groups compared to the control. The lightness and yellowness of meat were (P<0.05) higher in Buf1 and Buf4 compared to the control. The meat pH was (P<0.05) higher in Buf3 and Buf4 compared to Buf2 (at 1 h) and control (at 24 h). The visceral depot fat (%) was reduced with Buf3 and Buf4 compared to the control. The results indicated that dietary supplementation of different buffering agents improved feed efficiency, rumen pH, carcass characteristics and decreased the body fat in growing Awassi lambs.     

Effects of nitrate adaptation by rumen inocula donors and substrate fiber proportion on in vitro nitrate disappearance,methanogenesis, and rumen fermentation acid

A study was conducted to evaluate the main effects of dietary nitrate adaptation by cattle and alfalfa cell wall to starch ratio in in vitro substrates on nitrate disappearance and nitrite and volatile fatty acid (VFA) concentrations, as well as hydrogen (H₂) and methane (CH₄) accumulations. Rumen fluid from steers fed diets containing urea or nitrate was added into in vitro incubations containing sodium nitrate as the sole nitrogen source and 20 cell wall : 80 starch or 80 cell wall : 20 starch as the carbohydrate source. The results showed that during 24 h incubation, rumen fluid inoculums from steers adapted to dietary nitrate resulted in more rapid nitrate disappearance by 6 h of incubation (P < 0.01), no significant effect on nitrite concentration and diminished CH₄ accumulation (P < 0.05). Cell wall to starch ratio did not affect nitrate disappearance, CH₄ accumulation and total VFA concentration. The higher cell wall ratio had the lower total gas production and H₂ concentration (P < 0.05). Ammonia-N (NH₃-N) concentration increased because of adaptation of donors to nitrate feeding (P < 0.05). Nitrate adaptation did not alter total VFA concentration, but increased acetate, and decreased propionate and butyrate molar proportions (P < 0.01).     

Effect of lime, dicyandiamide and soil water content on ammonia and nitrous oxide emissions following application of liquid hog manure to a marshland soil

The loss of nitrogen (N) from field-applied animal manure through ammonia (NH₃) volatilisation and nitrous oxide (N₂O) emission is of major environmental concern. Both lime and dicyandiamide (DCD) have been suggested as amendments that can mitigate N₂O emissions, but simultaneously increase the risk of NH₃ volatilisation. This study evaluated the impact of lime and DCD on NH₃ and N₂O emissions following application of liquid hog manure. Hydrated lime (Ca(OH)₂) was added to an acidic soil to achieve three pH levels (4.7, 6.3 and 7.4). Soil samples (100 g) were then placed in 500 ml screw-top Mason-jars and de-ionised water was added to bring the samples to 50, 70 and 90% water-filled pore space (WFPS). Slurry was applied at a rate equivalent to 116,000 l ha⁻¹, while DCD was applied at 30% of the NH₄-N rate applied. Jars were sealed and incubated at 21°C for 21 d. Ammonia volatilisation was quantified using boric acid traps, while N₂O gas concentration was analysed using gas chromatography. Dicyandiamide had no effect (P>0.05) on either NH₃ or N₂O emissions. Both NH₃ and N₂O emissions increased (P<0.05) as WFPS increased, with emissions ranging from 0.9 to 1.4 kg NH₃-N ha⁻¹ and 123 to 353 g N₂O-N ha⁻¹, respectively. Liming decreased (P<0.01) N₂O emissions from 547 to 46 g N₂O-N ha⁻¹, but increased (p<0.01) NH₃ volatilisation from 0.36 to 1.92 kg NH₃-N ha⁻¹. Results suggest that liming to a pH ≥6.3 can reduce N₂O emissions, however, this reduction will be accompanied by a substantial loss of NH₃. Section Editor: H. Lambers     

Rumen enzyme profile and fermentation characteristics in sheep as affected by treatment with sodium lauryl sulfate as defaunating agent and presence of ciliate protozoa

The efficiency of sodium lauryl sulfate as a defaunating agent and effect of rumen protozoa on nutrient utilization, fermentation characteristics and enzyme profile were evaluated in adult sheep maintained on a mixed ration containing 65:35% Pala (Ziziphus numularia) leaf: concentrate. Twenty-one adult Malpura sheep divided into three equal groups (DF, RF and F) were either defaunated by oral administration of sodium lauryl sulfate at the rate of 8 g/100 kg body weight (DF), or defaunated and again refaunated (RF), or maintained faunated (F). Daily dry matter intake was similar in defaunated, refaunated and faunated sheep. However, digestibility of cell wall and cell wall contents (NDF, ADF and cellulose) were lower (P < 0.01) in defaunated than refaunated and faunated sheep. Irrespective of the presence or absence of rumen protozoa, daily intake of DCP and DE were similar in the three experimental groups. Even with similar DM, DCP and DE intake, N-retention, blood glucose level, ruminal concentration of total VFA and total-N were higher (P < 0.01), while rumen pH and NH₃-N concentration were lower (P < 0.01) in defaunated sheep. Ruminal activity of amylase, xylanase, protease and urease enzymes were not influenced by presence or absence of ciliate protozoa. However, carboxymethyl cellulase enzyme activity was lower (P < 0.01) in the rumen of defaunated sheep. The total and differential counts of rumen protozoa were similar in refaunated and faunated sheep indicating lack of residual toxic effect of sodium lauryl sulfate. It is concluded that absence of ciliate protozoa increased ruminal TVFA, total-N with lower NH₃-N concentration and fibre digestibility in sheep. Moreover, sodium lauryl sulfate was fully effective for complete removal of rumen ciliate protozoa and successfully defaunated the sheep.     

Effect of harvest time of red and white clover silage on chewing activity and particle size distribution in boli,rumen content and faeces in cows

The study examined the effects of harvest time of red and white clover silage on eating and ruminating activity and particle size distribution in feed boli, rumen content and faeces in cows. The clover crops were harvested at two stages of growth and ensiled in bales. Red clover crops had 36% and 45% NDF in dry matter (DM) at early (ER) and late (LR) harvest, respectively, and the white clover crops had 19% and 29% NDF in DM at the early (EW) and late (LW) harvest, respectively. The silages were fed restrictively (80% of ad libitum intake) twice daily to four rumen cannulated non-lactating Jersey cows (588 ± 52 kg) in a 4 × 4 Latin square design. Jaw movements (JM) were recorded for 96 h continuously. Swallowed boli, rumen mat, rumen fluid and faeces samples were collected, washed in nylon bags (0.01 mm pore size) and freeze-dried before dry sieving through 4.750, 2.360, 1.000, 0.500, 0.212 and 0.106 mm into seven fractions. The length (PL) and width (PW) values of rumen and faeces particles within each fraction were measured by use of image analysis. The eating activity (min/kg DM intake; P < 0.05) was higher in LR compared with the other treatments. The eating activity (min/kg NDF intake; P < 0.05) was affected by clover type with highest values for white clover silage. The mean ruminating time (min/kg DM), daily ruminating cycles (P < 0.001) and JM during ruminating (P < 0.05) were affected by treatment with increasing values at later harvest time. The proportion of washed particle DM of total DM in boli (P < 0.001), rumen mat (P < 0.001), rumen fluid (P < 0.01) and faeces was (P < 0.001) highest by feeding LR. There were identified two peaks (modes 1 and 2) on the probability density distribution (PDF) of PW values of rumen mat and faeces, but only one peak (mode 1) for PL values. There was no difference in the mean and mode 1 PW and PL value in rumen mat between the four treatments. The mean PL, mode PL, mode 2 PW and mean PW in faeces were highest for LR (P < 0.05). The mean particle size in boli measured by sieving was higher at white clover compared with red clover treatments (P < 0.001) and the highest value in faeces was found in LR (P < 0.01). The two peaks on PDF for width values of rumen mat and faeces particles are most likely related to the leaves and the stems/petioles. In conclusion, the mean total chewing activity per kg DM was lowest for the white clover silage and increased for both silages due to later harvest time. The mean particle size in boli was smallest for LR, whereas the mean PL and PW in faeces were highest for the LR.     

Associations of rumen parameters with feed efficiency and sampling routine in beef cattle

Characterizing ruminal parameters in the context of sampling routine and feed efficiency is fundamental to understand the efficiency of feed utilization in the bovine. Therefore, we evaluated microbial and volatile fatty acid (VFA) profiles, rumen papillae epithelial and stratum corneum thickness and rumen pH (RpH) and temperature (RT) in feedlot cattle. In all, 48 cattle (32 steers plus 16 bulls), fed a high moisture corn and haylage-based ration, underwent a productive performance test to determine residual feed intake (RFI) using feed intake, growth, BW and composition traits. Rumen fluid was collected, then RpH and RT logger were inserted 5.5±1 days before slaughter. At slaughter, the logger was recovered and rumen fluid and rumen tissue were sampled. The relative daily time spent in specific RpH and RT ranges were determined. Polynomial regression analysis was used to characterize RpH and RT circadian patterns. Animals were divided into efficient and inefficient groups based on RFI to compare productive performance and ruminal parameters. Efficient animals consumed 1.8 kg/day less dry matter than inefficient cattle (P⩽0.05) while achieving the same productive performance (P⩾0.10). Ruminal bacteria population was higher (P⩽0.05) (7.6×10¹¹ v. 4.3×10¹¹ copy number of 16S rRNA gene/ml rumen fluid) and methanogen population was lower (P⩽0.05) (2.3×10⁹ v. 4.9×10⁹ copy number of 16S rRNA gene/ml rumen fluid) in efficient compared with inefficient cattle at slaughter with no differences (P⩾0.10) between samples collected on-farm. No differences (P⩾0.10) in rumen fluid VFA were also observed between feed efficiency groups either on-farm or at slaughter. However, increased (P⩽0.05) acetate, and decreased (P⩽0.05) propionate, butyrate, valerate and caproate concentrations were observed at slaughter compared with on-farm. Efficient had increased (P⩽0.05) rumen epithelium thickness (136 v. 126 µm) compared with inefficient cattle. Efficient animals also spent 318% and 93.2% more time (P⩽0.05) in acidotic (4.14% v. 1.30%) (pH⩽5.6) and optimal (5.6<pH<6.0) (8.53% v. 4.42%) RpH range compared with inefficient cattle. The circadian patterns revealed lower (P⩽0.05) RpH and no differences (P⩾0.10) in RT pre-, during, and post-prandial periods in efficient compared with inefficient cattle. In essence, superior feed efficiency in cattle seems linked to rumen features consistent with improved efficiency of feed utilization. Microbial abundance, rumen epithelial histomorphology, and RpH, may serve as indicators for feed efficiency in cattle. The divergences of assessments made on-farm and at slaughter should be considered in the development of proxies for feed efficiency.     

Effects of feeding dried grass pasture and a grain ration differing in rumen undegradable protein at two feeding frequencies on nutrient digestibility and microbial protein synthesis during continuous culture

Four continuous culture fermenters were used in a randomized block design to evaluate the effects of grain feeding frequency and rumen undegradable protein (RUP) on nutrient utilization and microbial protein synthesis with high quality grass. Two grain rations fed two or four times per day were arranged in a 2×2 factorial with four replications. The grain rations contained 60% and 45% of CP as RUP, and similar total nonstructural carbohydrate (TNC) content (64% of DM). Grain was fed separately from freeze dried, pelleted pasture (56% of DM). Fermenters were maintained at a liquid dilution rate of 12%/h and a solids retention time of 20 h. Regardless of RUP level or grain feeding frequency, true DM, OM, and CP digestibilities averaged 72.1%, 73.3%, and 61.8%, respectively with no differences due to treatments. Apparent digestibility of ADF, NDF, and TNC were also not affected by treatments, and averaged 55.9%, 46.2%, and 80.9%, respectively. The production of the major VFA (acetic, propionic, and butyric) were not affected by treatment and averaged 56.4, 21.2 and 16.3 Mmol/ml, respectively. The interaction of grain feeding frequency and dietary RUP content was significant for isovalerate production. Increasing the grain feeding frequency significantly increased valerate production. Ammonia N (NH₃–N) concentration and flows were decreased with higher RUP supplementation, and by feeding grain 4X/day (P<0.05). Non NH₃–N flows were also higher with 4X/day grain feeding. Feeding a high RUP grain reduced the CP percentage in bacteria and tended to cause a reduction in rumen pH (P>0.10). The interaction of time during the day when pH was measured and feeding frequency was significant (P<0.001) reduced the diurnal variation in pH and when grain feeding frequency was measured to 4X/day.