Rumen degradation and intestinal digestion of grass and clover at two maturity levels during the season in dairy cows

A comparison was made of the effect of season and maturity on the in situ ruminal breakdown and intestinal protein digestion in dairy cows between intensively N-fertilized grass (whole sward) and moderately N-fertilized ryegrass and clover from a mixed sward. From May to September 1990, eight consecutive cuts were made, representing alternate harvests of late and early swards. Limited effects of fertilizer-N on chemical and ruminal degradation characteristics and intestinal digestion of grasses were observed. Clover had higher ash, crude protein (CP) and lignin and lower hemicellulose, cellulose and sugar contents than grass. Moreover, soluble fractions of organic matter (OM) and CP were higher, and rumen-undegradable OM and CP fractions were lower. Soluble fractions of grasses and clover decreased and undegradable fractions increased during the season. More mature swards showed increased undegradable fractions. Degradation rates of OM and CP in clover were, respectively, higher than or similar to those of grass. Seasonal effects on degradation rates differed between grass and clover. Effectively rumendegradable (g kg⁻¹ DM) carbohydrates and CP, escaped protein and intestinal digestion of escaped protein were higher in clover than in grasses. Inclusion of clover in swards may result in higher post-rumen protein supply. Supplementation of clover-based diets is suggested to compensate for an increased loss of N in the rumen.     

Seasonal productivity and nutritive value of temperate grasses found in semi-natural pastures in Europe: responses to cutting frequency and N supply

Monocultures of thirteen perennial C₃ grass species that co‐occur in temperate semi‐natural grassland communities in Europe were compared in a factorial field design of two levels of N supply and two levels of cutting frequency. Above‐ground yield of dry matter (DM), crude protein (CP) concentration and pepsin‐cellulase DM digestibility of herbage were measured in two successive years. Species was the largest source of variability in yield of DM and DM digestibility of herbage, while CP concentration of herbage responded more to management factors. The highest mean DM yields and values of DM digestibility of herbage were achieved in spring for Festuca arundinacea and in autumn for Phleum pratense. Poa trivialis and Festuca rubra had the lowest DM yield and DM digestibility values, respectively, regardless of seasons and treatments. For all species CP concentration in herbage increased in response to an increase in cutting frequency and N supply by an average of 46 and 34 g kg^?1 DM respectively. Differences between years and seasons indicated the importance of plant phenology on nutritional variables and the influence of environmental factors on species performance. Species ranking was compared according to their annual digestible DM and CP yields. The results show that some grasses have a nutritive value which is comparable to that of forages selected for high yields.     

Winter grazing stockpiled native warm‐season grasses in the Southeastern United States

In the Southeastern United States, native warm‐season grasses (NWSG) are not harvested during autumn to rebuild root reserves, resulting in de facto stockpiled winter forage. Senesced NWSG forage is considered nutritionally inadequate by temperate livestock managers, but comparable forage is regularly utilized in rangeland systems. This experiment compared the forage characteristics of two NWSG pastures: switchgrass [Panicum virgatum L. (SG)] and a two species mixture of big bluestem/indiangrass [Andropogon gerardii Vitman/Sorghastrum nutans L. (BBIG)] to tall fescue [Festuca arundinacea Schreb. (TF)]. During two winter periods (January‐April), monthly samples were collected and measured for dry‐matter herbage mass (HM), crude protein (CP), in‐vitro true dry‐matter digestibility (48 hr; IVTDMD), neutral detergent fibre (NDF), NDF digestibility (dNDF) and lignin. Across sampling dates, TF provided adequate forage for low‐input animal maintenance (90.3 CP g/kg; 488 g IVTDMD/kg; 4,040 kg DM/ha), while SG had lowest nutritive values and greatest DM (21.0 g CP/kg; 366 g IVTDMD/kg; 7,670 kg DM/ha). Samples of BBIG had results intermediate to SG and TF (32.1 g CP/kg; 410 g IVTDMD/kg; 5,160 kg DM/ha). Leaf sub‐samples of NWSG indicated greater forage nutritive value compared to whole plant samples (e.g., SG: 65 vs 27 g CP/kg respectively). This indicates that selective grazing could allow superior outcomes to those expected from whole plant NWSG nutritive values. Although consistently nutritionally inferior to TF, further research could reveal strategies to make stockpiled NWSG economically useful to livestock managers.     

Intake, rumen fermentation, degradability and digestion kinetics in beef cattle offered autumn grass herbage differing in regrowth interval

The effects of a 10-d increase in regrowth interval (35 and 45 d) of a predominantly perennial ryegrass sward harvested in two periods in the autumn in Ireland on feed intake, rumen fermentation, in situ degradability and rumen digesta kinetics was examined using six ruminally cannulated Holstein–Friesian steers in three replicates of a 2 × 2 crossover design. The longer regrowth interval had a higher grass dry-matter (DM) yield of herbage by 615 kg DM ha⁻¹ and a lower crude protein (CP) concentration of herbage by 27 g kg⁻¹ DM. There was no effect of regrowth interval on DM intake, rumen pH, total volatile fatty acid concentration or the molar proportions of acetate, propionate or butyrate in the rumen but the concentration of rumen ammonia (NH₃-N) was lower on the longer regrowth interval. The longer regrowth interval had a lower apparent total tract digestibility of DM, organic matter (OM), N and neutral-detergent fibre (NDF). There was no effect of regrowth interval on the in situ degradability of DM, OM, N or NDF. The passage rates ( k _p) of DM and OM were higher while the rate of digestion ( k _d) of DM and NDF was lower with the longer regrowth interval. The results indicated that, although increasing the regrowth interval by 10 d in autumn reduced the apparent digestibility of the grass herbage, there was no adverse effect on DM intake, rumen fermentation pattern or in situ rumen degradability. The reduction in rumen NH₃-N concentrations, reflecting the lower herbage CP concentration in herbage for the longer regrowth interval, may potentially reduce nitrogen excretion to the environment.     

SOURCES OF VARIATION IN THE IN VITRO DIGESTIBILITY OF TROPICAL GRASSES

The in vitro DM digestibility of four tropical pasture species, Cenchrus ciliaris, Chloris gayana, Digitaria spp., Setaria spp. and one temperate grass, Lolium perenne , were studied, using the method described by Tilley and Terry (13).
In vitro digestibility was affected by fineness of grinding, sample size, pH of original rumen fluid and size of rumen fluid inoculum. Different relations were found between the in vivo and in vitro results for the five species, with a maximum predicted difference of 3–5 digestibility units.
It was considered that the in vivo digestibility of tropical grasses could be accurately predicted by this method, provided that the procedure was standardized and samples of known in vivo digestibility similar to those being tested are included in each run.     

Simple prediction of crude protein content in vegetation growing on abandoned cultivated land

The accuracy of two simple methods was compared for the prediction of crude protein (CP) content of above‐ground plant material of mixed‐species composition on abandoned cultivated land in Japan. The first method is based on standard CP values (in g kg^?1 dry matter) for individual species (STV method) as listed in the literature. The second procedure (GLM method) was an application of the generalized linear model using the relative above‐ground biomass of monocots and legumes, total herbage mass, and day of year. Predictions were made at the quadrat scale, and for surveyed sites based on average of values for five or six quadrats in a single survey. A ‘leave‐site‐out’ method was adopted for model validation of the generalized linear model. The observed values of CP content ranged between 21·5 and 161·9 g kg^?1 dry matter (DM). With the STV method, the values of root mean square error (RMSE indicates average estimation error) were 50·9 at the quadrat level and 53·8 at the surveyed‐site level (both g kg^?1 DM). When a ‘leave‐site‐out’ validation was carried out, the RMSE‐values for the GLM method were 23·2 at the quadrat level and 13·2 at the surveyed‐site level (both g kg^?1 DM). We therefore propose adoption of the GLM method for the purpose of estimating the CP content in herbage on abandoned sites.     

Effects of addition of cell wall degrading enzymes on the chemical composition and the in sacco degradation of grass silage

Herbage (83% Lolium perenne and 17% Trifolium repens ) was harvested 15,28 and 42 d after second cut, and ensiled in 1.5 liter preserving jars either directly, at 20% dry matter (DM), or wilted (30 and 45% DM). Each variant was ensiled with and without a commercial preparation of cell wall degrading enzymes and stored for 90 d at 30°C. Samples were then incubated in nylon bags in the rumens of three cannulated cows for 3, 6, 12, 24, 48 and 288 h to study the in sacco degradation of organic matter (OM), crude protein (CP), and (hemi) cellulose.
Addition of cell wall degrading enzymes significantly decreased cell wall content. The magnitude Of the decrease was influenced by stage of maturity and DM percentage. Maturity increased the DM content as well as decreasing the effect of enzymes on cell wall components. Lactic acid content increased and the pH value and ammonia ( P < 0.05) decreased, indicating a greater extent of fermentation in the enzyme-treated silages. Enzyme treatment had no effect on the content of digestible OM estimated by in vitro incubations.
The undegradable fractions of OM, CP and cell wall components were not significantly changed by the addition of enzymes. The results suggest that the cell wall degrading enzymes affected the insoluble, rumen-degradable fractions, thereby increasing the instantly degradable fractions. Consequently, the calculated effective degradation of OM and CP in the enzyme-treated silages was significantly ( P < 0.05) higher than in the untreated silages.     

Diversity of non‐structural carbohydrates in grasses (Poaceae) from Brazil

Non‐structural carbohydrates (NSC) are the primary energy available for growth and dry‐mass production in forage grasses. They are also associated with tolerance to environmental stresses, including drought. Soluble carbohydrates, especially fructans of temperate forage grasses, have been extensively studied; however, little is known about NSC of tropical grasses. These plants are abundant in the Cerrado, a savanna‐like vegetation with a definite seasonality in rainfall distribution. Such an environment presents an ideal condition for the occurrence of fructans. However, the present analysis of carbohydrates in aerial parts of twenty‐four tropical grass species, mainly from the Panicoideae subfamily in the Cerrado, shows a distinctively different NSC profile when compared with temperate grasses. Free glucose and starch are common NSC found in most plant organs. However, free fructose and sucrose‐based oligosaccharides were only found in very low amounts. Sucrose was detected in higher amounts only in stems. A linear series of malto‐oligosaccharides was found in leaf blades, sheaths and stems of most of the Cerrado grasses, except for those from the Andropogoneae tribe. These results indicate a diversity of regulatory pathways of NSC metabolism in tropical forage grasses from the Cerrado.     

THE RELATION BETWEEN THE CRUDE PROTEIN CONTENT AND THE DIGESTIBLE CRUDE PROTEIN CONTENT OF TROPICAL PASTURE PLANTS

The digestible crude protein percentage (DCP) of 218 different feeds derived from 16 tropical grasses and 8 tropical legumes containing 2·2 to 25·3% crude protein (CP) was Treasured with sheep. DCP was closely related to CP (r =· 0·979) and could be predicted from the equation DCP=O·899 CP-3·25 (SE estimate · 0·84). Predicted values for tropical grasses and legumes were similar to, but more variable than, those calculated from a similar equation derived from temperate pasture species. It was suggested that CP per se is a useful criterion for selecting tropical pasture plants when direct in vivo measurements of DCP cannot be obtained.     

The effect of herbage allowance on daily intake by Creole heifers tethered on natural Dichanthium spp. pasture

Two experiments were carried out in Guadeloupe to estimate the organic matter intake (OMI) and digestibility (OMD) of a Dichanthium spp. sward, grazed by tethered Creole heifers [mean live weight (LW) 202 ± 2·0 kg], at three daily herbage allowances. Experiment 1 examined herbage allowances of 16, 25 and 31 kg of dry matter (DM) d^–1 on a fertilized sward at 21 days of regrowth whereas, in experiment 2, lower allowances of 11, 15 and 19 kg DM d^–1 were examined on the same sward, which was unfertilized and grazed at 14 days of regrowth. In each experiment, the herbage was grazed with three groups of two heifers in a 3 × 3 Latin square design. Sward characteristics were described before grazing. OMI was calculated from total faecal output, and OMD was predicted from the crude protein (CP) content of the faeces. The amount of herbage defoliated by the heifers was also estimated on tillers selected at random.
Organic matter intakes were on average 26 g and 19 g OM kg^–1 LW, and OMD values were 0·740 and 0·665 for Experiments 1 and 2, respectively, and were not affected by allowance. In Experiment 1, the herbage quality was high [0·50 of leaf and 116 g CP kg^–1 organic matter (OM)] for a tropical forage, whereas in Experiment 2, the quality of the herbage (0·27 of leaf and 73 g CP kg^–1 OM) was lower. These differences were reflected in differences in intake and digestibility in the two experiments.
The experimental tropical Dichanthium spp. swards can have intake characteristics similar to those of a temperate sward.     

THE VOLUNTARY INTAKE AND DIGESTIBILITY BY SHEEP OE LEAF AND STEM FRACTIONS OF LOLIUM PERENNE

The leaves of tropical grasses are eaten in larger quantities than stems of similar DM digestibility. To determine whether the same fact applied to a temperate grass, studies were made with leaf and stem fractions of Lolium perenne. The leaves of L. perenne had a 20% higher voluntary intake than the stems, white the DM digestibilities were only slightly higher (67·3%ν. 64·8%). The leaves also had a larger surface area/g, a higher initial (12 h) fermentation rate in vitro, larger content of pepsin-soluble DM, and a smaller energy require ment to grind I g DM in a laboratory mill compared with the stems. The difference in voluntary intake between the leaves and stems of L. perenne was smaller than that for a number of tropical grasses.     

Effect of extent and rate of wilting on nitrogen components of grass silage

Wilting grass prior to ensiling generally increases the dry matter (DM) intake but the effect of wilting on animal performance is still poorly understood. There is a need to improve understanding of the effects of wilting on the nutritional components and chemical composition of grass silage. This study focused on the effects of the extent and rate of wilting on N components of grass silage. Meadow grass was wilted to four DM contents (200, 350, 500, 650 g kg^?1) at two different rates (fast, slow), creating a total of eight silages. Crude protein (CP) fractions were measured using the Cornell Net Carbohydrate and Protein System. Utilizable CP at the duodenum (uCP), a measure of feed protein value, was estimated using the modified Hohenheim gas test. Ruminally insoluble, undegraded feed CP (RUP) was measured using an in situ technique. Amino acid (AA) composition prior to and after rumen incubation was also investigated. Utilizable CP at the duodenum, RUP and true protein fractions B2 and B3 were increased by rapid wilting and high DM content (DM > 500 g kg^?1), although the increase with DM was only mild for uCP, probably due to lower ME content in the DM‐650 silages. Non‐protein‐N decreased with increasing DM and rapid wilting. The higher RUP content from both DM‐650 silages leads to a higher total AA content after rumen incubation. Treatment also influenced the AA composition of the ensiled material, but the AA composition after rumen incubation was similar across treatments. Rapid and extensive wilting (DM > 500 g kg^?1) improved protein value and reduced CP degradability. Increased uCP may result in higher milk protein yield, while reduced degradability may reduce N lost from urinary excretion. The primary effect of wilting on post‐ruminal AA supply from RUP appeared to be quantitative, rather than qualitative.     

Productivity and nutritive value of some cultivated perennial grasses and mixtures in the alpine region of the Tibetan Plateau

The productivity and nutritive value of some cultivated perennial grasses, Bromus inermis (B), Elymus sibricus (S), E. nutans (N), Agropyron cristatum (A), Poa crymophila (P) and mixtures B + N, S + A, B + S + A, S + B + N, N + S + A, B + S + N + A, B + N + A + P, B + S +A + P and S + N + A + P, in the alpine region of the Tibetan Plateau were investigated. Elymus nutans and E. sibricus and the mixtures, B + S + N + A, B + S +A + P and S + N + A + P, were most productive with yields of dry matter (DM) of between 11 000 and 14 000 kg^?1 of biomass annually in the second harvest year. Acid‐detergent fibre (ADF) concentrations increased (P < 0·05), and crude protein (CP) concentrations and in sacco DM degradability values decreased (P < 0·05) with the maturity of the cultivated grasses. Swards, based on these species and mixtures, have the potential to be the main choices for cultivation in the Tibetan Plateau because they produce more nutrients than other grass species and mixtures. Late August (flowering stage of dominant grasses) is the optimum time for harvesting as the yield of rumen‐degradable CP is highest that of DM relatively high and the DM degradability is satisfactory.     

The composition of first-cut grass for ensilage in England and Wales from 1988 to 1991

A total of 2225 samples of herbage, typical of that taken for first-cut silage on commercial farms in England and Wales, was taken between 1988 and 1991. Samples were analysed for dry matter (DM), water soluble carbohydrate (WSC), crude protein (CP) and metabolizable energy calculated from modified acid detergent fibre. The results were used to investigate the effect of weather conditions upon herbage quality for ensilage. In general, in areas of high rainfall, i.e. western areas, herbage DM and WSC were significantly lower than in eastern areas, whilst the reverse situation occurred with CP. Italian ryegrass (IRG) had a significantly higher WSC and lower CP than other grasses, whilst samples from permanent pasture (PP) had significantly lower DM and WSC, and significantly higher CP than other grasses. It was calculated that to produce a WSC concentration in the fresh grass of 37 g kg⁻¹, to produce well-fermented silage without additive use, IRG grown in the east would require a DM of 160 g kg⁻¹, In contrast PP grown in the west would require a DM content of 250 gkg⁻¹.     

Seeding cool-season grasses into unimproved warm-season pasture in the southern Great Plains of the United States

Limited availability of herbage during the cool season creates a problem of a supply of nutrients for livestock producers throughout the southern Great Plains of the USA and, particularly, on small farms where resource constraints limit possible mitigating strategies. Six cool‐season grasses were individually sown into clean‐tilled ground, no‐till drilled into stubble of Korean lespedeza [Kummerowia stipulacea (Maxim) Makino] or no‐till over‐sown into dormant unimproved warm‐season pastures. The dry matter (DM) yields of mixtures of cool and warm‐season herbage species were measured to test their potential for increasing cool‐season herbage production in a low‐input pasture environment. Only mixtures containing Italian ryegrass (Lolium multiflorum Lam) produced greater year‐round DM yields than undisturbed warm‐season pasture with all establishment methods. When cool‐season grass was no‐till seeded into existing warm‐season pasture, there was on average a 0·61 kg DM increase in year‐round herbage production for each 1·0 kg DM of cool‐season grass herbage produced. Sowing into stubble of Korean lespedeza, or into clean‐tilled ground, required 700 or 1400 kg DM ha^?1, respectively, of cool‐season production before the year‐round DM yield of each species equalled that of undisturbed warm‐season pasture. Productive pastures of perennial cool‐season grasses were not sustained beyond two growing seasons with tall wheatgrass [Elytrigia elongata (Host) Nevski], intermediate wheatgrass [Elytrigia intermedia (Host) Nevski] and a creeping wheatgrass (Elytrigia repens L.) × bluebunch wheatgrass [Pseudoroegneria spicata (Pursh)] hybrid. Lack of persistence and low productivity limit the usefulness of cool‐season perennial grasses for over‐seeding unimproved warm‐season pasture in the southern Great Plains.     

In vitro rumen methane output of perennial ryegrass varieties and perennial grass species harvested throughout the growing season

The selection and feeding of perennial ryegrass (Lolium perenne L.) varieties (PRV) or perennial grass species (PGS) may affect enteric methane (CH₄) output because of changes in the fermentation dynamics in the rumen as a result of differences in herbage chemical composition. The objective of this study was to determine the effects of PRV and PGS harvested throughout the growing season on herbage chemical composition, and in vitro rumen fermentation variables and CH₄ output per unit of feed using a batch culture technique. Seven PRV (Experiment 1: Alto, Arrow, Bealey, Dunluce, Greengold, Malone, Tyrella) and six perennial grasses [Experiment 2: perennial ryegrass (Navan), perennial ryegrass (Portstewart), cocksfoot, meadow fescue, tall fescue, timothy; defined as PGS], managed under a simulated grazing regime, were incubated for 24 h with buffered rumen fluid in two separate experiments. The CH₄ output per unit of feed dry‐matter (DM) incubated was not affected (P > 0·05) by PRV (range of mean values across PRV of 23·9–25·3 (SEM 0·41) mL g^?1 DM) or by PGS (25·6–26·6 (SEM 0·37) mL g^?1 DM). The CH₄ output per unit feed DM disappearing during the in vitro rumen incubation was not affected by PRV (33·9–35·1 (SEM 0·70) mL g^?1 DM), and although there was an overall PGS effect (P < 0·05; 37·2–40·3 (SEM 0·71) mL g^?1 DM), none of the paired contrasts between PGS were significant when analysed using Tukey adjusted comparisons. This outcome reflected either small‐scale or a lack of treatment effects on individual herbage chemical composition (e.g. 454–483 g NDF kg^?1 DM, 215–224 g CP kg^?1 DM and 94–122 g water‐soluble carbohydrate (WSC) kg^?1 DM across PRV; 452–506 g NDF kg^?1 DM, 208–243 g CP kg^?1 DM and 73–131 g WSC kg^?1 DM across PGS) and in vitro rumen fermentation variables. Hence, these results provide no encouragement that choices among the grasses examined, produced within the management regimes operated, would reduce enteric CH₄ output per unit of feed in vivo. However, the technique utilized did not take account of animal × PRV or PGS interactions, such as potential differences in intake between animals, that may occur under farm conditions.     

Morphological development and nutritive value of herbage in five temperate grass species during primary growth: analysis of time dynamics

In a 2‐year field experiment, morphological development and measures of the nutritive value of herbage for livestock during primary growth in Meadow foxtail, Tall oatgrass, Cocksfoot, Perennial ryegrass and Yorkshire fog were investigated. All measured variables were affected significantly by both species and sampling date, and their interaction (P < 0·001), in the period of primary growth. Changes with time in mean stage weight for Meadow foxtail and Cocksfoot were different from the other species due to their indeterminate growth habits. Mean stage weight of Tall oatgrass and Yorkshire fog increased more rapidly than that of Perennial ryegrass with time. Changes in mean stage weight with time were described by linear, parabolic and sigmoid relationships. Crude protein (CP) concentration of herbage was higher for Cocksfoot and Meadow foxtail than for Perennial ryegrass. A parabolic relationship of CP concentration with time was typical for all the species. Concentrations of neutral‐detergent fibre (NDF) and acid‐detergent fibre (ADF) in herbage of the species differed most during the mid‐period of primary growth. Their increases with time showed curvilinear (sigmoid and parabolic) relationships. Perennial ryegrass had lower concentrations of both NDF and ADF in herbage than the other species. Differences between the in vitro dry matter (DM) digestibility among the grasses increased in mid‐ and late periods of primary growth. Perennial ryegrass had higher values for in vitro DM digestibility but the difference from other species was small in the early period of primary growth and from cocksfoot in the late period of primary growth. In vitro DM digestibility showed, in most cases, a sigmoid and, in others, a linear decrease with time. Principal component analysis showed that perennial ryegrass and meadow foxtail were the most distinctive of the species in characteristics relating to morphological development and the nutritive value of herbage to livestock.     

The management of Brassica for winter forage in the sub-tropics

In subtropical latitudes temperate crops can be grown during the cool months but the growing season is restricted by the termination and beginning of hot weather. Postponing sowing date in south Florida from October to November to January resulted in 150, 130 and 110-d growing seasons respectively. Dry matter (DM) yields of turnip, swede, rape and kale were lowered by each later sowing date and shorter growing season, and crude protein (CP) concentration was the same as for, or was increased by late sowing. In vitro organic matter digestibility (IVOMD) of turnip, swede and rape leaves was not affected by sowing date, but roots of turnip and swede from the earlier sowings and longer growing seasons were more digestible. Yield of the four species depended on harvest management as well as date of sowing and length of growing season. Total yield of turnip and swede were unaffected by harvest management but multiple cutting resulted in greater leaf yields and smaller root yields, whereas stockpiling resulted in smaller leaf yields and larger root yields. Kale produced more DM when harvested once at the end of the winter growing season but rape produced the greatest DM yield when sown in October and harvested     

Effects of gamma irradiation on ruminal DM and NDF degradation kinetics of alfalfa hay

The effects of gamma irradiation on ruminal dry matter, Neutral Detergent Fiber (NDF) degradation of alfalfa hay were investigated. Alfalfa hay samples were irradiated by gamma irradiator at doses of 50, 100 and 150 kGy under identical conditions of temperature and humidity. Nylon bags of untreated or irradiated samples were suspended in the rumen of three Taleshi bulls for up to 96 h and resulting data were fitted to non-linear degradation model to calculate degradation parameters. Results indicated that the washout fractions of dry matter and NDF increased linearly (p < 0.001) with increasing irradiation dose. The b fraction and the degradation rate of the b fraction (c) of DM and NDF were the highest at 50 kGy dose. Effective degradability of DM and NDF increased linearly with increasing irradiation dose. Gamma irradiation at doses of 50, 100 and 150 kGy increased the effective NDF degradability of alfalfa hay at rumen outflow rate of 0.05 h(-1) by about 8, 11 and 12%, respectively. Gamma irradiation affects on the hydrogenic bonds and with theirs breakdowning causes the wander-valls power weaken, that results in the degradation of cellulose and increasing of DM and NDF degradability.     

Supplementary feeding of grazing beef cattle

The effects of cereal and protein supplements on feed intake and liveweight gain were studied. In 1975, steers were continuously stocked on autumn pasture and fed no supplement or 8 g dry matter (DM) per kg liveweight (LW) per d as rolled barley (crude protein (CP) concentration 120 g kg^-1), lucerne cobs (CP concentration 190 g kg^-1) or a mixed concentrate (CP concentration 300 g kg^-1). In 1976, steers were continuously stocked or rotationally grazed in summer and fed no supplement or 7 g DM per kg LW per d as either rolled barley (CP concentration 130 g kg^-1) or a mixture of rolled barley and groundnut meal (CP concentration 210 g kg^-1). Herbage organic matter (OM) intakes in 1975 and 1976 were depressed on average by 22 and 15% respectively with supplementation, but total OM intakes were increased by 9 and 15% respectively. Daily liveweight gain was not significantly increased by supplementation in 1975 when herbage allowance was ample but was significantly increased in 1976 when herbage allowance was limited and herbage digestibility was lower. Protein concentration of the concentrate did not significantly affect daily gain in either year nor was there any difference in gain between rotational grazing and continuous stocking.