THE NUTRITIVE VALUE OF WEEPING LOVEGRASS DURING THE SPRING SEASON

Faecal samples from a continuous digestibility trial with Eragrostis curvula were analyzed for cell-wall contents, acid-detergent fibre, lignin, asb and N. DM digestibility was regressed on all these fractions and organic-matter digestibility was also regressed on faecal organic-matter N. The best predictions of digestibility were obtained by the use of faecal lignin as a percentage of acid-detergent fibre, and by cell-wall contents. N was a comparatively poor predictor and it is shown that its relationship with organic-matter digestibility varies with the level of N in the diet. It is concluded that both lignin and cell-wall contents could serve as useful internal indicators since their use is unlikely to be biassed by metabolic and microbial contamination.     

THE APPLICATION OF THE IN VITRO DIGESTION TECHNIQUE TO SOME ARID-ZONE FODDERS

The in vitro digestibility of organic matter and cellulose was determined in 17 fodders collected in western New South Wales. Further determinations were made on samples fortified or not by the addition of glucose, urea and yeast extract. There was a significant positive response to fortification in both organic-matter and cellulose digestibility, the magnitude of the response varying with the fodder sample tested. The relationship between organic-matter digestibility and cellulose digestibility was close only in the case of grasses, but for all samples consideration of both the amount and digestibility of cellulose accounted for 97% of the variation in organic-matter digestibility. The results suggest that an inhibitor preventing cellulose digestion was present in Cassia eremophila .     

A NOTE ON THE SUITABILITY OF THE IN VITRO DIGESTIBILITY TECHNIQUE FOR VERY SMALL PLANT SAMPLES

The two-stage in vitro digestibility technique was scaled down to use 0.1 g samples. The accuracy of predicting in vivo DM digestibility by the use of micro-samples was studied, using 35 samples of four grass species of known in vivo digestibility. When the sample size was reduced from the normal 0.5 g to 0.1 g, the residual standard deviation of the regression relating in vitro to in vivo DM digestibility was increased from ±2.5 to ±3.4 digestibility units. Grinding the samples more finely than through a 1.0 mm screen did not improve the accuracy of predicting in vivo digestibility. It was concluded that the in vitro method may be used with micro-samples where necessary, but with less accuracy than the macro-technique. For maximum accuracy, the use of standards of known in vivo digestibility is necessary.     

THE AD LIBITUM INTAKE AND DIGESTIBILITY OF DRIED GRASS PELLETS AND SILAGE BY SHEEP

Perennial ryegrass was conserved by ensiling, or by dehydration, grinding and pelleting. the two resultant feeds were given ad lib. to wether sheep, either separately or in different proportions. Pellets were consumed in greater quantities than the silage, but were lower in digestibility. There was a rectilinear relationship between the percentage of pellets in the ration consumed and organic-matter digestibility, but a curvilinear relationship between the percentage of pellets and organic-matter intake. Silage intake was little affected by the feeding of pellets until more than 40% of the ration consisted of pellets. The increase in total intake with an increase in pellets above 60% was small, with the result that intake of digestible organic matter was highest when 65% pellets was fed. the results suggest that dried-grass pellets may be a useful supplement for silage rations.     

A study of the nutritive value of white clover (Trifolium repens L.) in relation to different stages of phenological maturity in the primary growth phase in spring

This paper reports the effects of onset of phenological maturity on the nutritive value of white clover ( Trifolium repens L.). The study comprised (i) examination of an extensive data set on nutritive value and (ii) investigation of the constituents of nutritive value, in vivo feeding value, protein degradability and metabolizable protein content of white clover harvested at three stages of maturity (early-flowering, full-flowering, ripe seed stages) during the primary growth phase in spring in Australia. The data set on nutritive value showed a consistent pattern of high nutritive value during cool season months, progressive decline through spring and uniformly lower nutritive value over summer. Results from laboratory determinations, in sacco degradability studies and a digestibility trial on white clover harvested at early-flowering, full-flowering and ripe seed stages were consistent with results from the data set on nutritive value. Onset of maturity during the primary growth phase in spring was accompanied by large changes in nutritive value: neutral-detergent fibre (NDF) increased from 184 to 301 g kg⁻¹ dry matter (DM), nitrogen (N) declined from 36 to 20 g kg⁻¹ DM, in vitro digestibility declined from 0·74 to 0·65 and metabolizable protein content declined from 144 to 67 g kg⁻¹ DM from early-flowering to ripe seed stage. These nutritive value changes were accompanied by a decline of in vivo digestibility at the rate of 0·0032 d⁻¹ and an 0·2 reduction in voluntary intake.     

Apparent digestibility and nitrogen utilization of diets based on maize silage harvested at three stages of maturity and fed to steers

Advancing maize crop maturity is associated with changes in ear‐to‐stover ratio which may have consequences for the digestibility of the ensiled crop. The apparent digestibility and nitrogen retention of three diets (Early, Mid and Late) containing maize silages made from maize of advancing harvest date [dry matter (DM) contents of the maize silages were 273, 314 and 367 g kg^?1 for the silages in the Early, Mid and Late diets respectively], together with a protein supplement offered in sufficient quantities to make the diets isonitrogenous, were measured in six Holstein–Friesian steers in an incomplete Latin square design with four periods. Dry‐matter intake of maize silage tended to be least for the Early diet and greatest for the Medium diet (P = 0·182). Apparent digestibility of DM and organic matter did not differ between diets. Apparent digestibility of energy was lowest in the Late diet (P = 0·057) and the metabolizable energy concentrations of the three silages were calculated as 11·0, 11·1 and 10·6 MJ kg^?1 DM for the Early, Medium and Late diets respectively (P = 0·068). No differences were detected between diets in starch digestibility but the number of undamaged grains present in the faeces of animals fed the Late diet was significantly higher than with the Early and Mid diets (P = 0·006). The apparent digestibility of neutral‐detergent fibre of the diets reduced significantly as silage DM content increased (P = 0·012) with a similar trend for the apparent digestibility of acid‐detergent fibre (P = 0·078). Apparent digestibility of nitrogen (N) was similar for the Early and Mid diets, both being greater than the Late diet (P = 0·035). Nitrogen retention did not differ between diets. It was concluded that delaying harvest until the DM content is above 300 g kg^?1 can negatively affect the nutritive value of maize silage in the UK.     

THE EFFECT OF NITROGENOUS FERTILIZER ON THE RATE OF GROWTH OF ITALIAN RYEGRASS

This paper describes the rate of growth of Italian ryegrass in the spring, measured by recording DM yield at weekly intervals up to 10 weeks. There were 3 levels of applied N: 25, 75 aud 125 lhJac (28, S4 and 140 kgJha). Rate of growth declined after the sixth week at all 3 levels of N. Grass receiving 25 Ib N produced 5000 Ib DMJac (5600 kgJha) in 10 weeks, that receiving 75 lb N 6800 Ib (7700 kgJha) and that receiving 125 lb N 7100 lb (8000 kgJha). The DM content of herbage fell after the first week and subsequently increased steadily up to 10 weeks; the fall was least marked and the rate of increase most rapid at tbe lowest level of N. In vitro digestibility (measured in one year only) was much affected by stage of growth and little affected by level of N.     

Prediction of the digestibility of the diet of horses: evaluation of faecal indices

Data from in vivo digestibility trial with four to six horses fed twenty-seven forage-based diets are used to calculate prediction equations for the digestibility of dry and organic matter, based on the crude ash (CA), crude protein (CP) and crude fibre (CF) contents of diets and faeces. The most precise prediction of dry-matter digestibility (r.s.d. = 0.032, R²= 0.80) was derived from a multiple regression including faecal (CP, CF) and dietary parameters (CF). Among faecal parameters, CP was the best single predictor of both digestibility (r.s.d) = 0.040, r²= 0.63) and dietary CP content (r.s.d = 0.028, r²= 0.59). For biological reasons we propose a non-linear model that allows prediction of dry- and organic-matter digestibility from faecal CP Content with reasonable Precision (r.s.d = 0.038, 0.036, r²= 0.65, 0.74, respectively). This will be adequate for many studies, especially for free-living animals in rangelands.     

THE USE OF CATTLE WITH OESOPHAGEAL FISTULAE IN GRASSLAND EXPERIMENTS

Oesophageal-fistulated calves and cattle were used in various experiments during 1963 to 1966; results for 1966 are reported.
The method of inserting the fistula, the routine care of the animals and the methods of sampling through the fistula, are described.
Individual stall-feeding experiments in 1966 gave recovery values of 99.7% for herbage extruded through the fistulae, in relation to herbage eaten. The in vitro organic-matter digestibility of the grass offered and of the extrusa samples were identical. The digestibility of the grass fed in these experiments was high, but was comparable with that of herbage used in the grazing experiments reported. Grazing studies on grass/white clover pastures are reported. The digestibility was determined on all samples and they were separated into various plant fractions. Results obtained were compared with herbage samples cut at the same time. In most cases the digestibility and % N of the extrusa sample was higher than that of the corresponding herbage sample. The quantity of dead material present increased, and more was eaten, as the season advanced; it was of low digestibility. Results of intake studies with grazing animals are presented and the use of oesophagea-istulated cattle as an aid in such studies is discussed.     

Forage soybean performance in mediterranean environments

Livestock producers are interested in growing forage soybean [Glycine max (L.) Merr.] in summer and ensiling alone or in mixtures with corn or sorghum. Four row spacings (20, 40, 60, and 80 cm), four seeding rates (50, 100, 150, and 200 kg seeds per hectare) and four harvesting stages for forage production (V₅, R₂, R₄, and R₆) were evaluated under irrigated conditions in a randomized split–split plot design with three replications in three different locations in Turkey with Mediterranean-type climate in 2004 and 2005. Dry matter (DM) yield was significantly reduced with increased row spacings in all locations. There was no significant difference between 20, 40, or 60 cm row spacings while 80 cm provided the lowest yield. Increased seeding rates (50, 100, 150, and 200 kg seeds per hectare) generally increased DM yield, although the most suitable row spacing varied by location. DM yield was significantly affected by harvest maturity increasing with advancing maturity in all locations. DM constituent plant components were generally unaffected by row spacing and seeding rate but harvest maturity did significantly affect DM partitioning. As expected, leaf blade fractions decreased continually as plant maturity increased, while stem and flower plus pod fraction increased from V₅ to R₆. In general, row spacing and seeding rate did not significantly affect crude protein, degradable protein, and in vitro dry matter digestibility of soybean forage, but all decreased significantly with advancing maturity. These studies demonstrated soybeans managed for forage in a Mediterranean-type environment can average of 9.3 and 11.3 t ha⁻¹ dry matter yield at R₄ and R₆ stages, respectively, while averaging 13.3% crude protein, 8.2% degradable protein, and 60.6% in vitro dry matter digestibility.     

IN VITRO AND FAECAL NITROGEN TECHNIQUES FOR PREDICTING THE VOLUNTARY INTAKE OF CHLORIS GAYANA

The voluntary intake by penned sheep, of two Rhodes-grass varieties (Samford and Callide) cut at 4 stages of maturity was studied. Intake of dry matter was correlated with in vitro digestion of DM after 12 h incubation. The intake of digestible DM was correlated (r=0.99) with the sum of the digestion after 12 and 48 h incubation.
Coarsely ground samples (2.5 mm screen) were digested in vitro less rapidly than finely ground samples (0.4 mm screen), especially with the more mature forages. DM digestibility, voluntary intake of DM and digestible DM were also correlated (r>0.96) with faecal nitrogen, although different regression equations applied to the two varieties.     

THE EFFECT OF HEAVY DRESSINGS OF SLURRY ON FORAGE MAIZE PRODUCTION

Cow slony was incorporated into land at levels equivalent to 0, 125, 250 or 500 t/ha (0, 50, 100 or 200 tons/ac) shortly before sowing maize (INRA 200). Quantity and quality determinations were made on the crop at 73, 93, 115 and 137 days after plant emergence. The slurry dressings delayed the emergence of maize plants. The 250 t/ha (100 tons/ac) treatment gave a significant increase in DM yield at the final harvest, but 500 t/ha (200 tons/ac) tended to depress yields of the whole crop and of the ear. There was no significant effect on the percentage DM of the crop. Slurry applications increased the level of E and nitrate-N in the plants, but depressed Mg. Crude protein and in vitro digestibility were not affected.     

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.     

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.     

THE INTAKE AND NUTRITIVE VALUE OF FRESH, FROZEN AND DRIED SORGHUM ALMUM, DIGITARIA DECUMBENS AND PANICUM MAXIMUM

Sorghum almum, Digitaria decumbens and Panicum maximum were fed in fresh, frozen (−20 C) or dried (85° C) form to 21 wethers in metabolism cages. Neither freezing nor drying had a significant (P>0·05) effect on voluntary intake, dry-matter digestibility or organic-matter digestibility. Drying depressed the apparent digestibility of the nitrogen in all grasses but only in the case of D. decumbens was this significant (P<0·05). Freezing also depressed the apparent digestibility of N while both freezing and drying reduced N retention, compared with the fresh feed. None of these differences was significant.
Freezing and drying are thus methods of pasture preservation that can be used to study the intake and dry-matter digestibility of tropical pastures, but both methods may introduce bias into the measurement of N digestibility and retention.     

The effects of incorporating sugar beet pulp with forage maize at ensiling on silage fermentation and effluent output using drum silos

The effects of incorporating sugar beet pulp with forage maize at ensiling on silage fermentation, effluent output and pollution potential of the effluent was investigated using 200-litre drum silos. A forage maize crop (Zea mais) was harvested on four different dates, generating four different stages of maturity [dry-matter (DM) content 154–235 g kg⁻¹ DM], and molassed sugar beet pulp (MSBP) was added at five different rates (0, 2, 7, 13, 18 kg MSBP 100 kg⁻¹ fresh maize crop). A total of fourteen treatments (each replicated three times) were evaluated. The chemical analysis of the maize silages and the mixtures produced showed that MSBP addition increased DM, ash, neutral cellulase gaminase digestibility (NCGD) and metabolizable energy (ME) contents of the mixture significantly (P < 0·01) for all harvesting dates except for harvest date 1. Silage fermentation in terms of final pH was unaffected by MSBP addition, although lactic acid concentration of the effluent tended to increase with increased MSBP addition. When no MSBP was included, large volumes of effluent were produced, ranging from 200 g kg⁻¹ to 100 g kg⁻¹. MSBP addition significantly (P < 0·01) decreased effluent production except for the driest material. A curvilinear equation was fitted to predict effluent production from DM of the forage maize and pressure applied to the sample (adjusted r²=0·95). In addition, a curvilinear equation was fitted to predict the MSBP addition rate required to prevent effluent production (adjusted r²=0·65). For harvest dates 1, 2 and 3, the biological oxygen demand for 5 days (BOD₅) and the chemical oxygen demand (COD) concentration of the effluent were significantly increased (P < 0·05) with increased levels of MSBP addition. However, the pollution potential per kg of material ensiled was significantly reduced (P < 0·05) with increased MSBP addition, since less effluent was produced. The experiment indicates that ensiling low DM silages with appropriate levels of MSBP produces nutritionally valuable silages with reduced pollution potential.     

An evaluation of the effects of rate of nitrogen fertilization of grassland on silage fermentation, in-silo losses, effluent production and aerobic stability

A factorial experiment was carried out to evaluate the effects of level of nitrogen (N) application to grassland and subsequent treatment of the herbage at ensiling with formic acid on the rate of silage fermentation, dry-matter (DM) recovery, aerobic stability and effluent production. Herbage from the primary regrowth of predominantly perennial ryegrass swards received either 72 (LN), 126 (MN) or 180 (HN) kg N ha^?1. The herbages were harvested and yield estimated after a 50-day regrowth interval. After storage for 24 h in polythene bags, the herbages were ensiled, unwilled, in laboratory silos (6 kg capacity) either untreated (UT) or treated with formic acid (F) at 3 ml (kg herbage)^?1. Three silos per treatment were opened and sampled on days 1, 3, 6, 15, 50 and 105 after ensiling. The mean herbage yields for the LN, MN and HN swards were 5.2, 6.3 and 6.2 (s.e. = 0.27) t DM ha^?1 and there was no carryover effect of nitrogen treatment on the yield of a subsequent 22-day regrowth harvested on 2 September. As level of fertilizer N application increased, concentrations in the herbage at mowing of crude protein, nitrate and ash increased, DM decreased and water-soluble carbohydrate and in vitro DM digestibility remained unchanged. Increasing the rate of N fertilizer to the sward resulted in higher silage pH (P< 0.001) and ammonia N concentrations (P <0.001) at each time of sampling. Increasing the rate of fertilizer N increased effluent output (P < 0.001) and DM recovery (P < 0.001). Aerobic stability was improved (P <0.001) by use of high rates of N fertilizer application. Formic acid treatment restricted fermentation and increased effluent output (P <0.001) but had no effect (P > 0.05) on DM recovery. It is concluded that the rate and extent of pH decline was reduced with increasing N application, associated with increased buffering capacity and decreased DM concentrations of the herbage at ensiling. However, increasing the level of N fertilizer applied increased DM recovery and effluent output, and improved aerobic stability of the resulting silages.     

Effect of rotary-drum-drier exit temperature and length of pre-drying storage time on digestibility of dried grass cobs

The effect of exit temperature of a rotary-drum-drier and of the length of pre-drying storage time on chemical composition and digestibility of dried grass cobs was investigated in two experiments. Increasing exit temperature from 77 to 166°C reduced WSC, NFE and available lysine content and increased CF content of dried grass. In vitro and in vivo DM digestibility was reduced by 16.4 and 24.5 percentage units respectively. Increasing length of pre-drying storage time also reduced WSC and available lysine content and reduced in vitro and in vivo DM digestibility by 2.4 and 5.1 percentage units respectively. The greatest reduction in in vivo digestibility in both experiments occurred in the CP fraction.     

THE DRY-MATTER PRODUCTION, BOTANICAL COMPOSITION, IN VITRO DIGESTIBILITY AND PROTEIN PERCENTAGE OF PASTURE LAYERS

Irrigated plots of a mixed sward of four grasses and white clover were cut to a height of 3 cm in either June, August, October, December or February. The plots cut at each commencement date were harvested when the height of growth of the pasture was either 10, 18, 25, 32, 40, 48 or 55 cm. At each harvest, the pasture was cut at 7 to 8 cm intervals down to a height of 3 cm. DM production, botanical composition, in vitro digestibility (DOM) and CP of each layer was determined. DM production declined from the lower to the upper layers for pastures shorter than 32 cm. For pastures taller than 32 cm, DM production declined from the lower to the middle layers, then increased in the upper layers, due mainly to the presence of seed heads. Maximum percentages of DOM and CP were observed for the middle layers of the pastures taller than 25 cm. For pastures shorter than 25 cm, DOM and CP percentages increased from the lower to the upper layers, for all commencement dates. The percentages of DOM and CP of each layer decreased as the height of growth increased. The percentage of DOM showed a positive correlation with the percentages of Lolium perenne, Bromus unioloides and Trifolium repens, and a negative correlation with the percentages of Paspalum dilatatum and chlorotic material. The percentage of CP showed a positive correlation with the percentages of Paspalum dilatatum, Dactylis glomerata and Trifolium repens and a negative correlation with the percentages of chlorotic material and the total of the four grasses within the pasture layers. The lower layers of the pasture produced large quantities of DM and, despite the lower in vitro digestibility of these layers, they produced more DOM than the other pasture layers. The DOM production of the pasture increased with increasing height of growth, but decreased as the commencement date was altered from winter through to the end of summer.     

THE EFFECT ON FATTENING STEERS OF SUPPLEMENTING SILAGE WITH DRIED GRASS OR ROLLED BARLEY

Eighteen crossbred Aberdeen-Angus and six Shorthorn steers with an average liveweight of 382 kg were given silage (DM content 22.3%) ad lib., supplemented with 0, 1.2, 2.4 and 3.6 kg artificially dried grass, or 1.8 kg rolled barley, per day. A digestibility study carried out on the silage and dried grass showed that the concentration of the metabolizable energy was 52.7 and 45.6 kcal/100 kcal of food, respectively. Live-weight gain increased with each level of supplementation. Supplementation did not significantly affect the intake of silage DM, but differences in the intake of total DM were significant. The killing-out percentages of the steers were similar. The results suggest that dried grass pellets may be a usefid supplement for a silage diet. It was shown that 1.12 kg of dried grass was equivalent to 1.80 kg rolled barley as a supplement for silage.