The experiment forms part of a study to investigate methods of improving the use of sorghum stover as a feed for ruminants in Ethiopia. A previous experiment (Osafo, Owen, Said, Gill and McAllan, 1991) showed that intake and growth of cattle were improved when the amount of sorghum stover offered was increased from 25 to 50 g dry matter [DM] per kg weight [M] daily [d], and when the stover was offered unchopped rather than chopped. The present experiment investigated the intake and growth responses of yearling cattle to increasing the amount of stover offered, and to supplementing with cottonseed cake.

Earlier work (Rouzbehan et al, 1991) has shown that supplementation of baled silage with molassed sugar beet feed (MSBF, 60 g/kg fresh weight) improved live weight gain (LUG) and feed conversion efficiency (FCE) in sheep. It has been established that the protein in silage is not utilised as effectively by beef cattle as the protein in non-fermented forages (Thomas, 1982). Responses in the performance and carcass composition of finishing steers and heifers when silage-based diets have been supplemented with protein have proved to be variable. This trial was therefore carried out to examine the effects of feeding two levels of a protein supplement, fishmeal, in addition to MSBF, on the performance of beef steers fed big-bale silage ad libitum and to assess the nutritional value of such supplementation.

Grazing management systems for cattle in the tropics are variable due to environmental, social or economic conditions. Grazing may be during day light, at night or for 24 hours. The efficiency of animal performance is dependant upon how the animal can respond to different managements. In this work a simulation of three grazing management systems was attempted by offering forage at different times in order to study the intake of forage and of supplement (molasses block) when access to forage was restricted, but supplement was available continuously.

The need to speed up the rate of genetic progress in beef cattle, particularly in economically significant traits such as growth and carcase merit has always been recognised by the Meat and Livestock Commission. This is achieved through the Beefbreeder Pedigree Recording Service which records over 1,000 pedigree herds in Great Britain. Traditionally, analysis of performance records from pedigree herds has been carried out using within herd contemporary comparisons.

Average pedigree beef herd size in Great Britain is typically less than 20 cows which limits accuracy and scope for genetic improvement when making within herd selection decisions.

When different protein sources are infused direct into the abomasum of the dairy cow, the pattern of utilization of the amino acid-N supplied might be expected to be influenced by the amino acid composition of the infused protein. This suggestion was examined in a nitrogen-balance study with lactating cows.

When the proteins are given direct into the abomasum of dairy cows receiving diets based on grass silage, casein produces much greater responses of milk production than do equivalent amounts of soya-protein (Choung and Chamberlain 1991a, b). However, the cause of these differences of response is not known. In feeding trials, supplementation of silage diets containing soya bean meal with rumen-protected forms of the amino acids thought to be most limiting, methionine and lysine, has been without effect (Girdler et al 1988).

The cultivation and uses of trees is important and varied in many areas of the world. The benefits include soil improvement and stabilisation, shade for other plants, provision of wood and fodder for ruminant animals.

Tree leaves are important sources of micro- and macro-nutrients for ruminants in many parts of the world including Nepal and Portugal especially when other plant fodders are scarce (Topps, 1992). Thus improvements in livestock production may benefit from an increased and/or selective use of tree fodders. The proximate composition and tannin (flavanol) content of plants including tree leaves, considerably influences the nutritive value (Goodchild & McMeniman, 1991; Kumar & Vaithiyanathan, 1990; Longstaff, et al.,1991; Makkar et al 1991).

In recent years considerable attention has been given to Improving the feeding value of low-quality roughages through physiological, biological and chemical processes (Jackson, 1978). Many reviews of chemical treatment methods on the effect of digestibility have previously been undertaken by Homb (1984), Sundstøl (1984) and Wanapat et al (1985), but few have studied the effect on methane production. The values available are very variable. Since the importance of chemically upgrading low-quality forages is also increasing in developing countries, it is essential to investigate further the effect chemical upgrading has on methane production, in order to estimate its impact on global warming.

There has been Increased Interest 1n the making and feeding of whole-crop wheat (WCW) 1n recent years. WCW provides an alternative source of forage to grass silage, higher dry matter (DM) yields than grass and an alternative means of straw disposal. Conservation is often based on the Incorporation of urea which is hydrolysed to ammonia which preserves the crop without the losses associated with fermentation. Ørskov et al (19B3) have shown that urea applied to whole crop barley and oats at 60gkg-1 DM produced adequate crop preservation.

Since WCW is essentially a two component diet consisting of cell wall-rich straw and starch-rich grains, it is essential to understand the digestion characteristics of each. In addition, since urea has been extensively used to upgrade straws (eg Jayasurlya and Pearce, 1983; Williams et al, 1984) any upgrading effect of urea on WCW needs confirming.

The utilization of forage for ruminants is associated with prolonged retention times within the digestive tract, especially when they are consumed at low levels of intake. The nutritive value of forage is influenced by both the rate at which it is degraded in the rumen and the rate of its physical removal from the rumen. These two parameters are associated with the cell wall constituents of the forage, since its cell content is rapidly fermented in the rumen and hence does not occupy space for a long.

The purpose of the present expedients was to establish the relationships between the cell wall chacacterisitcs (composition and rumen degradation) of some hays and its retention time in the rumen.

Tropical forages found in Colombia are of low quality. Mixtures of urea and sugar cane molasses (UM) have been used as a supplement to stimulate microbial growth in the rumen and to maximise the intake of such forages by ruminants. Rice polishings (RP), a locally available by-product, could provide an alternative supplement. The experiment described here was designed to compare UM with three increasing amounts of RP on rumen fermentation and voluntary intake of a basal low quality grass hay when fed to sheep.

Pure cultures of rumen microorganisms usually grow better when amino acids are present, particularly if the amino acids are present as peptides. However, it is less clear how important peptides, compared to free amino acids and ammonia, are to the mixed microbial population of the rumen. In vitro mixed cultures suggest that peptides permit more rapid microbial growth on soluble carbohydrates and greater amino acid incorporation than free amino acids (Wright, 1967; Argyle & Baldwin, 1989). However, amino acid N may have no beneficial effect if the energy source is more slowly degraded (Merry et al., 1990). The present experiment was undertaken to assess whether the response of rumen fermentation to additional nitrogen is different depending on whether the N is present as non-protein N, free amino acids, or peptides in sheep receiving a grass hay diet.

The extent of uncertainties associated with most of the existing protein evaluation systems for ruminants necessitates the need for some alternative investigations. Recently Newbold and Rust (1990) have demonstrated a close relationship between rumen proteolysis and protein fractions of soybean meal. Such relationship may be helpful in describing different feed proteins in terms of their ability to supply amino acid N to ruminant tissues. Present experiments were, therefore, conducted to examine the feasibility of using parameters such as protein size, type and structure, determined by solubility and electrophoresis for the evaluation of a variety of feed proteins.

The practice of adding low levels of non-commensal yeast and fungi to ruminant diets is increasingly gaining acceptance as a means of manipulating rumen fermentation to benefit production. Reported benefits include an increased degradability of forages in the rumen and an improved flow of microbial protein from the rumen (Williams and Newbold, 1990).

Distillery by-products, such as pot ale syrup, are commonly included in ruminant diets as an energy source. However, pot ale syrup contains a substantial number of yeast cells. The aim of the present study was to establish if different yeasts and yeast-containing by-products had similar effects on rumen fermentation to those found with a commercial yeast culture feed additive.

Two commercial Saccharomyces cerevisiae preparations (Alkosel, Alko Biotechnology, Finland and Yea-sacc, Alltech, UK), active dried baker's yeast (United Distillers, UK) and two pot ale syrups from the Inchgower and Dailuaine distilleries were compared for their effects on the fermentation in the rumen simulation technique (Rusitec).

Yeast culture (YC) based on Saccharomyces cerevisiae is gaining increasing acceptance as a feed additive for ruminants. Production responses to YC have been reported in growing and lactating animals. It has been suggested that these responses are at least partly due to enhanced microbial growth in and microbial nitrogen flow from the rumen (Williams and Newbold, 1990). The aim of the present study was to investigate the effect of YC on rumen fermentation, microbial growth and liveweight gain in bulls fed isonitrogenous diets containing either urea or soya.

Thirty two Limousin cross Friesian bulls (liveweight 344 kg) were allocated to treatments on the basis of previous growth rate and initial liveweight. Animals received mixed diets of barley/urea (92% rolled barley, 5% cane molasses, 1.5% urea and 1.5% minerals/vitamin mix) or barley/soya (86.75% rolled barley, 5% cane molasses, 0.75% urea, 6% soyabean meal and 1.5% minerals/vitamin mix) plus or minus 1.5 kg/ tonne YC (Yea-sacc1026 , Alltech, UK) (Table 1). YC was added to the diet prior to mixing. All rations were offered ad libitum twice daily until slaughter (460 kg). Rumen fluid samples were withdrawn by stomach tube 5 and 10 weeks after the beginning of the trial. The outflow of microbial nitrogen from the rumen was estimated from the appearance of purine derivatives in the urine as described previously (Chen et al., 1990).

Extensive hydrolysis of cell wall polysaccharides by rumen bacteria or free enzymes has been reported when lignocellulosic materials had been treated with steam and pressure (Dekker & Wallis, 1983; Castro & Machado, 1989). This has mainly been explained by complete hydrolysis of hemicellulose, lignin depolymerization and redistribution within the cell wall and increasing accessible pore volume by swelling of the cell walls. Physical treatment based on use of steam and pressure alone (auto-hydrolysis) is always associated with the release of toxic levels of furfural and phenolic monomers. These chemicals are able to inhibit the activity of rumen microorganisms, yeasts and free enzymes. To overcome this effect, dilute-acid-hydrolysis at low temperatures and pressures has been proposed (Grohmann et al., 1985). The aim of this study was to evaluate the effect of temperature, sulphuric acid concentration and reaction time on the utilization of treated wheat straw by dilute-acid-hydrolysis, either by rumen bacteria and free enzymes.

Monensin and yeast culture are known to alter rumen fermentation. Their modes of action appear to be different, and a recent study showed that the combination of both yeast culture (YC) and monensin stimulated weight gain in bulls by 12-13% over monensin alone (Spedding, 1990). However, Edwards et al. (1991) found no complementary effects between YC and avoparcin when they were combined in a silage diet for steers. In addition to its action in the rumen, monensin is known to affect post-ruminal digestion (Armstrong, 1984). Viable Saccharomyces cerevisiae have been isolated from the duodenal digesta of sheep fed YC (Newbold et al., 1990), suggesting that YC too might have post-ruminal effects. The aim of the current study was to assess the effect of monensin and/or yeast culture in the diet or infused into the abomasum on rumen fermentation and blood parameters, and also on digestive physiology by monitoring plasma gastrin, insulin and CCK-8 concentration.

Utilization of low quality roughages is limited fundamentally by the low energy cont and low DM intake when fed to the ruminant animal. Supplementation with concentrates can al improved energy supply although their inclusion can lead to a negative effect upon rough intake and ruminal cellulolitic activity. Urinary excretion of purine derivatives, urea and may constitute a suitable index to detect possible effects on rumen fermentation.

The objective of this study was to determine the effect of changes in rumen fermentat: upon urinary excretion of these compounds induced by dietary supplementation of straw v differents sources of carbohydrates.

Twelve Rasa Aragonesa ewes (44±0.45 Kg) were fed “ad libitum” with urea-supplemer barley straw and allocated at random to 3 groups of 4 animals. Each group was supplemented barley grain, sugar beet pulp and grass hay, respectively, at 4 levels of supplementation (: 300, 450 and 600 g/d) in a 4 x 4 latin square design. Each 42-d experimental period compr: 35 days of adjustment period followed by a 7 days measurement period.

The ability of rumen microbes to synthesize protein from ammonia-N enables the use of non-protein-N as a N source in ruminant diets. The strategy for feed formulation therefore would be to meet the microbial N requirement with a cheap N source (such as urea) and to increase the proportion of dietary protein for use directly by the host animal. There has been some indication that the efficiency of rumen microbial protein synthesis could be higher if protein N is provided (Stock, Klopfenstein, Brink, Britton and Harmon, 1986). The objective of this experiment was to compare the use of urea and casein as a source of rumen degradable nitrogen (RDN) for the production of microbial protein in sheep.

Five male Blackface x Suffolk lambs (33-42 kg live weight) fitted with rumen cannula were used. The animals were fed a restricted amount (721 g DM/day) of a low-N basal diet with or without supplementation with either urea or casein.

Data reported in the literature indicate that the efficiency of microbial protein production to ruminants vary considerably, i.e. 14-49 g microbial N/kg digestible organic matter apparently fermented in the rumen (ARC, 1984). This variation could be due to the effects of several factors, e.g. different types of feeds, rumen digesta outflow rate. The present experiment was conducted to examine whether there were differences between types of carbohydrate feedstuffs, e.g. ammonia-treated straw, barley and sugar beet pulp, as energy sources for the synthesis of microbial protein in sheep.

Four Blackface x Suffolk wethers (body weight 39-42 kg) fitted with a rumen cannula were used. The animals were housed in metabolic cages and were offered 800 g/day of ammonia-treated straw (control) with or without supplementation with sugar beet pulp or barley at 20%, and 40% on fresh weight basis (SBP20, SBP40, B20 and B40 respectively). A 4 x 5 latin square design was used. The control diet also contained 20 g urea, 20 g casein, 3.4 g Na2SO4 and 10 g mineral & vitamin mixture per kg DM. Its N and ash contents were 25.6 and 74.1 g/kg DM respectively.