Triticale is a cereal grain that holds great promise as an alternative to wheat and other conventional grains used in poultry diets. Triticale generally has a higher yield than wheat and adapts to more difficult agronomic conditions than wheat (Korver et al., 2004). A crop breeding group at the University of New England (UNE) has developed varieties that are even more high-yielding and more disease-resistant than the current commercial strains. These varieties will need further evaluation to establish their potential for animal, and particularly poultry feeding.

In the Australian sheep industry, Estimated Breeding Values (EBVs) are being increasingly used to select Merino sheep for excellence in traits such as high clean fleece weight (CFW), low fibre diameter (FD) and high yearling live weight (YLW). It has been proposed that genetic differences in CFW may be related to skin protein metabolism and that it is sensitive to the level of nutrition (Williams and Morley 1994; Liu et al. 1998). The underlying physiological responses to EBV and plane of nutrition are not well understood.

This experiment was done to investigate microbial contamination and in situ disappearance rates of dry matter (DM), N and 15N of fresh labeled ryegrass. Perennial ryegrass (Lolium perenne) were labeled with 15N during growth in a glasshouse, harvested at 4th leaves stage and were incubated up to 34 h in situ in the rumen of 3 individually housed sheep. The animals were fed 800 g/d chopped alfalfa and had free access to drinking water. Six bags were placed in the rumen of ach sheep simultaneously and removed after 0, 3, 7, 12, 21 and 33 h after incubation. The results were fitted to a model describing the degradation of DM and total N with time. It was found that residues from the washed zero time bags had lower e 15N enrichments (7.7% vs. 8.3% enriched) than the original fresh samples. Under-estimation of effective degradability (ED) of protein in fresh forages by about 4% would have potential consequences for predictions of ruminally fermentable and escape protein and thus for dietary protein feeding management. However, because the correction assumes contaminating microbial N is unlabeled, but microbes attached to labeled ryegrass would become labeled to some extent, the true error and effective degradability may still be underestimated. Studies with two markers would help us to better understand the errors associated with the in situ technique.

The kinetics of allantoin metabolism were studied in rumen-cannulated sheep by means of a single intravenous injection of [4,5-¹⁴C]allantoin. The decline in the specific radioactivity of allantoin in plasma following the injection of tracer was best described by a double exponential function, indicating that allantoin moves in and out of two or more kinetically distinct compartments. Sequestering of tracer in secondary or tertiary compartments in the body water appears likely to have resulted in overestimation of net flux of allantoin through the blood in the present study. In future studies, sampling of blood for several days after administration of tracer should alleviate this problem. About 80 % of the [¹⁴C]allantoin injected was recovered as [¹⁴C]allantoin in urine during the 12 h after tracer injection, increasing to 94 % after 4 d. Allantoin-C also passed through the blood bicarbonate pool, suggesting that allantoin is degraded in the gastrointestinal tract. A small amount of allantoin-C (4 % of the net flux of allantoin through the blood pool) was apparently degraded to form bicarbonate-C in the rumen and postruminally, and subsequently appeared in blood bicarbonate-C. Transfer of allantoin-C into the rumen via saliva was insignificant. In view of these findings, the net flux of allantoin through the blood should be a better predictor of rumen microbial outflow than urinary allantoin excretion, because urinary excretion of purine derivatives must be adjusted for conversion of allantoin-C to blood bicarbonate when used to predict the flow of microbial protein from the rumen.

Current ruminant feeding systems depend on knowledge of the composition of feeds and the rate and extent of degradation of feed organic matter (OM) and crude protein (CP) in the rumen. The effect of storage and preparation of samples on in vitro gas production and fermentation characteristics of two common forage species, namely alfalfa and rye grass were studied. Samples were prepared as fresh (F), frozen-thawed (FT) and FT + starch (FT + S) before in vitro evaluation. The fractional rate of loss of organic matter (OM) and the total N and total VFA production during 12h of incubation were significantly faster for alfalfa than for rye grass. Model parameters describing changes in OM loss and total N appearance differed significantly between F samples and FT and FT + S samples; there was a significant interaction between forage species and preparation method for fractional degradation rate of total N. A significant interaction between forage species and preparation method at 6 h incubation changed the rankings. The propionate:acetate ratios after 12 h incubation were similar for alfalfa and rye grass but were lower for F and FT samples than for FT + S samples. After 12 h of incubation, alfalfa produced more gas, total VFA (mmol/g OM) and microbial crude protein (mg/g OM) than rye grass, whereas F samples produced more fermentation products than FT and FT + S samples. In vitro degradation characteristics of forage samples were influenced by forage species, but also by sample preparation method; therefore, consistent use of one sample preparation method is recommended when comparing degradation characteristics of forage species in vitro.

Supplementing low-quality straw with protein meal, fresh tropical grass or legume forage improves dry matter intake (DMI), digestion and live weight gain in cattle (Doyle et al., 1986). Smallholder cattle farmers in Cambodia mostly use rice ('Oryza sativa') straw as a basal diet, especially during feed shortages. Supplementation of such diets with C4 grasses such as Mulato II hybrid ('Brachiaria' spp.) increases the intake and digestibility of rice straw, but mixed diets of grass and rice straw may still be deficient in rumen degradable N (RDN), especially if the grass is mature when cut. Inclusion of a tropical legume such as Stylo CIAT 184 ('Stylosanthes guianensis') as a source of RDN may further increase microbial activity and DMI. Our objective was to measure the effect of adding Stylo 184 forage to a mixed diet of rice straw and C4 grass fed to cattle in terms of DMI, digestibility, microbial crude protein (MCP) production and live weight gain.

A total of 384 day-old male Ross 308 broiler chicks were allocated to 8 dietary treatments to examine the influence of supplementation with xylanase and phytase, individually or in combination, in diets based on two new cultivars of triticale (Bogong and Canobolas). The inclusion of phytase alone in either Bogong or Canobolas diets increased (P < 0.01) feed intake and body weight; however, the effect of grain was not significant. The ileal digestibility of crude protein, gross energy, starch, calcium, and phosphorus was increased by inclusion of phytase and xylanase (P < 0.05). The interaction between xylanase and phytase positively influenced (P < 0.01) the digestibility of crude protein, gross energy, calcium, and phosphorus. Ileal viscosity was decreased (P < 0.05) by the inclusion of xylanase and phytase individually or in combination. The inclusion of phytase and xylanase increased (P < 0.001) the phytate- P degradation. Birds on Bogong-based diet had a higher (P < 0.05) degradation of phytate than those on the Canobolas-based diet. The weight of various visceral organs on day 7 was not affected by the inclusion of enzymes, nevertheless the weight of proventriculus plus gizzard was higher (P < 0.01) for chickens offered Canobolas-based than chicks on the Bogong-based diets. On day 21, the liver weight was reduced (P < 0.001) by the inclusion of phytase. An interaction (P < 0.01) between grain and phytase inclusion led to an increased weight of proventriculus plus gizzard on the Bogong diets with phytase. The inclusion of xylanase increased (P < 0.01) maltase activity at the jejunum on day 7, while it decreased the pancreatic protein content on day 21. The activity of chymotrypsin amidase was reduced (P < 0.01) by the inclusion of phytase. These results show that supplementation of phytase and xylanase to triticale-based diets can improve broiler performance by increasing the activities of some digestive enzymes and nutrient utilization.

Three experiments were conducted to investigate interactions between acetate and glucose metabolism in sheep fed on roughage-based diets, and to establish whether the clearance rate of an intravenous acetate load would provide a valid index of the dietary acetate:glucogenic precursors ratio. In Expt 1 lambs were fed on a basal diet of wheat straw and supplemented with propionate and protein. Both supplements increased glucose irreversible loss rate (ILR) although not to the same degree. Acetate clearance rates were increased by protein and propionate supplementation and were positively related to glucose ILR irrespective of precursor. In Expt 2 the effects of an increased dietary load of acetate given with or without propionate were investigated. Glucose ILR did not respond to acetate supplementation, but was increased when propionate was fed in addition to acetate. This was reflected in an unchanged ability to clear an intravenous acetate load from the blood when acetate alone was added, but an increased acetate clearance rate when propionate was fed in addition to acetate. In Expt 3 the effects of supplementation with various propionate: Acetate ratios were investigated. Acetate clearance was consistently increased by an increased propionate: Acetate ratio. These results show that the metabolism of excess acetate is responsive to the dietary supply of glucose precursors, and provide support for the concept that additional glucose precursors are necessary for the efficient utilization of acetate when roughage diets low in protein are fed.

Methane production by ruminants has been estimated by isotope dilution... As with any technique of this type, its accuracy depends on the efficient mixing of the labelled material (tracer) within the pool that is to be measured (tracee),... in the rumen. The solubility... is low and its diffusibility is high, so these properties cause difficulties not encountered with non-gaseous solutes. However, with care these problems can be minimized, and the continuous infusion...into the rumen can yield valuable measurements of methane production. The technique can be used to estimate production in the rumen by sampling the gas phase in the dorsal rumen, or alternatively total tract... production (less a small correction for methane lost from the anus) if total expired gases are collected.

This communication describes the application of calculations for estimating basal metabolic rate (BMR) and metabolisable energy requirement to sheep exposed to hot climatic conditions. Graham et al. (1974) studied animal factors that affect BMR and found that the BMR of weaned sheep of up to 27 months of age was well described by the following equation. BMR (MJ/d) = 0.257 × FW0.75exp(–0.08A) + 2.8G + 0.046DE where FW is fasted live weight (kg), A is age in years, G is growth rate (kg/d) in the 2–4 weeks before fasting and DE is intake of digestible energy (DE, MJ/d) before fasting.