The effects of light intensity during rearing and beak trimming and dietary fiber sources on the incidence of cannibalism were investigated with 2,880 ISA Brown hens. During the rearing period, chicks were housed under two levels of light: dim light (i. e., 5 lx) and bright light (i. e., 60 to 80 lx) and two beak conditions: with or without trimming. At 15 wk of age, all birds were transferred to laying cages with five birds per cage. At 17 wk of age, four diets containing different concentrations of dietary fiber were offered: a commercial (wheat) diet, high insoluble fiber (millrun) diet, high soluble fiber (barley) diet, and high soluble fiber diet plus enzyme. Beak trimming had a profound effect (P < 0.001) on cannibalism with mortality occurring predominantly in untrimmed birds. Total mortality for the trimmed birds was 0.14 and 0.77% for the prelay (17 to 20 wk) and early lay periods (21 to 24 wk), whereas mortality was 13.4 and 37.7%, respectively, for the untrimmed birds. The beak-trimmed birds had lower feed intake than the nontrimmed birds (P < 0.05). Diet significantly affected cannibalism (P < 0.01). The highest mortality occurred in birds fed the commercial diet (13 and 29% for the prelay and early lay period, respectively). Diet also affected feed intake (P < 0.05), being lower (P < 0.05) on the commercial diet than on the higher fiber diets. Egg production per bird did not differ significantly between diets. Light intensity during rearing did not influence the incidence of cannibalism.

Inclusion of nitrate (NO₃⁻) in ruminant diets is a means of increasing non-protein nitrogen intake while at the same time reducing emissions of enteric methane (CH₄) and, in Australia, gaining carbon credits. Rumen microorganisms contain intracellular enzymes that use hydrogen (H₂) released during fermentation to reduce NO₃⁻ to nitrite (NO₂⁻), and then reduce the resulting NO₂⁻ to ammonia or gaseous intermediates such as nitrous oxide (N₂O) and nitric oxide (NO). This diversion of H2 reduces CH₄ formation in the rumen. If NO₂⁻ accumulates in the rumen, it may inhibit growth of methanogens and other microorganisms and this may further reduce CH4 production, but also lower feed digestibility. If NO₂⁻ is absorbed and enters red blood cells, methaemoglobin is formed and this lowers the oxygen-carrying capacity of the blood. Nitric oxide produced from absorbed NO₂⁻ reduces blood pressure, which, together with the effects of methaemoglobin, can, at times, lead to extreme hypoxia and death. Nitric oxide, which can be formed in the gut as well as in tissues, has a variety of physiological effects, e.g. it reduces primary rumen contractions and slows passage of digesta, potentially limiting feed intake. It is important to find management strategies that minimise the accumulation of NO₂⁻; these include slowing the rate of presentation of NO₃⁻ to rumen microbes or increasing the rate of removal of NO₂⁻, or both. The rate of reduction of NO₃⁻ to NO₂⁻ depends on the level of NO₃⁻ in feed and its ingestion rate, which is related to the animal's feeding behaviour. After NO₃⁻ is ingested, its peak concentration in the rumen depends on its rate of solubilisation. Once in solution, NO₃⁻ is imported by bacteria and protozoa and quickly reduced to NO₂⁻. One management option is to encapsulate the NO₃⁻ supplement to lower its solubility. Acclimating animals to NO₃⁻ is an established management strategy that appears to limit NO₂⁻ accumulation in the rumen by increasing microbial nitrite reductase activity more than nitrate reductase activity; however, it does not guarantee complete protection from NO₂⁻ poisoning. Adding concentrates into nitrate-containing diets also helps reduce the risk of poisoning and inclusion of microbial cultures with enhanced NO₂⁻ - reducing properties is another potential management option. A further possibility is to inhibit NO₂⁻ absorption. Animals differ in their tolerance to NO₃⁻ supplementation, so there may be opportunities for breeding animals more tolerant of dietary NO₃⁻. Our review aims to integrate current knowledge of microbial processes responsible for accumulation of NO₂⁻ in rumen fluid and to identify management options that could minimise the risks of NO₂⁻ poisoning while reducing methane emissions and maintaining or enhancing livestock production.

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.

Nitrate (NO₃¯) is an effective non‐protein nitrogen source for gut microbes and reduces enteric methane (CH₄) production in ruminants. Nitrate is reduced to ammonia by rumen bacteria with nitrite (NO₂¯) produced as an intermediate. The absorption of NO₂¯ can cause methaemoglobinaemia in ruminants. Metabolism of NO₃¯ and NO₂¯ in blood and animal tissues forms nitric oxide (NO) which has profound physiological effects in ruminants and has been shown to increase glucose uptake and insulin secretion in rodents and humans. We hypothesized that absorption of small quantities of NO₂¯ resulting from a low‐risk dose of dietary NO₃¯ will increase insulin sensitivity (SI) and glucose uptake in sheep. We evaluated the effect of feeding sheep with a diet supplemented with 18 g NO₃¯/kg DM or urea (Ur) isonitrogenously to NO₃¯, on insulin and glucose dynamics. A glucose tolerance test using an intravenous bolus of 1 ml/kg LW of 24% (w/v) glucose was conducted in twenty sheep, with 10 sheep receiving 1.8% supplementary NO₃¯ and 10 receiving supplementary urea isonitrogenously to NO₃¯. The MINMOD model used plasma glucose and insulin concentrations to estimate basal plasma insulin (Ib) and basal glucose concentration (Gb), insulin sensitivity (SI), glucose effectiveness (SG), acute insulin response (AIRg) and disposition index (DI). Nitrate supplementation had no effect on Ib (p > .05). The decrease in blood glucose occurred at the same rate in both dietary treatments (SG; p = .60), and there was no effect of NO³¯ on either Gb, SI, AIRg or DI. This experiment found that the insulin dynamics assessed using the MINMOD model were not affected by NO₃¯ administered to fasted sheep at a low dose of 1.8% NO₃¯ in the diet.

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.

We discovered that a food aversion could be conditioned in anesthetized sheep. Sheep were allowed to eat a familiar food (alfalfa-grain pellets) for 30 min, and 90 min later they were given either an intraruminal (IR) injection of water (C), an IR injection of LiCl (L), anesthesia followed by an IR injection of water (A), or anesthesia followed by an IR injection of LiCl (A+L). Induction of anesthesia was by an intraveneous injection of pentobarbitone sodium, and maintenance of deep anesthesia was by halothane. Sheep were maintained in deep anesthesia for 2 h to ensure that the effects of LiCl on the acquisition of a food aversion, which occur within about 1 h, were completed before they awakened. When tested 5 days later, sheep that received LiCl (treatments L and A+L) consumed less alfalfa-grain pellets than sheep that did not receive LiCl (treatments C and A) (241 g vs. 306 g; p = 0.057). Intake of sheep that were anesthetized (treatments A and A+L) did not differ from that of sheep that were not anesthetized (treatments C and L) (295 g vs. 252 g; p = 0.183). Nor was there an interaction between LiCl and anesthesia (p = 0.423). Thus, we conclude that changes in preferences for foods caused by postingestive feedback occur automatically every time food is ingested (i.e., they are noncognitive), and the kind and amount of feedback is a function of the match between the food's chemical characteristics and its ability to meet the animal's current demands for nutrients.

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.