Meat chickens fed a high protein diet produce increased levels of putrefactive metabolites in the caeca such as ammonia, amines, phenols, indoles, skatole, cresol and branched chain fatty acids (reviewed by Qaisrani et al., 2015). Some of these metabolites are toxic and odorous (Mackie et al., 1998). A low protein diet formulated to provide all the required amino acids without excesses may reduce putrefaction and therefore the production of toxic and odorous metabolites in the hindgut and litter. This study was conducted to investigate the effect of a low protein diet on odorous metabolites emitted from litter.

This case study reports the outcome of an extreme overconsumption of pasture by free-range laying birds. It outlines the consequences of malnutrition due to animal behavior and housing condition in free-range laying hens, such as increased mortality and morbidity, leading to reduced animal welfare outcomes and compromised bird performance. This paper suggests a number of practical solutions and outlines the significance of future studies on fibre intake in free range birds.

Soybean meal and meat and bone meal are the primary protein meals used in poultry diets. The high cost of soybean meal and nutrient variability of meat and bone meal suggests the industry needs to reduce protein meal dependence. High dietary protein is also associated with high water consumption, having a negative impact on litter quality and bird health (Alleman and Leclercq, 1997). The poultry industry currently supplements diets with methionine, lysine and threonine to reduce some dependence on protein meals. There is evidence that the supplementation of glycine in poultry diets can improve performance in low protein diets (Dean et al., 2006). Glycine is involved in a diverse range of metabolic pathways, including synthesis of proteins and purines. Although glycine is categorized as a non-essential amino acid, it may become limiting under certain circumstances (Corzo et al., 2004).

Wheat is a common raw material in Australian broiler diets because of its high starch and protein content. However, the main concern with wheat is the presence of soluble non starch polysaccharides (NSPs), especially arabinoxylans. Arabinoxylans may account for up to 61 g/kg of wheat dry matter (Choct and Annison, 1990). These NSPs are difficult to digest and may cause digesta to become viscous thereby reducing nutrient digestion and absorption. Many NSP degrading enzyme products are commercially available and are used in the poultry feed industry. This study was undertaken to compare the effect of different enzymes preparations on in vitro viscosity of different wheat varieties.

The objective of this study was to investigate the effect of processing conditions and chemical composition on ileal digestible energy (IDE), AME, and AMEn of 6 expeller-extracted canola meal (ECM) samples subjected to conditioning temperature at 90, 95, or 100°C and high or low screw torque over the second presses in a 3 x 2 factorial arrangement. The ECM samples were incorporated into a corn-soybean meal reference diet at 30% by replacing energy-yielding ingredients. A total of 210 one-day-old male broiler chicks (Ross 308) were fed common starter and grower diets until d 18, and then assigned to 7 experimental diets replicated 6 times, with 5 chicks per cage. After a 5-d diet acclimation period from d 18 to 22, excreta was collected for 72 h. The difference method was used to determine AME, which was corrected to zero N balance to obtain AMEn. Medium seed conditioning temperature resulted in the highest IDE, AME, and AMEn compared with low or high temperature, and high screw torque resulted in higher energy utilization compared with low torque (P < 0.001).

Ascaridia galli is one of the most prevalent helminths in free-range laying hens. This study was conducted to establish a reliable infection model for A. galli in laying hens. Materials and methods : A total of 20 Lohmann brown hens of 19 weeks age were assigned to 4 treatment groups (n=5 per group). Hens of group 1 were orally inoculated with 1000 A. galli eggs stored at 26°C, group 2 with 1000 A. galli eggs stored at 4°C and transferred to 26°C prior to inoculation. Hens were infected 3 times over a week period. Hens of group 3 were orally inoculated with 500 A. galli eggs stored at 26°C, 6 times over 2 week period. Hens in group 4 were infected with adult A. galli via cloaca. Intestinal immature worms were counted from 2 hens from each group after slaughter at 2 weeks post infection (p.i).Excreta was collected and analysed for A. galli eggs at 8 and 14 weeks p.i.. Blood was collected to examine A. galli specific antibodies and intestinal A. galli worms were counted at 16 weeks p.i. results: Hens in group 3 had the highest A. galli worm counts (P<0.001) after slaughter at 16 weeks p.i. compared to other groups. Excreta A. galli egg counts were highest in group 1 and 3 (P=0.02). Serum antibodies among the 3 orally infected groups was similar, but were higher than in hens of group 4 (P<0.01). conclusion: Thus, The method either of inoculating hens orally with 500 A. galli eggs 6 times over 2 weeks period, or with 1000 A. galli eggs 3 times over a week period was the most reliable method tested.

The effect of dietary crude protein (CP) and additives on odor flux from meat chicken litter was investigated using 180 day-old Ross 308 male chicks randomly allocated to five dietary treatments with three replicates of 12 birds each. A 5 x 3 factorial arrangement of treatments was employed. Factors were: diet (low CP, high CP, high CP+antibiotic, high CP+probiotic, high CP+saponin) and age (15, 29, 35 days). The antibiotic used was Zn bacitracin, the probiotic was a blend of three 'Bacillus subtilis' strains and the saponin came from a blend of 'Yucca' and 'Quillaja'. Odorants were collected from litter headspace with a flux hood and measured using selective ion flow tube mass spectrometry (SIFT-MS). Litter moisture, water activity (Aw), and litter headspace odorant concentrations were correlated. The results showed that low CP group produced lower flux of dimethyl amine, trimethyl amine, H2S, NH3, and phenol in litter compared to high CP group (P < 0.05). Similarly, high CP+probiotic group produced lower flux of H2S (P < 0.05) and high CP+saponin group produced lower flux of trimethylamine and phenol in litter compared to high CP group (P < 0.05). The dietary treatments tended (P = 0.065) to have higher flux of methanethiol in high CP group compared to others. There was a diet x age interaction for litter flux of diacetyl, 3-hydroxy-2-butanone (acetoin), 3-methyl-1-butanol, 3-methylbutanal, ethanethiol, propionic acid, and hexane (P < 0.05). Concentrations of diacetyl, acetoin, propionic acid, and hexane in litter were higher from low CP group compared to all other treatments on d 35 (P < 0.05) but not on d 15 and 29. A high litter moisture increased water activity (P < 0.01) and favored the emissions of methyl mercaptan, hydrogen sulfide, dimethyl sulfide, ammonia, trimethyl amine, phenol, indole, and 3-methylindole over others. Thus, the low CP diet, 'Bacillus subtilis' based probiotic and the blend of 'Yucca/Quillaja' saponin were effective in reducing the emissions of some key odorants from meat chicken litter.

Four experiments were conducted to assess the effects of processing conditions on nutritional value of expeller-extracted canola meal (ECM) and the replacement value of expeller and cold-pressed canola meals in broiler chicken diets. The first two experiments evaluated and characterized the effect of processing conditions such as conditioning temperature (90, 95 or 100 °C) and screw torque (high or low) during oil extraction process on apparent metabolizable energy (AME), apparent and standardised ileal digestibility of amino acids of ECM for broiler chickens. The values obtained in these two experiments were used to formulate diets with high inclusion of ECM to investigate the effect of a microbial multi-carbohydrase obtained by fermentation from 'Aspergillus aculeatus' (Ronozyme® VP), and a microbial mono-component protease (Ronozyme® ProAct), in diets on productive traits, nutrient digestibility and partitioning of energy in broiler chickens. The fourth experiment was designed to determine if reduced feed intake of birds fed CM-based diets, per se accounts for growth depression and if this retarded growth rate can be attenuated by increasing dietary digestible amino acid levels of the diet.

Necrotic enteritis (NE) is an important poultry disease that is currently controlled by the use of in-feed antibiotics in many countries, including Australia. The general public demands clean and green poultry products that require the discontinuation of the use of antibiotics in feed. To achieve this goal, the broiler chicken industry must address the impact of NE without the reliance on in-feed antibiotics. The current thesis has examined a variety of nutritional strategies to minimise the impact of NE in broiler chickens using a subclinical NE model.
Chapter 1 presents the summary of literature related to NE with particular emphasis on the role of nutritional tools in alleviating losses associated with NE outbreaks. Chapter 2 examined the effect of early feeding a high amino acid density diet on performance of broilers under NE challenge. Birds fed the high amino acid diet had greater body weight by d 35 and heightened Lactobacillus content in the ileum at d 16 (P < 0.05). Birds that were fed the high amino acid (HAA) diet after a period of fasting post-hatch performed better regarding feed conversion ratio (FCR) performance under challenge. The findings from this study suggest there are beneficial effects of feeding high amino acid diets to birds in response to external stresses, such as post-hatch fasting and subclinical NE.
Chapter 3 investigated the effect of the reintroduction of crude ileal and caecal contents from previously NE-challenged chickens on performance, mortality and intestinal lesions of young broilers under NE challenge. Cloacal administration of both ileal and caecal crude flora inoculants significantly (P < 0.05) improved feed conversion efficiency and alleviated (P = 0.049) the severity of NE-associated lesions at d35. These preliminary findings suggest that the gut microbiome of birds plays a significant role in the susceptibility of broilers to NE.
Chapter 4 examined the prebiotic properties of arabinoxylo-oligosaccharides (AXOS) produced both in situ and in vitro for their activity against the onset of necrotic enteritis in broiler chickens. Birds fed the AXOS diet had numerically less severe gross lesions, improved feed conversion at d0-16 (P=0.043) and lower ileal viscosity (P < 0.001) at d16 compared to birds fed intact arabinoxylans. Caecal short-chain fatty acid (SCFA) concentration was higher in birds fed AXOS compared to other diets and was higher in the challenged birds compared to the unchallenged birds. The results suggest that AXOS appear to be efficacious prebiotics, as highlighted by improvements in feed conversion ratio (FCR) and increased SCFA.
Chapter 5 explored whether supplementing diets with xylanase, pectinase and protease would alleviate the effects of key predisposing factors of NE, xylans (from cereals), pectic polysaccharides (from vegetable protein sources) and undigestible proteins on bird performance, caecal volatile fatty acid concentration and ileal pH and prevalence of intestinal lesions, in NE challenged birds. The protease enabled higher weight gain compared to that fed xylanase at d0-35 (P=0.040) and d0-24 in the unchallenged birds (P<0.001). Feed intake was higher at d0-35 (P=0.001), and d0-24 (P=0.011) in birds fed protease, resulting in better feed conversion (P=0.009) in birds fed xylanase compared to that fed protease. Findings from this study suggest that enzyme application can be used as a tool to reduce the amount of undigested nutrients reaching the hindgut and hence lessen the growth of pathogenic bacteria.
Chapter 6 examined the effects of arabinoxylan (AX) and AXOS on net energy and nutrient utilisation in broilers. Ileal dry matter digestibility was higher in birds fed AXOS compared to that fed AX (P=0.047). Ileal digestible energy and total tract dry matter digestibility was higher in birds fed AXOS compared to that fed AX or AX+E (P=0.004 and P=0.001, respectively). Birds fed AXOS had higher ME intake (P=0.049) and nitrogen retention (P=0.001) and a strong trend of higher NE (P=0.056), NE intake (P=0.057) and retained energy (P=0.054) compared to that fed AX. Total ileal SCFA concentration, including lactic and formic acid, was higher in birds fed AXOS compared to that fed AX (P=0.011, P=0.012 and P=0.023, respectively). These findings indicate that AXOS generation in the gastrointestinal tract via the use of enzymes is not as efficient as feeding AXOS directly.