An experiment was conducted to determine the effect of sorghum particle size and milling type on broiler performance and feed apparent metabolisable energy (AME). Results show that AME was improved by feeding a pelleted diet containing whole sorghum, but the best performance (lowest FCR) was elicited by feeding a rolled sorghum diet at a common commercial grind size. Feed particle size may influence the rate of excretion of different fractions of the digesta and AME of a feed. AME may not be an accurate indicator of the nutritive value of grain as the same feed can have a different AME values based on physical structure.

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.

Most work conducted to determine the effects of feed particle size on broiler performance and gut development has been done under experimental conditions in cage trials. The primary reason for this is that fibrous material (litter) may interfere with gut development and performance. This study was conducted under commercial conditions on deep litter to determine the effect of wheat as part of a commercial diet, particle size and milling type on broiler performance and gut development.

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.

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 modern broiler chicken increases its bodyweight by 5000% in the first six weeks of life. Even so, the genetic potential of the bird is ever increasing. The intensive nature of the modern broiler meat production system also potentially increases risk of transmissible diseases. Thus, the stresses on the bird's physiological systems; skeletal/muscular, digestive, immune and cardiovascular, are also increasing. Augmentation of suitable husbandry practices with appropriate nutrition will allow improved broiler production and health, by helping the birds’ physiological systems serve their respective intended purposes. That is, nutritionists need to present a feed to the broiler that more accurately meets its needs, not only on a nutritional level, but also on a physiological level, such that the bird is more able to effectively digest and absorb the feed due to improved physiological responses to the feed itself. The nutritionist can only do so much when it comes to feeding for profit. Aside from the nutritional needs of the bird, economic constraint is the largest factor that must be considered when formulating a broiler diet. It is therefore important that feed production costs are reduced, and at the other end, feed efficiency is improved, essentially enabling a more profitable product per unit cost of feed.

A trial was conducted to test the following hypothesis; broiler exposure to coarse insoluble fibre in the diet or litter will result in enhanced gizzard function and performance, improved adaptability to an intermittent feeding program and an increase in the occurrence of reverse peristalsis. Ross 308 broiler chickens were either intermittent or ad libitum fed a basal diet, a basal diet diluted with 15 % coarse hulls (barley and oats) or a basal diet diluted with 15 % finely ground hulls in a 2x3-factorial experiment (n = 17 birds/treatment). From 18 days of age, the birds were transferred to individual cages. Birds on intermittent feeding had restricted access to feed from 11 days of age. From 18 days of age, the restrictive feeding program consisted of four one-hour meals and one two-hour meal per day. AME value and faecal starch digestibility were determined by quantitative collection of excreta. At 31 and 32 days of age, birds were inoculated with CrEDTA via the cloaca. Weights were recorded and digesta samples collected from the gizzard, duodenum, jejunum, and ileum. There was no interaction between diet and feeding regime for any of the parameters measured. The addition of coarse oat and barley hulls resulted in birds with fuller, heavier gizzards (p < 0.001). Intermittently fed birds raised on the coarse hull diet exhibited an improved starch digestibility compared to birds not exposed to hulls (p < 0.001). The presence of chromium in all intestinal tract sections of birds from the six treatment groups, confirms that reflux occurs along the entire length of the gastro intestinal tract, irrespective of insoluble fiber content of the feed or feeding regime.

Individual or combined effects of xylanase and protease on nutritive value of diets containing sorghum distillers dried grains with solubles (sDDGS) and fed to broiler chickens were investigated. A total of 480 day-old male broiler chickens were assessed in a 3 x 2 x 2 (0, 150 or 300 g sDDGS/kg diet, with or without xylanase, and with or without protease) factorial design. Each of the 12 treatments was replicated 5 times accommodating 8 birds per replicate. Feed intake (FI) and body weight gain (BWG) of the birds were increased by inclusion of sDDGS to the diets independent of enzyme supplementation. Feed conversion ratio (FCR) deteriorated as sDDGS was incorporated into the diets at both levels. Regardless of sDDGS and protease, xylanase significantly improved FCR. Digestibility of protein and most amino acids were adversely affected by inclusion of 150 and 300 g/kg sDDGS. While protease, individually, improved amino acid digestibility in birds offered diets containing the highest amount of sDDGS (300 g/kg), an admixture of xylanase and protease did not result in further improvement in amino acid digestibility. Addition of xylanase reduced the concentration of insoluble non-starch polysaccharides (NSP) in the ileum. Noticeably, the response of birds to xylanase supplementation on the concentrations of arabinose, xylose and total insoluble NSP was compromised when xylanase and protease were added to the diet simultaneously. To conclude, xylanase and protease in combination were effective for the growth performance of the birds on sDDGS, in particular improving FCR.

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.

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.