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This thesis examined the efficacy of several alternative feed additives in enhancing performance and enteric health in broilers in the absence of antibiotics. Chapter 1 provides background information, leading to the objectives of conducting the experimental studies. This is followed by a review of literature in Chapter 2, covering the general characteristics of the gastrointestinal tract, gut microflora and the factors affecting gut health. The review also covers enteric diseases, namely necrotic enteritis, factors predisposing birds to necrotic enteritis and methods of controlling it.

Chapter 3 evaluates the efficacy of yeast cell wall extract derived from Saccharomyces cerevisiae as a replacement for zinc bacitracin and the anticoccidial ionophore salinomycin, using an established necrotic enteritis challenge model. The results showed that weight gain, feed intake and livability of challenged birds were lower than for unchallenged birds on d 24 and 35 (P < 0.05). All of the additives had a greater positive impact on weight gain, feed intake and livability in challenged compared to unchallenged birds. Birds given zinc bacitracin, yeast cell wall extract or salinomycin significantly improved in weight gain and livability when compared to control birds given no additives. Challenged birds fed yeast cell wall extract exhibited decreased crypt depth, increased villus height and increased villus to crypt ratio.

Chapter 4 investigates whether acetylated high amylose maize starch or butyralated high amylose maize starch play a positive role in digestion in broiler chickens and particularly in ameliorating the severity of necrotic enteritis in broilers under experimental disease challenge. The results showed that on d 24 and 35, all challenged birds had lower (P < 0.001) livability, weight gain and feed intake compared to unchallenged birds. Birds fed acetylated high amylose maize starch and butyralated high amylose maize starch diets had higher (P < 0.001) weight gain and feed intake compared with those fed the control diet. Birds fed acetylated or butyralated high amylose maize starch diets had poorer (P < 0.002) feed conversion ratio at d 35. Butyralated high amylose maize starch increased jejunal villus to crypt ratios, ileal and caecal butyrate levels and decreased caecal pH. Acetylated high amylose maize starch significantly improved ileal acetate content and decreased caecal pH.

Chapter 5 determines the efficacy of acylated starches on performance, heat production and energy efficiency of broiler chickens during an induced outbreak of necrotic enteritis. The data demonstrate that Eimeria sp. and Clostridium perfringens challenge reduces growth performance, heat production, respiratory quotient, heat increment, metabolisable energy and metabolisable energy intake of birds fed the control, acetylated or butyralated high amylose maize starch. However, birds fed antibiotics exhibited nearly total resistance to the challenge with necrotic enteritis.

Chapter 6 describes the effect of encapsulated sodium butyrate on growth performance and gut health in broilers fed wheat or corn based diets, at normal or high protein levels and normal or low energy levels. The inclusion of encapsulated sodium butyrate at 1 g/kg had no effect on growth performance, ileal and caecal pH and levels of SCFAs, but increasing the inclusion rate to 2 g/kg improved bird performance.

Chapter 7 discusses the major findings on the effects of some feed additives, namely microencapsulated sodium butyrate, yeast cell wall extract and acylated starches, on broiler chickens production and gut health, and the role of yeast cell wall extract and acylated starches in ameliorating the severity of necrotic enteritis in broilers under experimental disease challenge. In conclusion, necrotic enteritis is characterized by necrosis and inflammation of the gastrointestinal tract with a significant decline in growth performance. However, yeast cell wall extract and acylated starches can be used as tools for reducing the severity of necrotic enteritis outbreaks.

The series of experiments reported in this thesis suggests that the yeast cell wall extract consists mainly of mannano-oligosaccharides, butyralated starch and acylated starch products are able to partially ameliorate the impact of necrotic enteritis in broiler chickens by improving gut health, but are unable to replace antibiotics in terms of effectiveness against severe challenges. Further studies are required to investigate the modes of action of these feed additives in improving gut health and reducing the severity of necrotic enteritis.

Five industry-relevant animal experiments were completed to investigate amino acid supplementation in reduced protein diets and the impacts on meat-chicken performance, metabolism, and physiology. Specifically, the role of the non-essential amino acid glycine in reduced protein wheat-based diets was investigated. This work was developed in response of increasing expenses and environmental impacts associated with current dietary crude protein levels in broiler diets, however, reducing the crude protein and supplementing all assumed essential nutrients typically results in impaired performance. The work completed in this thesis contributes to our understanding of broiler amino acid requirements in reduced protein wheatbased diets.

The first experiment investigated the role of the non-essential amino acid, glycine, in broiler performance when fed reduced protein wheat-based diets. An industry-standard protein diet and three reduced protein diets with and without glycine supplementation were fed to Ross 308 cockerels. Glycine was supplemented to equal that in the standard protein diet at 0.712 and 0.648% in grower and finisher diets respectively. Performance, water intake, and amino acid digestibility were measured. Reducing crude protein reduced body weight gain by up to 18% and reduced water intake by 28%. However, supplementing glycine in reduced protein diets restored the impaired performance and increased water intake. Supplementing crystalline amino acids in reduced protein diets increased their respective apparent ileal digestibility, with the greatest difference in threonine digestibility increasing by up to 8.3 percentage points. When feeding reduced protein wheat-based diets, supplementing crystalline amino acids, including glycine, can maintain performance like that observed in standard protein diets.

A second experiment was completed to determine if supplementing glycine precursors have the same effect on performance as glycine in reduced protein diets. Ross 308 cockerels were fed one of two protein levels; an industry-standard protein diet with meat and bone meal or a plant-based diet approximately 3% lower in crude protein. In the reduced protein diet, glycine, serine, and threonine were assigned a glycine equivalence and supplemented to match the glycine in the standard protein diet at 1.558 and 1.390% in grower and finisher diets respectively. Reducing the dietary protein by 3% reduced feed efficiency by 10-points, however, the supplementation of glycine or serine did not restore performance. Threonine supplementation further reduced body weight gain in reduced protein diets by 6.8%. Therefore, glycine did not appear to be limiting in the reduced protein diet investigated, however, using threonine to supplement glycine requirements exacerbated the performance reducing effects of reduced protein diets.

A third experiment explored the effects of different crude protein diets and the supplementation of glycine precursors on the in vivo synthesis of glycine. To investigate this, a second glycine equivalence level was added to the reduced protein treatments described above at 1.8% giving a total of eight treatments. Using these treatments, the effects of reduced protein diets on glycine and uric acid metabolism was investigated. The in vivo conversion of serine and threonine to glycine was evident in the blood plasma, however, reducing dietary protein reduced blood serum uric acid. The expression of hepatic genes for enzymes associated with threonine degradation to glycine, glycine degradation, and uric acid-synthesis were downregulated in reduced protein diets. No effect of crude protein or supplementing different glycine precursors at differing levels was observed on the expression of the enzyme associated with the interconversion of glycine and serine. The supplementation of excess essential amino acids and non-specific nitrogen may not fulfil the non-essential amino acid requirements for efficient growth as the in vivo synthesis of non-essential amino acids is altered in reduced protein diets.

A fourth experiment investigated the differences in performance when increasing both the essential and non-essential amino acid densities by 15% in reduced protein diets. Ross 308 cockerels were fed one of three protein levels; standard, reduced, or low protein, with one of three amino acid profiles using AMINOChick®2.0 (Evonik Animal Nutrition, 2016) software recommendations; 100% amino acids (100% AA), 115% essential amino acids (115% EAA), or 115% amino acids (115% AA). In this experiment, glycine was considered an essential amino acid and formulated to 1.6% glycine equivalence. Performance, nitrogen digestibility, and blood parameters were measured. No significant difference was observed between feeding 100% AA and 115% EAA treatments at each protein level in body weight gain. However, feeding 115% AA increased body weight gain in standard and low protein diets by up to 18.7%. Blood parameters indicated reduced uric acid synthesis in low crude protein diets, despite glycine supplementation. Feeding 115% AA in the standard and low protein treatments increased nitrogen digestibility compared to the other amino acid profiles. The results from this study indicate that non-essential amino acids play key roles in growth and development that cannot be overcome with extra essential amino acid supplementation.

Finally, a fifth experiment assessed the efficacy of low protein diets and increasing amino acid densities by 15% on mitigating the effects of sub-clinical necrotic enteritis. To investigate this, the standard and low protein treatments and the 100% AA, 115% EAA, and 115% AA profiles of the previous experiment were used in birds either challenged or not with sub-clinical necrotic enteritis. Ross 308 cockerels were fed one of six dietary treatments across 12 replicates. Six replicates per treatment were challenged with sub-clinical necrotic enteritis using Eimeria spp. and Clostridium perfringens. Differences in bird performance between those fed the standard and low protein diets were not apparent in challenged birds. Feeding diets with 115% AA increased body weight gain after the challenge by 10.5%. As evident from the finisher body weight gain, regardless of amino acid profile, low protein diets delayed recovery. However, in standard protein diets, feeding 115% AA increased body weight gain by 16.7%. These results suggest reducing crude protein may not mitigate the effects of sub-clinical necrotic enteritis, however, increasing both essential and non-essential amino acids will assist with recovery.

The work completed has been highly industry-relevant and has highlighted the complex relationships between amino acids and the effects they have on meat-chicken performance, metabolism, and physiology. The Australian chicken meat industry now has a dataset of Australian diets for assessment to consider implementing reduced protein diets to improve industry sustainability and access potential diet cost savings .

The application of ultraviolet (UV) light in poultry production is garnering increased interest with the drive toward improved poultry welfare and optimized production. Poultry can see in the UV spectrum (UVA wavelengths: 320-400 nm) thus inclusion of these shorter wavelengths may be viewed as more natural but are typically excluded in conventional artificial lights. Furthermore, UVB wavelengths (280-315) have physiological impact through stimulation of vitamin D pathways that can then improve skeletal health. However, better understanding of the effects of UV supplementation must occur before implementation practically. This non-systematic literature review aimed to summarize the impacts of UV supplementation on the behavior, welfare, and production of laying hens, meat chickens (breeders and growers), and other domestic poultry species including directions for future research. The literature demonstrated that UVA light has positive impacts on reducing fear and stress responses but in some research, it significantly increases feather pecking over age during the production phase. UVB light will significantly improve skeletal health, but an optimum duration of exposure is necessary to get this benefit. Supplementation with UVB light may have more distinct impacts on egg production and eggshell quality when hens are experiencing a dietary vitamin D3 deficiency, or if they are at the terminal end of production. The relative benefits of UVB supplementation across different ages needs to be further verified along with commercial trials to confirm beneficial or detrimental impacts of adding UVA wavelengths. Further research is warranted to determine whether adding natural light wavelengths to indoor poultry production is indeed a positive step toward optimizing commercial housing systems.

A trial was conducted to determine if full matrix values for phytase alone or in combination with xylanase and beta-glucanase (XB) were appropriate across multiple inclusion levels and combinations. It may be concluded that these matrix values are appropriate, with birds offered diets containing either phytase alone or in combination with XB overall generating a similar or improved performance than those offered control diets.

Artificial gut models including both the gastric and intestinal phases have been used in poultry research for decades to predict the digestibility of nutrients, the efficacy of feed enzymes and additives, and caecal fermentation. However, the models used in the past are static and cannot be used to predict interactions between the feed, gut environment and microbiome. It is imperative that a standard artificial gut model for poultry is established, to enable these interactions to be examined without continual reliance on animals. To ensure the validity of an artificial model, it should be validated with in vivo studies. This review describes current practices in the use of artificial guts in research, their importance in poultry nutrition studies and highlights an opportunity to develop a dynamic gut model for poultry to reduce the number of in vivo experiments.

Poor feed efficiency (FE) in hens impacts body weight (BW) and may reflect suboptimal health. Fatty Liver Haemorrhagic Syndrome (FLHS) is mostly observed in laying hens and affects egg production and hen performance. The aim of this study was to investigate the relationships of FE and BW with organ characteristics, liver composition and incidence of FLHS of 150 individually housed ISA Brown hens ranked on the basis of feed conversion ratio (FCR) attained from early lay. At 45 weeks, 10 birds per FE group (HFE-High feed efficient; MFE-medium feed efficient; LFE-low feed efficient) were randomly selected and euthanized. Hen BW was positively associated with feed intake and FCR. The HFE hens had a lower abdominal fat pad and liver weight compared to LFE hens. FLHS lesion score was higher (worse) in the LFE than HFE hen group and was moderately positively associated with BW and abdominal fat pad, but strongly positively associated with liver weight. Liver pathology of LFE hens showed hepatocytes with abnormal retention of lipids causing distended cytoplasmic vacuoles compared to the HFE hens. Hens which exhibited poorer FE in early lay had heavier abdominal fat pads, heavier, fatter livers and were more prone to FLHS.

Nigerian indigenous chickens (NICs) have undergone several years of natural selection and still maintain their natural behavioural repertoire close to that of the red jungle fowl. The three common genotypes of the NICs are normal, frizzle and naked neck, with the normal feather closest to the red jungle fowl and consisting of >90% of the population. Currently, there is scanty information on the behaviour of NIC. This review will focus on various behaviours of NICs such as feeding/foraging, sexual, nesting, egg-laying, brooding, maternal care, vocalization, and sleeping. Special behavioural cases such as cock-hen preference and mixed brooding are also discussed. We also present here for the first time some preliminary vocalization characteristics of NICs. Comparisons of the behaviours of NICs, their ancestor red jungle fowl, and other native chickens are also made. The information obtained from this review will help chicken farmers to manage their birds better. Also, information obtained from this review contributes to the field of chicken behavioural science, since behaviours are linked with welfare issues in chickens.

Context. Mineralisation of the bone matrix is a pivotal factor affecting bone strength in broilers. Reduced bone strength might cause fracture during catching and transportation to slaughterhouses, leading to economic loss. Aims. This study was conducted to investigate the effects of L-arginine (Arg), guanidinoacetic acid (GAA), and L-citrulline (Cit) supplementation to Arg-deficient reduced protein diets on bone mineral composition and mineral digestibility of broiler chickens. Methods. Day-old Ross 308 males were allocated to one of eight dietary treatments with six replicates of 16 birds per treatment. The treatments were standard protein (SP), reduced protein deficient in Arg (RP), and RP with two levels of either Arg (0.238% and 0.476%), GAA (0.309% and 0.618%) or Cit (0.238% and 0.476%). The difference in crude protein content between RP and SP was five percentage points. Key results. Birds fed the RP diet had higher ileal digestibility of P, Na, Mg, S, Al, Fe, Cu and Zn than did those fed the SP on Day 23 (P < 0.01). Supplementation of both Arg, GAA and Cit to the RP reduced Mg digestibility on Day 23 (P < 0.001). The tibia and femur Ca and P concentrations were not different among the dietary treatments on either Day 23 or Day 35 (P > 0.05). Birds fed the RP had lower tibia and femur B concentrations and higher tibia and femur Zn concentrations on Day 23 and Day 35 and higher tibia and femur Mn concentrations on Day 35 than did those fed the SP (P < 0.01). Supplementation of Arg at the high level and Cit at both levels to the RP increased tibia S concentration on Day 23 (P < 0.001). Supplementation of Arg, Cit and GAA to the RP decreased femur Zn concentration on Day 35 (P < 0.001). Supplementation of GAA at the high level decreased concentrations of the tibia and femur B and Fe on Day 23, but increased tibia and femur Mn concentrations on Day 23 and Day 35 (P < 0.01). Conclusions. The findings indicated an increased mineral digestibility but relatively similar bone mineral concentrations in broilers fed the RP diets when compared with the SP diets. Implications. The results of the current study may provide useful information on the bird bone mineralisation and help expand the adoption of reduced-protein diets in the poultry industry.

This study was conducted to examine the efficacy of a bromelain-based supplementation coded ANR-pf on growth performance and intestinal lesion of broiler chickens under necrotic enteritis (NE) challenge. A total of 540 Ross 308 day-old male chicks were randomly allocated into 6 treatments of 6 replicates. The bromelain formulation was delivered to chickens through gavaging or in drinking water method twice, on d 8 and 13. Nonchallenged groups included 1) without or 2) with the specific bromelain formulation gavaged at 0.8 mL/kg. NE-challenged groups included 3) without the specific bromelain formulation; 4) gavaged with 0.4 mL/kg; 5) gavaged with 0.8 mL/kg and 6) supplemented with 0.8 mL/kg via drinking water. Birds were challenged with Eimeria spp. on d 9 and Clostridium perfringens (NE-18 strain) on d 14 and 15. On d 14 and 19, fresh faecal contents were collected for the determination of oocyst counts. Intestinal lesion scores were determined on d16. Performance and mortality were recorded throughout the entire experiment. Among challenged groups, birds received additive via drinking water had higher weight gain (WG ) compared to the remaining groups (P <0.001) in the grower phase and had lower FCR compared to 0.4 mL/kg inoculated group in the grower and finisher phases (P <0.001). Bromelain supplementation via drinking water improved the WG of challenged birds, similar to that of the nonchallenged birds (P <0.001), and lowered FCR compared to other challenged groups (P <0.001). Nonchallenged birds and birds that received bromelain formulation in drinking water did not have lesions throughout the small intestine whereas challenged birds, either un-supplemented or supplemented with bromelain via inoculation route recorded similar lesion score levels in the jejunum. At d 19, birds received bromelain in drinking water had lower fecal oocyst numbers compared to challenged birds without additive (P <0.001). In conclusion, bromelain administration via drinking water could ameliorate the negative impacts of NE-infection in broilers by improving performance, lowering the oocyst numbers and lesion scores.

The objective of this study was to evaluate the effect of 2 different doses of a partially buffered formic acid product (Amasil NA; 61% formic acid, 20.5% sodium formate), and a monoglyceride blend of short- and medium-chain fatty acids (BalanGut LS P) on necrotic enteritis (NE) infected broilers in terms of performance, intestinal microbial population and shortchain fatty acids concentrations in the gastrointestinal tract. A total of 528-day-old as hatched Ross 308 broilers were allocated to 48 pens with 11 birds in each pen. Six dietary treatments applied in the study were: T1) nonsupplemented diet (Control); T2) antibiotic supplemented diets; T3) and T4) high (Starter: 0.5%; Grower and Finisher: 0.5%) and low (Starter: 0.3%; Grower and Finisher: 0.2%) dose of Amasil NA; and groups T5) and T6) high (Starter: 0.3%; Grower and Finisher: 0.2%) and low dose (Starter: 0.3%; Grower: 0.15%; Finisher: 0.075%) of (BalanGut LS P). All birds in this study were fed starter (d 0-10), grower (d 11−24) and finisher (d 25−35) diets and challenged with NE. To induce subclinical NE, oral administrations of Eimeria oocysts (d 9) followed by inoculation of Clostridium perfringens strains (d 14 and 15) were applied. Results showed that birds fed the high dose of Amasil NA, had a higher feed conversion ratio (FCR, P < 0.05) compared to the nonsupplemented group during the starter period. Antibiotic supplementation reduced FCR during the grower (P < 0.001), finisher (P < 0.05) and overall (P < 0.001) periods of the experiment. Both levels of BalanGut LS P and low levels of Amasil NA enhanced overall FCR (P < 0.05) compared to the birds in the nonsupplemented group. Compared to the nonsupplemented group, high levels of Amasil NA and low levels of BalanGut LS P improved FCR in the finisher stage (P < 0.05). On d 16, cecum digesta of birds fed with antibiotic supplemented diets showed a significantly lower number of C. perfringens (P < 0.001) compared to the nonsupplemented and high level of BalanGut LS P group. Bacillus (P < 0.01) and Ruminococcus numbers were significantly lower in the birds fed with high level of Amasil NA (P < 0.05) compared to the antibiotic supplemented diets. High doses of Amasil NA, showed the highest propionate concentration in the cecum (P < 0.001). The study suggests that supplementation of BalanGut LS P and Amasil NA at different feeding phases may achieve optimal performance improvement in broilers under NE challenge.

It has been proposed that terminology on commercially available eggs can impact the manner in which the eggs are discussed and ultimately consumer support. In this paper we tested if the label of 'furnished cage' eggs is a barrier for its support in Australia. Furthermore, we examined if educational interventions could change support and the way furnished cages were discussed. Survey participants (n = 1,157) were recruited by a stratified random sample of Australian adults. The participants were surveyed on their demographics, attitudes toward the poultry industry and animal welfare, and their egg buying behavior. Participants were randomly assigned to one of four treatment groups" two control groups and two educational groups. Participants were shown one of three videos, the control groups were shown a video with general information about chickens, the educated groups were shown one of two almost identical videos that educated them on aspects of the egg-laying industry in Australia, and the welfare implications of different housing systems including furnished systems. The only difference between the two educational videos was the name given to the furnished housing system" one group was introduced to furnished cages, the other was introduced to furnished coops. Educated participants were more likely to support furnished eggs and discuss them more positively than the control groups. When asked to discuss their support for furnished systems, control group participants exposed to the term cage were more likely to discuss the impacts of caged environments than the other treatment groups. The study suggests any negative impacts of housing system terminology can be mitigated through educational interventions.