Effects of L-arginine, guanidinoacetic acid and L-citrulline supplementation in reduced-protein diets on bone morphology and mineralization of laying hens

The alterations in feed ingredients and the nutrient matrix to produce reduced-protein diets may affect bone morphology and mineralization in laying hens. This study was implemented to determine the effects of L-arginine (Arg), guanidinoacetic acid (GAA), and L-citrulline (Cit) supplementation to Arg-deficient reduced-protein diets on bone morphology, strength, and mineralization status of laying hens. Individually housed Hy-Line Brown laying hens were evenly distributed to five dietary treatments with 25 replicates per treatment from 20 to 40 wk of age. Treatments consisted of a standard protein diet (17% crude protein, SP), a reduced-protein diet deficient in Arg (13% crude protein, RP), and RP supplemented with Arg (0.35% Arg, RP-Arg), GAA (0.46% GAA equivalent to 0.35% Arg, RP-GAA), or Cit (0.35% Cit equivalent to 0.35% Arg, RP-Cit) to reach the Arg level of SP diets. Birds fed the SP diet had similar bone weight, ash, length, width, Seedor index, breaking strength, and serum mineral concentration, but higher toe B level (P < 0.001) compared to those fed the RP diet at wk 40. Birds fed the SP diet consumed more but also excreted more K and B compared to those fed the RP diet (P < 0.01). Birds fed the SP diet had lower Cu digestibility (P = 0.01) and higher B retention (P < 0.01) compared to those offered the RP diet. Supplementation of Arg, GAA, and Cit to the RP diet increased relative femur weight and length (P < 0.001). Citrulline supplementation also increased relative tibia and femur ash, and Zn digestibility (P < 0.05). Supplementation of GAA to the RP diet decreased serum Ca, P, and Mg levels, decreased tibia Fe and Mg levels and toe Mg level, but increased Al, Fe, Zn, and Mn digestibility (P < 0.05). The current findings demonstrated the capacity of laying hens to adapt to low mineral intake by increasing mineral utilization. Overall, bone morphology and breaking strength, and serum mineral level in laying hens were not influenced by dietary CP levels. Dietary Arg, GAA, or Cit supplementation were effective in improving bone morphology and mineralization in laying hens fed Arg-deficient RP diets.

Feeding recycled food waste improved feed efficiency in laying hens from 24 to 43 weeks of age

There is renewed interest in utilizing food waste as animal feed due to its potential benefits in reducing feed cost and environmental impact while improving global food security. This study was conducted to examine the efficacy of recycled food waste-based feed for laying hen performance, egg quality, and nutrient digestibility. Hy-Line Brown hens (n = 150) were randomly distributed to three dietary treatments with 50 replicate cages of a single bird per treatment from 24 to 43 weeks of age. The treatments were: a standard/control feed based on wheat, sorghum, and soybean meal; a recycled food waste based-feed; and a 50:50 blend of control and food waste based-feed. Hens offered the food waste-based diets had similar egg weight, hen day egg production, and egg mass, but lower feed intake and higher feed efficiency, compared to those fed the control diets (P < 0.001). Hens fed the food waste diets exhibited lower shell breaking strength and shell thickness at week 34, and higher yolk color score and higher fat digestibility compared to the control treatment at week 43 (P < 0.001). Thus, feeding the recycled food waste based-feed maintained egg production while improving feed efficiency compared to the control feed.

Organic acid blends improve intestinal integrity, modulate short-chain fatty acids profiles and alter microbiota of broilers under necrotic enteritis challenge

Controlling enteric diseases of broilers is crucial. Among many additives, organic acids (OA) and their blends are gaining attention to combat diseases in the post-antibiotic era. The current study evaluated the potentials of short-chain fatty acids (SCFA) and medium-chain fatty acids (MCFA) blends and/or phenolic compounds on intestinal integrity, intestinal pH, caecal microbiota, and caecal SCFA profiles of broilers under necrotic enteritis (NE) challenge. The additives used were: (A) a blend of SCFA, MCFA, and a phenolic compound (SMP), (B) a blend of free and buffered SCFA with MCFA (SMF), and (C) a blend of free and buffered SCFA with a high concentration of MCFA (SHM). A total of 1,404 male parental chicks of Ross 308 broilers were randomly allocated to 78 floor pens on hatching day with 6 treatments replicated 13 times with 18 birds per pen. The treatments were: UCC, unchallenged control; CHC, challenged control; BAC, challenged group plus zinc bacitracin; SMP, challenged group plus additive SMP; SMF, challenged group plus additive SMF; SHM, challenged group plus additive SHM. Birds were challenged with field-strain Eimeria spp. on d 9 and Clostridium perfringens on d 14. Birds challenged with NE increased fluorescein isothiocyanate dextran (FITC-d) concentration in serum, reduced acetate and butyrate concentrations, and increased Bacteroides and C. perfringens load in the caeca (P < 0.05). Birds fed additives decreased FITC-d from gut to serum, reduced Bacteroides (d 16, P < 0.05) and numerically reduced C. perfringens load compared to CHC group. Birds fed additive SHM had higher concentrations of acetate and butyrate (d 21, P < 0.05) than CHC group but were not different from SMP and SMF groups. All the additives exhibited similar intestinal protection against NE compared to the BAC group indicated by FITC-d concentration in serum, acetate, propionate and butyrate concentrations in the caeca, and caecal bacterial loads except for the C. perfringens (P > 0.05). The SMP group had a higher load compared to BAC (P < 0.05). These findings suggest the promising effects of OA blends as alternatives to BAC to ameliorate the impact of NE challenge of broilers as indicated by improved intestinal health.

Sources and levels of copper affect liver copper profile, intestinal morphology and cecal microbiota population of broiler chickens fed wheat-soybean meal diets

Super dosing copper (Cu) has long been used as an alternative to antibiotic growth-promoters in broiler chickens' diet to improve gut health. This study was designed to compare nutritional and growth-promoting levels of Cu hydroxychloride (CH) with CuSO4 on gut health bio-markers and liver mineral profile of broiler chickens. Ross 308 chicks (n = 864) were randomly assigned to eight treatments, as basal diet containing no supplemental Cu; the basal diet with 15 or 200 mg/kg Cu as CuSO4; or 15, 50, 100, 150 or 200 mg/kg Cu from CH. The highest liver Cu content was observed in birds fed the diets with 200 mg/kg CuSO4 (P < 0.01). Serum FITC-d concentration as the leaky gut marker, and liver malondialdehyde concentration were not affected. Copper level or source had no effect on cecal short chain fatty acid and the mRNA expression of five jejunal genes involved in gut integrity. Negative linear responses of Cu were observed on Lactobacillus (P = 0.032), Bacteroides (P = 0.033), and Enterobacteriaceae (P = 0.028) counts. The jejunal villus height increased in birds fed CH at 200 and 100 mg/kg (P < 0.05). Increasing Cu levels, linearly and quadratically (P < 0.001), increased Cu excretion.

Effects of L-arginine and L-citrulline supplementation in reduced protein diets for broilers under normal and cyclic warm temperature

Heat stress causes significant economic losses in the broiler industry. Dietary supplementation of arginine (Arg) and citrulline (Cit) might increase the performance of broilers raised under warm temperature due to vasodilation effects. This study investigated the effects of L-Arg or L-Cit supplementation in broilers fed a reduced protein wheat-based diet deficient in Arg under thermoneutral (NT) and cyclic warm temperature (WT). Ross 308 cockerels (n = 720) were randomly allocated to 4 dietary treatments with 12 replicates of 15 birds per pen from d 7 to 21. The 4 treatments were: normal protein (NP), i.e., 22.3% and 20.9% crude protein in grower and finisher, respectively; reduced protein (RP), i.e., 2.5% lower protein and deficient in Arg; and RP supplemented with 0.28% Arg (RP-Arg) or 0.28% Cit (RP-Cit). A factorial arrangement of treatments was applied during the finisher phase (21 to 35 d). Factors were: diet (4 diets above); and temperature, NT (24 °C) or cyclic WT (33 ± 1 °C for 6 h per day) with 6 replicate pens per treatment. During 7 to 35 d and 21 to 35 d, the birds fed the RP diet had lower body weight gain (BWG) and higher FCR compared to the NP diet (P < 0.01). The addition of Arg or Cit to RP decreased FCR compared to RP (P < 0.01). During 21 to 35 d, the birds exposed to WT had lower feed intake (FI), lower BWG (P < 0.001) but similar FCR (P > 0.05) compared to birds exposed to NT. Diet by temperature interactions were not observed for performance parameters during the period of WT (P > 0.05). On d 35, the RP-fed birds had a lower yield of thigh and drumstick, higher fat pad, lower femur ash, and breaking strength but similar serum uric acid level and higher nitrogen digestibility on d 21 compared to those offered NP (P < 0.05). Supplementation of Arg or Cit to RP resulted in increased femur ash on d 35 (P < 0.05). Thus, feeding the NP diets is necessary to maintain growth performance in broilers regardless of the temperature conditions.

Black soldier fly larvae in broiler diets improve broiler performance and modulate the immune system

Non-conventional feed ingredients are receiving more interest in their ability to increase farming efficiency, sustainability and animal performance. The objective of this study was to determine the optimal rate of inclusion level of the full-fat black soldier fly larvae (BSFL) in broiler diets and to evaluate their impact on performance, nutrient digestibility, and the immune system (blood cells and intraepithelial lymphocytes). A total of 400 male day-old Ross 308 broilers were randomly assigned to 5 treatment groups with 8 replicates each. Five inclusion levels of full-fat BSFL were investigated across starter (0, 2.5%, 5%, 7.5% and 10%), grower and finisher diets (0, 5%, 10%, 15% and 20%). All diets were formulated based on digestible amino acid values according to the Aviagen (2016) recommendations. A polynomial regression at different degrees was performed to analyse broiler performance parameters (body weight, body weight gain, feed intake, and feed conversion ratio), nutrient digestibility, and blood cell count. Intraepithelial lymphocyte population data was analysed performing univariate linear regression. During the entire experimental period (from 2 to 42 d), BSFL inclusion levels decreased the feed conversion ratio by 10% in broilers that received 20% BSFL in their diets (P < 0.05). Lymphocytes and white blood cell count decreased linearly by 47.7% and 35.9%, respectively, with up to 20% BSFL inclusion (P < 0.001). A 4-fold decrease in CD3+ T lymphocytes and a 9.7-fold decrease of CD3+CD8+ intestinal cytotoxic T lymphocytes occurred in broilers fed 20% BSFL compared to the control group. These findings suggest that the inclusion of BSFL can improve broiler performance and potentially reduce immune response energy expenditure in birds fed 20% BSFL for 42 d.

Multi-carbohydrase enzymes improve feed energy in broiler diets containing standard or low crude protein

This study evaluated the effect of multi-carbohydrase (MC) on energy and nitrogen (N) balance and gene expression in broilers fed diets with different crude protein (CP) contents. The study employed a 2 × 2 factorial arrangement of treatments. The factors were presence or absence of MC, and standard (SCP) or low (LCP) dietary CP concentration. A 3-phase feeding program was used, including starter (0 to 7 d), grower (8 to 17 d) and finisher (18 to 28 d) phases. The study was undertaken in closed calorimetry chambers. Each of the 4 dietary treatments was replicated 8 times in total across 2 runs, with 2 birds per replicate (n = 64). Data for energy partitioning and N balance were collected from d 25 to 28. On d 28, birds were euthanized to collect muscle and intestinal tissue samples for gene expression. The results showed that the MC increased apparent metabolizable energy (AME, P < 0.01) and net energy (NE, P < 0.05), and reduced the feed conversion ratio (FCR, P < 0.01) in all diets. The proportion of energy retained as fat per total energy retention (REf/RE) was positively correlated with feed AME and NE (r = 0.541, P < 0.01 and r = 0.665, P < 0.001, respectively), suggesting that feed energy augmented with increased fat gain. Muscle ATP synthase subunit alpha (ATP5A1W) gene expression had a positive correlation with REf/RE and feed NE (r = 0.587, P < 0.001 and r = 0.430, P < 0.05, respectively). Similarly, muscle peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1A) expression was negatively correlated with weight gain and positively correlated with FCR (r = −0.451, P < 0.05 and r = 0.359, P < 0.05, respectively). These correlations show that over-expressions of muscle genes related to energy production reduce bird performance. This study demonstrated that MC increase dietary energy utilization, regardless of dietary CP concentration. However, the energy released by the enzymes increases feed energy-to-CP ratio, meaning there is excess energy that is then deposited as body fat. This suggests that supplemental MC in broiler feeds is beneficial if diets are formulated to contain marginal energy levels.

Response of laying hens to l-arginine, l-citrulline and guanidinoacetic acid supplementation in reduced protein diet

A study was conducted with Hy-Line Brown laying hens to examine the effects of reduced protein diet, deficiency of arginine (Arg), and addition of crystalline Arg, citrulline (Cit) and guanidinoacetic acid (GAA) as substitutes for Arg. Hen performance, egg quality, serum uric acid, liver and reproductive organ weights, and energy and protein digestibility were measured using a completely randomized design with 5 treatments. Treatments were a standard diet (17% protein diet; SP), a reduced diet (13% protein diet deficient in Arg; RP) and RP with added Arg (0.35%, RP-Arg), GAA (0.46% equivalent to 0.35% Arg, RP-GAA) or Cit (0.35%, RP-Cit) to the level of SP. It was hypothesized that performance would decrease with Arg deficient RP diet and the addition of GAA or Cit in RP would allow birds to perform similar or greater than Arg-added RP treatment. The experiment was conducted from 20 to 39 wk of age but the treatment effect was seen only after 29 wk of age. The birds offered RP had reduced egg and albumin weights (P < 0.01), lower yolk color score (P < 0.01), lower protein intake and excretion (P < 0.01) than those offered SP. When Arg or Cit were added to RP to make them equivalent to SP, feed intake (FI) and egg production were not different than those of RP (P > 0.05). The birds offered RP-GAA decreased FI and egg production (P < 0.01) compared to those offered RP. The addition of Arg, Cit or GAA to the RP had no effect on egg quality parameters, protein and energy digestibilities (P > 0.05). However, birds offered the RP-Cit diet tended to have higher Haugh unit (P = 0.095) and lower shell breaking strength (P = 0.088) compared to all other treatments while those offered RP-GAA had higher energy digestibility (P < 0.05) than all other groups but RP. The limited performance response of hens fed RP with added Arg, GAA, or Cit may be due to deficiency of some other nutrients in RP such as phenylalanine, potassium or non-essential amino acids and other components of soybean meal in the diet.

Efficacy of supplemental multi-carbohydrases in broiler diets depends on soluble arabinoxylan-to-total arabinoxylan content

1. The objective of this study was to investigate the effect of multi-carbohydrase enzymes (MC) on net energy (NE), performance and gene expression in Cobb 500 broilers fed diets containing different levels of soluble and total arabinoxylan (sAX/tAX) ratios.2. The study employed a 2 × 3 factorial arrangement of treatments, with factors including with or without MC and three ratios of sAX/tAX: high (HS, 27.3%), intermediate (IS, 21.3%) and low (LS, 15.7%).3. Six dietary treatments were formulated, with each diet replicated five times in the calorimetric study (Experiment 1) and eight times for a floor pen feeding trial (Experiment 2).4. Experiment 1 showed significant (P < 0.01) MC × sAX/tAX interactions for apparent metabolisable energy (AME) and NE. These interactions indicated that the supplemental MC increased AME only in the HS diet, and NE in the HS and LS diets.5. Experiment 2 results showed MC × sAX/tAX interactions for feed conversion ratio (FCR, P < 0.01) and ileal digesta viscosity (P < 0.05), demonstrating that MC lowered FCR only in the LS-fed birds, and reduced digesta viscosity only in the HS-fed birds. Apparent ileal digestible crude protein (AID CP) was negatively correlated with ileal digesta viscosity (r = -0.735, P < 0.001), which suggested that increasing ileal digesta viscosity reduced AID CP.6. A significant (P < 0.05) MC × sAX/tAX interaction was observed for duodenal COX III mRNA gene expression, which indicated that this gene was upregulated in the IS-fed birds relative to the HS-fed birds, but only when MC was added. This gene was downregulated (P < 0.05) in the muscle in the presence of MC application in all diets.7. The results from this study showed that supplemental MC can improve NE and FCR in birds fed diets containing the low sAX/tAX ratios.

Bacillus amyloliquefaciens CECT 5940 improves performance and gut function in broilers fed different levels of protein and/or under necrotic enteritis challenge

Two studies were conducted to investigate the effect of Bacillus amyloliquefaciens CECT 5940 (BA) as a probiotic on growth performance, amino acid digestibility and bacteria population in broiler chickens under a subclinical necrotic enteritis (NE) challenge and/or fed diets with different levels of crude protein (CP). Both studies consisted of a 2 × 2 factorial arrangement of treatments with 480 Ross 308 mix-sexed broiler chickens. In study 1, treatments included 1) NE challenge (+/-), and 2) BA (1.0 × 10⁶ CFU/g of feed) supplementation (+/-). In study 2, all birds were under NE challenge, and treatments were 1) CP level (Standard/Reduced [2% less than standard]) and 2) BA (1.0 × 10⁶ CFU/g of feed) supplementation (+/-). After inducing NE infection, blood samples were taken on d 16 for uric acid evaluation, and cecal samples were collected for bacterial enumeration. In both studies, ileal digesta was collected on d 35 for nutrient digestibility evaluation. In study 1, the NE challenge reduced body weight gain (BWG), supressed feed conversion ratio (FCR) and serum uric acid levels (P < 0.001). Supplementation of BA increased BWG (P < 0.001) and reduced FCR (P = 0.043) across dietary treatments, regardless of challenge. Bacillus (P = 0.030) and Ruminococcus (P = 0.029) genomic DNA copy numbers and concentration of butyrate (P = 0.017) were higher in birds fed the diets supplemented with BA. In study 2, reduced protein (RCP) diets decreased BWG (P = 0.010) and uric acid levels in serum (P < 0.001). Supplementation of BA improved BWG (P = 0.001) and FCR (P = 0.005) and increased Ruminococcus numbers (P = 0.018) and butyrate concentration (P = 0.033) in the ceca, regardless of dietary CP level. Further, addition of BA reduced Clostridium perfringens numbers only in birds fed with RCP diets (P = 0.039). At d 35, BA supplemented diets showed higher apparent ileal digestibility of cystine (P = 0.013), valine (P = 0.020), and lysine (P = 0.014). In conclusion, this study suggests positive effects of BA supplementation in broiler diets via modulating gut microflora and improving nutrient uptake.

Over-processed meat and bone meal and phytase effects on broilers challenged with subclinical necrotic enteritis: Part 3. Bone mineralization and litter quality

This study was conducted to determine the effect of necrotic enteritis (NE), phytase level and meat and bone meal (MBM) processing on bone mineralization of broilers and litter quality. Ross 308 male broiler chicks (n = 768) were allotted to 48 pens with 16 birds each. There were 8 dietary treatments in a 2 × 2 × 2 factorial arrangement. Factors were NE challenge (no or yes), phytase level (500 or 5,000 FTU/kg), and MBM (as-received or over-processed). Half of the birds were challenged with field strains of Eimeria spp. at d 9 and 10⁸ CFU per mL of Clostridium perfringens strain EHE-NE18 on d 14 and 15. The middle toe, tibia and femur of 2 birds per pen were excised at d 16 and 29 for determination of ash, breaking strength (BS) and bone mineralization. At d 42, all were assessed for hock burns and litter was scored and assessed for dry matter (DM). At d 16, challenged birds had lower toe ash (P < 0.01), femur ash (P < 0.001), tibia ash (P < 0.001) and tibial BS (P < 0.001) than unchallenged birds. At d 16, challenged birds fed high phytase and over-processed MBM had higher toe Mn than those fed low phytase and as-received MBM. At d 29 unchallenged birds fed high phytase and as-received MBM had a higher toe Mn than those fed over-processed MBM. At d 16, a phytase × MBM interaction was detected for femur Zn concentration (P < 0.05), where a higher level of Zn was observed in the high phytase group fed over-processed MBM. At d 16, tibial Ca (P < 0.05) and P (P < 0.05) were lower in the challenged whereas the femur K (P < 0.001), Mn (P < 0.01) and Na (P < 0.001) were higher in the challenged at d 16. At d 42, challenged birds had higher litter DM (P = 0.058) and fewer hock burns than those unchallenged (P < 0.05). In conclusion, NE impaired bone traits but high phytase and over-processed MBM increased bone mineral contents. Cases of hock burns may be lower under NE incidences due to lower livability of birds reducing litter wetness.

Peroxisome proliferator-activated receptor gamma upregulation and dietary fat levels in laying hens

The present study was conducted to investigate the effect of feeding the different levels of the dietary fat on the expression of genes encoding proteins involving energy metabolism, oxidative phosphorylation, and lipid synthesis including peroxisome proliferator-activated receptor gamma (PPARγ) of laying hens in the intestine. Birds fed diets with 3 levels of fat, that is, low (LF), medium (MF), and high fat (HF) were reared from 22 to 42 wk of age. Jejunum tissue was collected at week 42 for gene expression analysis. Dietary fat content as ether extract, net energy to AME ratio, and CP content of 3 treatment groups were as follows: LF: 25, 0.735, 187 (g/kg, DM); MF: 61, 0.739, 185 (g/kg, DM); HF: 73, 0.752, 181 (g/kg, DM). The BW, fat pad weight (g), fat pad–to–BW ratio (%) was the same for all the treatments (P > 0·05). Birds fed a diet containing HF increased the AME daily intake per metabolic BW (BW^0.75) (P < 0.05). The expression of jejunal PPARγ was increased in the birds fed MF than that fed LF (P < 0.05). Dietary fat level did not affect the expression of other genes: protein kinase AMP-activated noncatalytic subunit gamma 2, NADH dehydrogenase subunit 2, succinate dehydrogenase complex flavoprotein subunit A, ubiquinol-cytochrome c reductase Rieske iron-sulfur polypeptide 1, cytochrome c oxidase subunit III, ATP synthase subunit alpha, avian adenine nucleotide translocator, and acetyl-CoA carboxylase alpha (P > 0·05). The mitochondrial count per cell showed no difference among the 3 groups with different dietary treatments (P > 0·05). The results suggest that PPARγ may be important to the energy expenditure during nutrient absorption, digestion, and metabolism, and respiratory chain complexes, and other genes involving mitochondrial energy metabolism and lipogenesis may be less responsive to dietary treatment.

Potential of blended organic acids to improve performance and health of broilers infected with necrotic enteritis

Organic acids (OA) and their blends have been shown to positively affect performance and health of broilers. However, the data in the literature are not consistent. This study examined the potential of blended short-chain fatty acids (SCFA) with medium-chain fatty acids (MCFA) as alternatives to antibiotic growth promoters (AGP) on performance, health and welfare of broilers infected with necrotic enteritis (NE). The additives used were: A) a blend of SCFA, MCFA, and a phenolic compound (SMP); B) a blend of free and buffered SCFA with MCFA (SMF); C) a blend of free and buffered SCFA with a high concentration of MCFA (SHM). A total of 1,404 Ross 308 one-day-old male parental chicks were randomly distributed into 78-floor pens with 13 replicates of 18 birds each. Six treatments were the following: T1, unchallenged control (UCC); T2, challenged control (CHC); T3, challenged group plus zinc bacitracin (BAC); T4, challenged group plus additive SMP; T5, challenged group plus additive SMF; T6, challenged group plus additive SHM. Challenged birds were gavaged with Eimeria spp. on d 9 and Clostridium perfringens EHE-NE18 on d 14. Post NE challenge and cumulatively, BWG, FCR, and nutrient digestibility of birds were compromised (P < 0.05) by NE challenge indicating a successful induction of sub-clinical NE. Additive SHM had higher BWG compared to CHC and BAC groups (P = 0.001; d 10 to 24) but not different from SMP and SMF groups (P > 0.05). All the 3 additive groups had lower FCR compared to CHC (P = 0.001; d 0 to 35), and exhibited similar jejunal lesions (d 16) compared to BAC and apparent ileal protein digestibility (d 21) compared to UCC and BAC groups (P > 0.05). Birds in additive SHM group had a higher concentration of serum IgA compared to all groups (P = 0.001) except additive SMF (P > 0.05; d 21). All the additive groups had lower footpad dermatitis and hock burns compared to CHC (P < 0.05). The findings suggest the potential of blended OA as alternatives to BAC to protect broilers from NE indicated by improved FCR, immunity, digestibility, and bird welfare.

Response of meat chickens to different sources of arginine in low-protein diets

Arginine activity in broiler diets can be supplied by L-arginine (Arg), guanidinoacetic acid (GAA) and L-citrulline (Cit), all of which are commercially available. This study was conducted to assess the effects of Arg source and level on broiler performance, nutrient digestibility and carcass parameters. Day-old Ross 308 cockerels (n = 768) were assigned to one of eight dietary treatments using a completely randomized design: normal protein (NP), low protein deficient in Arg (LP) and LP 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 LP was 5 percentage points lower in protein level than the NP. Wheat, sorghum, soya bean meal, canola meal, and meat and bone meal-based diets were fed over three feeding phases to 6 replicate floor pens with 16 birds each. Compared to NP, birds fed LP had reduced feed intake (FI, p < 0.001), reduced body weight gain (BWG, p < 0.001) and increased feed conversion ratio (FCR, p < 0.001) from day 0 to day 35. Additions of Arg or Cit to the LP at both levels resulted in increased BWG and reduced FCR (p < 0.05). Birds fed LP with GAA added had lower FCR (p < 0.05) but not higher BWG (p > 0.05) compared with the LP observed from day 0 to day 35. Supplementation of Arg, Cit and the low level of GAA to LP resulted in increased carcass yield, bone length, diameter and ash (p < 0.05) but did not increase ileal energy or nitrogen digestibility (p > 0.05). The findings indicate that Cit is an efficacious source of Arg activity in Arg-deficient diets.

Over-processed meat and bone meal and phytase effects on broilers challenged with subclinical necrotic enteritis: Part 2. Inositol phosphate esters hydrolysis, intestinal permeability, hematology, jejunal gene expression and intestinal morphology

This study investigated the hypothesis that feeding broilers over-processed meat and bone meal (MBM) would impair gut health in the absence of phytase and in turn, affect inositol phosphate (inositol x-phosphate, IPx: IP3, IP4, IP5 and IP6) ester hydrolysis, intestinal permeability, hematology, jejunal gene expression and intestinal morphology during necrotic enteritis (NE). Ross 308 male broilers (n = 768) were assigned to one of 8 dietary treatments in a 2 × 2 × 2 factorial arrangement, with 6 replicate pens per diet and 16 birds per pen in a completely randomized design. Factors were: NE challenge (no or yes), phytase level (500 or 5,000 FTU/kg) and MBM processing (as-received or over-processed). For the NE challenge, half of the birds were challenged with field strains of Eimeria spp. on d 9 and 10⁸ CFU/mL of Clostridium perfringens strain EHE-NE18 on d 14 and 15. A 3-way challenge, phytase and MBM processing interaction was detected for IP5 (P < 0.05) and IP6 (P < 0.05) levels in the ileum. Birds fed low phytase had increased IP5 and IP6 in unchallenged birds only when diets contained over-processed MBM. Challenge with NE increased intestinal permeability as measured by serum fluorescein isothiocyanate dextran (FITC-d; P < 0.001), increased white blood cells (WBC; P < 0.001), decreased mean corpuscular volume (MCV; P < 0.001) and mean corpuscular hemoglobin (MCH; P < 0.05), and decreased crypt-to-villi ratio (P < 0.05). The over-processed MBM reduced the villi-to-crypt ratio (P < 0.05). A 3-way challenge × phytase × MBM processing interaction was detected for mucin 2 (MUC-2) expression (P < 0.05) where only in unchallenged birds fed over-processed MBM did high phytase reduce MUC-2 expression. A lower expression of aminopeptidase N (APN; P < 0.001) and vitamin D receptor (VDR; P < 0.001) were recorded in NE challenged birds. In conclusion, NE has a negative impact on the gut and hematology of broilers, but its effect on phytate hydrolysis is minimal.

Multi-carbohydrase effects on energy utilization depend on soluble non-starch polysaccharides-to-total non-starch polysaccharides in broiler diets

Non-starch polysaccharides (NSP), especially in water-soluble form, are a common anti-nutritional factor in cereal-based poultry diets. Consequently, carbohydrases are applied to diets to combat the negative effects of NSP on bird performance and health, particularly when feeding viscous grains. This study investigated the effect of supplementing multi-carbohydrases (MC) to broiler diets containing either low (LS) or high (HS) soluble NSP (sNSP) to total NSP (tNSP) ratios on energy partitioning, nitrogen (N) balance, and performance. A 2 × 2 factorial arrangement of treatments (MC, no or yes; sNSP/tNSP, LS vs. HS) was applied, resulting in 4 dietary treatments, each replicated 8 times. These treatments were fed to Ross 308 broilers in closed-circuit indirect calorimetry chambers, with 2 birds (a male and a female) per replicate chamber (n = 64). The results showed that MC addition increased AME, net energy (NE), and AME/gross energy, regardless of sNSP/tNSP content (P < 0.01 for all). There was an MC × sNSP/tNSP interaction for feed intake (FI, P < 0.05), denoting that in the absence of MC, the HS-fed birds had lower FI than LS-fed birds, but this difference was eliminated when MC was present. There were MC × sNSP/tNSP interactions observed for AME intake (AMEi) per metabolic BW (BW^0.70, P < 0.05), AMEi/N retention (Nr, P < 0.01), NE intake (NEi)/Nr (P < 0.05), retained energy (RE) as fat per total RE (REf/RE, P < 0.01), and N efficiency (Nr/N intake, P < 0.05). These interactions showed that MC application increased AMEi/BW^0.70, AMEi/Nr, NEi/Nr, and REf/RE only in the HS-fed birds, and N efficiency only in the LS-fed broilers. This study demonstrated that MC application markedly increased feed energy utilization in all diets, and increased N efficiency in birds fed an LS diet.

Interactive effect of dietary calcium and phytase on broilers challenged with subclinical necrotic enteritis: part 2. Gut permeability, phytate ester concentrations, jejunal gene expression, and intestinal morphology

Calcium has the capacity to interact with phytate-P to form Ca-phytate complexes and decrease the ability of exogenous phytase to degrade phytic acid. This study investigated the hypothesis that high dietary Ca would impair gut permeability, phytate esters (inositol x-phosphate, IPx: IP3, IP4, IP5, and IP6) degradation, jejunal gene expression, and intestinal morphology. Ross 308 day-old male broilers (n = 768) were distributed into 48-floor pens each housing 16 birds in a factorial arrangement. Factors were NE challenge-no or yes; phytase level of 500 or 1,500 FTU/kg, and Ca level 0.6 or 1.0% starter, 0.5 or 0.9% grower, 0.4 or 0.8% finisher with available P in each phase. Challenged birds were gavaged with 3 field strains of Eimeria on day 9 and 108 CFU per mL of Clostridium perfringens Strain EHE-NE18 on day 14 and day 15. A phytase × Ca interaction was observed in the ileum for IP3 (P < 0.01), IP4 (P < 0.05), and IP6 (P < 0.01). The IP3 and IP4 concentrations were similar for both doses of phytase in the presence of low Ca, but with high Ca, both increased significantly but to a greater extent when the high dose of phytase was used. While IP6 concentrations were low and similar between both doses of phytase at low Ca levels, increasing dietary Ca levels increased IP6 concentrations regardless of phytase dose, but the effect was greater in the low phytase diet. A phytase × Ca interaction was detected for vitamin D receptor (VDR) (P < 0.05) expression where bird fed low phytase and low Ca recorded the highest expression of VDR, all other treatments being equivalent. The challenge decreased crypt depth to villus height ratio (P < 0.001). Challenge birds had higher fluorescein isothiocyanate dextran (P < 0.05) in blood compared with unchallenged birds. Thus, high Ca and high phytase, while not the best for IP6 destruction, did not lead to huge reductions in indicators of gut health.

Over-processed meat and bone meal and phytase effects on broilers challenged with subclinical necrotic enteritis: Part 1. Performance, intestinal lesions and pH, bacterial counts and apparent ileal digestibility

This feeding study investigated the hypothesis that over-processing of meat and bone meal (MBM) would impair the performance, gut health and ileal digestibility of nutrients in birds challenged with necrotic enteritis (NE). The effect of phytase (500 vs. 5,000 FTU/kg) was also examined using manufacturers recommended matrix values for 500 FTU for both levels. Ross 308 male broilers (n = 768) were assigned to 8 diets, with 6 replicate pens per diet and 16 birds per replicate pen using a randomized design with a factorial arrangement of treatments. Factors were NE challenge (no or yes), MBM (as received or over-processed), and phytase level (500 or 5,000 FTU/kg). Half of the birds were challenged with 5,000 oocysts of field strains of Eimeria acervulina and Eimeria brunetti, and 2,500 oocysts of Eimeria maxima on d 9 and 108 CFU/mL of Clostridium perfringens strain EHE-NE18 on d 14 and 15 post-hatch. Challenge × MBM interactions were detected for weight gain (WG), feed conversion ratio (FCR) and feed intake (FI) at d 14, 21 and 28, showing that challenged birds fed over-processed MBM had decreased WG (P < 0.05) and FI (P < 0.05) at d 14, increased FCR (P < 0.05) at d 21 and decreased WG (P < 0.05) and FI (P > 0.05) at d 28. Birds fed low phytase had increased livability (P < 0.05) at d 42. The challenge increased the prevalence and severity of NE induced lesions in the jejunum (P < 0.05) and ileum (P < 0.05). The birds fed over-processed MBM had decreased pH in the jejunum (P < 0.05) and ileum (P < 0.05) at d 16. High phytase increased apparent ileal digestibility (AID) of Ca (P < 0.05) and P (P < 0.05), and over-processed MBM increased AID of carbon (C; P < 0.05) and Ca (P < 0.05) at d 29. The challenge increased the caecal counts of Lactobacillus spp. (P < 0.05) and C. perfringens (P < 0.05) at d 16. The results indicated that supplementation of diets with high phytase reduces the negative impact on performance from over-processed MBM during NE as a result of increased nutrient digestibility.

Interactive effect of 2 dietary calcium and phytase levels on broilers challenged with subclinical necrotic enteritis: part 1-broiler performance, gut lesions and pH, bacterial counts, and apparent ileal digestibility

This study investigated the hypothesis that high dietary calcium (Ca) would stimulate necrotic enteritis (NE) and reduce performance, gut health, and nutrient digestibility, and if increased, phytase would reduce NE. Ross 308 male broilers (n = 768) were randomly distributed to 8 treatments in a factorial arrangement. Factors were NE challenge (no or yes), phytase level (500 or 1,500 FTU/kg using 500 FTU/kg matrix values), and Ca level (0.6 or 1.0% starter, 0.5 or 0.9% grower, 0.4 or 0.8% finisher) with the same level of available P (0.40 S, 0.35 G, and 0.35 F). There were 48 pens, 16 birds per pen and 6 replications. Half of the birds were challenged with Eimeria spp on day 9 and 10⁸ CFU per mL of Clostridium perfringens strain EHE-NE18 on day 14 and 15. Gain was higher in birds fed high phytase on day 14 (P < 0.01), day 21 (P < 0.01), day 28 (P < 0.01), and day 35 (P < 0.01). Birds fed high phytase had greater livability on day 21 (P < 0.01). Ca was more digestible in high-Ca diets on day 16, and an NE × Ca interaction (P < 0.05) showed this effect to be more pronounced in unchallenged than in challenged birds. A challenge × Ca interaction for apparent ileal digestibility (AID) of crude protein (CP) (P < 0.05) indicated lower AID of CP in challenged birds fed high Ca. The challenge decreased AID of Ca (P < 0.01). Ca level had no impact on C. perfringens count, but it decreased Lactobacillus (P < 0.05) and Bifidobacteria (P < 0.05) populations in the ceca. High dietary Ca decreased feed conversion ratio. Overall (42 D), the highest WG was observed in unchallenged birds fed high Ca and high phytase with the lowest WG observed in NE-challenged birds fed low Ca and low phytase. The results suggest that full matrix values for high doses of phytase may be appropriate during NE challenge.

Volatile basic nitrogen measurement in digesta using a Berthelot reaction in automated Skalar instrumentation

The undigested nitrogenous fraction entering the hindgut of chickens is further metabolized by microbiota present producing volatile basic metabolites including amines and ammonia (NH3). Ammonia increases pH and may result in overgrowth of Clostridium perfringens further producing toxic metabolites that cause dysbacteriosis or necrotic enteritis (NE). There are few reports in chickens examining the production and concentration of nitrogenous metabolites in the hindgut. A Berthelot reaction using an automated flow, reaction and spectrophotometric instrumentation to detect volatile basic nitrogen in the form of NH3 from cecal contents was carried out. In the Berthelot reaction, NH3 in the sample is chlorinated to monochloramine using dichloroisocyanuric acid that then reacts with salicylate to form 5-aminosalicylate which is stable under alkaline conditions (pH 12 to 13). After oxidation and oxidative coupling, a coloured complex is formed that can be measured at 660 nm. Cecal contents were collected and pooled from 2 birds per pen with 48 pens total in each of 3 experiments and stored in sealed containers at -20 °C prior to analysis. Experiment 1 compared samples collected from birds fed either no meat and bone meal (MBM) or 6% MBM from d 0 to 14, and samples collected from birds fed either no MBM or 5% MBM from d 14 to 42. All birds were challenged with Eimeria on d 9 and C. perfringens on d 14 and 15. Experiment 2 compared cecal contents from birds fed either 0.5% or 0.9% calcium (Ca), and Exp. 3 compared unchallenged with NE challenge on d 16 and 29. Results demonstrated an increase (P < 0.05) in cecal NH3 as a result of feeding MBM or high dietary Ca with a corresponding increase in pH. Birds experimentally challenged with NE had lower cecal NH3 and lower pH on d 16 but not d 29 compared to unchallenged controls. It was concluded that the Berthelot method using Skalar instrumentation equipment is suitable to measure the concentration of volatile nitrogen as NH3 in cecal contents of chickens.

Influence of meat and bone meal, phytase, and antibiotics on broiler chickens challenged with subclinical necrotic enteritis: 2. intestinal permeability, organ weights, hematology, intestinal morphology, and jejunal gene expression

Undigested proteins entering the hindgut may favor the proliferation of Clostridium perfringens. Using phytase to eliminate the need for meat and bone meal (MBM) as a P source may reduce potential infection with C. perfringens. A study was conducted to determine the impact of MBM, phytase, and antibiotics (AB) on intestinal permeability and morphology, organ weights, and jejunal gene expression in Ross 308 chickens challenged with subclinical necrotic enteritis (NE). Male Ross 308-day-old chicks (672 each) were randomly allocated to 8 treatments with 6 replicate pens each housing 14 birds. A 2 × 2 × 2 factorial arrangement of treatments was used: MBM (no or yes); AB (no or yes-Zn bacitracin 100 in S and 50 ppm in G/F and salinomycin Na 60 ppm in all phases); phytase (500 or 1,500 FTU/kg, both using 500 FTU matrix values) using wheat-SBM-canola meal diets. Birds were challenged with Eimeria spp on day 9, and C. perfringens strain EHE-NE18 on day 14 and 15. An AB × MBM interaction (P < 0.05) was detected for relative gizzard weight (with contents) being lower in birds fed MBM and AB compared to those fed MBM and no AB. A MBM × AB interaction (P > 0.01) was detected for lymphocyte counts being lower with MBM and AB compared to MBM without AB. A phytase × AB interaction (P < 0.05) was observed for villi length being increased with high phytase and no AB compared to with AB. Inclusion of MBM increased (P < 0.05) blood FICT-d concentration, whereas AB decreased it (P < 0.05). Antibiotics increased RBC (P < 0.05), Hgb (P < 0.05), and PCV (P < 0.05) and expression of Ca-binding protein, CALB1 (P > 0.05). Inclusion of MBM decreased expression of MUC2 (P < 0.05). Results indicate that dietary MBM has a detrimental effect on gut health of broilers but this may be counteracted using AB.

Interactive effect of dietary calcium and phytase on broilers challenged with subclinical necrotic enteritis: 3. Serum calcium and phosphorus, and bone mineralization

Calcium is chelated by phytic acid and forms phytate-mineral complexes reducing Ca availability and the ability of phytase to hydrolyze phytate. An increased Ca concentration in the gut favors the activity of Clostridium perfringens (C. perfringens). Therefore, it was hypothesized that high dietary calcium with high dietary phytase would decrease serum Ca and P and bone mineralization during necrotic enteritis occurrence. A total of 768 one-day-old Ross 308 male chicks were randomly allocated to 8 treatments with 6 replicate pens, each housing 16 birds. A 2 × 2 × 2 factorial arrangement of treatments was applied: dietary Ca (0.6 or 1.0%), phytase (500 or 1,500 FTU/kg), and challenge (no or yes). Half of the birds (384) were challenged with Eimeria spp. on day 9 and C. perfringens strain EHE-NE18 on day 14 and 15. Blood was collected from 2 birds per pen to determine Ca, P, and parathyroid hormone in the serum. The middle toe, tibia, and femur were excised from 2 birds per pen on day 16 and 29 for determination of ash, breaking strength (BS), and mineral concentration. The challenge decreased (P < 0.05) serum Ca⁺ in birds regardless of dietary Ca level (day 16). There was a challenge × Ca interaction (P < 0.05) for tibial BS (day 16), with challenge being more severe in birds fed high Ca than low Ca diets. A challenge × phytase interaction (P < 0.05) was present for femur ash (day 16), with high phytase only increasing ash in challenged birds. The challenge decreased (P < 0.05) the BS of femur and tibia at each time point. Birds fed high dietary Ca had lower tibial Mg (P < 0.001), Fe (P < 0.001), Na (P < 0.001), and Zn (P < 0.05) concentrations (day 29). Altogether, high dietary Ca and phytase improved bone mineralization showing that attention to Ca and P nutrition and phytase matrix values is warranted when high levels of phytase are used.

Two different Clostridium perfringens strains produce different levels of necrotic enteritis in broiler chickens

Subclinical necrotic enteritis (NE) is primarily caused by the gram-positive bacterium, Clostridium perfringens (Cp). The trend towards removal of in-feed antimicrobials and subsequent increased emergence of infection in poultry has resulted in a wide interest in better understanding of the mechanism behind this disease. The virulence of NE, to a large extent, depends on the virulence of Cp strains. Thus, this study was to assess how 2 different strains of Cp affect performance and gut characteristics of broiler chickens. Ross 308 male broilers (n = 468) were assigned to a 2 × 3 factorial arrangement of treatments with antibiotics (Salinomycin at 72 ppm and zinc bacitracin at 50 ppm -, or +) and challenge (non-challenge, Cp EHE-NE18, or Cp WER-NE36). Oral administration of Eimeria oocysts (day 9) followed by inoculation with 1 mL 108 CFU Cp strains (day 14 and 15) were used to induce NE. Broiler performance was analyzed at day 10, 24, and 35. On day 16, intestinal lesion score and intestinal pH were evaluated and samples of cecal content were analyzed for bacterial counts and short-chain fatty acid concentrations (SCFA). Birds in both challenged groups showed higher feed conversion ratio (FCR), lower weight gain (P < 0.001), increased lesion scores in the jejunum (P < 0.01), and reduced pH in the ileum and cecum (P < 0.01), compared to the non-challenged birds. They also showed decreased numbers of Bacillus spp. (P < 0.001), and Ruminococcus spp. (P < 0.01) in the cecal content. On day 35, the NE36 challenged birds had a lower weight gain (P < 0.001) and higher FCR (P < 0.001) compared to the NE18 challenged birds. Interestingly, cecal Lactobacillus and lactate were increased by the NE challenge (P < 0.001), and to a greater extent in birds challenged with NE36 compared to the NE18 strain (P < 0.001). This study suggests that Cp strains varying in virulence produce different levels of disease in broiler chickens through modulating the gut environment, intestinal microbiota, and SCFA profile to different extents.

Supplementing glycine, serine, and threonine in low protein diets for meat type chickens

Reducing dietary protein has been of interest to the global poultry industry to improve bird health, welfare, and industry sustainability. Low protein (LP) diets are typically glycine (Gly) deficient and produce poor performance. Supplementing the diet with Gly or precursors of Gly can overcome this deficiency. A feeding experiment was conducted with 330 Ross 308 off-sex males across 5 treatments in a randomized design using 11 birds per pen replicated 6 times. Grower and finisher treatments were fed from day 7 to 21 and day 21 to 35, respectively. The objective was to test the efficacy of supplementation with Gly and Gly equivalents (Glyequiv), serine (Ser) and threonine (Thr), in plant-based LP diets on bird performance against a standard protein (SP) diet containing meat and bone meal. Glycine, Ser, or Thr were supplemented on Glyequiv basis to an approximately 3% lower CP diet to achieve the same digestible Gly and Ser level as the SP diet. Nitrogen efficiency, serum uric acid, blood plasma amino acids (AA) and AA digestibility were also investigated to monitor potential metabolic effects. Birds fed the LP diet were only 3.3% lower in final body weight than the SP treatment (2,556 vs. 2,641 g) while the supplementation of Gly or Ser had no effect. Supplementation of Thr reduced final body weight by 9.5% (P < 0.05). Reducing CP increased N efficiency by 9.6% (P < 0.05) and decreased blood serum uric acid by 26.9% (P < 0.001) in the finisher treatments. Glycine and Ser supplementation in LP diets had no effect on these parameters. The LP diet reduced AA digestibility and blood plasma AA while the supplementation with either Gly, Ser, or Thr increased overall AA digestibility (P < 0.05) but had no overall effect on blood plasma AA. Further research is required into Gly metabolism; however, Thr supplementation depressed growth and therefore is not feasible to cover Gly deficiency in LP diets on a Glyequiv basis.

Reducing protein and supplementing crystalline amino acids, to alter dietary amino acid profiles in birds challenged for subclinical necrotic enteritis

Necrotic enteritis (NE) is an infection of the gastrointestinal tract and is estimated to cost the global poultry industry billions of dollars annually. A study was conducted to examine whether reducing the crude protein might offset the severity of NE in broilers experimentally challenged with Eimeria spp. on day 9 and Clostridium perfringens on days 14 and 15. Furthermore, increasing the dietary amino acid (AA) density of the diet was also examined owing to identified benefits of improving performance compromised from low protein (LP) diets or NE. A 2 × 2 × 3 factorial arrangement of treatments at 6 replicates per treatment was used with 972 Ross 308 cockerels fed wheat-sorghum-soy-based diets to 35 D. Factors were NE challenge: no or yes; protein: standard (SP) or LP; and AA density: 100% AA, 115% with only essential AA (115% EAA) increased, and 115% AA with both essential and nonessential AA (115% AA) increased. The performance was measured in grower (days 7–21), finisher (days 21–35), and overall (day 7–35) periods. In addition, on day 16, intestinal lesion score and cecal short-chain fatty acids were measured. Only in nonchallenged birds fed LP diets, 115% AA increased grower feed intake (P < 0.01) and body weight gain (P < 0.05) compared to 115% EAA treatments. Challenge increased jejunal lesions (P < 0.001) with no difference between dietary treatments. Finisher body weight gain was greater in nonchallenged birds fed the 115% AA diets than in challenged birds (P < 0.05). Feeding diets with higher nonessential AA encouraged faster recovery from NE challenge. When fed the SP diets, NE challenge increased cecal butyric acid (P < 0.01) and total short-chain fatty acids (P < 0.05). The nutrient matrix used in LP diets does not favor beneficial butyric acid–producing bacteria. Using LP diets to mitigate NE severity does not offset the predisposing effect of E. spp. when attacking the gastrointestinal tract, and NE recovery is favored when feeding SP diets or additional AA.

Using crystalline amino acids to supplement broiler chicken requirements in reduced protein diets

Reducing dietary CP can reduce N pollution. Much research has been reported in corn-based diets; however, the amino acid (AA) profiles of wheat-based diets differ. Poor performance as a result of reduced protein (RP) has been overcome in corn-based diets with essential AA and glycine (Gly) supplementation. The current study examined RP levels and Gly in wheat-based diets. An industry standard protein (SP) diet plus 3 RP diets with and without Gly supplementation, to match the SP treatment at 0.713 and 0.648% digestible Gly for the grower and finisher periods respectively, were fed to male broilers from day 10 of age. Grower CP included 22.5, 20.6, 18.3, and 17.7% (days 10–21) and finisher CP included 19.7, 17.8, 16.2, and 15.5% (days 21–35). Performance, meat yield, N efficiency, water intake, and apparent ileal digestibility of N and AA were measured. No difference in body weight gain (BWG), feed intake, or feed conversion ratio (FCR) were observed at 20% CP compared to the SP treatment. However, further reducing protein reduced BWG (P < 0.001), feed intake (P < 0.001), and increased FCR (P < 0.001). Supplementation of 0.713% Gly in the grower period increased BWG (P < 0.001) and reduced FCR (P < 0.001). Relative meat yield was not affected by dietary protein, however reducing CP increased relative fat pad weight (P < 0.001). Nitrogen efficiency increased with decreased CP in both grower (R² = 0.69) and finisher (R² = 0.80) treatments. Water intake decreased (R² = 0.83) with decreasing CP intake. Apparent ileal digestibility of AA and N were higher in RP diets (P < 0.05). The benefits of reduced water intake and increased N efficiency and the disadvantages of poor performance and increased body fat in RP corn-based diets have been identified in RP wheat-based diets. Furthermore, at 18.5% CP the supplementation of crystalline AA and Gly can maintain BWG and FCR observed in SP diets.

Influence of meat and bone meal, phytase, and antibiotics on broiler chickens challenged with subclinical necrotic enteritis: 1. growth performance, intestinal pH, apparent ileal digestibility, cecal microbiota, and tibial mineralization

This study investigated the influence of meat and bone meal (MBM), phytase, and antibiotics (AB) on the performance, intestinal pH, ileal digestibility, cecal microbiota, and tibial mineralization in Ross 308 broilers challenged with necrotic enteritis (NE). A total of 672-day-old male Ross 308 chicks were allocated to 8 treatments with 6 replicate pens, with 14 birds each. The study employed a 2 × 2 × 2 factorial arrangement of treatments: MBM (no or yes), AB (no or yes, zinc bacitracin + salinomycin), and phytase level (500 or 1,500 FTU/kg; both using 500 matrix recommendations). Diets were based on wheat–soybean meal–canola meal. All birds were challenged with Eimeria spp on day 9 and Clostridium perfringens (C. perfringens) strain EHE-NE18 on day 14 and day 15. On day 21 (postchallenge), birds fed MBM had reduced weight gain (WG; P < 0.05) relative to without MBM. A 2-way phytase × AB interaction for WG on day 14 (P < 0.001) and day 21 (P < 0.001) and feed conversion ratio on day 21 (P < 0.001) and day 42 (P < 0.01) indicated positive effects of high phytase on bird performance in the presence of AB. On day 42, a 3-way MBM × phytase × AB interaction (P < 0.01) was observed for WG, showing high phytase increased WG with AB, relative to the birds without AB in the presence of MBM. A 2-way MBM × phytase interaction (P < 0.01) was observed for apparent ileal digestibility of Ca and P on day 16, whereby there was a notable reduction in Ca and P digestibility in birds fed MBM-free diets and a low phytase level, but with the high phytase level, Ca and P digestibility was not influenced by MBM. In conclusion, in NE challenged birds, high phytase has a beneficial effect on leg health and mineral utilization to the extent that it can replace MBM and has beneficial effects on bird performance in the presence of AB.

Energy efficiency and net energy prediction of feed in laying hens

Using accurate nutrient values for ingredients is of vital importance for efficient diet formulation. The net energy (NE) system accounts for the real available amount of feedstuff energy for body maintenance and production as it considers energy dissipated as heat increment. The NE content of diets for pigs and broilers has been estimated from their nutrient contents. However, such estimates have not been made specifically for laying hens. This study reports the development of equations to predict NE for laying hens based on the chemical composition of 16 different diets meeting minimum nutrient specifications but varying in nutrient composition. Heat production and energy metabolism were measured in layers ranging from 32 to 62 weeks of age in closed-circuit calorimetry chambers with 8 replicates per diet in a randomized design. Each replicate consisted of a chamber with 3 layers that were adapted for 4 D to diets and chambers prior to measurement. The measurements included feed intake, metabolizable energy (ME) content, nitrogen balance, egg production, gas exchange, heat production, energy efficiency, and energy partition for a 3-D period. The average AME/GE and NE/AME ratios of the 16 diets were 77 and 74%, respectively. The latter ratio increased with energy efficiency (EE) content and decreased with CP content of diets. The results indicate that diet NE content can be predicted from AME, CP, and EE contents and the NE/AME ratio varied positively with EE and negatively with CP. A validation experiment with 2 diets fed to layers in calorimetry chambers confirmed the estimation from NE prediction equations. In conclusion, NE of diets can be predicted in laying hens from equations based on AME and CP and EE contents in laying hens being similar to those reported in broilers.

Factors affecting energy metabolism and evaluating net energy of poultry feed

Different energy evaluating systems have been used to formulate poultry diets including digestible energy, total digestible nutrients, true metabolizable energy, apparent metabolizable energy (AME), and effective energy. The AME values of raw materials are most commonly used to formulate poultry diets. The net energy (NE) system is currently used for pig and cattle diet formulation and there is interest for its application in poultry formulation. Each energy evaluating system has some limitations. The AME system, for example, is dependent on age, species, and feed intake level. The NE system takes AME a step further and incorporates the energy lost as heat when calculating the available energy for the production of meat and eggs. The NE system is, therefore, the most accurate representation of energy available for productive purposes. The NE prediction requires the accurate measurement of the AME value of feed and also an accurate measurement of total and fasting heat production using nutritionally balanced diets. At present, there is limited information on NE values of various ingredients for poultry feed formulation. The aim of this review is to examine poultry feed energy systems with the focus on the NE system and its development for chickens.

Metabolizable energy of corn, soybean meal and wheat for laying hens

Feed formulation using apparent metabolizable energy (AME) corrected to zero nitrogen retention (AMEn) is widely used by poultry nutritionists. Most available tabulated data are from experiments using adult cockerels or growing broilers. Specific values are rarely available for laying hens. A study was conducted to evaluate AME, AMEn, and AMEs (AME adjusted to 50% nitrogen retention) of corn, soybean meal (SBM) and wheat in laying hens using the reference diet substitution and regression methods. Forty eight 42-wk-old Hy-Line Brown hens were used, 2 birds per cage with six replicates per diet. Test diets contained 30% test ingredient (as is basis) and 65.7% reference diet (as is basis) with limestone, other minerals, vitamins, and amino acids held constant across the reference and test diets. Using the reference diet substitution method, AME values obtained for corn, SBM, and wheat were 3,791, 2,621, and 3,565 kcal/kg (DM), respectively. The corresponding AMEn values were 3,722, 2,496, and 3,479 kcal/kg (DM), and AMEs were 3,784, 2,835, and 3,562 kcal/kg (DM), respectively. Calculation of AME, AMEn, and AMEs of ingredients using regression based on the inclusion rate (DM) of dietary ingredients and reference diet gave identical values to those obtained by the reference diet substitution method. In addition, the measured AMEn values of ingredients using laying hens in this study were close to those calculated from proximate composition using the European Union prediction equation based on adult cockerels.

Feed particle selection and nutrient intake altered by pecking stone consumption and beak length in free-range laying hens

The present study investigated the effects of pecking stones on feeding behaviour of hens from 16 to 46 weeks of age. Eighteen flocks of Hy-Line Brown hens were housed in 2 commercial free-range housing systems. Farm A housed 10 flocks of beak trimmed (infrared beak treatment) hens in fixed sheds. Farm B housed 8 flocks of hens with intact beaks in mobile sheds. On each farm, flocks were equally assigned to control groups (no access to pecking stones) and treatment groups (access to pecking stones). Data were evaluated every 10 weeks. At each time point, 10 hens per flock were housed in individual pens, and each hen was provided with 250 g of mash diet and ad libitum water for 24 h. After 24 h, feed samples were collected and used to determine 24-h feed intake. Nutrient and particle selection was measured by subtracting nutrients and particles present in the leftover feed from the vaules obtained in the offered feed and expressed the change (Δ). In addition, pecking stone consumption was recorded for each flock. Data were analysed separately for each farm using fixed effects of pecking stone availability and hen age. Spearman's rho correlation coefficients and linear regression models were constructed to evaluate the relationship of beak length and pecking stone usage, discrete mean particle size (dMEAN) consumption (Δ dMEAN), and Δ nutrient intake. Hens with access to pecking stones consumed significantly lower quantities of large feed particles (>2.8 mm) on farm A (P = 0.029) and selected significantly more fine particles, on farm B (P = 0.013). Overall, positive relationships (P = 0.001) between beak length and pecking stone consumption, Δ dMEAN, and Δ phosphorus consumption were observed. In conclusion, pecking stone consumption resulted in reduced selection and consumption of feed particles in hens housed on both farms. Further research is warranted to investigate the effect of pecking stones on sensory innervation of the beak.

Dietary sources and levels of selenium supplements affect growth performance, carcass yield, meat quality and tissue selenium deposition in broilers

This study examined the effects of sources and levels of selenium (Se) on performance, carcass parts yield, meat quality and tissue Se concentration in broilers. A total of 960 one-day-old male broilers were divided into 8 treatments in a 4 × 2 factorial arrangement. Chicks were penned in groups of 20 with 6 pens per group. Selenium sources were sodium selenite (SS), Se enriched yeast (SY), DL-selenomethionine (SM) and nano-selenium (NS) and dietary supplemental Se levels were 0.1 and 0.3 mg/kg diet. The average daily gain (ADG), average daily feed intake (ADFI), feed:gain ratio, mortality, and carcass parts yield were not affected by dietary treatments. The level of 0.3 mg/kg Se decreased lightness and increased yellowness of the breast and thighs (P < 0.001). Nano-selenium improved yellowness, redness and meat quality (P < 0.05). The interactive effects of sources and the levels of Se affected Se retention (P < 0.001). Inorganic Se showed poor retention compared to other sources of Se; and NS showed equal retention with the organic sources. With consideration to meat quality responses, NS had a more significant positive effect compared to SS as an inorganic source of Se. Overall, NS and organic sources of Se resulted in better meat quality compared with the inorganic source. Moreover, the highest Se retention percentage was achieved by supplementation of NS followed by organic sources at 0.1 mg/kg compared to SS.

Net energy prediction and energy efficiency of feed for broiler chickens

Global consumption of chicken meat has increased at a faster rate than any other animal protein source, and thus refinements in energy formulation techniques for feed have continued to gain importance. Formulation of animal feed based on net energy (NE) has been implemented in ruminants and pigs but not in poultry. A closed-circuit respiratory calorimetry system was employed on 25- to 28-day-old broilers fed 19 diets formulated with varying nutrient composition to produce equations to predict NE and apparent metabolizable energy (AME) efficiency of feed for broiler chickens. Performance, energy and N balance, respiratory quotient, and energy utilization were measured in the birds. Linear regression analysis was performed to generate prediction equations for dietary energy content and AME efficiency. The NE content was positively related to AME and ether extract, but negatively to crude protein. The study generated equations that can accurately predict NE, and NE/AME using AME value and chemical composition of feeds. The NE prediction equations were further validated on a separate set of diets with high correlation (r = 0.99) and accuracy. The outcomes are an important step for the broiler industry to adapt to an NE system in place of AME systems for the formulation of broiler chicken feeds following robust validation experiments.

Enzymes and/or combination of organic acid and essential oils supplementation in pasture-fed free-range laying hens increased the digestibility of nutrients and non-starch polysaccharides

Pasture intake can be a major challenge for free-ranging hens. This study was conducted to examine pasture digestion and to manage its negative effects. A total of 300 ISA Brown laying hens were used to investigate the effect of time on range (T) in short-term (6 wk) and long-term (12 wk) of 2 range types (R) (gravel vs. pasture) and dietary supplements (F) (T1 = xylanase; T2 = xylanase/beta-glucanase/pectinase/protease; T3 = xylanase/benzoic acid/essential oils) on crude protein, crude fiber, acid detergent fiber, neutral detergent fiber, non-starch polysaccharides (NSP), calcium and phosphorus digestibility, pH of the crop, and ileum digesta viscosity and morphology. Hens exposed to the range for 12 wk had lower (P < 0.05) digestibility of crude protein, insoluble rhamnose, ribose, and lower ileal pH compared to hens that ranged for 6 wk. Hens ranging on pasture had lower digestibility (P < 0.05) of crude protein, acid detergent fiber, neutral detergent fiber, insoluble arabinose, and insoluble xylose, but higher digestibility (P < 0.05) of insoluble mannose and glucose compared to hens that ranged on gravel. Hens fed T2 and T3 had higher digestibility (P < 0.05) of CP, acid detergent fiber, and neutral detergent fiber compared to hens fed T1. Hens fed T2 had higher digestibility (P < 0.05) of free oligosaccharide arabinose and xylose than those fed T1 or T3 diets. A significant interaction between T × R was detected for crude fiber digestibility and villus height. Digestibility of crude fiber was reduced and villus height was increased in hens ranged on pasture for 12 wk compared to 6 wk. An interaction between R × F was observed on phosphorus and soluble NSP digestibility (P < 0.05). Hens fed T2 and T3 diets had lower digestibility of phosphorus and NSP on gravel than on pasture. In conclusion, pasture consumption impaired the digestibility of nutrients. Supplementing free-range diets with a multi-enzyme or xylanase/benzoic acid/essential oil product reduced these negative effects and increased the ileal nutrient digestibility.

Analysis of antibody levels in egg yolk for detection of exposure to Ascaridia galli parasites in commercial laying hens

Ascaridia galli is one of the most abundant nematode parasites in poultry. A. galli infections can significantly impact the profitability of egg farms and have negative implications for bird health and welfare. The main objectives of this study were to determine whether A. galli specific antibodies in egg yolks can be used to detect prior or current exposure to A. galli in laying hens, and to distinguish between eggs obtained from caged and free-range hens. Twenty-two laying hen flocks from different production systems (10 free-range, 2 barn-housed, and 9 caged flocks) were enrolled in the study. An in-house enzyme-linked immunosorbent assay was used to analyze levels of A. galli specific antibodies in yolk. The numbers of A. galli eggs in hen excreta were also determined in a subset of farms. Free-range flocks had higher and also more variable levels of anti-A. galli antibodies in the egg yolk compared to those of the cage flocks (0.50 ± 0.39 vs. 0.16 ± 0.13 OD units) (P < 0.001). Results also confirmed that excreta from free-range and barn-housed flocks contained higher numbers of A. galli eggs than did excreta from caged flocks in which no A. galli eggs were detected. In conclusion, analysis of anti-A. galli antibodies in the egg yolk can be used to detect worm exposure in commercial layer flocks. However, the method used in this study cannot be used in isolation to distinguish between eggs from cage and free-range production systems as anti-A galli antibodies were detected in egg yolk samples from all production systems, and the range of antibody levels overlapped between production systems.

Influence of trace mineral sources on broiler performance, lymphoid organ weights, apparent digestibility, and bone mineralization

This experiment was conducted to examine the effect of trace mineral sources on broiler performance, carcass composition, trace mineral digestibility, and tibia bone quality of broiler chickens. A total of 480 Ross 308 male day-old chicks were allocated to 24 pens and assigned to 4 dietary treatments in a completely randomized design. Treatments were as follows: inorganic (I) was basal diet supplemented with 750 g/t inorganic trace mineral premix; organic 1 (O1) and organic 2 (O2) was basal diet supplemented with 375 and 500 g/t organic yeast proteinate trace mineral premix respectively; and hydroxychloride (H) was basal diet supplemented with 1000 g/t salt encrusted trace mineral premix. On day 25, no differences in feed intake (FI), body weight gain (BWG), feed conversion ratio (FCR), or livability (LV) were observed between treatments (P > 0.05). On day 38 birds fed O1 and H had higher weight gain (P < 0.05) and lower FCR (P < 0.001) relative to I. Mineral sources had no impact on FI or LV (P > 0.05) on day 38. Spleen percentage of body weight on day 25 was increased in birds fed O1 and H treatments (P < 0.05) over the I treatment. Mineral sources had no effect on relative weights of thymus or bursa of Fabricius on day 25, or bone quality and carcass composition on day 39 (P > 0.05). Apparent digestibilities of Cu and Zn were greater in birds fed yeast proteinated trace minerals compared to other sources.

Dietary L-glutamine supplementation improves growth performance, gut morphology, and serum biochemical indices of broiler chickens during necrotic enteritis challenge

Necrotic enteritis (NE) causes significant economic losses in the broiler chicken industry, especially in birds raised without in-feed antibiotics. L-glutamine (Gln) is an amino acid that may compensate for metabolic losses from infection and improve the intestinal development. This study investigated the effects of dietary Gln (10 g/kg) supplementation on growth performance, intestinal lesions, jejunum morphology, and serum biochemical indices of broiler chickens during NE challenge. The study employed a factorial arrangement of treatments with factors: NE challenge, no or yes; dietary Gln inclusion, 0 g/kg in starter (S), d 0 to 10, grower (G) d 10 to 24, and finisher (F) d 24 to 35; 10 g/kg in S, G, F, or 10 g/kg in S, G only. Each treatment was replicated in 6 floor pens with 17 birds per pen as the experimental unit for performance and 2 birds for other measurements. Challenge significantly reduced bird performance, increased incidence of intestinal lesions, and affected intestinal development and serum biochemical indices. Regardless of challenge, Gln supplementation increased gain (P < 0.05), feed intake (P < 0.05), and decreased FCR (P < 0.05) on d 24. On d 35, Gln improved gain (P < 0.05) and FCR (P < 0.001) whereas withdrawing Gln from finisher tended to diminish the beneficial effect on weight gain but not FCR. Dietary Gln reduced lesion scores in the jejunum (P < 0.01) and ileum (P < 0.01) in challenged birds. On d 16, Gln increased villus height to crypt depth ratio in unchallenged birds (P < 0.05) and reduced crypt depth of challenged birds on d 24 (P < 0.05). Regardless of challenge, supplementation with Gln reduced crypt depth on d 16 (P < 0.05), and increased villus height (P < 0.01) and the villus height to crypt depth ratio (P < 0.001) on d 24. Dietary Gln lowered serum uric acid level regardless of challenge (P < 0.05). The current study indicates that dietary Gln alleviates adverse effects of NE and may be useful in antibiotic-free diets.

Dietary energy, digestible lysine, and available phosphorus levels affect growth performance, carcass traits, and amino acid digestibility of broilers

A 3-factor, 3-level Box-Behnken design was used to investigate the interaction effect of dietary digestible lysine (dLys, 9.5, 10.5, 11.5 g/kg), apparent metabolizable energy (AMEn, 12.77, 13.19, 13.61 MJ/kg) and available P (avP, 3.0, 4.0, 5.0 g/kg) levels on performance and amino acid (AA) digestibility of Ross 308 male broilers (n = 1,050) from d 14 to 34. The design consisted of 15 treatments each replicated 5 times with 12 birds per replicate. On d 34, 3 birds were sampled from each pen to collect ileal digesta (pooled per pen) to analyze AA. Response surface was fitted by first-, second-, or third-degree polynomial regressions in JMP statistical software v. 12.0.1. Feed intake (FI), weight gain (WG) and feed conversion ratio (FCR) were affected by dLys (linear and quadratic, P < 0.01), AMEn (linear, P < 0.01) and AMEn × avP (P < 0.01). Increased dLys increased FI but increased AMEn decreased FI in the birds fed the low-avP diet. However, when the avP level in the diet was increased, FI decreased to 13 MJ/kg AMEn and remained constant thereafter. Increased dLys increased WG whereas an increase in AMEn decreased WG in the birds fed the low-avP diet but had no effect on WG in those fed the high-avP diet. Increased dLys decreased FCR whereas increased AMEn decreased FCR in the birds fed the low-avP diet but had no effect on FCR in those fed the high-avP diet. Increased dLys increased breast yield percentage (linear, P < 0.01 and quadratic, P < 0.05) whereas increased AMEn decreased breast yield percentage (linear, P < 0.01). Dietary levels of dLys or avP had positive, linear effects on apparent ileal digestibility (AID) of methionine (P < 0.01) and threonine (P < 0.01) but had no effect on other AA (P > 0.05). These results indicate that increasing dLys levels above current industry standard would improve broiler performance irrespective of AMEn or avP levels of the diet.

Necrotic enteritis challenge and high dietary sodium level affect odorant composition or emission from broilers

Necrotic enteritis (NE) challenge and high dietary sodium (from sodium chloride) level on odor flux from broiler litter was investigated using 160 day-old Ross 308 male chicks randomly assigned to 4 dietary treatments with 4 replicates of 10 birds each. A 2 × 2 factorial arrangement of treatments was employed. Factors were: presence or absence of NE challenge and normal (1.6 g/kg) or high (4.0 g/kg) dietary sodium (Na) level. On d 20, odorants were collected from litter headspace with a flux hood and measured using selected ion flow tube mass spectrometry (SIFT-MS). On d 33, while challenge did not lead to higher mortality, it reduced feed intake by 5.48% (P < 0.05) and body weight gain by 9.02% (P < 0.01) and worsened FCR by 5 points (P < 0.01), indicating subclinical necrotic enteritis occurred in challenged birds. Challenge increased (P < 0.01) litter moisture and litter headspace concentrations of dimethyl sulfide (P < 0.05), propyl mercaptan (P < 0.05), total butanols (P < 0.05), acetoin (P < 0.01), skatole (P = 0.05), butyric acid (P < 0.05), and methyl amine (P < 0.05) and tended to increase concentrations of ethyl mercaptan (P = 0.07), carbon disulfide (P = 0.09), indole (P = 0.10), and formic acid (P = 0.10) compared to the unchallenged group. The birds fed a high Na diet produced higher litter moisture (P < 0.01) and higher litter headspace concentration of sulfur compounds and phenol (P < 0.01) compared to those fed a normal Na diet. In the birds fed a high Na diet, challenge increased the litter flux of some additional odorants, which included 2,3-butanedione (P < 0.05), acetic acid (P < 0.01), propionic acid (P < 0.01), isobutyric acid (P < 0.01), isovaleric acid (P < 0.01), pentanoic acid (P < 0.05), 2-butanone (P < 0.05), and 3-methyl-1-butanol (P < 0.05). These findings suggest that both a high Na diet and sub-clinical NE increase the odor nuisance potential of broiler farms.

Potential of pelleted wheat straw as an alternative bedding material for broilers

Broiler chickens are commonly placed on wood shavings as litter, but alternative litter sources are required due to the scarcity of wood shavings in many parts of the world. This study aimed to compare pelleted straw, chopped wheat straw, wood shavings, rice hulls, and shredded paper as litter candidates. Three-hundred-sixty Ross 308 one-day-old male chicks were used in this study. There were 5 litter treatments with 6 replicate pens, each with 12 birds. The feed conversion ratio (FCR) of birds reared on pelleted straw was improved compared (P < 0.05) to that of birds raised on rice hulls, whereas it did not differ for birds placed on wood shavings, rice hulls, chopped straw, or shredded paper. It was observed that the birds reared on wood shavings had higher relative gizzard weight at d 24 compared to those reared on pelleted straw (P < 0.05). Gizzard pH and measured cecal bacterial groups were not affected by the type of bedding material. Cecal bacterial groups measured at d 10 were not affected by bedding material. Birds reared on pelleted wheat straw had a lower incidence of footpad lesions than those on chopped straw and shredded paper on d 24 (P < 0.001) and 29 (P < 0.01). Litter source did not affect the occurrence of breast blisters at d 24, 29, or 35. On d 24, 29, and 35, pelleted straw litter was less caked than chopped straw and shredded paper (P < 0.001) whereas no significant differences were observed among pelleted straw, wood shavings, and rice hulls. The study demonstrated the potential benefits to using pelleted wheat straw as a bedding material. Further assessment of pelleting of wheat straw and other materials on broiler health, performance, and welfare are needed to determine the economic benefits of pelleted litter.

Effect of elevated dietary amino acid levels in high canola meal diets on productive traits and cecal microbiota population of broiler chickens in a pair-feeding study

A pair-feeding study was conducted to determine if reduced feed intake (FI) in broiler chickens fed high canola meal (CM) diets per se accounts for reduced growth performance and whether this lower growth rate can be mitigated by increasing dietary amino acid (AA) levels. Five experimental wheat-based diets were formulated as follows: soybean meal (SBM) diet, high CM diet with normal AA concentration, and high CM diets with 3, 6, or 9% additional AA concentration (Lys, Met+Cys, Thr, Ile, Arg, and Val). Another group of birds was pair-fed with SBM diet to the consumption levels of birds fed CM diet with normal AA. There were 6 replicates of 17 male 10-day-old Ross 308 chicks per treatment over grower and finisher periods. Birds fed the CM diets had reduced FI and BWG, but improved FCR (P < 0.01) compared to SBM ad libitum fed birds. The SBM pair-fed birds gained the same weight and exhibited similar FCR compared to CM fed birds. Additional 9% AA improved FCR (P < 0.01) compared to SBM and CM diets with normal AA. No significant differences were observed in ileal digestibility of DM, energy, crude protein, and AA between CM with normal AA and SBM diets. The additional 6 and 9% AA in CM diets increased digestibility of crude protein and some AA (P < 0.05). SBM ad libitum and CM + 6 and 9% AA fed birds had the highest and lowest relative weight of abdominal fat, respectively (P < 0.05). Addition of 6 and 9% AA in CM diets increased relative carcass and breast yields (P < 0.01). Serum triglyceride level was higher in SBM ad libitum fed birds (P < 0.05). The composition of microbiota in the ceca was not affected by treatments. This study showed that reduced growth of birds fed high CM diets is primarily mediated through reduced FI. This growth depression could partially be ameliorated by increasing dietary AA levels.