Essential amino acid recommendations for Isa Brown layers during peak and post peak production.

The present study was designed to re-evaluate the ideal amino acid ratios of total sulphur amino acids (TSAA), Thr, Val, Ile, Trp, and Arg relative to Lys during peak and post-peak production phases in laying hens by using seven independent amino acid assays in similar experimental setting. A total of 348 twenty wk old Isa Brown laying hens were allocated to individual battery cages. Each dietary treatment included 6 replicates with 2 single cages (2 birds) as one replicate. All diets were formulated based on maize, soybean meal, and canola meal to have identical crude protein (120 g/kg) concentrations and energy density (11.9 MJ/kg) but with 5 levels of dietary concentrations of tested amino acids. Hens were offered experimental diets from 27 to 33 wk of age in experiment 1 (Exp. 1) and from 42 to 48 wk of age in experiment 2 (Exp. 2). Daily egg production and weekly egg weights were recorded, and feed intakes were calculated for each experimental period to determine egg production rate, egg mass, and feed conversion ratio (FCR). Linear and quadratic broken line models were used to estimate amino acid requirements on egg production rate, egg mass and FCR. Overall, quadratic broken line models estimated higher amino acid requirements for egg mass, egg production rate and FCR than linear broken line models by 23, 25, and 20%, respectively. The predicted daily Lys intake recommendation was 720 mg/bird/day with linear broken line model and 897 mg/bird/day with quadratic broken line model and the recommended ideal amino acid ratios relative to Lys are 85 for TSAA, 69 for Thr, 83 for Val, 87 for Ile, 22 for Trp, and 82 for Arg based on linear broken line model and 87 for TSAA, 67 for Thr, 83 for Val, 86 for Ile, 22 for Trp, and 78 for Arg based on quadratic broken line model estimations.

Identifying the shortfalls of crude protein-reduced, wheat-based broiler diets.

The objective of this review is to identify the shortfalls of wheat-based, crude protein (CP)-reduced diets for broiler chickens as wheat is inferior to maize in this context but to inconsistent extents. Inherent factors in wheat may be compromising gut integrity; these include soluble non-starch polysaccharides (NSP), amylase trypsin inhibitors (ATI) and gluten. Soluble NSP in wheat induce increased gut viscosities, which can lead to compromised gut integrity, which is not entirely ameliorated by NSP-degrading feed enzymes. Wheat ATI probably compromise gut integrity and may also have the capacity to increase endogenous amino acid flows and decrease apparent starch and protein digestibilities. Gluten inclusions of 20 g/kg in a maize-soy diet depressed weight gain and feed intake and higher gluten inclusions have been shown to activate inflammatory cytokine-related genes in broiler chickens. Further research is required, perhaps particularly in relation to wheat ATI. The protein content of wheat is typically higher than maize; importantly, this results in higher inclusions of non-bound amino acids in CP-reduced broiler diets. These higher inclusions could trigger post-enteral amino acid imbalances, leading to the deamination of surplus amino acids and the generation of ammonia (NH3) which, if not adequately detoxified, results in compromised growth performance from NH3 overload. Thus, alternatives to non-bound amino acids to meet amino acid requirements in birds offered CP-reduced, wheat-based diets merit evaluation. The digestion of wheat starch is more rapid than that of maize starch which may be a disadvantage as the provision of some slowly digestible starch in broiler diets may enhance performance. Alternatively, slowly digestible starch may result in more de novo lipogenesis. Therefore, it may prove instructive to evaluate CP-reduced diets based on maize-wheat and/or sorghum-wheat blends rather than entirely wheat. This would reduce non-bound amino acid inclusions by lowering dietary CP derived from feed grains and may enhance starch digestive dynamics by retarding starch digestion rates. Also, the use of biomarkers to monitor gut integrity in broiler chickens is examined where calprotectin, ovotransferrin and possibly citrulline appear to hold promise, but their validation requires further research.

Dietary crude protein concentrations, feed grains, and whey protein interactively influence apparent digestibility coefficients of amino acids, protein, starch, and performance of broiler chickens.

The present study was designed to investigate the impacts of dietary crude protein (CP) concentrations (220 and 180 g/kg) in either maize- or wheat-based diets, without or with 25 g/kg inclusions of whey powder (WP) concentrate on performance parameters and apparent amino acid digestibility coefficients in broiler chickens. The maize and wheat used in this study had CP levels of 84 and 119 g/kg, respectively. The 2 × 2 × 2 factorial array of 8 dietary treatments was offered to a total of 336 off-sex, male Ross 308 chicks from 7 to 35 d post-hatch with 7 replicate cages (6 birds per cage) per treatment. A treatment interaction (P = 0.016) between dietary CP and feed grains was detected for weight gains, where birds offered 180 g/kg maize-based diets displayed a weight gain advantage of 6.74% (2,628 vs. 2,462 g/bird) compared to their wheat-based counterparts. An interaction (P = 0.022) between feed grains and whey protein was observed for FCR as the addition of WP to maize-based diets improved FCR by 3.45% (1.314 vs. 1.361), but compromised FCR in wheat-based diets by 2.98% (1.415 vs. 1.374). A treatment interaction (P = 0.038) between dietary CP and feed grains was recorded for relative abdominal fat-pad weights weight gains as birds offered 180 g/kg CP maize-based diets had 43.4% (11.17 vs. 7.79 g/kg) heavier fat-pads than their wheat-based counterparts. Following the reduction in dietary-CP, apparent amino acid digestibility coefficients were depressed to greater extents in wheat-based diets. However, significant interactions between CP and feed grains were found in 14 of the 16 amino acids assessed and significant interactions between CP and WP were observed for 15 amino acids. Maize was the more suitable feed grain in terms of weight gain and FCR in 180 g/kg CP diets despite causing greater fat deposition. The inclusion of WP in reduced-CP diets did not enhance bird performance. Data generated indicate concentrations of microbial amino acids in distal ileal digesta were depressing apparent amino acid digestibility coefficients, which was more evident in wheat-based diets. Higher gut viscosities in birds offered wheat-based diets may have facilitated the proliferation of microbiota along the small intestine.

A multivariate Box-Behnken assessment of elevated branched-chain amino acid concentrations in reduced crude protein diets offered to male broiler chickens.

In a Box-Behnken assessment of elevated branched-chain amino acids (BCAA), 13 nutritionally equivalent maize-based diets were offered to a total of 390 off-sex male Ross 308 broiler chickens from 7 to 28 days post-hatch. The BCAA concentrations investigated in reduced-crude protein diets were 12.5, 15.5, 18.3 g/kg leucine (125, 155, 183); 8.9, 10.2, 12.5 g/kg valine (89, 102, 125) and 7.2, 8.9, 10.8 g/kg isoleucine (72, 89, 109), where their relativity to 11.0 g/kg digestible lysine are shown in parentheses. Determined parameters included growth performance, relative abdominal fat-pad weights, nutrient utilisation, apparent digestibility coefficients, disappearance rates of 16 amino acids and free amino acid systemic plasma concentrations. Increasing dietary leucine linearly depressed weight gain and quadratically influenced FCR where the estimated minimum FCR of 1.418 was with 14.99 g/kg leucine. Polynomial regression analysis and surface response curves of determined parameters were generated for significant (P < 0.05) BCAA variables, based on lack of fit (P > 0.005). Quadratic and cross-product responses were observed for weight gain, FCR, AME, AMEn, N retention and apparent digestibility of 13 amino acids. Relative fat-pad weights declined linearly with increasing isoleucine and valine. The lowest N retention was estimated at a combination of 15.25 and 10.50 g/kg leucine and valine respectively whilst the highest mean digestibility coefficient (0.793) of amino acids was estimated at a combination of 15.74 and 10.47 g/kg of leucine and valine respectively. The remaining parameter minima or maxima responses were not able to be determined since they were outside the extreme BCAA treatment levels. Increasing dietary BCAA significantly increased apparent ileal digestibilities and disappearance rates of BCAA. Systemic plasma concentrations of valine increased (P < 0.001) with increasing dietary valine but leucine was not influenced (P > 0.25). Systemic plasma concentration of isoleucine was maximised (P < 0.001) only when accompanied by elevated dietary leucine. Also, dietary treatments influenced (P < 0.05) apparent disappearance rates of all the essential amino acids analysed, with the exception of methionine. Whilst overall growth performance was not disadvantaged (P > 0.10) by elevated BCAA levels, compared with 2019 Ross 308 performance objectives, polynomial regression analysis suggested both interaction and antagonism between BCAA.

Evaluation of dietary crude protein concentrations, fishmeal, and sorghum inclusions in broiler chickens offered wheat-based diet via Box-Behnken response surface design.

The objective of this study was to investigate the impacts of dietary crude protein (CP), fishmeal and sorghum on nutrient utilisation, digestibility coefficients and disappearance rates of starch and protein, amino acid concentrations in systemic plasma and their relevance to growth performance of broiler chickens using the Box-Behnken response surface design. The design consisted of three factors at three levels including dietary CP (190, 210, 230 g/kg), fishmeal (0, 50, 100 g/kg), and sorghum (0, 150, 300 g/kg). A total of 390 male, off-sex Ross 308 chicks were offered experimental diets from 14 to 35 days post-hatch. Growth performance, nutrient utilisation, starch and protein digestibilities and plasma free amino acids were determined. Dietary CP had a negative linear impact on weight gain where the transition from 230 to 190 g/kg CP increased weight gain by 9.43% (1835 versus 2008 g/bird, P = 0.006). Moreover, dietary CP linearly depressed feed intake (r = -0.486. P < 0.001). Fishmeal inclusions had negative linear impacts on weight gain (r = -0.751, P < 0.001) and feed intake (r = -0.495, P < 0.001). There was an interaction between dietary CP and fishmeal for FCR. However, growth performance was not influenced by dietary inclusions of sorghum. Total plasma amino acid concentrations were negatively related to weight gain (r = -0.519, P < 0.0001). The dietary transition from 0 to 100 g/kg fishmeal increased total amino acid concentrations in systemic plasma by 35% (771 versus 1037 µg/mL, P < 0.001). It may be deduced that optimal weight gain (2157 g/bird), optimal feed intake (3330 g/bird) and minimal FCR (1.544) were found in birds offered 190 g/kg CP diets without fishmeal inclusion, irrespective of sorghum inclusions. Both fishmeal and sorghum inclusions did not alter protein and starch digestion rate in broiler chickens; however, moderate reductions in dietary CP could advantage broiler growth performance.

Facilitating the acceptance of tangibly reduced-crude protein diets for chicken-meat production.

Inclusions of non-bound amino acids particularly methionine, lysine and threonine, together with the "ideal protein" concept have allowed nutritionists to formulate broiler diets with reduced crude protein (CP) and increased nutrient density of notionally "essential" amino acids and energy content in recent decades. However, chicken-meat production has been projected to double between now and 2050, providing incentives to reduce dietary soybean meal inclusions further by tangibly reducing dietary CP and utilising a larger array of non-bound amino acids. Whilst relatively conservative decreases in dietary CP, in the order of 20 to 30 g/kg, do not negatively impact broiler performance, further decreases in CP typically compromise broiler performance with associated increases in carcass lipid deposition. Increases in carcass lipid deposition suggest changes occur in dietary energy balance, the mechanisms of which are still not fully understood but discourage the acceptance of diets with reductions in CP. Nevertheless, the groundwork has been laid to investigate both amino acid and non-amino acid limitations and propose facilitative strategies for adoption of tangible dietary CP reductions; consequently, these aspects are considered in detail in this review. Unsurprisingly, investigations into reduced dietary CP are epitomised by variability broiler performance due to the wide range of dietary specifications used and the many variables that should, or could, be considered in formulation of experimental diets. Thus, a holistic approach encompassing many factors influencing limitations to the adoption of tangibly reduced CP diets must be considered if they are to be successful in maintaining broiler performance without increasing carcass lipid deposition.

Capping dietary starch:protein ratios in moderately reduced crude protein, wheat-based diets showed promise but further reductions generated inferior growth performance in broiler chickens.

The hypothesis that capping dietary starch:protein ratios would enhance the performance of broiler chickens offered reduced-crude protein (CP) diets was tested in this experiment. A total of 432 off-sex, male Ross 308 chicks were allocated to 7 dietary treatments from 7 to 35 d post-hatch. The experimental design consisted of a 3 × 2 factorial array of treatments with the seventh treatment serving as a positive control. Three levels of dietary CP (197.5, 180.0 and 162.5 g/kg) with either uncapped or capped dietary starch:protein ratios constituted the factorial array of treatments, whilst the positive control diet contained 215.0 g/kg CP. The positive control diet had an analysed dietary starch:protein ratio of 1.50 as opposed to a ratio of 1.68 in the uncapped 197.5 g/kg CP diet and 1.41 in the corresponding capped diet and the capped 197.5 g/kg CP diet displayed promise. The growth performance this diet matched the positive control but outperformed the uncapped 197.5 g/kg CP diet by 10.4% (2,161 vs. 1,958; P = 0.009) in weight gain, by 3.10% (3,492 vs. 3,387; P = 0.019) in feed intake on the basis of pair-wise comparisons and numerically improved FCR by 4.04% (1.616 vs. 1.684). However, the growth performance of birds offered the 180.0 and 162.5 g/kg CP dietary treatments was remarkably inferior, irrespective of dietary starch:protein ratios. This inferior growth performance was associated with poor feathering and even feather-pecking and significant linear relationships between feather scores and parameters of growth performance were observed. The amino acid profile of feathers was determined where cysteine, glutamic acid, glycine, proline and serine were dominant in a crude protein content of 931 g/kg. Presumably, the feathering issues observed were manifestations of amino acid inadequacies or imbalances in the more reduced-CP diets and consideration is given to the implications of these outcomes.

Hens ranked as highly feed efficient have an improved albumen quality profile and increased polyunsaturated fatty acids in the yolk.

The shelf life of eggs that contain elevated levels of polyunsaturated fatty acids (PUFA) is compromised due to the relative instability and therefore greater potential for lipid peroxidation of unsaturated fatty acids (FA). Poultry that is highly feed efficiency (HFE) exhibits higher systemic levels of antioxidant enzymes and therefore may produce eggs with improved albumen quality and favorable FA profiles that are stable over time. We tested the hypothesis that HFE-laying hens produce eggs with improved internal egg quality and a favorable yolk FA profile prior to and following storage. Following an initial screening phase (7 wk) using 140 Isa Brown layers (28 wk old), the 10 most efficient (FCR < 1.99 ± 0.05) and the 10 least efficient (FCR > 2.30 ± 0.05) hens were identified and designated as HFE and low feed efficiency (LFE) groups, respectively. Internal quality and composition were determined on eggs (n = 10 per group) stored at 15 °C for 0, 14, and 28 d. At 0, 14, and 28 d, the albumen weight, albumen height, Haugh unit (HU), and albumen:yolk ratio of eggs from the HFE group were significantly higher (P < 0.01), whereas the eggs from the LFE group had heavier (P < 0.01) yolk than the HFE group. After 28-d storage, the yolk color score of the LFE group was lower (paler; P < 0.05) compared with that of the HFE group. The relative proportions of total PUFA and the ratio of total PUFA and total saturated fatty acids (SFA) were higher (P < 0.05) in HFE group of eggs. The LFE group of eggs contained higher (P < 0.05) levels of lipid peroxidation marker (thiobarbituric acid reactive substances; TBARS) values both in fresh and in stored eggs. The results suggest that HFE hens produce eggs with greater albumen quality and higher levels of yolk PUFA both at lay and after storage.