Effect of varying dietary crude protein and metabolizable energy levels on leg abnormalities and performance in broiler chickens

Background: Nutrient restriction is a common strategy to prevent metabolic disorders in fast growing broiler chickens, but limited information is available regarding the impact of diets with low protein and energy on leg abnormalities Objective: Two experiments were conducted to evaluate the effect of varying crude protein (CP) and metabolizable energy (ME) levels on gastrocnemius tendon (GTeBS) and tibia breaking strength (TiBS), gait score (GS) and valgus/varus angulation (VAng). Methods: In Experiment 1, eight-d-old Ross 308 broilers (n=90) were randomly assigned into three treatments: 13/2,900 (13% CP and 2,900 kcal ME kg-1 of diet), 17/3,000 (17% CP and 3,000 kcal ME kg-1 of diet), and 21/3,025 or control (21% CP and 3,025 kcal ME kg-1 of diet). In Experiment 2, six-d-old Ross 308 chickens (n=192) were randomly distributed into two treatments: 16/3,000; 16% CP and 3,000 kcal ME kg-1 of diet and 21/3,000 or control; 21% CP and 3,000 kcal ME kg-1 of diet. In both experiments data were analyzed as one-way ANOVA. Results: In Experiment 1, broilers in the 17/3,000 and control treatments had similar (p>0.05) GTeBS (202 and 224 N, respectively), and TiBS (338 and 332 N, respectively). Birds in the 13/2,900 treatment showed higher GS (lower walking ability; 80% of birds with score >3), and greater VAng (53% of birds with score >2) than broilers in the control treatment (0% of birds with GS score >3 and 0% of birds with VAng score >2). Experiment 2, broilers in the 16/3,000 showed similar VAng, GS and TiBS than birds in the control treatment. However, birds in the 16/3,000 treatment showed lower (-26%) GTeBS than birds in the control treatment (p<0.05). Conclusions: Feeding broilers with 16% CP and 3,000 kcal ME kg-1 of diet did not affect tibia breaking strength, gait score and valgus/varus angulation. A diet containing 16% CP or less and 2,900-3,000 kcal ME kg-1 reduces tendon and tibia breaking strength.

Antecedentes: La restricción de nutrientes es una estrategia común para prevenir trastornos metabólicos en pollos de engorde, sin embargo, se dispone de información limitada sobre el impacto de las dietas bajas en proteína y energía en las anomalías de piernas. Objetivo: Se llevaron a cabo dos experimentos para evaluar el efecto de niveles variables de proteína cruda (PC) y energía metabolizable (EM) en la fuerza de rotura del tendón del gastrocnemio (GTeBS) y tibia (TiBS), la evaluación de marcha (GS) y la angulación en valgus/varus (VAng). Métodos: En el Experimento 1, pollos de engorde Ross 308 de ocho días de edad (n = 90) se asignaron al azar en tres tratamientos: 13/2.900; 13% PC y 2.900 kcal ME kg-1 de dieta, 17/3.000; 17% PC y 3.000 kcal ME kg-1 de dieta y 21/3.025 o control; 21% PC y 3.025 kcal ME kg-1 de dieta. En el Experimento 2, pollos Ross 308 de seis días de edad (n = 192) se distribuyeron aleatoriamente en dos tratamientos: 16/3.000; 16% PC y 3.000 kcal ME kg-1 de dieta y 21/3.000 o control; 21% PC y 3.000 kcal ME kg-1 de dieta. En ambos experimentos los datos se analizaron como ANOVA de una vía. Resultados: En el Experimento 1, los pollos de los tratamientos 17/3.000 y control tuvieron GTeBS (202 y 224 N, respectivamente) y TiBS (338 y 332 N, respectivamente) similares (p>0,05). Las aves del tratamiento 13/2.900 mostraron mayor GS (menor capacidad para caminar; 80% de las aves con puntaje >3) y mayor VAng (53% de las aves con puntaje >2) que los pollos del tratamiento control (0% de aves con un puntaje GS >3 y 0% de aves con un puntaje VAng >2). En el Experimento 2, los pollos del 16/3.000 mostraron VAng, GS y TiBS similares a los de las aves del tratamiento control. Sin embargo, las aves del tratamiento 16/3.000 mostraron menor (-26%) GTeBS que las aves control (p<0,05). Conclusiones: La alimentación de pollos de engorde con 16% PC y 3.000 kcal EM kg-1 de dieta no afecta la resistencia a la ruptura de la tibia, la marcha y la angulación valgus/varus. La dieta formulada con 16% de PC o menos y 2.900-3.000 kcal de EM kg-1 reduce la resistencia a la ruptura del tendón y de la tibia.

Antecedentes: A restrição de nutrientes é uma estratégia comum para prevenir distúrbios metabólicos em frangos de corte, no entanto, há informações limitadas disponíveis sobre o impacto de dietas de baixa proteína e baixa energia nas anormalidades de pernas destas aves. Objetivo: Dois experimentos foram realizados para avaliar o efeito de diferentes níveis de proteína bruta (PB) e energia metabolizável (EM) em força de ruptura do tendão do músculo gastrocnêmio (GTeBS), forca de ruptura da tíbia (TiBS), gait score (GS) e angulação em valgus/varus (VAng). Métodos: Experimento 1, foram utilizados 308 frangos de corte machos da linhagem Ross com oito dias de idade (n = 90) distribuidos aleatoriamente em três tratamentos: dieta controle com 21% PB e 3.025 kcal EM kg-1 13/2.900; dieta con 13% PB e 2.900 kcal EM kg-1, y 17% PB e 3.000 kcal EM kg-1 . Experimento 2, foram utilizados 308 frangos de corte da linhagem Ross com seis dias de idade (n = 192) distribuídos aleatoriamente em dois tratamentos: dieta controle con 21% PB e 3.000 kcal EM kg-1 e dieta com 16% PB e 3.000 kcal EM kg-1 . Em ambos os experimentos, os dados foram submetidos a ANOVA. Resultados: Experimento 1, os frangos de corte submetidos ao dos tratamentos 17/3.000 e controle nao apresentaram diferencas significativas (p>0,05) para as variáveis GteBS (202 y 224 N, respectivamente) e TiBS (338 y 332 N, respectivamente). Os frangos submetidos ao 13/2.900 apresentaram maior frequência de GS (menor capacidade de locomocao; 80% das aves com pontuação>3) e maior VAng (53% das aves com pontuação>2) do que os frangos do tratamento controle (0% das aves com pontuação GS>3 e 0% das aves com pontuação VAng>2). Experimento 2, os frangos do 16/3.000 apresentaram VAng, GS e TiBS semelhantes aos das aves do tratamento controle. Entretanto, as aves do tratamento 16/3.000 apresentaram GTeBS mais baixo (-26%) em comparacao as aves do tratamento de controle (p<0,05). Conclusões: A dieta com 16% PB e 3.000 kcal EM kg-1 não afetou a forca de ruptura da tíbia, gaite score marcha e angulação em valgus/varus de frangos de corte. Uma dieta com níveis de 16% de PB ou menos e 2.900-3.000 kcal EM kg-1 reduziu a resistência à ruptura do tendão e a resistência de tibia de frangos de corte.

Evaluation of growth production factors as predictors of the incidence and severity of white striping and woody breast in broiler chickens.

White striping (WS) and woody breast (WB) have been previously associated with older and heavier birds. However, there is limited information supporting the association between these 2 muscle conditions and growth parameters. The objectives of this study were 1) to investigate the relationship between WS and WB using different growth production factors and 2) to propose a predictive model that uses growth production factors to investigate the incidence and severity of WS and WB. A combined database of 4,332 broilers pooled from 7 research experiments conducted from 2016 to 2017 at Texas A&M University was used in this study. Parameters such as sex, age (4 wk, 6 wk, and 8 wk), strain (standard A vs. high-breast-yield [B and C]), live weight categories (500 g increments), and breast weight categories (250 g increments) were included in the model. Results showed that WS was 12% more likely to be present in non-WB fillets. The association between WS and WB suggests a moderate relationship between the ranks of both outcome variables (ρ = 0.57, P < 0.0001). Variables such as age, live weight, and sex were not as important as breast weight and strain in the severity prediction of WS and WB. Butterfly fillets above 750 g and with high-breast-yielding strains were more likely associated with higher severity of WS and WB scores. No post hoc variable selection was performed. Both models show good discrimination. The WS model produced an uncorrected area under the curve (AUC) of 0.739, with a bootstrap corrected estimate of 0.736. The WB model produced an uncorrected AUC of 0.753 and a bootstrap corrected estimate of 0.752. Therefore, the growth production factors analyzed in this study indicated that there is a moderate relationship between WS and WB myopathies and were jointly predictive of the severity of WS and WB. Potentially other factors not included in this study may play a major role in the relationship of these 2 myopathies. More research should be done to investigate this possibility.

Impacts of Dietary Protein and Prebiotic Inclusion on Liver and Spleen Gene Expression in Hy-Line Brown Caged Layers.

The ingredients of poultry feeds are chosen based on the least-cost formulation to meet nutritional requirements. However, this approach can lead to the introduction of anti-nutritional ingredients in the feed. The objective of this study was to evaluate the impacts of two diets (with or without prebiotic) on homeostatic genes in the liver and spleen of laying hens. Hy-Line Brown layers were raised either on a soybean meal or cottonseed meal-based diets with and without an added prebiotic (yeast cell wall), totaling four experimental diets. A total of 120, 63-week old layers were housed individually in a wire cage system. We investigated differences in the expression of select homeostatic marker genes in the liver and spleen of hens from each treatment. We then used the ΔΔCT and generalized linear models to assess significance. Results show that the inclusion of prebiotic yeast cell-wall (YCW) increased the expression of the BAK gene in the liver tissue for both the soybean meal (SBM) and cottonseed meal (CSM) diets. For splenic tissue, the combination of YCW with the CSM diet increased the POR gene over six log2 fold. Altogether, our results suggest altered homeostasis, which can have consequences for health and performance.

Performance of broilers fed diets supplemented with two yeast cell wall strains using two feeding strategies.

Different supplements or strategies have been proposed as alternatives to the use of antibiotics at sub-therapeutic levels in chickens. Mannan oligosaccharides and ß-glucans, yeast cell wall fractions (YCW), have been reported to beneficially influence broiler performance and health. Two differently produced yeast cell wall fractions derived from Saccharomyces cerevisiae were evaluated in this study using two different supplementation strategies offered to full-term broilers. The birds were placed in floor pens on used pine-shaving litter to increase potential microbial stress and mimic industry practice. The study utilized a three-phase feeding program with a 1- to 21-day starter, 21- to 35-day grower and 35- to 42-day finisher phases. Five dietary treatments were compared in this study. The experimental diets consisted of a control basal broiler diet; or the basal diet supplemented with the two differently produced fractions of YCW. The YCW products were supplemented at a constant 250 ppm or a decreasing concentration program (500, 250, 125 ppm) throughout the three feeding phases. Birds fed diets supplemented with either YCW products at any inclusion regimen demonstrated higher (P < 0.05) body weight (BW) in all three phases than control birds. The difference in final 42-day BW of the YCW treatments (3041 g) averaged 165 g higher (P < 0.05) than the control group. For all YCW treatments, productivity index was higher (P < 0.05) in the grower (418) and finisher phase (441) versus control birds (389 grower and 415 finisher). These results suggested that both YCW fractions prepared from Saccharomyces cerevisiae can improve broiler performance when added at either a constant rate (250 ppm) or at a decreasing rate from 500 ppm for the starter to 125 ppm for the finisher phase.

Developing a novel oral vitamin D3 intake bioassay to re-evaluate the vitamin D3 requirement for modern broiler chickens.

The present study was conducted to develop a non-traditional vitamin D3 (D3) intake bioassay with the objective of increasing the precision of D3 delivery to the chickens. For this purpose, newly hatched chickens (5 birds per cage) were allocated in battery brooders and randomly distributed into 8 treatments and 6 replicates per treatment. A basal corn-soy diet devoid of D3 containing calculated calcium and non-phytate phosphorus concentrations of 0.90 and 0.45%, respectively, was fed throughout a 21-D period. The first 9 D of the study served to deplete the maternal stores of D3 followed by a 12-h fasting period. From day 10 to the end of the trial, the birds were gavaged with graded levels of D3 obtained from a highly purified pharmaceutical grade D3 standard (99.8%) purchased from Sigma-Aldrich and dissolved in corn oil. Daily gavage treatments were based on estimated intake of 0, 50, 100, 200, 400, 800, 1,600, and 3,200 IU D3/kg of feed consumed over the last 12 D of the study. Precise cholecalciferol intake per kg of diet was adjusted based on actual daily feed intake per pen of birds. Performance data were evaluated from day 10 to 21. Percent tibia bone ash (TBA), tibia breaking strength (TBS), total mineral content, and total bone mineral density were obtained at day 21. The D3 treatments improved (P < 0.05) weight gain and feed efficiency. There was no linear or quadratic effect for any of the productivity performance variables. Graded levels of D3 improved (P < 0.05) TBA and TBS. Both were linearly increased (P < 0.05) in response to graded levels of D3. A quadratic response was observed for TBS only. Under the conditions of the present experiment and the average of 3 regression models, the D3 requirement for starter broilers was estimated at 285 IU D3/kg of feed when bone mineralization responses (TBA and TBS) were used as criteria to estimate the requirement.

Evaluation of high dietary phytase supplementation on performance, bone mineralization, and apparent ileal digestible energy of growing broilers.

The present study was conducted to evaluate four commercially available phytase sources supplemented at regular (R) and super-dose (S) levels on live performance, bone mineralization, and apparent ileal digestible energy. Broiler chickens were allocated in stainless steel battery brooders (six birds per cage and eight pen replicates per treatment). A basal diet formulated to contain 0.2% non-phytate phosphorus (NPP) and 0.7% Ca was subdivided to create 11 dietary treatments: (1) basal diet was kept as the negative control (NC); (2) NC + limestone and monoclacium phosphate to create positive controls 1 and 2 formulated to yield 0.3% and 0.4% NPP; (3) NC + phytase A (250 and 1,500 FTU/kg); (4) NC + phytase B (500 and 1,500 FTU/kg); (5) NC + phytase C (500 and 1,000 FTU/kg); (6) NC + phytase D (1,000 and 2,000 FYT/kg). Performance was evaluated on d 7, 14, and 22. Tibia bone ash, tibia breaking strength, bone mineral content, and bone mineral density were evaluated on d 22. Apparent energy digestibility was evaluated on d 24. At d 7, phytases A and C supplemented at S level improved (P < 0.05) body weight and weight gain when compared to the NC. At d 14 and 22, all phytase sources improved (P < 0.05) body weight, weight gain, and bone mineralization when compared to the chicks under the NC diet. Overall, phytase supplementation at S level improved 17% apparent ileal digestibility at 24 d. Throughout the grow out period, phytase super-dose yield (P < 0.05) better performance, bone characteristics, and energy digestibility than the regular dietary level. In conclusion, all phytase sources were able to compensate the phosphorus deficiency and promote performance and bone mineralization. High levels of phytase showed a higher response when compared to the lower levels of supplementation.

Phenamil, an amiloride derivative, restricts long bone growth and alters keeled-sternum bone architecture in growing chickens.

"Broiler-type" chickens are fast-grow-ing, heavy-bodied birds with high demands on bone quality. Phenamil increased mineralization in cultured murine mesenchymal stem cells. Phenamil effects were tested in 2 groups of weight and gender matched day-old broiler chickens (n = 13). Oral administration of 30 mg phenamil/kg body weight d 1 to 13 reduced growth of chicks d 5 to 14 (P = 0.002); with phenamil-treated (PT) chick body weight being 84% of vehicle-treated (VT) chicks' body weight on d 14. Tissues collected on d 15 showed that femur lengths and widths did not differ, but tibias from PT chicks were 6% shorter (P = 0.002) and 13% narrower (P = 0.012) with 18% thinner tibial cross-sections (P < 0.008) than in VT chicks. Angles of the caudal aspect of the anterior surface of keeled-sternums were 166° in PT chicks, flatter than the 148° found in VT chicks (P = 0.000). Total mineral content of both tibia and femur were lower in PT chicks (P = 0.005 for both). Bone Ca, P, and Mg (ppm) in ash were similar, but Ca:P was lower (1.70 vs 1.75) in PT versus VT chicks (P < 0.05). Osteocalcin was ∼20% lower (P = 0.020), PINP was ∼45% higher (P = 0.000) in PT chicks. Carboxy-terminal telopeptide type I collagen (ICTP) and cross-linked N-telopeptide of type I collagen (NTX1) were similar in the 2 groups. Phenamil had unexpected and detrimental effects on bone formation in growing broiler chicks, reducing linear skeletal growth and markedly changing bone architecture.