Dynamic of heat production partitioning in rooster by indirect calorimetry.

OBJECTIVE: The objective of this study was to describe a methodological procedure to quantify the heat production (HP) partitioning in basal metabolism or fasting heat production (FHP), heat production due to physical activity (HPA), and the thermic effect of feeding (TEF) in roosters. METHODS: Eighteen 54-wk-old Hy Line Brown roosters (2.916±0.15 kg) were allocated in an open-circuit chamber of respirometry for O2 consumption (VO2), CO2 production (VCO2), and physical activity (PA) measurements, under environmental comfort conditions, following the protocol: adaptation (3 d), ad libitum feeding (1 d), and fasting conditions (1 d). The Brouwer equation was used to calculate the HP from VO2 and VCO2. The plateau-FHP (parameter L) was estimated through the broken line model: HP = U×(R-t)×I+L; I = 1 if tR; Where the broken-point (R) was assigned as the time (t) that defined the difference between a short and long fasting period, I is conditional, and U is the decreasing rate after the feed was withdrawn. The HP components description was characterized by three events: ad libitum feeding and short and long fasting periods. Linear regression was adjusted between physical activity (PA) and HP to determine the HPA and to estimate the standardized FHP (st-FHP) as the intercept of PA = 0. RESULTS: The time when plateau-FHP was reached at 11.7 h after withdrawal feed, with a mean value of 386 kJ/kg0.75/d, differing in 32 kJ from st-FHP (354 kJ/kg0.75/d). The slope of HP per unit of PA was 4.52 kJ/mV. The total HP in roosters partitioned into the st-FHP, termal effect of feeding (TEF), and HPA was 56.6%, 25.7%, and 17.7%, respectively. CONCLUSION: The FHP represents the largest fraction of energy expenditure in roosters, followed by the TEF. Furthermore, the PA increased the variation of HP measurements.

Response of broilers to digestible sulfur amino acids and threonine intake: Maximum economic return / Respuesta de pollos de engorde a la ingesta de aminoácidos azufrados y treonina digestibles: máximo retorno económico / Resposta de frangos de corte ao consumo de aminoácidos sulfurados e treonina digestíveis: máximo retorno econômico

Abstract Background: The determination of amino acid supplements for broiler chicken requirements based on performance does not always reflect maximum profitability. Objective: To estimate the optimal levels of digestible threonine (Thr) and sulfur amino acids (SAA) in diets for broilers based on an economic analysis. Methods: Two dose-response assays were conducted, and each assay was divided into three phases: initial (1-14 days), grower (15-28 days), and finisher (29-42 days). Five hundred and sixty male Cobb 500® broilers were randomly distributed to seven treatments with increasing levels of the amino acid (SAA or Thr), with four replicates and 20 birds each. Bodyweight gain (BWG) and feed intake (FI) were used to fit a segmented model. Gross income (GI), total feed costs (TFC) and gross margin (GM) were calculated based on local values. Results: Increasing levels of amino acid elicited a response in BWG and FI for all evaluated phases. The estimates for maximum profit based on GI and TFC were 223, 504, and 975 mg SAA/bird/d, and 236, 696, and 1,042 mg Thr/bird/d in starter, grower and finisher phases, respectively. Conclusion: Varying the AA prices affected only slightly the economic optimal intake of Thr and sulfur amino acids. Despite market fluctuations, the economic approach presented in this study demonstrates to be a helpful tool to choose the ideal inclusion level of amino acids in the feed.

Resumen Antecedentes: La determinación de la suplementación de aminoácidos en las dietas de pollos de engorde, basados solamente en el desempeño productivo no siempre refleja la máxima rentabilidad. Objetivo: Estimar los niveles óptimos de treonina (Thr) y aminoácidos azufrados (SAA) en dietas para pollos de engorde basados en un análisis económico. Métodos: Se realizaron dos ensayos tipo dosis-respuesta divididos en tres fases cada uno: inicio (1-14 días), crecimiento (15-28 días) y finalización (29-42 días). Quinientos sesenta pollos de engorde machos Cobb 500® se distribuyeron aleatoriamente en siete tratamientos con niveles crecientes de aminoácidos (SAA o Thr) y cuatro repeticiones de 20 aves cada uno. La ganancia de peso (BWG) y el consumo de alimento (FI) fueron utilizados para ajustar un modelo segmentado. El ingreso bruto (GI), costo total de la ración (TFC) y el margen bruto (GM) se calcularon tomando como referencia valores locales. Resultados: Los niveles crecientes de aminoácidos influyeron en la respuesta de BWG y FI en todas las fases evaluadas. Los estimados para maximizar la rentabilidad según GI y TFC fueron 223, 504 y 975 mg SAA/ave/día, y 236, 696 y 1,042 mg Thr/ave/día para las fases de inicio, crecimiento y finalización, respectivamente. Conclusión: La variación de los precios de los AA tuvo solo un ligero efecto sobre el consumo óptimo de Thr y aminoácidos azufrados. A pesar de las fluctuaciones del mercado, el enfoque económico aquí expuesto demuestra ser una herramienta útil para la elección del nivel ideal de inclusión de aminoácidos en la formulación.

Resumo Antecedentes: A determinação da suplementação de aminoácidos em frangos de corte baseados somente no desempenho produtivo nem sempre reflete a rentabilidade máxima. Objetivo: Estimar os níveis ótimos de treonina (Thr) e aminoácidos sulfurados (SAA) em dietas para frangos de corte com base em uma análise econômica. Métodos: Foram realizados dois ensaios dose-resposta, divididos em três fases cada: inicial (1-14 dias), crescimento (15-28 dias) e final (29-42 dias). Quinhentos e sessenta frangos de corte machos Cobb 500® foram distribuídos aleatoriamente em sete tratamentos, representados por níveis crescentes de aminoácidos (SAA ou Thr), com quatro repetições de 20 aves cada. O ganho de peso (BWG) e o consumo de ração (FI) foram utilizados para ajustar um modelo segmentado. A receita bruta (GI), os custos totais de alimentação (TFC) e a margem bruta (GM) foram calculados com base nos custos locais. Resultados: Os níveis dos aminoácidos influenciaram as respostas de BWG e FI para todas as fases avaliadas. A estimativa para máximo lucro com base em GI e TFC para os ensaios com SAA foram 223, 504 e 975 mg/ave/d; para Thr foram 236, 696 e 1,042 mg/ave/d para as fases inicial, crescimento e final, respectivamente. Conclusão: A variação dos preços dos AA teve pouca influência sobre a ingestão econômica dos aminoácidos sulfurados e da Thr. Apesar do dinamismo de mercado, a abordagem econômica apresentada neste estudo demonstra ser uma ferramenta útil para a escolha do nível de inclusão ideal do aminoácido na ração.