Can shifts in metabolic scaling predict coevolution between diet quality and body size?

Larger species tend to feed on abundant resources, which nonetheless have lower quality or degradability, the so-called Jarman-Bell principle. The "eat more" hypothesis posits that larger animals compensate for lower quality diets through higher consumption rates. If so, evolutionary shifts in metabolic scaling should affect the scope for this compensation, but whether this has happened is unknown. Here, we investigated this issue using termites, major tropical detritivores that feed along a humification gradient ranging from dead plant tissue to mineral soil. Metabolic scaling is shallower in termites with pounding mandibles adapted to soil-like substrates than in termites with grinding mandibles adapted to fibrous plant tissue. Accordingly, we predicted that only larger species of the former group should have more humified, lower quality diets, given their higher scope to compensate for such a diet. Using literature data on 65 termite species, we show that diet humification does increase with body size in termites with pounding mandibles, but is weakly related to size in termites with grinding mandibles. Our findings suggest that evolution of metabolic scaling may shape the strength of the Jarman-Bell principle.

Individual diet specialisation in sparrows is driven by phenotypic plasticity in traits related to trade-offs in animal performance.

Individual diet specialisation (IS) is frequent in many animal taxa and affects population and community dynamics. The niche variation hypothesis (NVH) predicts that broader population niches should exhibit greater IS than populations with narrower niches, and most studies that examine the ecological factors driving IS focus on intraspecific competition. We show that phenotypic plasticity of traits associated with functional trade-offs is an important, but unrecognised mechanism that promotes and maintains IS. We measured nitrogen isotope (δ15 N) and digestive enzyme plasticity in four populations of sparrows (Zonotrichia capensis) to explore the relationship between IS and digestive plasticity. Our results show that phenotypic plasticity associated with functional trade-offs is related in a nonlinear fashion with the degree of IS and positively with population niche width. These findings are opposite to the NVH and suggest that among individual differences in diet can be maintained via acclimatisation and not necessarily require a genetic component.

Valores energéticos e coeficientes de digestibilidade de uma ração tradicional para aves Label Rouge em diferentes idades / Energy values and digestibility coefficients of a traditional ration for Label Rouge poultry in different ages

O conhecimento da composição química e energética dos ingredientes utilizados nas dietas de avesé necessário para a formulação de rações com níveis nutricionais ótimos, permitindo uma maior produtividade erentabilidade para atividade avícola. Neste contexto, objetivou-se determinar a digestibilidade aparente dosnutrientes e o valor de energia metabolizável de uma ração convencional para aves Label Rouge em diferentesidades. Foram utilizadas 36 aves (machos e fêmeas) distribuídas individualmente em um delineamentointeiramente casualizado, com dois tratamentos: aves jovens (8 semanas) e adultas (40 semanas). Durante operíodo experimental (14 dias), as aves foram alojadas em gaiolas metálicas adaptadas para coleta total deexcretas, sendo a ração pesada (250 g/ave/dia) e a água foi fornecida à vontade. Os coeficientes dedigestibilidade aparente (CDA) da ração para aves jovens e adultas, respectivamente, foram de 86,33 e 86,78%para matéria seca (MS), 83,46 e 86,48% para proteína bruta (PB), 93,76 e 91,50% para extrato etéreo (EE),34,45 e 32,77% para fibra em detergente neutro (FDN), 29,32 e 27,62% para fibra em detergente ácido (FDA) edisponibilidade de 27,66 e 21,42% para matéria mineral (MM). Por sua vez, o coeficiente de metabolização daenergia bruta (CMEB) e energia metabolizável aparente (EMA) para aves jovens e adultas foram,respectivamente,80,20 e 82,79%; 3.010 e 3.125 kcal/kg. As aves jovens obtiveram maior eficiência digestiva doEE, FDN, FDA e MM, enquanto as aves adultas foram mais eficientes no aproveitamento da proteína bruta eenergia de uma ração tradicional(AU)

Knowledge of the chemical composition and energy of the ingredients used in poultry diets isnecessary to formulate diets with optimal nutritional levels, allowing greater productivity and profitability forpoultry activity. In this context, we aimed to determine the nutrient digestibility and metabolizable energy valueof a conventional Label Rouge poultry feed at different ages. Was used 36 poultry (males and females)distributed in a completely randomized design with two treatments: young (8 weeks) and adult poultry (40weeks). During the experimental period (14 days), the birds were housed in cages adapted for excreta collection,with the heavy feed (250 g/chicken/day) and water was provided ad libitum. The apparent digestibilitycoefficients (ADC) of the diets for young and adult poultry, respectively, were 86.33 and 86.78% for dry matter(DM), 83.46 and 86.48% for crude protein (CP), 93.76 and 91.50% for ether extract (EE), 34.45 and 32.77% forneutral detergent fiber (NDF), 29.32 and 27.62% for acid detergent fiber (ADF) and availability of 27.66 and21.42% for mineral matter (MM). In turn, the coefficient of gross energy metabolism (CGEM) and apparentmetabolizable energy (AME) for young and adult poultry were, respectively, 80.20 and 82.79%, 3.010 and 3.125kcal/kg. The young poultry had higher digestive efficiency of EE, NDF, ADF and MM, while the adult poultrywere more efficient in the use of crude protein and energy of a traditional feed(AU)

Valores energéticos e coeficientes de digestibilidade de uma ração tradicional para aves Label Rouge em diferentes idades / Energy values and digestibility coefficients of a traditional ration for Label Rouge poultry in different ages

O conhecimento da composição química e energética dos ingredientes utilizados nas dietas de avesé necessário para a formulação de rações com níveis nutricionais ótimos, permitindo uma maior produtividade erentabilidade para atividade avícola. Neste contexto, objetivou-se determinar a digestibilidade aparente dosnutrientes e o valor de energia metabolizável de uma ração convencional para aves Label Rouge em diferentesidades. Foram utilizadas 36 aves (machos e fêmeas) distribuídas individualmente em um delineamentointeiramente casualizado, com dois tratamentos: aves jovens (8 semanas) e adultas (40 semanas). Durante operíodo experimental (14 dias), as aves foram alojadas em gaiolas metálicas adaptadas para coleta total deexcretas, sendo a ração pesada (250 g/ave/dia) e a água foi fornecida à vontade. Os coeficientes dedigestibilidade aparente (CDA) da ração para aves jovens e adultas, respectivamente, foram de 86,33 e 86,78%para matéria seca (MS), 83,46 e 86,48% para proteína bruta (PB), 93,76 e 91,50% para extrato etéreo (EE),34,45 e 32,77% para fibra em detergente neutro (FDN), 29,32 e 27,62% para fibra em detergente ácido (FDA) edisponibilidade de 27,66 e 21,42% para matéria mineral (MM). Por sua vez, o coeficiente de metabolização daenergia bruta (CMEB) e energia metabolizável aparente (EMA) para aves jovens e adultas foram,respectivamente,80,20 e 82,79%; 3.010 e 3.125 kcal/kg. As aves jovens obtiveram maior eficiência digestiva doEE, FDN, FDA e MM, enquanto as aves adultas foram mais eficientes no aproveitamento da proteína bruta eenergia de uma ração tradicional

Knowledge of the chemical composition and energy of the ingredients used in poultry diets isnecessary to formulate diets with optimal nutritional levels, allowing greater productivity and profitability forpoultry activity. In this context, we aimed to determine the nutrient digestibility and metabolizable energy valueof a conventional Label Rouge poultry feed at different ages. Was used 36 poultry (males and females)distributed in a completely randomized design with two treatments: young (8 weeks) and adult poultry (40weeks). During the experimental period (14 days), the birds were housed in cages adapted for excreta collection,with the heavy feed (250 g/chicken/day) and water was provided ad libitum. The apparent digestibilitycoefficients (ADC) of the diets for young and adult poultry, respectively, were 86.33 and 86.78% for dry matter(DM), 83.46 and 86.48% for crude protein (CP), 93.76 and 91.50% for ether extract (EE), 34.45 and 32.77% forneutral detergent fiber (NDF), 29.32 and 27.62% for acid detergent fiber (ADF) and availability of 27.66 and21.42% for mineral matter (MM). In turn, the coefficient of gross energy metabolism (CGEM) and apparentmetabolizable energy (AME) for young and adult poultry were, respectively, 80.20 and 82.79%, 3.010 and 3.125kcal/kg. The young poultry had higher digestive efficiency of EE, NDF, ADF and MM, while the adult poultrywere more efficient in the use of crude protein and energy of a traditional feed