Digestibility and nutritional parameters of maize ethanol coproducts and xylanase for broiler diets

1. The objective of this study was to determine the nutritional and energy values of four maize distiller's dried grains with solubles (DDGS) and one maize high protein distiller's dried grains (HP-DDG) from ethanol production plants in Brazil; to evaluate the digestibility, performance, nitrogen balance and energy values for broiler chickens fed diets containing these coproducts (Experiment I); and to evaluate the effects of xylanase inclusion in diets containing maize DDGS for broilers on energy availability, digestibility, nitrogen balance and gastrointestinal morphometry (Experiment II).2. For each experiment, 180 broiler chickens aged 17 and 30 days with initial weights of 450 ± 18 g and 1228 ± 33 g, respectively, were used; the chickens were distributed into 36 metabolism cages. The experimental design consisted of complete randomised blocks, with six replications per treatment and five birds per experimental unit. The treatments consisted of a basal diet (BD) and five test diets containing maize ethanol coproducts (Experiment I) one BD and five test diets containing DDGS with inclusions of 0, 8,000, 16,000, 24,000 and 32,000 BXU/kg xylanase (Experiment II). In Experiment I, HP-DDG and DDGS2 presented higher AME and AMEn values (14.1 and 13.9 MJ/kg and 13.4 and 13.3 MJ/kg, respectively), than did the other coproducts (p < 0.05). Compared with DDGS1 and DDGS3, DDGS4 and HP-DDG had higher digestible CP values (p < 0.05). In Experiment II, the inclusion of the enzyme quadratically affected the values of digestible CP and digestible EE (p < 0.05), with the maximum values occurring with the inclusion of 18 750 and 22,170 BXU/kg of xylanase, respectively.3. The digestible NDF and digestible MM values linearly increased with the inclusion of xylanase (p < 0.05). The addition of xylanase had no effect on gastrointestinal morphometry (p > 0.05). It was concluded that the inclusion of between 18,000 and 22,000 BXU/kg of xylanase resulted in better digestible CP and digestible EE values.

Implicações desfavoráveis do melhoramento animal nas espécies zootécnicas: uma revisão

Os efeitos desfavoráveis associados ao melhoramento de espécies zootécnicas têm se tornado mais evidentes devido a problemas de desempenho detectados em populações com elevado mérito genético, resultantes da seleção indireta para características comportamentais, fisiológicas e imunológicas. Especialmente no gado leiteiro, suínos e frangos de corte, a seleção para características de interesse econômico trouxe grande impacto sobre o crescimento, reprodução e metabolismo geral dos animais, muitas vezes exigindo mais atenção dos melhoristas às respostas correlacionadas dos critérios de seleção utilizados. Assim, esta revisão tem como objetivo discorrer sobre os principais aspectos desse impacto desfavorável do melhoramento das espécies zootécnicas, o que pode contribuir para um estabelecimento mais adequado das estratégias utilizadas nos programas de seleção.