An 8‐week feeding trial was conducted to quantify the dietary valine requirement of cultured juvenile Nile tilapia, Oreochromis niloticus. Six isonitrogenous (280 g/kg crude protein) and isoenergetic (16.06 MJ/kg gross energy) diets with graded levels of valine (amounting to 4.1, 7.2, 9.9, 12.7, 15.6 and 18.8 g/kg of dry diet) were formulated. Each diet was randomly assigned to triplicate groups of 20 fish (6.48 ± 0.06 g). Results showed that the weight gain, specific growth rate, protein efficiency ratio and protein retention efficiency all increased with an increasing level of dietary valine up to 12.7 g/kg, but remained relatively constant for fish fed higher levels of dietary valine. In addition, the total protein concentration and aspirate aminotransferase activity in plasma, hepatic lysozyme and catalase activities were all significantly (p < .05) improved by dietary valine supplementation. Based on the broken‐line regression analysis of weight gain and protein retention efficiency, the optimal dietary valine requirement for juvenile Nile tilapia occurred between a level of 11.5 g/kg of diet (equivalent to 41.1 g/kg of dietary protein) and 12.7 g/kg of diet (equivalent to 45.3 g/kg of dietary protein).

1. The effects of different fibre sources on the growth performance, carcass characteristics and gastrointestinal tract development were studied in growing Greylag geese (Anser anser). 2. Four experimental diets were formulated with corn (maize) straw silage (CSS), steam-exploded corn (maize) straw, steam-exploded wheat straw, and steam-exploded rice straw as fibre sources. A total of 224 male Greylag geese at 28 d of age were randomly assigned to one of the 4 experimental diets. 3. The birds fed on the CSS diets had higher average daily feed intakes than those fed on the steam-exploded straws. However, the 4 treatments had similar average daily gain, which contributed to significant differences in feed conversion ratios. The different fibre sources had no significant effects on the carcass characteristics. 4. The CSS-fed birds had larger gizzards and lower relative length of the caeca than the other three groups. However, the relative weights and lengths of the other gut segments, the relative weights of major organs and the pH values of the gastrointestinal contents were similar between the 4 treatments. It was concluded that straw fibres with different physico-chemical properties exerted an effect on daily feed intake and gastrointestinal development, especially for the gizzard. The pretreatment of straw had a large effect on utilisation efficiency and animal performance. Steam explosion is a promising straw pretreatment for inclusion in diets for geese.