1. Two experiments were performed to study the supplementation of valine, isoleucine, arginine and glycine (Val, Ile, Arg, Gly) in low-protein diets for broiler chickens in the starter (1-21 d; Exp. 1) and grower (22-42 d; Exp. 2) phases. 2. A low-crude protein (CP) diet was formulated to meet the requirements of all amino acids (AA) supplied by the control diet except for Val, Ile, Arg and Gly. The other experimental diets were obtained by the isolated or combined supplementation of the studied AA in the low-CP diet. 3. Growth, serum parameters and litter characteristics were taken in both of the experiments. Carcass measurements were taken in Experiment 2. 4. In the starter and grower phases, low-CP diets without supplementation resulted in birds with a poorer weight gain and feed conversion than those of the birds that received the control diet. 5. In the starter phase, individual supplementation with Val and Gly, but not Ile and Arg, restored the weight gain of the birds, while diets with the addition of Val + Gly, Val + Ile + Arg, Val + Ile + Gly and Val + Ile + Arg + Gly restored their feed conversion. 6. In the grower phase, weight gain was re-established at the same rate as the control diet for the diets supplemented with Val + Ile, Val + Ile + Arg, Val + Ile + Gly and Val + Ile + Arg + Gly. However, the feed conversion was restored only in birds that received the diet supplemented with all studied AA. 7. The supplementation of Val and Gly in low-CP diets was sufficient to avoid adverse effects in the performance and serum parameters of broilers in the starter phase. However, birds in the grower phase required the combined supplementation of Val, Ile, Arg and Gly, to prevent compromised performance.

The present study aimed to evaluate the effect of different levels of an ethanolic extract of propolis (EEP) on broiler performance, carcass characteristics, weight of gastrointestinal organs, intestinal morphometry and digestive enzyme activity. 1020 male broiler chicks were assigned in a completely randomised experimental design to six treatments (EEP supplement levels of 0, 1000, 2000, 3000, 4000 and 5000 ppm) and five replications, and 34 birds per experimental unit. The experimental diets were administered from 1 to 21 days of age, and the birds were subsequently provided a ration based on corn and soybean meal. EEP supplementation from 1 to 7 days negatively affected (p < 0.05) the weight gain and feed intake. The proventriculus weight at 7 days exhibited a quadratic response (p < 0.05), which predicted a lower weight at a dose of 2865 ppm of the EEP. For the duodenum at 21 days of age, the response pattern (p < 0.05) predicted that birds that were fed 2943 and 3047 ppm of the EEP would exhibit an improved crypt depth and villus-to-crypt ratio respectively. The villus height, crypt depth and villus-to-crypt ratio in the jejunum and the ileum were not affected (p > 0.05). With increased EEP doses, the duodenal sucrase activity linearly decreased at 7 days of age and linearly increased in the jejunum at 21 days of age (p < 0.05), while pancreatic enzyme activity was unaffected (p > 0.05). Although the carcass and cut yields did not improve, the percentage of abdominal fat decreased (p < 0.05). The supplementation of the broiler pre-starter diet with 1000-5000 ppm of the EEP impaired performance at this stage, most likely due to the decreased sucrase activity. However, the EEP supplementation from 3000 ppm improved intestinal morphophysiology at 21 days of age and did not affect the performance or carcass yield at 42 days of age.

The objective of this experiment was to assess the use of different vitamin D metabolites in the feed of broiler chickens and the effects of the metabolites on performance, bone parameters and meat quality. A total of 952 one-day-old male broiler chicks were distributed in a completely randomised design, with four treatments, seven replicates and 34 birds per experimental unit. The treatments consisted of four different sources of vitamin D included in the diet, D3, 25(OH)D3, 1,25(OH)2D3, and 1α(OH)D3, providing 2000 and 1600 IU of vitamin D in the starter (1 to 21 d) and growth phases (22 to 42 d), respectively. Mean weight, feed:gain and weight gain throughout the rearing period were less in animals fed 1α(OH)D3 when compared with the other treatments (p<0.05). No significant differences were noted among the treatments (p>0.05) for various bone parameters. Meat colour differed among the treatments (p>0.05). All of the metabolites used in the diets, with the exception of 1α(OH)D3, can be used for broiler chickens without problems for performance and bone quality, however, some aspects of meat quality were affected.

We studied the colour preference of isolated Nile tilapia (Oreochromis niloticus) and whether previous residence or body size can affect environmental colour choice. In the first phase, a cylindrical tank was divided into five differently coloured compartments (yellow, blue, green, white and red), a single fish was introduced into the tank and the frequency at which this fish visited each compartment was recorded over a 2-day study period. An increasingly larger fish (approx +2 cm in length each time) was then added into the tank on each of days 3, 5 and 7 (=four fish in the tank by day 7), and the frequency at which each fish visited the different compartments of the tank was observed twice a day to obtain visit frequency data on the differently sized fishes. This experiment was replicated six times. In the first phase, the solitary fish established residence inside the yellow compartment on the first and second days. Following theintroduction of a larger fish, the smaller fish was displaced from the occupied compartment. Nile tilapia possibly shows this preference for yellow as a function of its visual spectral sensitivity and/or the spectral characteristics of its natural environment. Moreover, body size is an important factor in determining hierarchical dominance and territorial defence, and dominant fish chose the preferred environmental colour compartment as their territory.

The objective of this study was to determine the requirements and interactions between the standardized ileal digestible (SID) Leu and Val levels in low-protein diets, and their effects on performance, serum characteristics, carcass yield and diameter of muscle fibers of broiler chickens from d 21 to 42 posthatch. A total of 1,500 21-day-old Cobb 500 male broiler chickens were distributed in a completely randomized design in a 5 × 5 factorial arrangement for a total of 25 treatments with 3 replicates of 20 birds each. Treatments consisted of 5 SID Leu levels (1.0, 1.2, 1.4, 1.6, or 1.8%) and 5 SID Val levels (0.52, 0.67, 0.82, 0.97, or 1.12%). At 42 d of age, there was interaction (P < 0.05) between the SID levels of Leu and Val on feed intake and weight gain. There was a quadratic effect (P < 0.05) of Leu and Val levels on feed conversion, with minimal point estimated at the levels of 1.19 and 0.86%, respectively. Dietary Leu supplementation reduced linearly (P < 0.05) serum concentrations of triglycerides and β-hydroxybutyrate. Dietary Leu increased (P ≤ 0.05) the fiber diameters of the pectoralis major muscle and breast yield at the levels of 1.24 and 1.13%, respectively, while the thigh yield was improved with the level of 0.71% Val. Abdominal fat decreased linearly (P < 0.05) with increasing levels of dietary Leu and Val. The SID Leu and Val levels needed to optimize weight gain and feed conversion in low-CP diets for broiler chickens from d 21 to 42 posthatch were estimated at 1.15 and 0.86%, and 1.19 and 0.86%, respectively. The supplementation of Leu and Val can reduce the abdominal fat deposition in birds fed low-CP diets during the grower phase. Leu and Val interactions can influence the performance but not the serum characteristics, carcass yield and diameter of muscle fibers of broilers fed low-protein diets. Therefore, it is necessary to consider the dietary Leu content to estimate the ideal level of Val in low-CP diets for optimum broiler performance.