Effects of a meal feeding regimen and the availability of fresh alfalfa on growth performance and meat and bone quality of broiler genotypes.

1. The aim of this study was to identify a feeding regimen that encourages good pasture use in slow (SG) and fast (FG) growing broiler genotypes under free-range management. 2. SG and FG birds fed on either an ad libitum (ADB) or a meal feeding (MEF) programme were given free outdoor access with or without fresh alfalfa from day 22 to 72 and from day 22 to 45, respectively. In two consecutive trials, 800 birds of each genotype were included in a factorial design using groups of 40 birds replicated 5 times. 3. Fresh alfalfa consumption did not improve growth performance and meat quality attributes, whereas the feeding regimen had significant implications. When compared with their ad libitum-fed counterparts, meal-fed birds showed a significantly lower body weight at a considerably lower feed consumption rate, leading to a more favourable feed conversion ratio (FCR) during the course of the experiment. 4. The MEF regimen with a strong feed limitation significantly increased crop and gizzard weight in both genotypes. In FG birds, water holding capacity, drip loss, cooking loss and pH 45 in the breast and thigh meat were adversely affected by MEF; however, feed restriction demonstrated benefits with significant decreases in muscle fat accumulation. In SG birds, decreases in protein and dry matter content of the breast and thigh muscle with meal feeding were conclusive. 5. In both genotypes, there was no treatment-related effect on meat yield, mineral composition of the meat or bone mechanical properties. 6. In conclusion, MEF, irrespective of alfalfa intake, may provide a viable method to decrease FCR; it may be able to contribute to the production of chickens with lean carcasses but it was not capable of improving overall meat quality.

Effects of dietary boron and phytase supplementation on growth performance and mineral profile of broiler chickens fed on diets adequate or deficient in calcium and phosphorus.

1. Two experiments were designed to determine the effect of dietary boron (B) in broiler chickens. In Experiment 1, a 2 × 4 factorial arrangement of treatments was used to investigate the effect of dietary calcium (Ca) and available phosphorus (aP) (adequate or deficient) and supplemental B (0, 20, 40, and 60 mg/kg diet). In Experiment 2, B, at 20 mg/kg, and phytase (PHY) (500 FTU/kg diet) were incorporated into a basal diet deficient in Ca and aP, either alone or in combination. 2. The parameters that were measured were growth performance indices, serum biochemical activity as well as ash and mineral (i.e. Ca, P, Mg, Fe, Cu and Zn) content of tibia, breast muscle and liver. 3. Results indicated that both supplemental B and dietary Ca and aP had marginal effects on performance indices of chickens grown for 42 d. 4. There were positive correlations (linear effect) between B concentrations of serum, bone, breast muscle and liver and the amount of B consumed. 5. Serum T3 and T4 activities increased linearly with higher B supplementation. 6. Increasing supplemental B had significant implications on breast muscle and liver mineral composition. Lowering dietary Ca and aP level increased Cu content in liver and both Fe and Zn retention in breast muscle. Tibia ash content and mineral composition did not respond to dietary modifications with either Ca-aP or B. 7. The results also suggested that dietary contents of Ca and aP do not affect the response to B regarding tissue mineral profile. Dietary combination with B and PHY did not create a synergism with regard to growth performance and bioavailability of the minerals.