Laying hens were fed diets containing sunflower, fish, linseed and rapeseed oil with 2 levels of inclusion (1.5 and 3.0%) for 12 weeks. Egg production, egg weight, feed intake, feed conversion and liveweight were not significantly affected by the treatments. Hens receiving sunflower oil produced...

1. The aim of the study was to investigate the effects of dietary threonine (Thr) and crude protein (CP) in maize–soybean meal based diets on the growth performance, carcase traits and meat composition of broiler chickens and to determine the dietary Thr requirement for optimum performance (weight gain and feed conversion efficiency (FCE)) at 0 to 3 weeks and 3 to 6 weeks of age. 2. Two basal diets that differed in CP (191·3 or 179·7 and 176·7 or 165·4 g/kg at 0 to 3 and 3 to 6 weeks, respectively) were formulated to have identical contents of Thr (6·0 and 5·4 g/kg), energy (12·97 and 13·39 MJ ME/kg) and other essential amino acids except for Gly + Ser. Basal diets were supplemented with l-Thr from 0·6 to 1·8 g/kg in 0·6 g/kg increments. Broiler chicks (540) were randomly allocated to 9 dietary treatments with 6 replicates of 10 (5 female, 5 male) chicks. 3. A significant interaction between dietary CP and Thr was found for feed intake, body weight (BW) gain and FCE. Increasing Thr supplementation improved feed intake, BW gain and FCE, especially in high CP diets in both feeding periods. 4. Incremental increases in dietary Thr increased breast yield at both CP levels and drumstick yield only on high CP diets. The proportion of thigh decreased with Thr concentration. Liver weight was significantly reduced by Thr supplementation; abdominal fat was not affected. 5. Estimated Thr requirements for FCE increased as dietary CP increased according to an exponential model. This model indicated higher Thr requirements than those of broken-line models for growth performance.

L-carnitine has indispensable functions in intermediary metabolism and is received by endogenous synthesis and from exogenous sources. It plays an obligate role in fatty acid metabolism by directing fatty acids into the mitochondrial oxidative pathway through the action of specialised acyltransferases. In poultry production, L-carnitine has a multi functional purpose, which includes: growth promotion, strengthening the immune system, antioxidant effects and improving semen quality. The concentration of L-carnitine in animals varies widely across species, tissue type, and nutritional status of the animal. It has been suggested that the L-carnitine requirement may be increased under certain circumstances such as via higher performance, various stress conditions and where the diet is deficient in animal protein sources. The review of L-carnitine functions uniquely includes the main aspects of this consequential feed supplementary inclusion in poultry nutrition.

Effects of dietary energy density and L-carnitine supplementation on growth performance, carcass traits and blood parameters of broiler chickens

High available phosphorus corn (HAP) developed using the low phytic acid 1-1 (lpal-1) allele of the corn LPA1 gene containing 0.27% P, with 0.17% nonphytate P (NPP), was compared to near isogenic normal corn (LPA1), which contained 0.23% P and 0.05% NPP. Five levels of NPP from either HAPC or normal corn (0.40, 0.35, 0.30, 0.25 and 0.20% + 300 phytase units (FTU)/kg microbial phytase) were combined in a 2 x 5 factorial experiment for a total of 10 dietary treatments. Each dietary treatment was fed to eight replicate cages with five Hy-Line W-36 hens per replicate cage from 20 to 40 wk of age. Feed consumption and egg production were not significantly affected by dietary NPP level or corn type. Feed conversion ratio (g feed:g egg mass) was improved at the 0.35% NPP level (1.856) compared to the other levels of NPP--0.40, 0.30, 0.25, and 0.20% + phytase having feed conversion ratios of 1.872, 1.905, 1.930, and 1.898, respectively. Egg weight and egg mass decreased significantly as dietary NPP decreased; diets with 0.20% NPP plus phytase had equal egg mass to the 0.35 and 0.40% NPP diets. A significant corn type x NPP interaction effect was observed for egg weight, such that within the HAP corn diets, egg weight decreased more markedly at the 0.25% NPP levels compared to the normal corn 0.25% NPP diets. Specific gravity was not affected by dietary treatment, but percent dry shell was improved at the lower AP levels and with phytase treatment. Dietary NPP level and corn type had no significant effect on bone ash. Excreta levels of total phosphorus decreased significantly as dietary NPP decreased and were lower in the HAP corn excreta compared to normal corn excreta. Total P, Ca, Zn, Cu, and Mn retention were significantly affected by NPP level and corn type. HAP corn reduced Ca, Zn, Cu, and Mn retention compared to normal corn; this negative effect was alleviated by phytase supplementation to HAP corn diets. HAP corn allowed less dicalcium phosphate supplementation in layer diets compared to normal corn while supporting equal egg production. Phytase supplementation of low NPP diets had no significant positive effects on egg production parameters in either corn type diets.