Prediction of maximum scaled feed intake in broiler chickens based on physical properties of bulky feeds

1. A trial was conducted to investigate the capacity of broiler chickens to consume bulky feeds during three stages of growth. These phases were from 1 to 15 d, 16 to 30 d and from 31 to 45 d. 2. A basal feed was serially diluted (0%, 2.5%, 5.0%, 10% or 15%) with one of five diluents (cellulose fibre, sawdust, rice husk, sand or vermiculite) to produce 25 feeds which were supplied on an ad libitum basis to the birds in each phase. Cobb 500® strain chicks were used, and, within each phase, each feed was given to nine individually-caged birds, 225 in total, distributed in a completely randomised design. 3. Intake increased initially, and then declined, as the proportion of each diluent increased. The consumption of feeds that limited intake were directly proportional to metabolic body weight and so a scaled feed intake, expressed as g/BW^0.67 per day, was calculated. There were large effects of feed type on intake, in the short term, with consumption of a bulky feed leading to higher intakes. 4. It was concluded the Water Holding Capacity (WHC) content of the feeds could be appropriate measurement of 'bulk' responsible for limiting intake and could be used to predict maximum feed intake capacities of broiler chickens fed bulky diets.

Estimation of desired feed intake for growth and reproductive organ development in pre-laying hens

The objective of the present study was to describe the growth of reproductive organs and, on the basis of this information, predict feed intake during the pre-laying phase of laying-type pullets and to evaluate the results of the models. Ninety-six ISA-Brown pullets from 15 to 28 weeks of age were used in the first experiment. The weights of the birds with and without feathers, ovaries and oviducts were measured, and samples were taken to analyse dry matter, gross energy and crude protein. Seventy-six ISA-Brown and 76 Hy-Line pullets from 15 to 24 weeks of age were used in the second experiment. Feed intake was measured daily for each hen until the first egg was laid. The energy for maintenance (EEM) was calculated on the basis of the actual protein content and protein weight at maturity. The effective energy (EE) requirement was calculated as EER = EEM + 50 deposition of protein (DP) + 56 deposition of lipids (DL). Feed intake was calculated by dividing the EE requirement by the EE content in the feed. The simulation of feed intake overestimated values of 0.41 g/day (P > 0.05) and 2.65 g/day (P < 0.001) for Hy-Line and ISA-Brown respectively. A significant linear bias was observed for Hy-Line (P < 0.001) but not for ISA-Brown (P > 0.05). The assessment of the results indicated that the models for predicting feed intake were more accurate and less precise for Hy-Line than for ISA-Brown. Thus, there was an agreement between the calculated and measured values for feed intake, which shows that the models provide a true estimation of feed intake during the pre-laying phase.

Partitioning the efficiency of utilization of amino acids in growing broilers: Multiple linear regression and multivariate approaches

Determining the efficiency of amino acid (AA) utilization in growing animals is crucial to estimate their requirement accurately. In broiler chickens, the composition of AA in feather is different from feather-free body and the proportion of feathers will change along broiler’s growth, which may impact the efficiency of utilization on AA consumed. Therefore, in order to establish a method that predicts the efficiency of utilization for feather-free body and feather, two approaches were evaluated: a multiple linear regression and a multivariate analysis. Additionally, a new factorial model was proposed to predict AA requirements in broiler chickens. Data from 13 trials that evaluated the requirements for lysine (Lys), sulphur AA (SAA), threonine (Thr), and valine (Val) in male broilers were used for the analyses. Both methods of analysis were consistent in showing that the efficiency of utilization in feather-free body and feather were different. Using multiple linear regression, the values of efficiency of utilization estimated in feather-free body were 0.68, 0.72, 0.81, 0.79 (mg of amino acid deposited / mg of amino acid consumed above maintenance) and in feather were 0.58, 0.77, 0.78, and 1.57 (mg/mg) for Lys, SAA, Thr, and Val, respectively. Applying the multivariate approach, the corresponding predicted values were 0.68, 0.67, 4.23, 0.27 (mg/mg) in feather-free body and 1.16, 0.86, 0.16, and 1.10 (mg/mg) in feather, respectively. According to the results, efficiency of utilization may be related, to some extent, on the concentration determined in each tissue. The uncertainty around the amount of AA consumed for gain directed to feather-free body or feather deposition could be a limitation for multivariate analyses. The results indicated that multiple linear regression predictions may be better estimates of utilization efficiency. However, more studies are needed to elucidate the effect of age on deposition and partitioning of dietary AA in different parts of the broiler.