Gut capacity of broiler breeder hens.

1. Broiler breeders are subjected to qualitative or quantitative feed restrictions to prevent obesity, which causes major health and welfare problems. Diluting their feed by adding inert or low nutrient, bulky materials can reduce obesity, but the capacity of the gut needs to be determined to apply this strategy successfully. Two trials were conducted to measure the bulk capacity of Ross 308 broiler breeders prior to and after the onset of lay. The trial was completely randomised, with nine individually-caged breeders, with each cage as a replicate, totalling 189 birds per trial2. Birds were given ad libitum access to one of 21 maize-soyabean based feeds, an undiluted control or progressive dilution (10, 20, 30 and 40%) with either cellulose fibre, rice husk, sand, vermiculite or sawdust. Feeds were analysed for density, crude-, acid detergent- and neutral detergent-fibre, water-holding capacity (WHC), cation-exchange capacity and oil-holding capacity.2. In general, feed intake (scaled to body weight0.67) increased and then declined as the proportion of each diluent increased. Intake increased linearly when rice hulls and sand were used as diluents.3. Water holding capacity was the most appropriate measure to define the gut capacity of broiler breeders.4. The trial data was used to estimate the maximum-scaled feed intake (SFImax) in broiler breeders, which was 240-56.1WHC + 4.34WHC2 g/kg0.67/d.

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/BW0.67 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.