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Over 50 years, broiler BW has increased over 450%, but the BW target considered optimal for broiler breeder reproductive efficiency has remained virtually constant. Thus, the gap between growth potential of broilers and broiler breeder target BW is increasing. Consequently, the intensity of broiler breeder feed restriction has increased. This creates intense competition for feed, and unevenly balanced feed distribution among individuals, which finally becomes apparent as poor flock uniformity. Technologies that ensure rapid and equal feed distribution are reaching their limit. Either the degree of broiler breeder feed restriction needs to be eased, or new feeding technologies to ensure equitable feed distribution are needed, or both. A novel precision feeding (PF) system was developed at the University of Alberta. The sequential feeding system was designed to use real-time BW measurement to determine whether or not to feed individual birds. By limiting meal size and feeding bout duration with the PF system, it is possible for birds to eat more often than once per d while at the same time achieving a high degree of flock uniformity. The objectives of the current broiler breeder pullet study were 1) for the first time, to use PF to control individual bird feed intake by precisely matching individual real-time BW measurements to BW targets; and 2) to quantify the degree to which metabolic rate fluctuates in response to continuous or stepwise increases in target BW.
The experiment consisted of 2 BW profile treatments applied from 35 to 140 d of age: 1) Control (CON), in which the BW target was updated hourly; and 2) stepwise (STEP), in which the BW target was updated once every 3 weeks. Both treatments followed the Ross 708 target BW profiles and had identical target BW once every 3 wk, at the midpoint of each STEP period. All birds on both treatments were fed individually by a precision feeding station that was capable of applying the treatment (BW profile) to each individual bird. Therefore, every bird was an experimental unit. There were 10 replicate birds randomly assigned to each treatment. At hatch, a total of 40 Ross 708 broiler breeder pullets were placed into a single pen at a stocking rate of 6.0 birds per m2. A single PF station was used as the sole means of feeding broiler breeder pullets from 35 to 140 d of age. The birds had free access to the feeding system 24 h per day. A low intensity green LED light (2 lux) provided minimal illumination inside the feeding station 24 h per day. This was intended to provide light during the night without stimulating deep brain photosensors. Feed intake was calculated for each feeding bout by subtracting the post-feeding from the pre-feeding feed weight. The number of visits to the station was determined from these records, as well as the number of meals and size of each meal. Daily feed intake was calculated as the sum of all meals for each bird from midnight to midnight, each day. At 20 wk of age, all birds were dissected. The weights of pectoralis major and pectoralis minor (supracoracoideus) muscles, abdominal fatpad, crop, proventriculus, gizzard, heart, liver, oviduct, ovary, gallbladder, pancreas, spleen, and intestines (full and empty) were recorded to determine whether any differences in body conformation existed.
Daily BW profiles of STEP treatment pullets were greater than those of the CON treatment from 47 to 52 d of age. By 62 d of age the BW of the CON treatment pullets was greater than the BW of birds in the STEP treatment. By 64 d of age, the BW of the STEP treatment had again increased significantly compared to the CON birds. This general pattern repeated around the time of each increment in target BW in the STEP treatment. The target BW differed the most just prior to and immediately following the target BW increments in the STEP treatment. In the current experiment, all pullets were fed multiple times per d, so in spite of the differences in timing of BW gain, the presence of some feed in the gut at regular intervals meant that the birds in both treatments used nutrients from the gastrointestinal tract more or less in real time, and did not have to rely on long-term storage and subsequent mobilization of nutrients, which is likely a trigger of body compositional changes. Body weight uniformity increased after implementing PF. Body weight CV decreased in the CON treatment from almost 14% to less than 2% by the end of the study. The pullets in both treatments visited the feeding station an average of approximately 17 times per d, and ate on average 4.2 meals per d, which varied in size due to management decisions made during the course of the study, but averaged approximately 17 g per meal. There was no difference in overall feed efficiency between the 2 treatments; cumulative feed conversion ratio at 20 wk of age averaged 4.06 ± 0.2.
Overall, the PF system was successful at precisely managing BW of individual free run broiler breeder pullets relative to a pre-programmed target BW. Precision feeding achieved unprecedented flock uniformity. There are no previous reports of a BW CV under 2% in free run broiler breeders. The high resolution data collected with the PF system allowed new insights into feeding behavior and quantification of parameters of importance to researchers and primary breeders, including estimates of metabolic rate and feed efficiency on individual birds in group-housing systems. With PF, it was possible to manage individual birds on different target BW treatments in the same pen. This will greatly enhance future experimental designs, and reduce the number of animals required to conduct important practical research.