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The intensity of broiler breeder feed restriction has increased, which creates difficulty for uniform feed distribution and poor flock uniformity. In commercial broiler parent flocks, it is increasingly difficult to distribute the right amount of feed to each individual bird. Poor BW uniformity may reduce reproductive success because of suboptimal performance in both overweight and underweight birds. Technologies that ensure rapid and equal feed distribution are reaching their limit, and because of its social responsibility to ensure the welfare of broiler breeders, the hatching egg industry cannot further reduce the frequency of feeding. 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. To achieve high BW uniformity, a precision feeding (PF) system was developed at the University of Alberta. The objectives of the current study were to compare the flock uniformity of broiler parent stocks raised conventionally and using a PF system, and the resulting impact on lifetime egg production and fertility. Assuming that breeder-recommended target BW profiles are adequate for optimal productivity, the hypothesis was that high flock uniformity in a precision-fed broiler grandparent would increase reproductive efficiency compared with conventionally fed birds, because each bird would respond similarly to photostimulation and feeding cues.
The study was divided into: rearing (0 to 22 wk) and laying (22 to 52 wk). During rearing, the experiment had 2 treatments in 6 replicate pens per treatment, each containing 40 pullets: control (CON)—fed conventionally, once per day, as a group; and PF—fed using a precision feeding station. During lay, there were 3 experimental treatments: CON—fed conventionally, once per day, as a group (n = 6 pens of 24 hens and 2 roosters); PF—fed by a PF station (n = 6 pens of 24 hens and 2 roosters); and a third treatment where some birds that had been reared on PF were fed conventionally, once per day, as a group (PFCON; n = 3 pens of 24 hens and 2 roosters). The laying phase was divided into 2 periods. From 23 to 42 wk of age, identical breeder-recommended target BW were used. The birds received a commercial phase feeding program with identical feeds provided to all treatments throughout the study. From 0 to 14 d of age, all PF birds were individually weighed daily. During this period, the CON chicks were weighed every second day. After that, median BW for each individual bird were determined from database records of all visits to the feeding station. Feed intake was calculated for every feeding bout. In the CON treatment, weekly individual BW were recorded from 4 to 35 wk of age. After 36 woa individual BW were recorded biweekly. At 16 wk of age, 25 females and 16 males per feeding treatment were dissected to evaluate carcass development. At 22 wk of age, an additional 8 pullets per feeding treatment were dissected to determine whether the feeding system treatments caused any developmental differences. At 52 wk of age, 18 females per feeding treatment, and all the males were dissected. Eggs were collected at least 2 times daily, and the number of eggs produced in each pen was recorded. Egg weights were recorded. Beginning at 30 wk of age, eggs were incubated for 7 d, after which fertility was assessed by candling and breakout.
Immediately after the start of individual feeding in the PF treatment on day 14, BW CV decreased rapidly, reaching 3.5% vs. 11.4% in the CON treatment by 6 wk of age, and 0.8% vs. 12.7% in the CON treatment by 11 wk of age. At 21 wk of age, pullet BW CV was 1.4% in the PF treatment compared with 13.8% in the CON treatment. At 21 wk of age, BW of the PF treatment was 99.0% of the target BW, compared with 95.3% in the CON treatment. From wk 22 to 52, there was no effect of treatment on ADG. In the PFCON treatment, hen BW CV increased from 3.5% at 23 wk of age to 12.6% by 30 wk, and more slowly thereafter to 14.7% by 52 wk of age. From 30 wk of age onward, the PFCON BW CV was significantly greater than in the CON treatment, which had a BW CV of 11.3% at 52 wk. Cumulative feed intake for pullets from 2 to 22 wk of age was 160 g higher in the CON treatment (8.29 kg) compared with the PF treatment (8.36 kg). From 22 to 52 wk of age, average daily feed intake (ADFI) of CON and PFCON treatment hens was higher compared with the PF treatment hens; cumulative feed intake was 3.4 kg higher in the CON treatment compared with the PF treatment. Cumulative egg production per hen to 52 wk of age was highest in the CON treatment (89.1 eggs), compared with 71.3 eggs in the PFCON treatment and 64.9 eggs per hen in the PF treatment. These are lower than commercial broiler breeder numbers and reflect the fact that these were male line grandparent hens. The PF treatment hens laid 73% of the number of eggs laid by CON hens. Egg weight was inversely related to egg production. Fertility in the PF and PFCON treatments (90.9 and 89.8%, respectively) was higher than in the CON treatment (87.1%). There was a treatment × age interaction for fertility due primarily to a drop in fertility in the CON treatment around 42 wk of age as male uniformity decreased. After spiking at 45 wk of age in the CON treatment, fertility increased to a level that was not significantly different from the PF and PFCON treatments. In the current study, only 44% of PF treatment hens were in lay at the end of the production period, compared with 67% and 72% in the CON and PFCON treatments, respectively. Precision-fed hens that were laying must have been laying at a higher rate than CON and PFCON hens because their overall rate of egg production was similar at 52 wk. Birds that were not in lay at 52 wk of age had less than 50% of the abdominal fat and over 7% more breast muscle compared with hens that had at least 1 LYF at 52 wk. It is possible that some of the PF hens never laid any eggs because of an insufficient metabolic status to stimulate onset of laying.
Precision-fed broiler breeders had a 3.8% increase in fertility and a 1.3% reduction in egg weight CV compared with conventionally fed broiler breeders. Precision feeding increased broiler breeder flock uniformity dramatically over conventional feeding. However, the expected increase in reproductive efficiency as a result of the highly uniform flock was not achieved. Precision feeding increased feeding frequency, which in turn reduced diurnal variation in energy balance. This is the most likely cause of higher lean tissue growth and lower carcass fat: breast muscle ratios in PF birds. It is hypothesized that some of the PF pullets had either insufficient carcass fat reserves or an insufficient daily nutrient pulse to trigger the onset of sexual maturation. It is also likely that individual birds have different optimal BW at the onset of lay, and the current target BW was not sufficient for some birds, particularly when precision fed according to BW. Because reproductive success was observed in other trials where BW and ME intake restrictions were relaxed, it is hypothesized that breeder-recommended levels of feed restriction must be relaxed to accommodate changes in metabolism that result from increased feeding frequency in precision-fed broiler breeders.