The effect of alternative feeding strategies for broiler breeder pullets: 1. Welfare and performance during rearing

Abstract

Broiler breeders have impaired reproductive performance when fed to satiety but they can achieve an optimal hatching egg production under feed restriction. Feed restriction is a welfare concern due to signs of hunger, lack of satiety, and frustrated feeding motivation. The objective of this research was to examine the effect of a rationed alternative diet and non-daily feeding schedules on the performance and welfare of broiler breeder pullets reared under simulated commercial conditions. At 3 wk of age, 1,680 Ross 308 pullets were allocated to 24 pens fed with 1 of 4 treatments: 1) daily control diet (control); 2) daily alternative diet (40% soybean hulls and 1 to 5% calcium propionate); 3) 4/3 control diet (4 on-feed days per week; 3 non-consecutive off-feed days per week); and 4) graduated control diet (feeding frequency varied with age). Body weight and body weight uniformity were recorded at 3, 5, 7, 11, 17, and 21 wk of age. Pullets were scored for feather coverage, foot lesions, and hock burns biweekly. Physiological indicators (plasma glucose, corticosterone, hematology, and feather traits) and feeding motivation were also determined throughout rearing during on- and off-feed days. Data were analyzed using a linear mixed regression model, with pen nested in the model and age as a repeated measure. Compared to control, pullets under the 3 alternative feeding strategies had a lower feeding motivation during early rearing (P = 0.03), better feather coverage throughout rearing (P = 0.001), fewer feather fault bars (P = 0.006), and a delayed increase in the basophil to lymphocyte ratio (P = 0.001). These results indicate that the 3 alternative feeding strategies (the alternative, the graduated, and the 4/3 schedule) may decrease feeding motivation and alleviate stress compared to the control, suggesting an overall improvement in broiler breeder welfare without negative consequences on their performance.

Keywords: alternative diet; feeding motivation; non-daily feeding; rearing feeding strategy; stress.

Figure 1.

The effect of diet and feeding frequency on the body weight of broiler breeder pullets during rearing (mean ± SE). The dotted black line refers to the performance objectives for Ross 308 (Aviagen, 2011). Pullets were weighed after being fed once there was no feed left in their feeder. Pullets fed non-daily (dashed lines) had a lighter body weight at 17 wk of age, pullets on the graduated schedule showed compensatory growth, while pullets on the 4/3 schedule remained lighter until 22 wk of age (P < 0.001).

Figure 2.

The effect of the alternative diet and feeding frequency on body weight uniformity of broiler breeder pullets during rearing (mean ± SE). Body weight uniformity was calculated as the coefficient of variation (CV) by dividing the standard deviation by the average body weight. The CV of body weight depended on treatment and age (P = 0.007).

Figure 3.

The effect of diet and feeding frequency on feather coverage score (mean ± SE). Light intensity decreased from 31 to 21 lux at 7 wk of age and increased to 54 lux at 22 wk of age. Pullets on the control treatment had a consistently higher feather coverage score than pullets on the all of the alternative feeding strategies (combination of the alternative diet, and the graduated and the 4/3 feeding schedule) (P = 0.001).

Figure 4.

The effect of diet and feeding frequency on the heterophil to lymphocyte ratio (H/L) in broiler breeder pullets by feeding day (mean ± SE). Solid lines represent daily-fed treatments (black for the control and gray for the alternative), and dashed lines for non-daily fed treatments (black for on-feed days and gray for lines off-feed days). During off-feed days, pullets on the 4/3 schedule and on the graduated treatment were not fed. At 11 wk of age, the H/L ratio was higher for the graduated treatment (regular dashed lines) during on-feed days compared to off-feed days (P = 0.001).

Figure 5.

The effect of the diet and feeding frequency on the basophil to lymphocyte ratio (B/L) in broiler breeder pullets (mean ± SE). The B/L ratio increased earlier in control (black solid line) than for the alternative feeding strategies (alternative: gray solid line, graduated: black dashed line, and the 4/3 schedule: black dashed line; P = 0.001).

Figure 6.

The effect of the diet and feeding frequency by feeding day on plasma CORT in broiler breeder pullets (mean ± SE). Solid lines represent daily-fed treatments and dashed lines non-daily-fed treatments (on-feed days: black, and off-feed days: dark gray). Pullets on the non-daily treatments were fed during on-feed days, and pullets fed the other treatments (solid lines) were fed on both days. Plasma corticosterone increased on off-feed days in non-daily fed treatments based on pullet's age (P < 0.001).

Figure 7.

The effect of the diet and feeding frequency on plasma glucose in broiler breeder days (mean ± SE). Plasma glucose concentration was higher during on-feed days (black dashed lines) compared to off-feed days (dark-gray dashed lines) depending on feeding frequency and pullets’ age (P < 0.001).

Figure 8.

The effect of the diet and feeding frequency on the feeding motivation of broiler breeder pullets by feeding day (mean ± SE). Feeding motivation is expressed as the feed intake for 20 min of ad libitum feeding relative to body weight during on-feed days (a) and off-feed days (B). Pullets on non-daily fed treatments were fed on the previous day during off-feed days and had their last meal 2 D prior to the test during on-feed days. Pullets on the daily-fed treatments (solid lines: the control in black and the alternative in gray) were both fed on the previous day. The effect of feeding strategies on the relative feed intake of broiler breeders varied based on age and feeding day (P = 0.03).

Figure 9.

The effect of the diet and feeding frequency on litter moisture during rearing (mean ± SE). Ground heaters were switched on at 5 wk of age and off at 12 wk of age. Litter moisture increased in pullets fed the alternative diet (gray solid line) compared to control (black solid line) during early rearing (P = 0.001).