The Beaker: June 2014

Broiler birds are known for their fast growth rates and voracious appetites but that growth potential creates an issue for breeding hens. How do we feed these birds without creating health problems with fat hens?

Masters candidate Krysta Morrissey of the Department of Animal Science, University of Guelph, described in her recently published paper how the selection for fast growth is correlated with obesity-related health problems, including increased susceptibility to lameness, cardiovascular disease, and premature death.

In North America, the practice of skip-a-day feeding is commonly used to avoid these health problems in parent stock. Broiler breeding hen rations are restricted by up to 75 per cent of the ad lib intake ingested by their broiler counterparts. Two times the daily ration allocation is typically fed every other day, and the feed allocations are often entirely consumed in less than ten minutes.

But this practice has raised welfare concerns, particularly in the United Kingdom (UK) where skip-a-day feeding is negatively perceived. Does skip-a-day feeding cause an increase in behavioural symptoms indicative of hunger?

As Morrissey describes in her paper, “Because broiler breeders have such large appetites, these severe dietary restrictions result in symptoms of chronic hunger. In behaviour thought to be indicative of frustration (such as pecking at nonfood objects), increased general activity and aggression, excessive drinking, and increased feather pecking.”

Morrissey’s research compared feeding regimes, skip-a-day versus daily feeding, and investigated “alternative” diets. Fibre and appetite suppressants were added to broiler breeder rations to possibly reduce stereotypic behaviour associated with hunger.

In her study, six groups of hens were observed by video monitoring from 11 to 28 weeks of age. Two control groups compared a typical ration (C) fed every day and on skip-a-day (SAD) frequency, while the remaining four groups were fed “alternative” diets with added fibre, (40 per cent soybean hulls), and either feed grade (F) or purified (P) Calcium propionate, on daily and skip-a-day routines.

Morrissey hypothesized that the alternative diets, F and P, would result in reduced hunger symptoms, expressed by reduced aggressive behaviours, such as excessive drinking, object pecking and feather pecking. She also hypothesized that SAD feeding frequency would increase behavioural indices of hunger and result in worse feather condition.

The birds were observed during and immediately following feeding, assuming that aggressive behaviour would increase at feeding time and would reveal more significant differences.

She found that both diet and frequency of feeding affected behaviour. The control birds on both daily and skip-a-day feeding routines were more active, displayed more feather pecking and object pecking. This increase in aggressive behaviours following feeding was less obvious with the SAD feeding frequency, presumably due to an increased satiety over the daily-fed birds in the control group.

The fibre and appetite suppressant diets, regardless of feeding frequency, resulted in fewer symptoms of hunger, presumably due to the larger volume of feed being ingested and the resulting increase in satiety.

“As hypothesized, we found that high-fiber diets including an appetite suppressant reduced behavioral indices of hunger, as indicated by the increased time spent resting, and decreased time spent feather pecking and object pecking and aggression. However, even with the alternative diets, some level of hunger was still present, as not all oral stereotypic behavior was completely abolished during rearing.”

She also suggested that, “Chronic hunger may be unavoidable as Hocking [1993] found that ad lib fed broiler breeders still spent a significant amount of time feeding throughout the night, suggesting a level of hunger sufficient to cause feeding behavior during the dark period when there normally would not be.”

Morrissey later investigated the birds’ preference for the diets, finding no dietary preference between the control ration (C) and the bulkier fibre and appetite suppressant ration (F). It is possible that the differences between the two diets were too subtle for the birds to detect. While the results did not support her hypothesis that the birds would prefer the bulkier ration, they did at least show that the alternative feed wasn’t aversive to the birds.

Her research provided no strong evidence to support the hypothesis that daily feeding would suppress hunger more effectively than SAD or vice versa. While Morrissey’s research did not generate behavioural data that would allow recommendations regarding skip-a-day feeding, she does suggest that producers adapt a dietary feeding regime that includes a fibre source and possibly an appetite suppressant that may improve broiler breeder welfare.

Morrissey’s work appears in Poultry Science 93:285-295. The Growing Forward I Poultry Cluster, Canadian Poultry Research Council and the Poultry Industry Council provided funding with special thanks to Margaret Quinton (University of Guelph) and Hank Classen (University of Saskatchewan) as well as the assistance of the Behaviour Laboratory at the University of Guelph. The birds were donated by Aviagen, via Horizon Poultry.