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Study: effects of different types of fiber-rich feed on welfare in broiler breeder pullets

21 July 2021, at 12:30am

Reduced energy content in the standard feed combined with a daily allocation of roughage may be the way to go to prevent problems of hunger and unsatisfied behavioural needs in conventional broiler parents. A comprehensive study was conducted by Aarhus University Department of Animal Science at the request of the Ministry of Environment and Food of Denmark.

If conventional broiler breeders are fed ad libitum, it results in obesity and consequently in health and fertility issues, as the birds are selected for increased appetite and growth. Therefore, broiler breeders are severely fed restricted, especially during rearing, in order to prevent health and reproductive problems. However, this results in other challenges.

Restrictive feeding results in welfare problems

“The restrictive feeding introduces other welfare problems, as it entails that basic behavioral and physiological needs are not met. This often results in abnormal behavior (indicating frustration and hunger) and physiological stress responses. Previous studies have tried to find solutions eliminating or at least reducing the extent of the welfare problems linked to feed restriction. However, an effective solution has not yet been found,” says senior researcher and project leader Anja Brinch Riber from Department of Animal Science, Aarhus University.

Qualitative feed restriction, however, is deemed to be a promising method for increasing satiety and improving the behavioral opportunities, hence increasing the welfare of the broiler breeders. The idea of qualitative feed restriction is to reduce the feed quality regarding the energy content by adding diluents, with no or poor value, to the standard feed. By increasing the fibre content, the daily feed ration can be increased.

“The optimum feed formula still needs to be determined, though. Therefore, we have conducted a feeding experiment in which we examined the effect of three fibre-rich types of feed on the animal welfare in broiler breeder pullets during rearing. The effect of the three different types of feed was measured using behavioral, stress-related physiological and clinical welfare indicators,” clarifies Riber.

Feeding-experiments with pullets

In total, 1200 day-old broiler breeder pullets (genotype Ross 308) were included in the experiment. They were divided into 24 groups of 50 chickens. Each of the 24 groups were provided with one of the four feeding types so that each treatment had six repetitions. The four types of feed were:

  1. Insoluble: standard feed diluted with insoluble fibers (oat hulls)
  2. Mixed: standard feed diluted with a combination of insoluble fibers (oat hulls) and a minor amount of soluble fibers (sugar beet pulp)
  3. Roughage: standard feed supplemented with roughage (maize silage)
  4. Control: standard feed (2-mm pellets, 11.8 MJ ME/kg, 200 g of protein/kg from DLG a.m.b.a.).

Effect of the three treatments

Roughage treatment

Overall, the study showed that the best results were obtained with the Roughage treatment. The pullets from the Roughage treatment showed signs of improved animal welfare, among others in the form of cleaner and less damaged plumage, reduced occurrence of foot pad dermatitis and cloacal discharge, and fewer and smaller stress lines in the feathers. In accordance to this, the litter quality of the roughage treatment was better than in the Control and Mixed treatments.

A likely explanation for the higher litter quality is the allocation of maize silage, leading to increased scratching activity, which increases aeration and drying of the litter. However, only limited evidence was found for the Roughage treatment resulting in increased satiety, as pullets from this treatment did not differentiate from Control pullets in the frustration test or in the motivation test in order to gain access to fresh litter.

Mixed treatment

Contrarily, pullets from the Mixed treatment showed several signs of reduced welfare. These signs included increased motivation for explorative behavior; higher occurrence of footpad dermatitis; cloacal discharge as well as damaged and dirty plumage; stress, indicated by reduced growth rate of feathers and the placement of stress lines on the feathers; and an increased motivation to gain access to fresh litter.

Many of the results showing signs of a negative effect of the welfare in pullets in the Mixed treatment are probably linked to the observed reduction of litter quality in the Mixed treatment. Under commercial conditions, this would not be acceptable.

Insoluble treatment

In the clinical study and in the registration of stress lines, the Insoluble treatment was almost comparable to the Control treatment. However, in the test for feeding motivation, pullets from the Insoluble treatment showed signs of reduced frustration and thus lower feeding motivation, and they had a lower compensatory feed intake, indicating increased satiety. These results show that the Insoluble treatment could partly alleviate hunger in broiler breeders, but the effect was not sufficient to obtain a significant improvement of animal welfare.

Recommendations for a future feeding strategy

Based on these results, the researchers recommend to further develop a feeding strategy which includes daily allocation of roughage to broiler breeders during rearing. For optimum effect, this should be combined with a dilution of standard feed with insoluble fibers such as oat hulls.

“A reduction of the energy content in the standard feed, combined with a daily allocation of roughage, will perhaps result in the same positive effects of the treatments ‘Insoluble’ and ‘Roughage’: reduction of the feeling of hunger, improvement of clinical welfare indicators and less stress, while the negative effects observed in the Mixed treatment are excluded,” concludes Riber.

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