Newsletter from DARCOF | December 2006

Forage may partly replace supplementary feed for laying hens

By Klaus Horsted, Danish Institute of Agricultural Sciences

High-producing layer strains are able to consume considerable amounts of herbage and that forage can provide laying hens with important nutrients. Notably, chicory and quinoa seem promising. Moreover, it seems possible to lower the standards of important nutrients in the supplementary feed, provided that good forage is available.Introduction and background

The hypothesis of the present work was that hens are capable of finding and utilizing a considerable amount of feed items from a forage area, dependent on the type of supplementary feed and forage vegetation offered. Thus, increased foraging in organic laying hens may be a way to increase the utilisation of local resources in organic egg production systems. This could increase the cycling of nutrients within the system, ease the transition to 100 pct organic feed supply, and benefit the economy of the egg production. Further, this may lead to a greater dispersion of the poultry in the open-air run that in turn may benefit the welfare of the hens and reduce the risk of nutrient leaching in the area closest to the henhouse.

On this background, the main objective of the conducted Ph.D. study was to provide better knowledge on the potential of utilizing the foraging of laying hens in a forage-based system. More specific the aims were:

to estimate the intake of herbage from the open-air run
to determine selectivity of forage material in relation to restriction of nutrients in the supplementary feed
to estimate the possible contribution of foraging in meeting nutritional requirements of the poultry
to suggest forage-based systems.

Here, an outline on major results from the Ph.D. report is presented. Further details are available on the background of the work. Also, the full report can be downloaded in pdf format.

Experimental design

Experimental work has been done concerning productivity and welfare in a foragebased system, egg quality, estimating feed intake from forage, and estimating selectivity of feed from forage. These subjects were investigated in relation to different forage crops and two types of supplementary feed (a complete layer ration versus whole wheat and oyster shells).

Three experimental setups were carried out in this study. In 2004, two short-term experiments (23 days each), each with 12 flocks with 20 hens and one cock in each flock, were carried out. The forage crops consisted of grass/clover versus a mixture of forbs in Experiment 1, and grass/clover versus chicory in Experiment 2. In 2005, a third experiment (130 days), with six flocks with 26 hens and one cock, were conducted. The flocks were moved regularly between grass/clover, pea/vetch/oats, lupin and quinoa.

Quantity an quality of herbage intake

A discussion on herbage intake from forage was made, using the results from a sward-based method and using the amount of herbage in the crops from hens slaughtered in the evening.

The results indicate that hens consume a considerable amount of herbage irrespectively of type of forage and type of supplementary feed, even though nutrient-restricted hens were found to have approximately 50 pct higher intake. Thus, intake of grass/clover may be 10-30 g per hen per day for non-restricted hens and 20-40 g per hen per day for nutrient-restricted hens. However, hens foraging the chicory plots particularly seemed to benefit from forage with approximately twice as high intake of this forage crop as of grass/clover.

Analyses of crop content indicate that selectivity among feed items was found to differ in relation to type of supplementary feed. Thus, it was found that wheat-fed hens had more plant material, grit stone, soil, and oyster shells in the crops and less seeds than concentrate-fed hens. Moreover, wheat-fed hens gave priority to earthworms and larvae even though the amount of this feed item seemed to decrease after a few days in a given forage vegetation. Only to a minor degree did type of forage influence the amount of different feed items in the crops, though the crop rotation experiment (Experiment 3) indicated a higher intake of quinoa seeds compared with seed of lupin and pea/vetch/oats.

Plant preferences

In Experiment 1 microhistological analyses of faeces indicated that nutrient-restricted hens had significantly more of the species of grass Elytriga repens in the faeces, whereas non-restricted hens had more white clover (Trifolium repens). Further, in the plots with the mixture of forbs, selectivity indices suggested that hens gave priority to plant species nearer the ground, since positive selectivity indices were found for the grasses, Elytriga repens and Lolium perenne as well as for the clover Trifolium repens. Negative selectivity indices were found for the much taller species of plants, Fagopyrum esculentum and Phacelia tanacetifolia.

Energy intake and amino acids

The possible contribution of metabolizable energy (ME), lysine, methionine and calcium from forage is estimated using the requirements for laying hens and the results on productivity. After a period of adaptation it was estimated that hens, irrespectively of type of supplementary feed, may consume up to 0.25 MJ ME of their requirements of ME from forage; presumably a little higher for nutrient-restricted hens due to a higher foraging activity. Moreover, it was estimated that the forage area on average had supplied the nutrient-restricted hens with approximately 70 pct of their requirements according to the feeding standards for lysine and methionine, and approximately 25 pct of their requirements according to the feeding standards for calcium. Concentrate-fed hens were fully covered through the supplementary feed.

Egg production, nutrient balances and welfare

On a short-term basis nutrient-restricted hens had a decline in egg production, except for hens foraging the chicory. Further, a tendency to a darker and redder yolk colour was found when hens were foraging the chicory plots. Also albumen DM was higher in eggs from hens foraging chicory.

Eggshell parameters were not affected by forage crops or by type of supplementary feed, suggesting that nutrient-restricted hens were provided with the required amount of calcium through oyster shells and foraging material.

After a period of adaptation nutrient-restricted hens were found to produce well in a crop rotation system, since laying rate was comparable to non-restricted hens. Egg weight and body weight was lower in nutrient-restricted hens, though increasing at the end of the experiment. In general, hens fed whole wheat had a lower intake of supplementary feed, even though a distinct increase in this feed was seen after a few weeks. At the end of the experiment, gizzards were found to be significantly larger for the wheat-fed hens than for the concentrate-fed hens.

The effects of productivity and intake of supplementary feed were reflected in the nitrogen and phosphorus balances in the way that N and P surpluses were considerably lower for nutrient-restricted hens. The welfare of hens in forage-based systems was found to be excellent irrespectively of type of supplementary feed.

Overall conclusion

It was concluded that high-producing layer strains are able to consume considerable amounts of herbage and that forage can provide laying hens with important nutrients. Chicory and quinoa seem promising, just as focus on earthworms has potential. Moreover, it seems possible to lower the standards of important nutrients in the supplementary feed, provided that good forage is available and that the production system supports good welfare of the poultry. A crop rotation system was suggested.

BACKGROUND

According to the Danish legislation for organic poultry production the range area for organic laying hens must be at least 4 m2 per hen. It is however, a commonly recognized problem that up to 90% of the hens stays inside the house or predominantly uses the area just in front of the henhouse. The reason for the lack of use of the range area is most likely because the hens do not find the large and open areas attractive and because the feed is provided indoors. This results in a high animal density inside the henhouse that in turn may lead to different kinds of health and welfare problems such as feather pecking and sometimes even cannibalism.

The very uneven distribution of hens outside with the majority staying close to the henhouse may enhance the risk of nutrient leaching to the ground water and parasitic infections. One way of minimizing these problems could be to make the range area more attractive by offering attractive forage crops as part of the daily ration. This may encourage the hens to use the entire range area, thus obtaining a lower animal density, and an increasing on-farm recycling of nutrients caused by a reduction in feed imports. This might in turn reduce the environmental load and the feed costs for the farmer. Since the feed costs account for more than 60 % of the total costs in Danish organic egg production systems, even a small reduction in feed costs will be noticeable.

Moreover, it seems to be difficult to procure 100 % organic raw materials for feeds, which until recently was stipulated for organic pig and poultry producers by the EU, but because of difficulties in fulfilling this requirement, the 100 % organic feeding requirement has been deferred until the end of 2011. A higher utilization of local resources may be a way of facilitating the transition to 100 % organic feed supply for organic egg producers.

Although laying hens are able to consume considerable amounts of roughages, information on herbage intake from range areas by high-performance layers is scarce. Some results suggest that layers on range consume 30-35 g DM/day of herbage besides ad libitum feeding of concentrates. However, different forage crops may vary in relation to nutritional value and attractiveness to laying hens. Moreover, restriction in nutrients supply has shown to increase forage intake in pullets. However, a drastic reduction in protein and some amino acids may have a negative effect on plumage condition due to feather pecking for which reason it is essential that plenty of foraging material is available.