Effect of Graded Levels of Feed Restriction on Performance of Layers

Abstract

Several reports have been published on the restricted feeding of layers. It has been demonstrated that performances of layers such as egg production, egg weight and body weight were decreased and the feed conversion was improved by feed restriction. There is no report, however, concerning the effect of graded levels of feed restriction on the performance of layers. It is considered that the economical profit will be increased by the improvement of feed conversion owing to the feed restriction.This report deals with the effect of graded levels of feed restriction on the performance of layers and the relationship between the graded levels of feed restriction and the economical profit was discussed.Numbers of layers used in this experiment were 918 and 946 of the commercial strain SA and SB respectively, which were hatched in the two hatcheries at the same time. Experiments were conducted at five poultry experiment stations under the same experimental design.Layers of each strain were divided into two groups and a control group. In one group, the restricted feeding was started at 24 weeks of age (T24) and in the other group the restricted feeding was started at 52 weeks of age (T52). Feed restriction was terminated at 72 weeks of age in the two groups. In the control group of each strain, no feed restriction was carried out. The layers of each restricted feeding group were divided into 4 sub-groups, in which feed restriction rate was 4, 8, 12 and 16% of the control layers, respectively. The feed supplied contained 16.4% of crude protein and 67.6% of total digestible nutrients. Natural and artificial light were supplied for 14 hours per day from 20 weeks of age until 72 weeks of age. During the restricted feeding period (24-72 or 52-72 weeks of age) egg production, egg weight, feed consumption, body weight and viability were recorded. Economical profit of each graded levels in the two groups were estimated based on the records of total egg weight and feed consumption from 24 weeks of age to 72 weeks of age.Egg production rate during the restriction feeding period was lower in all sub-groups of feed restriction than in the control group. The lower egg production was recorded in sub-groups of higher feed restriction. In the spring season, however, egg production in the sub-group of 16% restricted feeding did not differ from that in the control group. On the contrary, egg production was reduced even in the sub-group of 4% restricted feeding in the summer. This tendency was observed in the two groups. A different effect of feed restriction was observed, however, between strain SA and SB. Decrease in the egg production in strain SB was greater than that in strain SA. Egg weight in all sub-groups of feed restriction was slightly less than that in the control and there was no significant difference among the restriction sub-groups. Difference in the feed conversion was observed between strain SA and SB. Feed conversion in restricted subgroups of strain SA was better than that in the control. But in strain SB, the feed conversion in all of the restricted sub-groups was not improved comparing with that in the control. Seasonal variation was observed in the feed conversion. Feed conversion in the restricted sub-groups was better than that in the control in the spring season and an adverse effect was observed in the summer. Body weight gain in higher restricted sub-groups was lower than that in lower restricted sub-groups of both strains.In T24 group, crude profit of feed restriction in strain SA was much more than that in the control. It was considered that maximum crude profit would be obtained in 11-13% feed restriction. It was estimated that the higher feed restriction might result in the more profit when egg price was low (210 yen per kg weight).