Forage consumption of laying hens - the crop content as an indicator of feed intake and AME content of ingested forage

Knowledge on the grazing behavior and its nutritional value for modern strains of laying hens used in free-range systems today is scarce. In these sets of studies crop analysis as a method to estimate herbage intake was tested and apparent metabolizable energy (AME) of voluntarily selected grass was estimated in vivo. Crop analysis was used to estimate the contribution of grazing to the nutrition of free-range laying hens. Crops of hens sacrificed at noon (n=11) and in the evening (n=39) were examined. There was a great individual variation in crop contents and more and a higher proportion of grass in the crops was found in the evening than at noon. There was a significant linear relationship between the grass intake (x) and the grass content in the crop at the end of the day (y) of confined hens (n=17) with free access to whole wheat and grass. The AME of wheat and grass was estimated by regression to be 14.7 and 6.4 MJ/kg DM, respectively. These studies suggest that crop analysis can be used to get a rough estimate of herbage intake of hens on range. It is however a destructive method and as herbage intake varies between individuals in a flock an unacceptable number of hens must be taken to get a reliable estimate. Compared to other methods crop analysis gives additional information on grazing selectivity, its individual variation and also on other feed components found on range.