Nutritional adaptation of heifers to diets containing poultry litter

The effect of inclusion of poultry litter in the diet on the length of the adaptation period of dry matter intake and levels of rumen and blood N metabolites was studied in heifers. Twenty-four Israeli Friesian heifers were divided into three groups and fed diets containing 0%, 17.5% and 35% poultry litter silage over a period of 7 weeks. The following were determined: dry matter intake, dry matter digestibility (using chromic oxide as a marker), rumen ammonia and blood urea. Disappearance of crude protein and organic matter of poultry litter from dacron bags incubated in situ in the rumen was also measured. Poultry litter feeding was accompanied by a decrease in ruminal ammonia and urea, which was already pronounced in the first week and persisted throughout the experimental period. Digestibility of dry matter dropped for 1 week but returned gradually to the control level. Incubation of poultry litter samples in situ in dacron bags in the rumen revealed that 82% of its crude protein and 37% of its organic matter is rapidly degraded whereas an additional 11% of crude protein and 37% of the organic matter are degraded slowly. Inclusion of poultry litter in the diet was associated with an increase in dry matter intake. Our findings indicate that ruminants require a relatively long adaptation period, of 3 to 4 weeks, in order to reach the maximal dry matter intake when poultry litter is added to their diet. This is in spite of the relatively short time (about 1 week) required for adjustment for ammonia levels in the rumen and urea levels in the blood.