Deep-stacked broiler litter as a protein supplement for dairy replacement heifers

Fifty Holstein dairy heifers, [two replications of 25 heifers; average body weight (BW) 227 kg], were assigned to one of the following treatments for 105 d. Treatments 1 through 4 are given as the percentage of supplemental crude protein (CP) from soybean meal and deep-stacked broiler litter, respectively: 1) 100 and 0%; 2) 67 and 33%; 3) 33 and 67%; 4) 0 and 100%; and 5) 67% of supplementary CP from deep-stacked broiler litter and 33% from a source of rumen undegradable protein (RUP). All rations were formulated to contain 15% CP and 68% TDN on a dry matter basis. Dry matter intake was not significantly different among treatments at 10.1, 10.2, 10.4, 9.4, and 9.1 kg/d for treatments 1 through 5, respectively. Average daily BW gains (1.35, 1.37, 1.28, 1.17, and 1.24 kg/d for treatments 1 through 5, respectively) decreased linearly as the level of litter feeding increased and was not influenced by increasing RUP in treatment 5. Feed efficiency was not affected by the level of deep-stacked broiler litter feeding. Ruminal ammonia and plasma urea nitrogen concentrations decreased linearly as the level of litter feeding increased. Feeding additional RUP decreased ruminal ammonia concentration in treatment 5 to a level similar to treatment 4. This suggests that the protein in deep-stacked broiler litter may be more undegradable than that in soybean meal and that RUP in broiler litter may be higher than previously thought. Results from this study indicate that deep-stacked broiler litter has potential as a low-cost CP source for growing dairy heifers.