Effect of Supplementary Concentrates Differing in Partitioning Factor on Dry Matter Intake, Organic Matter Digestibility and Nitrogen Metabolism in Crossbred Heifers

The effect of differing partitioning factor (PF) of diets on feed intake, change in body weight, N metabolism and urinary allantoin excretion (UAe) was studied in crossbred dairy heifers. Four crossbred Karan Friesian dairy heifers were used in a 4 x 4 Latin square design experiment. The diet consisted of finger millet (Eleucine coracond) straw (FMS) as the sole source of forage and concentrate supplement (CS) to provide maintenance metabolizable energy and other nutrients. Four CS differing in PF were formulated using published PF data. The ratio of FMS and CS in the diets was 76:24. The rate of fermentation (k) and the PF for the four diets were e.0471 and 3.54, 0.0461 and 3.48,0.0462 and 3.37, 0.0462 and 3:33, respectively. The PF of the diets did not impact intake or digestion of nutrients. In addition, measures of microbial growth (UAe) and efficiency (g microbial N/kg ADOM) were unaffected. The microbial efficiency for PF 3.54, 3.48, 3.37 and 3.33 diets were 10.3, 9.6, 11.1 and 11.0 respectively. Results show that feeding diets differing in PF by about 6.3%, but similar in k (∼2.2%), did not impact estimated microbial N flow to the duodenum. This suggests that either the differences attained in this study in PF were insufficient to impact microbial growth or that PF, at least in the range used in this study, is not important in impacting microbial flow from the rumen.