Dry matter degradation kinetics of selected tropical forage in Nili-Ravi buffalo and Cholistani cows at heifer and lactating stages using NorFor in situ standards

Abstract

Current methods of ruminant ration formulation in Pakistan use foreign-based nutrient availability values. These values may not be optimal for all geographic areas, as variation in environment, agronomic factors, animal species, and diet characteristics may not be considered. The aim of present study was to establish a database of the chemical composition and dry matter degradation parameters of tropical forage commonly fed to ruminants in Pakistan and South Asian countries using Nili-Ravi buffalo and Cholistani cattle at heifer and lactating stages. Six cereal grain and four legume species were grown in 3 locations under standard agronomic conditions and sampled at booting and at 50% flowering stage for cereal and legumes, respectively. Dried and milled feeds were analyzed for chemical composition and in situ dry matter degradation parameters using 1 g samples in bags placed in the rumen of 2 Nili-Ravi buffalo heifers, 2 lactating Nili-Ravi buffaloes, 2 Cholistani heifers, and 2 lactating Cholistani cows. The forage family (cereal vs. legumes), species, and geographic location of growth significantly influenced (P < 0.001) chemical composition and in situ degradation fractions. Animal species and developmental stage showed no effect on degradation fractions (P > 0.05). Legume-by-heifer interactions significantly increased (P < 0.05), and legume-by-lactating cow interaction tended (P = 0.065), to increase the rate of degradation (Kd). The selected forages were degraded to a similar extent independent of animal species or developmental stage, and legumes are degraded at higher rates and to a greater extent than are cereals. A moderately significant relationship between Kd and effective dry matter degradability (DMD) suggests that Kd could be the single most important predictor of forage degradability in the rumen.