Characterization of the dynamics of dry matter production of a sward of kikuyu (pennisetum clandestinum) with trees and under grazing condition in a dairy system in the tropical higlands of colombia

Abstract

A one year experiment was carried out in the central highlands of Colombia in order to measure the biological composition, nutritional value, DM (dry matter) production of a kikuyo (Pennisetum clandestinum) sward under various conditions. These conditions included high and low rainfall, with and without animal interaction, on hills and plains, with and without trees. The results were used to design an efficient grazing system. The quality of the forage was determined through proximal chemical analysis and by determining GE (gross energy). The accumulation of DM and growth rate was defined by using a gauging measure as proposed by Hodgson (1990). Biological composition was determined by manual dissection of the paddock. Accumulated DM data was used to formulate the parameters of an equation to represent the paddocks’ growth curve, using iteration of non lineal regression based on Marquardt’s algorithm. The model of sigmoidial growth used was Y=Ymax/(1+βX(X)k). During the time of highest rainfall, CP (crude protein) content was higher and NDF (neutral detergent fiber) lower. The paddock associated with the forest (Alnus acuminata) had a higher content of CP and lower of NDF, in both seasons. Gross energy content was equal in the majority of samples. The proportion of leaves, in a Kilogram of DM, decreased by 8,6% for every 15 days of increase in the age of the paddock. Using this DM accumulation information it was possible to estimate the quantity of DM available for the feeding of the herd. The highest accumulation of DM happened during the rainy season and in the paddocks with animals interaction and in the flat areas. The grass’ growth pattern in the paddocks without animals and where grass was harvested using clippers down to the ground behave as a loan. The rotation that maximized the accumulation of DM during the first season was at approximately 50 days, in the second season it was closer to 30 days. This information constituted the basis to design a strategy of efficient paddock use, and to establish a plan of seasonal calving