Effects of burning on diet quality and associated production systems of cattle and goats in acacia savannahs of Kenya

Abstract

A one-year study on the seasonal effects of burning on the dietary nutrition of cattle and goats was conducted at Kiboko from March 1982 to March 1983. Four esophageally fistulated heifers and two goats were utilized to collect diet samples from two adjacent burned and unburned paddocks. Pre-burn and post-burn herbaceous plant species frequency and density were"evaluated in both paddocks. Post-burn shrub/woody plant species were evaluated for density and canopy parameters. Diet samples were subjected to laboratory analysis for crude protein CCP) and organic matter digestibility COMO). Digestible energy was calculated. Burning did not significantly affect the frequency and density of most of the important forage species but enhanced species diversity and density of forbs and subshrubs at the expense of some desirable forage grasses. Burning enhanced the regeneration of some important browse species. The highest diet quality values for cattle occurred during the wet seasons, while the dry seasons had the lowest values. Burning enhanced dietary CP content during the wet seasons and into the early part of the dry seasons. Also, burning had positive effects on dietary OMD during the wet seasons but for shorter durations. The seasonal trend of dietary quality contents for goats was similar to that of cattle but the seasonal variations were not as dramatic as in cattle. Burning had detectable positive effects on dietary CP and OMD of goat diets during the wet season only. A cattle nutritional profiles model for Sahiwal, Boran and small East African shorthorn zebu breeds with January, May and October mean calving dates was run to estimate daily CP and net energy (NE) balances at selected production levels and rainfall conditions. For above average rainfall conditions and unlimited forage availability, the heavier, higher milk-yield breeds benefited mare than the lighter breeds, and the October mean calving date was mare preferable. Under low rainfall conditions, there were many months of NE deficits, where the heavier Sahiwal had higher deficits than the Boran and zebu during lactation periods. No calving date was definitively better than the others because of prolonged NE deficits.