FACTORS INFLUENCING THE UTILIZATION BY RUMINANTS OF CORN SILAGE IN MARGINAL GROWING AREAS

Abstract

The effects of various factors which influence the utilization of silage, made from forage corn grown in marginal areas for production, by ruminant animals are reviewed, with particular reference to dairy cattle. Crop maturity and composition and their effects on important animal performance characteristics are discussed in detail. Effects of the dry matter and grain contents of the ensiled corn on the nature of silage and the resulting animal responses are also considered. The declining emphasis on assessing the quality of forage corn by its grain content, and the increased emphasis on the selection of hybrids based on shoot dry matter yields are discussed from both crop and animal production viewpoints. For instance, the results of feeding trials where high crop densities, various genetic mutants and tillering hybrids were studied are discussed. Consideration is given to the laboratory evaluation and use of various agronomic characteristics to assess the nutritive value of forage corn. It is concluded that more emphasis should be placed on the breeding of corn genotypes specifically for forage production by selecting for maximum digestible dry matter yields per unit land area, particularly when dry matter content is unlikely to exceed 25%. Evaluation of the forage potential of corn genotypes should be conducted under systems of management specifically suited to maximizing whole-crop, dry matter yields. Also, with the utilization of mutant types of corn with higher digestibilities than normal corn genotypes, routine laboratory analysis for digestibility will become necessary. The final comparison of promising genotypes will need to be done with animals capable of relatively high levels of production.