Analysis of starch digestibility in different particle size maize, effects of amylase enzyme and production parameters in dairy cows

In South Africa, maize is a key energy source for ruminant diets, but its price is influenced by environmental and political factors. In 2016, droughts drove maize prices to record highs, severely impacting the milk-to-feed price ratio and necessitating precise diet formulation for optimal dairy production. As production costs rise, optimizing nutrient balance and reducing nutrient wastage through improved digestibility is crucial.

Maize starch digestibility is primarily affected by prolamin protein encapsulation and the amylose-to-amylopectin ratio. Finer grinding of maize improves starch digestibility by damaging prolamin encapsulation. Additionally, starch digestibility is influenced by the amylose-to-amylopectin ratio, with higher amylose making digestion more challenging. Recent interest in nutrient feed additives and enzymes aims to enhance nutrient efficiency in ruminants. Feed additives like yeast and phytonutrients, and enzymes such as Ronozyme® Rumistar, have shown promise in improving digestion and overall performance in dairy cattle. Ronozyme® Rumistar, a pure amylase, enhances maize starch utilization and fiber digestion without affecting rumen pH.

This study explored how different maize particle sizes and the addition of the α-amylase enzyme Ronozyme® Rumistar affect starch digestion and dairy performance. It included evaluating milk production, faecal starch content, starch and NDF digestion through in vitro and in sacco methods, and rumen fermentation parameters. The research was conducted in two phases. Phase one took place on a commercial dairy farm and involved feeding cows diets with maize ground to different particle sizes (coarse, fine, and micro-milled) with or without the amylase enzyme. Results showed no significant impact on milk yield or fat, but smaller maize particles increased milk protein content. Finer maize reduced starch in manure, and enzyme supplementation decreased manure protein content, suggesting improved rumen fermentation.

Phase two, conducted at the University of Pretoria, involved rumen cannulated cows to measure starch degradability. The results indicated that finer maize particles improved digestibility, and enzyme addition enhanced total tract digestibility and volatile fatty acid production. Overall, the study suggests that enzyme supplementation and finer maize processing can improve starch digestion and nutrient efficiency in ruminant diets, though further research is needed to fully understand these effects.