Assessment of biomass and nutritive value of warm season annual forages, including prussic acid free sorghum

Abstract

High biomass and digestible alternative forages that thrive under limited water are imperative to meet the increasing demand for feed for the thriving livestock industry in West Texas. Compared to other forages that have high water requirement, sorghum [Sorghum bicolor L. Moench] and pearl millet [Pennisetum glaucum (L. R. Br.)] are recognized for their ability to produce higher biomass under semi-arid environments with low precipitation and soil nutrients. However, obstacles such as hydrocyanic acid accumulation, specifically in forage sorghum, and lower digestibility have impeded their broad adoption by livestock producers. The current study aimed to assess the productivity, fiber content, and digestibility of various forage hybrids under field and greenhouse conditions. Under field condition a total of 26 hybrids, including forage sorghum, brown midrib sorghum-sudangrass, and pearl millet hybrids were tested for biomass production and nutritional value under seven different growth stages starting at 30 days post emergence to the soft-dough stage. In addition to the above-mentioned forage classes, the greenhouse study included prussic acid free sorghum and maize (Zea mays L.) forage hybrids that were tested under three key growth stages. Total dry mater, neutral detergent fiber, acid detergent fiber, in-vitro dry matter digestibility, and in-vitro true dry matter digestibility varied significantly (p < 0.05) between different growth stages and among hybrids. The soft-dough stage emerged as the ideal growth stage to obtain maximum yield and nutritional benefits across the forage species. The study identified four forage sorghum hybrids and a pearl millet hybrid that performed better or on par with forage maize, suggesting them as viable forage alternatives to maize in semi-arid regions. Novel prussic acid-free sorghum hybrids had similar biomass and digestibility compared to maize, presenting different grazing and silage options to producers in water limited environments.