Silage fermentation characteristics of grass species grown under two nitrogen fertilizer inputs and harvested at advancing maturity in the spring growth

Abstract

Three of the main management factors affecting herbage chemical composition pre‐ensiling are plant species, rate of nitrogen (N) fertilizer application and stage of maturity at harvest. This study investigated the effects of N fertilizer input and harvest date in the spring growth on the fermentation characteristics, dry matter recovery and aerobic stability of silages prepared from five common grass species. Perennial ryegrass (Lolium perenne cv. Gandalf), Italian ryegrass (Lolium multiflorum cv. Prospect), tall fescue (Festuca arundinacea cv. Fuego), cocksfoot (orchardgrass, Dactylis glomerata cv. Pizza) and timothy (Phleum pratense cv. Erecta) were grown under two inorganic N fertilizer inputs (0 and 125 kg N ha−1), harvested at five dates in the spring growth (fortnightly from 12 May to 7 July; Harvests 1 to 5, respectively) and subsequently ensiled in laboratory pipe silos for a period of 100 days. The ryegrass and tall fescue silages exhibited a lactic acid dominant fermentation and showed little evidence of secondary clostridial activity. In contrast, the challenge to preservation proved greater for the timothy (Harvests 1 and 2) and cocksfoot (Harvests 1 and 5) herbages, with the high pH (>4.2) and high butyric acid (>10 g kg−1 dry matter) and ammonia‐N (>100 g kg−1 N) concentrations being indicative of secondary clostridial activity during storage. Despite the effects on herbage chemical composition prior to ensiling being indicative of a greater challenge to preservation, there was little effect of fertilizer N on the extent or direction of fermentation. Although the Italian ryegrass herbage avoided significant clostridial activity, this herbage incurred the greatest dry matter losses during ensiling. This was particularly evident at early harvest dates suggesting yeast fermentation of sugars, which were surplus to the requirement for a lactic acid dominant fermentation.

Effects of nitrogen fertilizer and harvesting stage on photosynthetic pigments and phytol contents of Italian ryegrass silage

“…However, the DM yields of herbages at an early stage are relatively low. In addition, high N fertilizer application could cause high volatile basic N content in silage (King et al 2013). Therefore, because the fermentation quality of silage is reduced by high N fertilizer application, especially at the early developmental stages, it would be necessary, for practical use, to improve fermentation quality of these silages rich in phytol and carotenoids through moisture control and/or by additives such as lactic acid bacteria.…”

“…Forage species, fertilization, harvesting stages and conservation methods all affect the nutritive value of forage (Nozi ere et al 2006;Van Ranst et al 2009;King et al 2012King et al , 2013. Nitrogen (N) fertilizers can increase the contents of crude protein (CP) and carotenoids (b-carotene) in forages (Kopsell et al 2007;King et al 2012).…”

The estimated nutritive value of three common grassland species at three primary growth harvest dates following ensiling and fractionation of press-cake

“…Similarly, the effect of harvest date and species on silage fermentation characteristics has been discussed in detail by King et al (2012c). The major focus of this paper is on the effects of ensiling and fractionation on indices of nutritive value and on the suitability of the separated press-cake fraction as a feedstuff for ruminants.…”

“…Further juice was extracted for the analysis of lactic acid (LA), volatile fatty acids (i.e. acetic acid and butyric acid), ethanol and ammonia-N as described previously by King et al (2012c).…”

Developments in grass-/forage-based biorefineries

“…A reduction in water soluble carbohydrate concentration during ensiling is generally the most evident change in herbage chemical composition and indicates its substantial use as a substrate for fermentation (King et al ., 2013a ). Water-soluble carbohydrates are available for fermentation by a variety of microorganisms, of which lactic acid bacteria are the most important.…”