Effects of peptidase inhibitors and other additives on fermentation and nitrogen distribution in perennial ryegrass silage

The effects of formic acid, three concentrations of formaldehyde ina formic acid/formaldehyde mixture and cysteine‐peptidaseinhibitors, 1‐ trans epoxysuccinyl‐leucylamido‐(4‐guanidino) butane ( E ‐64), N ‐ethylmaleimide and cystamine on nitrogen (N) distribution during ensilage of perennial ryegrass ( Lolium perenne ) were investigated. A third cut or perennial ryegrass (163 g dry matter kg −1 and 61 g water‐soluble carbohydrate kg −1 dry matter) was ensiled in two silo sizes; formaldehyde‐treated herbage was ensiled only in larger silos (500–550 g herbage) and cysteine‐peptidase inhibitor‐treated herbage only in smaller silos (130–150 g herbage). Control silages were poorly fermented but contained low concentrations of butyric acid and ammonia N indicating little activity of spoilage bacteria. Formic acid increased peptide N concentrations ( P <0.01) in silage from smaller silos but had little effect on other N constituents; in the larger silos, formic acid reduced soluble non protein nitrogen (NPN) and ammonia‐N concentrations and increased peptide N concentrations. Increments in formaldehyde reduced silage soluble and ammonia N concentrations (linear effect; P <0.001). N ‐Ethylmaleimide and E‐64 reduced soluble NPN concentrations ( P <0.05) but had little effect on other N constituents. Cystamine, however, increased silage peptide N concentrations. Gel filtration on Sephadex G‐25 of silage juice prepared from control and formic acid‐treated silages suggested that most silage peptides were small, with molecular weights of less than 520 Da. © 1999 Society of Chemical Industry