The effect of cultivar on the changes in protein quality during wilting and ensiling of red clover (Trifolium pratense L.)

Abstract

SUMMARYRed clover (Trifolium pratense L.) silage usually contains lower contents of non-protein nitrogen (NPN) compared with other forage legumes. This is often attributed to the polyphenol oxidase (PPO) activity in red clover, although in most field studies the PPO activity was not measured. Therefore, a laboratory ensiling experiment with three red clover cultivars and one white clover cultivar as control grown in two management systems (with and without mechanical stress) over 2 consecutive years was conducted. Fresh, wilted and ensiled clover herbage was sampled at four cutting dates per year to determine the crude protein (CP) fractions according to the Cornell Net Carbohydrate and Protein System. The specific PPO activity was measured photometrically in fresh clover leaves. The content of CP fraction A (NPN) increased from fresh over wilted to ensiled clover herbage at the expense of the content of CP fraction B (true protein), irrespective of species, cultivar and year. The most important source of variation for all CP fractions and the calculated rumen-undegradable protein contents was generally the herbage condition, except for CP fraction C (unavailable protein). White clover silage consisted of higher contents of CP fraction A and lower contents of CP fraction B3 in CP compared with red clover silage. As a result, the calculated rumen-undegradable protein content of white clover silage was lower than that of all red clover cultivars. In conclusion, the extent of proteolysis during ensiling among the silages made from the herbage of different red clover cultivars was primarily influenced by the stage of maturity at harvesting and the degree of wilting at ensiling. The variation in specific PPO activity could not be related to the extent of proteolysis.

Quality of alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) mixture silages depending on the share in the mixture and additives

“…In all of the mixtures, a higher value of the PA fraction content was achieved compared to the content value of the same in the forages before ensiling (Table 1). This is in accordance with the results of Krawutschke et al (2011), who reported increase of PA fraction in silages of the examined red clover cultivars, when compared with material before ensiling. With an increase in the content of red clover in the mixtures, there is a linear increase in the difference between the value of the PA fraction of the silages and the initial material (Figure 1A).…”

Field performance of a red clover germplasm selected for increased tolerance to 2,4-D

“…If the number of harvests is kept to two or three across the season in the second year after establishment, most modern red clover cultivars would yield comparably well in both the first year and second year after establishment (Wiersma et al 1998). Crude protein levels, and the general quality of the red clover forage, are significantly lower in the second year compared with the first year after establishment (Cassida et al 2000;Krawutschke et al 2012). Even though forage quality diminishes, forage producers would likely maintain red clover in their pastures after the first year because plants still provide reasonable yield, and pasture renovation is costly.…”

The effect of increased temperature and CO2 air enrichment on the nutritive value of orchard grass (Dactylis glomerata) in permanent grassland

“…In addition, in most forage plants, a large proportion of the N is present as non-protein N (NPN) at harvest (Gierus et al ., 2012; Krawutschke et al ., 2013 a ). After harvesting, NPN is extensively generated by plant-related proteases (Gierus et al ., 2016) or during the fermentation phase of forage conservation (Krawutschke et al ., 2013 b ). After ingestion, high amounts of NPN are counteracted by rapidly fermentable sugars, like water-soluble carbohydrates (WSC), as available energy, resulting in efficient ruminal microbial growth and N utilization (Miller et al ., 1999), contributing to uCP.…”