Changes in crude protein fractions of forage legumes during the spring growth and summer regrowth period

Abstract

Only a few previous studies have analysed the crude protein (CP) fractions of the Cornell Net Carbohydrate and Protein System during the growth period of forage legumes. The objective of the present study was to investigate the changes in CP fractions during the spring growth and summer-autumn regrowth period of five forage legume species (alfalfa (also known as lucerne, Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), kura clover (Trifolium ambiguum M.B.), red clover (Trifolium pratense L.) and white clover (Trifolium repens L.)) grown in binary mixtures with perennial ryegrass (Lolium perenne L.) and also in pure stands (two red clover cultivars). Additionally, the specific polyphenol oxidase (PPO) activity was measured photometrically in the leaves of pure red clover swards. In both pure and mixed cropping, CP fraction A increased with advancing maturity, except for the legumes from mixed cropping in the summer-autumn growth period 2004 and 2005. The variation of CP fraction A was mostly positively related to the N yield and the amount of dinitrogen fixation. Although CP fraction A of pure red clover was negatively correlated with the specific PPO activity in the spring growth period, the specific PPO activity was less relevant for the variation of CP fraction A with respect to the whole growing season. CP fraction B generally made up the largest proportion of the CP. Pure red clover stands showed reducing amounts of CP fraction C during the growth period, whereas in legumes grown with ryegrass an increase was usually observed. Despite these differences, there was generally an increase of CP fraction C when the content of nonstructural carbohydrates decreased. Red clover and birdsfoot trefoil herbage contained the highest proportions of CP fraction C in the CP, regardless of growth period and year. In conclusion, red clover and birdsfoot trefoil had a more favourable CP composition for ruminant nutrition compared to the other legume species, and in red clover this could not be clearly attributed to the specific PPO activity.

Dry matter yield, chemical composition and estimated extractable protein of legume and grass species during the spring growth

“…In a study by Krawutschke et al . a significant increase was observed in fraction A for red clover during the spring growth which was in contrast to our finding of no significant change.…”

“…Other studies claim that the size of fraction A is not affected by plant maturity in the spring season . The discrepancy in changes in fraction A across the growing period between studies may be explained by different environmental conditions such as the supply of mineral N, water stress and soil acidity . Our data pertaining to a higher accumulation of fraction A in legumes than in grasses is supported by the study of Yu et al .…”

Effects of fertilization and tillage system on growth and crude protein content of quinoa (Chenopodium quinoa Willd.): An alternative forage crop

“…Dugalić et al (2012) reported that crude protein content in alfalfa plants ranged between 21.7% -25.9%. The nutritional value of forage crops is also influenced by stage of maturity (Krawutschke et al, 2013). Our results indicated that the highest crude protein content was measured at 150 DAS (Figure 1).…”

“…In temperate regions, white clover (Trifolium repens L.) is the predominant species used for grazing, whereas red clover (Trifolium pratense L.) and alfalfa (Medicago sativa L.) are cultivated mainly for hay and silage making (Krawutschke et al, 2013). Drought is an adverse factor that forages must cope with in the Mediterranean region.…”

Differences in the crude protein fractions of lucerne leaves and stems under different stand structures

“…This potential benefit has led to intensive research interest in legume protein degradability in relation to the effects of different forage species (Broderick and Albrecht, ), plant maturity (Cassida et al ., ) and genetic variation within legume species (Broderick et al ., ). There is also interest in the role of plant compounds that may enhance legume protein utilization, such as specific polyphenol oxidases (Krawutschke et al ., ) or condensed tannins (Chen et al ., ). Among a range of in vitro procedures, the Cornell Net Carbohydrate and Protein System (CNCPS) (Sniffen et al ., ) has been widely used to characterize protein degradation in forage.…”