Epsilon Archive for Student Projects

Abstract

Variations in protein concentration and the ruminal nitrogen utilisation in diploid and tetraploid red
clover (Trifolium pretense L.) silage across two years (2022 and 2023) were studied by using in vitro
utilisable crude protein (uCP) method. A total of 45 in 2022 and 44 accessions in 2023 were assessed
including four control varieties. Plant materials were harvested with a haldrup plot harvester, which
was then allowed to wilt until they reached a dry matter (DM) concentration of 25% to 30%. After
the determination of DM content, wilted forage was chopped and treated with a formic acid-based
silage additive at a rate of 6 mL/kg fresh matter. Herbage was then vacuum-packed and placed to
ensile for 100 days, after which the samples of the ensiled silage were taken for analysis and the rest
was freeze-dried. The ammonia-N concentrations were determined during an in vitro incubation at
4, 9, 20 and 30h, used to determine the uCP at 16 h rumen retention time (uCP16). In both years all
silage samples exhibited good fermentation characteristics. Low pH values (lower than 4.06 in 2023)
and high concentration of lactic acid (35.15 g/kg DM in 2022 and 81.22 g/kg DM in 2023) compared
to other volatile fatty acids indicative of well-preserved silage. Diploid red clover (RC) was higher
in crude protein (CP) and lower in neutral detergent fibre (NDF) content than tetraploid RCs in both
years. A strong positive correlation (R2 = 0.78) was indicated between uCP16 and CP content in the
silage across the two years. A negative linear correlation between NDF and both uCP16 and CP
indicates that higher content of fibre levels may compromise the ruminal protein utilisation. The
uCP16 values of silages were significantly affected only by the year factor and not by ploidy. Three
RC accessions had 5 to 9 g/kg DM lower uCP16 concentration than predicted by the model based on
silage CP concentration, whereas 6 accessions had observed uCP16 values between 4 to 7 g/kg DM
higher than predicted values. Those results indicate that selecting accessions with higher CP
utilisation potential might be possible and that the CP concentration alone is not enough for selection for better CP efficiency in the rumen. Furthermore, numerical variations were observed in protein utilisation between tetraploids and diploids of RC accessions and significant differences between the years. Further research is warranted to evaluate the efficiency of protein utilisation in the rumen with red clover ploidies, and it is essential to further study, other parameters associated with protein utilisation in red clover.