Establishing phenotypic performance of grass varieties on Irish grassland farms

Abstract

SUMMARYConventionally perennial ryegrass evaluations are conducted under simulated grazing studies to identify varieties with the best phenotypic performance. However, cut-plot environments differ greatly to those experienced on commercial farms as varieties are not exposed to the same stress levels in test environments. It could be argued that plot-based testing regimes provide little direction to plant breeders in the development of advanced varieties. Varietal phenotypic performance needs to be quantified in ‘commercial’ situations. The objective of the current study was to evaluate the phenotypic performance of a range of perennial ryegrass varieties under commercial farm conditions. Monocultures of 11 Irish Recommended List perennial ryegrass varieties were sown on 66 commercial farms throughout Ireland where performance was evaluated over a 3-year period from 2013 to 2015, inclusive. A linear mixed model was used to quantify variety effects on grassland phenotypic performance characteristics. No significant variety effect was estimated for total, seasonal or silage herbage production. Despite the lack of variety effects, pairwise comparisons found significant performance differences between individual varieties. Grazed herbage yield is of primary importance and was shown to be correlated strongly with total production (0.71); Grazed herbage yield differed significantly by variety, with a range of 1927 kg dry matter (DM)/ha between the highest and lowest performing varieties. Sward quality (dry matter digestibility [DMD]) and density were influenced by variety with a range of 44 g/kg DM for DMD and 0.7 ground score units between the highest and lowest performing varieties. Results of the current study show that on-farm evaluation is effective in identifying the most suitable varieties for intensive grazing regimes, and the phenotypic variance identified among varieties performance for many traits should allow for improved genetic gain in areas such as DM production, persistence and grazing efficiency.

The relationship between the grazing efficiency and the production, morphology and nutritional traits of perennial ryegrass varieties

“…Achieving target pre-grazing covers and correct post-grazing residuals at each grazing are critical to optimizing milk production from the pasture (Macdonald et al ., 2010). Forbes (1988) identified a positive correlation between pre-grazing sward height and grazing efficiency and likewise, a similar relationship between grazing efficiency and pre-grazing sward height was found by (Byrne et al ., 2017) where a 1 cm increase in pre-grazing sward height resulted in a post-grazing sward height increase of 0.12 cm. The current finding that a 1 kg DM/ha increase in pre-grazing yield resulted in a +0.001 increase in RGH aligns with previous research also.…”

Comparison of perennial ryegrass,Lolium perenneL., ploidy and white clover,Trifolium repensL., inclusion for herbage production, utilization and nutritive value

“…More recent studies have also found similar herbage DM yields from diploid and tetraploid cultivars under animal grazing (Cashman, McEvoy, Gilliland, & O'Donovan, ). Cultivars were found to perform similarly in terms of herbage DM production in an evaluation of cultivars on commercial farms under animal grazing, regardless of perennial ryegrass ploidy (Byrne et al., ). Tetraploid and diploid swards in the current study were managed similarly, and postgrazing sward heights were maintained below 4.5 cm across the study, leading to similar total herbage DM production.…”

“…Through grass breeding, perennial ryegrass ( Lolium perenne L.) cultivars (both diploid and tetraploid) have been developed to support increased animal performance, herbage dry‐matter (DM) production and herbage nutritive value (Connolly, ; DAFM, ). Improving grassland management and increasing herbage DM production through the identification of perennial ryegrass cultivars suitable for grazing are important for a sustainable dairy sector (Byrne et al., ; O'Donovan et al., ). The inclusion of white clover, Trifolium repens L., in grass‐white clover (GC) swards can increase herbage DM production (Enriquez‐Hidalgo, Gilliland, & Hennessy, ; Frame & Newbould, ; Ledgard & Steele, ) and further improve herbage nutritive value (Beever et al., ).…”

Growth, morphology and biological nitrogen fixation potential of perennial ryegrass-white clover swards throughout the grazing season

“…More recent studies also found similar herbage DM yields from diploid and tetraploid cultivars under animal grazing (Cashman et al 2016). In an evaluation of cultivars on commercial farms under animal grazing, cultivars were found to perform similarly in terms of herbage DM production regardless of PRG ploidy (Byrne et al 2017). In the current study, excess herbage did not accumulate between grazings, and despite sward structural differences between PRG ploidies (Gilliland et al 2002), neither PRG ploidy provided superior herbage DM production under similar grazing managements.…”