Combining seasonal yield, silage dry matter yield, quality and persistency in an economic index to assist perennial ryegrass variety selection

Abstract

SUMMARYA total economic merit index (Pasture Profit Index, PPI) for perennial ryegrass variety selection was developed to rank perennial ryegrass varieties (Lolium perenne L.) based on their economic potential for grass-based ruminant production systems. The key traits of importance identified were: spring, mid-season (April 11–August 10) and autumn dry matter (DM) yield, first and second cut silage DM yield, grass quality April to July (inclusive) and sward persistency. Variety persistency was quantified by determining the ground score (GS) change across years, which was associated with a yield threshold which triggered sward replacement. Each one-unit decline in GS was associated with a 1683 kg loss in DM yield. Data generated in the Irish recommended list trials for value for cultivation and use were analysed to quantify the relative performance of each variety for each of the aforementioned traits. A previously developed methodology to generate economic values was used with updated price assumptions to develop economic values, which were applied to the analysed performance data of individual varieties. These data were used to estimate the total economic merit of each variety. Thirty-nine varieties were ranked on total economic merit with the highest performing variety (Cv111) generating €213 per ha/year compared with Cv201, which was the lowest ranking variety generating −€31 per ha/year. Use of the PPI provides information to end users in relation to the economic merit of one variety over another, facilitating a more informed decision-making process at farm level.

Identifying causes of low persistence of perennial ryegrass (Lolium perenne) dairy pasture using the Basic Grassland model (BASGRA)

“…The second pathway, population density decline, is frequently reported (Tozer, Cameron, & Thom, 2011;Tozer et al, 2014), especially where environmental conditions are marginal or turn unfavourable for the sown species (Chapman, Edwards, & Nie, 2011). This pathway is the basis for measures such as ground cover scores to assess sward productivity (Camlin & Stewart, 1976) and to compare the persistence of grass cultivars (e.g., in perennial ryegrass; Cashman, O'Donovan, Gilliland, & McEvoy, 2014;O'Donovan, McHugh, McEvoy, Grogan, & Shalloo, 2016). An important implicit assumption is that the rate of perennial grass tiller mortality exceeds the rate of tiller replacement (dominantly through clonal reproduction and site filling rates, Davies, 1976) such that the population of perennial grass tillers cannot be sustained and herbage production declines (Camlin & Stewart, 1978).…”

Ruminant grassland production systems in Ireland

“…Given that the recognition of digestibility improvement was only relatively recently introduced to the testing system, further advances will need to be realised. The introduction of the Pasture Profit Index (PPI, McEvoy et al, 2011;O'Donovan et al, 2017) into the Irish Recommended List for Grass and Clover, combined with the change to evaluation under intensive simulated grazing protocols and more on farm grass and clover variety evaluation using PastureBase Ireland will bridge the gap between farmers, evaluation and breeding. Although there is a general consensus amongst breeders internationally that individual varieties can perform well in a range of environments, in fact the evidence from the PPI and the Irish Recommended List for Grass and Clover clearly shows that the best performing breeding programs for Ireland are those based in Ireland and the United Kingdom.…”

Divergent Genomic Selection for Herbage Accumulation and Days-To-Heading in Perennial Ryegrass

“…The profitability of dairy farms in countries such as New Zealand and Australia, and the international competitiveness of these industries, are closely linked to the consumption of homegrown forage [2] because it is a low-cost feed source. The contribution of DM yield to farm profitability is formally recognised in economic indices used for ranking ryegrass cultivars in Ireland [3,4], New Zealand [5], and Australia [6]. Increasing the annual DM yield of perennial ryegrass, and manipulating the seasonal yield to align with animal nutritional requirements, are therefore critical targets for forage breeders [1,7].…”