Evaluation of the effects of ewe prolificacy potential and stocking rate on herbage production, utilization, quality and sward morphology in a temperate grazing system

Abstract

This study investigated the effect of ewe prolificacy potential (PP; predicted number of lambs born ewe−1 year−1), stocking rate (SR; ewes/ha) and their interaction on herbage dry matter (DM) production, utilization, quality and sward morphology within a temperate grass‐based lamb production system. The study had a 2 × 3 factorial design, consisting of two ewe PP as dictated by sire breed (180 medium prolificacy potential (MP—Suffolk crossbred) and 180 high prolificacy potential ewes (HP—Belclare crossbred)) and three SR: low (LSR; 10 ewes/ha), medium (MSR; 12 ewes/ha) and high (HSR: 14 ewes/ha). Each treatment was managed in a rotational grazing system, with LSR, MSR and HSR treatments grazing to target post‐grazing sward heights (PGSH) of 4.55, 4.15 and 3.75 cm respectively. Herbage DM production (above target PGSH) and utilization were highest at the HSR, intermediate at the MSR and lowest at the LSR (p < .001). Ewe PP had no effect on herbage DM production, utilization, quality or sward morphology (p > .05). The proportion of leaf in the sward (above target PGSH) was 4% greater in MSR and HSR compared with LSR (p < .05). In conclusion, findings demonstrate the potential to support increased ewe PP through the selection of ewe genotypes of a genetically higher PP and lower mature live weight and increased SR within a temperate grass‐based lamb production system.

The effect of increasing pasture species on herbage production, chemical composition and utilization under intensive sheep grazing

“…The stocking rate in the current study of 12.5 ewe ha −1 is between the medium and high stocking rate described by Earle et al. (). The same management and stocking rate was imposed on all sward types; however, utilization was higher in the 6S and 9S swards, this may have resulted from greater voluntary intake on these swards (Barry, ) caused by selective grazing of the plants with the highest nutritional value from the sward (Pain et al., ).…”

“…The primary objective of any herbage based ruminant production system is to achieve optimum herbage DM production and utilization (Earle et al., ) at the lowest possible cost while achieving high levels of animal performance. In this study, the multispecies swards had similar annual and seasonal herbage DM production to the PRG sward from lower N inputs.…”

“…The grazing management in this study is similar to that of Earle et al. () which aimed to optimize herbage production and quality for mid‐season lamb production systems following best practise grazing management for conventionally sown perennial ryegrass swards.…”

“…The PRG sward received 163 kg N ha −1 year −1 and all other sward types received 90 kg N ha −1 year −1 . The 163 kg N rate is based on the N requirements for this stocking rate calculated by Earle et al (2018). A reduced N rate of 90 kg N was applied to the PRGWC, 6S and 9S swards in line with recommendations for managing grass/ legume swards in intensive rotation grazing systems (Wall & Plunkett, 2016).…”

“…Herbage can supply up to 95% of the energy requirements of sheep (with the other 5% accounting for supplementation to ewes pre‐lambing; Davies & Penning, ), providing sheep producers in temperate regions of the world an opportunity to maximize output from herbage through increased herbage dry‐matter (DM) production and utilization (Bohan et al., ; Keady, Hanrahan, & Flanagan, ). Achieving a balance between the supply of high‐quality herbage and herbage utilization is paramount in optimizing temperate grass‐based lamb production systems (Earle et al., ); however, this remains a challenge for many producers.…”