Coopworth hogget and lamb liveweight gain on regenerative and conventional dryland pastures : A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Agricultural Science (Honours) at Lincoln University

Abstract

Regenerative systems have been proposed as a potential greenhouse gas mitigation strategy for New Zealand agricultural systems. They focus on a holistic approach which encompasses, plant, animal, soil and community health. Regenerative agriculture principles claim to naturally increase carbon storage, soil fertility and biodiversity while producing the equivalent harvestable product of conventional systems. This dissertation reports on the liveweight gain of Coopworth hoggets and lambs grazing conventional and regenerative dryland pastures under high (20 mg/kg) and low (10 mg/kg) Olsen P giving four treatment groups: high conventional (HC), low conventional (LC), high regenerative (HR) and low regenerative (LR). The research period was within the establishment phase of the ongoing regenerative agriculture dryland experiment at Lincoln University. Four 2-ha farmlets, of 20 paddocks each, were established between 10 December 2021 and 16 March 2023. Grazing management and pasture species were the main attributes under investigation. Animals under regenerative management grazed multi-species forages (>8 species), under high intensity, short duration, with high residual, rotational grazing. Whereas, conventional grazing management was rotational, with duration and rotation length based on pasture cover. Differences in animal liveweight gain (LWG), were explained by the pasture production and quality for each of the two Coopworth flocks (ewe hoggets and then ewe lambs) which grazed between 11 September 2022 and 3 August 2023. The first ewe hogget flock grazed between 11 September 2022 and 3 March 2023. These animals were replaced with new season ewe lambs from 3 March to 3 August 2023. Conventional treatments produced the greatest LWG. The Coopworth hoggets and lambs grazed on conventional pastures accumulated 42 to 60 (hoggets) kg LWG/ha and 15 to 28 (lambs) kg LWG/ha more than those on RA treatments. This difference was attributed to greater crude protein content (20% CA, compared with 15% RA) and lower neutral detergent fibre (40% CA, compared with 46% RA) due to increased legume in the lucerne-based conventional diet. This meant animals met their daily intake requirements sooner which enabled increased total intake, due to increased rate of rumination. Pasture production and quality were affected by water stress in this summer dry rainfed environment. Pastures were shown to be water stressed from 13 November 2022, when 157 mm actual soil moisture deficit was reached, until March 2023. During autumn and winter 2023 pasture grew based only on rainfall. Soil water had not recharged until July 2023. There was no effect on pasture quality or legume production during the experimental period due to Olsen P treatments, however, further research over time is required to confirm these results.