title: Integration of grazing management and gastro-intestinal parasite control in sheep
title: The integration of grazing management and gastro-intestinal parasite control in sheep
titleType: AlternativeTitle
Creators: name: Rae, Michael Craig
Publisher: name: The University of Edinburgh
Year: 1977
Subjects: subject: Annexe MSc Digitisation Project 2022 Block 39

description: The production of lambs from enclosed land at 0-300m is an important part of agriculture in S.E. Scotland. In this area stocking rates during summer grazing have traditionally been low (7 ewes and lambs per hectare). The reported major restriction to increased stocking rates is that of high gastro-intestinal parasite infections resulting from grazing ewes and lambs on the same grass, year after year. Attempts to achieve better grass utilization by increased stocking rates and higher nitrogen usage have proved disappointing in terms of individual lamb performance. This has led to farmers drawing the conclusion that high nitrogen use, high stocking rates and good lamb performance are not compatible. It is established that the simplest and most effective way of controlling gastro-intestinal parasites in lambs is to graze ewes and lambs on clean pasture, i.e. land that has not carried lambs or young sheep during the previous 12 months. A system of rotation was established at House O' Muir, Midlothian that ensured clean grass for the flocks every year and this system was used to ascertain whether clean worm free grazing allowed intensification of sheep without the normal reduction in individual lamb performance. Alongside this project the hypothesis that "given initially clean grazing and by dosing ewes after lambing, ewes and lambs can remain worm free under continuous summer grazing conditions", was investigated. A plot of 8.5 hectares was divided into J equal areas for (i) Ewe and lamb grazing, (ii) Cattle grazing, (iii) Hay production. Clean grazing was ensured by each area following a J course rotation of cattle: sheep: hay. Two methods of continuous summer grazing were compared with the t clean grazing experiment. Each treatment had similar stocking rates and fertilizer usage, and were:- A) Continuous sheep grazing with ewes dosed with Thibenzole before they had access to grass and lambs and ewes dosed with Nilzen only when they were observed to show clinical symptoms of worm infection. B) Continuous sheep grazing with ewes dosed with Thibenzole before they had access to grass and ewes and lambs given two routine nematodirus doses of Nilzan. C) Clean grazing provided for the sheep each year with ewes dosed before grazing and lambs dosed only when they were observed to show clinical symptoms of worm infection. Treatments A and B were considered to have lower performance than treatment C due to pasture contamination by over wintering larvae causing infection in young lambs early in the year. The hypothesis that given initially clean grazing and by dosing the ewes after lambing, ewes and lambs can remain worm free under continuous summer grazing conditions, was found to be invalid in practise. Due to limitations within the experimental design it was not possible to draw definitive conclusions from the results obtained. There were considerable between farm differences that confounded any between treatment differences that could have been due to helminthological effects. Also the very dry weather experienced in the summers of 1975 and 1976 will have further affected data due to poor grass growth affecting live weight gains and to desiccation affecting the helminth eggs and larvae surviving on the pasture. The results indicate that in treatment A the group mean daily live weight gain declined over time more than did that of treatments B and C. This was considered to be due to pasture contamination f by over wintering larvae causing infection in young lambs early in the year. This fact was not fully elucidated, but could have been, if pasture sampling for larvae had commenced earlier in the year and continued later. Treatments B and C were considered to be of similar merit in reducing helminth challenges to young grazing lambs. However Treatment B maintained its group mean daily live weight gains with considerable anthelmintic use Treatment C on the other hand required only strategic dosing of ewes and lambs at turn out to grazing and then again at weaning. There was little possibility of lambs being exposed to over wintered pasture helminth larvae in Treatment C (rotational clean grazing) whereas there is a continued risk of exposure to over wintered larvae in Treatment B. It would seem that continuous summer grazing at high stocking rates cannot maintain high individual lamb live weight gains without considerable anthelmintic support. This was due to the possibility of large numbers of autumn deposited helminth eggs developing and over wintering to offer early challenges to very young and susceptible lambs. By the application of the management principles involved in the production of clean grazing, this problem can be avoided. Clean grazing allowed good individual lamb performance at relatively high summer stocking rates (17-5 ewes and 29 lambs per ha) with minimal anthelmintic treatment. The productivity of lamb per grazing hectare was maintained at a high level without resorting to supplementary feeding or excessive anthelmintic treatment. Summer stocking rates and thus output per hectare are at least double those found under traditional management.