For a productive and sustainable sheep breeding on rangeland : an experimental system on the Causse du Larzac

Abstract

Efficient animal production together with environmental care, are both the global goals of the sheep production system reported here. The challenge was to succeed in establishing a perennial system of lamb production with prolific ewes fed mainly from dry steppic rangeland resources from a calcareous area of the south part of France.

A long term experiment was settled at the INRA Domaine de La Fage on the Causse du Larzac (44°N – 3°E; 800 m a.s.l.) in order to find a suitable animal breed and to elaborate management rules both for the sheep living outside and for innovative pastoral use of a spontaneous pasture. A multidisciplinary programme was developed according to the following objectives: i) reach the highest feeding auto-nomy from the rangeland grass, ii) succeed in the year to year renewal of the pasture, iii) achieve good growth rates for twin suckled lambs, iv) protect the countryside and maintain plant diversity, and v) limit inputs and costs.

In this context, suckling ewes of the INRA 401 breed are reared outside all year round. They lamb in the early spring and are fed mainly from rangeland pasture. In order to reduce supplements bought outside, the grass productivity of a limited area, i.e. 6 % of the rangeland was increased by means of fertilisers (65 kg N/ha/year + 120kg P2O5/ha every 3 years). Measured over 14 successive years, the average pasture yields were 1.0 t DM/ha on native rangeland and 4.4 t/ha on the fertilised one.

A comparison of four ways of combined use of native and fertilised grass in the spring was performed with ewes suckling an average of 1.5 lambs/dam. Average lambs’growth were 268 to 295 g/day on fertilised paddocks rotationally grazed (2 grazing cycles on 4 paddocks) from mid April until May 20th, with the stocking rate being 15-20 ewes/ha. Growth rates until weaning (end of June) were then kept around 250 g daily when the suckling ewes grazed native rangeland areas all preserved from previous grazing (6 paddocks, stocking rate 2-3 ewes/ha). Electric fences allowed rapid rotational grazing, the ewes staying no more than 4 days at the same place on fertilised grass and 8 days on native grass. From summer rise until January, the flock grazed mature grass as well as refusals from previous grazings. The grazing procedures ensured environmental care and control of invading vegetal species as a result of permanent rotational grazing and high instant stocking rates on mature vegetations. In this experiment, the rangeland resource was the only food offered to the ewes from mid-April until December-January and it represented 68 % of their total yearly energy intake. The remaining 32 % was made of hay from the farm (18 %) and concentrate (14 %) given at the end of pregnancy.

The INRA 401 sheep showed productive and adaptative abilities. It can be considered a suitable breed for the sustainable valorisation for harsh and less favoured areas as well as a good tool to test different ways of pasture management.