Estimating stocking rates in Natural Parks in Andalucía

Tim Treacher

Natural Parks cover about 17% of Andalucía. Most are in less-favoured mountainous areas with a tradition of extensive livestock production. Since the introduction of the CAP, the number of sheep and goats in Andalucía has increased by 48%. Systems are also changing, with strong market pressures to produce lambs reared indoors on concentrates, and increased housing of ewes in late pregnancy and lactation.

In 1995, when studies were made of the diverse plant ecosystems of the Sierra Mágina Natural Park in the province of Jáen, a parallel study estimated the stocking rates on three large grazing units, ranging in size from 760 to 1405 ha and consisting of both privately owned land and land rented from the Park Administration. Mean rainfall is 500 mm and altitude varies from 350 to 1200 m, with very steep slopes and shallow soils over calcareous rocks. The lower slopes have Quercus rotundifolia and Q. faginea trees and a large area replanted with Pinus species. The steeper slopes above are dominated by bushes, Quercus coccifera, Crataegus monogina, Ulex parviflorus, Berberis hispanica and on the south facing slopes, Pistacea terebinthus or cornicabra, whose fruit are an important bird feed in winter. Near the top are mountain pastures. The Sierra Mágina has the most important area of Pistacea terebinthus in Spain.

Annual stocking rates, calculated from total sheep numbers and total land areas, were 1.71, 0.87 and 0.86 sheep/ha in the three grazing units, but these make no allowance for the periods the sheep are housed or for areas that cannot be grazed. As a first step in calculating true stocking rates feed calendars were prepared after extensive interviews with the flock owners to obtain data on the distribution of lambing, periods of housing, use of different grazing areas, and levels of indoor feeding and supplementation at pasture.

The interviews established that, although rams were with the ewes throughout the year, lambing mostly occurred in autumn and spring. Ewes were housed from about one month before lambing until the lambs were weaned at two months of age. Two of the grazing units, which had large areas, 9 and 14% of the total, that could not be grazed, were divided into two or three separate areas. The third unit was grazed as one throughout the year.

Monthly stocking rates were calculated from the feed calendars for each grazing area, using the numbers of sheep actually present and the actual area available for grazing. Data from the first and third grazing units indicates the wide range of stocking rates that can occur in an area of Natural Park. In unit one, the three separate grazing areas were rested for 6, 8 and 10 months, respectively. Monthly stocking rates varied from 4.1-7.1, 5.2-8.8 and 1.4-1.6 sheep/ha, with mean annual stocking rates of 2.71, 2.36 and 0.25 sheep/ha. This gave a new estimate for the annual stocking rate of 1.16 sheep/ha for the whole grazing unit, compared to 1.71 sheep/ha calculated from the total flock size and land area. In unit three, which was not subdivided, removal of the animals to housing resulted in monthly stocking rates of 0.4-0.8 sheep/ha. The mean annual stocking rate was 0.60 compared to the original estimate of 0.87 sheep/ha. Clearly visible overgrazing was not necessarily associated with high stocking rates.

The contribution of grazing to the total annual energy requirements of the flocks was calculated, using the numbers of ewes in each physiological state and the French feeding standards. The energy value of feeds used indoors and at pasture was deducted and the balance was assumed to be the contribution from pasture. This was 62, 38 and 57% in the three grazing areas.

This study indicates that in extensive Mediterranean sheep systems a very clear description of the use of pasture, other grazing and feed resources, and of housing is needed to assess the true level of stocking. Such studies are an essential prerequisite before overall stocking rates are adjusted to prevent overgrazing of natural pastures.

This work was the final year project of Ignacio Monserrat, supervised by Dr Pilar Fernández of the Forestry Group and Dr Tim Treacher of the Animal Production Department of the Escuela Técnica Superior de Ingenieros Agrónomos y Montes (ETSIAM), University of Córdoba, Spain.

Similar work is also being done in the Cabo de Gata and Sierra Norte de Sevilla Natural Parks.

Dr Treacher is financed under the EU Training and Mobility Programme.

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