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Accueil du site → Doctorat → États-Unis → 1978 → GRAZING RATE AND SYSTEM TRIAL OVER FIVE YEARS IN A MEDIUM-HEIGHT GRASSLAND OF NORTHERN TANZANIA

University of Arizona (1978)

GRAZING RATE AND SYSTEM TRIAL OVER FIVE YEARS IN A MEDIUM-HEIGHT GRASSLAND OF NORTHERN TANZANIA

O’Rourke, James T

Titre : GRAZING RATE AND SYSTEM TRIAL OVER FIVE YEARS IN A MEDIUM-HEIGHT GRASSLAND OF NORTHERN TANZANIA

Auteur : O’Rourke, James T

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 1978

Résumé
Hie effects of three grazing rates and two grazing systems on native forage species, as well as on livestock performance, were studied for five years near Arusha, Tanzania. Grazing study literature suggests that moderate use under a rotation system of some sort is advisable for areas with <_ 800 mm rainfall. Literature on 24-hour grazing indicates a benefit only during dry periods. Heavy, moderate, and light grazing left 450, 2200, and 3500 kg/ha and utilized 87, 52, and 25% of the forage produced, respectively, following the long rains of the last year of the trials. Heavy grazing resulted in least forage production, total plant frequency, and litter cover, with most bare soil. Moderate and light use produced nearly equivalent amounts of forage, litter, cover, and bare soil but light use showed a higher total frequency of plants. Very little difference existed in terms of forage responses between continuous and rotation grazing. Livestock weight changes depended upon rainfall in the previous month(s). Weight losses occurred in the first month of the rainy season and after extremely high rainfall months when livestock were consuming feed high in moisture, as well as in the latter part of the dry season. Only slight differences existed in gain per animal when comparing grazing rates or grazing systems. Heavy use, then, contributed up to two times higher gain per hectare than moderate use and two to four times more than light grazing. Compared to daytime grazing, results from 24-hour grazing conducted only during the rainy season shewed no benefit to livestock gains.

Mots clés : Grazing — Tanzania. ; Animal nutrition — Tanzania. ; Range management — Tanzania.

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