Effects of sodium chloride on sheep. 1. Diet composition, body mass changes and wool production of young Merino wethers grazing native pasture

Abstract

Supplementary salt (NaCl) and crude protein (CP) were provided to young Merino wethers grazing native pasture. Twenty-eight wethers were divided into 7 groups and given the following supplements daily via rumen cannulae: 0, 5 (Control), 15 and 30 g NaCl; and 5, 15 and 30 g NaCl + 20 g CP each. During the experimental period (1 year) the wethers gained respectively 44,4%, 67,1%, 52,6%, 40,7%, 70,1%, 57,2% and 47,6% in body mass. The effect of NaCl on the growth rate of the wethers became evident within 4 weeks. Rate of clean wool production (g day^-1) by the wethers during the first 9 months was 9,02, 10,85, 9,32, 7,65, 10,53, 9,42 and 9,06, respectively. It was evident that young sheep grazing native grass pasture in the central Orange Free State do have a nutritional requirement for NaCl, but excessive ingestion from licks could depress growth rate and wool production. Furthermore, supplementary CP, in combination with high levels of NaCl, alleviated the adverse effect of NaCl to some extent.

Aanvullende sout (NaCl) en ruproteïen (RP) is op veldweiding aan jong Merinohamels verskaf. Sewe groepe van 4 hamels elk, het die volgende aanvullings daagliks via rumenkannules ontvang: 0, 5(Kontrole), 15 en 30
g NaCl; en 5, 15 en 30 g NaCl + 20 g RP elk. Tydens die proefperiode (1 jaar) het die hamels onderskeidelik 44,4%, 67,1%, 52,6%, 40,7%, 70,1%, 57,2% en 47,6% in massa toegeneem. NaCl het na 4 weke reeds 'n merkbare invloed op die groeitempo van die hamels uitgeoefen. Tempo van wolproduksie gedurende die eerste 9 maande was onderskeidelik: 9,02, 10,85, 9,32, 7,65, 10,53, 9,42 en 9,06 (g skoonwol dag^-1). Dit was duidelik dat jong skape op natuurlike grasweiding van die sentrale Oranje-Vrystaat 'n voedingsbehoefte aan NaCl het, maar oormatige inname vanaf lekke kan groeitempo en wolproduksie benadeel. Verder het aanvullende RP, in kombinasie met hoë NaCl-peile, die nadelige effek van NaCl in 'n mate verminder.

Keywords: Body mass changes, crude protein, grazing sheep, NaCl, supplementation, wool production