The effect of zinc deficiency on wool growth and skin and wool follicle histology of male Merino lambs

Abstract

___The aims of this work were to quantify the requirements of Zn for wool growth in growing male Merino lambs, and to describe the histological lesions of Zn deficiency in skin and wool follicles. Four groups of male Merino lambs (n 4) weighing 22 kg were fed ad lib. for 96 d on diets that contained 4 (basal diet), 10, 17 or 27 mg Zn/kg. Sheep in a fifth group were fed on the diet containing 27 mg Zn/kg, but were pair-fed to sheep on the 4 mg Zn/kg diet. Zn was added to the basal diet as ZnSO, to give the respective treatment concentrations. Sheep fed on the diet containing 4 mg Zn/kg showed clinical signs of Zn deficiency and lower feed intakes and wool growth than sheep in the other groups. Their wool fibres were improperly keratinized and the wool follicles contained a higher proportion of apoptotic bodies than other groups. There was no evidence of parakeratosis and the rate of bulb-cell production was not affected. Sheep from other groups showed no clinical signs of Zn deficiency, and mean feed intakes and growth rates did not differ significantly between sheep fed on diets containing 10, 17 or 27 mg Zn/kg. However, wool growth was reduced in sheep fed on the diet containing 10 mg Zn/kg compared with those fed on diets containing 17 or 27 mg/kg. The mean concentration of Zn in the plasma at which wool growth was 90 YO of maximum was 0.5 mg/l. The equivalent value for the diet was 12 mg/kg, with 95 YO confidence intervals of 8 to 16mg/kg. The results suggest that Zn deficiency reduces wool growth through a specific mechanism, perhaps involving impaired protein synthesis.

Effects of dietary supplements of zinc-methionine on milk production, udder health and zinc metabolism in dairy goats

“…268 g for the control and supplemented, respectively, but these differences were not significant. White et al (1994) suggested that a plasma Zn concentration of 0 . 5 mg /l supports normal wool growth in Merino sheep, whereas the mean plasma concentration of Zn in control animals of the present study (0 .…”

Skin lesions in alpacas and llamas with low zinc and copper status – a preliminary report

“…Sheep, South American camelids, yaks and musk oxen all produce a fleece, and wool from semi-domesticated individuals is harvested by humans. Wool production imposes a high demand for minerals (Grace and Clark, 1991;Neathery et al, 1972;White et al, 1994). Different breeds of sheep have differences in Cu and Zn metabolism (e.g., Van der Schee et al, 1983).…”

Wool fibre crimp is determined by mitotic asymmetry and position of final keratinisation and not ortho- and para-cortical cell segmentation

“…The differential pressures that would have been produced in the lower follicle would dissipate and the fibre would straighten. This is why disruptions to keratinisation induced by deficiencies of zinc (White et al, 1994) or copper (Marston and Lee, 1948), or as a result of keratin gene transgenesis (Bawden et al, 1998), result in straight or 'steely' fibres. This also explains how curved and asymmetric follicles can still produce straight fibres.…”