Effect of dry or hydrated bentonite on the wool growth and liveweight gain of sheep fed wheat chaff

Abstract

Many reports on the use of bentonite to increase wool growth indicate variable responses and it is often claimed that this variability is related to the chemical characteristics or the form in which the bentonite is fed. This paper describes 3 experiments in which there was consistency in the type and form of the clay. There was also comparison of the effects of dry and hydrated bentonite. In the first experiment, 64 sheep were individually penned and fed wheat chaff ad libitum. Thirty sheep were fed chaff only, 17 sheep received dry bentonite added to their chaff (20 g/kg chaff) and another 17 sheep had 23.7 g/day of bentonite added to their drinking water. Inclusion of bentonite in the drinking water significantly increased wool growth (P<0.05, 14.8%) and increased chaff intake (P = 0.08, 6%). In the second experiment, 105 sheep were penned in groups of 7 and each pen fed wheat chaff ad libitum. Five pens of sheep had dry bentonite added to their chaff (20 g/kg chaff) while another 5 pens had bentonite added to their drinking water (23.7 g/sheep.day). There were 5 pens of sheep which received no bentonite. Inclusion of bentonite either in the drinking water or in the chaff, significantly increased chaff intake (P<0.05, 6%), but had no effect on wool growth. In the third experiment, 60 sheep were divided into 12 groups and each group grazed individual 0.7 ha of cereal stubble. All groups were supplemented with the equivalent of 200 g of lupin grain/sheep.day fed twice weekly and 6 of the groups were watered by buckets containing hydrated bentonite (11.8 g bentonite/L). In experiments 2 and 3, inclusion of bentonite in the diet or in the drinking water had no effect on wool growth (P>0.05) but liveweight gain was significantly increased (P<0.05). It was concluded that the variability in the response to bentonite was not related to its chemical composition or the form in which it is administered and that, on balance, bentonite does not offer a practical or reliable means of increasing wool growth in sheep.