Frequency of feeding lupin and canola meal supplements to young sheep influences wool growth and mitotic rate but not staple strength

Abstract

In Australia, young sheep often require supplements for part of the year to survive. This study investigated the influence of supplementary-feeding interval, supplement type and pattern of weight loss on wool growth, fibre diameter and staple strength. Weaners (64, 6–7-month old) were fed a basal diet of oaten hay, oaten straw and minerals every day and, in addition, were fed 1 of 2 supplement types. The design was factorial (2 by 3) and the factors were: frequency of supplementation (daily or weekly), type of supplement (lupin seed or canola meal) and pattern of weight loss (88 g/day loss for 1 month followed by 16 g/day for the second month or a gradual loss of 36 g/day for the full 2 months). Feeding supplements daily did not have any significant effect on fibre diameter (16.2 v. 16.2 m) or coefficient of variation of fibre diameter (18.7 v. 19.2%) during the experiment, or on staple strength (27.0 v. 28.4 N/ktex) compared with the weekly feeding. Similarly, staple strength was not affected by the type of supplement (26.3 N/ktex for lupin-fed sheep v. 29.0 N/ktex for canola meal-fed sheep). There was a significant interaction between feeding interval and supplement type on the rate of wool growth. Weekly feeding of canola meal increased wool growth relative to daily feeding (0.067 v. 0.062 g/100 cm² .day) whereas, weekly feeding of lupins decreased wool growth relative to daily feeding (0.055 v. 0.059 g/100 cm².day). Weekly feeding of lupins also increased levels of urea in plasma relative to all other groups for 2 days after feeding and reduced mitotic rate in the skin (relative to the canola meal-fed group) 3 days after the supplementation. While there were also some differences between treatments in plasma glucose, creatine kinase and amino aspartate transaminase, all groups remained within the normal range. These results indicate that the interval between supplementary feeding is unlikely to contribute to low staple strength in grazing weaners but will influence the efficiency of use of nutrients for wool growth.