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Plant sciences, sustainable farming systems and food quality
RESEARCH ARTICLE

Factors associated with the rate of growth of clean wool on grazing sheep

HA Birrell

Australian Journal of Agricultural Research 43(2) 265 - 275
Published: 1992

Abstract

In a grazing study that spanned 2.5 years, the rate of clean wool growth (Wi, g/day) in 4 week periods on Corriedale wether sheep was measured on each side of the animal with dyebands that were applied, alternately, at 2 week intervals. The observations (n = 224) on wool growth from 3 contiguous periods Wi = 1, 2 and 3 with the middle overlapping the other two periods, were related to either the daily rate of organic matter intake (OMI, g/day), the digestible organic matter intake (g DOMI/day), the hourly rate of OMI (IR, g OMI/h) or the hourly rate of digestible organic matter intake (DR, g DOMI/h) in linear or quadratic expressions. The intake data were collected every 4 weeks over the 3 days that correspond to days 6 to 8 of W1. The variance accounted for in each of W1, W2 and W3 increased in the order OMI<DOMI<IR<DR. DR accounted for 33.2% of the variance in W1 with a significant quadratic fit (P < 0.01) and 24.3% and 7.8% with linear fits against W2 and W3, respectively. A relationship that comprised five factors and accounted for 68% of the variance in W1 was developed by nonlinear regression. Three factors that were associated with nutritional aspects, the hourly rate of digestible organic matter intake (DR, g DOMI/h), the organic matter digestibility (OMD %) and the average organic matter intake in a grazing period (M, g OMI/grazing period) accounted for 54.9% of the variance in W1 while the other two factors that were associated with the physiological state of the animal, fleece-free liveweight change (C, g/day) and the fleece-free liveweight (L, kg) accounted for a further 13.1% of the variance of W1. The study suggests that factors associated with phenomena within a daily period may have important effects on wool growth. Management aspects are discussed.

Keywords: grazing sheep; wool growth; grazing behaviour; herbage intake; digestibility; shearing

https://doi.org/10.1071/AR9920265

© CSIRO 1992

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