Author:
B. A. McGregor

Date of Publication:
June 2002

Publication:
Small Ruminant Research, Volume 44, Issue 3, Pages 219–232

Abstract:
Adult Huacaya alpaca (mixed sex, mean±S.D., age 5.2±2.7 years, live weight 72.0±9.5 kg) were grazed with Peppin Merino sheep (castrated male, age 3±0.1 years, live weight 54.0±3.9 kg) for 2 years on improved annual pasture at commercial grazing pressures (10–17 dry sheep equivalents/ha) near Melbourne, Australia. Alpacas and sheep gained weight during the first year and then lost weight (proportional loss: alpacas 22%, sheep 20%, NS) before commencing weight gain. Twice the alpacas gained when the sheep lost weight (P<0.001). Alpacas lost weight when green pasture was <0.5 t DM/ha and gained weight when green pasture exceeded 0.5 t DM/ha. The pasture was not grazed evenly. The behaviour of alpacas indicated a strong preference for short green grazed pasture and they generally avoided long dry grass. The alpacas did not increase the utilisation of the pasture until increased grazing pressure resulted in an expansion of the area utilised. Midside wool and alpaca fibre growth rates were depressed when animals lost weight and increased when animals gained weight. The effects of the adverse nutritional conditions on alpaca were: a significant reduction in clean fibre growth (CFW) 2.86 vs 1.91 kg, P<0.001; clean washing yield (CWY) 95.2 vs 91.5%, P<0.001; mean fibre diameter (MFD) 37.5 vs 35.2 μm, P<0.01; staple length (SL) 94 vs 77 mm, P<0.001; SL/MFD ratio 2.50 vs 2.20, P<0.001; an increase in mean fibre diameter coefficient of variation (MFD CV) 23.3 vs 25.1%, P<0.05; fibre curvature (FC) 24.6 vs 26.4°/mm, P<0.1 and no change in staple strength (SS) 54 vs 46 N/ktex; resistance to compression (Rc) 5.1 vs 5.1 kPa; staple crimp (SC) 1.2 vs 1.1 cm−1. The effects on wool were: a significant reduction of CFW 4.12 vs 3.42 kg, P<0.001; CWY 73.7 vs 69.1%, P<0.001; MFD 22.4 vs 20.5 μm, P<0.001; SL 96 vs 76 mm, P<0.001; SS 54 vs 40 N/ktex, P<0.001; an increase in MFD CV 16.1 vs 18.0%, P<0.005; FC 97.9 vs 105.5°/mm, P<0.005 and little change in SL/MFD ratio 4.43 vs 4.17, P<0.1; Rc 10.0 vs 10.4 kPa, ns; SC 5.8 vs 5.7 cm−1, ns. The live weight, fibre productivity and fibre attributes of Huacaya alpacas and Merino sheep were substantially affected by seasonal nutritional conditions in a similar manner. The annual clean alpaca fibre growth was affected to a greater extent than the annual wool growth (decline of 33 vs 17%). Under conditions when green pasture availability was <0.5 t DM/ha, alpacas utilised pasture more effectively than sheep. Managers can manipulate the provision of pasture to manage live weight change and manipulate alpaca productivity and fibre quality.

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