Factors involved in high ewe losses in winter lambing flocks grazing dual-purpose wheat in southern New South Wales: a producer survey
S. R. McGrath A B D , J. J. Lievaart A B , J. M. Virgona A C , M. S. Bhanugopan A B and M. A. Friend A BA EH Graham Centre for Agricultural Innovation, Charles Sturt University, PO Box 588, Wagga Wagga, NSW 2678, Australia.
B School of Animal and Veterinary Sciences, Charles Sturt University, PO Box 588, Wagga Wagga, NSW 2678, Australia.
C School of Agricultural and Wine Sciences, Charles Sturt University, PO Box 588, Wagga Wagga, NSW 2678, Australia.
D Corresponding author. Email: shmcgrath@csu.edu.au
Animal Production Science 53(5) 458-463 https://doi.org/10.1071/AN12134
Submitted: 17 April 2012 Accepted: 22 October 2012 Published: 12 February 2013
Abstract
A comparative survey was undertaken with 43 sheep producers in southern New South Wales using a semi-structured interview to investigate factors associated with high ewe mortality rates in winter lambing flocks grazing dual-purpose wheat. Participants were classified as either control (n = 23), who had not observed abnormally high ewe deaths, or case (n = 20), who had observed abnormally high ewe mortality rates when sheep grazed dual-purpose wheat. Ewe losses associated with grazing wheat were higher in the case group compared with the control group (8.6 vs 1.8%; P < 0.001) and there was also more deaths attributed to metabolic disease (3.4 vs 0.6%; P < 0.05). A higher proportion of control respondents had provided magnesium or sodium supplementation to ewes grazing wheat (P < 0.05). The body condition score of ewes entering the grazing period was significantly higher in the control group (3.2 vs 2.8; P < 0.05). The proportion of respondents who fed roughage to ewes grazing wheat did not differ significantly between control and case groups (48 vs 35%). A higher proportion of respondents in the case group had supplied grain to ewes (25 vs 0%; P < 0.05), which may have been associated with the lower body condition of sheep in these flocks compared with the control group. It was concluded that supplying ad libitum access to mineral supplements that include magnesium, sodium and possibly calcium, and maintaining adequate body condition score can reduce the risk of high ewe mortality rates when reproducing ewes graze dual-purpose wheat.
Additional keywords: grass tetany, hypocalcaemia, hypomagnesaemia, pregnancy toxaemia.
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