Effect of Facial Eczema on Production

Whatawhata trials (Sheath and Webby APS 1987), Rex Webby and Neale Towers

Each 100 unit increase in GGT meant a:

• 5 to 7 % increase in cull or ban-en ewes.
• 2 to 3 % less ewes present at lambing.
• 4 to 5 % decrease in multiples on a flock basis.
• a 7% reduction in the number of ewes lambing multilples.

Flock mean GGT in range 150 to 250 this meant 12% more cull or dry ewes and 14% less ewes lambing multiples.

Also an effect on lamb weaning weight is observed. For example:

Approximate relationships between GGT and lamb production

GGT	Expected drop in lambing %	Drop in wool production	Drop in weaning wt	lost income per ewe@ 100% lambing
100	2.4 to 11.4	0.6%	0.6kg	$3.30
200	4 to 15	1.5 %	1.4kg	$4.30
300	12 to 18	2.6 %	2.6kg	$8.98
400	14 to 30	2.6 %	2.6kg	$11.33

The effect on wool production and lamb weaning weights becomes confounded, as GGT increases, by the fact that there are fewer multiples and more dry ewes.

Interpretations of categories of damage based on GGT level vary but these may help:

GGT	Interpretation
<40	Normal
40-80	Minor
80-160	Mild
160-320	Moderate
>320	Severe

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