New Zealand is well-known for its lamb. Sheep and lambs feed in pastures. Barley grass is a common problematic weed in New Zealand pastures. The barbed spikes on barley grass seed can penetrate the eyes of sheep and can cause painful lesions, infections and blindness. Weight loss in lambs is attributed to their reluctance to feed in pastures infected with barley grass. Herbicides are used to remove the barley grass and early research in New Zealand demonstrated the benefits.
“An area of uniform barley grass (Hordeum murinum) infestation, in Waikato, was divided into twenty-four 0.2ha paddocks. Three chemicals… were used to control barley grass and the paddocks were grazed by lambs throughout the summer at two stocking rates.
All the chemicals reduced the barley grass content of the sward by over 96%, with pronamide giving 99% reduction, and significantly reduced Poa spp.
During the first month of the grazing period, the lambs on all chemical treatments at both stocking rates gained weight at approximately twice the rate of those on the untreated paddocks. …The control lambs (untreated paddocks) stopped gaining weight in mid-January and started to lose weight at the higher stocking rate.
The sudden growth check among the control lambs in mid-January coincided with maximum seed shed of the barley grass and is almost certainly attributable to the physical damage caused by the barley grass seed, especially to the eyes.
Initially the eye damage recorded was barley grass seed in the eyes but, at later stages, conjunctivitis and keratitis resulting from seed puncture and abrasion of the cornea.
During late January and throughout February, many of the control lambs were completely blind and were a pitiful sight. …this paper gives a clear indication of the benefits to stock and pasture that can arise from herbicide treatment.”
Authors: Hartley, M. J., and G. C. Atkinson.
Affiliation: Ruakura Agricultural Research Centre, Hamilton.
Title: Effect of chemical removal of barley grass on lamb growth rates.
Source: Proceedings of the New Zealand Plant Protection Society. 1972.