Feeding stations of feeder lambs (Ovis aires) as an indicator of diminished forage quality and supply while grazing south central Arizona alfalfa (Medicago sativa L.)

Abstract

Grazing trials were conducted on irrigated fall/winter pastures near Maricopa, Arizona where 270 feeder lambs were stocked in 16-ha paddocks to explore the use of grazing behavior as an indicator of forage quantity and quality. Sheep behavior was monitored by filming the grazing periods with a VHS camera and recording the length of time that an individual spent at a feeding station, defined here as a feeding station interval. Other measurements included observed steps between feeding stations (step-sets), feeding stations min⁻¹, steps min⁻¹ and biting rate. As grazing progressed, lambs increased the number of feeding station intervals that were less than 5 seconds long and increased the number of feeding stations min⁻¹ significantly (p ≤ 0.05). Feeding stations min⁻¹ were negatively correlated (r ≤ -0.94) with crude protein, digestible energy and quantity of selected forage. Throughout the grazing trial lambs appeared to prefer the leaves to the stems. Steps min⁻¹ were only moderately correlated to forage quantity and quality. Bites min⁻¹ were not correlated to forage quantity and quality. Feeding stations min⁻¹ as a method of monitoring animal behavior during feeding periods might allow the manager to recognize nutritional limitations in the available forage and perhaps adjust management strategies accordingly.