Cattle and Sheep Diets Under Short-duration Grazing

Abstract

Studies have shown a negative relationship between stocking rate and animal performance in conventional grazing systems. However, short-duration grazing (SDG) proponents state that stocking rates can be increased and still maintain acceptable animal performance by reducing the length of stay on a pasture. The objective of this study was to determine if sheep and cattle diet quality could be maintained in SDG as stocking rates increased from the level recommended for moderate continuous grazing to 2.67 times the recommended level. Small pastures ranging from 1.68 ha to .47 ha were fenced to give the desired stocking rates. Pastures were grazed 3 days and rested 51 days. Diets were collected from esophageally cannulated sheep and cattle during the 3-day grazing periods. Botanical composition of diets was determined and crude protein and IVOMD were analyzed to estimate diet quality. As live green forage was depleted diet selection shifted to reserve forage resulting in a decline in diet quality as stocking rate increased in pastures where reserve forage was abundant during the cool season. There were few shifts in diet selection and diet quality where vegetation was more homogenous and lacked reserve forage. Grazing pressure declined during the warm season in all pastures due to above-average forage production. Only cattle diets showed a decline in digestibility as stocking rates increased and diet selection switched from mature warm-season grass to reserve forages. Diet quality declined within the short 3-day grazing periods and the decline was greater at the higher stocking rates.