Production, utilization, and quality of irrigated grasses and legumes in the Mountain West USA under mob stocking or mowing at the same defoliation frequency and intensity

Background

Feed is the most costly input for US ruminant livestock production systems, and increasing the utilization efficiency of irrigated forage systems can improve system profitability. This study assessed the production, utilization, and quality of 22 intensively managed perennial grasses and legumes.

Methods

Forages were cultivated as monocultures under irrigation and subjected to mob stocking or similarly frequent and intense mowing for 2 years at 6-week intervals between May and September. Twenty-two grasses and legumes were randomly assigned to adjacent 1.5-m-wide × 9-m-long split subplots within each whole plot of eight replications, and the eight replications were grouped into four pairs, with the two replications per pair randomly assigned to defoliation either by grazing or mowing.

Results

Seven mostly warm-season grasses did not persist following the first defoliation, and accumulation for three legume species could be evaluated only twice in Year 1. For the 12 remaining forage species defoliated four times in both years, defoliation management did not affect dry matter accumulation or removal, but utilization was 10% greater under grazing than mowing (p = 0.0031).

Conclusions

Under 6-week-long rest periods, numerous irrigated cool-season grasses and temperate legumes were tolerant of repeated mob grazing.