Mixed grazing systems of sheep and cattle to improve liveweight gain: a quantitative review

Mixed grazing is an alternative pasture management which can be used to increase ruminant performance and reduce gastro-intestinal nematodes. A meta-analysis was performed on the results of previous studies from the literature to quantify the benefit of mixed grazing with sheep and cattle and identify determinants and enhancing factors. The analysis focused on papers reporting measurements of average daily weight gain (ADG) of sheep and cattle, carried out simultaneously in mixed grazing and in mono-grazing. The meta-analysis used 179 observations from 16 experiments published in nine carefully selected papers. The benefits of mixed grazing were appraised using the individual ADG of sheep (ADGi(sheep)), cattle (ADGi(cattle)) and the overall performances (ADG per hectare (ADGha), g/day/ha). A theoretical production value (ADGha-Theo) was calculated from the ADGha in mixed and mono-grazing at similar stocking rates (SRs)/ha. The ADGi(sheep) was greater in mixed treatments compared with control treatments (+ 14.5 g/day, P<0.001) and varied with physiological status and SR (P<0.001). The ADGi(cattle) was similar in mixed and mono-grazing. At a global level ADGha in mixed treatments (ADGha-Mtrt) was higher by 28.6% compared with sheep alone and by 25.1% compared with cattle alone; also, ADGha-Mtrt was 8% higher than ADGha-Theo. The ADGha varied with physiological status and decreased with the proportion of sheep in association (P<0.01). The contribution of ADGha in mixed grazing due to each species was lower compared with gains for each species reared alone (1438 v. 2423 g/day/ha for sheep and 1687 v. 2491 g/day/ha for cattle, P<0.001).