Stocking rates on pasture: effect on herbage quality and milk production

The effects of different stocking rates with grazing dairy cows, respectively post-grazing sward height (GHVP) were studied on herbage quality and milk production in a rotational grazing system under organic farming conditions. During three vegetation periods cows in production were divided into two groups on the organic farm l’Abbaye (Sorens, canton of Fribourg). 15% more grazing area was provided for the “low stocking rate” (BSN) group compared with the “high stocking rate” (BSH) group. GHVP of BSH was decisive for the simultaneous change of the sub-paddocks. Over the three vegetation periods the average stocking rates were 2.0, 2.3, 2.3 and 1.7, 2.0, 1.9 cows per ha for BSH and BSN respectively. The offered herbage mass for BSN contained significantly lower levels of RA, RP, APDE, APDN and K as well as higher levels of RF and NDF. The levels of ADF, sugar, Ca, P, Mg and NEL were unaffected by the treatments. No significant differences were found for milk production per cow. Only milk production per ha of BSH was higher. The treatments had hardly any influence on milk composition. The allocation of larger grazing area without pasture topping led to a lower pasture quality on average throughout vegetation period. Increasing the stocking rate, within certain limits, barely reduces the milk production per cow, but considerably improves the utilisation of grown herbage and hence milk production per ha.