Effects of different stocking rates with grazing dairy cows on herbage quality and milk production

The effects of different stocking rates with grazing dairy cows, respectively post-grazing sward height (HHSP), were studied on herbage quality and on milk production in a rotational grazing system under organic farming conditions. During three vegetation periods, cows in production were divided into two groups on an organic farm in Sorens (canton of Fribourg). 15% more grazing area was provided for the "low stocking rate" (CHF) group than to the "high stocking rate" (CHE) group. HHSP of CHE 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 cows per ha for CHE and 1.7, 2.0, 1.9 cows per ha for CHF. The offered herbage mass for CHF 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 in milk production per cow. Only milk production per ha of CHE 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.