Effect of herbage allowance on pasture utilization, regrowth and milk yield of dairy cows in early, mid and late season

Abstract

The effect of herbage allowance (HA) on milk yield of dairy cows, pasture utilization and pasture regrowth was studied in a field trial conducted at the North Savo Research Station, Maaninka, Finland in 1998. The experiment was conducted with 24 lactating Holstein-Friesian cows that were strip-grazed on Phleum pratense L.– Festuca pratensis Huds. pastures. The pastures received 220 kg ha −1 N divided into three allocations and adequate amounts of P and K. The experiment was conducted as a replicated 3×3 Latin square design with three HA levels and three periods. The three HA levels were 19, 23 and 27 kg dry matter (DM) per cow per day (cut over 3 cm stubble height). The cows did not receive any supplements except minerals. Data were collected during three 10 days periods: mid-June, mid-July and beginning of August. Increasing HA decreased pasture utilization from 77.7 to 61.0%. Increasing HA increased post-grazing leaf area index (LAI) in each period, but the regrowth rate was similar for each treatment. The calculated energy-corrected milk (ECM) yield per hectare during the 15 days collection periods increased with decreasing HA from 2116 to 2406 and to 2808 kg ECM ha −1, respectively. The reduction in individual animal performance of 6% led to a 33% increase in animal production per area (i.e. HA 27 versus HA 19). A post-grazing sward height (SH) of 9–10 cm indicated an effective utilization of P. pratense L.– Festuca pratensis Huds. pastures. Increasing HA from 19 to 27 kg DM increased the milk yield by 0.16 kg ECM kg −1 ( P<0.01). HA had no effect on the milk composition. Milk yield decreased from 25.6 to 18.8 kg ECM ( P<0.01) when the grazing season advanced. HA had no effect on the rumen DM content ( P=0.58), instead, the rumen DM content increased from June to August ( P<0.01).