The utilized metabolizable energy output of grassland on hill farms in Northern Ireland

Forty hill farms in Northern Ireland were surveyed to obtain information on stocking rates and output and to identify factors affecting output. The mean farm area of 194 ha was composed of 155 ha hill land and 39 ha inbye land with a mean stocking rate of 0–7 cow-equivalents ha⁻¹.
On the average farm most of the grassland (88%) was over 20 years old. The preferred species content of the swards averaged 22% over the whole farm and 42% in cut swards. This latter result may be attributed to the relatively high level of fertilizer N applied to these swards (131 kg ha⁻¹) compared to the mean application rate over the whole farm of only 29 kg N ha⁻¹ and 93 kg ha⁻¹ applied to the inbye land.
Output data calculated as utilized metabolizable energy (UME) per unit area for the whole farm and separately for hill and inbye components showed that although only 21% of the farm area was inbye land almost half the annual total metabolizable energy requirements of stock had to be met by grazing inbye. The capacity of herbage to meet stock energy demands was much lower on the hill with supplementary feed having to be provided over the winter.
Calculated output from inbye land was 39 GJ ha⁻¹ compared to 7 GJ ha⁻¹ from the hill and 15 GJ ha⁻¹ from the whole farm. UME output of the whole farm was negatively correlated with farm size (r=−0 55) and positively correlated with stocking rate (r = 0 89), applied N level (r = 0 63)