The effects of season and age of stand on the nutritive value of heather (Calluna vulgaris, L. Hull) to sheep

SUMMARY In two experiments frozen heather (Calluna vulgaris, L. Hull), which contained 85–90% of the current season's shoots, was offeredad libitumto castrated male sheep. In one experiment, heather harvested in July, September, November and March was offered to six sheep per harvest, D.M. digestibility fell from 55.9% in July to 41.9% in March, with the greatest decline occurring after flower development in August. There were no significant changes with season in voluntary intakes, which were low, ranging from 29 to 39 g D.M./kg W0.75/day. Apart from the July harvest, intakes of digestible D.M. were insufficient to maintain the sheep. The apparent digestibility of N(14·3–42·2%) and plasma urea N values (5–6 mg/100 ml) were low and undigested N of dietary origin in the faeces was high (25–45%). Sheep offered the September, November and March harvests were in considerable negative apparent balances of N and it was calculated that the sheep were in a negative balance of truly digested N. In a second ex-periment, heather harvested in August from pioneer, building and mature stands was offered to six sheep per harvest. There were no significant differences between stands in voluntary intake and digestibility.