Nutritive value of barley/kale bicrop for lactating dairy cows

Six mid-lactation multiparous Holstein–Friesian dairy cows were used to examine the potential of a fermented whole-crop barley (Hordeum vulgare)/kale (Brassica oleracea) bi-crop as a feed compared with a first-cut perennial ryegrass silage. The barley/kale bi-crop was grown as a strip intercrop, and was harvested and ensiled as an intimate mixture [0Æ80 barley and 0Æ20 kale on a dry-matter (DM) basis]. Animals were offered ad libitum access to one of three experimental diets in a duplicated Latin Square design experiment: (i) Bi-crop (the barley/kale bi-crop); (ii) Grass (the grass silage); and (iii) Mix (a 1:1 fresh mixture of Bi-crop and Grass). All animals also received a standard dairy concentrate at a rate of 4 kg d)1 in equal portions at each of two milkings. The Bi-crop and Grass silages contained 346 and 293 g DM kg)1, 108 and 168 g crude protein kg)1 DM, 268 and 36 g starch kg)1 DM, and had pH values of 3Æ87 and 3Æ80 respectively. Animals offered the two bi-crop silage-containing diets consumed more forage DM than those offered grass silage (14Æ6, 14Æ9 and 12Æ6 kgDM d)1 for Bi-crop, Mix and Grass respectively; s.e.d. 0Æ45, P <0Æ01) and yielded more milk (24Æ0, 23Æ9, 22Æ6 kg d)1 for Bi-crop, Mix and Grass respectively; s.e.d. 0Æ26, P <0Æ01). However, differences in the partitioning of dietary nitrogen towards milk protein and away from excretion in urine suggest a more efficient (rumen) utilization of feed protein by animals offered diets containing the bi-crop silage. It is concluded that, despite having a low crude protein concentration, barley/kale bi-crop silage offers excellent potential as a feed for lactating dairy cows.