Effects of barley intake and allocation regime on performance of growing dairy bulls offered highly digestible grass silage

The objective of this experiment was to examine effects of barley intake and allocation regime on performance of growing dairy bulls offered highly digestible grass silage, with digestible organic matter of 703 g/kg dry matter (DM). The feeding experiment comprised of a total of 33 bulls (17 Holstein and 16 Nordic Red) with an initial mean live weight of 230 kg and age of 200 days and a slaughter age of 566 days. During the feeding experiment the bulls were fed ad libitum either grass silage alone (GS) or a total mixed ration where rolled barley grain was added. Barley concentrations were either 300 g/kg DM during the whole experiment (SC) or 600 g/kg DM during only the early (DC) or late (IC) half of the growing period. When barley proportion was doubled in the diet during the early part of the growing period, it had no effect on the total DMI (SC vs. DC). Including barley in the diet during the late part of growing period increased barley intake by 30% (P<0.05) compared to the other treatments where barley was given. Silage DM intake decreased on average by 27% (P<0.05) when barley was included in the diet over the whole growing period (GS vs. others). Including barley in the diet during the late part of growing period increased LWG over the total growing period by 17% (P<0.05) compared to the silage only treatment (IC vs. GS). When barley was included in the diet during the early part of the growing period, carcass fat score decreased by 20% (P<0.05) compared to the treatment where barley was included in the diet during the late part of the growing period (DC vs. IC). Although good quality grass silage as a sole feed could support moderate to high levels of performance of growing cattle, including barley to the diet further improved the performance of animals. The present study demonstrated the ability of growing bulls to adapt to different feeding regimes without major effects on performance. This gives flexibility into choosing feeding strategies based on feed availability and prices resulting in potential benefits in the economy of beef production.