The influence of day length and temperature on food intake and growth rate of bulls given concentrate or grass silage ad libitum in two housing systems

Abstract

In order to study the effect of day length and temperature on performance, data from 495 growing, non-castrated bulls of the Swedish Red and White breed were analysed. Groups of 11 bulls were housed in either an insulated building in pens having slatted floors or in an uninsulated building with pens having both a deep straw bed and a concrete floor. The majority of the bulls (330) were given a concentrate diet ad libitum, while the remainder (165) were given grass silage ad libitum supplemented with concentrate. Energy intake, live-weight gain, housing temperature, day length and change in day length were calculated as 14-day period means for the two housing systems. Regression analyses showed that live-weight gain was associated with increasing day length in bulls on both feeding treatments. For bulls given concentrate ad libitum, metabolizable energy intake was associated with increasing day length. The intake of heavier animals was more influenced by day length than that of those which were lighter. The seasonal influence on daily energy intake in bulls given silage did not show the same pattern as for bulls given concentrate ad libitum. The intake was highest in June and lowest in December for the bulls given concentrate but for the bulls given silage it was highest in August, September and October and lowest in March and April. This was due to the varying quality of the grass silage over the year. No effect or very little effect of temperature or housing system on energy intake or on weight gain was found.