Dried distiller?s grains with solubles and Swedish grown soya beans as protein feeds for dairy bull calves
The cattle production in the world has been questioned in Sweden due to its negative impacts on the environment. The use of imported soya bean meal as a protein feed for Swedish cattle results in the cutting of rainforest and an extensive use of pesticides in the countries were the soya beans are produced. As a consequence, the environmental impacts caused by cattle production increases. A production of protein feeds in Sweden would decrease the transportations and the cutting of rainforest. For organic beef producers the possibility to produce home-grown protein feeds is important since organic protein feeds can be difficult to obtain in another way. The organic beef production has increased over tha last five years in Sweden and the knowledge about what kinds of protein feeds that are possible to grow locally and use with satisfying results needs to be developed.The purpose of the study was to compare feed intake, growth, feed utilisation and rumen function in dairy calves fed dried distiller?s grains with solubles (DDGS) or Swedish grown rolled soya beans (SSB) compared to imported soya bean meal (SBM) as protein feed in a total mixed ration.In the trial 84 dairy bull calves were used. At the start of the experiment the calves were weighed and assigned to the three different protein treatments. The experiment had a completely randomized design. For each treatment four pens were used and there were seven animals in each pen and, there were 12 pens used in total. At arrival, the calves had an average live weight of 93 (standard deviation, SD, 13) kg and at the end of the experiment the mean live weight was 271 (SD, 28) kg. Weighing of the calves was performed on two consecutive days at the start and at the end of the experiment and every 14 days between that.The total mixed rations contained grass-clover silage, rolled barley and sufficient amounts of minerals together with either SBM, DDGS or SSB. The target gain per day was 900 g and when balancing the diets firstly the content of crude protein and amino acids absorbed in the small intestine (AAT) were considered and, secondly, the content of metabolizable energy. Because the requirements of protein in relation to energy change when calves grow the diets were rebalanced four times for the weight intervals 75-125 kg, 126-175 kg, 176-225 kg and 226-275 kg. In the diets with DDGS and SSB cold-pressed rapeseed cake was included until the calves reached a weight of 175 kg to be able to meet the requirements of crude protein and AAT according to Swedish recommendations.Feed was offered ad libitum (> 5% refusals) and feeding was performed once per day. The feed was weighed every day before feeding and refusals were weighed three times per week and the amounts were thereafter used to calculate the intakes of the calves. The average daily live weight gain was calculated from the average value of the first two and the last two weighings of the calves. From the growth and feed intake during the experimental period the feed efficiency of the calves was calculated. Rumen function was estimated from the consistency of the faeces and faecal content of long (>10 mm) particles, whole and partial grains.The calves fed the DDGS diet had higher growth rates than calves fed the SBM or SSB diets (1.34 kg vs. 1.21 kg and 1.25 kg per day, P < 0.01). Calves fed DDGS also had a strong tendency for higher intake of DM (4.81 kg per day vs. 4.45 kg and 4.50 kg, P = 0.058) and had higher intakes of crude protein (811 g per day vs. 725 g and 750 g, P < 0,05) than the other calves. The feed efficiency did not differ between treatments and was around 22 g MJ-1 and 278 g kg-1 DM. The effect of protein feed on faecal traits varied between weight intervals. Generally faeces from calves fed DDGS had a firmer consistency than faeces from calves fed SBM (P< 0.001). The number of long particles (>10 mm) in faeces was similar in all treatments and indicated similar retention times of the protein feeds in the rumen and a good rumen function. In conclusion, SSB or DDGS work as well as SBM as a protein feed when cold-pressed rapeseed cake is included in the diets until the calves reach a live weight of 175 kg. The conclusion is supported by the fact that calves fed DDGS had a higher growth rate than calves fed SBM and calves fed SSB had the same growth rate as calves fed SBM. At the same time feed efficiency and rumen function did not differ between the protein feeds.