Stärkelsenedbrytningens betydelse för mjölkkors konsumtionsmönster och mjölkproduktion

Abstract: Feed intake in dairy cows is regulated by a variety of factors influencing hunger and satiety. One of the regulation systems includes the short chain fatty acids produced during feed degradation in the rumen. Starch can be digested either in the rumen where short chain fatty acids are produced or in the small intestine where glucose is the end product. Since glucose does not have the same effect on satiety that short chain fatty acids have, the site of starch digestion might be an important factor that affects feed intake and milk production. The aim of this study was to investigate the effects of site of starch digestion on feeding behaviour (feed intake, consumption time, and eating frequency) and milk production. Because feeding behaviour is closely connected to the cows' environment, the study also included observations of behaviour. Three different feed rations were compared. They were all total mixed rations that were formulated to have the same nutritional composition except for the ruminal starch degradability. To achieve three different levels of ruminal starch degradability different starch sources were used: • Feed A: Wheat, barley and oats ⇒ 92 % ruminal starch degradation • Feed B: Wheat, barley and maize ⇒ 76 % ruminal starch degradation • Feed C: Maize and peas ⇒ 61 % ruminal starch degradation. The experimental design was a change-over design with three periods using 48 dairy cows in mid-lactation. To get information about individual feeding behaviour, special feeding equipment was used that automatically registered all feeding visits that the cows performed during the experiment. The visits within a derived time-span were first grouped into meals, and then feeding behaviour was studied per meal and per day (24 h). Data were analysed with an Analysis of Variance (Mixed Effect Model, SAS vers. 8.2). During the later part of the feeding trial two different behaviour studies were made. One study included the cows' activity and the other was a study of the cause of cows terminating feeding visits. Feed intake per meal was not significantly affected by treatment but there were significant period effects (p<0.0001) and interactions between treatment and period (p<0.05). The cows ate 2.5 kg dry matter (DM) per meal in period 1, 2.7 kg DM in period 2 and 3.0 kg DM per meal in period 3. The consumption time per meal was significantly affected by treatment (p<0.05). The cows ate shorter time per meal with feed A than with the other two feed rations. The consumption per day (24 h) showed similar results to the consumption per meal. Daily feed intake was about 19 kg DM and was not affected by treatment. The consumption time per day was longer with feed B. The number of meals was about 7 per day, but feed A resulted in more meals per day (p< 0.05). Milk yield was not significantly affected by site of starch digestion, but the fat content was higher with feed A. The behaviour observations showed that activity was high just after feeding and the feed competition was also high at that time. The reason to why cows stopped eating was often displacements. Of all the recorded terminations 42 % were caused by cows displacing one another. In conclusion, the site of starch digestion did not affect the total daily feed intake or the milk production but the results indicate that it might have an effect of feed intake per meal, the number of meals per day and the consumption time.