The Influence of Physical Form of Ration on Chewing Activity and Rumen Motility in Lactating Cows

The effect of the physical form of diet on chewing activity and rumen motility was investigated in a study with 3 lactating cows using two 3x3 Latin square blocks with 3 experimental periods per block and 3 physical forms of the rations by means of different contents of long barley straw (LS): 4% LS, 10% LS and 20% LS. The rations consisted of long barley straw and pelleted fed in different proportions. All rations consisted of 80% concentrate mixture and 20% barley straw in either long or ground and pelleted physical form. The rations were fed restrictively every second hour throughout the experiment. The dry matter intake was adjusted to 16 kg daily and the content of nutrients was according to Danish Standards for 24 kg 4% FCM. The motility of the rumen was recorded by use of a pressure transducer in the reticulo-rumen, and the pattern of contractions was used for determination of the chewing activity. An increase in the content of LS from 4 to 20% led to linear increases in the time spent eating from 83 to 104 min/day (p<0.01), ruminating from 125 to 403 (min/day) (p<0.0001), total chewing time from 210 to 510 min/day (p<0.0001), in the daily number of ruminating periods from 8 to 17 (p<0.001), and in the average length of the ruminating periods from 15 to 24 min (p<0.006). The content of LS had a significant linearly stimulating effect on the frequency of primary contraction cycles (no/min) in the reticulo-rumen (PCC). By increasing the content of LS from 4 to 20% the frequency of PCC in total increased from 1.0 to 1.3 and the frequency of PCC at rest increased linearly from 0.9 to 1.2 (p<0.0001) and the frequency of PCC during eating increased from 1.45 to 1.55 (p<0.05). The frequency of PCC during rumination was not significantly affected by the physical form of the ration (p<0.4). At the same time a positive linear correlation was found between the time spent ruminating and the frequency of PCC at rest (p<0.001).