The role of migrating myoelectric complexes in the regulation of digesta transport in the preruminant calf

Abstract

Four calves were equipped with an electromagnetic flow probe inside the tranverse duodenum and with electrodes at intervals of 2 cm on either side of the probe. Amounts of 0.5, 2.0, 3.5, and 5.0 kg of whole milk were given according to a latin square design. Recordings of digesta flow and myoelectric activity were made during a 5.6-h period after feeding to quantify the influence of migrating myoelectric complexes on digesta flow through the transverse duodenum of preruminant calf under different levels of milk intake. Immediately after feeding, a phase of irregular spiking activity appeared; its length increasing linearly (p = 0.002) with the amount of milk fed. Increasing milk intake led to linear increases in duration (p = 0.001) and total electrical activity (p = 0.002) of the irregular activity phases, quadratic shortening of the quiescent phases (p = 0.021), and linear decrease (p = 0.006) in the numbers of migrating myoelectric complexes. Intermittent flows of digesta, each of them corresponding to a strong spike burst, appeared during irregular spiking activity phases. Augmentation of the milk ingested did not affect the volume of each gush of digesta but caused a cubic increase in the number of gushes (p = 0.023) and in the total volume of digesta (p = 0.009). These cubic effects implied that with increased intake of milk, the duodenum endeavoured to accelerate the flow of digesta in an attempt to return to an "empty state" in about the same time for all levels of milk consumed. This was achieved mainly through adjustments in the duration and activity of the irregular spiking activity phase.Key words: calf, myoelectric complex, digesta transport, milk intake.