The effect of differing duration of feed restriction gastrointestinal tract function in beef heifers: responses during recovery

The objective of this study was to evaluate the timeline required for recovery of gastrointestinal tract (GIT) function in response to the duration of feed restriction (FR). Six ruminally cannulated heifers were used in a 3  6 Latin rectangle, with periods consisting of a 5-d baseline, 10-d challenge, and 4 consecutive weeks of recovery. Treatments during the challenge phase included: ad libitum feed (CON); or feed restriction to 30% of their ad libitum DMI for 5 d (FR5); or for 10 d (FR10). DMI was less for FR10 heifers than for CON during recovery wk 1 but not thereafter, whereas DMI of FR5 heifers did not differ from other treatments (treatment × phase; P < 0.01). The duration and area that ruminal pH was <5.5 were greater for FR10 during recovery wk 1 than CON (treatment × phase; P < 0.01). No differences were observed for the rates of SCFA absorption. Post-ruminal permeability was greater for FR5 and FR10 than for CON during challenge but no differences were observed thereafter. These results indicate that while FR increases paracellular permeability of the GIT, particularly the post-ruminal regions, functional restoration occurs rapidly and is largely independent of the duration of FR.