The effect of differing duration of feed restriction on gastrointestinal tract function in beef heifers: response to feed restriction

This study evaluated the effects of 5 or 10 d of feed restriction (FR), relative to ad libitum feeding, on gastrointestinal tract (GIT) function using six ruminally cannulated beef heifers in a 3 × 6 Latin rectangle. Periods consisted of 5 d of baseline measurements, a 10-d challenge phase, and four consecutive 7-d recovery phases. During challenge, heifers were exposed to either: CON (ad libitum feed provision for 10 d); FR5 (ad libitum feed provision for 5 d followed by FR to 30% of baseline dry matter intake (DMI) for 5 d); or FR10 (FR to 30% of DMI for 10 d). Water intake, and total ruminal and fecal SCFA concentrations were less during challenge for FR5 and FR10 relative to CON (P < 0.015). No differences were observed for SCFA absorption (P ≥ 0.42). Ruminal digesta was 11 kg lighter for FR5 and FR10 than CON during challenge (P = 0.03). While paracellular permeability of the total GIT was not affected (P ≥ 0.65), post-ruminal permeability was greater for FR heifers during challenge than CON (P < 0.01). Independent of the duration, FR reduces GIT fermentation, does not affect SCFA absorption, and increases post-ruminal permeability.