Short-term feed restriction impairs the absorptive function of the reticulo-rumen and total tract barrier function in beef cattle1

Abstract

The objective of this study was to evaluate whether different severities of short-term feed restriction (FR) affect the absorptive function of the reticulo-rumen and total tract barrier function in beef cattle. Eighteen ruminally cannulated and ovariectomized Angus × Hereford heifers were blocked by BW into 3 blocks, with blocks conducted sequentially. Treatments were imposed during the 5-d FR period by restricting heifers to 75 (FR75), 50 (FR50) or 25% (FR25) of the ad libitum feed intake measured during a 5-d baseline period (BASE) occurring immediately before FR. Throughout the study, heifers were housed in individual pens (9 m(2)) and were fed the same diet (60% forage:40% concentrate) with free access to water. Dry matter intake was measured daily and ruminal pH was measured every 2 min throughout the study. Ruminal fluid and blood samples were collected on d 3 of the BASE and FR periods, and the temporarily isolated and washed reticulo-rumen technique was used to evaluate short-chain fatty acid (SCFA) absorption on d 5 of the BASE and FR periods. Total tract barrier function was evaluated starting on d 2 of the BASE and FR periods using a pulse dose of Cr-EDTA followed by 48 h of total urine collection. Data were analyzed using the Proc Mixed procedure of SAS with the fixed effects of block, treatment, period, and the treatment × period interaction, the random effect of cow nested in block with period included as a repeated measure. Dry matter intake did not differ among treatments during BASE but, as imposed by the experimental model, DMI during FR relative to BASE equated to 70, 49, and 25%, which was close to the targeted values of 75, 50, and 25% (treatment × period, P < 0.001). A treatment × period interaction (P < 0.001) was also detected for ruminal SCFA concentration with the concentration decreasing as the severity of FR increased, whereas there were no differences during BASE. Mean ruminal pH increased during FR with increasing severity of FR, but was not different during BASE (treatment × period, P < 0.001). Absorption of SCFA across the reticulo-rumen tended to decrease with increasing severity of FR (P = 0.08). For individual SCFA, acetate absorption (mmol/h) tended (P = 0.057) to be less for FR25 and FR50 when compared with FR75 and decreased (P = 0.05) by almost 70 mmol/h at FR25 and FR50 relative to BASE (322mmol/h). Heifers restricted to 25% (FR25) feed had greater urinary Cr recovery during FR than BASE, whereas no changes were detected for FR75 and FR50. This study indicates that moderate severities of short-term FR decrease the absorptive function of the reticulo-rumen, but more severe FR is required to compromise total tract barrier function in beef cattle.

The influence of age and weaning on permeability of the gastrointestinal tract in Holstein bull calves

“…Calves were kept in crates for 48 h to facilitate measurement of total urine excretion over 2 consecutive 24-h periods. Zhang et al (2013) validated the use of Cr-EDTA as an in vivo barrier function measurement and reported that 99% of the Cr excreted in urine was recovered within 48 h from the time of dosing. An initial validation was conducted for this study (data not shown) and results corroborated with Zhang et al (2013).…”

“…Zhang et al (2013) validated the use of Cr-EDTA as an in vivo barrier function measurement and reported that 99% of the Cr excreted in urine was recovered within 48 h from the time of dosing. An initial validation was conducted for this study (data not shown) and results corroborated with Zhang et al (2013). Each day, total urine weight was measured and a 40-mL sample was obtained and frozen at −20°C until being analyzed for Cr concentration as described by Vicente et al (2004) using atomic absorption (iCE 3000 series, Thermo Fisher Scientific Inc., Waltham, MA).…”

“…Plasma glucose and serum BHBA concentrations were analyzed using commercially available kits (Sigma Aldrich, Oakville, ON, Canada, and Roche, Mississauga, ON, Canada, respectively) as previously described by Zhang et al (2013). Serum insulin concentration was measured in duplicate (coefficients of variations ≤10%) using a commercially available bovine ELISA kit (Mercodia AB, Uppsala, Sweden).…”

“…Mannitol, inulin, and Cr-EDTA are markers that have been used to assess GIT permeability. These compounds are nonnutritive and are suggested to cross the GIT via paracellular movement, thus allowing for their use as markers of tissue permeability (Wijtten et al, 2011;Zhang et al, 2013;Penner et al, 2014). Using this approach, Penner et al (2014) demonstrated that in 6-mo-old calves, susceptibility for movement of mannitol was greatest in the jejunum, whereas movement of inulin was greatest in the omasum followed by the rumen.…”

“…It should be recognized that weaning also results in a major shift in the site of nutrient digestion, from the intestine to the reticulo-rumen, and correspondingly the primary energy source changes [short-chain fatty acids (SCFA) and microbial protein vs. glucose, galactose, and milk fat and protein]. It could be expected that these changes may compromise gastrointestinal barrier function (Wijtten et al, 2011) due to low ruminal pH at weaning (Laarman et al, 2012) and that short-term reductions in nutrient provision reduce total-tract barrier function in cattle (Gaebel et al, 1993;Gäbel and Aschenbach, 2002;Zhang et al, 2013). However, only one study known to us has evaluated barrier function in Holstein calves in response to weaning (Malmuthuge et al, 2013).…”