Feeding colostrum or a 1:1 colostrum:milk mixture for 3 days postnatal increases small intestinal development and minimally influences plasma glucagon-like peptide-2 and serum insulin-like growth factor-1 concentrations in Holstein bull calves

This study evaluated how feeding colostrum- or a colostrum-milk mixture for 3 d postnatal affects plasma glucagon-like peptide-2 (GLP-2), serum insulin-like growth factor-1 (IGF-1), and small intestinal histomorphology in calves. Holstein bulls (n = 24) were fed colostrum at 2 h postnatal and randomly assigned to receive either colostrum (COL), whole milk (WM), or a 1:1 COL:WM mixture (MIX) every 12 h from 12 to 72 h. A jugular venous catheter was placed at 1 h postnatal to sample blood frequently for the duration of the experiment. Samples were collected at 1, 2, 3, 6, 9, 11, and 12 h. Following the 12-h meal, blood was collected at half-hour intervals until 16 h and then at 1-h intervals from 16 to 24 h. A 27-h sample was taken, then blood was sampled every 6 h from 30 to 60 h. Again, blood was taken at half-intervals from 60 to 64 h, then at 65 and 66 h, following which, a 2-h sampling interval was used until 72 h. Plasma GLP-2 (all time points) and serum IGF-1 (at time points: 1, 6, 12, 18, 24, 36, 48, and 72 h) were both analyzed. Duodenal, jejunal, and ileal tissues were collected at 75 h of age to assess histomorphology and cellular proliferation. Feeding COL, rather than WM, increased plasma GLP-2 by 60% for 2 h and tended to increase GLP-2 by 49.4% for 4 h after the 60-h meal. Insulin-like growth factor-1 area under the curve (from 12 to 72 h) tended to be 27% greater for COL than WM calves but was otherwise unaffected by treatment. Ileal crypts tended to proliferate more with MIX than WM, whereas ileal crypt proliferation did not differ for COL compared with MIX or WM and was not different between treatments in the proximal jejunum. Villi height was increased 1.8 and 1.5× (COL and MIX vs. WM) in the proximal and distal jejunum, respectively, whereas MIX duodenal and ileal villi height tended to be 1.5 and 1.4× that of WM. Crypt depth did not differ in any region. Surface area of the gastrointestinal tract was reduced for WM by 60 and 58% (proximal jejunum) and 38 and 52% (ileum) relative to COL and MIX and was 54% less than MIX in the distal jejunum. Overall, extended COL feeding minimally increased plasma GLP-2 and serum IGF-1 compared with WM feeding. As COL and MIX similarly promoted small intestinal maturation, feeding calves transition milk to promote intestinal development could be a strategy for producers.

Effects of feeding hay and calf starter as a mixture or as separate components to Holstein calves on intake, growth, and blood metabolite and hormone concentrations

This study investigated how providing hay mixed with calf starter to dairy calves affected their solid feed intake, feed sorting, growth, and plasma metabolite and hormone concentrations. Forty Holstein heifer calves were fed a texturized calf starter (23.4% crude protein, 32.3% starch on a dry matter basis) and chopped Klein grass hay as separate components (CONT) or the same starter and hay mixed at a 90:10 ratio on an as-fed basis (MIX) ad libitum from the date transported to the research farm (4-7 d of life) to 90 d of life. Calves were provided milk replacer (28% crude protein, 15% fat) at up to 557 g/d before the study, 737 g/d from d 14 to 20, 1,105 g/d from d 21 to 41, 737 g/d from d 42 to 48, and 557 g/d from d 49 to 55 on a dry matter basis. calves were fully weaned on d 56. Feed sorting for the MIX calves was evaluated using the Penn State Particle Separator; the sorting index was calculated as the actual intake as a percentage of predicted intake, with values >100% indicating sorting for and values <100% indicating sorting against. Treatment did not affect solid feed intake, growth performance, or plasma metabolite or hormone concentration during the preweaning or weaning periods. However, calves in the MIX treatment had less neutral detergent fiber intake as a percentage of solid feed intake than CONT calves in the preweaning (23.3 vs. 37.0%) and weaning (23.5 vs. 25.8%) periods, although MIX calves sorted (107.2%) for long particles, which were primarily hay, during weaning. During the postweaning period, MIX calves had greater neutral detergent fiber intake as a percentage of solid feed intake compared with CONT calves (23.4 vs. 22.7%), although they sorted against long particles (84.4%), and decreased solid feed dry matter intake compared with CONT calves (3,292 vs. 3,536 g/d) and average daily gain (1.20 vs. 1.31 kg/d). Weaned calves in the MIX treatment also had lower plasma concentration of glucagon-like peptide 2 compared with CONT (0.46 vs. 0.77 ng/mg) but had higher plasma concentrations of ghrelin (0.05 vs. 0.03 ng/mg). These results suggest that feeding a mixture of texturized calf starter and chopped hay at the 90:10 ratio to postweaned calves may decrease solid feed intake and growth.

Effects of glucagon-like peptides 1 and 2 and epidermal growth factor on the epithelial barrier of the rumen of adult sheep

Epidermal growth factor (EGF) and glucagon-like peptides (GLP) modulate the tight junctions (TJ) of the intestinal epithelial barrier (EB) of monogastric animals. This work tried to elucidate whether GLP-1, GLP-2 and EGF can affect the EB of the rumen. Ovine ruminal epithelia were incubated in Ussing chambers for 7 hr with 25 or 250 nM of either GLP-1 or GLP-2 on the serosal side, with 2.5 nM of EGF on the serosal side or with 0.25 or 2.5 nM EGF on the mucosal side. No treatment affected tissue conductance. Short-circuit current (I_sc ) was affected by time and treatment and their interactions. Only 250 nM of either GLP-1 or GLP-2 decreased I_sc in certain periods compared with 25 nM GLP-1 or 0.25 nM mucosally applied EGF; however, not when compared to control epithelia. Fluorescein flux rates (J_fluor ) of ruminal epithelia were affected by treatment, time and time × treatment interaction. The time × treatment interaction was based on an increase in J_fluor between the first and last hour in epithelia incubated with 25 nM GLP-1 or GLP-2 and in epithelia incubated with EGF. After 7 hr incubation, claudin-7 mRNA expression was downregulated in all treatments. Claudin-1 mRNA was upregulated after incubation with 2.5 nM EGF on the serosal side, claudin-4 mRNA was downregulated by 2.5 nM EGF on the mucosal side, and occludin mRNA was increased after incubation with 250 nM GLP-2. The protein abundance of all tested TJ proteins was not influenced by treatment. We conclude that GLP-1, GLP-2, and EGF have no obvious acute effects on the EB of ruminal epithelia under simulated physiological conditions ex vivo. However, by decreasing the mRNA expression of claudin-7 and partly affecting other TJ proteins, they may modulate EB in the longer term or under certain conditions.

Response of plasma glucagon-like peptide-2 to feeding pattern and intraruminal administration of volatile fatty acids in sheep

Glucagon-like peptide-2 (GLP-2), a gut peptide secreted by enteroendocrine L cells, has recently been identified as a key regulator of intestinal growth and absorptive function in ruminants. However, reports on GLP-2 secretion are few, and more information regarding its secretion dynamics is needed. In this study, two experiments were conducted to elucidate the daily rhythm of GLP-2 secretion in response to feeding regimen and to investigate the effect of volatile fatty acids (VFA) on GLP-2 release in sheep. In experiment 1, blood samples were collected over 3 d from 4 Suffolk mature wethers adapted to a maintenance diet fed once daily; day 1 sampling was preceded by 24 h of fasting to reach steady state. On days 1 and 3, samples were collected every 10 min from 11:00 to 14:00 on both days and then every 1 h until 00:00 on day 1 only; feed was offered at 12:00. On day 2, feed was withheld, and sampling was performed every hour from 01:00 to 00:00. In experiment 2, 5 Suffolk mature wethers were assigned to 5 treatment groups of intraruminal administration of saline, acetate, propionate, butyrate, or VFA mix (acetate, propionate, and butyrate in a ratio of 65:20:15) in a 5 × 5 Latin square design. Blood samples were collected at 0, 1.5, 3, 6, 9, 12, 15, 20, 25, 30, 40, 50, 60, 90, and 120 min relative to the beginning of administration at 12:00. In both experiments, plasma GLP-2, glucagon-like peptide-1 (GLP-1), glucose, insulin, and β-hydroxy butyric acid (BHBA) levels were measured. In experiment 1, incremental area under the curve was greater (P < 0.05) post-feeding than pre-feeding on days 1 and 3 for GLP-2 and tended to be greater (P < 0.1) on day 1 for GLP-1. Plasma insulin, glucose, and BHBA levels increased (P < 0.05) on day 1 post-feeding. Plasma GLP-2 was poorly correlated with GLP-1 but positively correlated with insulin, glucose, and BHBA. In experiment 2, administration of butyrate and VFA mix remarkably increased plasma GLP-2 (P = 0.05) and BHBA (P < 0.0001) levels compared with those in other treatments. Plasma GLP-1 levels were higher with butyrate administration compared with those in the saline, acetate, and VFA mix (P = 0.019). Propionate administration increased plasma glucose (P = 0.013) and insulin (P = 0.053) levels. Thus, our data confirmed that GLP-2 release is responsive to feeding and might be promoted by BHBA produced by the rumen epithelial metabolism of butyrate. Further molecular- and cellular-level studies are needed to determine the role of butyrate as a signaling molecule for GLP-2 release.