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Most milk replacers (MR) contain more lactose compared with whole milk, which, when fed at a large meal size, could influence gut barrier function in calves. This study evaluated how replacing lactose in MR with fat (on a wt/wt basis) affects intestinal histomorphology and permeability in neonatal dairy calves. Thirty-four Holstein-Friesian bull calves were blocked by dam parity and randomly assigned to 1 of 2 treatments (n = 17): a high-lactose (46.1% lactose, 18.0% crude fat, and 23.9% crude protein of dry matter) or a high-fat MR (HF; 39.9% lactose, 24.6% crude fat, and 24.0% crude protein of dry matter). Calves were individually housed and fed pooled colostrum at 1.5 h and 12 h postnatally, at 18 and 9% of metabolic body weight (BW0.75), respectively. From 24 h postnatally until the end of the study (d 7), calves were transitioned to be fed MR (prepared at 15% solids) at 18% of BW0.75 twice daily at 0700 and 1900 h. During postprandial sampling on d 6, intestinal permeability was assessed by mixing lactulose (1.03 g/kg of BW0.75) and d-mannitol (0.31 g/kg of BW0.75) into the morning meal without altering total meal volume. Sequential blood samples were collected via jugular catheter, and total urine was collected for 12 h to measure the marker content. Calves were euthanized 3 h after the morning meal on d 7, and gastrointestinal tract tissues and digesta were collected for analysis of histomorphology, digesta osmolality, and gene expression. The empty gastrointestinal tracts of HF calves were heavier, although length did not differ and differences in histomorphology were minor. Digesta osmolality changed along the tract without differences between treatments. Plasma lactulose was greater in HF, although plasma d-mannitol and the recovery of both markers in urine were unaffected. No significant differences were detected in gene expression, although HF calves tended to have lower expression of TJP1 and CLDN2 and higher expression of proinflammatory cytokine IL1B in ileum tissue. In conclusion, partially replacing lactose in MR with fat resulted in a heavier and more permeable gut, with minor histomorphological differences.

Milk replacers (MR) formulated to contain more lactose than whole milk could potentially reduce insulin sensitivity in dairy calves. This study evaluated how partially replacing lactose in MR with fat on a weight/weight basis affects glucose-insulin kinetics in neonatal dairy calves fed high quantities of MR. Thirty-four Holstein bull calves were blocked by dam parity (1.6 ± 0.3) and randomly assigned to 1 of 2 treatments (n = 17): a high-lactose MR (HL; 46.1% lactose, 18.0% crude fat, and 23.9% crude protein on a dry matter basis) or a high fat MR (HF; 39.9% lactose, 24.6% crude fat, and 24.0% crude protein on a dry matter basis). Calves were individually housed and fed pooled colostrum at 1.5 h and 12 h postnatal at 18 and 9% of metabolic body weight (BW0.75), respectively. From 24 h postnatal until the end of the study (d 7), calves were transitioned to MR (prepared at 150 g/L) at 18% of BW0.75 twice daily at 0700 and 1900 h. On d 4, an insulin-modified intravenous glucose tolerance test was conducted 8 h after the morning meal by intravenous infusion of glucose (0.54 g/kg of BW0.75, min 0) and insulin (3.9 µg/kg of BW0.75, min 20). During postprandial sampling on d 6, abomasal emptying was assessed by dosing acetaminophen (0.13 g/kg of BW0.75) with MR and measuring its appearance within plasma. Sequential blood samples were collected and analyzed for plasma glucose, insulin, and acetaminophen concentrations. Calves were killed on d 7 and liver and pancreatic tissues were collected for histomorphological analysis. Partially replacing lactose in MR with fat increased body weight gain (679.6 vs. 462.0 ± 69.68 g/d) and gain:metabolizable energy intake (186.6 vs. 120.5 ± 20.21 g of body weight/Mcal) compared with feeding HL MR. Furthermore, abomasal emptying rate was reduced in calves fed HF MR. Calculated variables based on postprandial glucose and insulin concentrations, such as maximum concentration or area under the curve, were or tended to be lower in HF than in HL calves. Postprandial insulin sensitivity tended to be reduced in HL compared with HF, although insulin sensitivity estimated from the insulin-modified intravenous glucose tolerance test was not different. Calves fed HF MR showed enhanced glucose-stimulated insulin secretion. In conclusion, partially replacing lactose in MR with fat resulted in smaller fluctuations in postprandial glucose and insulin concentrations and tended to increase postprandial but not fasting insulin sensitivity in neonatal dairy calves.

Feeding of butyrate was found to have a positive effects in enhancing gut development and improving growth performance of calves. Equally, glucagon-like peptide 1 and 2 (GLP-1 and GLP-2), secreted from gastrointestinal L-cells in response to nutrient intake, were found to play a significant role in regulating blood glucose homeostasis and improving gut health. However, limited information is available about the relationship between butyrate and release of GLP-1 and GLP-2 in dairy calves. The objective of this study was to evaluate the effects of a pulse-dose ruminal infusion of butyrate on plasma GLP-1 and GLP-2 concentrations in dairy calves. Five ruminally cannulated mature Holstein bull calves (7.2 ± 0.10 mo, and 330 ± 16.0 kg of body weight; mean ± standard deviation) were used in a 5 × 5 Latin square with 4-d periods. On d 1 of each period at 0800 h, calves were ruminally infused with 1 of 5 treatments: 0 (saline), 0.3, 0.6, 0.9, and 1.2 g of butyrate per kg of body weight. Before butyrate infusion, calves were not offered feed overnight, and sequential blood and rumen fluid samples were taken before and after infusion on d 1 of each period. Ruminal butyrate and total volatile fatty acid concentrations increased linearly (2.65, 12.19, 20.99, 30.19, and 36.30; 23.68, 33.07, 40.94, 51.13, and 56.31 µmol/mL, for butyrate and total volatile fatty acids, respectively) in a dose-dependent manner, whereas propionate and isobutyrate increased quadratically. Ruminal and plasma butyrate, β-hydroxybutyrate, GLP-1, GLP-2, insulin, and glucose concentrations were all affected by treatment, time (except GLP-2), and interaction of treatment with time (except GLP-1). The area under the curve (AUC) summarized at different time points relative to the baseline (AUC30, AUC60, AUC120, and AUC240) for ruminal and plasma butyrate, and BHB, increased linearly with the dose of butyrate infused. However, AUC30, AUC60, AUC120, and AUC240 for plasma GLP-2 concentration were affected in a cubic manner unlike the linear effect on AUC30 and AUC60 for GLP-1. Plasma GLP-2 was not correlated with plasma butyrate (r = 0.16), GLP-1 (r = 0.03), or BHB (r = -0.05). This findings suggest that pulse-dosing of butyrate slightly increased both GLP-1 and GLP-2 concentrations at specific time points and this might be promoted by direct or indirect effect of butyrate on the intestinal L-cells.

The objective of this experiment was to determine how source of selenium (Se) affects dairy cow performance, antioxidant status, and apparent absorption and retention. Multiparous Holstein cows (n = 24; 597 ± 49 kg BW) were blocked by days in milk (161 ± 18) and randomly assigned to receive 0.3 mg/kg of either: 1) organic Se (selenized yeast; ORG; Sel-Plex-Alltech); or, 2) inorganic Se (sodium selenite; INO) premix, top dressed and mixed into a ration daily. After an 11-week adaptation period (blood and milk sampled monthly), cows received an intraruminal dose of Se77 (either Se77 yeast or NaSe77O3) followed by a 4-day period of blood and rumen fluid sampling, and total collection of feces, urine, and milk. Data were analyzed using PROC GLIMMIX in SAS with fixed effects of treatment, time, and their interaction, and random effect of block. Daily DMI (23 ± 0.6 kg), milk yield (35 ± 1.2 kg), plasma glutathione peroxidase (64 ± 4.2 U), and serum Se (0.11 ± 0.003 µg/g) were not different between treatments during the adaptation period. Serum Se77 maximum concentration and area under the curve (AUC) were not different between treatments for 72 hours following infusion, but rumen fluid Se77 AUC was higher (P = 0.02) for ORG cows. Apparent absorption (64 ± 1.3%) and retention (44 ± 1.5%) of the Se77 dose did not differ between treatments. The ORG cows had lower urinary excretion (13 vs. 17 ± 0.6%; P < 0.01), higher milk excretion (6 vs. 2 ± 0.3%; P < 0.01), and similar fecal excretion (36 ± 1.3%; P = 0.9) of Se77 compared to INO cows. These results indicate that ORG Se increased Se content of milk and decreased Se excretion in urine, but did not alter performance, antioxidant status, and apparent absorption and retention of Se in mid-lactation cows.

Chicken intestine harbors a vast number of bacterial strains. In the present study, antimicrobial substance produced by lactic acid bacteria (LAB) isolated from the gastrointestinal tract of healthy chicken was detected, characterized, and purified. Based on 16S rRNA sequencing, the bacteria were identified as Lactobacillus plantarum vN. The antimicrobial substance produced by this bacterium was designated vN-1 and exhibited a broad-spectrum of activity against many important pathogenic and spoilage microorganisms, including Pseudomonas aeruginosa, Staphylococcus aureus, Micrococcus luteus, Salmonella Typhimurium, and Erwinia amylovova. vN-1 was determined to be thermostable, insensitive to pH values ranging from 2.0 to 8.0, resistant to various organic solvents and to enzymatic inactivation. The inhibition kinetics displayed a bactericidal mode of action. This study revealed an antimicrobial substance with low molecular mass of less than 1 kDa as determined by ultrafiltration and having features not previously reported for LAB isolated from chicken intestines. The detection of this antimicrobial substance addresses an important aspect of biotechnological control agents of spoilage caused by Pseudomonas spp. and promises the possibility for preservation of refrigerated poultry meat. Practical Application: The newly characterized antimicrobial substance and designated as vN-1 may have the potential to be used in food preservation.