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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.

Most milk replacers (MR) contain a higher lactose:fat ratio compared to whole milk, potentially affecting nutrient absorption and use by the calf. This study evaluated how body composition and intestinal development were affected when lactose was replaced with fat in MR. Thirty-four calves (43.3 ± 0.8 kg) were blocked (BW and dam parity), and randomly assigned to a high-lactose (43.8% lactose and 17.1% crude fat) or high-fat (37.9% lactose and 23.4% crude fat) MR. Calves were fed pooled colostrum within 2 h (18% of metabolic body weight (MBW)) and 12 h (9 %MBW) postnatal, followed by MR feeding (18 %MBW) twice daily. Calves were weighed pre-prandially at birth and on d 7. Calves were euthanized on d 7 to sample intestinal tissue and analyze body composition using dual-energy x-ray absorptiometry. Samples of intestinal segments were processed to evaluate histomorphology using bright-field microscopy. Data were analyzed using PROC MIXED in SAS software. Total gain (3.90 vs. 2.29 ± 0.38 kg, P = 0.01) and gain:ME intake (44.64 vs. 28.61 ± 4.32 kg, P = 0.02) were greater for high-fat compared to high-lactose calves, whereas body composition was unaffected (P = 0.13). Proportionally, the large intestine was 0.11 ± 0.02 %BW heavier (P = 0.03) in high-fat calves compared to high-lactose calves, while their small intestine tended to be 0.16 ± 0.06 %BW heavier (P = 0.09). Small and large intestine length did not differ (P = 0.96). High-fat calves had wider villi (125.41 vs. 96.58 µm, P = 0.05) in the jejunum but shorter villi (414.17 vs. 470.96 µm, P = 0.02) in the ileum compared to high-lactose calves. Macronutrient composition affected intestinal histomorphology and improved efficiency of ME use for BW gain. Understanding how fat (including its source) influences nutrient efficiency in dairy calves may improve nutritional strategies on farm.

Inorganic sources of trace minerals are commonly supplemented in dairy cow diets; however, there has been an increase in the supplementation of minerals complexed with organic compounds. These organic trace minerals are thought to have greater bioavailability which may enhance rumen fermentation and absorption. The objective of this study was to assess the effects of dietary concentration and source of supplemental trace minerals on serum trace mineral status and rumen fermentation. Six lactating Holstein cows were used in a 6 x 6 Latin square design with a 23-day adaptation and 5-day experimental period. Cows were fed the same basal diet daily except for the difference in source [organic (ORG) versus inorganic (INO)] and concentration (50%, 100%, and 200% based on NRC recommendations) of trace mineral supplemented. During the experimental period feed intake and blood were collected daily. Rumen fluid was collected on the final two days of the experimental period. Data was analyzed with PROC MIXED in SAS 9.4. Dry matter intake (18.1 ± 0.70 kg), serum mineral concentrations (Cu, Mn, Se, and Zn), and rumen pH (6.5 ± 0.64) did not differ among the treatments. However, serum concentration of Co was higher in 200% ORG compared to 50% and 100% INO and 50% ORG. Ruminal concentration of acetate was higher in 50% and 100% ORG compared to 200% ORG. Butyrate ruminal concentration was higher at 50% ORG compared to 200% ORG. Ruminal propionate concentration was higher in 50% INO and 50% ORG compared to 100% INO and 200% ORG. These findings demonstrate serum trace mineral status and ruminal pH are not tightly controlled by the source of trace minerals when supplemented at 50%, 100% and 200% of the NRC recommendations, however rumen fermentation may be affected by the dietary concentration of trace minerals in the diet.

Citrate, a major determinant of citrus fruit quality, accumulates early in fruit development and declines towards maturation. The isomerization of citrate to isocitrate, catalyzed by aconitase is a key step in acid metabolism. Inhibition of mitochondrial aconitase activity early in fruit development contributes to acid accumulation, whereas increased cytosolic activity of aconitase causes citrate decline. It was previously hypothesized that the block in mitochondrial aconitase activity, inducing acid accumulation, is caused by citramalate. Here, we investigated the effect of citramalate and of another aconitase inhibitor, oxalomalate, on aconitase activity and regulation in callus originated from juice sacs. These compounds significantly increased citrate content and reduced the enzyme's activity, while slightly inducing its protein level. Citramalate inhibited the mitochondrial, but not cytosolic form of the enzyme. Its external application to mandarin fruits resulted in inhibition of aconitase activity, with a transient increase in fruit acidity detected a few weeks later. The endogenous level of citramalate was analyzed in five citrus varieties: its pattern of accumulation challenged the notion of its action as an endogenous inhibitor of mitochondrial aconitase. Metabolite profiling of oxalomalate-treated cells showed significant increases in a few amino acids and organic acids. The activities of alanine transaminase, aspartate transaminase and aspartate kinase, as well as these of two γ-aminobutyrate (GABA)-shunt enzymes, succinic semialdehyde reductase (SSAR) and succinic semialdehyde dehydrogenase (SSAD) were significantly induced in oxalomalate-treated cells. It is suggested that the increase in citrate, caused by aconitase inhibition, induces amino acid synthesis and the GABA shunt, in accordance with the suggested fate of citrate during the acid decline stage in citrus fruit.

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.