Effects of glucose and amino acids on ghrelin secretion in sheep

Two experiments were conducted to elucidate the effects of post‐ruminal administration of starch and casein (Exp. 1), plasma amino acids concentrations (Exp. 2), and plasma glucose and insulin concentrations (Exp. 2) on plasma ghrelin concentrations in sheep. In Exp. 1, plasma ghrelin concentrations were determined by four infusion treatments (water, cornstarch, casein and cornstarch plus casein) in four wethers. Abomasal infusion of casein increased plasma α‐amino N (AAN) concentrations. Infusion of starch or casein alone did not affect plasma ghrelin concentrations, but starch plus casein infusion increased plasma levels of ghrelin, glucose and AAN. In Exp 2, we investigated the effects of saline or amino acids on ghrelin secretion in four wethers. Two hours after the initiation of saline or amino acid infusion into the jugular vein, glucose was also continuously infused to investigate the effects of blood glucose and insulin by hyper‐glycemic clump on plasma ghrelin concentrations. Infusion of amino acids alone raised plasma levels of ghrelin, but the higher plasma glucose and insulin concentrations had no effect on plasma ghrelin concentrations. These results suggest that high plasma levels of amino acids can stimulate ghrelin secretion, but glucose and insulin do not affect ghrelin secretion in sheep.     

Evaluating the rumen‐protected lysine stability in forage‐based total mixed rations in vitro and determining the lysine Brix value

Three rumen‐protected lysine (RPL) products (AjiPro^®‐L, LysiPEARL^TM, and Feedtech Bypass Lysine^TM: A, B, and C, respectively) were tested for stability in two forage‐based total mixed rations (TMR1, 41.3% dry matter (DM), and TMR2, 49.5% DM) (experiment 1) and for Brix value (experiment 2). In experiment 1, each RPL product (2 g each) and TMR diet (200 g) were mixed and stored in plastic bags at 20°C for 0, 1, 3, 6, 12, 24, and 48 hr. In experiment 2, each RPL product (2 g) was dispensed into ion‐exchanged water (20 ml) and kept at 20°C for 0, 0.5, 1, 3, 6, 12, 24, and 48 hr. At each time point, free lysine (Lys) content and Brix values of extracts were measured, and Lys release (LR, %) was calculated. All RPL products LR% varied with varying diets DM and increased with increasing of time exposed to diets; it was highest in C, followed by B, and then A. Water LR% positively correlated with that from diets and with Brix values of Lys dissociated in water. Our results indicated that Lys dissociation from RPL products is affected by diet DM content. Brix value may be used as a potential marker for RPL protection efficacy.     

Oral administration of L-citrulline changes the concentrations of plasma hormones and biochemical profile in heat-exposed broilers

We examined the effects of oral administration of L-citrulline (L-Cit) on plasma metabolic hormones and biochemical profile in broilers. Food intake, water intake, and body temperature were also analyzed. After dual oral administration (20 mmol/head/administration) of L-Cit, broilers were exposed to a high ambient temperature (HT; 30 ± 1°C) chamber for 120 min. Oral administration of L-Cit reduced (p < .001) rectal temperature in broilers. Food intake was increased (p < .05) by heat stress, but it was reduced (p < .05) by L-Cit. Plasma levels of 3,5,3′-triiodothyronine, which initially increased (p < .0001) due to heat stress, were reduced (p < .01) by oral administration of L-Cit. Plasma insulin levels were increased by heat exposure (p < .01) and oral L-Cit (p < .05). Heat stress caused a decline (p < .05) in plasma thyroxine. Plasma lactic acid (p < .05) and non-esterified fatty acids (p < .01) were increased in L-Cit-treated heat-exposed broilers. In conclusion, our results suggest that oral L-Cit can modulate plasma concentrations of major metabolic hormones and reduces food intake in broilers.     

Exposure to blue LED light before the onset of darkness under a long‐day photoperiod alters melatonin secretion,feeding behaviour and growth in female dairy calves

The effect of blue LED on melatonin secretion, feeding behaviour and growth was addressed in Holstein female dairy calves. In Exp.1, six animals (8 weeks old, 97 ± 4.1 kg BW) were exposed to yellow or blue LED for 2 hr before darkness over 7 days under a long‐day photoperiod (LDPP). In Exp. 2, six animals (8 weeks old, 88.5 ± 4.8 kg BW) were exposed to blue light from a white LED all daytime or a yellow LED for 2 hr before the darkness of LDPP (blue light cut) over 3 weeks. In Exp. 1, blue light mildly suppressed melatonin secretion during the 2‐hr treatment but did not affect the timing of the nightly melatonin rise. However, the rise in nighty melatonin levels was higher with yellow than blue LED. In Exp. 2, white LED completely suppressed melatonin secretion during the 2‐hr treatment, but plasma melatonin concentrations were similar during the darkness. Grass hay intake, rumination time, frequency of water intake and body weight gain were higher in animals exposed to the yellow rather than the white LED. Overall results indicate that exposure to blue light from white LEDs under an LDPP suppresses melatonin secretion and might negatively impact the development of female dairy calves.     

Effects of oral administration of colostrum whey in peripartum goat on antimicrobial peptides in postpartum milk

The present study was conducted to examine whether colostrum supplementation in peripartum goats increases the antimicrobial peptides in their milk. Goats were orally administered 2 ml of colostrum whey products (colostrum group) or water (control group) daily, from 2 weeks before until 2 weeks after kidding. Body weights of mothers and kids were measured. Blood, milk, and fecal samples were collected from the mothers, and blood samples were collected from the kids. Concentrations of milk antimicrobial peptides (beta‐defensin, cathelicidin, lactoferrin, S100A7, lactoperoxidase, and immunoglobulin A [IgA]) were determined. IgA and nutritional parameters (glucose, total cholesterol, triglyceride, ketone bodies, and non‐esterified fatty acids) were also determined in the blood of mothers and kids. Milk IgA and lactoferrin concentrations were higher in the colostrum group than in the control group. Conversely, lower milk concentrations of S100A7 were observed in the colostrum group than that in the control group. Plasma IgA concentrations were higher for kids from the colostrum group than for those from the control group. These results suggest that oral administration of colostrum in pregnant goats increases IgA concentration in postpartum milk, which can subsequently improve the health of their kids.     

Effects of intravenous ghrelin injection on plasma growth hormone,insulin and glucose concentrations in calves at weaning

Ghrelin action, which stimulates growth hormone (GH) secretion, may alter during the weaning period in calves. Our objective was to compare the effects of intravenous ghrelin injection on plasma GH, insulin and glucose concentrations in calves around the weaning period. Four Holstein bull calves were fed whole milk and allowed free access to solid feeds, and weaned at 7 weeks of age. Measurements were performed at weeks 1, 2, 4, 6, 7, 9, 11 and 13, when calves were intravenously injected with ghrelin (1.0 μg/kg body weight (BW)) through a catheter, and jugular blood samples were obtained temporally relative to the injection time. Estimated digestible energy intake per metabolic BW transiently decreased at week 7 because of low solid intake immediately after weaning, and thereafter gradually increased. Plasma insulin and glucose concentrations were not affected by ghrelin injection at all ages. In contrast, plasma GH concentrations increased with ghrelin injection at all ages. The incremental area of GH at week 7 was greatest and significantly higher compared with weeks 2, 4, 6 and 9. This result suggests that nutrient insufficiency immediately after weaning enhances GH responsiveness to ghrelin.     

Ensiling of total mixed ration containing persimmon peel: Evaluation of chemical composition and in vitro rumen fermentation profiles

The effects of inclusion of persimmon peel (PP) in total mixed ration (TMR) silage on its nutrient composition, tannin content, and in vitro ruminal fermentation were studied. Four types of TMR silages containing 0, 50, 100, and 150 g/kg of PP on a dry matter basis were prepared. The dietary contents of non‐fiber carbohydrate (NFC) decreased, while soluble protein fraction increased after ensiling of the TMR. In the TMR silages, the content of insoluble tannin increased (p < .05) with increasing PP level. The fraction of soluble protein decreased linearly (p < .01), while that of neutral detergent insoluble protein increased linearly (p < .01) with increasing the PP level in the TMR silages. The total gas and methane yields from the in vitro rumen fermentation of the TMR silages were lower (p < .01) than those of pre‐ensiled TMR and declined linearly (p < .01) with increasing PP level. These results indicate that adding PP to TMR silage may resist the breakdown of dietary protein during the ensiling process, although the ruminal fermentability of TMR possibly decreased after ensiling due to the loss of NFC.     

Effects of high ambient temperature on urea‐nitrogen recycling in lactating dairy cows

Effects of exposure to hot environment on urea metabolism were studied in lactating Holstein cows. Four cows were fed ad libitum a total mixed ration and housed in a temperature‐controlled chamber at constant moderate (18°C) or high (28°C) ambient temperatures in a cross‐over design. Urea nitrogen (N) kinetics was measured by determining urea isotopomer in urine after single injection of [¹⁵N₂]urea into the jugular vein. Both dry matter intake and milk yield were decreased under high ambient temperature. Intakes of total N and digestible N were decreased under high ambient temperature but urinary urea‐N excretion was increased. The ratio of urea‐N production to digestible N was increased, whereas the proportion of gut urea‐N entry to urea‐N production tended to be decreased under high ambient temperature. Neither return to the ornithine cycle, anabolic use nor fecal excretion of urea‐N recycled to the gut was affected by ambient temperature. Under high ambient temperature, renal clearance of plasma urea was not affected but the gut clearance was decreased. Increase of urea‐N production and reduction of gut urea‐N entry, in relative terms, were associated with increased urinary urea‐N excretion of lactating dairy cows in higher thermal environments.     

Metabolomic profiling reveals differential effects of glucagon‐like peptide‐1 and insulin on nutrient partitioning in ovine liver

This study was conducted to identify the insulin‐independent actions of glucagon‐like peptide‐1 (GLP‐1 (7‐36 amide)) in partitioning nutrient metabolism in ovine liver. Four Suffolk wethers (60.0 ± 6.7 kg body weight (BW)) were used in a repeated‐measure design under euglycemic‐‐hyperinsulinemic and hyper ‐GLP‐1 clamps for 150 min with intravenous infusion of insulin (0.5 mU/kg BW/min; from 0 to 90 min), GLP‐1 (0.5 µg/kg BW/min; from 60 to 150 min) and both hormones co‐administered from 60 to 90 min. Liver biopsies were collected at 0, 60, 90 and 150 min to represent the metabolomic profiling of baseline, insulin, insulin plus GLP‐1, and GLP‐1, respectively, and were analyzed for metabolites using Capillary Electrophoresis Time‐of‐Flight Mass Spectrometer. Metabolomics analysis reveals 51 metabolites as being significantly altered (P < 0.05) by insulin and GLP‐1 infusion compared to baseline values. Insulin infusion enhanced glycolysis, lipogenesis, oxidative stress defense and cell proliferation pathways, but reduced protein breakdown, gluconeogenesis and ketogenesis pathways. Conversely, GLP‐1 infusion promoted lipolytic and ketogenic pathways accompanied by a lowered lipid clearance from the liver as well as elevated oxidative stress defense and nucleotide degradation. Despite further research still being warranted, our data suggest that GLP‐1 may exert insulin‐antagonistic effects on hepatic lipid and nucleotide metabolism in ruminants.