Metabolic adaptations to heat stress in growing cattle

To differentiate between the effects of heat stress (HS) and decreased dry matter intake (DMI) on physiological and metabolic variables in growing beef cattle, we conducted an experiment in which a thermoneutral (TN) control group (n = 6) was pair fed (PF) to match nutrient intake with heat-stressed Holstein bull calves (n = 6). Bulls (4 to 5 mo old, 135 kg body weight [BW]) housed in climate-controlled chambers were subjected to 2 experimental periods (P): (1) TN (18 °C to 20 °C) and ad libitum intake for 9 d, and (2) HS (cyclical daily temperatures ranging from 29.4 °C to 40.0 °C) and ad libitum intake or PF (in TN conditions) for 9 d. During each period, blood was collected daily and all calves were subjected to an intravenous insulin tolerance test (ITT) on day 7 and a glucose tolerance test (GTT) on day 8. Heat stress reduced (12%) DMI and by design, PF calves had similar nutrient intake reductions. During P1, BW gain was similar between environments and averaged 1.25 kg/d, and both HS and PF reduced (P < 0.01) average daily gain (-0.09 kg/d) during P2. Compared to PF, HS decreased (P < 0.05) basal circulating glucose concentrations (7%) and tended (P < 0.07) to increase (30%) plasma insulin concentrations, but neither HS nor PF altered plasma nonesterified fatty acid concentrations. Although there were no treatment differences in P2, both HS and PF increased (P < 0.05) plasma urea nitrogen concentrations (75%) compared with P1. In contrast to P1, both HS and PF had increased (16%) glucose disposal, but compared with PF, HS calves had a greater (67%; P < 0.05) insulin response to the GTT. Neither period nor environment acutely affected insulin action, but during P2, calves in both environments tended (P = 0.11) to have a blunted overall glucose response to the ITT. Independent of reduced nutrient intake, HS alters post-absorptive carbohydrate (basal and stimulated) metabolism, characterized primarily by increased basal insulin concentrations and insulin response to a GTT. However, HS-induced reduction in feed intake appears to fully explain decreased average daily gain in Holstein bull calves.     

Diet-induced central obesity and insulin resistance in rabbits

The present study was designed to examine whether rabbits fed a diet containing high fat and sucrose could develop obesity and insulin resistance (IR), the major pathophysiological features of metabolic syndrome. Male Japanese white rabbits were fed either a normal chow diet (control) or high fat and sucrose diet (HFSD) for 36 weeks. Plasma levels of triglycerides (TG), total cholesterol (TC), glucose and insulin were measured. To evaluate glucose metabolism, we performed an intravenous glucose tolerance test. In addition, we compared adipose tissue accumulation in HFSD-fed rabbits with that in normal rabbits. HFSD constantly and significantly led to an increase in body weight of HFSD-fed rabbits, caused by significantly higher visceral adipose tissue accumulation. Although there were no differences in plasma TG, TC, glucose, insulin levels and blood pressure between the two groups, HFSD-fed rabbits showed impaired glucose clearance associated with higher levels of insulin secretion compared to control rabbits. Our results showed that HFSD induced IR and increased adipose accumulation in rabbits, suggesting that HFSD-fed rabbits may become a model for research on human IR and obesity.     

Banding or Burdizzo castration and carprofen administration on peripheral leukocyte inflammatory cytokine transcripts

The objective was to investigate if Banding or Burdizzo castration of bulls would alter the gene expression profile of a range of peripheral leukocyte inflammatory cytokines (IL-1, IL-6, IL-8, IL-10, interferon-γ and tumor necrosis factor-α) and to determine if the administration of carprofen (C) before castration would affect the expression of these genes. Thirty Holstein-Friesian bulls (5.5 months; Mean 191 ± (SEM) 3.7 kg) were blocked by weight and randomly assigned to one of five treatments: (1) untreated control (CON); (2) Banding castration at 0 min (BAND); (3) BAND following an i.v. injection of 1.4 mg/kg BW of carprofen (C) at −20 min (BAND + C); (4) Burdizzo castration at 0 min (BURD); or (5) BURD following 1.4 mg/kg BW of carprofen at −20 min (BURD + C). Blood samples were collected at 1 h before castration and 6, 24 and 48 h post-castration for routine hematology and quantitative real-time PCR analysis of cytokine gene expression analysis. Generally, there were no differences (P > 0.05) among treatment groups in hematological variables following castration. Cortisol concentrations were unchanged throughout the experimental period in CON bulls. BURD animals had greater cortisol concentrations than BAND and CON animals at 6 h post treatment. Transitory effects were observed only in the expression of IL-6 and TNF-α. The relative expression of IL-6 was greater in the BURD than in the BAND treatment (P < 0.05) at 24 h post-castration and was greater in the BURD + C group than in the BURD group (P < 0.05) at 48 h. The relative expression of TNF-α was greater in BAND than in the BURD group (P < 0.05) at 48 h. In conclusion, these findings indicate that Banding or Burdizzo castration did not have any major effect on peripheral leukocyte inflammatory cytokine gene expression; Banding castration caused a greater pro-inflammatory cytokine gene expression reaction than Burdizzo castration and carprofen administration can affect IL-6 gene expression levels in BURD castrated animals.     

Insulin sensitivity and glucose dynamics during pre-weaning foal development and in response to maternal diet composition

Nutritional management of animals during pregnancy can affect glucose and insulin dynamics in the resulting offspring through influences on fetal development. Additionally, high starch feeding in mature horses is associated with reduced insulin sensitivity and an increased risk for diseases such as obesity and laminitis. However, no study has yet evaluated the effect of feeding a high starch diet to pregnant mares on glucose and insulin dynamics in their offspring. Twenty late-gestation mares maintained on pasture were provided two-thirds of digestible energy requirements from isocaloric, isonitrogenous low starch (LS, n = 10) or high starch (HS, n = 10) feed. Their foals were assessed with an insulin-modified frequently sampled intravenous glucose tolerance test at 5, 40, 80, and 160 d of age. Baseline glucose concentrations, insulin sensitivity, and insulin-independent glucose clearance in 5-d foals were all greater than values observed in mature horses and declined towards mature values as foals reached 160 d of age. Baseline glucose concentrations were all within normal range, but higher in foals born from HS mares through 80 d of age. Insulin sensitivity was not different between dietary groups until a trend for lower insulin sensitivity in HS foals emerged at 160 d of age. These data are the first to characterize decreasing insulin sensitivity and glucose tolerance in Thoroughbred foals from 5 to 160 d of age. This study also presents the first data examining glucose and insulin dynamics in developing foals in response to maternal high starch diet.     

Alfalfa polysaccharides improve the growth performance and antioxidant status of heat-stressed rabbits

The study was conducted to evaluate the antioxidant properties of alfalfa polysaccharides (APS) extracted from alfalfa (Medicago sativa L.) through 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical-scavenging assay and the effects of the inclusion (0%, 0.1%, and 0.5%) of APS in the diet on the growth performance and antioxidant status in heat-stressed rabbits. 120 New Zealand male rabbits (average body weight 1123 g, 40 d old) were divided into three groups (40 rabbits per group) and were fed with a basal diet or the basal diet with 1 g or 5 g of APS/kg of diet. Rabbits had free access to diets and water in an environmentally controlled room at 30 ± 1 °C and 55% relative humidity during the entire period (21 d). On days 7, 14 and 21 of the trial, body weight and feed intake were measured and blood samples were collected for assay of antioxidant induces. Liver tissue samples were collected on day 21 for assay of antioxidant induces. Results in vitro showed the scavenging effect of APS on DPPH radicals increased (P < 0.05) in a dose-dependent manner. The APS exerted an inhibitory effect on DPPH radical generation, with 66.3% inhibition at 100 µg/mL and 74.5% inhibition at 250 µg/mL. Results in vivo showed that APS 0.1% supplementation increased (P < 0.05) average daily gain (ADG) and reduced (P < 0.05) feed conversion rate (FCR) in the first week of trial. Compared with the control group, average daily feed intake (ADFI) was significantly (P < 0.01) reduced by APS treatment. From days 8 to 14 of the trial, ADG of the APS 0.5% group was greater (P < 0.05) than that of the control group. Compared with the control group, FCR was significantly (P < 0.05) reduced by APS treatment. From days 15 to 21 of the trial, ADFI of the APS 0.1% group was greater (P < 0.05) than that of the control group. For the overall period, APS 0.5% supplementation had a significantly (P < 0.05) positive effect on ADG. ADFI and FCR were lower (P < 0.05) with APS than without APS. Furthermore, on day 7, the inclusion of APS reduced significantly MDA (P < 0.01). The rabbits fed with APS 0.1% had significantly (P < 0.01) lower cortisol and greater (P < 0.05) T-AOC, SOD, and GSH-Px than the control group. On day 14, addition of APS increased T-AOC (P < 0.01) and reduced MDA (P < 0.05). The APS 0.5% group showed lower (P < 0.05) cortisol and greater (P < 0.05) GSH-Px than the control group. On day 21, the rabbits fed with the APS 0.5% diet had greater (P < 0.05) GSH-Px and T-AOC compared with the control rabbits. In contrast, the opposite was true for cortisol (P < 0.05) and MDA (P < 0.05). On day 21, MDA was lower (P < 0.01) with APS than without APS in the liver tissue. Hepatic GSH-Px activity of rabbits fed with the APS 0.5% diet was greater (P < 0.05) than those of other groups. APS supplementation seemed to have a positive influence on the growth performance and antioxidant status of heat-stressed rabbits.     

Effect of different dietary ratios of sunflower and linseed oils on growth and carcass traits of rabbits

As part of an experiment aiming to modify the meat fatty acid profile, this work studied the growth and carcass traits as affected by various dietary ratios of sunflower oil and linseed oil. A diet without added oil served as a control (C). Four other diets were equally 4% oil-enriched but they differed in the incorporation ratios of sunflower oil (S) to linseed oil (L), i.e. 4% S to 0% L (diet 4%S), 3% S to 1% L (diet 3:1%SL), 2% S to 2% L (diet 2:2%SL) and 0% S to 4% L (diet 4%L). The oil-rich diets had slightly higher digestible energy contents (11.4 vs 10.6 MJ/kg) than the C feed. In each group 10 litters of 7 to 9 Pannon White kits per litter were studied in the pre-weaning period from 21 to 35 days old. Growth and slaughter traits were assessed with 50 and 30 rabbits per group, respectively. No significant effects of diets were found on litter and doe performances. The only significant differences in growth performance of the C, 4%S, 3:1%SL, 2:2%SL and 4%L rabbits were for the 35–49 day feed intake (88, 86, 84, 84 and 83 g per day, respectively, P = 0.046), the 35–84 day growth rate (36, 38, 37, 35 and 37 g/day, P = 0.034) and the 84-day body weight (2608, 2703, 2664, 2565 and 2628 g, respectively, P = 0.022). There were several significant differences in carcass traits including the weight of reference carcass (1357, 1391, 1388, 1380 and 1369 g, respectively, P = 0.004) and left longisimus dorsi meat (78, 79, 81, 81 and 76 g, respectively, P = 0.046) of rabbits. The diets had major effects on the L*, a* and b* colour values (lightness, redness and yellowness) of meat and fat. Carcass colour of the C and 4%S rabbits was closer and the 4%L rabbits was further from the European consumer's preference of light coloured, less red and slightly yellow rabbit meat. Our result reveals the importance of age and body weight at slaughter. Taking the growth and slaughter performances and, the recent belief of human health benefits from lower n− 6/n− 3 FAs dietary ratios into account, the 2:2%SL diet seems most appropriate if the interests of the raisers, meat processors and buyers are considered equally.     

Effect of piglet birth weight on body weight,growth, backfat,and longissimus muscle area of commercial market swine

The objective of this study was to estimate the effect of piglet birth weight on future BW, growth, backfat, and longissimus muscle area of pigs in a commercial U.S. production system. Pigs (n = 5727) at a commercial farm were individually weighed and identified within 24 h of birth. Weights were collected prior to weaning (n = 4108), after finisher placement (n = 3439), and 7 (n = 1622) and 16 (n = 1586) weeks into finishing; hot carcass weight was also collected (n = 1693). Average daily gain during lactation, nursery, finishing, and overall (birth to 16 weeks into finishing) was calculated. During BW collection 16 weeks into finishing, real-time ultrasound backfat thickness and longissimus muscle area were measured. Sex × birth weight (linear and quadratic) interactions were observed for BW at weaning and finisher placement and daily gain during pre-weaning and nursery. Linear birth weight × cross foster interactions were observed for weaning weight and pre-weaning gain. Linear and quadratic effects of birth weight on BW at weaning, finisher placement, 7 and 16 weeks into finishing, and hot carcass weight and average daily gain during pre-weaning, nursery, finishing, and total were observed. For all measures of BW and average daily gain, as birth weight increased subsequent BW and average daily gain increased at a decreasing rate; however, for the sex × birth weight (linear and quadratic) interactions, heavier birth weight barrows were lighter and grew slower than gilts of comparable birth weight. Worth noting, the birth weight × sex interactions described very few pigs in the extreme portion of the birth weight distribution. For birth weight × cross foster interactions, non-cross fostered pigs were increasingly heavier and faster growing as birth weight increased compared to cross fostered pigs. Heavier birth weight pigs tended to have increased backfat depth (P = 0.07). Linear and quadratic effects of birth weight on longissimus muscle area were observed; as birth weight increased muscling increased at a decreasing rate. Regardless of interactions or period of production, increased birth weight resulted in heavier future BW, faster daily gain along with larger longissimus muscle area prior to harvest. In all instances the magnitude of the negative effect of birth weight increased as birth weight decreased.     

Effect of dietary energy source on in vitro substrate utilization and insulin sensitivity of muscle and adipose tissues of Angus and Wagyu steers

Angus (n = 8; 210 kg of BW) and 7/8 Wagyu (n = 8; 174 kg of BW) steers were used to evaluate the effects of dietary energy source on muscle and adipose tissue metabolism and insulin sensitivity. Steers were assigned to either a grain-based (corn) or hay-based (hay) diet and fed to similar final BW. At slaughter, LM and s.c. and i.m. adipose tissue samples were collected. Portions of the LM and adipose tissues were placed immediately in liquid N for later measurement of glycolytic intermediates. Fresh LM and s.c. and i.m. adipose tissues were incubated with [U-(14)C]glucose to assess glucose metabolism in vitro. All in vitro measures were in the presence of 0 or 500 ng/mL of insulin. Also, s.c. and i.m. adipose tissues were incubated with [1-(14)C]acetate to quantify lipid synthesis in vitro. Glucose-6-phosphate and fructose-6-phosphate concentrations were 12.6- and 2.4-fold greater in muscle than in s.c. and i.m. adipose tissues, respectively. Diet did not affect acetate incorporation into fatty acids (P = 0.86). Insulin did not increase conversion of glucose to CO(2), lactate, or total lipid in steers fed hay but caused an increase (per cell) of 97 to 110% in glucose conversion to CO(2), 46 to 54% in glucose conversion to lactate, and 65 to 160% in glucose conversion to total lipid content in adipose tissue from steers fed corn. On a per-cell basis, s.c. adipose tissue had 37% greater glucose oxidation than i.m. adipose (P = 0.04) and 290% greater acetate incorporation into fatty acids than i.m. adipose (P = 0.04). Insulin addition to s.c. adipose tissue from corn-fed steers failed to stimulate glucose incorporation into fatty acids, but exposing i.m. adipose tissue from corn-fed steers to insulin resulted in a 165% increase in glucose incorporation into fatty acids. These results suggest that feeding hay limited both glucose supply and tissue capacity to increase glucose utilization in response to insulin without altering acetate conversion to fatty acids. Because s.c. adipose tissue consistently utilized more acetate and oxidized more glucose than did i.m. adipose, these results suggest that hay-based diets may alter i.m. adipose tissue metabolism with less effect on s.c. adipose tissue.     

Effect of management factors and blood metabolites during the rearing period on growth in dairy heifers on UK farms

Growth rates during rearing affect the age and body weight (BW) of replacement heifers at first calving. Diet and disease can affect growth via altered metabolic hormone concentrations, but are difficult to monitor accurately on commercial farms. This study investigated the effect of management and metabolic indices (IGF-I, insulin, glucose and urea) on the growth rate of 509 Holstein-Friesian heifers on 19 UK dairy farms. Size (BW, heart girth, height and crown-rump length) was measured at approximately 1, 6 and 15 months. The mean daily weight gain up to 6 months for all calves was 0.77 kg/day, with extreme variability both between cohorts of calves (range 0.49–1.02 kg/day) and between individual calves within farms (range 0.45–1.13 kg/day). Growth was enhanced by supplemental colostrum, by milk replacer as opposed to whole milk and by ad libitum milk feeding and was reduced by gradual weaning and dehorning after weaning. Larger group size slowed growth before weaning (>6 calves) but increased it post-weaning (>20 calves). These management differences were reflected in altered plasma IGF-I concentrations, which were positively associated with growth throughout the rearing period. Larger calves at 1 month had a greater weight gain up to 6 months. Sub-optimum growth of some heifers within each cohort was established at an early age and resulted in animals reaching the start of breeding at an inadequate size (BW range 209–498 kg at 15 months). This could be alleviated by altered management strategies and improved monitoring of growing heifers.     

Obesity induced changes to plasma adiponectin concentration and cholesterol lipoprotein composition profile in cats

Feline obesity generally results in aberrations to plasma metabolite levels, such as lipid concentrations and lipoprotein composition. This study sought to investigate the resultant effect of obesity on cholesterol lipoprotein composition and circulating adiponectin concentrations in cats. Plasma glucose, lipids (triglyceride, cholesterol and free fatty acid), insulin and adiponectin concentrations, and cholesterol lipoprotein composition were measured and compared between body condition score (BCS) determined normal healthy control and obese cats. Although the obese group demonstrated higher levels of plasma cholesterol, glucose, and triglycerides, as compared to healthy controls, the difference was insignificant thus indicating that the BCS determined obese cats may have been overweight and not morbidly obese. Plasma insulin levels were significantly higher (25–30%) versus healthy control animals thereby possibly hinting at the ensuing emergence of obesity induced insulin resistance. However, the BCS determined obese cat demonstrated a significant reduction (p < 0.05) in plasma adiponectin concentration and a significant increase (p < 0.05) in LDL-cholesterol % as compared to age matched healthy control animals. This would indicate that changes in plasma adiponectin concentration and cholesterol lipoprotein composition may be good early indicators of obesity in cats.     

Characterization of Glucose Response Curves after Insulin Injection in Sensitive versus Insensitive Mares

The glucose responses to intravenous injections of a range of doses of recombinant human insulin were determined for six mares known to be insulin sensitive and six mares known to be insulin insensitive, with the goal of better characterizing the regression lines resulting from the two categories of mares. Insulin doses between 8 and 198 mU of insulin per kg of body weight (mU/kg BW) were administered intravenously between September 13 and 26, 2010, starting with 50 mU/kg BW on the first day. Higher and lower doses were administered on alternate days to obtain percentages of decreases in blood glucose concentrations between 10% and 70%. Linear regression analysis revealed that insulin-insensitive mares have glucose response curves with higher y intercepts (P = .066), less steep slopes (P = .0003), and less goodness of fit (P = .053) in addition to the expected greater dose required to produce a 50% reduction in blood glucose concentrations (ED50; P = .006), despite the similarities between their body weights and those of insulin-sensitive mares. Linear and nonlinear regression of responses to the 32, 50, and 79 mU/kg BW insulin doses with the overall estimates of ED50 and the natural log of ED50 indicated that the 50 mU/kg BW dose had the greatest coefficient of determination (>0.95). Generally, it appears that estimates of insulin sensitivity based on a single injection of insulin or on multiple injections of insulin are least variable for insulin-sensitive mares.     

Adipose tissue gene expression in obese dogs after weight loss

Body weight (BW) mainly depends on a balance between fat storage (lipogenesis) and fat mobilization (lipolysis) in adipocytes. BW changes play a role in insulin resistance (IR), the inability of insulin target tissue to respond to physiological levels of insulin. This results in inhibition of lipogenesis and stimulation of lipolysis. Weight gain leads to IR whereas, weight loss improves insulin sensitivity (IS). The aim of this study was to evaluate the effect of weight loss and recovery of IS on the expression of genes involved in lipogenesis and lipolysis in weight losing dogs. Gene expression was studied in both subcutaneous and visceral adipose tissue. Obese dogs received a hypoenergetic low fat high protein diet (0.6 x NRC recommendation). Before and after weight loss, IS was assessed using the euglycaemic hyperinsulinaemic clamp. Gene expression of IRS-2, SREBP, intracellular insulin effectors, ACC, FAS, FABP, ADRP, PEPCK, lipogenesis key proteins, perilipin and HSL, lipolysis key proteins were quantified using real-time RT-PCR in subcutaneous and visceral fat. BW decreased from 15.2 +/- 0.5 to 11.4 +/- 0.4 kg (p < 0.05) over 78 +/- 8 days. When obese, dogs were insulin resistant. After weight loss, IS was improved. In the subcutaneous adipose tissue, the expression of only the IRS-2 was increased. In the visceral adipose tissue, the expression of the genes involved in the lipogenesis was decreased whereas one of the genes implied in the lipolysis did not change. The expression profile of genes involved in lipid metabolism, as measured after weight loss, is indicative for a lower lipogenesis after weight loss than in obese dogs. Our results also confirm dramatic differences in the lipid metabolism of visceral and subcutaneous fat. They should be completed by comparing gene expression during weight losing and normal weight steady state.     

Effects of Epinephrine,Detomidine, and Butorphanol on Assessments of Insulin Sensitivity in Mares

Sympathoadrenal stimulation may perturb results of endocrine tests performed on fractious horses. Sedation may be beneficial; however, perturbation of results may preclude useful information. Four experiments were designed to 1) determine the effects of epinephrine on insulin response to glucose (IR2G), 2) assess the effects of detomidine (DET), alone or combined with butorphanol (DET/BUT), on IR2G and glucose response to insulin (GR2I), and 3) assess the effects of BUT alone on IR2G. In Experiment 1, mares were administered saline or epinephrine (5 μg/kg BW) immediately before infusion of glucose (100 mg/kg BW). Glucose stimulated (P < .05) insulin release in controls at 5 minutes that persisted through 30 minutes; insulin was suppressed (P < .05) by epinephrine from 5 to 15 minutes, rising gradually through 30 minutes. Experiments 2 (IR2G) and 3 (GR2I) were conducted as triplicated 3 × 3 Latin squares with the following treatments: saline (SAL), DET, and DET/BUT (all administered at .01 mg/kg BW). Glucose stimulated (P < .05) insulin release that persisted through 30 minutes in SAL mares; DET and DET/BUT severely suppressed (P < .0001) the IR2G. Sedation did not affect resting glucose and had inconsistent effects on the GR2I when mares were treated with 50 mIU/kg BW recombinant human insulin. Butorphanol had no effect on IR2G. In conclusion, adrenergic agonists severely suppress the IR2G and cannot be used for sedation for this test. The use of DET did not alter the GR2I, and therefore may be useful for conducting this test in fractious horses.     

Oxyntomodulin attenuates exendin-4-induced hypoglycemia in cattle

Oxyntomodulin (OXM), glucagon, glucagon-like peptide-1 (GLP-1), and exendin-4 (Ex-4) are peptide hormones that regulate glucose homeostasis in monogastric and ruminant animals. Recently, we reported that the insulin-releasing effects of OXM and glucagon in cattle are mediated through both GLP-1 and glucagon receptors. The purpose of this study was to examine the mechanisms of the glucoregulatory actions induced by Ex-4, GLP-1, OXM, and glucagon and the interrelationships among these hormones in cattle. Two experiments were performed in Holstein cattle. In Experiment 1, we initially assessed the effects of intravenous (iv) bolus injection of 0, 0.25, 1, and 2 μg/kg body weight (BW) of Ex-4, GLP-1, and OXM on insulin and glucose concentrations in 3-mo-old intact male Holstein calves. In Experiment 2, we studied insulin and glucose responses to iv coinjection of 0.25 μg of Ex-4 or GLP-1/kg BW with 2 μg of OXM or glucagon/kg BW in 4-mo-old Holstein steers. Administration of peptides and blood sampling were done via a jugular catheter. Plasma was separated and the concentrations of peptides and glucose in plasma were analyzed using radioimmunoassay and enzymatic methods, respectively. Results showed that the potent glucoregulatory action of Ex-4 in 4-mo-old steers was delayed and attenuated when Ex-4 was coinjected with OXM. The decline in plasma glucose concentrations began at 5 min in the Ex-4-injected group (P < 0.05) vs 15 min in the Ex-4 + OXM–injected group (P < 0.05). Plasma concentrations of glucose at 30 min were reduced 26% from basal concentrations in the Ex-4-injected group and 13% in the Ex-4 + OXM–injected group (P < 0.001). Results also showed that the glucose concentrations initially increased in the Ex-4 + glucagon–treated group, but declined to a relatively hypoglycemic condition by 90 to 120 min. In contrast, the glucose concentrations at specific time points between the GLP-1 + OXM–injected group and the OXM-injected group did not differ. Similarly, the glucose concentrations in the GLP-1 + glucagon–injected group did not differ from those in the glucagon-injected group. Because OXM and glucagon mediate glucose concentrations via the glucagon receptor, it is suggested that the potent glucose-lowering action of Ex-4 might include the glucagon receptor antagonistic action of Ex-4.     

Ghrelin differentially modulates the GH secretory response to GHRH between the fed and fasted states in sheep

The effect of energy balance on the growth hormone (GH) secretory responsiveness to growth hormone-releasing hormone (GHRH) has not been determined in ruminant animals. Therefore, we examined the effects of intravenous injections of 0, 3.3, and 6.6 μg ghrelin/kg body weight (BW), with and without GHRH at 0.25 μg/kg BW, on GH secretory responsiveness in both the fed and fasted sheep. The injections were carried out at 48 h (Fasting state) and 3 h (Satiety state) after feeding. Blood samples were taken every 10 minutes, from 30 minutes before to 120 minutes after the injection. Low (3.3 μg/kg BW) and high (6.6 μg/kg BW) doses of ghrelin stimulated GH secretion significantly (P < .05) greater in the Satiety state than in the Fasting state. Growth hormone-releasing hormone plus both doses of ghrelin stimulated GH secretion significantly (P < .05) greater in the Satiety state than in the Fasting state. Ghrelin and GHRH exerted a synergistic effect in the Satiety state, but not in the Fasting state. Plasma ghrelin levels were maintained significantly (P < .05) greater in the Fasting state than in the Satiety state except the temporal increases after ghrelin administration. Plasma free fatty acid (FFA) concentrations were significantly (P < .01) greater in the Fasting state than in the Satiety state. In conclusion, the present study has demonstrated for the first time that ghrelin differentially modulates GH secretory response to GHRH according to feeding states in ruminant animals.     

Vaccination of rabbits against coccidiosis using precocious lines of Eimeria magna and Eimeria media in Benin

Three groups of twelve 35-day-old rabbits were used for the experiment. Two groups were vaccinated with a mixture of precocious lines of Eimeria magna and Eimeria media originating from corresponding wild strains isolated in Benin. One group benefited of a booster whereas the second one was kept without booster. A third non-vaccinated group was used as control. All groups were challenged per os with an equal mixture of the wild strains of E. magna and E. media at a dose of 104 oocysts per animal. Three weeks after the challenge inoculation, no case of diarrhoea was recorded in the two groups of vaccinated rabbits, as compared to the non-vaccinated rabbits that developed diarrhoea. No mortality was recorded in the three groups. During the patent period, oocyst output of vaccinated rabbits was significantly lower than that of control animals (P < 0.01), confirming a good immunogenic characteristic of the precocious lines. No booster effect was noticed for the boost vaccinated group. The daily weigh gain of the two groups of vaccinated rabbits was significantly higher than that of the non-vaccinated rabbits (P < 0.05). Consequently the precocious lines of Benin origin turned out to be immunogenic and therefore constitute good potential candidates for vaccine production for this country.     

Seasonal and nutrients intake regulation of lipoprotein lipase (LPL) activity in grazing yak (Bos grunniens) in the Alpine Regions around Qinghai Lake

Lipoprotein lipase (LPL) is considered as a key enzyme in the lipid deposition and metabolism in tissues. To better understand fat cycling in grazing yak to adapt to the harsh environment on the Qinghai-Tibetan Plateau, and we have therefore explored seasonal and nutritional regulation of LPL in adipose tissue, liver and skeletal muscle. Sixty 3 year old growing yaks (BW. 120.3 ± 15.28 kg) were subdivided into six groups, each used to determine effects on chemical body composition and LPL activity in different tissues. The alpine pastures had the highest Crude protein (CP, 11.06%) contents and the gross energy (GE, 11.49 MJ/kg) in summer. Growth rates and body fat content were responsive to CP and GE intake regimen. Late spring up-regulation of LPL activity in the subcutaneous adipose tissue was consistent with a pronounced increase of body weight (BW) and whole body fat content. The highest LPL activity in the skeletal muscle was found in September (774 ± 64.1 mU/g tissue), which may serve to cover the increased energy demands for compensatory growth and maintenance of adiposity in the coming cold season. Furthermore, the seasonal regulation of LPL involves some factors in addition to insulin and triglycerides (TG). These results suggest that yaks could rely, in part, on LPL activity to adapt to the harsh forage environment. During the growing season, an enhanced synthesis of LPL production in the adipose tissues along with mechanisms for the recycling of fat contributes toward the rapid recovery of body weight.     

Effect of a transitory controlled nursing on days 9–11 or a 24-h fast on the production of free-nursing rabbits

Altered nursing or nutrition before artificial insemination (AI) can be used as a doe biostimulant to improve lactating rabbits reproduction. The timing of a shift from free to a 3-day controlled nursing to AI or the nursing method at fast-refeeding can affect the efficacy of these stimulations. In an earlier study the effects of a 3-day controlled nursing on days 8, 9 and 10 or in controlled nursing rabbits, the impact of a 24-h fast with 48–50 h re-feeding were investigated. This follow-up work tested a 3-day biostimulation with controlled nursing on days 9, 10 and 11. Another aim was to assess the same doe fast-refeeding but now in free-nursing rabbits. Pannon White does (n=480) were artificially inseminated 11 days post-partum. Control (C) does nursed freely. Rabbits simulating local farm practice (F) had controlled nursing until day 14 using a metal-plate as separation and then free nursing to weaning (day 35). In biostimulations with altered nursing, there was a shift from free to a 3-day controlled nursing (days 9–11) with a wire-mesh separation (BW), a metal-plate insertion (BM) or nest-tray removal (BN) and return to free nursing on day 12 until weaning. The C, F, BW, BM and BN does were fed ad libitum. At biostimulation with fast-refeeding (BF), the free-nursing does were subjected to a 24 h water-only fast between days 8 and 9 and a 48–50 h ad libitum re-feeding before AI. Doe reproduction and growth of the current litter were differently affected by the treatments. In the C, F, BW, BM, BN and BF does, sexual receptivity was 83, 90, 68, 80, 74 and 85% (P=0.05), the kindling rate was 79, 76, 74, 89, 68, 70% (P=0.05), the number of kits born alive was 7.9, 8.0, 8.8, 9.1, 7.9, 6.8 (P=0.005), kit weight at weaning 982, 991, 953, 986, 955, 964 g (P=0.012) and at 70 days of age 2383, 2407, 2220, 2350, 2279, 2382 g, respectively (P=0.001). Among biostimulations with altered nursing, the 3-day controlled nursing with a metal-plate separation (BM) can be advised for the practice because only this method was efficient in this (days 9–11) and previous (days 8–10) studies. There appears to be an interaction between doe nursing and feeding, since the same fast led to different production of free-nursing does compared to those in a previous work that nursed controlled.     

Effects of testosterone on lipid peroxidation, lipid profiles and some coagulation parameters in rabbits

The purpose of this study was to investigate the effects of testosterone on some risk factors of atherosclerosis. Twenty-four male New Zealand white rabbits were randomly divided into three groups of eight. The first group was used as control. Second group was injected with 10 mg of testosterone propionate. Third group was castrated bilaterally. At the end of 6 weeks, lipid peroxidation (LPO), lipid profile, fibrinogen (FBN) level and coagulation parameters were evaluated. Testosterone administration decreased the level of high-density lipoprotein cholesterol (HDL-C), while castration increased this level (P < 0.05). Triglyceride (TG) and total cholesterol (TC) levels in the castration group were significantly higher (P < 0.05) than those in the testosterone group. The ratio of HDL-C:low-density lipoprotein cholesterol (LDL-C) decreased, while TC:HDL-C ratio increased (P < 0.05) in the testosterone group. No significant differences were found in the LDL-C and FBN levels among groups. However, there was a tendency for higher FBN level in the testosterone group. Testosterone administration resulted in an increase in the level of LPO (P < 0.05). Clotting time and prothrombin time prolonged in the castration group compared with testosterone group (P < 0.05). As a result, testosterone has exacerbating effect on atherosclerosis risk factors including lipid profile, LPO, FBN and coagulation system.     

Transition period-related changes in the abundance of the mRNAs of adiponectin and its receptors,of visfatin,and of fatty acid binding receptors in adipose tissue of high-yielding dairy cows

Adipose tissue expresses adipokines, which are involved in regulation of energy expenditure, lipid metabolism, and insulin sensitivity. To adapt for the transition from pregnancy to lactation, particularly in high-yielding dairy cows, adipokines, their receptors, and particular G-protein coupled receptors (GPRs) are of potential importance. Signaling by GPR 41 stimulates leptin release via activation by short-chain fatty acids; GPR 43/109A inhibits lipolysis, and GPR 109A thereby mediates the lipid-lowering effects of nicotinic acid and β–hydroxybutyrate. The aim of this study was to compare the mRNA expression of adiponectin and visfatin, adiponectin receptors 1 and 2 (AdipoR1/2), leptin receptor (obRb), insulin receptor as of the aforementioned GPRs during the transition period in high-yielding dairy cows. Biopsies from subcutaneous fat and blood samples were obtained from 10 dairy cows 1 week before and 3 weeks after calving. For AdipoR1 and AdipoR2 mRNA abundance as well as for leptin concentrations in plasma, a reduction (P ≤ .05) was observed postpartum; for visfatin and putative GPR 109A mRNA abundance in adipose tissue, there was a trend (P < .1) for analogous changes. In contrast, the mRNA content of obRb and GPR 41 in adipose tissue was higher (P ≤ .05) in samples from early lactation than in those from late gestation. Our results indicate decreasing adiponectin sensitivity in adipose tissue after calving, which might be involved in the reduced insulin sensitivity of adipose tissue during early lactation. In addition, visfatin, GPR 41, and GPR 109A may further modulate insulin sensitivity.