Combined administration of ghrelin and GHRH synergistically stimulates GH release in Holstein preweaning calves

Ghrelin is a gut peptide which participates in growth regulation through its somatotropic, lipogenic and orexigenic effects. Synergism of ghrelin and growth hormone-releasing hormone (GHRH) on growth hormone (GH) secretion has been reported in humans and rats, but not in domestic animals in vivo. In this study, effects of a combination of ghrelin and GHRH on plasma GH and other metabolic parameters, and changes in plasma active and total ghrelin levels were studied in Holstein bull calves before and after weaning. Six calves were intravenously injected with vehicle (0.1% BSA-saline), ghrelin (1 microg/kg BW), GHRH (0.25 microg/kg BW) or a combination of ghrelin plus GHRH at the age of 5 weeks and 10 weeks (weaning at 6 weeks of age). Ghrelin stimulated GH release with similar potency as GHRH and their combined administration synergistically stimulated GH release in preweaning calves. After weaning, GH responses to ghrelin and GHRH became greater compared with the values of preweaning calves, but a synergistic effect of ghrelin and GHRH was not observed. The GH areas under the concentration curves for 2h post-injection were greater in weaned than in preweaning calves (P<0.05) if ghrelin or GHRH were injected alone, but were similar if ghrelin and GHRH were injected together. Basal plasma active and total ghrelin levels did not change around weaning, but transiently increased after ghrelin injection. Basal plasma insulin, glucose and non-esterified fatty acid levels were reduced after weaning, but no changes by treatments were observed. In conclusion, ghrelin and GHRH synergistically stimulated GH release in preweaning calves, but this effect was lost after weaning.     

GH secretory responses to ghrelin and GHRH in growing and lactating dairy cattle

Release of growth hormone (GH) is known to be regulated mainly by GH-releasing hormone (GHRH) and somatostatin (SRIF) secreted from the hypothalamus. A novel peripheral release-regulating hormone, ghrelin, was recently identified. In this study, differences of the GH secretory response to ghrelin and GHRH in growing and lactating dairy cattle were investigated and an alteration of plasma ghrelin levels was observed. The same amounts of ghrelin and GHRH (0.3 nmol/kg) were intravenously injected to suckling and weanling calves, early and mid-lactating cows and non-lactating cows. Plasma ghrelin levels were also determined in dairy cattle in various physiological conditions. The peak values of ghrelin-induced GH secretion were increased in early lactating cows compared to those in non-lactating cows. The relative responsiveness of GH secretion to ghrelin was also increased compared with that to GHRH in early lactating cows. GH secretory responses to GHRH were blunted in mature cows with and without lactation. Conversely, GHRH-induced GH secretory response was greater than that to ghrelin in calves, and also greater in calves than in mature cows. Plasma ghrelin concentrations were elevated in early lactating cows compared to those in non-lactating cows. Plasma GH concentrations were higher in suckling calves and early lactating cows compared with those in non-lactating cows. These results suggest that GHRH is an effective inducer of GH release in growing calves, and that the relative importance of ghrelin in contributing to the rise in plasma GH increases in early lactating cows.     

Effects of hypothalamic dopamine on growth hormone‐releasing hormone‐induced growth hormone secretion and thyrotropin‐releasing hormone‐induced prolactin secretion in goats

The aim of the present study was to clarify the effects of hypothalamic dopamine (DA) on the secretion of growth hormone (GH) in goats. The GH‐releasing response to an intravenous (i.v.) injection of GH‐releasing hormone (GHRH, 0.25 μg/kg body weight (BW)) was examined after treatments to augment central DA using carbidopa (carbi, 1 mg/kg BW) and L‐dopa (1 mg/kg BW) in male and female goats under a 16‐h photoperiod (16 h light, 8 h dark) condition. GHRH significantly and rapidly stimulated the release of GH after its i.v. administration to goats (P < 0.05). The carbi and L‐dopa treatments completely suppressed GH‐releasing responses to GHRH in both male and female goats (P < 0.05). The prolactin (PRL)‐releasing response to an i.v. injection of thyrotropin‐releasing hormone (TRH, 1 μg/kg BW) was additionally examined in male goats in this study to confirm modifications to central DA concentrations. The treatments with carbi and L‐dopa significantly reduced TRH‐induced PRL release in goats (P < 0.05). These results demonstrated that hypothalamic DA was involved in the regulatory mechanisms of GH, as well as PRL secretion in goats.     

Endogenous ghrelin released in response to endothelin stimulates growth hormone secretion in cattle

The purpose of this study was to evaluate whether circulating ghrelin and growth hormone (GH) concentrations in cattle are regulated by endothelin-1 (ET-1), endothelin-3 (ET-3), and secretin. Six Holstein steers (242 ± 1 d old, 280.5 ± 4.4 kg body weight [BW]; mean ± SEM) were allocated randomly in an incomplete Latin square design to receive each of 4 treatment compounds (vehicle, ET-1, ET-3, and secretin) with 1-d intervals between successive treatments. The treatment compounds were injected intravenously via a catheter inserted into the external jugular vein of each steer. Blood was sampled from the indwelling catheter at -30, -15, 0, 5, 10, 15, 20, 30, 45, 60, 90, 120, 150, and 180 min. Plasma ghrelin and GH responses to the treatment compounds were measured by a double-antibody radioimmunoassay system. Data were analyzed by using a MIXED procedure of SAS, version 9.1. Plasma acyl ghrelin, total ghrelin, and GH concentrations were increased by both ET-1 and ET-3 injection (ET-1 injection: 311 ± 15 pg/mL vs 245 ± 15 pg/mL, 2.4 ± 0.2 ng/mL vs 1.61 ± 0.05 ng/mL, 4.73 ± 0.92 ng/mL vs 1.17 ± 0.09 ng/mL for acyl ghrelin, total ghrelin, and GH, respectively; ET-3 injection: 337 ± 27 pg/mL vs 245 ± 15 pg/mL, 2.6 ± 0.1 ng/mL vs 1.61 ± 0.05 ng/mL, 5.56 ± 0.97 ng/mL vs 1.17 ± 0.09 ng/mL for acyl ghrelin, total ghrelin, and GH, respectively; P < 0.01). Ghrelin and GH concentrations were not changed by secretin injection throughout the experimental periods. These results indicate that ET-1 and ET-3 stimulate ghrelin and GH secretion in cattle and demonstrate for the first time that endogenous ghrelin released in response to endothelin injection stimulates GH secretion in vivo in cattle.     

Growth hormone-releasing hormone and somatostatin concentrations in the hypophysial portal blood of conscious sheep during the infusion of growth hormone-releasing peptide-6

The effects of growth hormone-releasing peptide-6 (GHRP-6) on peripheral plasma concentrations of growth hormone (GH) and hypophysial portal plasma concentrations of growth hormone-releasing hormone (GHRH) and somatostatin (SRIF) were investigated in conscious ewes. Paired blood samples were collected from the hypophysial portal vessels and from the jugular vein of nine ewes for at least 2 hr. The sheep were then given a bolus injection of 10 μg of GHRP-6 per kg followed by a 2-hr infusion of GHRP-6 (0.1 μ/kg · hr). Blood sampling continued throughout the infusion and for 2 hr afterwards. An increase in plasma GH concentration was observed in the jugular samples of six of the nine ewes (1.4 ± 0.3 vs 7.4 ± 2.0 ng/ml, P < 0.05) 5–10 min after the GHRP-6 bolus injection, but in no case did we observe a significant coincident release of GHRH. During the infusion period, mean plasma GHRH levels were not significantly increased but there was a 50% increase (P < 0.05) in GHRH pulse frequency; GHRH pulse amplitude was not changed. Mean SRIF concentration, pulse frequency, and pulse amplitude were unchanged by GHRP-6 treatment. These data indicate that GHRP-6 causes a small, but significant effect on the pulsatile secretion of GHRH, indicating action at the hypothalamus or higher centers of the brain. The large initial GH secretory response to GHRP-6 injection does not appear to be the result of GHRP-6 action on GHRH or SRIF secretion.     

Plasma hormone and metabolite concentrations involved in the somatotropic axis of Japanese Black heifers in association with growth hormone gene polymorphism

Bovine growth hormone (bGH) gene polymorphism of leucine (Leu)-threonine (Thr) (allele A), valine (Val)-Thr (allele B), and Val-methionine (Met) (allele C) at codons 127 and 172 was shown to relate with carcass trait variations in Japanese Black cattle. In this study, 10-mo-old Japanese Black heifers with growth hormone (GH) genotypes AA, AB, BB, AC, BC, and CC (N = 141) were compared for basal GH, insulin-like growth factor-1 (IGF-1), insulin, ghrelin, glucose, and nonesterified fatty acid (NEFA) concentrations. Growth hormone release was also measured as response to growth hormone–releasing hormone (GHRH) (0.4 μg/kg body weight [BW]) using 18 heifers with GH genotypes AA, BB, and CC (n = 6 for each group). The genotype AA heifers showed the greatest BW among genotypes (P < 0.05). Genotype AC, BC, and CC heifers showed greater GH concentrations than genotype AA, AB, or BB heifers, in which genotype CC heifers had the highest concentrations (P < 0.05). However, IGF-1 concentrations did not significantly differ. The genotype AA and BB heifers had a greater GH release at 60 min following GHRH injection than did the genotype CC heifers. The area under the curve (AUC; P < 0.07) and incremental area (IA; P < 0.08) of GH responses to the GHRH challenge tended to be the highest in the genotype AA heifers and the lowest in the genotype CC heifers. In conclusion, GH gene polymorphism altered GH, which may have contributed to differences in BW and carcass traits among genotypes.     

Effects of growth hormone secretagogues on the release of adenohypophyseal hormones in young and old healthy dogs

The effects of three growth hormone secretagogues (GHSs), ghrelin, growth hormone-releasing peptide-6 (GHRP-6), and growth hormone-releasing hormone (GHRH), on the release of adenohypophyseal hormones, growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), luteinising hormone (LH), prolactin (PRL) and on cortisol were investigated in young and old healthy Beagle dogs. Ghrelin proved to be the most potent GHS in young dogs, whereas in old dogs GHRH administration was associated with the highest plasma GH concentrations. The mean plasma GH response after administration of ghrelin was significantly lower in the old dogs compared with the young dogs. The mean plasma GH concentration after GHRH and GHRP-6 administration was lower in the old dogs compared with the young dogs, but this difference did not reach statistical significance. In both age groups, the GHSs were specific for GH release as they did not cause significant elevations in the plasma concentrations of ACTH, cortisol, TSH, LH, and PRL. It is concluded that in young dogs, ghrelin is a more powerful stimulator of GH release than either GHRH or GHRP-6. Ageing is associated with a decrease in GH-releasing capacity of ghrelin, whereas this decline is considerably lower for GHRH or GHRP-6.     

Characteristics of prolactin-releasing response to salsolinol in vivo in cattle

The aims of the present study were to clarify the effect of salsolinol (SAL), a dopamine (DA)-derived endogenous compound, on the secretion of prolactin (PRL) in cattle. The experiments were performed from April to June using calves and cows. A single intravenous (i.v.) injection of SAL (5 mg/kg body weight [BW]) or sulpiride (a DA receptor antagonist, 0.1 mg/kg BW) significantly stimulated the release of PRL in male and female calves (P < 0.05), though the response to SAL was smaller than that to sulpiride. The secretory pattern of PRL in response to SAL or sulpiride in female calves resembled that in male calves. A single i.v. injection of SAL or sulpiride significantly stimulated the release of PRL in cows (P < 0.05). There was no significant difference in the PRL-releasing response between the SAL- and sulpiride-injected groups in cows. A single intracerebroventricular injection of SAL (10 mg/head) also significantly stimulated the release of PRL in castrated calves (P < 0.05). These results show that SAL is involved in the regulatory process for the secretion of PRL, not only in male and female calves, but also in cows. The results also suggest that the potency of the PRL-releasing response to SAL differs with the physiological status of cattle.     

Pituitary adenylate cyclase-activating polypeptide induces secretion of growth hormone in cattle.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a hypothalamic neuropeptide that stimulates release of growth hormone (GH) from cultured bovine anterior pituitary gland cells, but the role of PACAP on the regulation of in vivo secretion of GH in cattle is not known. To test the hypothesis that PACAP induces secretion of GH in cattle, meal-fed Holstein steers were injected with incremental doses of PACAP (0, 0.1, 0.3, 1, 3, and 10 microg/kg BW) before feeding and concentrations of GH in serum were quantified. Compared with saline, injection of 3 and 10 microg PACAP/kg BW increased peak concentrations of GH in serum from 11.2 ng/ml to 23.7 and 21.8 ng/ml, respectively (P < 0.01). Peak concentrations of GH in serum were similar in steers injected with 3 or 10 microg PACAP/kg BW. Meal-fed Holstein steers were then injected with 3 microg/PACAP/kg BW either 1 hr before feeding or 1 hr after feeding to determine if PACAP-induced secretion of GH was suppressed after feeding. Feeding suppressed basal concentrations of GH in serum. Injection of PACAP before feeding induced greater peak concentrations of GH in serum (19.2 +/- 2.6 vs. 11.7 +/- 2.6 ng/ml) and area under the response curve (391 +/- 47 vs. 255 +/- 52 ng. ml(-1) min) than injection of PACAP after feeding, suggesting somatotropes become refractory to PACAP after feeding similar to that observed by us and others with growth hormone-releasing hormone (GHRH). We concluded that PACAP induces secretion of GH and could play a role in regulating endogenous secretion of GH in cattle, perhaps in concert with GHRH.     

A two-sample method for assessing growth hormone response to growth hormone-releasing hormone challenge: use as a predictor of gain in beef bulls

In two experiments, Black Angus bulls were challenged at weaning with GHRH analog and evaluated for their GH response to determine whether GH response can predict subsequent growth characteristics. The GH response was determined by measuring GH in blood serum collected 0 and 10 min after GHRH injection (Exp. 1: 1.5 microg/100 kg BW human GHRH, n = 34; Exp. 2: 1.5 and 4.5 microg/100 kg BW bovine GHRH [treatments LGHRH and HGHRH, respectively] administered 3 h after a 4.5 microg/100 kg BW "clearance dose" of GHRH, n = 38]. In Exp. 1, GH response did not predict growth or carcass measurements. In Exp. 2, GH response to LGHRH was positively related to ADG (R2 = .18; P = .007) during a 112-d controlled feeding trial. In addition, there was a tendency for bulls with a greater GH response to HGHRH to exhibit greater ADG than animals with a low response. However, GH response to GHRH was not related to changes in hip height (HH) or carcass ultrasound measurements at d 112 of the growth performance trial. Response of GH to repeated GHRH challenges was consistent within animal over time (r = .47; P = .003). The use of a clearance dose 3 h prior to GHRH challenge improved the relationship between GH response and ADG. Results of this study suggest that GH response to GHRH challenge is a useful tool for identifying beef bulls with superior growth potential.     

Variability in tumor necrosis factor-α, nitric oxide,and xanthine oxidase responses to endotoxin challenge in heifers: Effect of estrous cycle stage

The severity of host response to some disease agents differs between sexes and this dimorphism has been attributed to the immunomodulating effects of steroid hormones. Our objective was to determine in heifers whether the phase of estrous cycle affected immune response mediators after endotoxin challenge (LPS, 2.5 μg/kg BW, i.v.). Sixteen beef heifers (426 ± 9 kg) were reproductively synchronized with the two-injection protocol of dinoprost tromethamine (Lutalyse^®, Pfizer) to establish diestrus and estrus stages of the estrous cycle. Heifers were challenged with LPS on day 3 (E, estrus; n = 8) or day 10 (D, diestrus, n = 8) after the last i.m. injection of Lutalyse^®. In all heifers, plasma concentrations of tumor necrosis factor-α (TNF-α) peaked 2 h after LPS treatment (P < 0.01) and returned to basal level by 7 h. However, the integrated TNF-α response (area under the time × concentration curve, AUC) was greater in E than in D (P < 0.05). Plasma concentrations of nitrate + nitrite (NO_x, an estimate of NO production) increased (P < 0.01) in all heifers at 7 and 24 h after LPS; plasma NO_x AUC after LPS was greater in E than D (P < 0.01). Plasma xanthine oxidase activity (XO, a mediator of superoxide production) responses were also greater in E than D (P < 0.05). A companion LPS challenge study in steers validated that the protocol for and use of Lutalyse^® did not affect any of the immune parameters studied in heifers in response to LPS. Results indicate that the underlying physiological attributes of the estrus and diestrus phases of the estrous cycle constitute a major source of variability in the magnitude of proinflammatory response to bacterial toxins like LPS.     

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.     

Plasma ghrelin concentration is decreased by short chain fatty acids in wethers

To examine the effects of short chain fatty acids (SCFAs) on plasma ghrelin concentration, 4 wethers were injected intravenously with SCFA solutions [acetate (ACE), propionate (PRO), and butyrate (BUT) (0.8 mmol/kg BW)] and saline. The experiment was conducted after a 4 × 4 Latin square design. Each solution was injected into the jugular vein catheter with blood samples taken at −10, 0, 5, 10, 15, 20, 25, 30, 40, 50, and 60 min relative to the injection time also from this catheter. Plasma ghrelin concentrations decreased after injection with ACE, PRO, and BUT. Although plasma glucose concentrations increased after injection with PRO and BUT (P < 0.05), the increment areas were greater with BUT than with PRO. Plasma insulin concentrations increased after injection with PRO and BUT (P < 0.05). The decrement areas in plasma ghrelin concentrations were equal in ACE, PRO, and BUT. These data suggest that SCFAs inhibit ghrelin secretion in wethers and not through increased circulating glucose and insulin as previously proposed.     

Effects of short- and long-term fasting on plasma and stomach ghrelin,and the growth hormone/insulin-like growth factor I axis in the tilapia, Oreochromis mossambicus

Ghrelin is a highly conserved peptide hormone secreted by the stomach, which is involved in the regulation of food intake and energy expenditure. Ghrelin stimulates growth hormone (GH) release, and increases appetite in a variety of mammalian and non-mammalian vertebrates, including several fish species. Studies were conducted to investigate the effect of feeding and fasting on plasma and stomach ghrelin, and the growth hormone/insulin-like growth factor I (IGF-I) axis in the Mozambique tilapia, a euryhaline teleost. No postprandial changes in plasma and stomach ghrelin levels or stomach ghrelin mRNA levels were observed. Plasma levels of GH, IGF-I and glucose all increased postprandially which agrees with the anabolic roles of these factors. Fasting for 4 and 8 d did not affect ghrelin levels in plasma or stomach. Plasma GH was elevated significantly after 4 and 8 d of fasting, while plasma IGF-I levels were reduced. Plasma ghrelin levels were elevated significantly after 2 and 4 wk of fasting, but no change was detected in stomach ghrelin mRNA levels. Four weeks of fasting did not affect plasma GH levels, although plasma IGF-I and glucose were reduced significantly, indicating that GH resistance exists during a prolonged nutrient deficit (catabolic state). These results indicate that ghrelin may not be acting as a meal-initiated signal in tilapia, although it may be acting as a long-term indicator of negative energy balance.     

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.     

Effects of photoperiod on the secretion of growth hormone in female goats

The aim of the present study was to clarify the effect of photoperiod on the secretion of growth hormone (GH) in goats. Adult female goats were kept at 20°C with an 8‐h or 16‐h photoperiod, and secretory patterns of GH for 4 h (12.00 to 16.00 hours) were compared. In addition, the goats were kept under a 16‐h photoperiod and orally administered saline (controls) or melatonin, and the effects of melatonin on the secretion of GH were examined. GH was secreted in a pulsatile manner. There were no significant differences in pulse frequency between the 8‐ and 16‐h photoperiods; however, GH pulse amplitude tended to be greater in the group with the 16‐h photoperiod (P = 0.1), and mean GH concentrations were significantly greater in the 16‐h photoperiod (P < 0.05). The GH‐releasing response to GH‐releasing hormone (GHRH) was also significantly greater for the 16‐h photoperiod (P < 0.05). There were no significant differences in GH pulse frequency between the saline‐ and melatonin‐treated groups. However, GH pulse amplitude and mean GH concentrations were significantly greater in the saline‐treated group (P < 0.05). The present results show that a long photoperiod enhances the secretion of GH, and melatonin modifies GH secretion in female goats.     

Effectiveness of maifanite in reducing the detrimental effects of aflatoxin B1 on hematology,aflatoxin B1 residues,and antioxidant enzymes activities of weanling piglets

A feeding trial was conducted to evaluate the effectiveness of maifanite, which is mainly composed of aluminosilicate, in reducing the adverse effects of aflatoxin B₁ (AFB₁) on hematology, AFB₁ residues, and antioxidant enzymes activities in weaning piglets. A total of 32 (9.28±0.17 kg BW) individually housed crossbred piglets (Duroc×Landrace×Large white) were randomly allotted to 1 of 4 dietary treatments in a 2×2 factorial arrangement with 8 replicates per treatment. The dietary treatments included 2 AFB₁ levels (5.3 and 372.8 μg/kg) and 2 maifanite levels (0% and 1%). No differences in average daily gain, average daily feed intake, and gain to feed ratio were observed among treatments. Ingestion of the AFB₁-contaminated (AF) diets (372.8 μg/kg of AFB₁) reduced (P<0.05) the numbers of neutrophil, monocyte, and total leukocyte. There were no effects of AFB₁ on gamma glutamyltransferase, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase activities, and total protein, albumin, urea N, total bilirubin, IgG, IgA, and IgM concentrations in serum. Aflatoxin B₁ was found in the liver and kidney of piglets fed the AF diets. Piglets fed the AF diets reduced (P<0.05) the total superoxide dismutase, glutathione peroxidase, and catalase activities in serum. However, total superoxide dismutase activity in the liver was increased (P<0.05) in piglets fed the AF diets compared with those fed the basal diets (5.3 μg/kg of AFB₁). There was an interaction (P=0.003) in erythrocyte, but piglets fed the diets containing maifanite had greater erythrocyte and lymphocyte (P=0.035) numbers than those fed the diets without maifanite. The AFB₁ levels in the liver and kidney of piglets fed the AF diet containing maifanite were 29.6% and 41.2% lower, respectively, than those of piglets fed the AF diet alone. Although there was an interaction (P=0.011), piglets fed the diets containing AFB₁ and maifanite had greater serum T-SOD activity compared with those fed the diets with no maifanite. In conclusion, the addition of maifanite to the AF diet resulted in partial restoration of hematology and antioxidant enzymes activities and reduced AFB₁ levels in the liver and kidney.     

Changes in plasma melanocyte-stimulating hormone,ACTH, prolactin,GH, LH,FSH, and thyroid-stimulating hormone in response to injection of sulpiride,thyrotropin-releasing hormone,or vehicle in insulin-sensitive and -insensitive mares

Six insulin-sensitive and 6 insulin-insensitive mares were used in a replicated 3 by 3 Latin square design to determine the pituitary hormonal responses (compared with vehicle) to sulpiride and thyrotropin-releasing hormone (TRH), 2 compounds commonly used to diagnose pituitary pars intermedia dysfunction (PPID) in horses. Mares were classified as insulin sensitive or insensitive by their previous glucose responses to direct injection of human recombinant insulin. Treatment days were February 25, 2012, and March 10 and 24, 2012. Treatments were sulpiride (racemic mixture, 0.01 mg/kg BW), TRH (0.002 mg/kg BW), and vehicle (saline, 0.01 mL/kg BW) administered intravenously. Blood samples were collected via jugular catheters at −10, 0, 5, 10, 20, 30, 45, 60, 90, and 120 min relative to treatment injection. Plasma ACTH concentrations were variable and were not affected by treatment or insulin sensitivity category. Plasma melanocyte-stimulating hormone (MSH) concentrations responded (P < 0.01) to both sulpiride and TRH injection and were greater (P < 0.05) in insulin-insensitive mares than in sensitive mares. Plasma prolactin concentrations responded (P < 0.01) to both sulpiride and TRH injection, and the response was greater (P < 0.05) for sulpiride; no effect of insulin sensitivity was observed. Plasma thyroid-stimulating hormone (TSH) concentrations responded (P < 0.01) to TRH injection only and were higher (P < 0.05) in insulin-sensitive mares in almost all time periods. Plasma LH and FSH concentrations varied with time (P < 0.05), particularly in the first week of the experiment, but were not affected by treatment or insulin sensitivity category. Plasma GH concentrations were affected (P < 0.05) only by day of treatment. The greater MSH responses to sulpiride and TRH in insulin-insensitive mares were similar to, but not as exaggerated as, those observed by others for PPID horses. In addition, the reduced TSH concentrations in insulin-insensitive mares are consistent with our previous observation of elevated plasma triiodothyronine concentrations in hyperleptinemic horses (later shown to be insulin insensitive as well).     

Growth,carcass, fiber type,and meat quality characteristics in Large White pigs with different live weights

The aim of this study was to compare the growth, carcass, histochemical, and meat quality characteristics in Large White pig groups that were categorized by live weight (Heavy and Light) and type I fiber percentage (High and Low), a procedure which resulted in four groups (Heavy-High, Heavy-Low, Light-High, and Light-Low). As expected, the Heavy group showed heavier live weight (114 vs. 94.7 kg, P<0.001) and larger loin eye area (53.3 vs. 47.8 cm², P<0.001), as well as, higher total number (1,223,000 vs. 1,140,000, P<0.05) and greater mean value cross-sectional area (CSA; 4031 vs. 3798 μm²P<0.05) of muscle fibers than the Light group. However, there were no significant differences in start and finish days among the groups (P>0.05). Heavier pigs harboring a higher percentage of type I fibers (HH) exhibited a similar mean CSA (3894 vs. 4101 μm²) and total number (1,249,000 vs. 1,198,000) of muscle fibers, even though these pigs had a greater CSA of type I fibers (3181 vs. 2719 μm², P<0.05) and a smaller CSA of type IIB fibers (4048 vs. 4457 μm², P<0.05) compared to heavier pigs harboring a lower percentage of fiber type I (HL). Both the HL and Light-Low groups exhibited a rapid decline of muscle pH at the early postmortem period (5.90 and 5.85 vs. 6.08, P<0.05), paler surfaces (43.07 and 43.55 vs. 40.73_,P<0.05), and higher degrees of fluid loss by exudation (6.26 and 6.39 vs. 4.22%, P<0.05) compared to the HH group due to their muscle fiber type composition. Thus, the HH pigs showed better meat quality characteristics without significant differences in growth and carcass performance compared to the HL pigs. Therefore, selection for increased live weight at the same age and muscle fiber characteristics, especially the increased type I fiber CSA and proportion, is one of the relevant indicators to improve and control meat quality without reducing the growth and carcass performance.     

Role of ghrelin in regulating rabbit ovarian function and the response to LH and IGF-I

The aim of these in vivo and in vitro studies was to examine the role of ghrelin in the control of plasma hormone concentrations, the proliferation, apoptosis and secretory activity of ovarian granulosa cells and the response of these cells to hormonal treatments. Female rabbits were injected with ghrelin (10 μg/animal/day for one week before ovulation induced by 25 IU PMSG and 0.25 IU LHRH). On the day of ovulation, blood samples were collected and analyzed for concentrations of progesterone (P₄), testosterone (T), estradiol (E₂), estrone-sulphate (ES), insulin-like growth factor I (IGF-I) and leptin (L) by RIA. Some control and ghrelin-treated animals were killed in the periovulatory period, their ovaries were weighed and granulosa cells were isolated and cultured for 2 d. Cell proliferation (expression of PCNA) and apoptosis (expression of TdT) were evaluated by immunocytochemistry and TUNEL respectively. Secretion of P₄, T, E₂, IGF-I, and prostaglandin F (PGF) by granulosa cells cultured with and without LH or IGF-I (1, 10 or 100 ng/ml medium) was assessed by RIA. The remaining control and treated animals were kept until parturition, while the number, viability and body weight of pups were recorded.