Influence of diet and beta-agonist administration on plasma concentrations of growth hormone and insulin-like growth factor-1 in young steers

Investigations on Modulating Effect of Vanadium Supplementation on Growth and Metabolism Through Improved Immune Response, Antioxidative Profile and Endocrine Variables in Hariana heifers

This study was conducted to investigate the effect of vanadium (V) supplementation on growth, metabolism, antioxidant, and immunological and endocrine variables in Hariana heifers. Eighteen indigenous Hariana heifers (body weight 130.0 ± 3.0 kg; age 10.0 ± 2.0 months) were randomly blocked into three groups, each comprising of six animals. All the animals were on same dietary plan except that the respective groups were additionally supplemented with 0.0, 2.5, and 5.0 mg of V/kg dry matter (DM), during the experimental period of 90 days. There was a linear increase (p < 0.05) in mean DMI and ADG in 5.0 mg of V/kg DM-supplemented group. However, the feed efficiency remained unaffected. Although no effects (p > 0.05) of V supplementation were observed on hemato-biochemical attributes, the mean plasma V concentration showed dose-dependent increase (p < 0.001) on V supplementation. The activity of SOD was significantly higher (p < 0.001), whereas mean values of LPO decreased linearly (p < 0.05) in V-supplemented groups. Plasma total antioxidant status (TAS) also increased linearly (p < 0.05) in V-supplemented groups. Plasma IgG levels increased linearly (p < 0.05). Plasma IGF-1 concentrations showed significant effect (p < 0.05) of V supplementation. Plasma T4 concentration increased linearly (p < 0.05). The results suggest that V supplementation may play a role in modulating the immunity and antioxidant status of growing Hariana heifers. Graphical Abstract.

Dietary Energy Levels Affect Growth Performance through Growth Hormone and Insulin-Like Growth Factor 1 in Yak (Bos grunniens)

The objective of this study was to investigate the effects of different dietary energy levels on serum concentrations of growth hormone (GH) and insulin-like growth factor 1 (IGF-1), as well as gene expression of their associated binding proteins and receptors in yak. Fifteen adult male yaks with BW of 276.1 ± 3.5 kg were allotted in three dietary groups and were fed with low (LE), medium (ME), and high energy (HE) level diet having different NEg of 5.5 MJ/kg, 6.2 MJ/kg, 6.9 MJ/kg, respectively. The effects of these treatments on ADG, BW, ADFI, and feed conversion ratio were significant (p < 0.05) throughout the experimental period. Serum GH concentration decreased (p < 0.05) with an increase in dietary energy level on d 30 and d 60. While IGF-1 concentration was higher (p < 0.05) in ME group, as compared to LE and HE groups on d 60. The expression level of growth hormone receptor (GHR) was decreased (p < 0.001) and IGF-1 was increased with the increase in the dietary energy level. The relative expression of insulin-like growth factor binding protein 3 (IGFBP-3) was higher (p < 0.001) in ME and HE groups, except the LE group. In conclusion, our findings provide a first insight into the combined effect of GH and IGF-1 in controlling the metabolism and productivity of yak. It also showed that medium energy level diet contributed to promote growth performance of yak during the cold season.

Interaction between supplemental zinc oxide and zilpaterol hydrochloride on growth performance, carcass traits, and blood metabolites in feedlot steers

Interactive effects of supplemental Zn and zilpaterol hydrochloride (ZH) were evaluated in feedlot steers ( = 40; 652 kg ± 14 initial BW) to determine their impact on feedlot performance, blood constituents, and carcass traits. The study was conducted as a randomized complete block design with a 2 × 2 factorial treatment arrangement. Steers were blocked by BW and randomly assigned to treatments. Factors consisted of supplemental Zn (60 or 300 mg/kg diet DM) and ZH (0 or 8.33 mg/kg) in the diets. For diets supplemented with 300 mg Zn/kg DM, 60 mg Zn/kg was supplemented as zinc sulfate and 240 mg Zn/kg was supplemented as zinc oxide, and the diet was fed for 24 d. Zilpaterol hydrochloride was fed for 21 d followed by a 3-d withdrawal. Cattle were housed in partially covered individual feeding pens equipped with automatic waterers and fence-line feed bunks and were fed once daily for ad libitum intake. Plasma samples were collected on d 0 and 21 to assess changes in Zn, plasma urea nitrogen (PUN), glucose, and lactate concentrations, and serum samples were collected on d 21 to assess IGF-1 concentration. On d 25, cattle were weighed and transported 450 km to a commercial abattoir for harvest; HCW and incidence of liver abscesses were recorded. Carcass data were collected after 36 h of refrigeration. Data were analyzed as a mixed model with Zn, ZH, and Zn × ZH as fixed effects; block as a random effect; and steer as the experimental unit. No interaction or effects of Zn or ZH were observed for IGF-1 concentration, plasma glucose, or lactate concentrations ( ≥ 0.25). No interaction between Zn and ZH was observed for PUN concentration, but PUN decreased with ZH ( < 0.01). There were no effects of ZH or Zn on ADG, DMI, final BW, feed efficiency, HCW, back fat, KPH, quality grade, or incidence of liver abscesses ( > 0.05). Zinc supplementation tended ( = 0.08) to improve the proportion of carcasses grading USDA Choice. Feeding ZH decreased yield grade ( = 0.05) and tended to increase LM area ( = 0.07). In conclusion, increasing dietary concentrations of Zn does not impact response to ZH, but feeding ZH altered circulating concentrations of PUN.

Poor maternal nutrition during gestation in sheep reduces circulating concentrations of insulin-like growth factor-I and insulin-like growth factor binding protein-3 in offspring

To determine if poor maternal nutrition alters growth, body composition, circulating growth factors, and expression of genes involved in the development of muscle and adipose of offspring, 24 Dorset and Shropshire ewes were fed either 100% (control fed), 60% (restricted fed), or 126% (over fed) of National Research Council requirements. Diets began at day 116 ± 6 of gestation until parturition. At parturition, 1 lamb from each control fed (CON), restricted fed (RES), and over fed (OVER) ewe was necropsied within 24 h of birth (1 d; n = 3/treatment) or reared on a control diet for 3 mo (CON = 5, RES = 5, and OVER = 3/treatment) and then euthanized. Body weights and blood samples were collected from lambs from 1 d to 3 mo. Organ weights, back fat thickness, loin eye area, and tissue samples (quadriceps, adipose, and liver) were collected at 1 d and 3 mo of age. The RES lambs weighed 16% less than CON (P = 0.01) between 1 d and 3 mo of age. In RES, there was a tendency for reduced heart girth at 1 d and 3 mo (P < 0.07) and back fat was reduced 36% at 3 mo (P = 0.03). Heart weight was 30% greater in OVER at 1 d when compared with RES lambs (P = 0.02). Serum IGF-I and IGFBP-3 were reduced in RES and OVER lambs (P < 0.05). Leptin tended to be greater in OVER lambs compared with CON at 1 d and 3 mo (P ≤ 0.08). Triiodothyronine was reduced in RES at 1 d (P = 0.05) and triglycerides tended to be greater in OVER at 3 mo (P = 0.07). In liver, there was a tendency for increased expression of IGF-I in OVER (P = 0.06) and decreased IGFBP-3 in RES (P = 0.09) compared with CON lambs at 1 d. In adipose tissue, adiponectin expression was decreased in RES (P = 0.05) at 3 mo. At 1 d of age, muscle expression of IGF-I tended to increase in RES (P = 0.06). In conclusion, poor maternal nutrition during gestation reduced growth rate in offspring which may be because of reduced circulating IGF-I and IGFBP-3 and decreased expression of IGFBP-3 in the liver.

Deletion of β-adrenergic receptor 1, 2, or both leads to different bone phenotypes and response to mechanical stimulation

As they age, mice deficient for the β2-adrenergic receptor (Adrb2(-/-) ) maintain greater trabecular bone microarchitecture, as a result of lower bone resorption and increased bone formation. The role of β1-adrenergic receptor signaling and its interaction with β2-adrenergic receptor on bone mass regulation, however, remains poorly understood. We first investigated the skeletal response to mechanical stimulation in mice deficient for β1-adrenergic receptors and/or β2-adrenergic receptors. Upon axial compression loading of the tibia, bone density, cancellous and cortical microarchitecture, as well as histomorphometric bone forming indices, were increased in both Adrb2(-/-) and wild-type (WT) mice, but not in Adrb1(-/-) nor in Adrb1b2(-/-) mice. Moreover, in the unstimulated femur and vertebra, bone mass and microarchitecture were increased in Adrb2(-/-) mice, whereas in Adrb1(-/-) and Adrb1b2(-/-) double knockout mice, femur bone mineral density (BMD), cancellous bone volume/total volume (BV/TV), cortical size, and cortical thickness were lower compared to WT. Bone histomorphometry and biochemical markers showed markedly decreased bone formation in Adrb1b2(-/-) mice during growth, which paralleled a significant decline in circulating insulin-like growth factor 1 (IGF-1) and IGF-binding protein 3 (IGF-BP3). Finally, administration of the β-adrenergic agonist isoproterenol increased bone resorption and receptor activator of NF-κB ligand (RANKL) and decreased bone mass and microarchitecture in WT but not in Adrb1b2(-/-) mice. Altogether, these results demonstrate that β1- and β2-adrenergic signaling exert opposite effects on bone, with β1 exerting a predominant anabolic stimulus in response to mechanical stimulation and during growth, whereas β2-adrenergic receptor signaling mainly regulates bone resorption during aging.

Reduced response to an estrous induction program in postpartum beef cows treated with zilpaterol and gaining body weight

In beef cows, reduced energy intake delays first ovulation postpartum and is associated with lesser insulin, IGF-I and leptin concentrations. However, the close relationship among these hormones mask their individual roles in the reinitiation of ovarian activity. A β-adrenergic receptor agonist (βAR) was used to increase body condition score (BCS) and yet reduce body fat and leptin serum concentration to determine the specific role of leptin in the postpartum ovarian activity. Beef cows (n=77) with BCS 3.1 ± 1.4 received 2 kg/day of feed containing 0 or 0.15 mg/kg of zilpaterol (a synthethic βAR), for 33 days. Estrus was induced with a progestin implant applied for 9 d and cows in estrus were bred by artificial insemination (AI). Zilpaterol administration increased (P<0.05) daily weight gain, muscle depth and BCS, with no changes in back fat depth, reducing fat to muscle ratio (P<0.05). At the time of AI, insulin (38%) and IGF-I (26%) concentrations were less in zilpaterol-treated cows (P<0.05), but leptin concentration was unaffected. Ovulation rate and animal with luteal activity after estrus induction were also reduced by 35% (P=0.05) and 56.5% (P=0.007), respectively, in zilpaterol-treated cows. Logistic regression estimates for BCS (P=0.016) and IGF-I concentration (P=0.03) were positively related with the occurrence of luteal activity. In addition, whilst back fat (P=0.009) had a positive effect on luteal activity, leptin concentration did not show a significant relationship. In conclusion, despite an increase in body weight and a positive change in BCS, the reduction in insulin and IGF-I concentrations, associated with βAR treatment, reduced the response to induction of estrus. However only IGF-I, but not leptin or insulin, significantly influenced the odds for the occurrence of luteal activity after estrous induction in cattle with poor BCS.

The effect of immunization against somatostatin and β-agonist administration alone and in combination on growth and carcass composition in young steers

The effect of active immunization against somatostatin and β-agonist administration alone and in combination on growth, carcass composition and endocrine responses was investigated in young steers given a pelleted diet of dried grass and barley (0·7: 0·3) ad libitum for 16 weeks. Immunization alone increased growth rate by proportionately 0·10 but had no effect on plasma growth hormone (GH) or insulin-like growth factor-1 (IGF-1) concentrations (P > 0·10). Carcass protein content was unchanged but fat content tended to be increased. This was possibly associated with increased (P < 0·10) plasma insulin concentrations observed in these animals. Cimaterol administration significantly increased growth rate (P < 0·05) and carcass weight (P < 0·01). Carcass protein content was significantly (P < 0·01) increased and carcass fat was significantly (P < 0·001) reduced. Administration of cimaterol to immunized animals resulted in an enhancement of the repartitioning effect of the pagonist although growth rates were intermediate between the separate treatments. The mechanism by which this was achieved is unclear. Plasma IGF-1 concentrations tended (P < 0·10) to be lower in these animals compared with controls. Plasma insulin concentrations were also reduced (P < 0·05) in these animals. Both immunized animals and those given cimaterol alone showed an increased GH response to a single intravenous injection of growth hormone releasing factor (GRF) (P < 0·05). Animals given the combined treatment however showed a reduced response suggesting that the effects were not mediated through direct changes in GH secretion. The improved lean:fat ratio in the carcass was observed to be mediated through an enhancement of the lipolytic response to the /J-agonist with only small effects on protein accretion. It is suggested that immunoneutralization of somatostatin may increase the sensitivity of adipose tissue to lipolytic stimuli. This could occur through changes in the secretion of gastrointestinal or pancreatic hormones as a result of neutralization of the inhibitory influences of somatostatin. Further work is required to clarify these effects.

Effects of energy allowance and cimaterol feeding during the heifer rearing period on growth, puberty and milk production

Twenty-one 6-month-old Israeli Holstein heifers were used to determine the effect of three 6-month feeding regimes on growth, blood concentration of insulin, prolactin and insulin-like growth factor-1 (IGF-1), attainment of puberty and milk production during first lactation. Feeding regimes were as follows. (1) Restricted: the heifers were given food during months 1, 2 and 4, 5 of an experimental period, to support live-weight (LW) gain of 0·35 and 0·50 kg/day, respectively and during months 3 and 6 the heifers were given food to support compensatory growth. (2) Control: the heifers were given food to support LW gain of 1·0 kg/day. (3) Control + C: the heifers were given the same as the control, with a daily supplement of 0·05 mg/kg LW cimaterol (C) for 4 months. The total LW gain of the restricted heifers during the 6 months of the trial was significantly lower than that of the control heifers. Cimaterol improved growth rate only during the first 2 months of its application and its withdrawal was associated with severe LW gain retardation. The feeding regime employed in the restricted treatment was associated with a significant reduction in serum concentrations of insulin, prolactin and IGF-1 during the first restricted phase, followed by an elevation in the first compensatory phase. During the second restriction-compensation cycle, only the serum concentration of prolactin was significantly reduced. Cimaterol addition was also associated with a reduced blood concentration of the hormones. The animals in the restricted, control and control + C groups attained puberty at LW of 249·2, 277·6 and 304·9 kg (P<0·05), respectively. No effect of the treatments on milk yield was observed. The effect of the feeding regimes on skeletal growth and on metubolizable energy efficiency for growth is discussed.

Response to ractopamine-HCl in heifers is altered by implant strategy across days on feed1

Two experiments were conducted to investigate the effects of ractopamine-HCl (RAC) and implant strategy or days on feed (DOF) on feedlot performance and expression of beta-adrenergic receptors (AR). In Exp. 1, 1,147 feedlot heifers weighing 282 +/- 3 kg were used with implant treatments of Revalor-200 (R200) at arrival, or Revalor-IH at arrival with reimplantation with Finaplix-H on d 58 (RF). Ractopamine (0 vs. 200 mg/d) was fed the last 28 d in both experiments. Treatments were randomly assigned to 16 pens. At slaughter, semimembranosus muscle tissue was excised for RNA isolation. Ractopamine administration increased (P < 0.05) ADG, G:F, HCW, and LM; decreased (P < 0.05) 12th rib fat depth; and improved (P < 0.05) yield grade. There was no effect (P > 0.10) on the expression of beta1-AR mRNA; however, there was a tendency (P = 0.10) for RAC feeding to increase beta2-AR mRNA levels. For beta3-AR mRNA, there was an implant by RAC interaction (P = 0.05), with RAC numerically increasing beta3-AR mRNA in heifers implanted with RF, but a decrease (P < 0.05) in expression in heifers implanted with R200. Ractopamine also decreased (P < 0.05) IGF-I mRNA in heifers implanted with RF. In Exp. 2, 2,077 heifers were used to investigate the effects of RAC and DOF. Days on feed were 129, 150, and 170, and RAC was administered the last 28 d. Ractopamine improved (P < 0.05) G:F, but had no other effects (P > 0.05) on performance. Average daily gain decreased (P < 0.05) as DOF increased. Hot carcass weight, LM area, 12th rib fat, G:F, calculated yield grade, and marbling score increased (P < 0.05) and the percentage of KPH fat decreased (P < 0.05) as DOF increased. These data aid in our understanding of the effects of steroidal implants, DOF, and RAC administration in feedlot heifers.

Natural sex steroids and their xenobiotic analogs in animal production: growth, carcass quality, pharmacokinetics, metabolism, mode of action, residues, methods, and epidemiology

Natural and xenobiotic compounds having sex-related actions have long been used for growth promotion and various changes in carcass quality in meat animals. The first compounds used were synthetic estrogens; however, later on a whole battery of compounds having androgenic, and progestogenic actions have also been involved. In surveying the effects of these compounds in meat-producing animals, it became clear that these drugs increase the growth rate of the treated animals and bring about changes in the carcass that are generally characterized by lower fat content and more lean mass. Extensive studies undertaken in various countries, including the European Economic Community (EEC), have shown that if used according to good husbandry practices, the meat from treated animals does not have excessive amounts of residues compared with the endogenous amount of steroid production in the animals in question and also in human beings. The banning of these compounds in the European community brought a new phenomenon of illegal or black market cocktails. These mixtures of anabolic steroids are injected into the body of the animals rather than implanted in the ears, which is the normal practice in countries where they have not yet been banned. Several screening and confirmatory methods are now available for monitoring programs. However, these programs need excessive resources in terms of manpower, funds, and proper legislation, which in underdeveloped countries is questionable, particularly in the absence of strong scientific evidence for the exercise.