Plasma growth hormone, insulin-like growth factor, insulin, and thyroid hormone association with body protein and fat accretion in steers undergoing compensatory gain after dietary energy restriction

The Effect of the Feeding System on Fat Deposition in Yak Subcutaneous Fat

Fat deposition is very important to the growth and reproduction of yaks. In this study, the effect of the feeding system on fat deposition in yaks was explored by transcriptomics and lipidomics. The thickness of the subcutaneous fat in yaks under stall (SF) and graze feeding (GF) was evaluated. The transcriptomes and lipidomes of the subcutaneous fat in yaks under different feeding systems were detected by RNA-sequencing (RNA-Seq) and non-targeted lipidomics based on ultrahigh-phase liquid chromatography tandem mass spectrometry (UHPLC-MS), respectively. The differences in lipid metabolism were explored, and the function of differentially expressed genes (DEGs) was evaluated by gene ontology (GO) and Kyoto encyclopedia of genes and genome (KEGG) analysis. Compared with GF yaks, SF yaks possessed stronger fat deposition capacity. The abundance of 12 triglycerides (TGs), 3 phosphatidylethanolamines (PEs), 3 diglycerides (DGs), 2 sphingomyelins (SMs) and 1 phosphatidylcholine (PC) in the subcutaneous fat of SF and GF yaks was significantly different. Under the mediation of the cGMP-PKG signaling pathway, the blood volume of SF and GF yaks may be different, which resulted in the different concentrations of precursors for fat deposition, including non-esterified fatty acid (NEFA), glucose (GLU), TG and cholesterol (CH). The metabolism of C16:0, C16:1, C17:0, C18:0, C18:1, C18:2 and C18:3 in yak subcutaneous fat was mainly realized under the regulation of the INSIG1, ACACA, FASN, ELOVL6 and SCD genes, and TG synthesis was regulated by the AGPAT2 and DGAT2 genes. This study will provide a theoretical basis for yak genetic breeding and healthy feeding.

Comparing the responses of grain fed feedlot cattle under moderate heat load and during subsequent recovery with those of feed restricted thermoneutral counterparts: plasma biochemistry

Responses to heat stress in ruminants reflect the integration of local climatic conditions, environment/production system and the animal's homeostatic and homeorhetic capacities. Thus, the goal of ameliorating heat stress requires experimental settings that, within limits, closely resemble the target production system and cohort. We investigated the blood biochemical changes of two sequential cohorts of twelve 518 ± 23 kg grain fed Black Angus steers. Each cohort consisted of two treatments of 6 head/group: a thermally challenged (TC) treatment and a feed restricted thermoneutral (FRTN) treatment. Both groups were housed in climate controlled rooms for 19 days, with the TC group experiencing three distinct periods: PreChallenge, Challenge and Recovery. PreChallenge and Recovery delivered thermoneutral conditions, while Challenge consisted of 7 days of moderate diurnal heat load. The FRTN group was maintained in thermoneutral conditions at all times. Both groups were then relocated to outdoor pens for a further 40 days to detect any enduring change to metabolism as a consequence of the treatments. We compared blood biochemical responses of the treatments and inferred likely metabolic changes. Relative to the FRTN group, the TC animals experienced limited supply of triglycerides, cholesterol and glutamine during moderate heat load, suggesting constraints to energy metabolism. Lower blood urea during Recovery and in outdoor pens implied a requirement to capture N rather than allow its excretion. Altered liver enzyme profiles indicated a higher level of hepatic stress in the TC group. By the completion of feedlot finishing, the groups were not separable on most measures.

Evaluation of the association between plasma glucose-dependent insulinotropic polypeptide, respiratory quotient, and intramuscular fat deposition in feedlot cattle fed different levels of dry matter intake

The objectives of this trial were to evaluate the association between different levels of dry matter intake (DMI) on gas exchange, plasma glucose-dependent insulinotropic polypeptide (GIP) concentration, and intramuscular (IM) fat deposition. We used 60 individually fed backgrounded Angus × SimAngus-crossbred steers (n = 30) in a randomized complete block design. Steers (paired by body weight [BW] and gain to feed ratio [G:F]) were randomly allocated to one of the following treatments: ad libitum intake (AI) or restricted intake (RI; the same diet fed at 85% of the AI) of a finishing diet. The diet contained 61% cracked corn, 9% corn silage, 15% distillers’ dried grains with solubles, 5% soyhulls, and 10% of a protein-mineral-vitamin premix. Measurements of CO₂ emission and consumption of O₂, and respiratory quotient (RQ) were taken using the GreenFeed system (n = 15/treatment). Plasma and gas samples were collected 10 d before slaughter, 1 h before and 2 h after feeding. Plasma glucose, non-esterified fatty acids, GIP, and insulin concentration and gasses (O_2, CO_2, and RQ) were analyzed using the MIXED procedure of SAS evaluating the fixed effect of treatment, time (repeated measurement) and their interaction, and the random effect of the block. Final BW and carcass characteristics were analyzed with a similar model, without the time statement and its interaction. Compared with RI, AI steers had greater (P < 0.01) DMI and average daily gain (ADG). Steers on AI had greater final BW (P = 0.02), tended to have a greater ribeye area (P = 0.09), and had lower plasma GIP concentration (P = 0.04). There was no treatment effect (P ≥ 0.11) on G:F, subcutaneous backfat (BF), and IM fat, O₂ consumption, CO₂ emission, and RQ. Plasma glucose concentration of AI steers was greater before and after feeding than RI (P < 0.05). In conclusion, feeding steers ad libitum increased DMI, ADG, and plasma glucose and GIP concentration but does not affect G:F, BF, IM fat, CO₂ emission, and O₂ consumption. Plasma GIP concentration and RQ are not associated with IM fat deposition.

Effect of a high crude protein content diet during energy restriction and re-alimentation on animal performance, skeletal growth and metabolism of bone tissue in two genotypes of cattle

The objective of this study was to investigate the effect of diet crude protein (CP) content and metabolisable energy (ME) intake on skeletal growth and associated parameters of growing steers prior to and during compensatory growth in weight and catch-up growth in skeletal elongation. The experiment was a factorial design with two cattle genotypes [Brahman crossbred (BX, 178 ± 6 kg) and Holstein-Friesian (HF, 230 ± 34 kg)] and three nutritional treatments; high CP content and high ME intake (HCP-HME), high CP content and low ME intake (HCP-LME) and low CP content and low ME intake (LCP-LME) with the ME intake of HCP-LME matched to that of LCP-LME. Nutritional treatments were imposed over a 103 d period (Phase 1), and after this, all steers were offered ad libitum access to the HCP-HME nutritional treatment for 100 d (Phase 2). Steers fed the high CP content treatment with a low ME intake, showed higher hip height gain (P = 0.04), larger terminal hypertrophic chondrocytes (P = 0.02) and a higher concentration of total triiodothyronine in plasma (P = 0.01) than steers with the same ME intake of the low CP content treatment. In addition, the low CP treatment resulted in significant decreases in bone volume (P = 0.03), bone surface area (P = 0.03) and the concentration of bone-specific alkaline phosphatase in plasma (P < 0.001) compared to steers fed the HCP-HME treatment. A significant interaction between genotype and nutritional treatment existed for the concentration of thyroxine (T4) in plasma where HF steers fed LCP-LME had a lower T4 concentration in plasma (P = 0.05) than BX steers. All steers with a restricted ME intake during Phase 1 demonstrated compensatory growth during Phase 2. However, HF steers fed the LCP treatment during Phase 1 showed a tendency (P = 0.07) for a greater LWG during Phase 2 without any increase in dry matter intake. Results observed at the growth plate and hip height growth suggest that catch-up growth in cattle may also be explained by the growth plate senescence hypothesis. Contrary to our initial hypothesis, the results demonstrate that greater CP intake during ME restriction does not increase compensatory gain in cattle during re-alimentation.

Transcriptome assisted label free proteomics of hepatic tissue in response to both dietary restriction and compensatory growth in cattle

Compensatory growth (CG) is a naturally occurring phenomenon where, following a period of under nutrition, an animal exhibits accelerated growth upon re-alimentation. The objective was to identify and quantify hepatic proteins involved in the regulation of CG in cattle. Forty Holstein Friesian bulls were equally assigned to one of four groups. Groups; A1 and A2 had ad libitum access to feed for 125 days, groups R1 and R2 were feed restricted. Following this, R1 and A1 animals were slaughtered. Remaining animals (R2 and A2) were slaughtered following ad libitum feeding for a successive 55 days. At slaughter hepatic tissue samples were collected and label-free quantitative proteomics undertaken with spectra searched against a custom built transcriptome database specific to the animals in this study. 24 differentially abundant proteins were identified during CG (R2 vs. R1) including; PSPH, ASNS and GSTM1, which are involved in nutrient metabolism, immune response and cellular growth. Proteins involved in biochemical pathways related to nutrient metabolism were down-regulated during CG, indicating a possible adaptive response by the liver to a period of fluctuating nutrient availability. The livers ability to regulate its metabolic activity may have profound effects on the efficiency of whole body energy utilization during CG. SIGNIFICANCE: This study is the first to unravel the effect of compensatory growth on the hepatic proteome of cattle using transcriptome-assisted shot gun proteomics. Proteins identified as being affected by dietary restriction and subsequent expression of compensatory growth in this study may, following appropriate validation, contribute to the identification of functional genetic variants. Such information could be harnessed within the context of genomic selection in cattle breeding programs to identify animals with a greater genetic potential to undergo compensatory growth, thus increasing the profitability of the beef sector and accelerating genetic gain.

Age-related functional changes of total thyroid hormones and glycosaminoglycans in growing calves

Background and Aim:

During the physiological growing, thyroid and proteoglycan glycosaminoglycan (GAG) changes dynamically occur, according to genetic and non-genetic factors. The purpose of this research was to compare the effects of early postnatal development (10 days) until 210 days of life on the triiodothyronine (T₃), thyroxine (T₄), the relative T₄:T₃ ratio, and GAGs profile, and to define the different reference intervals of the calf’s development through the various growing phases.

Materials and Methods:

The effect of growing on total thyroid hormones and GAG profiles was studied from 10 days to 210days of age in 64 clinically healthy Brown calves, 30males and 34females. Blood samples were collected at 10, 20, 30, 60, 90, 120, 150, 180, and 210days of age.

Results:

The results showed a significant effect of a calf’s growth on T₃, T₄, and GAG values (p<0.0001). Significant correlations between T₃ and T₄ were observed. Compared to the previous time point, T₃ showed a significant decrease at 20days and at 60days (p<0.01), while a significant increase was observed at 90days and 210days (p<0.05); T₄ showed a significant decrease at 20days (p<0.01), while significant increases were observed at both 180days and 210days (p<0.05); GAGs showed a significant increase at 120days and 210days (p<0.05). Positive and significant correlations between BW and GAGs in both males (p<0.0057) and females (p<0.0059) were observed.

Conclusion:

It can be concluded that the highest T₃ and T₄ concentrations have been associated with the early growing process (10days), with an increasing trend also at 210days, it is possible to hypothesize a probable metabolic effect of thyroid function in anabolic and/or catabolic directions during the calves’ development. Likewise, it can be reasonably inferred that the highest plasma GAGs at 210days may be due to their metabolic role during the development of growing calves. Taken together, these findings suggest the potential and relative contribution made by thyroid and GAGs effects on the dynamics of growing calves.

Label-free quantitative proteomic analysis of M. longissimus dorsi from cattle during dietary restriction and subsequent compensatory growth

Compensatory growth (CG) is a naturally occurring physiological process whereby an animal has the ability to undergo enhanced growth following a period of restricted feeding. This studies objective was to identify key proteins involved in the expression of CG. Forty Holstein Friesian bulls were equally assigned to one of four groups. R1 and R2 groups were subjected to restricted feed allowance for 125 days (Period 1). A1 and A2 animals had ad libitum access to feed in Period 1. Following Period 1, all animals from R1 and A1 were slaughtered. Remaining animals (R2 and A2) were slaughtered following ad libitum access to feed for successive 55 days (Period 2). M. longissimus dorsi samples were collected at slaughter from all animals. Proteins were isolated from samples and subjected to label-free mass spectrometry proteomic quantification. Proteins which were differentially abundant during CG (n = 39) were involved in cellular binding processes, oxidative phosphorylation and mitochondrial function. There was also evidence for up regulation of three pathways involved in nucleotide biosynthesis. Genetic variants in or regulating genes pertaining to proteins identified in this study may hold potential for use as DNA based biomarkers for genomic selection of animals with a greater ability to undergo CG.

Post-weaning growth rate effects on body composition of Nellore bulls

Context Previously feed-restricted cattle may exhibit compensatory growth during the finishing phase. However, the efficiency in converting feed into carcass should be evaluated since cattle undergoing compensatory growth usually have high non-carcass weight gain. Aims The objective of this study was to evaluate the effect of growth rate throughout the post-weaning growing phase on subsequent feed efficiency, carcass gain, and gain composition. Methods Thirty-nine weaned young Nellore bulls averaging 230.4 ± 5.62 kg of bodyweight and 8.5 ± 0.25 months of age were used. Initially, five bulls were slaughtered as a reference initial group. The remaining bulls were randomly assigned to one of three nutritional plans to achieve Low (0 kg/day), Medium (0.6 kg/day) or High (1.2 kg/day) average daily gain (ADG) throughout the post-weaning growing phase, followed by high growth rate during the finishing phase. One-half of the bulls from each treatment were slaughtered at the end of the post-weaning growing phase, and the other one-half after the finishing phase. During both phases the feed intake, apparent digestibility, performance, and body composition were evaluated. Key results Throughout the post-weaning growing phase, High bulls had greater ADG and more efficiently converted feed into carcass, compared with other nutritional plans (P &lt; 0.01). Throughout the finishing phase, Low bulls had greater ADG, carcass gain, and feed efficiency than High and Medium bulls (P &lt; 0.01). Previous feed restriction did not affect (P &gt; 0.05) apparent digestibility. During the finishing phase, previously restricted bulls fully compensated for the lost visceral organ weight, whereas the losses of bodyweight and carcass weight were only partially compensated. Throughout finishing, Low bulls had the greatest feed efficiency and profitability among nutritional plans. However, considering the overall experiment, Hight bulls converted feed into carcass more efficiently than Low bulls (P = 0.02), but did not differ from Medium (P &gt; 0.05). Conclusions Although previously restricted bulls had greater performance and efficiency throughout finishing, the improvement was not enough to reach the same carcass weight at the same age of the unrestricted bulls. Implications Despite the greater profitability of previously restricted bulls throughout finishing, unrestricted bulls were more profitable considering both growing and finishing phases.

Effect of restricted-feeding strategies on blood concentrations of hormones, metabolites, and minerals in Holstein × Zebu finishing steers

Abstract The objectives were to determine the effects of restricted-feeding strategies on blood concentrations of hormones, metabolites, and minerals in Holstein × Zebu finishing steers. Twenty steers (body weight = 319 ± 16.2 kg; age = 19 ± 1 months) were randomly allotted in 4 groups of 5 steers, which were restricted to 85% ad libitum feed intake for either 0 (R0; n = 5), 28 (R28; n = 5), 42 (R42; n = 5) or 84 (R84; n = 5) days of an 84-d finishing period. Steers were individually housed and considered the experimental unit. Blood samples were collected on d 0, 21, 42, 63, and 84, and were assayed for insulin-like growth factor 1 (IGF-1), thyroid hormones (T3 and T4), albumin, creatinine, urea, total protein, glucose, triglycerides, calcium, and phosphorus. Steers had increasing IGF-1 concentrations until d 42 when restricted-fed. Steers fed R84 had the greatest IGF-1 concentrations on d 84. Urea concentrations were greatest in steers fed R0 and least in steers fed R28; steers fed R42 and R84 were intermediate and not different from one another. Concentrations of IGF-1, urea, albumin, and calcium, but not T3, T4, glucose, triglycerides, creatinine, total protein, and phosphorus were affected by restricted-feeding strategies in Holstein × Zebu finishing steers.

TRIENNIAL GROWTH SYMPOSIUM: THE NUTRITION OF MUSCLE GROWTH: Impacts of nutrition on the proliferation and differentiation of satellite cells in livestock species1,2

Nutrition and other external factors are known to have a marked effect on growth of skeletal muscle, modulated, at least in part, through effects on satellite cells. Satellite cells and their embryonic precursors play an integral role in both prenatal and postnatal skeletal muscle growth of mammals. Changes in maternal nutrition can impact embryonic muscle progenitor cells which ultimately impacts both prenatal and postnatal skeletal muscle development. Satellite cells are important in postnatal skeletal muscle growth as they support the hypertrophy of existing myofibers. Hypertrophy of existing fibers is the only mechanism of postnatal muscle growth because muscle fiber number is fixed at birth and fiber nuclei have exited the cell cycle. Because fiber nuclei do not divide, additional nuclei required for hypertrophy must be acquired from satellite cells. To date, little research has aimed at determining whether nutrition directly impacts satellite cell populations within skeletal muscle of livestock species. However, it is well established that nutrition alters circulating concentrations of various growth factors such as insulin-like growth factor 1, epidermal growth factor, hepatocyte growth factor, and fibroblast growth factor. Each of these different growth factors impacts satellite cell proliferation and/or activation, indicating that nutrition likely plays a large role in skeletal muscle growth through impacting the satellite cell pool in both prenatal and postnatal growth. The relationship among nutrition, growth factors, and satellite cells relative to skeletal muscle growth is an important area of research that warrants further consideration.

PERFIL METABÓLICO DE CORDEIROS SANTA INÊS TERMINADOS EM CONFINAMENTO COM MANEJO ALIMENTAR RESTRITIVO E AD LIBITUM

Resumo Objetivou-se avaliar o perfil metabólico de 24 ovinos Santa Inês, machos, com peso vivo médio inicial de 20±1,25 kg, submetidos à restrição alimentar seguida de realimentação em confinamento, distribuídos em quatro tratamentos com 0, 20, 40 ou 60% de restrição alimentar. Dois ensaios foram desenvolvidos, um referente à restrição e outro à realimentação. Para tanto, foi utilizado delineamento experimental inteiramente ao acaso, com quatro tratamentos e seis repetições. Observou-se na fase de restrição alimentar que houve um decréscimo linear para as concentrações bioquímicas de ureia, glicose, GGT e fósforo; contrariamente, a concentração de colesterol aumentou linearmente ao final do período restritivo. A restrição alimentar influenciou negativamente nas concentrações de triglicerídeos e creatinina, diferentemente, os valores de proteínas totais e albumina apresentaram aumento significativo com o período restritivo. Já na realimentação, observou-se comportamento linear decrescente para ureia, glicose, GGT e magnésio. No segundo ensaio, verificou-se que as concentrações de proteínas totais, globulina e creatinina apresentaram diferença (P<0,05) entre os períodos de coleta. Os níveis de restrição alimentar afetaram o metabolismo proteico e interferiram também no metabolismo energético e mineral e a realimentação resultou em alteração no metabolismo proteico e energético.

Association of preweaning and weaning serum cortisol and metabolites with ADG and incidence of respiratory disease in beef cattle

The objectives of this experiment were to determine the association of circulating cortisol, lactate, and glucose at, and prior to, weaning with ADG and incidences of bovine respiratory disease (BRD) in beef cattle. A blood sample was collected approximately 3 wk prior to weaning and at weaning from genetically diverse steers and heifers ( = 451). Cattle were weighed periodically throughout the study and ADG was calculated for the preweaning period (152 ± 15 d), the receiving period (45 d postweaning), the finishing period (200 d), and total postweaning ADG. Incidences of BRD were recorded and analyzed as a binary trait. Lung lesions were recorded at slaughter. Preweaning serum cortisol concentrations were positively associated ( = 0.040) with receiving ADG and explained 0.74% of the variance of receiving ADG. Preweaning glucose concentrations were positively associated ( < 0.001) with preweaning ADG and negatively associated with receiving ( = 0.003), finishing ( = 0.008), and total postweaning ADG ( = 0.002) and explained 2.0% of the variance in total postweaning ADG. Variation in preweaning serum glucose concentrations could be indicative of variation in milk consumption, and therefore indicate calves receiving less milk grow slower prior to weaning, but experience compensatory gain postweaning. Cattle that were diagnosed with BRD ( = 130) grew slower during the receiving phase ( = 0.004), but total postweaning ADG was not different from cattle not diagnosed with BRD ( = 0.683). Additionally, cattle that were diagnosed with BRD in the feedlot tended ( = 0.062) to have slightly lower preweaning serum glucose concentrations. Using a logistic regression analysis, none of the serum variables measured at or before weaning were predictive of developing BRD ( > 0.180). Weaning serum glucose concentrations tended to be predictive of the presence of lung lesions at weaning ( = 0.060). These data indicate that glucose measured early in life is associated with growth rate, and could indicate that carbohydrate metabolism could contribute to variation in ADG.

State-dependent behavior alters endocrine-energy relationship: implications for conservation and management

Glucocorticoids (GC) and triiodothyronine (T3) are two endocrine markers commonly used to quantify resource limitation, yet the relationships between these markers and the energetic state of animals has been studied primarily in small-bodied species in captivity. Free-ranging animals, however, adjust energy intake in accordance with their energy reserves, a behavior known as state-dependent foraging. Further, links between life-history strategies and metabolic allometries cause energy intake and energy reserves to be more strongly coupled in small animals relative to large animals. Because GC and T3 may reflect energy intake or energy reserves, state-dependent foraging and body size may cause endocrine-energy relationships to vary among taxa and environments. To extend the utility of endocrine markers to large-bodied, free-ranging animals, we evaluated how state-dependent foraging, energy reserves, and energy intake influenced fecal GC and fecal T3 concentrations in free-ranging moose (Alces alces). Compared with individuals possessing abundant energy reserves, individuals with few energy reserves had higher energy intake and high fecal T3 concentrations, thereby supporting state-dependent foraging. Although fecal GC did not vary strongly with energy reserves, individuals with higher fecal GC tended to have fewer energy reserves and substantially greater energy intake than those with low fecal GC. Consequently, individuals with greater energy intake had both high fecal T3 and high fecal GC concentrations, a pattern inconsistent with previous documentation from captive animal studies. We posit that a positive relationship between GC and T3 may be expected in animals exhibiting state-dependent foraging if GC is associated with increased foraging and energy intake. Thus, we recommend that additional investigations of GC- and T3-energy relationships be conducted in free-ranging animals across a diversity of body size and life-history strategies before these endocrine markers are applied broadly to wildlife conservation and management.

Active G protein-coupled receptors (GPCR), matrix metalloproteinases 2/9 (MMP2/9), heparin-binding epidermal growth factor (hbEGF), epidermal growth factor receptor (EGFR), erbB2, and insulin-like growth factor 1 receptor (IGF-1R) are necessary for trenbolone acetate-induced alterations in protein turnover rate of fused bovine satellite cell cultures

Trenbolone acetate (TBA), a testosterone analog, increases protein synthesis and decreases protein degradation in fused bovine satellite cell (BSC) cultures. However, the mechanism through which TBA alters these processes remains unknown. Recent studies indicate that androgens improve rate and extent of muscle growth through a nongenomic mechanism involving G protein-coupled receptors (GPCR), matrix metalloproteinases (MMP), heparin-binding epidermal growth factor (hbEGF), the epidermal growth factor receptor (EGFR), erbB2, and the insulin-like growth factor-1 receptor (IGF-1R). We hypothesized that TBA activates GPCR, resulting in activation of MMP2/9 that releases hbEGF, which activates the EGFR and/or erbB2. To determine whether the proposed nongenomic pathway is involved in TBA-mediated alterations in protein turnover, fused BSC cultures were treated with TBA in the presence or absence of inhibitors for GPCR, MMP2/9, hbEGF, EGFR, erbB2, or IGF-1R, and resultant protein synthesis and degradation rates were analyzed. Assays were replicated at least 9 times for each inhibitor experiment utilizing BSC cultures obtained from at least 3 different steers that had no previous exposure to steroid compounds. As expected, fused BSC cultures treated with 10 n TBA exhibited increased ( < 0.05) protein synthesis rates and decreased ( < 0.05) protein degradation rates when compared to control cultures. Treatment of fused BSC cultures with 10 n TBA in the presence of inhibitors for GPCR, MMP2/9, hbEGF, EGFR, erbB2, or IGF-1R suppressed ( < 0.05) TBA-mediated increases in protein synthesis rate. Alternatively, inhibition of GPCR, MMP2/9, hbEGF, EGFR, erbB2, or IGF-1R in the presence of 10 n TBA each had no ( > 0.05) effect on TBA-mediated decreases in protein degradation. However, inhibition of both EGFR and erbB2 in the presence of 10 n TBA resulted in decreased ( < 0.05) ability of TBA to decrease protein degradation rate. Additionally, fused BSC cultures treated with 10 n TBA exhibit increased ( < 0.05) pAKT protein levels. These data indicate the TBA-mediated increases in protein synthesis likely involve GPCR, MMP2/9, hbEGF, EGFR, erbB2, and IGF-1R. However, the mechanism through which TBA mediates changes in protein degradation is different and appears to involve only the EGFR and erbB2. Furthermore, it appears the protein kinase B pathway is involved in TBA's effects on fused BSC cultures.

Thyroid Hormones, Insulin, Body Fat, and Blood Biochemistry Indices in Dairy Cows During the Reproduction/Production Cycle

This study investigated the changes in: thyroid hormones, amount of subcutaneous fat, and selected indices of blood biochemistry in dairy cows in relation to the reproduction/production cycle. The blood samples were collected both ante- and post-partum every two weeks. When evaluating the mean values of the investigated indices, the major changes were recorded in dairy cows 3 to 14 days after calving. During this period, we observed a significant decrease in the mean serum levels of T3 (P < 0.05), T4 (P < 0.01), and triglycerides (P < 0.01). An opposite trend was observed with a significant increase after calving in the: mean serum levels of β-hydroxybutyrate (P < 0.05), urea (P < 0.01), and mean AST activities (P < 0.05). A significant increase over the normal range was recorded in the average levels of non-esterified fatty acids (P < 0.01) and total bilirubin (P < 0.01). From the next sampling (28 days after calving) onwards we recorded a significant increase in the blood serum levels of cholesterol (P < 0.01), total lipids (P < 0.01), total protein (P < 0.01), as well as a significant decrease in the insulin levels (P < 0.05) and a reduced layer of subcutaneous fat (P < 0.01). The blood serum iodine concentration showed only slight significant changes (P < 0.05) during the observation. Blood serum levels of glucose did not show any significant changes during the whole observation period. Within the whole observation period we found a negative correlation between T3 levels and the layer of subcutaneous fat (r = −0.2606; P < 0.05). This correlation was much more marked in cows 3 to 14 days after calving (r = −0.5077; P < 0.05), which may indicate a possible relationships between the thyroid status, body condition, and post partum negative energy balance.

Muscle-specific metabolic, histochemical and biochemical responses to a nutritionally induced discontinuous growth path

An experiment was conducted with 42 Montbéliard steers to determine if nutritionally induced interrupted growth could influence muscle characteristics of steers and hence meat quality. A restriction/refeeding path was designed in order to induce a discontinuous growth path. At 9 months of age, 21 steers were given a restricted amount of diet for 3 months and were then slaughtered (R steers; no. = 10; intake: 5·28 kg dry matter (DM) per day) or subjected to a 4-month ad libitum refeeding period (R/F steers; no. = 11; intake: 8·99 kg DM per day) with the same diet (11·03 to 11·12 MJ metabolizable energy (ME) per kg DM) prior to slaughter. An additional 21 control steers were offered the same diet but in amounts that allowed them to gain continuously between 9 and 12 months of age, and were then slaughtered (C steers; no. = 10; intake: 7·08 kg DM per day) or maintained on a continuous feeding protocol through to 16 months of age prior to slaughter (C/C steers; no. = 11; intake: 8·07 kg DM per day). M. semitendinosus (ST), m. longisssimus thoracis and m. triceps brachii (TB) were collected for biochemical and histochemical analyses. R steers had a lower average daily gain (ADG; P 0·001), a lower final weight (P 0·01) and a leaner carcass (P 0·01) than C steers. Upon refeeding, R/F steers had a higher ADG than C/C steers (P 0·05) and underwent compensatory growth resulting in compensation of body weight and composition at 16 months. In muscles, glycolytic lactate dehydrogenase activity was lower in R steers (P 0·01) and restored in R/F steers compared with control steers. Among oxidative enzymes, cytochrome-c oxidase activity was higher in the TB of R/F compared with C/C steers (P 0·001) indicating a muscle-specific metabolic adaptation to the feeding level. There was little effect of the nutritional treatment on muscle fibre size and type except for an increase in the frequency of hybrid fibres in R and R/F groups (P 0·05). Total and insoluble collagen content were affected by restriction (P 0·001) in a muscle-specific manner: insoluble collagen content was lower in ST, but total and insoluble collagen contents were higher in TB of R compared with C animals at 12 months of age. No differences were recorded in lipid contents nor in proteasome activities. The data suggest that an alternation of relatively mild nutritional restriction and ad libitumfeeding had only a small effect on muscle characteristics. However, muscles respond differentially to changes in feeding level.

Different modes of food restriction and compensatory growth in double-muscled Belgian Blue bulls: plasma metabolites and hormones

The effects of different sequences of food restriction and fattening have been studied on plasma metabolites and hormones in double-muscled Belgian Blue bulls. Twenty animals were divided into five groups. The first group (control, CG) was given,ad libitum, a fattening diet based on sugar-beet pulp. In G2 and G3, fattening was interrupted after 103 and 187 days, respectively, by a period of food restriction lasting about 2 months during which the animals received a maintenance ration. They were finished with the same diet as CG. The last two groups, G4 and G5, received a limited amount of the restriction diet to support 0·5 and 0 kg gain per day, respectively, for 4 months, before being fattened as CG. Plasma glucose, alpha-amino nitrogen, non-esterified fatty acids, urea, creatinine, thyroxine (T4), 3, 3’, 5’-tri-iodothyroxine (T3), and insulin-like growth factor-1 (IGF-1) were measured in blood samples taken every 2 weeks. Plasma GH and insulin profiles were measured in serial blood samples obtained at three different times during growth. Animals that showed compensatory growth had lower plasma urea, associated with high levels of T3, T4 and IGF–1. Animals from G2 and G3 failed to show compensatory growth. In Belgian Blue bulls, compensatory growth is markedly affected when food restriction is severe or fattening interrupted.

Effects of vitamin A deficiency on growth hormone secretion and circulating insulin-like growth factor-1 concentration in Japanese Black steers

The objectives of this study were to investigate the effects of vitamin A (retinol) on growth hormone (GH) secretion and circulating insulin-like growth factor-1 (IGF-1) concentration in Japanese Black steers. Thirteen 10-month-old Japanese Black steers were divided into two groups: high vitamin A (H) group and low vitamin A (L) group. The animals in the H group were injected with 20 ml retinol palmitate (303 mg as retinol) intramuscularly every month throughout the experimental period. The steers in the L group were injected with vitamin A similarly at the age of 10 to 14 months. All steers were given vitamin A with the food (approx. 100 μg as retinol per kg diet) at the age of 21 to 30 months to prevent clinical vitamin A deficiency. Blood samples for analyses of vitamin A and IGF-1 were collected every 2 months. Series of blood samples for analyses of GH were collected at 15-min intervals over a 6-h period from each animal at the age of 10, 20, and 30 months. Although there was no difference in food intake between the two groups (P > 0·05), the average daily gain of the H group was greater (P < 0·001) than that of the L group. The carcass weight and subcutaneous fat thickness of the H group were significantly greater (P < 0·05) than those of the L group. The longissimus muscle area (P < 0·01) and marbling score (P < 0·001) of the L group were significantly greater than those of the H group. The serum retinol concentrations of the L group were significantly lower (P < 0·01) than those of the H group from the age of 16 months. The serum IGF-1 concentrations of the L group gradually decreased and were significantly lower (P < 0·01) than those of the H group from the age of 18 months. The overall mean concentration, peak height, area under the curve, and nadir of GH in both groups decreased with age. However, there were no significant differences (P > 0·05) in overall mean GH concentration, peak number, peak height, area under the curve, or nadir between the two groups. These results indicate that vitamin A affects the IGF-1 levels, with little or no intermediary effect on GH.

The effect of red clover formononetin content on live-weight gain, carcass characteristics and muscle equol content of finishing lambs

To investigate the effect of red clover formononetin concentration on lamb growth rate and carcass characteristics, 20 lambs (10 ewe lambs and 10 wethers) were grazed on each of three forages : red clover with a high formononetin concentration (HF), red clover with a low formononetin concentration (LF) and a control perennial ryegrass. Animals were finished at condition score 3L, at which point half of all animals were slaughtered immediately, while the other half of the animals were moved to a common ryegrass plot for 3 weeks as a 'withdrawal' period. Mean formononetin concentrations were 0-0, 4-7 and 3-3 g/kg dry matter (DM) for grass, HF and LF swards respectively. The clover swards had higher crude protein concentrations and lower fibre and water-soluble carbohydrate concentrations than the control ryegrass sward. Lambs grazing the HF clover gained 40 g/day live weight more (P < 0-1) than lambs on the other two forages without an increase in forage DM intake as estimated using the nalkane technique. There was no difference in the empty body weight, killing-out proportion, carcass fat class or condition score between animals finished on any of the three forages. Following the 3-week withdrawal period on ryegrass, there were significant residual effects of previous grazed forage on carcass weight, with HF lambs producing heavier carcasses than other lambs. Plasma concentrations of growth hormone and insulin-like growth factor-1 were highest in lambs grazing the HF clover, and suggest a physiological mechanism for the increased growth rates of these animals. There were no differences in the equol contents of the meat of lambs finished on the clover, compared with animals finished on grass, suggesting that there would be no implications for human health following consumption of meat produced from lambs grazing red clover, even with a relatively high concentration of formo'nonetin.

Role of G protein-coupled receptors (GPCR), matrix metalloproteinases 2 and 9 (MMP2 and MMP9), heparin-binding epidermal growth factor-like growth factor (hbEGF), epidermal growth factor receptor (EGFR), erbB2, and insulin-like growth factor 1 receptor (IGF-1R) in trenbolone acetate-stimulated bovine satellite cell proliferation

Implanting cattle with steroids significantly enhances feed efficiency, rate of gain, and muscle growth. However, the mechanisms responsible for these improvements in muscle growth have not been fully elucidated. Trenbolone acetate (TBA), a testosterone analog, has been shown to increase proliferation rate in bovine satellite cell (BSC) cultures. The classical genomic actions of testosterone have been well characterized; however, our results indicate that TBA may also initiate a quicker, nongenomic response that involves activation of G protein-coupled receptors (GPCR) resulting in activation of matrix metalloproteinases 2 and 9 (MMP2 and MMP9) that release membrane-bound heparin-binding epidermal growth factor-like growth factor (hbEGF), which then binds to and activates the epidermal growth factor receptor (EGFR) and/or erbB2. Furthermore, the EGFR has been shown to regulate expression of the IGF-1 receptor (IGF-1R), which is well known for its role in modulating muscle growth. To determine whether this nongenomic pathway is potentially involved in TBA-stimulated BSC proliferation, we analyzed the effects of treating BSC with guanosine 5'-O-2-thiodiphosphate (GDPβS), an inhibitor of all GPCR; a MMP2 and MMP9 inhibitor (MMPI); CRM19, a specific inhibitor of hbEGF; AG1478, a specific EGFR tyrosine kinase inhibitor; AG879, a specific erbB2 kinase inhibitor; and AG1024, an IGF-1R tyrosine kinase inhibitor on TBA-stimulated proliferation rate (H-thymidine incorporation). Assays were replicated at least 9 times for each inhibitor experiment using BSC cultures obtained from at least 3 different animals. Bovine satellite cell cultures were obtained from yearling steers that had no previous exposure to androgenic or estrogenic compounds. As expected, BSC cultures treated with 10 n TBA showed ( < 0.05) increased proliferation rate when compared with control cultures. Additionally, treatment with 5 ng hbEGF/mL stimulated proliferation in BSC cultures ( < 0.05). Treatment with GDPβS, MMPI, CRM197, AG1024, AG1478, and/or AG879 all suppressed ( < 0.05) TBA-induced increases in proliferation. These data indicate that TBA likely initiates a nongenomic response involving GPCR, MMP2 and MMP9, hbEGF, EGFR, erbB2, and IGF-1R, which may play a role in TBA-mediated increases in BSC proliferation.

Effect of dietary restriction and subsequent re-alimentation on the transcriptional profile of hepatic tissue in cattle

Background

Compensatory growth (CG) is an accelerated growth phenomenon observed in animals upon re-alimentation following a period of dietary restriction. It is typically utilised in livestock systems to reduce feed costs during periods of reduced feed availability. The biochemical mechanisms controlling this phenomenon, however, are yet to be elucidated. This study aimed to uncover the molecular mechanisms regulating the hepatic expression of CG in cattle, utilising RNAseq. RNAseq was performed on hepatic tissue of bulls following 125 days of dietary restriction (RES) and again following 55 days of subsequent re-alimentation during which the animals exhibited significant CG. The data were compared with those of control animals offered the same diet on an ad libitum basis throughout (ADLIB). Elucidation of the molecular control of CG may yield critical information on genes and pathways which could be targeted as putative molecular biomarkers for the selection of animals with improved CG potential.

Results

Following a period of differential feeding, body-weight and liver weight were 161 and 4 kg higher, respectively, for ADLIB compared with RES animals. At this time RNAseq analysis of liver tissue revealed 1352 significantly differentially expressed genes (DEG) between the two treatments. DEGs indicated down-regulation of processes including nutrient transport, cell division and proliferation in RES. In addition, protein synthesis genes were up-regulated in RES following a period of restricted feeding. The subsequent 55 days of ad libitum feeding for both groups resulted in the body-weight difference reduced to 84 kg, with no difference in liver weight between treatment groups. At the end of 55 days of unrestricted feeding, 49 genes were differentially expressed between animals undergoing CG and their continuously fed counterparts. In particular, hepatic expression of cell proliferation and growth genes were greater in animals undergoing CG.

Conclusions

Greater expression of cell cycle and cell proliferation genes during CG was associated with a 100 % recovery of liver weight during re-alimentation. Additionally, an apparent up-regulation in capacity for cellular protein synthesis during restricted feeding may contribute to and sustain CG during re-alimentation. DEGs identified are potential candidate genes for the identification of biomarkers for CG, which may be incorporated into future breeding programmes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2578-5) contains supplementary material, which is available to authorized users.

Effect of Dietary Restriction and Subsequent Re-Alimentation on the Transcriptional Profile of Bovine Skeletal Muscle

Compensatory growth (CG), an accelerated growth phenomenon which occurs following a period of dietary restriction is exploited worldwide in animal production systems as a method to lower feed costs. However the molecular mechanisms regulated CG expression remain to be elucidated fully. This study aimed to uncover the underlying biology regulating CG in cattle, through an examination of skeletal muscle transcriptional profiles utilising next generation mRNA sequencing technology. Twenty Holstein Friesian bulls were fed either a restricted diet for 125 days, with a target growth rate of 0.6 kg/day (Period 1), following which they were allowed feed ad libitum for a further 55 days (Period 2) or fed ad libitum for the entirety of the trial. M. longissimus dorsi biopsies were harvested from all bulls on days 120 and 15 of periods 1 and 2 respectively and RNAseq analysis was performed. During re-alimentation in Period 2, previously restricted animals displayed CG, growing at 1.8 times the rate of the ad libitum control animals. Compensating animals were also more feed efficient during re-alimentation and compensated for 48% of their previous dietary restriction. 1,430 and 940 genes were identified as significantly differentially expressed (Benjamini Hochberg adjusted P < 0.1) in periods 1 and 2 respectively. Additionally, 2,237 genes were differentially expressed in animals undergoing CG relative to dietary restriction. Dietary restriction in Period 1 was associated with altered expression of genes involved in lipid metabolism and energy production. CG expression in Period 2 occurred in association with greater expression of genes involved in cellular function and organisation. This study highlights some of the molecular mechanisms regulating CG in cattle. Differentially expressed genes identified are potential candidate genes for the identification of biomarkers for CG and feed efficiency, which may be incorporated into future breeding programmes.

Effects of Dietary Restriction on the Expression of Lipid Metabolism and Growth Hormone Signaling Genes in the Longissimus dorsi Muscle of Korean Cattle Steers

This study determined the effects of dietary restriction on growth and the expression of lipid metabolism and growth hormone signaling genes in the longissimus dorsi muscle (LM) of Korean cattle. Thirty-one Korean cattle steers (average age 10.5 months) were allocated to normal (N; n = 16) or dietary restriction (DR; n = 15) groups. The feeding trial consisted of two stages: for the 8-month growing period, the DR group was fed 80% of the food intake of the normal diet, and for the 6-month growth-finishing period, the DR group was fed a DR total mixed ration with 78.4% of the crude protein and 64% of the net energy for gain of the normal diet. The LM was biopsied 5 months (period 1 [P1] at 15.5 months of age) and 14 months (period 2 [P2] at 24.5 months of age) after the start of feeding. The mRNA levels were determined using real-time polymerase chain reaction. Body weight, daily feed intake, average daily gain, and feed efficiency were lower in the DR group compared with the normal group at both P1 and P2. At P1, the lipogenic fatty acid synthase (FASN) mRNA levels were lower (p<0.05) in the DR group compared with the normal group. The DR group tended (p = 0.06) to have higher of levels of growth hormone receptor (GHR) mRNA than the normal group. At P2, the DR group tended to have lower (p = 0.06) androgen receptor (AR) mRNA levels than the normal group. In conclusion, our results demonstrate that dietary restriction partially decreases the transcription of lipogenic FASN and growth hormone signaling AR genes, but increases transcription of the GHR gene. These changes in gene transcription might affect body fat accumulation and the growth of the animals.

Insulin secretion and signaling in response to dietary restriction and subsequent re-alimentation in cattle

The objectives of this study were to examine systemic insulin response to a glucose tolerance test (GTT) and transcript abundance of genes of the insulin signaling pathway in skeletal muscle, during both dietary restriction and re-alimentation-induced compensatory growth. Holstein Friesian bulls were blocked to one of two groups: 1) restricted feed allowance for 125 days (period 1) (RES, n = 15) followed by ad libitum feeding for 55 days (period 2) or 2) ad libitum access to feed throughout (periods 1 and 2) (ADLIB, n = 15). On days 90 and 36 of periods 1 and 2, respectively, a GTT was performed. M. longissimus dorsi biopsies were harvested from all bulls on days 120 and 15 of periods 1 and 2, respectively, and RNA-Seq analysis was performed. RES displayed a lower growth rate during period 1 (RES: 0.6 kg/day, ADLIB: 1.9 kg/day; P < 0.001), subsequently gaining more during re-alimentation (RES: 2.5 kg/day, ADLIB: 1.4 kg/day; P < 0.001). Systemic insulin response to glucose administration was lower in RES in period 1 (P < 0.001) with no difference observed during period 2. The insulin signaling pathway in M. longissimus dorsi was enriched (P < 0.05) in response to dietary restriction but not during re-alimentation (P > 0.05). Genes differentially expressed in the insulin signaling pathway suggested a greater sensitivity to insulin in skeletal muscle, with pleiotropic effects of insulin signaling interrupted during dietary restriction. Collectively, these results indicate increased sensitivity to glucose clearance and skeletal muscle insulin signaling during dietary restriction; however, no overall role for insulin was apparent in expressing compensatory growth.

Restricted nutrient intake does not alter serum-mediated measures of implant response in cell culture

Background

During nutritional stress, reduced intake may reduce the efficacy of anabolic implants. This study was conducted to evaluate basic cellular responses to a growth promotant implant at two intake levels.

Methods

Sixteen crossbred steers (293 ± 19.3 kg) were used to evaluate the impact of anabolic implants in either an adequate or a restricted nutritional state. Steers were trained to individual Calan gates, and then randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement. Treatments consisted of: presence or absence of an anabolic growth implant (Revalor-XS, 200 mg TBA and 40 mg estradiol; IMPLANT or CONTROL) and a moderate energy, pelleted, starting cattle diet fed at either 2.0 × or 1.0 × maintenance energy (NE_M) requirements (HIGH or LOW). Serum (d 0, 14, and 28) was used for application to bovine muscle satellite cells. After treatment with the serum (20% of total media) from the trial cattle, the satellite cells were incubated for 72 h. Protein abundance of myosin heavy chain (MHC), phosphorylated extracellular signal-related kinase (phospho-ERK), and phosphorylated mammalian target of rapamycin (phospho-mTOR) were analyzed to determine the effects of implant, intake, and their interaction (applied via the serum).

Results

Intake had no effect on MHC (P = 0.85) but IMPLANT increased (P < 0.01) MHC abundance vs. CONTROL. Implant status, intake status, and the interaction had no effect on the abundance of phospho-ERK (P ≥ 0.23). Implanting increased phospho-mTOR (P < 0.01) but there was no effect (P ≥ 0.51) of intake or intake × implant.

Conclusions

The nearly complete lack of interaction between implant and nutritional status indicates that the signaling molecules measured herein respond to implants and nutritional status independently. Furthermore, results suggest that the muscle hypertrophic effects of anabolic implants may not be mediated by circulating IGF-1.

Efeito do regime alimentar sobre o perfil metabólico de ovinos Santa Inês em confinamento

Avaliou-se o perfil metabólico de 40 ovinos Santa Inês, inteiros, com peso vivo médio inicial de 17±1,7kg,, submetidos à restrição alimentar seguida de realimentação em confinamento, distribuídos em quatro tratamentos: 0, 20, 40 e 60% de restrição alimentar. Dois ensaios foram desenvolvidos, um referente à restrição e outro à realimentação. Para tanto, foi utilizado delineamento experimental inteiramente ao acaso, com quatro tratamentos e 10 repetições, e distribuído em fatorial cruzado 4x3. Observou-se na fase de restrição que os níveis de fósforo foram mais altos nos animais sob restrição alimentar; o mesmo ocorrendo na fase final para as concentrações de proteínas totais (PT), albumina (Alb) e colesterol total. A gama-glutamiltransferase (GGT) decresceu de forma linear com o aumento da restrição. No segundo ensaio, verificou-se que as concentrações de PT, Alb, globulina, colesterol total, lipoproteína de alta densidade, GGT e magnésio (Mg) apresentaram diferença (P<0,05) entre os períodos de coleta. Já na restrição prévia, observou-se comportamento linear decrescente para GGT e interação tratamento versus período de coleta para a concentração de cálcio. Os níveis de restrição alimentar afetaram o metabolismo proteico e não interferiram no metabolismo energético, e a realimentação resultou em alteração no metabolismo proteico, energético e mineral.

Iodine supplementation to a diet containing Leucaena leucocephala leaf meal: consequences on nutrient metabolism, clinical chemistry and immunity of goats

The present study was aimed at investigating the metabolic effects of iodine supplementation in goats when fed on a diet containing Leucaena leucocephala, intended to create mild iodine deficiency. Two groups of indigenous adult goats were fed on a leucaena leaf meal-based diet without (CON) or with 0.1 mg iodine per day per animal (EXP) for a period of 180 days. Dry matter intake and dry matter digestibility were higher (P < 0.05) in the EXP group. The retention of nitrogen and phosphorus was higher (P < 0.05) in the EXP group. Retention of calcium was also higher (P = 0.082) in the EXP group. The net loss of bodyweight in the CON group (−1.21 kg) was reversed in EXP goats, which showed a net gain (+1.79 kg). The serum metabolic profile reflected a positive influence of iodine supplementation, which also induced greater (P < 0.001) circulating thyroxine concentration. The cell-mediated immune response was higher (P < 0.05) in the EXP group, whereas humoral immunity remained unaltered. The results suggested that supplementation with extra iodine could be used as an effective strategy to counteract functional disorders of the thyroid and associated adverse effects induced in goats by feeding of leucaena leaf meal.

Effect of trenbolone acetate on protein synthesis and degradation rates in fused bovine satellite cell cultures

Although androgenic and estrogenic steroids are widely used to enhance muscle growth and increase feed efficiency in feedlot cattle, their mechanism of action is not well understood. Although in vivo studies have indicated that androgens affect protein synthesis and protein degradation rate in muscle, results from in vitro studies have been inconsistent. We have examined the effects of trenbolone acetate (TBA), a synthetic androgen, on protein synthesis and degradation rates in fused bovine satellite cell (BSC) cultures. Additionally, we have examined the effects of compounds that interfere with binding of TBA or insulin-like growth factor-1 (IGF-1) to their respective receptors on TBA-induced alterations in protein synthesis and degradation rates in BSC cultures. Treatment of fused BSC cultures with TBA results in a concentration-dependent increase (P < 0.05) in protein synthesis rate and a decrease (P < 0.05) in degradation rate, establishing that TBA directly affects these parameters. Flutamide, a compound that prevents androgen binding to the androgen receptor, suppresses (P < 0.05) TBA-induced alterations in protein synthesis and degradation in fused BSC cultures, indicating the androgen receptor is involved. JB1, a competitive inhibitor of IGF-1 binding to the type 1 IGF receptor (IGF1R), suppresses (P < 0.05) TBA-induced alterations in protein synthesis and degradation, indicating that this receptor also is involved in the actions of TBA on both synthesis and degradation. In summary, our data show that TBA acts directly to alter both protein synthesis and degradation rates in fused BSC cultures via mechanisms involving both the androgen receptor and IGF1R.

Effect of Estradiol-17beta on protein synthesis and degradation rates in fused bovine satellite cell cultures

Although androgenic and estrogenic steroids are widely used to enhance muscle growth and increase feed efficiency in feedlot cattle, their mechanism of action is not well understood. Further, in vivo studies indicate that estradiol (E2) affects muscle protein synthesis and/or degradation, but in vitro results are inconsistent. We have examined the effects of E2 treatment on protein synthesis and degradation rates in fused bovine satellite cell (BSC) cultures. Additionally, to learn more about the mechanisms involved in E2-enhanced muscle growth, we have examined the effects of compounds that interfere with binding of E2 or insulin-like growth factor (IGF)-1 to their respective receptors on E2-induced alterations in protein synthesis and degradation rates in BSC cultures. Treatment of fused BSC cultures with E2 results in a concentration-dependent increase (P < 0.05) in protein synthesis rate and a decrease (P < 0.05) in protein degradation rate. The pure estrogen antagonist ICI 182 780 suppresses (P < 0.05) E2-induced alterations in protein synthesis and degradation in fused BSC cultures. The G-protein coupled receptor (GPR)-30 agonist G1 does not affect either synthesis or degradation rate, which establishes that GPR30 does not play a role in E2-induced alterations in protein synthesis or degradation. JB1, a competitive inhibitor of IGF-1 binding to the Type 1 insulin-like growth factor receptor (IGFR-1), suppresses (P < 0.05) E2-induced alterations in protein synthesis and degradation. In summary, our data show that E2 treatment directly alters both protein synthesis and degradation rates in fused BSC cultures via mechanisms involving both the classical estrogen receptor (ER) and IGFR-1.

A spline polynomial model to describe serum IGF-I concentration from birth to slaughter in calves: effects of weaning age, pre-weaning concentrate feeding and breed

The statistical analysis of hormones sampled throughout the production cycle is complicated because factors such as age and weight at the measuring date interfere. Spline curves constructed from pieces of low-degree, random-effects polynomials could be used for a more accurate analysis of data. Concentration of insulin-like growth factor-1 (IGF-1), weight gain, and concentrate intake of Parda de Montaña (PM) (n=27) and Pirenaica calves (n=14) were modeled with a spline model according to age at weaning, pre-weaning concentrate feeding, and breed. At birth, calves were randomly assigned to early weaning (EW) at 90 d or traditional weaning (TW) at 150 d. During lactation, half of PM calves received concentrates (S), whereas the remainder received no concentrates (NS). After weaning, calves received concentrates on an ad libitum basis until they reached a weight of 450 kg. The spline model had better likelihood than a polynomial of 6 degrees or a split-plot model. Serum IGF-1 concentration was greatly affected by age at weaning and pre-weaning concentrate feeding, but not by breed. In NS calves, IGF-1 concentration was greater in EW than in TW calves from 120 to 300 d, irrespective of breed. During lactation, S calves had greater IGF-1 concentration than NS calves. After weaning, EWNS calves reached the IGF-1 concentration of EWS calves after 4 mo on concentrates, whereas TWNS calves attained IGF-1 concentration of TWS calves after only 2 mo, because of their increased concentrate intake relative to TWS calves. Concentration of IGF-1 was positively correlated with the immediate weight gains and intake, but it was not a good predictor of performance in the long term.

Roles of IGF-I and the estrogen, androgen and IGF-I receptors in estradiol-17beta- and trenbolone acetate-stimulated proliferation of cultured bovine satellite cells

Although numerous studies have shown that both androgenic and estrogenic steroids increase rate and efficiency of muscle growth in steers, there is little consensus as to their mechanism of action. A combined estradiol 17beta (E2)/trenbolone acetate (TBA) implant causes a significant increase in muscle IGF-I mRNA and both E2 and TBA stimulate a significant increase in IGF-I mRNA level in bovine satellite cell (BSC) cultures in media containing 10% fetal bovine serum (FBS). Consequently, increased IGF-I expression may play a role in anabolic-steroid-enhanced muscle growth. However, even though treatment of cultured BSC with E2 or TBA in media containing 1% IGFBP-3-free swine serum (SS) results in increased proliferation there is no effect on IGF-I mRNA expression, suggesting that increased IGF-I expression may not be responsible for anabolic-steroid-enhanced BSC proliferation. To further examine the role of estrogen, androgen and IGF-I receptors and their respective ligands in E2- and TBA-stimulated BSC proliferation, we assessed the effects of specific inhibitors on E2- or TBA-stimulated proliferation of BSC. Both ICI 182 780 (an estrogen receptor blocker) and flutamide (an inhibitor of androgen receptor) suppressed (p<0.05) E2- and TBA-stimulated BSC proliferation, respectively. JB1 (a competitive inhibitor of IGF-I binding to type I IGF receptor) reduced (p<0.05) both E2- and TBA-stimulated proliferation in BSC cultures. Both the Raf-1/MAPK kinase (MEK)1/2/ERK1/2, and the phosphatidylinositol 3-kinase (PI3K)/Akt pathways play significant roles in the actions of IGF-I on proliferation and differentiation of myogenic cells. PD98059, an inhibitor of the MAPK pathway, and wortmannin, an inhibitor of the PI3K pathway, both suppressed (p<0.05) E2- and TBA-stimulated proliferation of cultured BSC. Our data suggest that IGF-I plays a role in E2- and TBA-stimulated proliferation of cultured BSC even in the absence of increased IGF-I expression.

Cellular and molecular regulation of muscle growth and development in meat animals1,2

Although in vivo and in vitro studies have established that anabolic steroids, transforming growth factor-beta (TGF-beta), and myostatin affect muscle growth in meat-producing animals, their mechanisms of action are not completely understood. Anabolic steroids have been widely used as growth promoters in feedlot cattle for over 50 yr. A growing body of evidence suggests that increased muscle levels of IGF-I and increased muscle satellite cell numbers play a role in anabolic steroid enhanced muscle growth. In contrast to anabolic steroids, the members of the TGF-beta-myostatin family suppress muscle growth in vivo and suppress both proliferation and differentiation of cultured myogenic cells. Recent evidence suggests that IGFBP-3 and IGFBP-5 play a role in mediating the proliferation-suppressing actions of both TGF-beta and myostatin on cultured myogenic cells. Consequently, this review will focus on the roles of IGF-I and IGFBP in the cellular and molecular mechanisms of action of anabolic steroids and TGF-beta and myostatin, respectively.

Polymorphisms and haplotypes in the bovine neuropeptide Y, growth hormone receptor, ghrelin, insulin-like growth factor 2, and uncoupling proteins 2 and 3 genes and their associations with measures of growth, performance, feed efficiency, and carcass merit in beef cattle1

Genes that regulate metabolism and energy partitioning have the potential to influence economically important traits in farm animals, as do polymorphisms within these genes. In the current study, SNP in the bovine neuropeptide Y (NPY), growth hormone receptor (GHR), ghrelin (GHRL), uncoupling proteins 2 and 3 (UCP2 and UCP3), IGF2, corticotrophin-releasing hormone (CRH), cocaine and amphetamine regulated transcript (CART), melanocortin-4 receptor (MC4R), proopiomelanocortin (POMC), and GH genes were evaluated for associations with growth, feed efficiency, and carcass merit in beef steers. In total, 24 SNP were evaluated for associations with these traits and haplotypes were constructed within each gene when 2 or more SNP showed significant associations. An A/G SNP located in intron 4 of the GHR gene had the largest effects on BW of the animals (dominance effect P < 0.01) and feed efficiency (allele substitution effect P < 0.05). Another A/G SNP located in the promoter region of GHR had similar effects but the haplotypes of these 2 SNP reduced the effects of the SNP located in intron 4. Three SNP in the NPY gene showed associations to marbling (P < 0.001) as well as with ADG, BW, and feed conversion ratio (FCR; P < 0.05). The combination of these 3 SNP into haplotypes generally improved the association or had a similar scale of association as each single SNP. Only 1 SNP in UCP3, an A/G SNP in intron 3, was associated with ADG (P = 0.025), partial efficiency of growth, and FCR (P < 0.01). Three SNP in UCP2 gene were in almost complete linkage disequilibrium and showed associations with lean meat yield, yield grade, DMI, and BW (P < 0.05). Haplo-types between the SNP in UCP3 and UCP2 generally reduced the associations seen individually in each SNP. An A/G SNP in the GHRL gene tended to show effects on residual feed intake, FCR, and partial efficiency of growth (P < 0.10). The IGF2 SNP most strongly affected LM area (P < 0.01), back fat, ADG, and FCR (P < 0.05). The SNP in the CART, MC4R, POMC, GH, and CRH genes did not show associations at P < 0.05 with any of the traits. Although most of the SNP that showed associations do not cause amino acid changes, these SNP could be linked to other yet to be detected causative mutations or nearby QTL. It will be very important to verify these results in other cattle populations.