Evaluation of vitamin A status on myogenic gene expression and muscle fiber characteristics.

A randomized complete block design experiment with 30 yearling crossbred steers (average BW = 436.3 ± 39.8 kg) fed a steam-flaked corn-based diet was used to evaluate the effects dietary vitamin A (Rovimix A 1000; DSM Nutritional Products Ltd., Sisseln, SUI) supplementation on myogenic gene expression and skeletal muscle fiber characteristics during the finishing phase. Steers were blocked by BW (n = 5 blocks; 6 steers/block), randomly assigned to pens (n = 2 steers/pen), and one of the following treatments: no added vitamin A (0 IU; 0.0 IU/kg of dietary dry matter intake of additional vitamin A), vitamin A supplemented at the estimated requirement (2,200 IU; 2,200 IU/kg of dietary dry matter (DM) of additional vitamin A), and vitamin A supplemented at 5× the estimated requirement (11,000 IU; 11,000 IU/kg of dietary DM of additional vitamin A). After all treatments underwent a 91-d vitamin A depletion period, additional vitamin A was top-dressed at feeding via a ground corn carrier. Blood, longissimus muscle, and liver biopsy samples were obtained on days 0, 28, 56, 84, and 112. Biopsy samples were used for immunohistochemical and mRNA analysis. Sera and liver samples were used to monitor circulating vitamin A and true vitamin A status of the cattle. Expression for myosin heavy chain (MHC)-I diminished and rebounded (P = 0.04) over time. The intermediate fiber type, MHC-IIA, had a similar pattern of expression (P = 0.01) to that of MHC-I. On day 84, C/EBPß expression was also the greatest (P = 0.03). The pattern of PPARγ (P < 0.01) and PPARδ (P < 0.01) expression seemed to mimic that of MHC-I expression, increasing from days 84 to 112. Distribution of MHC-IIA demonstrated a change over time (P = 0.02). Muscle fiber cross-sectional area increased by day (P < 0.01) for each MHC with the notable increase between days 0 and 56. Total nuclei density decreased (P = 0.02) over time. Cells positive for only Myf5 increased (P < 0.01) in density early in the feeding period, then declined, indicating that satellite cells were fusing into fibers. The dual-positive (PAX7+Myf5) nuclei also peaked (P < 0.01) around day 56 then declined. These data indicated that gene expression associated with oxidative proteins may be independent of vitamin A status in yearling cattle.

Calcium salts of fatty acids with varying fatty acid profiles in diets of feedlot-finished Bos indicus bulls: impacts on intake, digestibility, performance, and carcass and meat characteristics.

We hypothesized that the inclusion of calcium salts of fatty acid (CSFA) into the diets and the fatty acid (FA) profile of the supplements would impact performance and meat characteristics of Bos indicus bulls. Hence, the objective was to evaluate the effects of CSFA profiles on intake, body weight (BW), carcass, and meat characteristics of feedlot-finished B indicus bulls. Fifty-three Nellore bulls [initial BW 315 ± 5.9 kg and 20 ± 2 mo] were used. At the beginning, 6 bulls were randomly chosen and slaughtered for determination of their BW composition, and the remaining 47 bulls were evaluated during a 140-d experimental period. The bulls were placed in individual pens, blocked according to initial BW and randomly allocated to 1 of the 3 following treatments: (1) control diet containing sugarcane bagasse, ground corn, citrus pulp, peanut meal, and mineral-vitamin mix (CON), (2) CON with the addition of 3.3% of CSFA from soybean oil (CSO), or (3) CON with the addition of a mixture of 3.3% of CSFA from palm, soybean, and cottonseed oils (CPSCO). Diets were offered ad libitum and formulated to be isonitrogenous. Bulls supplemented with CSFA had a greater (P < 0.01) final BW, dry matter intake, average daily gain (ADG), feed efficiency (FE), and FA intake vs. CON. Among carcass parameters, CSFA-supplemented bulls had greater (P < 0.01) carcass ether extract concentration vs. CON bulls. When the CSFA profile was evaluated (CSO vs. CPSCO), CPSCO bulls had a better (P ≤ 0.03) FE, carcass ADG, and hot carcass weight (HCW) vs. CSO bulls. The FA intakes differed among CSFA treatments, as the total saturated, palmitic, and oleic FA intakes were greater for CPSCO (P < 0.01), whereas lower intakes of total unsaturated and polyunsaturated FA (P < 0.01) were observed for CPSCO vs. CSO. Samples from the Longissimus muscle contained greater palmitoleic (P = 0.01) and reduced linoleic (P = 0.02) FA concentrations in CSFA-supplemented bulls vs. CON bulls. In agreement with the FA intakes, CPSCO-supplemented bulls had a greater (P ≤ 0.05) unsaturated FA concentration vs. CSO in Longissimus muscle. In summary, CSFA supplementation improved the performance of finishing B. indicus bulls vs. CON. Moreover, the inclusion of CSFA from palm, soybean, and cottonseed oil benefited the FE, carcass ADG, and HCW compared with the inclusion of CSFA from soybean oil, demonstrating the potential of specific FA for improving the performance and meat quality of B. indicus bulls.

Chromium propionate supplementation alters animal growth performance, carcass characteristics, and skeletal muscle properties in feedlot steers.

The objective of this study was to evaluate the effects of increasing concentrations of Cr propionate (CrP) on feedlot performance, blood parameters, carcass characteristics, and skeletal muscle fiber properties in feedlot steers. Crossbred steers (n = 32; 367 ± 2.5 kg; 16 pens; 2 hd/pen) were blocked by body weight (BW), and treatment was randomly assigned to pen: (1) 0 mg added Cr/kg diet dry matter (DM) (control), (2) 0.15 mg added Cr/kg diet DM (CrP; KemTRACE Chromium 0.04%, Kemin Industries, Des Moines, IA), (3) 0.30 mg added Cr/kg diet DM, and (4) 0.45 mg added Cr/kg diet DM. Steers were fed ad libitum, and the treatment was top-dressed at the time of feeding. Body weights, blood samples, and longissimus biopsies were collected before feeding on days 0, 28, 56, 91, 119, and 147. Blood sera were harvested for analysis of glucose, insulin, sera urea nitrogen, and non-esterified fatty acid concentrations. Longissimus biopsies were collected for gene expression, protein expression, and immunohistochemical (IHC) analysis. Pen was the experimental unit for live and carcass data, and steer was the experimental unit with day as a repeated measure for sera and IHC analyses. For the entire duration of the trial, a linear increase in average daily gain (ADG) (P = 0.01) and improvement in G:F was observed (P = 0.01) with no change in DMI (P = 0.11) with increasing CrP. A linear increase in hot carcass weight (HCW) (P ≤ 0.01) with no other changes in carcass composition were noted (P ≥ 0.38) as the level of dietary CrP increased. There was no effect of treatment on any sera parameters measured (P ≥ 0.10). No difference was detected for gene or protein expression of glucose transporter type 4 (GLUT4) due to CrP supplementation (P ≥ 0.10). For skeletal muscle fiber distribution and cross-sectional area, there was no effect of treatment (P ≥ 0.10). Density of total GLUT4 did not change due to CrP (P ≥ 0.10). Internalization of GLUT4 was increased in the 0.30 and 0.45 mg/kg treatments (P < 0.01). For total nuclei density and myonuclei density, there were treatment × day interaction tendencies (P ≤ 0.08). Supplementation of CrP did not alter density of satellite cells (P ≥ 0.10). The number of transporters located in the sarcolemma of skeletal muscle fibers did decrease, implying fewer proteins were needed to transport extracellular glucose into the muscle fiber. Therefore, CrP may augment cellular function and growth via increased efficiency of GLUT4 function. These results indicated CrP increases BW, ADG, and HCW, without changes in circulating sera parameters or total GLUT4 expression.

Evaluation of the dietary vitamin A requirement of finishing steers via systematic depletion and repletion, and its effects on performance and carcass characteristics.

A randomized complete block design experiment with 30 yearling crossbred steers (initial average body weight [BW] = 297.6 ± 32.8 kg) fed a steam-flaked corn-based diet was used to evaluate finishing performance and carcass characteristics when provided with different concentrations of vitamin A (Rovimix A 1000; DSM Nutritional Products Ltd., Sisseln, Switzerland) subsequent to a depletion phase. Steers were blocked by BW (n = 5 blocks; 6 steers per block), assigned to pens (n = 2 steers per pen), and randomly assigned to one of the following dietary treatments: no added vitamin A (0IU; 0.0 IU/kg dry matter [DM] basis of additional vitamin A), vitamin A supplemented at the estimated National Academies of Sciences, Engineering, and Medicine (NASEM) requirement (2,200IU; 2,200 IU/kg of dietary DM of additional vitamin A), and vitamin A supplemented at 5× the estimated requirement (11,000IU; 11,000 IU/kg of dietary DM of additional vitamin A). The basal diet included minimal vitamin A activity (<200 IU of vitamin A activity/kg of dietary DM) via the provitamin A, beta-carotene. After all animals underwent a 91-d vitamin A depletion period, additional vitamin A was top-dressed at feeding via a ground corn carrier. Liver biopsy samples, BW, and blood were obtained on days -91, -35, 0, 28, 56, 84, and 112. Final BW was collected prior to shipping on day 112. Carcass data were collected by trained personnel upon harvest. Sera and liver samples were used to monitor circulating vitamin A and evaluate true vitamin A status of the cattle. Vitamin A status did not affect interim average daily gain or feed efficiency (G:F; P > 0.05). Throughout the duration of the study, dry matter intake for the 0IU cattle was depressed (P = 0.01). Differences were not observed across treatments for hot carcass weight, rib eye area, back fat thickness, kidney-pelvic-heart fat %, marbling score, or dressing percent (P ≥ 0.10). A treatment × day interaction occurred for both (P < 0.01) sera retinol and liver retinol during phase 2 of the trial. The treatments and sera retinol concentrations were incorporated into a repletion model, resulting in an estimation of liver retinol changes (P < 0.01; R2 = 0.682). However, models used to evaluate depleted animals were less effective. The current NASEM recommended that vitamin A requirement of 2,200 IU/kg is adequate for repletion of vitamin A status of feedlot steers.

Effects of zinc propionate supplementation on growth performance, skeletal muscle fiber, and receptor characteristics in beef steers.

A randomized complete block design experiment with 32 yearling crossbred steers (average body weight [BW] = 442 ± 17.0 kg) fed a steam-flaked corn-based diet was used to evaluate the effects of dietary Zn (KemTRACE Zn propionate 27; Kemin Industries, Inc., Des Moines, IA) supplementation on live growth performance, skeletal muscle fiber, and beta-adrenergic receptor (ß-AR) characteristics during the finishing phase. Steers were blocked by BW (n = 4 blocks; 8 steers/block), assigned to pens (n = 4 steers/pen), and randomly assigned to the following treatments: control (CON; 0.0 g/[head (hd) · d] of additional Zn) or additional dietary Zn (ZnP; 1.0 g/[hd · d] additional Zn). The basal diet contained Zn (60 ppm dry matter basis) from ZnSO4; additional Zn was top-dressed at feeding. Ractopamine hydrochloride (RH; Optaflexx: Elanco Animal Health, Greenfield, IN) was included at 300 mg/(hd · d) for the final 28 d of the 111-d feeding period. Longissimus muscle biopsy samples, BW, and blood were obtained on days 0, 42, 79, and 107. Final BW was collected prior to shipping on day 111. Biopsy samples were used for immunohistochemical (IHC), mRNA, and protein analysis. Serum urea nitrogen (SUN) and nonesterified fatty acid (NEFA) concentrations were measured. Steers fed ZnP had a greater average daily gain (P = 0.02) and gain to feed ratio (G:F; P = 0.03) during the RH feeding period compared with CON. There were no differences (P > 0.05) in other growth performance variables, carcass traits, mRNA abundance, or relative protein concentration for fiber type and ß-AR. Fiber types I and IIA had no differences in the cross-sectional area; however, the IIX area was greater for CON (P < 0.04) compared with ZnP and increased (P < 0.02) over time. There were no differences between treatments for the ß1-AR density (P > 0.05) in skeletal muscle tissue throughout the study. A treatment × day interaction was observed in ß2-AR density (P = 0.02) and ß3-AR density (P = 0.02) during the RH feeding period, where the abundance of the receptors increased with ZnP but did not change in CON. Compared with CON, ZnP had greater (P < 0.01) mean NEFA concentrations. Mean SUN concentrations did increase by day (P < 0.01). Additional dietary Zn, supplied as Zn propionate, upregulates ß2-AR and ß3-AR and improves growth performance in feedlot steers during the RH feeding period, likely through a shift of resource utilization from lipogenesis to muscle maintenance and hypertrophy.

Chromium acetate stimulates adipogenesis through regulation of gene expression and phosphorylation of adenosine monophosphate-activated protein kinase in bovine intramuscular or subcutaneous adipocytes.

OBJECTIVE: We hypothesized that Cr source can alter adipogenic-related transcriptional regulations and cell signaling. Therefore, the objective of the study was to evaluate the biological effects of chromium acetate (CrAc) on bovine intramuscular (IM) and subcutaneous (SC) adipose cells. METHODS: Bovine preadipocytes isolated from two different adipose tissue depots; IM and SC were used to evaluate the effect of CrAc treatment during differentiation on adipogenic gene expression. Adipocytes were incubated with various doses of CrAc: 0 (differentiation media only, control), 0.1, 1, and 10 µM. Cells were harvested and then analyzed by real-time quantitative polymerase chain reaction in order to measure the quantity of adenosine monophosphate-activated protein kinase-α (AMPK-α), CCAAT enhancer binding protein-ß (C/EBPß), G protein-coupled receptor 41 (GPR41), GPR43, peroxisome proliferator-activated receptor-γ (PPARγ), and stearoyl CoA desaturase (SCD) mRNA relative to ribosomal protein subunit 9 (RPS9). The ratio of phosphorylated-AMPK (pAMPK) to AMPK was determined using a western blot technique in order to determine changing concentration. RESULTS: The high dose (10 µM) of CrAc increased C/EBPß, in both IM (p = 0.02) and SC (p = 0.02). Expression of PPARγ was upregulated by 10 µM of CrAc in IM but not in SC. Expression of SCD was also increased in both IM and SC with 10 µM of CrAc treatment. Addition of CrAc did not alter gene expression of glucose transporter 4, GPR41, or GPR43 in both IM and SC adipocytes. Addition of CrAc, resulted in a decreased pAMPKα to AMPKα ration (p<0.01) in IM. CONCLUSION: These data may indicate that Cr source may influence lipid filling in IM adipocytes via inhibitory action of AMPK phosphorylation and upregulating expression of adipogenic genes.

Yeast cell wall supplementation alters the metabolic responses of crossbred heifers to an endotoxin challenge.

This study examined the effect of feeding yeast cell wall (YCW) products on the metabolic responses of newly-received feedlot cattle to an endotoxin challenge. Heifers were separated into treatment groups receiving either a Control diet, YCW-A or YCW-C, and were fed for 52 d. Heifers were weighed on d 0, 14, 36, 38 and 52. On d 37 heifers were challenged i.v. with LPS [0.5 µg/kg body weight (BW)] and blood samples were collected relative to LPS challenge. Heifer BW increased from d 0 to 36 and from d 38 to 52, but was not affected by treatment. Post-LPS, glucose concentrations increased and were less in YCW-A than Control and YCW-C heifers. Pre-LPS, insulin concentrations were greater in YCW-A and YCW-C than Control heifers. Post-LPS, insulin concentrations increased with YCW-C having greater insulin than Control heifers. Pre-LPS, NEFA concentrations tended to be less in YCW-C than Control heifers. Post-LPS non-esterified fatty acids (NEFA) concentrations were less in YCW-C than Control and YCW-A heifers. Post-LPS, blood urea nitrogen (BUN) concentrations were greater in YCW-A than Control and YCW-C. These data indicate, based on NEFA and BUN data, that certain YCW products can enhance energy metabolism during an immune challenge without causing lipolysis or muscle catabolism.

Yeast cell wall supplementation alters aspects of the physiological and acute phase responses of crossbred heifers to an endotoxin challenge.

A study was conducted to determine the effect of feeding yeast cell wall (YCW) products on the physiological and acute phase responses of crossbred, newly-received feedlot heifers to an endotoxin challenge. Heifers (n = 24; 219 ± 2.4 kg) were separated into treatment groups receiving either a control diet (n = 8), YCW-A (2.5 g/heifer/d; n = 8) or YCW-C (2.5 g/heifer/d; n = 8) and were fed for 52 d. On d 37 heifers were challenged i.v. with LPS (0.5 µg/kg body mass) and blood samples were collected from -2 h to 8 h and again at 24 h relative to LPS challenge. There was an increase in vaginal temperature in all heifers post-LPS, with YCW-C maintaining a lower vaginal temperature post-LPS than control and YCW-A heifers. Sickness behavior scores increased post-LPS in all heifers, but were not affected by treatment. Cortisol concentrations were greatest in control heifers post-LPS compared with YCW-A or YCW-C heifers. Concentrations of IFN-γ and TNF-α increased post-LPS, but were not affected by treatment. Serum IL-6 concentrations increased post-LPS and were greater in control heifers than YCW-A and YCW-C heifers. These data indicate that YCW supplementation can decrease the physiological and acute phase responses of newly-received heifers following an endotoxin challenge.

Enhancement of the acute phase response to a lipopolysaccharide challenge in steers supplemented with chromium.

The study examined the effect of chromium supplementation on the response of steers to an LPS challenge. Steers received a premix that added 0 (control; n = 10) or 0.2 mg/kg of chromium (n = 10) to the total diet on a dry matter basis for 56 d. Steers were fitted with jugular catheters and rectal temperature (RT) recording devices on d 52. Blood samples were collected and sickness behavior scores assigned to each steer relative to an LPS challenge (0.5 µg/kg) on d 55. Pre-LPS RT were greater in chromium-supplemented than in control steers. Post-LPS RT increased in both treatments, with control steers producing a greater change in RT than chromium-supplemented steers. Sickness behavior scores were greater in control than in chromium-supplemented steers post-LPS (P = 0.03). Cortisol concentrations did not differ between treatments pre-LPS. Post-LPS cortisol concentrations increased but did not differ due to treatment. Concentrations of IL-4 increased post-LPS but were not affected by treatment pre- or post-LPS. Treatment did not affect pre-LPS TNF-α or IFN-γ. Post-LPS TNF-α and IFN-γ increased in both treatments, with chromium-supplemented steers producing greater TNF-α (P = 0.005) and IFN-γ (P = 0.004) than control steers. Pre-LPS IL-6 was greater (P = 0.027) in chromium-supplemented steers than in control steers. Post-LPS IL-6 increased in both treatments and was greater (P < 0.001) in chromium-supplemented than in control steers. These data suggest that chromium supplementation enhances the acute phase response of steers to an LPS challenge, which may expedite recovery.