Effect of low vitamin A diets with high-moisture or dry corn on marbling and adipose tissue fatty acid composition of beef steers

Vitamins and Trace Minerals in Ruminants: Confinement Feedlot

Trace minerals and vitamins are essential for optimizing feedlot cattle growth, health, and carcass characteristics. Understanding factors that influence trace mineral and vitamin absorption and metabolism is important when formulating feedlot cattle diets. Current feedlot industry supplementation practices typically exceed published trace mineral requirements by a factor of 2 to 4. Therefore, the intent of this review is to briefly discuss the functions of trace minerals and vitamins that are typically supplemented in feedlot diets and to examine the impact of dose of trace mineral or vitamin on growth performance, health, and carcass characteristics of feedlot cattle.

Effects of vitamin A on intramuscular fat development in beef cattle: A meta-analysis

Vitamin A, a fat-soluble vitamin, is the basic substance required to maintain healthy vision and the main physiological functions of cattle. The results from previous studies regarding the effect of vitamin A on intramuscular fat varied. This meta-analysis aimed to generate a more comprehensive understanding of the relationship between vitamin A and intramuscular fat content and to provide potential clues for future research and commercial practice. Electronic databases such as MEDLINE and Ovid were systematically searched, and studies investigating the relationship between vitamin A and intramuscular fat content were included. Standardized mean differences (SMDs) in intramuscular fat percentage and intramuscular fat score, with their respective 95% confidence intervals (CIs), were calculated. The heterogeneity and publication bias were evaluated. A total of 152 articles were identified through searches of databases. Seven articles were confirmed for inclusion in this meta-analysis. The SMD of IMF percentage derived from the analysis was−0.78 (-2.68, 1.12) (Q = 246.84, p < 0.01). The SMD of the IMF score was 1.25 (-2.75, 5.25) (Q = 87.20, p < 0.01). Our meta-analysis indicates that the addition of vitamin A could decrease intramuscular fat in cattle steers.

Effects of different vitamin A supplies on performance and the risk of ketosis in transition cows

This experiment investigated the effects of feeding low and high supplies of vitamin A (VA) during the transition period on plasma metabolites, prevalence of ketosis, and early milk production. In a randomized complete block design, 42 prefresh Holstein cows and 21 heifers were blocked by parity and calving date and assigned to 1 of 3 dietary treatments (n = 21 per treatment unless noted): CON, a transition diet with supplemental VA (75,000 IU/d) to meet the requirement; LVA, a transition diet with no supplemental VA; or HVA, a transition diet receiving supplemental VA (187,500 IU/d) 2.5 times greater than the requirement. Experimental periods were prepartum (-14 d prepartum), postpartum (1 to 30 d in milk), and carryover period (31 to 58 d in milk; common lactating diet with adequate VA was fed). Differences in dry matter intake in the pre- and postpartum periods and milk yield were not detected among treatment. Milk fat, protein, and lactose yields were similar among treatments and not affected by VA. Somatic cell count increased linearly with increasing VA. Body weight and body condition score decreased postpartum, but no VA effect was observed. Plasma retinol concentrations (n = 10 per treatment) decreased at d 2 postpartum and increased as lactation progressed, but the concentrations were unaffected by treatment. Plasma β-carotene (n = 10 per treatment) had a treatment by time interaction and its concentration decreased after parturition and remained low for 2 wk. Plasma fatty acids and β-hydroxybutyrate did not differ among treatments. Milk retinol concentration and yield (n = 10 per treatment) increased as VA supply increased. Segmented neutrophils (%) decreased, and lymphocytes (%) increased in blood with increasing VA supply. In conclusion, providing different supplies of VA did not affect production, mobilization of body fat, and risk of ketosis; however, excessive VA supply may have negatively affected the immune response, in part contributing to increased milk somatic cell counts during early lactation.

Association between rumen microbiota and marbling grade in Hu sheep

The marbling fat regulates the flavor of mutton and measures the fat density in the loin eye and is the most important parameter of carcass grading. The objective of this study was to explore the relationship of rumen microbiota and mutton marbling grade. One hundred and eighty-seven feedlot-finished Hu male lambs (Age: 180 day; Final BW: 46.32 ± 6.03 kg) were slaughtered, and ruminal contents and marbling grade were collected. Ruminal microbial DNA extraction and 16S rRNA gene sequencing was performed to investigate microbial composition and to predict microbial metabolic pathways. The animal cohort was then grouped based on marbling grades [low marbling (LM), marbling grade ≤ 1; Medium marbling (MM), 1 < marbling grade ≤ 3; High Marbling (HM), 3 < marbling grade ≤ 5] and intramuscular fat-associated microorganisms were pinpointed using LEfSe and random forest classification model. Intramuscular fat content had significantly differences among the three groups (P < 0.05), and was significantly correlated with VFAs profiling. HM sheep showed a higher abundance of one bacterial taxon (Kandleria), and two taxa were overrepresented in the MM sheep (Pseudobutyrivibrio and Monoglobus), respectively. In addition, the main intramuscular fat deposition pathway was found to involve peroxisome proliferator-activated receptor (PPAR) fatty acid synthesis. By studying the effect of the ruminal microbiome on the marbling of sheep, the present study provides insights into the production of high-quality mutton.

Preliminary system of rapid analysis of blood retinol level in cattle

Control of blood retinol levels in cattle during fattening is important in the production of marbled beef. However, it is difficult to easily measure the blood retinol concentration in the field. In this study, we attempted to develop an analysis method that does not require blood cell separation and uses a compact fluorescence analyzer that can be carried around as a preliminary system for measuring blood retinol concentration in the field. This system was used to monitor blood retinol levels in 12 fattening cattle (14 to 27 months old) and demonstrated a strong correlation (r = 0.78) with the results obtained by the standard high-performance liquid chromatography (HPLC) method. Stronger correlations (r = 0.87) were obtained until the cattle were 24 months of age. These results suggest that higher correlations can be expected to be obtained by improving the robustness of the extraction system. Refinements for practical use need to be considered, but whole blood extraction and the vitamin A analyzer that was developed show potential to be used for on-farm monitoring of retinol levels.

Vitamin A regulates intramuscular adipose tissue and muscle development: promoting high-quality beef production

During growth in cattle, the development of intramuscular adipose tissue and muscle is dependent upon cell hyperplasia (increased number of adipocytes) and hypertrophy (increased size of adipocytes). Based on the results of previous studies, other adipose tissue depots (e.g., perirenal and subcutaneous) develop from the fetal stage primarily as brown adipose tissue. The hyperplastic stage of intramuscular adipose is considered to develop from late pregnancy, but there is no evidence indicating that intramuscular adipose tissue develops initially as brown adipose tissue. Hyperplastic growth of intramuscular adipose continues well into postweaning and is dependent on the timing of the transition to grain-based diets; thereafter, the late-stage development of intramuscular adipose tissue is dominated by hypertrophy. For muscle development, hyperplasia of myoblasts lasts from early (following development of somites in the embryo) to middle pregnancy, after which growth of muscle is the result of hypertrophy of myofibers. Vitamin A is a fat-soluble compound that is required for the normal immunologic function, vision, cellular proliferation, and differentiation. Here we review the roles of vitamin A in intramuscular adipose tissue and muscle development in cattle. Vitamin A regulates both hyperplasia and hypertrophy in in vitro experiments. Vitamin A supplementation at the early stage and restriction at fattening stage generate opposite effects in the beef cattle. Appropriate vitamin A supplementation and restriction strategy increase intramuscular adipose tissue development (i.e., marbling or intramuscular fat) in some in vivo trials. Besides, hyperplasia and hypertrophy of myoblasts/myotubes were affected by vitamin A treatment in in vitro trials. Additionally, some studies reported an interaction between the alcohol dehydrogenase-1C (ADH1C) genotype and vitamin A feed restriction for the development of marbling and/or intramuscular adipose tissue, which was dependent on the timing and level of vitamin A restriction. Therefore, the feed strategy of vitamin A has the visible impact on the marbling and muscle development in the cattle, which will be helpful to promote the quality of the beef.

A comprehensive review on carotenoids in foods and feeds: status quo, applications, patents, and research needs

Carotenoids are isoprenoids widely distributed in foods that have been always part of the diet of humans. Unlike the other so-called food bioactives, some carotenoids can be converted into retinoids exhibiting vitamin A activity, which is essential for humans. Furthermore, they are much more versatile as they are relevant in foods not only as sources of vitamin A, but also as natural pigments, antioxidants, and health-promoting compounds. Lately, they are also attracting interest in the context of nutricosmetics, as they have been shown to provide cosmetic benefits when ingested in appropriate amounts. In this work, resulting from the collaborative work of participants of the COST Action European network to advance carotenoid research and applications in agro-food and health (EUROCAROTEN, www.eurocaroten.eu, https://www.cost.eu/actions/CA15136/#tabs|Name:overview) research on carotenoids in foods and feeds is thoroughly reviewed covering aspects such as analysis, carotenoid food sources, carotenoid databases, effect of processing and storage conditions, new trends in carotenoid extraction, daily intakes, use as human, and feed additives are addressed. Furthermore, classical and recent patents regarding the obtaining and formulation of carotenoids for several purposes are pinpointed and briefly discussed. Lastly, emerging research lines as well as research needs are highlighted.

Effect of feeding a low-vitamin A diet on carcass and production characteristics of steers with a high or low propensity for marbling

Our research group demonstrated that vitamin A restriction affected meat quality of Angus cross and Simmental steers. Therefore, the aim of this study is to highlight the genotype variations in response to dietary vitamin A levels. Commercial Angus and Simmental steers (n = 32 per breed; initial BW = 337.2 ± 5.9 kg; ~8 months of age) were fed a low-vitamin A (LVA) (1017 IU/kg DM) backgrounding diet for 95 days to reduce hepatic vitamin A stores. During finishing, steers were randomly assigned to treatments in a 2 × 2 factorial arrangement of genotype × dietary vitamin A concentration. The LVA treatment was a finishing diet with no supplemental vitamin A (723 IU vitamin A/kg DM); the control (CON) was the LVA diet plus supplementation with 2200 IU vitamin A/kg DM. Blood samples were collected at three time points throughout the study to analyze serum retinol concentration. At the completion of finishing, steers were slaughtered at a commercial abattoir. Meat characteristics assessed were intramuscular fat concentration, color, Warner-Bratzler shear force, cook loss and pH. Camera image analysis was used for determination of marbling, 12th rib back fat and longissimus muscle area (LMA). The LVA steers had lower (P < 0.001) serum retinol concentration than CON steers. The LVA treatment resulted in greater (P = 0.03) average daily gain than the CON treatment, 1.52 and 1.44 ± 0.03 kg/day, respectively; however, there was no effect of treatment on final BW, DM intake or feed efficiency. Cooking loss and yield grade were greater and LMA was smaller in LVA steers (P < 0.05). There was an interaction between breed and treatment for marbling score (P = 0.01) and percentage of carcasses grading United States Department of Agriculture (USDA) Prime (P = 0.02). For Angus steers, LVA treatment resulted in a 16% greater marbling score than CON (683 and 570 ± 40, respectively) and 27% of LVA Angus steers graded USDA Prime compared with 0% for CON. Conversely, there was no difference in marbling score or USDA Quality Grades between LVA and CON for Simmental steers. In conclusion, feeding a LVA diet during finishing increased marbling in Angus but not in Simmental steers. Reducing the vitamin A level of finishing diets fed to cattle with a high propensity to marble, such as Angus, has the potential to increase economically important traits such as marbling and quality grade without negatively impacting gain : feed or yield grade.

Association between Rumen Microbiota and Marbling Score in Korean Native Beef Cattle

Simple Summary

The ruminal microbiome affects various metabolic processes associated with animal development; however, few studies have focused on its correlation with marbling. Results of the present study show differences in ruminal microbiomes among Hanwoo Korean beef cattle, which have low or high marbling scores. By elucidating the effect of the ruminal microbiome on the marbling of Hanwoo, differentially abundant microbial taxa, ruminal taxonomic drivers of lipid metabolism, and the correlation with meat quality indices, the present study provides insights into the potential effects of microbial factors on marbling in beef cattle.

Abstract

This study demonstrated the potential effects of the rumen microbiota on the deposition of intramuscular fat, known as marbling. Previous studies on fatty acid metabolism in beef cattle have mostly focused on biohydrogenating rumen bacteria, whereas those on the overall rumen microbiota—to understand their roles in marbling—have not been systematically performed. The rumen microbiota of 14 Korean beef cattle (Hanwoo), which showed similar carcass characteristics and blood metabolites but different marbling scores, were analyzed by 16S rRNA gene sequencing. The rumen samples were grouped into two extreme marbling score groups of host animals as follows: LMS, marbling score≤ 4 or HMS, marbling score ≥7. Species richness tended to be higher in the HMS group, whereas the overall microbiota differed between LMS and HMS groups. RFP12, Verrucomicrobia, Oscillospira, Porphyromonadaceae, and Paludibacter were differentially abundant in the HMS group, whereas Olsenella was abundant in the LMS group. Some marbling-associated bacterial taxa also contributed to the enrichment of two lipid metabolic pathways including “alpha-linolenic acid metabolism” and “fatty acid biosynthesis” in the HMS microbiome. Taxonomic drivers of fatty acid biosynthesis, particularly in the rumen microbiome of high-marbled meat, could thus be further studied to increase the intramuscular fat content.

Influence of Megasphaera elsdenii and feeding strategies on feedlot performance, compositional growth, and carcass parameters of early weaned, beef calves

Simmental–Angus calves [n = 135; 72 steers and 63 heifers; body weight (BW) = 212.4 kg ± 36.1] were early weaned (~5 mo) to evaluate multiple feeding regimens (conventional vs. aggressive energy diets ± Megasphaera elsdenii NCIMB 41125 (M. elsdenii culture (MEC); Lactipro Advance; MS Biotec Inc., Wamego, KS) in order to elucidate the optimal development strategy. Objectives were measured by tracking the effects of caloric density and oral drenching of growing phase performance and subsequent carcass traits. The 72-d experiment featured three groups: 1) control (CON), fed exclusively a 35% roughage diet; 2) aggressive (AGR), fed a blend of a 10% and 35% roughage diets; 3) MEC, fed the same diet as AGR and drenched with 50 mL of M. elsdenii NCIMB 41125 on day 1. A subset of calves (n = 45) was equipped with wireless rumination tags (Allflex Flex Tag; SCR Engineers, Ltd; Netanya, Israel), which logged daily rumination and general activity. Skeletal growth variables were assessed by measuring wither and hip height pretrial and posttrial. Ultrasonography provided additional resolution concerning growing phase compositional gain, which was later verified by carcass data collection. Data were analyzed as a nested analysis of variance with BW and gender serving as blocking factors. The increased caloric density of the diets administered to MEC and AGR calves resulted in greater average daily gain and gain:feed values compared with CON even during the first 21 d of diet acclimation (P ≤ 0.05). Additional fiber concentration of CON diets led to increased rumination times in 9 of the 10 wk of trial (P ≤ 0.10). No differences amongst treatments were detected for skeletal variables or ultrasound 12th rib fat. Cattle fed CON diets posted 3.4% inferior BW at the end of the growing period trial and a 3.8% reduction in hot carcass weight (HCW), reinforcing the theory that intensifying caloric intake during the growing phase does not compromise future feedlot performance. Ultrasound marbling scores for MEC-treated cattle were 19° greater than AGR treated cattle (P ≤ 0.05) at the end of the growing phase trial. Nearly the exact same advantage (22°) was observed in the cooler 5 mo later (P = 0.42). Implying MEC metabolically imprinted cattle to favor marbling development. It appears that maximizing dietary caloric density in light-weight calves does not adversely affect the growth curve, while oral dosing of MEC during the growing period may be a precursor for enhanced quality grade.

Short communication: dietary vitamin A restriction may improve meat quality parameters in fat-tailed lambs

Thirty fat-tailed Mehraban ram lambs were randomly allotted into three vitamin A (VA) dietary treatment groups: either 100 (VA₁₀₀), 50 (VA₅₀), or 25% (VA₂₅) of the recommended daily vitamin A requirements. Treatment had no effect on feed intake, daily live weight gain, cold carcass weight, and dressing percentage. In M. longissimus lumborum (LL) of VA₁₀₀ lambs, malondialdehyde level was greater, but ether-extractable intramuscular fat concentration was lower. The proportion of C16:0 and C20:0 fatty acids in total fatty acids of LL was lower in VA₁₀₀ lambs, compared to VA₅₀ and VA₂₅ lambs. Conversely, greater proportions of C17:0, C17:1, C18:1, and C18:2 fatty acids were recorded in VA₁₀₀ lambs. Stearoyl-CoA desaturase activity index (the ratios of C16:0 to C16:1 and C18:0 to C18:1) was not influenced by dietary vitamin A level. Future research is needed to determine the optimum level of dietary vitamin A concentration for deposition of greater intramuscular fat in fat-tailed sheep.

Retinol binding protein 4 abundance in plasma and tissues is related to body fat deposition in cattle

Retinol binding protein 4 (RBP4) facilitates the transport of retinol in the body but is also an adipokine and fatty acid transporter. Our study was aimed at investigating the associations between RBP4 abundance and fat deposition in cattle. Blood samples of 246 crossbred bulls were taken at 8 months of age and at slaughter at 18 months of age for the determination of RBP4, hormone levels, and fatty acid composition. Significant correlations between plasma RBP4 abundance at 8 months of age and carcass traits at 18 months of age were detected (e.g., r = 0.3; P < 0.001 to carcass fat). Furthermore, RBP4 abundances in the plasma and subcutaneous fat were higher (P < 0.05) in bulls with increased fat deposition, whereas the liver RBP4 expression was not (P > 0.05). Retinol binding protein 4 was immunohistochemically localized in or close to adipocytes within muscle and adipose tissue and in liver stellate cells but not in hepatocytes. Overall, our results indicate that increased RBP4 levels were associated with increased fat deposition and altered fatty acid composition, but not with altered glucose tolerance, in crossbred bulls. Moreover, our results suggest that adipose-tissue-derived RBP4 may contribute to the circulating RBP4 level.

Effect of vitamin A restriction on carcass traits and blood metabolites in Korean native steers

The objective of the present study was to determine the effect of vitamin A restriction on serum metabolites and carcass performance in Korean native steers during a fattening period. In Study 1, 61 steers were divided into three groups and supplied diets with concentrate and roughage containing 890 IU/kg of provitamin A and then supplemented with either 8000 IU (control), 3000 IU (T1) or 0 IU (T2) of premix vitamin A per kilogram of dry matter. In Study 2, 19 steers were divided into two groups and provided with the same basic diets then supplemented with 8000 IU (control) or 0 IU (T) of premix vitamin A per kilogram of dry matter. In Study 1, we found that serum vitamin A concentrations were significantly (P &lt; 0.05) lower in the T2 group, along with significant (P &lt; 0.05) increases in blood urea nitrogen, albumin, creatinine and non-esterified fatty acid concentrations. In Study 2, the T group had a higher (P &lt; 0.05) skeletal muscle mRNA expression levels of myogenic factor 6 and a trend for the greater yield grade (P=0.095). However, marbling scores in the study showed no significant. Therefore, vitamin A restriction with vitamin premix during the fattening period was associated with a trend for a higher yield grade, but marbling scores that were not significantly higher. Metabolic parameters in this stage could be used as indicators in future metabolic studies and as early health status markers in Korean native steers.

All-trans retinoic acid increases the expression of oxidative myosin heavy chain through the PPARδ pathway in bovine muscle cells derived from satellite cells

All-trans retinoic acid (ATRA) has been associated with various physiological phenomenon in mammalian adipose tissue and skeletal muscle. We hypothesized that ATRA may affect skeletal muscle fiber type in bovine satellite cell culture through various transcriptional processes. Bovine primary satellite cell (BSC) culture experiments were conducted to determine dose effects of ATRA on expression of genes and protein levels related to skeletal muscle fiber type and metabolism. The semimembranosus from crossbred steers (n = 2 steers), aged approximately 24 mo, were used to isolate BSC for 3 separate assays. Myogenic differentiation was induced using 3% horse serum upon cultured BSC with increasing doses (0, 1, 10, 100, and 1,000 nM) of ATRA. After 96 h of incubation, cells were harvested and used to measure the gene expression of protein kinase B (Akt), AMP-activated protein kinase alpha (AMPK), glucose transporter 4 (GLUT4), myogenin, lipoprotein lipase (LPL), myosin heavy chain (MHC) I, MHC IIA, MHC IIX, insulin like growth factor-1 (IGF-1), Peroxisome proliferator activated receptor gamma (PPARγ), PPARδ, and Smad transcription factor 3 (SMAD3) mRNA relative to ribosomal protein subunit 9 (RPS9). The mRNA expression of LPL was increased (P < 0.05) with 100 and 1,000 nM of ATRA. Expression of GLUT4 was altered (P < 0.05) by ATRA. The treatment of ATRA (1,000 nM) also increased (P < 0.05) mRNA gene expression of SMAD3. The gene expression of both PPARδ and PPARγ were increased (P < 0.05) with 1,000 nM of ATRA. Protein level of PPARδ was also affected (P < 0.05) by 1,000 nM of ATRA and resulted in a greater (P < 0.05) protein level of PPARδ compared to CON. All-trans retinoic acid (10 nM) increased gene expression of MHC I (P < 0.05) compared to CON. Expression of MHC IIA was also influenced (P < 0.05) by ATRA. The mRNA expression of MHC IIX was decreased (P < 0.05) with 100 and 1,000 nM of ATRA. In muscle cells, ATRA may cause muscle fibers to transition towards the MHC isoform that prefers oxidative metabolism, as evidenced by increased expression of genes associated with the MHC I isoform. These changes in MHC isoforms appeared to be brought about by changing PPARδ gene expression and protein levels.

Neonatal vitamin A injection promotes cattle muscle growth and increases oxidative muscle fibers

Background

Vitamin A and its metabolite, retinoic acid (RA), are important regulators of cell differentiation and organ morphogenesis. Its impact on beef cattle muscle growth remains undefined.

Method

Angus steer calves were administrated with 0 (control) or 150,000 IU vitamin A (retinyl palmitate in glycerol, i.m.) per calf at birth and 1 month of age. At 2 months of age, a biopsy of the Biceps femoris muscle was obtained to analyze the immediate effects of vitamin A injection on myogenic capacity of muscle cells. The resulting steers were harvested at 14 months of age.

Results

Vitamin A administration increased cattle growth at 2 months. At 2 months of age, Vitamin A increased PAX7 positive satellite cells and the expression of myogenic marker genes including PAX7, MYF5, MYOD and MYOG. Muscle derived mononuclear cells were further isolated and induced myogenesis in vitro. More myotubes and a higher degree of myogenesis was observed in vitamin A groups. Consistently, vitamin A increased Latissimus dorsi (LD) muscle fiber size at harvest. In addition, vitamin A increased the ratio of oxidative type I and type IIA fibers and reduced the glycolic type IIX fibers. Furthermore, we found that RA, a key bioactive metabolite of vitamin A, activated PPARGC1A promoter, which explains the upregulated expression of PPARGC1A in skeletal muscle.

Conclusion

Vitamin A administration to neonatal calves enhanced postnatal muscle growth by promoting myogenesis and increasing satellite cell density, accompanied with a shift to oxidative muscle fibers.

Establishment of a quantitative in vivo method for estimating adipose tissue volumes and the effects of dietary soy sauce oil on adipogenesis in medaka, Oryzias latipes

Adipose tissue, which is conserved in higher eukaryotes, plays central roles in controlling the body’s energy balance, including excess energy storage and energy expenditure during starvation. In adipogenesis, intranuclear receptor, peroxisome proliferator–activated receptor gamma (PPARγ) is a key molecule, and PPARγ agonists can promote adipogenesis. Many studies on the in vitro screening of PPARγ agonists with compounds derived from various materials have been reported; however, in vivo assays for quick examination of these feeding effects have not been established. In this study, we developed a technique using a lipophilic fluorescent reagent, Nile red to quantitatively estimate the adipose tissue volumes by using Japanese rice fish, medaka (Oryzias latipes) and studied effects of dietary soy sauce oil (SSO), which is a discarded by-product from Japanese traditional food and is known to have PPARγ-agonistic activity, on adipogenesis. We found that SSO feeding increased the adipose tissue volumes, and the expression levels of adipogenesis-related genes increased in these medaka larvae. These results suggest that SSO feeding increases the adipose tissue volumes through adipogenesis promotion by PPARγ-agonistic activity in medaka, and medaka is a powerful model for studying adipogenesis. Furthermore, our study also demonstrates the availability of SSO as a dietary additive for farmed fish.

Vitamin A administration at birth promotes calf growth and intramuscular fat development in Angus beef cattle

Background

Marbling, or intramuscular fat, is an important factor contributing to the palatability of beef. Vitamin A, through its active metabolite, retinoic acid, promotes the formation of new fat cells (adipogenesis). As intramuscular adipogenesis is active during the neonatal stage, we hypothesized that vitamin A administration during the neonatal stage would enhance intramuscular adipogenesis and marbling.

Methods

Angus steer calves (n = 30), in a completely randomized design, were randomly allotted to three treatment groups at birth, receiving 0, 150,000, or 300,000 IU of vitamin A at both birth and one month of age. A biopsy of the biceps femoris muscle was collected at two months of age. After weaning at 210 d of age, steers were fed a backgrounding diet in a feedlot until 308 d of age, when they were transitioned to a high concentrate finishing diet and implanted with trenbolone/estradiol/tylosin mixture. Steers were harvested at an average of 438 d of age. All diets were formulated to meet nutrient requirements.

Results

Weaning weight and weight during the backgrounding phase were linearly increased (P <  0.05) by vitamin A level, though no difference in body weight was observed at harvest. Intramuscular fat of steers at 308 d of age, measured by ultrasound, quadratically increased (P <  0.05) with vitamin A level from 4.0±0.26 % to 4.9±0.26 %. Similarly, carcass marbling score in the ribeye quadratically increased (P < 0.05).

Conclusion

Administration of vitamin A at birth increased weaning weight and enhanced marbling fat development. Thus, vitamin A administration provides a practical method for increasing marbling and early growth of beef cattle.

Genetic, management, and nutritional factors affecting intramuscular fat deposition in beef cattle - A review

Intramuscular fat (IMF) content in skeletal muscle including the longissimus dorsi muscle (LM), also known as marbling fat, is one of the most important factors determining beef quality in several countries including Korea, Japan, Australia, and the United States. Genetics and breed, management, and nutrition affect IMF deposition. Japanese Black cattle breed has the highest IMF content in the world, and Korean cattle (also called Hanwoo) the second highest. Here, we review results of research on genetic factors (breed and sex differences and heritability) that affect IMF deposition. Cattle management factors are also important for IMF deposition. Castration of bulls increases IMF deposition in most cattle breeds. The effects of several management factors, including weaning age, castration, slaughter weight and age, and environmental conditions on IMF deposition are also reviewed. Nutritional factors, including fat metabolism, digestion and absorption of feed, glucose/starch availability, and vitamin A, D, and C levels are important for IMF deposition. Manipulating IMF deposition through developmental programming via metabolic imprinting is a recently proposed nutritional method to change potential IMF deposition during the fetal and neonatal periods in rodents and domestic animals. Application of fetal nutritional programming to increase IMF deposition of progeny in later life is reviewed. The coordination of several factors affects IMF deposition. Thus, a combination of several strategies may be needed to manipulate IMF deposition, depending on the consumer’s beef preference. In particular, stage-specific feeding programs with concentrate-based diets developed by Japan and Korea are described in this article.

Investigation of blood biomarkers related to meat quality and quantity in Hanwoo steers

Objective

This study was conducted to investigate the correlation between blood components and carcass traits, and to find the biomarkers related to meat quality and quantity in Hanwoo steers.

Methods

One hundred twenty-six Hanwoo steers (8 to 9 months of age, body weight of 185.6±24.38 kg) were used to find the correlation between blood compositions and carcass traits. The steers were fed concentrate and rice straw (30 steers) or total mixed rations (96 steers) during the whole experimental period. Blood samples were collected from the jugular vein at the growing (8 to 12 months), fattening (13 to 23 months) and finishing phases (24 to 30 months). Steers were slaughtered at 30 to 31 months of age (body weight of 701.6±60.45 kg) and the carcass traits were evaluated. Blood metabolites and hormones were analyzed and the correlation coefficients and regression equations with carcass traits were determined.

Results

Average concentrations of retinol, leptin and insulin were 1.10 IU, 30.34 ng, and 35.35 ng per mL of blood plasma, respectively. Retinol has negative correlations (p<0.01) with insulin and leptin. Blood insulin and total protein decreased with the age of steers, but retinol, aspartic acid transaminase (AST), glucose, cholesterol and triglyceride increased. In the finishing phase, significant (p<0.01) negative correlations occurred between blood retinol content and marbling score, and between blood AST content and longissimus muscle area of 13th rib, and the following regression equations were obtained: Marbling score (1–9) = −0.009×retinol (IU/100 mL)+ 9.125 (R² = 0.643), Longissimus muscle area (cm²) = −0.250× AST(U/L)+112.498 (R² = 0.450).

Conclusion

It is possible to make highly marbled beef by controlling the blood retinol content during the fattening and finishing phases of Hanwoo steers. Accordingly, blood retinol and AST could be biomarkers for determining beef quality and quantity, respectively, prior to slaughter.

Microarray analysis of Longissimus thoracis muscle gene expressions in vitamin A-restricted Japanese Black steers in middle fattening stage

Vitamin A (VA) restriction in beef cattle improves meat marbling; however, the underlying molecular mechanisms remain incompletely understood. We performed microarray analysis to clarify the effect of VA restriction on Longissimus thoracis gene expressions in Japanese Black steers. Six Japanese Black steers 13-14 months of age were divided into two groups: S group (n = 3), which received VA supplementation, and R group (n = 3), in which dietary VA intake was restricted. Steers were fattened for 7 months, following which tissue samples were obtained. Extracted RNA samples were analyzed by Affymetrix Genechip Bovine Genome Array. Lists of genes highly expressed in the R and S groups were obtained. The lists were functionally interpreted using functional annotation software, DAVID. In the R and S groups, 48 and 40 genes were significantly highly expressed, respectively. The gene list of the R group included CD36, LPL, GPAM, DGAT2, and SCD and additional genes annotated 'PPAR signaling pathway,' 'lipid biosynthesis' and 'mitochondrion,' whereas that of the S group included COL1A2, FN1 and DCN and additional genes annotated 'extracellular matrix.' Changes in the expression of these genes are possibly involved in marbling improvement in beef cattle by VA restriction.

Effects of feeding system on growth performance, plasma biochemical components and hormones, and carcass characteristics in Hanwoo steers

OBJECTIVE

This study was conducted to compare growth performance, blood components and carcass traits by two feeding systems (concentrate with roughage separately [CON] vs total mixed ration [TMR]) in Hanwoo steers, and to learn the relationship between blood components during fattening or finishing phases and carcass traits in Hanwoo steers.

METHODS

Sixty steers aged 8 months were allotted to two feeding systems and fed similar amounts of average dry matter and total digestible nutrient throughout whole experimental period according to each feeding program. Steers were weighed monthly, taken blood at the end of growing, fattening and finishing periods, and slaughtered at 30 month of age.

RESULTS

Growing performance was higher (p<0.05) in the CON group compared to the TMR group during fattening and finishing periods. The CON group was lower (p<0.05) in blood aspartic acid transaminase, blood urea nitrogen and retinol levels during growing period, but higher in triglyceride and cholesterol levels during fattening and finishing periods compared to the TMR group. The CON group was greater (p<0.05) in rib-eye area, and lighter (p<0.05) red in meat color compared to the TMR group. In the correlation coefficients between blood components of steers and carcass traits, retinol had a negative (p<0.05) correlation with marbling score and rib-eye area. Leptin had a positive (p<0.05) correlation with back fat thickness. Blood cholesterol and triglyceride were positively (p<0.05) correlated with carcass weight and rib-eye area.

CONCLUSION

Growth performance, carcass ribeye area and meat color showed a more desirable result in the CON compared to the TMR in Hanwoo steers. Assessing the accumulated data of carcass traits with blood components including hormones-particularly retinol, cholesterol, triglyceride, and leptin-during the fattening or finishing phases, it may be possible to find a biomarker for determining beef quality in living animals.

Retinoic acid modulates lipid accumulation glucose concentration dependently through inverse regulation of SREBP-1 expression in 3T3L1 adipocytes

It is well known that retinoic acid (RA) suppresses adipogenesis, although there are some contradicting reports. In this study, we examined the effect of extracellular glucose on RA-induced suppression of adipogenesis in 3T3L1 cell culture. When the cells were cultured in normal glucose medium (NG), the addition of RA suppressed lipid accumulation. However, when cultured in high glucose medium (HG), addition of RA to the cells enhanced lipid accumulation. These changes were accompanied by parallel alterations in fatty acid synthase (FAS) and sterol regulatory element-binding protein (SREBP)-1 gene expression. Transfection of SREBP-1 siRNA suppressed RA-induced enhancement of lipid accumulation and FAS expression in the cells cultured with HG. Transfection of the nuclear form of SREBP-1a cDNA into the cells cultured with NG inhibited RA-induced suppression of lipid accumulation and FAS expression. Moreover, RA- and HG-induced SREBP-1a expression occurred at the early phase of adipogenesis and was dependent on glucocorticoid to induce liver X receptor (LXR) β, peroxisomal proliferator-activated receptor (PPAR) γ and retinoid X receptor (RXR), the key nuclear factors influencing the SREBP-1a gene expression. These results suggest that RA suppresses and enhances lipid accumulation through extracellular glucose concentration-dependent modulation of SREBP-1 expression.

Nutrigenomic regulation of adipose tissue development - role of retinoic acid: A review

To improve the efficiency of animal production, livestock have been extensively selected or managed to reduce fat accumulation and increase lean growth, which reduces intramuscular or marbling fat content. To enhance marbling, a better understanding of the mechanisms regulating adipogenesis is needed. Vitamin A has recently been shown to have a profound impact on all stages of adipogenesis. Retinoic acid, an active metabolite of vitamin A, activates both retinoic acid receptors (RAR) and retinoid X receptors (RXR), inducing epigenetic changes in key regulatory genes governing adipogenesis. Additionally, Vitamin D and folates interact with the retinoic acid receptors to regulate adipogenesis. In this review, we discuss nutritional regulation of adipogenesis, focusing on retinoic acid and its impact on epigenetic modifications of key adipogenic genes.

Ophthalmologic manifestations of celiac disease

Celiac disease is an autoimmune disorder that affects the small intestine of genetically predisposed individuals. Ophthalmic manifestations are within the extra-intestinal manifestations, and can be divided into those of autoimmune disorders or those due to absorptive disabilities. This article reviewed the ophthalmologic manifestation of celiac disease. Ophthalmic symptoms are rare, but should be investigated in patients with celiac disease and taken into consideration as the first systemic manifestation.

Carotenoids in Adipose Tissue Biology and Obesity

Cell, animal and human studies dealing with carotenoids and carotenoid derivatives as nutritional regulators of adipose tissue biology with implications for the etiology and management of obesity and obesity-related metabolic diseases are reviewed. Most studied carotenoids in this context are β-carotene, cryptoxanthin, astaxanthin and fucoxanthin, together with β-carotene-derived retinoids and some other apocarotenoids. Studies indicate an impact of these compounds on essential aspects of adipose tissue biology including the control of adipocyte differentiation (adipogenesis), adipocyte metabolism, oxidative stress and the production of adipose tissue-derived regulatory signals and inflammatory mediators. Specific carotenoids and carotenoid derivatives restrain adipogenesis and adipocyte hypertrophy while enhancing fat oxidation and energy dissipation in brown and white adipocytes, and counteract obesity in animal models. Intake, blood levels and adipocyte content of carotenoids are reduced in human obesity. Specifically designed human intervention studies in the field, though still sparse, indicate a beneficial effect of carotenoid supplementation in the accrual of abdominal adiposity. In summary, studies support a role of specific carotenoids and carotenoid derivatives in the prevention of excess adiposity, and suggest that carotenoid requirements may be dependent on body composition.

Interaction of vitamin A supplementation level with ADH1C genotype on intramuscular fat in beef steers

Previously, the single nucleotide polymorphism in alcohol dehydrogenase (ADH1C c.-64T>C) was shown to have an association with intramuscular fat (IMF) in the longissimus thoracis (LT) muscle when vitamin A was limited in finishing rations of beef steers. The purpose of this study was to determine the optimum vitamin A supplementation level, in combination with ADH1C genotype, to increase IMF of the LT muscle. In total, 45 TT genotype, 45 CT and 27 CC Black Angus crossbred steers were backgrounded on a commercial ration containing 3360 IU vitamin A/kg dry matter (DM). During finishing, the steers were randomly assigned to one of three vitamin A treatments at 25%, 50% and 75% of the National Research Council recommendation of 2200 IU/kg DM. Treatments were administered via an oral bolus. Carcass quality was evaluated and a sample from the LT muscle was collected for analysis of IMF. A treatment×genotype interaction (P=0.04) was observed for IMF; TT steers on the 75% treatment had higher IMF relative to CT and CC steers on the same treatment. Western blot analysis showed that TT steers had higher (P=0.02) ADH1C protein expression in hepatic tissue. Previously, TT steers exhibited increased IMF when fed limited vitamin A. In the current study, the lack of variation in IMF between treatments and genotypes at the lower vitamin A treatment levels was likely due to the majority of the steers grading Canada AAA (USDA Choice). However, the western blot data supports that TT steers are expected to have higher IMF deposition, due to an increased production of ADH1C. The interaction between ADH1C genotype and vitamin A supplementation level has the potential for use in marker-assisted management programs to target niche markets based on increased marbling.

Effects of feeding β-carotene on levels of β-carotene and vitamin A in blood and tissues of beef cattle and the effects on beef quality

The effects of feeding β-carotene (βC) on levels of βC and vitamin A (retinol) in blood and tissues, and on beef quality, were evaluated in 120 steers. Each steer received supplementary βC (at concentrations of 0, 600, 1200, or 1800 mg/day) for 90 days and then received no supplementary βC for 60 days. βC significantly increased in blood serum, liver, and subcutaneous and omental fat; linearly increased in the intestine and muscle; and remained unchanged in perirenal fat during supplementation. Differences between treatment groups were eliminated in subcutaneous and omental fat and in the liver by days 120 and 150, respectively, but remained significant at day 150 in blood. Retinol increased significantly in the liver and intestine during supplementation. Intramuscular fat content, meat color, and retinol in blood, muscle, or adipose tissues were not affected. Backfat thickness decreased slightly with increasing βC supplementation and significantly differed between groups during depletion.

Effects of dietary potato by-product and rumen-protected histidine on growth, carcass characteristics and quality attributes of beef

We hypothesized that variable composition in finishing rations, more specifically; the proportion of potato-by-product (PBP) and rumen protected histidine (His) supplementation may influence growth and meat quality attributes. Two different diets were fed (1) finishing ration with corn and barley as grains (CB, n = 20) and (2) substitution of 10% corn, DM basis, with PBP (PBP, n = 20). Additionally, half of each dietary treatment received 50 g/hd/d rumen protected His (HS, n= 20) while the other half received no supplement (NS, n = 20). Inclusion of 10% PBP or HS did not affect growth or carcass traits. Color stability was analyzed using Hunter color values as well as AMSA visual appraisal in both longissimus thoracis (LT) and gluteus medius (GM) muscles. The LT, but not the GM, of CB steers was more color stable over a 9 d simulated retail display compared to those fed a PB diet. Steers receiving HS produced significantly (P < 0.05) more color stable LT and GM steaks.

Supplemental β-carotene I: effect on plasma vitamin A, growth, performance, and carcass characteristics of feedlot cattle

To evaluate the effects of β-carotene (βC) on performance and carcass characteristics, 112 crossbred calves were allotted to 4 treatments consisting of retinyl palmitate (RP) supplemented at 2200IU/kg, and synthetic β-carotene supplemented at 1 (SβC1X), 5 (SβC5X), or 10 (SβC10X) times RP. Compared to RP, SβC1X did not impact performance (P≥0.25) or plasma concentrations of retinoids or carotenoids (P≥0.26). Increasing dietary βC increased (P≤0.04) plasma concentrations of RP and all of the isomers of βC, but did not affect weight, gain, or gain:feed (P≥0.24). Marbling and fat thickness did not differ between RP and SβC1X or because of amount of βC (P≥0.35). Lightness (L*) of LM decreased with increasing concentration of SβC (linear; P=0.01). Yellowness (b*) increased (P=0.04) and redness (a*) tended to increase (P=0.09) in subcutaneous fat as SβC amount increased (quadratic).

Early metabolic imprinting events increase marbling scores in fed cattle

Early weaning of calves to a high concentrate diet results in greater fat deposition and suggests early postnatal metabolic imprinting events may be exploited as a management tool to improve cattle value. Our objective was to implement a short, high energy dietary intervention before a typical grazing period to manipulate intramuscular fat deposition in finishing cattle. Fall-born, Angus-sired steer calves (n = 24) were stratified by sire and randomly assigned to normal weaned (NW) or metabolic-imprinted (MIP) treatments. At 105 ± 6d (135kg), MIP calves were transitioned to a diet containing 20% CP and 1.26 Mcal/kg NEg. Metabolic-imprinted calves were fed ad libitum as a group. Normal weaned calves remained on their dam until 253 ± 6 d of age. At this time, treatment groups were combined and grazed for 156 d on a mixed summer pasture. Following the grazing phase, steers were adapted to a corn silage-based feedlot diet and performance was monitored on 28-d intervals. Calves were staged for harvest based on backfat endpoint (target 1.0 to 1.2 cm). Metabolic-imprinted calves were heavier (P < 0.05) than NW calves (341 vs. 265 ± 4.2 kg) at normal weaning age. During the grazing phase, NW steers gained more weight than (P < 0.05) MIP steers (0.69 vs. 0.35 ± 0.03 kg/d). Feedlot performance and USDA yield grade were similar (P > 0.20) between treatments. However, MIP steers produced heavier (P < 0.05) carcasses (564 vs. 524 ± 5.6 kg) with higher (P < 0.001) marbling scores (645 vs. 517 ± 23). Therefore, calves consuming a high concentrate diet for 148 d after early weaning produced higher quality carcasses. This suggests early weaning and feeding a high concentrate before grazing is a viable strategy to increase marbling deposition compared with a traditional production system.

Leptin in farm animals: where are we and where can we go?

Fat affects meat quality, value and production efficiency as well as providing energy reserves for pregnancy and lactation in farm livestock. Leptin, the adipocyte product of the obese (ob) gene, was quickly seen as a predictor of body fat content in animals approaching slaughter and an aid to assessing reproductive readiness in females. Its participation in inflammation and immune responses that help animals survive infection and trauma has clear additional relevance to meat and milk production. Furthermore, almost a decade of discoveries of nucleotide polymorphisms in the leptin and leptin receptor genes has suggested useful applications relating to feed intake regulation, the efficiency of feed use, the composition of growth, the timing of puberty, mammogenesis and mammary gland function and fertility in cattle, pigs and poultry. The current review attempts to summarise where research has taken us in each of these aspects and speculates on where future research might lead.

The impact of vitamin A restriction and ADH1C genotype on marbling in feedlot steers

A novel SNP was discovered within the promoter region of alcohol dehydrogenase 1C (ADH1C c.-64T>C), the C allele eliminating a potential binding site for the transcription factor C/EPBα. The purpose of this study was to examine if an interaction between this SNP and vitamin A restriction had an effect on carcass characteristics in beef cattle. Following backgrounding on a β-carotene-deficient diet, 130 steers (50 TT, 50 CT, and 30 CC) were finished for 5 mo and received either no supplemental vitamin A (unsupplemented) or 750,000 IU/mo (supplemented). A subgroup of 5 steers • genotype(-1) • treatment(-1) was randomly selected for pre- and postfinishing liver biopsies to assess vitamin A status and measure gene expression. Unsupplemented steers (Bos taurus) had significantly greater (P < 0.05) marbling scores than supplemented steers. There was a significant interaction between genotype and vitamin A supplementation on ether-extractable intramuscular fat (IMF). Within the unsupplemented treatment, TT steers had nearly 23% greater IMF than CC steers. Additionally, unsupplemented TT steers had over 24% greater IMF than supplemented TT steers. Expression of ADH1C in the liver was additive with each additional T allele, potentially due to the elimination of a possible binding site for C/EBPα. It is plausible that CC cattle have reduced ability to metabolize retinol to retinaldehyde (and subsequently retinoic acid) and that a phenotypic effect is only observed when vitamin A is limiting. Therefore, ADH1C c.-64T>C genotype, in combination with reduced vitamin A supplementation, could potentially be implemented in marker-assisted management to maximize marbling in finishing cattle.

Effects of timing and duration of dietary vitamin A reduction on carcass quality of finishing beef cattle

Two feedlot studies were conducted to investigate the timing and duration of supplemental vitamin A withdrawal from feedlot cattle (Bos taurus) diets to reduce intramuscular adipose tissue vitamin A concentration and improve carcass quality. In Exp. 1, Angus crossbred steers (n = 84, BW = 211 ± 4 kg) were allotted to 4 treatments: no supplemental vitamin A for 227 d, no supplemental vitamin A for 112 d followed by 115 d of supplemental vitamin A, supplemental vitamin A for 112 d followed by no supplemental vitamin A for 115 d, or supplemental vitamin A for 227 d. In Exp. 2, Angus crossbred steers (n = 80, BW = 210 ± 5 kg) were allotted to 4 treatments: early weaning with or without supplemental vitamin A, and traditional weaning with or without supplemental vitamin A. In both experiments, serum vitamin A concentrations were greatest (P < 0.05) 56 d after cattle were weaned and placed in the feedlot, regardless of feedlot dietary vitamin A concentration. Hepatic vitamin A stores were dramatically decreased (P < 0.05) in the first 56 d and remained depressed as long as steers were not supplemented with vitamin A. At the end of the finishing period, vitamin A concentrations were less in intramuscular than subcutaneous adipose tissue. Growth was not affected by finishing cattle without supplemental dietary vitamin A (P > 0.10). Dietary vitamin A supplementation did not affect USDA yield grades. However, in Exp. 2, cattle without supplemental vitamin A had greater (P < 0.001) ether extractable lipid in the LM. Ether extractable lipid in the LM or marbling scores were enhanced when intramuscular adipose tissue vitamin A concentration was reduced in response to feeding diets without supplemental vitamin A.

Concentration of pro-vitamin A carotenoids in common beef cattle feedstuffs

Quantification of the pro-vitamin A carotenoids in feedstuffs commonly fed to livestock has been ignored for many years. A greater dietary concentration of vitamin A has the potential to limit adipogenesis in cattle, thereby reducing carcass quality and value. A survey of 18 feedstuffs commonly fed to beef cattle was conducted for determination of vitamin A equivalents based on analysis of carotenoids. The pro-vitamin A carotenoids of interest were β-carotene, α-carotene, and β-cryptoxanthin. Collaborators in 5 states collected the feedstuffs and then shipped them to The Ohio State University for compilation and analysis. Carotenoids were extracted from the feedstuffs and then quantified using HPLC with photodiode array analysis. Fresh fescue pasture contained approximately 10 times more vitamin A equivalents than hay and 5 times more than corn silage (39,865, 2,750, and 6,900 IU of vitamin A/kg of DM for fresh pasture, hay, and corn silage, respectively). Beta-cryptoxanthin and α-carotene could not be detected in any forage samples. Hay and corn silage vitamin A equivalents decreased over extended periods of time from harvest to sample collection. Corn was the only feedstuff to have appreciable concentrations of all 3 pro-vitamin A carotenoids quantified. Corn processing had a minimal impact on the vitamin A equivalents. High-moisture corn contained 54% more vitamin A equivalents than whole shelled corn (378 and 174 IU of vitamin A/kg of DM, respectively). Pro-vitamin A carotenoids were more concentrated in corn coproducts than in whole shelled corn. The drying of distillers grains with solubles may significantly degrade β-carotene (800 and 480 IU/kg of DM for wet and dry distillers grains, respectively). Soybean-based feedstuffs contain a small concentration of pro-vitamin A carotenoids, at 55 and 45 IU of vitamin A/kg of DM for soybean meal and soybean hulls, respectively. Overall, there was considerable variation in the pro-vitamin A content of feedstuffs based on location and storage conditions. An extensive analysis of feedstuffs would need to be conducted for an accurate estimation of the vitamin A content of feedlot cattle diets.

Removal of supplemental vitamin A from barley-based diets improves marbling in feedlot heifers

Gibb, D. J., Van Herk, F. H., Mir, P. S., Loerch, S. and McAllister, T. A. 2011. Removal of supplemental vitamin A from barley-based diets improves marbling in feedlot heifers. Can. J. Anim. Sci. 91: 669–674. The objective of this research was to determine if removing supplemental vitamin A from barley-based feedlot diets affects animal performance, health, or carcass quality. Six pens per treatment (10 heifers per pen) were randomly assigned to receive zero (–VA) or 3640 (+VA) IU kg−1 dry matter of supplemental vitamin A in barley-based feedlot diets. Initial serum retinol was similar between treatments (28 µg dL−1; P=0.34), but –VA reduced levels by 40% (30 vs. 50 µg dL−1; P<0.001) by day 217. Removal of supplemental vitamin A reduced dry matter intake during the 58 d backgrounding period (6.93 vs. 7.07 kg d−1; P=0.007) and over the 218-d trial (9.18 vs. 9.35 kg d−1; P<0.001), but had no effect on average daily gain during backgrounding (1.22 kg d−1; P=0.46) or over all (1.46 kg d−1; P=0.15). Based on camera grading, –VA increased degree of marbling (480.6 vs. 439.3; P=0.02) without affecting backfat thickness (0.74 cm; P=0.62). Ultrasound measurements were highly correlated with camera grading, but did not detect treatment difference in marbling score (P=0.99). Results from this study show that the removal of supplemental vitamin A increased marbling without affecting backfat, gains, or animal health.

Lipid metabolism in mammalian tissues and its control by retinoic acid

Evidence has accumulated that specific retinoids impact on developmental and biochemical processes influencing mammalian adiposity including adipogenesis, lipogenesis, adaptive thermogenesis, lipolysis and fatty acid oxidation in tissues. Treatment with retinoic acid, in particular, has been shown to reduce body fat and improve insulin sensitivity in lean and obese rodents by enhancing fat mobilization and energy utilization systemically, in tissues including brown and white adipose tissues, skeletal muscle and the liver. Nevertheless, controversial data have been reported, particularly regarding retinoids' effects on hepatic lipid and lipoprotein metabolism and blood lipid profile. Moreover, the molecular mechanisms underlying retinoid effects on lipid metabolism are complex and remain incompletely understood. Here, we present a brief overview of mammalian lipid metabolism and its control, introduce mechanisms through which retinoids can impact on lipid metabolism, and review reported activities of retinoids on different aspects of lipid metabolism in key tissues, focusing on retinoic acid. Possible implications of this knowledge in the context of the management of obesity and the metabolic syndrome are also addressed. This article is part of a Special Issue entitled Retinoid and Lipid Metabolism.

Genetic parameters of serum vitamin A and total cholesterol concentrations and the genetic relationships with carcass traits in an F1 cross between Japanese Black sires and Holstein dams

Blood sample and carcass trait data were collected from 841 and 3,219 fattening animals of an F(1) cross between Japanese Black sires and Holstein dams, respectively. Data on serum vitamin A and total cholesterol concentrations containing 582 to 739 records at 4 stages of beef-fattening production were used to estimate variance components and heritabilities for the 2 traits, based on fattening periods: less than 13 mo of age (stage 1), 14 to 18 mo of age (stage 2), 19 to 21 mo of age (stage 3), and greater than 22 mo of age (stage 4). Furthermore, the genetic correlations of serum vitamin A and total cholesterol concentrations with beef marbling standards, carcass weight, ribeye area, rib thickness, and subcutaneous fat thickness were estimated. The heritability estimates of serum vitamin A concentration were consistently and drastically decreased from 0.37 ± 0.15 to 0.07 ± 0.07 from stages 1 to 4 because of considerable decreases in sire variances, whereas the residual variances remained large and stable throughout all 4 stages. Serum total cholesterol concentration was moderately heritable (approximately 0.35 to 0.64) throughout all 4 stages. The genetic correlations among serum vitamin A concentrations and beef marbling standards were high and negative (-0.94) in stage 4. The genetic correlations between serum vitamin A concentration and carcass weight in stages 3 and 4 were moderate and positive (approximately 0.26 to 0.36). Moderate to high positive genetic correlations between serum vitamin A concentration and subcutaneous fat thickness were obtained throughout the stages (approximately 0.40 to 0.75). Genetic correlations of serum total cholesterol concentration with carcass weight and rib thickness were moderate and positive (approximately 0.29 to 0.46) in stages 2, 3, and 4. These results indicate serum vitamin A and total cholesterol concentrations could be effective physiological indicators for improving carcass traits.

Allied industry approaches to alter intramuscular fat content and composition in beef animals

Biochemical and biophysical research tools are used to define the developmental dynamics of numerous cell lineages from a variety of tissues relevant to meat quality. With respect to the adipose cell lineage, much of our present understanding of adipogenesis and lipid metabolism was initially determined through the use of these methods, even though the in vitro or molecular environments are far removed from the tissues of meat animals. This concise review focuses on recent cellular and molecular biology-related research with adipocytes, and how the research might be extended to the endpoint of altering red meat quality. Moreover, economic and policy impacts of such in animal production regimens is discussed. These issues are important, not only with respect to palatability, but also to offer enhanced health benefits to the consumer by altering content of bioactive components in adipocytes.