Marbling Deposition Research Articles

PSVII-18 Applying the Marbling Window Concept to Enhance Intramuscular Fat Development in Beef Cattle

Abstract The increase in marbling deposition without increasing the overall fatness of the carcass is one of the most challenge goals in meat industry. Previous studies have suggested the nutritional interventions at the neonatal stages as a strategy to enhance the commitment of muscular mesenchymal stem cells to adipogenesis, which may contribute to enhance marbling deposition at the finishing phase. As such the objective of this study was designed the evaluate the impact nutrient supplementation during the pre-weaning stage of beef calves has on intramuscular adipogenic determination. Thirty-four female calves were assigned to two experimental treatments: Control (CON, n = 17), where calves received only a mineral mixture as a supplement; Supplemented (SUP, n = 17), where calves received an energy-protein supplement (0.5 kg·100 kg of BW-1·day-1; the same mineral mixture was used in the CON supplement). Calves were supplemented from 100 to 250 days of age. Once animals reached 250 days of age, skeletal muscle tissue samples were biopsied from the 10th and 11th rib and used for identification of mesenchymal stem cells and preadipocytes through immunofluorescence, mRNA and protein abundance of adipo-fibrogenic markers, and abundance of candidate miRNA controlling expression of adipogenic commitment. Data were analyzed considering the completely randomized design of the experiment. Heifers were randomized across paddocks, and paddocks were randomized across treatments. The PROC MIXED of SAS 9.2 was used for all analyses. The average daily gain (P = 0.08) and final body weight (P = 0.07) tended to be greater in SUP than CON calves. The number of fibro-adipogenic progenitor cells (P = 0.69) did not differ between treatments, while a greater number of intramuscular pre-adipocytes were observed in SUP than CON calves (P = 0.01). The expression of miRNA-4429 (P = 0.20) did not differ between treatments, while the expression of miRNA-129-5p (P = 0.09) and miRNA-129-2-3p (P = 0.05) tended to be greater in CON than SUP calves. Our findings demonstrate that energy-protein supplementation from 100 to 250 days of age is capable to enhance intramuscular adipogenesis in beef cattle. Moreover, our results suggest that regulation of adipogenic commitment occurs by post-transcriptional regulation through miR-129 family.

Effect of grain inclusion rates in diets provided to early-weaned calves and steroidal implants utilization on growth performance and carcass characteristics of beef steers

Abstract One hundred and twenty-one Angus × SimAngus-crossbred steers (body weight (BW) = 159 ± 22 kg) were used to evaluate the effects of different grain inclusion (GI) rates in diets provided to early-weaned calves and steroidal implants (SI) utilization on growth performance and carcass characteristics, particularly intramuscular fat deposition, of beef steers. The experiment was conducted as a randomized complete block design with a 2 × 2 factorial arrangement of treatments, consisting of two GI rates (35% vs. 58%, dry matter (DM) basis), each one associated or not to steroidal implant utilization (no implants vs. 80 mg trenbolone acetate (TA) + 16 mg estradiol followed by 120 mg TA + 24 mg of estradiol). After being early-weaned (124 ± 14 d of age), steers were offered an average of 4.5 kg/d (DM basis) of a concentrate-based diet with a greater or lesser GI rate for 60 d. After being fed a concentrate-based diet with different GI rates for 60 d, steers were fed a common backgrounding diet for 56 d and subsequently fed a common high-grain diet until harvested at a constant final BW (620 kg). Steers were not implanted until the beginning of the backgrounding phase and then re-implanted when initiating the finishing phase. Data were analyzed using PROC MIXED in SAS. There were no GI × SI interactions (P ≥ 0.62) for any of the growth performance parameters throughout the experimental period. Implanted steers tended to have a greater average daily gain (P = 0.10) during the finishing phase than nonimplanted steers. For the 12th rib fat thickness and yield grade (YG), a GI × SI interaction (P = 0.03) and a tendency for a GI × SI interaction (P = 0.10) was detected, respectively. Nonimplanted steers fed diets with greater GI rates presented the greatest 12th rib fat thickness and tended to have the greatest YG among treatments. No other interactions (P ≥ 0.33) were observed for the hot carcass weight, Longissimus muscle (LM) area, quality grade, marbling score, and kidney-pelvic-heart fat content. Steers fed diets with lesser GI rates tended to have a greater LM area than steers fed diets with greater GI rates (P = 0.10). Results from this experiment indicate that varying GI rates in diets provided to early-weaned calves and subsequent implantation with steroidal hormones did not affect marbling deposition.

Genetic and Genomic Characterization of a New Beef Cattle Composite Breed (Purunã) Developed for Production in Pasture-Based Systems

Purunã is a composite beef cattle breed, developed in Southern Brazil by crossing the Angus, Charolais, Canchim, and Caracu breeds. The goal of this study was to perform the first genetic characterization of the Purunã breed, based on both pedigree and genomic information. For this, 100 randomly selected animals were genotyped, and 11,205 animals born from 1997 to 2019 had pedigree information. The genetic analyses performed were principal component analysis, admixture, phylogenic tree, pedigree and genomic inbreeding, linkage disequilibrium (LD), effective population size (Ne), consistency of the gametic phase, runs of homozygosity (ROH), heterozygosity-enriched regions (HERs), and functional analyses of the ROH and HER regions identified. Our findings indicate that Purunã is more genetically related to the Charolais, Canchim, and Angus breeds than Caracu or Nellore. The levels of inbreeding were shown to be small based on all the metrics evaluated and ranged from −0.009 to 0.029. A low (−0.12–0.31) correlation of the pedigree-based inbreeding compared to all the genomic inbreeding coefficients evaluated was observed. The LD average was 0.031 (±0.0517), and the consistency of the gametic phase was shown to be low for all the breed pairs, ranging from 0.42 to 0.27 to the distance of 20 Mb. The Ne values based on pedigree and genomic information were 158 and 115, respectively. A total of 1,839 ROHs were found, and the majority of them are of small length (<4 Mb). An important homozygous region was identified on BTA5 with pathways related to behavioral traits (sensory perception, detection of stimulus, and others), as well as candidate genes related to heat tolerance (MY O 1A), feed conversion rate (RDH5), and reproduction (AMDHD1). A total of 1,799 HERs were identified in the Purunã breed with 92.3% of them classified within the 0.5–1 Mb length group, and 19 HER islands were identified in the autosomal genome. These HER islands harbor genes involved in growth pathways, carcass weight (SDCBP), meat and carcass quality (MT2A), and marbling deposition (CISH). Despite the genetic relationship between Purunã and the founder breeds, a multi-breed genomic evaluation is likely not feasible due to their population structure and low consistency of the gametic phase among them.

Improved tenderness of beef from bulls supplemented with active dry yeast is related to matrix metalloproteinases and reduced oxidative stress

Supplementing diets with active dry yeast (ADY, Saccharomyces cerevisiae) improves the carcass quality grade of beef cattle and the tenderness of beef. The relevant mechanisms have not been fully elucidated, but may be related to the effect of ADY on oxidative stress and the activity of matrix metalloproteinases (MMPs). To provide further insight into these mechanisms, this study evaluated the influence of ADY supplementation on growth performance, carcass traits, meat quality, concentrations of MMPs in serum (MMP-2, MMP-9 and MMP-13), oxidative stress indices and antioxidant capacity indices in beef cattle. Forty-six crossbred Simmental × Yanbian bulls (∼18 months of age, BW 436 ± 35 kg) participated in a 145-day finishing trial. ADY supplementation significantly improved marbling deposition, intramuscular fat content, and beef tenderness (P < 0.05); altered individual fatty acid proportions in the beef and increased saturated fatty acids while decreasing polyunsaturated fatty acids (P < 0.05); significantly decreased the abundance of reactive oxygen species in serum and meat; significantly increased the level of superoxide dismutase in meat (P < 0.05); tended to increase the level of catalase (P = 0.075) in serum and glutathione reductase (P = 0.066) in meat; and increased the secretion of MMPs. The improvement of beef tenderness following ADY supplementation of finishing bulls is related to the effects of ADY on the secretion of MMPs and the lowering of oxidative stress.

208 MicroRNA Expression in Longissimus Muscle Biopsies During Feedlot Finishing of Angus Steers

Abstract Intramuscular fat or marbling (IMF) is highly desired in beef products due to its ability to improve carcass value. Studies indicate that finishing cattle on high concentrate diets increase marbling deposition over time-on-feed (TOF). Angus-cross steers (n = 7; 433 + 17 kg) were individually fed a high concentrate diet for a period of 124 d. Steers were weighed and ultrasounded every 30 d on feed. Longissimus muscle biopsies were taken between the 11th and 13th rib on alternating sides at d 0, 90, and 124. RNA was extracted from the biopsy samples and subjected to microRNA (miRNA) sequencing and qPCR for mRNA expression of key lipogenic genes. Data were analyzed with time-on-feed in the model. ADG was increased between d30 and d90 (P &amp;lt; 0.05). The feed conversion ratio was lowest during d0 to d60 and increased from d90 to d124 (P &amp;lt; 0.05). Fat thickness increased (P &amp;lt; 0.05) between 90 to 124 d. Ultrasound intramuscular fat percentage increased (P &amp;lt; 0.05) between 60 and 90 d. miRNA sequencing results showed that mir-122 was differentially expressed from d0 to d90 (6.72 log fold change; P = 0.0048) and from d0 to 124 (3.83 log fold change; P = 0.026). Several miRNA were down regulated (&amp;gt; 2 log fold change; P &amp;lt; 0.05) during TOF, which included miR-2411, -449a, -1197, -323, and -485. Relative expression of key lipogenic genes, stearoyl Co-A desaturase (SCD-1) and fatty acid synthase, were up-regulated (P &amp;lt; 0.05) between d90 and 124 d. These results show that miR-122 appears to be a novel miRNA associated with marbling deposition and lipid metabolism.

162 Fetal Programming and Meat Quality

Abstract For many years, variation in carcass and meat quality traits was thought to result from actions taken throughout the animals’ life after birth. However, the quantity and quality of meat obtained at slaughter are not always as good as expected. The past decade has increased the number of evidence of the effects of intrauterine development of skeletal muscle on animal performance that affects the carcass and meat quality traits. The so-called “Fetal Programming” concept sheds light on the biology of skeletal muscle development in meat animals, revealing that this development stage appears to be a pivotal moment to invest efforts aiming to improve animal productivity and the quality of meat. Because most, if not all, of the muscle fibers are formed prenatally in livestock species, the impairment of muscle fiber formation at this stage will limit the overall muscle mass deposition throughout postnatal life. Intramuscular adipocytes also start their formation at the fetal stage. As such, since the intramuscular fat depot has a lower deposition rate than other fat depots, enhancement of intramuscular adipogenesis during the fetal stage may increase marbling deposition postnatally. Muscle fibers, adipocytes, and fibroblasts, which contribute to connective tissue formation, are derived from the same pool of mesenchymal stem (MS) cells. Depending on the insult suffered during intrauterine development, their commitment may shift from myogenic towards adipogenic/fibrogenic lineage. So far, most of the evidence in livestock animals has shown that maternal nutrition during gestation is the main factor that influences the mechanisms underlying the commitment of the MS cells. Although the majority of these studies have shown the consequences of maternal nutrition on myogenesis, adipogenesis, and fibrogenesis, the epigenetic markers that cause the programming of MS cells to undergo to one lineage or another needs to be further investigated.

Gene Expression and Carcass Traits Are Different between Different Quality Grade Groups in Red-Faced Hereford Steers.

Simple SummaryProducing a consistent and positive experience for beef consumers is challenging. The gene expression in muscle at harvest may provide insight into better prediction of United States Department of Agriculture (USDA) quality grade. In this pilot study muscle samples were collected at harvest on sixteen steers with a similar background and identical management. Muscle transcripts were sequenced to determine gene expression. Transcripts related to the extracellular matrix, stem cell differentiation, and focal cell adhesions were differentially expressed in muscle tissue from carcasses with differing USDA quality grades. This confirmed the application of this technique to provide insight into muscle development and fat deposition necessary for better prediction and selection to improve consistency and consumer experience.Fat deposition is important to carcass value and some palatability characteristics. Carcasses with higher USDA quality grades produce more value for producers and processors in the US system and are more likely to have greater eating satisfaction. Using genomics to identify genes impacting marbling deposition provides insight into muscle biochemistry that may lead to ways to better predict fat deposition, especially marbling and thus quality grade. Hereford steers (16) were managed the same from birth through harvest after 270 days on feed. Samples were obtained for tenderness and transcriptome profiling. As expected, steaks from Choice carcasses had a lower shear force value than steaks from Select carcasses; however, steaks from Standard carcasses were not different from steaks from Choice carcasses. A significant number of differentially expressed (DE) genes was observed in the longissimus lumborum between Choice and Standard carcass RNA pools (1257 genes, p < 0.05), but not many DE genes were observed between Choice and Select RNA pools. Exploratory analysis of global muscle tissue transcriptome from Standard and Choice carcasses provided insight into muscle biochemistry, specifically the upregulation of extracellular matrix development and focal adhesion pathways and the downregulation of RNA processing and metabolism in Choice versus Standard. Additional research is needed to explore the function and timing of gene expression changes.

Effect of Diet and Location Within the Longissimus Dorsi Muscle on the Quality and Fat Composition of Pork Loins Collected from Market Hog

Abstract In pigs, the longissimus muscle (LM) is an economically important tissue that largely dictates the quality grade assigned to the carcass. Still, this anatomically protracted muscle is not homogeneous in composition and these spatial differences across the LM can impact the overall predicted quality and quantity of pork produced. The objective of this study was to determine the impact of diet and location within the muscle on the quality and fatty acid composition of loins harvested from finishing pigs. A total of 80 pigs were subjected to 1 of 4 dietary treatments: lysine deficient diet (LysDef), vitamin A deficient diet (VitADef), lysine and vitamin A deficient diet (LysVitADef), and control diet (CON) formulated to meet NRC recommended requirements from weaning through finishing. The animals were then harvested to assess LM quality parameters including loin eye area, marbling score, and lean color. Samples from the proximal, medial, and distal portions of the LM were collected for fatty acid determination using gas chromatography and were expressed as a percentage of total fatty acids. Marbling score was greatest (P = 0.0024) in the proximal LM and was not impacted by treatment (P = 0.07). Treatment also had no effect (P = 0.14) on the percentage of saturated fatty acids (SFA); however, the percentage of SFA decreased (P &amp;lt; 0.001) from the proximal (40.9 ± 0.24) to distal (39.14 ± 0.24) portion. In contrast, the percentage of polyunsaturated fatty acids increased (P &amp;lt; 0.001) from the proximal (15.96 ± 0.57) to distal (19.27 ± 0.57) portion. Despite the lack of diet-induced differences in marbling scores, the biological data generated from the current study are informative in terms of the spatial and compositional marbling deposition patterns in the LM of the growing pigs and warrant further investigation to identify the mechanisms responsible for this paradigm.

217 Young Scholar Presentation: The use of diverse cattle breeds to understand marbling development and growth

Abstract Wagyu cattle have been genetically selected to have superior marbling deposition compared with many other cattle breeds, including Angus. It was hypothesized that greater marbling deposition by Wagyu influenced cattle may be due to an additional wave of adipogenic gene expression compared with Angus cattle. The present study compared the expression of lipid metabolism genes within the longissimus muscle (LM) of Wagyu and Angus sired cattle at similar harvest endpoints: days on feed and age, or body weight (613 kg). Angus sired steers were sired by an Angus bull selected for marbling (T1), while Wagyu sired steers were sired by either a Wagyu bull selected for growth (T2 &amp; T4) or marbling (T3 &amp; T5), at the respective age or body weight endpoints. Cattle were weaned at 7 months of age, entered the feedlot 54 d later, and consumed the same growing (119 d) and finishing ration. Muscle biopsies were collected from the LM posterior to the 13th rib at approximately 7, 9, 11, 14, and 17 months of age (harvest) for T1, T2, and T3 cattle. Muscle biopsies for T4 and T5 cattle were collected when their body weight was similar to T1 cattle at the time of biopsy, approximately 241, 276, 400, 531, and 613 kg (harvest). The high marbling sired Wagyu steers (T3 &amp;T5) had greater marbling scores and percent LM lipid compared with high growth Wagyu (T2 &amp; T4) and Angus sired steers. Gene expression results from high marbling sired Wagyu steers (T3 &amp;T5) demonstrated additional peaks of PPARδ mRNA expression, greater and earlier PPARγ mRNA expression, and greater or additional peaks of GPAM1, LPIN1, and HSL mRNA expression compared with high growth Wagyu (T2 &amp; T4) and Angus sired steers.

The Effects of Age at Weaning and Length of Lipid Supplementation on Growth, Metabolites, and Marbling of Young Steers.

Simple SummaryConsumers value quality beef and producers are starting to look at the ways production decisions affect the long-term performance of the animals. Early weaning is a production option in many beef cattle production environments. We are looking at the addition of rumen by-pass lipids in addition to early weaning to increase the marbling of steers. The supplementation of rumen protected lipids’ increased plasma concentrations of fatty acids. Supplementation of rumen-protected lipids improved carcass quality of young steers by increasing marbling scores and lipid concentration of steaks without negatively impacting dressing percentage. Therefore, a combination of early weaning and rumen by-pass lipid supplementation can be used as management practices to meet current consumer demands.The objective of this study was to determine how weaning age, days on supplements, and lipid supplementation affected the growth and marbling deposition of steers. Steers from a single sire were early weaned (n = 24) at 150 ± 11 days of age or traditionally weaned (n = 24) at 210 ± 11 days of age. Steers were assigned to control (n = 12/weaning group) or an isocaloric, isonitrogenous rumen by-pass lipid (RBL, n = 12/weaning group) for either 45 (n = 6/treatment) or 90 (n=6/treatment) days then harvested. Steer body weight (BW) was recorded on days −14 and −7, then BW and blood samples were collected on days 0, 22, 45, 66, and 90. The right rib section of each animal was collected for proximate analysis. Longissimus dorsi from RBL steers had increased lipids compared with control steers (3.6 ± 0.2 vs. 2.4 ± 0.2% on a wet basis; p < 0.0001). Steers fed for 90 days had greater (p = 0.02) concentrations of Longissimus dorsi lipid (3.3 ± 0.2%) than those fed for 45 days (2.7 ± 0.2%). There was a weaning age by treatment by days on feed interaction for intramuscular adipocyte diameter (p = 0.02) in which early weaned RBL fed for 90 days steers had an increased adipocyte diameter compared to the early weaned control fed for 90 and early weaned fed for 45 days steers with all other treatment groups as intermediates. Supplementation of RBL increased concentrations of C18:2, C20:4, and total fatty acids on days 45 and 90 (p ≤ 0.05). Data show that RBL supplementation increased the marbling content of the Longissimus dorsi. Furthermore, a longer period of supplementation resulted in increased adipose diameter.

Proteomic analysis reveals changes in energy metabolism of skeletal muscle in beef cattle supplemented with vitamin A.

Vitamin A has been reported as a factor influencing marbling deposition in meat from animals. Although the mechanisms by which vitamin A regulates lipid metabolism in mature adipocytes are already well-established, information regarding molecular mechanisms underlying the effects of vitamin A on the regulation of intramuscular fat deposition in beef cattle still remains limited. The present study aimed to assess the molecular mechanisms involved in the intramuscular fat deposition in beef cattle supplemented with vitamin A during the fattening phase using a proteomic approach. Vitamin A supplementation during the fattening phase decreased intramuscular fat deposition in beef cattle. Proteome and phospho-proteome analysis together with biological and networking analysis of the protein differentially abundant between treatments indicated that Vitamin A supplementation affects the overall energy metabolism of skeletal muscle, impairing lipid biosynthesis in skeletal muscle. Vitamin A supplementation at fattening phase impairs intramuscular fat deposition in beef cattle likely by changing the energy metabolism of skeletal muscle. The interaction of retinoic acid and heat shock 70-kDa protein may play a pivotal role in intramuscular fat deposition as a consequence of vitamin A supplementation by impairing de novo fatty acid synthesis as a result of a possible decrease in insulin sensitivity in the skeletal muscle. © 2020 Society of Chemical Industry.

Short Communication: Effects of low antioxidant mineral concentrations in the growing diet on marbling deposition in feedlot cattle

ABSTRACT Objectives This experiment investigates the effect of antioxidant mineral supplementation during a 28-d growing period on marbling deposition of feedlot steers. Materials and Methods After a 28-d adaptation period to the feedlot, 167 SimAngus steers (272 ± 28.2 kg, 219 ± 15 d of age) were divided into 4 weight blocks, placed in 1 of 24 pens, and randomly assigned a dietary treatment. Dietary treatments were applied during a 28-d growing period: (1) no supplemental Cu, Mn, Zn, and Se; (2) Cu, Mn, Zn, and Se supplemented at the requirement of growing beef steers; and (3) Cu, Mn, Zn, and Se supplemented at twice the requirement. Plasma was collected after the growing phase to quantify nonesterified fatty acid and thiobarbituric acid reactive substance concentrations. Afterward, steers were offered a common finishing diet until being removed from the experiment for slaughter at a similar backfat thickness. Statistical analyses used a mixed model in SAS, considering the fixed effect of treatment and the random effect of block. Results and Discussion There were no treatment differences (P > 0.35) for measures of feedlot performance, carcass, and blood metabolite. With the exception of Cu, it is possible adequate mineral concentrations supplied by the basal diet caused a lack of treatment differences. Additionally, liver and body mineral stores may not have been depleted during the 28 d of the experimental intervention. Implications and Applications Future research is needed to further investigate the effects of dietary antioxidant mineral level on marbling deposition of feedlot steers.

349 The use of low antioxidant mineral concentrations in the growing diet as a method to increase marbling deposition in feedlot cattle

Abstract The presence of reactive oxygen species has been associated with the differentiation of pre-adipocytes into lipid filled mature adipocytes in vitro. We hypothesized offering a diet without supplemental antioxidant minerals (Cu, Mg, Zn, and Se) to steers during the growing phase, a time when intramuscular fat cells are believed to be proliferating, would promote differentiation of pre-adipocytes, leading to more desirable marbling scores compared with steers supplemented to meet their mineral requirements. After adaptation to the feedlot, 168 Sim-Angus steers were divided into four weight blocks, placed in one of twenty-four pens, and randomly assigned a dietary treatment. Dietary treatments were: 1) no supplemental (Cu, Mg, Zn, and Se) minerals; 2) control diet with supplemented minerals to meet the mineral requirements of growing beef steers (NRC, 2016); 3) Cu, Mg, Zn, and Se concentrations supplemented at twice the concentration of the control diet. After dietary treatments were applied for the 4-wk long growing phase, steers were offered a common finishing diet until reaching a similar backfat thickness until harvest. Feedlot performance and carcass data were analyzed in SAS with pen as the experimental unit in the following model: Yij = μ+Di+wj+eij, where Di was the fixed effect of diet, wj was the random effect of weight block, and eij was the random error. No significant (P &gt; 0.35) treatment effects were found for feedlot performance and carcass measurements. The feedstuffs in the basal diet may have contained sufficient concentrations of antioxidant minerals to meet the mineral requirements of the steers and mask differences in marbling. Additionally, offering a similar diet during the finishing period may have resulted in compensatory marbling growth, which offset marbling differences after the growing phase and resulted in uniform marbling accumulation across dietary treatments.

Postweaning Exposure to High Concentrates versus Forages Alters Marbling Deposition and Lipid Metabolism in Steers

Angus-cross steers (n = 20; 261 ± 21.5 kg BW) were used to examine how early exposure to high concentrates or high quality forages altered marbling deposition and lipid metabolism. Steers were randomly assigned to high concentrate diet (CONC) or high quality forages (FOR) at 30-d postweaning, fed for 127 d, and slaughtered. Data were analyzed using a mixed model that included fixed effect(s) of dietary treatment (CONC vs. FOR), time (for plasma levels, ultrasound measures, and postmortem aging time) and two-way interaction (when appropriate). Steers fed CONC had greater (P &lt; 0.01) ADG and heavier (P &lt; 0.001) body weight at 127 d. Ultrasound measures over time showed greater (P &lt; 0.001) intramuscular fat deposition at d 98 and 126 for CONC than FOR steers. Steers fed CONC had elevated (P &lt; 0.05) plasma glucose and insulin concentrations from d 57 to 127 compared to FOR. Early exposure to CONC increased (P &lt; 0.01) dressing percent, HCW, LM area, 12th rib fat thickness, and marbling scores compared to FOR. Total lipid content of the LM was greater (P &lt; 0.01) for CONC than FOR; however, moisture, protein, and ash content was lower (P &lt; 0.01) for CONC than FOR. Concentrate fed steers had greater (P &lt; 0.01) MUFA content and lower (P &lt; 0.01) polyunsaturated fatty acids PUFA n-3 content than FOR. The n-6:n-3 ratio was greater (P &lt; 0.01) for CONC due to decreased (P &lt; 0.01) in n-3 fatty acid content with CONC. Gene expression was up-regulated (P &lt; 0.05) for key lipogenic genes and downregulated for glucose transporter 4 in steers fed CONC vs. FOR. Early exposure to CONC diets for 127 d at 30 d postweaning stimulated marbling deposition and resulted in these carcasses grading 80% Choice when slaughtered at 13 mo of age and 248 kg HCW.

Timing of Exposure to High-Concentrates versus High-Quality Forages on Growth and Marbling Deposition in Steers

Forty Angus-cross steers (280 ± 21.4 kg BW, 8 mo.) were used to examine the effects of exposure to 2 diets [high concentrate diets (CONC) versus high quality forages (FOR)] during 2 time periods [early (EARLY; at 30-d post weaning) or late (LATE; just prior to slaughter)] on animal growth, marbling deposition and tenderness. Steers were blocked by weight and randomly assigned to four dietary treatments: 1) CONC-FOR, 2) CONC-CONC, 3) FOR-CONC, or 4) FOR-FOR. Exposure to CONC during the EARLY or LATE period increased (P &lt; 0.05) growth and fat deposition compared to FOR-FOR. Hot carcass weight was greater (P &lt; 0.05) for CONC-CONC and FOR-CONC steers than FOR-FOR and CONC-FOR due to changes in dressing percent. Marbling score was greater (P &lt; 0.05) for CONC-CONC and CONC-FOR compared to FOR-FOR. Exposure to CONC during the EARLY period (CONC-FOR and CONC-CONC) increased (P &lt; 0.05) n-6 polyunsaturated fatty acids (PUFA) deposition in longissimus muscle (LM) and subcutaneous adipose tissue (SQ); whereas, exposure to CONC during the LATE period (CONC-CONC and FOR-CONC) reduced (P &lt; 0.05) n-3 PUFA, trans-11 octadecenoic acid and cis-9 trans-11 isomer of conjugated linoleic acid (CLA). Warner-Bratzler shear force at d 2 and 7 of postmortem aging in ribeye steaks from CONC-CONC and FOR-CONC was greater (P &lt; 0.05) than FOR-FOR and CONC-FOR. Lipogenic gene expression was up-regulated (P &lt; 0.05) and lipolytic gene expression was downregulated (P &lt; 0.06) in SQ from CONC-CONC and FOR-CONC compared to FOR-FOR. Overall, exposure to CONC in both periods increased growth rate and marbling deposition but LATE exposure had the greatest impact on adipose lipogenesis and lipolysis, fatty acid composition, and tenderness.

Effects of Post-Weaning Exposure to a High-Concentrate Based Diet vs. Pasture on Carcass Characteristics, Meat Quality, and Lipogenic Gene Expression of Early Harvested Steers

ObjectivesHigh-concentrate based diets fed during the finishing phase promotes marbling deposition in cattle. However, little has been reported that examines early exposure to high-concentrate diets during the post-weaning phase and the ability to accelerate marbling deposition. Our objective was to evaluate marbling deposition, meat quality, and lipogenic gene expression of post-weaned steers when started on a high-concentrate based diet or grazing high-quality forages.Materials and MethodsSteers (n = 20; initial BW = 261 ± 21.5 kg) were randomly assigned to 1 of 2 feeding treatments: high-concentrate based diet (cracked corn, corn gluten feed, and chopped hay [F]) or grazing high-quality pasture (winter annuals, alfalfa, and non-toxic fescue [P]) for 127-d. Steers were harvested at a commercial abattoir where subcutaneous (SC) adipose tissue was collected and flash frozen for total RNA isolation, and flash frozen in optimal cutting temperature compound for histology. On d 2 post-harvest, carcass characteristics and the 6 to 12 rib section of each carcass was collected for further analysis. RefFinder was used to evaluate reference gene candidates and data was analyzed with Proc Mixed of SAS 9.3 (SAS Inst. Inc., Cary, NC).ResultsSteers consuming grain had a greater overall ADG (1.36- vs. 0.68-kg/d for F and P, respectively; P < 0.01) resulting in heavier final BW and HCW, and greater dressing percentage (P < 0.01). Steers consuming grain had larger ribeye area (P < 0.01) and more fat at the 12th–rib (P < 0.01) than steers on forages, whereas there were no differences for KPH and calculated yield grade (P > 0.22). Grain consumption resulted in greater marbling scores than grazing pasture (P < 0.01; 448 vs. 240, respectively). Despite the increased marbling, longissimus muscle (LM) b* was not different (P > 0.95), whereas LM from F were brighter and more red (P < 0.01). Both SC L* and b* were not different between treatments (P > 0.20), whereas SC a* was greater for F than P (P < 0.01). Fat cell sizes of SC tissue were larger in perimeter and area for F (P < 0.01) whereas P had a greater fat cell number (P < 0.01). Steers on F had greater LM total lipid (P < 0.01), whereas P resulted in greater moisture, nitrogen and ash (P < 0.01). There were no differences in SFA or PUFA n-6 in LM (P > 0.49) whereas F had greater MUFA (P < 0.01) and P had greater PUFA and PUFA n-3 (P < 0.01) resulting in a more desirable PUFA n-6/PUFA n-3 ratio (P > 0.01; 1.46 v 7.35 for P and F, respectively). Furthermore, while Warner-Bratzler Shear Force (WBS) mean ± SD values were all well below 5 kg, and there was not an interaction between treatment and days aged (P = 0.106), there tended to be a higher shear force value for steers on F compared to P (P < 0.08; 2.99- vs. 2.75-kg, respectively) while WBS values decreased as steaks were aged 2-, 7-, and 14-d (P < 0.01). Fatty acid synthase and stearoyl CoA desaturase-9 were upregulated by 16 and 81 fold, respectively for steers on F when compared to P (P < 0.01). Additionally, F steers had a 42-fold increase in mRNA of elongase-5 compared to P steers (P < 0.01) and threefold more expression of lipoprotein lipase (P = 0.01).ConclusionThese data suggest that exposure to high-concentrate based diets during early post-weaning results in increased carcass quality, lipid deposition, and expression of key lipogenic genes.

Genetics of Marbling in Wagyu Revealed by the Melting Temperature of Intramuscular and Subcutaneous Lipids.

Extreme marbling or intramuscular deposition of lipid is associated with Wagyu breeds and is therefore assumed to be largely inherited. However, even within 100% full blood Wagyu prepared under standard conditions, there is unpredictable scatter of the degree of marbling. Here, we evaluate melting temperature (Tm) of intramuscular fat as an alternative to visual scores of marbling. We show that “long fed” Wagyu generally has Tm below body temperature but with a considerable range under standardized conditions. Individual sires have a major impact indicating that the variation is genetic rather than environmental or random error. In order to measure differences of lower marbling breeds and at shorter feeding periods, we have compared Tm in subcutaneous fat samples from over the striploin. Supplementary feeding for 100 to 150 days leads to a rapid decrease in Tm of 50% Red Wagyu (Akaushi) : 50% European crosses, when compared to 100% European. This improvement indicates that the genetic effect of Wagyu is useful, predictable, and highly penetrant. Contemporaneous DNA extraction does not affect the measurement of Tm. Thus, provenance can be traced and substitution can be eliminated in a simple and cost-effective manner.

Evaluation of the innate immune response of Angus heifers with genetic marker variation for intramuscular fat deposition following a lipopolysaccharide challenge

This study evaluated the effect of genetic selection for markers related to marbling deposition in Angus heifers on the immune response following a lipopolysaccharide (LPS) challenge. Fall-born heifers (n=19; ~7 months of age, 274±24kg) with genetic variation for marbling were utilized including 10 heifers with no genetic markers (No-MVP) and 9 heifers with ≥1 markers (1+MVP). Genotypic variation for quantitative trait loci QG1 and QG2 heifers was determined. Twenty-four hour (h) prior to the LPS challenge, heifers were fitted with jugular catheters and vaginal temperature (VT) monitoring devices. Temperature monitoring devises were programed to record VT in 1min intervals. On day (d) 0, 2h prior to LPS challenge and 8h post challenge, serum was collected in 0.5h intervals (0800–1800h). Serum was also collected at 12, 16, 20, and 24h post LPS challenge. The LPS challenge was administered to the heifers at 1000h via intravenous bolus (0.5μg/kg BW). Serum was analyzed for cortisol, TNF-α, IL-6, IFN-γ, and haptoglobin (HAPT). A treatment×time interaction existed (P≤0.001) for VT; prior the LPS challenge, VT was similar. Vaginal temperature was elevated from 6 to 21h post-LPS in 1+MVP compared to No-MVP. A treatment×time interaction (P=0.02) was observed for IFN-γ. Prior to the LPS challenge, IFN-γ concentrations were similar between the two groups. However, 3.5–7h post-LPS concentrations of IFN-γ were greater (P≤0.05) for 1+MVP compared to No-MVP. There was no treatment effect (P≥0.17) for cortisol, TNF-α or IL-6. A treatment effect (P=0.02) was observed for HAPT; 1+MVP had decreased HAPT compared to No-MVP. Overall, results suggest that heifers selected based upon genetic markers for marbling may have an altered immune in response when challenged with LPS.

Supplementation of glycerol or fructose via drinking water to enhance marbling deposition and meat quality of finishing cattle.

Thirty-six Angus-cross steers (667 ± 34.4 kg initial BW, 24.5 mo) were used to assess the impact of short-term glycerin or high-fructose corn syrup administration via drinking water on meat quality and marbling deposition. Steers blocked by BW (3 blocks) were assigned randomly to 1 of 3 drinking water treatments: 1) control (CON), 2) 4.3% crude glycerin (GLYC), or 3) 4.3% high-fructose corn syrup (HFCS) for the final 25 d before slaughter. Average daily gain was lower ( = 0.01) and final live weight was lower ( < 0.01) with HFCS administration compared with CON. Dry matter intake and water intake did not differ among treatments. Fat thickness, muscle depth, and intramuscular fat measured by ultrasound did not differ among treatments. Crude glycerin or HFCS via water supplementation did not alter HCW, dressing percentage, rib eye area, fat thickness, KPH, skeletal maturity, or marbling score. Longissimus muscle and subcutaneous fat color (L*, a*, and b*) were not affected by drinking water treatment. Total lipid content, total fatty acid content, and fatty acid composition of the LM did not differ among drinking water treatments. Supplementation of drinking water with GLYC or HFCS did not alter Warner-Bratzler shear force values or water-holding capacity (drip loss, cook shrink). Intramuscular mean adipocyte diameter was greater ( = 0.02) for steers offered HFCS compared with steers offered GLYC, with CON steers being intermediate. These differences in mean adipocyte size were related to changes in the adipocyte size distribution. There were greater proportions of small (20 to 30 μm) adipocytes in GLYC compared with HFCS and CON. In contrast, HFCS and CON had greater proportions of medium (40 to 50 μm) adipocytes than GLYC. The relative mRNA expression of lipogenic genes (acetyl Co-A carboxylase [ACC], fatty acid binding protein 4 [FABP4], fatty acid synthase [FASN], glycerol-3-phosphate acyltransferase [GPAT], retinol-binding protein 4 [RBP4], and stearoyl-CoA desaturase [SCD]), adipocyte differentiation genes (delta-like 1 homolog [DLK1]), and transcription factors (CCAAT/enhancer-binding protein α [C/EBPα], and PPARγ) was similar for GLYC and HFCS compared with CON. Longissimus glycogen and lactate concentrations and glycolytic potential were not affected by drinking water treatments. Overall, HFCS or GLYC supplementation via drinking water did not alter carcass or meat quality variables but did alter the size and distribution of intramuscular adipocytes. These results indicate that a longer supplementation time or a higher substrate level may be needed to obtain differences in meat quality.

The effect of supplementing rumen undegradable unsaturated fatty acids on marbling in early-weaned steers.

The objective of this study was to determine if supplementation with a rumen undegradable unsaturated fatty acids (FA) source improved marbling deposition in early-weaned steers. All steers (Angus, = 23; Angus × Hereford, = 24) were weaned at 150 ± 5 d of age. Steers were blocked by BW and breed and then randomly assigned to either control (CON; average 1.5 kg of corn gluten feed [CGF], = 23) or isocaloric supplementation containing a rumen undegradable fat source (RUF; 200 g of Megalac-R added to an average of 1.06 kg of CGF, = 24) offered 5 d/wk for 110 d. All steers had ad libitum access to pastures throughout treatment and received supplements individually. Steer BW and blood samples were collected at 0, 55, and 110 d of supplementation, and real-time ultrasound measurements were collected at d 110. Following treatment, steers were transported to Oklahoma State University for finishing and subsequent harvesting at a commercial plant. All data were analyzed using the PROC MIXED procedure of SAS either as repeated measures or ANOVA depending on parameters. There were no significant changes in BW from the beginning of treatment to harvest due to treatment. Ultrasound data showed that RUF steers tended ( = 0.08) to have more i.m. fat than CON at d 110. Serum concentrations of FA showed a treatment × day interaction ( < 0.02) for 16:0, 18:0, 18:1-9, 18:2, 20:4, and total FA. These specific FA concentrations slightly increased in CON steers, but there was a more pronounced increase in the concentration of these FA across the supplementation period in RUF steers. Serum triglyceride and cholesterol concentrations were increased ( < 0.01) on d 55 and 110 in RUF steers compared with those in CON steers. Serum leptin concentration in RUF steers was greater ( < 0.01) than CON steers at d 110. After harvest, RUF carcasses had greater ( = 0.01) marbling scores than those of CON carcasses. All other carcass measures were similar between treatments. The percentage of total lipids was increased ( = 0.011) in steaks from RUF compared to CON. There was a decrease ( < 0.05) in adipocyte diameter in i.m. fat depot of RUF steers compared to CON. There was also a tendency ( = 0.06) for RUF steers to have a greater percentage of 20 to 30 μm adipocytes in their i.m. depot than CON steers. This study indicates that supplementation of unsaturated FA can positively impact marbling deposition in early-weaned steers without impacting other carcass measures.