Molecular and Cellular Mechanisms of Intramuscular Fat Development and Growth in Cattle

Intramuscular fat, also referred to as marbling fat, is the white fat deposited within skeletal muscle tissue. The content of intramuscular fat in the skeletal muscle, particularly the longissimus dorsi muscle, of cattle is a critical determinant of beef quality and value. In this review, we summarize the process of intramuscular fat development and growth, the factors that affect this process, and the molecular and epigenetic mechanisms that mediate this process in cattle. Compared to other species, cattle have a remarkable ability to accumulate intramuscular fat, partly attributed to the abundance of sources of fatty acids for synthesizing triglycerides. Compared to other adipose depots such as subcutaneous fat, intramuscular fat develops later and grows more slowly. The commitment and differentiation of adipose precursor cells into adipocytes as well as the maturation of adipocytes are crucial steps in intramuscular fat development and growth in cattle. Each of these steps is controlled by various factors, underscoring the complexity of the regulatory network governing adipogenesis in the skeletal muscle. These factors include genetics, epigenetics, nutrition (including maternal nutrition), rumen microbiome, vitamins, hormones, weaning age, slaughter age, slaughter weight, and stress. Many of these factors seem to affect intramuscular fat deposition through the transcriptional or epigenetic regulation of genes directly involved in the development and growth of intramuscular fat. A better understanding of the molecular and cellular mechanisms by which intramuscular fat develops and grows in cattle will help us develop more effective strategies to optimize intramuscular fat deposition in cattle, thereby maximizing the quality and value of beef meat.

Polymorphism of Genes and Their Impact on Beef Quality

The single-nucleotide polymorphism (SNP) form of genes is a valuable source of information regarding their suitability for use as specific markers of desirable traits in beef cattle breeding. For several decades, breeding work focused on improving production efficiency through optimizing the feed conversion ratio and improving daily gains and meat quality. Many research teams previously undertook research work on single-nucleotide polymorphism in myostatin (MSTN), thyroglobulin (TG), calpain (CAPN), and calpastatin (CAST) proteins. The literature review focuses on the most frequently addressed issues concerning these genes in beef cattle production and points to a number of relevant studies on the genes' polymorphic forms. The four genes presented are worth considering during breeding work as a set of genes that can positively influence productivity and production quality.

Transformation of highly marbled meats under various cooking processes

Cooking induces modifications in meat structure and composition, affecting its sensory and nutritional properties. These changes depend on the cooking method and meat characteristics. In the present study, beef were cooked in three different ways-grilling, boiling, and sous-vide cooking-with two endpoint temperatures, 55 °C and 77 °C, to better understand the general impact of cooking on the structure of fatty meat. Light microscopy was used to visualize muscle, connective, and adipose tissues. After cooking, muscle fibers were more compact, which can be attributed to perimysium shrinkage and water transfer, for all cooking processes except grilling at 55 °C. The cross-sectional area of muscle fibers was not impacted by cooking, regardless of the temperature or cooking method. Connective tissue between adipocytes was affected by cooking at 77 °C, but not at 55 °C. Despite the cooking method used, cooking to well-done (77 °C) clearly affected the structure of the perimysium of beef, possibly because of collagen denaturation.

Main regulatory factors of marbling level in beef cattle

The content of intramuscular fat (IMF), that determines marbling levels is considered as one of the vital factors influencing beef sensory quality including tenderness, juiciness, flavour and colour. The IMF formation in cattle commences around six months after conception, and continuously grows throughout the life of the animal. The accumulation of marbling is remarkably affected by genetic, sexual, nutritional and management factors. In this review, the adipogenesis and lipogenesis process regulated by various factors and genes during fetal and growing stages is briefly presented. We also discuss the findings of recent studies on the effects of breed, gene, heritability and gender on the marbling accumulation. Various research reported that feeding during pregnancy, concentrate to roughage ratios and the supplementation or restriction of vitamin A, C, and D are crucial nutritional factors affecting the formation and development of IMF. Castration and early weaning combined with high energy feeding are effective management strategies for improving the accumulation of IMF. Furthermore, age and weight at slaughter are also reviewed because they have significant effects on marbling levels. The combination of several factors could positively affect the improvement of the IMF deposition. Therefore, advanced strategies that simultaneously apply genetic, sexual, nutritional and management factors to achieve desired IMF content without detrimental impacts on feed efficiency in high-marbling beef production are essential.

Effects of Management, Dietary Intake, and Genotype on Rumen Morphology, Fermentation, and Microbiota, and on Meat Quality in Yaks and Cattle

Traditionally, yaks graze only natural grassland, even in harsh winters. Meat from grazing yaks is considered very healthy; however, feedlot fattening, which includes concentrate, has been introduced. We questioned whether this change in management and diet would have an impact on the rumen and meat quality of yaks. This study examined the morphology, fermentation, and microbiota of the rumen and the quality of meat of three groups of bovines: (1) grazing yaks (GYs, 4-year olds), without dietary supplements; (2) yaks (FYs, 2.5-year olds) feedlot-fattened for 5 months after grazing natural pasture; and (3) feedlot-fattened cattle (FC, Simmental, 2-year olds). This design allowed us to determine the role of diet (with and without concentrate) and genotype (yaks vs. cattle) on variables measured. Ruminal papillae surface area was greater in the FYs than in the GYs (P = 0.02), and ruminal microbial diversity was greater but richness was lesser in the GYs than in the FC and FYs. Concentrations of ruminal volatile fatty acids were greater in the yaks than in the cattle. In addition, both yak groups had higher protein and lower fat contents in meat than the FC. Meat of GY had a lower n6:n3 ratio than FY and FC, and was the only group with a ratio below r, which is recommended for healthy food. Essential amino acids (EAA), as a proportion of total AA and of non-essential AA of yak meat, met WHO criteria for healthy food; whereas FC did not.

Effects of chilling duration on USDA Quality Grade of beef carcasses

Two hundred and nine beef carcasses (BW of 361 ± 53 kg) from crossbred, grain-finished cattle were harvested in a commercial abattoir and subjected to a 96-h spray chilling treatment, conducted at 0 to 3°C in a commercial hot box with a wind speed of 3.1 m/s and 153-lux of fluorescent light. At the 24, 48, 72, and 96 h points of the treatment, the carcasses were analyzed for fatty acid composition, marbling score, core temperature (n = 1), pH, shrinkage, color, and aerobic plate count (n = 50). Carcasses reached 3ºC after 12 to 16 h of chilling. There were minimal changes in shrinkage among time point (-0.4 to 1.2%; P ≤ 0.002), pH (5.56 to 5.69; P ≤ 0.001), and aerobic plate count (APC) (0.1 to 0.7 log; P ˂ 0.001). Initial 24-h grading revealed a grade composition of 21.1% Slight (SL, n = 44), 34.0% Small (SM, n = 71), 17.2% Modest (MT, n = 37), 17.7% Moderate (MD, n = 36), and 10.1% Slightly Abundant (SA, n = 21). With marbling score in numeric values between 200 (Practically Devoid00) and 1100 (Abundant00), carcasses that had SM or greater marbling score at 24 h experienced a deduction of 34 to 60 points by the 96th hour of spray chilling (P ≤ 0.042). Comparatively, the marbling scores of the SL carcasses increased from 442 points at 24 h to 469 points at 96 h. Moreover, SL carcasses had a greater percentage of polyunsaturated fats (PUFA) (P < 0.001). Results indicate that spray chilling for 96 h may slightly increase the marbling score of USDA Select, but has minimal impacts on marbling score of greater USDA quality grades.

The Meat Quality Characteristics of Holstein Calves: The Story of Israeli 'Dairy Beef'

Global animal production systems are often criticized for their lack of sustainability and insufficient resilience to ensure food security. The ‘farm-to-fork’ approach aims at orienting food systems towards the creation of a positive environmental impact, nutritious, healthy, safe and sufficient foods, and fairer economic returns for primary producers. Many countries rely on an imported supply of live animals to fulfill their needs for fresh meat. In Israel, ~60% of the sources of fresh beef come from the import of live animals. In order to encourage sustainable beef production in Israel, the proportion of local beef should be raised at the expense of imported animals. However, for this to be achieved, the superior performance of local beef should be justified. The current study was conducted to compare between the meat quality characteristics of local (Israeli Holstein; N = 205) vs. imported (Australian; N = 169) animals. Generally, while the imported calves presented a higher dressing percentage (p < 0.0001), the local animals were characterized by tenderer meat (p < 0.0001), longer sarcomeres (p < 0.0001), higher a* color attributes and pH (p < 0.001), superior cooking (p = 0.002) and thawing loss (p < 0.0001), higher intra-muscular fat (IMF) content, and a higher PUFA proportion (p < 0.01 and p < 0.0001, respectively) and PUFA:SFA ratio. The findings shown herein may provide sound arguments for stakeholders and policy makers to facilitate sustainable local beef production in Israel.

Fatty Acid Composition of Meat Animals as Flavor Precursors

This article provides an overview of fatty acids in meat, their variation among animal species, and the roles of fatty acids as flavor precursors. Animal fat mostly consists of triglycerides and phospholipids. Fats from ruminant (cattle, sheep, and goats) and monogastric (pigs and horses) animals have similar fatty acids with more saturated fatty acids and monounsaturated fatty acids than polyunsaturated fatty acids. In monogastric animals, fatty acids in the muscle reflect the composition of diets, whereas ruminant fatty acids are more saturated because of biohydrogenation in the rumen. Lipid- derived flavor compounds are formed from the thermal oxidation of fatty acids during cooking, producing more desirable aromatic compounds than autoxidation. Monounsaturated fatty acids such as oleic acid and polyunsaturated fatty acids such as linoleic acid in meat produce various volatile compounds contributing to cooked meat aromas. Under most cooking conditions, lipid-derived flavor compounds are usually predominant. However, these compounds have greater thresholds than those derived from water-soluble compounds, such as the Maillard reaction products. The interactions between lipid oxidation products and Maillard compounds are more important for the development of meat flavor than originally thought. Moreover, fat-derived volatile compounds provide flavor notes indicative of species identification.

Comparison of carcass characteristics and meat quality between Simmental crossbred cattle, cattle-yaks and Xuanhan yellow cattle

BACKGROUND

The study compared the growth performance, carcass characteristics and meat quality of steers of Xuanhan yellow cattle, Simmental crossbreed cattle (Simmental × Xuanhan yellow cattle) and cattle-yak (Jersey × yak). All steers were feed with the same diet from 6 months until slaughter at 30 months. The longissimus dorsi muscle was used to compare the meat quality traits.

RESULTS

By comparison, Simmental crossbreed cattle had higher growth performance (P < 0.05) and carcass characteristics (P < 0.05); cattle-yak had higher value of a*, b* of meat color (P < 0.05) and higher protein contents of meat (P < 0.05); Xuanhan yellow cattle had higher water holding capacity (P < 0.05) and lower shear force (P < 0.05).

CONCLUSIONS

The results show that Simmental crossbred cattle had better meat performance and provided low-fat meat with a beneficial fatty acid composition, but with lower meat quality; cattle-yaks provided greater meat color and higher protein content; Xuanhan yellow cattle provided meat with preferable tenderness. © 2020 Society of Chemical Industry.

Effect of dietary restriction and compensatory growth on performance, carcass characteristics, and metabolic hormone concentrations in Angus and Belgian Blue steers

Compensatory growth (CG) is the ability of an animal to undergo accelerated growth after a period of restricted feeding. However, there is a dearth of information in relation to the effect of genotype on CG response, thus the objective of this study was to evaluate CG response in two contrasting breed types, namely Aberdeen Angus (AN) and Belgian Blue (BB). Crossbred AN × Holstein-Friesian or BB × Holstein-Friesian steers were assigned to one of two treatment groups in a two (genotypes) × two (diets) factorial design. For 99 days, one group (11 AN and 12 BB) was offered a high energy control diet (H-H) whereas the second group (11 AN and 12 BB) was offered an energy restricted diet (L-H). At the end of the differential feeding period (99 days), both groups of animals were then offered a high energy control diet for a further 200 days. All animals were then slaughtered on day-299 of the study. During feed restriction, L-H had lower DM intake (DMI), had greater feed conversion ratio (FCR) and lower plasma concentrations of insulin, IGF-1, leptin, glucose, urea, betahydroxybutyrate and smaller M. longissimus thoracis or lumborum muscle and fat depths compared to H-H steers. During realimentation, there was no difference in DMI between diets; however, L-H had greater live weight gain compared to H-H steers. Overall, H-H consumed greater quantities on a DM basis, however, had a higher FCR compared to L-H steers. By the end of the realimentation period, there was no difference in plasma metabolite or hormone concentrations, linear body measurements, ultrasonically scanned fat depths, carcass conformation, dressing percentage or fat class between H-H and L-H steers. At slaughter, carcass weights were affected by diet with greater values for H-H compared to L-H steers. Genotype affected measures associated with body composition including pelvic width and both muscle and fat depths (P < 0.05). Overall, L-H had a CG (or recovery) index of 0.52 and did not make up for the loss of gains during the differential feeding period; however, M. longissimus thoracis et lumborum, a tissue of high economic value, recovered completely making it a target of interest for further investigation.

Tissue-specific fatty acid composition, cellularity, and gene expression in diverse cattle breeds

The nutritional quality of beef relates to the fatty acid (FA) composition of bovine adipose tissue. Those molecular mechanisms that induce the differing amounts and composition of fat in cattle breeds according to age at maturity and purpose of production remain unclear. Therefore, this study investigated the composition of total FAs, adipocyte size, and expression of some key genes involved in several adipogenesis and lipogenesis pathways measured in distinct adipose tissue depots from bulls of the genetically diverse cattle breeds Aberdeen Angus (n = 9), Gascon (n = 10), Holstein (n = 9), and Fleckvieh (n = 10). The animals were finished under identical housing and feeding conditions until slaughter at a similar age of 17 months. After slaughter, cod adipose tissue (CAT), subcutaneous adipose tissue (SAT), and M. longissimus lumborum (MLL) samples were collected. The saturated FA proportions were higher (P < .01) in CAT than in SAT across all breeds, whereas monounsaturated FA proportions were consistently higher (P < .001) in SAT compared to CAT and MLL. Aberdeen Angus bulls were distinguished from the other breeds in the proportions of mostly de novo synthesized C14:0, C16:0, C14:1n-5, C16:1n-7, and conjugated linoleic acid (P < .05). Adipocyte size decreased in the order CAT > SAT > MLL, and the largest adipocytes were observed in CAT of Holstein bulls (P < .05). Gene expression differences were more pronounced between adipose tissue depots than between breeds. The expression levels of ACACA, FASN, and SCD1 genes were related to tissue-specific, and to a lesser extent also breed-specific, differences in FA composition.

Lipidomic markers of sperm cryotolerance in cattle

The objective of the current study was to determine the fatty acid composition of sperm from Holstein bulls with different freezability (Good and Poor; n = 12). Fatty acids were extracted from frozen sperm in 1:2 (v/v) chloroform-methanol solvent, fractionated into neutral and polar fractions, and composition determined by gas chromatography-mass spectrometry. Thirty-four fatty acids were quantified and their concentrations and percentages within each lipid fraction were calculated. Overall, saturated fatty acids (SFA) were predominant, accounting for 71 to 80% of fatty acids in neutral and polar lipid factions. There were marked differences in fatty acid composition between the lipid fractions (P < 0.001). The branched chain fatty acid (BCFA) concentration (15 to 18 µg) was almost twice as much as polyunsaturated fatty acids (PUFA) concentration found in the polar lipid fraction (8 to 9 µg; P < 0.001). Sperm with different freezability phenotypes only had a few differences in 22:0, 18:1 cis 9, and 14:0 13-methyl fatty acids (P ≤ 0.011). These results are significant because they reveal key understandings of fatty acid composition of sperm membrane and lay a foundation for the manipulation of membrane integrity, fluidity, and stability to advance the assisted reproductive technologies.

The Study of the Response of Fat Metabolism to Long-Term Energy Stress Based on Serum, Fatty Acid and Transcriptome Profiles in Yaks

Simple Summary

The serum, fatty acid and transcriptome profiles in the subcutaneous fat of yaks were measured to explore the effect of long-term energy stress (ES) on fat metabolism during the cold season. The study indicated that under long-term ES during the cold season, the amount of fat in yaks was less, and fat mobilization was one of the main ways by which energy was obtained in yaks. Yaks regulated fat metabolism in subcutaneous fat primarily through adenosine 5′-monophosphate-activated protein kinase (AMPK) signaling. Glucose (GLU) intake, fat catabolism, fatty acid synthesis and fatty acid oxidation in the subcutaneous fat of yaks were all inhibited, which resulted in the fat mobilization of yaks slowing as much as possible under long-term ES. In addition, the energy expenditures in fat cells were inhibited by regulating phosphatidylinositol 3’ -kinase (PI3K)-serine/threonine-protein kinase (Akt) andmammalian target of rapamycin (mTOR) signaling, and the limited energy obtained from GLU and fat was consumed by muscle and organs as much as possible. These factors led to an energy balance in yaks under long-term ES. The fat stored in yaks can be expended for as long as possible, and yaks can survive for as long as necessary under long-term ES.

Abstract

Long-term energy stress (ES) during the cold season is a serious problem for the breeding of yaks. In this paper, the response of fat metabolism in yaks to long-term ES during the cold season was studied. Gas chromatography (GC) analysis showed that the percentage of saturated fatty acids (SFAs) in the subcutaneous fat of the yaks in the ES group was 42.7%, which was less than the 56.6% in the CO group (p < 0.01) and the percentage of polyunsaturated unsaturated fatty acids (PUFAs) in the subcutaneous fat of the yaks in the ES group was 38.3%, which was more than the 26.0% in the CO group (p < 0.01). The serum analysis showed that fatty acid oxidation in yaks was increased under long-term ES. In the subcutaneous fat of yaks under long-term ES, the gene expression levels of glycerol-3-phosphate acyltransferase 4 (GPAT4), hormone-sensitive lipase (HSL), patatin-like phospholipase domain-containing protein 2 (PNPLA2), acyl-CoA dehydrogenase (ACAD), acyl-coenzyme A thioesterase 8 (ACOT8), facilitated glucose transporter (GLUT4), 3-oxoacyl-[acyl-carrier-protein] synthase (OXSM), oestradiol 17-beta-dehydrogenase 8 (HSD17B8) and malonate-Co-A ligase ACSF3 (ACSF3) were downregulated (q < 0.05), whereas the gene expression levels of aquaporin-7 (AQP7), long-chain-fatty-acid-CoA ligase (ACSL), elongation of very long chain fatty acids protein (ELOVL) and fatty acid desaturase 1 (FADS1) were upregulated (q < 0.05), indicating the inhibition of fat catabolism, fat anabolism, fatty acid oxidation, glucose (GLU) intake and SFA synthesis and the promotion of glycerinum (GLY) transportation and PUFA synthesis. Additional findings showed that the gene expression levels of leptin (LEP), adenosine 5′-monophosphate-activated protein kinase (AMPK) and phosphatidylinositol 3-kinase (PI3K) were upregulated (q < 0.05), whereas the gene expression levels of malonyl-CoA decarboxylase (MCD), sterol regulatory element-binding protein 1 (SREBF1), mammalian target of rapamycin (mTOR) and serine/threonine-protein kinase (AKT) were downregulated (q < 0.05), indicating that fat metabolism in the subcutaneous fat of yaks under ES was mainly regulated by AMPK signaling and mTOR and PI3K-AKT signaling were also involved. Energy consumption was inhibited in the subcutaneous fat itself. This study can provide a theoretical basis for the healthy breeding and genetic breeding of yaks.

Biology, strategies, and fresh meat consequences of manipulating the fatty acid composition of meat

The utility and attractiveness of adipose tissue within meat products vary based on species, cut, and consumer preference. In beef, producers are rewarded for producing carcasses with greater visual marbling at the 12th and 13th rib juncture, while pork producers are either not rewarded or penalized for producing carcasses with too much adipose tissue. Some consumers prefer to purchase leaner meat cuts, while other consumers pay premiums to consume products with elevated fat content. While no clear consumer adipose tissue preference standard exists, advances in beef and swine nutrition have enabled producers to target markets that enable them to maximize profits. One niche market that has increased in popularity over the last decade is manipulating the fatty acid profile, specifically increasing omega-3 fatty acid content, of beef and pork products to increase their appeal in a healthy diet. While much research has documented the ability of preharvest diet to alter the fatty acid profile of beef and pork, the same studies have indicated both the color and palatability of these products were negatively affected if preharvest diets were not managed properly. The following review discusses the biology of adipose tissue and lipid accumulation, altering the omega-3 fatty acid profile of beef and pork, negative fresh meat color and palatability associated with these studies, and strategies to mitigate the negative effects of increased omega-3 fatty acid content.

Fatty acid profile, mineral content, and palatability of beef from a multibreed Angus-Brahman population

Consumers demand meat that is both healthy and palatable, 2 attributes of meat that are affected by lipid content. Many cattle in the southern United States are Bos indicus influenced, as this improves the ability to survive and thrive in these subtropical regions. However, these animals tend to have leaner carcasses and less marbled meat products. Thus, the objective of this study was to examine the effect of percent Brahman genetics on carcass characteristics, palatability, fatty acids profile, and minerals content in LM of steers from a multibreed population ranging from 100% Angus to 100% Brahman. Breed effect was significant for birth weight (P = 0.0003), weaning weight (P < 0.0001), HCW (P < 0.0001), dressing percentage (P = 0.0008), ribeye area (P = 0.002), quality grade (P < 0.0001), and marbling score (P < 0.0001), and all these traits except dressing percentage decreased as the percentage of Brahman increased. Among palatability traits, breed group had a significant effect only on tenderness (TEND) and connective tissue (CT) scores (P < 0.0001). Least squares means decreased from Angus (5.75 ± 0.13 TEND score and 6.29 ± 0.14 CT score, respectively) to Brahman (4.84 ± 0.10 TEND score and 5.49 ± 0.11 CT score, respectively) as indicated by a significant linear effect. Breed group significantly affected the percentage of several individual fatty acids, saturated fatty acids (SFA), and polyunsaturated fatty acids (PUFA), but not monounsaturated fatty acids (MUFA). The 100% Angus group had the highest percentage of SFA at 49.92%, which was significantly higher (P < 0.05) than the SFA percentage in the 50%, 75%, and 100% Brahman breed groups. Brangus animals also had an increased SFA percentage compared with the 100% Brahman animals (P < 0.05). No significant effect was identified for the concentration of PUFA across the 6 breed groups (P = 0.14). Least squares means decreased from 100% Angus to 100% Brahman for concentration of total fat, SFA, and MUFA (g/mg meat). The concentration of magnesium (P < 0.0001), phosphorus (P = 0.06), and potassium (P = 0.06) increased as the percentage of Brahman increased. Our study shows that breed has a significant effect on the fatty acid profile of beef. Cattle with high Brahman percentage, which are characterized by lower marbled meat, will present a more favorable healthfulness profile with reduced content of SFA and MUFA but the same content of PUFA as purebred Angus animals.

Effects of dietary lysine level on the content and fatty acid composition of intramuscular fat in late-stage finishing pigs

This study was conducted to investigate how dietary lysine level affects the intramuscular fat (IMF) content and fatty acid (FA) composition in late-stage finishing pigs. Nine crossbred barrows [94.4 ± 6.7 kg body weight (BW)] were randomly allotted to three treatment groups (n = 3). Three corn- and soybean-meal-based diets were formulated to meet the National Research Council (2012) requirements for various nutrients except for lysine, whose concentrations were 0.43%, 0.71%, and 0.98% (as-fed basis) for Diets 1 (lysine-deficient), 2 (lysine-adequate), and 3 (lysine-excess), respectively. After 5 wk of ad libitum access to diets, pigs were harvested and longissimus dorsi samples were collected. The IMF content and FA composition of the samples were analyzed by gas chromatography. Results showed that the IMF content of the muscle was increased linearly (P < 0.05) with decreasing dietary lysine level from 0.98% to 0.43%. Dietary lysine level altered the composition of FA, especially the unsaturated FA, in the muscle. Particularly, the percentages of C18:1 n-9 and total monounsaturated FA were higher, whereas the percentages of C18:2 n-6 and total polyunsaturated FA were lower, in the muscle of the pigs fed Diet 1. Collectively, dietary lysine deficiency increased the proportion of monounsaturated FA and decreased the proportion of polyunsaturated FA, which may benefit pork palatability.

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.

Adiposity, lipogenesis, and fatty acid composition of subcutaneous and intramuscular adipose tissues of Brahman and Angus crossbred cattle

The objective of this study was to demonstrate differences in aspects of adipose tissue cellularity, lipid metabolism, and fatty and cholesterol composition in Angus and Brahman crossbred cattle. We hypothesized that in vitro measures of lipogenesis would be greater in three-fourths Angus progeny than in three-fourths Brahman progeny, especially in intramuscular (i.m.) adipose tissue. Progeny ( = 227) were fed a standard, corn-based diet for approximately 150 d before slaughter. Breed was considered to be the effect of interest and was forced into the model. There were 9 breed groups including all 4 kinds of three-fourths Angus calves: Angus bulls Angus-sired F cows ( = 32), Angus bulls Brahman-sired F cows ( = 20), Brahman-sired F bulls Angus cows ( = 24), and Angus-sired F bulls Angus cows ( = 20). There were all 4 kinds of three-fourths Brahman calves: Brahman bulls Brahman-sired F cows ( = 21), Brahman bulls Angus-sired F cows ( = 43), Brahman-sired F bulls Brahman cows ( = 26), and Angus-sired F bulls Brahman cows ( = 13). Additionally, F calves (one-half Brahman and one-half Angus) were produced only from Brahman-sired F bulls Angus-sired F cows ( = 28). Contrasts were calculated when breed was an important fixed effect, using the random effect family(breed) as the error term. Most contrasts were nonsignificant ( > 0.10). Those that were significant ( < 0.05) included cholesterol concentration of subcutaneous (s.c.) adipose tissue (three-fourths Angus > F, three-fourths Brahman > F, and three-fourths crossbred progeny combined > F), s.c. adipocyte volume (three-fourths Angus > F and three-fourths bloods combined > F), lipogenesis from acetate in s.c. adipose tissue (three-fourths Brahman calves from Brahman dams > three-fourths Brahman calves from F dams), and percentage 18:3-3 in s.c. adipose tissue (three-fourths Brahman calves from Brahman-sired F dams < three-fourths Brahman calves from Angus-sired F dams). Intramuscular adipocyte volume ( < 0.001) was less in three-fourths Brahman cattle than in three-fourths Angus cattle. Additionally, several differences were observed in i.m. adipose tissue that were consistent with this being a less-developed adipose tissue in three-fourths Brahman cattle than in three-fourths Angus cattle.

Fatty acid composition and physicochemical and sensory characteristics of meat from ewe lambs supplemented with zilpaterol hydrochloride and soybean oil

The effects of supplementation of zilpaterol hydrochloride (ZH; 0 or 10 mg/lamb daily) and soybean oil (SBO; 0% or 6%) on carcass traits, body fat deposition, chemical, physicochemical, sensory quality, and fatty acid composition of the longissimus thoracis muscle (LTM) of ewe lambs were studied using a randomised complete design with a 2 × 2 factorial arrangement. After a 32-day feeding period, all ewes were slaughtered and LTM collected. Interactions between ZH × SBO were not observed (P > 0.05) for any of the variables evaluated. Feedlot performance was not modified (P > 0.05) by ZH and SBO supplementation. Biological yield and hot carcass weight were increased by ZH supplementation (P < 0.05). ZH and SBO supplementation did not alter body fat deposition (kidney, pelvic and heart, renal, thickness and intramuscular fat) and the empty bodyweight (P > 0.05). Meanwhile, feeding ZH decreased colour parameters (L*, a*, b* and CHROMA) (P < 0.05), but not others characteristics of LTM (P > 0.05). Sensory panelists observed an increase in appearance (P < 0.001) by ZH supplementation. Additionally, ZH decreased (P < 0.05) the content of C20:5n3 (eicosapentaenoic acid), C22:6n-3 (docosahexaenoic acid) and total omega-3 fatty acids, compared with the zero ZH group. Physicochemicals and sensory characteristics, and fatty acid composition of meat were not modified by SBO (P > 0.05). In conclusion, ZH supplementation to ewe lambs increased biological yield and hot carcass weight, without changes in body fat deposition and decreased eicosapentaenoic acid, docosahexaenoic acid and omega-3 contents and caused a decrease in colour of LTM. However, feeding SBO caused no changes in the carcass or meat quality traits and minimal changes in fatty acid composition of LTM.

Fatty Acid Profiles of Ten Muscles from High and Low Marbled (Quality Grade 1++ and 2) Hanwoo Steers

The aim of this research was to evaluate: 1) the fatty acid profile of ten muscles from high marbled (HM, quality grade 1⁺⁺) and low marbled (LM, quality grade 2) Hanwoo carcass, 2) the relationship between the fatty acid profile and sensory traits. There were significant (p<0.001) differences in fat content and fatty acid composition among the 10 muscles obtained from HM and LM Hanwoo steers. The proportions of SFA (saturated fatty acid), MUFA (monounsaturated fatty acid) and PUFA (polyunsaturated fatty acid) were significantly (p<0.001) different among the 10 muscles due to differences in all fatty acids except eicosapentaenoic acid (EPA, C20:5n-3). The high-fat muscles had a lower n-6/n-3 ratio compared to the low-fat muscles (p<0.001). LM muscles had a significantly (p<0.05) higher proportion of SFA than HM muscles due to a higher proportion of stearic acid (C18:0). On the contrary, HM muscles had a significantly (p<0.01) higher proportion of MUFA than LM muscles due to higher oleic acid (C18:1n-9) proportion. SFA had a significant correlation with CIE a* (r=0.281; p<0.01) and drip loss (%) (r=-0.233; p<0.001). Cooking loss (%) had a significantly (p<0.05) negative correlation with PUFA (r=-0.233; p<0.05). Overall palatability was positively correlated with SFA (r=0.262; p<0.01), but negatively correlated with PUFA (r=-0.567; p<0.001). There was no significant correlation between oleic acid and any of the sensory traits (p>0.05).

Strategies to enable the adoption of animal biotechnology to sustainably improve global food safety and security

The ability to generate transgenic animals has existed for over 30 years, and from those early days many predicted that the technology would have beneficial applications in agriculture. Numerous transgenic agricultural animals now exist, however to date only one product from a transgenic animal has been approved for the food chain, due in part to cumbersome regulations. Recently, new techniques such as precision breeding have emerged, which enables the introduction of desired traits without the use of transgenes. The rapidly growing human population, environmental degradation, and concerns related to zoonotic and pandemic diseases have increased pressure on the animal agriculture sector to provide a safe, secure and sustainable food supply. There is a clear need to adopt transgenic technologies as well as new methods such as gene editing and precision breeding to meet these challenges and the rising demand for animal products. To achieve this goal, cooperation, education, and communication between multiple stakeholders-including scientists, industry, farmers, governments, trade organizations, NGOs and the public-is necessary. This report is the culmination of concepts first discussed at an OECD sponsored conference and aims to identify the main barriers to the adoption of animal biotechnology, tactics for navigating those barriers, strategies to improve public perception and trust, as well as industry engagement, and actions for governments and trade organizations including the OECD to harmonize regulations and trade agreements. Specifically, the report focuses on animal biotechnologies that are intended to improve breeding and genetics and currently are not routinely used in commercial animal agriculture. We put forward recommendations on how scientists, regulators, and trade organizations can work together to ensure that the potential benefits of animal biotechnology can be realized to meet the future needs of agriculture to feed the world.

Putative regulatory factors associated with intramuscular fat content

Intramuscular fat (IMF) content is related to insulin resistance, which is an important prediction factor for disorders, such as cardiovascular disease, obesity and type 2 diabetes in human. At the same time, it is an economically important trait, which influences the sensorial and nutritional value of meat. The deposition of IMF is influenced by many factors such as sex, age, nutrition, and genetics. In this study Nellore steers (Bos taurus indicus subspecies) were used to better understand the molecular mechanisms involved in IMF content. This was accomplished by identifying differentially expressed genes (DEG), biological pathways and putative regulatory factors. Animals included in this study had extreme genomic estimated breeding value (GEBV) for IMF. RNA-seq analysis, gene set enrichment analysis (GSEA) and co-expression network methods, such as partial correlation coefficient with information theory (PCIT), regulatory impact factor (RIF) and phenotypic impact factor (PIF) were utilized to better understand intramuscular adipogenesis. A total of 16,101 genes were analyzed in both groups (high (H) and low (L) GEBV) and 77 DEG (FDR 10%) were identified between the two groups. Pathway Studio software identified 13 significantly over-represented pathways, functional classes and small molecule signaling pathways within the DEG list. PCIT analyses identified genes with a difference in the number of gene-gene correlations between H and L group and detected putative regulatory factors involved in IMF content. Candidate genes identified by PCIT include: ANKRD26, HOXC5 and PPAPDC2. RIF and PIF analyses identified several candidate genes: GLI2 and IGF2 (RIF1), MPC1 and UBL5 (RIF2) and a host of small RNAs, including miR-1281 (PIF). These findings contribute to a better understanding of the molecular mechanisms that underlie fat content and energy balance in muscle and provide important information for the production of healthier beef for human consumption.

Effects of different dietary energy and protein levels and sex on growth performance, carcass characteristics and meat quality of F1 Angus × Chinese Xiangxi yellow cattle

BACKGROUND

The experiment evaluated the effect of nutrition levels and sex on the growth performance, carcass characteristics and meat quality of F1 Angus × Chinese Xiangxi yellow cattle.

METHODS

During the background period of 184 d,23 steers and 24 heifers were fed the same ration,then put into a 2 × 2 × 2 factorial arrangement under two levels of - dietary energy (TDN: 70/80% DM), protein (CP: 11.9/14.3% DM) and sex (S: male/female) during the finishing phase of 146 d. The treatments were - (1) high energy/low protein (HELP), (2) high energy/high protein (HEHP), (3) low energy/low protein (LELP) and (4) low energy/high protein (LEHP). Each treatment used 6 steers and 6 heifers, except for HELP- 5 steers and 6 heifers.

RESULTS

Growth rate and final carcass weight were unaffected by dietary energy and protein levels or by sex. Compared with the LE diet group, the HE group had significantly lower dry matter intake (DMI, 6.76 vs. 7.48 kg DM/d), greater chest girth increments (46.1 vs. 36.8 cm), higher carcass fat (19.9 vs.16.3%) and intramuscular fat content (29.9 vs. 22.8% DM). The HE group also had improved yields of top and medium top grade commercial meat cuts (39.9 vs.36.5%). The dressing percentage was higher for the HP group than the LP group (53.4 vs. 54.9%). Steers had a greater length increment (9.0 vs. 8.3 cm), but lower carcass fat content (16.8 vs. 19.4%) than heifers. The meat quality traits (shear force value, drip loss, cooking loss and water holding capacity) were not affected by treatments or sex, averaging 3.14 kg, 2.5, 31.5 and 52.9%, respectively. The nutritive profiles (both fatty and amino acid composition) were not influenced by the energy or protein levels or by sex.

CONCLUSIONS

The dietary energy and protein levels and sex significantly influenced the carcass characteristics and chemical composition of meat but not thegrowth performance, meat quality traits and nutritive profiles.

Comparison of meat quality between eland (Taurotragus oryx) and cattle (Bos taurus) raised under similar conditions

Physical, chemical and sensory characteristics of meat were compared between non-domestic eland (Taurotragus oryx) bulls (n=6) and domestic Fleckvieh (Bos taurus) bulls (n=6) which were finished under controlled conditions of feeding and management. Musculus longissimus lumborum from eland were darker and less yellow in colour, with a higher pH24 and lower contents of intramuscular fat and total collagen, compared to cattle. Contents (mg/100 g muscle tissue) and proportions (g/100 g of FA determined) of SFA and MUFA were higher (P<0.01) in cattle. Although the proportion of total PUFA were higher (P<0.001) in eland, contents of PUFA were similar between species. Meat from cattle was consistently scored higher (P<0.05) for sensory texture characteristics, juiciness, flavour, and overall acceptance. We concluded that bulls of eland provided low-fat meat with a beneficial fatty acid composition from a human nutrition perspective, but with lower sensory scores, compared to bull beef.

Fatty acid composition and interrelationships among eight retail cuts of grass-feed beef

The aim of this research was to evaluate: 1) fatty acid (FA) profile of eight retail cuts (eye of round, ribeye, top round, striploin, tenderloin, top-sirloin, underblade, ground beef) from grass-fed steers, 2) the association between striploin (longissimus muscle) FA profile and that from the other retail cuts, and 3) the changes in FA profile associated with retail cut total FA content. All of the retail cuts, except underblade and ground beef, would be considered lean (<10 g) based on total FA content. Total saturated fatty acids were positively correlated to total FA content; whereas, negative correlations were observed with total FA content and total monounsaturated and polyunsaturated fatty acids. No correlation was observed between total FA and CLA cis-9, trans-11. Striploin trans-11 C18:1 and CLA cis-9, trans-11 proportions, and n-6:n-3 ratio were positive and highly correlated with those in the other retail cuts.

The effect of corn distiller's dried grains with solubles, ractopamine, and conjugated linoleic acid on the carcass performance, meat quality, and shelf-life characteristics of fresh pork following three different storage methods

The objective of this study was to evaluate dietary corn distiller's dried grains with solubles (DDGS), ractopamine hydrochloride (RAC), and conjugated linoleic acid (CLA) on growth performance, carcass and fat quality, and shelf-life of fresh pork from finishing pigs. Barrows (n=72) were fed one of eight treatments consisting of two diet sources (corn-soy and corn-soy+20% DDGS), two levels of RAC (0 and 7.4ppm), and two levels of CLA (0 and 0.6%) for 28days. Loins were portioned (n=3) into one of three storage conditions (fresh, cold, frozen); each followed with seven days of retail display. Feeding RAC improved ADG and G:F (P<0.05), whereas DDGS decreased belly fat firmness (P<0.05). Dietary DDGS increased total polyunsaturated fatty acids in jowl and belly samples and increased Iodine Value (IV) (P<0.05), but addition of CLA decreased IV. Dietary DDGS, RAC, or CLA had minimal impact on pork quality following varied storage methods.

Effect of sire breed and genetic merit for carcass weight on the transcriptional regulation of the somatotropic axis in longissimus dorsi of crossbred steers

The somatotropic axis plays an important role in postnatal growth, development, and differentiation of skeletal muscle. The aim of this study was to examine the effect of sire breed and sire EPD for carcass weight (EPD(cwt)) on the expression of components of the somatotropic axis in LM of beef cattle at slaughter. Crossbred Aberdeen Angus (AA; n = 17) and Belgian Blue (BB; n = 16) steers born to Holstein-Friesian dams and sired by bulls with either high (H) or low (L) EPD(cwt) were used in the study. Thus, there were 4 genetic groups [i.e., BBH (n = 8), BBL (n = 8), AAH (n = 8), and AAL (n = 9)]. Blood samples were collected via jugular venipuncture at regular intervals for analysis of plasma concentrations of IGF-1 and insulin. Total RNA was isolated from LM collected at slaughter, and the mRNA expression of IGF-1, IGF-2, their receptors (IGF-1R; IGF-2R), 6 IGFBP, acid labile subunit (ALS), and GH receptor (GHR) was measured by real-time reverse-transcription quantitative PCR. There was no effect of either sire breed or EPD(cwt) on concentrations of circulating IGF or insulin (P > 0.05). Gene expression of IGF-1R and IGFBP3 was upregulated in AA (P < 0.001) compared with BB, whereas IGF-1 was upregulated in H compared with L animals (P < 0.01). Correlation analysis indicated moderate positive associations between gene expression of IGFBP3 and IGF-1 (r = 0.54; P < 0.001) and IGF-1R (r = 0.48; P < 0.01). In addition, correlation analysis revealed that mRNA expression of IGFBP3 was moderately negatively associated with LM area per kilogram of carcass weight (r = -0.40; P < 0.05). Greater gene expression of IGF-1 and reduced transcript abundance of IGFBP3 in muscle may have a role in increased muscle growth potential in steers during the finishing period. These data will contribute to a better understanding of the molecular control of muscle growth at a tissue level in cattle.

Ultrasound velocity and attenuation of porcine soft tissues with respect to structure and composition: II. Skin and backfat

Ultrasound is regarded as a promising method to determine the intramuscular fat content of pork loin. At intact carcasses, the signal passes the backfat whose ultrasound parameters (sound velocity and attenuation) have not been fully investigated. This study intended to collect a dataset of ultrasound parameters for individual backfat layers and to elucidate relationships with structural and compositional characteristics. In-vitro measurements at 10 MHz were conducted on backfat samples of pork carcasses representative for German populations. The average sound velocity ranged from 1436 ± 9 to 1470 ± 37 ms(-1) for the fat layers, and 1682 ± 23 ms(-1) for skin. Velocity of the compound backfat decreased with overall thickness. Attenuation was not affected by thickness ranging between 1.6 ± 0.7 and 2.7 ± 1.5 dB MHz(-1)cm(-1) for all layers. Sound velocity was negatively correlated with fat content and dry matter. The obtained results are anticipated to improve signal correction prior to spectral analysis of ultrasound measurements at intact carcasses.