Effects of dietary glycerol supplementation on meat quality, palatability, and lipid metabolism gene expression in the longissimus thoracis of Hanwoo steers.

This study tested the hypothesis that dietary glycerol supplementation (GS) would affect growth of Hanwoo steers, beef marbling and palatability, and gene expression for lipid uptake and transport and lipogenesis in the longissimus thoracis (LT). Diets with or without 45.2 g daily glycerol supplementation/kg dry matter concentrate were tested in fourteen Hanwoo steers during a 16-week feeding trial. GS did not affect (P ≥ 0.40) the average daily gain or the gain-to-feed ratio. GS increased the LT marbling score (P = 0.01). GS enhanced (P ≤ 0.01) the sensory traits, including the flavor and overall acceptance of the LT. GS tended (0.05 < P ≤ 0.10) to upregulate mRNA levels of fatty acid translocase, lipoprotein lipase, and fatty acid binding protein 4 genes in the LT. These tendencies of upregulated expression of fatty acid uptake and cytosolic transport genes may, in part, contribute to the increased marbling by GS. The increased marbling degree caused by GS may improve palatability including the flavor and overall acceptance of the LT.

Understanding the role of rumen epithelial host-microbe interactions in cattle feed efficiency.

Feed efficiency is one of the economically important traits for the cattle industry that affects profit (feed costs) and the environment (production of manure and methane). Due to that feed efficiency is driven by multi-factors, mechanisms contributing to the animal to animal variation in this trait have not been well defined, limiting the development of precision feeding strategies to improve the herd production efficiency. Rumen microbial fermentation and volatile fatty acids (VFA) production have been recently reported to be associated with cattle feed efficiency, however the roles of rumen epithelial function in feed efficiency are less studied although the rumen epithelium has an important function in VFA absorption and metabolism which can affect host feed efficiency. Rumen epithelium is colonized with a diverse microbial population, termed epimural microbiota, which has proposed functions in tissue development, barrier and inflammation, urea transport, and oxygen scavenging, suggesting that they can affect rumen epithelial functions and subsequently cattle feed efficiency. Especially, prospective functions of epimural microbiota, enhanced rumen immunity and increased rumen epithelial thickness, might contribute to less nutritional requirement for tissue recuperation. Thus, the understanding of the functions of rumen epithelium, epimural microbiota, and rumen epithelial host-microbe interactions is essential to identify their roles in contributing to feed efficiency. In this review, we will focus on to date research findings on the structure of rumen epithelium, epimural microbiota, and epithelial host-microbe interactions together with their functions and how these are associated with feed efficiency, aiming to provide insights on future directions to study rumen epithelial host-microbe interactions and improve the rumen functions in cattle.

Partial Substitution of Corn Grain in the Diet with Beet Pulp Reveals Increased Ruminal Acetate Proportion and Circulating Insulin Levels in Korean Cattle Steers.

We investigated the effects of the partial substitution of corn grain in the diet with beet pulp on growth performance, ruminal fermentation characteristics, microbial profiles, and blood lipogenic parameters in fattening steers. Twelve Korean cattle steers (body weight, 485 ± 19.32 kg; age, 18.0 ± 0.17 months) were equally divided into corn grain (CG) and beet pulp (BP) groups. Approximately 75% of dry matter of the requirement was offered as a concentrate portion, and the remaining 25% was offered as oat straw. Eighty percent of the concentrate portion was provided by a pelleted basal concentrate, and the remaining 20% with corn grain for the CG group, or 18% beet pulp plus 2.0% rumen-protected fat for the BP group, respectively, by top dressing. The experiment was conducted for 14 weeks, including a 2-week acclimation period. Growth rate was not affected by beet pulp feeding (p = 0.55). The molar proportions of ruminal acetate (p < 0.05) on wk 4, the relative abundances of ruminal cellulolytic bacteria, including Fibrobacter succinogenes (p = 0.01) and Ruminococcus albus (p = 0.04) on wk 12, and serum insulin concentrations (p < 0.05) on wk 12 were higher in the BP group than in the CG group, whereas the molar proportions of propionate (p < 0.05) on wks 8 and 12 and serum nonesterified fatty acids (p < 0.05) on wk 12 were lower in the BP group. Beet pulp could be used as a lipogenic energy source without affecting growth performance during the fattening period of cattle.

Pseudoprevotella muciniphila gen. nov., sp. nov., a mucin-degrading bacterium attached to the bovine rumen epithelium.

A Gram-negative, strictly anaerobic mucin-degrading bacterium, which we designated strain E39T, was isolated from the rumen epithelium of Korean cattle. The cells were non-motile and had a coccus morphology. Growth of strain E39T was observed at 30-45°C (optimum, 39°C), pH 6.5-8.5 (optimum, pH 7.5), and in the presence of 0.0-1.0% (w/v) NaCl (optimum, 0.0-0.5%). Strain E39T contained C16:0, C18:0, C18:1 ω9c, iso-C15:0, and anteiso-C15:0 as the major fatty acids. The major polar lipids were phosphatidylethanolamine, unidentified aminophospholipid, and unidentified lipids. The major respiratory isoprenoid quinones were MK-8 and MK-9. The major fermented end-products of mucin were acetate and succinate. The G+C content of the genomic DNA was 46.4 mol%. Strain E39T was most closely related to Alloprevotella rava 81/4-12T with an 87.3% 16S rRNA gene sequence similarity. On the basis of phenotypic, chemotaxonomic, and molecular properties, strain E39T represents a novel genus of the family Prevotellaceae; as such, the name Pseudoprevotella muciniphila gen. nov., sp. nov. is proposed. A functional annotation of the whole genome sequences of P. muciniphila E39T revealed that this bacterium has a putative mucin-degrading pathway and biosynthetic pathways of extracellular polymeric substances and virulence factors which enable bacteria to adhere to the epithelial cells and avoid the host's immune responses.

Transcriptome changes associated with fat deposition in the longissimus thoracis of Korean cattle following castration.

The castration of bulls increases the intramuscular fat (IMF) content in skeletal muscle. However, the biological processes of IMF accumulation in skeletal muscle after castration are not completely understood at the molecular level. This study examined the global transcriptomic changes in the longissimus thoracis muscle (LT) of bulls following castration using RNA sequencing (RNA-Seq) and identified new genes or pathways associated with beef quality. Ten bulls and 10 steers castrated at 6 months of age were slaughtered at 26 and 32 months of age respectively. For transcriptome analysis, six LT samples from three bulls and three steers were selected based on age, carcass weight, carcass quantity and beef quality grades. Using RNA-Seq, transcriptomic profiles of the LT were compared between bulls and steers. In all, 640 of the 18,027 genes identified through RNA-Seq were differentially expressed genes (DEGs) between bulls and steers. Pathway analysis of these 640 DEGs showed significant (p < .05) changes in seven Kyoto Encyclopedia of Genes and Genomes pathways, and the most significant terms were complement and coagulation cascade pathways. The transcriptomic expression patterns of 10 genes in the complement and coagulation cascades were validated using all animals through quantitative real-time polymerase chain reaction analysis. In conclusion, transcriptome changes associated with the complement and coagulation cascade pathways provide novel insights into understanding molecular mechanisms responsible for IMF accumulation following castration in beef cattle.

Effects of heat stress and rumen-protected fat supplementation on growth performance, rumen characteristics, and blood parameters in growing Korean cattle steers.

OBJECTIVE: This study was performed to evaluate whether hot temperature and rumen-protected fat (RPF) supplementation affect growth performance, rumen characteristics, and serum metabolites in growing stage of Korean cattle steers. METHODS: Twenty Korean cattle steers (230.4±4.09 kg of body weight [BW], 10.7±0.09 months of age) were divided into a conventional control diet group (n = 10) and a 0.8% RPF supplementation group (n = 10). Steers were fed 1.5% BW of a concentrate diet and 4 kg of tall fescue hay for 16 weeks (July 10 to August 6 [P1], August 7 to September 3 [P2], September 4 to October 1 [P3], October 2 to 30 [P4], of 2015). RESULTS: The mean temperature-humidity index (THI) was higher (p<0.001) in P1 (76.8), P2 (76.3), and P3 (75.9) than in P4 (50.9). The mean THI of P1-3 were within the alert heat stress (HS) category range according to previously reported categories for feedlot cattle, and the mean THI of P4 was under the thermo-neutral range. Neither month nor RPF supplementation affected (p>0.05) average daily gain and gain to feed ratio. Month and RPF supplementation affected concentrations of glucose, albumin, and high-density lipoprotein (HDL); those of albumin and glucose tended to decrease (p<0.10), but HDL concentration increased (p<0.01) by RPF supplementation. Neither month nor RPF affected (p>0.05) ruminal pH, NH3-N, and volatile fatty acid concentrations, whereas the C2:C3 ratio was affected (p<0.05) by month. CONCLUSION: Korean cattle may not have been significantly affected by alert HS during the growing stage. Growth performance was higher during hotter months, although some changes in blood metabolites were observed. The RPF supplementation affected some blood lipids and carbohydrate metabolites but did not affect growth performance.

Effects of ambient temperature and rumen-protected fat supplementation on growth performance, rumen fermentation and blood parameters during cold season in Korean cattle steers.

OBJECTIVE: This study was performed to evaluate whether cold ambient temperature and dietary rumen-protected fat (RPF) supplementation affect growth performance, rumen fermentation, and blood parameters in Korean cattle steers. METHODS: Twenty Korean cattle steers (body weight [BW], 550.6±9.14 kg; age, 19.7±0.13 months) were divided into a conventional control diet group (n = 10) and a 0.5% RPF supplementation group (n = 10). Steers were fed a concentrate diet (1.6% BW) and a rice straw diet (1 kg/d) for 16 weeks (January 9 to February 5 [P1], February 6 to March 5 [P2], March 6 to April 3 [P3], and April 4 to May 2 [P4]). RESULTS: The mean and minimum indoor ambient temperatures in P1 (-3.44°C, -9.40°C) were lower (p<0.001) than those in P3 (5.87°C, -1.86°C) and P4 (11.18°C, 4.28°C). The minimum temperature in P1 fell within the moderate cold-stress (CS) category, as previously reported for dairy cattle, and the minimum temperatures of P2 and P3 were within the mild CS category. Neither month nor RPF supplementation affected the average daily gain or gain-to-feed ratio (p>0.05). Ruminal ammonia nitrogen concentrations were higher (p<0.05) in cold winter than spring. Plasma cortisol concentrations were lower (p<0.05) in the coldest month than in the other months. Serum glucose concentrations were generally higher in colder months than in the other months but were unaffected by RPF supplementation. RPF supplementation increased both total cholesterol (p = 0.004) and high-density lipoprotein (HDL) concentrations (p = 0.03). CONCLUSION: Korean cattle may not be significantly affected by moderate CS, considering that the growth performance of cattle remained unchanged, although variations in blood parameters were observed among the studied months. RPF supplementation altered cholesterol and HDL concentrations but did not affect growth performance.

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.

Deletion of liver-specific STAT5 gene alters the expression of bile acid metabolism genes and reduces liver damage in lithogenic diet-fed mice.

Signal transducers and activators of transcription 5 (STAT5) mediates growth hormone signals, which may control hepatic cholesterol uptake and bile acid metabolism. Deregulation of liver cholesterol homeostasis and bile acid metabolism may cause liver damage and cholesterol gallstone development. The purpose of this study was to understand the role of local STAT5 signaling in cholesterol and bile acid metabolism using liver-specific STAT5 knock-out (STAT5 LKO) mice on a normal diet and a cholesterol- and bile acid-containing lithogenic diet. STAT5 LKO mice showed significant down-regulation of STAT5 and insulin-like growth factor-1 genes. STAT5 gene deletion had a minor effect on cholesterol metabolism, as evidenced by a minor change in circulating cholesterol levels and no changes in expression of hepatic low-density lipoprotein receptor and cholesterol synthesis genes in STAT5 LKO mice. In contrast, bile acid synthesis and uptake genes were profoundly down-regulated and bile acid detoxification genes were up-regulated in STAT5 LKO mice. In STAT5 fl/fl mice, a lithogenic diet induced liver damage, as evidenced by moderate increases in liver ballooning, inflammation and fibrosis. However, STAT5 deletion ameliorated the degree of liver damage induced by the lithogenic diet. In STAT5 LKO mice, a lithogenic diet did not alter the incidence or severity of cholesterol gallstones. In conclusion, local STAT5 signaling does not have a significant role in cholesterol metabolism. In contrast, hepatic STAT5 signaling has significant roles in regulating transcription of genes for synthesis, transport and detoxification of bile acids, but it has only a minor role in bile acid metabolism.