The present study examined the impact of conjugated linoleic acid (CLA) on the differentiation and proliferation of bovine intramuscular preadipocyte (BIP) cells, specifically exploring the role of G protein-coupled receptor 41 (GPCR41). Cells were exposed to CLA at various concentrations ranging from 50 to 150 μmol/L. Flow cytometry revealed that treatment with 100 μmol/L CLA led to a significant increase in the proliferation rate. During differentiation, 100 and 150 μmol/L CLA markedly enhanced lipid droplet accumulation. Maximal cytoplasmic lipid content was observed when CLA was combined with insulin and dexamethasone. CLA treatment significantly enhanced the transcript abundance of the adipogenic transcription factors peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT-enhancer binding protein alpha (C/EBPα). Knockdown of GPCR41 via RNA interference in CLA-treated cells led to a significant suppression of GPCR41 expression, accompanied by decreased PPARγ mRNA levels and diminished cytoplasmic lipid droplet formation, indicating impaired differentiation. Taken together, these results show that CLA enhances both differentiation and proliferation of bovine intramuscular preadipocytes, possibly via activation of C/EBPα and PPARγ, with GPCR41 playing a critical role in mediating this adipogenic effect.

China's beef production and consumption have steadily increased over the past decade. However, China's current beef grading standards have not effectively guided the market. In this context, the low profitability of the industry and the lack of consumer confidence in China's local products are issues that need to be addressed. The first section of this article reviewed trends in production, consumption, and profitability within the industry over the past decade, highlighting key challenges currently faced. The second section evaluated the quality attributes prioritized by Chinese consumers related to their eating experiences and their decision to purchase beef products. The third part introduced China's current beef grading standards and its potential development space, drawing on international grading approaches that align with consumer expectations. Finally, the paper explores potential strategies to enhance the attractiveness and sustainability of China's domestic beef market.

To meet the rising global demand for premium animal protein, efficient utilisation of non-grain feedstuffs like corn stover has become critical for sustainable beef production. However, the high lignocellulosic content and structural rigidity of corn stover restrict its digestibility and nutritional availability in the rumen. This study assessed how steam explosion treatment influences the nutritional quality of corn stover and examined its effects on growth, serum biochemistry, slaughter characteristics, and meat quality of beef cattle. In Experiment 1, a rumen nylon bag study using three rumen-fistulated Simmental bulls showed that steam explosion significantly increased the in situ degradability of DM and organic matter, while reducing the fibre content. In Experiment 2, thirty Simmental bulls were randomly assigned to either a control group (CON) receiving 50% untreated corn stover in their roughage or a test group (SCS) where steam explosion-treated corn stover replaced the untreated portion. Over a 108-day trial, the SCS group exhibited significantly greater average daily gain (ADG) and dry matter intake (DMI) compared with CON (P < 0.05). Serum biochemical analysis revealed significantly elevated triglycerides, total protein, and high-density lipoprotein (P < 0.05), indicating enhanced protein metabolism and lipid transport. Slaughter performance was unaffected. However, meat from SCS-fed cattle showed higher pH and lower cooking and pressing losses (P < 0.05), indicating improved water-holding capacity. No differences were observed in meat nutrient composition. These results indicate that steam explosion serves as a valuable pretreatment for improving the ruminal digestibility and nutritional value of corn stover, thereby improving animal performance and meat quality in beef production systems, offering a promising strategy for utilising low-quality roughage in beef production.

This study investigated lipid metabolism differences between low and high residual feed intake (LRFI and HRFI) bulls. Fifty-five Simmental bulls (449.84 ± 8.49 kg) were fed the same diet for 161 d to determine RFI values. At the end of experiment, back fat thickness (BFT) and rib eye area (REA) were measured via ultrasound, and serum samples were collected for lipid metabolism indicators. Post-slaughter, subcutaneous adipose tissue was analyzed for lipid metabolism indicators, histology, transcriptomics, and lipid metabolomics. Results 1) Ultrasound showed LRFI bulls had lower BFT (P = 0.031) but higher REA (P = 0.021). 2) Serum total cholesterol (P = 0.028) and low-density lipoprotein cholesterol (P = 0.015) were lower in LRFI bulls. Leptin levels were lower in both serum (P = 0.007) and adipose tissue (P = 0.001) in LRFI bulls, as were acetyl-CoA carboxylase levels in serum (P = 0.032) and adipose tissue (P = 0.043). Conversely, adipose triglyceride lipase levels were higher in both serum (P = 0.045) and adipose tissue (P = 0.043), while adipose tissue fatty acid synthase levels were lower (P = 0.035) in LRFI bulls. 3) Transcriptomics identified two pathways, adenosine monophosphate-activated protein kinase (AMPK) and cyclic adenosine monophosphate (cAMP), involving five lipid metabolism-related genes. Among these, adenylate cyclase activating polypeptide 1 receptor type 1 (ADCYAP1R1), adenylate cyclase 10 (ADCY10), and adenylate cyclase activating polypeptide 1 (ADCYAP1) were significantly upregulated (P < 0.05), while leptin receptor (LEPR) was downregulated (P = 0.047) in LRFI bulls. Additionally, leptin (LEP) showed a downward trend (P = 0.098) in LRFI bulls. 4) Lipid metabolomics revealed that the LRFI group had significantly higher levels of wax ester (WE) (P = 0.040) and significantly lower levels of monogalactosyldiacylglycerol (MGDG) (P = 0.040) compared to the HRFI group. Additionally, sphingomyelin (SPH) showed a trend towards lower abundance (P = 0.054), and C12:0 levels tended to be higher (P = 0.089) in the LRFI group. In conclusion, differences in the AMPK and cAMP signaling in adipose tissue are associated with reduced lipid synthesis and enhanced lipid degradation in LRFI bulls, which may contribute to reduced lipid deposition.

In vitro rumen gas production experiment was conducted with 57 kinds of feedstuff, which were categorized into energy feed, protein feed, and roughage, collected within China. Eight mathematical models were employed to describe the kinetics of in vitro rumen gas production. The results found that for energy feeds, protein feeds, and roughages, respectively, Michaelis–Menten (MM) or Logistic-Exponential with lag (LEL), MM, and Mitscherlich (MIT) exhibited the highest or shown no significant difference compared to the highest coefficient of determination (R2) (P < 0.05) for all categories of feed. Furthermore, regression estimation of intercept and slope for regression estimates of intercept and slope for Observed versus Predicted of aforementioned models shown no significant difference from 0 and 1, respectively (P < 0.05), except LEL for energy feed. Mean absolute error (MAE), root mean squared error of prediction (RMSEP), mean squared error of prediction (MSEP) of those models were relatively lower, with minimal systematic bias and regression bias. Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) rankings were higher compared with other models. Given these results, in studies where feedstuff categories are not distinguished or multiple feedstuffs categories are included, the MM model proves to be a good choice. MM or LEL was considered to better fit energy feedstuffs. The MM model was the optimal choice for fitting protein feedstuffs. MIT provided the best accuracy and moderate precision when fitting roughages.

Guanidinoacetic acid (GAA) has been used in ruminant feeding, but it is still unclear whether the exogenous addition of methyl donors, such as methionine (Met), can enhance the effects of GAA. This study investigated the effects of dietary GAA alone or combined with Met on beef cattle growth performance and explored the underlying mechanisms via blood analysis, liver metabolomics, and transcriptomics. Forty-five Simmental bulls (453.43 ± 29.05 kg) were assigned to three groups for 140 days: CON (control), GAA (0.1% GAA), and GAM (0.1% GAA + 0.1% Met), where each group consisted of 15 bulls. Compared with the CON group, the average daily gain (ADG) and feed conversion efficiency (FCE) of the two feed additive groups were significantly increased, and the digestibility of neutral detergent fiber (NDF) was improved (p < 0.05). Among the three treatment groups, the GAM group showed a higher rumen total volatile fatty acids (TVFAs) content and digestibility of dry matter (DM) and crude protein (CP) in the beef cattle. The serum indices showed that the contents of indicators related to protein metabolism, lipid metabolism, and creatine metabolism showed different increases in the additive groups (p < 0.05). It is worth noting that the antioxidant indexes in the serum and liver tissues of beef cattle in the two additive groups were significantly improved (p < 0.05). The liver metabolites related to protein metabolism (e.g., L-asparagine, L-glutamic acid) and lipid metabolism (e.g., PC (17:0/0:0)) were elevated in two additive groups, where Met further enhanced the amino acid metabolism in GAM. In the two additive groups, transcriptomic profiling identified significant changes in the expression of genes associated with protein metabolism (including PIK3CD, AKT3, EIF4E, HDC, and SDS) and lipid metabolism (such as CD36, SCD5, ABCA1, APOC2, GPD2, and LPCAT2) in the hepatic tissues of cattle (p < 0.05). Overall, the GAA and Met supplementation enhanced the growth performance by improving the nutrient digestibility, serum protein and creatine metabolisms, antioxidant capacity, and hepatic energy and protein and lipid metabolisms. The inclusion of Met in the diet was shown to enhance the nutrient digestibility and promote more efficient amino acid metabolism within the liver of the beef cattle.

The aim of this experiment is to explore the effect of sodium sulfate (Na2SO4) on methane reduction in the rumen, and its impact on anaerobic methane-oxidizing archaea (ANME). Using mixed rumen fluid from four Angus cattle fistulas, this study conducted an in vitro fermentation. Adding Na2SO4 to the fermentation substrate resulted in sulfur concentrations in the substrate of 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, and 2.4%. The gas production rate and methane yield were measured using an in vitro gas production method. Subsequently, the fermentation fluid was collected to determine the fermentation parameters. The presence of ANME in the fermentation broth, as well as the relationship between the number of bacteria, archaea, sulfate reducing bacteria (SRB), ANME, and the amount of Na2SO4 added to the substrate, were measured using qPCR. The results showed that: (1) the addition of Na2SO4 could significantly reduce CH4 production and was negatively correlated with CO2 production; (2) ANME-1 and ANME-2c did exist in the fermentation broth; (3) the total number of archaea, SRB, ANME-1, and ANME-2c increased with the elevation of Na2SO4. The above results indicated that Na2SO4 could mitigate methane production via sulfate-dependent anaerobic methane oxidation (S-DAMO) in the rumen. In the future management of beef cattle, including sodium sulfate in their diet can stimulate S-DAMO activity, thereby promoting a reduction in methane emissions.

Methionine plays a vital role in protein synthesis, and regulation of antioxidant response in ruminants. This study aimed to assess the effects of dietary supplementation with N-acetyl-L-methionine (NALM), which serves a source of rumen-protected methionine, on growth performance, carcass traits, meat quality, and oxidative stability. Sixty Angus heifers (initial body weight = 408 +/- 51.2 kg, 15-18 months) were stratified by body weight and randomly assigned to four dietary treatments: a control group (0% NALM), and experimental groups receiving diets containing 0.125%, 0.25%, and 0.50% NALM (dry matter (DM) basis), respectively. The experiment included a 2-week adaptation and a 22-week data and sample collection period. Results indicated that blood urea nitrogen in the plasma of the 0.25% NALM group was lower compared to the control and the 0.50% NALM groups (P = 0.02). The plasma methionine (P = 0.04), proline (P < 0.01), and tryptophan (P = 0.05) were higher in the 0.25% and 0.50% NALM groups, as well as the methionine and proline in the muscle of the 0.25% NALM group (P < 0.01). The muscle pH (P < 0.01) was increased by supplementing 0.25% and 0.50% NALM in diets but decreased the lactate (P < 0.01). The 0.25% NALM group also increased a* (P = 0.05), decreased L* (P = 0.05), drip loss (P = 0.01), and glycolytic potential in the muscle (P < 0.01). The total antioxidant capacity, superoxide dismutase, glutathione peroxidase, catalase, and glutathione in muscle of 0.25% NALM group were higher than that of the control (P < 0.01), and the malondialdehyde and protein carbonyl were lower (P < 0.01). In conclusion, the dietary supplement with NALM improves meat quality by enhancing the antioxidant effect of lipids and proteins.

The present study investigated whether replacing dietary rice straw with peanut vine (PEV) and Broussonetia papyrifera silage (BPS) reduces the use of soybean meal and explored its effects on the growth performance, blood biochemical indicators, serum metabolomics, and meat quality of fattening bulls. Forty-five Simmental crossbred bulls (initial body weight = 484.29 ± 8.49 kg) were randomly allotted into three dietary treatment groups (n = 15): (1) CON, 5% rice straw (DM basis); (2) PEV, 5% peanut vine (DM basis); and (3) BPS, 5% B. papyrifera silage (DM basis). The remaining roughage for all three treatment groups was supplemented with 25% corn silage (DM basis). The experiment lasted for 123 d, with the first 14 d serving as an adaptive period. Throughout the experiment, dietary BPS decreased the average daily dry matter intake (P < 0.001) and feed cost (P < 0.001). Serum metabolomics analysis showed that PEV affected the phenylalanine, tyrosine, and tryptophan biosynthesis pathways (P = 0.021) and lysine degradation pathway (P = 0.042), whereas BPS affected the phenylalanine, tyrosine and tryptophan biosynthesis pathways (P = 0.004), lysine degradation pathway (P = 0.012), and serotonergic synapse pathway (P < 0.001). Regarding meat quality, the redness (P = 0.025) and hue angle values (P < 0.001) of the longissimus dorsi muscle were lower in the BPS group than in the CON and PEV groups. The yellowness of the longissimus dorsi muscle was lower in the BPS group than in the PEV group (P = 0.024), and the shear force was lower in the PEV group than in the BPS group (P = 0.014). However, lysine content in beef was higher in the BPS group than in the CON group (P = 0.005). In conclusion, replacing rice straw with PEV and BPS reduced the use of soybean meal but had no adverse effects on growth performance. BPS affected the amino acid metabolism of bulls, thus decreasing feed intake and increasing the lysine content in meat. The PEV group showed better meat quality than the BPS group.

Conjugated linoleic acid (CLA), a mixture of isomers of linoleic acid, has previously been shown to be able to increase intramuscular fat content in vivo and stimulate adipogenesis in intramuscular preadipocytes in vitro in pig. Unfortunately, there is little data to evaluate the effect of CLA on proliferation and differentiation of bovine intramuscular preadipocytes. This study investigated the regulation by CLA in proliferation and differentiation of bovine intramuscular preadipocytes. The results demonstrated that CLA significantly induced the expression of PPARγ and C/EBPα mRNA of bovine intramuscular preadipocytes as well as the accumulation of lipid in cultured intramuscular preadipocytes. Additionally, CLA significantly decreased the cell proportion of phase G0/G1, and remarkably increased the proportion of phase S+G2/M. Collectively, these results suggest that CLA promotes bovine intramuscular preadipocyte proliferation and differentiation.

This study was conducted to explore the potential effect of Yucca schidigera extract (YSE) on the metabolism of beef cattle. Thirty Angus crossbreed steers were selected, with an initial mean body weight of 506.6 ± 33.3 kg, and assigned to two treatments: a diet with no additives (CON group) and a diet supplemented with 1.75 g/kg of YSE (YSE group) (on a dry matter basis). The experiment lasted for 104 days, with 14 days for adaptation. The results showed that adding YSE could significantly improve the average daily gain (ADG) from 1 to 59 d (15.38%) (p = 0.01) and 1 to 90 d (11.38%) (p < 0.01), as well as dry matter digestibility (DMD) (0.84%) (p < 0.05). The contents of alanine aminotransferase, aspartate aminotransferase, and bilirubin and the total antioxidant capacity were increased and blood urea was reduced in the YSE group, compared to the CON group (p < 0.05). Both the glycerophospholipids and bile acids, including phosphocholine, glycerophosphocholine, PC(15:0/18:2(9Z,12Z)), PE(18:0/20:3(5Z,8Z,11Z)), PE(18:3(6Z,9Z,12Z)/P-18:0), LysoPC(15:0), LysoPC(17:0), LysoPC(18:0), LysoPC(20:5(5Z,8Z,11Z,14Z,17Z)), deoxycholic acid, glycocholic acid, and cholic acid, were upregulated by the addition of YSE. In summary, YSE may improve the ADG by increasing the blood total antioxidant capacity and glycerophospholipid synthesis, maintaining steers under a healthy status that is beneficial for growth. Furthermore, YSE may also increase the expression of bile acid synthesis, thereby promoting DMD, which, in turn, offers more nutrients available for growth.

This study examined the impact of dietary guanidino acetic acid (GAA) and rumen-protected methionine (RPM) on beef quality in Simmental bulls. For 140 days, forty-five bulls (453.43 ± 29.05 kg) were randomly divided into control (CON), 0.1% GAA (GAA), and 0.1% GAA + 0.1% RPM (GAM) groups with 15 bulls in each group and containing 3 pen with 5 bulls in each pen. Significant improvements in eye muscle area, pH48h, redness (a*) value, and crude protein (CP) content of longissimus lumborum (LL) muscles were observed in the GAA and GAM groups (P < 0.05). Conversely, the lightness (L*) value, drip loss, cooking loss, and moisture contents decreased (P < 0.05). Additionally, glutathione (GSH) and glutathione peroxidase (GSH-PX) concentrations of LL muscles in GAM were higher (P < 0.05), while malondialdehyde (MDA) content of LL muscles in GAA and GAM groups were lower (P < 0.05). Polyunsaturated fatty acids (PUFA) profiles were enriched in beef from GAM group (P < 0.05). The addition of GAA and RPM affected the expression of genes in LL muscle, such as HMOX1, EIF4E, SCD5, and NOS2, which are related to hypoxia metabolism, protein synthesis, and unsaturated fatty acid synthesis-related signaling pathways. In addition, GAA and RPM also affected the content of a series of metabolites such as L-tyrosine, L-tryptophan, and PC (O-16:0/0:0) involved in amino acid and lipid metabolism-related signaling pathways. In summary, GAA and RPM can improve the beef quality and its nutritional composition. These changes may be related to changes in gene expression and metabolic pathways related to protein metabolism and lipid metabolism in beef.

Guanidinoacetic acid (GAA) functions as a precursor for creatine synthesis in the animal body, and maintaining ample creatine reserves is essential for fostering rapid growth. This study aimed to explore the impact of GAA supplementation on growth performance, rumen fermentation, blood indices, nutrient digestion, and nitrogen metabolism in Angus steers through two experiments: a feeding experiment (Experiment 1) and a digestive metabolism experiment (Experiment 2). In Experiment 1, thirty-six Angus steers (485.64 ± 39.41 kg of BW) at 16 months of age were randomly assigned to three groups: control (CON), a conventional dose of GAA (CGAA, 0.8 g/kg), and a high dose of GAA (HGAA, 1.6 g/kg), each with twelve steers. The adaptation period lasted 14 days, and the test period was 130 days. Weighing occurred before morning feeding on days 0, 65, and 130, with rumen fluid and blood collected before morning feeding on day 130. Experiment 2 involved fifteen 18-month-old Angus steers (575.60 ± 7.78 kg of BW) randomly assigned to the same three groups as in Experiment 1, with a 7-day adaptation period and a 3-day test period. Fecal and urine samples were collected from all steers during this period. Results showed a significantly higher average daily gain (ADG) in the CGAA and HGAA groups compared to the CON group (p = 0.043). Additionally, the feed conversion efficiency (FCE) was significantly higher in the CGAA and HGAA groups than in the CON group (p = 0.018). The concentrations of acetate and the acetate:propionate ratio were significantly lower in the CGAA and HGAA groups, while propionate concentration was significantly higher (p < 0.01). Serum concentration of urea (UREA), blood ammonia (BA), GAA, creatine, and catalase (CAT) in the CGAA and HGAA groups were significantly higher than in the CON group, whereas malondialdehyde (MDA) concentrations were significantly lower (p < 0.05). Digestibility of dry matter (DM) and crude protein (CP) and the nitrogen retention ratio were significantly higher in the CGAA and HGAA groups than in the CON group (p < 0.05). In conclusion, dietary addition of both 0.8 g/kg and 1.6 g/kg of GAA increased growth performance, regulated rumen fermentation and blood indices, and improved digestibility and nitrogen metabolism in Angus steers. However, higher doses of GAA did not demonstrate a linear stacking effect.

Capsaicin (CAP) and Yucca schidigera extract (YSE) are two types of plant extracts that can change rumen fermentation. This study was conducted to investigate whether supplementation of beef cattle diets with CAP and YSE for 90 days would affect rumen fermentation and microflora. Forty-five healthy Angus steers (initial body weight = 510.54 ± 41.27 kg) were divided into three groups: control (CON), CAP, and YSE. Ammonia nitrogen (NH3-N) and total volatile fatty acid (TVFA) concentrations were significantly higher in the YSE group than in the CON group and significantly lower in the CAP group than in the CON group. At the phylum level, YSE increased the relative abundances of Bacteroidota and Patescibacteria and reduced that of Bacillota. At the genus level, CAP and YSE both increased the relative abundances of genera subordinate to Bacteroidota and decreased the relative abundances of genera subordinate to Bacillota. Our study shows that YSE and CAP have different effects on rumen fermentation and microflora after long-term supplementation.

Hotpot is a widely popular cooking method for sheepmeat in China. This study measured the sensory responses of 720 untrained Chinese consumers to Australian sheepmeat cooked using a hotpot technique with methods based on Meat Standards Australia protocols. Shoulder and leg cuts of 108 lambs and 109 yearlings were scored on tenderness, juiciness, flavour and overall liking with linear mixed effects models used to analyse the influence of muscle type and animal factors on these scores. On average, shoulder cuts were more palatable than legs cuts for all sensory traits (p < 0.01) and lambs compared to yearlings (p < 0.05). Intramuscular fat and muscularity were identified as strong drivers of eating quality (p < 0.05), with greater palatability for both cuts as intramuscular fat increased (range 2.5 to 7.5%), and muscularity decreased (as measured through loin weight adjusted for hot carcase weight). Consumers were unable to detect differences between animal sire type and sex in sheepmeat hotpot. These findings suggest shoulder and leg cuts performed comparatively well in hotpot compared to previously tested sheepmeat cooking methods and emphasise the importance of balanced selection for quality and yield traits to ensure that consumer satisfaction is maintained.

Yak (Bos grunniens) is an important economic animal species on the Qinghai-Tibet Plateau. Yaks grazed in the cold season often suffer from nutritional stress, resulting in low production performance. This situation can be improved by properly feeding the grazing yaks in the cold season; however, there is still little information about the effect of different feeding levels on the intestinal microflora and metabolites of yaks. Therefore, this study aimed to explore the effect of feeding different doses of concentrate supplements on rumen bacterial communities and metabolites in grazing yaks during the cold season. Feed concentrate supplementation significantly improved the production performance and rumen fermentation status of grazing yaks during the cold season, and switched the type of ruminal fermentation from acetic acid fermentation to propionic acid fermentation. Ruminal fermentation parameters and ruminal bacterial abundance correlated strongly. At the phylum level, the abundance of Firmicutes increased with increasing concentrate supplementation, while the opposite was true for Bacteroidota. At the genus level, the abundance of Christensenellaceae_R-7_group, NK4A214_group, Ruminococcus, norank_f__Eubacterium_coprostanoligenes_group, norank_f__norank_o__ Clostridia_UCG-014, Lachnospiraceae_NK3A20_group, Acetitomaculum, and Family_XIII_AD3011_group increased with increasing concentrate supplementation, while the abundance of Rikenellaceae_RC9_gut_ group decreased. Dietary concentrate supplementation altered the concentration and metabolic mode of metabolites in the rumen, significantly affecting the concentration of metabolites involved in amino acid and derivative metabolism (e.g., L-aspartic acid, L-glutamate, and L-histidine), purine metabolism (e.g., guanine, guanosine, and hypoxanthine), and glycerophospholipid metabolism (e.g., phosphatidate, phosphatidylcholine, and phosphocholine), and other metabolic pathways. The strong correlation between yak rumen microorganisms and metabolites provided a more comprehensive understanding of microbial community composition and function. This study showed significant changes in the composition and abundance of bacteria and metabolites in the rumen of cool season grazing yaks fed with concentrate supplements. Changes in ruminal fermentation parameters and metabolite concentration also showed a strong correlation with ruminal bacterial communities. These findings will be helpful to formulate supplementary feeding strategies for grazing yaks in the cold season from the perspective of intestinal microorganisms.

本试验旨在通过体外产气法和尼龙袋法对6种肉牛常用蛋白质饲料的饲用价值进行评定,探究体外产气量参数和发酵参数与粗蛋白质有效降解率(EDCP)之间的关系,并利用体外产气法建立饲料中EDCP的预测模型,为丰富我国蛋白质饲料营养价值数据库提供数据基础.试验利用体外产气法测定了棉籽粕、菜籽粕、豆粕、向 日葵粕、啤酒糟和干酒糟及其可溶物(DDGS)的72 h动态产气量和体外发酵参数,并计算产气量参数;利用尼龙袋法测定了上述6种蛋白质饲料的蛋白质降解率,计算降解参数.结果表明:1)豆粕的产气量显著高于其他蛋白质饲料(P＜0.05).2)豆粕的24 h体外发酵液的总挥发性脂肪酸(TVFA)含量最高,氨态氮(NH3-N)含量与向日葵粕相似(P＞0.05);向日葵粕的24 h体外发酵液的pH显著高于其他蛋白质饲料(P＜0.05).3)向日葵粕的72 h蛋白质降解率及EDCP最高.4)EDCP与体外产气量参数相关关系不显著(P＞0.05),但与发酵液pH和NH3-N含量呈显著正相关(P＜0.05),与乙酸含量和乙酸/丙酸值呈显著负相关(P＜0.05).5)采用pH、酸性洗涤纤维(ADF)含量和24 h产气量(GP24 h)作为预测因子预测EDCP,决定系数(R2)达到0.998(P＜0.05),预测方程为:EDCP=-833.690+138.088pH-1.219ADF-0.689GP24h.由此可见,不同饲料之间的体外发酵和瘤胃降解特性差异较大,豆粕的体外发酵指标高于其他饲料,向日葵粕的EDCP高于其他饲料;在正常的pH范围内,采用pH、ADF含量和GP24h能准确预测EDCP.

Feed cost is the greatest expense during cattle production; therefore, reducing it is critical to increasing producer profits. In ruminants, the microbial population is important to nutrient digestion and absorption in the rumen. The objective of this study was to investigate the relationships among rumen bacteria, rumen metabolites, and the residual feed intake (RFI) phenotype of beef cattle. Twelve Angus heifers were selected to be sampled and divided into high RFI (HRFI; n = 6) group and low RFI (LRFI; n = 6) group according to their RFI classification determined during the feedlot-finishing period. After the ruminal liquid samples were collected at slaughter, Illumina MiSeq sequencing of the 16S rRNA V3-V4 region and liquid chromatography-mass spectrometry (LC-MS) were performed to determine their bacterial composition and metabolites, respectively. At the phylum level, the relative abundance of Proteobacteria was higher in the LRFI group than in the HRFI group (P < 0.01). At the family level, the relative abundances of Rikenellaceae (P < 0.01), Ruminococcaceae, Bacteroidales_S24-7_group, and Lachnospiraceae (P < 0.05) were significantly higher in the LRFI group. At the genus level, the relative abundances of Rikenellaceae_RC9_gut_group and Ruminiclostridium_1 were higher in the LRFI group (P < 0.01), as were the relative abundances of norank_f__Bacteroidales_S24-7_group, Lachnospiraceae_ND3007_group, and Lachnospiraceae_NK3A20_group (P < 0.05). Moreover, the genera Rikenellaceae_RC9_gut_group, Ruminococcaceae_NK4A214_group, Christensenellaceae_R-7_group, Ruminococcaceae_UCG-010, Lachnospiraceae_ND3007_group, Ruminiclostridium_1, and Lachnospiraceae_NK3A20_group were negatively associated with the RFI; both foundational and key species are associated with feed efficiency phenotype. In addition, rumen metabolomics analysis revealed that the RFI was associated with significantly altered concentrations of rumen metabolites involved in protein digestion and absorption, Linoleic acid metabolism, Lysine degradation, and Fatty acid degradation. Correlation analysis revealed the potential relationships between the significantly differential ruminal metabolites and the genera ruminal bacteria. The present study provides a better understanding of rumen bacteria and metabolites of beef cattle with different RFI phenotypes and the relationships among them, which are potentially important for the improvement of beef cattle feed efficiency.