This study determined the effects of rumen-protected methionine (RPM) supplementation on the growth performance, nutrient digestibility, nitrogen (N) utilisation and plasma amino acid profiles of Liaoning cashmere goats during cashmere fibre growth. Twenty-four yearling male cashmere goats (body weight: 35.41 ± 1.13 kg) were randomly assigned to four dietary treatments: a corn–soybean meal basal diet deficient in methionine (negative control, NC) and a basal diet supplemented with 1, 2 and 3 g/kg of RPM. The RPM supplementation quadratically increased the average daily gain (ADG) and decreased the feed to gain ratio (p = 0.001) without affecting the final body weight and dry matter intake. In particular, compared to NC, 2 g/kg RPM supplementation increased the ADG by 35 g/d (p < 0.001) and resulted in the lowest feed to gain ratio (p < 0.001). RPM increased the apparent total tract digestibility of N and decreased the faecal N levels, both in a linear fashion (p = 0.005). Urinary N levels did not have an effect, but the N retention levels increased linearly with PRM (p = 0.032). Moreover, the RPM decreased the plasma urea N levels (p < 0.001) and increased the plasma Met levels quadratically (p < 0.001). In conclusion, RPM supplementation in the diet of cashmere goats can enhance the utilisation of N and improve ADG during the cashmere fibre growing period, and 2 g/kg of RPM in the diet is suggested.

Liaoning cashmere goats is a dual-purpose breed valued for premium cashmere fiber and meat yields, and there is currently a lack of optimized strategies for meat quality, including skeletal muscle development and lipid partitioning. This investigation systematically examines how melatonin administration modulates gastrointestinal microbiota and antioxidant capacity to concurrently enhance skeletal muscle hypertrophy and redirect lipid deposition patterns, ultimately improving meat quality and carcass traits in Liaoning cashmere goats. Thirty female half-sibling kids were randomized into control and melatonin-treated groups (2 mg/kg live weight with subcutaneous implants). Postmortem analyses at 8 months assessed carcass traits, meat quality, muscle histology, plasma metabolites, and gut microbiota (16S rRNA sequencing). Melatonin supplementation decreased visceral adiposity (perirenal, omental, and mesenteric fat depots with a p < 0.05) while inducing muscle fiber hypertrophy (longissimus thoracis et lumborum (LTL) and biceps femoris (BF) with p < 0.05). The melatonin-treated group demonstrated elevated postmortem pH₂₄h values, attenuated muscle drip loss, enhanced intramuscular protein deposition, and improved systemic antioxidant status (characterized by increased catalase and glutathione levels with concomitant reduction in malondialdehyde with p < 0.05). Melatonin reshaped gut microbiota, increasing α-diversity (p < 0.05) and enriching beneficial genera (Prevotella, Romboutsia, and Akkermansia), while suppressing lipogenic Desulfovibrio populations, and concomitant with improved intestinal morphology as evidenced by elevated villus height-to-crypt depth ratios. These findings establish that melatonin-mediated gastrointestinal microbiota remodeling drives anabolic muscle protein synthesis while optimizing fat deposition, providing a scientifically grounded strategy to enhance meat quality.

Melatonin’s capacity to improve cashmere production and quality in goats is well established, but its underlying mechanisms, particularly those concerning the gastrointestinal microbiome, remain inadequately understood. This study aims to elucidate the effects of melatonin implantation on the production performance, blood biochemical parameters, nutrient digestibility, and gastrointestinal microbiome of Liaoning cashmere goats. Thirty newborn Liaoning cashmere goat lambs were selected and randomly assigned to control and melatonin groups using a paired test design. The melatonin group received three melatonin implantations at 15, 75, and 135 days of age, respectively, with a dosage of 2 mg/kg body weight, while the control group received no treatment. Digestive metabolism tests were conducted at 150 and 300 days of age; prior to these tests, blood, rumen fluid, and rectal feces were collected. Apparent nutrient digestibility and blood biochemical indexes were determined, and rumen fluid and rectal feces were analyzed using microbial 16S rRNA sequencing. The results indicated that melatonin significantly reduced daily weight gain and body weight at 60 days (p < 0.05) while significantly increasing daily weight gain at 300 days (p < 0.05). Additionally, it significantly increased cashmere length and reduced its fineness (p < 0.05). Melatonin significantly enhanced nitrogen deposition (p < 0.05), elevated plasma levels of T-AOC, CAT, GSH-PX, and BUN (p < 0.05), and reduced plasma levels of MDA, GOT, GPT, and AKP (p < 0.05). Moreover, melatonin significantly elevated the microbial Ace and Chao1 indices in rectal feces (p < 0.05), increasing genera beneficial for feed digestion and absorption, including Prevotella, Lachnospiraceae, Ruminococcus, and Synergistaceae (p < 0.05); the abundance of these beneficial genera were positively correlated with improved cashmere production performance, antioxidant activity, and liver and kidney function. In conclusion, melatonin enhances cashmere production by modulating gastrointestinal microbiota, antioxidant activity, liver and kidney function, and nitrogen metabolism in cashmere goats. This study provides a theoretical foundation for melatonin’s role in microbiota modulation, which is essential for promoting high-quality and sustainable development in the cashmere goat industry.

This study was conducted to compare the effects of hydrolysable versus condensed tannins on growth performance, nutrient digestion, and rumen fermentation in goats. A total of 27 Liaoning cashmere goats with similar initial body weights were randomly distributed into three groups: a basal diet, a basal diet +0.5% tannic acid (hydrolysable tannin, HT), or a basal diet +0.5% quebracho tannin (condensed tannin, CT), respectively. Compared to the control group, HT showed a decreased (p < 0.05) feed intake, while CT showed an increased (p < 0.05) feed intake and body weight gain. Digestibility of dry matter, crude protein, neutral detergent fiber, and acid detergent fiber did not differ (p > 0.05) among groups. The HT group showed lower pH and acetic acid concentration in the rumen (p < 0.05), while the CT group showed a decrease (p < 0.05) in the abundances of Verrucomicrobia and Methanobrevibacter. Supplementation of CT decreased (p < 0.05) the levels of dihydrouracil, xanthosine, alpha-D-mannose, and L-tryptophan, while HT increased (p < 0.05) these metabolites. In conclusion, this study suggested that responses of ruminal microbiota and metabolite profiles to the type of tannins varied, and CT displayed a more positive effect on the growth performance of goats than HT when supplemented at the same level in the diets.

Objective: This study was conducted to investigate the effects of hydrolyzable versus condensed tannins on growth performance, nitrogen (N) metabolism, rumen fermentation, and blood parameters in Liaoning cashmere goats.Methods: A control diet and three experimental diets—supplemented with 0.5% chestnut tannin (CT), tannic acid (TA), or quebracho tannin (QT)—were compared.Results: Goats consuming the QT diet had higher average daily gain and average daily feed intake compared to those on the TA diet (p<0.05). Compared to the control group, the QT group exhibited lower fecal N, urine N, and total N output (g/d, p<0.05), as well as higher N retention (g/d) and N utilization (g/kg N intake) relative to the CT and TA groups (p<0.05). The QT group had lowest urine uric acid level, while the CT and TA groups showed lower creatinine levels compared to the control (p<0.05). Tannin supplementation increased rumen ammonia-N (NH3-N) concentration and reduced protozoa counts (p<0.05). Plasma concentrations of total protein, globulin, superoxide dismutase, catalase, and lysozyme were higher in the QT group than in the CT and TA groups (p<0.05).Conclusion: These results suggest that condensed tannin provides greater advantages than hydrolyzable tannin on growth, N balance, and antioxidant function at equivalent dietary inclusion levels.

Goat meat is widely valued as a healthy option due to its lean nature, yet strategies to further optimize its intrinsic nutritional composition remain a key objective. This study examined the influence of melatonin on muscle development and visceral fat deposition in cashmere goats, focusing on its role in augmenting systemic antioxidant capacity and modifying gut microbiota. Thirty goat kids were randomly assigned to a control or a melatonin-treated (2 mg/kg body weight) group. Melatonin implantation induced a metabolic shift characterized by reduced visceral fat deposition (perirenal, omental, and mesenteric fat; p < 0.05) without impacting intramuscular fat. Concurrently, it promoted muscle accretion, as demonstrated by an increase in crude protein content and hypertrophy of muscle fibers in the Longissimus thoracis et lumborum, Gluteus medius, and Biceps femoris muscles (p < 0.05). These effects were underpinned by an enhanced systemic antioxidant capacity (elevated CAT, GSH-Px, T-AOC, and reduced MDA; p < 0.05), changes in gut microbiota, and a concomitant improvement in gastrointestinal morphology, evidenced by increased rumen papilla length and intestinal villus height. Melatonin enriched beneficial genera (e.g., Succiniclasticum, Butyrivibrio, Akkermansia), which were significantly correlated with reduced adiposity and improved protein deposition. These improvements resulted from the concerted actions of an enhanced systemic antioxidant defense system and a beneficially modulated gut microbial community. This trial observed no effect on intramuscular fat deposition, suggesting that improving intramuscular fat may require a systematic fattening regimen. This study provides a scientific foundation for employing melatonin as a nutritional strategy in goat production to improve meat quality.