Search Results (182)

Wool has distinctive biological, physical, and chemical properties that contribute to its value both for the sheep and in global fibre and textile markets. Its fibres are primarily composed of proteins, principally keratin and keratin-associated proteins (KAPs). To better comprehend the genes that underpin key wool traits, this study examined the keratin-associated protein 36-1 gene (KRTAP36-1) in Chinese Tan lambs. We identified three previously reported alleles of the gene (named A, B and C) that were present in the lambs studied, with genotype frequencies as follows: 2.0% (n = 5; AA), 6.9% (n = 17; AB), 13.8% (n = 34; AC), 8.9% (n = 22; BB), 33.4% (n = 82; BC) and 35.0% (n = 86; CC). The frequencies of the individual alleles in the Chinese Tan lambs were 12.4%, 29.1% and 58.5% for alleles A, B and C, respectively. The three alleles were in Hardy–Weinberg Equilibrium. In an association analysis, it was revealed that allele C was associated with variation in the mean fibre curvature of the fine wool of the Chinese Tan lambs, but this association was not observed in their heterotypic hair fibres. This finding suggests that KRTAP36-1 might be differentially expressed in the wool follicles that produce the two fibre types, and that along with other KRTAP genes, it may be involved in determining fibre curvature and the distinctive curly coat of the lambs. Full article

Reproductive efficiency is a critical determinant of productivity and profitability in sheep farming. Traditional selection methods have largely relied on phenotypic traits and historical reproductive records, which are often limited by subjectivity and delayed feedback. Recent advancements in artificial intelligence (AI), including video tracking, wearable sensors, and machine learning (ML) algorithms, offer new opportunities to identify behavior-based indicators linked to key reproductive traits such as estrus, lambing, and maternal behavior. This review synthesizes the current research on AI-powered behavioral monitoring tools and proposes a conceptual model, ReproBehaviorNet, that maps age- and sex-specific behaviors to biological processes and AI applications, supporting real-time decision-making in both intensive and semi-intensive systems. The integration of accelerometers, GPS systems, and computer vision models enables continuous, non-invasive monitoring, leading to earlier detection of reproductive events and greater breeding precision. However, the implementation of such technologies also presents challenges, including the need for high-quality data, a costly infrastructure, and technical expertise that may limit access for small-scale producers. Despite these barriers, AI-assisted behavioral phenotyping has the potential to improve genetic progress, animal welfare, and sustainability. Interdisciplinary collaboration and responsible innovation are essential to ensure the equitable and effective adoption of these technologies in diverse farming contexts. Full article

Background: Heat stress challenges small ruminants in semi-arid regions, requiring integrative multi-modeling approaches to identify adaptive thermotolerance traits. This study aimed to identify phenotypic biomarkers and explore the relationships between thermoregulatory responses and hematological, behavioral, morphometric, carcass, and meat traits in lambs. Methods: Twenty 4-month-old non-castrated male lambs, with an average body weight of 19.0 ± 5.11 kg, were evaluated under natural heat stress. Results: Thermoregulatory variables were significantly associated with non-carcass components (p = 0.002), carcass performance (p = 0.027), commercial meat cuts (p = 0.032), and morphometric measures (p = 0.029), with a trend for behavioral responses (p = 0.078). The main phenotypic traits related to thermoregulation included idleness duration, cold carcass weight, blood, liver, spleen, shank, chest circumference, and body length. Exploratory factor analysis reduced the significant indicators to seven latent domains: carcass traits, commercial meat cuts, non-carcass components, idleness and feeding behavior, and morphometric and thermoregulatory responses. Bayesian network modeling revealed interdependencies, showing carcass traits influenced by morphometric and thermoregulatory responses and non-carcass traits linked to ingestive behavior. Thermoregulatory variables were not associated with meat quality or hematological traits. Conclusions: These findings highlight the complex biological relationships underlying heat adaptation and emphasize the potential of combining phenomic data with computational tools to support genomic selection for climate-resilient and welfare-oriented breeding programs. Full article

Skeletal muscle fiber type composition critically influences lamb meat quality. This study examined the relationships between muscle fiber types and key quality traits, including tenderness, color, lipid and amino acid profiles, and volatile flavor compounds. MyHC I (slow-twitch oxidative fibers) positively correlated with desirable traits such as increased redness, water-holding capacity, unsaturated fatty acids, and essential amino acids. Conversely, MyHC IIb (fast glycolytic fibers) was linked to reduced tenderness and higher levels of off-flavor compounds. MyHC IIa and IIx showed minimal effects. Untargeted metabolomics comparing muscles with high versus low slow-twitch fiber proportions revealed differential metabolites enriched in sphingolipid and arginine-proline metabolism pathways. These results suggest that a higher proportion of oxidative fibers enhances both the sensory and nutritional qualities of lamb meat by modulating lipid metabolism, amino acid availability, and flavor formation. Full article

Background/Objectives: Wool is an important product in sheep production, but the genetic mechanisms underpinning variation in wool growth are not fully understood. Identifying the genes and genomic variants that play a role in increasing fleece weight may allow for increased selection accuracy and improved economic return to producers. Methods: A genome-wide association study (GWAS) was conducted to investigate genetic associations with lifetime fleece weight, average fleece weight and average post-lambing ewe weight for Rambouillet, Polypay, Suffolk and Columbia ewes (N = 1125). Weir–Cockerham F_ST and runs of homozygosity (ROH) analyses were conducted to improve detection of putative wool-related signatures. Results: Twenty-four SNPs were identified through GWAS for lifetime fleece weight, average fleece weight and average post-lambing ewe weight. Chromosomes 2 and 6 contained ROH islands in Rambouillet, and chromosomes 2, 3 and 10 contained ROH islands in Suffolk. The F_ST analysis identified 18 SNPs in proximity to 37 genes of interest. Conclusions: Many of the SNPs and signatures of selection reported in this study are near or within current candidate genes for wool production and wool quality, including ADAR, KCNN3, NTN1, SETBP1, TP53 and TNFSF12. The significant SNPs implicated by GWAS may be used to predict ewes’ potential for lifetime wool production and are suggested as candidates for further study to continue to elucidate the genetic mechanisms underlying wool production traits in United States sheep breeds. Full article

This study evaluated the effects of dietary Rhodotorula yeast culture (RYC) supplementation on carcass traits, meat quality, antioxidant capacity, shelf life, and flavor substance in fattening lambs. Twenty-four three-month-old male Dorper × Han crossbred sheep (body weight: 36 ± 4 kg) were randomly assigned to four groups: R0 (basal diet), R10 (basal diet + 10 g RYC/day), R20 (basal diet + 20 g RYC/day), and R40 (basal diet + 40 g RYC/day). The experiment lasted 75 days. Compared to the control group, the R10, R20, and R40 groups exhibited significant reductions in shear force (p < 0.01), malondialdehyde levels (p < 0.01), and day-15 total volatile basic nitrogen values (p < 0.05), along with significant increases in glutathione peroxidase activity (p < 0.05) and total umami-taste amino acid content (p < 0.01). The R20 group also demonstrated significant increases in backfat thickness, muscle crude protein content, and total antioxidant capacity (p < 0.05). These results indicate that dietary supplementation with 20 g RYC improves physicochemical properties, antioxidant capacity, shelf life, and flavor compounds in fattening lambs. Full article

This study evaluated the effects of dietary supplementation with guanidinoacetic acid (GAA) and zilpaterol hydrochloride (ZLH) on productive performance, carcass traits, and blood chemistry in non-castrated male lambs over 60 days. Twenty-four Pelibuey × Dorper crossbred lambs (16.3 ± 2.7 kg) were adapted to housing and diet for 14 days before being randomly assigned to one of three treatments: (1) Control: total mixed ration (TMR) without additives; (2) GAA: TMR with 0.06% GAA; and (3) ZLH: TMR with 6 mg/kg dry matter (DM) of ZLH for the last 30 days. No significant differences were observed in productive performance or carcass traits among treatments. However, lambs fed GAA showed higher serum glucose and creatinine levels than the control group (p < 0.05), suggesting a potential effect on energy metabolism. ZLH supplementation had no measurable impact on the parameters evaluated. These findings indicate that while GAA may influence certain metabolic indicators, further research with extended feeding periods or varying dosages is needed to clarify its effects on growth and carcass characteristics in lambs. Full article

Glycerol can effectively replace corn as an energy source in lamb diets without negatively impacting productive performance. This study evaluated the effects of substituting ground corn with different glycerol levels on the productive performance, ruminal fermentation, carcass characteristics, and meat quality at 24 h, 7, 14, and 21 d post-slaughter. A total of 40 male Suffolk × Hampshire crossbred lambs (25 ± 5 kg live weight) were used in a completely randomized design with four treatment groups (n = 10 each): 0% glycerol (GLY₀), 5% glycerol (GLY0₅), 10% glycerol (GLY₁₀), and 15% glycerol (GLY₁₅). Including glycerol in the diet did not affect growth performance (p > 0.05). However, it did lead to an increase (p < 0.05) in the concentrations of NH₃-N and the proportions of propionic and butyric acids, while the acetic acid levels decreased (p < 0.05). The backfat thickness, loin eye area (LEA), and carcass yield were not significantly affected (p > 0.05) by the addition of glycerol. Additionally, pH and color were also unaffected (p > 0.05), although the water-holding capacity showed a decrease (p < 0.05) over the shelf life of the meat. The chemical composition of the meat remained similar across all treatments, time points, and interactions (p > 0.05). In contrast, the protein content was significantly affected (p < 0.05) by the glycerol inclusion, time, and interactions between treatment and time. The results indicate that substituting up to 15% of ground corn with glycerol in lamb diets does not negatively impact productive performance, backfat thickness, LEA, carcass traits, or meat quality during shelf life. Throughout the shelf life, the crude protein concentrations and water-holding capacity decreased, while the propionic acid and NH₃-N concentrations increased. Full article

Leonardite (LEO), a microbial derived product rich in humic and fulvic acids, has been tested, due to its beneficial properties for health and well-being, as a feed additive, mainly in non-ruminant species. Although there are some reports of LEO supplementation in ruminants fed with high-to medium-forage based diets, there is no information available of the potential effects of LEO in ruminants fed, under sub-tropical climate conditions, with high-energy diets during long-term fattening. For this reason, the objective of the present experiment was to evaluate the effects of LEO levels inclusion in diets for feedlot lambs finished over a long-term period. For this reason, 48 Pelibuey × Katahdin lambs (initial weight = 20.09 ± 3.55 kg) were fed with a high-energy diet (88:12 concentrate to forage ratio) supplemented with LEO (with a minimum of 75% total humic acids) for 130 days as follows: (1) diet without LEO, (2) diet supplemented with 0.20% LEO, (3) diet supplemented with 0.40% LEO, and (4) diet supplemented with 0.60% LEO. For each treatment, Leonardite was incorporated with the mineral premix. Lambs were blocked by weight and housed in 24 pens (2 lambs/pen). Treatment effects were contrasted by orthogonal polynomials. The average climatic conditions that occurred during the experimental period were 31.6 ± 2.4 °C ambient temperature and 42.2 ± 8.1% relative humidity (RH). Those values of ambient temperature and RH represent a temperature humidity index (THI) of 79.07; thus, lambs were finished under high heat load conditions. The inclusion of LEO in diet did not affect dry matter intake (p ≥ 0.25) and average daily gain (p ≥ 0.21); therefore, feed to gain ratio was not affected (p ≥ 0.18). The observed to expected dietary net energy averaged 0.96 and was not affected by LEO inclusion (p ≥ 0.26). The lower efficiency (−4%) of dietary energy utilization is an expected response given the climatic conditions of high ambient heat load presented during fattening. Lambs that were slaughtered at an average weight of 49.15 ± 6.00 kg did not show differences on the variables measured for carcass traits (p ≥ 0.16), shoulder tissue composition (p ≥ 0.59), nor in visceral mass (p ≥ 0.46) by inclusion of LEO. Under the climatic conditions in which this experiment was carried out, LEO supplementation up to 0.60% in diet (equivalent to 0.45% of humic substances) did not did not help to alleviate the extra-energy expenditure used to dissipate the excessive heat and did not change the gained tissue composition of the lambs that were fed with high-energy diets during long-term period under sub-tropical climate conditions. Full article

This study aimed to assess the effect of co-supplementing rumen-protected fat and rumen-protected choline on growth performance, carcass traits, and meat quality in lambs. Using a randomized experimental design, 45 weaned female Tian×Hu crossbred lambs (3 months old; average body weight: 27.34 ± 0.57 kg, mean ± SD) were randomly allocated to one of three dietary treatment groups. The three dietary treatments were as follows: a basal diet group (CON), a group receiving 2% rumen-protected fat in place of 2% barley (RPF), and a group supplemented with 2% rumen-protected fat and 0.4% rumen-protected choline, replacing 2% barley and 0.4% corn germ in the basal diet (RPFC). Compared to the CON group, neither the RPF nor RPFC treatments resulted in significant differences in growth performance (p > 0.05). However, the RPFC group showed a 5.3% increase in dry matter intake (DMI) compared to the RPF group (p < 0.05). Compared with the CON, the RPF treatment increased 69.23% the relative abundance of C18:2n-6t (p < 0.05), but the content of C17:0, C17:1, C18:1n-9c, and iso-C18:0 in Longissimus lumborum was decreased by 16.49%, 15.78%, 6.45% and 27.78%, respectively (p < 0.05). The RPFC treatment increased the relative abundance of C16:1 in Longissimus lumborum (p < 0.05). The RPF and RPFC treatments significantly increased serum levels of high-density lipoprotein (HDL) and total cholesterol compared to the CON group (p < 0.05). The RPF treatment raised HDL by 50.00% and total cholesterol by 38.03%, while the RPFC treatment increased HDL by 39.47% and total cholesterol by 26.03%. Furthermore, compared to the RPF group, the RPFC treatment led to a 13.47% increase in the 45 min b* color value of the Longissimus lumborum (p < 0.01) and a significant 45.45% reduction in the relative abundance of C18:2n-6t fatty acid in the same muscle (p < 0.05). In summary, rumen-protected choline reduces the negative effects of rumen-protected fat on feed intake in lambs and changes fatty acid profile in meat. Full article

With economic development and improved living standards, the demand for mutton and wool continues to grow, and improving the production performance and genetic potential of sheep breeds has become the key to promoting the high-quality development of the sheep industry. Thus, this study analyzes the influencing factors of the early production traits of Yunnan semi-fine wool sheep, optimizes the genetic evaluation model, and relies on accurate genetic parameter estimation to provide a theoretical basis for formulating a scientific and efficient breeding strategy for this breed. Data were collected from the Laishishan and Xiaohai breeding farms in Qiaojia, Yunnan, covering production records of the core flock from 2018 to 2022. Using the GLM procedure in SAS 9.4 software, this study analyzed the non-genetic influences on early production traits in Yunnan semi-fine wool sheep. Concurrently, Danish Milk Unit 5 (DMU 5) software estimated the variance components across various animal models for each trait. Employing the Akaike Information Criterion (AIC) and likelihood ratio test (LRT), six models were tested, incorporating or excluding maternal inheritance and environmental impacts, to identify the optimal model for deriving the genetic parameters. The results show that the birth year, dam age, sex, flock and litter size significantly affect both the Birth Weight (BWT) and Weaning Weight (WWT) (p < 0.01). Additionally, the birth month was found to exert a significant effect on Birth Weight (BWT) (p < 0.01), the weaning month has a significant effect on the Weaning Weight (WWT) (p < 0.05). No significant effects of farm location were observed on either trait (p > 0.05). The most accurate genetic evaluation model determined the heritability of the Birth Weight (BWT) and Weaning Weight (WWT) as 0.3123 and 0.3471. From a production perspective, improving lamb birth, Weaning Weight (WWT), feed composition, and maternal nutrition during gestation is vital for breeding efficiency. This study not only identified the optimal animal models for early growth traits in Yunnan semi-fine wool sheep, offering a precise basis for estimating genetic parameters but also provides theoretical guidance for genetic selection and breed improvement in this population. Full article

Cold stress impacts lamb mortality, welfare, and productivity. Wool and skin insulate lambs, but the mechanisms underlying their response to colder environments remain unclear. Shorn lambs (n = 20) of similar age (8 months), of the Hulunbuir (n = 10; average 34.5 ± 0.70 kg) and Hu (n = 10; average 34.9 ± 0.79 kg) breeds, were raised at the Ecological and Agricultural Experimental Station, Gaolan, Gansu Province, People’s Republic of China (36°13″ N, 103°47″ E), at an altitude of 1780 m above sea level. These lambs were divided into four equal groups: Hulunbuir at −20 °C (HB−20), Hulunbuir at 15 °C (HB+15), Hu at −20 °C (HU−20), and Hu at 15 °C (HU+15). The groups were maintained at these temperatures in temperature-controlled facilities for 38 days. Skin tissues were analyzed with transcriptome sequencing, and selected wool and physiological traits were assessed. The HB−20 lambs had greater wool length growth (1.8 ± 0.13 vs. 1.0 ± 0.46 cm, p < 0.001) and epidermis thickness (20.0 ± 1.20 vs. 14.6 ± 0.87 μm, p = 0.006) but lower hair follicle density (33.6 ± 2.11 vs. 42.7 ± 3.06 per mm², p = 0.041), rectal temperature (38.1 ± 0.10 vs. 38.8 ± 0.04 °C, p < 0.001), and respiratory rate (15.5 ± 1.08 vs. 24.0 ± 1.89 breaths/min, p = 0.004), compared to the HB+15 lambs. Similar differences in these traits were observed with the Hu lambs at the two temperatures. Transcriptome analyses revealed the activation of pathways related to immune and endocrine systems, signal transduction, and development and regeneration, irrespective of breed at −20 °C. The TNF signaling pathway and osteoclast differentiation may play roles in cold adaptation, as they are associated with differentially expressed genes (DEGs) identified in the Hulunbuir lambs, as well as shared DEGs between both breeds. This study revealed physiological and molecular differences in lambs exposed to lower temperatures and suggests potential targets for improving cold tolerance, welfare, and productivity. Full article

Haemonchus contortus is a highly pathogenic blood-sucking nematode from the abomasum of small ruminants. To develop effective control strategies, it is essential to understand the initial mechanisms involved in host resistance to this parasite. In this study, we used computational tools to analyze the complement and coagulation pathways generated from RNA sequencing of abomasal tissue from resistant (Santa Ines) and susceptible (Ile de France) young sheep artificially infected with H. contortus. Thirty-two differentially expressed genes annotated to the ovine genome were associated with the complement and coagulation cascades, of which 29 of them were overexpressed in Santa Ines. Our data identified potential markers for resistance trait selection in sheep, such as C3 (complement C3), F3 (tissue factor), F5 (coagulation factor V), CFB (complement factor B), and CFI (complement factor I). Santa Ines may have a more robust coagulation system, being activated by extrinsic pathways associated with tissue damage. The complement may act as a mediator of the innate immunity, and its activation in Santa Ines is associated with the classical, the lectin, and the alternative pathway. Finally, resistant Santa Ines lambs had a polygenic overexpressed architecture controlling both complement and coagulation cascades, which probably contributed to the early-onset protection against H. contortus. Full article

Adequate management of replacement ewe lambs (F0) in dairy sheep farms during postnatal life may modify the germline cells, thus promoting transmission of intergenerational effects to the offspring (F1). To test this hypothesis, 18 newborn male lambs (F1), either born from methionine-supplemented ewe lambs (F0 ewe lambs being fed ad libitum with a milk replacer supplemented with 1 g methionine/kg DM) or not supplemented (F0 ewe lambs being fed ad libitum with the same milk replacer with no methionine added), were included in the present study. All the male F1 lambs were managed exactly in the same way along the whole lifespan in order to bring out the differences caused by methionine supplementation of F0 dams. Our data show that the methionine supplementation of dams (F0) during the suckling period did not promote significant (p > 0.05) changes on feed intake, growth rate, or feed efficiency of F1 male lambs during the fattening period. Moreover, the meat chemical composition (proximal, fatty acid profile, and volatile compounds) was similar for both groups (p > 0.05), but the meat of F1-MET lambs presented higher redness and hardness (p < 0.05) when compared to F1-CTRL lambs. The biochemical profile also highlighted significant (p < 0.05) differences in the serum creatinine and calcium content that may be at least partially related to the meat quality traits observed. Overall, all these results suggest that methionine supplementation of lambs (F0) during early postnatal life causes permanent changes in the offspring. This has positive effects, such as achieving a more attractive color of lamb meat (F1) for consumers, and negative effects, such as reduced meat tenderness. Full article