Identifying meat from grazing or feedlot yaks using visible and near-infrared spectroscopy with chemometrics.

Quality of meat can differ between grazing and feedlot yaks. The present study examined whether spectral fingerprints by visible and near-infrared (Vis-NIR) spectroscopy and chemo-metrics could be employed to identify the meat of grazing and feedlot yaks. Thirty-six 3.5 year old castrated male yaks (164 ± 8.38 kg) were divided into grazing and feedlot yaks. After 5 months on treatment, liveweight, carcass weight and dressing percentage were greater in the feedlot than grazing yaks. The grazing yaks had greater protein content but lesser fat content than feedlot yaks. Principal component analysis (PCA) was able to identify the meat of the two groups to a great extent. Using either partial least squares discriminant analysis (PLS-DA) or the soft independent modeling of class analogies (SIMCA) classification, the meat could be differentiated between the groups. Both the original and processed spectral data had a high discrimination percentage, especially the PLS-DA classification algorithm, with a 100% discrimination in the 400-2500 nm band. The spectral pre-processing methods can improve the discrimination percentage, especially for the SIMCA classification. It was concluded that the method can be employed to identify meat from grazing or feedlot yaks. The unerring consistency across different wavelengths and data treatments highlights the model's robustness and the potential use of NIR spectroscopy combined with chemometric techniques for meat classification. PLS-DA's accurate classification model is crucial for the unique evaluation of yak meat in the meat industry, ensuring product traceability and meeting consumer expectations for the authenticity and quality of yak meat raised in different ways.

The Effects of Zinc Supplementation on Growth, Diarrhea, Antioxidant Capacity, and Immune Function in Holstein Dairy Calves.

The current study examined the effects of supplementary zinc proteinate (ZnPro) and zinc oxide (ZnO) on growth performance, diarrhea, antioxidant capacity, immune function, and mineral element concentrations of calves aged 1 to 28 days. A total of twenty-four newborn calves were divided randomly into 3 groups (n = 8; 2 males and 6 females per group), and each received: 0 mg/d Zn (CON), 627 mg/d ZnPro (80 mg/d Zn; ZnPro group), and 101 mg/d ZnO (80 mg/d Zn; ZnO group). The calves received the additive in their milk during the first 28 days of life. Compared with the CON group: ZnPro and ZnO improved average daily gain (ADG) and decreased the feed:gain ratio (FGR) between days 1 and 14 (p < 0.05), while the ADG increased and FGR decreased only in the ZnPro group between days 1 and 28 (p < 0.05). The incidence of diarrhea decreased (p < 0.05) in the ZnPro and ZnO groups between days 15 and 28 as well as days 1 and 28, but decreased (p < 0.05) only in the ZnPro group between days 1 and 14. The serum immunoglobulin G (IgG) concentration of the ZnPro and ZnO groups increased on days 14 and 28 (p < 0.05). ZnPro supplementation increased serum IgM concentration during the whole study, while ZnO enhanced serum IgM concentration only on day 14 (p < 0.05). In the ZnO group, the serum concentration of cytokines interleukin (IL)-10 increased on day 14, while that of IL-1ß increased on day 28 (p < 0.05). In addition, ZnPro reduced the serum malondialdehyde (MDA) concentration on days 14 and 28 (p < 0.05). Both ZnPro and ZnO increased the serum concentrations of alkaline phosphatase (ALP) and metallothionein (MT) on day 14 (p < 0.05). With zinc supplementation, plasma Zn concentration increased (p < 0.05) on days 14 and 28 of age. We concluded that supplementary ZnPro and ZnO reduced incidences of diarrhea and promoted the immune function, but ZnPro improved the growth performance and antioxidant capacity of Holstein dairy calves to a greater extent.

Transmission of fungi and protozoa under grazing conditions from lactating yaks to sucking yak calves in early life.

Microbiota from mothers is an essential source of microbes in early-life rumen microbiota, but the contribution of microbiota from different maternal sites to the rumen microbiota establishment in neonates needs more data. To fill this gap, we collected samples from the mouth, teat skin, and rumen of lactating yaks and from the rumen of sucking calves concomitantly on seven occasions between days 7 and 180 after birth under grazing conditions. We observed that the eukaryotic communities clustered based on sample sites, except for the protozoal community in the teat skin, with negative correlations between fungal and protozoal diversities in the rumen of calves. Furthermore, fungi in the dam's mouth, which is the greatest source of the calf's rumen fungi, accounted for only 0.1%, and the contribution of the dam's rumen to the calf's rumen fungi decreased with age and even disappeared after day 60. In contrast, the average contribution of the dam's rumen protozoa to the calf's rumen protozoa was 3.7%, and the contributions from the dam's teat skin (from 0.7 to 2.7%) and mouth (from 0.4 to 3.3%) increased with age. Thus, the divergence in dam-to-calf transmissibility between fungi and protozoa indicates that the foundation of these eukaryotic communities is shaped by different rules. This study provides the first measurements of the maternal contribution to the fungal and protozoal establishment in the rumen of sucking and grazing yak calves in early life, which could be beneficial for future microbiota manipulation in neonatal ruminants. KEY POINTS: • Dam to calf transfer of rumen eukaryotes occurs from multiple body sites. • A minor proportion of rumen fungi in calves originated from maternal sites. • The inter-generation transmission between rumen fungi and protozoa differs.

A comparison of average daily gain, apparent digestibilities, energy balance, rumen fermentation parameters, and serum metabolites between yaks (Bos grunniens) and Qaidam cattle (Bos taurus) consuming diets differing in energy level.

Yaks (Bos grunniens), indigenous to the harsh Qinghai-Tibetan Plateau, are well adapted to the severe conditions, and graze natural pasture without supplements all year round. Qaidam cattle (Bos taurus), introduced to the Qinghai-Tibetan Plateau 1,700 years ago, are raised at a lower altitude than yaks, provided with shelter at night and offered supplements in winter. Based on their different backgrounds, we hypothesized that yaks have lower energy requirements for maintenance than cattle. To test this hypothesis, we measured average daily gain (ADG), apparent digestibilities, energy balance, rumen fermentation parameters, and serum metabolites in growing yaks and cattle offered diets differing in metabolizable energy (ME) levels (6.62, 8.02, 9.42 and 10.80 MJ/kg), but with the same crude protein concentration. Six castrated yaks (155 ± 5.8 kg) and 6 castrated Qaidam cattle (154 ± 8.0 kg), all 2.5 years old, were used in 2 concurrent 4 × 4 Latin square designs. Neutral and acid detergent fiber digestibilities were greater (P < 0.05) in yaks than in cattle, and decreased linearly (P < 0.05) with increasing dietary energy level; whereas, digestibilities of dry matter, organic matter, crude protein and ether extract increased (P < 0.05) linearly with increasing energy level. The ADG was greater (P < 0.001) in yaks than in cattle, and increased (P < 0.05) linearly with increasing energy levels. From the regressions of ADG on ME intake, the estimated ME requirement for maintenance was lower (P < 0.05) in yaks than in cattle (0.43 vs. 0.57 MJ/kg BW0.75). The ratios of digestible energy (DE):gross energy and ME:DE were higher (P < 0.05) in yaks than in cattle, and increased (P < 0.05) linearly with increasing dietary energy level. Ruminal pH decreased (P < 0.05), whereas concentrations of total volatile fatty acids (VFAs) and ammonia increased (P < 0.01) with increasing dietary energy level, and all were greater (P < 0.05) in yaks than in cattle. Concentrations of ruminal acetate and iso-VFAs were greater (P < 0.05), whereas propionate was lower (P < 0.05) in yaks than in cattle; acetate decreased (P < 0.001), whereas butyrate and propionate increased (P < 0.001) linearly with increasing dietary energy level. Serum concentrations of ß-hydroxybutyrate were lower (interaction, P < 0.001) in yaks than in cattle fed diets of 9.42 and 10.80 MJ/kg, whereas non-esterified fatty acids were greater (interaction, P < 0.01) in yaks than in cattle fed diets of 6.62 and 8.02 MJ/kg. Concentrations of serum leptin and growth hormone were greater in yaks than in cattle and serum insulin and growth hormone increased (P < 0.01) linearly with increasing dietary energy level. Our hypothesis that yaks have lower energy requirements for maintenance than cattle was supported. This lower requirement confers an advantage to yaks over Qaidam cattle in consuming low energy diets during the long winter on the Qinghai-Tibetan Plateau.

Effect of the ratio of dietary metabolizable energy to nitrogen content on production performance, serum metabolites, rumen fermentation parameters, and bacterial diversity in yaks.

This study examined the effect of the ratio of dietary metabolizable energy (MJ) to nitrogen (g) content (ME:N) on average daily gain (ADG), blood biochemical indices, rumen fermentation parameters, and rumen bacterial community in yaks. Thirty-six male yaks, aged 2-3 years, were divided into three groups and received a ME:N ratio of 0.42 (HY), 0.36 (MY,) or 0.32 (LY) MJ/g. Dry matter intake ranged between 3.16 and 3.63 kg/d and was lesser (p < 0.001) in the LY group than the other two groups. ME intake increased (p < 0.001) with an increase in the ME:N ratio, while N intake did not differ among groups. The ADG was 660 g/day for the MY group, which was higher (p < 0.005) than the 430 g/day in the LY group, while the HY group gained 560 g/day and did not differ from the other two groups. Feed intake to ADG ratio ranged between 5.95 and 7.95, and numerically was highest in the LY group and lowest in the MY group. In general, the concentration of ruminal total volatile fatty acids (p < 0.03) and molar proportions of propionate (p < 0.04), increased, while the molar proportion of acetate (p < 0.005) and the acetate:propionate ratio decreased (p < 0.001) with a decrease in the ME:N ratio. The molar proportion of butyrate did not differ among groups (p = 0.112). Group MY had higher ruminal NH3-N content than group HY and had a higher serum glucose content but lower urea content, lactate dehydrogenase, and creatine kinase content than group LY. In ruminal bacteria at the phylum level, the relative abundance of Firmicutes (F) was greater and of Bacteroidetes (B) was lesser, while the F:B ratio was greater in group MY than in groups HY an LY. We concluded that the yaks consuming the diet containing a ME:N ratio of 0.36 MJ/g had the best performance of the three groups.

Comparison of rumen bacterial communities between yaks (Bos grunniens) and Qaidam cattle (Bos taurus) fed a low protein diet with different energy levels.

The yak (Bos grunniens), an indigenous bovine on the Qinghai-Tibetan plateau (QTP), is reported to digest low quality forage to a greater extent and to require less protein and energy for maintenance than the introduced Qaidam cattle (Bos taurus). Ruminal bacteria play a major role in feed degradation, and therefore, we hypothesized that ruminal bacteria composition would differ between yaks and cattle, and confer an advantage to yaks for poor quality diets. To test our hypothesis, we determined the ruminal bacteria profiles, rumen fermentation parameters, and enzyme activities in these bovine species consuming a low-protein diet differing in energy level. Six castrated yaks (155 ± 5.8 kg) and 6 castrated Qaidam cattle (154 ± 8.0 kg) were used in two concurrent 4 × 4 Latin square designs with 2 additional animals of each species in each period. The animals were offered a low-protein diet of 70.4 g/kg dry matter (DM) and one of four metabolizable energy levels, namely 6.62, 8.02, 9.42, and 10.80 MJ/kg. Ruminal pH, concentrations of ammonia-N and total volatile fatty acids (VFAs), the molar proportion of acetate, and the ratio of acetate to propionate (A:P) were greater (P < 0.05), whereas the molar proportion of propionate was lesser (P = 0.043) in yaks than in cattle. With increasing dietary energy level, ruminal pH, the molar proportion of acetate and the ratio of A:P decreased linearly (P < 0.05), whereas, the concentration of total VFAs, molar proportions of propionate, butyrate, iso-butyrate, and iso-valerate and concentration of ammonia-N increased linearly (P < 0.05). The relative abundance (RA) of Firmicutes increased linearly (P < 0.01), whereas, the RA of Bacteroidetes decreased linearly (P < 0.001) with increasing energy level in both bovine species. The RAs of Prevotella and Rikenellaceae_RC9_gut_group decreased linearly (P < 0.05) with increasing energy level in both yaks and cattle. The RAs of fibrolytic (e.g., Rikenellaceae_RC9_gut_group), and H2-incorporating (e.g., Quinella) bacteria were greater (P < 0.05) in yaks than in cattle. We concluded that the two bovines differ in ruminal bacterial profiles and rumen fermentation parameters, and confer an advantage to yaks over cattle in consuming a low protein diet with differing energy level.

Yak rumen fluid inoculum increases biogas production from sheep manure substrate.

Hydrolytic bacteria are essential for the degradation of lignocellulose to produce biogas and organic fertilizers. In this study, sheep manure was used as substrate, and sheep manure slurry, yak rumen fluid and slurry from a biogas reactor (SBR) were used as inocula in single-stage anaerobic digestion. The SBR and rumen fluid inocula increased biogas production by 23% and 43%, respectively, when compared to solely sheep manure in the single-stage anaerobic digestion. The two-stage anaerobic digestion, with yak rumen fluid as inoculum in the hydrolytic reactor, increased the biogas production by 59, 86, and 58% compared with the control. Microbial analysis of the effluent revealed that yak rumen fluid contained hydrolytic bacteria such as Proteiniphilum, Jeotgalibaca, Fermentimonas, and Atopostipes to enhance the degradation of sheep manure and increase biogas production. It was concluded that yak rumen fluid, rich in hydrolytic bacteria, increases the degradability of sheep manure and improves production of volatile fatt acids and biogas.

The adaptive strategies of yaks to live in the Asian highlands.

The yak (Bos grunniens), an indigenous herbivore raised at altitudes between 3,000 and 5,000 m above sea level, is closely linked to more than 40 ethnic communities and plays a vital role in the ecological stability, livelihood security, socio-economic development, and ethnic cultural traditions in the Asian highlands. They provide the highlanders with meat, milk, fibres, leather and dung (fuel). They are also used as pack animals to transport goods, for travel and ploughing, and are important in many religious and traditional ceremonies. The Asian highlands are known for an extremely, harsh environment, namely low air temperature and oxygen content and high ultraviolet light and winds. Pasture availability fluctuates greatly, with sparse pasture of poor quality over the long seven-month cold winter. After long-term natural and artificial selections, yaks have adapted excellently to the harsh conditions: 1) by genomics, with positively selected genes involved in hypoxia response and energy metabolism; 2) anatomically, including a short tongue with a weak sense of taste, and large lung and heart; 3) physiologically, by insensitivity to hypoxic pulmonary vasoconstriction, maintaining foetal haemoglobin throughout life, and low heart rate and heat production in the cold season; 4) behaviourlly, by efficient grazing and selecting forbs with high nutritional contents; 5) by low nitrogen and energy requirements for maintenance and low methane emission and nitrogen excretion, namely, 'Low-Carbon' and 'Nitrogen-Saving' traits; 6) by harboring unique rumen microbiota with a distinct maturation pattern, that has co-evolved with host metabolism. This review aims to provide an overview of the comprehensive adaptive strategies of the yak to the severe conditions of the highlands. A better understanding of these strategies that yaks employ to adapt to the harsh environment could be used in improving their production, breeding and management, and gaining benefits in ecosystem service and a more resilient livelihood to climate change in the Asian highlands.

Hypothalamic regulation of energy homoeostasis when consuming diets of different energy concentrations: comparison between Tibetan and Small-tailed Han sheep.

Seasonal energy intake of Tibetan sheep on the harsh Qinghai-Tibetan Plateau (QTP) fluctuates greatly and is often well below maintenance requirements. The aim of this study was to gain insight into how the hypothalamus regulates energy homoeostasis in Tibetan sheep. We compared Tibetan and Small-tailed Han sheep (n 24 of each breed), which were each allocated randomly into four groups and offered one of four diets that differed in digestible energy densities: 8·21, 9·33, 10·45 and 11·57 MJ/kg DM. Sheep were weighed every 2 weeks, and it was assumed that the change in body weight (BW) reflected the change in energy balance. The arcuate nucleus of the hypothalamus in Tibetan sheep had greater protein expressions of neuropeptide Y (NPY) and agouti-related peptide (AgRP) when in negative energy balance, but lesser protein expressions of proopiomelanocortin (POMC) and cocaine and amphetamine-regulated transcript (CART) when in positive energy balance than Small-tailed Han sheep. As a result, Tibetan sheep had a lesser BW loss when in negative energy balance and stored more energy and gained more BW when in positive energy balance than Small-tailed Han sheep with the same dietary intake. Moreover, in the hypothalamic adenosine monophosphate-activated protein kinase (AMPK) regulation pathway, Tibetan sheep had greater adenosine monophosphate-activated protein kinase-α 2 protein expression than Small-tailed Han sheep, which supported the premise of a better ability to regulate energy homoeostasis and better growth performance. These differences in the hypothalamic NPY/AgRP, POMC/CART and AMPK pathways between breeds conferred an advantage to the Tibetan over Small-tailed Han sheep to cope with low energy intake on the harsh QTP.

Rumen Bacterial Community of Grazing Lactating Yaks (Poephagus grunniens) Supplemented with Concentrate Feed and/or Rumen-Protected Lysine and Methionine.

Traditionally, yaks graze only natural pasture all year round without supplements. Forage intake of lactating yaks is below energy and protein requirements, even in the summer, and suckling yaks lose a substantial amount of significant body weight. Today, to mitigate the loss in body weight, supplementary feed is being offered to lactating yaks. However, the effects of supplementary feed on ruminal bacterial communities in lactating yaks is unknown. In the current study, we examined the effect of supplementary feed on ruminal microbiota, using 16S rRNA sequencing, and on volatile fatty acids (VFAs). Twenty-four lactating yaks of similar body weight (218 ± 19.5 kg) and grazing natural pasture were divided randomly into four groups and received different supplements: (1) rumen-protected amino acids (RPA); (2) concentrate feed (C); (3) RPA plus C (RPA+C); and (4) no supplements (control-CON). The concentrations of total VFAs, acetate, and butyrate were greater (p < 0.05) when supplemented with concentrate feed (C and RPA+C) than without concentrate feed (CON and RPA). Bacteroidetes (B) and Firmicutes (F) were the dominant ruminal bacterial phyla in all groups. The ratio of relative abundance of F:B in RPA+C was greater than in the RPA group, while there was no difference between CON and RPC (interaction, p = 0.026). At the genus level, the relative abundances of Absconditabacteriales_SR1, Bacteroidales-RF16-group, Bacteroidales_BS11_gut_group, Prevotellaceae, and Rikenellaceae_RC9_gut_group were lesser (p < 0.05) with supplementary concentrate feed (C and RPA+C) than without concentrate feed (CON and RPA), whereas Butyrivibrio_2 and Pseudobutyrivibrio were greater (p < 0.05) with supplementary rumen-protected amino acids (RPA and RPA+C) than without rumen-protected amino acids (CON and C). These results demonstrate that supplementary feed: (1) alters the composition of rumen microbiota and concentrations of ruminal VFAs in lactating yaks; and (2) can be used to manipulate the composition of rumen microbiota.

Transcriptome Analysis Reveals Genes Involved in Thermogenesis in Two Cold-Exposed Sheep Breeds.

Thermogenesis plays an important role in the survival of sheep exposed to low temperatures; however, little is known about the genetic mechanisms underlying cold adaptation in sheep. We examined 6 Altay (A) and 6 Hu (H) six-month-old ewe lambs. Altay sheep are raised in northern China and are adapted to dry, cold climates, while Hu sheep are raised in southern China and are adapted to warm, humid climates. Each breed was divided into two groups: chronic cold sheep, exposed to -5 °C for 25 days (3 Ac; 3 Hc), and thermo-neutral sheep, maintained at 20 °C (3 Aw; 3 Hw). The transcriptome profiles of hypothalamus, tail-fat and perirenal fat tissues from these four groups were determined using paired-end sequencing for RNA expression analysis. There are differences in cold tolerance between Hu and Altay sheep. Under cold exposure of the lambs: (1) UCP1-dependent thermogenesis and calcium- and cAMP-signaling pathways were activated; and (2) different fat tissues were activated in Hu and Altay lambs. Several candidate genes involved in thermogenesis including UCP1, ADRB3, ADORA2A, ATP2A1, RYR1 and IP6K1 were identified. Molecular mechanisms of thermogenesis in the sheep are discussed and new avenues for research are suggested.

An increase in dietary lipid content from different forms of double-low rapeseed reduces enteric methane emission in Datong yaks on the Qinghai-Tibetan Plateau.

Enteric methane (CH4 ) emission in cattle generally decreases by approximately 1 g/g dry matter intake (DMI) with an increase in dietary lipids of 10 g/kg dry matter (DM). The effect of dietary lipids on CH4 emission in yaks has not been reported and is the subject of this study. Four Datong yaks were used in a 4 × 4 Latin-square design in which the four treatments included restricted intakes of double-low rapeseed differing in form and lipid (ether extract-EE) content: (a) rapeseed meal (EE 32.6 g/kg DM); (b) rapeseed meal and rapeseed cake (EE 45.8 g/kg DM); (c) rapeseed meal and whole cracked rapeseed (EE 54.5 g/kg DM) and (d) rapeseed meal and rapeseed oil (EE 62.7 g/kg DM). The digestibility of feed components did not differ among treatments. The ruminal total volatile fatty acids (p = .082) and acetic acid (p = .062) concentrations tended to be lowest in yaks consuming the diet with highest lipid content. In addition, CH4 production was lowest in this group (p = .004), and declined by 1.75 g/g DMI per 10 g/kg DM reduction in dietary lipid content, a rate substantially faster than in cattle.

Effect of the level and source of supplementary dietary zinc on egg production, quality, and zinc content and on serum antioxidant parameters and zinc concentration in laying hens.

Zinc is vital for proper functioning of an animal. Two sources of zinc are commonly supplemented in animal feed, organic and inorganic zinc, and there are reports that the former is absorbed to a greater extent than the latter. We hypothesized that supplementary zinc would increase zinc content in eggs of laying hens and that organic zinc would be more effective than inorganic zinc. To test these hypotheses, we examined the effect of levels and sources of supplemental dietary zinc on average daily feed intake (ADFI), egg production, and zinc content in eggs and on serum antioxidant capacity and zinc concentration in laying hens. A total of 720 Roman laying hens (21-week-old) were randomly assigned to 5 treatment groups with 6 replicates, with 24 hens in each replicate. Two sources of zinc, organic (zinc amino acid complex) and inorganic (zinc sulfate), each with 2 levels, low (35 mg/kg) and high (70 mg/kg), comprised 4 treatment groups, and a control group without supplementary zinc was the fifth group. Seven days were allowed for adjustment to the conditions, and then measurements were taken over 42 D. There was no difference in ADFI, average egg weight (EW), ADFI-to-EW ratio, and egg quality (P > 0.05) among the 5 treatment groups; supplemental zinc increased serum concentrations of Zn2+ and Cu-Zn superoxide dismutase and tended to increase superoxide dismutase content (P = 0.065). Zinc content in eggs increased linearly with supplementary organic zinc (N = 18, R2 = 0.363, P = 0.008) and with supplementary inorganic zinc (N = 18, R2 = 0.366, P = 0.008) treatment, but there was no difference between the source treatments of zinc. Therefore, our first hypothesis was supported, but our second one was not supported. We concluded that zinc supplementation is effective in enhancing zinc content in eggs and in improving antioxidant capacity in laying hens.

Comparison between Tibetan and Small-tailed Han sheep in adipocyte phenotype, lipid metabolism and energy homoeostasis regulation of adipose tissues when consuming diets of different energy levels.

This study aimed to gain insight into how adipose tissue of Tibetan sheep regulates energy homoeostasis to cope with low energy intake under the harsh environment of the Qinghai-Tibetan Plateau (QTP). We compared Tibetan and Small-tailed Han sheep (n 24 of each breed), all wethers and 1·5 years of age, which were each divided randomly into four groups and offered diets of different digestible energy (DE) densities: 8·21, 9·33, 10·45 and 11·57 MJ DE/kg DM. When the sheep lost body mass and were assumed to be in negative energy balance: (1) adipocyte diameter in subcutaneous adipose tissue was smaller and decreased to a greater extent in Tibetan than in Small-tailed Han sheep, but the opposite occurred in the visceral adipose tissue; (2) Tibetan sheep showed higher insulin receptor mRNA expression and lower concentrations of catabolic hormones than Small-tailed Han sheep and (3) Tibetan sheep had lower capacity for glucose and fatty acid uptake than Small-tailed Han sheep. Moreover, Tibetan sheep had lower AMPKα mRNA expression but higher mammalian target of rapamycin mRNA expression in the adipocytes than Small-tailed Han sheep. We concluded that Tibetan sheep had lower catabolism but higher anabolism in adipose tissue and reduced the capacity for glucose and fatty acid uptake to a greater extent than Small-tailed Han sheep to maintain energy homoeostasis when in negative energy balance. These responses provide Tibetan sheep with a high ability to cope with low energy intake and with the harsh environment of the QTP.

Tibetan sheep have a high capacity to absorb and to regulate metabolism of SCFA in the rumen epithelium to adapt to low energy intake.

The nutritional intake of Tibetan sheep on the harsh Qinghai-Tibetan Plateau is often under maintenance requirements, especially during the long, cold winter. However, they have adapted well and even thrive under these conditions. The aim of the present study was to gain insight into how the rumen epithelium of Tibetan sheep has adapted to the consumption of low-energy-level diets. For this purpose, we compared Tibetan and small-tailed Han sheep (n 24 of each breed, all wethers and 1·5 years of age), which were divided randomly into one of four groups and offered ad libitum diets of different digestible energy (DE) densities: 8·21, 9·33, 10·45 and 11·57 MJ DE/kg DM. The Tibetan sheep had higher rumen concentrations of total SCFA, acetate, butyrate and iso-acids but lower concentrations of propionate than small-tailed Han sheep. The Tibetan sheep had higher absorption capability of SCFA due to the greater absorption surface area and higher mRNA expression of the SCFA absorption relative genes than small-tailed Han sheep. For the metabolism of SCFA in the rumen epithelium, the small-tailed Han sheep showed higher utilisation of the ketogenesis pathway than Tibetan sheep; however, Tibetan sheep had greater regulation capacity in SCFA metabolism pathways. These differences between breeds allowed the Tibetan sheep to have greater capability of absorbing SCFA and better capacity to regulate the metabolism of SCFA, which would allow them to cope with low energy intake better than small-tailed Han sheep.

Protective Effect of Resveratrol Improves Systemic Inflammation Responses in LPS-Injected Lambs.

Highly intensive livestock production often causes immune stress to animals, which makes them more susceptible to infections. The aim of this study was to examine whether resveratrol (Res) alleviates inflammation in lambs. In Experiment 1, 16 male lambs were injected with lipopolysaccharides (LPS) at an initial dose of 0.25, 1.25, and 2.5 µg/kg body weight (BW) for 9 days. Average daily gain and blood parameters were measured and clinical symptoms were recorded. In Experiment 2, 20 male lambs were injected intravenously with LPS (0 mg/kg) + Res (0 mg), LPS (2.5 µg /kg) + Res (0 mg, 82.5 mg, 165 mg, 330 mg), 4 h after LPS injection. Jugular blood was collected from each lamb to determine white blood cell (WBC) counts and the expression of inflammatory genes. In Experiment 1, all LPS-treated lambs showed clinical signs of sickness including rhinorrhea, lethargy, and shivering, and systemic inflammatory responses of increased inflammatory genes levels and cortisol concentration. The lambs had increased respiratory and heart rates and rectal temperature and decreased average daily gain and feed intake. In Experiment 2, resveratrol significantly reduced WBCs and the expression levels of several genes associated with inflammation response (TLR4, NF-κB, c-jun) and inhibited the signaling cascades of NF-κB and MAPKs by down-regulating the expression levels of inflammatory cytokines (IL-1ß, IL-4, IL-6, TNF-α, IFN-γ) induced by LPS. Resveratrol attenuated the LPS-evoked inflammatory responses in lambs by suppressing expression levels of inflammatory cytokines, and blocking NF-κB and MAPK signaling pathways.

Adding heat-treated rapeseed to the diet of yak improves growth performance and tenderness and nutritional quality of the meat.

Heat-treated rapeseed was supplemented to indoor fed yaks in winter to test the effect on dry matter intake (DMI), body mass change, and meat quality. Sixteen 3-year-old yak steers (124 ± 15.3 kg) were divided randomly into two groups and were offered either heat-treated rapeseed (HTR) or rapeseed meal (CONT). The yaks were allowed 14 days for adjustment and measurements were made over 120 d. There was no difference in DMI between groups (p = 0.67), but average daily gain tended to be higher (p < 0.056) and feed to gain ratio tended to be lower (p = 0.050) in HTR than in CONT yaks. Meat from HTR yaks was more tender (p = 0.006), had higher intramuscular fat (p = 0.013), and had lower cholesterol content (p = 0.009) than from CONT yaks. In addition, the atherogenic index was lower (0.37 vs. 0.43; p = 0.049), the PUFA:SFA ratio was higher (0.55 vs. 0.37; p = 0.049), and the n-6:n-3 (n-6 PUFA to n-3 PUFA) ratio was lower (2.76 vs. 4.78; p = 0.003) in HTR than in CONT yaks, which all favoured the HTR yaks. Meat from HTR yaks met human health standards of a PUFA:SFA ratio of above 0.4 and n-6:n-3 ratio of less than 4, whereas meat from CONT yaks just missed these standards.

Effect of dietary energy on digestibilities, rumen fermentation, urinary purine derivatives and serum metabolites in Tibetan and small-tailed Han sheep.

Tibetan sheep are indigenous to the Qinghai-Tibetan Plateau, graze the grassland all year round without supplementation and are well-adapted to the harsh conditions. Small-tailed Han sheep were introduced to the plateau and are raised mainly in feedlots. Based on their different backgrounds, we hypothesized that the ability to cope with poor diets would be better in Tibetan than in Han sheep. To test our prediction, we examined the effect of dietary energy on apparent digestibilities, rumen fermentation, urinary purine derivatives and serum metabolites by using a 4 × 4 Latin square design in each sheep breed. Four diets were formulated to be low in crude protein (~7%) but to differ in metabolizable energy concentration. Average daily gain was greater in Tibetan than in Han sheep (p < 0.01) and increased linearly with an increase in energy intake (p < 0.001). The digestibilities of dry matter, organic matter, gross energy, and neutral and acid detergent fibres were greater in Tibetan than in Han sheep (p < 0.05). Ruminal pH was lower (p < 0.05), while volatile fatty acids (VFAs), urea-N, ammonia-N and soluble protein-N concentrations were higher (p < 0.05) in Tibetan than in Han sheep. As a molar proportion of total VFA, acetate decreased (p < 0.001) with an increase in dietary energy whereas propionate and butyrate increased (p < 0.05). Urinary purine derivative excretion was greater in Tibetan than in Han sheep (p < 0.01), as was microbial nitrogen production; both parameters increased with dietary energy (p < 0.01). Serum concentrations of glucose, insulin and insulin-like growth factor-1 increased (p < 0.05) as energy level increased, while non-esterified fatty acids and growth hormone decreased (p < 0.05). It was concluded that Tibetan sheep were better able to cope with low-protein, low-energy diets and, consequently, our prediction was supported.

Postpartum oestrous cycling resumption of yak cows following different calf weaning strategies under range conditions.

Early weaning can improve body condition and reproductive performance of cows. The objectives of this study were to examine and compare oestrous cycling resumption, behaviour and blood parameters of yak cows following four different strategies of calf weaning. Twenty-six yak cows (4-8 years) and their calves (94.3 ± 2.4 days) were studied in which calves were: weaned naturally with free access to their mothers (NW; n = 13); weaned abruptly and separated permanently from their mothers (PW; n = 5); separated temporarily from their mothers for 15 days (TW; n = 5); and fitted with nose plates for 15 days, but allowed free access to their mothers (NP; n = 3). Yak cows with sucking calves (NW) spent more time grazing in the cold season (from d 39 to 84). Based on serum progesterone concentrations, none of nine NW yak cows resumed oestrous cycling during the study, while seven of nine yak cows with weaned calves resumed cycling (3/3 for PW; 2/3 for TW; and 2/3 for NP yaks). We concluded that early weaning improved postpartum reproductive performance of yak cows on the Qinghai-Tibetan plateau and that abrupt and permanent weaning was an appropriate strategy.

Effect of supplemental dietary slow-release urea on growth performance and physiological status of dairy heifers.

We examined the effect of supplemental dietary slow-release urea on the growth performance and physiological status of 16 dairy Holstein heifers (10 months of age, 322 ± 10 kg). The heifers were offered a formulated isocaloric and isonitrogenous 70:30 roughage : concentrate ration and were assigned randomly to one of four levels of slow-release urea supplementation (0% [U0 ], 1% [U1 ], 1.5% [U1.5 ] and 2% [U2 ] dry matter [DM]). The total study lasted 95 days, which included a 20 days adaptation period. Dry matter intake (DMI) of U2 was lower than the intakes of U0 and U1 (p < .05), while average daily gains (ADG) of U1 and U1.5 were higher than U0 and U2 (p < .05). Rumen volatile fatty acids concentration did not differ among the four treatments, while ammonia nitrogen concentration increased with an increase in urea level (p < .05). Serum blood urea nitrogen concentration was lower in U1.5 than in U0 and U2 while serum free fatty acids concentration in U2 was higher than in the other three treatments (p < .05). We concluded that the addition of urea at a level of 1.5 to 2.0% DM resulted in a reduction in DMI but the addition of 1.0%-1.5% urea resulted in the highest ADG, with no negative effects on rumen fermentation and health status of the calves.