Echinococcosis poses a significant threat to public health. The Chinese government has implemented prevention and control measures to mitigate the impact of the disease. By analyzing data from the Chinese Center for Disease Control and Prevention and the State Council of the People’s Republic of China, we found that implementation of these measures has reduced the infection rate by nearly 50% between 2004 to 2022 (from 0.3975 to 0.1944 per 100,000 person-years). Nonetheless, some regions still bear a significant disease burden, and lack of detailed information limites further evaluation of the effects on both alveolar and cystic echinococcosis. Our analysis supports the continuing implementation of these measures and suggests that enhanced wildlife management, case-based strategies, and surveillance systems will facilitate disease control.

Competition among the two-plasmon decay (TPD) of backscattered light of stimulated Raman scattering (SRS), filamentation of the electron-plasma wave (EPW) and forward side SRS is investigated by two-dimensional particle-in-cell simulations. Our previous work [K. Q. Pan et al., Nucl. Fusion 58, 096035 (2018)] showed that in a plasma with the density near 1/10 of the critical density, the backscattered light would excite the TPD, which results in suppression of the backward SRS. However, this work further shows that when the laser intensity is so high ($>{10}^{16}$ W/cm2) that the backward SRS cannot be totally suppressed, filamentation of the EPW and forward side SRS will be excited. Then the TPD of the backscattered light only occurs in the early stage and is suppressed in the latter stage. Electron distribution functions further show that trapped-particle-modulation instability should be responsible for filamentation of the EPW. This research can promote the understanding of hot-electron generation and SRS saturation in inertial confinement fusion experiments.

In this paper, to address the cooperative localisation of a heterogeneous UAV swarm in the GNSS-denied environment, an adaptive simulated annealing-particle swarm optimisation (SA-PSO) cooperative localisation algorithm is proposed. Firstly, the forming principle of the communication and measurement framework is investigated in light of a heterogeneous UAV swarm composition. Secondly, a reasonably cooperative localisation function is established based on the proposed forming principle, which can minimise the relative localisation error with limited available information. Then, an adaptive weight principle is incorporated into the particle swarm optimisation (PSO) for better performance. Furthermore, in order to overcome the drawbacks of PSO algorithm easily falling into the local extreme point, an adaptive SA-PSO algorithm is improved to promote the convergence speed of cooperative localisation. Finally, comparative simulations are performed among the adaptive SA-PSO, adaptive PSO, and PSO algorithms to demonstrate the feasibility and superiority of the proposed adaptive SA-PSO algorithm. Simulation results show that the proposed algorithm has better performance in convergence speed, and the cooperative localisation precision can be guaranteed.

To investigate the influences of dietary riboflavin (RF) addition on nutrient digestion and rumen fermentation, eight rumen cannulated Holstein bulls were randomly allocated into four treatments in a repeated 4 × 4 Latin square design. Daily addition level of RF for each bull in control, low RF, medium RF and high RF was 0, 300, 600 and 900 mg, respectively. Increasing the addition level of RF, DM intake was not affected, average daily gain tended to be increased linearly and feed conversion ratio decreased linearly. Total tract digestibilities of DM, organic matter, crude protein (CP) and neutral-detergent fibre (NDF) increased linearly. Rumen pH decreased quadratically, and total volatile fatty acids (VFA) increased quadratically. Acetate molar percentage and acetate:propionate ratio increased linearly, but propionate molar percentage and ammonia-N content decreased linearly. Rumen effective degradability of DM increased linearly, NDF increased quadratically but CP was unaltered. Activity of cellulase and populations of total bacteria, protozoa, fungi, dominant cellulolytic bacteria, Prevotella ruminicola and Ruminobacter amylophilus increased linearly. Linear increase was observed for urinary total purine derivatives excretion. The data suggested that dietary RF addition was essential for rumen microbial growth, and no further increase in performance and rumen total VFA concentration was observed when increasing RF level from 600 to 900 mg/d in dairy bulls.

Severe fever with thrombocytopenia syndrome (SFTS) is a disease with a high case-fatality rate that is caused by infection with the SFTS virus (SFTSV). Five electronic databases were systematically searched to identify relevant articles published from 1 January 2011 to 1 December 2019. The pooled rates with 95% confidence interval (CI) were calculated by a fixed-effect or random-effect model analysis. The results showed that 92 articles were included in this meta-analysis. For the confirmed SFTS cases, the case-fatality rate was 0.15 (95% CI 0.11, 0.18). Two hundred and ninety-six of 1384 SFTS patients indicated that they had been bitten by ticks and the biting rate was 0.21 (95% CI 0.16, 0.26). The overall pooled seroprevalence of SFTSV antibodies among the healthy population was 0.04 (95% CI 0.03, 0.05). For the overall seroprevalence of SFTSV in animals, the seroprevalence of SFTSV was 0.25 (95% CI 0.20, 0.29). The infection rate of SFTSV in ticks was 0.08 (95% CI 0.05, 0.11). In conclusion, ticks can serve as transmitting vectors of SFTSVs and reservoir hosts. Animals can be infected by tick bites, and as a reservoir host, SFTSV circulates continuously between animals and ticks in nature. Humans are infected by tick bites and direct contact with patient secretions.

Coated copper sulphate (CCS) could be used as a Cu supplement in cows. To investigate the influences of copper sulphate (CS) and CCS on milk performance, nutrient digestion and rumen fermentation, fifty Holstein dairy cows were arranged in a randomised block design to five groups: control, CS addition (7·5 mg Cu/kg DM from CS) or CCS addition (5, 7·5 and 10 mg Cu/kg DM from CCS, respectively). When comparing Cu source at equal inclusion rates (7·5 mg/kg DM), cows receiving CCS addition had higher yields of fat-corrected milk, milk fat and protein; digestibility of DM, organic matter (OM) and neutral-detergent fibre (NDF); ruminal total volatile fatty acid (VFA) concentration; activities of carboxymethyl cellulase, cellobiase, pectinase and α-amylase; populations of Ruminococcus albus, Ruminococcus flavefaciens and Fibrobacter succinogenes; and liver Cu content than cows receiving CS addition. Increasing CCS addition, DM intake was unchanged, yields of milk, milk fat and protein; feed efficiency; digestibility of DM, OM, NDF and acid-detergent fibre; ruminal total VFA concentration; acetate:propionate ratio; activity of cellulolytic enzyme; populations of total bacteria, protozoa and dominant cellulolytic bacteria; and concentrations of Cu in serum and liver increased linearly, but ruminal propionate percentage, ammonia-N concentration, α-amylase activity and populations of Prevotella ruminicola and Ruminobacter amylophilus decreased linearly. The results indicated that supplement of CS could be substituted with CCS and addition of CCS improved milk performance and nutrient digestion in dairy cows.

Guanidinoacetic acid (GAA) can improve the growth performance of bulls. This study investigated the influences of GAA addition on growth, nutrient digestion, ruminal fermentation and serum metabolites in bulls. Forty-eight Angus bulls were randomly allocated to experimental treatments, that is, control, low-GAA (LGAA), medium-GAA (MGAA) and high-GAA (HGAA), with GAA supplementation at 0, 0.3, 0.6 and 0.9 g/kg DM, respectively. Bulls were fed a basal diet containing 500 g/kg DM concentrate and 500 g/kg DM roughage. The experimental period was 104 days, with 14 days for adaptation and 90 days for data collection. Bulls in the MGAA and HGAA groups had higher DM intake and average daily gain than bulls in the LGAA and control groups. The feed conversion ratio was lowest in MGAA and highest in the control. Bulls receiving 0.9 g/kg DM GAA addition had higher digestibility of DM, organic matter, NDF and ADF than bulls in other groups. The digestibility of CP was higher for HGAA than for LGAA and control. The ruminal pH was lower for MGAA, and the total volatile fatty acid concentration was greater for MGAA and HGAA than for the control. The acetate proportion and acetate-to-propionate ratio were lower for MGAA than for LGAA and control. The propionate proportion was higher for MGAA than for control. Bulls receiving GAA addition showed decreased ruminal ammonia N. Bulls in MGAA and HGAA had higher cellobiase, pectinase and protease activities and Butyrivibrio fibrisolvens, Prevotella ruminicola and Ruminobacter amylophilus populations than bulls in LGAA and control. However, the total protozoan population was lower for MGAA and HGAA than for LGAA and control. The total bacterial and Ruminococcus flavefaciens populations increased with GAA addition. The blood level of creatine was higher for HGAA, and the activity of l-arginine glycine amidine transferase was lower for MGAA and HGAA, than for control. The blood activity of guanidine acetate N-methyltransferase and the level of folate decreased in the GAA addition groups. The results indicated that dietary addition of 0.6 or 0.9 g/kg DM GAA improved growth performance, nutrient digestion and ruminal fermentation in bulls.

Se can enhance lactation performance by improving nutrient utilization and antioxidant status. However, sodium selenite (SS) can be reduced to non-absorbable elemental Se in the rumen, thereby reducing the intestinal availability of Se. The study investigated the impacts of SS and coated SS (CSS) supplementation on lactation performance, nutrient digestibility, ruminal fermentation and microbiota in dairy cows. Sixty multiparous Holstein dairy cows were blocked by parity, daily milk yield and days in milk and randomly assigned to five treatments: control, SS addition (0.3 mg Se/kg DM as SS addition) or CSS addition (0.1, 0.2 and 0.3 mg Se/kg DM as CSS addition for low CSS (LCSS), medium CSS (MCSS) and high CSS (HCSS), respectively). Experiment period was 110 days with 20 days of adaptation and 90 days of sample collection. Dry matter intake was higher for MCSS and HCSS compared with control. Yields of milk, milk fat and milk protein and feed efficiency were higher for MCSS and HCSS than for control, SS and LCSS. Digestibility of DM and organic matter was highest for CSS addition, followed by SS addition and then control. Digestibility of CP was higher for MCSS and HCSS than for control, SS and LCSS. Higher digestibility of ether extract, NDF and ADF was observed for SS or CSS addition. Ruminal pH decreased with dietary Se addition. Acetate to propionate ratio and ammonia N were lower, and total volatile fatty acids (VFAs) concentration was greater for SS, MCSS and HCSS than control. Ruminal H ion concentration was highest for MCSS and HCSS and lowest for control. Activities of cellobiase, carboxymethyl-cellulase, xylanase and protease and copies of total bacteria, fungi, Ruminococcus flavefaciens, Fibrobacter succinogenes and Ruminococcus amylophilus increased with SS or CSS addition. Activity of α-amylase, copies of protozoa, Ruminococcus albus and Butyrivibrio fibrisolvens and serum glucose, total protein, albumin and glutathione peroxidase were higher for SS, MCSS and HCSS than for control and LCSS. Dietary SS or CSS supplementation elevated blood Se concentration and total antioxidant capacity activity. The data implied that milk yield was elevated due to the increase in total tract nutrient digestibility, total VFA concentration and microorganism population with 0.2 or 0.3 mg Se/kg DM from CSS supplementation in dairy cows. Compared with SS, HCSS addition was more efficient in promoting lactation performance of dairy cows.

This study evaluated the effects of rumen-protected folic acid (RPFA) and betaine (BT) on growth performance, nutrient digestion and blood metabolites in bulls. Forty-eight Angus bulls were blocked by body weight and randomly assigned to four treatments in a 2 × 2 factorial design. BT of 0 or 0·6 g/kg DM was supplemented to diet without or with the addition of 6 mg/kg DM of folic acid from RPFA, respectively. Average daily gain increased by 25·2 and 6·29 % for addition of BT without RPFA and with RPFA, respectively. Digestibility and ruminal total volatile fatty acids of neutral-detergent fibre and acid-detergent fibre increased, feed conversion ratio and blood folate decreased with the addition of BT without RPFA, but these parameters were unchanged with BT addition in diet with RPFA. Digestibility of DM, organic matter and crude protein as well as acetate:propionate ratio increased with RPFA or BT addition. Ruminal ammonia-N decreased with RPFA addition. Activity of carboxymethyl cellulase, cellobiase, xylanase, pectinase and protease as well as population of total bacteria, protozoa, Fibrobacter succinogenes and Ruminobacter amylophilus increased with RPFA or BT addition. Laccase activity and total fungi, Ruminococcus flavefaciens and Prevotella ruminicola population increased with RPFA addition, whereas Ruminococcus albus population increased with BT addition. Blood glucose, total protein, albumin, growth hormone and insulin-like growth factor-1 increased with RPFA addition. Addition of RPFA or BT decreased blood homocysteine. The results indicated that addition of BT stimulated growth and nutrient digestion in bulls only when RPFA was not supplemented.

The combined addition of branched-chain volatile fatty acids (BCVFAs) and folic acid (FA) could improve growth performance and nutrient utilization by stimulating ruminal microbial growth and enzyme activity. This study was conducted to evaluate the effects of BCVFA and FA addition on growth performance, ruminal fermentation, nutrient digestibility, microbial enzyme activity, microflora and excretion of urinary purine derivatives (PDs) in calves. Thirty-six Chinese Holstein weaned calves (60 ± 5.4 days of age and 107 ± 4.7 kg of BW) were assigned to one of four groups in a randomized block design. Treatments were control (without additives), FA (with 10 mg FA/kg dietary DM), BCVFA (with 5 g BCVFA/kg dietary DM) and the combined addition of FA and BCVFA (10 mg/kg DM of FA and 5 g/kg DM of BCVFA). Supplements were hand-mixed into the top one-third of total mixed ration. Dietary concentrate to maize silage ratio was 50 : 50 on a DM basis. Dietary BCVFA or FA addition did not affect dry matter intake but increased average daily gain (ADG) and feed conversion efficiency. Ruminal pH and ammonia N were lower, and total volatile fatty acids (VFAs) concentration was higher for BCVFA or FA addition than for control. Dietary BCVFA or FA addition did not affect acetate proportion but decreased propionate proportion and increased acetate to propionate ratio. Total tract digestibility of DM, organic matter, CP and NDF was higher for BCVFA or FA addition than for control. Dietary BCVFA or FA addition increased activity of carboxymethyl cellulase and cellobiase, population of total bacteria, fungi, Ruminococcus albus, R. flavefaciens, Fibrobacter succinogenes and Prevotella ruminicola as well as total PD excretion. Ruminal xylanase, pectinase and protease activity and Butyrivibrio fibrisolvens population were increased by BCVFA addition, whereas population of protozoa and methanogens was increased by FA addition. The BCVFA × FA interaction was significant for acetate to propionate ratio, cellobiase activity and total PD excretion, and these variables increased more with FA addition in diet without BCVFA than in diet with BCVFA. The data indicated that supplementation with BCVFA or FA increased ADG, nutrient digestibility, ruminal total VFA concentration and microbial protein synthesis by stimulating ruminal microbial growth and enzyme activity in calves.

The effects of pantothenic acid (PA) and folic acid (FA) addition on digestibility coefficient, ruminal fermentation and urinary purine derivative (PD) excretion in dairy bulls were evaluated. Eight rumen-cannulated Holstein dairy bulls were allocated to a replicated 4 × 4 Latin square design according to a 2 × 2 factorial arrangement. Diets were supplemented with two levels of FA (0 or 8.0 mg/kg dietary dry matter [DM]) and two of PA (0 or 60 mg/kg DM). The PA × FA interaction was not significant for all variables. Both supplements increased DM intake and average daily gain, but decreased a feed conversion ratio. Digestibility of DM, organic matter, crude protein and neutral detergent fibre increased, but ether extract digestibility was unchanged for both supplements. Digestibility of acid detergent fibre only increased with FA supplementation. For both supplements, ruminal pH and ammonia nitrogen (N) decreased, but total volatile fatty acid (VFA) concentration increased. Acetate proportion only increased with FA supplementation. Propionate proportion decreased for both supplements. Consequently, the acetate to propionate ratio increased. For both supplements, activity of xylanase and pectinase, population of Ruminococcus albus, R. flavefaciens, Fibrobacter succinogenes and Ruminobacter amylophilus and total PD excretion increased. Additionally, activity of carboxymethylcellulase, cellobiase, α-amylase and protease, and population of total bacteria, fungi, protozoa, methanogens, Butyrivibrio fibrisolvens and Prevotella ruminicola increased with FA addition. The results suggested that PA and FA supplementation stimulated ruminal microbial growth and enzyme activity, resulting in an increased digestibility coefficient and ruminal total VFA concentration in dairy bulls.

Laser interaction with an ultra-thin pre-structured target is investigated with the help of both two-dimensional and three-dimensional particle-in-cell simulations. With the existence of a periodic structure on the target surface, the laser seems to penetrate through the target at its fundamental frequency even if the plasma density of the target is much higher than the laser’s relativistically critical density. The particle-in-cell simulations show that the transmitted laser energy behind the pre-structured target is increased by about two orders of magnitude compared to that behind the flat target. Theoretical analyses show that the transmitted energy behind the pre-structured target is actually re-emitted by electron ‘islands’ formed by the surface plasma waves on the target surfaces. In other words, the radiation with the fundamental frequency is actually ‘surface emission’ on the target rear surface. Besides the intensity of the component with the fundamental frequency, the intensity of the high-order harmonics behind the pre-structured target is also much enhanced compared to that behind the flat target. The enhancement of the high-order harmonics is also related to the surface plasma waves generated on the target surfaces.

Estimating the feed intake of grazing herbivores is critical for determining their nutrition, overall productivity and utilization of grassland resources. A 17-day indoor feeding experiment was conducted to evaluate the potential use of Medicago sativa as a natural supplement for estimating the total feed intake of sheep. A total of 16 sheep were randomly assigned to four diets (four sheep per diet) containing a known amount of M. sativa together with up to seven forages common to typical steppes. The diets were: diet 1, M. sativa + Leymus chinensis + Puccinellia distans; diet 2, species in diet 1 + Phragmites australis; diet 3, species in diet 2 + Chenopodium album + Elymus sibiricus; and diet 4, species in diet 3 + Artemisia scoparia + Artemisia tanacetifolia. After faecal marker concentrations were corrected by individual sheep recovery, treatment mean recovery or overall recovery, the proportions of M. sativa and other dietary forages were estimated from a combination of alkanes and long-chain alcohols using a least-square procedure. Total intake was the ratio of the known intake of M. sativa to its estimated dietary proportion. Each dietary component intake was obtained using total intake and the corresponding dietary proportions. The estimated values were compared with actual values to assess the estimation accuracy. The results showed that M. sativa exhibited a distinguishable marker pattern in comparison to the other dietary forage species. The accuracy of the dietary composition estimates was significantly (P < 0.001) affected by both diet diversity and the faecal recovery method. The proportion of M. sativa and total intake across all diets could be accurately estimated using the individual sheep or the treatment mean recovery methods. The largest differences between the estimated and observed total intake were 2.6 g and 19.2 g, respectively, representing only 0.4% and 2.6% of the total intake. However, they were significantly (P < 0.05) biased for most diets when using the overall recovery method. Due to the difficulty in obtaining individual sheep recovery under field conditions, treatment mean recovery is recommended. This study suggests that M. sativa, a natural roughage instead of a labelled concentrate, can be utilized as a dietary supplement to accurately estimate the total feed intake of sheep indoors and further indicates that it has potential to be used in steppe grassland of northern China, where the marker patterns of M. sativa differ markedly from commonly occurring plant species.

In this paper, a novel single-cavity triangular substrate-integrated waveguide (TSIW) dual-band filter loading a complementary triangular split ring resonator (CTSRR) is proposed, which has three transmission zeros (TZs) in the stopband in total. The dual-band response is achieved by the CTSRR and the degenerate modes of the TSIW cavity. In order to control the TZs, we propose two adjustment techniques, shift feeding technique and adding via perturbation. In addition, the CTSRR etched on the surface can produce a new TZ in the upper first-passband. Finally, a dual-band filter with three TZs is simulated, fabricated, and measured. There is a good agreement between the simulated results and measured ones.

Cobalt-rich spinel is found as a ∼200 µm inclusion, together with a glassy phase, in a gem-quality blue sapphire from Bo Ploi, Thailand. This is the first reported natural occurrence of such a spinel. Its composition is directly analogous with that of cochromite, a previously reported rare cobalt-rich chromite. The compositional ranges for the cobalt-rich spinel, obtained using electron microprobe and proton microprobe (methods described below), are Al2O3 48.18–61.27 %, CoO 19.7–22.84 %, Cr2O3 0–12.28 %, FeO 8.64–9.67 %, MgO 6.04–6.89, TiO2 0.49–0.73 %, Ni 2251–2532 p.p.m., Zn 335–371 p.p.m., Mn < 177–849 p.p.m., Ga 113–153 p.p.m., Nb 24–1252 p.p.m., Zr <4–167 p.p.m., Sn 22–428 p.p.m., As <4–56 p.p.m., Sr <4–59 p.p.m., Ag 13–64 p.p.m. Transition elements decrease in abundance from core to rim of the spinel while the other elements increase. Crystal chemical considerations suggest that a vacancy-creating substitution mechanism may be operative in the cobalt-rich spinel despite the small scale, i.e. 3Co2+ = 2Al3+ + [4]□. The glassy phase coexisting with the spinel is likely to be the product of heating by the host basaltic magma. The mode of occurrence of the cobalt-rich spinel prevents further physical investigation. This unusual spinel is considered to be the result of a complex magma mixing process in the lower crust.

The present study evaluated the effects of isovalerate supplementation on the development of the small intestinal mucosa in dairy calves. Forty-eight Chinese Holstein bull calves at 15 days of age and 45.1 ± 0.36 kg of body weight were assigned randomly to four groups. The treatments were control, low-isovalerate, moderate-isovalerate and high-isovalerate with 0, 3, 6 and 9 g isovalerate per calf per day, respectively. The study comprised 75 days with a 15-day adaptation period followed by a 60-day sampling period. Calves were weaned at 60 days of age. Six calves were chosen from each treatment at random and slaughtered at 30 and 90 days of age. The small intestine morphology and activities of amylase and trypsin improved significantly with increasing age. No interaction between treatments and age was observed. The small intestine length, mucosa layer thickness, villus height and crypt depth increased linearly with increasing isovalerate supplementation. However, the ratio of villus height to crypt depth was not affected by treatment. Activities of amylase and trypsin increased linearly. The lactase activity increased linearly during the 75-day period and for pre-weaned calves but was unaltered for post-weaned calves. The relative mRNA expressions of growth hormone receptor, insulin-like growth factor-1 receptor and sodium-glucose co-transporter-1 in the small intestine mucosa increased linearly, and a similar pattern was observed for the expression of peptide transporter-1 in the duodenum and proximal jejunum. The results suggested that small intestine development was promoted by isovalerate in a dose-dependent manner.

Branched-chain volatile fatty acids (BCVFA) supplements could promote lactation performance and milk quality by improving ruminal fermentation and milk fatty acid synthesis. This study was conducted to evaluate the effects of BCVFA supplementation on milk performance, ruminal fermentation, nutrient digestibility and mRNA expression of genes related to fatty acid synthesis in mammary gland of dairy cows. A total of 36 multiparous Chinese Holstein cows averaging 606±4.7 kg of BW, 65±5.2 day in milk (DIM) with daily milk production of 30.6±0.72 kg were assigned to one of four groups blocked by lactation number, milk yield and DIM. The treatments were control, low-BCVFA (LBCVFA), medium-BCVFA (MBCVFA) and high-BCVFA (HBCVFA) with 0, 30, 60 and 90 g BCVFA per cow per day, respectively. Experimental periods were 105 days with 15 days of adaptation and 90 days of data collection. Dry matter (DM) intake tended to increase, but BW changes were similar among treatments. Yields of actual milk, 4% fat corrected milk, milk fat and true protein linearly increased, but feed conversion ratio (FCR) linearly decreased with increasing BCVFA supplementation. Milk fat content linearly increased, but true protein content tended to increase. Contents of C4:0, C6:0, C8:0, C10:0, C12:0, C14:0 and C15:0 fatty acids in milk fat linearly increased, whereas other fatty acids were not affected with increasing BCVFA supplementation. Ruminal pH, ammonia N concentration and propionate molar proportion linearly decreased, but total VFA production and molar proportions of acetate and butyrate linearly increased with increasing BCVFA supplementation. Consequently, acetate to propionate ratios linearly increased. Digestibilities of DM, organic matter, CP, NDF and ADF also linearly increased. In addition, mRNA expressions of peroxisome proliferator-activated receptor γ, sterol regulatory element-binding factor 1 and fatty acid-binding protein 3 linearly increased, mRNA expressions of acetyl-coenzyme A carboxylase-α, fatty acid synthase and stearoyl-CoA desaturase quadratically increased. However, lipoprotein lipase mRNA expression was not affected by treatments. The results indicated that lactation performance and milk fat synthesis increased with BCVFA supplementation by improving ruminal fermentation, nutrient digestibility and mRNA expressions of genes related to milk fat synthesis.

The current experiment was conducted to evaluate the effects of different dietary protein levels and rumen-protected folic acid (RPFA) supplementation on ruminal fermentation, microbial enzyme activity, bacterial populations and urinary excretion of purine derivatives (PD) in growing beef steers. Low-protein (LP) or high-protein (HP) diets were fed to eight ruminally cannulated first-generation cross-bred (Blonde d'Aquitaine × Simmental) beef steers with or without RPFA supplementation. Steers were fed a total mixed ration, and dietary concentrate to maize silage ratio was 50 : 50 (dry matter (DM) basis). No interaction between dietary crude protein (CP) levels and RPFA supplementation was observed during the experiment. Ruminal pH was unaffected by RPFA supplementation, but decreased with increasing dietary CP levels. Ruminal total volatile fatty acid concentration increased with increasing dietary CP levels or RPFA supplementation. Molar proportion of acetate increased with RPFA supplementation, but tended to decrease with increasing dietary CP levels. The proportion of propionate decreased with RPFA supplementation, but was unaffected by dietary CP levels. As a result, the acetate to propionate ratio increased with RPFA supplementation, but tended to be lower for the HP diets than the LP diets. Ammonia-nitrogen content decreased with RPFA supplementation, but increased with increasing dietary CP levels. In situ ruminal degradability of maize straw and concentrate increased with increasing dietary CP levels or RPFA supplementation. Microbial enzyme (carboxymethyl-cellulase, cellobiase, xylanase, pectinase, α-amylase and protease) activity, bacterial populations (Ruminococcus albus, Ruminococcus flavefaciens, Butyrivibrio fibrisolvens, Prevotella ruminicola, Fibrobacter succinogenes and Ruminobacter amylophilus) and urinary PD excretion increased with increasing dietary CP levels or RPFA supplementation. The current study showed that increasing dietary CP levels from 109·1 to 130·7 g/kg DM or supplementing 75 mg RPFA improved ruminal fermentation and microbial protein synthesis by increasing bacterial population and microbial enzyme activity.

Isovalerate supplements could stimulate rumen development by improving morphology and function of rumen mucosa, and then promote the growth of calves. This study was done to evaluate the effects of isovalerate supplements on morphology and functional gene expression of rumen mucosa in dairy calves. In total, 48 Chinese Holstein male calves with 15 days of age and 45.1±0.36 kg of BW were randomly assigned to four groups. The treatments were: control, low-isovalerate, moderate-isovalerate and high-isovalerate with 0, 3, 6 and 9 g isovalerate per calf per day, respectively. Supplementary isovalerate was hand-mixed into milk in pre-weaning calves and into concentrate portion in post-weaning calves. The study consisted of a 15-day-adaptation period and a 60-day-sampling period. Calves were weaned at 60 days of age. Three calves were slaughtered from each of the four treatments at 30, 60 and 90 days of age. The weight of body and stomach were measured, samples of ruminal tissues and blood were analyzed. Total stomach weight, total stomach to BW ratio, rumen wall and keratinized layer thickness, serum growth hormone and IGF-1 for both pre- and post-weaning calves increased linearly with increasing isovalerate supplements. Rumen to total stomach weight ratio, the length and width of rumen papillae, and serum β-hydroxybutyrate increased linearly for post-weaning calves. However, abomasum weight to total stomach weight ratio decreased linearly for both pre- and post-weaning calves. The relative messenger RNA expression for growth hormone receptor, IGF-1 receptor and 3-hydroxy-3-methylglutaryl-CoA synthase 1 in rumen mucosa increased linearly for post-weaning calves. Our results suggested that isovalerate supplements promoted rumen development in a dose-dependent manner. The optimum dose was 6.0 g isovalerate per calf per day.