高精料饲粮条件下反刍动物瘤胃适应机制的解析

饲喂高能、高淀粉饲粮是集约化生产中提高反刍动物生产性能的常用策略,但高精料饲粮易引起一系列的营养代谢疾病,其中以瘤胃酸中毒最为常见。反刍动物瘤胃不仅具有消化、吸收营养物质的功能,瘤胃上皮亦是重要的免疫屏障,故瘤胃健康对反刍动物至关重要。本文主要从反刍动物采食高精料饲粮时其瘤胃组织形态、瘤胃上皮适应分子机制和瘤胃微生物区系3个方面的变化进行阐述,以期为高精料饲粮条件下瘤胃适应机制的研究提供参考。     

Retrospective evaluation of the prognostic utility of plasma lactate concentration,base deficit,pH, and anion gap in canine and feline emergency patients

Objective

To determine the association of plasma lactate concentration, pH, base deficit (BD), and anion gap (AG) in dogs and cats on presentation to an emergency room with outcome, and to compare the prognostic significance of hyperlactatemia with a concurrent metabolic acidosis with that of hyperlactatemia and a normal metabolic acid–base balance.

Design

Retrospective study.

Setting

University teaching hospital.

Animals

Five hundred sixty‐six dogs and 185 cats that had venous blood gas analysis performed.

Interventions

None.

Measurements and Main Results

Medical records were reviewed for plasma lactate concentrations, electrolyte concentrations, and acid–base parameters obtained on emergency room admission, clinical diagnosis, and in‐hospital mortality. The primary outcome measure was all‐cause mortality for the hospitalized visit. Median plasma lactate concentration and AG were higher, BD was more negative, and pH was lower, in non‐survivor dogs and cats. The prevalence of hyperlactatemia was 53% in dogs and 30% in cats. Lactic acidosis was present in 42% and 80% of hyperlactatemic dogs and cats, respectively. Multivariate regression analyses revealed that plasma lactate concentration, BD, and pH, but not AG, were independent predictors of mortality in dogs, and that only plasma lactate concentration was an independent predictor of mortality in cats. Mortality was highest for animals with lactic acidosis, at 59.8% in dogs and 49% in cats. Mortality in dogs with lactic acidosis was significantly higher than dogs with hyperlactatemia and a normal acid–base status (P < 0.0001).

Conclusions

The presence and magnitude of hyperlactatemia on presentation to the emergency room may help identify dogs and cats with high likelihood of in‐hospital mortality, and the presence of lactic acidosis specifically may help identify dogs with yet higher risk of in‐hospital mortality.     

预防亚急性瘤胃酸中毒的营养调控措施

高淀粉、低纤维日粮已成为当前高产奶牛或育肥牛羊的典型营养特征,在提高生产效益的同时,也会增加亚急性瘤胃酸中毒的发病率。本文分析了亚急性瘤胃酸中毒的发病机理、负面影响,并总结了其营养调控措施,旨在为养殖业预防瘤胃酸中毒提供理论参考。     

An appraisal of the in vivo role of phosphate as a modulator of urinary ammonium and titratable acid excretion in the acidotic rabbit

Previous studies have shown that the intravenous infusion of inorganic phosphate increased urinary ammonium excretion 8‐ to 10‐fold in the acidotic rabbit. This was considered to be a very important observation at the time and to be unique to the rabbit. While investigating this finding, we discovered that the formol titration procedure, used to measure urinary ammonium by this research group, is subject to interference by phosphate, casting doubt on the validity of the urinary ammonium excretion data reported by them in the literature. In order to re‐assess the importance of phosphate as a potential modulator of urinary ammonium excretion in the acidotic rabbit, renal net acid excretion studies were carried out in phosphate‐loaded acidotic animals. We observed that while urinary ammonium excretion increased significantly (p < 0.05) after 50 min of phosphate infusion, the maximum concentrations excreted were substantially less than previously reported in the literature. However, through its urinary buffering capacity, we observed that inorganic phosphate, via an experimentally induced phosphaturia, could substantially enhance titratable acid excretion. Contrary to earlier reports, we demonstrated that phosphate plays a relatively minor in vivo modulator role in enhancing renal net acid excretion through the vehicle of ammonium during acute metabolic acidosis in the hyperphosphataemic rabbit. The findings reported in this study constitute an important update on ammonia metabolism in the acidotic rabbit.     

Differences between pH of indwelling sensors and the pH of fluid and solid phase in the rumen of dairy cows fed varying concentrate levels

Feeding of high‐concentrate diets to cattle increases the risk of subacute ruminal acidosis (SARA). Indwelling wireless pH sensors have become popular as an early diagnostic tool for SARA recently. However, the recommended pH thresholds of SARA derive from measurements taken from free‐rumen liquid (FRL) in the ventral rumen, and not from the reticulum, where the mentioned sensors are located. The aim of this study was to evaluate commercially available indwelling pH boli for the accuracy and precision in predicting ruminal pH of FRL and the particle‐associated rumen liquid (PARL) under varying dietary concentrate levels. An additional aim was to define SARA pH thresholds of indwelled pH boli, which can be used for SARA diagnostics. The experiment was conducted with eight nonlactating rumen cannulated Holstein cows fed 0% or 65% concentrate. Data showed that the mean pH of indwelled boli was consistently higher than in FRL and PARL (pH 6.62 ± 0.02, 6.43 ± 0.02 and 6.18 ±0.02, respectively) across feeding regimens. Interestingly, the diurnal differences in pH among indwelled boli, FRL and PARL became greater during concentrate feeding, especially at 8 h after the morning feeding, suggesting that with high‐concentrate diets a particular adjustment of reticular sensor pH vs. ruminal pH in FRL and PARL is needed. The concordance correlation coefficient analysis, representing the reproducibility of the bolus measurements, was high for bolus‐FRL (0.733) and moderate for bolus‐PARL (0.510) associations. Furthermore, the quantitative relationship of the pH in FRL and PARL to the pH of the boli was described by linear regression analysis. The study determined that the common SARA threshold of pH 5.8 in FRL corresponds to a bolus pH of 6.0.     

牛链球菌在瘤胃中产酸的代谢机制及调控

牛链球菌(S.bovis)是瘤胃主要的乳酸产生菌,在饲喂高精料饲粮导致瘤胃乳酸中毒进程中扮演重要角色。已有研究证实S.bovis利用碳水化合物代谢产酸主要受葡萄糖转运方式、酵解产酸途径中酶和中间代谢物调控。另外,研究也发现环境p H、增殖生长阶段及分解代谢控制蛋白(Ccp A)等对其产酸速率和模式也有显著影响。本文对近年来有关S.bovis利用饲料中碳水化合物发酵产酸代谢途径及影响因素研究加以综述,为从微生物代谢角度解析瘤胃乳酸中毒机制提供参考。     

Plant Availability of Boron Adsorbed or Occulted on Goethite to Rape (Brassica napus L.) Seedling

The purpose of the study was to determine plant availability of boron (B) and relaxation of soil acid to rape seedling exhibited by B-doped goethite in acidic soil. For this purpose, two kinds of B-doped goethite were synthesized: one was goethite with adsorbed B prepared by reacting goethite with borax solution, and the other was goethite with occluded B by synthesizing goethite in the presence of boric acid. The reaction process in soil-like natural minerals of the B-doped goethite was simulated in a rhizobox culture system. Results showed that the B-doped goethite can provide available B for rape growth. Its addition on acidic soil can alleviate soil acidification by increasing soil pH and decreasing soil exchangeable acid. The observation that nutrient uptake was improved supports the view that the B-doped goethite improved soil quality, as also proved by the increase of root morphology and dry weight.     

Floppy kid syndrome caused by D-lactic acidosis in goat kids

BACKGROUND: Goat kids with floppy kid syndrome have metabolic acidosis, muscle weakness, and depression but no dehydration. HYPOTHESIS: D-Lactate is the major component of acidemia in goat kids with floppy kid syndrome. ANIMALS: Fifty-five goat kids with floppy kid syndrome (group F) and 35 clinically healthy goat kids (group C). METHODS: Clinical, biochemical, microbiologic, virologic, parasitologic, and pathologic examinations. RESULTS: The animals in group F had a blood pH of 7.13 +/- 0.11 and a base excess of -17.8 +/- 3.8 mM, which were both lower than the values in the control animals (pH, 7.32 +/- 0.31; base excess, -0.1 +/- 2.7 mM; P < .001). Floppy kids had a significantly larger anion gap than healthy kids (31.2 +/- 3.7 versus 21.5 +/- 8.5 mM; P < .001). The concentration of L-lactate was lower in floppy kids than in healthy kids (0.67 +/- 0.49 versus 1.60 +/- 1.02 mM), but the concentration of D-lactate was higher in floppy kids (7.43 +/- 2.71 versus 0.26 +/- 0.24 mM; P < .001). Intravenous and oral administration of sodium bicarbonate in floppy kids resulted in a significant increase in blood pH and base excess and a decrease in the anion gap (P < .001). In addition, the concentration of L-lactate increased (P = .039). CONCLUSIONS AND CLINICAL IMPORTANCE: Metabolic acidosis in goat kids with floppy kid syndrome is caused by an increase in the plasma concentration of D-lactate.     

Lactobacillus GG does not affect D-lactic acidosis in diarrheic calves, in a clinical setting

D-lactate, produced by gastrointestinal fermentation, is a major contributor to metabolic acidosis in diarrheic calves. Lactobacillus rhamnosus GG survives gastrointestinal transit in the neonatal calf and does not produce D-lactate. To determine whether this probiotic reduces gastrointestinal D-lactate production or severity of diarrhea or both, 48 calves (mean, 11 days old; range, 2-30 days) admitted to the clinic for treatment of diarrhea were randomly allocated to 2 groups. The experimental group was given Lactobacillus rhamnosus GG (1 x 10(11) cfu/d) PO, dissolved in milk or oral electrolyte solution, in addition to clinic treatment protocols; the other group served as a control. Serum and fecal samples were obtained at admission and at 24 and 48 hours after initial administration of Lactobacillus rhamnosus GG. All samples were analyzed for D- and L-lactate by using high-pressure liquid chromatography. Feces were also analyzed for pathogens, Lactobacillus rhamnosus GG recovery, and dry matter. D-lactic acidemia (>3 mmol/L) was present in 37/48 calves at admission. Lactobacillus rhamnosus GG was recovered in the feces of 13 experimental calves and 0 control calves 24 hours after administration. No difference in serum or fecal D- or L-lactate between the groups was detected at any time point. After therapy, D-lactic acidosis was absent at 48 hours in all but 1 calf. No relation between fecal pathogen (viral, bacterial, or protozoal) and degree of D-lactic acidosis was observed. The reduction in mortality and greater fecal dry matter in Lactobacillus rhamnosus GG-treated calves was not statistically significant.