The role of dietary calcium concentration in the use of anionic salts to prevent parturient paresis in dairy cows

The role of dietary calcium concentration during the feeding of anionic salts (AS) was reviewed. Hypocalcaemia is still the major cause of parturient paresis in dairy cows. Feeding AS is an established method for preventing severe hypocalcaemia by activating the calcium metabolism in the last two to three weeks before parturition by inducing a metabolic acidosis. In compensation for this acidosis, the organism increases the concentrations of ionised Ca [Ca2+] in the blood. This increase leads to an increasing excretion of calcium via the urine, which is ensued by an increased calcium absorption in the intestine. The ongoing metabolic acidosis changed the flux of Ca. The size of the Ca pool, however, remained unchanged. As the calcium metabolism is activated by AS, it seems necessary to increase the amount of calcium that is fed to the cows. Several studies examined the impact of different dietary calcium concentrations on the acid-base balance and the calcium metabolism in cows fed anionic salts. The study designs vary concerning the amounts of calcium fed and the use of pregnant or non-pregnant cows. Only one study combined the feeding of AS with a very low amount of calcium, which fell below the daily requirements of pregnant cows in the last three weeks before parturition. In this study, the calcium balance post partum was better in the cows that were administered AS and a high calcium diet. In the other studies, the amount of calcium in the different experimental groups and the difference between the amounts of calcium fed varied greatly. As far as it was monitored in the studies, the calcium concentration of the diet did not have a significant impact on the degree of acidosis induced by AS. In pregnant cows, no significant differences in the calcium concentration in serum or urine occurred before parturition. Some of the researchers found a lower incidence of parturient paresis when cows were fed a combination of AS and a higher amount of calcium, but some other researches did not. Interestingly, the parameters of bone metabolism did not change between experimental groups. According to what is currently known, the feeding of AS to transition cows should not be combined with a dietary calcium concentration that falls below the requirement of cows in this stage of lactation. On the other hand, there is no need to increase the Ca concentration. When AS are used the dietary calcium concentration should be between 9 g and 12 g/kg dry matter. Further research is needed to investigate the role of dietary calcium regarding the use of AS for improving Ca metabolism in dairy cows around parturition.     

Effect of intravenous calcium and oral sodium phosphate in cows with parturient paresis

The goal of this study was to determine whether oral administration of sodium phosphate in conjunction with intravenous calcium is more efficaceous than intravenous calcium alone for the treatment of parturient paresis. Thirty cows with parturient paresis were examined and treated by the same veterinarian. The cows were divided randomly into two groups of 15 cows each. Cows in group A received 500 ml of a 40 per cent calcium borogluconate solution containing 15.65 g calcium gluconate and borogluconate, with a supplement of 6 per cent magnesium hypophosphite (9.85 g magnesium hypophosphite) intravenously over a period of approximately 15 min. Cows in group B received the same treatment as well as 350 g of monobasic sodium phosphate (70 g inorganic phosphate, NaH2PO4 2 H2O, Streuli) dissolved in 0.5 litres of distilled water orally via a stomach tube. After treatment, the heart rate, respiratory rate, rectal temperature, superficial body temperature, rumen motility, appetite and defecation of the cows were monitored every hour for eight h. The cows' attempts to rise and their ability to stand were also noted. Initially, the results of clinical examination and serum electrolyte analyses did not differ between the two groups of cows.Within one hour of treatment, stupor was not observed in any of the cows. The general demeanour after treatment did not differ significantly between the two groups. In both groups, the average rectal temperature increased within two hours of the initiation of treatment, from 38.0 +/- 0.95 degrees C to 38.5 +/- 0.40 degrees C. There was no significant difference in the recovery rate between the groups. Of the 30 cows, 22 (73.3 per cent) stood within eight hours of treatment (10 cows from group A and 12 cows from group B). The type of treatment did not affect the time required to stand: cows in group A stood within 47.3 +/- 44 minutes and cows in group B stood within 24.2 +/- 32 minutes after the start of treatment. Our findings do not support the hypothesis that oral treatment with 350 g of sodium phosphate together with intravenous infusion of calcium in cows with parturient paresis results in an improved outcome, even though all the cows had hypophosphataemia as well as hypocalcaemia.     

Studies on parturient paresis in dairy cows. V. On the composition and calcium binding capacity of two bovine serum protein fractions, with special regard to parturient paresis

In healthy cows unaffected by imminent or recent calving the protein in serum can directly bind the overwhelming proportion of the bound calcium. In recent calvers this capacity is considerably less. When adding ammonium sulphate to blood serum to 62 % of total saturation a protein fraction precipitates which is mainly albumin. This fraction has a far greater calcium binding capacity than the soluble fraction, which contains most of the serum globulin, and the lowering of this capacity after calving is entirely referable to the former fraction. No difference has been found in these respects between normal cows after calving and cows with parturient paresis.An analysis of 10 amino acids in the two protein fractions described above showed that the amino acid composition of both exhibits differences between recent calvers and cows outside the calving period, and likewise that each of the two fractions differs in composition between healthy cows after calving and cows with parturient paresis.     

日粮阴阳离子对反刍动物的最新研究进展

作者就日粮中阴阳离子平衡(dietary cation-anion balance,DCAB)对奶牛的机体健康、生产性能等方面的最新概况作一概述,提出DCAB可作为反刍动物瘤胃缓冲技术重要的研究内容,并指出DCAB现阶段的研究成果和发展方向.     

日粮阴阳离子平衡对泌乳中后期奶牛生产性能的影响

试验选择泌乳中后期奶牛15头,随机分成3组,每组5头,采用3×3重复拉丁方设计,分别饲喂3种不同阴阳离子平衡水平的日粮。其中对照组A(DCAB为DM 77 m eq/kg),B组(DCAB为DM 175 m eq/kg),C组(DCAB为DM 325 m eq/kg)。结果表明,DCAB对热应激奶牛的生产性能具有显著影响,其中B组和C组的产奶量分别比对照组提高6.6%(P>0.05)和0.1%(P>0.05);而4%标准乳产量则分别提高8.3%(P<0.05)和0。DCAB对奶牛的乳脂率和乳蛋白率无显著影响。说明在泌乳中后期当DCAB为175 m eq/kgDM,饲喂效果最佳。     

Efficacy of oral calcium and/or sodium phosphate in the prevention of parturient paresis in cows

The goal of this study was to investigate the efficacy of calcium chloride, sodium phosphate or a combination of these two substances administered orally immediately postpartum for the prevention of parturient paresis in cows. Thirty-two cows that had had parturient paresis at the previous calving, and in which serum biochemistry had shown hypocalcaemia and hypophosphataemia, were used in the study. The cows were transferred to the Department of Farm Animals, University of Zurich, five days before their expected due dates. On a randomized trial, the cows were given calcium chloride, sodium phosphate, both substances or no treatment (controls) via a stomach tube immediately postpartum and 12 hours later. The cows were monitored for 96 hours during which time blood was collected on a regular basis for the determination of total calcium, ionized calcium, inorganic phosphorus and magnesium concentrations. Of the 32 cows treated, 19 (59%) had parturient paresis and 13 (41%) did not. The incidence of parturient paresis did not differ significantly among the groups although there was a tendency for a lower incidence in cows treated with both calcium chloride and sodium phosphate. The various treatments had no apparent effect on serum calcium concentration. The concentration of inorganic phosphorus increased significantly in cows treated with sodium phosphate compared with the controls. The results of this study showed that cows treated with both calcium chloride and sodium phosphate orally tended to have a lower incidence of parturient paresis. Further investigation into multiple administrations of oral calcium chloride and sodium phosphate, started before parturition, for the prevention of parturient paresis is required.     

Effects of an inadequate dietary intake of magnesium on osteogenesis in dairy cows during the dry period

The osteogenic activity in the rib bones of 33 dairy cows (14 of parity 1 or 2, and 19 of parity 3 or more) during their last two months of pregnancy, and the effects upon it of a deficient supply of dietary magnesium, were studied by means of intravenous infusions of the fluorochromes oxytetracycline hydrochloride, calcein and chlortetracycline given nine weeks, five weeks and one week, respectively, before the expected time of parturition. Seven weeks before this date the cows' ration was changed to one containing either 0.22 per cent magnesium (LMg) or 0.82 per cent magnesium (HMg) in the dry matter, and the potassium content of both rations was increased to approximately 4.1 per cent in the dry matter to reduce the absorption of magnesium. Four of the 10 LMg-high parity cows showed signs of periparturient hypocalcaemia. A significant decrease in the number of labelled osteons towards parturition was demonstrated in both the low parity (P less than 0.05) and high parity cows (P less than 0.001). The mean bone apposition rate in high parity cows was significantly lower (P less than 0.001) than in low parity cows. The different levels of magnesium in the diets of the cows had no significant effects on the numbers of osteons which were labelled nine weeks, five weeks or one week before parturition, or on the numbers of osteons which took more than one label or on the bone apposition rate. These results show that in these cows the rate of bone remodelling decreased as parturition approached.     

Effects of dietary cation-anion balance on acid-base status in horses

Four mature, sedentary geldings were used in a 4x4 Latin square design experiment to study the effects of dietary cationanion balance (DCAB), defined as meq ((Na + K) - C1)/kg of dietary dry matter, on urine pH, blood pH and blood gasses. Four diets with actual DCAB levels of +21 (Low, L), +125 (Medium Low, ML), +231 (Medium High, MH) and +350 (High, H) were fed for a 21-day adjustment period and a 72 hour collection period. Total urine output was collected every 4 hours post feeding for 72 hours, and like times across days were combined for analyses. Arterial and venous blood samples were drawn, via indwelling catheters, hourly for 12 hours beginning at feeding. All samples were analyzed immediately after collection for pH, blood gasses and blood acid-base measures. Urine pH was lower (p<.05) at all measured intervals when geldings consumed diet L than when they consumed diets MI, MH and H. Least squares means for urine pH ranges from 5.40 to 5.86 on diet L, 6.79 to 7.30 on diet ML, 7.35 to 7.63 on diet MH and 7.52 to 8.14 on diet H. Blood pH, pCO₂ and HCO₃ values were also significantly lower in both arterial and venous samples when geldings consumed diet L than when fed diets MH and H. Results of this trial indicate that horses consuming highly anionic diets may experience a nutritionally-induced metabolic acidosis.     

Influence of a deficient supply of magnesium during the dry period on the rate of calcium mobilisation by dairy cows at parturition

The influence of a deficient magnesium supply during the dry period on the ability of dairy cows to mobilise calcium at parturition was investigated. The daily rations pre-partum consisted of 6 kg grass hay, and 4 kg concentrates containing either 1.58 per cent magnesium (HMg) or 0.22 per cent magnesium (LMg). Nine cows of parity one to six received the LMg diet and 10 cows of parity one to seven the HMg diet. Both rations provided 1.40 times maintenance on an energy basis and contained 4 per cent potassium in the dry matter. Throughout the dry period the mean concentration of magnesium in the plasma of the LMg group was significantly lower than in the HMg group and at parturition the mean plasma concentrations were 0.65 mmol litre-1 and 1.16 mmol litre-1, respectively. After parturition two cows in the LMg group showed clinical signs of hypocalcaemia but none of the HMg group did so. Cows of the LMg group had a lower mean rate of calcium mobilisation (0.27 mmol min-1) than those of the HMg group (0.34 mmol min-1) but the difference could not be explained by differences in bone turnover as reflected by urinary hydroxyproline excretion. Such a reduced rate of calcium mobilisation may be a contributory factor in the high incidence of milk fever in some herds fed inadequate magnesium in the dry period.     

日粮阴阳离子差在泌乳奶牛日粮中的应用

日粮阴阳离子差（DCAD）可调控家畜体内的酸碱平衡。近年来,由于其对泌乳奶牛生产性能的影响而越来越受到研究者的重视。文章就阴阳离子差的计算,阴阳离子差对泌乳奶牛干物质采食量、泌乳量和乳成分、瘤胃参数的影响,及对DCAD在我国泌乳奶牛日粮中的应用的展望作了综合阐述。     

Effect of dietary cation-anion balance in mineral balance in anaerobically exercised and sedentary horses

Eight geldings and four mares were randomly assigned treatments within three 4x4 Latin square design experiments to study the effects of dietary cation-anion balance (DCAB) on mineral balance and dry matter digestibility in sedentary and anaerobically exercised horses. Four diets with an average DCAB (calculated as meq ((Na+K+) - Cl-)/kg of diet dry matter) of +24 (Low, L), +127 (Medium Low, ML), +227 (Medium High, MH) and +352 (High, H) were fed for a 21 day adjustment period followed by a 72 hour collection period. Diets consisted of a pelleted base concentrate of com, soybean meal and cottonseed hulls fed with either native prairie grass or bermuda grass hay in a 60:40 ratio. Diet L was formed by adding calcium chloride and ammonium chloride to the base concentrate, diet ML was formed by adding calcium chloride, and diet H was formed by adding potassium citrate and sodium bicarbonate. Diet MI-I received no supplementation and served as the control. Representative samples of feed, feces and urine were analyzed for mineral content and mineral balances were calculated by difference. Fecal output was greater (p <.05), and thus, dry matter digestibility was lower in exercised homes consuming diet L versus diet H. Sodium balance was greater (p <.05) in sedentary horses consuming diet MH as compared to those consuming diets ML and L Sodium balance was greater (p <.05) in exercised homes consuming diet H as compared to those consuming diets ML and L Potassium balance was greater (p <.05) in sedentary horses consuming diet H as compared to those horses consuming diet ML, however, potassium balance was not affected by DCAB in exercised horses. No significant differences were detected in chloride or magnesium balances in the sedentary horses, although chloride balance was greater (p <.05) and magnesium balance was lower (p <.05) in exercised homes consuming diet L as compared to all other diets. In sedentary homes, phosphorus balance was reflective of intake with differences (p <.05) observed between all treatments. However, in exercised homes, phosphorus balance was lower (p <.05) oniy for those consuming diet L. Calcium balance decreased significantly as DCAB decreased between all treatments in sedentary horses, while calcium balance in exercised homes was greater (p <.05) for homes consuming diet H as compared to those consum- ing diet L.Previous research from our laboratory has shown that both exercised and sedentary horses consuming diets with a low DCAB experience a nutritionally induced metabolic acidosis. The current data indicate that anaerobically exercised and sedentary horses consuming these diets excrete significantly more calcium in the urine resulting in decreased calcium balances. Prolonged consumption of diets with a low DCAB may lead to a significant demineralization of bone and a subsequent weakening of the skeleton.     

The effect of dietary potassium and chloride on cation-anion balance in swine

The apparent retention and excretion of cations and anions were evaluated in 20 growing pigs to study the mechanisms by which an interaction between dietary K and Cl levels affected growth. All pigs maintained a positive retention of K+ and Cl- regardless of the dietary levels. The K x Cl interaction observed in growth studies previously but not in this study could not be explained by a simple interaction of one ion on the retention of the other. When pooled across dietary Cl levels, an increase in dietary K levels from .10 to .60% resulted in a calculated increase in daily K+ intake of 4.86 meq/kg of BW. Sixty percent (2.99 meq) of the increased K+ intake was excreted in the urine and counterbalanced by a decrease in urine NH4+ (3.06 meq). This decrease in NH4+ excretion could account for essentially all of the increase in N retention (3.51 mmol) observed when dietary K levels were increased from .10 to .60%. Thirty-three percent of the increased K+ intake (1.62 meq) was retained, but the counter ion could not be determined. Retention of Cl- was not changed as dietary K levels were changed. When dietary Cl levels were increased from .03 to .57%, 69% (4.06 meq) of the calculated difference in Cl- intake (5.90 meq) was excreted in the urine, which must have been counterbalanced by a decrease in undetermined organic anions (1.77 meq) and HPO4 = (1.50 meq) excretion, with a tendency for an increased NH4+ (.82 meq) excretion. The counter ions required to balance the increased Cl- retention (1.82 meq) as dietary Cl levels were increased from .03 to .57% could not be identified. Shifts in the retention and urinary excretion of Ca++, Na+, HCO3-, and SO4= did not seem to be quantitatively important in identifying the mechanisms by which dietary K and Cl levels alter growth. Based on these results, we conclude that alterations in growth caused by changes in dietary K and possibly Cl levels are mediated via mechanisms involving renal NH4+ metabolism.     

Effect of dietary cation-anion balance on urinary mineral excretion in exercised horses

Four mares and four geldings of Quarter Horse and Thoroughbred breeding were used in two simultaneous 4x4 Latin square experiments to study the effects of dietary cation-anion balance (DCAB), defined as meq ((Na+K)-C1)/kg dry matter, on urinary pH and mineral excretion in exercised horses. Diets consisted of a pelleted concentrate of corn, soybean meal and cottonseed hulls fed with bermudagrass hay. Treatments with DCAB of +5 (Low, L), +107 (Medium Low, ML), +201 (Medium High, MH) and +327 (High, H), meq ((Na+K)-Cl)/kg dry matter were formed by supplementing diet L with calcium chloride and ammonium chloride, diet ML with calcium chloride and diet H with sodium bicarbonate and potassium citrate (Table 1). Diet MH was not supplemented and served as the control treatment. Horses were conditioned aerobically for 6 weeks using long, slow, distance (LSD) workouts. During the experimental periods, horses were subjected to a combined exercise regimen alternating LSD with an interval-training protocol 6 days/week. There was a significant (P<.01) treatment effect on urine pH; least squares means for L, ML, MH and H were 6.73, 7.17, 7.38, and 7.92. Horses consuming diet L excreted more calcium in the urine (P<.05) than those consuming MH or H. Least squares means for daily urine calcium excretion tended to be linear across treatments and ranged from 19.66 g/day for diet L to 9.12 g/day for diet H. Urinary chloride excretion was higher (P<.05) for L than for MH or H. Horses fed diet H excreted more sodium (P<.05) in urine than horses fed the other diets. Lowering DCAB, increases urinary calcium loss; depending on the level of calcium intake, this could lead to negative calcium balance in exercising horses.