Long-term effects of dietary anion-cation balance on acid-base status and bone morphology in reproducing ewes

Effects of feeding a negative dietary cation and anion difference diet to twin-bearing Merino ewes in late gestation on parturition outcomes

In Australia, dystocia is responsible for 53% of lamb mortalities, and calcium deficiencies may be a contributing factor. A negative dietary cation-anion difference (DCAD) diet can increase calcium concentrations in sheep. Therefore, this study aimed to investigate the effects of a negative DCAD diet on metabolic state, mineral status, and parturition duration in ewes compared with those fed a positive DCAD diet. At approximately day 130 of gestation (dG), 71 twin-bearing ewes were placed in the following treatment groups; ewes receiving a positive DCAD TMR (total mixed ration; DCAD of total diet = 281.8 mEq/kg DM; n = 35) and twin-bearing ewes receiving a negative DCAD TMR (DCAD of total diet = -89.0 mEq/kg DM; n = 36). Urine and blood were sampled on dG 130, 140, and 145, and blood was also sampled at the onset of parturition and 4 h postpartum. Urine was analyzed for pH and blood was analyzed for metabolites, mineral concentration, and acid-base balance. Lambs' liveweight, rectal temperature, blood glucose and lactate, and body morphology were measured. Serum phosphate concentrations at dG 145 were significantly lower for negative DCAD ewes compared with positive DCAD ewes (1.9 ± 0.1 vs. 2.1 ± 0.1 mmol/L, P = 0.047). Ionized calcium (P = 0.09) and serum magnesium (P = 0.09) prepartum were marginally greater in the negative DCAD ewes (1.35 ± 0.06 and 1.06 ± 0.03 mmol/L, respectively) compared with the positive DCAD ewes (1.18 ± 0.08 and 0.98 ± 0.04 mmol/L, respectively). Urine pH was lower in the negative DCAD ewes compared with positive DCAD ewes at both dG 140 (7.38 ± 0.17 vs. and 8.10 ± 0.19. P = 0.01) and dG 145 (and 7.20 ± 0.19 vs. 8.25. P < 0.01). The birth interval between the first the second-born lamb was shorter in the negative DCAD ewes compared with the positive DCAD ewes (P = 0.02), but no differences in lamb survival or lamb viability (P > 0.05) were seen. The negative DCAD diet reduced parturition duration, most likely due to the marginally greater ionized calcium and magnesium concentrations. Despite this improvement, the negative DCAD ewes did not reach urinary acidification, indicating that the marginally significant greater ionized calcium and serum magnesium concentrations were due to the magnesium in the diets and not metabolic acidosis. Further research testing a negative DCAD diet that can achieve the target urine pH is required to determine whether this diet can decrease parturition duration and improve lamb viability.

Negative dietary cation and anion difference supplementation of twin-bearing Merino ewes grazing pasture in late gestation did not affect lamb growth or survival

Each year in Australia, 53% of lamb mortalities are attributed to dystocia, with subclinical maternal calcium deficiencies likely contributing to dystocia rates. A negative dietary cation and anion difference (DCAD) diet has increased circulating calcium in sheep. Therefore, this study aimed to investigate the effects of supplementing twin-bearing, grazing ewes with a negative DCAD partial mixed ration (PMR) during late gestation on ewe calcium and magnesium concentrations and subsequent lamb growth and survival. On day 120 of gestation (dG), blood samples were collected from 115 twin-bearing Merino ewes and analyzed for glucose, ketone bodies, pH, ionized calcium, and serum calcium and magnesium. On dG 130, ewes were moved into lambing paddocks and placed in the following 2 treatment groups; ewes receiving a positive DCAD PMR (DCAD = 287 mEq/kg DM; n = 58) and ewes receiving a negative DCAD PMR (DCAD = -125 mEq/kg DM; n = 57) fed as a PMR. On dG 140, a blood and urine sample were collected. The urine was tested for pH. Pasture samples were taken on dG 133 and 149 and tested for DCAD and mineral content. When a lamb was 6 to 18 h old, survival, vigor score, liveweight (LW), rectal temperature, blood glucose, and body morphology were recorded. At 10 d of age, lamb LW and survival were recorded and a milk sample was collected from ewes. At 44 d of age, lamb LW and survival were recorded. The DCAD of the pastures across the 6 paddocks ranged from 598 to 893 mEq/kg DM. There were no differences in lamb survival, weight, or viability at any timepoint (P > 0.05). There were no differences in mineral status, metabolic state, or acid-base balance between the positive and negative DCAD-supplemented ewes (P > 0.05) during supplementation (dG 140). Supplementing a negative DCAD diet to ewes grazing pasture during late gestation did not improve lamb survival. The blood and urine pH of the negative DCAD-supplemented ewes indicated a mild metabolic acidosis was not reached due to the high DCAD of the pastures. Further research needs to take careful consideration of the DCAD of pasture when designing a negative DCAD supplement in order for it to be effective.

Influence of Strain and Diet on Urinary pH in Laboratory Mice

Simple Summary

Dietary cation anion balance (DCAB) influences urine pH in several species, e.g., cats, dogs, pigs and cattle suggesting a species-specific impact. In the present study, we aimed to explore the impact of three diets with different DACB on wildtype laboratory mice. During a two-month feeding trial urine pH and body weight were measured in C57Bl/6J and CD1 male mice. Remarkable, we observed strong impact of the genetic background and diet on urine pH levels. A plausible explanation is that differences in renal phosphorus excretion and, in turn, phosphate buffering capacity account for these differences. It is tempting to speculate that standard laboratory mouse models show DCAB dependent variations in urine pH.

Abstract

Acid base homeostasis and urine pH is influenced by the dietary cation anion balance (DCAB) in many species. Here, a negative DCAB acidifies the urine, while higher DCABs alkalize the urine. The dimension of the DCAB effect can be species-specific, because of differences in urine buffer systems. The aim of the present study was to describe the response of laboratory mice to diets with different DCAB. We used 8-week-old wildtype male mice of the C57Bl/6J inbred strain and CD1 outbred stock. Three groups (n = 15 animals/group) were formed and fed standard diet A for adaptation. For the 7-week feeding trial, mice were either kept on diet A (DCAB −7 mmol/kg dry matter (DM) or switched to diet B (246 mmol/kg DM) or C (−257 mmol/kg DM). Urine pH was measured weekly from a pooled sample per cage. There was a significant difference in the basal urine pH on diet A between C57Bl6/J and CD1 mice. The shift in urine pH was also significantly different between the two groups investigated.

Feeding a Negative Dietary Cation-Anion Difference to Female Goats Is Feasible, as Indicated by the Non-Deleterious Effect on Rumen Fermentation and Rumen Microbial Population and Increased Plasma Calcium Level

Simple Summary

Diets with a lower dietary cation-anion difference could prevent hypocalcemia, enhance health, and extend the economic life of transition mammary animals. However, there is less information on rumen fermentation, cellulolytic bacteria populations, and microbiota for female goats fed a negative dietary cation-anion difference diet. We speculate that a negative dietary cation-anion difference would not affect the rumen fermentation parameters. Therefore, the present study was conducted to evaluate the effect of a negative dietary cation-anion difference diet on rumen pH, buffering capability, volatile fatty acids of acetic acid, propionic acid, butyric acid, total volatile fatty acid and acetic acid/propionic acid profiles, ruminal cellulolytic bacteria populations, and microbiota. These results provide a further evaluation on the feasibility of feeding a negative dietary cation-anion difference diet to goats.

Abstract

The dietary cation-anion difference (DCAD) has been receiving increased attention in recent years; however, information on rumen fermentation, cellulolytic bacteria populations, and microbiota of female goats fed a negative DCAD diet is less. This study aimed to evaluate the feasibility of feeding a negative DCAD diet for goats with emphasis on rumen fermentation parameters, cellulolytic bacteria populations, and microbiota. Eighteen female goats were randomly blocked to 3 treatments of 6 replicates with 1 goat per replicate. Animals were fed diets with varying DCAD levels at +338 (high DCAD; HD), +152 (control; CON), and −181 (low DCAD; LD). This study lasted 45 days with a 30-d adaption and 15-d trial period. The results showed that the different DCAD levels did not affect the rumen fermentation parameters including pH, buffering capability, acetic acid, propionic acid, butyric acid, sum of acetic acid, propionic acid, and butyric acid, or the ratio of acetic acid/propionic acid (p > 0.05). The 4 main ruminal cellulolytic bacteria populations containing Fibrobacter succinogenes, Ruminococcus flavefaciens, Butyrivibrio fibrisolvens, and Ruminococcus albus did not differ from DCAD treatments (p > 0.05). There was no difference in bacterial richness and diversity indicated by the indices Chao, Abundance Coverage-based Estimator (Ace), or Simpson and Shannon, respectively (p > 0.05), among 3 DCAD levels. Both principal coordinate analysis (PCoA) weighted UniFrac distance and unweighted UniFrac distance showed no difference in the composition of rumen microbiota for CON, HD, and LD (p > 0.05). At the phylum level, Bacteroidetes was the predominant phylum followed by Firmicutes, Synergistetes, Proteobacteria, Spirochaetae, and Tenericutes, and they showed no difference (p > 0.05) in relative abundances except for Firmicutes, which was higher in HD and LD compared to CON (p < 0.05). At the genus level, the relative abundances of 11 genera were not affected by DCAD treatments (p > 0.05). The level of DCAD had no effect (p > 0.05) on growth performance (p > 0.05). Urine pH in LD was lower than HD and CON (p < 0.05). Goats fed LD had higher plasma calcium over HD and CON (p < 0.05). In summary, we conclude that feeding a negative DCAD has no deleterious effects on rumen fermentation and rumen microbiota and can increase the blood calcium level, and is therefore feasible for female goats.

Effects of pH and the plasma or serum concentrations of total calcium, chloride, magnesium, l-lactate, and albumin on the plasma ionized calcium concentration in calves

BACKGROUND

The plasma ionized calcium concentration (cCa2+ ) represents the biologically active form of calcium and is the preferred method for evaluating calcium status in animals. Different pH-corrective equations have been developed for human plasma, but the validity of the equations for bovine plasma is unknown.

HYPOTHESIS

We hypothesized that pH-corrective equations for bovine plasma would be similar to those used for human plasma; cCa2+ was dependent on the plasma concentrations of total calcium (cTCa), chloride (cCl), L-lactate (cLactate), and albumin (cAlbumin); and the in vitro and in vivo cCa2+ -pH relationships would differ.

ANIMALS

Ten healthy calves (in vitro study), 1426 critically ill calves.

METHODS

The in vitro plasma log10 (cCa2+ )-pH relationship was determined by CO2 tonometry of 465 plasma samples. Plasma cCl was altered by equivolume dilution of plasma with 3 electrolyte solutions of different cCl. The in vivo plasma cCa2+ -pH relationship was investigated and validated using clinicopathologic data extracted from the medical records of 950 (model development) and 476 (model validation) critically ill calves.

RESULTS

pH-corrective equations for bovine plasma were similar to those used for human plasma. Plasma cCa2+ increased in vitro with increases in plasma cCl. Plasma cCa2+ in critically ill calves was associated with plasma cTCa, blood pH, plasma cCl, serum cMg, and cL-lactate (R2  = 0.69) but not plasma cAlbumin.

CONCLUSIONS AND CLINICAL IMPORTANCE

Calculation of cCa2+ from cTCa in calf plasma or serum requires adjustment for at least pH and cCl when 1 or both are outside the reference range.

Can neutral dietary cation-anion difference (DCAD) decrease occurrence of clinical periparturient hypocalcaemia in dairy cattle?

BACKGROUND

Adjusting the dietary cation-anion difference (DCAD) is one of the most efficient ways to stimulate calcium homeostasis in periparturient dairy cattle. However, adjusting DCAD to the recommended negative values (-100 to -150 mEq/kg) is associated with decreased food intake and metabolic acidosis. The critical conditions of the animals at peripartum (i.e. drastic hormonal changes, decreased appetite and negative energy balance) can be detrimental to the health, productivity and welfare of the animals if combined with decreased feed intake caused by unpalatable acidogenic salts.

METHODS

In a cross-sectional study, we analysed the ration of eight small to large dairy herds with intensive husbandry systems, including 6949 dry cows. Sodium, potassium, chlorine and sulfur concentrations in the feed were determined and DCAD was calculated. The DCAD of the ration of the farms ranged from -33.5 to +24.7 mEq/kg. Parturient paresis (PP, or milk fever) prevalence was investigated and correlated to DCAD values.

RESULTS

Clinical PP occurrence in the dairies of this investigation on average declined by 87% (ranging from a 97% decline to 5% increase). This indicates that adjusting DCAD at neutral values (0 ± 30 mEq/kg range) may both lower the PP prevalence and increase ration palatability by lowering acidogenic salts in the ration.

CONCLUSIONS

Further research is recommended to investigate the effects of neutral DCAD on subclinical hypocalcaemia and food intake of the cattle.

Efeito da suplementação de cloreto de amônio sobre os equilíbrios eletrolítico e ácido-básico e o pH urinário de ovinos confinados

A incidência da urolitíase obstrutiva em ovinos é elevada, principalmente em machos confinados, tanto para produção de carne, quanto reprodutores de alto valor genético. A acidificação urinária é um dos métodos para prevenção desta enfermidade e pode ser realizada de forma eficaz com a suplementação de cloreto de amônio na dieta, que pode propiciar a instalação de acidose metabólica. A hemogasometria avalia o equilíbrio ácido-básico sanguíneo de forma prática e fácil. Neste trabalho, avaliou-se o efeito do cloreto de amônio sobre o equilíbrio ácido-básico e eletrolítico de ovinos em confinamento para quantificar a acidose metabólica desenvolvida. Utilizaram-se 100 ovinos, machos, confinados, com idade aproximada de três meses. Constituíram-se três grupos experimentais: Grupo I (n=40), recebeu 400mg/kg/PV de cloreto de amônio/animal/dia por 21 dias consecutivos, momento da interrupção da administração do acidificante urinário (M3) e continuidade do acompanhamento clinico até o final do experimento (M6); Grupo II (n=40), 400mg/kg/PV de cloreto de amônio/animal/dia por 42 dias consecutivos; Grupo III (n=20), não recebeu cloreto de amônio durante todo o período do experimento. Os Momentos (M) de colheita de amostras e avaliação clínica foram estabelecidos com intervalo de sete dias, sendo M0 (imediatamente antes do início do tratamento com cloreto de amônio), M1 (sete dias após), M2, M3, M4, M5 e M6, totalizando 56 dias de confinamento. A alimentação consistiu de ração total, composta por 15% de feno triturado e 85% de concentrado, água e sal mineral ad libitum. Após adaptação de 15 dias à dieta de confinamento, colheram-se de todos os animais amostras de urina para mensuração do pH, e sangue venoso para hemogasometria, nos diferentes momentos. A acidificação urinária foi mantida enquanto houve a administração de cloreto de amônio nos grupos GI e GII. Os valores de Na+ e K+ permaneceram dentro da normalidade para a espécie. O cloreto de amônio provocou acidose metabólica hiperclorêmica compensada nos grupos GI e GII, comprovada pelos valores reduzidos de HCO3-, EB e SID, pelos valores elevados de Cl- e pelo pH normal. Concluiu-se que o cloreto de amônio apesar de provocar diminuição da reserva alcalina no organismo, não interferiu com o desenvolvimento dos animais, podendo ser empregado como agente preventivo da urolitíase obstrutiva em ovinos.

Use of dietary cation anion difference for control of urolithiasis risk factors in goats

OBJECTIVE

To determine correlations between dietary cation anion difference (DCAD) and urine pH, urine specific gravity, and blood pH in goats.

ANIMALS

24 crossbred goat wethers.

PROCEDURES

Goats were randomly assigned to 1 of 4 DCAD groups (-150, -75, 0, or +75 mEq/kg of feed) and fed pelleted feed and ground hay for 7 days. The diet was then supplemented with ammonium chloride to achieve the assigned DCAD of each group for 7 days. Urine was obtained for pH and specific gravity measurements at hours -3 to -1, 1 to 3, 5 to 7, 9 to 11, and 13 to 15 relative to the morning feeding. Blood pH was determined on alternate days of the study period.

RESULTS

Goats in the -150 and -75 mEq/kg groups had a urine pH of 6.0 to 6.5 two days after initiation of administration of ammonium chloride, and urine pH decreased to < 6.0 by day 7. Goats in the 0 mEq/kg group had a urine pH from 6.0 to 6.5 on day 5, whereas urine pH in goats in the +75 mEq/kg group remained > 6.5 throughout the trial. Urine specific gravity differed only between the -150 mEq/kg and the -75 mEq/kg groups. Blood pH in the -150 mEq/kg group was significantly lower than that in the other groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Goats in the 0 mEq/kg DCAD group had a urine pH of 6.0 to 6.5 five days after intitiation of feeding the diet, and that pH was maintained through day 7, without significant reduction in blood pH. This may serve as a target for diet formulation for the prevention of urolithiasis.

Effects of Dietary Cation-Anion Difference on Blood Cortisol and ACTH Levels in Reproducing Ewes

Formulation of rations to induce a compensated metabolic acidosis in the post-partum cow has proved a useful strategy for prevention of milk fever. Such acidification improves the ability of the animal to maintain calcium homeostasis by promoting the absorption of calcium from the intestine and mobilization of calcium from the bone. In humans, an acidogenic diet results in mild metabolic acidosis in association with a state of cortisol excess and this increase in plasma cortisol may increase bone catabolism. The objective of our experiment was to induce acidification by anionic salt supplementation and to study the effects of anionic supplementation on plasma cortisol and adrenocorticotropic hormone (ACTH) levels in sheep. Twenty-seven twin-bearing sheep were assigned to two experimental groups and a control group, depending on dietary cation-anion difference (DCAD) (+272.6, -88.9 and +164.5 mEq/kg DM respectively). Sheep assigned to each dietary treatment received their respective rations beginning 6 weeks pre-partum and continuing until 12 days post-partum. Anionic diet induced a non-respiratory systemic acidosis in association with a mild increase in plasma cortisol concentration without changes in plasma ACTH levels. Our data suggest that the mild hypercortisolism observed in sheep fed the anionic diet may not be an effector for bone resorption induced by anionic salts. A mild hypercortisolism of this magnitude may lead to osteoporosis but this might require many years of adrenal hypersecretion while anionic salts are only used during the last weeks of pregnancy.