Effects of oral or parenteral iron supplementation on haematological parameters, blood iron status and growth in newborn calves fed milk replacer.

BACKGROUND: This study aimed to assess the influence of early life iron supplementation on the haematological parameters of calves fed milk replacer on a high plane of nutrition. METHODS: Thirty calves were allocated to receive either a sham treatment (CON), injection of 1000 mg Fe3+ (INJ) or oral administration of 1050 mg Fe3+ (ORAL), all administered less than 1 hour after birth. Blood was obtained before treatment, on days 1, 3, 5 and 7 of life and once weekly until week 9. Samples were analysed for haemoglobin (Hb), packed cell volume (PCV) and estimated transferrin saturation (%TSAT). RESULTS: The Hb and PCV of calves in the INJ and ORAL groups were above the values of those in the CON group throughout the study. Hb and PCV of the CON group remained within the reference range for calves. The %TSAT exceeded reported ranges in the ORAL group in the first week. Values for the CON group were below the INJ and ORAL groups throughout the entire study. Average daily gain did not differ between treatments. LIMITATIONS: The sample size was insufficient to assess the influence of iron supplementation on disease development. Furthermore, the study was set in a controlled environment and not performed under field conditions. CONCLUSIONS: Oral and subcutaneous iron administration had similar effects on haematological development but resulted in numerically different transferrin saturation. Control animals showed lower Hb and PCV but did not develop overt anaemia.

Phosphorus Metabolism During Transition.

Phosphorus (P) in ruminant nutrition is under ongoing scrutiny because of concerns with P in animal waste polluting the environment. Laws aiming at containing the amount of P of animal origin leaching into surface waters are implemented in many parts of the world. Concerns with restricting the dietary P supply to high-producing animals do however persist. Overall, with the current pressure to be as restrictive as possible with the dietary P supply in high-producing dairy cows, a more in-depth understanding of the metabolic effects of P balance disorders in fresh cows is urgently needed.

Dietary phosphorus restriction affects bone metabolism, vitamin D metabolism and rumen fermentation traits in sheep.

Homeostasis of calcium (Ca) and phosphate (Pi ) is maintained by a concerted interplay of absorption and reabsorption via the gastrointestinal tract and the kidney and by storage and mobilization from the bone regulated mainly by parathyroid hormone (PTH), 1,25-dihydroxycholecalciferol and calcitonin. The present study aimed at characterizing the effects of dietary P restriction on bone, vitamin D metabolism and rumen fermentation traits reflecting the endogenous P cycle maintaining the ruminal P supply for microbial metabolism. The experiments were done in eleven female, non-pregnant, non-lactating four- to nine-year-old Black Headed Mutton sheep allotted to two feeding groups: "P-restricted" (0.11% P/kg DM and 0.88% Ca/kg DM) and "Control" (0.38% P/kg DM and 0.88% Ca/kg DM). Dietary P restriction did not lead to hypophosphataemia, probably due to a compensation by bone mobilization, demonstrated by increased serum concentrations of a resorption marker and altered gene expression in bone tissue. In addition, the RNA expression of fibroblast growth factor 23, a bone-derived factor involved in the regulation of vitamin D metabolism, was significantly reduced with dietary P restriction. Furthermore, several genes related to vitamin D metabolism and plasma concentrations of 1,25-(OH)2 D were associated with serum concentrations of phosphate (Pi ). In the parotid gland, the expression of the Pi transporter NaPi2b was negatively associated with serum Pi and positively with parathyroid PTH expression. Although Pi concentrations in saliva and the gastrointestinal tract were significantly reduced, we found no adverse effects of the P-restricted ration on the production of short chain fatty acids, but slight differences in the production of butyrate as well as its relationship to rumen Pi and ammonia concentrations that might indicate an impact on ruminal fermentation.

Liver phosphorus content and liver function in states of phosphorus deficiency in transition dairy cows.

Phosphorus (P) deficiency in early lactating dairy cows is receiving increased attention because of incentives aiming at curtailing environmental pollution with P by reducing dietary P in ruminant diets. An in-vitro study using bovine hepatocytes incubated for 7 days with phosphate (Pi) concentrations of 0.9, 1.8 or 2.7 mmol/L, and an in-vivo study feeding late pregnant dairy cows diets with either adequate (0.28% and 0.44% in DM ante-partum and post-partum respectively) or low P content (0.15% and 0.20% in DM ante-partum and post-partum respectively) from 4 weeks before to 4 weeks after calving were conducted to explore effects of P deprivation on liver function. In vitro the relative abundance of mRNA of key enzymes of the carbohydrate metabolism in incubated hepatocytes and liver metabolites in culture medium were determined. In vivo health and productivity of experimental cows on low and adequate dietary P supply were monitored, and liver tissue and blood samples were obtained repeatedly. Liver tissue was assayed for its triacylglycerol-, mineral and water content as well as for the relative abundance of mRNA of enzymes of the carbohydrate-, fat- and protein metabolism. Reduced Pi-availability was not associated with altered enzyme transcription rates or metabolic activity in-vitro. The most prominent clinical finding associated with P deprivation in-vivo was feed intake depression developing after the first week of lactation. Accordingly cows on low P diets had lower milk yield and showed more pronounced increases in liver triacylglycerol after calving. Although the liver P content decreased in P deficient cows, neither negative effects on enzyme transcription rates nor on blood parameters indicative of impaired liver metabolic activity or liver injury were identified. These results indicate the P deprivation only indirectly affects the liver through exacerbation of the negative energy balance occurring as P deficient cows become anorectic.

Suitability of oral administration of monosodium phosphate, disodium phosphate, and magnesium phosphate for the rapid correction of hypophosphatemia in cattle.

BACKGROUND: Hypophosphatemia is commonly associated with disease and decreased productivity in dairy cows particularly in early lactation. Oral supplementation with phosphate salts is recognized as suitable for the rapid correction of hypophosphatemia. Little information is available about the differences in efficacy between salts used for oral phosphorus supplementation. OBJECTIVES: Comparison of efficacy of oral administration of NaH2 PO4 , Na2 HPO4 , and MgHPO4 in treating hypophosphatemia in cattle. ANIMALS: 12 healthy dairy cows in the fourth week of lactation in their second to fifth lactation. METHODS: Randomized clinical study. Phosphorus deficient, hypophosphatemic cows underwent a sham treatment and were afterwards assigned to 1 of 3 treatments-NaH2 PO4 , Na2 HPO4 , or MgHPO4 (each provided the equivalent of 60 g of phosphorus). Blood samples were obtained immediately before and repeatedly after treatment. RESULTS: Treatment with NaH2 PO4 and Na2 HPO4 resulted in rapid and sustained increases of plasma phosphate concentrations ([Pi]). Significant effects were apparent within 1 hour (NaH2 PO4 : P = .0044; Na2 HPO4 : P = .0077). Peak increments of plasma [Pi] of 5.33 mg/dL [5.26-5.36] and 4.30 mg/dL [3.59-4.68] (median and interquartile range) were reached after 7 and 6 hours in animals treated with NaPH2 PO4 and Na2 HPO4 , respectively, whereas treatment with MgHPO4 led to peak increments 14 hours after treatment (3.19 mg/dL [2.11-4.04]). CONCLUSIONS AND CLINICAL IMPORTANCE: NaH2 PO4 and Na2 HPO4 are suitable to rapidly correct hypophosphatemia in cattle. Because of the protracted and weaker effect, MgHPO4 cannot be recommended for this purpose. Despite important differences in solubility of NaH2 PO4 and Na2 HPO4 only small plasma [Pi] differences were observed after treatment.

Treatment of phosphorus balance disorders.

Phosphorus (P) homeostasis in ruminants has received increased attention over the past decades. Although environmental concerns associated with excessive P excretion in cattle manure have led to incentives to lower dietary P intake, hypophosphatemia-particularly in the periparturient dairy cow-has been associated with conditions, such as the downer cow syndrome or postparturient hemoglobinuria. The objective of this article is to revisit current understanding of P homeostasis in ruminants, to discuss the pathophysiology and clinical presentation of P balance disorders, and to review different treatment approaches to correct imbalances of the body's P equilibrium.

Kinetics of phosphate absorption in lactating dairy cows after enteral administration of sodium phosphate or calcium phosphate salts.

Hypophosphataemia is frequently encountered in dairy cows during early lactation. Although supplementation of P is generally recommended, controversy exists over the suitability of oral P supplementation in animals with decreased or absent rumen motility. Since the effects of transruminal P absorption and the reticular groove reflex on the absorption kinetics of P are not well understood, it is unclear in how far treatment efficacy of oral P supplementation is affected by decreased rumen motility. Phosphate absorption was studied in six phosphate-depleted dairy cows fitted with rumen cannulas and treated with test solutions containing either NaH2PO4 or CaHPO4 with acetaminophen. Each animal was treated orally, intraruminally and intra-abomasally in randomised order. Absorption kinetics of P were studied and compared with the absorption kinetics of acetaminophen, a marker substance only absorbed from the small intestine. Intra-abomasal treatment with NaH2PO4 resulted in the most rapid and highest peaks in plasma inorganic P (Pi) concentration. Oral and intraruminal administration of NaH2PO4 resulted in similar increases in plasma Pi concentration from 4 to 7 h in both groups. Treatment with NaH2PO4 caused more pronounced peaks in plasma Pi concentration compared with CaHPO4. Neither transruminal P absorption nor the reticular groove reflex affected P absorption kinetics as determined by comparing plasma concentration­time curves of P and acetaminophen after administration of 1M-phosphate salt solutions. It is concluded that oral treatment with NaH2PO4 but not CaHPO4 is effective in supplementing P in hypophosphataemic cows with adequate rumen motility. Decreased rumen motility is likely to hamper the efficacy of oral phosphate treatment.

Effect of rapid intravenous administration of 50% dextrose solution on phosphorus homeostasis in postparturient dairy cows.

BACKGROUND: Dextrose is commonly administered to postparturient dairy cows, which often have low plasma phosphorus concentration ([P]) as a result of anorexia and sudden onset of lactation. Intravenous (IV) dextrose administration causes hypophosphatemia in other species. HYPOTHESIS: Bolus administration of dextrose to postparturient dairy cows results in a transient decrease in plasma [P]. ANIMALS: Six healthy postparturient dairy cows. METHODS: Using a crossover design, cows were administered 500 mL of 50% dextrose solution IV or a sham treatment. Plasma concentrations of glucose ([glucose]), immunoreactive insulin ([IRI]), and phosphorus were monitored for 12 hours after each treatment. Urine [P], [glucose], and volume and salivary [P] were also determined. RESULTS: Plasma [glucose], [IRI], and [P] were stable during sham treatment. Plasma [P] decreased rapidly after dextrose administration, dropping by 35% in 1 hour and remaining below baseline for 90 minutes. Salivary [P], urine [P], and urine volume per hour remained stable after dextrose administration, but glucose was detected in urine for up to 6 hours. The amount of glucose excreted in urine in 12 hours (11.9+/-4.5 g) was less than 5% of the administered dose. Regression analysis revealed a stronger association between plasma [P] and [IRI] than between plasma [P] and [glucose], suggesting that hyperinsulinemia drove the hypophosphatemia. CONCLUSION AND CLINICAL IMPORTANCE: Results indicate that low plasma [P] should be expected in cows that have received IV dextrose within 1 hour before blood sampling. Caution is advised when administering dextrose solution to cows already at risk of hypophosphatemia.

Effect of continuous intravenous administration of a 50% dextrose solution on phosphorus homeostasis in dairy cows.

OBJECTIVE: To determine the effect of continuous IV administration of 50% dextrose solution on phosphorus homeostasis in lactating dairy cows. DESIGN: Clinical trial. ANIMALS: 4 multiparous Jersey cows. PROCEDURES: Cows were administered 50% dextrose solution IV (0.3 g/kg/h [0.14 g/lb/h]) for 5 days. Plasma concentrations of glucose, immune-reactive insulin (IRI), and phosphorus were determined before, during, and for 72 hours after dextrose infusion. Phosphorus intake and losses of phosphorus in urine, feces, and milk were determined. Each cow received a sham treatment that included instrumentation and sampling but not administration of dextrose. RESULTS: Plasma glucose, IRI, and phosphorus concentrations were stable during sham treatment. Plasma phosphorus concentration decreased rapidly after onset of dextrose infusion, reaching a nadir in 24 hours and remaining less than baseline value for 36 hours. Plasma phosphorus concentration increased after dextrose infusion was stopped, peaking in 6 hours. Urinary phosphorus excretion did not change during dextrose infusion, but phosphorus intake decreased because of reduced feed intake, followed by decreased fecal phosphorus loss and milk yield. Rapid changes in plasma phosphorus concentration at the start and end of dextrose infusion were temporally associated with changes in plasma glucose and IRI concentrations and most likely caused by compartmental shifts of phosphorus. CONCLUSIONS AND CLINICAL RELEVANCE: Hypophosphatemia developed in response to hyperglycemia or hyperinsulinemia in dairy cows administered dextrose via continuous IV infusion. Veterinarians should monitor plasma phosphorus concentration when administering dextrose in this manner, particularly in cows with decreased appetite or preexisting hypophosphatemia.

Phosphorus homeostasis in dairy cows with abomasal displacement or abomasal volvulus.

Abnormal phosphorus homeostasis occurs in dairy cows with an abomasal displacement or volvulus. The goal of this study was to identify potential mechanisms for hypophosphatemia and hyperphosphatemia in cows with a left displaced abomasum (LDA), right displaced abomasum (RDA), or abomasal volvulus (AV). Accordingly, the results of preoperative clinicopathologic analyses for 1,368 dairy cows with an LDA (n = 1,189), RDA, or AV (n = 179) (data set 1) and for 44 cows with an AV (data set 2) were retrieved. Laboratory values were compared by Student's t-tests, and correlation and regression analyses were performed. Thirty-four percent of the animals from data set 1 (463/1,368) were hypophosphatemic (serum phosphorus concentration ([Pi]) < 1.4 mmol/L), and 9% (122/1,368) were hyperphosphatemic ([Pi] >2.3 mmol/L). Serum [Pi] was significantly lower (P < .05) in cows with an LDA (1.60 +/- 0.53 mmol/L; mean +/- SD) than in cows with an RDA or AV (1.85 +/- 0.68 mmol/L). For cows with an LDA, [Pi] was correlated with serum urea nitrogen concentration ([SUN]) (r = 0.34) and serum concentration of magnesium ([Mg]) (r = 0.20). For cows with an RDA or AV, linear correlations existed between [Pi] and [SUN] (r = 0.45), [Mg] (r = 0.43), and serum chloride concentration ([Cl]) (r = -0.27). Stepwise logistic regression analysis indicated that low [SUN] and the diagnosis of an LDA had the strongest associations with hypophosphatemia. In cows with hyperphosphatemia, [Pi] was most strongly associated with azotemia. In cows with an AV, the strongest correlations with [Pi] were found for [SUN] and serum creatinine. We conclude that hypophosphatemia in cows with an LDA is primarily due to decreased feed intake. In contrast, hyperphosphatemia in cattle with an RDA or AV appears to result from dehydration and decreased renal blood flow.