Bone mineral response to ammonium sulphate offered as a lick supplement in beef calves.

Sixteen Bonsmara calves (4 males, 12 females) between 10 and 18 months of age were blocked according to age and sex and randomly assigned to 2 groups. They were offered licks containing bone meal and salt (50:50 ratio) (control) and bone meal and ammonium sulphate (NH4SO4) at 1.25, 2.5, 5, 10, 15, and 18% (treatment) to evaluate the effects of dietary anions on bone phosphate (P) concentration. Bone P concentration was significantly (P < 0.05) higher in the NH4SO4 group compared with the control group, indicating that NH4SO4 was able to increase the P content of bone at each of the 6 concentrations used in the lick relative to the control animals, thereby improving the P status of the animals. Ammonium sulphate at 15% and 18 % in the lick also significantly (P < 0.05) increased bone P compared with the lower concentrations of NH4SO4. Bone calcium (Ca) fluctuated as a result of the acidogenic lick. There was absorption of Ca when P was being resorbed and resorption of Ca when P was being absorbed into and out of bone. Bone Ca:P ratio ranged from 3.2 to 6.4 among the control group and 1.6 to 4.3 among the treatment group. Animals receiving the acidogenic lick had a higher percentage ash compared to the control group for most of the experimental period. Bone magnesium (Mg) fluctuated in response to the acidogenic lick, and it was difficult to show a relationship between bone Mg and Ca or P. The overall mean cortical bone thickness was significantly (P < 0.05) greater in treatment (1.60 mm) compared with control (1.43 mm) calves and this was also true at sampling periods 2, 4, 5 and 6. Bone thickness followed bone P and not bone Ca. Results from this research indicate that the addition of ammonium sulphate to a lick had a beneficial effect in improving the P status by increasing bone P and improving the mineral status of bone by increasing the thickness of cortical bone and percentage ash.

Evaluation of the mineral status of cattle on communal grazing in the North West Province of South Africa.

Twenty five cattle were randomly selected from a herd of animals grazing communally around Mogosane village in the North West Province to evaluate their mineral status based on blood and faecal analysis. Mean faecal phosphorus (P) concentration was curvilinear, increasing from July (0.99 mg/g) to December (3.63 mg/g) and decreasing to 1.29 mg/g in June. Mean P concentration in grass was also curvilinear, increasing from July (0.87 mg/g) to January (1.8 mg/g) and decreasing to 0.9 mg/g in June. There was a high correlation (r2 = 0.89) between faecal and grass P concentrations. Faecal:grass P ratios suggest that the animals were conserving P by reducing faecal P excretion during times of low dietary P. Animals maintained consistent but very low serum inorganic P (SiP) throughout the year (range 1.33-1.95 mg%) and SiP was not correlated with either faecal or grass P. Mean faecal and grass calcium (Ca) concentrations followed a similar pattern to P. There was also a positive correlation (r2 = 0.95) between grass and faecal Ca concentrations. Faecal:grass Ca ratios indicated a conservation of Ca by reducing faecal Ca when dietary Ca was low. Animals were better able to conserve dietary Ca by reducing losses in the faeces than they were P, based on a higher faecal:grass P ratio (1.56) compared with Ca (1.18). Magnesium (Mg) was lost through the faeces during times of high dietary Mg concentrations but was conserved when grass Mg was low.

Bone, blood and faecal response to an acidogenic lick for range cattle using different concentrations of ammonium chloride.

Thirty Brahman-Angus cross heifers at breeding age on extensive grazing were used to test the effectiveness of NH4Cl as an acidogenic agent at 15,18, 21 and 26 % of a dicalcium phosphate lick (A+), compared to a lick of 5 parts dicalcium phosphate and 3 parts salt (A-). Blood and faecal phosphorus (P), faecal calcium (Ca) and faecal magnesium (Mg) were significantly (P<0.05) higher in A+ compared to A-animals at different stages of the experiment. Bone P did not increase in response to NH4Cl but bone Ca was significantly (P<0.05) higher in A+ animals offered 18% NH4Cl and significantly (P<0.05) lower at 15 and 26%. Bone Mg in A+ animals was significantly (P<0.05) higher at 15 and 18% NH4Cl and lower at 26% NH4Cl compared to A- animals. Percentage ash in bone increased linearly from 62.5 to 64.9% in A+ animals as NH4Cl was increased in the lick from 15 to 21% and then decreased to 63.3% but was significantly (P<0.05) greater than the percentage ash in A-animals when the NH4Cl was increased to 26%. Bone mineral status was only marginally improved by adding NH4Cl to the lick in this study but blood P was significantly (P<0.05) improved in A+ compared to A- animals when the lick contained 15, 21 and 26% NH4Cl. Based on bone mineral results reported here, it is recommended that, when NH4Cl is used as an acidogenic agent in licks for range cattle, the amount in the lick should not exceed 21%.

The effect of gestation and lactation on bone calcium, phosphorus and magnesium in dairy cows.

A study was conducted to monitor changes in cortical bone mineral in the dairy cow in response to demands of lactation and pregnancy using rib bone biopsies in serial sampling. Sixteen Friesian cows from the University dairy herd were used to collect 9 samples during the lactation period and 5 samples during the dry period. The data were analysed using a split-plot design analysis of variance. There were no significant (P > 0.05) differences in cortical bone phosphorus concentrations in rib bone during the lactation period, but calcium concentrations in cortical bone were significantly (P < 0.05) higher at parturition and during the first 30 days of lactation compared to the next 30 days and between 90 and 120 days. Results reported here indicate that the cow resorbs cortical bone during the middle of the lactation period and not during the periparturient period as previously thought. Magnesium concentrations were also significantly (P < 0.05) higher at the beginning of lactation compared to some of the other sampling times, but cortical bone was significantly (P < 0.05) thinner at the beginning of lactation compared to several of the other sampling times. There were no significant (P > 0.05) differences in cortical bone Ca or Mg concentrations during the gestation period. Cortical bone P concentrations significantly (P < 0.05) decreased during the first 180 days, but significantly (P < 0.05) increased at 181-230 days and significantly (P < 0.05) decreased again at 231 days to term. Cortical bone thickness decreased significantly (P < 0.05) from the beginning of gestation to term. There were no significant (P > 0.05) differences in cortical bone thickness or Ca or Mg concentrations in cortical bone during the dry period, but cortical bone P concentrations were significantly (P < 0.05) greater at the end of the dry period compared to the first 30 days of the period. In general, cortical bone Ca and Mg values decreased as milk production increased up to 20 kg/day and cortical bone P values and bone thickness increased. In animals producing over 20 kg/day, however, cortical bone mineral values were greater and cortical bone thickness was lower compared to those animals producing less than 20 kg.

Acute effects of an anionic diet on bone mineral homeostasis in the bovine.

Fifteen Friesian oxen between 12 and 18 months of age with a mean body mass of 240.7 kg were randomly assigned to diets containing 0.25% phosphorus (P) or less to evaluate the acute effects of an acidiogenic diet of -11.1 meq/100 g of diet dry matter, compared with a basiogenic diet of +25.6 meq/100 g or a control diet of +16.5 meq/100 g of diet dry matter calculated as (Na + K)-(Cl + S), on blood, bone and faecal P, calcium (Ca) and magnesium (Mg) for a period of 9 weeks. Blood, bone and faecal responses to an anionic diet are described. An inverse relationship existed between bone and blood Ca, in which there was resorption from bone with increased blood Ca in response to the anionic diet. The anionic treatment group demonstrated simultaneous increases in bone, blood and faecal P concentrations at various stages of the experiment compared to the cationic and control treatment groups. Results indicate independent absorption and resorption of Ca and P into and out of bone. There was wide variation in the bone Ca:P ratio between 2.02 and 1.51 among animals fed the anionic diet, with the Ca:P ratio following Ca values and not bone P values. Bone and blood P had a linear relationship with dietary cation:anion balance (DCAB), increasing as the diet became more anionic in nature, but faecal P was curvilinear with highest concentrations at -11.1 and +25.6 meq/100 g compared to +16.5 meq/100 g. Concurrent blood, bone and faecal P increases at some stages of the experiment indicate a P-sparing effect of the anionic diet and warrants further research into the long-term effects of anions in the diet, leading to their use as a possible addition to improved licks in P-deficient areas.

Short-term effects of dietary cation:anion balance on bone mineral homeostasis in the bovine.

Fifteen Friesian oxen between 12 and 18 months of age with a mean body mass of 240.7 kg, were randomly assigned to diets containing 0.25% phosphorus (P) or less, to evaluate the acute effects of a dietary cation:anion balance (DCAB) of either -11.1, +16.5 or +25.6 mmol 100 g-1 diet dry matter calculated as (Na+K) - (Cl+S), on blood, bone and faecal P, calcium (Ca) and magnesium (Mg) for a period of 9 weeks. Bone and faecal P concentrations were significantly (P < 0.05) higher in the anionic treatment group compared with the cationic and control treatment groups. The same was true for blood P, but significant (P < 0.05) only when compared with the cationic treatment group. Bone Ca was lower (NS) and blood Ca was significantly (P < 0.05) higher in the cationic compared to the anionic and control treatment groups, but faecal Ca was significantly (P < 0.05) higher in the anionic compared to the cationic, and control treatments groups. There was little difference in blood and bone Mg content among treatment groups, but faecal Mg was significantly (P < 0.05) higher in the anionic treatment group compared to the other 2 treatment groups. Whether this was due to the anionic nature of the diet or dietary concentration of Mg is unclear. Results from this research indicate a P sparing effect in which a low DCAB may improve the availability of P in animals where dietary P is limiting. In critical evaluations, weekly sampling of rib bone should be used to give a more accurate assessment of acute changes in bone mineral.

Determination of calcium, phosphorus, and magnesium values in rib bones from clinically normal cattle.

Mean phosphorus (P) content in bovine rib bone was 102.9, 108.3, and 182.7 mg/g of bone on fresh, dry, and ash weight bases, respectively. Values for calcium (Ca) were 194.3, 203.7, and 344.6 mg/g, respectively, and for magnesium (Mg) were 5.3, 5.5, and 9.4 mg/g, respectively. Mean percentage of ash in rib bone was 59.12%. Expected concentrations of Ca, P, and Mg were determined on fresh, dry, and ash weight bases and for 3 age groups, 3 breeds, and bulls, females, and steers. On an ash weight basis, cattle 6 to 18 months old had 185.74 mg of P/g, 372.52 mg of Ca/g, and 12.37 mg of Mg/g. Those 19 to 36 months old had 182.02 mg of P/g, 322.35 mg of P/g, and 8.09 mg of Mg/g. Those > 36 months old had 174.80 mg of P/g, 340.36 mg of Ca/g, and 6.62 mg of Mg/g. Steers had 183.93 mg of P/g, 352.73 mg of Ca/g, and 10.15 mg of Mg/g. Females had 178.47 mg of P/g, 320.28 mg of Ca/g, and 6.5 mg of Mg/g. Males had 176.15 mg of P/g, all on an ash weight basis. Dairy breeds were found to have 186.08 mg of P/g, 351.25 mg of Ca/g, and 10.47 mg of Mg/g. Cattle of mixed breeding had 177.42 mg of P/g, 341.28 mg of Ca/g, and 6.54 mg of Mg/g. The Africander breed of beef cattle had 167.07 mg of P/g, all on an ash weight basis.

Use of bovine rib bone in serial sampling for mineral analysis.

A total of 2160 samples of rib bone were used in a split-plot design analysis of variance to show that, on an ash weight basis, P content is not different among the right and left 9th, 10th, 11th, and 12th ribs of cattle above 6 mo of age. Results were similar for Ca on a fresh or dry weight basis. Some differences existed in Mg content among some of the ribs. Location on the rib from which samples were taken was responsible for significant differences in mineral concentrations. Based on results reported herein, ribs 9, 10, 11, and 12 of the right and left side may be used in the serial sampling of bone tissue in the bovine for the purpose of comparing the content of P, Ca, and--to some extent--Mg. Serial sampling makes possible comparison of bovine mineral status based on bone tissue over an extended experimental period that includes eight sampling dates.

Interactions of dietary cation-anion balance and phosphorus: effects on blood, bone and faecal phosphorus concentration in dairy calves.

Dietary levels of cations and anions are shown to have an effect on concentrations of phosphorus (P) in blood, bone and faeces of dairy calves between 9 and 19 weeks of age. Calves fed diets high in anions, demonstrated higher concentrations of P in blood and faeces than calves whose diets were high in cations, and at the same time demonstrated lower concentrations of P in bone. Compared to diets with high cation levels, diets high in anions produced significantly (p less than 0.05) higher concentrations of total P in the faeces at different stages in the experiment, higher serum inorganic phosphorus (SiP) concentrations and lower P concentrations in the bone, which were significant at the end of the trial (P less than 0.06). When the diet was low in P (0.22%), the cation-anion balance of the diet seemed to have the greatest effect, so that the interaction of dietary P and dietary cation-anion balance (DCAB) was responsible for changes in blood, bone and faeces.

Interactions of dietary cation-anion balance and phosphorus: effects on growth and serum inorganic phosphorus in dairy calves.

Thirty-six male and female Holstein and Jersey calves were assigned at weaning to a randomized complete block design in a 2 x 3 factorial arrangement to evaluate the influence of two dietary cation-anion balances (-14 and +39 meq(Na + K)-(Cl + S) per 100 g diet DM) and three amounts of dietary P (.22, .29, and .37%) on performance and P metabolism from 9 to 19 wk of age. Feed intake, average daily gain, and serum inorganic P were higher on the anionic diets and increased with increasing dietary P. Body weights were higher on the .37% P diets by wk 3 and on the anionic diets by wk 6. The interaction of dietary P and cation-anion balance was responsible for significant differences in calf performance; the anionic diet exhibited marked improvement over the cationic diet at the lowest P concentration. Results indicate that the availability of P for young dairy calves may be higher with anionic than cationic diets.