Biomedical subjects

R W Hemken

Publications and source records attributed to R W Hemken.

At least 19 recordsLinked to original sources

PubMed1995

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.

Animal Feed↗

PubMed1994

Calcium and cation-anion balance effects on feed intake, body weight gain, and humoral response of dairy calves.

Our objective was to examine whether feeding low cation-anion diets altered the Ca status of the growing calf. Holstein calves (n = 32; 16 males) were blocked at 56 to 70 d after birth according to sex and birth date and assigned randomly to dietary treatments containing Ca content and cation-anion balances as milliequivalents of (Na+K)-(Cl+S)/100 g of dietary DM of .42% and -18, .52% and -18, .42% and 13, and .52% and 13. Feed intake did not differ among treatments. Calves fed the diet with cation-anion balance of 13 had higher gain (.85 vs. .71 kg/d) than those fed the diet with balance of -18. Venous blood pH (7.374 vs. 7.323), partial pressure of CO2 (47.9 vs. 45.6 mm Hg), and bicarbonate (28.3 vs. 23.3 mmol/L) were higher for calves fed the 13 versus -18 balances. Plasma Ca and P were unaffected by Ca or cation-anion balance. Urinary pH was higher for calves fed the high than the low balance (7.442 vs. 6.047). Urinary Cl and Ca excretion was higher for calves fed the low than the high balance. Breaking strengths for 7th and 9th ribs were higher for calves fed the high balance and higher for the 7th rib only for calves fed the high Ca diet. Cation-anion balance altered Ca metabolism, but it is unclear whether Ca requirements were also altered.

Acid-Base Equilibrium↗

PubMed1994

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.

Aging↗

PubMed1993

Effect of copper status on luteinizing hormone secretion in dairy steers.

Two experiments were conducted to examine the effects of Cu status on neuroendocrine regulation of LH secretion in dairy steers. In Experiment 1, 18 Holstein steers were assigned randomly to treatment groups in a completely randomized design. Treatments consisted of basal diet alone (control) or supplemented with 5 ppm of Mo or with 20 ppm of Cu. At 8 and 16 wk, Cu concentrations in liver were higher in the group receiving Cu and lower in the group receiving Mo than in the control. Pulse frequencies of LH were not affected by any treatment. Serum LH concentration at 16 wk tended to be lower in the group receiving Mo than in either the control or the group receiving Cu. The ability of the pituitary gland to release LH in response to GnRH was not affected at 17 wk. Concentrations of LH in the pituitary glands were lower in the group receiving Mo than in that receiving Cu or in the controls. No differences in Cu or Mo concentrations were observed in pituitary, median eminence, or hypothalamic tissues. In Experiment 2, 12 Holstein steers were assigned to treatment groups receiving the basal diet supplemented with either 20 ppm or Cu or with 10 ppm of Mo. Spontaneous and GnRH-induced secretion of LH were not influenced by treatments after 8 mo of experiment. Reduction in Cu status has little effect on the endogenous secretion of LH in dairy steers.

Animals↗

PubMed1993

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.

Animals↗

PubMed1993

Copper status and requirement during the dry period and early lactation in multiparous Holstein cows.

Eighteen multiparous Holstein cows were assigned randomly to three treatments at the beginning of the dry period (8 wk before expected parturition). Treatments were: 1) the basal diet containing 5.5 ppm of Cu (control), 2) the basal diet supplemented with 10 ppm of Cu, and 3) the basal diet supplemented with 20 ppm of Cu. The objectives were to measure the changes of Cu and other trace mineral element concentrations in blood and liver from the onset of the dry period (approximately 8 wk prepartum) to 8 wk postpartum and to assess the requirement of Cu during this time. Liver Cu concentration in the control group declined continuously during the 8-wk dry period, and the nadir occurred at parturition. This decline was prevented by dietary Cu supplementation of 10 or 20 ppm. Liver Cu concentration in the control group started to increase slowly after the dramatic decline. Liver Zn concentration changed cubically as a function of week during the treatment period. Plasma Cu and Zn exhibited a quadratic pattern as a function of week. The plasma Cu concentration was lowest 5 wk prior to parturition.

Animals↗

PubMed1992

Effects of high iron and sulfate ion concentrations on dry matter digestion and volatile fatty acid production by ruminal microorganisms.

The inhibitory effects of iron- and sulfate-containing compounds on the in vitro digestion of a balanced forage diet by mixed populations of ruminal microorganisms were examined in batch cultures. Compounds containing ferrous and ferric cations consistently inhibited DM digestion by up to 36% when added Fe concentrations in cultures were between 100 and 1,000 mg/L. Increased sulfate concentrations of up to 200 mg/L or chloride concentrations of up to 635 mg/L were not associated with decreased DM digestion. Ammonium sulfate additions that provided 200 mg/L of added sulfur increased (P less than .05) digestibility by 10%. Sulfate-containing iron salts tended to be less inhibitory than chloride salts and were associated with increased gas production during digestion. Ferric chloride inhibited (P less than .05) microbial activities at lower concentrations than ferrous chloride. Data suggest that excessive iron supplementation or contamination of feeds with iron-containing pollutants may decrease microbial activities in the rumen.

Ammonium Sulfate↗

PubMed1992

Influence of cation-anion balance on feed intake, body weight gain, and humoral response of dairy calves.

The objective of this study was to examine the influence of diets with varying cation-anion balance on performance and humoral responses in young, growing dairy calves. Twenty-eight Holstein and 4 Jersey female calves were blocked at 56 to 70 d after birth according to breed and age and assigned randomly to dietary treatments of 0, 21, 37, and 52 meq(Na + K) - Cl/100 g of dietary DM. Diets were based on cracked corn, dried brewers grains, and oats and were fed for 8 wk. Feed intake and average daily gain tended to increase quadratically, being highest for calves fed the +37-meq diet and lowest for those fed the 0-meq diet. Blood and urine pH increased linearly with increasing dietary cation-anion balance. Plasma Ca increased linearly, and Mg and Cl decreased linearly with increasing cation-anion balance. Plasma Na and P were unaffected by dietary treatments. Urinary Ca, Mg, and Cl excretions decreased linearly; urinary P, Na, and K excretion increased linearly with increasing dietary cation-anion balance. Blood pH increased linearly with increasing dietary cation-anion balance. Blood partial pressure of CO2 and HCO3 increased concurrently with increasing dietary cation-anion balance. Results indicate that altering cation-anion balance may impact DMI and average daily gain in the young ruminant.

Animal Feed↗

PubMed1991

Role of sulfur and chloride in the dietary cation-anion balance equation for lactating dairy cattle.

Ten Holstein cows averaging 120 d in lactation were arranged in replicated 5 x 5 Latin squares with 3-wk periods to evaluate the role of sulfur (S) in the dietary cation-anion balance equation. Diets were based on corn silage in Exp. 1 and sorghum silage in Exp. 2. Supplemental S and chloride (Cl) from the double sulfate of potassium and magnesium and CaCl2 were used to manipulate dietary cation-anion balance from 0 to +30 meq when expressed as meq [(Na + K)-(Cl + S)]/100 g diet DM and from +19 to +49 meq when expressed as meq [(Na + K)-Cl]/100 g diet DM. Blood pH was not affected by cation-anion balance, although both S and Cl supplementation tended to lower pH. Blood HCO3- and urine pH decreased and plasma calcium (Ca) and urinary Ca excretion increased as anion was added to the diet. Milk fat production tended to be increased by the low S supplementation. Dietary Cl and S had similar effects on acid-base status. Therefore, we suggest that S be included with Cl in the dietary cation-anion balance equation for lactating dairy cows as follows: meq [(Na + K)-(Cl + S)]/100 g diet DM. Although response of acid-base status to S and Cl was similar, as more data comparing the acidogenicity of S vs Cl become available, it may be necessary to include a modifying coefficient for S in the equation to adjust for differences between S and Cl in acid-generating potential. This coefficient may be further dependent on the dietary source of S.

Acid-Base Equilibrium↗

PubMed1991

Tall fescue endophyte: effect on congenital development and pup growth in mice.

This study was designed to assess effects of a diet containing endophyte (Acremonium coenophialum)-infected tall fescue seed on litter growth and development in mice. Twenty pairs of mature CD-1 mice were allocated to dietary treatments containing 50% (wt/wt) rodent chow plus either 50% endophyte-infected tall fescue seed or seed that was not infected. At parturition, six pups of approximately equal BW and sex ratio were selected from each litter and fostered to each of the dams for suckling, resulting in four suckling groups. Pups born to dams fed the infected diet weighed less at birth and experienced developmental delays in BW gain and in eye opening (16.7 vs. 13.7 d) regardless of the foster dam's diet. Pups born of dams fed the diet that was not infected attained the greatest growth rates and weaning weights; those suckling dams fed the diet that was not infected demonstrated the largest gains. Pups born of and suckled by dams fed the infected diet demonstrated greatly reduced growth rates and weaning weights compared with the other groups. Results suggest that the congenital effect on pups born of dams fed an infected diet was significant in lowering the growth rate of the pups during suckling. The dam's ability to provide nourishment to the pups also was lowered when fed this diet. When these two factors were combined, the differences were greater than for either factor separately.

Acremonium↗

PubMed1991

Influence of calcium chloride on systemic acid-base status and calcium metabolism in dairy heifers.

Twenty heifers (12 Holsteins and 8 Jerseys) ranging from 15 to 22 mo of age (SD = 2.2 mo) and weighing 271 to 486 kg (SD = 72 kg) were offered diets containing 0, .5, 1, and 1.5% CaCl2 for 3 wk followed by a 1-wk readjustment period to evaluate the effect of CaCl2 on acid-base status, diuresis, and Ca metabolism. These evaluations were conducted under conditions simulating changes in dietary cation-anion balance that potentially can be utilized as prophylaxis for parturient paresis during transition from dry cow period to lactation. Free proton concentration in blood increased and blood bicarbonate decreased with increasing dietary CaCl2. Plasma protein and blood hematocrit were unaffected by dietary CaCl2. Plasma Ca and urinary hydroxyproline excretion also were unaffected, but urinary Ca excretion rose with increasing dietary CaCl2, possibly reflecting either increased bone mobilization or intestinal absorption of Ca. Elevating dietary Cl increased both plasma Cl and urinary Cl excretion. During the readjustment period, all differences caused by CaCl2 disappeared. Based on the responses of acid-base status and Ca metabolism to the different dietary concentrations of CaCl2, we suggest that feeding 1% CaCl2 to dry cows for 3 wk prepartum could be a suitable method to prevent parturient paresis without causing detrimental acid-base disturbances.

Acid-Base Equilibrium↗

PubMed1991

Endotoxin mastitis in cows milked four times daily.

As part of a project to identify the pathophysiological cause or causes of mastitic hypogalactia, midlactation cows were infused in two homolateral quarters with 10 micrograms of endotoxin while being milked four times daily to resolve better the temporal changes in mammary synthetic activity during endotoxin mastitis. Milk fat was decreased by the first milking (5 h) postinfusion and then recovered rapidly. In contrast, milk yield and the yields of protein and lactose were not significantly inhibited until the second milking, and these yields recovered slowly thereafter. The decline in milk yield by infused quarters was only 20% greater than the decline by uninfused quarters in this experiment. Mammary inflammation developed rapidly in infused quarters as milk serum albumin concentration was maximal at the first milking. Milk SCC and NAGase were also elevated at this time, and maximal levels occurred at milkings 2 to 4. Increased temperature, increased cortisol, and a mild anorexia were apparent at the first milking only. Endotoxin treatment had no effect on serum prolactin or glucose. These data suggest that the delayed hypogalactia is consequent to the mammary inflammation and systemic responses following endotoxin infusion. The results indicate that different pathophysiological events may inhibit synthesis of the different milk components.

Animals↗

PubMed1991

Role of magnesium in the dietary cation-anion balance equation for ruminants.

Eight midlactation Holstein cows (four primiparous) were assigned to replicated 4 x 4 Latin squares with a 2 x 2 factorial arrangement of treatments. The basal diet was formulated to contain 0 milliequivalents (Na + K) - Cl/100 g of diet DM. Treatment diets of high and low dietary cation-anion balance were achieved by adding appropriate amounts of supplemental Na + K (added on an equivalent basis) or Mg to the basal diet. Milk and protein yield were increased as well as DMI and FCM for Na + K diets The high concentration of cation increased milk fat percentage. The cation-anion balance (using Mg as a cation) had no effect on any of the production parameters observed. The higher cation-anion balances increased blood bicarbonate levels and plasma Na. Urinary Ca excretion was increased for the Mg diets. Urinary pH increased with both the source of cation (Na + K) and the concentration of cation (high) in the diet. other minerals were unaffected in milk, plasma, or urine. Responses measured in this trial reflect treatments calculated using the equation milliequivalents (Na + K) - Cl/100 g diet DM or (Na + K) - (Cl + S)/100 g diet DM, suggesting that Mg plays a minor role in dietary cation-anion balance.

Animal Feed↗

PubMed1991

Effects of copper status on neutrophil function, superoxide dismutase, and copper distribution in steers.

Twelve Holstein steers in a completely randomized block design were fed either a basal diet (concentrate:silage or hay at a DM ratio of 35:65) plus Cu sulfate at 20 ppm of Cu (Cu-supplemented diet) or a basal diet plus ammonium molybdate to obtain 10 ppm of Mo (Cu-depleting diet) on a DM basis in the whole diet for 8 mo. Supplemental Mo was utilized in the Cu-depleting diet to develop a Cu-deficient group. Molybdenum slowly accumulated in the liver in the group fed the Cu-depleting diet. Copper concentrations in the liver and polymorphonuclear neutrophils decreased in the Cu-deficient group compared with the Cu-sufficient group. Plasma Cu concentration did not change during the trial for the Cu-sufficient group. In the Cu-deficient group, plasma Cu concentrations increased during the first 3 mo of the trial, then declined, and remained unchanged for the last 5 mo. Superoxide dismutase activities in red blood cells, polymorphonuclear neutrophils, and whole blood decreased in the Cu-deficient group. Phagocytic capacity was not affected by Cu status, but killing capacity was decreased by low Cu status in the Cu-deficient group by the end of the trial. Glutathione peroxidase activity was unaffected by Cu status. Clinical symptoms of Cu-deficiency were not observed in this trial; there was no evidence of blood hemoglobin or BW gain difference between the two groups. In this study, Cu status affected its distribution in the tissues and related enzyme activities as well as bactericidal function of neutrophils.

Animals↗

PubMed1991

Effects of copper sources and dietary cation-anion balance on copper availability and acid-base status in dairy calves.

Twenty-four Holstein and Jersey calves (14 Holstein), 4 to 11 d of age, were assigned randomly to six treatments in a 2 x 3 factorial arrangement to examine the effects of Cu sources and dietary cation-anion balance on Cu availability and acid-base balance. Treatments were cationic basal diet (20 meq of dietary cation-anion balance on a DM basis), cationic basal diet supplemented with CuO, cationic basal diet supplemented with CuSO4, anionic basal diet (-10 meq), anionic basal diet supplemented with CuO, and anionic basal diet supplemented with CuSO4. Copper sources did not show any effect on growth of calves. The cationic diet increased calf growth compared with the anionic diet at wk 12 of the experiment. Blood pH was increased by the cationic diet in comparison with the anionic diet at wk 8 and 12. Blood pH also was increased by CuSO4 compared with CuO treatment in the early period of the treatment. Blood bicarbonate concentration was decreased by CuO and the anionic diet. Interactions between Cu sources and cation-anion balance were found for blood pH and bicarbonate concentration. Liver Cu concentration was increased by CuSO4 but not by CuO supplementation compared with control. Therefore, CuSO4 was found to be highly available, whereas CuO was a very poorly available source of Cu for young calves.

Acid-Base Equilibrium↗

PubMed1991

Reduced lactational performance following intravenous endotoxin administration to dairy cows.

Nonpregnant lactating cows were given 100 micrograms of endotoxin via the jugular vein to determine effects of intravenous endotoxin administration on mammary inflammation and lactational performance. At the first milking (11 h) posttreatment, milk yield was reduced 33%. Milk fat percentage was elevated at this time, but lactose concentration was decreased. Milk yield and composition returned to pretreatment levels within 2 d. Clinical mastitis was not induced by endotoxin treatment, but milk SCC, NAGase, serum albumin, and lactoferrin were increased by 50%. This increase was small compared with increases during mastitis and may have resulted from lower milk volume. These results support the hypothesis that part of the reduced lactational performance during endotoxin mastitis is mediated by systemic pathophysiological responses and indicate that intravenous endotoxin administration may be a useful model to study adverse effects of infectious disease on lactational performance.

Animals↗

PubMed1991

Suppression of milk production during endotoxin-induced mastitis.

Healthy, midlactation cows were given intramammary infusions of 10 micrograms of endotoxin in two homolateral quarters. Productive, inflammatory, and systemic responses were studied to investigate the pathophysiological effects of mastitis on lactational performance. Endotoxin suppressed milk yield in all quarters of treated cows. A more severe and prolonged suppression occurred in infused quarters compared with uninfused quarters. The fat percentage of milk from all quarters was increased with a greater increase occurring in infused quarters. The protein composition of milk was elevated, and the lactose concentration was depressed in infused quarters. Mammary inflammation--as measured by milk SCC, NAGase, serum albumin, and lactoferrin--was limited to infused quarters. Changes in milk NAGase closely paralleled changes in milk SCC. Daily feed intake was unaffected, and serum glucose levels did not decline following infusion. The lactose concentration of urine increased rapidly after infusion. Reduction in milk yield in all quarters, but varying changes in milk composition in infused versus uninfused quarters suggest that mastitic hypogalactia is mediated by multiple pathophysiological events and is not solely due to inflammatory damage to the mammary epithelium. Part of the reduced lactational performance may result from escape of milk components from the udder into the circulation.

Acetylglucosaminidase↗

PubMed1991

Effect of dietary energy and previous bovine somatotropin on milk yield, mastitis, and reproduction in dairy cows.

Thirty multiparous lactating Holstein cows were blocked according to time of calving and assigned to a 2 x 3 factorial arrangement of treatments in a randomized complete block design to evaluate the effects of two dietary energy concentrations either without or with bST (20.6 mg/d per cow) administered to cows that had not or had received bST during the preceding lactation. Subcutaneous injection of bST began 28 to 35 d postpartum and continued for 39 wk. The dietary energy concentration x bST interaction was not significant for any response variable. Compared with DMI of control cows, DMI was higher for cows receiving bST, being 1.6 and 2.4 kg/d higher for cows receiving bST for one and two lactations, respectively. Milk, fat, and protein yields were higher for cows receiving bST than for controls. Those receiving bST for a second lactation also produced more milk than controls until wk 20; thereafter, milk yields were similar to those of controls. Somatotropin administration had no adverse effect on udder health. Cows receiving bST tended to ovulate less regularly than controls, which may be attributed to their higher milk yield. However, BW gains during lactation were similar for all treatments, indicating that bST-treated cows built energy reserves for the subsequent lactation. Although energy concentrations of the diets had no significant impact on yield, the higher energy diet tended to depress milk fat concentration. Administration of bST to dairy cows for a second, consecutive lactation yielded responses similar for the first 20 wk of the study to those receiving bST for the first time. However, after wk 20, milk yield was less than that by cows receiving bST for the first lactation but similar to that of control cows.

Animals↗