Effects of sometribove on zinc metabolism and tissue mineral concentration in dairy calves.

The metabolism of Zn and tissue mineral concentrations were studied after a single oral 65Zn dose in 10 6-wk-old Holstein calves injected subcutaneously daily with 0 (control) or 10 mg of sometribove (recombinant methionyl bST) for 6 wk. Zinc-65 absorption was not significantly affected by bST; its concentration in the semitendinosus muscle was reduced by 32% in the bST calves, but concentrations in liver, pancreas, spleen, kidney, heart, small intestine, testicle, and rib were not different from controls. Manganese content was reduced by 27% in liver, 60% in kidney, 99% in spleen, 92% in testicles, and 33% in rib. Iron content of pancreas, spleen, and testicle and Zn content of rib were increased in the bST calves. The data indicate that Zn metabolism was not affected adversely by bST. Manganese content of several tissues was significantly reduced in the bST calves; however, no clinical signs of an Mn deficiency were evident.

Effects of sometribove on performance, carcass composition, and chemical blood characteristics of dairy calves.

Ten intact male Holstein calves averaging 75 kg of BW and 59 d of age were used to study the effects of daily injections of 0 (control) or 10 mg of sometribove (recombinant methionyl bST) for 6 wk on performance, health, carcass composition, N metabolism, chemical blood characteristics, and hormone profiles. Average daily gain, feed intake, feed:gain ratio, and height at withers, hip, and hock were not influenced by bST. Carcasses from bST-treated calves contained 5% more protein and 36% less lipid than controls. Circulating concentrations of Ca, P, glucose, urea N, alkaline phosphatase, creatine phosphokinase, insulin-like growth factor-I, and insulin were not affected by bST. Packed cell volume was decreased about 7% (29.9 vs. 32.4%) in the bST calves. Hormone injection did not adversely affect health of the calves as measured by body temperature and by pulse and respiration rates. The most profound effects of sometribove were a reduction in carcass lipid and an increase in body proteins. These effects may be of some practical importance when leanness of carcass is desirable.

Influence of dietary aluminum and phosphorus on zinc metabolism in dairy calves.

The metabolism of a single oral zinc-65 dose was studied in young dairy calves fed two concentrations of added A1 (0 and .20% A1) and two concentrations of added P (0 and .22% P) for 7 wk. The four treatments were 1) normal P-low A1, 2) low P-low A1, 3) normal P-high A1 and 4) low P-high A1. The basal diet (low P-low AL) contained, by analysis, .132% P, .74% Ca, .021% A1 and 59 ppm Zn. Zinc-65 absorption was greater (66.5 vs 63.2% of dose, P less than .10) with the low-P diet; added A1 reduced (P less than .05) 65Zn absorption. Calves fed low-P diets had higher (P less than .10) concentrations of 65Zn in liver, kidney, spleen, heart, small intestine and testicle than those fed normal-P diets. Zinc-65 was reduced (P less than .10) in pancreas, heart, testicle and muscle of calves fed high A1. Iron was increased in liver and kidney (P less than .10), Zn (P less than .10) and Mn (P less than .01) were increased in liver, but Fe in small intestine and Cu in muscle and tibia shaft were decreased (P less than .10) in calves fed the low-P diets compared to those fed adequate-P diets. High A1 reduced (P less than .10) Cu in small intestine and tibia shaft. The results suggest that zinc metabolism may be moderately affected in calves fed either low-P or high-A1 diets.

Effects of high dietary lead on the metabolism of intravenously dosed selenium-75 in dairy calves.

The metabolism of intravenously dosed 75Se was studied in 10 Holstein bull calves fed for ad libitum access a control diet containing no added Pb or a control diet supplemented with 1000 ppm Pb as PbSO4 for 4 wk. The Pb-supplemented calves exhibited no clinical signs often ascribed to lead toxicity. Likewise, feed intake and body weight gains were not affected adversely. The lead content of rib, kidney, liver, and brain was increased. Serum glutamic oxaloacetate transaminase activity increased in the calves fed Pb during the last 2 wk of the experiment. The kidneys of the calves supplemented with lead were 34% larger than those of controls. The total endogenous 75Se in the feces over the 4-d collection period was not different between treatments (4.14% of dose versus 3.31% of dose). Likewise, urinary 75Se excretion values were similar. About 97% of the 75Se dose disappeared from the blood within 6 h after dosing four calves on both treatments. Tissue concentrations of 75Se were reduced in kidney, spleen, pancreas, brain, and spinal cord. In summary, ingested Pb had very little effect on the endogenous excretion of 75Se in urine and feces; therefore, the data are consistent with earlier research in which the main effect of Pb on Se occurs at the absorption site.

Effects of dietary aluminum and phosphorus on magnesium metabolism in dairy calves.

The metabolism of Mg was studied in young dairy calves fed two levels of added Al (0 and .20% Al) and two levels of added P (0 and .22% P) for 7 wk. The four treatments were 1) normal P-low Al, 2) low P-low Al, 3) normal P-high Al and 4) low P-high Al. The basal diet (low P-low Al) contained, by analysis, .132% P, .021% Al and .17% Mg. Added Al did not affect (P greater than .10) serum Mg. An Al x P interaction on bone Mg was detected (P less than .01). Magnesium was reduced in tibia shaft (.34 vs .44%) and in tibia joint (.43 vs .53%) in calves fed high Al in the presence of normal dietary P, but Mg was not reduced in the calves fed low-P diets. Apparent absorption of Mg was reduced by approximately five-fold (.18 g/d vs -.84 g/d, P less than .01); urinary Mg excretion was reduced 31% (1.12 g/d vs .77 g/d, P less than .01); and Mg retention declined 41% (-95 g/d vs -1.61 g/d, P less than .01) in calves fed added A1. Compared with calves fed low-P diets, calves fed normal levels of P had a higher Mg concentration in tibia shaft (P less than .01) and tibia joint (P less than .05). The data indicate that supplemental Al may adversely affect Mg metabolism in calves.

Influence of high dietary aluminum on performance and phosphorus bioavailability in dairy calves.

Sixteen male intact Holstein calves averaging 72 kg and 64 d of age were used to study the effects of high dietary Al on calf performance and P bioavailability. The main effects were two concentrations of added aluminum (0 and .20% Al) and two of added P (0 and .22% P). The basal diet contained, by analysis, .132% P, .74% Ca, and .021% Al. The calves were assigned to four treatment groups balanced according to body weight. The four treatments were 1) normal P, low Al; 2) low P, low Al; 3) low P, high Al; and 4) normal P, high Al. Calved had ad libitum access to their respective diets for 7 wk. Metabolism of a single oral 32P dose was determined during wk 6. The adverse effects of high dietary Al include a 17% reduction in feed intake and a 47% reduction in body weight gains. Alkaline phosphatase and plasma glutamic oxaloacetate transaminase activities increased in calves receiving the high Al diets. A negative balance of P and Ca was noted in the calves fed high concentrations of Al. Apparent absorption of 32P was reduced (37%) in calved fed diets high in Al (44% of dose vs. 69%). Urinary excretion of 32P was not affected by dietary Al concentrations. Calves fed the low P (deficient) diet showed significant reductions in feed intake, weight gain, serum inorganic P, bone ash, and P content of bone. Dietary P did not significantly affect 32P absorption. Adding .20% dietary Al severely affects P metabolism and performance of young growing calves.

Long-term feeding of high zinc sulfate diets to lactating and gestating dairy cows.

Thirty dairy cows, fed a control diet consisting of silage and concentrates, were given either 0, 1000, or 2000 ppm of supplemental Zn (DM basis), from zinc sulfate monohydrate (ZnSO4.H2O) for most of a lactation. Feeding 2000 ppm Zn decreased milk yield and feed intake after several weeks. Some cows were affected more severely than others. Generally, primiparous animals were more tolerant of the high Zn diet than multiparous cows. Milk Zn was materially higher for cows fed 1000 ppm added Zn than controls. With 2000 ppm Zn, milk Zn was elevated further but returned to control values when the high Zn diet was discontinued. Plasma Zn was higher in cows fed supplemental Zn with the increase from 1000 to 2000 greater than that for the first addition. Plasma Cu was lower in cows feed 2000 ppm Zn but milk Cu was not reduced. Milk fat content was not affected, but protein and SNF were reduced by the 12th wk with the 2000 ppm Zn diet. There was no apparent effect on long-term health or performance after the cows were removed from the 2000 ppm Zn diet. Except for lower calf weights with 2000 ppm Zn, reproductive performance was not measurably affected by the dietary treatments. The 1000 ppm added Zn diet had no adverse effect on the cows in any parameter measured.

Influence of a wide range of calcium intakes on tissue distribution of macroelements and microelements in dairy calves.

Sixteen intact male Holstein calves averaging 86 kg and 63 d of age were assigned randomly to four treatment groups. The four treatment diets contained .17, .67, 1.31, and 2.35% Ca on an as-fed basis. The resulting Ca:P ratios with P held constant at about .34% were .47:1, 1.92:1, 3.83:1, and 7.20:1. Calves were fed diets at 3% of their body weights for 4 wk. Magnesium in the bone ash and serum was lowered by the 2.35% Ca treatment. Serum inorganic P was also reduced by the highest Ca diet during the last 2 wk of the experiment. Liver had the highest concentration of Zn in calves fed .67% Ca, and the muscle from calves fed 1.31% Ca diet had the lowest amount of Zn. Copper was reduced in pancreas for 1.31% Ca diet, but Ca was highest in the muscle and heart at the .67% Ca treatment. Weight gains and feed efficiencies were not affected by Ca. Fecal pH was different among treatments and increased as Ca intake increased. Young growing dairy calves can adapt to a wide range of Ca intakes and Ca:P ratios and maintain a moderate growth rate for 4 wk. It appears that excessive dietary Ca may affect concentrations of Zn, Fe, Cu, and Mn in some body tissues, but the magnitude of the effect is relatively small.

Metabolism of manganese in calves as affected by dietary manganese and intravenous or duodenal manganese-54 dosing.

Fifteen intact male Holstein calves averaging 101 d of age were utilized to determine the effects of dietary Mn concentration and routes of administration on its metabolism. They were fed a practical grain diet containing 23 ppm Mn with 0, 100, or 1000 ppm supplemental Mn (MnSO4.H2O) for 7 d prior to intravenous or duodenal dosing with 54Mn. Animals were killed 4 h later. With added Mn there was a significant decrease in 54Mn content of some small intestine parts. However, in most tissue, including organs, bones, intestinal tract tissues, and blood, added Mn did not have a significant effect on 54Mn concentrations. Concentrations of 54Mn in tissues, except in small intestine, were far higher following intravenous dosing than with duodenal dosing. This further confirms that absorption of Mn is very low. Dosing method had a sizable effect on the relative amounts of 54Mn in different tissues. This suggests that intravenously administered Mn, at least initially, is not metabolized in the same way as that absorbed. In most tissues, unlabeled Mn was not affected greatly by supplemental Mn. This is in contrast to earlier results with very young calves and indicates that Mn metabolism changes sharply before 3 to 4 mo of calf age.

Bioavailability of phosphorus from defluorinated and dicalcium phosphates and phosphorus requirement of calves.

Bioavailability of P from defluorinated phosphate and dicalcium phosphate and the P requirement were studied with 63 male Holstein calves. A P depletion diet containing .08% total P on a dry matter basis was fed to all animals for 4 wk beginning at 6 wk of age and 61 kg weight. Calves developed typical signs of P deficiency. The depletion period was followed by a 6-wk experimental period in which the same depletion diet was used as a control. Phosphorus from each of the two sources was added to make diets containing .14, .20, and .32% total P. Source of supplemental P did not affect weight gains, feed consumption, feed efficiency, serum inorganic P, serum alkaline phosphatase, or bone ash.

Effects of varying the amounts of dietary calcium on selenium metabolism in dairy calves.

Influence of dietary Ca on Se metabolism was studied with 16 intact male Holstein calves averaging 86 kg. Calves were assigned randomly and fed one of four diets containing, .17, .67, 1.31, and 2.35% Ca at 3% of their body weight for 4 wk. The diets contained .062 ppm Se and .34% P. Four days prior to the end of the experiment, calves were dosed orally with radioactive 75Se. Dietary Ca had no significant effect on 75Se absorption. There was a slight curvilinear relationship between apparent 75Se absorption and dietary Ca intakes. Urinary excretion of 75Se and stable Se tended to decrease with increasing dietary Ca, but differences were not significant. No significant differences were found in concentration of 75Se in several tissues. Kidney and liver had the highest concentration with that in kidney being about four times that of liver. Apparent 75Se absorption was decreased 10 to 6%, respectively, in calves fed extremely low and high amounts of Ca, compared with those receiving the requirement (.67% Ca). These small reductions along with a small R2 suggest that dietary Ca probably is of little practical importance relative to Se metabolism in calves.

Effect of added dietary cobalt on metabolism and distribution of radioactive selenium and stable minerals.

Retention of 75Se following a single oral dose and stable Co, Cu, Zn, and Mg were determined in tissues of calves fed a diet containing 0, 10, or 40 ppm supplemental Co for 21 d. Concentrations of 75Se in tissue were numerically higher with 10 ppm Co than with the other two diets, but the effect was significant only in small intestine tissues of calves fed 40 ppm Co. Dietary Co did not affect fecal 75Se. Average total fecal 75Se excretion was 53, 48, and 51% of the dose over 6 d in calves fed 0, 10, and 40 ppm added Co. Concentrations of Co in tissues increased with increased supplementation. Dietary Co did not significantly affect growth, feed intake, tissue Zn, tissue Cu, blood hemoglobin, packed cell volume, plasma alkaline phosphatase, or plasma glutamic oxaloacetic transaminase. Magnesium in heart and skeletal muscle was increased in calves fed 40 ppm Co. Although high amounts of added dietary Co had some influence on metabolism of Se, the magnitude and extent of the effects appeared to be too small to be of practical concern.

Influence of high dietary lead on selenium metabolism in dairy calves.

Metabolism of orally dosed 75Se was studied in 10 intact male Holstein calves that were fed ad libitum a control diet containing no added Pb or supplemented with 1000 ppm Pb as PbSO4 for 4 wk. Lead-supplemented calves did not exhibit any clinical signs of Pb toxicity. Voluntary feed intake was reduced by 9.5% and average daily gain by 23%. Lead content of rib, liver, and kidney increased. Serum glutamic oxaloacetate transaminase activity was increased during the last 2 wk of the experiment in calves fed Pb. In calves receiving supplemental Pb, 75Se absorption, blood concentration, and urine concentration were reduced by 26, 21, and 42%, respectively. Tissue 75Se concentrations were significantly lower in kidney, liver, testicle, pancreas, small intestine, heart, spinal cord, and muscle in calves fed Pb. There was a significant negative correlation (r = -.78) between 75Se and stable Pb concentrations in the liver. It is not clear whether the ingestion of subclinical amounts of Pb could affect the absorption and utilization of Se in dairy calves to the extent of Se deficiency when dairy calves are kept in areas known to be low in Se.

Effect of calcium and fat intake on calcium metabolism in calves.

Ten male Holstein calves were fed diets with or without 5% added animal fat in combination with low and high dietary calcium (.15 or .98%) for 4 wk. After 3 wk, the animals were orally dosed with calcium-45. One week later they were killed and tissue samples taken. Except for lower calcium-45 in bile, added dietary fat had no marked influence on calcium metabolism. Net absorption of calcium-45 (not excreted in feces) ranged from 82% for calves fed low calcium to 53% for those given high calcium. Calcium-45 in bone was substantially higher in calves fed .15% calcium. Tailbone biopsies revealed rapid uptake of calcium-45 with approximately as much incorporated during the 1st d as in the following 6 d. Calcium-45 in blood peaked 24 h following dosing. Calves fed .15% calcium had higher calcium-45 in blood and bile than those receiving .98% calcium. Calcium-45 values in soft tissue were low and did not differ materially among treatments. The decreases in radioactive calcium absorption and bone deposition with higher dietary calcium indicated that variable absorption was a major factor in calcium homeostasis. Added fat did not materially effect calcium metabolism with either low or high dietary calcium.

Influence of high dietary iron as ferrous carbonate and ferrous sulfate on iron metabolism in young calves.

Twelve intact male Holstein calves averaging 90 kg and 12 wk of age were fed one of three dietary treatments for 28 d. The diets were A) control, B) control plus 1000 ppm iron as ferrous carbonate, and C) control plus 1000 ppm iron as ferrous sulfate monohydrate. Calves were dosed orally on d 15 of the treatment period with 1 mCi of iron-59. Neither source of added iron had a significant effect on weight gains, feed consumption, hemoglobin, packed cell volume, serum total iron, serum total iron-binding capacity, unbound iron-binding capacity, serum copper, tissue copper, fecal dry matter, or a consistent effect on fecal pH. The ferrous carbonate had no significant effect on stable zinc or stable iron in any tissue studied. Calves fed ferrous sulfate had higher average stable iron in most tissues and significantly more in the small intestine. Tissue zinc was lower in spleen and pancreas of ferrous sulfate-fed calves. Both sources of added iron sharply reduced iron-59 in serum, whole blood, and body tissues. The reduction was substantially greater in calves fed the ferrous sulfate iron. Iron in ferrous sulfate had a higher biological availability than that in the ferrous carbonate; however, bioavailability of the ferrous carbonate iron appeared to be substantial and considerably more than that noted in previous studies in which a different source of ferrous carbonate was used. The maximum safe level of dietary iron is materially influenced by the source of iron with a higher tolerance indicated for ferrous carbonated than ferrous sulfate monohydrate.

The effect of low to normal dietary phosphorus levels on zinc metabolism and tissue distribution in calves.

Sixteen 10-wk-old, phosphorus (P)-depleted Holstein bull calves were fed for 6 wk a control diet containing .08% P or P-supplemented diets containing .14, .20 or .32% P with supplemental P from two sources (CDP and Dynafos). The diets contained .45, .56, .66 and .87% Ca. After 5 wk of the experiment, the calves were dosed orally with 65Zn, and daily total fecal collections were initiated. At the end of the experimental period, the calves were killed and tissue samples were taken for total Zn and 65Zn analyses. Growth, feed intake and feed efficiency improved with increasing dietary P levels. Level of dietary P and Ca had little or no effect (P greater than .05) on total Zn content of rib, tibia, liver, heart, kidney, muscle or blood. Likewise, 65Zn absorption and content in most tissues were not affected (P greater than .05). The results do not preclude the possibility of some minor effects of P levels on Zn metabolism. However, it is apparent that when adequate Zn is fed, any effects are likely to be of little or no practical importance.

The effects of different levels of dietary lead on zinc metabolism in dairy calves.

The effects of feeding diets containing 500 or 1500 ppm added lead as lead sulfate on zinc and zinc-65 metabolism in Holstein bull calves were investigated. Zinc absorption was slightly (not significantly) reduced in the calves fed lead. Fecal zinc excretion was increased by the lead diets by day 24 of the experiment. Dietary lead had no significant effect on zinc in blood. Except for the tibia, muscle, and brain, stable zinc decreased in all tissues of calves fed the 1500 ppm lead diets, and differences were significant in pancreas, heart, and testicle. A significant decrease was noted in pancreatic zinc in pancreas of calves fed 500 ppm lead. Tissue zinc-65 concentrations were decreased significantly by lead in the tibia and muscle. Intestinal tissue zinc was not affected materially by lead. Dietary lead had very little effect on cellular distribution of zinc in the liver and kidney. In the mucosal cells of the small intestine, lead increased zinc-65 in the cytosol while decreasing it in the crude nuclear fraction. This effect occurred in a linear fashion in all three sections of the small intestine as dietary lead increased.

Effects of dietary aflatoxin and zinc on enzymes and other blood constituents in dairy calves.

Young male Holstein calves were fed diets containing 40 or 640 ppm zinc with 0 or 5 ppm aflatoxin for 3 wk. The aflatoxin mixture contained 80.5% B1 and the calves consumed 143 mg of B1 over 3 wk. Plasma glutamic-oxaloacetic transaminase and alkaline phosphatase concentrations were increased substantially, and lactic dehydrogenase was reduced in aflatoxin-fed calves. Supplemental zinc partially counteracted the effect of aflatoxin on these enzymes. Hemoglobin, packed cell volume, and total solids in blood plasma were increased in aflatoxin-fed calves, but high dietary zinc had no effect on these blood constituents. Glucose in plasma was reduced in calves receiving aflatoxin. High dietary zinc was only partially effective in protecting against the reduced glucose effect for about 1 wk. Total protein, albumin, globulin, ratio of albumin/globulin in blood plasma, and liver lipid were not affected by aflatoxin. Several enzymes and blood constituents are affected by aflatoxin in calves. The protection of zinc against aflatoxicosis appears to be no more than a partial effect.

Clinical aspects of experimentally induced chloride deficiency in Holstein calves.

A severe total body chloride deficit was induced in Holstein calves by feeding a low-chloride ration (0.063% Cl) and removing digesta daily from the abomasum through a surgically implanted cannula. Clinical signs of the deficit observed included polydipsia, polyuria, dehydration, anorexia, scleral injection, decreased respiratory rate, and blood and mucus in the feces. Necropsy findings included dehydration, blood in the lumen of the small intestine, and renal lesions. The most extensive histopathologic changes occurred in the renal tubular epithelium of the outer medulla where mineralization of the tubular epithelium and basement membranes was frequently seen.

Effects of high but nontoxic dietary manganese and iron on their metabolism by calves.

Sixteen male Holstein calves were fed one of four diets for 18 days in an experiment consisting of 0 and 1000 ppm supplemental manganese and 0 and 1000 ppm added iron as manganese carbonate and ferrous carbonate. The control diet contained 55 ppm manganese and 220 ppm iron. All calves were dosed orally 48 h prior to sacrifice with 500 muCi of manganese-54. Small intestinal iron was less in calves fed a high manganese diet, a possible interaction of these two elements at the absorption site. Feeding a high manganese diet tended to decrease iron (total) concentrations in liver and pancreas. When the high manganese diet was supplemented with additional iron, antagonistic effects of manganese on iron were eliminated. Neither iron nor manganese concentrations in tissues were affected by an increase of dietary iron. Manganese-54 content of tissue was reduced by the high manganese diet but was not affected by dietary iron. Total manganese and iron in feces fairly closely reflected dietary intake of each element with no evidence of interaction. Calves fed the high iron diet excreted less manganese-54 in their feces over 2 days. Total iron in blood serum was not affected significantly by the dietary treatments.