Transient osteoporosis of the hip: review of the literature.

Transient osteoporosis of the hip (TOH) is a temporary clinical condition of unknown etiology which usually resolves with conservative therapy though may be complicated by fracture or progression to avascular necrosis (AVN). TOH may be slightly more prevalent in men but when it occurs in women, it is most often seen in the latter part of pregnancy. Though fracture is a rare complication of TOH when it occurs, it is most often associated with TOH occurring in pregnancy. Magnetic resonance imaging (MRI) is the best method to diagnosis TOH. Low signal intensity on T1-weighted images, high signal intensity on T2-weighted images, and homogenous pattern of edema (the femoral head and/or neck) with normal subchondral area are in favor of TOH. A shortened course to recovery is reported by use of bisphosphonates, calcitonin, or teriparatide. Based on reported cases, core decompression is not superior to medical therapy. Transient osteoporosis of the hip, which often has no known etiology, usually resolves with conservative therapy but may predispose the patient to fracture or avascular necrosis. Diagnostic method of choice is magnetic resonance imaging. Bisphosphonates, calcitonin, or teriparatide are reported as a useful approach to reduce duration of recovery.

Adrenal insufficiency after laparoscopic hysterectomy in a patient with primary antiphospholipid syndrome.

BACKGROUND: We report a case of bilateral adrenal hemorrhage and subsequent adrenal insufficiency after a laparoscopic hysterectomy in a patient with anticardiolipin antibody syndrome. CASE: A 55-year-old woman with a history of anticardiolipin antibody syndrome presented with nausea and vomiting 1 week after laparoscopic hysterectomy and staging for endometrial adenocarcinoma. Based on a diagnosis of adrenal insufficiency, the patient was started on oral hydrocortisone 20 mg in the morning and 10 mg in the afternoon, and fludrocortisone 0.05 mg twice daily on day 5. Her symptoms resolved completely within 24 hours of beginning steroids. CONCLUSION: The diagnosis of adrenal insufficiency should be entertained in any patient with a history of thrombophilias presenting with general abdominal complaints.

BILL E. KUNKLE INTERDISCIPLINARY BEEF SYMPOSIUM: Assessing the mineral supplementation needs in pasture-based beef operations in the Southeastern United States.

Macro- and microminerals are required for all physiological processes in beef cattle. When mineral deficiencies occur in pasture-based production systems, a multitude of deficiency symptoms may occur, and most often, these deficiencies result in hidden losses to include reduced production potential, reduced immunity, and reproductive failure. More severe deficiencies will result in specific deficiency symptoms, depending on the specific mineral deficiency. In pasture-based beef operations, specific deficiency symptoms are seldom observed. Forage mineral supply is highly variable and dependent on the forage type, stage of forage growth, and soil fertility. Grazing cattle mineral requirements change throughout the production cycle. With the variability of forage mineral supply and the changing mineral requirements, care must be taken when developing mineral supplementation programs for grazing cattle. The macrominerals function in nerve transmission, bone development, and metabolism and as electrolytes. These are Ca, P, Mg, Na, K, Cl, and S. The microminerals function in various areas of metabolism, immune responsiveness, reproductive efficiency, and many other functions. These minerals are Zn, Cu, Fe, I, Mn, Se, Mo, and Co. Of these macro- and microminerals, those that are important for supplementation to pasture-based cattle include Ca, P, Mg, Na, Cl, Zn, Cu, I, Mn, Se, and Co. However, the amounts to be supplemented will depend on the specific mineral requirements and the forage supply of the minerals. Consequently, the development of free-choice mineral supplementation programs is a moving target. Generally, this entangled mess is sorted by taking one mineral at a time into consideration. However, in doing so, one has to be cognizant of the many interactions that occur when changing intake of just 1 mineral in the supplement with respect to the amount supplied in the base forage. Often times, mineral nutrition problems of one or more minerals are created when trying to correct a deficiency of another mineral. This paper will address specific factors that are important to consider when developing and delivering mineral supplementation programs in pasture-based production systems in the Southeastern United States.

Computerized axial tomography in the diagnosis and management of thyroid and parathyroid disorders.

Computerized axial tomography (CAT) was used to study 39 patients with known thyroid disease and 14 patients with primary hyperparathyroidism. In all, CAT was performed only when information that was required for diagnosis or therapy was not available from other less expensive techniques. The greatest value was found in the evaluation of cryptic symptoms or structures in the neck after surgery for thyroid cancer, the assessment of the extent of thyroid cancer, the localization of aberrant thyroid tissue, the etiology of unexplained recurrent laryngeal nerve paralysis and the identification and delineation of mediastinal goiter. In six of 14 patients undergoing neck exploration for primary hyperparathyroidism CAT correctly localized the site of the enlarged parathyroid glands including one mediastinal parathyroid adenoma and one patient with two parathyroid adenomas.

Mineral and nitrogen balance in lambs implanted with zeranol.

Fourteen crossbred wether lambs (average BW, 28 kg +/- 2.3) were either implanted (12 mg of zeranol) or not implanted and group-fed an 86% concentrate diet for 21 d. Lambs were then moved to metabolism stalls and fed .8 kg/d for a 10-d stall adjustment followed by a 7-d total collection of feces and urine. Feed, feces and urine were analyzed for Ca, P, Mg, Zn, Mn, Cu, and N. Apparent absorption of Mn, Cu, and N, were similar for implanted and nonimplanted lambs. Zeranol did not affect (P > .10) the retention of Mn or Cu. Zeranol decreased fecal excretion of CA 22% (P < .01), P 27% (P < .05), Mg 11% (P < .03) and Zn 9% (P < .10). This increased apparent absorption of CA 88% (P < .01), P 193% ( P < .05), Mg 9% (P < .05) and Zn 45% (P < .10) in zeranol-treated lambs. Urinary excretion of all nutrients analyzed was similar for implanted and control lambs with the exception of N, which was reduced by 24% (P < .06) in implanted lambs. The amount of Ca, Mg, and Zn retained increased 98% (P < .01), 138% (P < .03), and 60% (P < .10), respectively, in implanted lambs compared with controls. These results indicate that zeranol improved N balance and enhanced the absorption and retention of Ca, P, Mg, and Zn in lambs.

Forage mineral concentration, animal performance, and mineral status of heifers grazing cereal pastures fertilized with sulfur.

Thirty yearling Santa Gertrudis-sired heifers (average initial weight 238 kg) were continuously grazed (five heifers/pasture) on six 2-ha oat-wheat small grain pastures for 112 d to determine the effect of fertilization of pastures with urea (U) vs ammonium sulfate (AS) on mineral status and performance of heifers. Pastures were fertilized with either U, at 200 kg/ha, or AS, at 438 kg/ha, to provide 92 kg of N/ha in November 1987 and March 1988. Ammonium sulfate provided 107 kg of S/ha. Forage samples were collected during each month. Heifers were initially weighed following an overnight fast and at the end of four consecutive 28-d intervals (Periods 1 to 4). Serum and ruminal fluid were collected on d 56 and 112. Pastures fertilized with AS had a greater (P less than .10) in vitro dry matter disappearance during Periods 2 and 3. Ammonium sulfate-fertilized pastures had greater than (P less than .05) S concentrations from January 29 through termination of the trial. There were no differences in ADG (P less than .28) or gain/ha (GPH; P less than .43) over 112 d; however, heifer ADG was greater (P less than .08) in Period 3 and tended to be greater (P less than .16) in Period 2 for those animals grazing U-fertilized pastures. Pastures receiving AS produced less (P less than .04) GPH during Period 2. Ammonium sulfate fertilization in this trial had no effect on forage K, Ca, P, Mg, Cu, or Mo mineral concentrations or on serum mineral and ruminal VFA concentrations, but it did result in an increase in IVDMD and a trend for decreased ADG apparently associated with a decrease in forage intake.

Alterations in metacarpal characteristics in steers and heifers sequentially implanted with Synovex from 45 days of birth.

Forty-two heifers and 38 steers sired by either Charolais (n = 47) or Salers (n = 33) from Bos indicus x Hereford dams were used to determine the effects of an anabolic agent on metacarpal characteristics and accompanying weight gain and carcass characteristics. Calves were blocked by sex and sire breed and either not implanted or implanted with Synovex-C within 45 d of birth, and with Synovex-S or -H at weaning and 84 and 169 d postweaning. Calves grazed oat pastures immediately after weaning for 169 d, after which calves received a feedlot diet for 124 d and were slaughtered. Live weight and hip height were recorded at initial implanting, weaning, d 84 and d 169 postweaning, and at approximately 28-d intervals during the feedlot period. Metacarpal and carcass characteristics were determined after slaughter. Metacarpals from implanted calves had greater medio-lateral axis (P < .01), cortical areas (P < .05), and cross-sectional areas (P < .05) and tended to have a greater breaking load (P < .08) than bones from nonimplanted calves. Implanted steers had shorter (P < .05) metacarpals than nonimplanted steers. Implanted calves had a greater (P < .05) ADG to weaning and over the postweaning grazing and feedlot periods than control calves. The implant did not alter backfat thickness but decreased (P < .05) percentage of kidney, pelvic, and heart fat and quality grade and tended (P < .07) to improve yield grade in heifers, but not in steers. Implanted calves tended (P < .08) to have a lower marbling score.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dietary potassium on absorption of magnesium and other macroelements in sheep fed different levels of magnesium.

Two metabolism trials were conducted with 24 crossbred wether lambs. Two levels of Mg (.1 and .2%) and four levels of K (.6, 1.2, 2.4 and 4.8%) were fed in a 2 x 4 factorial arrangement of treatments. Each trial consisted of a 10-d preliminary period followed by a 10-d collection of feed, feces and urine. Increasing levels of dietary K resulted in a linear increase in fecal Mg excretion and a linear decrease in Mg absorption. A large depression in Mg absorption occurred when K was increased from 1.2 to 2.4% with a further decrease when K was increased to 4.8%. Lambs fed the high level of Mg (.2%) absorbed and retained more (P less than .05) total Mg (g/d, but not percentage of intake) compared with the low magnesium level (.1%). Dietary Mg did not affect the amount of K excreted, absorbed or retained. Increasing the level of dietary K resulted in a linear increase in urinary, fecal and total K excreted, absorbed and retained (P less than .05).

Effect of potassium level on site of absorption of magnesium and other macroelements in sheep.

Eighteen wether lambs, surgically equipped with abomasal and ileal cannulae, were used in two metabolism trials. Two levels of dietary Mg (.1 and .2%) and three levels of K (.6, 2.4 and 4.8%, dry basis) were fed with a 2 x 3 factorial arrangement. Each trial consisted of a 10-d preliminary period, a 7-d collection of feed, feces and urine for determining mineral balance and a 6-d sampling of feed, abomasal and ileal fluid and feces to determine flow and site of mineral absorption. Magnesium absorption occurred before the small intestine. Feeding 2.4 and 4.8% K decreased (P less than .05) Mg absorption by 24.4 and 61.2%, respectively. Preintestinal absorption of Mg was depressed linearly with increases in dietary potassium. Larger amounts of Mg flowed to the small intestine and were excreted in the feces when the high level of Mg was fed. A net secretion of Mg into the small intestine followed by a small amount of Mg absorption in the large intestine was also found. Serum Mg was depressed 7 and 10% when diets containing 2.4 and 4.8% potassium were fed, respectively. Magnesium level did not affect K absorption or balance. Potassium absorption, retention and urinary excretion increased (P less than .05) with increasing K level. Animals fed the low K diet had a negative absorption of K preintestinally with the small intestine being the main site of absorption. Increasing K level resulted in approximately equal amounts of K being absorbed in the stomach and small intestine.

Absorption of magnesium and other macrominerals in sheep infused with potassium in different parts of the digestive tract.

Two metabolism trials were conducted with 12 crossbred wether lambs, each surgically equipped with a ruminal catheter and abomasal and ileal cannulae, to study the effect of K infusion in different sites of the digestive tract on site of absorption and flow of minerals. The treatments consisted of the infusion of 33.6, 12.0 or 12.0 g K/d as bicarbonate into either the rumen, abomasum or ileum, respectively. Each trial consisted of a minimum 5-d preliminary period, five 3-d collection periods to determine mineral balance and a 6-d sampling period to determine mineral flow and site of absorption. Chromic oxide was incorporated into the diet for use as a marker. Magnesium was absorbed primarily from the preintestinal region. Ruminal infusion of K tended to decrease preintestinal Mg absorption. Absorption of Mg in the entire tract was decreased (P less than .05) 43% when K was infused into the rumen. There was a slight absorption of Mg in the small intestine, followed by a net secretion into the large intestine. Serum Mg levels tended to be depressed in lambs infused with K intraruminally. Calcium flow from the preintestinal region was decreased (P less than .05) by infusion of K into the rumen. Only lambs infused with K in the rumen had a net secretion of Na into the small intestine. The large intestine was the primary site of net Na absorption for ruminal-infused lambs. Phosphorus flow from the preintestinal region was decreased (P less than .05) by infusion of K into the rumen. Potassium flow from both the preintestine and small intestine was increased (P less than .05) by ruminal K infusion. The infusion of K into the rumen, abomasum or ileum increased (P less than .05) the total absorption of K, with the small intestine being the major absorptive site. The infusion of potassium bicarbonate into the rumen of sheep raised (P less than .05) the pH of the ruminal contents 15%. Ruminal infusion of K depresses Mg absorption, while the infusion of K into the abomasum or ileum does not affect Mg absorption. Therefore, the role of K in grass tetany may be via this depression of Mg absorption.

Site of magnesium and other macromineral absorption in steers fed high levels of potassium.

Six Angus x Simmental steers, surgically equipped with abomasal and ileal cannulae, were used during three metabolism trials. Steers were blocked according to weight ad were allotted to three dietary K levels (.6, 2.4 and 4.8% dry basis) for each trial with the restriction that no animal would receive the same level during two successive trials. Each trial consisted of a 5-d transition, a 10-d preliminary period, a 7-d collection of feed, feces and urine and a 6-d sampling of feed, feces and abomasal and ileal fluid. Chromic oxide (.5%) was used as an indicator to measure flow through the digestive tract. Magnesium absorption decreased linearly (P less than .05) with increasing level of dietary K. The primary site of Mg absorption was the preintestinal region followed by a net secretion into the small intestine. Preintestinal Mg absorption was decreased 39% when 4.8% K was fed. Serum Mg was lower at high levels of dietary K. Potassium absorption increased linearly when expressed as g/d and curvilinearly when expressed as percentage of intake, with increasing levels of dietary K. When .6% K was fed, the primary site of K absorption was the small intestine, but with the high levels of K, the preintestinal region was also an important site of absorption. The effect of high K level on Mg absorption in steers was similar to that observed previously in sheep.

Effects of dietary monensin and potassium on apparent absorption of magnesium and other macroelements in sheep.

Twelve ruminally cannulated lambs (average weight, 31.1 kg) were used to determine the effects of monensin and K on apparent absorption of Mg in lambs. Lambs were assigned randomly to two groups and fed a basal high concentrate diet containing .44% K with or without 20 mg/kg monensin for 19 d of dietary adjustment. During adjustment, lambs were housed by treatment group and given ad libitum access to their diets. Following dietary adjustment, lambs were placed in individual metabolism stalls and fed 450 g of their respective diet twice daily. Within each monensin group, lambs were infused ruminally with 0, 7.6 or 31.6 g K/d (equal amounts at each feeding in 158 ml of distilled-deionized water) during three periods in a 3 X 3 Latin-square arrangement of K treatments. Each period consisted of a 10-d preliminary phase and a 7-d collection phase followed by a 3-d D2O infusion phase to determine water turnover. Addition of monensin to the diet decreased (P less than .05) fecal Mg excretion 15.9%. Apparent absorption and retention of Mg were increased (P less than .05) with the addition of monensin. Increasing K level increased (P less than .05) fecal Mg excretion. Apparent absorption of Mg decreased (P less than .05) from .93 to .80 g/d when either level of K was infused into the rumen. Monensin decreased the acetate:propionate (A:P) ratio. There was a significant interaction between monensin and K level for acetate and propionate (molar %), and A:P ratio. In the presence of higher K concentrations, monensin appears to be more effective in decreasing the A:P ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of animal breeds and breeding to overcome the incidence of grass tetany: a review.

British breeds of cattle are not so effective as Zebu in extracting nutrients from low-quality roughages, and these breeds differ in their nutrient metabolism and animal physiology. Breeds of cattle may differ in their requirements for Mg. Brahman cows are less susceptible to death from disease and metabolic disorders than are British breeds of cattle, whereas cows with 50% or greater dairy breeding (Holstein and Jersey) are more susceptible than British or Brahman breeds when maintained in beef production herds. Brahman or Brahman crossbred cows are less susceptible than other breeds to metabolic disorders such as grass tetany. Magnesium absorption has been shown to be greater in Brahman than in Jersey, Holstein and Hereford cows. These differences in the efficiency of Mg absorption between different breeds of cows may be due to genetic variation in the absorptive mechanisms of Mg, in feeding behavior, in gastrointestinal tract motility, in gastrointestinal tract fill or to some combination.

Effects of dietary gossypol consumption on metabolic homeostasis and reproductive endocrine function in beef heifers and cows.

Our objectives were to determine the effects of incremental increases in dietary gossypol on metabolic homeostasis and reproductive endocrine function in postpubertal beef heifers and the long-term effects of elevated dietary gossypol on various metabolic and reproductive endocrine characteristics in mature cows. In Exp. 1, heifers (n = 6/group) were fed either 0, .5, 2.5, 5, 10, or 20 g.animal-1 x d-1 of dietary free gossypol for 62 d. Erythrocyte membrane osmotic fragility was increased (P < .0001) in both the 10- and 20-g groups. Slight alterations in plasma concentrations of sorbitol dehydrogenase and K+ were also detected in the latter group. Treatment did not affect ADG, body condition scores, or concentrations of progesterone during the estrous cycle; however, mean concentrations of LH were higher (P < .001) in heifers fed 20 g/d of gossypol than in heifers in all other groups. In Exp. 2, lactating cows (n = 17) exhibiting regular estrous cycles were fed a control (no gossypol, n = 8) or high-gossypol (20 mg.kg BW-1 x d-1 free gossypol, n = 9) diet for 33 wk. Mean BW and body condition scores did not differ during the feeding period. Erythrocyte membrane fragility was greater (P < .05) in the high-gossypol than in the control group. Magnitude of the preovulatory LH surge, luteal phase concentrations of progesterone, follicular fluid concentrations of estradiol and progesterone, in vitro granulosa cell estradiol production, and 60-d pregnancy rates were similar between groups. The amounts of gossypol fed in these experiments are not likely to affect reproductive performance adversely in beef heifers or cows.

Influence of oscillating dietary crude protein concentration on performance, acid-base balance, and nitrogen excretion of steers.

Decreasing dietary N inputs into beef cattle feeding operations could potentially decrease environmental concerns relating to air and water quality. Previous studies with sheep suggest that oscillating dietary CP concentrations may improve N use efficiency and thereby decrease dietary N requirements. Therefore, two studies were conducted to determine the effects of oscillating dietary CP concentrations on performance, acid-base balance, and manure characteristics of steers fed high-concentrate diets. Steers were fed to a constant backfat thickness in both studies. In the first trial, 92 steers (mean BW = 408 +/- 2.8 kg; four pens/treatment) were fed the following diets: 1) constant 12% CP, 2) constant 14% CP, and 3) 10 and 14% CP oscillated at 2-d intervals. Steer performance and carcass characteristics were measured. In the second trial, 27 steers were individually fed the same three experimental dietary regimens (nine steers/treatment). Animal performance, arterial acid-base balance, plasma metabolites, and fecal characteristics were measured. In both trials, steers fed the 14% CP diet tended (P < 0.10) to have greater ADG and gain:feed than steers fed the 12% CP diet. Steers fed the oscillating CP regimen had intermediate performance. In Trial 1, steers fed the 14% CP diet tended (P = 0.09) to have smaller longissimus area and higher quality grades than steers fed the oscillating CP regimen. Protein retentions (g/d) calculated from NRC (2000) equations were greater (P = 0.04) for steers fed the 14% CP diet than steers fed the 12% CP diet. Steers fed the oscillating CP regimen tended (P = 0.08) to have greater calculated protein retention (g/d) than steers fed the 12% CP diet. Steers fed the 14% CP diet had greater (P < 0.05) calculated urinary N excretion than steers fed the 12% CP or oscillating CP regimens. Venous plasma concentrations of urea N were greater (P < 0.001) in steers fed the 14% CP diet than in steers fed the 12% CP diet; steers fed the oscillating CP regimen were intermediate but fluctuated over days. Based on arterial blood gas concentrations, acid-base balance was not significantly affected by dietary CP regimen. Results of these trials suggest that the CP requirement of steers in these studies was greater than 12% of the diet DM, and/or that the degradable CP requirement was greater than 6.3% of diet DM. However, the effects of oscillating dietary CP were minimal.

Influence of incremental zeranol implant doses on the chemical and physical characteristics of third metacarpal bone and chemical composition of liver and soft tissue from feedlot steers.

Chemical and physical characteristics of third metacarpal bones and liver and rib soft tissue composition from feedlot steers were determined. Steers were selected (32 from each experimental location) to represent the range in slaughter weight and composition for each treatment group in three (total n = 1,088) feedlot experiments. Steers were implanted with 0, 24, 36, 48, 60, 72, 84, or 96 mg of zeranol at approximately 140 d before slaughter. Cattle at each location were fed for the same number of days and slaughtered as a group. Zeranol dose had no effect on the chemical composition of bone, liver, or rib soft tissue with the following exceptions: zeranol decreased (P < .01) bone Ca concentration and increased (P < .07) liver P concentration. Zeranol implantation decreased medullary cavity anterioposterior (AP) diameters and AP cortical width (P < .08). Loads withstood by the bones up to flexure (P < .08) and the strain at flexure (P < .09) were inversely related to the quadratic of zeranol dose. However, modulus of elasticity at flexure and breaking increased numerically with zeranol dose. Stress withstood by bones at flexure was greater (P < .09) for implanted steers. Strain data indicate that metacarpals from steers receiving zeranol would exhibit less deformation upon loading to flexure (P < .09) than controls. These data indicate that administration of intermediate doses of zeranol altered bone deposition of Ca, which resulted in modified third metacarpal physical and mechanical characteristics.

Copper status of ewes fed increasing amounts of copper from copper sulfate or copper proteinate.

The Cu status of mature, crossbred ewes fed two sources (CuSO4 vs. Cu proteinate) and three levels (10, 20, or 30 mg/kg) of dietary Cu was determined in a 73-d feeding trial. Ewes (n = 30) were fed a basal diet containing rice meal feed, cottonseed hulls, cottonseed meal, meat and bone meal, cracked corn, and vitamin-mineral supplements at 2.5% of BW to meet NRC requirements for protein, energy, macrominerals, and microminerals, excluding Cu. The basal diet contained 5 mg/kg Cu, 113 mg/kg Fe, .1 mg/kg Mo, and .17% S. Copper sulfate or Cu proteinate was added to the basal diet to supply 10, 20, or 30 mg/kg of dietary copper in a 2x3 factorial arrangement of treatments. Ewes were housed in 3.7- x 9.1-m pens in an open-sided barn. Blood samples were collected on d 28 and 73. Ewes were slaughtered on d 74, and liver and other tissues were collected to determine Cu concentrations. An interaction (P = .08) occurred between source and level for liver Cu. The interaction existed due to an increase in liver Cu concentrations when ewes were fed increasing dietary Cu from CuSO4 but not when fed Cu proteinate diets. There was no source x level interaction (P>.10) for the blood constituents measured. On d 73, plasma ceruloplasmin activity was greater (P<.05) in ewes fed Cu proteinate than in those fed CuSO4 (33.1 vs. 26.8 microM x min(-1) x L(-1)). Increasing the concentration of dietary Cu did not affect (P>.10) plasma ceruloplasmin. Packed cell volume (PCV), red blood cell count (RBC), white blood cell count, whole blood hemoglobin (wHb), plasma hemoglobin, and plasma Cu were similar between sources of Cu. Ewes fed 20 mg/kg Cu had lower (P<.05) PCV, RBC, and wHb than those fed 10 or 30 mg/kg Cu diets. Feeding up to 30 mg/kg Cu from these sources did not cause an observable Cu toxicity during the 73-d period.

Physiological and hormonal responses of lambs repeatedly implanted with zeranol and provided two levels of feed intake.

Forty crossbred wethers (average weight 30 kg) were implanted with zeranol (12 mg) at 30-d intervals and fed at two levels of intake in a 2 x 2 factorial arrangement of treatments to determine performance, carcass and bone characteristics, blood metabolites, and hormones. Restricted lambs were fed to gain one-half the BW gained by lambs with ad libitum feed access. Lambs with ad libitum and restricted access to feed were slaughtered after 98 and 154 d, respectively. Zeranol increased ADG (P = .047; 20%), gain to feed (P = .023; 17%), metacarpal length (P = .004; 6%) and weight (P = .013; 13%), and tended to increase carcass crude protein gain (P = .106; 63%) while reducing kidney pelvic fat (P = .001; 33%) and dressing percentage (P = .038; 3%). Restricted feed intake increased the percentage of carcass ash and metacarpal length and weight by 27% (P = .048), 5% (P = .006), and 10% (P = .045), respectively, while reducing quality grade scores (P = .022; 5%), gain to feed (P = .001; 49%), longissimus muscle area (P = .001; 28%), the percentage of kidney pelvic fat (P = .033; 13%), and daily fat gain (P = .001; 54%). Zeranol increased pituitary weight (P = .001; 166%), plasma glucose (P = .036; 13%), mean serum growth hormone (GH; P = .011; 52%), baseline GH (P = .048; 34%), GH pulse amplitude (P = .003; 59%), and IGF-I (P = .001; 53%) concentrations. The results indicate that continuous administration of zeranol from 60 d of age to slaughter increases GH release, which directs nutrient utilization such that a carcass with more desirable lean and fat deposition patterns is obtained when nutrient availability is adequate.

Site and extent of apparent magnesium absorption by lambs fed different sources of magnesium.

Ten abomasally cannulated crossbred wether lambs (avg wt, 33 kg) were used in a replicated 5 x 5 latin square design to determine the site and extent of apparent absorption of Mg when fed different sources of Mg. Lambs were fed twice daily 220 g of chopped mixed grass hay and 180 g of a corn-based supplement (control; .13% mg, DM basis), or the control diet supplemented with Mg (.26% Mg, DM basis) from MgO, magnesium citrate (MgC), smectite-vermiculite (Mg-Mica) or MgOH. Lambs were maintained in metabolism stalls during each of the five experimental periods. Each period consisted of a 7-d dietary adjustment followed by a 3-d collection of abomasal samples, feces and urine. Abomasal contents were sampled four times daily during the 3-d collection period. The diet contained .5% chromium oxide as a digestion marker. Apparent absorption of Mg was .17, .55, .85, .78 and .82 g/d for lambs fed the control, MgO, MgC, Mg-Mica and MgOH diets, respectively. Apparent absorption of Mg (g/d) was similar (P greater than .05) in the lambs fed the supplemented diets and greater (P less than .05) than in those fed the control diet. Preintestinal absorption of Mg was .21, .57, 1.08, .14 and .92 g/d when the control, MgO, MgC, Mg-Mica and MgOH diets were fed. Lambs fed the control and Mg-Mica diets absorbed similar (P greater than .05) quantities of Mg in the preintestinal region and less (P less than .05) than lambs fed the MgO, MgC and MgOH diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of season on the maintenance requirements of mature beef cows.

Sixty mature, nonpregnant, nonlactating beef cows of two breed types, Angus and Simmental, were used in a four-period, split-plot study to determine the effects of season on maintenance requirements. Periods were chosen to represent each of the four seasons and ran consecutively from June 14, 1986 through June 20, 1987. All cows were fed at one of four feeding levels (75, 87.5, 112.5, and 125% of estimated ME required for maintenance) a cottonseed hull-based diet in each of the four seasons and were rotated such that all cows received all feeding levels during the study. Retained energy for all cows within periods was determined through changes in body composition determined initially and at the end of each period. Mean DM digestibility (DMD) was similar for both breeds (54.4%), and in both breeds DMD was similar in the summer, fall, and spring and lower (P less than .05) in the winter. Mean DE was 61.4% and also was similar between breeds. Season affected DE, which was greatest (P less than .05) for both breeds in the fall (62.5%). Simmental cows had a 16.1% greater (P less than .05) overall daily ME requirement for weight maintenance than Angus cows (123.5 vs 103.6 kcal/kg.75), and both breeds had greater (P less than .05) requirements during the summer and lower (P less than .05) requirements during the winter (122.6 vs 91.4 and 145.9 vs 109.3 kcal/kg.75 for Angus and Simmental cows, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)