Biomedical subjects

A C Hammond

Publications and source records attributed to A C Hammond.

At least 55 records · Page 3Linked to original sources

PubMed1991

Endocrine characteristics of a miniature condition in Brahman cattle: circulating concentrations of some growth-related hormones.

Four miniature Brahman calves born in 1988 and 1989, along with four contemporary sex-matched Brahman control calves, were used in experiments to determine circulating concentrations of insulin-like growth factor I (IGF-I), growth hormone (GH), insulin, triiodothyronine, and thyroxine, and plasma glucose response to insulin challenge. The effect of plane of nutrition on plasma concentrations of IGF-I and insulin was also determined and a clinical screen of blood chemistries was conducted to determine effects of calf type. Plasma IGF-I was six times higher in control calves compared with miniature calves (209.0 vs 35.0 ng/ml; P = 0.001). However, miniature calves had mean plasma GH about six times higher (37.8 vs 6.2 ng/ml; P = 0.004) and had twice as many secretory episodes (9 vs 4.5; P = 0.005) over an 8-hr sampling period. Plasma concentrations of triiodothyronine (2.54 vs 1.80 ng/ml) and thyroxine (88.8 vs 56.2 ng/ml) were higher in control compared with miniature calves (P = 0.001), but concentrations of triiodothyronine and thyroxine in both calf types were within normal ranges. Although miniature calves displayed similar plasma glucose concentrations to controls, hypoglycemic response to insulin challenge tended to be greater in miniature calves. Nutritional regulation of circulating IGF-I appeared to be intact in miniature as well as control calves, as evidenced by a reduction in plasma IGF-I concentration following a decrease in plane of nutrition, and a subsequent increase in plasma IGF-I concentration following realimentation. Serum urea nitrogen was lower (P = 0.02) in control compared with miniature calves. These data describe a miniature condition in Brahman cattle that is manifested by apparently normal proportioned growth but small stature, and that is associated most notably with abnormally low circulating concentrations of IGF-I in the presence of paradoxically high circulating concentrations of GH. This condition appears to be similar to Laron dwarfism in humans, in which the low IGF-I is caused by an abnormality in the GH receptor.

Animals↗

PubMed1990

Effects of winter nutrition and summer pasture or a feedlot diet on plasma insulin-like growth factor I (IGF-I) and the relationship between circulating concentrations of IGF-I and thyroid hormones in steers.

Effects of two winter nutritional levels (LOW, MOD) and two summer pastures (bahiagrass, BG; perennial peanut, PP) on plasma IGF-I, and the relationship between IGF-I and average daily gain (ADG), thyroid hormones, plasma urea, packed cell volume (PCV) and steer type were determined in 101 steers (217 kg) varying in breed composition, frame size and initial condition. Relationships between body composition or composition of gain and IGF-I were determined in 11 contemporary steers assigned directly to the feedlot. Initial IGF-I (57.9 +/- 3.5 ng/ml) was positively correlated (P less than .05) to initial condition, estimated percentage of Brahman and plasma T3, but not related to subsequent ADG. During the 126-day wintering period, ADG was .21 kg for the LOW winter treatment and .47 kg for the MOD winter treatment. Concentration of IGF-I in the wintering period was affected (P less than .01) by nutritional level (LOW = 71.8 ng/ml, MOD = 150.6 ng/ml) and was positively related to winter ADG in MOD steers (P less than .01) but not in LOW steers. Concentration of IGF-I in winter was also positively related to condition at the end of the winter period (P less than .01), T3 (P less than .05) and T4 (P less than .05). There were no effects of winter treatment on IGF-I during the subsequent summer pasture period. During the 145-d summer period, ADG was .53 kg for BG and .68 kg for PP. Concentration of IGF-I during the summer period was affected (P less than .05) by pasture treatment (BG = 138.6 ng/ml, PP = 181.9 ng/ml), was positively related (P less than .01) to PCV and percentage of Brahman, and was negatively related (P less than .05) to estimated percentage of English breeding. In steers assigned directly to the feedlot, IGF-I was correlated with empty body (EB) weight (r = -.59, P less than .10), EB water (r = -.59, P less than .10) and EB protein (r = -.60, P less than .10) at slaughter, and with days on feed (r = -.65, P less than .05), but was not correlated with ADG or rate of component gain. These data indicate that IGF-I is related to nutritional status in steers as in other species, that there may be significant breed or cattle type differences in circulating concentrations of IGF-I, and that circulating concentration of IGF-I may be functionally related to plasma concentration of thyroid hormones.

Animal Feed↗

PubMed1990

Plasma and tissue concentrations and molecular forms of somatostatin in calves infected with Sarcocystis cruzi.

The effects of parasitic infection on plasma and tissue content of immunoreactive somatostatin (SRIF) were studied in 4-mo old male calves inoculated with the protozoan Sarcocystis cruzi. Because feed intake significantly decreased (70%) in infected calves around day 28 postinfection (pi), concomitant with the asexual replication of S. cruzi and outward expression of clinical signs, the relative contributions of infection and associated reduction in nutrition on plasma SRIF were evaluated. Treatment groups were: noninfected ad libitum fed (C), infected (250,000 S. cruzi oocysts per os) ad libitum fed (I) and noninfected calves pairfed to the level of intake of each infected calf (PF). Mean plasma concentrations of SRIF (pg/ml) on day 30 pi were: C, 224 +/- 22; I, 742 +/- 150; PF, 246 +/- 31 (effect of infection P less than .05). In another study, SRIF was measured in plasma and in pancreatic, duodenal, jejunal and ileal tissue extracts from normal and S. cruzi infected calves. Plasma and tissue samples were collected on day 42 pi. Mean plasma SRIF were 2.5 times higher in infected than control calves. Plasma insulin and insulin-like growth factor 1 was lower in infected v control calves (P less than .02). Plasma glucagon was similar between groups. Duodenal (P less than .05) and jejunal (P less than .02) SRIF content was higher in infected than control calves. Chromatography of tissue extracts on Sephadex G-50 revealed that the increase in SRIF was accounted for, in part, by molecular forms larger than cyclic SRIF-14. Data suggest that peripheral SRIF is increased in calves during S. cruzi infection. The increase in SRIF is not solely related to plane of nutrition. Altered levels of gut SRIF(s) may be associated with perturbed metabolic regulation in parasitized animals through direct effects on the gut.

Animals↗

PubMed1990

Evidence that bovine growth hormone treatment increases the rate of extrathyroidal 5'-monodeiodinase activity in cattle.

This study examined the influence of bovine growth hormone (bGH) on liver and kidney thyroxine-5'-monodeiodinase activity (TMA) in growing beef cattle. In a preliminary trial (trial 1), tissue samples were obtained at slaughter from two placebo-injected and two bGH-injected (29.2 IU/day for 14 days before slaughter) Hereford heifers (398 kg avg slaughter wt), with one heifer on each treatment fed at either 1.0 or 2.0 times maintenance energy requirement. In a second trial, tissue and plasma samples were obtained from six placebo-injected and six bGH-injected (29.2 IU/day for 19 days) Hereford steers (331 kg avg slaughter wt) fed at 1.8 times maintenance energy requirement. In a third trial, liver tissue and plasma samples were obtained from 14 Angus X Hereford steers (270 kg avg wt) fed either an 8% protein, 1.96 Mcal-metabolizable energy/kg diet (8 steers) or a 14% protein, 2.67 Mcal-metabolizable energy/kg diet (6 steers) in association with acute administration of bGH. Half the steers in each group were given two injections per steer of either placebo or 37.8 IU bGH at 24-hr intervals and slaughtered 24 hr after the second injection. Units of tissue TMA in all trials were measured at slaughter; one unit defined as 1 ng T3 generated/hr/mg protein during incubation with T4 (1.3 fM). In trial 1, TMA in liver and kidney was 2.86 and 1.21 times greater, respectively, for bGH than for placebo treatments. In trial 2, units of TMA in liver homogenates were higher (P less than .05) for bGH (4.14) than for placebo (2.83) treatments and higher (P less than .02) in liver microsomal preparations for bGH (32.7) than for placebo (27.3) treatments. Units of TMA in kidney homogenates were also higher (P less than .10) for bGH (1.48) than for placebo (.87) treatments and higher (P less than .02) in kidney microsomal preparations for bGH (23.0) than for placebo (16.4) treatments. Following acute injection of bGH (trial 3), units of TMA in liver homogenates were higher (P less than .01) for bGH (2.5) than for placebo (1.8) treatments. Plasma T4 (70.0 vs 73.5 ng/ml) and T3 (1.08 vs 1.18 ng/ml) concentrations appeared slightly higher in bGH-treated steers (trial 2) and increased by 20 and .5 ng/ml, respectively, (P less than .01) within 6 to 12 h after acute injection of bGH (trial 3). Concurrently, plasma TSH concentration increased following acute GH injection (trial 3).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1990

Detection of ruminal bacteria that degrade toxic dihydroxypyridine compounds produced from mimosine.

Leucaena leucocephala, a tropical leguminous shrub, contains a toxic amino acid, mimosine. Successful utilization of leucaena as a ruminant forage depends on colonization of the rumen by bacteria that degrade dihydroxypyridines (DHP), which are toxic intermediates in the metabolism of mimosine. Populations in the rumina of animals in some parts of the world, however, do not include bacteria that are able to carry out this degradation. We thus describe tests for the presence of DHP degraders in ruminal populations that are based on degradation (loss) of DHP compounds from culture media. Results obtained with the tests indicate that DHP degraders were not part of microbial populations in the rumina of cattle, sheep, and goats in Iowa, while most rumen samples examined from animals from the Virgin Islands and Haiti contained DHP degraders. These results confirm and extend the findings of others about geographic limits to the distribution of these important ruminal bacteria.

Animals↗

PubMed1990

Effects of intake level on metabolic response to estrogenic growth promoters in beef steers.

Effects of diethylstilbestrol (DES, 10 mg/d orally, Trial 1) or Synovex-S (SYN, 220 mg ear implant, Trial 2) on gain and N balance (g/d) were determined in steers that consumed 1.3, 2.7, 4.4 and 7.4 kg DM/d (Trial 1) and 1.3, 2.9, 4.3 and 6.6 kg DM/d (Trial 2). Each trial was a replicated 4 x 4 Latin square with four pairs of steers per trial (BW:322 kg, Trial 1; 278 kg Trial 2) and a control and growth promoter steer in each pair. Steers were fed a pelleted 75% concentrate diet containing 16.7% (DM basis). Each period consisted of 1 wk of intake adaptation, 5 wk of feeding and 1 wk in metabolism crates (2-d adjustment and 5-d collection). Steers were switched among DMI but not among promoter treatments. Intercept and slope, respectively, for the regression of BW gain (kg/d) on DMI (kg/d) were -.66 and .276 for control vs -.84 and .328 for DES steers and -.69 and .276 for control vs -.89 and .356 for SYN steers. Similar regression values for N balance (g/d) on DMI (kg/d) were -10.3 and 6.91 for control vs -17.2 and 9.10 for DES steers and -4.5 and 4.67 for control vs -7.6 and 5.85 for SYN steers. Across trials, slopes differed from zero (P less than .01), and promoter slopes differed from controls for gain (P less than .01) and N balance (P less than .10). During an extra period at the end of each trial, all steers were fed the high intake level for 6 wk, followed by N balance determinations the last 3 d of a 7-d fast.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1990

Prediction of body composition in Holstein steers using urea space.

Our objective was to evaluate urea space estimate of body composition in Holstein steers by examining prediction equations based on chemical composition and by comparison of these equations to those developed for beef steers. Urea space was determined in 38 Holstein steers ranging in full-fed live weight from 143 to 404 kg by the change in plasma urea N concentration before and 12 min after the midpoint of an intravenous infusion of 130 mg urea/kg live weight (20% solution in .9% saline). The relationship between empty body water (mean, 159.9 kg) and urea space in Holstein steers (Sy.x = 7.9 kg, R2 = .95) showed slope (.93) and intercept (20.6) similar to those of beef steers (.92 and 21.8). Predictions of empty body water, fat, and protein were slightly improved by including urea space in multiple regression equations with full-fed live weight over equations based on full-fed live weight alone. Predicted mean body protein in Holstein steers based on previous equations developed with beef steers was not different from chemically determined empty body protein. Beef steer equations underestimated mean empty body water (155.4 vs. 159.9 kg) and overestimated mean empty body fat (29.8 vs. 25.8 kg). These data suggest that urea space can be used to improve predictions of body composition on a mass basis in Holstein steers over that using of live weight measurements alone and that prediction equations may be different for different types of cattle.

Animals↗

PubMed1989

Tissue protein synthesis and nucleic acid concentrations in steers treated with somatotropin.

The effect of injection with bovine somatotropin (bST) on the fractional rate of protein synthesis (FSR) in tissues of beef steers was studied using a continuous infusion of [1-14C]leucine. Minimum and maximum FSR were calculated from free leucine specific radioactivity (SRA) in plasma or tissue homogenate respectively. Tissue nucleic acid concentrations were also quantified. Tissue samples were obtained from several muscles, sections of the small intestine and liver. In response to bST, both minimum and maximum FSR increased in muscle but not liver or intestinal tissues. Absolute synthesis rate increased in several muscles and small intestine tissues. Treatment with bST increased the relative SRA of protein-bound leucine in muscles compared with liver; increased the amount of protein synthesis per unit empty body-weight (EBW) in most muscles; and increased weight of small intestine relative to EBW, suggesting a differential response between liver and the other tissues measured. Compositional changes in response to bST occurred only in muscles. DNA concentration increased while protein:DNA decreased in the gastrocnemius muscle and RNA:DNA increased in the longissimus dorsi. The maximum percentage contribution of tissue protein synthesis to whole-body protein synthesis was 12.6, 25.7 and 20.5, and 13.0, 29.4 and 25.8 for liver, muscle, and small intestine in placebo-treated and bST-injected steers respectively.

Animals↗

PubMed1989

Nitrogen and protein metabolism and metabolites in plasma and urine of beef steers treated with somatotropin.

The objectives of this study were to determine the effects of daily injection of bovine somatotropin (bST) on the metabolism of N and 1-[14C]leucine and on hormone and metabolite concentrations in growing beef steers. Injection of bST increased N retention (P less than .05) primarily through decreased (P less than .10) urinary N excretion. Plasma concentration of somatotropin, insulin and glucose increased (P less than .01) and of urea-N (P less than .01) and alpha-amino-N (P less than .10) decreased with bST compared with excipient injection. Total leucine flux was not altered by treatment; however, the partition of flux was. Leucine oxidation decreased (P less than .05) and leucine used for protein synthesis (P less than .10) increased, with bST compared with excipient injection. During excipient injection, 10.3 g protein were synthesized for each gram crude protein deposited, whereas during bST injections only 6.4 g were required. The average maximum contribution of myofibrillar protein degradation to whole body protein degradation, calculated from excretion of 3-methylhistidine, was 16%. Although the ratio of protein deposition/protein synthesis was low for both excipient- and bST-injected steers, the incremental efficiency of protein deposition was 50%, reflecting a dilution of protein synthesis required for turnover and a proportionately greater increase in protein synthesis than protein degradation with bST injection. In growing beef steers, bST stimulated whole body protein synthesis and decreased leucine oxidation. The change in partition of leucine flux, but not of total flux (irreversible loss), demonstrates a chronic redirection in metabolism consistent with homeorhetic control. These data from steers injected with bST suggest mechanisms by which bST affects metabolism during normal growth.

Amino Acids↗

PubMed1989

Influence of diet on basal and growth hormone-stimulated plasma concentrations of IGF-I in beef cattle.

The effects of nutrition on plasma concentrations of insulin-like growth factor-I (IGF-I) were characterized in steers under basal conditions and following single i.m. injection of bovine growth hormone (bGH, .1 mg/kg BW). Nutritional effects on IGF-I were studied in three trials. In all trials steers were individually fed and penned Angus or Hereford x Angus (280 kg). In the first trial, two diets (LPLE1: 8% CP and 1.96 Mcal ME/kg, 4.5 kg.hd-1.d-1; MPHE1: 11% CP, 2.67 Mcal ME/kg, 6.5 kg.hd-1.d-1) were fed (n = 5/diet). Plasma IGF-I concentrations averaged 74 (LPLE1) and 152 (MPHE1) ng/ml (P less than .02). Following bGH injection, IGF-I increased to peak concentrations between 12 and 24 h (averaging 105 and 208 ng/ml at peak for LPLE and MPLE, respectively, P less than .01). In the second trial, steers were fed diets composed of 8, 11 or 14% CP and 1.96 or 2.67 Mcal ME/kg dry matter (6.35 kg.hd-1.d-1 in a factorial arrangement for 84 d, n = 4/diet). Within the low ME diet groups, plasma IGF-I was similar in steers fed 11 and 14% CP but greater at these two CP levels than in steers fed 8% CP (P less than .05). Within the high ME diet groups, plasma IGF-I increased linearly with CP (P less than .01). In the third trial, steers were fed diets to result in a negative N status. Insulin-like growth factor-I was lower (P less than .02) during feed restriction than when steers were full-fed. The IGF-I response to bGH was diminished or absent in underfed steers (P less than .01). These data are interpreted to suggest that diet composition and intake affect plasma concentrations of IGF-I in steers. In cattle, CP may be the primary nutritional determinant of basal IGF-I, but the IGF-I response to CP may be affected by the available ME. Undernutrition can attenuate the IGF-I response to GH and uncouple the regulation of IGF-I normally ascribed to GH.

Animals↗

PubMed1989

Prevention of leucaena toxicosis of cattle in Florida by ruminal inoculation with 3-hydroxy-4-(1H)-pyridone-degrading bacteria.

Ruminal microorganisms in cattle at a Florida agriculture research station did not have the ability to detoxify leucaena by degradation of 3-hydroxy-4(1H)-pyridone (3,4,-DHP), but a DHP isomer (2,3-DHP) was degraded in some cattle. Cattle with microorganisms that degraded 2,3-DHP were mostly Senepol cattle imported from St. Croix, US Virgin Islands, where leucaena is an indigenous species. Hereford cattle at the research station in Florida generally did not degrade 3,4-DHP or 2,3-DHP. An experiment was conducted in which a pure culture of 3,4-DHP-degrading bacteria was inoculated into Hereford cattle (with ruminal fistula) grazing leucaena. The bacteria successfully colonized the rumen of recipient cattle and persisted through the following winter when there was no leucaena in the diet.

Animals↗

PubMed1988

Influence of parasitism on plasma concentrations of growth hormone, somatomedin-C and somatomedin-binding proteins in calves.

A parasitic disease model (sarcocystosis) was used to study the effects of infection and associated plane of nutrition on GH and somatomedin-C (SM-C) patterns in plasma, and SM-C binding protein patterns in plasma from 4-month-old male Holstein calves. Calves, matched by age and rate of growth before the experiment, were divided into three treatment groups (n = 7). In the first (control), animals were uninfected and food was available ad libitum; in the second, animals were infected with Sarcocystis cruzi and food was available ad libitum. The third group consisted of uninfected animals pair-fed to the level of feed intake of the infected animals. Blood samples were obtained at various times after infection for analysis of the secretory patterns of GH (day 27 after infection, samples every 10 min for 6 h), SM-C (days 27, 35 and 58 after infection) or binding protein (day 42 after infection). Samples were analysed for GH and SM-C by radioimmunoassay. Relative molecular weights of binding proteins were assessed by elution patterns from gel permeation columns. Clinical signs of infection were manifest abruptly on day 26 after infection. Voluntary feed intakes of infected calves as a per cent of control calves were 18, 46 and 78 on days 27, 35 and 58 after infection respectively. Plasma GH concentrations were lower in infected and pair-fed than in control calves (P less than 0.05). Plasma SM-C concentrations were reduced in calves with diminished feed intakes and lower still in infected calves (P less than 0.05). Plasma SM-C was positively correlated with nitrogen retention across treatment groups (r = 0.81). Two classes of binding proteins differing in molecular weight were identified. The relative amounts of each binding protein in plasma were reduced during low feed intake with some differences in the endogenous saturation affected by infection. These data suggest that altered growth and metabolism in parasitized calves may arise in part from both nutritional and infection-mediated effects on the regulation of GH, SM-C and SM-C binding proteins.

Animals↗

PubMed1988

Prediction of empty body components in steers by urea dilution.

Empty body composition of 68 mixed-breed and 50 Angus steers was determined by chemical analysis of the right half-carcass and entire noncarcass fraction of each steer. Chemical composition was used to develop prediction equations for empty body protein (EBPRO) and fat (EBFAT) in steers using urea space (US) and body weight measurements. Previous research showed a significant positive correlation between empty body water (EBH2O) and urea space in these steers. For all steers studied, the percentage of EBH2O ranged from 44.8 to 69.2 (mean = 56.0), the percentage of EBPRO ranged from 14.1 to 19.8 (mean = 17.0) and the percentage of EBFAT ranged from 6.1 to 38.1 (mean = 22.1). The best predictions obtained were multiple regression equations with actual weight of body components as dependent variables and US and empty body weight (EB) as independent variables. Urea space alone was a poor predictor of EBFAT, but US improved predictions based on live weight (LW) or EB alone. Coefficients of determination for the best predictions of percentage of composition were not as high as coefficients of determination for the best predictions of actual weight of body components. These data suggest that US measurements can be used to predict empty body composition of live steers, but this may require repeated measurements and an independent estimate of EB from LW for greatest accuracy.

Adipose Tissue↗

PubMed1987

Absorption, plasma flux and oxidation of L-leucine in heifers at two levels of intake.

Four Hereford X Angus heifers (379 +/- 11 kg) with indwelling hepatic portal vein, iliac artery and mesenteric vein catheters were used in a switchback design to measure net portal absorption of leucine at two levels of energy intake, 130 and 260 kcal metabolizable energy.(kg.75.d)-1. Nine hourly measurements were made through two consecutive 4-h feeding periods on each heifer at each intake level. In separate experiments, N balance was determined and 6-h continuous infusions of L-[1-14C]-leucine were used to measure total plasma flux and oxidation of leucine with two of these heifers, one at each level of intake, and one additional Hereford heifer at both levels of intake. Net portal absorption of leucine increased with increasing intake from 5.4 to 12.4 mmol/h, and was associated with average leucine flux and oxidation rates of 30.7 and 4.7 mmol/h at low intake and 49.9 and 8.8 mmol/h at high intake. Protein synthesis (flux - oxidation) and protein accretion (N balance X 6.25) averaged 1,367 and 39 g/d at low intake and 2,156 and 219 g/d at high intake, respectively. Percent contributions of absorption and oxidation to total leucine flux were 17.6 and 15.3 at low intake and were 24.9 and 17.6 at high intake, respectively.

Absorption↗

PubMed1986

Effect of bovine growth hormone administration on metabolism of growing Hereford heifers: dietary digestibility, energy and nitrogen balance.

The objective was to determine the effect of daily s.c. injection of bovine growth hormone (bGH) on nitrogen and energy balance in six Hereford heifers. In addition, effects on urinary excretion of 3-methylhistidine and hydroxyproline and on serum mineral concentrations were monitored. A single reversal design was used with two 14-d injection periods of placebo or bGH (29.2 IU/d). Measurements were made on d 8-14 of each period. Injection of bGH did not alter apparent digestibility of dry matter, energy or nitrogen, nor urinary excretion of 3-methylhistidine or hydroxyproline. Serum concentrations of calcium, phosphorus and magnesium were normal with bGH treatment. Nitrogen retention was higher and urinary nitrogen excretion was lower when the heifers were injected with bGH than with the placebo demonstrating an effect of bGH on postabsorptive metabolism of nitrogen. Total energy balance was not altered by treatment. Energy retained as protein was higher after bGH treatment than after the placebo, implying decreased energy retained as fat and demonstrating a role for GH in altering energy partition in growing animals. Total heat production was not altered by treatment indicating no change in the gross efficiency of metabolizable energy use with bGH treatment.

Animal Feed↗

PubMed1986

Effect of bovine growth hormone administration on metabolism of growing Hereford heifers: protein and lipid metabolism and plasma concentrations of metabolites and hormones.

The objectives were to determine the effects of daily injection of bovine growth hormone (bGH) on the metabolism of [1-14C]leucine and [1-14C]palmitate and on hormone and metabolite concentrations in growing Hereford heifers. The experimental design was a 28-d single reversal with two 14-d injection periods of placebo or bGH. Energy intake was restricted to a level slightly above maintenance. Injection of bGH did not affect circulating concentrations of glucose, beta-hydroxybutyrate, urea nitrogen, prolactin, triiodothyronine or thyroxine. Plasma concentrations of insulin and nonesterified fatty acids (NEFA) were chronically elevated whereas leucine concentration was chronically decreased after 1 wk of bGH injection compared to placebo injection. Leucine oxidation was lower and whole-body protein synthesis was higher during bGH injection than during placebo injection. There were increases in both total irreversible loss and oxidation of NEFA during bGH injection compared to placebo injection. These results suggest mobilization of stored fatty acids and increased reliance on NEFA to provide energy for cellular processes. The dual and reciprocal effects of bGH on nitrogen and NEFA metabolism demonstrate its role as a homeorhetic regulator, affecting metabolism of several body tissues to support lean body accretion in Hereford heifers at near-maintenance intake of metabolizable energy.

Animals↗

PubMed1984

Estimation of empty body water in steers by urea dilution.

Urea dilution has been proposed as a practical method for estimating body composition in live cattle. The objectives of this study were to evaluate the urea dilution technique by comparing urea space to direct measurement of empty body water in steers and to develop prediction equations for empty body water in live steers using urea space parameters. Urea space was determined in 68 mixed-breed and 50 Angus steers ranging in live weight from 210 to 517 kg by the measurement of change in plasma urea nitrogen concentration before and 12 minutes after the midpoint of an intravenous infusion of 130 mg urea (20% solution w/v in 0.9% saline infused over 2 minutes) per kg live weight. Water in ground samples from carcass and digesta-free non-carcass fractions was determined by lyophilization. Linear relationships for pooled data of both groups of steers existed between empty body water and urea space (r = 0.96, P less than 0.001). Prediction of empty body water in live steers was improved by including live weight as an independent variable in a multiple regression equation (Sy X x = 7.2 kg for pooled data). Live weight alone predicted empty body water with a standard error of the estimate 36% larger than the multiple regression prediction using urea space and live weight.

Animals↗

PubMed1984

Effect of pH on in vitro ruminal conversion of L-tryptophan to 3-methylindole and indole.

Three in vitro experiments were conducted to determine the effects of pH on ruminal conversion of L-tryptophan (TRP) to 3-methylindole (3-MI) and indole (IND). Experiment 1 involved 2 closed-system incubations, each with triplicate replications of buffered ruminal fluid at initial pH of 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, and 8.0. Highest molar conversions of TRP to 3-MI were 61.5 +/- 2.7% and 64.3 +/- 0.8% at initial pH treatments of 7.5 and 7.0 (final pH 7.3 and 6.9) for the 2 incubations, respectively. Experiment 2 used duplicate continuous cultures at each of 4 pH treatments. Following a common 5-day pretreatment period, effluent pH averaged 5.6, 6.1, 6.5, and 6.9 for the respective treatments. Data for 4 subsequent 5-day time periods showed production of 3-MI was affected by pH treatment (P less than 0.01), time (P greater than 0.01), and treatment X time (P less than 0.01); conversion of TRP to 3-MI reached 78% at pH 6.9 and decreased to less than 1% at pH 5.6. Production of IND was not related to pH treatment (P greater than 0.10). Total moles of volatile fatty acid (VFA) carbon produced showed a pH treatment X time interaction (P less than 0.01) which reflected a trend toward decreasing VFA production at lower pH and increasing VFA production at higher pH. Experiment 3 consisted of 2 pH treatments with additional continuous culture fermenters.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗