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Biomedical subjects

R H Pritchard

Publications and source records attributed to R H Pritchard.

At least 19 recordsLinked to original sources
PubMed2006

Circulating ghrelin concentrations fluctuate relative to nutritional status and influence feeding behavior in cattle.

The objective of these experiments was to establish the relationship of plasma ghrelin concentrations with feed intake and hormones indicative of nutritional state of cattle. In Exp.1, 4 steers (BW 450 +/- 14.3 kg) were used in a crossover design to compare plasma ghrelin concentrations of feed-deprived steers with those of steers allowed to consume feed and to establish the relationship of plasma ghrelin concentrations with those of GH, insulin (INS), glucose (GLU), and NEFA. After adaptation to a once-daily feed offering (0800), 2 steers continued the once-daily feeding schedule (FED), whereas feed was withheld from the other 2 steers (FAST). Serial blood samples were collected via indwelling jugular catheter from times equivalent to 22 h through 48 h of feed deprivation. Average plasma ghrelin concentrations were greater (P < 0.001) in FAST compared with FED (690 and 123 +/- 6.5 pg/mL) steers. Average plasma ghrelin concentrations for FED steers prefeeding were elevated (P < 0.001) when compared with those postfeeding (174 and 102 +/- 4.2 pg/mL, respectively). Average plasma GH concentration was elevated (P < 0.05) for FAST steers compared with FED steers. Plasma GLU concentrations were not different; however, for FAST steers, NEFA concentrations were elevated (P < 0.001) and INS concentrations were decreased (P < 0.001). In Exp. 2, 4 steers (BW 416 +/- 17.2 kg) were used in a crossover design to determine the effects of i.v. injection of bovine ghrelin (bGR) on plasma GH, INS, GLU, and NEFA concentrations; length of time spent eating; and DMI. Steers were offered feed once daily (0800). Serial blood samples were collected from steers via indwelling jugular catheter. Saline or bGR was injected via jugular catheter at 1200 and 1400. A dosage of 0.08 microg/kg of BW bGR was used to achieve a plasma ghrelin concentration similar to the physiological concentration measured in a FAST steer in Exp. 1 (1,000 pg/mL). Injection of bGR resulted in elevated (P < 0.005) plasma GH concentrations after the 1200 but not the 1400 injection. Plasma INS, GLU, and NEFA concentrations were not affected by bGR injection. For the combined 1-h periods postinjection, length of time spent eating was greater (P = 0.02) and DMI tended to be increased (P = 0.06) for bGR steers. These data are consistent with the hypothesis that ghrelin serves as a metabolic signal for feed intake or energy balance in ruminants.

Animal Nutritional Physiological Phenomena↗
PubMed2005

The effect of stage of growth and implant exposure on performance and carcass composition in steers.

Angus and Angus x Limousin cross steers (n = 182; initial BW = 309 +/- 27.8 kg) were used to evaluate the influence of an estradiol-trenbolone acetate implant (containing 24 mg of estradiol and 125 mg of trenbolone acetate) on production efficiency and carcass traits when administered at specific stages of growth. Treatments were 1) control, no implant (NI); 2) early implant (EI) on d 1 (BW = 309 kg); or 3) delayed implant (DI) on d 57 (BW = 385 kg). Comparisons were also made between the NI and implanted treatments (I; EI + DI). Steers were procured at weaning and were backgrounded (47 d) before the initiation of the experiment. Initial predicted carcass composition was 14.9% protein, 13.3% fat, 54.6% moisture, and 17.2% bone. Days on feed were constant across treatment. After 56 d, ADG and G:F were improved (P < 0.01) by implants, NI vs. EI (1.68 vs. 1.90 kg and 0.227 vs. 0.257). At d 57, predicted carcass composition did not differ among treatments. From 57 to 112 d, DI caused higher ADG than NI or EI (NI = 1.65, EI = 1.57, and DI = 1.78 kg; P < 0.05) and higher G:F (NI = 0.155, EI = 0.150, and DI = 0.173; P < 0.01). Cumulative ADG and G:F were improved by implants (1.65 vs. 1.73 kg; P < 0.05) and (0.175 vs. 0.186; P < 0.01) for NI vs. I, respectively, with no differences between treatments that involved implants. Cumulative DMI was similar for all treatments. Implanting increased dressing percentage (63.5 vs. 64.1%; P < 0.05) and increased (P < 0.01) hot carcass weight (341 vs. 353 kg) and LM area (76.5 vs. 81.4 cm(2)) for NI vs. I, respectively. Rib fat and kidney, pelvic, and heart fat were not affected by treatment, and treatment had no effect on the whole carcass proportions of fat, protein, or water. Implants advanced maturity scores (NI = A(51) vs. EI + DI = A(59); P < 0.01). Marbling scores were decreased (P < 0.05) by EI but not by DI (NI = Small(65), EI = Small(20), DI = Small(36)). The percentage of i.m. fat content of the LM was decreased (P < 0.10) by EI and was not affected by DI (NI = 5.1, EI = 4.0, DI = 4.8%). Treatment affected (P < 0.10) the proportion of carcasses with marbling scores greater than Modest(0) (NI = 23.6, EI = 7.8, DI = 22.6%). The results of this study suggest that growth of i.m. fat is sensitive to anabolic growth promotants administered during early periods of growth.

Adipose Tissue↗
PubMed2004

The relationships among body weight, body composition, and intramuscular fat content in steers.

Angus steers of known age (265 +/- 17 d) and parentage were used in a 2-yr study (yr 1, n = 40; yr 2, n = 45) to evaluate the relationship between percentage of i.m. fat content of the longissimus dorsi at the 12th rib and carcass characteristics during growth of nonimplanted steers. Steers were sorted by age and EPD of paternal grandsire for marbling into high- and low-marbling groups so that steers with varying degrees of genetic potential for marbling were evenly distributed across slaughter groups. All steers were fed a 90% concentrate corn-based diet. Steers were allotted to five slaughter groups targeted to achieve hot carcass weights (HCW) of 204, 250, 295, 340, and 386 kg over the course of the feeding period. Data were analyzed as a completely random design with a factorial arrangement of treatments (year, marbling group, and slaughter group). Marbling group did not affect backfat, LM area, yield grade (YG), or marbling score. Regression equations were developed to quantify the change in carcass characteristics and composition over slaughter groups. Hot carcass weight increased in a linear fashion and differed (P < 0.01) among the slaughter groups as anticipated by design. Yield grade followed a quadratic upward pattern (P < 0.01) as HCW increased. Slaughter group affected the degree of marbling linearly (P < 0.01). There were no slaughter group x marbling group interactions, indicating that no differences occurred in the pattern of marbling attributable to paternal grandsire EPD. Carcasses expressed small degrees of marbling at 266 kg of HCW and obtained a YG of 3.0 at 291 kg of HCW. Fractional growth rates decelerated with increasing HCW. Greater advances in marbling relative to total carcass fatness occurred at HCW less than 300 kg. Management practices early in growth may influence final quality grade if compensatory i.m. fat content development does not occur.

Adipose Tissue↗
PubMed1997

Grain processing: effects on mixing, prehension, and other characteristics of feeds.

The primary objective of most grain processing of cattle diets is to increase starch availability. Evaluation of processing methods is usually based on ruminal or total tract starch disappearance and relative production rates (ADG, DMI, and gain: feed) demonstrated by cattle. Grain processing alters the mixing characteristics of grains and also influences steer preference for a grain and the manner in which grain is consumed. It is possible that mixing characteristics and selective eating influence production rates independent of starch availability when processed grains are fed. The magnitude of influence may depend upon the physical characteristics of other diet ingredients and feed intake. These relationships may work to improve or worsen production efficiencies. There is sufficient evidence to justify a closer evaluation of the influence of grain processing and feed ingredient combinations on mix quality, eating behavior, and true nutrient intakes of group-fed cattle.

Animals↗
PubMed1995

Effects of dietary virginiamycin on performance and liver abscess incidence in feedlot cattle.

The effects of dietary virginiamycin level on performance and liver abscesses in feedlot cattle were evaluated in seven dose-response studies. Steers and heifers were fed finishing diets ranging in energy content from 1.34 to 1.51 Mcal of NEg/kg of DM. In all studies, virginiamycin added to the diet improved average daily gain and(or) feed conversion, with no substantial effect on dry matter intake. Pooled analyses of four studies providing virginiamycin at 11.0, 19.3, and 27.6 mg/kg of DM in the complete diet indicated that growth and feed conversion were linearly improved (P < .05); feeding 19.3 mg/kg improved these measurements by 3.0 and 3.8%, respectively. Overall incidence (score 0 vs score 1, 2, and 3) and severity (score 0, 1, and 2 vs score 3) of liver abscesses were reduced (P < .01) by feeding virginiamycin at either 19.3 or 27.6 mg/kg. Linear plateau modeling indicated that the effective dose range for virginiamycin in feedlot diets (DM basis) was 19.3 to 27.3 mg/kg for increasing average daily gain, 13.2 to 19.3 mg/kg for improving feed conversion, and 16.5 to 19.3 mg/kg for reducing liver abscess incidence.

Animals↗
PubMed1992

Alternate day supplementation of corn stalk diets with soybean meal or corn gluten meal fed to ruminants.

Four experiments were conducted to determine the effect of adding corn gluten mean (CGM) or soybean meal (SBM) at 24- or 48-h intervals to diets based on corn stalks. In each experiment corn stalks was the primary diet ingredient fed to wethers or steers. Monensin was also fed to determine whether its effects on ruminal fermentation would improve the efficiency of N utilization under these conditions. Evaluation criteria included ruminal fermentation characteristics, DM intake and utilization, N balance in sheep, and steer feedlot performance. Ruminal ammonia nitrogen (NH3 N) concentrations measured over time were higher (P < .05) when diets contained SBM. Diet did not influence (P > .10) total VFA concentrations in ruminal fluid. Differences in diurnal shifts in ruminal NH3 N and total VFA due to protein source resulted in diet x hour interactions (P < .05). Dry matter intake response to protein source and frequency of supplement feeding was variable. Dry matter digestibility and nitrogen digestibility were not affected (P > .10) by protein source or feeding interval. The 48-h interval feeding of CGM was favorable compared with 24-h interval feeding (P < .05). The opposite response occurred with SBM, resulting in a diet x feeding interval interaction (P < .05). Nitrogen retention was greater (P < .05) when CGM was fed and with alternate day feeding. Diets that contained CGM supported higher (P < .05) ADG and gain/feed than diets that contained SBM when fed to steer calves. Alternate day feeding of supplements that contained monensin was detrimental to steer performance under the conditions of these experiments. Corn gluten meal is an effective substitute for SBM when alternate day protein supplementation is practiced.

Ammonia↗
PubMed1992

Feeding value of frost-damaged soybeans for lambs.

Three experiments were conducted to determine the relative feeding value of frost-damaged soybeans (FDS) for ruminants. Frost-damaged soybean ether-extract content was variable and differed (P less than .05) from mature soybeans. Isonitrogenous supplementation of corn silage diets with soybean meal (SBM), SBM+soybean oil (SBO), mature raw soybeans (MSB), and FDS was compared in sheep. Acid detergent fiber and apparent N digestion were lower (P less than .001) for supplements containing oil. Nitrogen retention was reduced (P less than .07) only for raw soybean supplements. Ruminal NH3 N and branched-chain VFA concentrations differed (P less than .01) between SBM and supplements containing oil. Maximum tolerable inclusion level of FDS in corn silage diets was tested in wethers using diets containing 0, 7, 14, or 21% FDS. Dry matter and ADF digestibility declined linearly (P less than .01) with increasing dietary FDS. Ether extract digestibility was unchanged due to treatment, but GE digestibility decreased quadratically (P less than .01). The most pronounced decline in GE digestibility occurred when FDS increased from 14 to 21% of the diet. The effects of FDS on corn silage utilization were similar to MSB effects. Oil content and antinutritional factors contributed to detrimental effects. Frost-damaged soybeans should not exceed 14% of corn silage diets fed to growing wethers.

Ammonia↗
PubMed1991

Effects of dietary ammonium chloride and variations in calcium to phosphorus ratio on silica urolithiasis in sheep.

Ammonium chloride was added to diets varying in Ca content to evaluate its potential in preventing silica urolith formation in sheep. A 2 x 2 factorial experiment involved wether lambs with ad libitum access to a diet of 50% grass hay and 50% ground oats plus supplement. The basal diet contained on a DM basis 3.3% SiO2, .31% Ca, .22% P, 11.6% CP, and 26% ADF. Treatments (38 to 39 lambs/treatment) consisted of a control (C), limestone to increase dietary calcium to .6% (L), 1% ammonium chloride (A), and L + A (LA). After a 118-d experimental period, siliceous kidney deposits were found only in C and L, with silica making up 93% to 95% of the urolithic ash. Urolith incidences were 13% (C) and 18% (L), respectively. The lack of urolith development in lambs fed A and LA (ammonium chloride effect, P less than .01) and a trend toward a lower urolith incidence in C vs L (P less than .02) support the hypothesis that acid-forming effects of the diet and a reduction in the dietary Ca to P ratio reduce silica urolith formation.

Ammonium Chloride↗
PubMed1991

Nitrogen utilization by ruminants during restricted intake of high-concentrate diets.

A series of experiments was conducted to determine the effects of limit-feeding high-concentrate (LFHC) diets on dietary CP requirements of steer calves. When steer calves were fed 80% concentrate diets at 78 g/kg of BW.75, increasing dietary CP resulted in increased ADG (P less than .001). Average daily gain was increased in steers as daily monensin dosage increased from 120 to 180 mg (P less than .05). Increasing the daily monensin dosage to 240 mg did not increase ADG further. There were no (P greater than .10) CP X monensin interactions, suggesting that the monensin response was caused by improved energy utilization and not be the possible protein-sparing effects of ionophores. Steer calves in the second feedyard experiment expressed similar ADG when provided equal NEg as limit-fed, high-moisture ear corn (HMEC) or when given ad libitum access to corn silage. The basal diet did not affect the steers' daily N requirement for growth. Gain per unit of protein intake declined quadratically (P less than .05) with increasing CP intake, indicating that CP requirements were near NRC estimates on both diets. The corn silage-based diet was less digestible (70.3 vs 77.4%; P less than .01) than the HMEC diet when fed to lambs. Fecal output differed (P less than .10) substantially (342 g/d of corn silage vs 205 g/d of HMEC), whereas fecal N output was only slightly higher (6.97 vs 6.34 g/d, respectively; P less than .10). Limited feeding of higher-concentrate diets to steer calves seemed to be an effective management procedure and did not cause acute digestion upset.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1990

Effects of preconditioning on pre- and post-shipment performance of feeder calves.

A preconditioning (PC) program that involved preweaning vaccination and preshipment weaning was evaluated utilizing 600 calves produced on four South Dakota ranches. Nonpreconditioned (NPC) controls were herd mates that were maintained with their dams during the preconditioning process. All calves were shipped from the ranch to the feedlot on the same date. In Exp. I, PC caused lower (P less than .001) preshipment gains. However, management x ranch and management x year effects indicated that response to PC was variable. Preconditioning reduced (P less than .001) transit shrink in Exp. I but caused greater (P less than .05) shrink in Exp. II. Ranch and management x ranch effects accounted for more of the variation in shrink than PC did. In the feedlot, PC calves consumed more feed initially (d 1 to 28; P less than .001) and during the entire (P less than .10) feeding period when fed to slaughter condition. During the 28-d postshipment period, calves fed higher-grain diets consumed more feed (P less than .001) and were less efficient (P less than .001) than calves fed corn silage. When fed for longer periods (greater than 28 d), higher-energy diets improved feedlot gains and feed efficiency independent of preconditioning. Health and performance responses to this preconditioning procedure were variable. Our preconditioning procedure did not improve beef production efficiency.

Animals↗
PubMed1990

High dietary calcium to phosphorus ratio and alkali-forming potential as factors promoting silica urolithiasis in sheep.

Sheep were used to study factors previously found to promote silica urolithiasis in a rat model. In addition to high silica, these dietary factors included elevated calcium, a high calcium to phosphorus ratio and alkali-forming effects. Wether lambs had ad libitum access to a diet of 50% of grass hay and 50% ground oats plus supplement. Diet analysis was 3.4% total SiO2, .29% calcium, .25% phosphorus, 11.3% CP and 28% ADF. Treatments (40 lambs/treatment) consisted of a control (C), limestone to increase dietary calcium to .6% (L), L + 1% sodium bicarbonate (LS) and L + 1% ammonium chloride (LA). After a 91-d experimental period followed by a 56-d postexperimental finishing period, silica kidney deposits were found in all treatments, and SiO2 made up 74% to 97% of the urolithic ash. Kidney urolith incidences in the four treatments were C, 7/40; L, 12/40; LS, 20/40; and LA, 9/40. A higher urolith incidence in LS (LS vs C, P less than .05) and a trend toward a higher incidence in L (L vs C, P less than .2), accompanied by elevated urine pH (L = LS greater than C greater than LA, P less than .01), lend support to the concept that high-silica diets having high calcium to phosphorus ratios and alkali-forming potentials contribute to silica urolithiasis.

Alkalies↗
PubMed1988

Heat stress in the presence of low RNA polymerase activity increases chromosome copy number of Escherichia coli.

A temperature shift-up accompanied by a reduction in RNA polymerase activity in Escherichia coli causes an increased rate of initiation leading to a 1.7- to 2.2-fold increase in chromosome copy number. A temperature shift-up without a reduction in polymerase activity induces only a transient non-scheduled initiation of chromosome replication caused by heat shock with no detectable effect on chromosome copy number.

Chromosomes, Bacterial↗
PubMed1986

Functioning of the F-plasmid origin of replication in an Escherichia coli K12 Hfr strain during exponential growth.

The pattern of chromosome replication in the Escherichia coli K12 Hfr strain KL99 was investigated during exponential growth by DNA-DNA hybridization. The levels of chromosomal markers close to the point of insertion of F (near pyrC) were raised in relation to other markers by comparison with the situation in an isogenic F- strain. The data are shown to be consistent with the proposal that the integrated F plasmid was regulating its copy number by a mass-titration mechanism.

Cell Division↗
PubMed1985

Feedlot performance and carcass characteristics of steers fed diets containing ammonium salts of the branched-chain fatty acids and valeric acid.

Two trials were conducted to study the effects of feeding a mixture of ammonium salts of isovaleric, 2-methylbutyric, isobutyric and valeric acids (AS-VFA) on feedlot performance and carcass characteristics of growing and finishing Angus, Hereford and Angus X Hereford steers. In trial 1,192 steers (8 steers/pen, 6 pen/treatment) averaging 251 kg body weight and in trial 2, 240 steers (8 steer/pen, 7 pens/treatment, 9 pens/control treatment) averaging 216 kg body weight were randomly assigned to four anhydrous ammonium salt-volatile fatty acid (AS-VFA) treatment levels: 0 (control), .14, .28 and .42% of the diet dry matter (DM). In each trial, the growing and finishing diets were isocaloric, isonitrogenous and supplemented with monensin (26 mg/kg diet). In both trials, steers received implants of 200 mg progesterone and 20 mg estradiol benzoate. Combined data from the trials confirmed the absence of average daily gain and feed conversion responses during the growing period. During the finishing period, the combined data for gain and feed conversion for the control steers and the steers fed .14, .28 and .42% AS-VFA were 1.43, 7.09; 1.43, 6.99; 1.48, 6.67 and 1.45, 6.80, respectively. Gains increased 3.5% (P less than .10) and feed conversion improved 5.9% (P less than .07) in steers fed .28% AS-VFA compared with gain and feed conversion of the control steers. At the end of the growing period in the first trial, a urea dilution technique was used to estimate the body composition of 12 steers from each treatment. Estimates of percent body fat and percent body protein were similar (P greater than .20) for all steers, irrespective of treatment. At the end of the trials, carcass yield grades for the combined data were 2.6 and 2.8 (P less than .10) for steers fed .28% AS-VFA and for the control steers, respectively. Carcass weight, dressing percentage and marbling score were lower (P less than .10) in steers fed AS-VFA than for steers fed the control. However, in general, carcass characteristics were not greatly influenced by AS-VFA. A possible use for a supplement containing branched-chain fatty acids and valeric acid in finishing steer diets is suggested by the improvement in feedlot performance and by the slight increase in carcass yield.

Animals↗
PubMed1980

Chloramphenicol releases a block in initiation of chromosome replication in a dnaA strain of Escherichia coli K12.

DNA-DNA hybridisation experiments show that chloramphenicol induces a burst of initiation from the oriC region of a dnaA46 mutant of Escherichia coli at 36.5 degrees C but not from the isogenic dnaA+ strain. Following this stimulation of initiation is in parallel with the induced stimulation of RNA synthesis caused by chloramphenicol in the same strain. This is consistent with the hypothesis that the stimulation of initiation in the dnaA mutant is the result of the stimulation of the synthesis of an RNA species.

Chloramphenicol↗
PubMed1979

Isolation and characterisation of a strain carrying a conditional lethal mutation in the cou gene of Escherichia coli K12.

A strain which carries a mutation conferring clorobiocin resistance and temperature sensitivity for growth was isolated from Escherichia coli K12. Genetic mapping and the molecular weight of the gene product suggest that the mutation is in the cou gene, specifying a sub-unit of DNA gyrase. Nuclear organisation and segregation and placement of septa are grossly abnormal in the mutant at 42 degrees C. RNA synthesis and initiation of DNA replication are also affected at the restrictive temperature but the rate of DNA chain elongation continues almost undisturbed.

Chromosome Mapping↗
PubMed1979

Location and characterisation of a new replication origin in the E. coli K12 chromosome.

A segment of DNA located in the region of the E. coli K12 chromosome previously identified by the Rac phenotype can function as a self-replicating plasmid. Evidence is presented that this plasmid, the oriJ plasmid, contains the origin of replication of a defective prophage postulated to be located in this chromosomal region by Low (1973). The plasmid can only be maintained in strains in which this postulated prophage has been deleted. In strains which possess the prophage selection for plasmid maintenance permits the isolation of clones containing new deletions which we postulate are the result of prophage excision.

Chromosome Mapping↗