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Biomedical subjects

J B McLaren

Publications and source records attributed to J B McLaren.

9 recordsLinked to original sources
PubMed1989

Effects of endophyte-infected fescue and cimetidine on respiration rates, rectal temperatures and hepatic mixed function oxidase activity as measured by hepatic antipyrine metabolism in sheep.

The effects of endophyte-infected fescue (Kentucky 31) hay and cimetidine on respiration rates, rectal temperatures and hepatic antipyrine uptakes of three mature ewes were measured in 15 experiments. Hepatic antipyrine uptake was measured as an indirect indicator of hepatic mixed-function oxidase (MFO) activity. Five experiments on each ewe were conducted during consumption of endophyte-free (one exp/ewe, control), endophyte-infected (two exp/ewe, EIF) and endophyte-infected fescue hay plus cimetidine (800 mg/d i.v., two exp/ewe, EIFC). Respiration rates increased (P less than .05) 2.6-fold after 11 d on EIF from 26 to 68 and decreased (P less than .025) to 27 breaths/min after 4 d of cimetidine treatment. Rectal temperatures increased (P less than .05) 1.1 degrees C after 8 d on EIF. Cimetidine lowered temperatures to control levels by d 4. Endophyte-infected fescue hay increased (P less than .05) hepatic antipyrine uptake 70% after 11 d, but uptake was lowered to control levels by cimetidine by d 4. Increased respiration rates and rectal temperatures in animals consuming EIF seem to be related to increased MFO activity. Cimetidine reversed some of these effects.

Alkaloids↗
PubMed1984

Influence of pretransit zeranol implant and receiving diet protein and urea levels on performance of yearling steers.

Two trials were conducted to determine the influence of preshipment zeranol implant and protein and urea levels of the feedlot receiving diet on the performance of yearling steers. In each trial, one-half of the steers were implanted with 36 mg of zeranol 30 d before shipment from El Reno, Oklahoma to Bushland, Texas. In trial 1, receiving diets were fed to 14 d and contained 10.6 (LP), 12.6 (MP), or 16.0% (HP) crude protein (DM basis). A fourth diet contained 10.8% protein with 7% of total N from urea (LPU). In trial 2, receiving diets were also fed for 14 d and contained 12.4 (MP) or 16.7 (HP) protein. Two other diets contained about 16% protein with either 15% HPMU) or 30% (HPHU) of total N from urea. After 14 d on the receiving diets, calves were fed a 70% concentrate intermediate diet for 7 d and were fed an 85% concentrate finishing diet until the end of both trials. Zeranol implants did not significantly affect marketing-transit weight changes, but increased (P less than .05) daily weight gains at all time periods in both trials. In trial 1 on d 14, steers fed the HP diet tended (P less than .10) to have faster gains and greater gain/feed than steers fed the LP and LPU diets, with steers fed the MP diet being intermediate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Effects of pretransit diets and post-transit potassium levels for feeder calves.

Two trails were conducted to study effects of K addition to receiving diets and the effects of feeding either a 55% concentrate diet or hay before shipment on the health, performance and blood chemistry of transported calves. One-hundred seven steer calves were used in trial 1 and 160 steer calves in trial 2. Postshipment diets for trial 1 contained .9 or 1.4% K and for trial 2 were .7, 1.3, 2.2 or 3.1% K. The preshipment diets were fed 3 d before shipment and the receiving diets were fed for 2 wk after feedlot arrival. Performance data were collected for 28 and 49 d for trials 1 and 2, respectively. Feeding a 55% concentrate diet before shipment significantly reduced mortality of transported calves. Potassium additions to the diet after arrival improved performance of transported calves. Upon arrival at the feedlot, calves fed the 55% concentrate diet preshipment had lower (P less than .05) plasma urea-nitrogen (PUN) values than calves fed hay preshipment. Blood packed cell volume (PCV) increased (P less than .05) as the receiving diet K level increased from .7 to 2.2%. The K recommended for transported calves was calculated to be 24.7 g/100 kg of body weight for the first 2 wk after arrival, 20% more than the requirement for nontransported calves.

Animals↗
PubMed1983

Occurrence of the Rumen Ciliate Oligoisotricha bubali in Domestic Cattle (Bos taurus).

Oligoisotricha bubali, previously observed twice in water buffalo, was detected in rumen contents of domestic cattle (Bos taurus) in two different areas of Tennessee. Concentrations ranged from <1 to 35% of the total protozoa in unweaned calves and up to 72% in older animals in feedlot. In contrast to the other genera of holotrichs, both total numbers and percent composition of O. bubali increased when animals were fed a corn silage-concentrate diet.

Journal Article↗
PubMed1982

Impact of numbers and frequency of weighings on bovine weight-age curve parameters.

Estimates of mature weight (A) and maturing rate (K), determined by asymptotic regression, were studied to evaluate the effects of using quarterly weights taken in different seasons of the year for estimating growth curve parameters. Quarterly weights of 102 Angus cows were used to calculate eight sets of weight-age curves. Four sets of estimates were calculated from weights from birth to 5 yr of age (FIVE-YEAR curves) and four sets were calculated from all weights collected throughout the life of each cow (LIFETIME curves). Within each age group, one set of parameters was estimated from all weights up to the respective ages (FIVE-YEAR and LIFETIME). The other three sets, within each age, were based on quarterly weights from birth to 1 yr of age plus one weight/year taken during the summer, fall or winter. The symbols A and K were used with the following subscripts: 0 or 5 as a first digit to represent weight-age parameters estimated from all weights taken during the life of the cow and from weights taken before the cow was 5 yr old, respectively; and 0, 2, 3, or 4 as a second digit to represent all quarterly weight, summer, fall or winter weights, respectively. Mean estimates of mature weight were 496, 492, 492, 522, 483, 478, 487 and 508 kg for A00, A02, A03, A04, A50, A52, A53, and A54, respectively. Season of weighing affected both A and K. Coefficients of correlation among the estimates of mature weights were all positive and larger than .70. Coefficients of correlation among estimates of rate of maturing were larger than .50, except those involving the correlation of K00 and FIVE-YEAR estimates. This study indicates that weight-age characteristics estimated from quarterly weights from birth to 1 yr of age and a single annual weight from 1 to 5 yr are adequate for estimating practical weight-age parameters at an early cow age. However, in FIVE-YEAR estimates, the effect of a cow's being nonpregnant at 2, 3 or 5 yr of age and, in LIFETIME estimates, any open year, especially the terminal year, may result in serious bias.

Aging↗
PubMed1969

Vaginal faradism.

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Electric Stimulation Therapy↗