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Biomedical subjects

R A Bellows

Publications and source records attributed to R A Bellows.

At least 55 records · Page 3Linked to original sources
PubMed1983

Growth and reproductive traits in beef heifers implanted with zeranol.

Weaned replacement heifers were implanted with zeranol at 8 and 11 mo of age in two trials to evaluate growth and reproductive traits. Approximately 100 beef heifers were used in each trial, and the heifers were divided into categories of heavier than average (H) and lighter than average (L) weaning weight. Weight categories were further divided into control (HC and LC) and zeranol-implanted (HI and LI) groups. Heifers were kept in drylot from weaning to just before the start of the breeding season and were fed to reach a predetermined body weight by the start of the breeding season and were fed to reach a predetermined body weight by the start of the breeding season. Rates of gain in the drylot were greater in implanted than in control heifers in both trial 1 (.53 vs .48 kg/d; P less than .09) and trial 2 (.70 vs .63 kg/d; P less than .01). Pelvic areas were greater (P less than .01) in implanted than in control heifers of both trial 1 (175 vs 159 cm2) and trial 2 (175 vs 164 cm2). This increase in pelvic size was still present at the end of the summer pasture period, which followed the drylot period. Zeranol had no major effect (P greater than .10) on age of weight at puberty. Fall pregnancy rate was 16% lower in implanted heifers than in control heifers in trial 1 (62 vs 78%, P = .08) but did not differ in trial 2 (88 vs 87%, I and C, respectively).

Animals↗
PubMed1981

Effects of caesarean section, retained placenta and vaginal or uterine prolapse on subsequent fertility in beef cattle.

Data collected at the Livestock and Range Research Station, Miles City, Montana, on 13,296 calving from the years 1963 through 1977 were used to evaluate subsequent reproductive performance of dams experiencing caesarean section, retained placenta or vaginal or uterine prolapse. A total of 121 caesarean sections (.9% of all calvings) was performed from 1963 through 1977, with the highest incidence reported among first-calf 2- and 3-year-old dams. Fall pregnancy rate among the 105 dams that had caesarean deliveries was 52.4%, which was 26.6% lower (p less than .01) than the herd average. Fetal membranes were retained after 49 natural parturitions. Pregnancy rates among dams retaining fetal membranes were not significantly altered (82.2 vs 79.4%). A total of 153 calvings was associated with prolapse of the reproductive tract, including 124 (81.0%) vaginal prolapses and 29 (19.0%) uterine prolapses. Subsequent pregnancy rate of all dams experiencing prolapse was lower (p less than .01) than the herd average. Pregnancy rates following prolapse among primiparous and multiparous dams were 28.0 and 57.9%, respectively. These data indicate that caesarean section and vaginal or uterine prolapse result in significant reductions in subsequent pregnancy rates of affected dams, with no detrimental effect on dams retaining fetal membranes.

Animals↗
PubMed1979

Steroid levels after intramuscular injection of radioactive estradiol-17beta, estrone, progesterone and testosterone in the bovine.

Eight 2 year old Hereford cows from days 8 to 12 of the estrous cycle were injected intramuscularly with 5 ml of corn oil containing 5 mg of estradiol-17beta (two cows), estrone (two cows), progesterone (two cows) or testosterone (two cows). Each cow treated with estradiol received 494 microc of estradiol-17beta-6, 7 H3 and each cow treated with estrone received 492 microc of estrone-6, 7 H3. Each cow treated with progesterone or testosterone received 400 muc of H3 compound labeled in the 7 position. Total urine was collected by urethral catheterization of the cows treated with estrogens. Blood samples for plasma and serum were collected via jugular cannulae. Blood and urine samples from estrogen-treated cows were collected hourly for the first 24 hr, at 2 hr intervals for the next 26 hr, at 4 hr intervals for the next 12 hr and at 12 hr intervals until background was reached. Blood samples were collected hourly from 1 to 8 hr after injection from progesterone or testosterone-treated cows. Plasma and serum levels of radioactive estradiol-17beta, estrone, progesterone and testosterone were similar. Blood levels of radioactivity peaked at 2 hr post-injection in cows receiving estradiol-17beta and at 3 hr in cows receiving estrone. Blood levels of labeled estradiol-17beta and estrone were nondetectable by 54 hr and 83 hr, respectively. Peak urinary excretion of radioactivity was reached at 7 hr for estradiol-17beta and at 14 hr for estrone and nondetectable levels were reached by 95 hr for estradiol-17beta and 14 hr for estrone. At these times, 15.5% of the total dose of radioactive estradiol-17beta and 17.5% of the injected estrone had been excreted in the urine. Peak blood and urinary excretion levels were reached earlier for radioactive estradiol-17beta than for estrone, and excretion of estradiol-17beta was completed more rapidly. No difference was found in plasma and serum levels for any steroid studies; thus, endogenous steroid titers in blood plasma and serum are not different in the cow.

Journal Article↗
PubMed1979

Effect of mating stimuli on LH release in bulls.

Fourteen crossbred beef bulls were assigned at random to receive one of four sexual stimuli treatments. Treatments consisted of: (1) controls (four bulls), no visual or physical contact with any cows; (2) false mount (two bulls), allowed to mount an estrual cow; (3) mated (four bulls), allowed to mount an estrual cow with intromission and ejaculation; (4) electroejaculated (four bulls), no exposure to cows. Serum from blood samples taken at 15-min intervals from -15 min to 2 hr from sexual stimuli were radioimmunoassayed for luteinizing hormone (LH). Four bulls had elevated levels at the pretreatment bleeding, but none of the stimuli induced or were associated with LH releases. Basal levels of LH were consistent within bulls but varied considerably among bulls. Conclusion is that stimuli associated with mating do not cause a release of LH.

Journal Article↗
PubMed1979

Multiple linear and nonlinear regression analyses of factors causing calving difficulty.

Calving difficulty (CD) was analyzed as the dependent variable from observations on 592 first-calf, 2-year-old heifers that were either Angus X Hereford (AH), Charolais X AH or Simmental X AH. Independent variables were birth weight (BW), pelvic area (PA), BW.(33), PA.(5), cow weight (CW), cow condition score (CS) and sex of calf (S). CD was analyzed as score (1 = no difficulty through 4 = extreme difficulty) CD-I, % CD (1 vs 2 + 3 + 4 , CD-II) or % high CD (1 + 2 vs 3 + 4 , CD-III). R(2) values from CD-II and CD-III multiple correlation (R) analyses were consistently lower (.10 to .13) than from the CD-I analysis. When only BW and PA were included in the model, R(2) values for CD-I were .36, .39 and .39 for the linear, quadratic and cubic analyses, respectively. When BW, PA, CW, CS and S were included in the model, the R(2) values for CD-I were .40 and .42 for the linear and quadratic analyses (cubic effects were not tested). In the linear analysis with BW.(33) and PA.(5), the R(2) for CD-I was .36. In all analyses, the order of importance of the factors studied was BW and PA, with a much lower contribution from CW and S. CS did not account for a significant increase in R(2) in any analysis. CD remained below 50% whenever the PA BW ratio exceeded 8.4. This ratio is a convenient practical method to relate PA and BW to CD. Conclusions are that the linear effects of BW and PA account for the majority of the identified variation in CD (R(2)) and that small increases in R(2) can be obtained by adding CW, CS and S to the model and/or by expanding the model to include quadratic effects.

Journal Article↗
PubMed1975

Effects of organic phosphate systemic insecticides on bovine embryonic survival and development.

Experiments were conducted to determine effects of 2 organic phosphate systemic insecticides on embryonic survival and possible teratogenesis in cattle. A total of 726 heifers at 3 locations were treated with either crufomate (4-tert-butyl-2-chlorophenyl methyl methylphos-phoramidate) or coumaphos (O,O-diethyl O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl) phosphorothioate). The compounds were administered to pregnant bovine females at various stages of gestation by pouring along the dorsal midline. None of the treatments, including those at recommended one-time doses, one-time doses at double or triple the recommended dose levels, or doses at recommended one-time dose levels repeated each day for 10 days, gave evidence of increasing embryonic death rates or of teratogenic effects. In one experiment, the crufomate compound had apparent erratic effects on serum ace5ylcholinesterase activities, but no effects on electrocardiographic patterns, heart rate, or respiration rate. Rectal palpation for pregnancy determination during the 35- to 44-day stages of pregnancy is discussed as a possible, but unsubstantiated, cause of congenital malformation of the caudal portion of the intestinal tract in 1 calf born during these studies and in other calves previously observed.

Abnormalities, Drug-Induced↗