Biomedical subjects

R E Short

Publications and source records attributed to R E Short.

At least 37 records · Page 2Linked to original sources

PubMed1997

Estrus and luteal function in suckled beef cows that were anestrous when treated with an intravaginal device containing progesterone with or without a subsequent injection of estradiol benzoate.

The objectives in this study were to determine whether treatment with progesterone (P4) via an intravaginal device would induce estrus and development of corpora lutea (CL) with typical life spans and whether treatment with estradiol benzoate (EB) following device removal would enhance the responses. At treatment initiation (d 0), suckled beef cows (n = 362) that were anestrous received one of the following: 1) an intravaginal device containing P4 for 7 d plus an injection of 1 mg of EB 24 to 30 h after device removal (P4+EB), 2) an intravaginal device containing P4 for 7 d (P4), 3) a sham device for 7 d plus an injection of 1 mg of EB 24 to 30 h after device removal (EB), or 4) a sham device for 7 d (control). Progesterone treatment increased the proportion of cows that formed CL with a typical lifespan (P < .001) and exhibited behavioral estrus (P < .05). Treatment with EB in combination with P4 increased (P < .001) the proportion of cows that exhibited estrus. Treatment with P4 alone had no effect, but the combination of P4 and EB increased (P < .01) the proportion of cows that formed short-lived or typical lifespan CL by the end of the experiment compared with untreated cows. In summary, treatment with P4 increased the incidence of estrus and the proportion of cows that formed CL with a typical lifespan. Treatment with P4 resulted in resumption of luteal function in suckled beef cows that were anestrous, with most cows developing CL with a typical lifespan, whereas EB enhanced the expression of estrus.

Administration, Intravaginal↗

PubMed1997

Body temperature and endocrine interactions before and after calving in beef cows.

Multiparous beef cows (n = 7) were used to evaluate peripartum changes and interactions among body temperature (BT) and circulating progesterone (P4), estradiol-17beta (E2), triiodothyronine (T3), cortisol, thyroxine (T4), and 13,14-dihydro-15-keto-prostaglandin F2alpha (PGFM) concentrations. Electronic temperature monitors were placed under the obliquus abdominis internus muscle of the left flank, and BT was measured using radiotelemetry every 3 min for 10-s periods from 144 h before to 24 h after calving. Environmental temperatures (ET) were recorded hourly. Body and environmental temperatures were averaged, separately, within 8-h periods. Blood samples were collected every 8 h, and hormone concentrations were measured. Time of day affected BT (P < .01), at 0300 cows had the lowest BT, at 1900 the highest, and at 1100 values were intermediate. Body temperature remained relatively constant (P > .10) from 144 to 56 h before calving and from 8 to 24 h after calving but decreased (P < .01) from 48 to 8 h before calving. Precalving BT was affected (P < .01) by ET, but hour-before-calving (time) had the greatest effect on BT during the 48 to 8 h immediately preceding parturition (b' = .41, P < .01) and was independent of ET effects. Before the BT decrease, cows gestating heifers had lower (P < .01) BT than cows gestating bulls. Plasma E2, PGFM, T3, and T4 concentrations before the precalving decrease in body temperature were greater (P < .03) in cows gestating bull rather than heifer calves. Approximately 30% of the variation (R2) during the temperature decrease was explained by plasma hormone concentrations; PGFM (b' = -.30, P < .05) and T3 (b' = -.22, P < .10) had the most significant effects. In conclusion, BT of the cow before the precalving decrease was affected by ET and sex of calf. However, the prepartum BT decrease was independent of these variables, and seemed partially endocrine-induced.

Animals↗

PubMed1996

Efficiency of production in cattle of two growth potentials on northern great plains rangelands during spring-summer grazing.

A study was conducted to evaluate the effect of sire growth potential, steer age, and cow size on intake, growth, and production efficiency in grazing cattle. Data were collected on 24 cow-calf pairs during each of four summers (1989 to 1992) and on 12, 7-mo-old and 12 yearling steers during three summers (1990 to 1992). Suckling calves and older steers were sired by either high-(Charolais with high EPD for yearling weight) or moderate-growth-potential (Line 1 Hereford with average yearling weight ratios) bulls. Cow size was defined by principal component scores developed from cow weights, condition scores, and hip heights. Forage, but not milk, OM intake by suckling calves was influenced (P < .05) by sire growth potential. Yearling high-growth-potential steers tended to consume more OM than yearling moderate growth potential steers (P < .10) when expressed as kilograms/day but not when expressed as grams/kilogram BW (P > .10). Seven-month-old steers ate less (P < .01) forage (4.3 kg/d) than yearlings (5.6 kg/d) when expressed as kilograms/day but more (P < .01) when expressed as grams/kilogram BW (7-mo-old, 15.9 vs yearling, 14.4 g/kg BW). Cow OM intake was affected by cow size and milk production but not calf growth potential. Milk production but not cow size was a significant covariate for cow efficiency (grams of calf BW gain/kilogram of forage OM intake by cow-calf pair). Calf sire growth potential did not affect cow efficiency. We conclude that growth potential of sire for suckling calves and steers and cow size for cows affected intake of rangeland forage in summer but did not affect efficiency of production from Northern Great Plains rangelands.

Analysis of Variance↗

PubMed1996

Acute and chronic changes in luteinizing hormone secretion and postpartum interval to estrus in first-calf suckled beef cows exposed continuously or intermittently to mature bulls.

The objective of this study was to determine whether patterns of LH secretion are acutely or chronically affected by the presence of mature bulls in postpartum first-calf suckled beef cows exposed to bulls either continuously or intermittently beginning on d 30 after birth. Crossbred cows were assigned randomly to be either continuously exposed to (BE; n = 20) or isolated from bulls (NE; n = 32) at calving, or exposed continuously (NEBE; n = 10) or intermittently (BEI; n = 21) to bulls beginning on d 30. The BEI cows were exposed to bulls for 2 h every 3rd d for 18 d. Ten cows from the NEBE, BEI, and NE treatments only were fitted with indwelling jugular catheters. Intensive blood sampling of NEBE and BEI cows began within 45 min after they were placed with bulls for 2 h on d 30, and for BEI cows on each d after 2 h exposure. Samples were collected at 15-min intervals for 6 h beginning on d 30 for NEBE, BEI, and NE cows; sampling continued at 3-d intervals until d 48. Samples were assayed for LH by RIA. Cows were observed twice daily (am:pm) for estrus. More (P = .07) BE and NEBE (75%) cows showed estrus by the end of the study than BEI and NE cows (48%). Interval to estrus was longer (P < .05) in BEI and NE cows (95.6 +/- 6.1 d) than in BE and NEBE cows (75.9 +/- 6.1 d). Baseline LH and amplitude and interpeak interval of LH peaks during the first 6 h after 2 h of bull exposure did not differ (P > .10) among treatments on d 30 after birth. However, mean LH and LH pulse frequency were higher (P = .06) for NEBE and BEI cows than in NE cows. Baseline LH and amplitude and duration of LH peaks did not differ (P > .10) over the seven sampling periods among NEBE, BEI, or NE cows. Mean LH and LH pulse frequency were higher (P < .05) in NEBE and BEI cows than in NE cows on each sampling period. Exposing first-calf suckled beef cows to bulls on d 30 after birth increased mean LH concentrations by increasing pulse frequency within a short period after a 2-h exposure. Thereafter, mean LH concentrations were higher in cows that were either continuously or intermittently exposed to bulls. Although mean LH and LH pulse frequency in NEBE and BEI cows were similar, intervals to estrus after bull exposure differed between treatments. The mechanism whereby bulls alter postpartum interval to estrus seems to involve other factors that may be related to but not directly linked with LH secretion.

Animals↗

PubMed1996

Ecosystems, sustainability, and animal agriculture.

The long-term sustainability of animal agriculture is examined in an ecological context. As an aid to defining agriculture, animal agriculture, and sustainable agriculture, a broad overview of the structural and functional aspects of ecosystems is presented. Energy output/cultural energy input ratios were then calculated for 11 beef cattle management systems as relative measures of their long-term sustainability. Energy output was estimated by direct conversion of whole body mass of steers to caloric values. Cultural energy inputs were estimated using published forage and cereal grain production budgets in combination with estimated organic matter intakes. Cultural energy inputs included raw materials, manufacturing, distribution, maintenance, and depreciation of all equipment and products used in a 250-animal cow-calf farm/ranch operation. Management systems evaluated included 1) spring calving with slaughter beginning at either weaning (age of calf approximately 6 mo) or after 84, 168, or 252 d in postweaning finishing lot; 2) spring calving with slaughter beginning at about 18 mo of age after either 0, 42, 84, or 126 d in finishing lot; and 3) fall calving with slaughter beginning at about 14 mo of age after either 63, 126, or 189 d in finishing lot. Estimated efficiencies were < 1.0 in all treatments, even when assumed marketed calf crop was 100%. Product energy output/cultural energy input ratios ranged from a high of .40 in the spring calving--stocker--126 d in finishing lot treatment to a low of .23 in the spring calving--slaughter at weaning treatment. The low levels of efficiency were found to be largely the result of the interaction effects of the high levels of cultural energy required to maintain a productive cow herd and grow and finish calves in the rather harsh environment of the Northern Great Plains. Results pointedly reveal the high level of dependency of the U.S. beef cattle industry on fossil fuels. These findings in turn bring into question the ecological and economic risks associated with the current technology driving North American animal agriculture.

Animal Feed↗

PubMed1996

Effects of time of weaning, supplement, and sire breed of calf during the fall grazing period on cow and calf performance.

A 4-yr experiment was conducted to determine effects of protein supplementation, age at weaning, and calf sire breed on cow and calf performance during fall grazing. Each year 48 pregnant, crossbred cows nursing steer calves (mean calving date = April 8) were assigned to a 2 x 2 x 2 factorial experiment replicated in three native range pastures. Treatment factors were: 1) no supplement (NS) or an individually fed supplement (S, 3 kg of a 34% protein supplement fed to cows every 3rd d); 2) calves weaned at the beginning (W, mid to late September) or at the end (NW, mid to late December) of the trial each year; or 3) calves sired by Hereford or Charolais bulls. Data were adjusted for cow size (initial hip height and initial and final weights and condition scores) by analyses of covariance using principal component coefficients as covariates. Change in cow weight and condition score were increased by S and W (P < .01), but these responses interacted and were not the same each year (yr x S, year x W, and year x S x W, P < .01). Forage intake was decreased (P < .1) by S and W. Total intake (forage+supplement) was not affected by S but was decreased by W (P < .1). Digestibility of OM was decreased by S (P < .01). Some carryover effects of treatments were observed the next spring in cow weight, condition score, and birth weight (NW decreased birth weight by 2 kg, P < .01), but there were no effects by the next fall on weaning weights or pregnancy rates. Milk yield decreased during the experimental period, and S maintained higher milk production in late lactation (P < .01). Calf ADG was increased by S and Charolais sires (P < .01). Efficiency (grams of output/ megacalorie of input) was not affected by sire breed but was enhanced by S (P < .01). Our conclusions are that 1) effects of feeding a 34% protein supplement to cows were to increase calf gains and improve persistency of lactation and efficiency; 2) delaying weaning decreased cow weight and condition score; 3) effects of weaning age and protein supplementation were highly dependent on forage and environmental conditions in any given year; and 4) whatever effects existed in a given year did not carry over to effects on next year's production as measured by pregnancy rates and weaning weights.

Aging↗

PubMed1995

The effect of estrus synchronization scheme, injection protocol and large ovarian follicle on response to superovulation in beef heifers.

Two trials were conducted to examine the effects of estrus synchronization scheme, gonadotropin injection protocol and presence of a large ovarian follicle on response to superstimulation of follicular development and the ensuing superovulation. Estrus was synchronized with either a progestin compound (MGA) or by the use of a luteolytic agent (PGF). Superstimulation was induced with 280 mg equivalents of pFSH administered either by a single subcutaneous injection or by a series of 8 intramuscular injections over 4 d. Follicular development was followed for 5 d with real-time ultrasound, and the heifers were retrospectively classified as to the presence or absence of a large follicle (> or = 8 mm; morphologically dominant follicle) at the start of superstimulation. The 2 trials differed by season of the year and genetic origin of the heifers. In Trial I (20 heifers), the ovulation rate was influenced by the 3-way interaction of the synchronization scheme, injection protocol and morphologically dominant follicle (P = 0.05). The number of large follicles on Day 5 (Day 0 = day of start of superstimulation) and ovarian score (scale 1 to 5 based on extent of follicular development; 1 = least, 5 = most) on Day 5 were significantly correlated (P < 0.05) with ovulation rate. In Trial II (20 heifers), the ovulation rate, number of embryos recovered, number of transferable embryos and ovarian weights were all greater (P < 0.05 to P < 0.01) with the 8-injection protocol than the 1-injection protocol. The number of medium follicles (5 to 7 mm) on Days 2 and 3, number of large follicles (> or = 8 mm) on Days 3, 4 and 5 and ovarian scores on Days 4 and 5 were all significantly correlated (P < 0.05) with ovulation rate. In both trials, differences in follicle populations were not seen until Day 3 of the superstimulation procedure. Collectively, these trials do not provide strong support for a single injection of FSH, as used here, nor does it indicate a clear advantage for either MGA or PGF as a means of enhancing the ovulation rate or embryo quality.

Journal Article↗

PubMed1995

Body composition and metabolic profiles associated with puberty in beef heifers.

Rapid growth large frame (RL, n = 61) or average growth medium frame (AM, n = 71) biotype heifers fed to achieve either moderate (MOD, .6 kg/d) or high ADG (HI, 1.0 kg/d) were used to determine whether puberty occurs at similar body composition or metabolic status. A heifer was considered pubertal after being detected in estrus and then forming a functional corpus luteum. Live animal estimates of body composition and blood samples for assessment of metabolic status were taken at 13 +/- .2 d after estrus for all heifers. Body composition and metabolic status were assessed every 56 d from 7 mo of age until puberty in a subset of 80 heifers representing all biotype-diet combinations. At puberty, 32 of these 80 heifers were slaughtered and physical and chemical composition of the empty body were determined. High-gain diet heifers were younger, heavier, taller, and more muscular (all P < .01) at puberty than MOD heifers. Slaughter measurements paralleled live animal estimates; bodies of HI and RL heifers contained more (P < .01) carcass and noncarcass components than those of MOD and AM heifers, respectively. Carcasses of RL and HI heifers were more (P < .05) muscular and fatter than AM and MOD heifers. At puberty, HI heifers had a greater (P < .01) mass of moisture, fat, and fat-free organic matter (FFOM) than MOD, whereas RL heifers had more moisture, ash, and FFOM than AM. Percentage of fat was greater (22.1 +/- 1.0 vs 1.0 vs 19.1 +/- 1.0; P < .05) and percentage of moisture was less (55.4 +/- .6 vs 58.1 +/- .6; P < .01) in bodies of HI than in those of MOD heifers. Concentrations of blood urea nitrogen and insulin were greater (P < .05) in HI than in MOD heifers. Diet did not influence concentration of IGF-I or glucose, and metabolic markers were unaffected by biotype. No dramatic changes in body composition or metabolic signals were detected before puberty. Puberty did not occur at similar body composition or metabolic status in all heifers.

Animals↗

PubMed1995

Endocrine responses in cows fed Ponderosa pine needles and the effects of stress, corpus luteum regression, progestin, and ketoprofen.

Pregnant cows were fed pine needles (PN, 2 kg.cow-1.d-1) mixed with the diet to determine factors that affect abortion response. In Exp. 1, treatments were used to determine the effects of experimental stress and pelleting of pine needles. Pelleting needles and experimental stress delayed abortion response (P < .01). Stress-induced delay was associated with abnormal patterns of progesterone and cortisol (P < .01). In Exp. 2A and 2B, the role of the corpus luteum (CL) in abortion response to PN consumption was investigated by regressing the CL with prostaglandin F2 alpha. Regression of the CL and PN feeding reduced interval to parturition, but the effect of PN feeding was less when the CL was regressed (PN x CL, P < .01). The progesterone increase in response to experimental stress was decreased by CL regression (P < .01). In Exp. 3, melengestrol acetate (MGA) was fed (0, 2, or 4 mg.cow-1.d-1) in addition to PN. Parturition was blocked more effectively as dose of MGA increased (P = .075), but only parturition was blocked rather than the effects of PN. In Exp. 4, CL regression was blocked by feeding ketoprofen. Ketoprofen delayed response to PN, but the effect was only temporary (P < .01). Our conclusions are that 1) experimental stress delays abortion response to PN by increased concentrations of progesterone, 2) pelleting PN decreases their abortifacient activity, and 3) abortions caused by PN can be blocked by feeding a progestin or a prostaglandin inhibitor, but these compounds do not block the primary abortifacient effects of PN.

Abortion, Veterinary↗

PubMed1995

Abortifacient response and plasma vasoconstrictive activity after feeding needles from ponderosa pine trees to cattle and sheep.

Consumption of needles from Pinus ponderosa (PN) during late pregnancy causes cattle, but not sheep, to abort. This differential response may be caused by differences in ruminal microflora or postabsorptive metabolism. Pine needles were fed (2 kg.cow-1.d-1 or .4 kg.ewe-1.d-1) mixed with corn silage. In Exp. 1, cows were assigned at 250 d of pregnancy to feed treatments (T): 1) silage, 2) PN+silage, or 3) pretreated with sheep ruminal fluid and fed PN+silage. Interval to parturition was 34.3, 11.3, and 8.3 d for the T1, T2, and T3, respectively (T1 vs T2 + T3, P < .01; T2 vs T3, P > .5). Inoculation with sheep ruminal fluid did not alter activity of the abortifacient agent of PN. In Exp. 2, pregnant and nonpregnant ewes and cows were fed silage or PN mixed with silage, and plasma was analyzed for uterine vasoconstrictive activity in an in vitro placentome perfusion bioassay. Consumption of PN decreased interval to parturition in cattle (P < .01) but not in sheep (P > .5) and increased vasoconstrictive activity (P < .05) in plasma from nonpregnant and pregnant cows and ewes. The PN-fed ewes had a greater incidence of dead lambs at parturition (0/8 vs 5/8 for control vs PN-fed, P < .01). We conclude that pregnancy is not required for increased vasoconstrictive activity induced by pine needles, that sheep and cattle do not differ in ruminal metabolism of the abortifacient compounds in PN, and that species differences are subtle and due to postdigestive differences in response to the abortifacient agent.

Abortifacient Agents↗

PubMed1994

Pine needle abortion in cattle: effects of diet variables on consumption of pine needles and parturition response.

Cows that consume needles from Pinus ponderosa (PN) abort, but little is known about variables that affect consumption or response. These experiments were conducted to test the effects of several variables on pine needle-induced abortion. Cows were placed on experiment at 250 d of pregnancy and were either given ad libitum (AL) access to PN separate from other feed sources or the PN were ground and fed (2 kg.cow-1.d-1) mixed with the diet. In Exp. 1, cows were assigned to a 2 x 2 factorial experiment with adequate (AP) vs high-protein (HP) diets and no straw vs AL straw (S). All cows ate PN and aborted, and there were no effects (P > .5) on interval to parturition (IP). Consumption of PN (kg/d) was increased by HP (P < .1). In Exp. 2, cows were assigned to five treatments to test the effects on response to PN of magnesium supplementation, weathering the PN, and using silage rather than hay as the basal diet. Consumption of PN shortened IP (P < .01), but magnesium, weathering PN, and silage-based diets did not decrease the response to PN (P > .5). In Exp. 3, cows were assigned to five treatments to test the effects of aging needles after they were ground, feeding bentonite, and feeding a complete mineral supplement. Pine needles decreased IP (P < .01), and the effects of PN were greater when PN were aged or bentonite or minerals were added (all P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Veterinary↗

PubMed1994

Comparison of AOAC and light spectroscopy analyses of uncooked, ground beef.

Ground beef samples (n = 302) were analyzed for DM and fat content with standard laboratory procedures. Samples were also analyzed by light spectroscopy with either a NIRSystems model 6250 or a model 6500. Samples were thawed at room temperature, packed in cups (three/sample), and scanned every 2 nm with the model 6250 in the mid wavelength (MW) region from 1,100 to 2,500 nm (MW-6250). Whirl-pak bags containing the thawed samples were also scanned every 2 nm with the model 6500 using a fiber optic attachment in the short wavelength (SW) region from 400 to 1,100 nm (SW-6500), 1,100 to 2,500 nm (MW-6500), and 400 to 2,500 nm (SW+MW-6500). Each sample was scanned at two different locations on the Whirl-pak bags. The MW-6250 produced the lowest standard errors of calibration (1.62 and 1.62%) and highest R2 values (.97 and .98) for DM and fat, respectively, during calibration. However, SW-6500 produced the lowest standard errors of performance (2.34 and 1.92%) and the highest r2 values (.86 and .95) for DM and fat, respectively, during validation. The MW-6500 and SW+MW-6500 produced intermediate results. Results with fiber optic scanning in the SW region were better than with cups and scanning in the MW region. Light spectroscopy for determining DM and fat content of ground beef samples can replace wet chemistry.

Animals↗

PubMed1994

Exercise and induced-parturition effects on dystocia and rebreeding in beef cattle.

The study involved 44 primiparous, 2-yr-old heifers and 74 multiparous cows, 3 or 4 yr old, bred to a single Charolais bull. Variables were dam age (heifer, H; or cow, C), restricted (RE) or forced (FE) exercise for the last 90 d precalving, and natural (NP) or induced (IP) parturition. The RE dams were held in drylots; FE dams were on range until d 260 to 267 and walked 3.2 km/d for feed and water. Dams with IP received 10 mg of flumethazone on d 269 of gestation. Diets for FE and RE dams contained the same hay and grain, but FE dams were fed in amounts projected to give weight changes approximating those of RE dams. All dams were calved in drylots; thereafter, all pairs were maintained together on pasture to the end of the study. Exercise did not affect dystocia score or incidence, increased feed requirement 31% (P < .01), and gave a 14.8% higher (P < .05) pregnancy rate in the subsequent 45-d breeding season. We hypothesize the increased pregnancy may have resulted from a feed-endocrine effect related to body weight gain, body composition-metabolic changes, or subsequent higher feed intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

The time required for the presence of bulls to alter the interval from parturition to resumption of ovarian activity and reproductive performance in first-calf suckled beef cows.

This experiment was designed to determine 1) if exposure of firstcalf suckled beef cows to mature bulls in the first 30 days, after 30 days, or continuously post partum reduces the postpartum anestrous period and 2) if exposure to bulls alters the first service pregnancy rate. Postpartum first-calf suckled crossbred (Angus x Hereford; Hereford x Angus) cows were randomly assigned to be 1) exposed continuously to mature, epididectomized bulls (BE; n = 18); 2) exposed to bulls for the first 30 days post partum (BE/NE; n = 17); 3) exposed to bulls after the first 30 days post partum (NE/BE; n = 16); or not exposed to bulls (NE; n = 18). Blood samples were collected weekly to be assayed for progesterone to determine resumption of ovarian cyclic activity. All the cows were bred for 21 days by AI while under their respective treatment regimens and were then exposed to fertile bulls for an additional 35 days. The postpartum interval to resumption of ovarian cyclic activity did not differ (P>0.10) among the 3 (BE, BE/NE, and NE/BE) treatment groups, but it was 15.4 d shorter (P<0.05) than for cows in the NE group. The overall pregnancy rates did not differ (P>0.10) among the treatment groups. The AI pregnancy rates for the BE/NE and NE/BE treatment groups were higher (P<0.05) than for the NE group. The AI pregnancy rates for the BE and NE treatment groups did not differ (P>0.10). The results showed that all three treatments (BE, BE/NE and NE/BE) similarly decrease the postpartum interval and that exposure to bulls may improve the reproductive performance of first-calf suckled beef cows.

Journal Article↗

PubMed1993

Effects of ingestion of pine needles (Pinus ponderosa) by late-pregnant beef cows on potential sensitive Ca2+ channel activity of caruncular arteries.

Cows were fed either a control (n = 6) or pine needle (n = 12) diet beginning on day 249 of pregnancy. On day 3 and day 5 of feeding, control-fed and pine needle-fed cows were slaughtered and placentomes were collected for in vitro perfusion of the caruncular artery. Potential sensitive Ca2+ channel (PSC) activity as well as the responsiveness to phenylephrine (alpha 1-adrenergic agonist) and adrenaline (alpha 1- and alpha 2-adrenergic agonist) were determined. Selected gravid uterine tissues (endometrium and myometrium, as well as caruncular and cotyledonary tissues) and associated arteries (caruncular, intercaruncular and umbilical) were isolated, minced and portions either extracted immediately for measurement of PSC or frozen at -90 degrees C until assayed for peroxidase activity or number of alpha 2-adrenergic receptors and affinities or for both. In vitro perfused placentomes from day 5 pine needle-fed cows had greater (P < 0.05) PSC activity, as measured by the increase in perfusion pressure in response to a depolarizing dose of KCl, than day 3 pine needle-fed or control-fed cows (10.3 +/- 2.5 versus 6.1 +/- 1.2, and 4.3 +/- 0.7 kPa, respectively). Furthermore, day 5 pine needle-fed cows also exhibited greater (P < 0.05) contractile responses to adrenaline than day 3 pine needle-fed or control-fed cows. Contractile responses to phenylephrine were similar (P > 0.1) for all three treatment groups. The observed increase in PSC activity and responsiveness to adrenaline, however, was not reflected by increasing numbers or affinities of PSC or alpha 2-adrenergic receptors on caruncular arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1993

Effects of sire and dam on late-pregnancy conceptus and hormone traits in beef cattle.

Forty-six primiparous F1 heifers produced from mating Brahman (B), Charolais (C), Jersey (J), Longhorn (L), or Shorthorn (S) sires to crossbred cows were bred by AI to one of two Angus sires selected to produce high (H) or moderate (M) fetal growth. Dams were slaughtered at an average of 231 d of gestation. Daily blood samples were obtained from the dam on d 228 to 231 to determine serum estradiol, progesterone, and testosterone concentrations. Pelvic height was greatest (P < .05) in B, C, and L and pelvic width was greatest (P < .05) in S, C, and J dams, but pelvic areas did not differ (P > .10). Dams with greater hip height had larger pelvic areas (r = .45; P < .01). Intact fetuses from C and S dams were heaviest (P < .05), those from S dams had the greatest (P < .05) head width, and heart girth was greatest (P < .05) in fetuses from L dams. Fetuses from H sires were greater in weight (P < .01), body length (P < .01), and cannon circumference (P < .01). Dam differences were found in fetal heart weight (P < .01), trimmed placental membrane weight (P < .01), and average placentome weight (P < .05). Weights of eviscerated fetuses were greatest from C dams (P < .05). Placentome number was lowest (P < .05) in J dams, but J dams had the highest (P < .05) average placentome weight. Interactions between fetal genotype and breed of maternal environment were found for weight of eviscerated fetus (P < .05), body length, and heart weight (P < .01) and resulted from both magnitude and direction of change in the sire effect. The H sire increase in fetal weight was greatest in J dams, whereas B dams allowed expression of the fetal growth potential but at a lower level. Fetal trait interactions were also found for breed x sex and sex x sire (P < .05 to P < .01) and were due to the magnitude of differences expressed between the M and H sires. Serum testosterone concentrations were highest (P < .05) in B and L dams, dams gestating fetuses sired by the H sire (P = .08), and those with male fetuses (P < .01). We interpret these results to indicate that some maternal environments can suppress fetal growth, whereas others seem to complement the growth and allow maximum expression of the fetal genetic growth potential.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1993

Paternal half-sib heritabilities and genetic, environmental, and phenotypic correlation estimates from randomly selected Hereford cattle.

Growth and carcass data were collected during 10 yr at the Fort Keogh Livestock and Range Research Laboratory in Miles City, MT from a Hereford herd selected at random. The objective was to compare genetic parameter estimates from this randomly selected herd with estimates from published selection studies. Only bulls were included in the data set. Bulls were slaughtered between 14 and 17 mo of age. Genetic parameters were estimated by the paternal half-sib procedure. Data were subdivided into three subgroups: 1) all bulls that had birth weights, 2) bulls with complete records for growth traits, and 3) bulls with complete carcass and growth records. The heritability estimate for birth weight on 736 progeny from 86 sires was .18. The second group included 616 progeny representing 85 sires and heritability estimates were weaning weight, .17; daily gain from birth to weaning, .20; final test weight, .42; and daily gain on test, .47. The third group included 401 progeny from 75 sires and heritability estimates were carcass weight, .38; longissimus muscle area, .51; marbling, .31; slaughter weight, .42; and dressing percentage, .25. Thus, these estimates of heritability were in quite good agreement with previously published values, with a tendency for these estimates to be lower for early growth weights. Phenotypic and environmental correlations were in good agreement and genetic correlations were in general agreement with the data reviewed. Estimates of heritabilities from this herd selected at random were not larger than previous estimates from selected herds.

Adipose Tissue↗

PubMed1992

Effects of feeding ponderosa pine needles during pregnancy: comparative studies with bison, cattle, goats, and sheep.

Four experiments were conducted to determine the effect of feeding dried pine needles (Pinus ponderosa; PN) on the abortion rate of ruminants. In Exp. 1, cattle were fed 5.4 kg of PN daily for 21 d starting at 116, 167, 215, or 254 d of pregnancy. The PN did not cause abortions when started at 116 d; thereafter, the percentage of cows that aborted increased linearly, and the interval to abortion decreased linearly (both P < .01); all cows fed PN beginning at 254 d aborted. In Exp. 2, cattle were fed .7, 1.4, or 2.7 kg of PN for 21 d or 2.7 kg for 1 or 3 d. Sheep and goats were fed .8 and .5 kg of PN, respectively, starting at 121 d of pregnancy. The PN induced some abortions in cattle when fed for 1 (11%) or 3 (30%) d, but the abortion rate was greater (P < .01) when the PN were fed for longer periods of time (80, 90, and 100% aborted in 19, 17, and 10 d for .7-, 1.4-, and 2.7-kg doses, respectively). No goats or sheep aborted in response to PN feeding. Pregnancy rates during the next breeding season for cows that aborted in response to the PN were slightly higher than rates for control cows (94 vs 87%). In Exp. 3, buffalo (Bison bison) and cattle were fed 2.25 kg of PN from the same collection. Abortions were induced in all buffalo and cattle that were fed PN.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Veterinary↗