Biomedical subjects

R A Bellows

Publications and source records attributed to R A Bellows.

At least 37 records · Page 2Linked to original sources

PubMed1992

Superovulation of cattle with equine pituitary extract and porcine ESH.

Superovulation has been practiced in cattle for more than 50 years but the results have been highly variable. Scientists at six locations compared a horse pituitary extract (HAP) with a single batch of porcine FSH (pFSH) to determine the efficacy of these hormones to induce superovulation and to test for variability in the superovulatory response. Acetone-dried equine pituitaries were suspended in 40% ethanol containing 6% ammonium acetate, and the supernatant was mixed with 2.5 volumes of cold ethanol. The resulting precipitate was washed with cold ether and dried. Total doses of 18 mg of HAP and 36 mg of pFSH were injected intramuscularly (i.m.) over 4 days, two injections per day, and prostaglandin (PGF(2)alpha; 25 mg, i.m.) was administered on Day 3. Injections were begun on Days 6 to 13 of the estrous cycle. The overall ovulation rates (mean +/- SEM) for HAP and FSH were 8.8 +/- 0.7 and 15.1 +/- 1.0, respectively (n=231; P<0.01). Location interacted (P<0.01) with the type of gonadotropin for the ovulation rate. When expressed as a proportion of the number of corpora lutea, the total number of embryos recovered was greater (P=0.03) for pFSH than for HAP, but there was no difference in the number of Quality 1 and 2 embryos. The results show that HAP can induce a satisfactory superovulatory response, but there was no evidence of reduced variability of response to HAP compared with pFSH.

Journal Article↗

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↗

PubMed1992

Management considerations in heifer development and puberty.

Management of replacement beef heifers should focus on factors that enhance physiological processes that promote puberty. Age at puberty is important as a production trait when heifers are bred to calve as 2-yr-olds and in systems that impose restricted breeding periods. Calving by 24 mo of age is necessary to obtain maximum lifetime productivity. Because the reproductive system is the last major organ system to mature, factors that influence puberty are critical. The influence of environment on the sequence of events leading to puberty in the heifer is dictated largely by the nutritional status of the animal and related effects on growth rate and development. Management strategies have been designed to ensure that heifers reach a prebreeding target weight that supports optimum reproductive performance, and consequences of inadequate or excessive development have been evaluated. Those strategies are based on evidence linking postweaning nutritional development with key reproductive events that include age at puberty and first breeding, conception, pregnancy loss, incidence and severity of dystocia, and postpartum interval to estrus. Management alternatives that ultimately affect lifetime productivity and reproductive performance of heifers begin at birth and include decisions that involve growth-promoting implants, creep-feeding, breed type and(or) species, birth date and weaning weight, social interaction, sire selection, and exogenous hormonal treatments to synchronize or induce estrus. Basic and applied future research efforts should converge to match in a realistic manner the production potential of the animal with available resources. Strategies that incorporate consideration of nutrition, genetics, and emerging management techniques will need to be tested to enable producers to make decisions that result in profit. This review evaluates the current status of knowledge relating to management of the replacement beef heifer and serves to stimulate research needed to enhance management techniques to ensure puberty at an optimal age.

Animal Feed↗

PubMed1991

Production from first-calf beef heifers fed a maintenance or low level of prepartum nutrition and ruminally undegradable or degradable protein postpartum.

Two experiments were conducted in consecutive years to determine the effects of prepartum nutrient level and postpartum ruminally undegraded protein intake on nutrient status, milk production, subsequent calf production, and reproductive performance of 126 crossbred, primiparous beef heifers. Prepartum treatments were low nutrient intake (LN) (approximately 2.5 kg of TDN, .5 kg of CP animal-1.d-1 and maintenance nutrient intake (MN) (5 kg of TDN, 1 kg of CP animal-1.d-1), which were fed for 75 d before parturition. Two postpartum protein supplements were formulated to provide 250 g/d of ruminally degradable protein (RD) and one to supply ruminally undegraded protein (UD) at 250 g/d of additional UD CP compared to the RD supplement. Cholesterol was lower (P less than .01) in heifers given UD than in heifers given RD. Blood urea nitrogen was higher (P less than .01) for UD-fed heifers than for RD-fed heifers and was higher in LN heifers (P less than .06) than in MN heifers. Milk production did not differ (P greater than .11) as a result of LN, MN, UD, or RD. Postpartum cow weight gain was greatest (P less than .01) for UD and LN heifers. The percentage of heifers bred during the first estrous cycle of the breeding season was greater (P less than .02) for UD than for RD. Overall, prepartum nutrition did not interact with postpartum protein supplement, nor did it have any effect on postpartum interval, whereas UD increased cow weight gain postpartum and reduced postpartum interval.

Animal Nutritional Physiological Phenomena↗

PubMed1990

Influence of sire, sex of fetus and type of pregnancy on conceptus development.

Estrus was synchronized in 93 crossbred cows 3 to 7 yr old which were then superovulated with 10 mg FSH-P and bred artificially to either a Jersey or Charolais bull. Females pregnant to the Jersey sire were slaughtered at 95, 180 or 250 d of gestation; low pregnancy rate from the Charolais sire resulted in enough dams for slaughter and valid comparisons at 95 d only. Conceptus tissue and organ weights and dam carcass weights and measurements were collected at slaughter. At 95 d of gestation, sire differences were not significant; type of pregnancy (single vs multiple) had significant effects on placentome and membrane weight; fetus sex had highly significant effects on fetus weight and crown-rump length. Fetal brain and heart weights showed little effect of sire, fetus sex or type of pregnancy, indicating these early differentiating tissues are highly competitive for available nutrients for growth. Fetal data at 180 and 250 d of gestation showed highly significant effects of gestation stage on placentome, membrane and fetus weights, crown-rump and metatarsal lengths, and liver, kidney, heart and total brain weights. Type of pregnancy had greater effects on the conceptus traits than did fetus sex at these stages. Nonorthogonal analyses of data from the Jersey-sired pregnancies indicated growth of fetuses in multiple pregnancies was suppressed, and the reduction in fetus weight became more pronounced as gestation progressed. Correlations among conceptus traits and dam carcass data showed different relationships within single and multiple pregnancies. We suggest that the genetic contribution for fetal growth has a positive effect on fetal size throughout gestation while the importance of metabolite availability may change during gestation depending on the genetic growth potential of the fetus and on whether the pregnancy is single or multiple. We speculate that these fetus-dam relationships involve systems controlling fetus growth that arise from the fetus genetic growth potential interacting with positive and negative dam effects that are linked or related to the carcass skeletal-fat-muscle endpoints studied.

Journal Article↗

PubMed1990

Administration of pig relaxin to beef heifers 4 or 7 days pre partum.

Crossbred beef heifers (N = 36) were assigned to one of three treatment groups: untreated controls (C; N = 15); Group R4, treated with pig relaxin (1.0 mg i.m.) 4 days pre partum (N = 11); or Group R7, treated with pig relaxin (1.0 mg i.m.) 7 days pre partum (N = 10). Bioactivity of the pig relaxin (UMC-R-P8) was determined by the mouse interpubic ligament assay to be greater than or equal to 3000 U/mg, both before and after the experiment was conducted. Peripheral serum immunoreactive relaxin values were 7.5, 3.4, 2.5, and 1.5 ng/ml at 2, 4, 6 and 8 h after injection of relaxin, respectively. Gestation lengths were 282.9 +/- 1.1, 285.5 +/- 1.3 and 285.6 +/- 1.5 days for Groups C, R4 and R7 (C vs R4 + R7; P congruent to 0.08). Calving difficulty score (1 to 4) tended to be greater (P congruent to 0.08) for Group R4 and R7 heifers (C vs R4 + R7; 1.3 +/- 0.24 vs 1.75 +/- 0.28 + 2.04 +/- 0.32), but the incidences of dystocia and retained placentae were not influenced by treatment (P greater than or equal to 0.10). The mean concentration and concentration profile of daily serum progesterone, oestradiol-17 beta, dihydroprostaglandin F-2 alpha and relaxin were not affected by treatment from 6 days pre partum through 2 days post partum. Cervical diameter, cervical softness score, pelvic measurements, and vulva opening length during the periparturient period were not affected (P greater than or equal to 0.10) by treatment, but all of these characteristics changed over time (P less than or equal to 0.01), relative to calving. We conclude that i.m. administration of pig relaxin (greater than or equal to 3000 U) does not effectively alter periparturient characteristics of beef heifers. Discrepancies between these results and those reported for intracervical administration cannot be readily explained.

Animals↗

PubMed1990

Physiological mechanisms controlling anestrus and infertility in postpartum beef cattle.

Postpartum infertility is caused by four factors: general infertility, lack of uterine involution, short estrous cycles and anestrus. The general infertility component is common to any estrous cycle and reduces potential fertility by 20 to 30%. Incomplete uterine involution prevents fertilization during the first 20 d after calving but is not related to anestrus. Short estrous cycles prevent fertility during the first 40 d after calving by causing the cow to return to estrus before pregnancy recognition occurs. Anestrus is the major component of postpartum infertility and is affected by several minor factors: season, breed, parity, dystocia, presence of a bull, uterine palpation and carryover effects from the previous pregnancy as well as two major factors: suckling and nutrition. These major factors have direct effects on anestrus but also interact with one or more other factors to control postpartum anestrus. Physiological mechanisms associated with anestrus involve blockage of the GnRH "pulse generator" in the hypothalamus, but other pathways also must be involved because bypassing the pulse generator is not an effective treatment for all cows. The primary cause of anestrus probably is different for different stages of anestrus. The mediating mechanisms for anestrus are not involved with prolactin, oxytocin, the adrenal or direct neural input from the mammary gland but are at least partially involved with blood glucose and the endogenous opioid peptide system. Management options to decrease the impact of anestrus and infertility include: 1) restrict breeding season to less than or equal to 45 d; 2) manage nutrition so body condition score is 5 to 7 before calving; 3) minimize effects of dystocia and stimulate estrous activity with a sterile bull and estrous synchronization; and 4) judicious use of complete, partial or short-term weaning.

Anestrus↗

PubMed1990

The effects of ruminal escape protein or fat on nutritional status of pregnant winter-grazing beef cows.

This study was designed to determine the influence of soybean meal supplementation, with or without additional ruminal escape protein or fat, on the nutritional status of pregnant winter-grazing beef cows. During two winters (Trials 1 and 2), approximately 60 prepartum beef cows grazed native foothills range each year. Cows were allotted randomly to five groups and supplemented (g/d) with either none (control); 570 soybean meal (SOY); 450 soybean meal plus 230 blood meal (SOY + BM); 140 soybean meal, 16 urea plus 450 corn gluten meal (SOY + CGM); or 570 soybean meal plus 210 animal fat (SOY + FAT). These supplements were designed to supply similar quantities of ruminal degraded protein while varying in escape protein quantity and source (SOY + BM and SOY + CGM). Condition scores and body weights were determined at trial initiation (mid-December) and conclusion (early March). Eight blood samples obtained over 4 d during three periods (9, 4 and 1 wk prior to parturition) were analyzed for concentrations of glucose, urea nitrogen (N), total bilirubin, creatinine, albumin, total protein and cholesterol. Cows in the control treatment experienced the greatest BW loss in both trials. In Trial 2, escape protein tended to decrease (P less than .06) BW loss compared to SOY, though loss tended to be greater (P less than .08) with SOY + CGM than with SOY + BM. Escape protein can enhance nutritional status when supplemented with .6 kg/d of soybean meal.

Animal Feed↗

PubMed1989

Failure to find an association between ocular squamous cell carcinoma and class I antigens of the bovine major histocompatibility system.

We tested 53 cattle with ocular squamous cell carcinoma (cancer-eye) and 53 paired, matched controls for 25 class I antigens of the bovine major histocompatibility system. The most common antigen was W5 which was present in 40% of the animals with cancer-eye and 36% of the controls. There were no statistically significant differences in BoLA antigen frequency between cattle with and cattle without cancer-eye.

Animals↗

PubMed1989

Pine needle abortion in cattle: a review and report of 1973-1984 research.

Research has verified field observations that cows grazing ponderosa pine needles may abort. The incidence and nature of the abortions produced experimentally simulate very closely those reported by livestock producers and veterinarians. The incidence of experimentally-produced abortions varied markedly from year to year even though the needles were collected in the same general area each year. This suggests that the abortifacient compound(s) in the needles vary from year to year, probably due to environmental and site conditions. The impact of stress (cold and nutrition) as a factor in the abortions was examined. It was concluded that the only effects would be on the willingness of cows to eat the needles. The pine needle abortion problem, what is known of the etiology, and mechanisms of the abortion are reviewed. The usefulness of bioassay systems to study pine needle abortions is discussed.

Abortion, Veterinary↗

PubMed1988

Effects of induced parturition and early obstetrical assistance in beef cattle.

Pregnant crossbred beef females (33 second-calf cows and 73 primiparous heifers) bred to a single Hereford sire were assigned to a 2(3) factorial study involving age of dam, natural (NP) or induced (IP) parturition and late emergency (LA) or forced early (EA) obstetrical assistance. Parturition was induced with 10 mg flumethazone given i.m. between 1400 and 1600 on d 272 of gestation; EA was given when the cervix and birth canal were fully dilated. Average IP occurred 39.6 h postinjection, and 95.3% of the treated dams responded within 60 h postinjection; gestation was shortened 2.9 d (P approximately equal to .07). Dystocia score (from 1 = no assist to 4 = major traction required and 5 = abnormal presentation) was 1.12 vs 2.40 for LA and EA, respectively (P less than .01), and 11% of LA vs 84% of EA were assisted. Calf vigor score (1 = normal to 3 = severely depressed or dying) at birth was 1.3 for NP and 1.1 for IP (P approximately equal to .06) and 1.3 for EA and 1.1 for LA (P less than .05). This effect of EA was due to reduced vigor of calves experiencing abnormal presentation. Birth weights (BW) and weaning weights (WW) of calves from cows exceeded those from heifers (32.6 vs 30.8 kg, P less than .05; 210.9 vs 156.3 kg, P less than .01, respectively). Differences due to IP and EA in BW, WW, postpartum interval and conception rate were not significant, but weight gain of calves from EA dams tended (P approximately equal to .09) to be greater than weight gain of calves from LA dams.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Occurrence of neonatal and postnatal mortality in range beef cattle. I. Calf loss incidence from birth to weaning, backward and breech presentations and effects of calf loss on subsequent pregnancy rate of dams.

Data from 13,296 calvings collected over a 15-yr period indicated 893 calves died from birth to weaning for an average loss of 6.7%. Calves lost from birth through Day 3 postcalving accounted for a 4.6% loss with an additional 2.1% loss from Day 4 through weaning. Calf deaths from primiparous 2- and 3-yr-old dams accounted for 41.0% of total mortality. Losses within groups were primiparous 2-yr-olds, 10.9%; primiparous 3-yr-olds, 8.7%; second-calf 3-yr-olds, 4.1%; second-calf 4-yr-olds, 8.3%; multiparous 4-yr-olds, 4.8%; and dams 5 yr and older, 5.3%. The majority of calf deaths (57.4%) occurred within the first 24 h postpartum with 75% of the total occurring Days 0 through 7. This loss was similar among all dam age and parity groups. Calf death due to dystocia accounted for the single largest loss category through the first 96 h postpartum, resulting in 69.6, 39.6, 30.8 and 33.3% of the loss incidence for Day 0, 1, 2 and 3 postpartum, respectively. More (P < 0.01) male calves (510, 57.6%) died than females (376, 42.4%). Backward presentations occurred more frequently (P < 0.01) than breech (1.6 vs 0.6% of all births, respectively). Incidence of backward presentation was 2.3%, 5.6% and 0.9% for primiparous 2-yr-old, 3-yr-old and multiparous dams, respectively (P < 0.01); 64.2% of the backward calves were males and 35.8% females (P < 0.01). Survival of calves in backward presentation exceeded (P < 0.01) that of breech calves (70.7 vs 32.9%). Fall pregnancy rate of dams that lost calves and reentered the breeding herd that same year was 72.4% compared to 79.4% (P < 0.01) for contemporary females that did not lose calves. The depression in pregnancy rate was not specifically due to dystocia but apparently to some general effect of calf loss.

Journal Article↗

PubMed1987

Occurrence of neonatal and postnatal mortality in range beef cattle. II. Factors contributing to calf death.

Results are summarized of necropsy findings from 798 calves lost from birth to weaning over a 15-yr period. Autopsies determined cause of death and ascertained anatomical normalcy of the skeletal, musculature and organ systems and functinal status of the lungs. Of the 798 calves, 77.7% were anatomically normal and 22.3% were abnormal (P < 0.01) and 75.0% of the total deaths of abnormal calves occurred by Day 2 postpartum. Birth weights of normal calves averaged 4.2 kg heavier (P < 0.05) than that of abnormal calves. Internal hydrocephalus was identified and confirmed heritable as a lethal recessive trait. The number of calves lost from dystocia (406 calves, 50.9%) exceeded losses from all other causes (392 calves, 49.1%). Lung status was determined for 492 calves dying at birth, with 39.6 and 60.4% having functional and nonfunctional lungs, respectively (P < 0.01). Diseases, mainly scours and pneumonia, ranked second in importance as cause of death (12.8%), followed by exposure-chilling (5.6%) due to cold and wet conditions. Abnormalities observed included heart anomalies (24 calves), hydrocephalus (38 calves) and a missing segment of the caudal gut (8 calves). Multiple congenital malformations were found in 15 calves with findings similar to those resulting from maternal consumption of toxins from poison hemlock (Conium maculatum) during gestation. Twelve calves died from peritonitis resulting from a perforated abomasal ulcer caused by accumulated hair. Of the 373 dystocia deaths in anatomically normal calves, 121 (32.4%) involved abnormal presentation, with calves involved in backward or breech presentation accounting for 62.0% of the losses from abnormal presentation. Calves experiencing hiplock or retained forelimb were heavier (P < 0.05) than calves presented in normal, back-ward or breech positions. Dystocia scores were assigned to 253 calves dying at parturition. Percentage losses within score were 52.6, 6.7, 30.8 and 9.9 (P < 0.05) and birth weights were 33.9, 36.1, 39.2 and 37.4 kg (P < 0.05) for scores of 1, 2, 3 and 4, respectively.

Journal Article↗

PubMed1986

Fetal growth of beef calves. I. Effect of prepartum dietary crude protein on birth weight, blood metabolites and steroid hormone concentrations.

Fifty-nine crossbred heifers (427 kg) bred to one Hereford sire were randomly assigned at 75 d prepartum to two diets. Heifers were individually fed, and diets were isocaloric but contained either a low (LP = 81% NRC, .56 kg/d) or high (HP = 141% NRC, .98 kg/d) level of crude protein. Jugular vein cannulae were inserted into 16 LP and 16 HP heifers at 10 prepartum. Daily preprandial blood samples that were collected until parturition were analyzed for serum estradiol-17 beta (E2), progesterone (P4), glucose (G) and urea nitrogen (UN). Heifers fed LP gained slower than HP-fed heifers before calving (.73 vs 1.02 kg/d; P less than .01); immediate post-calving weights and condition scores were 418 vs 444 kg (P less than .01) and 5.4 vs 6.1 (P less than .01; LP vs HP, respectively). Calf birth weights (35.3 vs 36.1 kg), average calving difficulty score (1.6 vs 1.6) and percent assisted births (35.5 vs 35.7%) did not differ (P greater than .10; LP vs HP, respectively). Prepartum concentrations of UN (6.2 vs 13.5 mg/dl) and G (52.9 vs 58.2 mg/dl) were lower (P less than .05) and P4 (5.94 vs 4.26 ng/ml) was higher (P approximately equal to .07) in LP heifers. Prepartum concentration profiles were related to calving difficulty score (CD, 1 = no assistance to 3 = hard pull) for E2 (CD1 vs CD2 + CD3, P less than .01; CD2 vs CD3, P approximately equal to .01), P4 (CD1 vs CD2 + CD3, P less than .05), G (CD1 vs CD2 + CD3, P less than .05) and UN (CD2 vs CD3, P less than .05). After calving, all dams were maintained together on pasture and supplemented with alfalfa hay and grain mix until adequate range forage was available to maintain weight gains. Dams that were fed LP prepartum gained faster than HP dams during this period (.49 vs .15 kg/d; P less than .01). Prebreeding weights (443 vs 453 kg; LP vs HP) and condition scores (5.1 vs 5.1) did not differ, nor was the postpartum interval affected (44 vs 40 d; LP vs HP). There was no effect of dietary protein on dystocia or postpartum interval, although there were diet-induced differences in body weight and condition of the dams at calving. Results indicate that differences in prepartum profiles of serum steroid hormones and metabolites may be related to dystocia, in addition to relative fetal oversize.

Animals↗

PubMed1986

Fetal growth of beef calves. II. Effect of sire on prenatal development of the calf and related placental characteristics.

Fifteen Hereford and 47 crossbred heifers were allotted by breed and body weight to be artificially inseminated to one of two Angus sires selected for progeny birth weights (L = low; H = high). Forty-two of the heifers were randomly assigned to be slaughtered at 200, 215, 230, 245 or 260 d of gestation for measurement of fetal and placental characteristics. Twenty heifers were allowed to go to term and five calves from each sire group were randomly assigned to be euthanized and dissected within 24 h after birth. Sire differences in birth weight (BW) and dystocia score (32.9 vs 35.4 kg; 1.8 vs 3.1, L vs H sires, respectively) existed (P less than .01), and there was a sire effect (P less than .01) for fetal calf weights (FW) and eviscerated calf weights (EW). However, there was a sire X calf sex interaction for BW (P less than .05), EW (P less than .01), FW (P less than .01), femur length (P less than .05), heart weight (P less than .05), kidney weight (P less than .01) and pituitary weight (P less than .01). Weight differences suggested these interactions were a result of the relationship of the organ weights to fetal body weights and the interaction effects on calf weights resulted from limitations in the maternal environment which restricted growth of H-sired male calves in utero. Sire X fetal age interaction effects were all nonsignificant (P greater than .10) except for cerebrum weight. This finding indicates that fetus and calf growth rates were parallel for the L and H sires. A sire effect was found for biceps (P less than .01) and liver weights (P less than .01), but not for cerebrum weights (P greater than .10). Increasing weight due to fetal age was attributed to hypertrophy for the cerebrum (P less than .05) and liver (P approximately equal to .01), while the biceps increased (P less than .05) by both hypertrophy and hyperplasia, as determined from deoxyribonucleic acid and protein analyses. All measured fetal organ weights except heart, when expressed as a ratio with EW, decreased (P less than .05) with increasing fetal age. Brain (cerebrum + cerebellum):liver weight ratios were higher (P less than .01) in L-sired calves (.32 vs. .28) than in H-sired calves. Total placentome weight (b' = 91; P less than .01) and placental fluid volume (b' = .32; P less than .01) were highly associated with FW, accounting for 84% of the variation in FW.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1986

Crossing beef x beef and beef x Brown Swiss: pregnancy rate, calf survival, weaning age and rate.

October pregnancy rate, calf survival to weaning, weaning age, weaning rate and actual kg of calf weaned/cow exposed were determined in a 4-yr study involving 880 matings of Angus (A), Hereford (H) and Charolais (C) sires to A, H, C and Brown Swiss (BS) dams. Cows were mated in single-sire herds for 45 or 60 d under pasture conditions; heifers were bred to produce their first calf at 3 yr of age. Pregnancy rate of lactating dams was 9.4% higher (P less than .01) than for non-lactating dams. Pregnancy rates for straightbred matings were 87.5%, 80.6% and 75.4%, respectively, for A, H and C groups (P less than .05). No differences (P greater than .10) due to sire breed were found for any of the traits studied except for calf age at weaning. Calves from C sires were younger (P less than .01) at weaning than calves from H and A sires. Breed-of-dam differences (P less than .05 to P less than .01) were found for all traits studied except calf survival rate. All BS dams produced crossbred calves and had lower pregnancy and weaning rates (both P less than .01), calves were younger at weaning (P less than .05), had lower kg of calf weaned/cow exposed (P less than .05) than for beef-breed dams producing crossbred calves. Crossbred calves from BS dams were 4.9, 11.0 and 3.4 d younger (P less than .05 to P less than .01) at weaning, respectively, than crossbred calves from H, A and C dams.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1984

Effects of dam age, prepartum nutrition and duration of labor on productivity and postpartum reproduction in beef females.

Sixty-two, 2-yr-old heifers and 65 cows, 4 to 7 yr old, were assigned randomly at 60 d before the median predicted calving date to a factorially designed study. Main effects were: age of dam (heifer or cow), moderate (M) or high (H) precalving feed level (110 or 135% of National Research Council recommendation) and short (S) or prolonged (P) duration of Stage II of parturition. After calving, all dams were placed in the same range pastures and received supplemental hay and a grain-salt mix until adequate range forage was available to produce weight gains in the lactating dams. Dams were bred in a 45-d artificial insemination period. Calving difficulty scores and duration of labor (Stage II) were greater (both P less than .01) in heifers than in cows; calf birth weight (P less than .01), calf vigor at birth (P less than .05) and calf gains birth to weaning (P less than .01) were higher in cows. Effect of gestation feed level on precalving, calving and postpartum data were nonsignificant. Eighty-two percent of the S females were given obstetrical assistance and 15% of the P females required assistance at parturition (P less than .01). More S dams exhibited estrus by the beginning of the breeding season than P dams (91.4 vs 81.7%, P less than .10), and October pregnancy of S dams was higher than P dams (89.5 vs 75.6%, P less than .05). Interaction effects of dam X duration of Stage II were not significant, but short duration of labor had beneficial effects on postpartum reproduction in both dam age groups. Results of this study indicate prolonged labor may result in depressed subsequent reproduction in beef dams.

Age Factors↗

PubMed1983

Clitoral stimulation and the effect of age, breed, technician, and postpartum interval on pregnancy rate to artificial insemination in beef cattle.

An experiment was conducted to assess the effect of clitoral stimulation on pregnancy rate to artificial insemination in 1,856 beef females. For unadjusted data, pregnancy rate to first service in nonstimulated females was 61% for cows and 59% for heifers, and that of females receiving clitoral stimulation was 69% for cows and 58% for heifers. After adjusting the data for the influences of age, breed, technician, and postpartum interval, clitoral stimulation increased first service pregnancy rate in cows (74+/-3% vs 59+/-3%, P<0.05), but not in heifers (53+/-5% vs 57+/-5%, P>0.10). Postpartum interval significantly influenced pregnancy rate, regardless of treatment, and clitoral stimulation was beneficial when applied to cows with relatively short postpartum intervals. Variation in the effect of clitoral stimulation on pregnancy rate was observed among technicians. Clitoral stimulation improved pregnancy rate more effectively in 3 to 4 year old cows than in cows 2 years old and cows 5 years of age or older. We concluded that clitoral stimulation at the time of artificial insemination was an effective means of increasing pregnancy rate in cows, but not in heifers.

Journal Article↗