Biomedical subjects

S E Echternkamp

Publications and source records attributed to S E Echternkamp.

At least 19 recordsLinked to original sources

PubMed2006

Association of a single nucleotide polymorphism in SPP1 with growth traits and twinning in a cattle population selected for twinning rate.

Continued validation of genetic markers for economically important traits is crucial to establishing marker-assisted selection as a tool in the cattle industry. The objective of the current study was to evaluate the association of a SNP (T(9)/T(10)) in the osteopontin gene (SPP1) with growth rate in a large cattle population spanning multiple generations and representing alleles from 12 founding breeds. This population has been maintained at the US Meat Animal Research Center since 1981 and subjected to selection for twinning rate. Phenotypic records for this population included twinning rate and ovulation rate, providing an opportunity to examine the potential effects of SPP1 genotype on reproductive traits. A set of 2,701 animals was geno-typed for the T(9)/T(10) polymorphism at SPP1. The geno-typic data, including previously genotyped markers on chromosome 6 (BTA6), were used in conjunction with pedigree information to estimate genotypic probabilities for all 14,714 animals with phenotypic records. The genotypic probabilities for females were used to calculate independent variables for regressions of additive, dominance, and imprinting effects. Genotypic regressions were fit as fixed effects in a mixed model analysis, in which each trait was analyzed in a 2-trait model where single births were treated as a separate trait from twin births. The association of the SPP1 marker with birth weight (P < 0.006), weaning weight (P < 0.007), and yearling weight (P < 0.003) was consistent with the previously reported effects of SPP1 genotype on yearling weight. Our data supports the conclusion that the SNP successfully tracks functional alleles affecting growth in cattle. The previously undetected effect of the SNP on birth and weaning weight suggests this particular SPP1 marker may explain a portion of the phenotypic variance explained by QTL for birth and HCW on BTA6.

Animals↗

PubMed2006

Localization of Period 1 mRNA in the ruminant oocyte and investigations of its role in ovarian function.

The clock gene Period 1 (Per1) may be a prolificacy gene, because it localized to the mouse oocyte and Per1-null drosophila shed fewer eggs. Because Per1 mapped to a region of mouse chromosome 11 syntenic to bovine chromosome 19 where a quantitative trait loci (QTL) for ovulation rate existed, we hypothesized that Per1 influenced folliculogenesis and ovulation rate in ruminants. Ovarian cortex was collected at slaughter on days 5, 12, 15, 17, and 20 after estrus for real-time RT-PCR evaluation of Per1 mRNA expression in Dorset (n = 18), Romanov (n = 10), Romanov/Dorset (n = 21), and Composite (n = 22) ewes. Ovarian cortex was also collected from cows selected for increased ovulation rate (n=37) or unselected controls (n = 28) on days 4, 5, and 6 of the estrous cycle for in situ hybridization and real-time RT-PCR. To examine the role of Per1 in early follicular development, ovarian cortex from neonatal calves (n = 5) was cultured for 10 days and Per1 mRNA levels were measured on day 0 and on day 10 of culture. The primers generated a 483bp amplicon with 100% sequence homology to bovine RIGUI-like protein (Per1). In silico mapping of this sequence placed Per1 on bovine chromosome 19; however, it was 20cM from the QTL. Per1 mRNA expression was unaffected by prolificacy, day of the cycle, or pregnancy status in ewes or cows. The riboprobe hybridized to oocytes of bovine preantral and antral follicles. In bovine ovarian cortical cultures on day 0, the tissue contained mostly primordial follicles (5.6+/-0.6 follicles/section); however, after 10 days in culture, the number of primordial follicles per section decreased (0.5 follicles/section) and the number of primary follicles increased as follicles activated (day 0 = 0.5+/- 0.6 versus day 10 = 10.4 +/-0.6 primary follicles/section; P < 0.001). Per1 mRNA did not change over time in culture. We conclude that Per1 mRNA is expressed by ruminant oocytes in preantral and antral follicles; however, its physiological role in mammalian ovarian function remains to be elucidated.

Animals↗

PubMed2006

Increased vascular endothelial growth factor and pregnancy-associated glycoproteins, but not insulin-like growth factor-I, in maternal blood of cows gestating twin fetuses.

Differences in placental mass and vascularity exist between cows gestating single vs. multiple fetuses. Therefore, the association between fetal number and placental development or function was assessed by comparing concentrations of vascular endothelial growth factor (VEGF), pregnancy-associated glycoproteins (PAG), IGF-I, and progesterone in the maternal blood of cattle selected for twin births and gestating 1 (n = 23) vs. 2 (n = 17) fetuses. Samples of jugular venous blood were collected serially at a mean of 57, 121, 192, and 234 d (range within groups was 20 d) after AI. Plasma concentrations of VEGF, IGF-I, and progesterone were measured by double-antibody RIA, and of PAG by an indirect sandwich ELISA. Concentrations of VEGF and progesterone were greater (P < 0.05) in dams with twin vs. single fetuses. Maternal VEGF concentrations did not differ among collection times, but progesterone concentrations increased (P < 0.01) between d 192 and 234. Conversely, PAG concentrations were low at d 57 and 121 and did not differ between dams carrying singles or twins. However, the subsequent increase (P < 0.01) in PAG was greater in dams with twins, resulting in greater (P < 0.01) PAG concentrations for dams with twins at d 192 and 234 (type of birth x time; P < 0.01). Maternal IGF-I concentrations were unaffected by fetal number. Because corpora lutea persisted for the duration of the evaluation period, maternal progesterone concentrations were likely related to the number of corpora lutea rather than the number of fetuses. It is postulated that the greater PAG and VEGF concentrations in the blood of dams gestating twins are the result of a larger uteroplacental mass, including increased numbers of binucleate cells and increased angiogenesis and vasculogenesis associated with a twin pregnancy. Although PAG and VEGF were elevated in dams gestating twins, variability within and among birth groups limits the use of PAG or VEGF measurements for the diagnosis of twins.

Animals↗

PubMed2006

Large variation in steroid concentrations and insulin-like growth factor binding proteins exists among individual small antral follicles collected from within cows at random stages of the estrous cycle.

Variation in the biochemical status of individual small (< or = 5 mm diameter) antral follicles within the ovaries of a cow at any given time likely influences the capacity for undergoing recruitment, selection, and establishing dominance. The objectives of this study were to provide insight into the magnitude of variation in follicular fluid concentrations of steroids and activities of IGFBP that exists among individual small antral follicles within and between cows, and to determine the relationships between follicular fluid IGFBP and steroid concentrations in these follicles. A total of 108 small antral follicles were collected from 6 cows at random stages of the estrous cycle, with 10 to 26 follicles/cow. Concentrations of steroids (ng/mL of follicular fluid) in the overall population of follicles ranged from 0.1 (lowest detectable limit) to 51 for estradiol (E2), 4 to 1,149 for progesterone (P4), and 5 to 504 for androstenedione (A4). Concentrations of E2 and A4 were associated positively (r = 0.2; P < 0.02), but E2 (r = -0.4) and A4 (r = -0.4) were associated negatively, with P4. The proportion of variation in steroid concentrations accounted for by differences among animals (P < 0.05) was small for E2 (12%), moderate for P4 (43%), and greatest for A4 (74%). Least differences between minimum and maximum concentrations of steroids observed in follicles from within a cow were 21-, 5.5-, and 3.5-fold for E2, P4, and A4, respectively, whereas the greatest differences between minimum and maximum concentrations were 505-, 108-, and 26-fold for E2, P4, and A4, respectively. Ranges of IGFBP concentrations (arbitrary densitometer units) detected in fluid from a sub-sample of 43 follicles were 1.18 to 4.50 for IGFBP-3, 0.54 to 4.68 for IGFBP-2, 0.07 to 2.56 for IGFBP-4, and 0.01 to 6.71 for IGFBP-5. Concentrations of E2 were correlated negatively with each IGFBP (r = -0.4 to -0.8; P < 0.05) except IGFBP-3. In contrast, concentrations of A4 were correlated positively with IGFBP-3 (r = 0.4; P < 0.05) but were not correlated with other IGFBP. Concentrations of P4 were correlated positively (r > 0.4; P < 0.05) with IGFBP-4 and -5. The results indicate that steroid concentrations and IGFBP activities vary substantially among small antral follicles collected from within and among individual animals and that increasing production of E2, the hallmark of a developing follicle, was associated with reduced activity of all IGFBP except IGFBP-3, thereby implicating these IGFBP in the regulation of follicular recruitment.

Androstenedione↗

PubMed2005

Evaluation of ovulation rate and ovarian phenotype in puberal heifers from a cattle population selected for increased ovulation rate.

Long-term selection for increased ovulation rate (1984 to 2002) has resulted in a unique ovarian phenotype in the MARC Twinner cattle population. Ovulation rate and frequency of bilateral ovulations were examined by rectal palpation in 29,547 estrous cycles for 3,910 heifers (12 to 18 mo of age) in this population. Bilateral ovulations (one corpus lutuem [CL] on each ovary) were of interest because bilateral twin pregnancies result in decreased dystocia and increased calf survival. Ovulation rate increased linearly at a rate of 0.026 CL per year, and it currently averages 1.48 +/- 0.04 CL per estrous cycle. Concurrent with the increase in ovulation rate, the frequency of triplet ovulations increased from 0% to 2.3 +/- 0.8% (P < 0.001). Ovulation rate of both the right and left ovary increased equally at a rate of 0.013 CL per year, and mean ovulation rate of the right ovary remained greater than mean ovulation rate of the left ovary throughout the study (0.66 vs. 0.55 +/- 0.003 CL per estrous cycle; P < 0.001). Although correlations were low, ovulation rate of one ovary was negatively correlated (P < 0.001; r = -0.07) with ovulation rate of the same ovary in the previous estrous cycle, but positively correlated (P < 0.001; r = 0.13) with the contralateral ovary of the previous estrous cycle. The proportion of bilateral ovulations averaged 55.7 +/- 0.7%, a value greater than the predicted 49.5% (P < 0.001). In addition to dystocia and retained placenta, triplet pregnancies increase the incidence of pregnancies gestating fetuses of opposite sexes and subsequent incidence of freemartins; thus, selection pressure on ovulation rate may need to be adjusted in the MARC Twinner population. The proportion of bilateral ovulations in the population is greater than expected, and this may be an economically important trait, which will respond to selection and be beneficial for improving bovine reproductive efficiency. Understanding factors controlling the increased functional activity of the right ovary and bilateral ovulations may provide further insights into the mechanisms controlling follicle selection and methods to improve reproductive management of cattle.

Animals↗

PubMed2004

Ovarian follicular development in cattle selected for twin ovulations and births.

Comparisons of numbers of antral ovarian follicles and corpora lutea (CL), of blood hormone concentrations, and of follicular fluid steroid concentrations and IGFBP activity were conducted between cows selected (twinner) and unselected (control) for twin births to elucidate genetic differences in the regulation of ovarian follicular development. Ovarian follicular development was synchronized among cows by a single i.m. injection of PGF2alpha on d 18 of the estrous cycle; six cows per population were slaughtered at 0, 24, 48, and 72 h after PGF2alpha. Jugular vein blood was collected from each animal at PGF2alpha injection and at 24-h intervals until slaughter. Ovaries of twinner cows contained more small (< or = 5 mm in diameter, P < 0.05), medium (5.1 to 9.9 mm, P < 0.05), and large (> or = 10.0 mm, P < 0.01) follicles and more (P < 0.01) CL than ovaries of controls. Follicular fluid concentrations of estradiol, androstenedione, testosterone, and progesterone reflected the stage of follicular development and were similar for twinner and control follicles at the same stage. Earlier initiation of follicular development and/or selection of twin-dominant follicles in some twinner cows resulted in greater concentrations of estradiol in plasma at 0, 24, and 48 h and of estradiol, androstenedione, and testosterone in follicular fluid of large follicles at 0 h after PGF2alpha for twinner vs. control cows (follicular status x time x population, P < 0.01). Binding activities of IGFBP-5 and -4 were absent or reduced (P < 0.01) in follicular fluid of developing medium and large estro-gen-active (estradiol:progesterone ratio > 1) follicles but increased with atresia. Only preovulatory Graafian follicles lacked IGFBP-2 binding, suggesting a possible role for IGFBP-2 in selection of the dominant follicle. Concentrations of IGF-I were twofold greater (P < 0.01), but GH (P = 0.10) and cholesterol (P < 0.05) were less in blood of twinners. Three generations of selection of cattle for twin ovulations and births enhanced ovarian follicular development as manifested by increased numbers of follicles within a follicular wave and subsequent selection of twin dominant follicles. Because gonadotropin secretion and ovarian steroidogenesis were similar for control and twinner cattle, enhanced follicular development in twinners may result from decreased inhibition by the dominant follicle(s), increased ovarian sensitivity to gonadotropins, and/or increased intragonadal stimulation, possibly by increased IGF-I.

Androstenedione↗

PubMed2003

Characterization of gene expression in double-muscled and normal-muscled bovine embryos.

Myostatin, a member of the transforming growth factor-beta superfamily, is a negative regulator of skeletal muscle growth. Cattle with mutations that inactivate myostatin exhibit a remarkable increase in mass of skeletal muscle called double muscling that is accompanied by an equally remarkable decrease in carcass fat. Although a mouse knockout model has been created which results in mice with a 200% increase in skeletal muscle mass, molecular mechanisms whereby myostatin regulates skeletal muscle and fat mass are not fully understood. Using suppressive subtractive hybridization, genes that were differentially expressed in double-muscled vs. normal-muscled cattle embryos were identified. Genetic variation at other loci was minimized by using embryonic samples collected from related Piedmontese x Angus dams or Belgian Blue x Hereford dams bred to a single sire of the same breed composition. Embryos were collected at 31-33 days of gestation, which is 2-4 days after high-level expression of myostatin in the developing bovine embryo. The suppressive subtraction resulted in 30 clones that were potentially differentially expressed, 19 of which were confirmed by macroarray analysis. Several of these genes have biological functions that suggest that they are directly involved in myostatin's regulation of skeletal muscle development. Furthermore, several of these genes map to quantitative trait loci known to interact with variation in the myostatin gene.

Animals↗

PubMed2003

Insulin-like growth factor binding proteins in granulosa and thecal cells from bovine ovarian follicles at different stages of development.

Because IGFBP inhibit IGF-stimulated cellular proliferation and differentiation, it is hypothesized that variations among IGFBP in individual follicles might contribute to the regulation of recruitment, selection, dominance, and turnover of ovarian follicles. Sources of IGFBP in fluid of bovine follicles are not well established; thus, objectives of this study were to determine levels of IGFBP binding activities and messenger RNA (mRNA) in granulosa and theca interna cells at different stages of follicular development (small [< 6 mm], medium [6 to < 8 mm], and large [> or = 8 mm]) and to characterize associations of these levels measured in the cells with levels of IGFBP and steroids in follicular fluid. Thecal and granulosa cells from large healthy follicles contained two- to twentyfold less (P < 0.05) IGFBP-2, -3, and -5 than cells from small, medium, and large atretic follicles. Thecal cells from small, medium, and large atretic follicles contained more (P < 0.05) IGFBP-3 and -4 than granulosa cells from these follicles, whereas granulosa cells from these follicles contained more IGFBP-2 activity than thecal cells. Differences in IGF binding activity were paralleled by differences in levels of mRNA for the respective IGFBP. Developmental differences in IGFBP activity in follicular fluid were positively associated with activity in granulosa and/or thecal cells, with the exception of IGFBP-4, which was low in fluid from large healthy follicles but markedly increased (mRNA and binding activity) in granulosa cells from these follicles. It is concluded that developmental changes in follicular fluid IGFBP-2 and -5 binding activities seem to be controlled in part by alterations in synthesis of these IGFBP by granulosa and thecal cells, whereas diminished IGFBP-4 in fluid from large healthy follicles occurs concomitantly with increased levels of IGFBP-4 mRNA and activity in granulosa cells, implicating posttranslational regulation by specific proteases.

Animals↗

PubMed2000

Initial results of genomic scans for ovulation rate in a cattle population selected for increased twinning rate.

Genomic scans were conducted with 273 markers on 181 sires from a cattle population selected for increased twinning rate to identify chromosomal regions containing genes that influence ovulation rate. Criteria used for selecting markers were number of alleles, ease of scoring, and relative position within linkage group. Markers were multiplexed or multiple-loaded on the gels to reduce the costs and labor required to obtain genotypic data. This approach reduced the number of gels by 45% when compared with running each marker independently. Male animals selected for the genomic scan sired the majority of the population. A modified interval analysis was used in a granddaughter design to compare effects of each allele within sire for 10 different sire families. The midparent deviation of the son's estimated breeding value for ovulation rate was used as the phenotype. Forty-one potential peaks were identified with a nominal significance level < or = 0.05. The 10 peaks with the highest significance levels (P < 0.02) were selected for further analysis. Markers were genotyped across daughters of the sire where nominal significance was found for each of the 10 peaks. One peak (BTA5, relative position 40 cM) was found to be nominally significant in the daughters. The nominal significance levels were P = 0.01 for the sons (n = 32) and P = 0.02 for the daughters (n = 94) of sire 784403. A combined genomewide significance value (P = 0.07) was calculated that accounted for the 10 analyses with sons and the 10 analyses with daughters. These results strongly suggest that this region contains a gene(s) that is involved in the follicular recruitment and development process.

Animals↗

PubMed2000

Evaluation of numbers of microscopic and macroscopic follicles in cattle selected for twinning.

We hypothesized that the number of microscopic follicles present in the ovaries of cattle selected for twin births (Twinner) would be greater than in the ovaries of contemporary Controls. Ovaries were collected from seven Control and seven Twinner cows at slaughter. The number of Small (1 to 3.9 mm), Medium (4 to 7.9), and Large (> 8 mm) surface follicles was counted and one ovary was fixed for histological evaluation. Fifty to sixty consecutive 6-microm slices were taken from a piece of cortical tissue, approximately 1 cm x 1 cm in area, located between the surface follicles. Microscopic follicles were classified as primordial (oocyte surrounded by a single layer of squamous pregranulosa cells), primary (oocyte surrounded by a single layer of one or more cuboidal granulosa cells), secondary (oocyte surrounded by two or more layers of granulosa cells), or tertiary (oocyte surrounded by multiple layers of granulosa cells with initiation of antrum formation to < or = 1 mm in diameter). The total number of follicles was counted in 200 fields (2 mm x 2 mm) per ovary. A field containing no follicles was classified as empty. There were significantly more secondary follicles in Twinner compared with Control ovaries (12.9 vs 6.3; P < .05). Twinners also tended to have more small surface follicles (35.4 vs 49.0; P < 0.1). We conclude that ovaries of Control and Twinner cows do not differ in the number of primordial follicles or in the number of follicles activated into the growing pool; however, Twinner cows are able to maintain more growing follicles at the secondary and subsequent stages of development.

Animals↗

PubMed1999

Effects of twinning on gestation length, retained placenta, and dystocia.

Constraints to maximal productivity from twinning in beef cattle include increased incidence of dystocia and retained placenta, longer postpartum interval, and lower conception rate. Incidence and cause(s) of the shorter gestation length and of the increased retained placenta and dystocia associated with twinning were evaluated for 3,370 single and 1,014 twin births produced in a population of cattle selected for natural twin births. Gestation length was shorter for twin than for single pregnancies (275.6 vs. 281.3 d, P<.01) and likely contributed to the higher incidence of retained placenta associated with twin births (27.9 vs. 1.9%; P<.01). Incidence of retained placenta was also higher in the spring (March-April) than in the fall (August-September) calving season (18.3 vs. 11.4%; P<.01). The higher incidence of dystocia with twins than with singles (46.9 vs. 20.6%, P<.01) was primarily due to abnormal presentation (37.0 vs. 4.5%, respectively) of one or both twin calves at parturition. First- (40.5%) and second- (22.7%) parity dams with a single birth had more (P<.01) dystocia than older dams (13.4%), whereas dystocia was not affected (P>.10) by parity with twin births. Because of the shorter gestation length and the increased incidence of retained placenta and(or) dystocia, achievement of increased productivity with twinning in cattle necessitates intensive management of twin-producing dams and their calves during the calving season. Management of the increased dystocia can be facilitated by preparturient diagnosis of twin pregnancies, enabling timely administration of obstetrical assistance to facilitate delivery of twin calves and to increase their neonatal survival.

Animals↗

PubMed1999

Effects of twinning on postpartum reproductive performance in cattle selected for twin births.

The effects of twinning, dystocia, retained placenta, and body weight on postpartum reproduction were evaluated for 3,370 single and 1,014 twin births. Females were bred by AI for 40 d followed by 20 or 30 d of natural service with equal numbers bred and calved in spring and fall. Percentage of dams cyclic by the end of the AI period was lower (P<.05) for dams birthing and nursing a single calf (92.4%) than for dams birthing twins and nursing zero (98.7%) or two (94.7%) calves. Whereas the interval from parturition to first estrus was shorter (P<.01) for dams birthing and nursing a single (56.9 d) than for dams birthing twins and nursing one (68.5 d) or two (69.6 d) calves, length of the interval was further reduced by dystocia in nonlactating dams of either twins or singles (type of birth x dystocia, P<.05). Ensuing pregnancy rates were also affected by type of birth and dystocia. Without dystocia, dams birthing and nursing a single calf had a higher pregnancy rate (79.2%) than dams birthing twins and nursing one (61.7%) or two (66.3%) calves, whereas the lower ensuing pregnancy rates associated with dystocia in dams of singles (71.9%) resulted in similar rates among dams of singles and twins with dystocia (type of birth x dystocia; P<.01). Having a retained placenta resulted in a lower incidence of (93.5 vs. 96.4%, with vs. without; P<.05) and a longer interval to (64.7 vs. 59.2 d; P<.01) estrus while reducing subsequent pregnancy rates (X = 9.6%) in 3 of the 7 yr evaluated (retained placenta x year, P<.01). Because all parous females were bred during the same calendrical period, the shorter gestation length for twin calves (275.6 vs. 281.3 d) resulted in a longer interval from parturition to conception for twin births, whereas means for conception date differed by only 2 d between dams of twins and singles. Furthermore, a reduction (P<.01) in the interval to conception occurred with dystocia in dams of singles (89.3 vs. 85.0 d, without vs. with dystocia) and of twins nursed by zero (116.9 vs. 83.5 d), one (100.2 vs. 92.8 d), or two (96.1 vs. 97.2 d) calves. Another detriment to fertility was the higher incidence of fetal mortality or abortions associated with twin vs. single pregnancies (12.4 vs. 3.5%; P<.01). However, despite the lower conception rates for dams of twins, the increased prolificacy provides an opportunity to increase total beef production with a twinning technology.

Animals↗

PubMed1998

A model of litter size distribution in cattle.

Genetic increases in twinning of cattle could result in increased frequency of triplet or higher-order births. There are no estimates of the incidence of triplets in populations with genetic levels of twinning over 40% because these populations either have not existed or have not been documented. A model of the distribution of litter size in cattle is proposed. Empirical estimates of ovulation rate distribution in sheep were combined with biological hypotheses about the fate of embryos in cattle. Two phases of embryo loss were hypothesized. The first phase is considered to be preimplantation. Losses in this phase occur independently (i.e., the loss of one embryo does not affect the loss of the remaining embryos). The second phase occurs after implantation. The loss of one embryo in this stage results in the loss of all embryos. Fewer than 5% triplet births are predicted when 50% of births are twins and triplets. Above 60% multiple births, increased triplets accounted for most of the increase in litter size. Predictions were compared with data from 5,142 calvings by 14 groups of heifers and cows with average litter sizes ranging from 1.14 to 1.36 calves. The predicted number of triplets was not significantly different (chi2 = 16.85, df = 14) from the observed number. The model also predicted differences in conception rates. A cow ovulating two ova was predicted to have the highest conception rate in a single breeding cycle. As mean ovulation rate increased, predicted conception to one breeding cycle increased. Conception to two or three breeding cycles decreased as mean ovulation increased because late-pregnancy failures increased. An alternative model of the fate of ova in cattle based on embryo and uterine competency predicts very similar proportions of singles, twins, and triplets but different conception rates. The proposed model of litter size distribution in cattle accurately predicts the proportion of triplets found in cattle with genetically high twinning rates. This model can be used in projecting efficiency changes resulting from genetically increasing the twinning rate in cattle.

Animals↗

PubMed1997

Genetic and environmental parameters for ovulation rate, twinning rate, and weight traits in a cattle population selected for twinning.

A project was implemented in 1981 with the objective of increasing twinning rate in cattle. Daughters of foundation sires had twin calves at a frequency of from 8 to 13%, and foundation females had twin calves at an average frequency of 50%. Data were analyzed on twinning rate, ovulation rate, and weight traits. The h2 of ovulation rate increased from .11 to .38 for a single estrous cycle to the mean of eight estrous cycles. From all data, h2 for single observation of ovulation rate and twinning rate were .10 and .09, respectively. The r(g) between them was .75. The h2 of weight traits ranged from .42 to .54 when weight traits were analyzed pair-wise with ovulation rate and with twinning rate. The r(g) between weight traits with ovulation rate ranged from .15 to .30 and with twinning rate ranged from .24 to .39. Phenotypic mean twinning rate increased from 1.07 to 1.29 calves per parturition for females born 1981 through 1993, and adjusted mean predicted breeding value (PBV) increased from 1.07 to 1.33 calves per parturition. Phenotypic mean ovulation rate for fall of 1984 through fall 1994 birth groups increased from 1.11 to 1.26 per estrous cycle, and adjusted mean PBV for ovulation rate increased from 1.11 to 1.29 per estrous cycle. Because of the high r(g) (i.e., .75) between ovulation rate and twinning rate, and because of a h2 of .35 for ovulation rate for the mean of six estrous cycles, repeated records of ovulation rate in puberal heifers is an effective indirect selection criterion for twinning rate. The positive r(g) between growth traits and ovulation and twinning rate suggest the need for some compromise when the selection goal is increased twinning rate with no increase in growth and size.

Animals↗

PubMed1996

Levels of insulin-like growth factor (IGF) binding proteins, luteinizing hormone and IGF-I receptors, and steroids in dominant follicles during the first follicular wave in cattle exhibiting regular estrous cycles.

Objectives of this study were to determine if concentrations of steroids, insulin-like growth factor -I (IGF-I), and IGF binding proteins (IGFBP) in follicular fluid and numbers of LH and IGF-I receptors change during growth of the dominant follicle. Ovarian follicular development was monitored daily via ultrasound in lactating Holstein cows. Animals underwent bilateral ovariectomy when the dominant follicle was first identified (days 4-6; estrus = day 0; early; n = 5) or when it stopped growing (days 8-12; late; n = 8). All follicles were classified as dominant (DF), large (LG; > = 6 mm in diameter, excluding DF) or small (SM; < 6 mm), follicular fluid was aspirated, and theca and granulosa cells were collected. Levels of IGFBP-2, assessed via ligand blotting, were greater (P < 0.05) in LG and SM follicles compared with DF in early cows. Levels of IGFBP-3 in follicular fluid were unaffected by follicle class. Numbers of specific 125I-hCG/LH binding sites in thecal cells were greater (P < 0.01) in DF compared with LG and SM follicles of both early and late cows. Numbers of specific 125I-hCG/LH binding sites in granulosa cells were similar for follicle sizes in early cows, but, in late cows, were greater (P < 0.01) in DF compared with SM follicles and were severalfold greater (P < 0.01) in late DF compared with early DF. Numbers of receptors for IGF-I in thecal cells were 2-fold greater (P < 0.05) in DP and LG compared with SM in late cows. Numbers of IGF-I receptors in granulosa cells were unaffected by size or growth of follicles, but were severalfold greater than in theca cells. Concentrations of estradiol were severalfold greater (P < 0.01) in DF compared with LG and SM in both early and late cows. Concentrations of androstenedione in early cows were greater (P < 0.05) in DF and SM compared with LG follicles. Concentrations of progesterone and IGF-I did not differ (P > 0.10) among follicle classes, but both were greater (P < 0.10) in late LG compared with early LG follicles. Concentrations of IGF-II in follicular fluid did not differ (P > 0.10) between early and late cows but were greater (P < 0.10) in SM than DF or LG follicles. We conclude that low amounts of IGFBP-2 and increased thecal binding sites for hCG/LH appear to be related to establishment of the dominant follicle during the first follicular wave in cattle exhibiting regular estrous cycles during late lactation.

Androstenedione↗

PubMed1996

Effects of twinning on dystocia, calf survival, calf growth, carcass traits, and cow productivity.

This paper reports results from a long-term experiment with a primary objective to increase twinning rate in cattle at the Roman L. Hruska U.S. Meat Animal Research Center. Survival of singles was 13% higher (P < .01) than that of twins at birth, and the difference in survival in favor of singles was of similar magnitude at 72 h (12.9%, P < .01), 150 d (14.8%, P < .01), and 200 d (15.2%, P < .01). Survival of calves with no dystocia was higher than survival of calves with dystocia: 8.6% (P < .01) at birth, 10.8% (P < .01) at 72 h, 12% (P < .01) at 150 d, and 12.2% (P < .01) at 200 d. The effect of dystocia on survival was greater (P < .01) in twins than in singles at birth and at 72 h. Least squares means for dystocia were 20.4% in singles compared with 42.2% in twins. Most of the dystocia in singles resulted from a traction requirement (84.7%) of normal presentations, whereas most of the dystocia in twins (77.8%) resulted from malpresentations, with 59.2% of the malpresentations accompanied with a requirement for traction. Survival in singles ranged from 10.7% to 15.3% greater than in twins at different ages when there was no requirement for assistance in either singles or twins. Calves born as singles were 8.8 kg heavier (P < .01) at birth and 28 kg heavier (P < .01) at 200 d than calves born and reared as twins. Calf weight produced per cow calving was 53.1%, 54.7%, and 58.4% greater (P < .01) at birth, 150 d, and 200 d, respectively, in cows producing twins than in cows producing singles. Cows producing twins had 65.2% more (P < .01) live calves at 200 d than cows producing singles. Single male calves gained 74 g more per day than twin males from birth to 200 d, 45 g more (P < .01) per day from 200 d to slaughter and 57 g more (P < .01) per day from birth to slaughter. Differences between twin and single males in carcass traits were small. A sample of steers from the Twinning Project gained significantly faster and produced significantly more desirable carcasses than a sample of steers from a high performance reference population. Freemartins did not differ (P < .05) from normal females in growth traits, but freemartins had higher (P < .05) scores for marbling with a higher percentage (P < .05) of USDA Choice or better quality grade carcasses and lower estimated percentage retail product.

Analysis of Variance↗

PubMed1995

The ovarian insulin and insulin-like growth factor system with an emphasis on domestic animals.

Insulin and insulin-like growth factors (IGFs) have direct effects on cultured ovarian cells. These effects include stimulation of granulosa cell mitogenesis, granulosa and luteal cell progesterone production, and thecal cell androgen production and appear similar among species. However, species differences exist with regard to insulin and IGF-I effects on granulosa cell estradiol production. In addition to endocrine effects of insulin and IGFs, IGFs are produced by granulosa, thecal, and luteal cells, allowing for an intraovarian autocrine and paracrine system. Granulosa, thecal, and luteal cells contain receptors for insulin and IGFs, and these receptors appear to mediate the effects of insulin and IGFs. Adding to the complexity of the regulatory role of IGFs is the presence of IGF-binding proteins (IGFBPs) within the ovary. These IGFBPs are produced by granulosa, thecal, and luteal cells, and their production is hormonally regulated. Evidence for a coherent mechanism by which insulin, IGFs, and IGFBPs interact and regulate ovarian function in vivo has yet to be found.

Animals↗

PubMed1995

Serum hormones, follicular fluid steroids, insulin-like growth factors and their binding proteins, and ovarian IGF mRNA in sheep with different ovulation rates.

Ovulation rate, serum hormone concentrations, follicular fluid (FFL) concentrations of steroids and IGF, IGF binding protein (IGFBP) activity in FFL, and follicular IGF-I and -II mRNA were compared during the follicular phase among five genotypes of ewes: Finn (F), Composite III (C), 1/2 Booroola Merino (B) x 1/2 F (B x F), 1/2 F x 1/2 C (F x C), 1/2 B x 1/2 C (B x C). Composite III ewes were a Columbia x Suffolk x Hampshire crossbred. Ovulation rates for F (n = 7), C (n = 5), B x F (n = 6), F x C (n = 3), and B x C (n = 8) ewes were 3.1, 1.6, 3.8, 2.9, and 2.9 (Pooled SEM = .5), respectively. Concentrations of IGF-I in FFL were 53% greater (P < .05) in large (> or = 4.1 mm) than in small (< 4.1 mm) follicles but did not differ (P > .10) among genotypes. In contrast, FFL IGF-II concentrations were greater (P < .05) in B x C and B x F ewes than in C or F x C ewes but did not differ between small and large follicles. Ligand blotting revealed that IGFBP activity of three species (34, 27 to 29, and 24 kDa) were lower (P < .05) in FFL of large than in FFL of small follicles but did not differ (P < .10) among genotypes. Follicular wall IGF-I mRNA and IGF-II mRNA was detected in 5 and 32% of the samples from preovulatory follicles, respectively, using reverse transcriptase-PCR and ethidiumbromide staining. Ovarian IGF-I mRNA levels, assessed by Northern analysis, in B x F and B x C ewes were greater (P < .05) than those in C ewes; ovarian IGF-I mRNA levels in F and F x C ewes were intermediate and did not differ (P > .10) from those in C ewes. Small follicles from B x C and B x F ewes had severalfold greater (P < .05) estradiol concentrations than those from F or C ewes, whereas large follicles from B x F ewes had twice (P < .05) the estradiol concentrations of follicles from F or C ewes. Progesterone in FFL did not differ among genotypes. Serum LH, FSH, inhibin, IGF-I, and progesterone did not differ (P > .10) among genotypes.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗