Biomedical subjects

J J Ford

Publications and source records attributed to J J Ford.

At least 73 records · Page 4Linked to original sources

PubMed1992

Effects of weaning on concentrations of inhibin in follicular fluid and plasma of sows.

Changes in plasma and follicular fluid concentrations of inhibin were examined in sows after weaning at 28-32 days post partum. From 0 to 48 h after weaning, inhibin concentrations were 200-300 times higher in follicular fluid from small (less than 4 mm) and medium-large (greater than or equal to 4 mm) follicles than in ovarian venous plasma. Inhibin concentrations increased in follicular fluid from medium-large follicles at 24 and 48 h after weaning; concentrations in ovarian venous plasma were positively correlated with the number of medium-large follicles (r = 0.40) and with ovarian venous plasma concentrations of oestradiol (r = 0.61). Blood samples were collected for 30 days from sows (n = 6) that exhibited oestrus within 5 days after weaning and from sows (n = 5) that remained anoestrous for 11 days after weaning. Plasma inhibin concentrations rose in oestrous and anoestrous sows by 12 h and continued to rise for 60 h after weaning. Plasma inhibin concentrations rose further and were higher at 3.5-4.5 days after weaning in oestrous sows than in sows that remained anoestrous. After oestrus, plasma inhibin concentrations declined. At weaning, plasma concentrations of follicle-stimulating hormone (FSH) were higher in sows that subsequently exhibited oestrus than in sows that remained anoestrous. After weaning, plasma concentrations of FSH declined in both groups, reached a nadir at 2.5 days, and increased gradually in anoestrous sows; oestrous sows exhibited an FSH surge at oestrus. Plasma FSH returned to preweaning concentrations in both groups of sows at Days 7-8.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Ovarian follicular changes after weaning in sows.

Three experiments investigated ovarian follicular development in sows whose litters were weaned at 28 to 31 d of lactation. Unilateral ovariectomy near the time of weaning was used to assess early follicular characteristics and to identify those sows that would not return to estrus within 10 d after weaning. This allowed segregation of and exclusion from the study those sows that had a prolonged interval from weaning to first estrus. In Exp. 1, 82 and 72% of the large follicles that were marked at 48 or 72 h after weaning (10 sows per time point) were subsequently identified as corpora lutea. In Exp. 2, sows (seven to nine per time point) were unilaterally ovariectomized at 0, 6, 12, 18, 24, or 48 h after weaning, and follicular fluid was evaluated for changes in steroid concentrations. Progesterone concentrations in fluid from medium-sized (4 to 6 mm) follicles increased by 6 h after weaning and then declined through 24 h concomitant with increases in testosterone and estradiol. For Exp. 3, follicular fluid and granulosa cells from individual follicles were obtained from sows (seven to nine per time point) at 0, 6, and 24 h after weaning. In follicular fluid, insulin-like growth factor I (IGF-I) concentrations were not correlated (P greater than .05) with concentrations of progesterone, testosterone, or estradiol, or with granulosa cell production of estradiol during culture in androstenedione-supplemented medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Characterization of thymic weight and thymic peptide thymosin-beta 4: effects of hypophysectomy, sex, and neonatal sexual differentiation.

An initial experiment was conducted to analyze the effects of hypophysectomy (Days 5-30 post hypophysectomy) on thymic weight and thymosin-beta 4 concentrations. After hypophysectomy, thymic weight and thymosin-beta 4 concentrations decreased with time (5, 10, 15, and 30 days post hypophysectomy) and by 30 days post hypophysectomy were reduced by 50%. Exp. II investigated the effects of early sexual differentiation on thymic weight and thymosin-beta 4 concentrations in pituitary intact and hypophysectomized male, female, nonmasculinized rats (via castration of males at Day 2 or 11 of age and androgenized female (at Day 3 of age) rats. Rats were hypophysectomized at 30 days of age and, at 17 days post hypophysectomy, the thymus gland was dissected and weighed. Serum was collected for thymosin-beta 4 analysis. At 47 days of age, males have a greater thymic weight when compared to females (p less than 0.01) but hypophysectomy eliminated any sex differences and significantly reduced thymic weights (p less than 0.05). Hypophysectomy did produce increased thymosin-beta 4 concentrations across all treatments (p less than 0.01) and is considered to be a combination response of decreased gonadal function via lack of pituitary hormonal stimulation (luteinizing hormone and follicle stimulating hormone) and lack of gonadotrophic effects on the thymus gland and its secretory capacity. Hypophysectomized males and Day-2 castrate males had increased thymosin-beta 4 concentrations when compared to hypophysectomized females and neonatally androgenized females (p less than 0.05). Differences of thymic weights between male and female rats during prepubertal development are probably related more to presence or absence of gonads, gonadal steroids, and response of the thymus to pituitary secretagogues rather than to neonatal sexual differentiation of thymic function and secretion of thymosin-beta 4.

Animals↗

PubMed1991

Effects of neonatal sexual differentiation, growth hormone and testosterone on thymic weights and thymosin-beta 4 in hypophysectomized rats.

Experiments were conducted to analyze the effects of growth hormone and testosterone in conjunction with the effects of neonatal sexual differentiation (via castration of males at days 2 or 11 of age and androgenization of females at day 3 of age) on thymic weight and thymosin-beta 4 concentrations in hypophysectomized rats (day 30 of age). Ten days post-hypophysectomy, hormonal treatments were initiated on males, male castrates, females, and androgenized females. Growth hormone (25 micrograms daily), testosterone propionate (100 micrograms/day), and the combination of the two hormonal treatments were administered for seven days, then thymic weights and blood samples were collected. Administration of growth hormone to hypophysectomized rats increased thymosin-beta 4 concentration in a dose-dependent manner, but injection of testosterone had no effect on thymosin-beta 4 concentrations. Testosterone treatment decreased thymic weights whereas growth hormone increased thymic weights. Hypophysectomized males had increased thymosin-beta 4 concentrations compared with female and neonatally-androgenized female rats. However, hypophysectomy eliminated any thymic weight differences between males and females. The data support a possible endocrine role for the thymus gland and thymic peptides in that they are integrated into the control and support of other endocrine systems. Although differences in thymosin-beta 4 concentrations were noted between males and females, sexual differentiation of the immune system was unaltered by neonatal castration of males or testosterone treatment of females and may indicate sexual differences in immune function are established in utero.

Animals↗

PubMed1991

Growth hormone and prolactin secretion in hypophysial stalk-transected pigs as affected by growth hormone and prolactin-releasing and inhibiting factors.

Control of growth hormone (GH) and prolactin (PRL) release was investigated in hypophysial stalk-transected (HST) and stalk-intact pigs by determining the effects of analogs of GH-releasing factors (GHRF), somatostatin (SRIF), arginine, thyrotropin-releasing hormone, alpha-methyl-rho-tyrosine, and haloperidol. HST and control gilts were challenged with intravenous injections of human pancreatic GHRF(1-40)OH, thyrotropin-releasing hormone, and analogs of rat hypothalamic GHRF. HST animals remained acutely responsive to GHRF by releasing 2-fold greater quantities of GH than seen in controls. This occurred in spite of a 38% reduction in pituitary gland weight and a 32 and 55% decrease in GH concentration and total content. During SRIF infusion, GH remained at similar basal concentrations in HST and control gilts, but increased immediately after stopping SRIF infusion only in the controls. Releasable pituitary GH appears to accumulate during SRIF infusion. GHRF given during SRIF infusion caused a 2-fold greater release of GH than seen in animals receiving only GHRF. Arginine increased (P less than 0.05) GH release in controls, but not in HST gilts, which suggests that it acts through the central nervous system. Basal PRL concentrations were greater (P less than 0.05) in HST gilts than in control gilts. TRH acutely elevated circulating PRL (P less than 0.001) in HST gilts, suggesting that it acts directly on the pituitary gland. Haloperidol, a dopamine receptor antagonist, increased circulating PRL in controls but not in HST animals. alpha-Methyl-rho-tyrosine did not consistently increase circulating PRL, however, suggesting that it did not sufficiently alter turnover rate of the tyrosine hydroxylase pool. The results indicate that the isolated pituitary after HST remains acutely responsive to hypothalamic releasing and inhibiting factors for both GH and PRL release in the pig.

Adrenal Glands↗

PubMed1990

Sustained influence of previous estradiol or testosterone treatments on sexual behaviors of female pigs.

Two studies were conducted to determine the consequences of extended treatment with estradiol or testosterone on sexual behavior in postpubertal, female pigs. After ovariectomy, either steroid was administered for 6 weeks at dosages sufficient to maintain serum concentrations similar to those observed in mature male pigs. Behavioral evaluations were initiated 2 months after the last steroid treatment. These treatments reduced receptivity (immobile stance when placed with a mature male) and proceptivity (preference to remain near a mature male) in association with an increase in aggressive behavior. In females treated previously with both estradiol and progesterone, sexual behaviors 2 months later were similar to those of control females. When evaluations were repeated 5 months after extended estradiol treatment had ceased, receptivity and proceptivity had returned to that of control pigs and aggressive behavior had diminished greatly. Interpretation of these changes in behavior is that extended periods of estradiol or testosterone treatment sustain activational influences for a considerable amount of time after treatments cease and progesterone antagonizes estradiol's effect on these behaviors. In a companion study, pubertal and post-pubertal females were similar for receptivity but pubertal females spent less time near a mature male. This difference in proceptivity likely reflects a maturational change associated with sexual development in female pigs. Collectively, these observations in postpubertal, female pigs document that prolonged estrogen treatment will activate aggressive behaviors in association with reduced proceptivity and receptivity. Because these behavioral changes are reversible by 5 months after cessation of treatment, they are not the result of sexual differentiation.

Animals↗

PubMed1990

Follicle-stimulating hormone regulation of cytochrome P-450 side-chain cleavage messenger ribonucleic acid accumulation by porcine granulosa cells isolated from small and medium follicles.

The experiments described here were conducted to examine regulation of cytochrome P-450 side-chain cleavage (SCC) mRNA accumulation in porcine granulosa cells isolated from small (1-4-mm) and medium (5-6-mm) follicles. Granulosa cells were cultured under the following conditions: 1) for 48 h or 96 h with 0, 50, or 200 ng/ml porcine FSH; 2) for 96 h with 200 ng/ml FSH and aminoglutethimide (100 microM); and 3) for 96 h with forskolin (100 microM). Total RNA was extracted and examined by Northern and dot-blot hybridization analysis, and culture media were assayed for progesterone concentration. Northern blot analysis revealed a single band approximately 2.1 kb in size. Accumulation of SCC mRNA by granulosa cells was both FSH dose- and culture time-dependent (p less than 0.05) with maximal increases approximately 4.5 times control levels. Aminoglutethimide reduced progesterone production by about 80% while having no effect on granulosa cell accumulation of SCC mRNA compared to cells stimulated with 200 ng/ml of FSH. Forskolin-treated cells produced significantly more progesterone than did cells treated with FSH, but accumulation of SCC mRNA was similar. In response to FSH, concentration of SCC mRNA did not vary with follicle size, but granulosa cells from small follicles produced significantly more progesterone than did those from medium follicles. These results demonstrate that concentration of SCC mRNA in cultured porcine granulosa cells is FSH dose-dependent, does not vary significantly in cells from small- and medium-sized follicles, and is correlated with progesterone production, but may not parallel progesterone secretion. This last observation indicates that control at sites other than SCC mRNA can affect progesterone production.

Aminoglutethimide↗

PubMed1990

Temporal changes in the oxidation state in in vitro blood.

The rates at which the paramagnetic compounds deoxyhemoglobin (Hb) and methemoglobin (MHb) form in vivo within an area of hemorrhage are unknown. The present experiment establishes the baseline concentrations and rates of change in paramagnetic hemoglobin concentrations, as well as the pH in normal heparinized and clotted human blood maintained in vitro at 37 degrees C under anaerobic conditions over 30 hours. There was a moderate increase in Hb concentration in normal heparinized blood (average increase was 15.5%, rate = 0.50%/hour) and a slight increase in MHb concentration in the heparinized blood and clots (average increase was 1.4%, rate = 0.044%/hour). A second experiment was done to verify the activity of the RBC systems responsible for maintaining the hemoglobin molecule in the reduced state. Conversion of MHb to Hb in these samples proceeded at a rate of 5.6%/hour. In a third experiment, blood from 11 normal subjects maintained at 4 degrees C 25 degrees C was analyzed for MHb concentration over the course of 28 days. The level of MHb formation remained in the range of normal for at least 11 days in all subjects. The authors conclude that at basal conditions created in vitro, the blood levels of both Hb and MHb remain at relatively low levels. Therefore, if the accumulation of Hb and/or MHb occurs in acute in vivo hematomas it must be driven by intrinsic tissue factors.

Cerebral Hemorrhage↗

PubMed1990

Safety of 4-T MR imaging: study of effects on developing frog embryos.

Fertilized eggs of Rana pipiens (leopard frogs) were exposed to 0.15- or 4.5-T magnetic resonance (MR) imaging and were compared with unexposed fertilized eggs with respect to the percentage of embryos cleaving and percentage of tail buds forming normally. Similarly exposed or unexposed sperm were used to fertilize unexposed eggs, and the same parameters were observed. There was no evidence that MR imaging exposure at 0.15 or 4.5 T had any effect on cleaving embryos or tail bud formation. Since embryogenesis in amphibians is very sensitive to foreign insult, the authors conclude that exposure to a magnetic field of up to 4.5 T has no adverse effect on early development.

Animals↗

PubMed1990

Synergism of testosterone propionate with growth hormone in promoting growth of hypophysectomized rats: effect of sexual differentiation.

The effect of testosterone propionate (TP), alone and in combination with porcine GH, on the growth of hypophysectomized rats was investigated. An initial study determined doses of TP and GH which would result in a synergistic response. Hypophysectomized male rats, approximately 40 days of age, received GH at doses of 5, 25 and 62.5 micrograms/day administered in two injections/day at 08.00 and 16.00 h. At all doses of GH, administration of TP at 100 micrograms/day significantly enhanced the GH-stimulated rate of growth. This growth enhancement by TP was greatest in combination with GH at 25 micrograms/day. In a subsequent study, growth responses to 25 micrograms GH/day and 100 micrograms TP/day were examined in animals with differing degrees of sexual differentiation. Sex groups were: intact males, males castrated at 11 days of age and females administered 100 micrograms TP at 3 days of age (masculinized rats), and males castrated at 2 days of age and normal females (non-masculinized rats). In all sex groups, growth of hypophysectomized rats was stimulated by GH. Genetic sex and masculinization did not influence the response to GH. Masculinized hypophysectomized rats exhibited significantly greater rates of growth and final live, empty body, liver and kidney weights than non-masculinized hypophysectomized rats. All sex groups other than normal females responded synergistically to the combination treatment of GH plus TP. Rats that experienced neonatal exposure to testosterone became programmed to respond to testosterone and demonstrated greater rates of growth and body and organ weights when administered the combination of GH plus TP. These data indicate that TP synergizes with GH to promote growth of hypophysectomized rats appropriately programmed to respond.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Thymosin-beta 4 concentrations during the estrous cycle and after hypophyseal stalk transection of female pigs.

Thymosin-beta 4 (ThB4) concentrations in the peripheral circulation of pigs were investigated during the first 30 days after weaning and after hypophyseal stalk transection of ovariectomized females. Significant increases in ThB4 were observed during the day of weaning, during follicular development, and during early luteal formation. During the first period of follicular development (Days 1 to 5 after weaning), ThB4 was uniformly elevated for 3 days whereas during the second period of follicular development (days 21 to 25 after weaning), the increase in ThB4 was bimodal. This period of bimodal secretion was closely associated with luteolysis. ThB4 concentrations were low during the luteal phase when progesterone concentrations were at their greatest. In ovariectomized pigs, ThB4 concentrations were not influenced acutely by a single intravenous injection (2 micrograms) of luteinizing hormone-releasing hormone in control (hypophyseal stalk intact) or hypophyseal stalk transected females. Both of these treatment groups responded to luteinizing hormone-releasing hormone with increased secretion of luteinizing hormone. These studies determined that ThB4 secretion changed dramatically throughout the estrous cycle of pigs but failed to identify an acute association between increased luteinizing hormone secretion and ThB4 in ovariectomized pigs. Our observations support the hypothesis that the thymus gland interacts with the hypothalamopituitary-ovarian axis primarily through changes in secretion of ovarian steroids.

Animals↗

PubMed1990

Differentiation of sexual behaviour in pigs.

Behaviour in pigs is sexually dimorphic as early as 1 month of age; mounting of penmates is observed more frequently for males than for females. This mounting reaches its highest frequency during the 2nd month of life and then declines to a low frequency in prepubertal pigs. During the prepubertal period (3-5 months of age), bipotentiality of sexual behaviour is apparent in boars because they will not only mount oestrous females but they are also receptive to mounts by older, mature boars. If males are castrated during neonatal development (first 2 months of life) and treated acutely with oestrogen during adulthood, they display sexual behaviour that is characteristic of females; i.e. show a selective preference to remain near mature boars in a choice test, are receptive to mounts by mature boars, and have a short latency to receptivity after contact with a mature boar. Males that are castrated at 6 months of age or later, or males that are castrated neonatally and treated chronically with oestrogen or testosterone during the prepubertal period, display significantly less female behaviour after acute oestrogen treatment than do males castrated neonatally. Additionally, exposure of females to elevated testosterone during early fetal development results in no detectable changes in oestrous behaviour as adults. These observations support the hypothesis that defeminization of sexual behaviour in boars occurs as a result of elevated testicular steroids during pubertal development. The limited data available on masculine sexual behaviour in pigs indicate an activational role for gonadal steroids with little evidence for true masculinization per se. After prolonged testosterone treatment of mature females or males that are castrated before puberty, considerable courtship and mounting behaviours are exhibited by these individuals when placed with oestrous females. Studies have not evaluated differential sensitivity of such animals to dosage or duration of testosterone treatment. Differentiation of sexual behaviour in boars therefore involves primarily a loss of sensitivity to display female-typical behaviours. Presently, pigs differ from other mammals that have been investigated because sexual differentiation of reproductive behaviour occurs during pubertal development and not during gestation.

Animals↗

PubMed1989

The influence of androgenic and estrogenic hormones on sexual behavior in castrated adult male pigs.

The objectives of these studies were to evaluate the influence of testosterone propionate (TP), estradiol cypionate (EC), dihydrotestosterone propionate (DHTP), EC + TP, EC + DHTP, and TP + DHTP on traits of masculine sexual behavior in castrated adult male pigs of different breeds. Masculine sexual behavior was restored and maintained by TP, whereas EC initially activated sexual behavior, including copulation and ejaculation, but was unable to sustain copulatory behavior for the 8- to 18-week periods that were evaluated. Treatment with DHTP was ineffective for stimulation of sexual behavior; thus, it is suggested that testosterone promotes some aspects of masculine sexual behavior in male pigs via aromatization to estrogen, but both androgen and estrogen are required for maintenance of the full complement of masculine sexual behavior traits.

Androgens↗

PubMed1989

Adrenal and behavioral responses of swine restricted to varying degrees of mobility.

Adrenal and behavioral responses in swine restricted to varying degrees of mobility were examined to determine what component may impose chronic stress. The components of restriction considered were the inability to turn around and/or move freely. For 5 to 6 weeks 32 pigs were restrained such that pigs A) could move freely; B) could not turn around or move freely; C) could not turn around but could move back and forth the same distance as pigs in A; or D) could turn around but not move freely. After 4 weeks no significant differences due to degree of restraint were found in the profile of serum cortisol concentrations, neutrophil:lymphocyte ratio and ambulatory abilities; however overall cortisol concentrations were higher in pigs that could turn around but not move freely. Increases in serum cortisol due to ACTH injection were higher in pigs that could turn around but not move freely. No alterations in the manner in which gilts stood up and layed down could be observed. Collectively these data suggest that swine adapt when mobility is restricted to not turning around and not moving freely but cannot when animals can turn around but not move freely.

Adrenocorticotropic Hormone↗

PubMed1989

Purification, measurement, and tissue distribution of a dansyl-derivatized glycopeptide from low-molecular weight follicle-stimulating hormone-inhibitor-containing fractions of porcine follicular fluid.

We have used dansyl chloride (5-dimethylamino-1-naphthalenesulfonyl choloride) to form dansyl derivatives of amine-containing compounds in follicular fluid or highly purified fractions containing a low molecular weight (MW) inhibitor of follicle-stimulating hormone (FSH) binding to receptor (FSH-BI). This approach allowed sensitive detection of the derivatives based on their fluorescent properties. By taking advantage of the hydrophobic nature of the dansyl group, a dansyl derivative (RF = 0.15) identified in low MW FSH-BI preparations was purified from porcine follicular fluid. Based on chromatographic criteria using four different systems (thin-layer chromatography [TLC] and high performance liquid chromatography), the derivatized factor (D15) that was purified appeared to be homogeneous. A direct, chemical assay was developed for quantification of D15 from follicular fluid or tissue extracts. The highest concentration (153 ng/mg) of D15 was found in ovarian tissue of adult rats, lesser amounts were observed in kidney and liver tissues (93 and 62 ng/mg, respectively) and even less in diaphram and heart tissues (5 and 0.5 ng/mg, respectively). High concentrations of D15 were observed in derivatized extracts of tests from immature rats in which approximately twice as much D15 was found in Leydig cells (241 ng/mg) as in seminiferous tubules (136 ng/mg). In porcine ovarian tissue, granulosa cells from large follicles and corpora lutea (69 and 91 ng/mg, respectively) contained at least 4-fold higher concentrations than follicle wall tissue (14 ng/ml). Relative concentrations of D15 material were also determined in pools of bovine follicular fluid previously shown to contain low MW FSH-BI.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Differentiation of sexual behavior in cattle, sheep and swine.

Gonadal steroid hormones influence an animal's sexual behavior through two primary means. During development they affect differentiation of the brain (primarily in males), and after puberty, circulating concentrations of steroids influence expression of sexual behaviors. In mammals, sexual behaviors of females are regarded as inherent (independent of steroids secreted by the developing ovary). Males, on the other hand, must undergo active differentiation that is brought about by actions of testicular steroids on the brain during discrete sensitive periods of early development. Sexual differentiation in mammals is referred to as processes of defeminization and masculinization. Defeminization is loss of behavioral traits inherent to females and occurs prenatally in sheep but postnatally in swine. Comparative data are lacking for cattle, but preliminary evidence indicates prenatal defeminization of sexual behaviors. Masculinization is acquisition of behavioral traits characteristic of males. Adult females of all three species show mounting behavior after prolonged treatment with testosterone, and in cattle and swine, there is, as yet, no strong evidence that males undergo masculinization of sexual behaviors. In sheep, limited observations are suggestive of two sensitive periods for masculinization; one prenatally and one postnatally. The earlier concept that differentiation of sexual behaviors in mammals occurs prenatally in species with a long gestation and postnatally in species with a short gestation must now be modified in view of recent findings in swine, in which defeminization occurs postnatally. Further studies will likely identify additional species differences with respect to differentiation of sexual behaviors.

Animals↗

PubMed1988

T2 effect of hemoglobin concentration: assessment with in vitro MR spectroscopy.

T2 values were measured at 0.23 and 4.7 T for deoxygenated blood samples (43%-73% O2 saturation) with hematocrits of 18%-100%. An increase in the hematocrit produced a marked reduction in T2 at both field strengths. Cell lysis did not abolish the T2 effect at either field strength. The authors conclude that the increase in hemoglobin concentration caused by formation of a retracted clot is a cause of the hypointense appearance of acute hemorrhage compared with brain on T2-weighted clinical magnetic resonance images. This is particularly important on low-field-strength systems, which are not sensitive to the T2 shortening effects of paramagnetic intracellular deoxyhemoglobin.

Animals↗

PubMed1988

Postweaning growth, feed efficiency and chemical composition of sheep as affected by prenatal and postnatal testosterone.

Data were collected from intact males, castrated males and ewe lambs to investigate the effect of presence or absence of testosterone prenatally and during the postweaning period on postweaning growth, feed intake and carcass chemical composition. Half the lambs from each sex were the progeny of dams that had received five injections of testosterone cyprionate from d 32 through d 87 of gestation. Linear contrasts were used to detect differences. Postweaning daily gain of intact males was greater (P less than .01) than that of male castrates. Ewe lambs from treated dams had approximately 12% greater rate of growth (P less than .04) than ewe lambs from control dams. Ewe lambs from dams that had been treated were 28% more efficient (P less than .01) in the conversion of food to weight than those from untreated dams. Ewe lambs from treated dams had heavier livers (P less than .07). Carcass protein for intact males was greater (P less than .11) than for castrates, and extractable fat was less (P less than .05). Masculinization of growth characteristics of ewe lambs affected the quantity of carcass fat relative to control ewes (7.59 vs 8.92 kg). These ewe lambs also had more water in the carcass than did the control ewes (13.93 vs 12.29 kg). Administration of exogenous testosterone to pregnant ewes over an interval of time approximating time of sexual differentiation in the fetus enhances postweaning growth rate, feed conversion efficiency and chemical composition of genetic females.

Animal Nutritional Physiological Phenomena↗