Effects Of Active Immunization Research Articles

Feedlot performance of beef heifers implanted with Synovex-H: effect of melengestrol acetate, ovariectomy or active immunization against GnRH.

The effects on anabolic steroid implantation on feedlot performance and carcass composition and quality were examined in control (CNTRL), ovariectomized (OVX) or melengestrol acetate-fed (MGA) beef heifers or heifers actively immunized against GnRH (Anti-GnRH). Heifers (n = 112) were assigned randomly to a 2 x 4 factorial experiment. The two classes were made up of heifers not implanted and those implanted with Synovex-H. The four treatments were 1) CNTRL, 2) MGA, 3) OVX and 4) Anti-GnRH. Heifers were housed in individual pens and fed a high-energy diet for the 4-mo study. Synovex-H increased final live weight (P less than .005), carcass weight (P less than .005), ADG (P less than .0001) and feed efficiency (P less than .005) but did not alter carcass quality and yield grade (P greater than .05). Synovex-H increased deposition of protein (P less than .0001) and reduced deposition of fat (P less than .0001). Oral administration of MGA had no significant effect on feedlot performance or carcass quality. For heifers not implanted, active immunization against GnRH, but not ovariectomy, depressed ADG (P less than .05) and increased fat deposition (P less than .05) while reducing protein deposition (P less than .05). These effects of active immunization were reversed by concurrent administration of Synovex-H. Feedlot performance and carcass composition of heifers were improved by administration of anabolic steroids. When heifers were housed singly, neither ovariectomy, active immunization against GnRH nor oral administration of MGA improved feedlot performance of heifers implanted with Synovex-H.

Effects of active immunization against GnRH on LH, FSH and prolactin storage, secretion and response to their secretagogues in pony geldings.

Six pony geldings were actively immunized against GnRH conjugated to bovine serum albumin (BSA) to study 1) the relative dependency of LH and FSH storage, secretion and response to GnRH analog on GnRH bioavailability and 2) the effects of reduced GnRH bioavailability on GnRH storage in the hypothalamus. Five geldings were immunized against BSA. Geldings were immunized in December and 4, 8, 14, 20, 26 and 32 wk later. Ponies immunized against GnRH had increased (P less than .01) GnRH binding in plasma within 6 wk. By June, plasma concentrations of LH and FSH in ponies immunized against GnRH had decreased (P less than .02) by 86 and 59%, respectively, relative to ponies immunized against BSA. The LH response to an injection of GnRH analog, which did not bind to anti-GnRH antibodies, was reduced (P less than .005) by 90% in ponies immunized against GnRH relative to ponies immunized against BSA. In contrast, the FSH response to GnRH analog was similar (P greater than .1) for both groups. Immunization against GnRH reduced (P less than .05) weight of the anterior pituitary (AP) by 31%, LH content in AP by 91% and FSH content in AP by 55% relative to ponies immunized against BSA. There was no effect of GnRH immunization on prolactin characteristics or on GnRH concentrations in the median eminence, preoptic area or body of the hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

Active immunization of pigs against growth hormone-releasing factor: effect on concentrations of growth hormone and insulin-like growth factor 1.

Cyclic gilts (96 +/- 1 kg) were used to determine the effect of active immunization against growth hormone-releasing factor GRF(1-29)-NH2 on concentrations of growth hormone (GH) and insulin-like growth factor 1 (IGF-1). Gilts were immunized against GRF conjugated to human serum albumin (GRF-HSA, n = 5) or HSA alone at 180 d of age (wk 0). Booster doses were administered at wk 9 and 13. Seven days after the second booster (wk 14), blood samples were collected at 15-min intervals for 6 h before feeding and 30, 60, 120, 180 and 240 min after feeding. Eight days after the second booster, all gilts were administered a GRF analog, [desNH2Tyr1,Ala15]-GRF(1-29)-NH2, followed by an opioid agonist, FK33-824. Blood samples were collected at 15-min intervals from -30 to 240 min after injection. Immunization against GRF-HSA resulted in antibody titers, expressed as dilution required to bind 50% of [125I]GRF, ranging from 1:11,000 to 1:60,000 (wk 11 and 14); binding was not detectable or was less than 50% at 1:100 in HSA gilts (P less than .05). Episodic release of GH was abolished by immunization against GRF-HSA (P less than .05). Mean GH was decreased (P less than .07), but basal GH concentrations were not altered (P greater than .15) by immunization against GRF-HSA. Serum concentrations of IGF-1 were similar at wk 0, but concentrations were lower in GRF-HSA than in HSA gilts (P less than .05) at wk 14.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional morphology of testis and its excurrent ducts in rats immunized with synthetic luteinizing hormone releasing hormone conjugated to tetanus toxoid

The effects of active immunization against luteinizing hormone releasing hormone (LHRH) on the testis and its excurrent ducts in rats were studied using a synthetic LHRH peptide conjugated to tetanus toxoid (TT), with or without an adjuvant. The study demonstrated that LHRH-TT given alone did not elicit an appreciable immune response and that its immunogenicity could be enhanced by administration with an adjuvant, such as species-specific IgG or SPLPS. The anti-LHRH antibody response showed a corresponding regressive effect on the morphology of the testis and its excurrent ducts. The functional involution of the testis was reflected in the form of a block in spermatogenesis and the lowering of testosterone production; the basic structural organization of the testicular components was, however, maintained. Epididymal ducts displayed rather drastic atrophic changes, indicating that prolonged immunization may result in irreversible damage to the excurrent ducts and could, therefore, adversely affect the restoration of fertility even after the return of testicular function following decline in the immune response against LHRH. This could be an important consideration if LHRH immunization is to be used for male contraception.

Effects of Active Immunization Against Somatostatin on Serum Growth Hormone Concentration in Growing Pigs: Influence of Fasting and Repetitive Somatocrinin Injections*

Three experiments were conducted with growing pigs actively immunized against a protein-conjugated somatostatin (SRIF) in Freund's adjuvant. In the first experiment, blood from 24-week-old pigs (seven immunized and eight control) was sampled at 20-min intervals for 6 h to evaluate basal GH concentrations. The animals were then injected iv with porcine GH-releasing factor (GRF)-(1-29)NH2 (10 micrograms/kg). Before GRF stimulation, immunized animals had higher (P less than 0.05) baseline mean GH levels (2.6 vs. 1.4 ng/ml) and area under the GH curve (AUC; 1632 vs. 779 ng/min.ml); they also had higher AUC after GRF administration (4268 vs. 1972 ng/min.ml). In a second experiment eight immunized and eight control pigs were injected iv four times at 90-min intervals with porcine GRF (10 micrograms/kg). Control pigs responding to the first injection did not respond to the second and third, and those responding to the second did not respond to the first, third, and fourth, indicating a decreased responsiveness that was longer than 3 h post-GRF response in control pigs. SRIF-immunized pigs had a more consistent GH response to the GRF injections. Overall, a reduced response was observed after the second and the fourth injections in immunized pigs, although five and six of eight animals had a GH peak response higher than 10 ng/ml during these periods. In a third experiment, effects of fasting, GRF, and SRIF immunization were studied. Immunization and fasting had their own positive effects on serum GH levels. Immunization increased baseline mean GH levels (5.0 vs. 2.2 ng/ml) and total AUC before (2318 vs. 1073 ng/min.ml) and after (1886 vs. 910 ng/min.ml) iv GRF stimulation (10 micrograms/kg) compared to controls. Fasting increased the mean baseline GH level (4.5 vs. 2.6 ng/ml), and it increased AUC before exogenous GRF stimulation (2009 vs. 1392 ng/min.ml). In conclusion, SRIF in pigs seems to be a potent GH-governing factor, since, when inhibited, baseline mean GH levels increase, and a consistent response to GRF is observed. Fasting could increase GH concentrations by different ways: decreasing SRIF release and increasing GRF release or modifying the sensitivity of the somatotrophs to both factors.

Effect of active immunization against oxytocin on gonadotrophin secretion and the establishment of pregnancy in the ewe

A group of 14 ewes was actively immunized against oxytocin coupled to carrier protein, and comparisons of the reproductive status of these animals were made against ewes immunized against carrier protein only (N = 5) and untreated controls (N = 6). The last two groups were indistinguishable and were therefore combined as a single control group for analysis of the results. Oestrous cycle lengths were significantly extended in oxytocin-immunized ewes (P less than 0.005) with 42% of cycles lasting greater than 18 days. Cloprostenol treatment in the mid-luteal phase resulted in apparently normal luteal regression and re-ovulation, but luteal phase FSH concentrations and follicular phase LH concentrations were elevated in the immunized ewes, although surge levels of both hormones were unaffected. Measurements of free oxytocin concentrations in the blood suggested that these were significantly raised in treated animals. Progesterone concentrations in peripheral plasma were not altered by treatment. Mating resulted in a conception rate of 91% in control ewes compared with only 28% in oxytocin-immunized animals (P less than 0.01). There was no evidence of any conceptus material in the uteri of non-pregnant immunized ewes 25 days after service. Some had re-ovulated, whereas the ovaries of others contained mature corpora lutea which had been maintained. Ovarian histology appeared normal. We conclude that active immunization against oxytocin influences gonadotrophin secretion and reduces fertility. The site(s) of action for both of these effects needs to be determined.

Effect of Active Immunization against Estrogen on Gonadotropin Response to Testosterone Propionate Treatment in Ovariectomized Pony Mares

An experiment was conducted to determine whether partial neutralization of estrogens via active immunization alters testosterone propionate (TP)-induced increases in FSH secretion after GnRH administration in ovariectomized pony mares. Twenty mares were used in a 2 X 2 factorial arrangement of treatments (n = 5/group). Factor 1 was long-term active immunization against either bovine serum albumin (BSA) or estrone-17-oxime-BSA. Factor 2 was 11-d administration of either vehicle (vegetable oil) or TP (175 micrograms/kg BW). Plasma concentrations of FSH were not affected (P greater than .1) by either factor. As expected, the FSH response to exogenous GnRH was threefold greater (P less than .05) in BSA-immunized mares treated with TP than in BSA-immunized mares receiving oil. However, immunization against estrogens reduced (P less than .05) this TP-induced increase in FSH response by 52%. Plasma concentrations of LH were decreased (P less than .08) by TP; this effect was not altered (P greater than .1) by immunization against estrogen. The LH response to exogenous GnRH was not affected (P greater than .1) by either factor. We conclude that aromatization of testosterone to estrogen is partially responsible for the increased FSH response to exogenous GnRH in TP-treated mares. In contrast, suppression of LH concentrations by TP appears to involve only the androgenic effect of TP.

A note on the effect of active immunization against somatostatin on milk production and growth in sheep

It has been reported that a purified extract from sheep hypothalami inhibited growth hormone (GH) release in rats. This somatotropin-release-inhibiting factor (SRIF), or somatostatin, is a tetradecapeptide and has been prepared synthetically (Brazeau, Vale, Burgus, Ling, Butcher, Rivier and Guillemin, 1973). In addition, _SRIF has been reported t o inhibit the release of other hormones which have major effects upon growth and metabolism such as insulin (Koerker, Ruch, Chideckel, Palmer, Goodner, Ensinck and Gale, 1974), glucagon (Ruch, Koerker, Carino, Johnson, Webster, Ensinck, Goodner and Gale, 1973) and thyroid stimulating hormone (Vale, Rivier, Brazeau and Guillemin, 1974). Furthermore, SRIF has also been shown to be present in large quantities i n the gastrointestinal tract where it controls the release of many gut hormones (Schusdziarra, Zyzhar and Rouiller, 1980). Somatostatin seems, therefore, to be centrally involved in regulating digestion and absorption of food and the subsequent distribution of the absorbed nutrients into tissues within the body. Its removal from the blood circulation by passive immunization increased GH concentrations in plasma in rats (Arimura and Schally, 1976) and prevented decreases in GH concentration as a result of stress (Arimura, Smith and Schally, 1976). Similarly, removal of SRIF by active immunization has been reported to result in higher plasma GH levels in lambs (Varner, Davis and Reeves, 1980; Spencer, Garssen and Hart, 1983b). However, this increase in circulating GH did not appear to have a constant effect in later studies and resulted in inconclusive effects on sheep growth. Laarveld, Chaplin and Kerr (1986) and Spencer, Garssen and Bergstrom (1983a) observed increased growth with improved food efficiency in crossbred and Dutch moor lambs respectively, immunized against SRIF, whereas Varner et al. (1980) reported a significantly lower growth rate in male Columbia lambs and others (Fitzsimons and Hanrahan, 1984; Galbraith, Wigzell, Scaife and Henderson, 1985; Garssen, Welling and Spencer, 1984) concluded that immunization against SRIF did not affect growth in crossbred lambs. It has also been reported that immuno-neutralization of SRIF can lead to enhanced milk production early in lactation n i goats (Spencer and Garssen, 1985).

Effect of Fecundin on ovulation rate and prolificacy in Suffolk ewes during the breeding and non-breeding seasons.

Effect of active immunization against androstenedione-human serum albumin conjugate (Fecundin), in combination with or without methyl-acetoxy-progesterone (MAP) and pregnant mare's serum gonadotropin (PMSG), on both ovulation rate and prolificacy was investigated in Suffolk ewes during the breeding (Experiment 1) and the non-breeding seasons (Experiment 2). Nineteen to 20 ewes were treated as follows: control (Group I), two injections of 2 ml Fecundin (Group II), administration of combined 60 mg MAP and 500 IU PMSG (Group III), and treatment with combined Fecundin, MAP and 250 IU PMSG (Group IV). In Experiment 1, the mean ovulation rates in all the treated groups were respectively higher than the rate in Group I. Prolificacy was significantly higher in Groups II and III than in Group I. In Experiment 2, ovulation occurred in Groups I and II without estrous behavior. The mean ovulation rates in Groups III and IV were respectively higher than the rate in Group I or II. Compared with Group III, prolificacy remained higher in Group IV. In Experiment 3, a single booster injection of Fecundin in the following breeding season elevated the prolificacy. These results indicate that the Fecundin treatment during the breeding season is effective in increasing both ovulation rate and prolificacy in the Suffolk ewe.

Effects of active immunization against gonadotropin releasing hormone on gonadotropin secretion after ovariectomy and testosterone propionate administration to mares.

Five lighthorse mares were actively immunized against gonadotropin releasing hormone (GnRH) conjugated to bovine serum albumin (BSA) to study the involvement of GnRH in luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion following ovariectomy (OVX) and after administration of testosterone propionate (TP). Five mares immunized against BSA served as controls. Immunizations were started on November 1, and OVX was performed in June (d 1). All mares were treated with TP from d 50 to 59 after OVX. On the day of OVX, concentrations of LH were lower (P less than .05) in GnRH-immunized mares than in BSA-immunized mares and were generally nondetectable; FSH concentrations were reduced (P less than .05) by 50% in GnRH-immunized mares relative to BSA-immunized mares. In contrast to BSA-immunized mares, plasma concentrations of LH or FSH did not increase after OVX in GnRH-immunized mares. The LH response to GnRH analog (less than .1% cross-reactive with GnRH antibodies) on d 50 was reduced (P less than .05) by 97% in GnRH-immunized mares relative to BSA-immunized mares, whereas the FSH response was similar for both groups. Treatment with TP for 10 d reduced (P less than .01) the LH response and increased (P less than .01) the FSH response to GnRH analog in BSA-immunized mares, but it had no effect (P greater than .1) on the response of either gonadotropin in GnRH-immunized mares.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of active immunization against progesterone on plasma concentrations of total and free progesterone, estradiol-17β and LH in the cyclic ewe

Nine mature cyclic ewes were actively immunized against progesterone which was rendered immunogenic by conjugation to bovine serum albumin (BSA). Seven control ewes were immunized with BSA. In ewes immunized against progesterone, the concentration of total plasma progesterone increased to 24.3 ng/ml vs 2.8 ng/ml in control animals (P<0.001). However, immunization did not affect the plasma levels of free, unbound progesterone. The correlation coefficient between total plasma progesterone concentrations on Days 4 to 11 of the estrous cycle and antibody titer was r=0.983. Estradiol-17β concentrations in immunized ewes were higher than in controls on Days 6 to 15 of the estrous cycle (P∼0.05). Frequent sampling for LH over a 6-h period on Days 2, 5, 8, 11 and 14 of the cycle revealed no significant differences in the frequency and amplitude of LH pulses between immunized and control ewes. The immunized ewes had estrous cycles of normal length and maintained normal pregnancies. It is suggested that the immunized cyclic ewe is capable of maintaining adequate levels of free progesterone by greatly increasing progesterone synthesis, thus neutralizing the effect of the antibodies.

Increased luteinizing hormone secretion and ovarian function in heifers actively immunized against estrogen and progesterone.

This study was designed to test the effects of active immunization against estrogen and progesterone on patterns of luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion, ovarian characteristics and growth rate of heifers. Heifers were randomly assigned to four treatments: 1) control injection (n = 10); 2) ovariectomy (n = 9); 3) immunization against estrogen (anti-E, n = 10); and 4) immunization against estrogen and progesterone (anti-E+P4, n = 10). Three booster immunizations were administered at 1, 1.5 and 6 mo after primary immunization. Progesterone antibody binding was 40% (34 fmol at 1:600 final dilution) in the anti-E+P4 heifers, and estradiol-17 beta binding was 35% (30 fmol) and 60% (52 fmol at 1:100 final dilution) in the anti-E+P4 and anti-E heifers, respectively, after the final immunization. Anti-E+P4 heifers had more pulses of LH and higher basal concentrations of LH than anti-E or control heifers (P less than .05). Concentrations of LH in anti-E+P4 heifers did not increase to concentrations found in ovariectomized heifers (P less than .05). Immunization against steroids did not alter the secretion of FSH. The number of large follicles (greater than 15 mm diameter) in anti-E+P4 and anti-E heifers was greater than in control heifers (P less than .05). Ovarian weight was increased in anti-E+P4 heifers (P less than .05). Average daily gain was not different among groups (P greater than .05). It was concluded that active immunization against estrogen and progesterone in heifers increased LH secretion and stimulated ovarian function.

Effect of immunization against progesterone on oestrus, cycle length, ovulation rate, luteal regression and LH secretion in the ewe.

The effects of active immunization against progesterone on reproductive activity were studied in Merino ewes. Immunization against progesterone caused a shortening (P less than 0.01) of the interval between ovulations from 17-18 days (controls) to between 6 and 10 days (immunized group); this was associated with a corresponding reduction in the interval between LH surges. The immunized ewes also had higher (P less than 0.05) ovulation rates (1.72) than controls (1.25) and exhibited a reduced (P less than 0.01) incidence of oestrus (26% v. 95%). Many immunized ewes continued to ovulate despite the persistence of corpora lutea from earlier ovulations which led to an accumulation on the ovaries of many corpora lutea of different ages. The frequency of LH pulses in ewes immunized against progesterone (1.8 +/- 0.2 pulses/4 h) was significantly (P less than 0.001) higher than that of control ewes (0.3 +/- 0.1 pulses/4 h). This study highlights the importance of progesterone in the control of oestrus, ovulation, ovulation rate, luteal regression and the secretion of LH in the ewe.

Effect of active immunization against LHRH or LH in boars: reproductive consequences and performance traits.

Forty crossbred boars were equally divided into eight groups at birth. Four groups were immunized (200 micrograms/boar) at 12 wk of age against either luteinizing hormone-releasing hormone (LHRH) conjugated to human serum globulin (LHRH-hSG) in complete Freund's adjuvant (CFA), LHRH-hSG in muramyldipeptide adjuvant (PEP), procine luteinizing hormone (LH) conjugated to hSG (pLH-hSG) in CFA or ovine LH (oLH) in CFA. Equal doses of boosters were given in either PEP or incomplete Freund's adjuvant (IFA) at 16 and 18 wk of age. Two groups of boars were immunized with either hSG + CFA or hSG + PEP (adjuvant controls). Two groups were castrated either at the time of weaning (castrate weaning) or at 16 wk when immunized boars were given their first booster injections (castrate booster). All pigs were slaughtered at 24 wk of age. Serum levels of LH and testosterone (T), LHRH or LH antibody titers, as well as testicular and accessory sex gland weights and histology were determined. By wk 16, LHRH antibody titers began to rise in those boars immunized against LHRH-hSG. Luteinizing hormone-releasing hormone antibody titers on wk 18, 20 and 22 were greater than those at wk 16. By 22 wk of age, LHRH-hSG boars had non-detectable plasma LH and T and reduced weights of testes and acessory sex glands. Boars immunized against oLH did not respond to treatment, whereas pLH-hSG boars showed a reduction in serum T levels and accessory sex gland weights. Immunization had no effect on average daily gain, hot carcass weights or loin eye area.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of active immunization against androstenedione on ovulation rate and fecundity in Galway and Finnish landrace sheep

Galway and Finnish Landrace ewes were immunized with an androstenedione protein conjugate (Fecundin, trademark of Glaxo Group Ltd.) on two occasions 30 days apart at the beginning of the breeding season. All sheep were treated with intravaginal progestagen sponges to synchronize cycles and exposed to rams for 6 weeks. The antibody titre to androstenedione, plasma androstenedione concentrations, display of oestrus, ovulation rate and litter size were determined. The results were compared with those for non-immunized animals and, in the case of the Galway breed, with ewes given 750 i.u. PMSG at the time of sponge removal. Over 98% of all ewes were mated within 30 days of sponge removal, but immunized ewes were delayed in their expression of oestrous cycles after withdrawal of progestagen treatment. The proportion of ewes mated that ultimately lambed was similar for all treatments, although during the first 5 days after sponge removal the conception rate was lower in immunized ewes. The mean ovulation rates for control, immunized and PMSG-treated Galway ewes were 1.75, 2.52 and 2.05, respectively; the corresponding values for litter size at birth were 1.48, 1.89 and 1.53, respectively. Comparison of the effects of immunization in the Galway and Finnish Landrace breeds indicated that ovulation rate increased in response to treatment in both breeds. Although litter size also increased in the Galway there was no evidence for a similar effect in the Finnish Landrace breed. Plasma concentrations of androstenedione were significantly higher following immunization in Galway than in Finnish Landrace ewes. There was an association between high antibody titres to androstenedione and the reduction in behavioural oestrus and conception rate immediately after sponge removal. The implication of this effect in sheep management is to initiate the immunization earlier in the season so that the introduction of the ram can take place 3–4 weeks after the booster injection when as these data have shown, the fertility of the ewes is similar to untreated ewes but the fecundity is higher.

Effect of active immunization against androstenedione on ovarian function in dairy cows and prepubertal gilts

Two experiments were performed to assess the effects of immunization against androstenedione on ovarian function in cows during the first 100 days after calving and in gilts at the onset of puberty. Seven Holstein-Friesian cows were immunized against androstenedione-11α-human serum albumin (AND-HSA) at 3 weeks before and at 3 weekly intervals after calving and compared with ten cows immunized against HSA. Titres against androstenedione were significant but low and variable (1: 280-1: 4). Two cows with the highest titres exhibited abnormal ovarian function which could be attributable to treatment. One cow developed a large follicular cyst and nymphomania. The other cow exhibited mild super ovulation in her first cycle after calving and multiple ovulations during later cycles. Other cows in the AND-HSA group also had a tendency to develop larger than normal follicles and follicular cysts. Groups of twelve prepubertal gilts were immunized against either androstenedione 11α-hemisuccinyl bovine serum albumin (AND-BSA) or BSA at 100, 121 and 142 days of age. Titres against AND were significant but were low and variable (1: 2500-1: 10). There was no effect of immunization against AND on onset of ovulation, puberty or ovulation rate in the first or second ovulatory cycles.

Ovarian response to PMSG treatment in ewes immunized against oestradiol-17 beta.

The effects of active immunization against oestradiol-17 beta on the ovarian response to pregnant mare serum gonadotrophin (PMSG) was investigated in Merino ewes. Immunized (79) and control (41) ewes were synchronized with intravaginal sponges, given either 750 or 1500 i.u. PMSG and then mated to rams or inseminated laparoscopically with fresh diluted semen. All control ewes mated naturally exhibited oestrus and 40 out of 41 control ewes ovulated. The ovulation rate was higher in the controls receiving 1500 i.u. PMSG than in those ewes which received 750 i.u. PMSG (10.2 v. 3.3). Immunization against oestradiol-17 beta resulted in antibody titres varying from 100 to more than 100 000 in plasma taken 1-4 days after mating. The ovarian response increased significantly in the lowest titre group (100-1000) in conjunction with stimulation with 1500 i.u. PMSG. In these ewes the ovulation rate increased over controls (16.7 v. 10.2) as did the total ovarian response, which includes follicles greater than 10 mm diameter (22.3 v. 11.1). The total ovarian response was also increased in those ewes given 750 i.u. PMSG which had titres in the 1000-10 000 and 10 000-100 000 range, but this was not accompanied by significant increases in the ovulation rate. In general, the higher titre levels (greater than 1000) were correlated with decreases in the proportion of ewes showing oestrus and ovulating and in the embryo recovery rate. The 1500 i.u. PMSG treatment group with the highest titres (greater than 10 000) also showed a significant drop in the ovulation rate as compared to the 1500 i.u. PMSG controls.

Effects of immunization of heifers against estradiol on growth, reproductive traits, and carcass characteristics.

An experiment was performed to evaluate the effects of active immunization of heifers against estradiol on feedlot performance (growth and efficiency), carcass characteristics, and reproductive functions. Seventy-two crossbred heifers were divided into four equal treatment groups consisting of controls, ovariectomized heifers, and heifers actively immunized against keyhole limpet-estradiol antigen and bovine serum albumin-estradiol antigen. Heifers were fed ad libitum for 170 days. Both groups of heifers immunized against estradiol had higher (P less than 0.05) average daily gains than controls. Heifers immunized against bovine serum albumin-estradiol had increased feed efficiency (P less than 0.05) over controls. Ovariectomized heifers did not perform at levels sufficient to compensate for the initial setback from surgery. No differences were noted in carcass grade, quality, or concentration of water, fat, or protein. Uterine weights were increased in estrogen-immunized animals but were not significantly greater than controls. Ovarian weights and numbers of large follicles (greater than 9 mm diam) in immunized animals were significantly greater than in controls. Twenty-eight percent of the animals (n = 5) in the bovine serum albumin-estradiol-immunized group had cystic follicles (greater than 20 mm diam) and 50% (n = 9) of this group had no detectable corpus luteum. Low titer (1:100) systemic binding of estrogens may act as a steroid reservoir in which systemic estrogen clearance is decreased and availability to target tissues is increased.

Effects of active immunization against estradiol-17 beta on luteinizing hormone and testosterone in male rats.

The role of endogenous estradiol-17 beta (E2) in regulating luteinizing hormone (LH) and testosterone secretion was investigated in adult male rats actively immunized against the E2-bovine serum albumin (BSA) conjugate. The antigen was injected intradermally 4 times at 2-week intervals and additional boosters were continued once a month. A pooled antiserum from immunized animals cross-reacted 8% to estrone, 1% to testosterone and 5 alpha-dihydrotestosterone, and less than 1% to estradiol-17 alpha, estriol, dehydroepiandrosterone, corticosterone, cortisol, progesterone and 20 alpha-dihydroprogesterone when compared with E2 (100%). Serum E2 in immunized rats was not adsorbed with dextran-coated charcoal, indicating that most of the serum E2 was bound to the antibody. In serum of immunized rats, LH and testosterone concentrations were significantly higher than those in intact rats. The metabolic clearance rate of testosterone was not changed, but the production rate of testosterone was significantly increased by the immunization. By the implantation of a micropellet of E2 in one testis, testosterone concentrations in the testicular vein blood from either the implanted or intact side were significantly decreased in intact rats, but not in immunized rats. In both groups, there were no significant differences between the testosterone concentration in testicular vein blood in the implanted and intact sides. It is concluded that circulating E2 physiologically participates in maintaining LH-testosterone homeostasis by inhibiting LH secretion in adult male rats.

Effect of Active Immunization Against Estradiol on Egg Shell Quality

Seven 31-week-old White Leghorn hens were immunized with estradiol-17-6-(0-carboxymethyl) oxime-bovine serum albumin (.5 to 1 mg/hen; 1- to 7-week intervals for 44 weeks). Six control hens of similar egg shell quality received only bovine serum albumin. Within 35 weeks of immunization, four of the estradiol-17β(E2) antigen-treated birds developed significant titers of antibodies to E2 based on a four- to fivefold increased binding of tritiated labeled E2 to plasma; two hens had low titers (twofold increase), and one had none. Forty-eight weeks after the first injection, the specific gravity (1.0768) and percent shell (8.32) of the four high-titer birds were lower (P<.05) than those of the controls (1.0810 and 8.80, respectively).The six positively immunized hens laid a total of 29 soft-shell eggs out of a total of 1,626 eggs as compared with 7 out of a total of 1,658 eggs laid by the six control birds. No significant increase in plasma binding was observed for the nonphenolic steroid hormones such as progesterone, corticosterone, and testosterone.It was concluded that the effect of immunization on egg shell quality was due to neutralization of estrogen activity.