Successful fostering of orphan lambs by non-pregnant ewes induced to lactate using exogenous hormone treatment

Six nonpregnant ewes were induced to lactate by an exogenous hormone treatment lasting 6 weeks. At the end of the treatment one alien lamb was adopted by each ewe. Each ewe was initially indifferent to the alien lamb and required only mild restraint to allow the lambs to suck successfully. Maternal interest subsequently increased and strong ewe-lamb bonding was evident by 80 minutes (n=1), 10 hours (n=4) or 24 hours (n=1) in different cases. The lambs required supplementary milk for 4-6 days while milk production by the ewes increased to adequate levels. Thereafter they were reared entirely by the ewes. Another four nonpregnant ewes were induced to lactate by a similar hormone treatment and were then hand-milked thrice daily for 23 weeks. One alien lamb was then removed after 10-30 minutes. The ewes were then injected subcutaneously with 5 mg of oestradiol-17beta and were placed in fostering stocks. After a further 3-5 hours the lambs were re-introduced. Strong ewe-lamb bonding occurred during the subsequent 10 hours in all cases. All 10 lambs were reared successfully by these ewes until at least 3 months of age, when observations stopped. It was concluded firstly that nonpregnant ewes induced to lactate artificially will adopt and rear orphan lambs successfully, provided that additional milk is given to meet shortfalls during the first 4-6 days; and secondly that a 5 mg injection of oestradiol-17beta may facilitate fostering of lambs by ewes in established lactation whether the lactation is induced artificially or not.     

Behavior of ewes and lambs subjected to restraint fostering

The objective of this study was to investigate the development of maternal-filial social attachments between ewes and alien lambs using the technique of "restraint fostering." Forty-eight to 72 h after parturition, 22 Targhee -type ewes were separated from their natural lambs, placed in restraining devices ( stanchions ) and each exposed to a single alien lamb. After a period of 1 or 4 d of restraint, the ewes were subjected to five 10-min lamb acceptance tests over a 48-h period. The observer recorded butts and butt attempts by the ewe and successful and unsuccessful suckle attempts by the lamb. The ewe-lamb pairs were then housed in pens with other groups of ewes and lambs and observed intermittently for acceptance behaviors. Six of the 14 ewes restrained for 4 d and none of the eight ewes restrained for 24 h met the criterion for successful adoption within 48 h. After being housed in group pens, adoptions were achieved by three ewes in the 1-d group and an additional four ewes in the group restrained for 4 d. Ewes restrained for 24 h were significantly more aggressive toward fostered young than ewes restrained for 4 d. In addition, the proportion of successful suckling attempts was significantly lower for lambs fostered on ewes in the 1-d group. Both groups showed a decline in butts and butt attempts over successive acceptance tests, but while the proportion of successful suckling attempts declined for lambs housed with 1-d ewes, they increased over time for lambs fostered on ewes restrained for 4 d.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma somatotropin response to exogenous growth hormone releasing factor in lambs

Two experiments were performed to examine the ability of human pancreatic growth hormone releasing factor (hGRF) administration to stimulate endogenous growth hormone (GH) secretion in lambs. Each study utilized eight Dorset wether lambs in replicated 4 X 4 Latin square experiments. Growth hormone response (integrated area under the curve for 150 min post-injection) for 0, 1, 5 and 10 micrograms hGRF/kg body weight averaged 13, 23, 92 and 134 units, respectively. While the 1-microgram hGRF dose was not different (P greater than .05) than the response to saline injection, there was an increased (P less than .01) GH response to 5 or 10 micrograms hGRF. Overall the GH response increased in a log dose-response fashion. There was distinct variation between lambs in their response to hGRF. Study II examined the optimal method to administer 40 micrograms hGRF/kg body weight to maximize GH concentration over 24 h. Continuous infusion (CI) was compared with eight (8X), four (4X), or two (2X) injections/d. Hourly blood samples were obtained from all lambs. Growth hormone response (area under the curve for 24 h) was 162, 305, 306 and 220 units for CI, 8X, 4X and 2X, respectively. Growth hormone response to CI was inferior to discrete injections, and the GH response to 4X or 8X was superior to 2X/d. Results demonstrate that, in spite of lamb-to-lamb variation, one can utilize exogenous hGRF to enhance GH secretion in lambs. Thus, the ability of exogenous hGRF to enhance growth performance merits further study.     

外源激素FSH提高滩羊繁殖率初探

采用阴道栓塞、FSH和加强饲养管理相结合的方法,对35只空怀滩母羊进行两个胎次67只次的处理.结果表明,外源激素FSH诱导滩母羊同期发情和第一情期配种妊娠率综合比较,以撤拴前12 h和撤拴同时两次肌注FSH的处理方法效果较好;繁殖季节60IU和非繁殖季节70～/80IUFSH能有效的诱导滩母羊的同期发情,并增加母羊的排卵数;采用适宜的外源激素处理基本实现滩羊一年两产并诱导一产多羔,两胎次共处理67只次,母羊年繁殖率为179.10%,年只均繁殖成活羔羊1.56只,母羊只均增加收入54.67元.     

Response of the bovine corpus luteum to increased secretion of luteinizing hormone induced by exogenous gonadotropin releasing hormone

Two experiments were conducted to investigate the response of the bovine corpus luteum to surges of luteinizing hormone (LH) induced by natural gonadotropin-releasing hormone (GnRH) administered twice during the same estrous cycle. In experiment 1, eight mature beef cows, each cow serving as her own control, were injected intravenously (iv) with saline on days 2 and 8 of the cycle (day of estrus = day 0 of the cycle), then with 100 micrograms GnRH on days 2 and 8 of the subsequent cycle. Jugular blood samples were taken immediately prior to an injection and at 15, 30, 45, 60, 120 and 240 min postinjection, to quantitate changes in serum luteinizing hormone. Blood was also collected on alternate days after an injection until day 16 of the cycle, to characterize changes in serum progesterone concentrations. Although exogenous GnRH caused release of LH on days 2 and 8 of the cycle, the quantity of LH released was greater on day 8 (P less than .025). Serum levels of progesterone after treatment with GnRH on day 8 of the cycle did not differ significantly from those observed during the control cycles of the heifers. Because exposure of the bovine corpus luteum to excess LH, induced by GnRH early during the estrous cycle, causes attenuated progesterone secretion during the same cycle, these data suggest that a second surge of endogenous LH may ameliorate the suppressive effect of the initial release of LH on luteal function. Duration of the estrous cycle was not altered by treatment (control, 20.4 +/- .5 vs. treated, 20.4 +/- .4 days).(ABSTRACT TRUNCATED AT 250 WORDS)     

Protection of lambs against enteric colibacillosis by vaccination of ewes

Pregnant ewes were vaccinated twice, seven weeks and three weeks before lambing, with a multivalent formalin-killed Escherichia coli vaccine containing an added K99, F41 antigen preparation. Lambs born to vaccinated and unvaccinated ewes were exposed to oral infection with E coli B44 (09:K30, K99, F41). All 10 lambs from vaccinated ewes were protected whereas all 10 control lambs developed severe diarrhoea and five died or were killed in extremis. In the following year, previously immunised ewes were given a single dose of the vaccine two weeks before lambing. Eleven of their 12 lambs were protected against a similar challenge, which caused the death of six of eight control lambs and severe diarrhoea in the two survivors. Higher levels of antibody to the K99, F41 preparation were detected by enzyme-linked immunosorbent assay in the serum and colostrum from vaccinated ewes and in the serum of their lambs when compared with similar samples from control ewes and lambs.     

Responses of pregnant ewes and young lambs to cold exposure

The effects of cold stress were studied in pregnant ewes during the last three weeks of gestation and in their progeny during the first three days of life. In general, ewes were unaffected by treatment whereas changes were observed in the cold-stressed lambs. Cold-induced changes in lambs included physical weakness, depression, and poor nursing response. Serum concentrations of glucose and insulin were lowered whereas concentrations of blood urea nitrogen, alkaline phosphatase, aspartate aminotransferase, lactate dehydrogenase, triglycerides, and cortisol tended to be higher in cold exposed lambs. The mortality rate was higher (40%) in cold-stressed lambs than in lambs kept at warmer temperatures (10%). At necropsy, cold-exposed lambs had reduced amounts of adipose tissue in perirenal areas, and extensive subcutaneous hemorrhages and edema in the distal portions of the thoracic and pelvic limbs.     

Factors affecting productivity of Rambouillet ewes mated to ram lambs

Objectives of this study were to estimate the magnitude of the effects of various factors associated with ewes and their ram lamb mates on fertility, prolificacy, lamb survival, lamb weaning weight and ewe productivity and to estimate the heritability and repeatability of each trait. Records from 731 ewe-years, 75 ram lamb sires and 616 lambs born from the University of Illinois Rambouillet flock were used. Ewes mated to single-born ram lambs had higher fertility rates (P less than .01), gave birth to lambs with higher survival rates (P less than .01), weaned lighter (P less than .05) individual lambs but weaned more weight of lamb per ewe exposed (P less than .01) than ewes mated to multiple-born ram lambs. Ram lamb breeding weight, ram lamb scrotal circumference, ewe breeding weight and ewe age had relatively large and positive effects on the composite trait of weight of lamb weaned per ewe exposed and significant effects on a number of the component traits. Heritability and repeatability estimates were, respectively, as follows: fertility, 3%, 3%; prolificacy, 34%, 19%; lamb survival, 15%, 8%; lamb weaning weight, 7%, 36%; and ewe productivity, 27%, 10%.     

Cardiac changes induced by excess exogenous growth hormone in juvenile miniature poodles

The transient elevated plasma growth hormone (GH) levels that occur at a young age in giant breed dogs may have consequences in adult life. The aim of this study was to investigate whether excess juvenile GH has consequences for cardiac function and morphology. To simulate the naturally occurring juvenile hypersomatotropism in giant breed dogs, elevated plasma GH and insulin-like growth factor-I (IGF-I) concentrations were induced in six miniature poodles (GH dogs) by daily administration of supraphysiological doses of GH starting at 12 weeks of age. Eight miniature poodles of the same age that received vehicle only served as controls. Cardiac anatomy and function were evaluated by echocardiography. After euthanasia at 21 weeks of age, the hearts were examined for weight, myocyte dimensions and collagen fraction. The hearts of the GH dogs had larger atria (+22%), a thicker left ventricular wall (+21%), greater weight (+84%), and their cardiomyocytes were 15% longer, 25% thicker, and 92% greater in volume than those of control dogs. The mean collagen fraction was also higher in the GH dogs (5.6%) than in the controls (3.1%). In conclusion, excess GH in juvenile miniature poodles resulted in myocardial hypertrophy and increased collagen content. These findings are consistent with observations in acromegalic human patients and in rats treated with GH.     

Roles of pattern of secretion of luteinizing hormone and the ovary in attainment of puberty in ewes lambs

Four experiments were conducted to examine (1) how patterns of luteinizing hormone (LH) change as lambs approach first estrus, (2) whether mimicry of these changes by exogenous LH will initiate events of the pubertal process, (3) aspects of possible roles of the ovary and estradiol in the initiation of an ovulatory surge of LH in prepubertal lambs and (4) the time requirements for the presence of the ovary in induction of that surge of LH.In 19 lambs (Exp. 1), concentrations of LH in plasma were higher at puberty than 7 weeks earlier. Increased concentrations of LH in samples taken every 20 min for 6 hr during the luteal and follicular phases preceding first estrus were attributed to increased amplitude, but not increased frequency, of episodic pulses of LH. In Exp. 2, endocrine events which are included in the natural onset of ovarian cyclic activity (i.e. surge of LH and subsequent rise in progesterone) were initiated in $\text{5}\text{6}$, $\text{4}\text{6}$, $\text{1}\text{5}$, $\text{1}\text{6}$, and $\text{3}\text{6}$ lambs, receiving either injections of 7.5 μg/hr, 15 μg/hr, 30 μg/2hr, 45 μg/3hr or constant infusions of 15 μg/hr of purified ovine LH, respectively. However, these lambs did not exhibit estrus or cyclic ovarian activity. In Exp. 3, the mechanism by which hourly injections of LH prompted surges of LH was determined to be mediated through ovarian stimulation and not through a direct effect of exogenous LH on the hypothalamo-pituitary axis. All the intact (n=5) but no acutely (two weeks) ovariectomized (n=5) lambs had a preovulatory-like surge in response to exogenous LH. Further, (Exp. 4) it was shown that the ovarian signal must be maintained or evoked within 6 hr preceding the surge of LH, because lambs (n=20) ovariectomized at or 9, 18 or 27 hr after initiation of the exogenous LH with the one exception failed to show a surge of LH. It could not be demonstrated that the ovarian signal involved changes in peripheral concentrations of androstenedione, testosterone or estradiol-17β, although patterns of LH in ovariectomized lambs were responsive to both negative and positive feedback effects of estradiol (n=6, Exp. 3) and in general estradiol levels were increasing prior to the induced surge of LH.     

A radiographic method for measuring the effect of exogenous hormone therapy on uterine involution in ewes.

Twenty-six pluriparous Suffolk ewes were used to monitor the effects of four hormone treatments on the rate of uterine involution, which was assessed by means of radio-opaque markers and radiography. The close correlation between measurements of the genital tract in live sheep and after slaughter indicated that this method of monitoring uterine involution was acceptably accurate. Uterine involution was complete by about 29 days after lambing. None of the hormone treatments with progesterone, oestradiol-17 beta, prostaglandin F2 alpha or an oxytocin analogue, administered shortly after lambing, had any effects on the rate of uterine involution. There was no correlation between the duration of increased plasma concentrations of 13.14 dihydro-15-keto-prostaglandin F2 (PGFM) and the rate of uterine involution.     

The effect of experimentally induced subclinical mastitis on milk yield of ewes and on the growth of lambs

In each of two experiments, subclinical mastitis was induced by inoculating both mammary glands of Welsh-Mountain and Dorset-Horn ewes with a coagulase-negative staphylococcus; groups of control ewes were also included. After inoculation, the somatic cell counts of milk of the inoculated ewes increased (P less than 0.01) and the milk yield decreased (P less than 0.01). The lambs of the inoculated ewes had a poorer growth than lambs of the control ewes (P less than 0.01).     

Effects of exogenous estradiol-17 beta and progesterone on naloxone-reversible inhibition of the release of luteinizing hormone in ewes

The role of endogenous opioids in controlling luteinizing hormone (LH) secretion was studied by injecting the opioid antagonist naloxone into intact and ovariectomized ewes that were treated with estradiol-17 beta (E2) and progesterone (P4). The existence of a naloxone-reversible inhibition of LH release was examined in five experiments using a total of 52 mature ewes. Naloxone at a dosage of 1 mg/kg disinhibited release of LH and abruptly increased serum concentrations of LH in a variety of experimental models. This naloxone-reversible inhibition of LH secretion was apparent in all experimental models that involved P4-induced inhibition of basal LH secretion but not in one model in which P4 inhibited the LH surge. Specific effects of E2 on naloxone-reversible inhibition of LH varied among experimental models. When prolonged administration of P4 alone appeared to lose its LH-inhibitory potency, E2 restored inhibition of LH as well as the naloxone-reversible state. Whenever E2 acted synergistically to suppress basal LH secretion in models involving brief (5 d) exposure to P4, E2 appeared to antagonize the naloxone-reversible state. In summary, P4-induced suppression of LH secretion appeared to be mediated by endogenous opioids, but the apparent interaction of E2 and opioids in LH suppression varied among experiments.     

PGFM response to exogenous oxytocin and determination of the half-life of oxytocin in nonpregnant mares.

We investigated the half-life of oxytocin in reproductively normal mares and the prostaglandin response after oxytocin administrations. Mares were given oxytocin, 10 or 25 iu, i.v., on the day of, or 2 days after, ovulation, and frequent jugular blood samples were collected for analysis of oxytocin and Prostaglandin F metabolite (PGFM) by RIA. Neither dose of oxytocin nor day of treatment affected the half-life of the exogenous oxytocin, which was determined to be 6.8 min. A significant increase in PGFM was observed within 6 min of oxytocin administration and peak values were observed within 10 min. PGFM response after oxytocin administration on the day of ovulation appeared elevated compared to the response 2 days after ovulation.