Activity In Ewes Research Articles

EFFECTS OF DIETARY MOLYBDENUM ON PRODUCTIVITY AND METABOLIC PARAMETERS OF LACTATING EWES AND THEIR OFFSPRING

A trial was undertaken to determine ewe lactation, lamb growth and metabolic responses to varying concentrations of molybdenum (Mo) in the diet of ewes. Twelve lactating ewes with twin lambs were assigned to one of three dietary treatments for the first 6 wk of lactation. Ewes were individually fed a corn silage-barley diet supplemented to contain 0.9 (0 Mo), 18.4 (20 Mo) or 40.7 (40 Mo) mg Mo kg−1 dry matter (DM) using ammonium molybdate [(NH4)6Mo7O24∙4H2O]. No feed was offered to lambs. Ewe milk yield and composition, ewe and lamb body weight and blood samples were obtained weekly. Two ewes assigned to 40 Mo and one ewe assigned to 20 Mo developed a condition that was corrected by thiamin administration during their fourth to fifth week on test. Diet did not influence (P > 0.05) milk yield or composition with the exception of milk Mo which increased (P < 0.05) for ewes fed Mo-supplemented rations. Dietary Mo concentration did not influence (P > 0.05) ewe plasma copper (Cu), trichloroacetic acid soluble plasma Cu or ceruloplasmin activity in ewes. Ewe plasma Mo concentrations increased (P < 0.05) 11- and 16-fold, respectively, for ewes fed 20 Mo and 40 Mo relative to those fed 0 Mo. Ewe liver Cu and Mo concentrations at the end of the trial tended (P < 0.10) to be greater for the Mo-supplemented diets. Lamb plasma and liver Cu concentration were not influenced by ewe diet. Milk Mo concentration did not influence (P > 0.05) lamb weight gain but did influence (P < 0.05) plasma Mo. Lamb age influenced (P < 0.05) plasma Mo levels which peaked when lambs were 2–3 wk old and declined thereafter. Key words: Ewe, lamb, lactation, growth, molybdenum, copper

Seasonal fluctuations in plasma progesterone concentrations in Gentile-di-Puglia and Ile-de-France ewes in southern Italy.

Ile-de-France ewes had high plasma progesterone concentrations during early summer-late winter. Gentile-di-Puglia ewes had high progesterone values during the winter-spring-summer period but during autumn progesterone values were very low and oestrous behaviour was not displayed. The comparison with Ile-de-France ewes indicates that a phase shift occurs in the annual ovarian activity in ewes of the Gentile-di-Puglia breed.

Year and season effects on oestrus and ovarian activity in ewes of different breeds and crosses

The dates of onset and cessation of ovulation and oestrus and the duration of the ovulatory, oestrous, anovulatory and anoestrous seasons were determined for Suffolk, Rambouillet, Dorset, Finnish Landrace and reciprocal F 1 crosses between the last three breeds in a study which extended over 3 years. Ovulation rate, duration of oestrus and cycle length were also examined. Among the purebreds the major source of variation in these traits could be attributed to differences between the Rambouillet and the remaining breeds. Rambouillet ewes commenced and ceased ovarian and oestrous activity earlier than the Finn; first ovulation also occurred earlier in the Rambouillet than in the Suffolk and the duration of ovarian activity was longer for the Rambouillet than for either of these breeds. The oestrous season was 27 days shorter for the Rambouillet than for the Dorset, due to a higher incidence of ovulation without oestrus in the Rambouillet. The anoestrum was between 27 and 65 days longer for the Rambouillet than for any of the other purebreds. The period of anovulation was longest for the Suffolk breed. There was little evidence for heterosis in the duration of the breeding and non-breeding seasons. The repeatability of components of the breeding season was generally low. Ovulation rate increased slightly from early to mid-season and then declined significantly as the breeding season advanced, in all breeds.

Duration of melatonin treatment and ovarian activity in ewes

Daily oral dosing in mid afternoon with 3 mg of the indoleamine, melatonin, from early June onwards is highly effective in advancing the breeding season of both Greyface and Scottish Blackface ewes kept under a natural photoperiod; the mean reaction interval from initial dosing to the onset of ovarian activity in Scottish Blackface ewes being around 65 days compared with 110 days for untreated controls (Robinson et al 1985). Advancing the starting time for the melatonin treatment to mid-March gave a similar reaction interval with behavioural oestrus occurring in late May/early June (Wigzell et al 1986a). Following this reversal of the breeding season by melatonin, continued melatonin treatment in unmated ewes resulted in a period of oestrous cyclicity lasting 4 to 5 months. Thereafter the ewes became refractory to melatonin and returned to anoestrus at a time when untreated controls were commencing ovarian activity (Wigzell et al 1986b). These observations prompted us to investigate the effects of different durations of melatonin treatment on ovarian activity.

Effect of melatonin implants on reproductive performance in ewes

It has been known for many years that the annual breeding cycle of the sheep is controlled by photoperiod. More recently it has become apparent that this process involves the pineal gland. Light is effectively monitored by retinal photoreceptors within the eye which transmit a neural signal to the pineal gland, and this in turn responds by secreting melatonin during the period of darkness. As daylength decreases in the autumn, the duration of elevated melatonin secretion increases, and this changing ratio of high:low melatonin during each 24h period stimulates breeding activity.Both timed (by afternoon feeding or injection) and continuous (by subcutaneous or vaginal implant) administration of exogenous melatonin to ewes in mid-summer have recently been shown to mimic the effects of decreasing photoperiod by advancing the onset of the breeding season. The present experiment was undertaken to investigate the ability of a subcutaneous implant of melatonin to manipulate reproductive activity of ewes under field conditions in the U.K.

Interaction of epidermal growth factor with the hypothalamic-pituitary-adrenal axis: potential physiologic relevance.

Epidermal growth factor (EGF), a polypeptide mitogen that participates in wound healing, has ACTH-like activity in ewes. We examined its effects on the primate hypothalamic-pituitary-adrenal (HPA) axis by administering mouse EGF (mEGF) iv (0-100 micrograms/kg) to rhesus monkeys. mEGF caused dose-dependent elevations of plasma ACTH and cortisol in these animals. To define whether the locus of stimulation was the hypothalamus and/or the pituitary gland we examined the capacity of mEGF to directly stimulate hypothalamic CRH or pituitary ACTH secretion in a rat hypothalamic organ culture system and a rat pituitary cell system, respectively. mEGF stimulated hypothalamic CRH release in a dose-dependent manner, but failed to cause pituitary ACTH release. We conclude that EGF is a stimulator of the HPA axis in primates. Thus, EGF, and/or one of its naturally occurring analogs, may participate in the physiological activation of the HPA axis at times during which the concentrations of these factors are raised in the systemic circulation and/or locally in the hypothalamus. Such states may include trauma, surgery, and possibly emotional stress.

Influence of phenobarbital dosage, dietary crude protein level and interval to measurement on hepatic monoxygenase activity in ewes.

Hepatic monoxygenases metabolize steroids that in turn influence reproduction. Experiments were conducted to establish the effect of dose of phenobarbital and level of dietary protein on hepatic monoxygenase. In Exp. 1, ewes were given either 0, .5, 1, 2 or 3 g phenobarbital (PB) daily for 4 to 8 d. After 48 h after last dose of PB, cytochrome P-450 was higher (P less than .01) in all ewes given PB than in controls and was higher (P less than .01) in ewes given PB for 8 d than in ewes treated for 4 d. In Exp. 2, either 0 or 1 g of PB was given orally for 8 d. Liver samples were collected 1, 4, 7 or 10 d after last treatment. Both cytochrome P-450 (P less than .01) and nicotinamide adenine dinucleotide phosphate (NADPH) cytochrome c reductase (P less than .06) were higher in ewes receiving PB than in controls. Cytochrome P-450 was twice as high in treated ewes as in control ewes on the 8th d of treatment, but concentrations returned to control levels 10 d after last treatment. Microsomal protein and cytochrome b5 were not affected by PB (P greater than .10). Ewes in Exp. 3 receiving a diet containing 14.8% crude protein for 10 d had higher levels of cytochrome P-450 (P less than .01) than ewes fed 4.7% crude protein. Protein did not affect microsomal protein or NADPH cytochrome c reductase. These data suggest that a relationship among PB, dietary protein and monoxygenases exists and provide information that will lead to a better understanding of the relationship between diet and reproduction.

Intraruminal soluble glass boluses containing melatonin can induce early onset of ovarian activity in ewes.

Soluble phosphate glass boluses (preparations A, B, and C) have been developed to release melatonin into the reticulo-rumen of ewes at relatively different (fast, medium or slow) rates. A fourth type (preparation D) containing no melatonin was used as a sham control. Four groups of seasonally anoestrous Suffolk-cross ewes were respectively dosed with preparations A, B, C or D on 4 July. Plasma samples were collected twice weekly for melatonin and progesterone assay. In Groups A, B and C, elevated daytime plasma concentrations of melatonin could be detected for about 5 weeks after bolus administration. However, the pattern of hormone release was variable between groups, with Group C animals maintaining higher plasma melatonin concentrations for a longer period. The control animals had undetectable daytime melatonin levels. The onset of cyclic ovarian activity in the animals treated with the 'slow' release bolus (Group C) was significantly (P less than 0.05) advanced compared to the control group. The 'fast' and 'medium' release treatments (Groups A and B) did not significantly alter the onset of ovarian activity. The results indicate the potential of a novel and convenient method of melatonin delivery for induction of early breeding activity in ewes.

The effect of the oral administration of melatonin at two times of the year on ovarian activity in ewes

It has previously been shown (Robinson et al., 1985) that the normal breeding season of Greyface and Scottish Blackface ewes can be advanced by the daily administration of the indoleamine melatonin; the administration of the melatonin beginning midway during the anoestrous period. If melatonin is administered towards the end of the normal breeding season, oestrous activity can be extended, but only for a period of about six weeks until the ewe becomes refractory to the melatonin treatment (Nett and Niswender, 1981). There is no information on the administration of melatonin at the beginning of the anoestrous period.In the following experiments we report results for the influence on the subsequent breeding activity of Greyface ewes of the oral administration of melatonin at the beginning of their normal period of anoestrus. We also report the results of an investigation on the effects of melatonin in advancing the breeding season of Scottish Blackface ewes maintained on either a high or low plane of nutrition. The experiments were carried out under natural daylength conditions at 57°N.

Evidence that the onset of the breeding season in the ewe may be independent of decreasing plasma prolactin concentrations.

Ten ewes of each of two breeds, Dorset Horn (long breeding season) and Welsh Mountain (short breeding season), were given subcutaneous oestradiol-17 beta implants and then ovariectomized. Another 10 ewes of each breed were left intact. On 3 May 1982, all the ewes were housed in an artificial photoperiod of 16L:8D. After 4 weeks, half of the ewes of each breed and physiological state were abruptly exposed to a short-day (8L:16D) photoperiod while the others remained in long days (16L:8D). The time of onset of the breeding season was significantly (P less than 0.05) advanced in ewes switched to short days (12 August +/- 10 days) compared to those maintained in long days (4 September +/- 14 days). Dorset Horn ewes began to cycle (20 July +/- 7 days) significantly (P less than 0.001) earlier than Welsh Mountain ewes (19 September +/- 6 days). Disparities in the time of onset of cyclic activity in ewes of different breeds and daylength groups were echoed in disparities in the time at which plasma LH and FSH concentrations rose in oestrogen-implanted, ovariectomized ewes of the same light treatment group. Prolactin concentrations showed an immediate decrease in ewes switched to short days, but remained elevated in long-day ewes. Since the breeding season started in the presence of high prolactin concentrations in long-day ewes, it seems unlikely that prolactin is an important factor determining the timing of the onset of cyclic activity.

Inhibitory activity of heated ewe serum for ewe and ram serum complement

In the presence of an indicator antigen-antibody complex, the complement (C) activity in ewe and ram serum was reduced or abolished by addition of ewe serum that had been heated at 56 degrees C for 10 minutes. Pre-incubation of heated ewe serum at 39 degrees C for 30 minutes with the C source prior to addition of the indicator system or addition at the same time caused similar reductions in C activity. Results from the haemolytic, conglutinating and haemagglutinating activities studied indicate that the ewe serum inhibitor(s) reacts with activated classical or alternative activating pathway components and/or the third component of C (C3). The presence of a potent C inhibitor(s) in ewe serum probably accounts for the low sheep C titres with some assay systems. As the heated ewe serum did not appear to activate ewe or ram C per se, it is more appropriate to regard it as 'inhibitory' rather than 'anticomplementary'.

Oestradiol-17 beta both inhibits and stimulates myometrial activity in ewes in vivo.

Spontaneous intrauterine pressure cycles were abolished for periods of several hours in ovariectomized non-pregnant ewes within 8 h of an injection of 50 micrograms oestradiol-17 beta. Following the quiescent period, a phase of intense uterine activity ensued for several hours before again being replaced by several hours of quiescence. This active/inactive cycle disappeared after 2-4 days if further daily injections of oestradiol were not given. During the quiescent periods the uterus retained its responsiveness to oxytocin and PGF-2 alpha. Increasing the dose of oestradiol failed to prolong the periods of quiescence.

Induction of ovulation and cyclic activity in anestrous ewes with testosterone treated wethers and ewes

An experiment was conducted to evaluate the effectiveness of wethers and ewes treated with testosterone preparations to induce ovulation and breeding activity in anestrous ewes. The testosterone was administered three times at weekly intervals. Wethers and ewes treated with 105 mg testosterone propionate and wethers treated with 100 mg testosterone from testosterone cyclopentyl propionate were as successful as vasectomised rams in inducing ovulation and cyclic activity in ewes. Seven days after the last injection the concentrations of testosterone in peripheral bloods were not significantly different from that in the vasectomised rams. By day 28 the concentrations were significantly lower than in the rams. The testosterone preparations tested are suitable for the induction of male sexual behavior and are rapidly excreted by sheep.

Uterine contractions and electrical activity in ewes treated with selenium and vitamin E.

The effects of selenium (Se) and vitamin E (E) on uterine contractions and electrical activity were investigated in 40 yearling Dorset ewes. Control ewes were deficient in Se and E, while remaining ewes received periodic injections of Se, E or Se + E. The number of contractions of the uterine horns was recorded for a 10 mm interval in anesthetized estrous ewes. Contractions recorded as moving were visible as constrictions that moved lengthwise along the horn toward the oviduct, cervix, or in neither direction (to be defined later). Number of contractions migrating toward the oviduct was greater (P<0.01) in Se- and Se + E-treated ewes (41.6 and 43.2, respectively). Total number of contractions was greater (P<0.05) in Se- and Se + E-treated ewes (75.7 and 73.5, respectively) than in control ewes (58.5). In estradiol-17#{216}(E2-17#{216})-treated ovariectomized ewes, number of contractions migrating toward the oviduct was twofold greater (P<0.01) in Se- and Se + E-treated ewes (30.6 and 30.4, respectively) than in control and E-treated ewes (15.8 and 12.2, respectively). An eleetromyographic record was constructed for each uterine horn of E2-170-treated ovariectomized ewes for the determination of mean amplitude of electrical activity, number of electrical spikes per minute, and velocity of uterine contractions. Mean amplitude for the two hours combined was greater (P<0.01) in Se- than in E-treated ewes; however, mean amplitude in these groups was not different from mean amplitude of control ewes. Velocity of contractions was greater (P<0.05) in Se- and Se + E-treated ewes (17.9 and 18.9 mm/see, respectively) than in control and E-treated ewes (11.0 and 8.0 mm/see, respectively). These results indicate that selenium is more important than vitamin E in influencing uterine motility and contraction velocity but does not appear to influence the number of electrical spikes per minute or the mean amplitude of these spikes.

Plasma prolactin variations and cyclic ovarian activity in ewes submitted to different light regimens

Plasma prolactin variations and cyclic ovarian activity in ewes submitted to different light regimens

Antiluteolytic effect of the conceptus and of PGE2 in ewes.

SUMMARY The responses of pregnant and nonpregnant ewes on day 13 post-estrus to a dose of prostaglandin (PG)F2a known to be luteolytic in nonpregnant ewes were compared (experi- ment I). Either 270 /ag PGF2~ THAM salt (eight nonmated and 11 mated ewes) or saline (eight nonmated and 10 mated ewes) was injected into the largest follicle on each ovary bearing a corpus luteum. Jugular plasma sam- ples taken just prior to surgery and 4, 8, 12, 16, 20, 24, 28, 32 and 36 hr after injection were analyzed for progesterone, estradiol-1713 and luteinizing hormone (LH) by radioimmuno- assay. Treatment with PGF2a shortened the estrous cycle by 1.5 days in nonmated ewes and mated ewes without embryos (P<.05). Mated ewes with embryos did not return to estrus. The linear regression of progesterone over time varied with treatment (P<.01), pregnancy status (P<.01) and treatment x pregnancy status (P<.09). Progesterone did not reach as low a level (1.3 vs .4 ng/ml; P<.05) in pregnant as in nonmated ewes. Both LH and estradiol- 17/3 increased in treated ewes after progesterone had decreased to approximately 50% of pre- treatment levels; the increase in estradiol was transient in the pregnant ewes. The pattern of LH did not differ with pregnancy status. It is concluded that pregnancy overcame the luteo- lytic effects of PGF2c~ (i.e., had an antiluteo- lytic effect). Experiment II was designed to ascertain whether PGE 2 has antiluteolytic properties. A catheter was inserted into each uterine horn that was ipsilateral to a corpus luteum in nonmated ewes on day 11 postestrus. Intrauter- ine injections of 0, 300, 600 or 900/agof PGE2 were begun on the morning of day 12 and continued every 8 hr until estrus or day 20. Jugular plasma samples were taken just before the first injection and every 24 hr thereafter in all ewes and at .25, .5, 1, 2, 4 and 8 hr from several ewes in each group and were assayed for progesterone. The estrous cycle was lengthened and the decline in progesterone delayed by 2 days by PGE2 (P<.05). Frequent samples on day 12 did not differ in progesterone levels among treatments or over time. Prostaglandin E 2 had antiluteolytic activity in ewes but no in vivo steroidogenic effect was observed. (Key Words: Ewe, Corpus Luteum, PGF2c~, PGE2, Antiluteolytic Factors, Early Preg- nancy.) 1 Division of Animal and Veterinary Science. Sup- ported by NICHD Contract No. 69-2215 and Hatch Project 224 (NE-72). We thank the Upjohn Company and Drs. James Lauderdale and John E. Pike

Changes in steroid hormones in plasma and myometrium and uterine activity in ewes during late pregnancy and parturition.

In 7 ewes during late pregnancy, peripheral plasma concentrations of oestrogens were correlated with uterine activity (P less than 0-01; r=+0-47). In myometrial tissue, the concentration of progesterone was similar to that in plasma; it rose to a plateau from Days 115 to 130 of pregnancy and then fell, but was still detectable during parturition. Myometrial oestrogen concentration was much higher than in plasma; from a peak at Days 100-115 it decreased, but rose sharply just before parturition.

Factors affecting the cessation of oestrous activity in ewes

SUMMARYIn the first experiment, 10 ewes (¼ Finnish Landrace: ¾ Clun Forest) were maintained under natural daylength conditions and 10 were exposed to a constant daylength of 8 hr from 22 December until 1 June. No difference was demonstrated between treatments in dates of cessation of oestrous activity. It was concluded that oestrous activity will eventually cease, whether or not daylength increases after the shortest day.In the second experiment, 40 similar ewes were mated at first oestrus of the natural breeding season (mean 7 September) and lambed in January. Twenty ewes suckled lambs and 20 had lambs removed within 24 hr of birth. No sucked ewes showed oestrus before the end of the breeding season, but 9 non-sucked ewes showed oestrus at a mean interval of 37·5 days after lambing and 4 of these subsequently lambed. Suckling appeared to inhibit oestrous activity and conception in ewes at this time of year.

Peritoneoscopy via a chronically implanted cannula to observe ovarian activity in ewes.

Peritoneoscopy via a chronically implanted cannula to observe ovarian activity in ewes.

Ovarian activity in ewes treated with glucose and triiodothyronine.

Thirty-two mature, white-faced western ewes were studied in a 22 factorial experiment of one estrous cycle duration. The factors studied were the feeding of glucose and the administration of triiodothyronine (T3). Both treatments were effective in elevating the blood glucose level. Treatment with T3 caused a loss in body weight; the greatest loss occurred in the T3-treated, glucose-fed ewes. The estrous cycle was longer for animals on T3 treatment. Both glucose alone and T3 alone appeared to depress follicular development. No difference in follicular activity from the controls was observed when both treatments were used together.