Gestation In Ewes Research Articles

Determination of gestational age in sheep and goats using transrectal ultrasonographic measurement of placentomes

Three experiments were conducted to determine gestational age in the ewe and doe by measuring placentomes with a B-mode ultrasonograph and a 5 MHz transducer. Transrectal measurements were obtained by placing the female over a bale of hay. In Experiment 1, ewes (n = 12) and does (n = 15) were examined by transrectal ultrasonography every week from breeding to parturition to determine the growth pattern of placentomes during pregnancy. In Experiment 2, placentomes from 132 ewes and 169 does were measured between 30 and 90 d of gestation. A linear regression relationship between fetal age in days and placentome size in mm was calculated and adjusted for does (gestational age = 28.74 + 1.80PL + e, r(2) = 70.34) and for ewes (age = 47.98 + 0.62PL + e, r(2) = 15.59). In Experiment 3, the placentomes of 63 does were measured to validate this relationship by using linear regression. Gestational age was determined correctly in 66% of the does, with a range of +/- 7 d and in 96% with a margin of +/- 14 d. In conclusion, transrectal ultrasonography allowed for the measurement of placentome size, which increased rapidly during the first 70 to 90 d of gestation in ewes and does. In ewes, however, there was a poor correlation of placentome size with gestational age, while in goats, measurement of placentomes could be used along with pregnancy diagnosis by transrectal ultrasonography as an indication of gestation age.

Maternal undernutrition during late pregnancy in sheep. Its relationship to maternal condition, gestation length, hepatic physiology and glucose metabolism.

There is a paucity of information on the metabolic effects of undernutrition of the ewe carrying multiple fetuses in late pregnancy. In the present study the effects of induction of ketosis from 132 d gestation in ewes carrying twin fetuses were compared with a control group. The ewes were well fed up to 132 d. Ketotic ewes showed a loss of condition score from 3.7 (SE 0.11) at 130 d gestation to 3.0 (SE 0.15) 10 d later after clinical recovery, compared with control twin-pregnant ewes (P < 0.01). The weight loss during the same time period was from 70.6 (SE 2.7) kg at 130 d to 64.2 (SE 2.7) kg at 140.d gestation. As expected, both groups lost weight and condition score in the first 28 d of lactation. Induction of ketosis caused a significant shortening of the gestation period to 142.8 (SE 0.7) d compared with 150 (SE 0.4) d in normal twin-pregnant ewes (P < 0.001). Ewes with induced ketosis recovered clinically and showed a normal feed intake by 3.4 (SE 0.07) d; three required treatment. Induction of ketosis resulted in reduction of hepatic uptake of bromosulphthalein (P < 0.01) and its biliary excretion (P < 0.05), metabolic clearance rate (P < 0.001), fractional clearance (P < 0.001) and 15 and 30 min retention compared with control twin-pregnant ewes. Most values had returned to normal by the first week of lactation. It is thought that in human pregnancy similar changes in bromosulphthalein clearance may be related to reduced binding sites for bromosulphthalein in the liver caused by increased circulating oestrogens. Induction of ketosis resulted in a significant hypoglycaemic (P < 0.01), ketotic (P < 0.001) state compared with well-fed twin-pregnant ewes. These changes could be correlated with the severity of the clinical signs, together with a significant rise in plasma urea (P < 0.001) and NH3 (P < 0.05) concentrations. Again, the return of most of these values to normal by the first week of lactation lends support to the reversibility of hepatic lesions caused by fatty infiltration of the liver. The severity of this condition in naturally occurring cases suggests that factors other than undernutrition may be contributory, such as the general body condition of the ewe and glucose metabolism by the liver, including the conversion of propionate to glucose.

Serum and milk folates during the first two gestations and lactations in Romanov, Finnsheep, and Suffolk ewes.

Concentrations of folates in serum and milk were determined during the first two parities in 7 Suffolk, 12 Finnsheep, and 15 Romanov ewes at 0 (mating), 60, 110, and 140 d of gestation and 1, 7, 14, 21, and 50 d of lactation. The number of lambs born at first and second parturitions was 1.38 +/- .13 and 1.71 +/- .13 for Suffolk, 2.00 +/- .32 and 2.33 +/- .57 for Finnsheep, and 2.67 +/- .24 and 3.20 +/- .22 for Romanov, respectively, and the concentration of folates at d 0 was 1.17 +/- .21, 1.87 +/- .19, and 2.14 +/- .17 ng/mL, respectively. During gestation, serum concentrations of folates declined in the three breeds, more quickly in Romanov and Finnsheep (from d 0 to 60) than in Suffolk (from d 0 to 110). This decline was followed by an increase in serum concentrations of folates from d 110 to 140 of gestation in the three breeds; the largest increase was observed in Romanov (breed x quadratic effect of time, P = .001). During lactation, Romanov had higher serum concentrations of folates than Finnsheep, which in turn had a higher concentration than Suffolk (P = .001). Colostrum of Romanov had the highest concentration of folates (164.9 +/- 11.9 ng/mL), followed by that of Finnsheep (125.0 +/- 9.5 ng/mL) and Suffolk (98.2 +/- 13.3 ng/mL). On d 7 of lactation, concentration of folates was similar in milk of Romanov (97.1 +/- 5.6 ng/mL) and Finnsheep (94.9 +/- 4.0 ng/mL) and was higher than in Suffolk (72.4 +/- 3.7 ng/mL). From d 14, the concentration of milk folates was similar among breeds and decreased slowly to approximately 40 ng/mL at d 50 (breed x quadratic effect of time, P = .005). The changes in serum concentration of folates during gestation of ewes were similar to those observed in sows, suggesting that exogenous supply of folates may not be optimal in ewes during gestation and lactation.

Effects of angiotensin II on plasma atrial natriuretic factor in nonpregnant and pregnant ewes.

The release of atrial natriuretic factor (ANF) is primarily determined by atrial stretch, but may also be modulated by circulating angiotensin II (AngII). During pregnancy, the circulating concentrations of both ANF and AngII are increased. To further define possible effects of AngII on ANF release, four doses of AngII (0.5, 5, 20, 40 ng.kg-1.min-1) were intravenously infused into five nonpregnant and five pregnant (105-140 days of gestation) ewes alone and during the simultaneous infusion of sodium nitroprusside at doses sufficient to abolish the pressor effects of AngII. Mean arterial pressure (MAP) was increased from 80 +/- 2 to a maximum of 121 +/- 5 mmHg (1 mmHg = 133.3 Pa) in nonpregnant ewes (p < 0.01) and from 79 +/- 2 to 116 +/- 4 mmHg in pregnant ewes (p < 0.01) over the range of AngII infusion. MAP was unaltered during AngII plus nitroprusside infusion, averaging 78 +/- 3 mmHg in nonpregnant ewes and 80 +/- 2 mmHg in pregnant ewes. Basal ANF was higher (p < 0.01) in pregnant sheep than in nonpregnant sheep. With AngII infusion alone, plasma ANF was increased from 13 +/- 2 to 42 +/- 4 fmol/microL in nonpregnant ewes (p < 0.01) and from 23 +/- 5 to 72 +/- 16 fmol/microL in pregnant ewes (p < 0.01). However, during AngII plus nitroprusside infusion, the increases in plasma ANF observed were completely abolished in both nonpregnant and pregnant ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxytocin-induced prostaglandin F2 alpha release and endometrial oxytocin receptor concentrations throughout pregnancy in ewes.

Endometrial oxytocin receptor concentrations and oxytocin-induced plasma concentrations of 13,14,dihydro-15-keto prostaglandin F2 alpha were investigated on days 14 and 17 of the oestrous cycle and on days 14, 17, 25, 65, 85 and 145 of gestation in ewes. Total 13,14,dihydro-15-keto prostaglandin F2 alpha release in response to a bolus injection of oxytocin was significantly (P < 0.05) higher at luteolysis (day 17 of the oestrous cycle) than at any other stage of the oestrous cycle or in early gestation. On days 65, 85 and 145 of gestation, total prostaglandin release was significantly (P < 0.05) increased compared with earlier in gestation. Maximum concentrations of 13,14,dihydro-15-keto prostaglandin F2 alpha in response to oxytocin followed a similar pattern. Oxytocin receptor concentrations reflected total oxytocin-induced 13,14,dihydro-15-keto prostaglandin F2 alpha release, with increased oxytocin receptor concentrations occurring on day 17 of the oestrous cycle, compared with those observed on day 14 of the oestrous cycle and on days 14, 17 and 25 of gestation. By day 65 of gestation, oxytocin receptor concentrations were again increased. However, on days 85 and 145 of gestation, oxytocin receptor concentrations had decreased to concentrations similar to those observed in early gestation. These results indicate that oxytocin-induced 13,14,dihydro-15-keto prostaglandin F2 alpha release during early gestation is minimal despite the presence of endometrial oxytocin receptors. In mid-gestation, oxytocin-stimulated 13,14,dihydro-15-keto prostaglandin F2 alpha release is increased with a concomitant increase in uterine oxytocin receptor concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasmatic profiles of pregnancy-associated glycoprotein and progesterone levels during gestation in Churra and Merino sheep

This study was carried out to determine ovine pregnancy-associated glycoprotein (oPAG) and progesterone (P4) levels in the serum of Churra and Merino ewes throughout gestation and the first month post partum. The oPAG levels were determined with an heterologus RIA using bovine PAG as standard and tracer and rabbit antiserum against oPAG, sensitivity was 4.0 ng/ml. The P4 levels were measured with a radioimmunological procedure, including a specific extraction step with petroleum ether (bp 60-80 degrees C) with a sensitivity of less than 0.1 ng/ml. There were no differences (P<0.10) in the oPAG profile between breeds from Weeks 1 to 18. From Week 18 to lambing, oPAG concentrations increased rapidly in Churra ewes (on average, from 250 to 650 ng/ml) while remaining relatively constant in the Merino ewes (around 250 ng/ml). No significant differences (P>0.05) were observed for mean weekly P4 levels between the 2 breeds. In both breeds, P4 increased throughout the whole length of gestation, with the highest level measured at Weeks 19-20, then declined 2 wk before parturition. No correlation was found between P4 and oPAG concentrations during gestation in either of the breeds. After lambing, oPAG and P4 levels decreased rapidly in 4 wk to basal values. In both breeds the oPAG concentrations at Weeks 19, 20 and 21 of gestation in ewes carrying male fetuses were higher than in those carrying female fetuses. From the results, we conclude that the breed and sex of the fetus could influence the production of oPAG.

The timing of a moderate nutritional restriction in mid pregnancy and its effect on lamb birth weight and ewe gestation length

Lamb birth weight and ewe gestation length data were collected from a flock of 300-600 parous Border Leicester x Merino ewes over 4 years, as part of a study on nutritional restriction of pregnant ewes. One half of these ewes were nutritionally restricted for a 4-week period commencing 75-95 days post coitus, in order to achieve loss of maternal liveweight and reduction in body fat score to a minimum of 3. The remaining ewes with no nutritional restriction were &gt;6 kg heavier and had a body fat score &gt;0.8 higher at the end of the restriction period. Nutritional restriction affected (P&lt;0.05) birth weight of lambs. With each day's delay in commencing restriction, from day 75 to day 95, gestation length was increased (P&lt;0.001). For each additional day in utero, birth weight was increased by 40-50 g. Restriction and refeeding produced lambs of birth weights and weaning weights indistinguishable from the control ewes, and since there were no apparent disadvantages, mid pregnancy restriction is an alternative nutritional strategy for pregnant ewes.

HORMONALLY-INDUCED ABORTION AND PARTURITION IN GOATS AND EWES

Induced abortion and parturition have been practiced in both goats and ewes following the hormonal treatments. The intervals between injection and parturition or abortion in goats were 47.29+ 3.981 and 47.5+2.872 hours with intramuscular injection of 1 ml. Luprostiol (each 1 ml. contains 7.5 mg. prostaglandin F2 x) and 58.8+6.681 and 91.2+6.652 hours with double intramuscular injection of 3 ml. corticotets (each 1 ml. contains 2.5 mg prednisolone acetate and 5 mg dexamethasone) respectively. The intervals between injection and either the parturition over 148 days or abortion at 138 days of gestation in ewes were 40.4+4.019 and 66.5+5.852 hours. respectively with double intramuscular injection of 3 ml. corticotets, however, there was no response with luprostiol. &#x0D; The commbination of the compounds gave better results in bothe the goat and ewes, although better results were obtained following Luprostiol treatment in goat and corticotets in ewes in both parturition and abortion.

Relationships between plasma concentrations of placental lactogen, insulin-like growth factors, metabolites and lamb size in late gestation ewes subject to nutritional supplementation and in their lambs at birth

The relationships between placental lactogen (PL), insulin-like growth factor (IGF) -1 and -2, insulin, glucose and nonesterified fatty acids (NEFA) were studied in 10 triplet-bearing ewes in late gestation (120-129 days) which were on ad libitum feeding. To extend the range of plasma metabolite concentrations the ewes received a continuous abomasal infusion from 100 days of gestation until delivery. Three were infused with glucose (160 g/day), 2 received sodium caseinate and 3 were infused with control fluid alone. From 120 days the animals were fed 3 hourly intervals from a belt feeder to achieve steady state and at 125-130 days had intravenous plasma samples pooled for analysis. There was no effect of nutritional supplementation on birth weight. Casein supplementation was associated with reduced maternal PL concentrations but glucose supplementation had no effect on PL concentrations. Circulating PL concentrations showed a positive correlation to IGF-2 activity (r = 0.64, P less than 0.05) and a negative relation to IGF-1 concentrations (r = -0.73, P less than 0.05). IGF-1 levels were higher (P less than 0.05) and IGF-2 levels were lower (P less than 0.05) in nutritionally supplemented ewes. In the ewe, NEFA concentrations showed a negative relationship to IGF-1 (r = -0.75, P less than 0.05) and a positive relationship with IGF-2 (r = 0.87, P less than 0.1). Similar relationships were observed in the ewe at term. These observations suggest that nutritional factors and PL may be important determinants of IGF-2 secretion in the late-gestation ewe. They suggest the possibility that IGF-2 mediates the lipolytic effects of PL.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of maternal fasting on ovine fetal and maternal branched-chain amino acid transaminase activities.

Activities of branched-chain amino acid transaminase were assayed in maternal skeletal muscle, liver and fetal skeletal muscle, cardiac muscle, liver, kidney and placenta obtained from fed and 5-day-fasted late gestation ewes. Very high activities were found in placenta; fetal skeletal muscle also had high activity. Fetal brain had intermediate activity, followed by cardiac muscle and kidney. Fetal liver possessed negligible activity. Activities were low in both maternal liver and skeletal muscle. Trends were seen for fasting to increase activities in fetal placenta, skeletal muscle, brain, kidney, heart and maternal liver, but these changes were statistically significant only for fetal brain and placental tissue. Fetal skeletal muscle activity was 100 times that of maternal skeletal muscle. These data imply differences in the metabolism of the branched-chain amino acids by fetal and adult ruminants and expand the thesis that branched-chain amino acids are important to the metabolism of the ovine fetus.

Length of gestation in ewes carrying lambs of two different breeds

Length of gestation was studied in pregnancies established by intrabreed, interbreed, and mixed-breed embryo transfers of Finnish Landrace (Finn; mean gestation: 144.9 days) and Targhee (mean gestation: 150.4 days) embryos to Finn cross and Targhee recipients. At least one lamb of each breed comprised mixed-breed pregnancies. There was a significant effect of the breed of lamb (Finn, Targhee, or Finn and Targhee) on the length of gestation (P<.01), but not of breed of recipient. Mixed-breed pregnancies had a mean gestation period intermediate between those for pregnancies which contained only one breed of lamb. The mean gestation period for mixed-breed pregnancies was 2.10+/-.70 (x+/-S.E.) days longer than for pregnancies with only Finn lambs (P<.01) and 2.99+/-.73 days shorter than for pregnancies with only Targhee lambs (P<.001). The delay in parturition in mixed-breed pregnancies beyond the normal gestation period for Finn lambs occurred even in litters with a majority of Finn lambs. These results demonstrate an interaction between fetuses in the processes leading to parturition. Possible mechanisms by which the Targhee lamb delayed parturition in mixed-breed pregnancies are discussed.

Uterine blood flow and nutrient uptake during late gestation in ewes with different number of fetuses.

Uterine blood flow and nutrient uptake during late gestation in ewes with different number of fetuses.

The effects of foetal thyroidectomy on the development of the ovine foetus.

SUMMARY Thyroid glands were surgically ablated from foetal sheep between 81 and 96 days of gestation in order to study the role of the thyroid gland in foetal development. Gestation of ewes bearing thyroidectomized foetuses was prolonged by about 5 days, and athyroid lambs failed to survive more than 24 h. Athyroid foetuses delivered by Caesarian section 1 week before term were characterized by low body weight, low thymus gland weight, and shortened limbs. Foetal thyroidectomy markedly retarded both the maturation and growth of wool follicles and osseous tissue. Plasma concentrations of growth hormone, calcium and phosphorus were normal in the athyroid foetuses, but cholesterol levels were increased. The absence of thyroxine in the foetal circulation agrees with previous findings that the ovine placenta is impermeable to maternal thyroxine.

Plasma progesterone concentrations during pregnancy and parturition of ewes grazing yarloop clover.

Summary. Progesterone concentrations in the peripheral plasma of pregnant ewes grazing oestrogenic (yarloop clover) and non-oestrogenic (rye grass) pastures were compared. Whilst the overall pattern of plasma progesterone throughout pregnancy in the two groups was similar, the mean of values determined from the 90th day of gestation in ewes on yarloop was significantly lower than those on grass. No significant differences were recorded in the length of pregnancy or birth weight of lambs (P>0\m=.\05)although some evidence of maternal dystocia was obtained for the ewes on yarloop. In relation to parturition, mean plasma progesterone values in both groups began to fall 96 hr before birth, at first gradually then rapidly in the 16 hr preceding birth. Ewes on grass had a higher (P<0\m=.\01) plasma progesterone concentration 0 to 8 hr before birth but neither the level nor the pattern of progesterone disappearance appeared to be related to the lambing difficulties observed. Two classical symptoms of clover disease in ewes, infertility and dystocia were described by Bennetts, Underwood & Shier (1946). Determination of plasma progesterone concentrations throughout the oestrous cycle of young ewes grazing oestrogenic (yarloop clover) pastures indicated that corpus luteum function in the infertile animals was reduced (Obst & Seamark, 1970). To investigate the possibility of there being similar endocrinological disturbance underlying dystocia, the concentrations of plasma progesterone of pregnant ewes exposed to oestrogenic pastures have been determined throughout pregnancy and parturition. The observations made reveal that plasma pro¬ gesterone levels in ewes grazing yarloop pastures are significantly lower in late

Prolonged gestation in ewes after foetal adrenalectomy.

SUMMARY Complete bilateral removal of the adrenal glands of sheep foetuses in utero resulted in failure of the ewes to undergo labour. Thirty-seven ewes with dated pregnancies were operated on approximately 1 month before term. Eight foetuses were carried in utero past term; all showed definite signs of postmaturity.

Studies on the carbohydrate metabolism of sheep. I. The range of blood-sugar values under several conditions

The considerable volume of literature dealing with the normal range of blood-sugar values in ruminants and with the effect of varying nutritive conditions upon it is reviewed in some detail. Attention is drawn to differences between ruminant and non-ruminant mammals, and an attempt is made to explain them in the light of present knowledge of digestive processes in the ruminant. Data are presented on the normal range of blood-sugar values in sheep, both in Australia and in England, and on the effect of nutritive factors and of pregnancy on these values. The mean blood-sugar values determined by the author in non-pregnant ewes in Australia and in England were 34.8 ± 3.06 and 39.1 ± 3.37 mg. per cent. respectively. The observed range in both pregnant and non-pregnant ewes was 18-57 mg. per cent., but 94 per cent. of values fell between 25 and 46 mg. per cent. This range was obtained in sheep bled usually in the morning, before feeding. A delayed rise, which is slight and always below hyperglycaemic levels, was observed after feeding; the afternoon samples showed higher values than the morning samples. Thus, the normal range of blood-sugar values in fed sheep, at any time of day, is considered to be 25-50 mg. per cent. The level of blood sugar was affected neither by the plane of nutrition nor by the bodily condition of non-pregnant ewes. Gestation in ewes in good condition was observed not to affect the level, although evidence was obtained of lowered blood-sugar levels during the last two months of gestation in ewes in poor condition. Expressed as a percentage of the pre-fasting level, the decrease in blood sugar observed during a four-day fast was similar to that observed in non-ruminants, but the response was delayed. Fasting for a period of 24 hours had little effect on the blood-sugar level in non-pregnant sheep in good condition; in many cases there was little change after the period had been extended to 46 hours. On the other hand, a fast of 24 hours' duration produced a marked hypoglycaemia in ewes in poor bodily condition during the last two months of gestation, blood-sugar levels as low as 8.6 mg. per cent. being recorded.