Effects of Age and Reproductive Stage on Certain Serum Biochemical Parameters of Chios Sheep Under Greek Rearing Conditions

The aim of the present study was to determine the normal ranges of the most commonly used serum biochemical parameters of sheep reared under Greek breeding conditions, as well as to test for the effects of the age and reproductive status of the animals on the normal values of these parameters. In total, 200 clinically healthy Chios sheep from 10 farms were used in the experiment. For the determination of the effect of age 150 sheep were assigned in three groups. Group A consisting of 50 lambs aged 2–6 months (mean ± SD: 4.15 ± 1.08), group B of 50 non‐pregnant ewes into lactation aged 1–3 years (mean ± SD: 2.12 ± 0.86) and group C of 50 non‐pregnant ewes into lactation aged more than 3 years (mean ± SD: 5.98 ± 1.66). For evaluating the effect of reproductive status 50 pregnant ewes in dry period were used, 15–30 days before the expected day of lambing (group D), along with the 100 non‐pregnant ewes into lactation of groups B and C (group E). Blood sampling was performed once, in dry ewes from December to January, and in lambs and lactating ewes from March to May. The results showed that of the 14 biochemical parameters determined in serum, six were significantly affected by the age and eight by the reproductive stage of the animals.     

Natural Immunity of Sheep and Lambs Against the Schmallenberg Virus Infection

Since the first reports of the Schmallenberg disease (SBD) outbreaks in late 2011, the disease has spread across Europe, affecting cattle and sheep farms. While Schmallenberg virus (SBV) causes a mild clinical disease in adults, infection of pregnant females may lead to the production of typical congenital malformations (CMFs) in their offspring. It is speculated that the immunity acquired after a SBV infection is effective in preventing further infections. However, this has not been proven in naturally infected sheep, especially if they are pregnant when reinfected. The aim of this study was to monitor the natural immunity in SBV‐infected sheep. Twenty‐four ewes from the only Spanish farm with a SBV OIE‐notified outbreak were sampled. Subsequently, nine pregnant ewes were inoculated with SBV infectious plasma under controlled conditions. Six of them were euthanized before delivery, and their fetuses were inspected for lesions indicative for the SBV infection. The three remaining ewes were allowed to deliver one lamb each. Inoculation of the lambs was scheduled at approx. 3 months after birth. All samples were analyzed for viral RNA by RT‐PCR, and for antibodies by an indirect ELISA and a virus neutralization test (VNT). The majority of the 24 ewes showed a serological reaction against SBV. The three ewes that were allowed to lamb down demonstrated variable degrees of seroconversion which corresponded to the levels of immune reaction observed in their lambs. Moreover, no viral RNA was detected, no lesions were observed in the fetuses, and no clinical signs were detected in the inoculated animals. These findings suggest that the immunity acquired by sheep following a natural SBV infection could be sufficient to stop SBV reinfection. However, vaccination could be a valuable tool to control SBV infections and associated economic losses as it affords a more uniform and predictable protection at the flock/herd level.     

Preliminary Survey on the Impact of Schmallenberg Virus on Sheep Flocks in South of Belgium

Between late February and May 2012, a preliminary anonym survey was conducted among sheep farmers in south of Belgium in order to contribute to future estimations of the economic losses caused by Schmallenberg virus (SBV). Based on clinical signs consistent with SBV infection, this survey involved 13 meat sheep flocks considered as positive flocks with subsequent SBV detection by RT‐qPCR [SBV‐positive flocks (PF); total of 961 animals], and 13 meat sheep flocks considered as negative flocks (NF; total of 331 animals). These preliminary results indicated several significant characteristics that were more present in PF than in NF. These include an increased rate of abortions (6.7% in PF versus 3.2% in NF), of lambs born at term but presenting malformations (10.1% in PF versus 2.0% in NF) and of dystocia (10.1% in PF versus 3.4% in NF). Lamb mortality during the first week of life was reported more frequently in PF (8 of 13 PF, 61.5%) than in NF (1 of 13 NF, 7.7%). In PF, the observed prolificacy rate was 2‐fold lower (93%) than expected (186%). The implementation of a survey at larger scale, including a high number of breeders, is necessary to allow a more detailed analysis of the SBV impact in the sheep sector.     

Effects of Palm Oil on Lipid Peroxidation,Reduced Glutathione,Glutathione Peroxidase,and Vitamin A Levels in the Corpus uteri,Cornu uteri and Corpus luteum of Young and Adult Female Sheep

The aim of the current study was to determine whether a rumen protected palm oil based diet affect malondialdehyde (MDA), glutathione peroxidase (GSH‐Px), reduced glutathione (rGSH) and vitamin A levels in the tissues of cornu uteri, corpus uteri and corpus luteum over the barley based isoenergetic and isonitrogenous diet, and whether the response is different between ewes and ewe‐lambs. During the breeding season, half of Morkaraman ewes (2–4‐year‐old, n=10) and ewe‐lambs (7–8‐months‐old, n=10) was offered a barley based diet and the other half was offered a protected palm oil based diet for 42 ± 0.7 days. At the end of the experiment all animals were slaughtered and measurements carried out in the tissues collected. In all animals tested, cornu uteri had the highest MDA levels followed by corpus uteri and corpus luteum (P<0.01) but no differences were between the tissues observed in GSH‐Px and rGSH levels (P>0.05). Vitamin A levels were, however, higher in corpus luteum than in cornu uteri and corpus uteri (P<0.05). Corpus uteri MDA levels were not different (P>0.05) but rGSH levels were higher for the palm oil fed groups (P<0.05). GSH‐Px and rGSH levels were higher for ewe‐lambs than ewes (P<0.05). In conclusion, it appears that MDA, rGSH, GSH‐Px, and vitamin A work in a different fashion for corpus uteri, cornu uteri and corpus luteum, and for ewes and ewe‐lambs. Dietary palm oil did not significantly affect the parameters studied except higher rGSH levels in corpus uteri. Levels of anti‐oxidatively active substances, such as rGSH and GSH‐Px were lower in ewes compared with those in ewe‐lambs.     

Effect of Bacillus licheniformis and Bacillus subtilis Supplementation of Ewe's Feed on Sheep Milk Production and Young Lamb Mortality

The purpose of this pilot study was to evaluate under field conditions the effect of a probiotic containing Bacillus licheniformis and Bacillus subtilis on young lamb mortality and sheep milk production when administered in the late pregnancy and lactation feed of ewes. In a sheep farm, two groups of milking ewes with identical genetic material, management, nutrition, health status and similar production characteristics were formed. One group (46 ewes) served as control, while the other one (48 ewes) served as a probiotic‐treated group. Both groups of ewes received a similar feeding regiment, but the ewes of the second group were additionally offered a probiotic product containing B. licheniformis and B. subtilis (BioPlus 2B, Chr. Hansen, Denmark) at the approximate dose of 2.56 × 10⁹ viable spores per ewe per day. Lamb mortality during the 1.5 months suckling period, and milk yield during the 2 months of milk collection for commercial purposes have been recorded. In the non‐treated control group, 13.1% mortality was observed versus 7.8% in the probiotic‐treated group (P = 0.33), with mortality being mainly due to diarrhoea. Microbiological examination of diarrhoeic faeces from some of the dead lambs in both groups revealed the presence of Escherichia coli. The average daily milk yield per ewe was significantly lower in the control group (0.80 l) than that in the probiotic‐treated group (0.93 l) (P < 0.05). Fat and protein content of milk in ewes that received probiotics was significantly (P < 0.05) increased compared with untreated ewes. It was concluded that supplementing ewe's feed with probiotics may have beneficial effect on subsequent milk yields, fat and protein content.     

Relative distribution and crosslinking of collagen distinguish fetal from adult sheep wound repair

BACKGROUND/PURPOSE: Collagen deposition in midgestation fetal skin wounds occurs rapidly and in a normal reticular pattern unlike adult scar. Although collagen types I, III, and V are present in both fetal and adult skin wounds, their relative distribution and pattern of crosslinking are unknown. We compared the quantity, distribution, and crosslinking of specific collagen types in fetal and adult sheep wounds. METHODS: Nine fetal lambs at 75, 100, and 120 days' gestation (term, 145 days) and their ewes received subcutaneous polyvinylalcohol (PVA) sponge implants. PVA sponges were harvested at 3, 7, or 14 days after implantation, were processed, and then analyzed for collagen content, distribution, and crosslinking by two-dimensional cyanogenbromide (2-D CNBr) peptide mapping. Collagen types were further analyzed in normal skin of fetal sheep at 75, 90, 125, and 140 days' gestation and in their ewes. RESULTS: Between days 3 and 14 after implantation, total collagen deposition within PVA sponges increased 25-fold in fetal lambs but only 10-fold in adult sheep. The type I to III ratios inside 14-day sponges of 75-day gestation fetuses and adult ewes were 6.4 and 1.3, respectively. Thus, by day 14 in both fetal and adult sponges, type I collagen emerged as the major constituent. Although type V comprised less than 2% of normal skin collagen, alpha1(V) chains constituted the greatest collagen fraction in 3-day fetal implants, whereas within 3-day adult sponges only alpha2(V) collagen was detected. The total collagen content of unwounded fetal sheep skin increased twofold from 75 to 90 days' gestation. However, noncrosslinked forms of collagen type I diminished rapidly after 90 days' gestation, corresponding with the transition to scarring of fetal sheep wounds. CONCLUSIONS: Collagen types I, III, and V are deposited rapidly in fetal wounds and display an ontogenic transition in their metabolism from a fetal to an adult phenotype. Crosslinking of type I collagen increases during development and corresponds with the transition to scarring of fetal wounds after midgestation. These observations may help design strategies that induce a more fetallike repair of adult wounds.     

Serosurvey of Schmallenberg Virus Infections in Sheep and Goat Flocks in Lower Saxony,Germany

Schmallenberg virus (SBV) infections can cause congenital musculoskeletal and vertebral malformations as well as neurological failures in foetuses of several ruminant species if susceptible mother animals were infected during early gestation. Blood samples gained from 17 goat and 64 sheep flocks in Lower Saxony (LS), Germany (January–May 2012), which is located in the core region of the 2011/2012 epidemic were tested for antibodies against SBV by ELISA to detect past exposure to SBV. A SBV‐specific questionnaire was raised in all flocks. The calculated median within‐herd prevalence was 43.8% (min–max: 5.6–93.3%) for goats and 58.7% (min–max: 6.5–100%) for sheep, showing that small ruminants in LS, especially goats, are still at risk of novel SBV infections in the following lambing seasons as not all animals have seroconverted yet. Statistical analysis revealed that goats have a significantly lower risk of SBV infections than sheep which might be explained by different host preferences of Culicoides ssp. as main vectors for SBV and different housing conditions.     

Maternal Vitamin D Status During Pregnancy and Bone Mass in Offspring at 20 Years of Age: A Prospective Cohort Study

It is uncertain whether the vitamin D status of pregnant women influences bone mass of their children. Cohort studies have yielded conflicting results; none have examined offspring at skeletal maturity. This longitudinal, prospective study investigated the association between maternal vitamin D status and peak bone mass of offspring in 341 mother and offspring pairs in the Western Australian Pregnancy Cohort (Raine) Study. Maternal serum samples collected at 18 weeks gestation were assayed for 25‐hydroxyvitamin D (25OHD). Outcomes were total body bone mineral content (BMC) and bone mineral density (BMD) measured by dual‐energy X‐ray absorptiometry in offspring at 20 years of age. The mean (± SD) maternal serum 25OHD concentration was 57.2 ± 19.2 nmol/L; 132 women (38.7%) were vitamin D‐deficient (25OHD <50 nmol/L). After adjustment for season of sample collection, maternal factors, and offspring factors (sex, birth weight, and age, height, lean mass, and fat mass at 20 years), maternal 25OHD concentration was positively associated with total body BMC and BMD in offspring, with a mean difference of 19.2 (95% confidence interval [CI], 5.6–32.7) g for BMC and 4.6 (95% CI, 0.1–9.1) mg/cm² for BMD per 10.0 nmol/L of maternal 25OHD. Maternal vitamin D deficiency was associated with 2.7% lower total body BMC (mean ± SE) (2846 ± 20 versus 2924 ± 16 g, p = 0.004) and 1.7% lower total body BMD (1053 ± 7 versus 1071 ± 5 mg/cm², p = 0.043) in the offspring. We conclude that vitamin D deficiency in pregnant women is associated with lower peak bone mass in their children. This may increase fracture risk in the offspring in later life. © 2014 American Society for Bone and Mineral Research.     

Investigations into the Cause of Foot‐and‐Mouth Disease Virus Seropositive Small Ruminants in Cyprus During 2007

In 2007, serological evidence for foot‐and‐mouth disease (FMD) infection was found as a result of differential diagnostic testing of Cypriot sheep suspected to be infected with bluetongue or contagious ecthyma. Seropositive sheep and goats were subsequently uncovered on ten geographically clustered flocks, while cattle and pigs in neighbouring herds were all seronegative. These antibodies were specific for serotype‐O FMD virus, reacting with both structural and non‐structural (NS) FMD viral proteins. However, no FMD virus could be recovered from the seropositive flocks. FMD had not been recorded in Cyprus since 1964 and there has been no vaccination programme since 1984. Since all the seropositive animals were at least 3 years old and home‐bred, it was concluded that infection had occurred approximately 3 years previously had passed un‐noticed and died out spontaneously. It therefore appears that antibodies to FMD virus NS proteins can still be detected around 3 years after infection of small ruminants, but that virus carriers cannot be detected at this time. This unusual situation of finding evidence of historical infection in a FMD‐free country caused considerable disruption and alarm and posed questions about the definition of what constitutes a FMD outbreak.     

Vitamin D metabolism during pregnancy

Vitamin D metabolism is altered in the pregnant animal, presumably in response to fetal demands for calcium. Circulating levels of 1,25-dihydroxyvitamin D are elevated in the pregnant animal. The stimulus of this increase and the hydroxylase(s) (placental or renal) responsible are unknown. Maternal plasma 25-hydroxyvitamin D levels have been reported to be both unchanged and decreased during pregnancy but very much dependent upon exposure to ultraviolet light and vitamin D supplementation. The major vitamin D metabolites (25-hydroxyvitamin D, 24,25-dihydroxyvitamin D, and 1,25-dihydroxyvitamin D) circulate in fetal plasma but generally at lower concentrations than in the mother (exception is the sheep). All of these metabolites are able to cross the placenta. The fetal kidney and placenta both have 25-hydroxyvitamin D1 alpha- and 24-hydroxylase activity. However, the relative contribution of mother, fetus, and placenta to fetal vitamin D metabolism has yet to be fully determined.     

Low maternal vitamin D status and fetal bone development: Cohort study

Recent findings suggest that maternal vitamin D insufficiency during pregnancy has consequences for the offspring's bone health in later life. To investigate whether maternal vitamin D insufficiency affects fetal femur growth in ways similar to those seen in childhood rickets and study the timing during gestation of any effect of maternal vitamin D status, we studied 424 pregnant women within a prospective longitudinal study of maternal nutrition and lifestyle before and during pregnancy (Southampton Women's Survey). Using high‐resolution 3D ultrasound, we measured fetal femur length and distal metaphyseal cross‐sectional area, together with the ratio of femoral metaphyseal cross‐sectional area to femur length (femoral splaying index). Lower maternal 25‐hydroxyvitamin vitamin D concentration was not related to fetal femur length but was associated with greater femoral metaphyseal cross‐sectional area and a higher femoral splaying index at 19 weeks' gestation [r = ?0.16, 95% confidence interbal (CI) ?0.25 to ?0.06 and r = ?0.17, 95% CI ?0.26 to ?0.07, respectively] and at 34 weeks' gestation (r = –0.10, 95% CI ?0.20 to 0.00 and r = ?0.11, 95% CI ?0.21 to ?0.01, respectively). Three groups of women were identified with 25‐hydroxyvitamin vitamin D concentrations that were sufficient/borderline (>50 nmol/L, 63.4%), insufficient (25 to 50 nmol/L, 30.7%), and deficient (≤25 nmol/L, 5.9%). Across these groups, the geometric mean femoral splaying indices at 19 weeks' gestation increased from 0.074 (sufficient/borderline) to 0.078 (insufficient) and 0.084 (deficient). Our observations suggest that maternal vitamin D insufficiency can influence fetal femoral development as early as 19 weeks' gestation. This suggests that measures to improve maternal vitamin D status should be instituted in early pregnancy. © 2010 American Society for Bone and Mineral Research     

Leptospira interrogans serogroup Pomona serovar Kennewicki infection in two sheep flocks with acute leptospirosis in Uruguay

Acute leptospirosis is an infrequent disease in sheep that can cause jaundice, haemolysis, haemoglobinuria, hepatitis and nephritis. In most reports the diagnoses have been made by clinical, pathological or serological evidence without isolation or direct identification of the agent. Here, we report one confirmed and one presumptive outbreak of acute leptospirosis in suckling lambs from two unrelated sheep farms in Uruguay with mortalities of 9/60 (15%) and 9/163 (5.5%) lambs. Both outbreaks occurred in Sep–Oct 2017 after heavy rainfall and flooding events. The main gross and histologic pathological findings in two autopsied lambs, one from each farm, included severe diffuse jaundice, haemoglobinuria, acute necrotizing hepatitis with cholestasis and interstitial nephritis. Leptospira interrogans serogroup Pomona serovar Kennewicki was isolated from sheep in both flocks and the same genotype was identified directly in clinical samples from infected animals, including one of the deceased lambs subjected to autopsy, by amplification and partial sequencing of rrs and secY genes. This serovar has recently been identified in infected cattle and humans in Uruguay. The impact of Leptospira spp. infection in ovine health, and the epidemiologic role of sheep as reservoirs of leptospirosis for humans and animals need further investigation.     

The effects of first gestation and lactation on bone metabolism in dairy goats and milk sheep

The goal of the present study was to compare mobilization rate of calcium (Ca) from bone in pregnant and lactating goats and sheep. Blood samples were collected from goats and sheep monthly during pregnancy and at 1, 2, and 4 weeks postpartum (pp) and monthly during lactation until 6 months after parturition. Total bone mineral content (BMC) and total bone mineral density (BMD) were quantified using peripheral quantitative computed tomography at the same intervals as the blood was taken. Bone resorption was assessed by immunoassays quantitating two epitopes of the carboxyterminal telopeptide of type I collagen (ICTP, CTX). Bone formation was estimated by quantifying serum osteocalcin (OC) and bone-specific alkaline phosphatase (bAP). In addition, Ca and 1,25-dihydroxy vitamin D (1,25-VITD) concentrations were determined in serum.

Mean ICTP and CTX concentrations of both animal species increased the first week after parturition. By the second week pp, the concentrations of both markers had decreased toward early gestation levels. In contrast, mean OC concentrations continually decreased until the 1st week pp. By the 2nd week pp, the mean concentrations of OC started to increase again. Mean bAP activities decreased during gestation and reached a nadir in the first week pp in goats and 4 weeks pp in sheep. Afterwards, mean bAP activities increased again in goats and sheep. 1,25-VITD concentrations peaked the first week pp and returned to early gestation values thereafter. Total BMC and BMD decreased from the 4th month of pregnancy until the 1st week pp in both species. Afterwards, BMC increased throughout the first month pp in goats and the first 3 months pp in sheep. BMD levels of sheep and goats returned to prepartum levels during lactation.

The resorptive phase of bone remodeling is accelerated at parturition and in early lactation and is uncoupled from the process of bone formation. This allows the animal to achieve Ca homeostasis at the expense of bone. Increased bone remodeling during lactation may represent physiological mechanisms to help replace the maternal skeleton lost as the animal adapted to enormously increased Ca losses to the fetus and milk in late gestation and early lactation.     

Vitamin D Does Not Increase Calcium Absorption in Young Women: A Randomized Clinical Trial

It is commonly said that vitamin D should be used to increase calcium absorption. We tested this statement in a dose‐response study of vitamin D on calcium absorption. A total of 198 white and African American women, aged 25 to 45 years, with vitamin D insufficiency, serum 25‐hydroxyvitamin D (25OHD) <20 ng/mL, were randomized in a double‐blind study to vitamin D3 400, 800, 1600, 2400 IU, or placebo. A calcium supplement was given to increase mean calcium intake at baseline from 706 mg/d to 1031 mg/d. Calcium absorption was measured at baseline and after 12 months using a single isotope method with radiocalcium45 and 100 mg of calcium. Mean baseline serum 25OHD was 13.4 ng/mL (33.5 nmol/L) and increased to 40 ng/mL (100 nmol/L) on the highest dose of 2400 IU. Using a multivariate regression analysis with significant predictors, baseline absorption, calcium intake, and weight, there was no increase in 12‐month calcium absorption compared with baseline on any dose of vitamin D in either whites or African Americans. There was no significant relationship between 12‐month calcium absorption and final serum 25OHD. In an analysis of calcium absorption and serum 25OHD at baseline, serum 25OHD levels were divided into groups: 0 to 5, 6 to 10, 11 to 15, or 16 to 20 ng/mL. There was no evidence of a threshold decrease in calcium absorption or serum 1,25 dihydroxyvitamin D (1,25(OH)₂D) amongst the lowest groups. Vitamin D doses up to 2400 IU daily did not increase calcium absorption. No threshold level of serum 25OHD for calcium absorption was found at baseline or in the longitudinal study, suggesting that active transport of calcium is saturated at very low serum 25OHD levels <5 ng/mL. There is no need to recommend vitamin D for increasing calcium absorption in normal subjects. Very efficient calcium absorption at very low levels of serum 25OHD explains why people do not develop osteomalacia provided that dietary intakes of calcium and phosphorus are adequate. © 2014 American Society for Bone and Mineral Research.     

Vitamin D insufficiency is prevalent and vitamin D is inversely associated with parathyroid hormone and calcitriol in pregnant adolescents

Few large studies have assessed changes in calcitropic hormones and maternal 25‐hydroxyvitamin D (25(OH)D) status across pregnancy, and how this may impact maternal bone turnover and neonatal hormone status. We aimed to identify determinants of 25(OH)D, parathyroid hormone (PTH), and calcitriol across pregnancy in a longitudinal study of 168 pregnant adolescents (≤18 years of age). Maternal 25(OH)D, PTH, and calcitriol were assessed at mid‐gestation (～26 weeks), delivery, and in cord blood. Data were related to measures of maternal anthropometrics, dietary intake, physical activity, and bone turnover markers. Approximately 50% of teens and their infants had serum 25(OH)D ≤ 20 ng/mL; 25(OH)D was lower in African Americans versus whites (p < 0.001). PTH increased across gestation (p < 0.001). Elevated PTH (≥60 pg/mL) was detected in 25% of adolescents at delivery, and was associated with increased concentrations of serum N‐telopeptide (NTX) (p = 0.028). PTH and calcitriol did not significantly differ across the range of Ca intake consumed (257–3220 mg/d). In the group as a whole, PTH was inversely associated with 25(OH)D in maternal circulation at mid‐gestation (p = 0.023) and at delivery (p = 0.019). However, when the cohort was partitioned by 25(OH)D status, this relationship was only present in those with 25(OH)D ≤ 20 ng/mL, suggestive of a threshold below which 25(OH)D impacts PTH during pregnancy. Mid‐gestation 25(OH)D was inversely associated with calcitriol at delivery (p = 0.023), irrespective of Ca intake. Neonatal PTH and calcitriol were significantly lower than (p < 0.001), but unrelated to maternal concentrations. These findings indicate that maternal 25(OH)D status plays a role in calcitropic hormone regulation in pregnant adolescents. © 2012 American Society for Bone and Mineral Research     

Wound healing in foetal sheep: a histological and electron microscope study.

A study was made of the healing of excised, unsutured and sutured skin wounds in foetal sheep of 75, 90 and 120 days gestation and of wounds in newborn lambs and adult ewes. Foetal and postnatal wounds were found to heal in a very similar way. At each stage of development studied, excised wounds contract rapidly and histological and electron microscope examination demonstrates formation of granulation tissue and its maturation to scar tissue in all types of wound. Examination of polyvinyl sponges 7 and 14 days after subcutaneous implantation confirms the ability of foetal sheep to form vascularised scar tissue. The cellular inflammatory response to wounding is much less prominent in foetal than in postnatal sheep, the number and type of extravascular cells reflecting the changes in blood leucocyte content during development. From a very early stage foetal sheep react to insoluble irritants by the formation of multinucleate giant cells.     

Clinical Signs and Diagnosis of Scrapie in Italy: A Comparative Study in Sheep and Goats

This article reports the clinical signs of scrapie occurring in sheep–goat flocks in Italy. The research, carried out on over 500 goats and 550 sheep, yielded an interesting clinical picture, especially of goat scrapie. The affected animals, aged between 2 and 8 years, showed neurological signs that could be classified into three categories: changes in mental status, abnormalities of movement and changes in sensation. Some general clinical signs were also observed. The clinical suspicion was confirmed by histopathological and biochemical investigations.     

Immunological tolerance of sheep to skin allografts

A majority of grafts of adult sheep skin placed on fetal lambs at 55 days gestation were retained and increased 50-100-fold in area by the time of birth. Although the original grafts placed in utero survived, second and third grafts from the same donors were rejected. Lambs bearing skin grafts attained full mixed leukocyte reactivity against cells from the skin donors.