Twin Lambs Research Articles

First Report of a Cyclops Lamb Associated With a Normal Twin Lamb From Iran

A four- year-old Moghanian breed ewe was admitted to the large animal veterinary clinic, University of Tabriz due to dystocia. During obstetrical examination, it was revealed that the cervix has been closed firmly and vagina protruded about 5 cm through the vulva (vaginal prolaps). Based on clinical findings and for saving the dam and lamb(s), the cesarean section was done. A normal alive female lamb twin to a monster dead male was delivered. According to the facial deformity, the monster twin was diagnosed as Cyclops lamb. This is the first report of a Cyclops lamb’s giving birth twine to a normal lamb from Iran.

Does milk supply have long-term benefits for resistance and resilience to nematode parasites in sheep?

The long-term benefit of suckling for the resistance and resilience of lambs to Teladorsagia circumcincta infection was investigated in a 20-week after-lambing trial period; during which time the immune response was anticipated to be strengthening. In a two by two factorial arrangement, one factor was ‘suckling’ with one twin lamb from each of 34 pairs being either weaned (W−) at 39 days of age or allowed to continue suckling (S−) until necropsy at mean ages of either 84, 112 or 140 days. The second factor was ‘parasite infection’ with lambs in each ‘suckling’ treatment group either artificially challenged with an equivalent of 1000 L 3 T. circumcincta larvae d −1 (−I) from day 42 of age until necropsy or not artificially challenged (−N). All lambs and their dams grazed ryegrass pastures throughout the trial; these were intended to be relatively parasite safe, although worm burdens of SN and WN groups suggested there was a considerable parasite challenge from pasture from day 84 onwards. Despite this, suckled lambs consistently exhibited lower faecal egg counts (FECs; P < 0.05) and worm burdens at slaughter on days 84 and 112 ( P < 0.05 for both). Worms from suckled lambs appeared to have reduced egg production indicating either a direct effect of milk proteins on parasite fecundity or an indirect benefit of suckling through the provision of nutrients for enhance immune capacity. Lamb growth rate was reduced by weaning but not by artificial challenge ( P > 0.05). It was concluded that while the enhanced protein supply from suckling will facilitate greater growth rates in young lambs, weaning may not necessarily be associated with reduced resilience to T. circumcincta infection. Furthermore, suckling appears to assist in reducing worm burdens and parasite fecundity either through a direct anti-parasitic effect or through hastening the acquisition of immunity when lambs are exposed to larvae early in life.

Effects of ewe size and nutrition during pregnancy on performance of 2-year-old female offspring

SUMMARYThe current study investigated the effects of dam weight and nutrition during gestation on the reproductive performance of female primiparous offspring at 2 years of age. Four hundred and fifty heavy (H) (mean±s.e.m.: 60·8 kg±0·18) and 450 light (L) (42·5 kg±0·17) dams were randomly allocated to ad libitum (A) or maintenance (M) nutritional regimens from day 21 until day 140 of pregnancy, under pastoral grazing conditions. One week prior to lambing, all dams and their lambs were provided with ad libitum feeding through to weaning. After weaning, female progeny were managed and fed to requirements as one group. At 2 years of age, the oestrous cycles of the female offspring (n=207) were synchronized and the offspring were naturally mated. Ewes were scanned for pregnancy by ultrasound at day 70 of pregnancy. Within 24 h of birth, lambs were weighed and body dimensions were measured. Lambs were also weighed at day 24 (L24) and weaning. No effects of dam nutrition or dam weight were found (P&gt;0·10) on the reproductive performance of the ewe offspring. Lambs of M-grand-dams were heavier at birth (P=0·024) and weaning (P=0·031) than lambs of A-grand-dams. Twin lambs of H-grand-dams were heavier at birth (P=0·014) than twin lambs of L-grand-dams; however, grand-dam weight had no effect (P&gt;0·10) on lamb weaning weight. In summary, dam weight had no effect on reproductive performance of the female offspring, with only a minor effect on the weight of grand-offspring. Thus, being born to a larger dam has no advantages over being born to a smaller dam, in terms of number of lambs born and weight of lambs at birth and weaning. Grand-dam maintenance nutrition had no effect on reproductive performance although it increased lamb birth and weaning weight and lamb growth rates of the grand-offspring. Therefore, this indicates that ewes born to dams fed at maintenance during pregnancy have an advantage over A-ewes in physiological stressful situations including pregnancy or lactation.

Effects of maternal protein nutrition and subsequent grazing on chicory (Cichorium intybus) on parasitism and performance of lambs.

Forty-eight 4- to 5-yr-old Blackface x Bluefaced Leicester (Mule) ewes and their 24-d-old twin lambs were used to assess the effects of maternal protein nutrition and subsequent grazing on chicory (Cichorium intybus) on performance and parasitism. The experiment consisted of 2 grazing periods: safe pasture period and experimental pasture period. During an adaptation period of 66 d, ewes were infected through oral dosing with Teladorsagia circumcincta infective larvae (3 d per wk) and were supplemented with protein (HP) or not (LP) for the last 45 d of this period. At the end of this period, ewes and their lambs were turned out onto a parasitologically safe pasture; all ewes continued to be dosed with parasite (once a week), and HP ewes received protein supplementation for the first 35 d. Ewes and lambs grazed the safe pasture for an additional 43 d after termination of protein supplementation and of oral dosing with parasites. Ewes and their lambs were then moved onto newly established experimental pastures sown with chicory or grass/clover (Lolium perenne/Trifolium repens). During the safe pasture period, HP ewes had decreased fecal egg counts (FEC) compared with LP ewes, whereas HP lambs had temporarily less (P < 0.05) FEC, decreased (P < 0.001) plasma pepsinogen concentrations, and grew faster (P = 0.028) than LP lambs. Lambs grazing chicory had consistently less (P < 0.001) FEC and grew faster (P = 0.013) than lambs grazing grass/clover but had greater (P < 0.001) concentrations of pepsinogen. Pasture larvae counts were decreased (P = 0.07) for the chicory compared with the grass/clover plots. There were no interactions (P > 0.10) between maternal nutrition and grazed forage type on performance or parasitological measurements. Our results suggest that increased maternal protein nutrition and subsequent grazing of chicory independently improve lamb performance and reduce lamb parasitism.

Ewe and lamb contact at lambing is influenced by both shelter type and birth number

A significant number of lambs born each year in Australia die within 72 h of birth. Periods of high wind, combined with rain and low temperatures can lead to marked increases in the mortality level. Under these climatic conditions mortality levels may be reduced with the provision of shelter. This study used contact loggers to compare interactions between ewes with twin lambs across two shelter types (Hessian and shrubs), while also comparing ewes with single and twin lambs in a single shelter type (Hessian). The contact loggers record the time of the initial contact (within approximately 4 to 5 m) between collared animals and the duration of each contact. Contact levels between ewes immediately after lambing were only 10% of the initial levels (1 h/day). For single-born lambs, lambs averaged 11 h contact per day with their mother, while for twinborn lambs, each lamb averaged 9.25 h/day with its mother and 14.7 h/day with its sibling. The level of contact between ewes and each of their offspring in the Hessian was 24% lower (P < 0.05) for ewes with twin lambs than with singles. For ewes with twin lambs the level of contact was 17% lower (P < 0.05) in the Hessian shelter compared with shrub shelter. We conclude that shelter type and birth number can affect the level of contact between ewes and their offspring.

Pre-partum shearing of ewes under pastoral conditions improves the early vigour of both single and twin lambs

This study tested the hypothesis that ewes bearing single or twin lambs shorn at 70 or 120 days of pregnancy would give birth to lambs more vigorous than those born to unshorn ewes, increasing the chances of lamb survival. This was tested in two experiments. In the first, 57 adult Corriedale ewes bearing single lambs were allocated to three treatments; shearing at Day 70 of gestation (S70, n = 18), shearing at Day 120 of gestation (S120, n = 19) or unshorn (US, n = 20). In the second, 57 Corriedale ewes bearing twins were allocated to the same treatments: S70, n = 18; S120, n = 20; or US, n = 19. All ewes grazed native pasture until penned and fed individually to requirements during the last 10 days of pregnancy. Gestation length, lamb birthweight, lamb behaviour during their first hour of life, blood glucose and colostrum amount and composition were measured. In the first experiment, with single lambs, birthweights were similar (4.8, 4.7 and 4.7 kg for S70, S120 and US ewes, respectively; s.e. = 0.17, P = 0.47) and the ewes had lengths of gestation of 149 ± 0.6, 148 ± 0.5 and 147 ± 0.6 days respectively. Seventy-eight percent of S70 and 61% of S120 lambs sucked compared with 21% of US lambs (P &lt; 0.001). In the second experiment, with twin lambs, S70 lambs were heavier than S120, which were heavier than US lambs (3.9, 3.4 and 3.1 kg; s.e. = 0.1, P &lt; 0.0001). Ninety-seven percent of S70 and 92% of S120 lambs stood in their first hour of life compared with 68% of US lambs (P &lt; 0.05). Sixty-seven percent of S70 and 63% of S120 lambs sucked compared with 22% of US lambs (P &lt; 0.001). The length of gestation was 148 ± 0.4, 147 ± 0.5 and 144 ± 0.5 days for S70, S120 and US ewes. In both experiments there was no difference in the amount or quality of the colostrum produced by the ewes of the different treatments. We conclude that pre-partum shearing improves lambs’ behaviour independently of their birthweight and suggest that this could be because the lambs are more physiologically mature at birth.

Effect of birthweight and birth rank on the survival of single and twin lambs born to ewe lambs

Benefits of ewe lamb mating include improved lifetime production, increased rates of genetic gain and higher net profits. These benefits are only achieved if the ewe lamb successfully rears its offspring to weaning. A meta-analytic approach was used to assess the effects of birthweight and the interacting effect of birth rank on the survival to weaning of lambs born to ewe lambs. The data were from eight studies where birthweight and weight at weaning had been recorded for lambs born from ewe lambs. Data were for single- (n = 1392) or twin-born lambs (n = 456). The twin lambs were further classified as the ‘heavier’ or ‘lighter’ of the pair to give three birth rank categories. To compare the probability of dying before weaning between birth ranks, but with lambs compared at a similar birthweight, lambs were categorised by their birthweight as heavy (&gt;3.8 kg) or light (&lt;3.8 kg) and also categorised within their birth rank on their placement around the mean birthweight (birthweight deviation). A mid-range birthweight deviation fell between one standard deviation above or below the mean for each birth rank, whereas a low- and high-range birthweight fell below and above the mid-range, respectively. Logistic regression was used to assess the effect of birth rank (single, heavier twin and lighter twin) and birthweight on lamb mortality up to weaning. To compare the probability of surviving up to weaning between the different birth ranks, relative risk ratios were calculated. Birth ranks were compared for lambs within the same birthweight group (heavy or light) and same birthweight deviation (low-, mid-, high-range). Decreasing birthweight increased mortality before weaning in twins and the change in mortality was greater for the lighter twin. Birthweight did not alter mortality before weaning in singles. Comparison of the birth ranks showed that there were differences (P &lt; 0.05) in the probability of dying for lambs of different birth ranks but similar birthweight. The results suggest that management options for ewe lambs that increase the birthweight of the lighter twin could increase the weaning percentage.

Effect of Age and Sex on Histomorphometrical Characteristics of Two Muscles of Laticauda Lambs

The aim of the present experiment was to determine the effect of sex and age on histochemical and morphometric characteristics of muscle fibres (myocytes) in lambs born by single, twin, triplet and quadruplet birth. Thirty lambs were slaughtered at 60 days of age; thirty were weaned at 60 days and fed until 120 days with flakes (60%) and food supplements, and then slaughtered. Muscle tissues were obtained from two muscles, namely m. semitendinosus and m. longissimus dorsi of all lambs. For each fibre type, area perimeter and diameter (maximum and minimum) were measured and slow-twitch oxidative fibres, fast-twitch glycolytic fibres, fast-twitch oxidative-glycolytic fibres were histochemically differentiated. The muscles were stained for myosin ATPase, and succinic dehydrogenase. At 60 days, females had fibres larger than males, whereas the opposite was observed at 120 days. Besides, at 60 days, the lambs born by single birth had fibres larger than those born by multiple birth, whereas the opposite was observed at 120 days. Single lambs were heavier than twin lambs and multiple lambs. Fast-twitch glycolytic fibres had the largest size, followed by slow-twitch oxidative and fast-twitch oxidative glycolytic fibres. The dimensions of fibre types in m. longissimus dorsi were larger than in m. semitendinosus (P &lt; 0.001).These muscle fibre characteristics are thought to be important factors influencing meat quality, which is often related to metabolic and contractile properties as determined by the muscle fibre type distribution.

Sexage structure of bovids in Ghameshlou, Central Iran

Ghameshlou National Park and Wildlife Refuge is home to three bovids, Goitered Gazelle, Gazella subgutturosa (Güldenstädt, 1780), Wild Sheep, Ovis orientalis Gmelin, 1774, and Wild Goat, Capra aegagrus Erzleben, 1777. These have been subject to predation by Grey Wolf, Canis lupus Linnaeus, 1758, as well as to annual trophy hunting. In a demographic study between July 2007 and April 2009, we assessed the seasonal group size variation among the bovids and found that Goitered Gazelles have the largest groups in winter, while Wild Sheep form the largest groups in autumn. This difference is thought to be the result of patchily distributed, poor quality vegetation during the autumn and winter seasons, and the pursuit of different foraging strategies. Sex ratio was highly skewed toward females in Wild Sheep, but appears to be more balanced for the other two bovids. Twin lambs were encountered rarely in gazelles and Wild Sheep herds. Severe drought and wolf predation were considered to br the main causes of lower reproductive success in these two species compared to the Wild Goat. It is recommended that population parameters of the species should be monitored in order to predict potential demographic trends.

Effects of dam parity and rearing rank on the glucose and fat metabolism, and adrenal function of post-pubertal single and twin-ewe progeny

In an effort to increase the number of lambs produced per ewe’s productive lifetime in New Zealand, an increasing number of ewe lambs (8–9 months old) are being bred. This, in turn, results in an increased proportion of second-parity 2-year-old ewes in New Zealand’s breeding flock, rather than the more usual first-parity 2-year olds. The longer-term effects of dam parity on resulting ewe progeny are of interest and few studies have examined this. The present study was designed to determine whether parity (first or second) of Romney 2-year-old dams had any effect on the metabolic function of their single- and twin-born and reared ewe lamb progeny at 10 months of age. Ten-month-old, single and twin ewe lamb progeny born to first- or second-parity dams (n = 8 per group) were catheterised and given intravenous glucose (0.17 g/kg liveweight) (GTT), insulin (0.15 IU/kg liveweight) (ITT) and epinephrine (1 μg/kg liveweight) (ETT) tolerance tests to assess their glucose and fat metabolism and adrenal function. Rearing rank reduced (P &lt; 0.05) the insulin response of twins to a glucose challenge, but increased (P &lt; 0.05) their glucose response to an insulin challenge. Offspring from first-parity dams had higher (P &lt; 0.05) basal plasma concentrations of cortisol and cortisone, whereas their cortisol/cortisone responses to an insulin challenge were unaffected by either dam parity or rearing rank. Neither dam parity nor rearing rank appeared to influence responses to an epinephrine challenge. The present study suggests that both dam parity and rearing rank alter the glucose and insulin metabolism of the offspring, which may have longer-term impacts on the growth and reproductive efficiency of the animal.

Introduction of meat sheep breeds in extensive systems of Patagonia: Lamb growth and survival1

Genotype effects on lamb growth, survival, and commercial finishing were estimated in a 5-yr study aimed at assessing potential benefits from introducing meat breeds into extensive sheep systems of northeastern Patagonia. Five ram [Corriedale: CO; Border Leicester: BL; Ile de France: IF; Texel: TX; and synthetic CRIII (25% Merino, 37.5% IF, 37.5% TX)] and 5 dam (CO; synthetic CRIII; BLCO: BL x CO; IFCO: IF x CO; and TXCO: TX x CO) genotypes were represented in the study. Data were collected from 1,426 born and 1,258 weaned lambs of 9 resulting genotypes (CO x CO, BL x CO, IF x CO, TX x CO, CRIII x CO, CRIII x BLCO, CRIII x IFCO, CRIII x TXCO, and CRIII x CRIII). Birth weight was recorded on all lambs; subsequently, BW and BCS (scale 1 to 5) were recorded at regular intervals until weaning. Body weights were adjusted to 60 and 90 (weaning) d of age, and ADG were calculated from the adjusted BW for the periods 0 to 60 d and 60 to 90 d; BCS was adjusted to 90 d. Survival to weaning and percentage of lambs reaching commercial finishing (BW >or= 23 kg and BCS >or= 2.5 points) were also recorded. Significant (P < 0.05) genotype x litter size interactions were detected for birth weight and ADG 60 to 90 d. With the exception of CRIII x CO, crossbred and synthetic genotypes presented greater (P < 0.05) ADG 0 to 60 d and BW at 60 and 90 d than CO x CO lambs. Second cross lambs reared as singles presented greater ADG 60 to 90 d (P < 0.05) than BL x CO, TX x CO, and CRIII x CO, but less (P < 0.05) ADG 60 to 90 d, and no differences were observed for twins. The IF x CO, CRIII x BLCO, CRIII x IFCO, and CRIII x CRIII genotypes showed greater BCS at 90 d (P < 0.05) than CO x CO. The probability of greater commercial finishing for crossbred and synthetic genotypes relative to CO x CO was at least 79%. Probabilities of greater survival to weaning in CO x CO and CRIII x BLCO lambs relative to IF x CO, TX x CO, CRIII x CO, and CRIII x CRIII lambs were greater than 81%. Results indicate significant improvements in lamb BW and saleable lambs from the introduction of meat genotypes. Among the terminal sire breeds evaluated, BL and IF would produce the greatest impact. Differential nutritional management of pregnant ewes carrying twins and of twin lambs beyond 60 d should be implemented to mitigate litter size x genotype interactions constraining growth potential benefits, which may be critical for northeastern Patagonia conditions.

Adaptability of pregnant Merino ewes to the cold desert climate in Nevada1

Grazing ability is difficult to record in animals under free-ranging conditions without sophisticated methods. Alternatively, grazing ability may be indirectly inferred from changes in BW and production characteristics during the grazing period. The present study investigated the effect of grazing on resource-limited rangelands on BW, wool characteristics, and offspring weaning weights in nine hundred five 5/8, 7/8, and fullblood Merino ewes of 2 to 7 yr of age during a grazing period of approximately 2.5 mo (between January and March). A total of 469 ewes gave birth to a single lamb, 248 to twin lambs, and 188 did not give birth. Body weights were measured and wool samples taken before and after the ewes were allowed to graze freely on the rangelands; absolute change in BW and change in BW as a percentage of initial BW were estimated. On average, grazing on resource-poor rangelands resulted in BW loss, a reduction in fiber diameter and its CV, and increased staple length. Animals with finer wool at the start of the grazing period lost phenotypically (r = -0.07, P < 0.05) and genetically (r = -0.23, P < 0.05) less BW during the grazing period and had a greater probability to carry 1 lamb (or 2) to term (P < 0.05). Animals that lost less BW produced more greasy fleece (r = 0.09, P < 0.01). Body weight change did not significantly influence offspring weaning weights. Change in BW was moderately heritable at h(2) = 0.29; fiber diameter was strongly heritable at h(2) = 0.51. Animals with the least inclusion of Merino genetics lost more BW (P < 0.01) during the grazing period and had a more uniform fiber diameter (P < 0.05) but shorter staples (P < 0.05) and less fleece (P < 0.0001) than animals with a greater level of Merino genetics. Our results indicate that animals with finer wool appeared to be better adapted to the cold Nevada desert. Thus, selection for finer wool may positively influence adaptability to resource-limited cold climate conditions; alternatively, BW change may be selected for directly. Because nutritional deficiencies during pregnancy can have adverse consequences for the offspring, indirect selection for grazing ability would foremost result in healthier ewes that can produce lambs and wool without compromising their welfare.

TRANSFERÊNCIA DE IMUNIDADE PASSIVA EM CORDEIROS CUJAS MÃES RECEBERAM DIETAS COM DIFERENTES NÍVEIS DE ENERGIA OU PROTEÍNA NO TERÇO FINAL DA GESTAÇÃO

This study assesses the passive immunity transfer in lambs from ewes that were fed diets with different energy or protein supplements during the last trimester of the gestational period. Blood samples were collected from 70 lambs born from 50 ewes to determine serum gamma-glutamyl transferase activity, total protein, gammaglobulin, and immunoglobulin G concentrations. Statistical analysis showed no differences related to the type of diet ingested by the ewe. Furthermore, findings from single and twin lambs were compared, revealing that the latter group presented lower levels for all variables.

Estimating the cost of subclinical parasitism in grazing ewes

The aim of the study was to quantify the cost of gastrointestinal nematode parasitism in a typical New Zealand sheep flock. On the 9th January 2007, 500 ewes from a mixed age flock of 3000 Romney cross-bred ewes were selected. Of these, 250 were given a controlled release capsule releasing a continuous dose of either albendazole or ivermectin over a 100-day period. The other 250 ewes remained as untreated controls. Further capsules were administered to the treatment group on the 12th March, the 12th June and the 26th July. At each of these times, the ewes were weighed and faecal samples were collected for worm egg counts and larval cultures. The initial worm burdens in January were low (mean: 34 epg), but in the untreated ewes rose to high levels before mating in March and reached a mean of 1416 epg. Haemonchus was identified as the principal parasitic genus. In June, epg were reduced to a mean of 526 epg, with Trichostrongylus being the principal genus (48%), whilst in late July mean epg was 826 with Cooperia being the principal genus (60%). Epg of treated ewes were zero throughout that period. Throughout the study, there was a significant difference in body weight of treated ewes over controls, which was 2.7 kg (March), 4.3 kg (June), 5.7 kg (July) and 3.6 kg (November). There were more multiple pregnancies among treated ewes, identified at ultrasound scanning as 12.4 foetuses per 100 ewes ( p < 0.05). At weaning of lambs, on the 26th November, mean body weight of twin lambs born to treated ewes were on average heavier by 2.15 kg ( p < 0.05). Assuming that in treated ewes no adverse effects were observed from subclinical parasitism alone, the benefits of controlling the problem could be clearly evaluated. Innovative ways of controlling subclinical parasitism on pastoral farming systems need to be considered. It should be taken into account that the authors do not recommend repeated anthelmintic treatments, which was performed in the trial, only with a view to meet the specific objectives of the work.

Birth weight effect in twin‐born lambs from mid‐pregnancy shearing is associated with changes in maternal IGF‐I concentration

A number of studies have shown an increase in the birth weight of lambs in response to mid pregnancy shearing. The present study sought to determine whether the birth weight effect of mid‐pregnancy shearing is mediated through changes in maternal insulin‐like growth factor‐I (IGF‐I) and insulin‐like growth factor binding protein‐I (IGFBP‐I) concentrations. Single‐ and twin‐bearing ewes from three genetically divergent IGF‐I lines were either left unshorn or shorn at a mean day 90 of pregnancy (P90). Maternal plasma concentrations of IGF‐I and IGFBP‐I were measured at P89, P108 and P136. Lamb liveweight at birth and weaning weremeasured, andplasmaconcentrations of IGF‐I determined at weaning. Shearing increased the birth weight of twin lambs by over 350 g (P < 0.05) without having any effect on singleton birth weight. The increased birth weight of twin lambs born to shorn ewes was associated with a decline in maternal plasma IGF‐I concentration (P < 0.05) from P108 toP136. Low IGF‐I line ewes had lower (P < 0.001) plasma IGF‐I than high IGF‐I line ewes at each stage measured but higher plasma IGFBP‐I at P89 and P108. Birth weights were higher in lambs born to low IGF‐I line ewes than in those born to high IGF line ewes. These results suggest that the difference in birth weight between twin lambs from shorn and unshorn dams was mediated through a decline in maternal plasma IGF‐I concentrations in late pregnancy. In support of previous studies, there was an inverse relationship between IGF‐I selection line and lamb birth weight.

Metabolic maturity at birth and neonate lamb survival and growth: The effects of maternal low-dose dexamethasone treatment

Perinatal mortality is a major contributing factor to reproductive wastage in grazing sheep industries. Enhanced metabolic and endocrine maturity at birth may improve the behavioral competency and thermoregulatory ability of neonates, potentially improving lamb survival over the first 72 h of life. Maternal glucocorticoid treatment in late gestation was investigated as a mechanism for manipulating metabolic and endocrine maturity in the ovine neonate. Multiparous, fine-wool Merino ewes (n = 150) were divided into 3 groups to lamb on pasture. Within each group, 5 single-lamb and 5 twin-lamb bearing ewes were randomly allocated to 1 of 5 treatments. Treatments included a saline control (1 mL), or dexamethasone (2 mg/mL as the sodium phosphate) injected intramuscularly at 1 of 2 dose rates (1.5 or 3.0 mg) at d 130 or 141 of gestation. One-half of the control ewes were injected at d 130 and the remainder at d 141. Dexamethasone treatment had no effect on lamb survival to 72 h after birth, although there tended (P = 0.09) to be a smaller proportion of lambs dying due to dystocia than for control lambs. Heart girth at birth in singleton and twin lambs was reduced (P < 0.01) at the greater dose rate. Further, treatment also reduced birth weight (by about 5%) and presuckling rectal temperatures in twin lambs, but not in singleton lambs. These reductions were also dependent on the sex of the lamb. Dexamethasone treatment did not alter gestation length or lamb presuckling plasma glucose, NEFA, urea, or leptin concentrations, but treatment at d 141 increased (P < 0.05) ghrelin concentrations in singleton and male lambs. Behavioral interactions between ewes and neonatal lambs were generally unaffected, although treatment at d 130 produced lambs that took longer to bleat than lambs of untreated ewes (P < 0.05). Treatment did not affect the concentration of measured blood metabolites or hormones at weaning. Although there were interactions between litter size, lamb sex, and the dose rate and time of treatment on weaning weight, BW recorded 73 d after weaning was unaffected by treatment. Despite changes in birth weight, rectal temperature, lamb behavior, and presuckling plasma ghrelin concentrations, survival in the first 72 h of life, and lamb growth performance were unaffected by periparturient maternal glucocorticoid treatment.

Effects of environmental factors on growth traits in Ghezel sheep

The present study was carried out to study the effects of environmental factors on growth traits in Ghezel sheep breed. Growth related data (birth weight, weaning weight, month 6 weight, average daily gain from birth to weaning and weaning to month 6) were collected from lambs that have been born during 1994 - 2006 at Ghezel sheep breeding station in west Azerbaijan and data was analyzed using SAS software. The birth year and herd had a significant effect on all traits (P < 0.01) while the effect of birth type significantly (P < 0.01) affected all traits except birth weight and daily gain from birth to weaning periods. The lamb's sex had a significant effect on all traits except daily gain from weaning to month 6 weight periods. The effect of dam’s age had a significant effect only on daily gain from weaning to month 6 weight periods. The interactions between birth year and lamb’s sex, birth year and birth type, birth year and herd, lamb's sex and herd and also dam's age and herd were significantly affected on all traits (P < 0.01). The interactions between lamb’s sex and dam's age and birth type and dam's age significantly affected weight of birth, daily gain from birth to weaning period and month 6 ages, respectively (P < 0.05). In all ages, the male and single lambs were heavier than female and twin lambs. Results showed that environmental factors have an important role in expressing of genetic potential in the lambs.

The effect of ewe size and nutritional regimen beginning in early pregnancy on ewe and lamb performance to weaning

Ewe size, pregnancy nutrition and pregnancy rank are known to affect the productive performance of ewes and their offspring. The aim of the present study was to compare the effects of two nutritional regimens, from day 21 to day 140 of pregnancy, in singleton‐ and twin‐bearing ewes of two different mean weights, taken from a single flock. The study included Large ewes offered Ad lib (Large‐Ad lib, n= 151), Large ewes offered Maintenance (Large‐Maintenance, n = 153), Small ewes offered Ad lib (Small‐Ad lib, n = 155) and Small ewes offered Maintenance (Small‐Maintenance, n = 153) that were either singleton‐ or twin‐bearing. During the period day 21 to day 140 Maintenance and Ad lib feeding regimens included Large and Small ewes and singleton‐ and twin‐bearing ewes. At days 1 and 140 of pregnancy Large ewes were heavier (P < 0.05) and of greater (P < 0.05) body condition than Small ewes. Similarly, at days 1 and 140 of pregnancy twin‐bearing ewes were heavier (P < 0.05) than single‐bearing ewes. At day 1 of pregnancy there was no difference in ewe liveweight and body condition scores between Maintenance and Ad lib‐fed ewes, but by day 140 ewes in the Ad lib regimen were heavier (P < 0.05) and had greater (P < 0.05) body condition than Maintenance ewes. There was an interaction (P < 0.05) between ewe nutritional regimen and lamb birth rank for lamb birth weight such that twin lambs born to Maintenance regimen ewes were lighter (P < 0.05) than their counterparts born to Ad lib ewes (4.52 ± 0.06 versus 5.23 ± 0.06 kg respectively). This relationship was not observed in singletons. There was also an interaction (P < 0.05) between ewe size and nutritional regimen for lamb birthweight. Birth weights did not differ between lambs born to either Small or Large ewes on the Ad lib feeding regimen. However, lambs born to Small ewes on the Maintenance feeding regimen were lighter (P < 0.05) than their counterparts born to Large ewes (5.09 ± 0.07 versus 5.37 ± 0.07 kg respectively). At day 100 of lactation lambs born to Large ewes were heavier (P < 0.05) than those born to Small ewes (32.65 ± 0.37 versus 31.16 ± 0.35 kg respectively) and those born to Ad lib ewes were heavier (P < 0.05) than those born to Maintenance ewes (32.77 ± 0.37 versus 31.03 ± 0.36 kg respectively). This study shows that level of dam pregnancy nutrition has a greater effect on twin‐born lambs than their singleton‐born counterparts. Furthermore, the data suggests that the heavier liveweights at weaning of lambs born to Large ewes may not have compensated for their dams’ greater nutritional requirements compared to their smaller counterparts.

Synchronization of estrus with short- and long-term progestagen treatments and the use of GnRH prior to short-term progestagen treatment in ewes

The objective of the present study was to determine the efficacy of the synchronization of estrus using short- and long-term progestagen treatments in ewes at the onset of the breeding season, and to evaluate the effect of the exogenous GnRH administration immediately prior to short-term progestagen treatment on the reproductive performance. A total of 240 Tahirova cross-bred ewes, aged 18–24 months, and 40 rams, aged 2–4 years-old, were used in the trial. Ewes were divided equally into 3 groups ( n = 80 per group). Intravaginal progestagen sponges containing FGA (30 mg) were inserted in the ewes for 7 d in the FGA1 (short-term) and GnRH treatment groups, and for 12 d in the FGA2 group (long-term). The ewes in the GnRH group received 10.5 μg busereline acetate i.m. at the time of sponge insertion. Tiaprost tromethamol (PGF 2α; 0.294 mg) and eCG (400 IU) were injected i.m. on the 6th day of progestagen treatment in the GnRH and FGA1 groups, and on the 11th day in the FGA2 group following sponge insertion. All ewes were hand-mated once at the detection of estrus. The estrous response, fertility rate, multiple birth rate and litter size recorded was 88.7, 87.3, 51.6% and 1.6 in the FGA1 group, 92.5, 71.6, 50.9% and 1.5 in the FGA2 group, and 96.2, 89.6, 71.0% and 1.8 in the GnRH group, respectively. No significant difference in estrous response between the groups was recorded, but the fertility rate in the FGA1 and GnRH groups was significantly ( P < 0.05) higher than in the FGA2 group. The occurrence of multiple births and litter sizes were significantly ( P < 0.05) higher in the GnRH group, compared to both the FGA1 and FGA2 groups, with the number of single lambs being significantly ( P < 0.05) higher in the FGA1 (48.4%) and FGA2 (49.0%) groups than in the GnRH (29.0%) group. However, the differences recorded between any of the groups in terms of the number of twin and triplet lambs were insignificant. In conclusion, it can be said that estrous synchronization using the 12-d-FGA-eCG-PGF 2α regimen could be replaced with the 7-d-FGA-eCG-PGF 2α regime in sheep at the onset of the breeding season. However, the combination of GnRH with the latter regimen (7-d-GnRH-FGA-eCG-PGF 2α) increased the multiple birth rate and litter size in the ewes.

The Influence of Naturally Occurring Differences in Birthweight on Ventricular Cardiomyocyte Number in Sheep

In most species including man, cardiomyocytes cease proliferating soon after birth when they become terminally differentiated. A reduced complement of cardiomyocytes in infancy may adversely impact on the function and adaptive capabilities of the heart in later life. Low birthweight is associated with an increased risk of heart disease in adults, but little is known about its effect on the number of cardiomyocytes. Using naturally occurring differences in birthweight, our aim was to determine the effect of birthweight on cardiomyocyte number in postnatal lambs. At 9 weeks after term birth, when the final number of cardiomyocytes is considered to be established, hearts were collected at necropsy from seven singleton and seven twin lambs. Hearts were perfusion-fixed, and tissue samples were systematically taken from the left ventricle plus intraventricular septum (LV+S) and the right ventricle (RV). The number of cardiomyocyte nuclei was estimated using an unbiased optical disector-fractionator stereological technique, and the total number of cardiomyocytes was determined. Weights of the total heart, LV+S and RV were significantly related to both birthweight and necropsy weight. In the LV+S but not the RV, cardiomyocyte number was significantly and directly related to heart tissue weight, birthweight, and necropsy weight. We conclude that the final number of cardiomyocytes in the LV+S is related to prenatal and early postnatal growth, and is proportionate to the weight of heart tissue. A low cardiomyocyte number in the LV+S following restricted fetal growth may contribute to the increased incidence of heart disease in adults born with low birthweight. Anat Rec, 2009. (c) 2008 Wiley-Liss, Inc.