The duration of passive protection against Taenia ovis larvae in lambs

In an attempt to induce passive protection in lambs against Taenia ovis larvae that would last for the 15-20 weeks from birth to slaughter as fat lambs, one group of ewes was immunized by a series of injections of 2000, 4000, 8000, 16 000 and 32 000 activated oncospheres of Taenia ovis prior to parturition. Another group of ewes was not immunized. All ewes had previously grazed pasture lightly infected with T. ovis eggs. Most lambs from non-immunized ewes developed cysts after oral infection with T. ovis eggs. However, no lambs from immunized ewes developed cysts up to and including 6 weeks after birth. Between 8 and 16 weeks after birth a proportion of lambs were found to be susceptible to infection. By 18 weeks after birth all lambs were apparently susceptible. The 99% confidence band for the mean duration of demonstrable complement-fixing antibody titres was 6.2-7.8 weeks for lambs from immunized ewes. The persistence of maternal protective antibody in some lambs could possibly preclude successful active immunization of all lambs against T. ovis larvae before 18 weeks of age.     

Early prepartum shearing increases milk production of wool sheep and the weight of the lambs at birth and weaning

The use of mid prepartum shearing has been described as a possible tool to increase the weight of the lambs at birth and at weaning. The effect of prepartum shearing (53 days of gestation) on production and chemical composition of milk, weight of the lambs at birth and weaning and growth rate were evaluated in this trial. Twenty Polwarth ewes were inseminated with rams of the same breed in May (autumn), 2009. All ewes bore singletons and were maintained together under cultivated grazing conditions, during the experimental period. The ewes were allocated to two treatments groups, based on expected day of parturition, body weight and BCS of the dams. Ten ewes were shorn at 53 days of gestation (S53) and 10 ewes were kept unshorn during gestation (US). Milking of the ewes was recorded 7 days after parturition, and this was repeated weekly for 15 weeks. Milk production of the S53 ewes was 22.2% higher (P < 0.05), when compared to US control ewes - with no change in the milk composition. At lambing, the lambs born to the S53 ewes were 1.41 kg (P < 0.05), and at weaning 4.5 kg heavier (P < 0.05), than lambs born to US ewes. In conclusion, it can be said that the higher weaning weight of the S53 lambs was the result of both a higher birth weight and an increased growth rate up to weaning in part, due to an improved milk production of the ewes.     

Studies on the abomasal pathology of immunized and non-immunized sheep infected with Haemonchus contortus

Five adult ewes and five lambs were repeatedly immunized with weekly doses of 10,000 irradiated Haemonchus contortus L3 before challenge with 100,000 and 10,000 normal larvae respectively. Two groups of non-immunized ewes and lambs were similarly challenged and one animal from each of the four groups killed on days 3, 5, 7, 10 and 24 post-challenge. The cellular changes in the abomasal mucosa were less marked in the non-immunized groups than in the immunized animals and appeared later in the lambs than in the ewes. Thus, in the immunized ewes increases in the numbers of mast cells and eosinophils were evident within five days of challenge whereas similar changes appeared later in the immunized lambs. Also marked lymphoid aggregates at the base of the mucosa and in the submucosa were detected only in the immunized ewes. However, both immunized and non-immunized ewes showed rises in the numbers of IgA plasma cells after challenge which were not evident in either group of lambs.     

Effect of early shearing during gestation on the productive and reproductive behavior of female sheep offspring in their first 18 months of age

The research has shown the interesting contributions of shearing in mid-gestation on the performance of lambs from birth to weaning. Other studies have reported that shearing at early pregnancy influences the development of the placenta and lamb live weight at birth. However, there was a lack of information on the effect of early-prepartum shearing on the behavior of the offspring from weaning onward. This study evaluated the effect of shearing ewes at 50 days of gestation on the growth, reproductive behavior and response to a gastrointestinal parasite challenge in the female offspring from weaning to 18 months old. Fifty-seven Polwarth female lambs were used, 22 being singles and 35 twins born to ewes either shorn at 50 days of pregnancy (PS, n = 23) or shorn at 62 days postpartum (U, control, n = 34) resulting in four subgroups: single lambs born to PS ewes (n = 8), born to U ewes (n = 14), twin lambs born to PS ewes (n = 15) or born to U ewes (n = 20). All progeny were managed together under improved pasture with a minimum forage allowance of 6% live weight on dry basis. Body weight, body condition score and fecal eggs count were recorded every 14 days from weaning to 18 months of age. Concentrations of progesterone were measured weekly (from 4 to 10 months of age and from 14 to 18 months of age) to establish the onset of puberty. Ovulation rate at an induced and a natural heat (545 ± 1.0 and 562 ± 1.0 day old) was recorded. Prepartum shearing did not affect the age at puberty or the ovulation rate of female offspring, but those born as singles were more precocious ( P = 0.03) and heavier ( P = 0.02) at puberty than twin born lambs. Both the average value of parasite egg count ( P = 0.0 7) and the Famacha index ( P = 0.02) for the entire study period were lower in lambs born to prepartum shorn ewes than those born to postpartum shorn ewes. In conclusion, shearing at 50 days of gestation did not affect the growth or the reproductive behavior of female offspring. However, female lambs born from ewe shorn during gestation showed a better response to the parasitic challenge, and further research is required to confirm this.     

Feeding pregnant ewes a high-salt diet or saltbush suppresses their offspring's postnatal renin activity

If ewes consumed a high-salt diet or saltbush during the last 3 months of pregnancy and for 3 weeks after birth, we expected the renin activity of their lamb to be suppressed at birth and at 3 weeks of age. We also expected an increase in the concentration of cations other than sodium in the ewe's milk and an increase in the plasma Na concentration of the lamb at birth. To test these hypotheses, Merino ewes were fed a high-salt diet (14% NaCl) in an animal house and compared to control ewes eating a control diet (2% NaCl). In addition, we compared ewes grazing saltbush (about 13% salt in diet) to ewes grazing pasture from day 60 of pregnancy to 3 weeks after birth. Lambs born to ewes consuming saltbush had 85% lower (P < 0.001) renin activity than offspring from ewes consuming pasture at 3 weeks of age. Similarly, lambs born to ewes consuming a high-salt diet had 20% lower renin activity at birth and 3 weeks (P = 0.07). Feeding ewes a high-salt diet or saltbush altered the mineral composition of the milk; the largest change was a 10% increase in K levels (P 0.05). Consuming a high-salt diet or saltbush lowered the plasma Na of ewes at 130 days of gestation (by 3-5 mmol/l; P < 0.001), but only lambs from ewes fed the high-salt diet had a lower plasma Na at birth (P < 0.05). Suppression of the renin activity of lambs could lead to permanent physiological changes in salt balance in later life.     

Litter-size-dependent intrauterine growth restriction in sheep

Regulation of foetal development in sheep depends on interactions between the intrinsic capacity of the foetus for growth and the maternal environment. Lambs born in multi-foetus litters have relatively small placentae with fewer cotelydons, and lower birth weights. Litter-size-dependent intrauterine growth restriction (IUGR) is evident at mid gestation when metabolic needs of the conceptus are moderate, and overnutrition of ewes with multiple foetuses does not promote growth of their foetuses to the size of singletons. Those observations suggest that placental and conceptus growth in multi-foetus pregnancies is reprogrammed at mid gestation by an as yet undefined mechanism to attenuate foetal growth. This may protect the foetus from severe nutritional insult during late gestation, when its daily growth rate is at a maximum. In that way, lambs born in large litters with relatively lower birth weights may not experience the long-term physiological insults that can be observed in small lambs born to undernourished ewes.     

Effect of maternal nutrient restriction in early to mid gestation and thyrotrophin-releasing hormone on lamb survival following Caesarean section delivery near to term

We investigated the influence of restricted maternal nutrition between 28 and 77 days gestation on survival and thermoregulatory adaptation following Caesarean section delivery near to term. This study was designed to examine the hypothesis that adaptation after birth would be compromised in those lambs born to nutrient restricted ewes. We further hypothesised that this would be due in part to inadequate hypothalamic-pituitary-thyroidal function. Lambs born to nutrient restricted ewes were untreated (RU) or treated with thyrotrophin-releasing hormone (TRH; RT) immediately prior to umbilical cord clamping. Single bearing ewes consumed either 6.60 MJ x day(-1) (controls, n = 4) or 3.00 MJ x day(-1) (nutrient restricted, n = 15) from 28-77 days gestation, after which all ewes consumed 7.20 MJ x day(-1). All lambs born to control ewes commenced continuous breathing and began to shiver following Caesarean section delivery and survived to 6 h after birth. Only 4 out of 9 RU lambs established continuous breathing and survived to 6 h after birth compared with all RT lambs. Six hours after birth, RT lambs possessed perirenal brown adipose tissue with a higher thermogenic activity than 6 h old RU or control lambs. Lamb birth weight was similar in all groups. In conclusion, near-term lambs born to ewes nutrient restricted in early to mid gestation are at increased risk of death following Caesarean section delivery. Survival after birth can be significantly enhanced if TRH is administered to the lambs immediately before delivery.     

Effects of the Booroola (FecB) genotypes on growth performance, ewe's productivity efficiency and litter size in Garole x Malpura sheep

The present study was conducted to evaluate the effects of FecB genotypes on body weight, average daily gain (ADG), ewe's productivity efficiency (EPE) and litter size in FecB introgressed GarolexMalpura (GM) crossbred sheep. A total of 235 GM lambs were selected randomly and screened for FecB mutation using forced RFLP-PCR. The majority (69.8%) of GM individuals were carriers (BB and B+) for the FecB mutation and frequency of the FecB allele was about 0.40. The FecB genotypes were significantly (P<0.01) associated with the lamb's body weights from birth to 12 months of age. The generation wise (F(1), F(2) and F(3)), lamb's body weight did not differ significantly at birth, 6 and 12 months of the age, while it differed significantly (P<0.05) at 3 and 9 months of age. The ADG1 (0-3 months) was significantly associated (P<0.05), but not the ADG2 (3-6 months) and ADG3 (6-12 months) between genotypes. Type of birth and sex significantly (P<0.01) affected the body weight from birth to 12 months of age; and body weight of single born lambs was significantly higher (P<0.01) than that of twins and triplets from birth to 12 months of age. Type of birth significantly (P<0.01) affected the ADG1, but had no significant effect on ADG2 and ADG3. Year of birth did not affect the birth and weaning weights, but it significantly affected (P<0.01) the body weight and ADG's after weaning ages. The EPE was affected significantly (P<0.01) by the FecB genotypes at birth, 3 and 12 months of age. The EPE of B+ and BB ewes were 7.86 kg (36.9%) and 2.32 kg (10.9%) higher as compared to ++ ewes at 12 months of age, respectively. The mean litter size of BB ewes (2.17+/-0.24) was significantly higher (P<0.01) than that of B+ ewes (1.73+/-0.04) and ++ ewes (1.03+/-0.23). The present study indicated that the body weight and ADG of carrier lambs (BB and B+) was comparatively lower than that of non-carriers (++), while EPE of B+ ewes was comparatively higher than that of BB and ++ ewes. Further, it is interesting to note that heterozygous and homozygous state of individuals increased 0.70 and 1.14 extra lambs as compared to non-carriers (++), respectively.     

The effects of pasture availability for twin- and triplet-bearing ewes in mid and late pregnancy on ewe and lamb behaviour 12 to 24 h after birth

This experiment was conducted to evaluate the effect of offering ewes two different feeding levels, during mid and late pregnancy, on ewe and lamb behaviour 12 to 24 h after birth. Romney ewes, bearing twin (n = 80) or triplet foetuses (n = 56), were allocated to a pasture sward height of 2 or 4 cm between 70 and 107 days of pregnancy. In late pregnancy (day 107 to 147), half of the ewes were reallocated the alternate sward height, which produced four treatments: 2-2, 2-4, 4-2 and 4-4. Ewes were weighed on days 65, 92, 107 and 130 of pregnancy and lamb live weights were recorded 12 to 24 h after birth. Twelve to 24 h after birth the maternal behaviour score (MBS) of the ewes were determined, whilst their lambs were tagged. After the lambs were released, the behaviour of each ewe and her lambs was observed for 5 min. Ewe treatment and litter size had no effect on ewe MBS. However, as MBS increased (ewes stayed closer to lambs during tagging), ewes bleated less in a high-pitch and were quicker to make contact with their lamb. During the observation period, ewes in the 4-4 treatment had a greater percentage of their bleats in a low pitch (P < 0.05) than ewes in the 2-2 and 4-2 treatment (61.3% v. 41.3% and 38.8% low bleats, respectively) and more lambs born to 4-4 ewes (95%) bleated than lambs born to 2-2 ewes (84%; P < 0.05). However, lambs born to ewes in the 2-2 treatment bleated earlier than lambs in all other treatments (P < 0.05). Lambs born to 4-4 ewes were less likely (P < 0.05) to move towards their dam in order to make contact than lambs born to 2-2 or 4-2 ewes (3.1% v. 16.9% and 16.7%, respectively). These findings suggest that under the conditions of the present study, ewe nutrition had little effect on maternal behaviour. However, lambs born to ewes offered 2 cm pasture sward heights during mid and/or late pregnancy (2-2, 2-4 and 4-2 treatments) displayed behaviour that demonstrated greater 'need' whereas lambs born to ewes offered 4 cm during mid and late pregnancy sought less attention from their dam.     

Echinococcus granulosus in sheep: transfer from ewe to lamb of 'Arc 5' antibodies and oncosphere-killing activity, but not protection.

Fourteen ewes were orally dosed with 2000 E. granulosus eggs at 2 weeks of age, were mated at 19 months, and produced lambs when the cysts were 2 years old. One week after parturition, all 14 ewes had 'Arc 5' antibodies in their serum, as did 11/14 of their lambs. Fourteen uninfected ewes were immunized three times before parturition with E. granulosus eggs injected intramuscularly. Cysts grew at the first, or first and second site, but not the third, indicating that the ewes were immune prior to parturition. Most sera from these ewes and their lambs, and from 14 control ewes and their lambs, produced precipitin arcs with hydatid cyst fluid, but no 'Arc 5'. All lambs were challenged with 500 eggs 2 weeks after birth. At necropsy, cyst numbers within groups ranged from 3 to > 200, but there was no significant difference between the three groups of lambs. The immunized ewes did not pass a protection to their lambs that was effective when the lambs were challenged. 'Arc 5' antibodies were induced by prolonged infection with cysts, and were not seen in the sera of ewes immunized with eggs, although the eggs developed into cysts at the injection sites. 'Arc 5' antibodies did not protect lambs against infection, and were not correlated with protection in ewes. Subcutaneous injection of oncospheres into four ewes from each group at the time of lamb challenge showed that the immunized ewes were immune to this method of challenge, but the infected and control ewes were not.(ABSTRACT TRUNCATED AT 250 WORDS)     

Behavioural development in the neonatal lamb: effect of maternal and birth-related factors

The survival of the neonate relies on the integrated expression of appropriate behaviours from both the mother and young. In precocious species, like the sheep, the speed with which the lamb stands and seeks the udder is related to lamb survival. In this study the effects of birth difficulty, lamb birth weight, ewe loss or gain in backfat from conception to delivery, ewe parity, litter size, and lamb sex on neonatal lamb behavioural development were investigated in over 500 lambs of two breeds (Scottish Blackface and Suffolk). Lambs that required assistance to be delivered were significantly slower to perform all neonatal behaviours than unassisted lambs (P<0.001), and were less active over the first 3 days after delivery (P<0.05). There were no effects of lamb birthweight that were not accounted for by the increased likelihood of requiring assistance in heavier birth weight lambs. Ewes that mobilised less body fat during their pregnancy produced lambs that stood and sucked quickly (P<0.001), and were more active over the first 3 days of life. Lambs born to first parity ewes were slower to stand and suck than lambs born to experienced ewes (P<0.001). There was an improvement in time taken by lambs to stand, seek the udder and to suck with each increase in ewe parity. Litter size had an additional retarding influence on the behaviour of multiple-born lambs that could not be accounted for by birthweight. In the Suffolk breed male lambs were slower to stand and suck than female lambs, this effect was not seen in Blackface lambs. These data demonstrate that lambs that require assistance at birth, even if they survive the birth process, lambs born to ewes that lose a lot of condition over pregnancy or first parity ewes, triplet lambs and, at least in some breeds, male lambs are slower to progress through the sequence of neonatal behaviours. These lambs are, therefore, at greater risk of not surviving to weaning.     

Late foetal life nutrient restriction and sire genotype affect postnatal performance of lambs

This experiment investigates the effects of maternal nutrient restriction in late gestation on the offsprings' postnatal metabolism and performance. Forty purebred Shropshire twin lambs born to ewes fed either a high-nutrition diet (H) (according to standard) or a low-nutrition (L) diet (50% during the last 6 weeks of gestation) were studied from birth until 145 days of age. In each feeding group, two different sires were represented, 'growth' (G) and 'meat' (M), having different breeding indices for the lean : fat ratio. Post partum all ewes were fed the same diet. Lambs born to L-ewes had significantly lower birth weights and pre-weaning growth rates. This was especially pronounced in L-lambs born to the M-ram, which also had markedly lower pre-weaning glucose concentrations than the other three groups of lambs. L-lambs converted milk to live weight with an increased efficiency in week 3 of life. Their glucose concentrations and growth rates were both increased. Plasma glucose concentrations in LM-lambs became similar to those observed in H-lambs post-weaning. However, LM-lambs continued to be lighter than the other groups throughout the experimental period and were unable to compensate for the reduced weight at birth despite having the highest daily fractional growth rates. LG-lambs had the highest plasma glucose concentrations of all four groups of lambs, and they indeed reached body weights comparable to those of the H-lambs by 145 days of age. The increased growth rate post-weaning in L-lambs was not reflected in fat deposition, as L-lambs had lower fat deposition than H-lambs. This may relate to the lower plasma insulin levels found in the L-lambs than in the H-lambs. In conclusion, a 50% reduction of maternal nutrient supply in the last 6 weeks of gestation reduces the birth weight and pre-weaning growth of the offspring due to lower milk intake. Growth rates can be restored when an adequate post-weaning diet is provided, but the prenatal nutrition may programme postnatal metabolism differentially depending on genotype, thus affecting the ability of the ad libitum-fed lamb to achieve a given body weight by a certain age.     

The effect of different types of stressors during mid- and late pregnancy on lamb weight and body size at birth

Mid-pregnancy shearing has consistently been shown to increase lamb birth weight, which can lead to an increase in lamb survival rates. However, shearing ewes during the winter months and under outdoor pastoral farming conditions can expose the recently shorn ewe to a greater risk of hypothermia. The aim of this study was to determine if exposure of ewes to repeated stressors, in mid- and late pregnancy, would result in an increase in lamb birth weight. This information may assist in the elucidation of the mechanism for the birth weight response to mid-pregnancy shearing, which in turn could assist in the design of management options to increase lamb birth weight without placing the ewe at risk. One hundred and forty-four twin-bearing Romney ewes were allocated to one of six mid-pregnancy treatments: control, isolation on 2 or 10 occasions, sham-shearing on 10 occasions, intramuscular cortisol injection on 10 occasions or shearing. Isolation, sham-shearing and cortisol treatments were conducted twice a week beginning, on average, day 74 of pregnancy and shearing occurred on day 76. During pregnancy, ewe treatment had no effect on ewe live weight. However, average ewe body condition scores were higher in the shorn group than in the sham-shorn or cortisol groups (P < 0.05). Intramuscular injections of cortisol had a greater effect on ewe plasma cortisol concentrations than all other treatments (P < 0.05). Shearing produced a greater plasma cortisol response than isolation × 10 and sham-shearing (P < 0.05). Ewe plasma cortisol responses decreased during the 5 weeks of isolation and sham-shearing but cortisol injections produced a greater response during the fifth treatment than the first or ninth treatments (P < 0.05). Lambs born to shorn ewes were heavier and had a longer crown rump, forelimb and hind limb lengths than all other lambs (P < 0.05). In addition, lambs born to ewes in the cortisol treatment were lighter than lambs born to control, isolation × 2, isolation × 10 and shorn ewes (P < 0.05). The plasma cortisol concentrations observed for ewes injected with cortisol were far greater than those observed in all other groups, which is likely to explain the low birth weights of lambs born to ewes in that group. These results indicate that the mechanism by which mid-pregnancy shearing increases lamb birth weight is unlikely to be repeated stressors.     

Economic weights of production and functional traits for Merinolandschaf, Romney, Romanov and Sumavska sheep in the Czech Republic

Economic weights of production and functional traits were estimated for the dual-purpose sheep breeds Romney (RY), Merinolandschaf (ML), Romanov (RV) and Sumavska (SA). A bio-economic computer model simulating the profit function for production systems with one lambing per year was used for the calculations. First, marginal economic values were calculated which were defined as partial derivatives of the profit function with respect to the average level for each trait. Applying gene-flow methodology, absolute and relative economic weights for direct and maternal components of the traits were then estimated for pure-bred production systems and systems which included partial terminal cross-breeding. The following traits were evaluated: birth weight, daily gain till weaning and during rearing, mature weight, dressing percentage, fleece weight, conception rate of ewe lambs and ewes, litter size at lambing (total number of lambs born per ewe lambing), survival rate of lambs at birth and till weaning and productive lifetime of ewes. Standardized economic weights were calculated as the product of the economic weight and the genetic standard deviation of each trait or trait component. The total economic importance was defined as the sum of the absolute (not taking into account the sign) standardized economic weights over all traits and trait components, and relative economic weights were then computed as the standardized economic weights expressed as percentages of total economic importance. The direct components of survival rate at birth and till weaning, the direct component of daily gain till weaning and litter size had the highest relative economic weights (greater than 10%) in pure-bred systems in all four breeds. In ML and RV, the maternal component of lamb survival rate till weaning also had a relative economic weight exceeding 10%. In systems with partial terminal cross-breeding for all four breeds, relative economic weights of maternal traits and trait components were slightly larger than in pure-bred production systems, particularly for litter size. Based upon comparison of relative economic weights of traits among breeds, separate breeding goals for RY and RV are recommended, whereas a common breeding goal is deemed appropriate for ML and SA.     

Iodine nutrition in ewes. 2. Effects of low to high iodine intake by ewes on the I content of biological fluids and plasma immunoglobulins G in newborn lambs

1. In two experiments samples of blood and organs were taken from newborn and young lambs born to five groups of ewes that received different dietary iodine (I) levels. Dietary I contents (mg/kg dry matter [DM]) in pregnancy and lactation, respectively, were: Experiment 1--0.36 and 0.26 for group C, 2.01 and 1.94 for group D; Experiment 2--0.13 and 0.12 for group A, 0.22 and 0.20 for group B, 10.77 and 8.88 for group E. 2. I intake of ewes had no effect on birthweight, body weight gain, or mortality between birth and wk 2 of life. No difference between the groups was recorded in the weights of brain, heart, lungs, and liver of lambs killed at birth. However, the weight of both the thyroid lobes in lambs from group E was lower than that of the other groups. The I content of the thyroid lobes of lambs from group A was 30-40% lower than that of the other groups. 3. The plasma inorganic iodine (PII) of lambs from birth to d42 of life was affected by ewe I intake, except for groups A and B, during the first 16 h of life. The PII of lambs increased with the I intake via milk in each group. The ratio of PII of lambs at birth/PII of ewes at d7 prepartum was 3.77, 2.96, 1.68, 1.39 and 8.62, respectively, for groups A, B, C, D and E. 4. The high I intake by group E ewes induced a higher plasma T4 concentration in lambs at birth. The decrease in plasma immunoglobulins G (IgG) recorded for the lambs in this group might be explained by this increase in plasma concentration.     

Serum thyroid hormones and performance of offspring in ewes receiving propylthiouracil with or without melatonin

Two experiments were conducted during mid-gestation to examine effects in ewes of propylthiouracil (PTU) treatment alone or with melatonin on serum thyroid hormones, postpartum reproduction, and lamb performance. In the first experiment, beginning on day 0 (first day of treatment when all animals were 72.2+/-0.9 days of gestation), ewes received daily treatments (gavage) consisting of either 0mg (n=6) or 40 mg (n=6) PTU/kg body weight/day for 15 days. After 15 days, the 40 mg dosage was decreased to 20mg/kg body weight for an additional 20 days (35 days of PTU). Serum thyroxine (T4) did not differ (P>0.10) between groups through day 4; but on day 5, control females had a serum value of 67 ng/ml compared with 46 (+/-5)ng/ml for PTU-treated ewes (P=0.02). On the last day that 40 mg of PTU was administered, serum T4 averaged 67 and 7 (+/-5)ng/ml (P<0.001) in the two respective groups. Serum T4 remained low and was 80 and 1 ng/ml (P<0.001) in control and treated ewes on day 34. Serum T4 rose gradually after PTU but remained different from that observed in control ewes through day 48. Lambs from control and treated ewes had similar (P=0.46) T4 values at birth but lambs from PTU-treated ewes had lower (P=0.03) birth weights than did those from control ewes. Serum progesterone (P4) after parturition indicated a lack of cyclicity in all ewes. In the second experiment, beginning on day 0 (76.8+/-4.7 days of gestation), ewes received PTU as in Experiment 1. In addition, after 15 days of PTU, melatonin was given (i.m. injections at 5mg/day) for 30 days. Propylthiouracil decreased (P0.60) for lambs born to control and treated ewes. Female offspring of PTU+melatonin-treated dams reached puberty, became anestrus, and returned to cyclicity at similar (P>0.10) times to contemporary ewe lambs. Results indicate that 40/20mg PTU alone or with melatonin does not induce cyclicity after lambing in spring lambing ewes and has little effect on offspring performance.     

Effect of dam weight and pregnancy nutrition on average lactation performance of ewe offspring over 5 years

The foetal mammary gland is sensitive to maternal weight and nutrition during gestation, which could affect offspring milk production. It has previously been shown that ewes born to dams offered maintenance nutrition during pregnancy (day 21 to 140 of gestation) produced greater milk, lactose and CP yields in their first lactation when compared with ewes born to dams offered ad libitum nutrition. In addition, ewes born to heavier dams produced greater milk and lactose yields when compared with ewes born to lighter dams. The objective of this study was to analyse and compare the 5-year lactation performance of the previously mentioned ewes, born to heavy or light dams that were offered maintenance or ad libitum pregnancy nutrition. Ewes were milked once per week, for the first 6 weeks of their lactation, for 5 years. Using milk yield and composition data, accumulated yields were calculated over a 42-day period for each year for milk, milk fat, CP, true protein, casein and lactose using a Legendre orthogonal polynomial model. Over the 5-year period, ewes born to heavy dams produced greater average milk (P=0.04), lactose (P=0.01) and CP (P=0.04) yields than offspring born to light dams. In contrast, over the 5-year period dam nutrition during pregnancy did not affect average (P>0.05) offspring milk yields or composition, but did increase milk and lactose accumulated yield (P=0.03 and 0.01, respectively) in the first lactation. These results indicate that maternal gestational nutrition appears to only affect the first lactational performance of ewe offspring. Neither dam nutrition nor size affected grand-offspring live weight gain to, or live weight at weaning (P>0.05). Combined these data indicate that under the conditions of the present study, manipulating dam weight or nutrition in pregnancy can have some effects of offspring lactational performance, however, these effects are not large enough to alter grand-offspring growth to weaning. Therefore, such manipulations are not a viable management tool for farmers to influence lamb growth to weaning.     

Nursing behaviour of bighorn sheep: correlates of ewe age,parasitism, lamb age,birthdate and sex

The nursing behaviour of marked bighorn ewes, Ovis canadensis, and their lambs was observed in Alberta, Canada, for 2 years. Suckle duration decreased as lambs grew older. Nursing behaviour in midlactation was correlated with maternal condition; young ewes, ewes with high faecal counts of lungworm (Protostrongylus spp.) larvae, and ewes whose lambs were born late allowed shorter suckles and were less likely to nuzzle their lamb's rump during a suckle. Sons did not appear to receive more milk than daughters. Suckle duration in mid-lactation was correlated with survival for female lambs but not for males. Lambs born late were disadvantaged, probably because nutritious forage was accessible to their mothers only in early lactation.     

Birthdate and survival in bighorn lambs (Ovis canadensis)

The relationship between parturition date and lamb survival was investigated among individually marked bighorn ewes in south-western Alberta, Canada. Lambs were born from 17 May to 21 July. Most births occurred in the first two weeks of the lambing period. Lambs born in May enjoyed greater survival than lambs born in June and July. The viability of lambs born after 10 June was extremely low. Inadequate nutrition is suggested as the cause of greater mortality of lateborn lambs. Ewes that give birth late are at an earlier stage of lactation when forage quality declines and may not produce sufficient milk to ensure lamb survival. Their lambs have access to high-quality forage for a shortened period. The proportion of late lambs appeared to be correlated with ewe density in the winter range.     

Behavior of parturient ewes in group-lambing pens with and without cubicles

Maternal behavior was examined in 301 multiparous ewes (2–6 years of age) that were of predominantly Suffolk or Targhee breeding. The ewes gave birth in either a normal lambing pen (control) or in a similar pen modified by the addition of 8 cubicles (cubicles). Approximately 100 ewes were present in each pen at a time, creating a density of 1 ewe m^?2.Within the cubicle treatment, comparisons were made between the ewes which gave birth inside a cubicle (CUB-I, n = 64) and those that gave birth outside the cubicles (CUB-O, n = 92). CUB-I ewes spent less time moving about (P<0.01), travelled less distance (P<0.001), investigated fewer potential birth-sites (P<0.001) and spent more time in the cubicles (P<0.001) during the 60 min prior to giving birth than did CUB-O ewes. After giving birth, CUB-I ewes remained close to their lambs, which always remained in the cubicles. This resulted in CUB-I ewes and their lambs remaining closer to each other and to the birth-site than CUB-O ewes and lambs (P<0.001). CUB-I ewes were rarely interfered with by other ewes (17 vs. 82% interference for CUB-I and CUB-O ewes, respectively) and had fewer (0) lambs separated or stolen from them than did CUB-O ewes (13 of 144 lambs).In comparing the cubicle system and the control pen, it was found that interference with ewes and lambs was less in the cubicle treatment (P<0.01). In the cubicle system, there tended to be fewer lambs separated from their dams (5.4 vs. 9.6%) and less stealing of lambs (3.1 vs. 5.2%) compared to the control pen. It is concluded that the use of cubicles under these conditions reduces the incidence of poor maternal behavior in ewes.