Barren Ewes Research Articles

The reproductive performance of naturally mated and artificially inseminated ewes treated with Fecundin at various intervals before the start of breeding

Two experiments were conducted to determine whether an interval longer than 2 wk between the last injection of Fecundin and the start of breeding would improve the reproductive performance of mature Merino ewes. In both experiments the ovulation and twinning rates of the immunized ewes were significantly higher than in the untreated ewes irrespective of whether the interval was 2, 3 or 4 wk. In Experiment 1, ovulation rates (ORs) for untreated and 2 and 4 wk were 1.02, 1.24, and 1.17, respectively (P < 0.001). Percentage lambing ewes with twin lambs for untreated and 2 and 4 wk: 5.8, 21.2, 17.4, respectively (P < 0.05). In Experiment 2, ORs for untreated and 2, 3, and 4 wk were 1.45, 1.92, 1.90, and 1.98, respectively (P < 0.01). Percentage of lambing ewes with twin lambs for untreated and 2, 3, and 4 wk were 36.8, 93.3, 63.0 and 68.6, respectively (P < 0.001). There were significantly more barren ewes when the interval between the last injection and the start of breeding was only 2 wk compared with either the untreated ewes or those injected 4 wk before the start of breeding (Experiment 1, 11.0, 32.5, 11.5% and Experiment 2, 7.4, 20.2, 9.5% for the untreated, 2- or 4-wk groups, respectively). An interval of approximately 4 wk should avoid a depression in the reproductive performances of immunized ewes.

Breeding ewes - an evaluation of the use of Fecundin under field conditions

Immunisation against ovarian steroids has been shown to improve the reproductive performance of ewes. Using this principle the drug Fecundin was developed by Glaxo Animal Health Ltd. and is marketed by Coopers Animal Health Ltd. who supplied the drug for this study. The response to Fecundin was evaluated in ewes lambing in the spring under a wide range of commercial conditions in an ADAS co-ordinated trial.ADAS Sheep Specialists and Advisers co-operated in locating and collecting the data from suitable commercial flocks and 2 EHF's with a minimum of 150 but more usually 200 ewes and where accurate lambing records could be obtained. Potentially naturally prolific types of ewes eg. Mules and Finn crosses were excluded. Approximately eight weeks before the rams were introduced all the ewes were condition scored and randomised to treatment or control. Treated ewes were injected with Fecundin and again 21-28 days later. At lambing the number of lambs born alive and dead and barren ewes were recorded in all flocks. Lambing dates, lamb birthweights and lamb survival were available in a limited number of flocks.

The mating of Libyan fat-tailed ewe lambs

The observations were made on 370 grazing Libyan fat-tailed ewe lambs commencing on 29 April 1981 when the lambs were 169 ± 11·47 days old ( x ̄ ± SD ). Half the lambs (group H) were offered a commercial pelleted sheep meal (0·5 kg/ewe/day) and broken cereal grains. The other lambs (group L) were controls. The lambs were isolated from rams until the start of the experiment. Although the group H ewe lambs tended to be heavier than group L ewes the difference was not significant. Within each group lambing ewe lambs tended to be heavier than barren ewes. More ewe lambs in group H lambed (65·0%) than in group L (52·72%) ( P<0·001). The mean date of effective mating (25 August and 18 August, 1981 in groups H and L respectively) and the mean (± SE) age at mating (287·7 ± 2·74 and 280·91 ± 2·80 days in groups H and L respectively) were not significantly different. The age at ram introduction had no influence on incidence of effective mating ( r = 0·09) but a significant positive correlation was found between body weight at ram introduction and lambing (group H: r = 0·98, P<0·001; group L: r = 0·91, P<0·001). A peak of mating which occurred 21 to 25 days after introduction of the ram suggests a synchronization and/or a stimulating effect associated with the sudden introduction of the ram. It is concluded that an acceptable level of lambing could be obtained by breeding from Libyan fat-tailed ewe lambs, and that measures leading to higher body weight when they are put to the ram would be expected to improve the overall performance.

The effect of physiological state on digestion in the ewe and its influence on the quantity of protein reaching the abomasum

Three experiments were carried out on Finnish Landrace × Dorset Horn ewes in various physiological states and given daily 2 kg of a diet containing equal parts of hay and concentrate. In experiment 1 six ewes, each fitted with cannulae in the rumen and abomasum, gave mean estimates for the proportion of their digestible organic matter intake that was apparently digested in the rumen of 0.50 in late pregnancy, 0.64 in early lactation and 0.65 post-weaning ( P < 0.01). The quantities ( g/d) of non-ammonia nitrogen reaching the abomasum were 46.9 for pregnancy, 36.4 for lactation and 40.4 post weaning ( P < 0.001). In experiment 2 the time required to recover an oral dose of chromic oxide in the faeces was significantly ( P < 0.001) lower for ewes in late pregnancy than for barren ewes and the effect was not influenced significantly by the physical form of the roughage (milled versus chopped). In experiment 3 the fractional outflow rate per hour of a chromium-mordanted fish meal supplement from the rumens of eight ewes in the 18th week of pregnancy was 0.053 compared with 0.044 for the same ewes in early lactation ( P < 0.025). It is suggested that the stimulatory effects of pregnancy on the rate of outflow of material from the rumen and on the quantity of protein reaching the abomasum may play a role in the nitrogen economy of the pregnant ewe.

Observations on a skin sensitivity test for ovine enzootic abortion

A delayed hypersensitivity skin test for ovine enzootic abortion (OEA) was evaluated using a Chlamydia psittaci (ovis) A22 strain antigen prepared from infected avian yolk sacs. A control antigen was also prepared from uninfected yolk sacs. Twenty-eight ewes and eight of their lambs were tested; 16 of the 28 had lambed three to five months earlier, the remaining 12 had not conceived. They had all been challenged with a field strain of C. psittaci (ovis) by various routes. Two of the 16 pregnant ewes had been clinically affected with C. psittaci (ovis) when they lambed and the chlamydiae they excreted contaminated the environment of the other ewes and the lambs as they were born. Consequently, 23 of the 28 ewes seroconverted in this perinatal period. However, seroconversion was transient and all except three had insignificant titres at the time of the skin test. Fifteen control sheep with no experimental contact with C. psittaci (ovis) were also tested. Twelve of the 16 ewes that had lambed developed positive skin tests, whereas only three of the 12 barren ewes, two of the eight lambs and two of the 15 control sheep were positive. Only three sheep subsequently developed clinical OEA. They were two of the experimental sheep that had lambed and one of the lambs. None of these three had a skin reaction. The results suggest that ewes aborting following C. psittaci (ovis) infection may be those which failed to mount an effective cellular immune response as demonstrated by the delayed hypersensitivity skin reaction. The sheep that had not conceived and the lambs were less able to mount a cellular immune response to chlamydial infection than the ewes that had lambed. Cellular, rather than humoral immune responses were more frequently detectable after infection of mature sheep.

Real-time ultrasonic scanning in the diagnosis of pregnancy and the determination of fetal numbers in sheep.

Two trials were conducted on a total of 1120 ewes of four breeds to evaluate the use of real-time ultrasonic scanning as a means of diagnosing pregnancy, differentiating barren, single- and multiple-bearing ewes and determining actual fetal numbers in pregnant ewes. In trial 1 (566 ewes) the accuracy of an inexperienced operator, as judged against assessments of an experienced operator, improved from 81 to 100 per cent for the classification of ewes as carrying no, one or more than one fetus, and from 69 to 100 per cent for the determination of actual fetal numbers more than one. In trial 2 the accuracies of the same operator, judged against the lambing performance of 267 ewes, ranged from 90 to 97 per cent for both types of assessment, and for an experienced operator from 95 to 100 per cent (554 ewes). In both trials pregnancy was diagnosed with an accuracy of 100 per cent. It is concluded that real-time ultrasonic scanning of sheep between days 50 and 100 of gestation offers a safe and practicable means of diagnosing pregnancy and of determining fetal numbers. Accuracies of diagnosis of pregnancy of more than 99 per cent, of differentiation of barren, single- and multiple-bearing ewes of 98 per cent, and of determination of actual fetal numbers of 97 per cent can be achieved in practice at scanning rates of at least one ewe per minute. Some of the benefits to flock management and performance likely to result from the use of the technique are considered.

An XO/XX mosaic sheep with associated gonadal dysgenesis

A female sheep with an apparent XO/XX karyotype was discovered while screening barren ewes. The animal exhibited a normal phenotype. This is the first reported case of mosaicism associated with gonadal dysgenesis in the sheep.

Short and long term effects of feeding supplements of oats, wheat and lupin grain on the production of ewes lambing in autumn

Four groups, each of about 40 Border Leicester x Merino ewes due to lamb in May, 1978, were held on bare ground and hand-fed poor quality hay, either alone or with oat, wheat or lupin grain at 270 g dry matter/head.d, from two weeks before until six weeks after lambing. A fifth group of ewes grazed separately on green pasture. After hand-feeding ceased in July 1978, ewes from all five groups grazed together and were re-joined with rams in November-December. Increases in wool production (90-230 g greasy fleece), milk production (9-23 ml/h) and growth of lambs (20-4 1 g/d) resulted from feeding supplements to the hay-fed ewes. Ewes fed oats and lupins performed best and, compared with those fed wheat, produced fewer fleeces with major faults (8 and 12% vs 29%, respectively) and less milk (58 and 62 ml/h vs 49 ml/h, respectively). At the end of hand-feeding, the ewes were 18-23 kg lighter than those that had been at pasture, but by the time joining took place in November-December, the difference was only 4-8 kg. Ewes fed hay alone mated 8-12 d later and lambed 5-9 d later (May 1979) than ewes in all other groups. Also, 6% of the ewes fed lupins or allowed to graze pasture during lambing in 1978 were barren in 1979, compared with 25% of barren ewes in all other treatments. It was concluded that wheat, in contrast to lupins and oats, was an inadequate supplement for lambing ewes consuming only low quality roughage.

Supplementing Merino ewes at mating for reproductive gain in central western New South Wales

In four experiments at Condobolin on the Central Western slopes of New South Wales between 1976 and 1979, mature Merino ewes were given supplements for four to five weeks over mating and the effects on their reproductive performance were recorded. The ewes were run on barrel medic or native pasture with mating commencing in late February or early March each year. The supplements were: experiment 1 -1upins (0.25 kg/d), oats (0.25 kg/d); experiment 2-lupins (0.25 kg/d), oats (0.25 kg/d); experiment 3-lupins (0 25 kg/d), lupins (ad libitum), lupins (0.25 kg/d) with ad libitum oats and lucerne hay; experiment 4-lupins (0.25 kg/d). In experiment 4, ewe liveweight was manipulated in the pre-feeding period to obtain two liveweight classes at the start of supplementation. In the three to four weeks before mating, ewes either maintained or lost weight in experiments 1,2 and 4. However, in experiment 3, ewe liveweight increased after heavy summer rains caused an abundance of pasture. The only significant effect of any supplement on flock reproduction was to increase the ovulation rate. This resulted from lupin supplementation but only in two of four years (experiments 1 and 4). However, on these occasions, lambing rates did not significantly increase due to three factors: more barren ewes, higher ova loss or greater peri-natal lamb loss. Oats supplementation in experiments 1 and 2 did not significantly increase reproductive performance, nor was there an effect of any supplement in experiment 3. The results indicate that repeatable reproductive responses to lupin supplementation are unlikely to occur in the area of the study.

The association between lambing status and future reproductive performance of ewes grazing oestrogenic pastures

Eight flocks of ewes grazing improved pastures which contained oestrogenic clover (Trifolium subterraneum cv. Yarloop) were studied. Two data-sets were available for analysis: Data-set 1-four flocks, three with age-structure unknown. Records on the number of ewes lambing per ewe exposed to the ram (EPJ) and the number of lambs born per ewe exposed to the ram (LBJ) were collected during 1972-75. The repeatability of EPJ and LBJ were estimated within flocks by the regression methods. There was considerable variation between flocks in the values obtained. An analysis of variance was conducted including lambing status (0, 1 or 2 lambs at birth) of the ewes in 1972 as a main effect. Class 1 ewes had a better reproductive performance in subsequent years than either class 0 or class 2 ewes. The effects on flock performance of culling barren ewes were simulated, showing that little improvement in subsequent performance would result. Data-set 2-four flocks, age-structure known. EPJ and LBJ were recorded in 1973 and 1974. The repeatabilities of EPJ and LBJ were estimated within age groups of each flock by regression methods. The results were less variable than in data-set 1. An analysis of variance was conducted, including lambing status (0 or 1 lamb at birth) in 1973 as a main effect. Class 1 ewes had a better reproductive performance in 1974 than class 0 ewes. Simulation of the effects of culling ewes which were barren in 1973 showed that only a small improvement in reproductive performance of ewes in 1974 could be obtained. It was concluded that the culling of barren ewes is unlikely to provide a solution to the low reproduction rate of ewes grazing oestrogenic pastures.

Influence of sex hormones on the subcellular distribution of copper in sheep liver

At the 14th to 16th week of pregnancy the copper content in the maternal liver was low while that in the fetus was high. After ovariectomy there was a decrease in liver copper and ceruloplasmin which was prevented by treatment with oestrogens but not with progesterone. Five groups of sheep were studied: control (barren ewes), pregnant, ovariectomised and ovariectomised treated with oestrogens or progesterone. In all, with high or low liver copper, the nuclear fraction contained the most copper. This suggests a species specificity of the copper metabolism in sheep.

A 53,X female sheep (Ovis aries).

A female sheep with a 53, X karyotype was discovered while screening barren ewes at a commercial sheep ranch in New Mexico. She was physically normal in phenotype, in very good flesh due to freedom from nursing offspring, and her external genitalia were normal. This is the first case of monosomy X to be documented in sheep.

The effect of strategic anthelmintic treatment on the breeding performance of hill ewes

A series of field trials involving 3500 Scottish hill ewes was carried out to determine the effect of different worming routines on subsequent flock performance. Combinations of the following seasonal dosings were examined in April lambing flocks: “early winter” (November/early December); “winter” (mid-January to early February) and “spring” (mid-March to early April). The effects upon numbers of barren ewes and on rearing percentages in comparison with untreated control sheep were evaluated. Barrenness was significantly reduced by the following treatments: “early winter” by 70% ( P<0.10); “winter” by 7.8% ( P<0.05); “early winter and winter” by 4.3% ( P<0.05). Rearing percentages were significantly increased by the following treatments: “early winter and winter” by 10.7% ( P<0.01); “early winter and spring” by 9.2% ( P<0.01); “spring” by 7.9% ( P<0.05). The increased rearing percentages indicated that a strategic dosing programme for breeding ewes between mating and parturition is worthwhile, with the routines involving two doses — either ”early winter and winter” and “early winter and spring” giving the greatest benefit. Attention is drawn to the high incidence of barrenness and low rearing percentages which was a constant feature in all the flocks used in the trial.

Significance of inhibited development in the epidemiology of Chabertia ovina and Oesophagostomum venulosum

Worm counts from ewes, lambs and tracer lambs during a study on the epidemiology of gastro-intestinal nematode infections in sheep at Utrecht State University between 1974 and 1977 substantiated the following descriptions of the epidemiology of Chabertia ovina and Oesophagostomum venulosum infections. Development of inhibitated larvae and recently acquired infection from pasture leads to a spring rise in the numbers of adult worms and developing stages in lactating ewes and some barren yearling sheep. However, in barren ewes and some barren yearling sheep very few adult worms develop. The low residue of overwintered larvae on pasture results in infection of the lambs in spring and early summer. These larvae develop without inhibition. Numbers of infective larvae on pasture remain low until the autumn. This autumn increase leads to substantial worm burdens in lambs and ewes, but a high proportion of these worm burdens, especially in ewes, consists of inhibited larvae. A decrease in pasture larval contamination occurs during winter and the propensity of the larvae for inhibited development diminishes. The lambs lose most of their worms during winter. Experimental infection of worm free sheep shows that it is possible to condition infective larvae, especially of O. venulosum , for inhibition of the development, by storage of the larvae for 5 weeks at 15 or 4°C.

Fertility in Cheviot ewes. 3. The effect of level of nutrition before and after mating on ovulation rate and early embryo mortality in South Country Cheviot ewes in moderate condition at mating

ABSTRACTOne hundred and twenty South Country Cheviot hill ewes were differentially group-fed indoors over a 2-month period to achieve either moderately-good or poor body condition. Over 5 weeks prior to mating, ewes in moderately-good condition were brought down in condition by restricted feeding and ewes in poor body condition were raised in condition by a high level of feeding. The ewes were thus in moderate condition at mating. During the first 4 weeks after mating, half the ewes from each original condition group were fed at a high level and the other half were fed at a low level. Ewes were killed either on return to service or at 30 ± 10 days forcounts of corpora lutea and viable embryos.Ovulation rate was not significantly related to the level of pre-mating food intake at the condition level studied, although the trend was positive. Embryo mortality, as ova loss, was reduced by a high level of post-mating food intake but was increased by a high level of pre-mating intake. This latter result, however, may be influenced by the experimental confounding of high pre-mating food intake and very low initial body condition. The greatest loss was incurred by ewes, originally in poor condition, which were fed at a high pre-mating level and a low post-mating level. Potential lambing rate at slaughter was not affected by the level of food intake either before or after mating although the trend was for a low level of post-mating intake to be associated with an increase in the proportion of barren ewes.

Identification of barren ewes by vasectomised rams

Abstract The ability of harnessed vasectomised (teaser) rams to identify barren ewes over the 4-6 weeks after joining with entire rams, has been calculated from 4–6 years' data from 2 flocks. Of the total barren ewes, 29.6% (range 18.2%–46.6%) in one flock and 48.0% (range 31.3%–66.9%) in the other flock were marked in the 4 weeks after joining. The percentage of barren ewes marked by the teasers increased with increasing prejoining live weight of the ewes. There was no effect of breed of ewe on the percentage of barren ewes marked but there were large variations among years. There was only a small increase in the percentage of barren ewes marked when the period of joining with teasers increased from 4 to 6 weeks. The teasers marked 7.1%–8.1% of the total ewes in one flock and 9.5%–10.8% in the other in 4 weeks, but the proportion marked varied among years. In both flocks, pregnant ewes were marked by the teasers, but in all except one year these formed only a small percentage (0.6%–1.2%) of the total pre...

Haemonchus contortus infection in ewes: Blastogenic responses of peripheral blood leukocytes to third stage larval antigen

Ewes were infected weekly with infective third-stage Haemonchus contortus larvae until parturition (1–16 doses of infective larvae). Peripheral blood leukocytes from these ewes were tested for in vitro blastogenic responses to phytohemagglutinin, to a non-helminth antigen the purified protein derivative of tuberculin (PPD), and to third-stage larval H. contortus antigen during pregnancy, parturition and lactation. Fecal egg counts were determined on a weekly basis for all ewes. Parturient lactating ewes showed a peri-parturient rise in fecal egg counts while barren ewes or parturient, nonlactating ewes did not. Blastogenic responses of a majority of parturient lactating ewes indicated an inverse relationship to fecal egg counts. In contrast, blastogenic responses of barren or nonlactating ewes did not demonstrate this inverse relationship. It is suggestive that hormonal factors or other serum factors affect antigen-induced blastogenesis during parturition and lactation in the sheep.

Periparturient rise in faecal helminth egg counts of Udah sheep in the Zaria area of Nigeria

The trichostrongylid egg output in the faeces of seven lambing and seven barren Udah ewes was compared during the beginning of the rainy season in 1974. Both groups showed an increase in egg counts which reached a considerably higher level in the lambing ewes. The highest level, a mean count of 2 650 eggs/g, was reached 2 weeks after lambing. It is suggested that the increase was due to helminths, mainly Haemonchus sp., which had been inhibited during the dry season and resumed their development at the beginning of the rainy season. The rapid decline in egg counts recorded 5–6 weeks after lambing was considered to be due to self cure associated with high rainfall.

Maternal performance in sheep as affected by breed, crossbreeding and other factors

SUMMARYMaternal performance of female sheep of three hill breeds, Scottish Blackface, Cheviot and Welsh Mountain, and the crosses among these breeds has been studied in terms of lifetime production and some of its components. The data are based on 193 ewes, which were given the opportunity of having four annual lamb crops, and their lambs.There was no significant variation among the breeds and crosses in ewe survival or in the proportion of barren ewes at each lambing. There was significant variation among the breeds and crosses in the number of lambs born per ewe lambing, in lamb survival and in weights of lamb at birth and at weaning. Crossbred ewes (producing crossbred lambs) had more and heavier lambs than expected from the average of the pure breeds contributing to each cross, but the three crossbred types differed in the amount of heterosis shown. Over their lifetime in the flock there were significant breed differences in the total weight of lambs weaned, with crossbred ewes producing about 9% more than the average of the parent breeds involved. The crossbred ewes produced more weight of lambs over their lifetime than pure Cheviot or pure Welsh Mountain ewes, but not as much as pure Scottish Blackface.Effects of parity of dam and of sex, birth type, and type of rearing of lamb are given.

Survey observations on the reproductive performance of both romney stud and commercial flocks throughout new zealand

Abstract The results of a survey conducted during 1962–67, which examined the reproductive performance of commercial pure-bred Romney flocks in five geographical areas throughout New Zealand, are given. Within each area, flocks were grouped into one of four property-type classifications: unimproved hill, improved hill, rolling, hill, and intensive flat land. Overall, the reproductive performance of approximately 1 1/2 million ewes was examined. Significant between-area differences were demonstrated in the age structure of flocks, the time and duration of mating, and the percentages of barren ewes, ewes lambing, and ewes which lost all their lambs. Significant linear increases in lamb tailing and weaning percentages were shown from north to south. There were highly significant interactions between areas and property types in the time of mating and the percentages of lambs tailed and weaned. Significant between-year differences were demonstrated in the age structure and mean size of flocks and in lamb tailing and weaning percentages, which increased linearly from 1962–65 inclusive.