Proportion Of Ewes Research Articles

Plasma progesterone profiles in ewes using different injectable progesterone formulations

Context The use of progesterone vaginal implants in sheep is frequently associated with vaginitis and adherences; and can hamper fertility in estrus synchronization programs. Aims The aim of this study was to characterize the plasma hormone profile induced by two injectable progesterone (iP4) formulations in ewes. Methods In Experiment 1, ewes received 20 or 40 mg of an iP4, with a third group as a control. In Experiment 2, 75 or 150 mg of a long-acting iP4 were administered, again with a control group. Key results In Experiment 1, progesterone concentrations remained at luteal levels for less than 24 h. The intervals from iP4 treatment to the onset of estrus and ovulation were greater in treated than in control ewes (P < 0.01). The proportion of ewes that ovulated within 8 days after treatment was lower in ewes that received 40 mg iP4 than in control ewes (P < 0.05). In Experiment 2, mean progesterone concentrations remained at luteal levels for 120 h. The interval from iP4 administration to estrus was longer in 150 mg treated ewes than in control ewes (P < 0.01). The interval from treatment to ovulation was longer in ewes treated with 150 mg than 75 mg and control ewes (P < 0.05). The proportion of ewes that ovulated was lower at 150 mg (P < 0.05). Conclusions The iP4 formula used in Experiment 1 could not maintain luteal levels for more than 24 h. The use of long-acting iP4 maintained plasma progesterone concentrations above luteal levels for at least 5 days. The long-acting treatment can therefore be tested for estrous synchronization treatments. Implications The long-acting progesterone may be an alternative to short estrous synchronization protocols.

Dietary n-3 PUFA augments pre-ovulatory follicle turnover and prolificacy in well-fed ewes

The present study evaluated the effect of dietary supplementation with n-3 polyunsaturated fatty acids (PUFA) on preovulatory follicle (POF) turnover, prolificacy, and endocrine and metabolic milieu in Malpura sheep. Fifty cyclic ewes with 3–3.5 body condition scores on a five-point scale were allocated equally to two groups (n = 25) following estrus synchronization and were supplemented with 0.6 mL/kg body weight of n-3 PUFA-rich fish oil (FO) or palm oil (PO) as control, for 60 d following an acclimatization period of 7 d. All ewes were mated with sexually active rams at the end of the supplementation period. On ultrasonographic ovarian scanning at the last fourth estrus, the mean number of POFs was 77.8% greater (P < 0.01) in FO ewes than in the PO ewes. The proportion of ewes with multiple ovulations two months after the beginning of supplementation was 56% in the FO group as compared to 8% in the PO group. The number of fetuses was 46% higher (P < 0.01) in the FO than in the PO ewes at d 45 of gestation. At lambing, the twinning percent in the FO ewes was three times greater than in the PO ewes (27.3 vs. 9.1%). Plasma cholesterol, estradiol, and insulin concentrations were lower (P < 0.01) in ewes fed with FO than those offered PO group at the end of the feeding period. It was concluded that the dietary supplementation of n-3 PUFA-rich FO in well-fed Malpura ewes improved the number of follicles and ovulation rate which led to an increased prolificacy, accompanied by a reduction of plasma cholesterols, estradiol, and insulin.

GnRH administration after estrus induction protocol decreases the pregnancy rate of recipient ewes following transfer of frozen-thawed embryos

The objective of this study was to investigate the effects of GnRH on the pregnancy rate and the embryo survival rate of recipient ewes following embryo transfer. Estrus was synchronized in 83 nulliparous Huyang ewes using intravaginal sponges impregnated with 45 mg flurogestone acetate. The sponge was left in the vagina for 12 days followed with an injection of 330 IU of eCG at sponge removal. The treatment group (n = 34) was subjected 48 h after sponge removal to intramuscular administration with 16 μg of the GnRH agonist triptorelin and the control group (n = 49) with 1 mL of saline solution. Embryo transfer was performed by laparoscopy on day 8 after sponge removal, which transferred frozen-thawed embryos of Suffolk ewes directly to the anterior third of the corpus luteum ipsilateral uterine horn of the recipient ewe.Each recipient with at least one normal corpus luteum received one grade I embryo. The proportion of ewes with at least one normal corpus luteum in the control group was significantly lower compared to the treatment group (73.5 % vs 91.2 %, P < 0.05). In total, 62 embryos were transferred into 62 ewes and 29 lambs were born. The pregnancy rate (59.4 % vs 33.3 %, P < 0.05) and the embryo survival rate (56.3 % vs 30.0 %, P < 0.05) in the control group were significantly higher compared to the treatment group. In conclusion, a single dose of GnRH administered 48 h after sponge removal significantly decreased the pregnancy rate and the embryo survival rate of recipient ewes following transfer of frozen-thawed embryos.

SEASONAL EFFECTS ON OESTRUS PATTERNS AND PROGESTERONE PROFILES OF YANKASA EWES OF DIFFERENT AGE-GROUPS IN THE SUB-HUMID TROPICS

Oestrus patterns and serum progesterone profiles of 10 adult and 10 yearling Yankasa ewes were investigated in the late hot-dry and late-wet seasons in the subhumid tropical climate of Zaria, Nigeria. The proportions of ewes which came on heat once, twice or thrice within the experimental periods in the late hot-dry and late-wet seasons were 25, 15 and 0%, and 5, 10 and 85% respectively, while mean oestrous cycle length was significantly longer (P&lt;0.001) in the hot-dry season than in the late-wet season (30.9 vs 18.4 days) due to the higher incidence of anoestrus in the former. However, the mean duration of oestrus was not affected by season. Mean serum progesterone levels were significantly (P&lt;0.05) higher in the late-wet season than in the late hot-dry season (1.57 vs 0.52 ng/ml). However, there was a highly significant (P&lt;0.001) interaction between season and age group in mean serum progesterone levels due to a relatively greater depression in progesterone levels in yearling ewes during the hot-dry season compared with adult ewes. The observed disruptions in the oestrus cycle and serum progesterone levels of the ewes in the hot-dry season confirm the adverse effect of heat stress on the reproductive behaviour of ewes.

Direct and correlated responses to selection for autumn lambing in sheep

BackgroundSeasonal reproduction limits productivity, flexibility, and profitability in commercial sheep production. Hormonal and (or) photoperiodic manipulation can be used to control estrous cycles in sheep and reduce limitations that are imposed by the seasonal anestrous but are often impractical or incompatible with the extensive management systems preferred for ruminant livestock. Thus, the current study investigated the use of selection to improve realized fertility (i.e., the proportion of ewes that lambed) following an out-of-season spring joining period (May and June) in a crossbred sheep population.ResultsOver 17 years, estimated breeding values (EBV) for fertility in selected (S) ewes increased by 0.175 (0.01 per year). The mean EBV for fertility of S ewes was greater than that of control ewes by year 10 (P = 0.02), and the fertility of adult (≥ 3 years old) ewes reached 0.88 ± 0.05 by year 17. Lambing began approximately 140 days after the introduction of rams, and 64% of the S ewes that lambed did so in the first 17 days of the potential lambing season, which indicated that most of the S ewes were cycling at the time of ram introduction and were not induced to cycle by the introduction of breeding males (i.e., the so-called “ram effect”). Animals in the S line had modest increases in body weight and scrotal circumference. A modest negative trend in the additive maternal effect on birth weight was observed but was reversed by additional selection on EBV for maternal birth weight. The heritability of litter size in autumn lambing was low (0.04) and could potentially limit the response to selection for this trait.ConclusionsSelection improved realized ewe fertility in out-of-season mating, with absolute increases of approximately 1% per year in the percentage of joined ewes that lambed in the autumn. Genetic antagonisms with other performance traits were generally small. A modest antagonism with maternal breeding values for birth weight was observed but it could be accommodated by selection on EBV for maternal birth weight. Our results support results of previous studies that indicate that these selected ewes had one of the shortest seasonal anestrous periods reported for temperate sheep breeds and that spring-lambing lactating ewes from the selection line were capable of relatively rapid rebreeding in the spring.

Field synchronization of Ethiopian Highland sheep for fixed time artificial insemination: improvement of conception rate with a double injection of prostaglandin at 11 days

ABSTRACT The study investigated, for fixed time artificially inseminated (AI) Menz ewes in field trials, the reproductive performance of prostaglandin-based treatments simultaneously to the standard ‘P4+eCG’ protocol. A total of 483 Menz ewes were assigned to either the ‘P4+eCG’ protocol, using progesterone impregnated intravaginal sponges in combination with equine chorionic gonadotropin (eCG) injection at sponge withdrawal, or the ‘PGFs’ treatment where sheep received a single injection of prostaglandin or ‘PGF7’ and ‘PGF11’ where ewes were synchronized with 2 injections of prostaglandin 7 or 11 days apart, respectively. AI was implemented with fresh semen at 55 ± 1 h after the end of the hormonal treatment. Conception rate (CR; 60.87 ± 4.2) was highest for PGF11 ewes (P < 0.05); PGFs ewes had the lowest CR (34.07 ± 4.1). Other factors did not affect variation in CR (P > 0.05). A higher proportion of ewes in the P4+eCG group yielded twins and triplets compared to the 3 prostaglandin-based protocols (P < 0.01). Nevertheless, a higher (P = 0.02) proportion (17.11 ± 4.3) of PGF11 ewes yielded twins by comparison to their PGF7 counterparts (2.50 ± 2.5). PGF-based protocol with 2 injections 11 days apart, preceded by a careful selection of non-pregnant ewes for cervical fixed-time AI, is a feasible reproductive management for sheep breeding programmes in Ethiopia.

Assessment of targeted selective treatment criteria to control subclinical gastrointestinal nematode infections on sheep farms

Control of sheep gastrointestinal nematode (GIN) infections mostly relies on the use of anthelmintics. Refugia-based control strategies as targeted selective treatments (TST) can delay anthelmintic resistance development, but the optimal decision criteria for selecting individuals to be treated in subclinical infection scenarios remain unclear. The present study aimed to evaluate the suitability of body condition score (BCS) and faecal egg counts (FEC) as treatment indicators and to determine their optimized threshold values for treatment in TST by determining the relationships of BCS, FEC and anthelmintic treatment with several productive parameters in pre-mating and pre-partum periods at an individual level. Deworming in pre-mating period increased BCS gain, but its magnitude was directly associated with strongyle FEC before treatment. Deworming also increased fertility in ewes with BCS < 2.75 and the proportion of lambing ewes that got pregnant during the first ovulation cycle. Nevertheless, treatment did not yield productive benefits in ewes with higher BCS values. On the other hand, deworming in the pre-partum lowered lamb peri-partum mortality and increased lamb weight at birth and the growth of lambs during lactation, especially in lambs born from ewes with strongyle FEC > 400 epg before treatment. These results showed that FEC and especially BCS can be potential decision criteria for the implementation of TST in these types of scenarios. The TST scheme derived from the present results on the control of GIN infections should include anthelmintic treatment of ewes with BCS lower than ≈ 3 approximately five weeks before mating and lambing. In the pre-lambing period, treatment may be unnecessary if flock mean strongyle FEC is lower than ≈ 200 epg, as the proportion of ewes with individual FEC > 400 epg would be very low. The results suggest that implementation of this TST scheme would provide benefits, such as the improvement of productivity, a rational management of parasites in refugia, and preservation of future efficacy of anthelmintics, in comparison to traditional deworming schemes.

The effect of ewe wastage in New Zealand sheep and beef farms on flock productivity and farm profitability

Changes in the relative value of meat and coarse wool have led to the majority of income for New Zealand sheep farms now coming from the sale of animals for slaughter rather than wool, shifting the production focus for many farmers. Ewe wastage, on-farm mortality and premature culling before the potential end of the ewe's productive life, is a limiting factor for sheep meat production. Current estimates of wastage rates in New Zealand commercial ewe flocks range from approximately 3 to 20%. A bio-economic model of a representative New Zealand North Island Hill Country sheep farm was constructed to investigate the effects of wastage rates on farm profitability. The model used system dynamics with annual time steps over 30 years. The proportion of ewes that were culled up to 6 years of age and all mature ewe deaths combined were considered as wastage in this study. Modelled scenarios covered ewe wastage rates ranging from 5 to 21% for a self-replacing flock of 1879 ewes producing coarse wool and lambs for sale on 423 ha where 63% of total feed was consumed by sheep. Greater wastage of ewes resulted in higher numbers of young, less productive replacement ewes in the flock, lowering average flock age from 4.18 years to 3.54 years over the wastage rate range tested. The reproductive performance of the flock decreased with flock age from 1.33 lambs weaned per ewe presented for breeding to 1.22 lambs weaned per ewe presented for breeding with wastage rates of 5% and 21%, respectively. The lower numbers of lambs weaned and lower proportion available for sale reduced income from lamb sales. Subsequently, total cash operating surplus for the sheep enterprise of the representative farm was reduced by NZ$ 1069 per year per 1% increase in ewe wastage. For a New Zealand North Island Hill Country sheep farm with 15% of the flock lost due to wastage, a 10% reduction in wastage could increase cash profit by 17%. Sheep energy requirements were reduced across the production year with greater ewe wastage leading to a greater positive end of year cumulative feed surplus.

Reducing mob size increases the survival of twin-born Merino lambs when feed-on-offer from pasture is limited and ewes are supplementary fed during lambing

Improving the survival of twin-born lambs is a high priority for the Australian sheep industry. Higher mob sizes at lambing have been suggested to decrease the survival of twin-born lambs. However, our recent work indicated that this effect may not occur when feed-on-offer (FOO) exceeds 2400 kg DM/ha during the lambing period. Increasing mob size at lambing when FOO is limited may exacerbate the risk of mismothering due to the need for ewes to seek feed and thus result in poorer lamb survival. Therefore, this study tested the hypothesis that (i) a higher mob size at lambing will decrease lamb survival when FOO from pasture is limited and ewes are supplementary fed and (ii) that this is related to a greater rate of interaction with foreign ewes and lambs during the periparturient period. Twin-bearing Merino ewes (n = 795) were allocated into one of two treatments on day 140 of pregnancy; high (n = 210) or low (n = 55) mob size, with three replicates of each treatment. Feed-on-offer from live pasture at lambing was below 390 kg DM/ha and ewes were supplementary fed until lamb marking. Behaviour during the periparturient period was observed and dead lambs were collected for autopsy for 14 days during the peak of lambing. The survival of lambs to marking was recorded for each mob. Lamb survival was 6.2% higher at the low compared to the high mob size (P < 0.05). The proportion of ewes which interacted with a foreign ewe or foreign lamb at lambing did not differ significantly between mob sizes. Whilst the relationship between mob size, ewe-lamb behaviour and lamb survival remains unclear, this study has shown that the survival of twin-born Merino lambs is improved by lambing ewes in smaller mobs when FOO from live pasture is limited and ewes are supplementary fed.

Mob size of single-bearing or twin-bearing Merino ewes at lambing may not influence lamb survival when feed-on-offer is high

Limited research has suggested that higher lambing densities increase interference from foreign ewes at lambing which disrupts the ewe-lamb bond and compromises lamb survival. This may be particularly evident in mobs of twin-bearing ewes compared to single-bearing ewes because a greater number of lambs are born per day. Therefore, we hypothesised that; (i) decreasing the mob size of ewes at lambing has a greater impact on the survival of twin-born lambs than single-born lambs; (ii) the relationship between mob size and lamb survival can be explained by differences in the rate of interaction with foreign ewes and lambs at lambing; and (iii) ewes will utilise a limited area of the paddock at lambing and thus lambing density will be defined by the distribution of ewes in the paddock rather than the paddock area. Merino ewes were allocated into a 2×2 factorial combination of ewe pregnancy status (single- or twin-bearing) and mob size (high (n=130 ewes) or low (n=50 ewes)) on day 140 from the start of joining. Each treatment had two replicates excepting the low mob size for twins which had a third replicate. Ewes lambed at a stocking rate of 11 ewes/ha. Feed-on-offer during lambing exceeded 2400 kg dry matter (DM)/ha. Ewe-lamb behaviour was observed and dead lambs were autopsied over 11 days during the peak of lambing. The distribution of ewes in each paddock was recorded every 2 h during daylight hours by counting the number of ewes occupying 2500 m2 grids. The proportion of ewes and their newborn progeny which interacted with foreign ewes at lambing did not differ between the high and low mob sizes for single- (24.9% v. 20.8%) or twin-bearing ewes (14.3% v. 19.6%; P=0.74). Similarly, interaction with foreign lambs did not differ between the high and low mob sizes for single- (14.5% v. 25.2%) and twin-bearing ewes (34.5% v. 26.4%; P=0.44). The distribution of ewes within the paddock did not differ between treatments (P=0.95). On average, single-bearing ewes which lambed at the high and low mob sizes occupied 34% and 36% of the paddock during daylight hours, and the corresponding values for twin-bearing ewes were 40% and 43%. Survival of twin-born lambs was lower than single-born lambs (75.3% v. 87.9%; P<0.01), however, lamb survival was not influenced by mob size regardless of birth type. These results suggest that higher mob sizes may not compromise lamb survival when feed-on-offer during lambing exceeds 2400 kg DM/ha.

Influence of fecundity gene on oestrus synchronization and gonadal steroid levels in booroola carrier and Non-Carrier ewes

Prolificacy in Garole sheep is due to the effect of a single point mutation in the bone morphogenetic protein receptor 1B (BMPR-1B) and expressed in the granulosa cells and oocytes. The GMM (25% Garole-75% Malpura) sheep was developed by FecB introgression from Garole sheep. An experiment was conducted in the major breeding season (July-August, 2016) to study the oestrus synchronization response and plasma progesterone and oestradiol hormone concentrations in prolific GMM ewes (FecBBB), non-prolific GMM (FecB++) and Malpura ewes (FecB++). GMM strain was developed from Malpura (75%) and Garole (25%) breed so considered as control group for estrus response. A total of 28 ewes (carrier GMM (n=9), non-carrier GMM (n=10) and Malpura (n=9)) were synchronized with progesterone impregnated intravaginal sponges. It was observed that the proportion of ewes that exhibited oestrus did not differ significantly between the carrier and non-carrier GMM ewes; however, the oestrus response was early in carrier GMM compared to non-carrier GMM and Malpura ewes. The interval time for the onset of oestrus was non-significantly lower in carrier GMM (32.00±5.93) as compared to noncarrier GMM (36.00±3.70h) and Malpura (39.43±3.43h) ewes. The duration of oestrus did not differ significantly between the genotypes. The plasma progesterone concentration was significantly (P<0.05) higher in carrier GMM ewes (2.73±1.29ng/ml) as compared to non-carrier GMM ewes (1.28±0.62ng/ml). The oestradiol concentration was significantly higher (P<0.001) in non-carrier GMM (181.95±30.38pg/ml) as compared to carrier GMM ewes (124.43±15.87pg/ml). The results indicated that the FecB mutation alters the circulating concentration of progesterone and estradiol in Booroola carrier GMM (FecBBB) ewes.

84 Effect of Embryo Stage and Cryopreservation Method on Pregnancy Rates Obtained Following the Transfer of In Vivo-Derived Ovine Embryos on Small-Scale Farms in Thailand

Assisted reproductive technologies including superovulation, laparoscopic AI (LAI), and embryo transfer (ET) are important tools for genetic improvement in the sheep industry. The present study aimed to determine the effects of embryo stage and cryopreservation method on field trial outcomes of embryo transfer on small-scale farms in Thailand. Black Dorper ewes (n = 16) were used as donors and mixed breed ewes (n = 21) were used as recipients. Donors were superovulated as previously described (Tríbulo et al. 2012 Theriogenology 77, 1679-1685, 10.1016/j.theriogenology.2011.12.013) and inseminated by LAI within 22 to 24 h after standing heat (Day 0). Donors females were flushed on Day 2 to recover 2- to 8-cell embryos (n = 8) or on Day 6 to recover blastocyst-stage embryos (n = 8). Recovered embryos were randomly cryopreserved by either slow freezing or vitrification methods. Into 21 recipients was inserted an intravaginal device impregnated with CIDR® that was left in place for 10 days. Those received 300 IU of pregnant mare serum gonadotropin (PMSG) on Day 9 and randomly assigned to receive embryos on either Day 2 or 6 after oestrus. Two- to 8-cell embryos were thawed and transferred into the ipsilateral oviduct (n = 1-5 embryos/recipient) on Day 2. Five recipients received 15 slow-frozen embryos and 5 received 13 vitrified embryos. Blastocyst stage embryos were thawed and transferred into the ipsilateral uterine horn (n = 1-4 embryos/recipient) on Day 6. Five recipients received 11 slow-frozen embryos and 4 received 7 embryos. Pregnancy diagnosis was determined by ultrasonography 45 days after embryo transfer. Pregnancy rate was calculated as the proportion of ewes with at least one pregnancy out of the total number of ewes that received embryos. Chi-squared analysis was used to determine the effects of embryo freezing technique and embryo stage on pregnancy rate (SAS 9.2, SAS Institute Inc., Cary, NC, USA). All donor ewes responded to the superovulation program (donor had 3 to 6 corpora lutea). The mean number of viable embryos recovered was 4.3 ± 2.4 and 3.1 ± 3.7 for Day 2 and Day 6, respectively. Nineteen of the 21 recipient ewes responded to the synchronization program and received embryos in the study. There was no effect (P &gt; 0.05) of embryo stage (5/10 = 50% v. 3/9 = 33.3% for 2- to 8-cell v. blastocyst, respectively) or cryopreservation method (4/10 = 40% v. 4/9 = 44.4% for slow-freezing and vitrification, respectively) on pregnancy rate following embryo transfer. Results of the present study suggest that similar pregnancy rates following embryo transfer in sheep under tropical conditions in Thailand can be obtained using either 2- to 8-cell embryos or blastocyst-stage embryos and with embryos that have been cryopreserved by slow-freezing or vitrification. Further research with larger numbers of animals is necessary to confirm the preliminary results of the present study.

Effet de l’acide ascorbique sur le taux de fécondation des brebis Yankasa après synchronisation de l’œstrus

L’objectif de cette étude était d’évaluer les effets d’une admi­nistration d’acide ascorbique (AA) sur le taux de fécondation de brebis dont les chaleurs étaient induites par deux traite­ments à base de progestogènes. Des brebis de race Yankasa (n = 64) ont été réparties de façon égale en deux groupes. Dans l’un, les brebis ont été traitées avec un dispositif intra­vaginal de libération continue du médicament (CIDR). Dans l’autre, les brebis ont été traitées avec 45 mg d’acétate de fluo­rogestone (FGA) au moyen d’une éponge vaginale. Après le retrait des progestogènes, les brebis de chaque groupe expri­mant des chaleurs ont été réparties en quatre sous-groupes : CIDR témoin (CDNN, n = 12), CIDR plus AA (CDAA, n = 11), FGA témoin (FGNN, n = 13) et FGA plus AA (FGAA, n = 12). La détection des chaleurs a été réalisée au moyen de béliers sexuellement actifs et laissés libres de s’accoupler avec les femelles. Le taux d’expression des chaleurs n’a pas différé entre les sous-groupes. L’intervalle entre le retrait des dis­positifs et l’apparition des chaleurs a été significativement (p &lt; 0,05) plus court chez les brebis du groupe FGA que chez celles du groupe CIDR (respectivement 30,35 ± 2,72 et 48,56 ± 7,52 heures). La durée de l’oestrus n’a pas différé (p &lt; 0,05) entre les traitements (FGA 37,22 ± 4,22 et CIDR 39,75 ± 2,51 heures). Les taux de fécondation ont été comparables entre sous-groupes. En conclusion, l’administration d’AA lors du retrait des dispositifs progestogéniques n’a pas amélioré le taux de fécondation des brebis Yankasa.

Feed supplementation improves estrus response and increases fertility of sheep induced to breed out of season.

To test the efficacy on reproductive performance of nutritional supplementation in an out-of-season mating system, 66 adult prolific Barbarine ewes were selected and induced to breed using "ram effect". The ewes were allocated to two homogeneous groups; each ewe received on a daily basis 700g of hay and 500g of barley grains starting 3weeks before or 1week after rams' introduction in group 1 and group 2, respectively. Supplementation ended 1month after rams' introduction and mating lasted 60days. Final live weight 30days after introduction of rams was higher (P < 0.05) for ewes in group1 (39.45 vs. 36.72kg). Seven days after introduction of rams, ewes in group 1 recorded higher plasma glucose levels than females in group 2 (4.12 and 3.9S.E.M. 0.05mmoll-1). Proportions of ewes which displayed estrus between days 16 and 26 were 48 and 38% in group 1 and group 2, respectively (P < 0.05), and those which had a normal induced cycle (16-17days) were 25 and 11% in group 1 and group 2, respectively (P < 0.05). Fertilities were higher (P < 0.05) for ewes in group 1 than in group 2 (91.17 vs. 75.75% and 97.1 vs. 81.8% for fertility at induced estrus and total fertility, respectively). It is concluded that a timed supplementation starting 3weeks before introduction of rams is effective in yielding high reproductive performance for the prolific strain of the Barbarine breed.

Estimation of risk factors associated with difficult birth in ewes

In eight closely recorded Australian Merino and crossbred sheep flocks, all lamb deaths were examined and the cause of deaths identified if possible. Dystocia was identified as one of the major causes of lamb death and this study examined factors that could be used to identify ewes at high risk of dystocia, either to avoid dystocia or to assist with early intervention where possible. Dystocia was least common in lambs of ~4.8 kg, but there was a higher risk at both lower and higher birthweights. Dystocia with both low and high birthweight was more common in older ewes, ranging from negligible low birthweight dystocia in ewes less than 3 years old at lambing, to 5% in older ewes. Low birthweight dystocia increased with increasing litter size, with 40% dystocia in ewes at least 4 years of age with triplets. In contrast, high birthweight dystocia was not affected by litter size. A previous record of low birthweight dystocia was a risk factor for future low birthweight dystocia, but the same relationship was not observed for high birthweight dystocia. A high lambing ease score (difficult birth) with high birthweight was a risk factor for future high birthweight dystocia, but this was not the case for low birthweight dystocia. These differences between the risk factors for low and high birthweight dystocia suggest that they have different causes. High ewe liveweight and condition score during pregnancy may be additional indicators of the risk of dystocia, particularly for ewes with high liveweight in the first 60 days of pregnancy. For most ewes dystocia was difficult to predict, but there was a small proportion of ewes with a very high risk of dystocia and if these could be identified in advance they could be monitored much more closely than the rest of the flock.

Lambing rate and prolificacy in inseminated hair sheep treated with bovine somatotropin.

This study evaluated whether the administration of 50 and 100 mg bovine somatotropin (bST) at the start of estrous synchronization and at the time of artificial insemination improves lambing rate and prolificacy in hair sheep. Four hundred eighty adult hair ewes (Pelibuey, Blackbelly, Dorper, Katahdin, and their crosses) were synchronized with intravaginal sponge containing 40 mg of fluorogestone acetate. On the day of sponge insertion, ewes were assigned to three treatments: the bST-100 treatment (n = 156) received 100 mg bST at the start of synchronization (d 0) and at the time of insemination (d 14), the bST-50 treatment (n = 159) received 50 mg bST in the same schedule as the previous group, and the control (n = 165) did not receive any bST. Lambing rate and percentage of multiple births were analyzed using the GENMOD procedure of SAS. Prolificacy data were analyzed using the MIXED procedure of SAS. The IGF-1 and insulin concentrations were analyzed with ANOVA for repeated measures. The bST application did not affect the lambing rate (P = 0.06). The proportion of ewes with multiple births (P = 0.01) and prolificacy (P = 0.04) were higher in the bST-50 (54.3% and 1.57 ± 0.1) than the bST-100 (18.2% and 1.25 ± 0.1) and control (33.3% and 1.28 ± 0.1) groups. The IGF-1 and insulin concentrations were higher (P < 0.05) in the bST-treated groups, but the insulin concentration was higher (P = 0.001) in the bST-100 group than in the bST-50 group. The administration of 50 or 100 mg bST at the start of synchronization and at the time of artificial insemination does not increase lambing rate. However, the dose of 50 mg increased the proportion of multiple births and prolificacy.

Strategic Feeding Alternating a 2-months’ Feeding Restriction and a Short Boost of the Feeding Level Increases Conception Rate in Sheep

&lt;p class="1Body"&gt;This study aimed to investigate if feeding patterns prior to and after artificial insemination (AI) affect the reproductive performances of ewes. Two breeds were used; the Barbarine (n = 133) and Queue Fine de l’Ouest (QFO; n = 129). For each breed, 2 experimental groups balanced for age and live weight were formed. For 75 days before AI, ewes in treatment High daily grazed for 6 hours and were supplemented with 0.6 kg of concentrate. For those in treatment Low-High, grazing was restricted to 3 hours only. From 21 days before insemination and the following 20 days, feeding pattern for Low-High ewes was switched to the High feeding regime. Changes in live weight and ovarian activity were monitored; conception rate and litter size were recorded. At the end of the restriction period and for both breeds, Low-High ewes reached lower live weights than High ewes (p &amp;lt; 0.05). Prior to AI and for both breeds, Low-High ewes weighed less than those in the High treatment group but no statistical differences were observed. At the end of the restriction period, more QFO ewes were cycling than for the Barbarine breed (75/129 vs. 55/133; p &amp;lt; 0.01). Further, less QFO ewes in the Low-High treatment were cycling than High ewes (30/65 vs. 45/64; p &amp;lt; 0.01). More QFO ewes conceived to AI than Barbarine counterparts (77/112 vs. 73/130; p &amp;lt; 0.05). For both breeds, higher proportions of ewes in the Low-High treatment groups conceived to AI but differences reached statistical significance only for Barbarine breed. Following a food-restriction period between weaning and mating, improved conception rates are achieved if the plane of nutrition is increased few weeks prior to and after AI in comparison to a continuous increase in live weight during the same period.&lt;/p&gt;

Reproductive seasonality in creole hair sheep in the tropic

The objective of the present study was to evaluate the annual ovulatory activity of hair sheep at 15° N. Nineteen Creole ewes with body weight of 40.8 ± 0.3 kg were used. The ovulatory activity was monitored for a year by quantifying progesterone concentrations in blood samples obtained from all the ewes every 7 days. The differences in monthly proportions of ewes with ovulatory activity were analyzed by the chi-square test. Ovulatory activity decreased from May to July and in September, and 42% of ewes ovulated year round. It is concluded that at 15° N, a high proportion of ewes is capable of ovulating throughout the year in the tropical southeastern region of Mexico.

Relationships among Puberty, Muscle and Fat, and Liveweight Gain during Mating in Young Female Sheep.

Greater depths of muscle are associated with better reproductive performance in ewe lambs, but, in adult ewes, reproductive performance also seems to vary with liveweight gain during the mating period. Therefore, in a large field study with Merino ewe lambs, we tested whether the relationships among eye muscle depth (EMD), fat depth (FAT) and reproductive performance depend on liveweight gain during the mating period. We selected lambs with a wide range in phenotypic values for depths of eye muscle (EMD) and fat (FAT) and assigned them to dietary treatments designed to achieve low (LOW, n=244) or high (HIGH, n=237) rates of liveweight gain during a 28-day mating period. The LOW treatment maintained live weight, whereas the HIGH treatment gained 179±3.8g/day (p<0.001). From those ewe lambs that attained puberty, first oestrus was detected at live weight 37.8±0.2kg and age 232days. The proportion of ewes that attained puberty increased with EMD (p<0.01). Ewes from the HIGH treatment were more fertile (pregnant ewes per 100 ewes exposed to rams) and had a higher reproductive rate (foetuses in utero per 100 ewes exposed to rams; p<0.001) than those from the LOW treatment. Fertility and reproductive rate were positively correlated with weight gain during mating as well as live weight at the start of mating, FAT and EMD (p<0.05 to <0.001). We conclude that faster growth, due to either extra nutrition during mating or higher phenotypic potential for fat and muscle, will increase reproductive performance in ewe lambs mated at 8months of age.

Initial experiments with an electronic feeding station for ewes

Through four different experiments we investigated the effect of design of an electronic feeding station (EFS) and management factors on the behaviour of ewes. Eighty-nine percent of the ewes had completed their first visit to the EFS within the first six hours, but a major proportion of all rewarded visits were interrupted by displacements. The entrance-exit gate eliminated displacements, but also discouraged some ewes from entering the EFS. Neither reduced access to roughage nor enclosing the ewes around the feeding station increased the proportion of ewes visiting the EFS. Of the different training methods investigated the method of gently pushing the animals into the EFS was successful for older ewes. For young ewes, spreading small amounts of concentrates inside the EFS worked better. In conclusion, sheep can learn to use an EFS for obtaining concentrates, but an entrance – exit gate is essential to protect the feeding ewe.