Oestrous Ewes Research Articles

Comparison of four strategies of ram management in a semen collection centre.

Thirty Merino rams were used to determine the effect of four management systems of rams on semen quality during the anoestrous season. Animals were divided into four groups: Artificial-Photoperiod group (AP; n=8), which were isolated from females and exposed to artificial long days (16hr/d) from 1 Feb to 15 Mar; Natural-Photoperiod (NP; n=8), isolated from females and exposed to the natural photoperiod throughout the experiment; Oestrous-Ewe group (EE; n=7), housed in a pen adjacent to another pen that housed three ewes in oestrus, and Anestric-Ewe group (AE; n=7), housed adjacent to another pen that housed three ovariectomized ewes. From 20 Mar to the end of May (10weeks), semen samples were collected weekly, and blood samples were collected to determine plasma testosterone concentrations. Mean plasma testosterone concentrations, ejaculate volume and reaction time were not affected either by treatment or week. There was a significant effect (p<.01) of ram treatment on sperm concentration, and both TM y PM, and their interaction, were significantly affected by group and week (p<.001). Rams exposed to ewes in oestrus presented the largest sperm concentration (p<.05) compared with the other three groups, although they had the lowest total and progressive motilities (p<.01). In conclusion, management strategy in spring affects semen quality of rams, with the presence of ewes in oestrus being the best plan to increase sperm concentration.

Effect of adding carrots as feed supplementation on reproductive performance in Awassi ewes

The present study was designed to estimate the effect of carrots supplementation on reproductive performance in ewes. Thirty Awassi ewes. Ewes were randomly divided into three equal groups, distributed as 10 ewes for each group. First group consider as control, second group feed 400 g carrot/animal daily, third group feed 800 g carrot/animal daily. Each group were synchronized with intra vaginal sponges and injected with 400 IU of eCG at the time of sponge withdrawal. Estrus ewes were conceived naturally with rams and pregnant ewes were followed until parturition. The results of current study demonstrated that G3 had high estrus response and fertility rate 90% compared with G2 and control 80 and 70% respectively. Fecundity rate increased significant in G3 200% compared to G2 and 125 and 100% respectively. Ewes in G3 showed the highest multiple lambing rate 66.67% compared with G2 25% and control 0%. Blood progesterone concentration was high increasing at the 18th day of estrus in the ewes for G3 and G2 compared with control, also, estrogen level at the day of estrus showed high increasing in G3 compared with G2 and control group. We concluded that carrots fed as a supplementation have essential effect on enhancement of reproductive performance in ewes.

Effect of Dorper Rams’ Social-Sexual Hierarchy on Their Sexual Behavior and Capacity to Induce Estrus in Ewes

This study aimed to assess the influence of the social rank of rams and quality of stimuli to ewes between dominant and subordinate Dorper rams joined to anestrus ewes. Social rank was evaluated for two days (ESR; n = 36); rams were exposed to estrogenized ewes in a competitive test. According to the reproductive response, anovulatory ewes (n = 76) were divided into two groups: LHRe (n = 38; ewes exposed to four low hierarchy rams (LHR)) and HHRe (n = 38; ewes exposed to four high hierarchy rams (HHR)). Regarding aggressive behaviors, HHR showed a higher (p &lt; 0.05) proportion of rams showing threatening, knocking, and blocking behaviors than LHR. Appetitive behavior was higher (p &lt; 0.05) in HHR than LHR rams (3576 ± 0.7 vs. 3054 ± 0.7 number of events). Consummatory sexual behavior was higher (p &lt; 0.05) in HHR than LHR (499 ± 0.3 vs. 205 ± 0.1 number of events). Indicators of sexual inactivity (SRI) were similar between HHR and LHR (499 ± 0.3 vs. 433 ± 0.1; p &gt; 0.05). The estrus response (&gt;80%; p &gt; 0.05) and ovarian response (70%, p &gt; 0.05) were similar for both groups of ewes. It was concluded that LHR are equally effective as HHR in inducing sexual activity in ewes showing postpartum anestrus.

Social Stress during the Estrus or Luteal Phase in Sheep

ABSTRACT In mammals, progesterone and estrogens affect the stress response. The study aimed to compare the physiological and behavioral responses to the social isolation of ewes during the estrus or luteal phase. Estrous and diestrous ewes (n = 10 and 8 respectively) were individually isolated in a novel place for 10 min. Ewes’ behavior was recorded during the test. Cortisol, blood proteins and glucose concentrations, and the skin surface temperature were determined before and after the test. Cortisol increased immediately after the test ended (P = 0.02). Serum total protein (P = 0.02), globulin (P < 0.0001), and plasma glucose (P = 0.006) concentrations were greater in estrus than in the luteal phase. The abdominal skin surface temperature was greater during estrus than during the luteal phase (P = 0.02). Ewes in estrus spent more time standing up immobile than ewes in the luteal phase (P = 0.05). In conclusion, the physiological and behavioral responses changed according to the phase of the estrous cycle. These results highlight the need for future studies focusing on how reproductive status influences the stress response to different management practices in sheep.

Identification of lncRNAs Differentially Expressed during Natural and Induced Estrus in Sheep

Background: The manipulation of the estrous cycle or induction of estrus is a commonly used technique in sheep industry. The goal of this study was to identify and characterize differences of non-coding RNAs (lincRNAs) expression between induced estrus and natural estrus using the BGISEQ-500 plat form in 7 Mongolian sheep, which will provide insights into the regulation mechanisms of lncRNAs in different reproduction mode of sheep. Methods: During the late spring, ovarian, pituitary, hypothalamic, pineal and uterine tissue samples were collected from four artificially induced estrus and three naturally estrus Mongolian sheep. Total RNA was extracted from the five tissues using TRIzol reagent (Invitrogen) and treated with DNase I following the manufacturer’s instructions. A total of 35 sheep samples were sequenced using the BGISEQ-500 plat form. Bioinformatics methods were used to analysis expression difference analysis between groups, SNP and InDel, alternative splicing, lncRNA’s miRNA precursor prediction, lncRNA target gene and family prediction. Result: 211 novel lncRNAs were systematically identified using RNA-Seq technology. Meanwhile, we found that there are diversifications of lncRNAs in induced estrus vs. nature estrus of ewes. Therefore, we predict that, under the action of exogenous hormones, many physiological processes of ewes may be affected to varying degrees through the change of LncRNA to a variety of pathways.

PSX-28 Using estrus detection patches or a ram wearing a marking harness to monitor estrus in synchronized hair sheep ewes

Abstract Determining when a ewe is in estrus is important when using estrous synchronization and artificial insemination in sheep. This study was conducted to compare the efficacy of estrus detection patches (Estrotect™) and rams wearing marking harnesses for monitoring estrus in synchronized hair sheep ewes. St. Croix White (STX) ewes (3.5 ± 0.3 y of age, 89.7 ± 2.2 d post-partum) were synchronized using progesterone releasing inserts (Eazi-Breed™ CIDR) for 12 d. On the day of CIDR removal (d 1) ewes were administered prostaglandin (Lutalyse®; 15 mg i.m.) and placed with fertile STX rams in 0.55 ha pastures. One group of ewes (n =10; MH) was placed with a ram wearing a marking harness and a second group (n = 16; EP) had estrus detection patches placed on their rumps before being placed with a ram without a harness. Estrus detection was conducted using visual observations twice a day through d 7. A ewe was considered to be in estrus when crayon marks were observed on the rump or the patch was activated, based on product guidelines. Cumulative percentage of ewes in estrus was analyzed using the CATMOD procedure with treatment, day and the interaction in the model. All patches stayed in place on the EP ewes through d 7. By d 4 90% of MH ewes and 75% of EP ewes had been observed in estrus (P &amp;lt; 0.05). By d 7 90% of MH ewes and 81.25% of EP ewes had been observed in estrus (P &amp;lt; 0.05). With costs of $1.33 per patch or $29.33 for one harness and crayon the patches may be more economical when dealing with up to 21 ewes per ram. Estrus detection patches can be used on hair sheep ewes to detect estrus just as effectively as a ram with a marking harness.

78 Evaluation of extended hair sheep ram semen stored as liquid at 5°C

Abstract This study was designed to evaluate the quality of extended hair sheep ram semen stored as a liquid at 5°C. St Croix White (STX; n = 6) and Dorper x STX (DRPX, n = 5) rams were collected weekly for 3 wk using estrus ewes fitted with an intravaginal collection vial. Semen was kept at 32°C during transport to the lab and during processing. Semen was evaluated for percent motility (MOT), viability (LIVE) using eosin-nigrosin stain and concentration using a hemocytometer counting chamber. Semen was extended to a final concentration of 250 x 106/mL in a one-step dilution with a skim UHT milk extender with 10% egg yolk by volume and packaged into 0.5 mL straws. Straws were stored in a styrofoam box in a refrigerator at 5°C for 96 h, or in an Equitainer® set up using the manufacturer’s instructions, for 24 h at which time they were transferred to the styrofoam box in the refrigerator for 72 h. Semen was evaluated for MOT and LIVE at -1, 0, 24, 48 72 and 96 h relative to cooling. Semen traits were analyzed using GLM of SAS for repeated measures with ram, time, breed and cooling method in the model. There was no difference (P &amp;gt; 0.10) in MOT or LIVE over time between breeds or cooling method. One STX ram did not produce any samples that survived extension; one STX and four DRPX rams produced at least one sample that did not survive extension and all were removed from analysis. The MOT decreased (P &amp;lt; 0.0001) from 81.7 ± 2.9 % at -1 h to 52.2 ± 2.9% at 96 h. The LIVE decreased (P &amp;lt; 0.0001) from 83.1 ± 3.6% at -1 h to 50.4 ± 3.6% at 96 h. These results show that ram semen stored as a liquid at 5°C can maintain motility and viability for 96 h. Further studies will be conducted to evaluate cooling of extended ram semen and fertility after artificial insemination.

Reusing intravaginal progesterone releasing devices for oestrous synchoronization in ewes

In this study, the second use of an intravaginal progesterone-releasing device or controlled intravaginal drug release device (CIDR) was evaluated. After a first use of 11 days, the CIDR was again used for either nine or 12 days with 200 or 300 IU equine chorionic gonadotrophin (eCG) being injected on its removal. Sixty-four ewes were randomly distributed to four treatments (n=16/group): CIDR9+eCG200, CIDR9+eCG300, CIDR12+eCG200, and CIDR12+eCG300. The eCG was administered intramuscularly on withdrawal of the device. Thus, the experiment was a completely randomized design with a 2×2 factorial arrangement of treatments. Oestrus presentation did not differ between treatments (P =0.29). However, with the dose of 200 IU of eCG, oestrus presentation tended to increase (P =0.08). The onset and duration of oestrus, percentage of gestation, and return to oestrus did not differ between treatments (P &gt;0.05). Progesterone concentration in serum was greater (P &lt; 0.05) in ewes treated with CIDR12+eCG300. Prolificacy was greatest (1.44) with the CIDR12+eCG300 treatment and was different (P = 0.001) from the treatments CIDR9+eCG200 (1.21) and CIDR9+eCG300 (1.20), but not from the CIDR12+eCG200 treated ewes (1.31). The CIDR12+eCG300 treatement produced the highest percentage of twin births (45.8%) (P =0.001). Leaving the device in place for 12 days increased (P =0.001) the incidence of twin births. Use of the CIDR for a second time synchronized oestrus in ewes successfully with better fertility being obtained when the device was left in place for 12 days, and 300 IU of eCG was injected on its removal.&#x0D; Key words: gonadotropin, progesterone device, synchronization

Effects of flaxseed-rich diet on reproductive performance in estrous-synchronized Baluchi ewes.

The purpose of this study was to compare the effects of using different levels of flaxseed in diets on the reproductive performance of estrous-synchronized Baluchi ewes (para 3). Diets contained either basal diet (control) or different levels of extruded flaxseed (2%, 5%, 7%, 10%, and 12%) and were fed from lambing to 60 days after lambing. The ewe estrus cycles were synchronized using controlled internal drug release (CIDR) for 14 days starting from day 16 of fat supplementation. The rams were introduced 24 h after CIDR removal. The ewes fed control diets had the highest mean dry matter intake (1,800&amp;plusmn;35 g) which was declined with the increase of flaxseed levels. The experimental diets exerted no effects of urea concentration in blood plasma. However, plasma glucose concentration was lower (p &amp;lt;0.05) in the ewes fed the control diet and 2% flaxseed, compared to those in other groups. Nonetheless, there was no difference among the ewes fed 5%, 7%, 10%, and 12% flaxseed in terms of plasma glucose concentrations (p &amp;lt;0.05). The ewes fed 2% flaxseed had the highest level of plasma triglyceride concentration among other groups. In addition, the control group had the lowest level of plasma total cholesterol and low-density lipoproteins concentration in comparison to other groups (p &amp;lt;0.05). However, plasma nonesterified fatty acids and &amp;beta;-hydroxybutyrate concentrations were similar among the groups (P&amp;gt;0.05). The mean interval between CIDR removal and the exhibition of estrus ranged from 30 to 40 h with the shortest interval being recorded in the ewes fed 12% flaxseed (p &amp;lt;0.05). The control group had the lowest number of follicles on estrus day among other groups (p &amp;lt;0.05). Furthermore, the ewes fed 10% and 12% flaxseed had the highest ovulation, pregnancy, and lambing rates, compared to other groups (p &amp;lt;0.05). In conclusion, the findings revealed that feeding the ewes with 10% and 12% flaxseed resulted in the improvement of reproductive performance.

Comparative DNA methylome analysis of estrus ewes reveals the complex regulatory pathways of sheep fecundity

Background/aimsSheep are important livestock with variant ovulation rate and fertility. Dorset sheep is a typical breed with low prolificacy, whereas Small Tail Han sheep with FecB mutation (HanBB) have hyperprolificacy. Our previous studies have revealed the gene expression difference between the ovaries from Dorset and HanBB sheep contributes to the difference of fecundity, however, what leads to these gene expression difference remains unclear. DNA methylation, an important epigenetic process, plays a crucial role in gene expression regulation.MethodsIn the present study, we constructed a methylated DNA immunoprecipitation combined with high throughput sequencing (MeDIP-seq) strategy to investigate the differentially methylated genes between the Dorset and HanBB ovaries.ResultsOur findings suggest the genes involved in immune response, branched-chain amino acid metabolism, cell growth and cell junction were differentially methylated in or around the gene body regions.ConclusionsThese findings provide prospective insights on the epigenetic basis of sheep fecundity.

Non Hormonal Induction of Oestrus in Nellore Ewes

A non hormonal induction of synchronization of estrus in ewes of Nellore breed, in two seasons June-July and September – October, covering 39980 and 42370 ewes respectively, spread over 2015 to 2019, with micro minerals (Bioplex High Seven), after onset of monsoon and deworming the sheep, appropriate to the season and type of prevailing parasitic infection, were studied. All the supplemented ewes came to estrus within a week, and were bred with stud rams. After the completion of gestation period all the ewes were lambed within a week uniformly. This may be due to elimination of stress due to environment, nutrition, parasites, replenishment of minerals and stimulation of folliculogenesis with Bioplex. The current extension method induction of estrus is safe, economical, easy to adopt and eco-friendly.

Using Progesterone and Prostaglandin F2α for Ewes Estrus Synchronization during Summer Season in Egypt

This study was carried out to investigate the effect of administration of progesterone (P4) and prostaglandin F2α (PGF2α) hormones on ewe estrus synchronization during summer season in Egypt. The study was performed on thirty four non-pregnant or lactating local ewes, 2 - 4 years old and 42.1 ± 1.8 kg average live body weight. Ewes were randomly divided into three groups as follows: natural estrus (control n = 10), intervaginal progesterone sponges (P4 = 12 ewes) for 12 days and two injections of PGF2α (12 ewes) 12 days apart. Parameters of estrus, conception and body weight of lambs were measured. Results showed that the percentage of estrus signs exhibition in PGF2α group reached 83.3%, while the lowest percentage (60%) was observed in control group (P<0.05). The time of starting estrus was earlier (P<0.05) in PGF2α and P4 groups (44.8 and 46h, respectively) than that in control group (58.4 h). The estrus duration was significantly longer (P<0.05) in PGF2α and P4 groups (44 and 41.6 h, respectively) than control group (31.2 h). The percentages of pregnant and lambing rates were 100% in all animals came to heat in all groups. While pregnancy rates and lambing rates according to initial number used were 83.3, 75% and 60% for PGF2α, P4 and control groups (P<0.05), respectively. The litter size, birth weight and weaning weight of lambs born did not differ significantly among groups. Weaning rate was the highest (P<0.05) in PGF2α group (92.9%) and the lowest in P4 group (85.7%). The percentage of ewes lambed twins was the highest (P<0.05) in P4 group (56%) and the lowest percentage in control group (33%). The percentage of male lambs was the highest (P<0.05) for ewes in PGF2α group (57.1%) and the lowest for ewes in control group (37.5%). In conclusion, PGF2α and P4 protocols could adequately induce estrus synchronization and improve some reproductive and productive traits in local ewes during summer season in Egypt. Further studies are recommended to proof results using more number of ewes.

Reversible Techniques of Ruffian in Sheep (Ovis aires)

Background: The use of teaser rams is an essential practice for detecting estrus in ewes as well as for accelerating puberty and synchronizing ovulation in the animal. There are several methods for preparing teasers, and the method used should be based on an assessment of the producer’s requirements. The ideal technique should be low cost and safe, ensuring the non-fertilization of ewes. This study evaluated the feasibility and effectiveness of two reversible teaser preparation techniques using a reversible plastic clamp. The techniques were compared in terms of functionality, possible post-surgical complications, and hematological changes of the rams as well as durability and reversibility.Materials, Methods &amp; Results: Twelve healthy rams, aged 14-20 months, were divided into two groups (G1 and G2). Blood samples were collected through the jugular vein to perform the following analyses: blood count, total plasma protein, and fibrinogen. Following local infiltrative anesthesia with 5.0 mL 2% lidocaine without vasoconstrictor, the procedure was performed as follows: in G1, the preputial ostium was partially closed, and in G2, sigmoid flexure was performed in the cranial region, approximately 5-8 cm immediately caudal to the scrotal sac. In the postoperative period, 20 mg/kg oxytetracycline and 2.2 mg/kg flunixinmeglumine were intramuscularly administered as a single dose. The wounds were dressed, sprayed with repellent, and allowed to heal for seven days. The procedures in both groups were simple to perform, low cost, and low risk; caused minimal tissue injury; enabled rapid recovery; promoted little or no stress to the animals; are reversible; and left no complications. The animals of both groups satisfactorily identified the females in estrus during the three-month experimental period, maintained libido, and failed to mate with any female. The blood count levels remained within normal range in both groups evaluated at different time intervals. Hyperfibrinogenemia was observed in four animals of G1 and in three animals of G2 at T2, with a mean level of 600 mg/dL. However, the values returned to normal at T3 in both G1 and G2, when the mean observed fibrinogen level was 400 mg/dL.Discussion: Since these are simple, rapid procedures with low tissue injury and a simple anesthetic protocol, the animals showed rapid recovery, without intra or postoperative complications, enabling the immediate initiation of work. The techniques, therefore, demonstrate several advantages over the other techniques described above. It is estimated that the techniques used in this study are more economically viable than other techniques described in the literature, which require medium to high complexity procedures and long postoperative treatments and carry the risk of affecting the animal’s libido, making the animal unviable and more liable to be disposed. However, disposing of such animals represents great losses, as it interferes with the reproductive management and pregnancy of several females on the farm. In addition, the conventional techniques are irreversible, which means that these animals cannot be used for other purposes. The reversible techniques presented in this study allowed the teasers to successfully identify females in heat without mating with them because there was no exteriorization of the penis. The results of the blood count confirm that the procedures did not generate extensive tissue lesions, stress, pain, inflammation, or infection.

The continuous presence of ewes in estrus in spring influences testicular volume, testicular echogenicity and testosterone concentration, but not LH pulsatility in rams

The continuous presence of active male small ruminants prevents seasonal anestrus in females, but evidence of the same mechanism operating from the females to the males is scarce. This study assessed the effects of the continuous presence of ewes in estrus in spring on ram sexual activity, testicular size and echogenicity, and LH and testosterone concentrations. On 1 March, 20 rams were assigned to two groups (n = 10 each): isolated (ISO) from other sheep, or stimulated (STI) by 12 ewes, which were separated from the rams by an openwork metal barrier, allowing contact between sexes. Each week, four ewes were induced into estrus by intravaginal sponges. Live weight, scrotal circumference, testicular width (TW) and length (TL) were recorded at the beginning and at the end of the experiment, and testicular volume (TV) was calculated; at the same time, testicular ultrasonography and color Doppler scanning were performed. Blood samples (March to May) were collected once per week for testosterone determinations, and at the end of the experiment, blood samples were collected for 6 h at 20-min intervals for LH analysis. Rams were exposed to four estrous ewes in a serving-capacity test. Scrotal circumference, TW and TL were higher in the STI than in the ISO rams (P < 0.05) in May, and TV was higher (P < 0.05) in the STI (391 ± 17 cm3) than in the ISO rams (354 ± 24 cm3). In ISO rams, the number of white pixels was higher (P < 0.01) in May (348 ± 74) than in March (94 ± 21) and differed significantly (P < 0.01) from that of the STI rams in May (160 ± 33). In ISO rams, the number of grey pixels was higher (P < 0.05) in May (107 ± 3) than it was in March (99 ± 1). Stimulated and ISO rams did not differ significantly in mean LH plasma concentrations (0.8 ± 0.5 v. 0.9 ± 0.4 ng/ml), LH pulses (2.1 ± 0.5 v. 2.2 ± 0.2) and amplitude (2.0 ± 0.4 v. 3.2 ± 0.7 ng/ml, respectively). Stimulated rams had significantly higher testosterone concentrations than ISO rams from April to the end of the experiment. Stimulated rams performed more (P < 0.05) mountings with intromission (3.0 ± 0.4) than did ISO rams (1.5 ± 0.5). In conclusion, after 3 months in the continuous presence of ewes in estrus in spring, rams had higher TV and some testicular echogenic parameters were modified than isolated rams. Although exposed rams also had higher levels of testosterone after 2 months in the presence of estrous ewes, their LH pulsatility at the end of the study was not modified.

225 Evaluation of superovulatory response in Brazilian native sheep by B-mode ultrasonography

The objective of this study was to evaluate the correlation between the number of corpora lutea (CL), as determined by B-mode ultrasonography, and the total number of structures recovery by non-surgical embryo recovery (NSER) from superovulated ewes. Somali (n=18), Santa Inês (n=18), and Morada Nova (n=16) ewes received an intravaginal device with progesterone (0.33g, controlled internal drug release device, CIDR, Zoetis), which was maintained for 9 days. The superovulatory protocol started 60h before device removal, with 6 decreasing doses (25, 25, 15, 15, 10, and 10%) of p-FSH (IM 133mg, Folltropin V, Vetoquinol) injected every 12h. D-Cloprostenol (IM 37.5μg, Prolise, Agener Union) was injected 12h before and at the moment of device removal. Ewes in oestrus were mated by fertile male rams three times after the onset of oestrus with a 12-h interval. Flunixin meglumine (24.9 mg; Banamine, MSD Animal Health) was injected IM on Days 12, 13, and 15. One day before NSER, B-mode ultrasound evaluations were performed using portable equipment (Z5 Vet, Mindray) with a stiffened multifrequency linear probe to evaluate the number of structures present in the ovaries. Embryo recovery was performed 7 days after progesterone CIDR removal (Day 16). The number of CL and the number of recovered structures were determined and their association evaluated using the Pearson correlation test (P&amp;lt;0.05). Only 17 Somali, 16 Santa Inês, and 15 Morada Nova ewes were submitted to NSER; the other 4 ewes could not be flushed because of low cervical dilation or cervical puncture. After B-mode ultrasound evaluation, 168, 217, and 131 CL were observed, with an average of 9.9 (range: 1 to 12), 13.5 (range: 2 to 47), and 8.7 (range: 3 to 18) CL per donor for Somali, Santa Inês, and Morada Nova ewes, respectively. The recovery rates (i.e. structures recovered by the number of CL counted) were 60.1% (101/168), 96.3% (209/217), and 103.5% (135/131) for the 3 breeds, respectively. There was a positive correlation (r=0.69; P&amp;lt;0.01) between the number of recovered structures and number of CL. Those findings confirm results from other studies, in which the recovery rate varied from 35 to 91%. In some cases, recovery rate can be overestimated because of the difficulty in quantifying CL. In conclusion, B-mode ultrasonography can be used to estimate superovulatory response in ewes and thus as a criterion to decide whether a donor will undergo embryo flushing. Financial support for this study was provided by Embrapa (02.13.06.026.00.04) and Fapemig (CVZ-PPM 00201-17).

Ewes express increased proceptive behavior toward high-sexually active rams

Variable expression of male reproductive behavior has been observed in all species studied. Approximately 25% of male sheep exhibit low sexual interest, but usually mate and have limited numbers of offspring. In domesticated, promiscuous species like sheep, the female may have mate preference, but mate choice is usually constrained by breeding strategies. It was hypothesized that when mate choice is limited, ewes would exhibit more proceptive behavior toward rams with low sexual interest to ensure reproductive success. Recorded serving capacity tests (n = 56) were utilized for this analysis. Rams were individually exposed to two ewes in estrus with behavior recorded for 20 min. From those recordings, a 10 min time period was utilized to assess ewe proceptive behavior. Ram anticipatory and consumatory behaviors were recorded. Anticpatory behaviors included ano-genitial sniffs, vocalization, fore-leg kicks, head butts, and nudges. Consumatory behavior included mount attempts, mounts, and ejaculations. Rams were categorized as high performing if they achieved two or more mounts during the 10 min period. Ewe behavior was determined by the number of solicitation looks and movements toward and away from the ram. During the 10 min of observed behavior, time spent in close proximity (less than 0.3 m) to the ram was determined and considered time in affiliation with the ram. Percent of time spent in affiliation with high sexually performing rams was greater (P < 0.001) 57.7% (±3.3) than when exposed to rams exhibiting low sexual behavior (23.8% [±3.4]). Affiliation time was highly correlated (P < 0.001; r2 ≥ 0.6) with ram behaviors: number of mounts, total anticipatory, and consummatory behavior. High sexually performing rams garnered more (P < 0.001) solicitous looks from ewe than did low performing rams. Ewes exhibited increased number of purposeful moves toward (P = 0.02), but not away (P = 0.58) from, high performing rams. These data indicate that ewes express more proceptive behavior toward rams expressing greater sexual interest. In conclusion, ewe behavior does not compensate for low sexual interest from the ram and would not be expected to contribute to the reproductive success of rams expressing low sexual interest.

‘Surprise’ lambs 18 months after sterilisation of a teaser ram

The owner of a flock of a phenotypically distinct sheep breed purchased a ‘sterilised’ teaser ram to mark oestrus ewes for mating with purebred rams. Lambing in the subsequent year...

Effects of long-term controlled internal drug release reuse on reproductive performance, hormone profiles, and economic profit of sheep

ABSTRACT Fifty-seven multiparous Awassi ewes in the breeding season were used to compare the effects of controlled internal drug release (CIDR) reuse on hormone profiles, reproductive performance, and economic production. Ewes were randomly allotted to one of three CIDR treatments: new (control), once-used, and twice-used; treatment lasted 12 days. Blood samples were collected from all groups at the time of CIDR insertion, three and six days following insertion, at withdrawal time, and at insemination. Serum estradiol (E2) and progesterone (P4) concentrations were measured. Timed insemination was performed 48 h post CIDR withdrawal in all groups. Pregnancy was diagnosed by ultrasonography at day 23 post insemination. No significant differences were detected among groups in pregnancy rate/ewes in heat, twinning rate, fecundity, abortion rate, and prolificacy. However, estrus detection rate was significantly higher in control (100%) than in other groups. The P4 concentration was significantly higher in control than in other groups during treatment period; at insemination, P4 concentration was significantly higher in control than in other groups; at insemination time, E2 concentration was significantly higher in control than in the other groups; and the net profit was higher in once-used than in other groups. One-time reuse of CIDR for the long term (12 days) can synchronize estrus in ewes efficiently with higher net profit than the new or twice-used CIDR.

Effectiveness of a low-dose Norgestomet ear implant in short-term protocols to induce estrus in ewes during the non-breeding season in Brazil.

ABSTRACT The objective of this study was to evaluate the reproductive performance of ewes subjected to a short-term protocol for estrus induction using 1 mg of Norgestomet during the non-breeding season in Brazil. A total of 84 ewes were randomly divided into two equal groups (n = 42 per group). Controlled Internal Drug Release (CIDR) containing 330 mg progesterone was inserted into the vagina in the first 42 ewes, and for the other 42 ewes in the second group, 1 [...]

Seasonality in Saint Croix male lamb reproductive development in northern Mexico.

The aim of this study was to determine the influence of the season of birth on the body weight, testicular size, testosterone concentrations, semen output and sexual behaviour in Saint Croix male lambs. Thirty-three lambs were born in spring (n=10), summer (Sum; n=12) or autumn (n=11). Body weight and the scrotal circumference were weekly recorded; semen was also weekly collected by electroejaculation; and sexual behaviour towards oestrous ewes was weekly evaluated. Data were recorded from 15 to 33weeks of age. The reproductive development of Saint Croix male lambs differed according to the period in which they were born. More lambs born in spring than in summer and autumn achieved puberty during this study and were also more precocious in semen production and displayed sexual behaviour earlier. Lambs born in summer delayed their semen production; however, season-related negative effects were less pronounced at the end of the study than in autumn born lambs born. In conclusion, despite the apparently low seasonality of the breed, Saint Croix male lambs showed in this study a seasonal pattern in their reproductive development at least until they achieve the puberty.