Effects of strategic helminthosis control on age at first lambing and lambing interval of communally grazed Menz ewes in Ethiopia

A three-year longitudinal study was conducted to evaluate effects of strategic anthelmintic treatment regimes on age at first lambing (AFL), weight at first lambing (WFL) and lambing interval (LI) of 356 communally grazed ewes and 675 lambs owned by 10 smallholder farmers in the central highlands of Ethiopia. The ewes were stratified by weight and randomly allocated to three treatment groups as untreated control (TG1), twice-dosed per year (TG2) for both nematodes and trematodes in mid-January and mid-June and four-time-dosed per year (TG3) in June for nematodes, in August–September for nematodes and adult Fasciola, in November–December and January–February for immature flukes. The fixed effect of anthelmintic treatments, parity, season and year of lambing on AFL and LI was evaluated. Mean ± standard error (SE) of lambing interval was 292 ± 3 days. Both anthelmintic treatments (TG2 and TG3) shortened (P < 0.01) LI by about 23 days compared to non-treated ewes (TG1). Season and year of lambing had a significant (P < 0.001) effect on LI. Mean ± SE of AFL and WFL was 598 ± 10 days and 17.2 ± 1.37 kg, respectively. Anthelmintic treatments and parity of dam of the ewe lamb did not affect AFL (P > 0.05). Birth and lambing seasons of the ewe lamb had significant (P < 0.05) effect on AFL. On the other hand, lambing season of the ewe had significant (P < 0.05) effect on WFL. Ewe lambs born in the long rains lambed more than 50 days earlier than the ewe lambs born in short rainy and dry seasons. Lambing occurred year-round with two peaks in August–September and December–January, each 5 months after the two rainy seasons. Anthelmintic treatment at the beginning of the two rainy seasons should improve reproductive performance of Menz ewe lambs in similar agro-ecology in the central highlands of Ethiopia.     

The onset of puberty of Pelibuey male hair sheep is not delayed by the short term consumption of Morus alba or Hibiscus rosa-sinensis foliage

The present trial evaluated the effect of phytoestrogens consumed from Mulberry (Morus alba) or Hibiscus (Hibiscus rosa-sinensis) foliage, on the onset of puberty of Pelibuey male lambs. The design of the study aimed at identifying possible acute changes on the onset of puberty. Eighteen male lambs were used (107±9 days of age, 16±3 cm scrotal circumference (SC), 3.4±0.1 body condition score (BCS) and 17±1 kg bodyweight (BW)). At weaning, the lambs were distributed in three groups (n=6 each): (i) Control group (balanced feed based on grains+star grass), (ii) Mulberry Group (Mulberry foliage+balanced feed) and (iii) Hibiscus Group (Hibiscus foliage+balanced feed). BW, SC and body condition score (BCS) were determined every 14 days. An estrogenized adult female was used to attempt the collection of semen samples from the males two times per week. The onset of puberty was determined as the presence of sperm showing progressive movement in the ejaculate. From then, semen collections continued in the males (once a week) until the first normal ejaculate was obtained. The nutritional value of the foliages, as well as the content of total phenols, total tannins and condensed tannins, was determined. The phytoestrogen content (Equol, 4′7-dimetoxyisoflavone, Genistein, Rutin and Ononin) was determined from the methanolic extract of both plants. Total dry matter consumptions were similar between the Control and Mulberry groups and both were higher than the Hibiscus group (P<0.05). The total consumption of phytoestrogens and tannins was similar in the Mulberry and the Hibiscus group. The short-term consumption of phytoestrogens from Mulberry or Hibiscus foliage failed to delay the onset of puberty. The mean age at the onset of puberty was similar in the three groups (146 days in the control and Mulberry groups and 154 days in the Hibiscus group; P>0.05). The mean age at the first normal ejaculate was also similar between groups (167 days for Mulberry and Hibiscus groups and 169 days in the control group; P>0.05). The BW (Control: 21.6±3.1; Mulberry: 20.7±1.9; Hibiscus: 19.8±2.8 kg), the BCS and the SC were similar between groups at the onset of puberty. The present trial showed that a short exposure to M. Alba or H. rosa-sinensis foliage through diet did not influence the onset of puberty of Pelibuey male lambs.     

Comparison of Booroola Merino and Finnsheep: effects on productivity of mates and performance of crossbred lambs

Booroola Merino (BM) and Finnsheep (FS) rams were mated to FS and crossbred (CO) ewes to compare their effects on the productivity of their mates and the performance of their progeny. Effects of breed of ram and the interaction of breed of ram X breed of ewe were no significant for fertility, total number born, number born alive, litter birth weight, or number of lambs weaned by the ewe or in the nursery. Birth weights of FS- and BM-sired lambs were equal, but FS-sired lambs were heavier at weaning and 147 d of age. Compared with BM-sired lambs, survival from birth to weaning of dam-reared lambs was greater for FS-sired lambs produced by CO dams than for FS-sired lambs produced by FS dams. At a constant live weight, FS-sired lambs had a heavier carcass with less external fat thickness than BM-sired lambs. Percentage of ewe lambs reaching puberty was lowest and age at puberty was highest for the BM X CO cross; relatively small differences existed between the other three genotypes for these traits. Ewe lambs sired by BM had a greater ovulation rate than FS-sired ewe lambs. Embryo mortality was greater in BM X CO ewe lambs than in ewe lambs of the other three genotypes; the difference was larger for ewes with three ovulations than for ewes with two ovulations. The net result was that BM X CO ewe lambs averaged slightly fewer lambs born than FS X CO ewes. The BM X FS ewe lambs had larger litters than the FS ewes due to a substantially higher ovulation rate and only a slightly lower overall embryo survival rate. With the exception of ovulation rate and litter size, FS rams produced lambs with a more desirable level of performance than did BM rams.     

Analyses of parental and seasonal influences on the synchrony of dexamethasone-induced lambing and lamb characteristics

Synchronization of parturition in a commercial flock of sheep has many advantages including the maintenance of the efficiency of the operation as well as optimization of care for periparturient animals. In a research setting, using an ovine model for experiments involving the induction of parturition yields the results that can be applied to other mammalian species. In sheep, as well as in a variety of other farmed species, dexamethasone is the drug used to induce synchronized parturition at the end of gestation. However, considerable variations have been noticed in the time between induction and the onset of lambing. This study set out to determine the role that the breed of dam and sire, the age and reproductive history of ewes, the month of induction and the litter/lamb characteristics played in determining the time between dexamethasone treatment and parturition. The lambing was induced in 146 ewes (4 purebred Dorset, 19 purebred Rideau Arcott and 123 Rideau Arcott × Dorset ewes) using a single i.m. dose of 20 mg dexamethasone (Unidex^®, Univet Pharmaceuticals, Milton, ON, Canada) on day 140 of gestation. The ewe breed was weakly correlated (r = − 0.19, P < 0.05) whereas the sire breed was moderately correlated (r = − 0.37, P < 0.001) to the time between dexamethasone treatment and the onset of parturition (the breed in this study was defined as the % of the Rideau Arcott genotype). The time between induction and the onset of labour averaged 57.3 ± 5.3 h and 64.3 ± 8.2 h in February and April, respectively, and it was significantly longer (P < 0.05) compared with the times recorded in July, September and November (42.0 ± 2.0 h, 38.7 ± 2.8 h and 36.1 ± 5.0 h, respectively). There was a negative correlation (r = − 0.41, P < 0.001) between the proportion of ram lambs and the mean birth weight of ewe lambs. These results can be interpreted to suggest that the breed and time of the year may both affect the synchrony of dexamethasone-induced lambing. The reasons for the associations found between the month of induction and the time elapsed to the onset of parturition as well as between the proportion of ram lambs and birth weights of ewe lambs are not fully understood and warrant further studies.     

Immunization of Sheep Against GNRH Early in Life: Effects on Gonadotropins,Follicular Growth and Responsiveness of Granulosa Cells To FSH and IGF-I in Two Breeds of Sheep With Different Prolificacy (Romanov and ILE-DE-France)

The prolific Romanov (R, ovulation rate = 3) and non-prolific Ile-de-France (IF, ovulation rate = 1) breeds were compared for their ovarian sensitivity to gonadotropins and IGF-I before puberty. For this purpose, the effects of in vivo immunization against GnRH on populations of ovarian follicles and in vitro sensitivity of granulosa cells to FSH and IGF-I were studied in prepuberal lambs from both breeds. Seventeen prepuberal lambs of each breed were actively immunized against GnRH between 3 wk and 6 mo of age. Relative to untreated lambs, FSH levels at 4, 5, and 6 mo of age were (respectively) 41%, 25%, and 29% for IF, and 43%, 24%, and 36% for R lambs. In a first experiment, histological analysis of ovaries was performed. Immunization treatment decreased the number of small (100–390 μm in diameter) and large size follicles (<1500 μm) in both breeds at 6 mo of age. In both breeds, gonadotropin (FSH - LH -hCG) treatment increased the number of large size follicles (<1500 μm in diameter) and induced the formation of preovulatory follicles in immunized as well as untreated lambs. The ovulation rate was less in immunized animals, but it was not different between breeds. In a second experiment, the effects of FSH and IGF-I were studied on granulosa cells from follicles between 1000 and 2000 μm in diameter. In both breeds, IGF-I increased granulosa cell proliferation, but enhanced progesterone secretion was observed only in R lambs after FSH and IGF-I stimulation. Granulosa cell response to FSH treatment was lost by immunization, whereas response to IGF-I remained unchanged in both breeds. These results indicate that long-term immunization of prepuberal lambs against GnRH reduced systemic concentrations of FSH, follicular development, and response to gonadotropins in vivo, similarly in the prolific R and the non-prolific IF breed. However, granulosa cells from R lambs had higher steroidogenic capacities and were more responsive to FSH. In addition, these results suggest that IGF-I could play an important role in regulating growth of small follicles both in immunized and non-immunized lambs.     

The effects of allowance and frequency of allocation of autumn-saved pasture, when offered to spring lambing ewes in mid pregnancy, on ewe and lamb performance and subsequent herbage yield

The effects of (i) frequency of herbage allocation and (ii) herbage allowance on ewe and subsequent lamb performance, when autumn-saved (extended grazed, deferred grazed) pasture is grazed (between 28 Nov and 30 Jan) by spring lambing ewes during mid gestation, were studied in Experiment 1. This involved 72 crossbred ewes from days 41 to 104 of gestation allocated to one of four treatments; two herbage dry matter (DM) allowances (1.0 and 1.8 kg per ewe) by two frequencies of herbage allocation (daily or twice weekly). From day 105 of gestation to parturition all ewes were housed and offered grass silage (ad libitum) plus a total of 19 kg concentrate. Increasing herbage allowance improved ewe body condition score (P < 0.01) and live weight (P < 0.01) at the end of deferred grazing, and tended to increase herbage intake (P = 0.08) during deferred grazing. Reducing the frequency of herbage allocation increased lamb birth weight (P < 0.05). Otherwise frequency of herbage allocation did not alter (P > 0.05) forage intake or utilization, or ewe or subsequent lamb performance. In Experiment 2, the effects of herbage allowance (1.0 or 1.8 kg DM per ewe), frequency of allocation (daily, twice weekly) and grazing date (28 Nov. to 4 Dec., 12 to 18 Dec., 2 to 8 Jan. and 23 to 29 Jan.) during deferred grazing on herbage yield and composition at four subsequent harvest dates (4, 18 and 25 Apr., and 25 May) were evaluated in a split-plot design consisting of 128 plots. Delaying grazing date reduced herbage yield (P < 0.05) and the concentrations of neutral detergent fibre (NDF; P < 0.01) and acid detergent fibre (ADF; P < 0.01). Delaying harvest date increased herbage yield (P < 0.001) and reduced (P < 0.001) the concentrations of NDF, ADF and metabolisable energy. Increasing herbage allowance at grazing increased (P < 0.05) subsequent herbage yield. Frequency of herbage allocation during deferred grazing did not affect (P > 0.05) subsequent herbage yield. There was a significant interaction (P < 0.001) between grazing date and harvest date for herbage yield. It is concluded that to maximise stock carrying capacity and reduce labour requirement a herbage DM allowance of 1 kg per ewe per day, allocated twice weekly, is sufficient for ewes on deferred grazed pasture in mid pregnancy.     

Huizache (<Emphasis Type="Italic">Acacia farnesiana</Emphasis>) whole pods (flesh and seeds) as an alternative feed for sheep in Mexico

Two experiments were undertaken to evaluate the use of pods from Huizache (Acacia farnesiana), common in the arid and semiarid regions of Mexico, on the perfromance and apparent digestibility in Pelibuey Mexican hair growing ewe lambs. Twenty-four Pelibuey ewe lambs were used in the animal performance experiment, with a mean live weight of 14.91 ± 1.48 kg, randomnly allocated to three groups which received ad libitum for 77 days (11 weeks) experimental whole rations T0 with 0%, T12 with 12% or T24 with 24% inclusión of dried and ground Huizache pods. Dry matter intakes (g/kg ^0.75 daily) were 83, 95, 90 for T0, T12, and T24 respectively (P > 0.05). Mean daily live-weight gain was 90, 75, and 63 g/day for T0, T12, and T24 (P < 0.001). Nine Pelibuey ewe lambs were used to determine apparent digestibility in vivo of the experimental diets using a 3 × 3 latin square design repeated three times. There were differences in the digestibility of dry matter (P < 0.001), organic matter (P < 0.001), nitrogen (P < 0.031), neutral detergent fibre (P < 0.002), and acid detergent fibre (P < 0.001) being lower in T24. Huizache pods may be an alternative feed when included up to 12% of dry matter in the diets for sheep growing moderately.     

Frequent lambing of sheep flocks in Spain: productivity and management consequences

The first part of this paper reviews the Spanish literature dealing with the possibility of increased lambing frequency in Spanish flocks. Seasonal anoestrus occurs in all the Spanish breeds considered, although even in the most unfavourable month some sexual activity is observed, such as in Aragonesa flocks, where it reaches up to 80% in some years. The percentage of cyclical ewes in spring is favourably influenced by good feeding levels and by the introduction of males previously removed from the flock for a few months.In the second part we deal with the results obtained in several commercial farms in Aragon differing in mating management. No hormone treatments are used in these farms. In the farms where orderly and short matings are practised more lambings (1.39 vs. 1.29) and more lambs/ewe/year (1.76 vs. 1.40) are obtained than in those with continuous or nearly continuous mating periods. They can also choose the most favourable dates to obtain their lambs with regard to sale prices and ewe supplementary feed costs. In these conditions, Romanov × Aragonesa ewes give 40% more lambs/ewe than Aragonesa ewes without decreasing the number of lambings per year.     

Effect of ractopamine hydrochloride and zilpaterol hydrochloride on growth,diet digestibility,intake and carcass characteristics of feedlot lambs

The effects of the β-adrenergic agonists ractopamine hydrochloride (RH; 0.35, 0.70 and 1.05 mg kg^− 1 of BW d^− 1) and zilpaterol hydrochloride (ZH; 0.10, 0.20 and 0.30 mg kg^− 1 of BW d^− 1) on growth performance and carcass characteristics were determined in 84 Dorper × Katahdin lambs (12 lambs per treatment), that were randomly assigned to a complete block design during a 42-day feeding trial. Lambs were fed a corn grain-based diet (18.71% CP and 12.9 MJ/kg ME). Nutrient digestibility of diets and blood serum metabolites were also determined. There were no significant (P > 0.05) differences in growth characteristics by effect of ZH or RH administration. However, lambs final weight, total weight gain and ADG increased linearly (P < 0.05) as levels of both β-adrenergic agonist increased. RH or ZH administration did not affect feed efficiency, diet digestibility or particular blood serum metabolites of lambs. Carcass characteristics of lambs consuming ZH were significantly better (P < 0.01) than RH or control lambs; RH produced significant linear response on carcass weight, dressing percentage, longissimus muscle area, carcass conformation and quality grade, and improved quadratically (P < 0.05) fat thickness and USDA yield grade of lamb carcasses. On the other hand, increasing levels of ZH decreased linearly (P > 0.01) fat thickness and improved (P > 0.05) USDA yield grade and carcass quality grade. Both β-adrenergic agonists improved carcass characteristics; although greater improvements were obtained with ZH than RH for most carcass characteristics.     

Intra-uterine insemination with low numbers of frozen–thawed boar spermatozoa in spontaneous and induced ovulating sows under field conditions

The present study was conducted to evaluate non-return rate (NR), farrowing rate (FR), and number of total pigs born/litter (TB) of weaned sows after intra-uterine insemination (IUI) using low numbers of frozen–thawed (FT) spermatozoa. Semen from 6 boars was cryopreserved individually in a 0.5-ml straw, at a concentration of 1 × 10⁹ spermatozoa/ml. A total of 40 multiparous sows with weaning-to-estrus interval of 3 to 7 days were included. The sows were detected for standing estrus twice daily and randomly assigned to two groups: I) spontaneous ovulation (n = 20) and II) induced ovulation (n = 20) which the sows were given 750 IU human chorionic gonadotrophin (hCG) i.m. immediately at estrus detection. Ovulation was determined every 12 h using transrectal ultrasonography. FT semen containing 1 × 10⁹ motile spermatozoa/dose was used to IUI. In group I, the sows were inseminated at 24 h after the detection of estrus and repeated every 12 h until ovulation. In group II, the sows were inseminated at 36, 42 and/or 48 h after hCG treatment. The results showed that the interval from standing estrus to ovulation (EOI) differed significantly between group I (40.2 h) and group II (35.6 h; P = 0.01). Variation of EOI among sows within each group seemed to be lower in group II (4.5 h SD) than in group I (5.5 h SD; P = 0.5). The number of IUI per sow was 2.9 ± 0.6 times in group I and was 2.4 ± 0.5 times in group II. There were no significant differences (P > 0.05) in the NR (80 vs 85%), FR (60 vs 65%) and the TB (8.0 ± 2.8 vs 9.4 ± 3.7 piglets/litter) between the groups. These results indicated that multiple doses of IUI with a low number of FT boar spermatozoa provided a fairly good NR, and reasonable FR and TB both in spontaneous and induced ovulating sows. The number of inseminations required for attaining acceptable fertility tended to be lower in the weaned sows with induced ovulation.     

Number of mature follicles ovulating after a challenge of human chorionic gonadotropin in different breeds of sheep at different physiological stages

The ovulatory response of ewes from breeds that differ widely in prolificacy (Ile-de-France, ++ Booroola Merino, Romanov, F+ Booroola Merino and F+ Booroola Romanov with adult ovulation rates of about 1.5, 1.2, 3, 3 and 3.5 respectively) to 750 IU of hCG given at different physiological stages (before puberty, during anestrus or during the luteal phase) was compared. In all except one experiment, hCG induced ovulation in 73 to 98% of the lambs, indicating that follicles sensitive to LH were present at all stages studied. Ranking of the breeds according to hCG-induced ovulation rate in prepuberal lambs was similar to that based on adult ovulation rate. Furthermore, hCG induced more ovulations in prepuberal F+ than in ++ lambs (3.7 +/- 1.4 vs 1.7 +/- .8 at 4.5 mo of age) as well as in anestrous ewes (F + at 3.1 +/- 1.8 vs ++ at 1.6 +/- .7). Within ewes, the correlation between hCG-induced ovulation rate and mature ovulation rate was positive in nonprolific breeds but not significant in prolific breeds. We conclude that 1) the number of hCG-induced ovulations can be used to identify sheep that are carriers of the Booroola gene and 2) the mechanisms responsible for a number of large ovulatory follicles typical of a breed are present at stages (prepuberal, anestrus, luteal phase) other than the follicular phase.     

Onset of puberty and duration of the breeding season in Suffolk, Rambouillet, Finnish Landrace, Dorset and Finn-Dorset ewe lambs

Sixty ewe lambs, 12 each of Suffolk, Dorset, Finnish Landrace, Finn-Dorset and Rambouillet born in January and February were used in a study of puberty and duration of the first breeding season. Ovulation was monitored via progesterone assay of weekly blood samples beginning in July, and estrus via daily checking with vasectomized rams. All 60 ewes ovulated but three, one Dorset and two Rambouillet failed to show estrus although each had five to seven ovulatory cycles. Several ewes showed small progesterone rises, 300 to 500 pg/ml, before first ovulation and six (10%) failed to initiate regular cyclicity following the first ovulation as defined by progesterone greater than 500 pg/ml. Mean number of ovulatory events before the first behavioral estrus ranged from 1.25 for Finnish Landrace to 2.20 for Rambouillet ewe lambs (P less than .1). Rambouillets were older (277 d; P less than .05) at first estrus than Finns (258 d) and Finn-Dorsets (260 d), but differences in age at first ovulation were not significant: Finn-Dorset, 233 d; Dorset, 234 d; Finn, 235 d; Rambouillet, 240 d; Suffolk, 245 d. Most cycles were of normal length, with 91.4% between 14 and 20 d. Repeatability of cycle length within breed group was .38. Suffolks had significantly shorter cycles (16.1 d) than the other four groups (17.0 to 17.4 d). Finnish Landrace and Finn-Dorset ewes continued to cycle much longer than the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

The timing of the onset of puberty, extension of the breeding season, and length of postpartum anestrus in the female mouflon (Ovis gmelini musimon).

The timing of the onset of puberty, duration of seasonal ovulatory activity, and length of postpartum anestrus were studied by means of blood plasma progesterone concentrations in a flock of European female mouflons (Ovis gmelini musimon) maintained in captivity under natural photoperiod (40 degrees 25'N). Concentrations of progesterone in the peripheral blood were determined by radioimmunoassay in samples collected from the jugular vein twice a week. First ovulations in the breeding season were highly synchronized and occurred in mid-October. In contrast, the cessation of ovulatory cycles showed significant variation among females and extended from February to May, depending on age, with 2-yr-old animals exhibiting the longest anovulatory period (P < 0.01). When lambing occurred within the breeding season (February-April), 12 out of 26 animals had their first ovulation 25 +/- 1.8 days after parturition. The 14 late-lambing females had the first postpartum ovulation delayed until the next breeding season. March/April-born mouflon lambs that reached a minimum threshold body weight (23.8 +/- 0.6 kg) in their first breeding season reached puberty at 8 mo of age. In those with slower growth rates, however, the prepubertal period was extended throughout the first breeding and nonbreeding seasons, reaching puberty during the breeding season of the following year at 19 mo of age and 27 +/- 0.3 kg body weight. Further, attainment of puberty in ewe lambs born in June/July was also delayed until the breeding season of the following year, when animals had reached a threshold body weight at 17 mo of age.     

Differences in Reproductive Performance, Embryo Development, Interferon-tau Secretion by the Conceptus and Luteal Function in Ewe Lambs Synchronized in Oestrus before or after the Spontaneous Onset of Luteal Activity Preceding Puberty

In mid-September, 1 month before the insertion of intravaginal pessaries to induce sexual activity, blood samples were collected every 4 days from 16 ewe lambs aged 7 months, in order to determine the incidence of ovulations by measurement of plasma progesterone concentrations. It has been studied whether the response to a progestagen treatment of ewe lambs apparently close to puberty could be modified by the onset of the ovarian events preceding puberty. The effect of the presence or absence of ovulations prior to progestagen treatment on the potential reproductive performance (fertility, litter size and fecundity), embryo development [embryo quality and interferon-tau (IFNτ) secretion], luteal function (progesterone secretion in vitro ) and endometrial progesterone content was studied in seven ovulating (Ov+) and nine nonovulating ewe lambs (Ov−) on day 14 after mating. The best potential reproductive results were obtained with Ov+ animals, although these differences could not be initially attributed to either different progesterone secretion in vitro or concentration of endometrial progesterone. Irrespective of the experimental groups, secretion of progesterone by luteal tissue from ewe lambs with normal embryos was significantly greater (p<0.05) than that of animals with abnormal embryos or with no embryos. Normal embryos secreted a higher amount of IFN-τ than those embryos classified as abnormal (p<0.07). In conclusion, ewe lambs which exhibit luteal activity before puberty have the highest levels of reproductive performances after a progestagen treatment. Corpora lutea from ewe lambs with normal embryos had higher rates of progesterone secretion in vitro and their embryos had a higher IFN-τ production by the embryos, indicating greater capacity for subsequent development.     

Intrafollicular Concentrations of Steroid Hormones and PGF2α in Relation to Follicular Development in the Mares during the Breeding Season

The concentrations of androstenedione, estradiol-17β, progesterone and PGF_2α contained in the follicular fluid produced by the follicles in collected ovaries of mares that have had estrous phase during the breeding season were measured and analyzed the relation between the growth stage of follicles and the hormone levels in the follicular fluid. An ultrasonographic diagnostic instrument was used to measure the diameter of the follicles in order to categorize the follicles into three groups the following: 8 small follicles (from 1.0 to less than1.5 cm), 8 medium follicles (from 1.5 to less than 3.0 cm), and 8 large follicles (from 3.0 to 5.0 cm), respectively. The analysis of the follicular fluid in ovaries of estrous mares showed that the concentrations of androstenedione were significantly higher in the medium or large follicles than in the small follicles and the concentrations of estradiol-17β were significantly higher in larger follicles than in the small or medium follicles (P<0.05). The concentrations of progesterone and PGF_2α, on the other hand, did not significantly vary regardless of follicluar size. In the follicles within the mare ovaries that have had estrous stage, the concentrations of the hormones related the ovulation, namely androstenedione and estradiol-17β, were higher with larger follicles.     

Interaction between ascorbic acid and follicle-stimulating hormone maintains follicular viability after long-term in vitro culture of caprine preantral follicles

This study evaluates the effects of ascorbic acid and its interaction with follicle-stimulating hormone (FSH) on the morphology, activation, and in vitro growth of caprine preantral follicles. Ovarian fragments were cultured for 1, 7, or 14 d in minimum essential medium (MEM) containing ascorbic acid (50 or 100 μg/mL), FSH (50 ng/mL), or both of these substances. Ovarian tissue that was either fresh (control) or cultured for 1, 7, or 14 d was processed for histological and ultrastructural evaluation. The results showed that after 14 d of culture, medium supplemented with 50 μg/mL of ascorbic acid alone or combined with FSH showed higher rates of follicular survival compared with MEM. After 7 d of culture, FSH, ascorbic acid at 50 μg/mL with or without FSH, and ascorbic acid at 100 μg/mL increased the percentage of follicular activation compared to fresh control. In addition, FSH alone significantly increased the percentage of growing follicles after 14 d. The combination of 50 μg/mL of ascorbic acid and FSH promoted a significant increase in oocyte and follicular diameter after 7 d of culture. Ultrastructural and fluorescent analysis confirmed the integrity of follicles cultured with 50 μg/mL of ascorbic acid and FSH after 14 d. In conclusion, the combination of 50 μg/mL of ascorbic acid and FSH maintained follicular integrity and promoted follicular activation and growth after long-term in vitro culture of caprine preantral follicles.     

The use of melatonin and progestagen–eCG to initiate reproductive activity in prepuberal Awassi ewe lambs

This experiment was conducted to evaluate the effect of administering hormonal treatments (melatonin and progestagen/equine chronic gonadotropin (eCG)) on advancing puberty in Awassi ewe lambs. Fifty-one 6-month-old ewe lambs of similar body weights (around 28 kg) were randomly assigned into four treatment groups; control (CON; n?=?14), melatonin (MEL; n?=?13), melatonin plus progestagen–eCG (MELPP; n?=?11), and progestagen–eCG (PP; n?=?13). Ewe lambs in the PP and MELPP groups were fitted with intravaginal progestagen sponges containing 60 mg medroxyprogesterone acetate for 14 days; 400 IU eCG were administered to each of these ewe lambs on the day of sponge removal. Ewe lambs in the MEL and MELPP groups received subcutaneous melatonin implants (Regulin®, 18 mg melatonin) 36 days before sponge insertion. Hormonal treatment had no effect on ewe lamb body weight change. Estrous behavior was greater (p?p?p?p?相似文献   

Immunohistochemical Localization of Luteinizing Hormone Receptor in the Cyclic Gilt Ovary

Luteinizing hormone receptor (LHR) is a specific membrane receptor on the granulosa and theca cells that bind to luteinizing hormone (LH), resulting in androgen and progesterone production. Hence, the regulation of LHR expression is necessary for follicle maturation, ovulation and corpus luteum formation. We examined the immunolocalization of LHR in cyclic gilt ovaries. The ovaries were obtained from 21 gilts aged 326.0 ± 38.7 days and weighing 154.6 ± 15.7 kg. The ovarian tissues were incubated with rabbit anti‐LHR polyclonal antibody. The follicles were categorized as primordial, primary, preantral and antral follicles. Ovarian phase was categorized as either follicular or luteal phases. The immunolocalization of LHR was clearly expressed in primary, preantral and antral follicles. LHR immunostaining was detected in the cytoplasm of granulosa, theca interna and luteal cells. LHR immunostaining was evaluated using imaging software. LHR immunostaining in the theca interna cells in antral follicles was almost twice as intense as that in preantral follicles (65.4% versus 38.3%, P < 0.01). LHR immunostaining was higher in the follicular phase than in the luteal phase (58.6% versus 45.2%, P < 0.05). In conclusion, the expression of LHR in the theca interna cells of antral follicles in the follicular phase was higher than in the luteal phase. The expression of LHR in all types of the follicles indicates that LHR may impact follicular development from the primary follicle stage onwards.     

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 ± 3.8 g/day (p < 0.001). From those ewe lambs that attained puberty, first oestrus was detected at live weight 37.8 ± 0.2 kg and age 232 days. 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 8 months of age.