FecB基因在9个绵羊品种中的多态性及其与产羔数和羔羊生长发育的相关性

以绵羊BMPR-IB基因为候选基因,应用PCR-RFLP方法通过分析湖羊、夏洛来、陶赛特、萨福克、罗米丽、中国美利奴羊、中国美利奴肉用多胎品系以及陶赛特×中国美利奴羊和萨福克×中国美利奴羊杂交后代共615只个体的FecB基因多态性,以及BMPR-IB基因多态性对产羔数、体尺和体重的影响.结果表明,BMPR-IB基因在不同品种(系)绵羊中共有3种基因型(BB、B+和++),但基因型频率分布在各品种(系)间差异极显著(P<0.01).在湖羊中仅有BB基因型;在中国美利奴肉用多胎品系中BB、B+和++基因型频率分别为51%、30%和19%;而其他品种(系)羊中则仅有++基因型.对中国美利奴羊肉用多胎品系研究,发现BB和B+基因型群体平均产羔数分别为2.8和2.3,显著高于++基因型群体(1.2,P<0.01).在90日龄时,BB和B+基因型群体的体重分别为18.6±3.70 kg和18.0±3.31 kg,显著高于++基因型群体(15.6±2.22kg,P<0.05);此外,90日龄时,BB和B+基因型群体比++基因型群体胸围、胸宽较大(P<0.05);但这些差异在120日龄时消失.另外,我们还发现不同地区群体的第一胎产羔数存在明显差别.这些结果表明,BMPR-IB基因为影响绵羊产羔数的主效基因,并首次证明该基因对后代羔羊出生后生长发育具有加性效应.     

Polymorphism of FecB gene in nine sheep breeds or strains and its effects on litter size, lamb growth and development

Nine sheep breeds or strains, including 615 individuals were screened with forced PCR RFLP method for the FecB gene to study the polymorphism and its effects on litter sizes, body weights and body sizes. Results show that the polymorphism frequencies of FecB gene are significantly imbalanced in these breeds or strains. The Hu sheep were all homozygous carriers (BB). In the Chinese Merino prolific meat strain, the genotype frequencies of BB, B+ and ++ are 51%, 30% and 19%, respectively, whereas all the other flocks had only the wild-type (++) genotype. Results within Chinese Merino prolific meat strain showed that mean litter sizes of ewes with genotype BB and B+ are 2.8 (+/-0.74) and 2.3 (+/-0.63) (P > 0.05), whereas ++ ewes had a litter size of only 1.2 (+/-0.68) (P < 0.01). At 90 days after birth, the body weights of BB/B+ lambs were higher than that of ++ lambs (18.6 +/- 3.70 kg, 18.0 +/- 3.71 kg versus 15.6 +/- 2.22 kg, P < 0.05). In addition, the heart girth and chest width of BB/B+ lambs were significantly longer than ++ lambs (P < 0.05). No significant differences were observed in either body weight or body size at day 120. Litter size at first lambing from Hu at Natural Source Conservative Region was found to be significantly higher than that from the other two regions sampled (P < 0.05). In addition to the additive effect on litter size, these findings show for the first time that the FecB gene had a positive effect on early postnatal body growth.     

Studies on effect of Booroola (FecB) genotype on lifetime ewes' productivity efficiency, litter size and number of weaned lambs in Garole x Malpura sheep

The FecB gene of Garole was introgressed into non-prolific Malpura sheep. The present study was conducted to evaluate the effects of FecB genotypes on cumulative lifetime (three lamb crops) litter size (CLS), cumulative number of weaned lambs (CWL) and cumulative ewe's productivity efficiency (CEPE) in 51 Garole x Malpura (GM) crossbred sheep. The GM ewes of F(1) were selected and screened for FecB mutation using forced RFLP-PCR technique. The majority (78.4%) of F(1) GM individuals were carriers (FecB(B+)) for the FecB mutation. In first parity 55% FecB(B+) ewes gave births to multiple lambs. The FecB genotypes were significantly (P<0.01) associated with the CLS and CWL. The FecB(B+) ewes resulted in 65.6 and 62.1% higher CLS and CWL, respectively compared to non-carriers. The CEPE was also affected significantly by the FecB genotypes at birth, weaning, 6 and 12 months of age. The FecB(B+) ewes weaned 20.9% higher total litter weight as compared to FecB++ ewes and at 12 months age the difference was 43.5% in favor of B+ ewes. The study indicated that the CLS, CWL and CEPE of carrier ewes (FecB(B+)) were comparatively higher than that of non-carriers (FecB++).     

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

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

Factors influencing lamb survival in a high fecundity Booroola Merino x South Australian Merino flock

The effects of year of lambing, age of ewe and litter size on lamb survival and birthweight, and the effects of ewe mating weight and pregnancy wastage (ovulation rate minus litter size) on birthweight were examined in Booroola Merino x South Australian Merino ewes. Year of lambing, litter size and their interaction were significant (P<0.001) sources of variation for lamb survival. When birthweight was included as a linear and quadratic covariate for lamb survival, year of lambing and litter size and their interaction remained as statistically significant sources of variation. Year of lambing, litter size and pregnancy wastage contributed significantly (P<0.05) to variation in birthweight. Ewe liveweight at mating was not an important source of variation (P>0.05). Birthweight was significantly (P<0.05) reduced with an increase in pregnancy wastage. Improvement of birthweight of multiple birth lambs has some potential for increasing lamb survival. Other factors influencing lamb survival (year of lambing, litter size, pregnancy wastage) require further study so that strategies for reducing lamb loss in high fecundity Merino flocks can be developed.     

Highly prolific Booroola sheep have a mutation in the intracellular kinase domain of bone morphogenetic protein IB receptor (ALK-6) that is expressed in both oocytes and granulosa cells

The Booroola fecundity gene (FecB) increases ovulation rate and litter size in sheep and is inherited as a single autosomal locus. The effect of FecB is additive for ovulation rate (increasing by about 1.6 corpora lutea per cycle for each copy) and has been mapped to sheep chromosome 6q23-31, which is syntenic to human chromosome 4q21-25. Bone morphogenetic protein IB (BMP-IB) receptor (also known as ALK-6), which binds members of the transforming growth factor-beta (TGF-beta) superfamily, is located in the region containing the FecB locus. Booroola sheep have a mutation (Q249R) in the highly conserved intracellular kinase signaling domain of the BMP-IB receptor. The mutation segregated with the FecB phenotype in the Booroola backcross and half-sib flocks of sheep with no recombinants. The mutation was not found in individuals from a number of sheep breeds not derived from the Booroola strain. BMPR-IB was expressed in the ovary and in situ hybridization revealed its specific location to the oocyte and the granulosa cell. Expression of mRNA encoding the BMP type II receptor was widespread throughout the ovary. The mutation in BMPR-IB found in Booroola sheep is the second reported defect in a gene from the TGF-beta pathway affecting fertility in sheep following the recent discovery of mutations in the growth factor, GDF9b/BMP15.     

Fec基因及BMPR-IB基因的突变特性与生物学意义

FecB基因位于Booroola绵羊的常染色体上,具有提高排卵率和产羔数等生物学作用。FecB基因已被定位在绵羊6号染色体6q23~q31的狭窄区域内,并且已从分子水平上找到了控制Booroola绵羊排卵数的主效基因。本文详细阐述了近年来对FecB基因的定位及分子生物学作用机制方面的研究进展。     

绵羊微卫星BMS2508和FecB基因的多态及连锁分析

文章分析与绵羊高繁殖力主效基因FecB紧密连锁的微卫星座位BMS2508在高繁殖力绵羊品种(小尾寒羊)和低繁殖力绵羊品种(特克塞尔、多赛特和中国美利奴)中的遗传多态性, 同时探讨该微卫星座位与小尾寒羊FecB基因的连锁不平衡关系。高繁殖力品种小尾寒羊在骨形态发生蛋白受体IB(Bone morphogenetic protein receptor IB, BMPR-IB)基因编码序列第746位碱基处发生了与Booroola Merino绵羊相同的FecB突变(A746G), 而在低繁殖力的特克塞尔、多赛特和中国美利奴绵羊中没有检测到该突变; 小尾寒羊BB、B+、++的基因型频率分别为0.485、0.398和0.117。微卫星座位BMS2508在4个绵羊品种的438个个体中共检测到8个等位基因和15种基因型, 最小等位基因为94 bp, 最大等位基因为116 bp; 小尾寒羊(n = 307)、特克塞尔(n = 45)、多赛特(n = 46)、中国美利奴(n = 40)和BB型(n = 149)、B+型(n = 122)、++型(n = 36)小尾寒羊群体中优势等位基因分别是100 bp、94 bp、94 bp、112 bp、100 bp、100 bp、112 bp, 其频率分别为0.453、0.544、0.802、0.475、0.483、0.439、0.389。连锁不平衡分析显示小尾寒羊FecB基因B等位基因与BMS2508微卫星座位100 bp等位基因之间存在一定的连锁不平衡(D′=0.408), 而+等位基因与BMS2508微卫星座位110 bp和114b p等位基因均存在一定的连锁不平衡(D′=0.513)。     

Reproductive biology of the Booroola Merino sheep

This paper reviews the genetic and physiological characteristics of the Booroola Merino, one of the four most prolific sheep breeds in the world, and which was acquired by CSIRO in 1958 from a commercial sheep property, 'Booroola', Cooma, N.S.W. The exceptional prolificacy of this genotype--e.g. mean flock ovulation rate in 1982 of 4.2 (range 1-10) and mean litter size of 2.5 (range 1-7)--is largely attributable to a single gene (F) of uncertain origin which increases ovulation rate. Crosses of the Booroola with other Merinos produce progeny which have a 47-87% increase in ovulation rate, a 45-56% increase in litter size at birth, and a 1-33% reduction in lamb survival relative to control Merinos. This represents a 16-37% increase in the number of lambs weaned per ewe joined in favour of the Booroola crosses. The exact site of action of the F gene is not well established, although it is expressed primarily at the ovary, where more than the normal number of follicles mature and ovulate each oestrous cycle. This may result from some abnormality of the Booroola follicle itself or it may reflect differences in Booroola gonadotrophin secretion. There is some evidence that Booroola ewes have elevated plasma concentrations of follicle stimulating hormone (FSH) early in life and during the oestrous cycle, and that FSH concentrations in the pituitary gland and urine of the adult ewe are also high. These elevated FSH levels in the adult are attributed to an ovarian feedback deficiency, probably because the inhibin content of the Booroola ovary is only one-third that of normal Merino ovaries. The low inhibin content appears to be due to Booroola follicles having significantly fewer granulosa cells than control Merinos. Analogous studies of the prolific D'man sheep of Morocco point to FSH as the main correlate of prolificacy. The testis growth rate, testis size and total daily production of spermatozoa of the Booroola ram are similar to those of normal Merinos, as also are the endocrine characteristics of adult rams. The Booroola gene's expression is evidently sex-limited. Several theories concerning the mode of action of the F gene are being tested.     

Fertility in South Australian commercial Merino flocks: sources of reproductive wastage

To identify reasons for low fertility in the Merino in South Australia, we defined the extent and sources of reproductive wastage in flocks of maiden (n=14) and mature age (n=54) Merino ewes managed on 43 properties over 4 year. In a second study, reproductive wastage was examined in a very high ovulating flock of mature age South Australian Merino ewes heterozygous for the FecB gene, mated to lamb in either the autumn or spring. Losses in the latter flock were examined in less detail than the large-scale study, but allowed wastage to be partitioned between pre- and peri/post-natal sources. In the first experiment, reproductive wastage between mating and weaning was estimated at 59.7 potential lambs or ova lost per 100 ewes exposed to rams, representing 42.4% of ova shed. The main source of wastage occurred at lambing (55.6% of total loss), with death of twins a major contributor (35.3% of total loss). Other important sources of wastage were from partial failure of multiple ovulation (PFMO; 20.4% of total loss) and from ewes mating but not lambing (13.2% of total loss). Reproductive wastage did not vary with either age of ewe (maiden versus mature) or season of mating (October-December versus January-March). Mean ovulation rate, estimated as 141 per 100 ewes ovulating (range 100-200), varied with age of ewe (129 versus 144; maiden versus mature) but not with season of mating or year (1990-1991). Values for fertility, fecundity and lamb survival were 90, 127 and 73%, respectively. Fecundity of maiden ewes was lower than that of mature ewes (116 versus 130). Survival of single and twin lambs between birth and tail docking was 83 and 56%, respectively. Net reproductive efficiency, or lambs weaned per 100 ewes exposed to rams, averaged 81 (range 31-122). In the second experiment, mean ovulation rate of FecB Merino ewes was 316 per 100 ewes ovulating, with 242 ova (potential lambs) lost between ovulation and tail docking. This loss was equally shared between pre- and peri/post-natal sources (123 versus 119), and demonstrates severe limitation of the Merino to successfully bear and rear multiple litters. We concluded that future research in commercial Merino flocks be focused on lamb mortality, particularly of twins, and on PFMO, the major source of embryo loss.     

Increasing ovulation rate and lambing percentage by active immunization against androstenedione in dairy sheep breeds

A total of 1200 ewes, two hundred from each of six dairy breeds-the Karagouniko (K), the Serres (S), the Vlachiko (V), the Florinis (F), the Kimis (Km) and the Chios (Ch)-were used to examine the efficacy of a new immunogen (androstenedione-7a-HSA + DEAE-dextran) in improving reproductive performance. Ewes of each breed were randomly allotted to two groups, the control and the treated. Treated ewes were given two injections of 2 ml immunogen three weeks apart, while the control ewes were untreated. Rams were introduced to all ewes after the second injection. Twenty ewes in each group for each breed were laparotimized 7 to 10 days post-mating. Incidence of estrus and mating, the ovulation rate (OR), lambing percentage (Lp. 100), litter size (LS), and lamb (LbW) and litter weight (LW) were recorded. The OR was increased in immunized ewes compared to controls from 1.60, 1.46, 1.50, 2.50, 2.50 and 2.90 to 2.50, 2.06, 2.20, 3.20 (P<0.05), 4.20 and 4.80 (P<0.01), respectively, in K, S, V, F, Km and Ch breeds. No significant difference on Lp. 100 was observed between control and treated ewes of all breeds. The LS was increased in immunized ewes by 17, 20, 18, 28, 57 and 0 lambs compared to control ewes in K, S, V, F, Km and Ch breeds, respectively; however, the increase was statistically significant (P<0.05) only in Km and F breeds. The LbW was decreased in immunized ewes compared to controls; however, the decrease was statistically significant (P<0.05) only in the V breed. When compared to control ewes the LW was greater in immunized ewes of S, K, Km and F breeds while in Ch and V breeds LW was smaller. It was concluded that an increase in ovulation rate by active immunization against androstenedione may not be reflected in an increase of litter size in dairy sheep. Breed differences must be considered when producers intend to use this technique to improve litter size.     

Variations in patterns of follicle development in prolific breeds of sheep

Prolific breeds of sheep (Romanov, Finn and Booroola Romanov crosses heterozygous for the Booroola gene (F+) were compared with breeds of lower prolificacy (Ile-de-France, Finn X Scottish Blackface, Merino X Blackface and Booroola X Romanov not carrying a copy of Booroola gene (++] by in-vivo monitoring of follicular kinetics by ink labelling during the late luteal phase and follicular phase of the oestrous cycle followed by histological examination of the ovaries or follicle dissection. At each of 3 successive laparotomies, the 3 largest follicles of each ovary were measured and ink labelled. At the final laparotomy, around the beginning of oestrus, all ewes were ovariectomized. High ovulation rate was not associated with the total number of antral follicles in any of the breeds. However, there were more follicles greater than 2 mm in diameter in Romanov and Booroola X Romanov crosses (F+) compared to their respective controls. Such a feature was not observed in Finnish Landrace compared to Finn X Blackface and Merino X Blackface ewes. A more numerous population of recruitable follicles, together with a similar incidence of selection through atresia, were the features associated with the high ovulation rate of Romanov compared to Ile-de-France ewes. The high ovulatory potential of the Finn ewes resulted from a markedly reduced incidence of selection through atresia. Booroola X Romanov ewes carrying a copy of the Booroola gene (F+) appeared to possess features of both parental breeds, including high numbers of recruitable follicles, smaller follicular size when recruitment occurs and an extended time for recruitment. Booroola X Romanov (++) ewes, not carrying the gene, appeared to have lost part of the 'Romanov characteristics' of a more numerous population of recruitable follicles. The variability in the kinetics of preovulatory enlargement, seen in these breeds of sheep, demonstrates that there are a number of pathways through which high ovulation rate can be achieved and hence through which ovulation rate might be manipulated.     

Polymorphism of FecB Gene in Nine Sheep Breeds or Strains and Its Effects on Litter Size, Lamb Growth and Development

Nine sheep breeds or strains, including 615 individuals were screened with forced PCR RFLP method for the FecB gene to study the polymorphism and its effects on litter size, body weight and body size. Results showed that the polymorphism frequencies of FecB gene were significantly imbalanced in these breeds or strains. The Hu sheep were all homozygous carriers of FecB gene(BB). In the Chinese Merino prolific meat strain, the genotype frequencies of BB, B+ and ++ were 51%, 30% and 19%, respectively, whereas all the other flocks had only the wild-type (++) genotype. Results within the Chinese Merino prolific meat strain showed that the mean litter size of ewes with genotype BB and B+ were 2.8 (±0.74) and 2.3 (±0.63) (P<0.05). whereas ++ genotype ewes had a litter size of only 1.2 (±0.68) (P<0.01). At day 90 after birth, the body weights of BB/B+ genotype lambs were higher than that of ++ genotype lambs (18.6±3.70 kg. 18.0±3.71 kg vs 15.6±2.22 kg, P<0.05). In addition, the heart girth and chest width of BB/B+ genotype lambs were significantly longer than those of the ++ lambs (P<0.05). No significant differences were observed in either body weight or body size at day 120. Litter size at first lambing from Hu at Natural Source Conservative Region was found to be significantly higher than that from the other two regions sampled (P<0.05). In addition to the additive effect on litter size, these findings showed for the first time that the FecB gene had a positive effect on early postnatal body growth.     

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

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

Effects of breed and age on the performance of crossbred hill ewes sourced from Scottish Blackface dams

The aim of this study was to evaluate the effects of age and breed on the reproductive performance and lamb output of crossbred hill ewes relative to purebred Scottish Blackface (BF). BF ewes were compared alongside Swaledale (SW) × BF, North Country Cheviot (CH) × BF, Lleyn (LL) × BF and Texel (T) × BF ewes on six commercial hill farms across Northern Ireland, on which all the ewes were born and reared. Ewes were mated to a range of sire breeds, balanced across breeds, for up to five successive breeding seasons. Mature live weight of adult BF, SW × BF, CH × BF, LL × BF and T × BF ewes was 52.8, 54.9, 60.3, 55.6 and 58.6 kg (P < 0.001), respectively. Compared with the pure BF, the number of lambs born per ewe lambed was higher with LL × BF and SW × BF (P < 0.05), whereas the number of lambs weaned per ewe lambed was greater for LL × BF and T × BF (P < 0.01). Total litter weight at birth of all the crossbred ewes was heavier (P < 0.01) than the pure BF, except in primiparous 2-year-old ewes. Lambs born to CH × BF and T × BF dams were 0.24 to 0.35 kg heavier at birth (P < 0.01) than the other ewe breeds, whereas lambs born to CH × BF, LL × BF and T × BF dams were, on average, 1.7, 1.3 and 1.5 kg, respectively, heavier (P < 0.01) at weaning than those from BF dams due to their higher (P < 0.05) average daily gain. Compared with the pure BF, total weaned lamb output per ewe lambed was 3.7, 4.8, 6.7 and 5.4 kg heavier (P < 0.05) for SW × BF, CH × BF, LL × BF and T × BF, respectively. However, as a result of the heavier live weight of the crossbred ewes, production efficiency (lamb output per kilogram live weight (W) and lamb output per kilogram metabolic live weight (W0.75)) was higher (P < 0.001) for LL × BF ewes only. For all ewe breeds, litter size at birth per ewe lambed, total lamb birth weight per ewe lambed and litter size at weaning increased (P < 0.001) with age up to 5 years, but decreased in 6-year-old ewes. Average lamb weaning weight and total weaned lamb output per ewe lambed increased (P < 0.001) with age up to 4 years . Production efficiency of the 6-year-old ewes was lower (P < 0.01) than the younger ewes. This study shows that adopting a flock replacement policy based on crossing BF ewes with LL, SW, T and CH sires can lead to significant improvements in the productivity of hill flocks.     

Ovarian response to hCG injections during the prepubertal period in three breeds of sheep with different ovulation rates and litter sizes

A positive correlation was reported between ovulation (OR) rate in response to hCG in prepubertal ewe lambs and adult ewes. The finding suggested that the response to hCG may be used to select prepubertal ewe lambs for prolificacy. We studied plasma FSH concentrations and ovarian response to hCG injection during the prepubertal period in breeds with high (Chios), medium (Florina) and low (Karagouniki) OR and litter sizes (LS). The results showed that Chios ewe lambs presented a higher profile of plasma FSH during the 3rd to 7th wk of age when compared to the breeds with medium (Florina) and low (Karagouniki) OR and LS. The ovarian response to hCG showed that the Chios ewe lambs responded earlier, by exhibiting ovulation at 6 wks and more effectively, by demonstrating a higher OR than the other two breeds. There was no correlation among plasma FSH concentrations during prepubertal age (3rd to 7th wk), ovulation rate after hCG injection, or litter size at first and second lambing for all breeds. Therefore we concluded that the plasma FSH concentrations and/or the ovarian response to hCG injection during the prepubertal period is not a suitable criterion for early selection for litter size in the adult ewe of these breeds.     

Concentrations of progesterone,follistatin, and follicle-stimulating hormone in peripheral plasma across the estrous cycle and pregnancy in merino ewes that are homozygous or noncarriers of the Booroola gene

The circulating concentrations of progesterone, FSH, and follistatin across the estrous cycle and gestation were compared in Australian merino sheep that were homozygous for the Booroola gene, FecB, or were noncarriers. The Booroola phenotype is due to a point mutation in the bone morphogenetic protein receptor 1B. Progesterone concentrations began to rise earlier and were higher in the Booroola ewes than in the noncarriers on most days of the luteal phase but not during the follicular phase of the cycle. Follistatin concentrations remained unchanged across the estrous cycle in both groups of ewes, with no differences between genotypes. FSH concentrations were higher in Booroola ewes than in noncarrier ewes on most days of the estrous cycle, with a significantly higher and broader peak of FSH around the time of estrus. Progesterone concentrations were significantly higher in early and midgestation in Booroola ewes but were lower toward the end of gestation than those in noncarriers. FSH declined in both groups across gestation, with lower concentrations of FSH in Booroola ewes during midgestation. Follistatin remained unchanged across gestation in Booroola ewes and noncarrier ewes with a twin pregnancy but declined across gestation in noncarrier ewes with a singleton pregnancy. These results suggest that follistatin concentration is not regulated by the FecB gene during the estrous cycle and pregnancy but is influenced by the number of fetuses. However, the FecB gene appears to positively affect both progesterone and FSH during the estrous cycle and across pregnancy, which suggests that bone morphogenetic proteins play an important role in the regulation of both hormones.     

Natural and induced ovulation rate in prolific and non-prolific breeds of sheep in Ireland, Morocco and New Zealand

Ovulation rate, in mixed-age groups of prolific and non-prolific ewe breed types, after administration of a range of doses of PMSG (0, 375, 750 and 1500 i.u.) during the follicular phase of the oestrous cycle, were compared in Ireland, Morocco and New Zealand. The ewes in Ireland and Morocco were from the Finnish Landrace and Galway, and D'Man and Timhadite breeds, respectively. In New Zealand Booroola Merino x Romney ewes which had been previously identified as heterozygous carriers (F+) of the Booroola high fecundity gene and purebred Romneys were used to represent the prolific and non-prolific genotypes respectively; in addition a group of Booroola Merino x Romney non-carriers (++) of the major gene were also included for comparison. Ovulation rate at the oestrus which preceded stimulation with PMSG was also measured in all animals. In all 3 locations the ewes of the prolific genotype had a greater ovulation rate after PMSG stimulation than did the non-prolific controls. However, this association between prolificacy and response to PMSG was removed when ovulation rate after PMSG was transformed by dividing by the ovulation rate observed before PMSG administration. Despite the differences in the genetic basis of their high prolificacy the pattern of response to PMSG over the range of dosages used was similar in Finnish Landrace, D'Man and Booroola Merino x Romney (F+) ewes and all breeds had means of about 10 ovulations in response to 1500 i.u. PMSG. Amongst the non-prolific breeds, the Timhadite was the most responsive to PMSG although it had the lowest natural ovulation rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ovulation rates of first cross booroola compared with local breed ewes following differential feeding

The effect of at least 6 weeks of differential nutrition (high v. low plane) on live weight and ovulation rate was studied in Booroola cross ewes with (F+) and without (++) the putative Booroola gene for fecundity, and non-Booroola local breed ewes. In three experiments, significant differences (range 8–9.6 kg) in live weight at laparoscopy resulted from the differential feeding. Across genotypes, differences in ovulation rate between high and low plane ewes approached significance in Exp. 1 (2.11 vs. 1.76) and were significant in Exp. 2 (1.83 vs. 1.59) and Exp. 3 (2.68 vs. 2.20). Despite significantly higher ovulation rates in F+ Booroola cross ewes compared with ++ ewes (2.99 vs. 1.45), there was no significant interaction between nutrition and genotype; that is, both Booroola genotypes, and non-Booroola ewes exhibited similar ovulation rate responses to nutritionally induced differences in live weight.     

Effects of sire breed on ewe dystocia, lamb survival and weaned lamb output in hill sheep systems

A study was carried out on six hill farms, located in the main hill regions of Northern Ireland, over three breeding seasons to investigate the effect of sire breed on ewe dystocia, lamb survival and weaned lamb output. On each farm, groups of 26 to 40 purebred Scottish Blackface ewes (n = 3174) were crossed with Blackface, Swaledale, North Country Cheviot, Lleyn and Texel sires by natural service (year 1) and artificial insemination (years 2 and 3). Each of the mating groups was initially balanced for ewe age, live weight and condition score, and a total of 15 sires of each breed were used over the 3 years. In total, 2272 ewes were recorded at lambing, producing 3451 lambs, over the 3 years. Sire breed had a significant effect (P < 0.001) on lamb birth weight with Blackface and Swaledale the lowest and Texel the highest. The proportion of ewes with dystocia was higher with Texel sires compared with Lleyn, Swaledale and Blackface sires (P < 0.05). Ewes mated to Cheviot sires had more dystocia than those mated to Blackface and Swaledale sires (P < 0.05), while ewes mated to Lleyn sire breed had more dystocia (P < 0.05) than those mated to Blackface sire breed. Most of the incidence of dystocia was attributable to increased lamb birth weight (P < 0.001), and some to litter size (P < 0.05). Swaledale, Cheviot, Lleyn and Texel sire breeds increased the incidence of malpresentations (P < 0.05). Lamb live weight at weaning was higher with Texel- and Cheviot- and Lleyn-sired lambs compared with Blackface- and Swaledale-sired lambs (P < 0.01). The level of lamb mortality at birth was not affected by sire breed. However, lamb mortality at weaning was lower for Lleyn-sired lambs compared with the other lamb genotypes (P < 0.05). These results indicate that the use of sires from larger breeds, such as Lleyn and Texel, within the Blackface ewe flocks can increase lamb output, with no apparent detrimental effects on lamb mortality or ewe survival, but increased assistance at lambing will be required.