Ewes carrying the Booroola and Vacaria prolificacy alleles respond differently to ovulation induction with equine chorionic gonadotrophin.

The magnitude of ovulation rate (OR) after hormonal induction in sheep should be considered when prolific genotypes are used. We investigated for the first time the effect of the Vacaria allele and its combined effect with the Booroola prolificacy mutation on OR after hormonal treatment during breeding and anoestrous season. A hundred forty-nine Ile de France crossbred ewes, raised in natural pastures in South Brazil, were used to evaluate the OR after treatment with progestagen (MAP) followed or not by equine chorionic gonadotrophin (eCG) treatment (MAP + eCG). During the breeding season, 96% MAP-treated ewes ovulated in comparison to 97% of MAP + eCG-treated females. The double heterozygous carriers (BNVN) presented the higher OR, followed by the single Vacaria (NNVN) and Booroola (BNNN) heterozygous females and least the wild-type (NNNN) ewes. During anoestrus, 96% eCG-treated ewes ovulated, in contrast to 6% treated with MAP alone. The OR of the gonadotrophin-treated females was higher in BNVN and BNNN than NNVN and NNNN ewes. An additive effect in the OR of the two mutations was observed since OR in double heterozygous ewes was similar to the sum of the effects of the alleles of the single heterozygous carrier ewes.

Mutation in the protease cleavage site of GDF9 increases ovulation rate and litter size in heterozygous ewes and causes infertility in homozygous ewes.

Litter size (LS) in sheep is determined mainly by ovulation rate (OR). Several polymorphisms have been identified in the growth differentiation factor 9 (GDF9) gene that result in an increase in OR and prolificacy of sheep. Screening the databank of the Brazilian Sheep Breeders Association for triplet delivery, we identified flocks of prolific Ile de France ewes. After resequencing of GDF9, a point mutation (c.943C>T) was identified, resulting in a non-conservative amino acid change (p.Arg315Cys) in the cleavage site of the propeptide. This new allele was called Vacaria (FecG(v) ). A flock of half-sib ewes was evaluated for OR in the first three breeding seasons, and Vacaria heterozygotes had higher OR (P < 0.001), averaging 2.1 ± 0.1 when compared to 1.2 ± 0.1 in wild-type ewes. The OR was also influenced by age, increasing in the second and third breeding seasons (P < 0.001). In flocks segregating this allele, the LS was higher in mutant sheep (P < 0.001), averaging 1.61 ± 0.07 in heterozygotes and 1.29 ± 0.03 in wild-type ewes. Analysis of homozygote reproductive tract morphology revealed uterine and ovarian hypoplasia. Ovarian follicles continue to develop up to small antral stages, although with abnormal oocyte morphology and altered arrangement of granulosa cells. After the collapse of the oocyte in most follicles, the remaining cells formed clusters that persisted in the ovary. This SNP is useful to improve selection for dam prolificacy and also as a model to investigate GDF9 post-translation processing and the fate of the follicular cells that remain after the oocyte demise.

Effect of polymorphisms linked to LEP gene on its expression on adipose tissues in beef cattle.

In cattle, genetic markers at the leptin (LEP) gene and at those linked to the gene have been described as affecting calving interval (markers LEPSau3AI and IDVGA51), or daily weight gain (BMS1074 and BM1500). This work investigated the effect of these alleles on LEP mRNA levels in cattle subcutaneous and omental adipose tissues. A sample of 137 females of a Brangus-Ibage beef cattle herd was analysed to evaluate the distribution of the polymorphisms; then, animals having at least one of the IDVGA51*181 (allele 181 at marker IDVGA51; six animals), LEPSau3AI*2 (four), BMS1074*151 (13), BM1500*135 (six) alleles and a control group composed of animals without any of these alleles (four animals) were submitted to surgery to obtain omental and subcutaneous adipose tissues. Leptin mRNA expression was quantified by TaqMan RT-PCR, using 18S rRNA as internal control and adjusted for the effect of body condition score, through regression analysis. Omental fat had LEP gene expression 33% lower than the subcutaneous tissue. Carriers of IDVGA*181 and BMS1074*151 showed subcutaneous fat leptin mRNA levels higher than the controls. Leptin controls feed intake and coordinates reproduction; therefore, animals with higher LEP gene expression will probably have lower daily weight gain than others with similar forage offer and nutritional condition and probably will also have longer calving interval.

Follicular development and steroid concentrations in cows with different levels of fertility raised under nutritional stress.

The aim of the present study was to characterize ovarian follicular development and steroid concentrations during postpartum and the estrous cycle of Brangus Ibagé cows (3/8 Nelore + 5/8 Aberdeen Angus) with different levels of fertility. Cows were classified as having high or low fertility according to the calving interval (CI). The average CI of the herd from which cows used in this study were selected was 404.6+/-5.44 and 711.2+/-20.89 days for the high and low fertility groups, respectively. Four cows of high fertility and five cows of low fertility had calves removed between 70 and 100 days after parturition. Ovarian activity was monitored daily by ultrasound for 16 days after calf removal. Days to emergency of the first follicular wave after calf removal, number of follicles with diameter >9 mm, growth rate of largest follicle, maximum diameter of largest follicle, length (days) and number of follicular waves were recorded. During this period, blood was collected daily for measurements of serum progesterone (P(4)) and estradiol (E(2)) concentrations. In another experiment, ovarian activity and P(4) and E(2) concentrations were examined during estrous cycle in five cows of high fertility and four cows of low fertility. Ovarian activity and steroid concentrations were assessed from the day prior to estrus to the 15th day of the estrous cycle (estrus = day 0). In postpartum cows of high fertility, the total number of follicles >5mm and the maximum diameter of the largest follicle were higher than in cows of low fertility (P < 0.05). Concentrations of P(4) and E(2) did not differ between groups in the postpartum cows. However, E(2) increased 5 days after calf removal (around 90 days of postpartum) in the high fertility group, followed by an increase in P(4) with average values indicating ovulation around 100 days postpartum. In cycling cows, the profile of follicular development was similar between cows of high and low fertility. There was no difference between groups for number of follicles >5mm, but the day effect was significant (P < 0.01). Plasma concentrations of P(4) and E(2) were similar in both groups. These data suggest that cows, from a population raised in the same environment have different fertility as a consequence of individual physiological characteristics.

Introduçäo e avaliaçäo dos efeitos de um gene determinante de prolificidade em ovinos Romney Marsh / Introduction and evaluation of the effects of a prolificacy gene in Romney Marsh sheep breed

Um gene de efeito principal, denominado F, responsável por altas taxas de ovulaçäo numa linhagem da raça Merino Australiano, foi introduzido através de acasalamento de três carneiros 1/2 Romney x 1/2 Merino com ovelhas Romney, como uma alternativa para aumentar a fertilidade da raça Romney criadano Rio Grande do Sul. O objetivo deste estudo foi o de fixar o gene F e avaliar o desempenho reprodutivo da populaçäo onde este passou a segregar. Como esperado, a presença do gene F, em heterozigose, elevou significativamente (P<0,001) a taxa de cordeiros nascidos. A disponibilidade local de animais portadoras deste gene é importante para estudos avançados em biologia reprodutiva, porém seu uso em rebanhos comerciais carece ainda de maiores estudos, principalmente relacionados aos objetivos de produçäo nos atuais sistemas exploratórios

Induçäo de estro ovulatório em ovelhas com emprego de estímulos elétricos e/ou hormonais - Nota prévia / Estrus and ovulatory response of ewes treated by eletric and/or hormonal stimulus

A induçäo do estro ovulatório em ovelhas, durante o anestro estacional, é obtida com gestágenos em associaçäo ao eCG. Na estaçäo reprodutiva, cinco ovelhas adultas da raça Corriedale receberam esponjas vaginais impregnadas com 50mg de medroxiprogesterona por 14 dias e, no momento de sua retirada, três sessöes de eletrochoque intervaladas de 12h. O estro induzido e o subsequente foram controlados por machos vasectomizados e o controle ovárico feito por laparoscopia aos 6 e 35 dias após a retirada da esponja. Na estaçäo anestral, 40 ovelhas adultas da raça Corriedale, subdivididas em grupos similares, foram submetidas a quatro tratamentos: EC, constituído de oito sessöes de eletrochoque (10 v, 3 vezes, durante 5", com 5" de descanso, no espaço de 2 dias); MAP + EC, tratamento com gestágeno por 14 dias e posteriormente eletrochoque na forma do primeiro grupo; MAP + GnRH, tratamento com gestágeno pelo mesmo período, e posteriormente 2 injeçöes endovenosas de GnRH; MAP + eCG, gestágeno 14 dias e uma injeçäo de 400 ui de eCG, via intramuscular. A partir do dia da retirada da esponja vaginal e por um período de 26 dias as ovelhas foram expostas a carneiros vasectomizados. Todos os grupos foram inseminados 48 a 60 horas após a retirada da esponja. No grupo MAP + eCG foi procedida laparoscopia adicional para colher informaçöes sobre mortalidade embrionária e/ou indicaçäo de prenhez. Quanto à manifestaçäo de estro, este foi verificado apenas nos tratamentos MAP + GnRH e MAP + eCG, respectivamente em 10 e 60% das fêmeas. No que diz respeito às condiçöes ovarianas, a ovulaçäo foi observada apenas nos tratamentos MAP + eCG (100%) e EC (20%). Em todos os grupos, as condiçöes vaginais às 60h após o início dos tratamentos, revelaram atividade estrogênica pela presença de hiperemia com muco hialino e/ou muco turvo abundante. Quanto à ovulaçäo, esta foi verificada numa freqüência de 20% no grupo EC e de 180% no grupo do tratamento convencional (MAP + eCG). No grupo MAP + eCG, na segunda laparoscopia, observou-se a persistência de corpos lúteos em 6 das 10 ovelhas, em uma a presença de "corpus albicans" sugerindo mortalidade embrionária e as três remanescentes provavelmente retornaram ao anestro, isto é, pela presença de ovários lisos. Os resultados säo indicativos de que o eletrochoque durante o anestro induziu desenvolvimento folicular, atividade estrogênica, ovulaçäo e até mesmo prenhez. Sempre que o gestágeno foi empregado obteve-se atividade estrogênica em grau var

Biometria testicular em ovinos de raças de corte. I. Reprodutores racionados / Scrotal circumference in meat sheep. I. Concentrate suplemented rams

Foram obtidos dados de perímetro escrotal e peso corporal de 666 carneiros apresentados em exposiçöes feiras realizadas nos anos de 1985, 1986 e 1987, das raças Suffolk, Hampshire Down, Ile de France e Texel, com diferentes idades. Os resultados mostraram diferença no perímetro escrotal quanto à idade apenas na raça Hampshire Down. Para todas as raças observou-se correlaçäo significativa entre peso corporal e perímetro escrotal. Os baixos coeficientes de determinaçäo no entanto, näo recomendam o peso corporal como único estimador do perímetro escrotal