The association of two single nucleotide polymorphisms (SNPs) in growth hormone (GH) gene with litter size and superovulation response in goat-breeds

Two active mutations (A 781 G and A 1575 G) in growth hormone (GH) gene, and their associations with litter size (LS), were investigated in both a high prolificacy (Matou, n = 182) and a low prolificacy breed (Boer, n = 352) by using the PCR-RFLP method. Superovulation experiments were designed in 57 dams, in order to evaluate the effect of different genotypes of the GH gene on superovulation response. Two genotypes (AA and AB, CC and CD) in each mutation were detected in these two goat breeds. Neither BB nor DD homozygous genotypes were observed. The genotypic frequencies of AB and CC were significantly higher than those of AA and CD. In the third parity, Matou dams with AB or CC genotypes had significantly larger litter sizes than those with AA and CD (p < 0.05). On combining the two loci, both Matou and Boer dams with ABCD genotype had the largest litter sizes when compared to the other genotypes (p < 0.05). When undergoing like superovulation treatments, a significantly higher number of corpora lutea and ova, with a lower incidence of ovarian cysts, were harvested in the AB and CC genotypes than in AA and CD. These results show that the two loci of GH gene are highly associated with abundant prolificacy and superovulation response in goat breeds

Ovine ultrasonography: Use of ultrasonographic examination in sheep health management

[No abstract available

Oestradiol concentration as a predictor of ovarian response in FSH stimulated ewe-lambs

We investigated the prediction of ovarian response using oestradiol determination, in 37 gonadotrophin stimulated Karagouniko ewe-lambs. Ovarian stimulation was induced by serial FSH administrations, and laparoscopic follicular aspiration (OPU) was conducted 12 h after the last FSH injection. Oestradiol concentration was assessed in six blood samples collected prior to each FSH injection and in one sample collected prior to follicular aspiration. According to ovarian response, ewe-lambs were allotted in three groups: good, L1 (n = 17); moderate, L2 (it = 10); and poor, L3 (n = 10). Based on the data obtained from 28 (75%) randomly selected animals, a statistical model was designed and tested on the remaining nine lambs for its ability to predict the probability of good ovarian response. From the 2nd sample, oestradiol concentration was constantly higher in group L I in comparison with L3 lambs (all p-values for the contrasts were <= 0.02), while this difference between L I and L2 lambs was significant only in the 6th and 7th sample (both p < 0.005). Using as criterion the oestradiol concentration of the 6th sample, the statistical model predicted all lambs that did not belong to group L1 and three of four lambs that belonged to group L1. Our results indicate that the moderate- and poor-donors could be safely predicted on the basis of oestradiol concentration 12 h prior to the scheduled follicular aspiration. Moreover, poor-donors could be identified-and rejected from further manipulations-on the basis of their inability to exhibit increased oestradiol levels in response to gonadotrophin stimulus. (c) 2007 Elsevier B.V. All rights reserved

The application of in vitro fertilization techniques for the evaluation of ram fertility

The prediction of field fertility of a given ram by using in vitro tests would be of great importance for the reproductive management in sheep flocks. There are many in vitro procedures available for evaluating semen quality and fertilizing ability, and the method chosen depends on the objective of evaluating the sperm and the available resources. The in vitro evaluation of semen fertilizing ability was firstly developed for the artificial insemination (AI) purposes and secondly for the application of in vitro fertilization (IVF) technique. The IVF techniques allow the assessment of fertility in terms of ability to penetrate and fertilize in vitro mature oocytes and ultimately to yield component embryos following IVF and culture. In this review are briefly presented in vitro studies performed in an attempt to establish an accurate laboratory test for the evaluation and, even more, the prediction of field fertility in sheep

Oocyte pick-up in juvenile lambs affects neither onset of puberty nor their future fertility

A study was designed to evaluate whether the time of onset of puberty and fertility of young ewe lambs would be affected by oocyte pick-up conducted in single or repeated sessions during the first months of lambs' live. Five groups of lambs from the Karagouniko breed were used (A-E each n = 12). In group A no treatments were applied (control group) while, laparoscopical follicular aspiration (OPU) was performed early in the third, fourth and fifth month of lambs age (groups C-E, respectively). From the second to fifth month of their age, group B lambs were aspirated four times in monthly intervals. All lambs were weighed at birth, weaning, at second month and monthly thereafter until the eighth month of age. Progesterone priming and ovarian stimulation by serial FSH administrations proceeded each OPU session. To determine onset of puberty blood progesterone concentration was assayed in samples collected initially every week and after the seventh month of age twice weekly. From the seventh month a fertile ram was introduced in each group and oestrous behavior/mating was daily monitored and recorded. Pregnancy diagnosis was carried out by transabdominal ultrasound scanning 55 days after rams' removal. At the fourth and fifth month of age group B lambs were lighter (p < 0.05) than controls, but this difference was later equalized. The time of onset of puberty did not differ between groups (p = 0.069) and ranged between 224 and 270 days. Some animals (n = 15) entered puberty with a full-length luteal phase having progesterone concentration greater than 1 ng/ml, while others (n = 32) exhibited one or two short luteal phases before luteal length restoration. During the first breeding season 41 animals were fertilized and maintained pregnancy to term, without noticeable differences between groups (p = 0.555). During the second breeding season, all ewes were naturally served and lambed at the expected time. It is concluded that OPU in young dairy lambs does not affect the time of onset of puberty, the endocrine profile of the lambs and it does not compromise their future fertility even if it is applied at four successive months. © 2006 Elsevier Inc. All rights reserved

Management of pre-pubertal small ruminants: Physiological basis and clinical approach

Puberty is a gradual process, during which animal reproductive competence is attained with respect to physiology, morphology and behaviour. Onset of puberty in small ruminants differs between sexes, due to early sexual differentiation in the control of steroid feedback systems and, thus, GnRH secretion. A number of puberty determinants have been identified, which include genetic factors, as well as endogenous signals, such as energy balance and environmental cues, whose dynamic interplay is responsible for the timing of puberty onset. Puberty timing affects reproduction through age at first lambing, which impacts on subsequent reproductive life and productivity of small ruminants. Thus, a greater knowledge of the mechanisms underlying puberty process would lead to optimisation of commonly applied strategies for selection of replacement animals. In addition, understanding reproductive responses of animals to exteroceptive factors, such as photoperiod, nutrition and socio-sexual signals, will enable development and improvement of those management tools that that will fulfil the requirements of a 'clean, green and ethical' production. (C) 2012 Elsevier B.V. All rights reserved