Effect of nutrition during calfhood and peripubertal period on serum metabolic hormones, gonadotropins and testosterone concentrations, and on sexual development in bulls

The objective of the present study was to characterize the effects of nutrition on circulating concentrations of metabolic hormones, gonadotropins, and testosterone during sexual development in bulls. Nutrition regulated the hypothalamus-pituitary-testes axis through effects on the GnRH pulse generator in the hypothalamus and through direct effects on the testes. Pituitary function (gonadotropin secretion after GnRH challenge) was not affected by nutrition. However, nutrition affected LH pulse frequency and basal LH concentration during the early gonadotropin rise (10-26 weeks of age). There were close temporal associations between changes in insulin-like growth factor-I (IGF-I) concentrations and changes in LH pulse frequency, suggesting a role for IGF-I in regulating the early gonadotropin rise in bulls. The peripubertal increase in testosterone concentration was delayed in bulls with lesser serum IGF-I concentrations (low nutrition), suggesting a role for IGF-I in regulating Leydig cell function. Serum IGF-I concentrations accounted for 72 and 67% of the variation in scrotal circumference and paired-testes volume, respectively (at any given age), indicating that IGF-I may regulate testicular growth. Bulls with a more sustained elevated LH pulse frequency during the early gonadotropin rise (high nutrition) had greater testicular mass at 70 weeks of age relative to the control group (medium nutrition), despite no differences in metabolic hormone concentrations after 26 weeks of age. Therefore, gonadotropin-independent mechanism regulating testicular growth might be dependent on previous gonadotropin milieu.     

Reproductive characteristics in female Swedish moose (Alces alces), with emphasis on puberty,timing of oestrus,and mating

Background

The moose (Alces alces) is an intensively managed keystone species in Fennoscandia. Several aspects of reproduction in moose have not been fully elucidated, including puberty, timing of mating and oestrus, and the length of the oestrus period. These aspects are relevant for an adaptive management of moose with respect to harvest, population size, demography and environmental conditions. Therefore, an investigation of female moose reproduction was conducted during the moose-hunting period in southern Sweden from 2008 to 2011.

Results

A total of 250 reproductive organs and information on carcass weight and age was collected from four different hunting areas (provinces of Öland, Småland, Södermanland, and Västergötland) in southern Sweden. The results showed that puberty in female moose varied with carcass weight, age, and time of season. The period for oestrous/mating lasted from about mid September to the beginning of November.

Conclusions

The oestrus period (predominantly for heifers) is longer than previously reported and was not finished when the hunting period started. Sampling the uterine cervix to detect spermatozoa was a useful method to determine if mating had occurred. To avoid hunting of moose during oestrus, we suggest that the hunting period should be postponed by at least 14 days in southern Sweden.     

Ovarian activity in F1 prepubertal ewe lambs under tropical conditions

Seventy crossbred ewe lambs, born from Pelibuey (PB) dams mated with five sire breeds: White Dorper × PB (WD × PB), Black Head Dorper × PB (BHD × PB), Ile de France × PB (Ile × PB) Katahdin × PB (KT × PB) and Pelibuey (PB × PB), were used to determine age and weight to puberty, follicular populations during prepubertal development, ovulation rate at first ovulation and function of the first corpus luteum (FCL). Ewe lambs were maintained under grazing conditions and were supplemented with 300 g head^− 1 day^− 1 of a concentrate with 14% CP and 3.0 Mcal ME kg^− 1 of DM. From 145 days of age, monthly observations were performed by endoscopy to monitor follicular populations and luteal structures. Ovarian follicles were classified according to size into small (≥ 1 and < 3 mm), medium (≥ 3 and ≤ 4 mm) and large (> 4 mm). Additionally, weekly observations by ultrasonography were performed in four ewes per genotype to assess follicular populations. Luteal function from first ovulation was determined by circulating concentrations of progesterone. Ovulation rate was not affected by genotype (P > 0.05). All breed groups had the same pattern of follicular populations, where most of follicles were small, followed by medium and a small proportion of large follicles. Maximum diameter of follicles was similar for all genotypes during prepubertal development (P > 0.05), with an average range of 3.9 ± 0.20 to 4.4 ± 0.20 mm. The BHD × PB reached puberty at the youngest age of 240.9 ± 13.0 days, compared to all other genotypes (P < 0.05), 259.1 ± 11.7 for WD × PB, 279.3 ± 9.6 for KT × PB and 289.0 ± 15.3 days for PB × PB and 308.6 ± 11.9 days for Ile × PB ewe lambs. Ile × PB had greater weight to first ovulation (31.5 ± 1.19 kg) as compared to other breed groups (P < 0.01). The largest percentage of FCL was for KT × PB ewes (100%) (P < 0.05), followed by BHD × PB (88.9%), PB × PB (83.3), WD × PB (78.6%) and Ile × PB (77.8%). There were no differences in ovulation rate attributable to type of lambing from which ewe lambs came from (P > 0.05). BHD × PB ewe lambs reached puberty at an earlier age than other in this study. KT × PB ewe lambs had the highest percentage of FCL in their first ovulation. Breed of sire Ile de France increased weight to puberty and decreased FCL at first ovulation. In conclusion, the BHD × PB ewe showed puberty at an earlier age than other genotypes, while the KT × PB had the highest percentage of functional corpus luteum in their first ovulation. Ewe lambs coming from single lambings reach puberty at a heavier weight than those coming from multiple lambings. The ovulation rate in the first ovulation of ewe lambs is not affected by genotype and type of lambing.     

猪初情期前后瘦素长型受体Ob-Rb mRNA在垂体内表达变化的研究

[目的]观察猪初情期前后瘦素长型受体Ob-RbmRNA在垂体内的表达变化,探讨其与猪初情期发育的关系。[方法]随机选取苏姜猪120日龄、初情期、180日龄各3头,屠宰,采集垂体组织,提取垂体组织总RNA,设计引物,利用实时荧光定量RT-PCR方法检测垂体内Ob-RbmRNA表达变化。[结果]在三个时期猪的垂体内都能检测到Ob-RbmRNA的表达,初情期表达量最低,与120日龄比较差异显著（P〈0.05）,与180日龄比较差异不显著（P〉0.05）。[结论]低表达量的Ob-RbmRNA有利于初情期的发生。     

Factors effecting reproductive performance in Rwandan cattle

The objective of this study was to assess the reproductive performance of Rwandan cattle and determine the effects of husbandry practices on reproduction. One hundred and fifty Ankole and Crossbreed cattle from 87 farms, were body condition scored (BCS) on a scale of 1(lean) to 5 (fat), and examined rectally for pregnancy and ovary size and structures present. Questionnaires were completed by the farmers to obtain information on husbandry and management practices. The mean age of onset of puberty was 27.7 ± 10.4 months, the interval from parturition to first oestrus was 8.7 ± 7.8 months, calving index was 16.8 ± 5.2 months and 44% (95% CL 0.36-0.52) of cows examined rectally were anoestrus. Crossbred cattle reached puberty younger than Ankole cattle, 23.4 ± 10.4 and 28.4 ± 9.6 months respectively (p < 0.05; t = 1.944; df = 121). Cows in poor BCS (< 2.5) are 1.67 times as likely to be in anoestrus as those with higher BCS (≥ 2.5) (χ² = 9.476; df = 2; p < 0.01). Increased weaning age resulted in increased calving index (p < 0.001; t = −3.60; df = 38). Reproductive performance of Rwandan cattle is poor. Many of the problems can be attributed to husbandry practices and lack of experience and training in raising cattle.     

枫泾公猪初情期前后外周血清中睾酮、促黄体素及皮质醇的含量变化

用放射免疫法测定并研究了在初情期间24小时内和交配过程中的3头枫泾公猪外周血清促黄体素(LH)、睾酮(T)和皮质醇(F)的含量及分泌范型。3头公猪平均于102日具有射精能力,开始进入初情期。初情期前(76～88日龄)T和LH含量较低,其平均值分别为1.28±0.44和1.57±0.09ng/ml。102日龄后,T含量迅速升高,平均为8.43±0.87ng/ml,与初情期前比较,差异极显著,(P<0.01);LH也随之升高,平均为2.04±0.15ng/ml,但前、后差异不明显(P>0.05)。初情期间24小时内,LH含量波动在1.04±0.40～2.25±0.87ng/ml之间,总平均为1.64±0.28ng/ml;T和F均呈突发性分泌方式,总平均值分别为4.32±1.49和14.79±9.61ng/ml,二者的分泌呈极显著正相关(r=0.88)。T和F的含量早上显著高于夜间(24点)。3头公猪在106日龄分别与发情母猪交配过程中,三种激素均处于较高水平,射精阶段T值显著高于爬下后5～6分钟的值,而LH和F值无显著变化。综上所述,初步揭示枫泾公猪平均于108日龄已建立睾酮、促黄体素和皮质醇性成熟的分泌范型。     

Timing of Puberty and Its Relationship with Body Growth and Season in Male Raccoons (Procyon lotor) in Hokkaido

The raccoon (Procyon lotor), indigenous to North America, has naturalized in Japan as an invasive alien species, having been introduced into the country in the 1970s. In Hokkaido, the northernmost island of Japan, feral raccoons have been increasing in number and spreading throughout the island. The age at the onset of puberty for raccoons is important for estimating individual lifetime reproductive success and population growth. The present study investigated the timing of and potential factors affecting the onset of puberty in male raccoons in Hokkaido. External characteristics and histology of testes were studied in 151 male feral raccoons and in 1 captive juvenile. For the majority of feral yearling raccoons, prepubertal development began in May, and spermatozoa production began in October prior to their second mating season. However, some larger juveniles attained puberty during the juvenile period. The captive juvenile, which was fed throughout the winter, attained puberty only 11 months after birth. These results suggest that if male raccoons can achieve enough body growth before the first mating season, puberty can be attained early. In both juveniles and yearlings, spermatozoa production was only observed after autumn. This timing coincided with the recrudescence of seasonally active spermatogenesis in adult males. Therefore, attaining puberty in male raccoons appears to require both adequate body nutrient development and several environmental factors that control seasonal testicular changes.