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  • Author: Martin Nikolovski x
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Abstract

Reduced glutathione (GSH) and homologous ram seminal plasma (HSP), used as additives in cryopreserving (CP) media prior to freezing, showed conflicting results in retaining structural integrity and progressive motility in post-thawed ram spermatozoa. The aims of this research were: (1) to assess the effect of GSH and/or HSP supplementation via soybean-lecithin CP extender on cryopreserved ram spermatozoa viability, morphology and motility pattern; and (2) to assess the effect of incubation in the context of the previous aim. Quantitatively and qualitatively, homogenized and pooled ram ejaculates (N=10) were extended with one of the following extenders: control (C) – tris-based, GSH and HSP-free, experimental-1 (E1) – C + GSH 5 mM, experimental-2 (E2) – C + HSP 20 % and experimental-3 (E3) - GSH 5 mM + HSP 20 %. Following thawing, samples were taken at 0- and 3-hours from each group (n=10) and were assessed for spermatozoa viability, morphology, and motility pattern. C-0h samples yielded a spermatozoa population with low viability, altered head morphology and highly deviated motility pattern. E3-3h samples yielded spermatozoa with unaffected viability, head morphology and high progressive motility. In conclusion, E3 extender added to cryopreserved-thawed ram spermatozoa is most efficient in obtaining high viability, unaltered head morphology, and progressive motility.

Abstract

Several reports indicated that a large proportion of dairy cows have not resumed cyclicity until day 60 after calving. These cows are traditionally classified as non-cycling (anoestrous or anovular cows). Static ovaries (SO, lack of luteal tissue and follicles >8 mm, and progesterone < 0.5 ng/mL) could be a possible underlying reason that contributes to a non-cycling status. Although SO affects both primiparous (PP) and multiparous (MP) cows, PP cows are more prone to be non-cycling than MP. Therefore, this study aims to compare the metabolic profiles and hormonal status between non-cycling PP and MP cows diagnosed with SO. One hundred and twenty one animals that did not express signs of oestrus until day 60 postpartum were grouped by parity (PP, n=58 and MP, n=63), then blood sampled and examined using transrectal ultrasonography. Blood samples were collected before the ultrasonographic examination. Out of those, 42 PP (72.4%) and 28 MP (44.4%) were diagnosed as non-cycling (bearing SO). Serum concentrations of triglycerides, cholesterol, total protein and albumin did not differ between parity groups. The glucose concentrations in PP cows (1.43 ± 0.59 mmol/L) and MP cows (1.69 ± 0.71 mmol/L) did not differ, however, they were less than the normal physiological concentration. In addition, no differences were detected between parity groups for concentrations of NEFA, β-HBA, progesterone and estradiol. In summary, we concluded that non-cycling PP and MP cows bearing SO have similar hormonal status and metabolic profiles.

Abstract

Postpartum anestrus is a physiological phenomenon in high-producing dairy cows. Static ovaries have been related as major contributors for its occurrence causing a significant reproductive problem to the dairy industry. Different treatment methods have been employed with inconsistent rate of success in initiation of cyclicity, requiring further investigations in order to achieve satisfactory results. The aim of the present study was to compare the ovarian response in cows diagnosed with static ovaries, more than 60 days postpartum using two different hormonal treatment (GnRH and eCG) methods. A total of 58 acyclic cows (no CL, follicles<8mm, P4<0.5ng/mL) were randomly divided into three groups: GnRH (Group 1, n=23), eCG (Group 2, n=23) and Controls (n=12), and allocated thereafter, into subgroups according to the applied doses of GnRH (100μg or 250μg); eCG (750 IU or 1000 IU) whilst control group cows were left untreated. Daily follicular growth rate and treatment respond interval were estimated based on repeated ultrasound examinations. Blood serum P4 sampling was done on d -7, d-0 (start of the experiment) and on d 7 after ovulation. Resumption of cyclic activity occurred in 55.17% (32/58) of the treated cows, 56.52% in Group 1; 60.86% in Group 2 and 41.66% in the control group. Overall, the follicular growth rate was similar between the trials group and significant with regard to the cows in the control group (p<0.05). eCG or GnRH treated cows responded significantly faster 6.85±0.2 and 7.84±0.2 days, respectively, in comparison to the control group cows (17±0.7 days, p<0.001). Treatment with a single dose of GnRH or eCG caused resumption of follicular growth and ovulation following luteogenesis (forming CL) without significant changes in P4 concentrations on day 7 after ovulation (p>0.05). Cows in Group 2 had significantly higher incidence of multiple ovulations than cows in Group 1 (p<0.05). The eCG treatment resulted in a faster response and higher ovulation rate compared to GnRH treatment. In conclusion, both treatments have shown acceptable results in resumption of cyclicity in dairy cows with static ovaries.

Abstract

The bovine kappa-casein (κ-CN) is a phospho-protein with 169 amino acids encoded by the CSN3 gene. The two most common gene variants in the HF breed are CSN3*A and CSN3*B while CSN3*E has been found with lower frequency. The aim of this study was to optimize a laboratory method for genotyping of these three alleles as well as to determine their genotype and allele frequencies in the HF cattle population in the Republic of North Macedonia. Genomic DNA was extracted from full blood from 250 cows. The target DNA sequence was amplified with newly designed pair of primers and the products were subjected to enzymatic restriction with HindIII and HaeIII endonucleases. Genotype determination was achieved in all animals. The primers successfully amplified a fragment of 458 bp and the digestion of this fragment with both endonucleases enabled differentiation of five different genotypes with the following observed frequencies: AA (0.39), AB (0.29), BB (0.16), AE (0.10), and BE (0.06). The estimated allele frequencies were: CSN3*A (0.584), CSN3*B (0.336) and CSN3*E (0.08). The observed genotype frequencies differed significantly (P<0.01) from those that would be expected under HW equilibrium, while the fixation index (F=0.17) indicated moderate heterozygosity deficiency. Nevertheless, the CSN3*B allele was present with relatively high frequency which should be used to positively select for its carriers, since increasing its frequency could help to improve the rheological properties of the milk intended for cheese production.

Abstract

Motility patterns of spermatozoa are an indicator of their fertilizing capacity. Reduced glutathione (GSH) has been reported to induce positive effects on the biological quality of the frozen-thawed spermatozoa. The aim of this study was to investigate the effects of GSH addition to semen extender based on the following kinetic parameters: continuous line velocity (VSL), average path velocity (VAP), curvilinear velocity (VCL), amplitude of lateral head displacement (ALH), linearity (LIN), straightness (STR), beat cross frequency (BCF), total motility (tMOT) and progressive motility (pMOT), and to appoint them as indicators of its presence. A soybean-based extender was used for dilution of the semen samples, fractioned in two parts, one containing GSH (5 mMol/ml) and second without GSH. The ejaculates (n=48) were collected from two rams (January - May, 2013) which were classified in two groups according to the used extender: Group 1 (with GSH, n=24) and Group 2 (without GSH, n=24), and then frozen in liquid nitrogen on -196°C degrees in a programmable freezer. Assessment of the samples has been performed post-thawing (30 sec. at 37°C) on CASA equipment, acquiring kinetic parameters. Results showed that only VSL and BCF have a statistically significant difference between group1 and group 2 (102.98±15.13 vs. 88.47±20.63, t=2.77, p<0.01 and 32.01±2.68 vs. 89.47±2.92, t=3.13, p<0.01, respectively). The summary of the investigation concludes that none of the kinetic parameters could be appointed as indicators that confer the positive effect of GSH as an additive to soy-bean semen extender.

Abstract

The present study aimed to evaluate whether the induction and the formation of an accessory corpus luteum (CL) after AI might increase the pregnancy per AI (P/AI) in heat stressed dairy cows. Starting at d 50±3 post-partum, 113 lactating Holstein cows from one commercial herd during summer were scored for body condition, blood sampled and examined by ultrasound. Those bearing a CL>25mm and progesterone (P4) level>2ng/mL were synchronized using a double PGF2α injection given 12 h apart and AI-ed at detected estrus. In total 18 cows, there were not any signs of estrus (n=10) nor a P4 level <2ng/mL at the time of enrolment (n=8) and therefore they were excluded from the study, leading to 95 cows finally enrolled.. At d5 post-AI, cows were randomly allocated into 2 groups: control group (CON, n=45) without any additional treatment, and treatment group (GnRH, n=50), treated with 0.008 mg Buserelin – a GnRH agonist. Blood sampling and ultrasound examination were done at d5, d14 and at d21 after AI, whereas the pregnancy diagnosis was done at d21 and d30 after AI. Average daily temperature and relative humidity values were used to calculate the temperature-humidity index (THI). The average THI during the experiment was 79.5±0.6. At d5, no differences were observed neither between the number of the CL nor between the P4 level in both groups. At d14 and d21, 82% of the GnRH-treated cows had more than one CL versus 0% of the CON cows. Both at d14 and 21, GnRH-treated cows had higher P4 levels compared to the CON cows (p<0.05). In addition, P/AI were higher in the GnRH group than in the CON group (65% vs. 48.3%, p<0.05), whereas late embryonic losses were higher in CON in comparison to GnRH cows (10.6 vs. 4%, respectively). The BCS at the moment of insemination did not affect P/AI (p>0.05). In conclusion, the induction of an accessory CL at d 5 after AI might increase P/AI in heat stressed dairy cows.