Semen quality of Nellore and Angus bulls classified by fertility indices and relations with field fertility in fixed-time artificial insemination.

Despite being the most important form of biotechnology in animal reproduction, artificial insemination was used in about 23% of Brazilian bovine herds in 2021. This is due to the variability of results caused by varying bull fertility and body condition of the cows. This study aimed to correlate the fertility indices of bulls with qualitative attributes of the semen. Semen samples from 28 bulls (Nellore and Angus) were used to evaluate postthaw sperm morphology and kinetics using conventional analysis, image-based flow cytometry (IBFC) and computer-assisted semen analysis (CASA). The fertility index was effective in separating bulls into 4 different fertility classes (P < 0.001), and fertility rates in timed artificial insemination (TAI) remained constant between the cows' fertility categories (P < 0.001) and in the different grades of female body condition (P < 0.005). After partial least squares regression (PLS) analysis, four models were proposed with different variables. The coefficients of determination for the conventional analysis, CASA, and IBCFC models were 0.154, 0.380, and 0.259, respectively. The composite model, including select IBFC and CASA parameters, showed a greater R2 (0.481) with progressive motility, average speed (VAP, µm/s), membrane integrity, and mitochondrial potential, showing a positive effect. Linear speed (VSL, µm/s) and acrosomal integrity had a negative effect on bull fertility indices. Bulls classified by the fertility index attained dispersed pregnancy rates in different cow body condition score (BCS) classes, and the sperm quality pattern was consistent with this classification. In conclusion, this novel composite model including CASA and IBFC parameters improves the prediction of bull fertility used in TAI.

Impact of quercetin, carnosine, and ozone in the cryopreservation on Nellore (Bos indicus) semen.

The objective of this study was to reduce the effects of cryoinjury caused in bovine semen by cryopreservation. Ejaculates were collected from Nellore bulls and subjected to freezing in C (control), ozone (15, 30, and 60 µg mL-1 of ozone), quercetin (25, 50, and 100 µg mL-1 of quercetin), and carnosine groups (100, 200, and 300 ng mL-1 of carnosine). Samples were evaluated post-thaw (M0) and post-rapid thermoresistance test (M30) for sperm kinetics (total motility, progressive motility, curvilinear speed, linearity and amplitude of lateral head displacement) and cell structure viability (plasma membrane integrity, acrosomal integrity, mitochondrial potential, membrane fluidity, and lipid peroxidation). There were no differences (P > 0.05) between the control, quercetin, and carnosine-treated groups for the parameters evaluated at M0 and M30. In turn, supplementation with ozone resulted in lower values for sperm kinetics (P < 0.05) and lower mitochondrial potential at M30 (P < 0.05). Quercetin and carnosine at the concentrations used did not promote significant gains in frozen semen, nor did they demonstrate cytotoxicity. We expected to obtain positive results with the use of ozone. Nonetheless, the addition was harmful to the parameters of sperm kinetics, and its effect was not observed as a possible pro-antioxidant. We believe that the fact that the gas did not harm the sperm structure opens avenues for tests with lower dosages, since, by reducing its concentration, we could minimize the damage to sperm kinetics.

P4/E2-based protocol for synchronisation of ovulation of mares during the breeding and non-breeding season.

Dispersed ovulation at the breeding (BS) and anestrus at non-breeding season (NBS) are major impediments to embryo transfer and insemination programmes. The present study aimed to evaluate a hormonal P4/E2-based synchronisation protocol in mares during both the BS and the NBS on ovarian/follicle behaviour. Mares underwent a hormone protocol to synchronise their ovulation during the BS (n = 8) and NBS (n = 10), starting (D0) with the insertion of an intravaginal device containing 1 g of P4 and 7 mg Estradiol Benzoate IM. (EB). On D9, the device was removed and injected with 0.25 mg of cloprostenol sodic IM and 2 mg of EB IM. Follicular behaviour was evaluated using a daily transrectal ultrasound (24/24 h) from D0 until ovulation. When the dominant follicle (DF) measured at least 35 mm, females were injected with 0.25 mg of gonadorelin acetate IM to induce ovulation. The DF on D0 were similar in animals between BS (18.9 ± 8.4 mm) and NBS (23.7 ± 9.2 mm; p = 0.2700). However, in the BS the DF was smaller (14.2 ± 4.7 mm) on D9 than during NBS (22.0 ± 7.1 mm; p = 0.0177). During the BS, the ovulatory follicle is smaller (p = 0.0042) than during NBS, measured at 33.5 ± 4.6 mm and 41.3 ± 2.8 mm, respectively. Ovulation time after P4 removal was similar during BS (173.1 ± 68.8 h) and NBS (192 ± 58.2 h; p = 0.3507). There was no difference towards an ovulation rate during BS (88%) and NBS (60%; p = 0.0978). There was no difference in spontaneous ovulation during BS (43%) and NBS (0%; p = 0.6085). This hormonal protocol would be an effective tool for inducing cyclicity/ovulation in mares during BS and NBS.

The gynecological examination in Pantaneiro mares.

Gynecological examination is essential to assess the reproductive tract of mares and can provide important information about the uterine environment. It includes physical, vaginal, and rectal examination, ultrasound, cytology, culture, and endometrial biopsy. The present study aimed to perform gynecological examination and fertility to assess the fertility prognosis of Pantaneiro mares that have not been reproductively active and to determine their reproductive ability. Eight mares underwent ultrasound and gynecological examination and artificial insemination. Ultrasound revealed changes only in one mare. Histopathological findings were mild, such as periglandular and perivascular inflammatory cell infiltrates, fibrotic areas, glandular dilation, glandular island formation, and edema due to the phase of the estrous cycle. One animal was classified in category I and the others in category IIA. Cytological changes were found in only one mare. Endometrial culture from five mares resulted in isolation of Pseudomonas sp., Bacillus sp., Escherichia coli and Candida sp. Only four mares resulted pregnant through artificial insemination, using the same stallion with fresh semen, which has been proving fertility. Thus, mares with better uterine conditions will not always become pregnant and those with mild changes will not always be barren.

Effects of ascorbic acid 2-glucoside and alpha-tocopherol on the characteristics of equine spermatozoa stored at 5°C.

The aim of this experiment was to evaluate the effects of adding ascorbic acid 2-glucoside (AA2G), a water-soluble antioxidant and stable derivative of ascorbate, to the semen extender and compare it to the addition of vitamin C (Vit. C) and the fat-soluble antioxidant α-tocopherol (α-Toh), both individually and in combination, on the seminal variables of equine sperm submitted to cooling for 72 h. We used two ejaculates from 10 stallions and evaluated them for motility, membrane integrity, chromatin fragmentation, mitochondrial activity and lipid peroxidation. In the analysis of lipid peroxidation, the control group showed 2506.2 ± 796.4 ng malondialdehyde/108 sperm, which was higher (P < 0.05) than the groups treated with antioxidants. The average value of motility in the AA2G group was 68.4 ± 18.1%, which was higher (P < 0.05) than that observed in the control group (62.1 ± 16.2%). The variables membrane integrity, chromatin fragmentation and mitochondrial activity did not show significant difference (P > 0.05) between treatments. It was concluded that the antioxidants protected sperm cells from lipid peroxidation and that AA2G was effective during the cooling process of equine semen at 5°C for72 h, providing increased levels of total motility.