Relationship between age, scrotal circumference, postweaning weight and semen quality in Nellore and Caracu bulls: a cross sectional study.

The aim of this study was to investigate the relationship between age, scrotal circumference, postweaning weight and semen quality in Nellore and Caracu bulls selected for postweaning weight. Data from the andrological evaluation of 836 bulls born between 2000 and 2019, including 583 Nellore animals (Bos indicus) and 253 Caracu animals (Bos taurus), were used. The bulls were divided into categories of age at the time of assessment: category 1 consisted of animals aged 20 to 23 months (22 ± 0.76 months, 518 ± 94.17 kg), category 2 consisted of animals aged 24 to 35 months (30 ± 4.42 months, 679 ± 137.19 kg), and category 3 consisted of animals ≥ 36 months (60 ± 14.12 months, 907 ± 161.73 kg). The statistical model included the effects of breed, age category, date of semen collection, and breed x age category interaction. Heritability estimates for scrotal circumference at 13 months of age (SC1year) and semen quality traits were obtained for the sample of Nellore animals. Most semen quality traits improved with increasing age in both Nellore and Caracu animals. High heritability was observed for SC1year (0.45), while sperm motility, vigor, turbulence, and major, minor and total sperm defects exhibited low heritability (0.11, 0.019, 0.047, 0.017, 0.017 and 0.019, respectively). Spearman correlations of breeding values for postweaning weight (W378) and SC1year with the semen quality traits were low. Nellore and Caracu bulls have similar semen quality that improves with increasing age. In the Nellore breed, the heritability of SC is high, while semen quality traits exhibit low heritability. Selection for higher postweaning weight does not phenotypically affect the semen quality of bulls at breeding age.

Relationship of residual feed intake with semen parameters and testicular ultrasound of Nellore bulls

The objective of this study was to evaluate characteristics of the testicular parenchyma and vascular parameters of the pampiniform plexus obtained by ultrasound, semen quality parameters, and sperm freezability in Nellore bulls classified based on residual feed intake (RFI). Twenty-seven bulls (21.82±0.88 months of age) evaluated for feed efficiency were sampled for the study, including 15 with low RFI (−0.592±0.09 kg dry matter/day) and 12 with high RFI (0.792±0.10 kg dry matter/day). In ultrasound and Doppler assessment, the most efficient animals (low RFI) showed higher pulsatility and resistive indexes, as well as a tendency towards greater heterogeneity of the testicular parenchyma (0.625±0.032 vs. 0.508±0.032, 1.012±0.072 vs. 0.802±0.072, and 12.9±0.96 vs. 10.2±0.96, respectively, for low vs. high RFI). However, these animals tended to have lower peak diastolic velocity (5.19±0.50 for low RFI vs. 6.54±0.50 for high RFI). Analysis of fresh semen showed a lower percentage of minor defects in low RFI animals (2.67±1.19%) compared with high RFI animals (8.10±1.19%), without differences in the other parameters in fresh or thawed semen and after thermoresistance testing. Evaluation of flow cytometry parameters showed a higher quality of mitochondrial respiration in semen samples of low RFI animals (22.04±2.50%) compared with high RFI animals (12.29±2.71%). Therefore, although RFI exerts an effect on the Doppler parameters of the pampiniform plexus, it is not sufficient to affect the quality of fresh or thawed semen.(AU)

Use of auxiliary techniques for assessing the reproductive capacity of natural service Nellore bulls.

The aim of this study was to investigate whether parameters obtained by computer-assisted sperm analysis (CASA), infrared thermography (IRT), and testicular B-mode and Doppler ultrasound can be used as indicators of fertility in natural service Nellore bulls. Twenty-nine Nellore bulls were evaluated on days 66 (-D66), 38 (-D38), and 10 (-D10) before the beginning of natural service mating. In all assessments, semen samples were collected and sperm kinetics were evaluated by CASA, thermographic imaging of the scrotal and ocular region, testicular B-mode ultrasound, and Doppler ultrasound of the spermatic cord. At the end of natural service, the bulls were classified based on the pregnancy rate of individual batches into low fertility (pregnancy rate 66.57 ± 0.62 %), medium fertility (76.47 ± 0.51 %), and high fertility (84.80 ± 0.60 %) groups. No difference in the IRT parameters was observed between groups. High fertility animals exhibited higher average path velocity (VAP = 110.98 µm/s), straight line velocity (VSL = 87.05 µm/s), curvilinear velocity (VCL = 190.78 µm/s), pulsatility index (PI = 0.93), and resistive index (RI = 0.57) than low fertility animals (VAP = 100.02 µm/s; VSL = 79.84 µm/s; VCL = 173.22 µm/s; PI = 0.69; RI = 0.48). Positive correlations were observed between pregnancy rate and VSL (0.21), PI (0.28) and RI (0.32). In conclusion, IRT does not provide fertility indicators in Nellore bulls. The VAP, VSL and VCL obtained by CASA and PI and RI obtained by Doppler ultrasound can be used as indicators of fertility in Nellore bulls.

Effect of Nellore (Bos indicus) donor age on in-vitro embryo production and pregnancy rate.

The aim of this study was to evaluate the effect of age of Nellore (Bos indicus) donors on the efficiency of in vitro embryo production (IVEP) and pregnancy rate. Thirty-six donors, including 11 female calves (13 ± 0.61 months), 17 prepubertal heifers (25 ± 0.78 months) and 8 cows (83 ± 28 months), were submitted to 3 procedures of ovum pickup (OPU) on random days of the estrous cycle at intervals of 21 days. Caspase-3 and IGFBP2 were quantified in oocytes and blastocysts for the evaluation of oocyte and embryo quality. The produced embryos were vitrified (n = 445) and transferred to synchronized recipients. Cows produced a larger number of follicles (cows: 54.5 ± 6.2; calves: 20.0 ± 0.57; prepubertal heifers: 20.8 ± 0.46), total oocytes (cows: 45.97 ± 7.22; calves: 28.93 ± 6.14; prepubertal heifers: 27.21 ± 4.94) and cleaved oocytes (cows: 21.14 ± 4.22; calves: 13.09 ± 3.72; prepubertal heifers: 12.4 ± 3.19). The cleavage rate was similar between age categories; however, cows tended (p < 0.07) to produce a larger number of blastocysts (9.74 ± 2.26) per OPU than calves (5.57 ± 1.99) and prepubertal heifers tended to have a higher blastocyst yield (35.4%) than calves (27.1%) (p < .07). The expression levels of IGFBP2 and caspase-3 were higher in oocytes derived from calves compared to the other two categories. The pregnancy rate was higher in calves (43.1%) and cows (40.4%) than in prepubertal heifers (33.8%) (p = .03). Despite the larger numbers of follicles and viable oocytes in cows, the blastocyst production results and pregnancy rates obtained indicate that the use of young females as oocyte donors in IVEP is feasible and may contribute to reduce the generation interval.

Cinética e integridade de espermatozoides caprinos criopreservados utilizando Red Cushion® como estratégia de proteção espermática durante a centrifugação do sêmen / Kinetics and integrity of cryopreserved goat sperm using Red Cushion® as a strategy to sperm protection during semen centrifugation

Objetivou-se avaliar o efeito do gradiente de Iodixanol (Red Cushion®, RC) como método deproteção espermática durante a centrifugação (CE) do sêmen caprino destinado à criopreservação. Foramrealizadas colheitas de sêmen de cinco reprodutores caprinos da raça Anglo Nubiana (N= cincoejaculados/bode). Os ejaculados foram divididos em três grupos experimentais: GC (Controle); G1 (CEutilizado 1ml de RC) e G2 (foi utilizado 0,5mL de RC, misturado ao pellet espermático após a CE). Asamostras foram centrifugadas, diluídas, envasadas e criopreservadas. A cinética espermática foi avaliada porsistema computadorizado de análise (CASA) após a descongelação e pós-teste de termorresistência (TTR), efoi avaliada a integridade de membrana plasmática e acrossomal (MPAI, %). Não foram observadasdiferenças para a motilidade total (p=0,1849) avaliada pós-descongelação (GC=45,1%, G1=51,86% eG2=55,28%) ou pós-TTR (GC=10,32%, G1=11,44% e G2=13,16%), bem como para nenhum outroparâmetro cinético avaliado. Também não foram encontradas diferenças para a MPAI (GC=43,70% ±16,60; G1=36,68 ± 17,40; G2=41,72 ± 14,76; p=0,2523). Conclui-se que a utilização de Red Cushion®não promove nenhum benefício à manutenção da cinética e integridade de espermatozoides caprinossubmetidos a centrifugação previamente ao processo de criopreservação do sêmen.

The aim of this study was to evaluate the efficacy of iodixanol gradient centrifugation (RedCushion®, RC) as a method of protection of goat semen submitted to centrifugation previously tocryopreservation process. Semen were collected from five Anglo Nubian goats (n = five ejaculates/goat).The ejaculates were divided into three experimental groups: GC (Control; conventional centrifugation);G1 (centrifugation using 1ml RC) and G2 (centrifugation using 0.5 mL RC, mixed to sperm pellet beforethe cryopreservation). Samples were centrifuged (CE) at 600xg for 10 minutes, diluted, packed andcryopreserved. Sperm kinetics were evaluated using a computer assisted semen analysis (CASA) afterthawing and after thermoresistance test (TTR), and the integrity of the plasma and acrosomal membranewas evaluated (MPAI, %). No differences were observed for total motility (P =0.1849) assessed afterthawing (GC=45.1%, G1=51.86% and G2=55.28%) or post-TTR (GC=10.32%, G1=11.44% andG2=13.16%), as well as for the other kinetic parameters analyzed. Furthermore, no differences for MPAI(CG =43.70% ± 16.60; G1=36.68 ± 17.40; G2=41.72 ± 14.76; P=0.2523) were found comparing thedifferent groups. In conclusion, Red Cushion® was not able to improve the kinetics and integrity of thegoat semen submitted to the cryopreservation process.

Cinética e integridade de espermatozoides caprinos criopreservados utilizando Red Cushion® como estratégia de proteção espermática durante a centrifugação do sêmen / Kinetics and integrity of cryopreserved goat sperm using Red Cushion® as a strategy to sperm protection during semen centrifugation

Objetivou-se avaliar o efeito do gradiente de Iodixanol (Red Cushion®, RC) como método deproteção espermática durante a centrifugação (CE) do sêmen caprino destinado à criopreservação. Foramrealizadas colheitas de sêmen de cinco reprodutores caprinos da raça Anglo Nubiana (N= cincoejaculados/bode). Os ejaculados foram divididos em três grupos experimentais: GC (Controle); G1 (CEutilizado 1ml de RC) e G2 (foi utilizado 0,5mL de RC, misturado ao pellet espermático após a CE). Asamostras foram centrifugadas, diluídas, envasadas e criopreservadas. A cinética espermática foi avaliada porsistema computadorizado de análise (CASA) após a descongelação e pós-teste de termorresistência (TTR), efoi avaliada a integridade de membrana plasmática e acrossomal (MPAI, %). Não foram observadasdiferenças para a motilidade total (p=0,1849) avaliada pós-descongelação (GC=45,1%, G1=51,86% eG2=55,28%) ou pós-TTR (GC=10,32%, G1=11,44% e G2=13,16%), bem como para nenhum outroparâmetro cinético avaliado. Também não foram encontradas diferenças para a MPAI (GC=43,70% ±16,60; G1=36,68 ± 17,40; G2=41,72 ± 14,76; p=0,2523). Conclui-se que a utilização de Red Cushion®não promove nenhum benefício à manutenção da cinética e integridade de espermatozoides caprinossubmetidos a centrifugação previamente ao processo de criopreservação do sêmen.(AU)

The aim of this study was to evaluate the efficacy of iodixanol gradient centrifugation (RedCushion®, RC) as a method of protection of goat semen submitted to centrifugation previously tocryopreservation process. Semen were collected from five Anglo Nubian goats (n = five ejaculates/goat).The ejaculates were divided into three experimental groups: GC (Control; conventional centrifugation);G1 (centrifugation using 1ml RC) and G2 (centrifugation using 0.5 mL RC, mixed to sperm pellet beforethe cryopreservation). Samples were centrifuged (CE) at 600xg for 10 minutes, diluted, packed andcryopreserved. Sperm kinetics were evaluated using a computer assisted semen analysis (CASA) afterthawing and after thermoresistance test (TTR), and the integrity of the plasma and acrosomal membranewas evaluated (MPAI, %). No differences were observed for total motility (P =0.1849) assessed afterthawing (GC=45.1%, G1=51.86% and G2=55.28%) or post-TTR (GC=10.32%, G1=11.44% andG2=13.16%), as well as for the other kinetic parameters analyzed. Furthermore, no differences for MPAI(CG =43.70% ± 16.60; G1=36.68 ± 17.40; G2=41.72 ± 14.76; P=0.2523) were found comparing thedifferent groups. In conclusion, Red Cushion® was not able to improve the kinetics and integrity of thegoat semen submitted to the cryopreservation process.(AU)