Effect of sequence of insemination after simultaneous thawing of multiple semen straws on conception rate to timed AI in suckled multiparous Nelore cows

Frozen Bovine Semen Storage, Semen Handling, and Site of Deposition

Artificial insemination (AI) is an effective strategy to distribute semen from elite sires and improve the genetics of a herd. Commercial studs provide a fertile semen product to their customers. Consequently, the maintenance of sire fertility is dependent upon appropriate semen storage, handing, and site of semen deposition. When retrieving a straw of frozen semen, the cane (and canister containing canes) should be held below the frost-line and limited to 8 seconds in the neck of the tank. After appropriate thawing, and continuous thermoregulation of the AI gun containing the thawed semen, semen should be deposited in the uterine body.

Dual-Purpose Cattle Raised in Tropical Conditions: What Are Their Shortcomings in Sound Productive and Reproductive Function?

Dual-purpose husbandry might well be the most commonly employed cattle management system in tropical regions worldwide. The advantages of producing both meat and milk, although in reduced quantities, gives an edge to the farmer in coping with the volatile economic conditions that prevail in the region. Herein, we discuss the different methods of cattle management under tropical conditions based on the financial and social structure of this system. An account of the sanitary and nutritional conditions available to the farmers and how these factors affect the profitability of the enterprise will also be given. Finally, we will discuss how these systems can take advantage of several biotechnological procedures, and how these tools (such as controlled natural mating, artificial insemination, and embryo transfer) affect reproductive outcomes. The present review will mainly concentrate on production systems located less than 1000 m above sea level, as the problems and shortcomings of cattle raised above this arbitrary landmark are quite different.

Effects of supplemental antioxidants on in vitro fertility measures for cryopreserved boar spermatozoa

This work aims to evaluate how supplementing a commercial freezing media with butylated hydroxytoluene (BHT), or reduced glutathione (GSH), or their combination affected in-vitro measures of boar sperm after cryopreservation. One ejaculate was collected from 30 high-fertility boars in a weekly collection rotation. Samples were diluted 1:1 in an extender and cooled before overnight shipping at 17 °C to the freezing lab. On arrival, samples were split into the treatments with the following additions before cryopreservation; 1) semen without additional antioxidants (Control), 2) semen with 1 mM BHT, 3) semen with 2 mM GSH, and 4) semen with 1 mM BHT+2 mM GSH. Semen was evaluated for motility kinetics at 30, 120, and 240 min after thawing. Flow cytometry assessments were performed at 60 min after thawing. At all-time points evaluated, total and progressive motility were greater (P ≤ 0.05) in semen cryopreserved with GSH than in Control. No (P > 0.05) differences between Control and other treatment groups were observed in viability, or acrosomal and mitochondrial membrane integrity; however, the proportion of capacitated spermatozoa were reduced (by -21.17%) in semen treated with BHT + GSH compared to Control (P ≤ 0.05). In contrast, there was a higher (P ≤ 0.05, +21.18%) superoxide anion production in the Control than in the BHT + GSH. For IVF, semen cryopreserved with both antioxidants (BHT + GSH) had a negative (P < 0.05) impact on fertilization rate (-54.11%) compared to Control. However, for the blastocysts rate, there were more (+22.75%) blastocysts (P ≤ 0.05) for BHT compared to Control. These results indicate that commercial media supplemented with GSH increased motility but impaired in vitro fertilization rate. On the other hand, media supplemented with BHT improved the in vitro fertilizing ability of the frozen-thawed sperm cells. Therefore, we suggest the supplementation with 1 mM of BHT in the formula of commercial freezing media used in the present experiment.

In vitro sperm characteristics and in vivo fertility of sex-sorted and conventional semen in suckled Nelore cows at a traditional schedule for timed-AI with estrus detection

ABSTRACT The aim of this study was to assess in vitro sperm characteristics and pregnancies/AI (P/AI) of conventional and sex-sorted semen at timed-AI of suckled, multiparous Nelore cows. All cows (n=348) were submitted to a traditional estradiol/progesterone(P4)-based protocol. At 48h after P4-device removal, the estrous behavior was recorded, and AI was performed with conventional or sex-sorted semen from two bulls. The following sperm assessments were performed: CASA, Hyposmotic Test, sperm morphometry and chromatin structure by TB staining. P/AI were reduced (P<0.001) for sex-sorted compared to conventional semen in cows expressing estrus (27vs47%) or not (11vs.37%). Membrane integrity (Bull1: 30.3±9.6 vs. 52.3±12.4%, P=0.01; Bull2: 24.5±3.0 vs. 48.7±1.6%, P=0.006) and sperm concentration (Bull1: 23.2±0.6 vs. 43.0±0.8x10⁶sperm/mL, P<0.001; Bull2: 25.1±2.8 vs. 42.1±0.7x10⁶sperm/mL; P<0.001) were reduced in sex-sorted compared to conventional semen, for both bulls. Total and progressive motility were reduced in sex-sorted semen for Bull1 (TM: 49.7±15.9 vs. 94.9±1.9%, P=0.007; PM: 16.7±3.4 vs. 44.1±13.2%, P=0.009) and no differences were detected for Bull2 (TM: 45.0±17.5 vs. 68.2±19.1%, P=0.098; PM: 12.8±4.7 vs. 30.0±13.0%, P=0.065). Sperm ellipticity from sex-sorted was lower than conventional semen for Bull2 (0.306±0.01 vs. 0.342±0.02, P=0.02) and no difference was detected for Bull1 (0.332±0.01 vs. 0.330±0.01, P=0.55). Reduced in vivo fertility was observed for sex-sorted semen, regardless of estrous behavior. In vitro sperm quality of sex-sorted semen was compromised for both bulls, but differently affected for each sire.

Influência da dificuldade de inseminação, temperamento e cortisol plasmático sobre a taxa de concepção de vacas e novilhas da raça Nelore inseminadas em tempo fixo

RESUMO O objetivo do presente experimento foi avaliar efeito do estresse e da dificuldade de inseminação (DifIA) sobre a taxa de concepção (TC) de vacas (n=93) e novilhas (n= 72) Nelore submetidas à IATF. No D9, anotou-se nota de temperamento (NTe) e tempo da saída do brete (TSB) de todos os animais e coletou-se sangue das novilhas. No dia da IATF (D11), anotou-se NTe, TSB, DifIA e tempo de IA. A TC foi 36% para vacas e 46% para novilhas (P>0,05). Não foi observado efeito de Nte sobre TC (P>0,05). Porém, houve tendência para maior (P<0,10) TC nos animais que não apresentaram dificuldade de inseminação (DifIA1; TP=42%) em comparação aos animais com moderada ou alta dificuldade (DifIA2+DifIA3; TP=27%). Foi observado menor (P<0,05) tempo de IA para animais DifIA1 (17:31±06:02s) que animais DifIA2-3 (30:10±15:45s). Novilhas com maiores (P<0,05) níveis de cortisol apresentaram maior NTe (P<0,05). Entretanto, TC (59%) das novilhas menos reativas (cortisol=4,12±1,12ng/mL; NTe=3,2±0,6) não diferiu da TC (41%; P>0,05) das mais agitadas (cortisol=7,76±1,33ng/mL; NTe=3,82±0,79). Concluiu-se que avaliações de temperamento se relacionaram com nível de estresse, embora esses parâmetros não tenham afetado a TC deste trabalho. A maior dificuldade e/ou tempo necessário para se completar a IA demonstrou ser um potencial fator para a redução da fertilidade na IATF.

Effect of sex on cryotolerance of bovine embryos produced in vitro

Male and female embryos are known to be different in developmental kinetics, metabolism, gene expression, and epigenetic patterns. Therefore, the objective of this study was to clarify whether the morphological criteria used to select embryos for cryopreservation lead to a deviation in the male:female ratio, and whether vitrification effects vary according to embryo sex. Initially, five sires were tested to evaluate the effect of the bull on embryo development, sex ratio, speed of development, and response to cryopreservation. Results showed that bulls affected (P < 0.05) embryo production, response to cryopreservation, and sex ratio. Then, one bull was selected, and used to produce embryos in vitro to characterize the responses of male and female embryos to vitrification. Results suggested that male and female embryos have the same morphological responses to vitrification, as no differences (P > 0.05) were observed between the two sexes in post-warming survival and re-expansion rates. However, their molecular responses as evaluated by gene expression (FOSL1, HSPB1, CASP3, CASP8, HSPA5, HSPA1A, G6PD, and PGK1) analysis indicated an effect of sex on vitrification; vitrified female embryos exhibited higher mRNA levels of HSPA1A, CASP3, and G6PD compared to their male counterparts. In conclusion, bulls affected embryo production, speed of development, sex ratio, and response to cryopreservation. Male and female embryos differed in their molecular responses to vitrification; and also, deviations in the male:female ratio when selecting embryos for cryopreservation were confirmed.

Influence of post-thawing thermal environment on bovine sperm characteristics and in vitro fertility

Our aim was to evaluate the effects of three thermal environments over time on kinetics, functionality and in vitro fertility of cryopreserved bovine spermatozoa. Four ejaculates from five bulls (n = 20) were cryopreserved. After thawing, semen was evaluated (0 hr), incubated for 4 hr in T36.0 (36.0°C), T38.0 (38.0°C) and T39.5 (39.5°C), and analysed every hour (1 hr, 2 hr, 3 hr, 4 hr). In vitro production of embryos was performed at 0 hr and 4 hr. Sperm motility and cell kinetics (Computer-Assisted Sperm Analysis) were impaired after 2 hr at T38.0 and T39.5 (p < 0.05). Flow cytometry revealed an increase in the cells with injured plasma membrane to 39.5°C and a general reduction in the mitochondrial potential over time (p < 0.05). In vitro fertility was impaired in all temperatures after 4 hr, but there was no difference between 36.0°C and 38.0°C. Our results suggest that the ex situ resilience of semen at 36.0°C after thawing with no major damage to the quality is limited to 3 hr. In normothermia or in thermal stress, sperm cells present a gradual reduction of movement and functionality, which were more significant after 1 hr of incubation. The in vitro production of embryos is impaired when the semen is kept in a thermal environment ≥36.0°C for 4 hr.

In vitro evaluation of cryopreserved bovine sperm and its relation to field fertility in fixed-time artificial insemination

This study aimed to assess characteristics of bovine cryopreserved sperm and evaluate its relation to field fertility in fixed-time artificial insemination (FTAI). Semen samples of 16 bulls were used to inseminate 811 Nellore cows, and four of these bulls were also used to inseminate 101 Nellore heifers. Samples of the same ejaculate used for FTAI from each bull were analysed in the laboratory after thawing. Sperm motility and vigour were subjectively assessed by light microscope, and integrity of the plasma and acrosome membranes, and H₂ O₂ production were evaluated by flow cytometer. Relation among sperm characteristics and pregnancy rate of cows and heifers were evaluated by univariate and multivariate logistic regression. Subjective sperm motility and vigour did not affect the probability of pregnancy in cows or heifers. In univariate analysis for pregnancy in cows, sperm traits related to acrosome injury positively affected probability of pregnancy mainly when associated with plasma membrane integrity; H₂ O₂ production seems to be less important than plasma membrane integrity in affecting probability of pregnancy. In multivariate analysis, sperm traits related to injured acrosome positively affected probability of cow and heifer pregnancies while intact acrosome was negatively related to cow pregnancy. Intact plasma membrane and high H₂ O₂ production were positively related to cow pregnancy but negatively related to heifer pregnancy. Results suggest that a capacitation-like status of the acrosome may benefit probability of pregnancy in cows.

Profile and artificial insemination practices of technicians and the artificial insemination success rates in Leyte, Samar, and Biliran, Philippines (2011-2015)

BACKGROUND

Artificial insemination (AI) is a reproductive biotechnology that may be influenced by several factors, including the profile of the technicians and the practices used. Assessing technician's profile and their AI practices can be significant in improving AI success rate.

AIM

This study aimed to know the profile and current practices used by AI technicians (AITs), to determine the success rates of AI in water buffaloes in Leyte, Samar, and Biliran from 2011 to 2015, and to evaluate the possible association between the parameters investigated.

MATERIALS AND METHODS

A total of 50 AITs from Leyte, Samar and Biliran, Philippines, were interviewed using a fixed questionnaire about their profile and employed AI practices, and 20,455 AI-related records of the Philippine Carabao Center (PCC) at Visayas State University (VSU), Baybay City, Leyte, were screened and analyzed. AI success rates were determined by retrospective analysis of the gathered data. Statistical analysis was performed between the technician profile and practices and the AI success rates.

RESULTS

Results revealed that most of the technicians were male, around 31-40 years old, married, college graduates, working under local government units, had other sources of income, and with 1-5 years of continuous AI practice averaging 51-100 inseminations per year. Most of them attended only one basic training seminar, which was conducted more than 3 years ago in PCC in VSU. AI success rates were recorded highest in 2011 and lowest in 2015. Statistical analyses showed that some technician profile parameters (civil status, average AI per year, and the training center) and several practices (checking of soft cervix, rectal palpation, thawing temperature method, straw cutting method, and semen deposition) might have an influence on the success of AI.

CONCLUSION

This study documents the first report on AIT's profile and their employed AI practices and the AI success rates in Leyte, Samar, and Biliran, Philippines. Selected profile parameters and AI practices may influence AI success rates. AITs should perform more AI services and revisit the employed practices.

PREGNANCY RATES AND BODY MORPHOMETRY IN NELLORE COWS SUBMITTED TO PROGESTERONE AND TEMPORARY WEANING OF CALVES

Body morphometry and temporary weaning (TW) associated to two protocols of fixed-time artificial insemination (FTAI) with intravaginal progesterone releasing device (IPRD) upon pregnancy rates were evaluated. Cows, at 45-59 days post-partum, were randomly divided into group 1 (n=147) and group 2 (n=197). Group 1: received 1g progesterone (IPRD) and 2mg estradiol benzoate on day 0 (EB-D0); 150μg D-cloprostenol on day 7 (PGF-2α-D7); 0,5mg estradiol cypionate and (TW-48 hours) on day 9 (EC+TW-D9); FTAI on day 11 (D11); group 2: IPRD+EB (D0); PGF-2α+EC+TW (72 hours) on D8; FTAI (D11). The pregnancy rate was higher in cows submitted to TW (72 hours) than in cows with TW (48 hours), or rather, 49.74% vs 30.60% (p<0.05). There was a statistical difference (p<0.05) in groups 1 and 2 between pregnant or non-pregnant cows with regard to body weight (412kg vs 400kg and 419kg vs 390kg) and body condition score (BCS) (3.33 vs 3.08 and 3.53 vs 3/32) respectively. Further, 72-hour weaning associated to the applied protocol improved the pregnancy rate. The evaluation of BCS during post-partum may adjust the start of the breeding season.

Impaired protamination and sperm DNA damage in a Nellore bull with high percentages of morphological sperm defects in comparison to normospermic bulls

The routine semen evaluation assessing sperm concentration, motility and morphology, does not identify subtle defects in sperm chromatin architecture. Bulls appear to have stable chromatin, with low levels of DNA fragmentation. However, the nature of fragmentation and its impact on fertility remain unclear and there are no detailed reports characterizing the DNA organization and damage in this species. The intensive genetic selection, the use of artificial insemination and in vitro embryo production associated to the cryopreservation process can contribute to the chromatin damage and highlights the importance of sperm DNA integrity for the success of these technologies. Frozen-thawed semen samples from three ejaculates from a Nellore bull showed high levels of morphological sperm abnormalities (55.8±5.1%), and were selected for complementary tests. Damage of acrosomal (76.9±8.9%) and plasma membranes (75.7±9.3%) as well as sperm DNA strand breaks (13.8±9.5%) and protamination deficiency (3.7±0.6%) were significantly higher compared to the values measured in the semen of five Nellore bulls with normospermia (24.3±3.3%; 24.5±6.1%; 0.6±0.5%; 0.4±0.6% for acrosome, plasma membrane, DNA breaks and protamine deficiency, respectively) (P<0.05). Motility and percentage of spermatozoa with low mitochondrial potential showed no differences between groups. This study shows how routine semen analyses (in this case morphology) may point to the length and complexity of sperm cell damage emphasizing the importance of sperm function testing.

Assessment of in vitro sperm characteristics and their importance in the prediction of conception rate in a bovine timed-AI program

The aims of this study were to assess in vivo fertility and in vitro sperm characteristics of different sires and to identify sperm variables important for the prediction of conception rate. Multiparous Nelore cows (n = 191) from a commercial farm underwent the same timed artificial insemination (timed-AI) protocol. Three batches of frozen semen from three Angus bulls were used (n = 9). A routine semen thawing protocol was performed in the laboratory to mimic field conditions. The following in vitro sperm analyses were performed: Computer Assisted Semen Analysis (CASA), Thermal Resistance Test (TRT), Hyposmotic Swelling Test (HOST), assessment of plasma and acrosomal membrane integrity, assessment of sperm plasma membrane stability and of lipid peroxidation by flow cytometry and assessment of sperm morphometry and chromatin structure by Toluidine Blue staining. For statistical analyses, Partial Least Squares (PLS) regression was used to explore the importance of various sperm variables in the prediction of conception rate. The following in vitro sperm variables were determined to be important predictors of conception rate: total motility (TM), progressive motility (PM), TM after 2 h of thermal incubation (TM_2 h), PM after 2 h of thermal incubation (PM_2 h), Beat Cross Frequency after 2 h of thermal incubation (BCF_2 h), percentage of rapidly moving cells after 2 h of thermal incubation (RAP_2 h), intact plasma membrane evaluated by HOST, intact plasma and acrosomal membranes evaluated by flow cytometry, intact plasma membrane suffering lipid peroxidation, major defects, total defects, morphometric width/length ratio, Fourier_0 and Fourier_2 and Chromatin Heterogeneity. We concluded that PLS regression is a suitable statistical method to identify in vitro sperm characteristics that have an important relationship with in vivo bull fertility.