Calving date as a potential predictor for the probability of approval in the first breeding soundness evaluation of Nellore bulls.

Beef production systems primarily use natural service (NS) for breeding. However, a significant number of bulls used for NS are subfertile, limiting the profitability of the cow-calf operations. Therefore, producers should select bulls based on breeding soundness evolutions (BSE) to ensure higher pregnancy rates. Several factors can affect the bull ability to pass a BSE. We hypothesize that calving date would be a factor that affects the bull probability of approval at the first BSE. For this purpose, a multivariate logistic regression in a dataset of 14,737 BSEs from young Nellore bulls was used. Correlations between calving date, biometrics, and semen traits were evaluated using Pearson's correlation coefficient. Our results demonstrated that the calving date affected the probability of approval at the first BSE (p < .05). Indeed, the variable that added more information to our model was the calving date, far more than the age group of the bulls according to Akaike's information criterion. Hence, bulls born on day 0 of the calving season have 1.26 more chances to be approved at the first BSE than bulls born 21 days later. This result highlights the importance of getting the dams of future bulls pregnant as soon as possible in the breeding season. In addition, the calving season should be no longer than 47 days to achieve 80% BSE approval in 20-22 months old Nellore bulls. The strongest correlation was with SC, which decreased as the calving date increased. Therefore, the calving date may be used as a predictor of the outcome of the first BSE in young bulls. In that way, the calving date can help seedstock producers to maximize efficiency in making crucial management decisions during the breeding and calving season including nutrition, reproductive, and culling.

Interaction of Mycobacterium avium subsp. paratuberculosis with bovine sperm.

Mycobacterium avium subsp. paratuberculosis (MAP) is responsible for Paratuberculosis mainly affecting domestic ruminants. The interaction between MAP and sperm and/or germ cells has not yet been established, however the adherence between MAP and the host cell surface is associated to the 85 complex proteins that bind to the host cell's fibronectin. Therefore, this study aimed to evaluate the binding of MAP to bovine sperm and to verify changes in these cells by the presence of MAP before and after sperm cryopreservation. Polyclonal antibodies to MAP 85 complex proteins were produced and utilized in the analyzes. Two Nelore bulls were used for semen collection and MAP dilutions (103-108 CFU/mL) were inoculated in the samples; sperm motility and vigor were evaluated using light microscopy at different times before and after cryopreservation and in the presence and absence of the antibodies 85A and 85B. Interaction of MAP and sperm, interaction of MAP and sperm in the presence of Ab 85A and in the presence of Ab 85B were analyzed by scanning electron microscopy. The viability of MAP after sperm cryopreservation were evaluated by plating the samples after thawing. It was observed that sperm in the presence of MAP shows a decrease in motility and vigor, and that the higher the MAP concentration, the lower the sperm performance. It was possible to determine the viability of MAP after cryopreservation in samples of higher concentrations, which demonstrates the potential of transmission of this pathogen through artificial insemination. The interaction of MAP with bovine sperm occurs mainly in the midpiece and may be linked to the proteins 85A and 85B present in the MAP membrane.

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.

Peça intermediária de espermatozoides bovinos: funções e anormalidades / Midpiece of bovine spermatozoa: functions and abnormalities

O reprodutor tem grande importância na cadeia produtiva por possuir maior potencial de difusão do seu material genético dentro do rebanho do que as fêmeas que produzem apenas uma cria por ano, em manejo de monta natural. Entretanto, este potencial somente se torna real quando os machos apresentam boa qualidade seminal, resultando em menores taxas de retorno ao estro. No entanto, apesar das características reprodutivas apresentarem baixa herdabilidade, é consensual que algumas patologias espermáticas possam apresentar características hereditárias e neste caso podem permanecer disseminadas nos rebanhos. Entre as anomalias espermáticas identificadas nos ejaculados de bovinos, as patologias de peça intermediária são classificadas como defeitos espermáticos maiores, comprometendo a fertilidade dos reprodutores, porém estas têm recebido pouca atenção. O objetivo deste trabalho de revisão é apresentar os principais estudos sobre a formação da peça intermediária, sua importância e como esta pode sofrer anormalidades, visto que ejaculados com presença destas anomalias apresentam baixa motilidade espermática e fertilidade.

Bulls are of immense importance in the productive chain because they have a greater potential of diffusion of genetic material within the herd than females that produce only one calf per year in natural mating management. However, this potential is only achieved when males present good seminal quality, resulting in lower rates of return to estrus. Although the reproductive traits have low heritability, it is consensual that some sperm pathologies may present hereditary characteristics and in this case they can remain disseminated in the herds. Among the sperm abnormalities identified in bovine ejaculates, the midpiece pathologies are classified as a major sperm defect, compromising bull fertility, but these pathologies have received little attention. The objective of this review is to present the main studies on the midpiece formation, its importance and how it can undergo abnormalities, since ejaculates with the presence of this pathology present low sperm motility and fertility.

Peça intermediária de espermatozoides bovinos: funções e anormalidades / Midpiece of bovine spermatozoa: functions and abnormalities

O reprodutor tem grande importância na cadeia produtiva por possuir maior potencial de difusão do seu material genético dentro do rebanho do que as fêmeas que produzem apenas uma cria por ano, em manejo de monta natural. Entretanto, este potencial somente se torna real quando os machos apresentam boa qualidade seminal, resultando em menores taxas de retorno ao estro. No entanto, apesar das características reprodutivas apresentarem baixa herdabilidade, é consensual que algumas patologias espermáticas possam apresentar características hereditárias e neste caso podem permanecer disseminadas nos rebanhos. Entre as anomalias espermáticas identificadas nos ejaculados de bovinos, as patologias de peça intermediária são classificadas como defeitos espermáticos maiores, comprometendo a fertilidade dos reprodutores, porém estas têm recebido pouca atenção. O objetivo deste trabalho de revisão é apresentar os principais estudos sobre a formação da peça intermediária, sua importância e como esta pode sofrer anormalidades, visto que ejaculados com presença destas anomalias apresentam baixa motilidade espermática e fertilidade.(AU)

Bulls are of immense importance in the productive chain because they have a greater potential of diffusion of genetic material within the herd than females that produce only one calf per year in natural mating management. However, this potential is only achieved when males present good seminal quality, resulting in lower rates of return to estrus. Although the reproductive traits have low heritability, it is consensual that some sperm pathologies may present hereditary characteristics and in this case they can remain disseminated in the herds. Among the sperm abnormalities identified in bovine ejaculates, the midpiece pathologies are classified as a major sperm defect, compromising bull fertility, but these pathologies have received little attention. The objective of this review is to present the main studies on the midpiece formation, its importance and how it can undergo abnormalities, since ejaculates with the presence of this pathology present low sperm motility and fertility.(AU)