Objective: The aim of the present study was to determine the effect of supplementing pasture-finished steers with corn silage on the expression level of the calpain system proteins and beef tenderization.Methods: Thirty Braford steers grazing on summer pasture were used for the study. For 120 days fifteen animals were supplemented with corn silage at 1% of body weight per head per day (Suppl) whereas the remaining 15 steers only received pasture (Contr). Carcass and meat traits were evaluated and compared between groups. Gene expression and activities of proteases (calpain 1 and calpain 2) and inhibitor (calpastatin) were measured using real-time polymerase chain reaction and casein zymography.Results: Carcass and meat traits were significantly different between feeding systems. Supplemented steers showed higher hot carcass weight (p<0.01), fat content (p = 0.02), and Warner-Bratzler shear force (p = 0.03). Furthermore, the control group showed higher protease:inhibitor ratios, at mRNA (p = 0.01) and protein levels (p<0.10). Warner-Bratzler shear force and mRNA calpains:calpastatin ratio were associated in both feeding systems (p<0.01).Conclusion: Based on the results obtained in the study, beef tenderness differences among finishing strategies could be modulated through differential expression of the calpain system proteins.
Tenderness is considered the most important meat quality trait regarding its eating quality. Post mortem meat tenderization is primarily the result of calpain mediated degradation of key proteins within muscles fibers. The calpain system originally comprised three molecules: two Ca 2+ -dependent proteases and a specific inhibitor. Numerous studies have shown that the calpain system plays a central role in postmortem proteolysis and meat tenderization. The objective of this review is to describe the last biochemical and molecular findings in connection with this proteolytic system and their relation with meat tenderness in bovine. Findings of DNA polymorphisms and mRNA and protein expression are described as tools to predict meat tenderness. Understanding the molecular basis of meat tenderization may be useful particularly to the meat industry and may allow amendment of pre-slaughter handling practices and postmortem treatments that improves meat quality.Keywords: Bovine, Molecular Markers, Tenderness (Source: AGROVOC). RESUMENLa terneza de la carne es considerada como el atributo de mayor importancia en el concepto de calidad de carne. El proceso de tenderización de la carne post mortem es principalmente el resultado de la degradación de proteínas clave de las fibras musculares, mediado por las proteasas del sistema calpaína. Este sistema proteico está compuesto por tres moléculas: dos proteasas calcio-dependientes y su inhibidor específico. Numerosos estudios han demostrado que el sistema calpaína desempeña un papel central en la proteólisis postmortem y en la tenderización de la carne. El objetivo de esta revisión es describir los últimos descubrimientos bioquímicos y moleculares de este sistema proteolítico y su relación con la terneza de la carne bovina. Se describen los hallazgos de polimorfismos de ADN y de expresión de ARNm y proteínas, como herramientas para predecir la terneza de la carne. La comprensión de las bases moleculares de la tenderización de la carne puede ser de utilidad para la industria cárnica, permitiendo la modificación de las prácticas de manipulación antes del sacrificio y los tratamientos post mortem, mejorando la calidad de la carne bovina.
Introduction. Growth and follicular maturation involve transformations of various components of the follicle, such as the oocyte, granulosa and techa cells. Several growth factors, including differentiation growth factor 9 (GDF9), bone morphogenic protein 15 (BMP15) and basic fibroblast growth factor (FGF2) are important for follicular development and oocyte maturation, by its ability to increase the proliferation of granulosa, techa cells and the ovarian stroma. Objetive. Evaluate mRNA expression of GDF9, BMP15, FGF2 and their main receptors, transforming growth factor beta receptor 1 (TGFβ-R1), bone morphogenetic protein receptor, type IB (BMPR-IB) and fibroblast growth factor receptor 2 (FGFR2) in bovine follicular cells. Materials and methods. Total RNA was isolated from pooled samples of oocytes (OOs), cumulus cells (CCs) of cumulus oocyte complexes (COCs) and follicular cell pellets (PCs) of 70 ovaries obtained from 96 beef heifers, collected at a local abattoir. The expression pattern of growth factors and their receptors in follicular bovine cells was evaluated by reverse transcriptase polymerase chain reaction (RT-PCR). Results. The mRNA transcripts encoding GDF9, BMP15, FGF2, TGFβ-R1, BMPR-IB and FGFR2 genes were detected, by RT-PCR, in all studied cells. This is the first time that the expression of TGFβ-R1 and BMPR-IB receptors is reported in bovine oocytes. Conclusions. The presence of growth factors and receptor transcripts in the studied cells indicate that these factors could act as paracrine and autocrine regulators of folliculogenesis.
The objective of the present work was to evaluate the effect of J-Synch protocol on pregnancy rate (PR) of heifers artificially inseminated after detected estrus (DEAI) or at fixed-time (FTAI). Two hundred ninety-three Braford heifers were used. On day 0, all animals received 2.0 mg of estradiol benzoate administered intramuscularly (IM) and an intravaginal progesterone-releasing device (DIB, 0.5 g). Heifers were assigned to the following group: 1) J-Synch: on day 6, DIB devices were removed and 500 µg of d-Cloprostenol sodium (d-CS) was administered IM and paint was applied on tail base (tail-paint). On day 9 (60 h after DIB removal), heifers with ≥ 40% of the tail-paint rubbed off were inseminated. Those not showing estrus by 72 h after DIB removal received 100 µg of GnRH at that time and were FTAI. 2) Conventional: on day 7, DIB devices were removed, and 500 µg of d-CS and 0.5 mg of estradiol cypionate were administered IM and tail-paint. Fortyeight hours after DIB removal, heifers with the tail-paint rubbed off were DEAI. Those not showing estrus by 54 h after DIB removal were FTAI. Pregnancy rate was diagnosed by ultrasonography 30 days after FTAI in all heifers and did not differ between protocols (44.28% and 42.48%, P = 0.673). In both protocols, higher PR was observed in DEAI heifers (P = 0.047). In conclusion, the use of the J-Synch protocol generated similar PR to the Conventional protocol, allowing its use with the same efficiency. Furthermore, the DEAI generated better PR than the FTAI, regardless of the protocol used.
We certify that there are no conflicts of interest with any financial organization regarding the material discussed in the manuscript.
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