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Myostatin (MSTN), a member of the TGF-β superfamily, is a negative regulator of skeletal muscle mass. We have previously shown that the cell survival/apoptosis pathway is a downstream target of MSTN loss-of-function in mice through the regulation of the expression or abundance of many survival and apoptotic factors. In this study, we used western-blot and quantitative PCR (qPCR) analyses to validate these novel downstream targets of MSTN in double-muscled (DM) cattle v. their controls including 260-day-old foetuses and adult cows from the INRA95 strain. MSTN loss-of-function in DM foetuses and DM cows resulted in a glycolytic shift of the muscles (e.g. upregulation of H-MyBP, PGM1 and SNTA1 and downregulation of H-FABP), activation of cell survival pathway through regulation of some components of the PI3K/Akt pathway (e.g. upregulation of DJ-1 and Gsk-3βser9/Gsk-3βtotal ratio and downregulation of PTEN) and upregulation of cell survival factors translationally controlled tumour protein (14-3-3E, Pink1). We also found a lower abundance of pro-apoptotic transcripts and/or proteins (Caspase-3, caspase-8, caspase-9, BID, ID2 and Daxx) and a higher expression of anti-apoptotic transcripts (Traf2 and Bcl2l2) in DM muscles. All together, these results are in favour of activation of the cell survival pathway and loss of apoptosis pathway within the muscles of DM animals. Alteration of both pathways may increase myonuclear or satellite cell survival, which is crucial for protein synthesis. This could contribute to muscle hypertrophy in DM foetuses and DM cows. [ABSTRACT FROM AUTHOR]

Abstract: The temporal relationships between thyroid status and differentiation of liver, heart and different skeletal muscles were examined in 42 bovine fetuses from day 110 to day 260 of development using principal component analysis of the data. Plasma concentrations of reverse-triiodothyronine (rT3) and thyroxine (T4) increased during development from day 110 to day 210 or 260, respectively, whereas concentration of triiodothyronine (T3) and hepatic type-1 5′-deiodinase activity (5′D1) increased from day 180 onwards. On day 260, high T4 and rT3 and low T3 concentrations were observed together with a mature 5′D1 activity. Cytochrome-c oxidase (COX) activity expressed per mg protein increased at day 180 in masseter and near birth in masseter, rectus abdominis and cutaneus trunci muscles (P <0.05). Significant changes in citrate synthase (CS) activity per mg protein were observed between day 110 and day 180 in the liver and between day 210 and day 260 in the liver, the heart and the longissimus thoracis muscle (P <0.05). Muscle contractile differentiation was shown by the disappearance of the fetal myosin heavy chain from day 180 onwards. A positive correlation (r >0.47, P <0.01) was shown between thyroid status parameters (5′D1, concentrations of T4 and T3) and COX activity in muscles known to be oxidative after birth (masseter, rectus abdominis) but not in liver and heart, nor in muscles known to be glycolytic after birth (cutaneus trunci, longissimus thoracis). A similar correlation was found between thyroid parameters and CS activity in liver and masseter. Results indicate that elevation of plasma T3 concentrations in the last gestational trimester could be involved in the differentiation of oxidative skeletal muscles. [Copyright &y& Elsevier]

The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. Our objective was to compare the production and metabolic responses of 22 Montbéliarde (MONT) and 18 Holstein (HOLS) multiparous cows during the periparturient period, and during a sequential nutritional challenge (SNC), consisting of 4 successive induced short feed restrictions each separated by a refeeding period, to explore breed differences in robustness (ability to maintain lactation function during successive challenges) and resilience (ability to recover after each challenge). Cows were studied from 4 wk before expected calving until 158 ± 9 DIM (mean ± SD). Milk and ECM yields were greater in HOLS than in MONT during both the early- (i.e., from calving to wk 10) and mid-lactation (i.e., from wk 18 to 22) periods, whereas BCS was greater in MONT than HOLS. During early lactation, energy balance was lower (5 vs. 16 MJ/d) and plasma NEFA (270 vs. 163 µ M) were greater for HOLS than MONT, respectively. Cows in third-and-greater lactation secreted more ECM, and had delayed resumption of luteal activity compared with second-lactation cows. The SNC started at 87 ± 9 DIM and consisted of a sequence of four 4-d periods of feed restriction (FR), during which feed allowance was calculated to meet 50% of individual energy requirements (FR1, FR2, FR3, FR4), each of them being followed by an ad libitum intake period. Cows were allowed 10 d of ad libitum intake between FR1 and FR2 to study the recovery and compare it with the recovery following FR4, and 3 d of ad libitum intake between FR2, FR3, and FR4 to study responses to repeated FR. Feed allowance met 59% to 67% of energy requirements during FR1 through FR4, as milk secretion decreased with successive FR. Breed differences in milk secretion persisted throughout the nutritional challenges, but were more pronounced during the first 2 FR: Uncorrected milk yield was greater for HOLS throughout the entire SNC, whereas ECM and plasma NEFA concentrations and milk fat yield were greater for HOLS than MONT during FR1 and FR2, but not FR3 and FR4, suggesting a reduced ability of HOLS to mobilize and transfer fatty acids into milk with successive FR, and indicating altered robustness of HOLS to maintain high milk yield. Resilience for ECM yield did not differ between breeds. Cows were able to respond to and recover from the SNC by decreasing milk secretion during FR, undergoing acute metabolic adaptations to support lactation, and recovering DMI during each refeeding period. Cow rankings for ECM yield were maintained consistently from early lactation throughout the SNC periods (r s = 0.59 to 0.90), suggesting that dairy potential was a major driver of responses during the SNC for both HOLS and MONT. [ABSTRACT FROM AUTHOR]

The knowledge of the molecular organization of living organisms evolved considerably during the last years. The methodologies associated also progressed with the development of the high-throughput sequencing (SNP array, RNAseq, etc.) and of genomic tools allowing the simultaneous analysis of hundreds or thousands of genes, proteins or metabolites. In farm animals, some proteins, mRNAs or metabolites whose abundance has been associated with meat quality traits have been detected in pig, cattle, chicken. They constitute biomarkers for the assessment and prediction of qualities of interest in each species, with potential biomarkers across species. The ongoing development of rapid methods will allow their use for decision-making and management tools in slaughterhouses, to better allocate carcasses or cuts to the appropriate markets. Besides, their application on living animals will help to improve genetic selection and to adapt a breeding system to fulfill expected quality level. The ultimate goal is to propose effective molecular tools for the management of product quality in meat production chains. [ABSTRACT FROM AUTHOR]