Relative Late Gestational Muscle and Adipose Thickness Reflect the Amount of Mobilization of These Tissues in Periparturient Dairy Cattle

Assessment of skeletal muscle dynamics and milk production across a 300-day lactation in multiparous dairy cattle

The objective of this study was to evaluate changes in longissimus dorsi muscle depth (LDD) across lactation (0 to 300 DIM) and identify the effect of low versus high muscle reserves immediately after parturition on BW and body reserve changes as well as production variables across a 300-d lactation. Forty multiparous cows were classified as high muscle (HM; LDD > 5.0 cm; n = 18) or low muscle (LM; LDD ≤ 5.0 cm; n = 22) based on LDD measurements collected within 24 h of parturition. Body weights and ultrasound scans to assess LDD and back fat depth (BFD) were collected monthly from parturition until 300 DIM. Ultrasound scans captured and measured using available software. Blood samples were taken at 7, 150 and 300 DIM, and plasma was analyzed for markers of metabolic status by measuring insulin, nonesterified fatty acids (NEFA), creatinine, and 3-methylhistidine (3-MH). Milk yield was recorded daily and milk components were analyzed monthly. Data analysis was performed and the statistical models included the fixed effect of muscle group, time, their interaction, and the random effect of cow nested within muscle group with repeated measures using a first-order autoregressive covariance structure. Muscle group was not related to BW or BFD for any of the time points measured. Cows lost BW from 0 to 60 DIM and gained weight from 60 to 300 DIM. Similarly, BFD decreased between 0 to 90 DIM and increased BFD after 90 DIM until 300 DIM. A muscle group by time interaction was observed for LDD. The HM cows had more muscle at 0 DIM, indicative of treatment assignment (1.34 cm more), and 300 DIM (0.78 cm more) and tended to have more muscle at 60 DIM (0.66 cm more) compared with LM. After 240 DIM, both muscle groups began net accretion of muscle reserves until 300 DIM. No differences were observed for blood metabolites measured based on muscle group. However, significant time effects for creatinine, 3-MH, and NEFA concentrations existed, which reflected the observed changes in BFD and LDD measured in ultrasound scans. For statistical analysis of daily milk production, observations were grouped into 3 stages of lactation, early (0-60 DIM), mid (60-240 DIM), and late lactation (240-300 DIM). A muscle group by stage of lactation interaction was present, where in early and mid-lactation, HM cows produced, on average, 1.9 kg more milk/d; however, in late lactation, LM cows produced 1.8 kg more milk/d. Our results indicate that muscle reserves are depleted in early lactation, and accreted in late lactation, whereas BW and BFD started to increase by 90 DIM. Data also supports that cows with more extensive muscle depletion in early lactation had greater milk production, however, substantial muscle accretion in late lactation may result in reduced milk production.

Molecular signatures of longissimus dorsi differ between dairy cattle based on prepartum muscle reserves and branched-chain volatile fatty acid supplementation

Dairy cattle with high (HM) versus low muscle (LM) reserves as determined by longissimus dorsi muscle depth (LDD) in late gestation exhibit differential muscle mobilization related to subsequent milk production. Moreover, branched-chain volatile fatty acid (BCVFA) supplementation increased blood glucose levels. We hypothesized that differences in HM and LM reflect distinct muscle metabolism and that BCVFA supplementation altered metabolic pathways. At 42 days before expected calving (BEC), Holstein dairy cows were enrolled in a 2 × 2 factorial study of diet and muscle reserves, by assignment to control (CON)- or BCVFA-supplemented diets and LDD of HM (>4.6 cm) or LM (≤4.6 cm) groups: HM-CON (n = 13), HM-BCVFA (n = 10), LM-CON (n = 9), and LM-BCVFA (n = 9). Longisumus dorsi muscle was biopsied at 21 days BEC, total RNA was isolated, and protein-coding gene expression was measured with RNA sequencing. Between HM and LM, 713 genes were differentially expressed and 481 between BCVFA and CON (P < 0.05). Transcriptional signatures indicated differential distribution of type II fibers between groups, with MYH1 greater in LM cattle and MYH2 greater in HM cattle (P < 0.05). Signatures of LM cattle relative to HM cattle indicated greater activation of autophagy, ubiquitin-proteasome, and Ca2+-calpain pathways. HM cattle displayed greater expression of genes that encode extracellular matrix proteins and factors that regulate their proteolysis and turnover. BCVFA modified transcriptomes by increasing expression of genes that regulate fatty acid degradation and flux of carbons into the tricarboxylic acid cycle as acetyl CoA. Molecular signatures support distinct metabolic strategies between LM and HM cattle and that BCVFA supplementation increased substrates for energy generation.NEW & NOTEWORTHY Muscle biopsies of the longissimus dorsi of prepartum dairy cattle indicate that molecular signatures support distinct metabolic strategies between low- and high-muscle cattle and that branched-chain volatile fatty acid supplementation increased substrates for energy generation.

Variation in protein metabolism biomarkers during the transition period and associations with health, colostrum quality, reproduction, and milk production traits in Holstein cows

The aims of this study were to assess (1) the variation of protein metabolism biomarkers and factors affecting them during the transition period, (2) the association of each biomarker with skeletal muscle reserves and their changes, and (3) the association of these biomarkers with postpartum health, colostrum quality, reproduction, and milk production. For this purpose, 238 multiparous Holstein cows from 6 herds were used in a prospective cohort study. Plasma concentrations of 3-methylhistidine (3-MH) and 1-methylhistidine (1-MH) and serum concentrations of total protein (TP), albumin (ALB), urea nitrogen (BUN), and creatinine (SCR) were determined for each cow at -21, -7, 7, 21, and 28 d relative to calving. Clinical diseases were recorded during the first 28 d postcalving, and presence of subclinical ketosis (scKET) was investigated at 7 and 21 d. Colostrum quality was estimated by Brix refractometry. Reproduction data by 150 d in milk (DIM) and milk production records were also available. Linear mixed models including the fixed effects of time point, herd, parity, body condition score (-21 d), duration of dry period and postparturient diseases were fitted to assess the variation in each biomarker's concentration. The association between the biomarkers' concentration during the prepartum period with the odds for each postparturient disease and for a combined trait (CD_1-28), defined as the presence of at least one clinical condition during the first 28 d after calving, were assessed with separate binary logistic models for time points -21 d and -7 d. The relationship of each biomarker's concentration with longissimus dorsi thickness (LDT) and the changes in LDT (ΔLDT) was assessed with pairwise correlations. Separate general linear models were used to assess the association of each biomarker with colostrum Brix values and milk production traits. Finally, the associated hazard for first artificial insemination (AI) and for pregnancy by 150 DIM (PREG_150DIM) was assessed with Cox proportional hazard models, whereas odds for pregnancy to the first AI (PREG_1stAI) were assessed with binary logistic models. The level of 3-MH was affected mainly by herd, time points, and their interaction. Higher 3-MH was associated with increased odds for metritis and CD_1-28, increased hazard for PREG_150 DIM and with increased milk production. 1-Methylhistidine was affected mainly by herd, scKET and occurrence of displaced abomasum. Higher 1-MH was associated with better colostrum quality, increased odds for scKET, increased hazard for first AI by 150 DIM and with decreased milk production. Both 3-MH and 1-MH were weakly to moderately negatively correlated with LDT and moderately to strongly negatively correlated with ΔLDT at the corresponding time periods. Additionally, higher TP was associated with increased odds for metritis and CD_1-28 and increased milk production, while higher ALB was associated with increased odds for scKET and increased milk production. Moreover, higher BUN was associated with decreased odds for scKET, increased odds for PREG_1stAI and increased milk production. Higher SCR was associated with decreased odds for retained fetal membranes, metritis, and CD_1-28. Periparturient protein metabolism is significantly associated with postpartum health, colostrum quality, reproduction, and milk production; mechanisms involved require further investigation.

Invited review: Muscle protein breakdown and its assessment in periparturient dairy cows

Mobilization of body reserves including fat, protein, and glycogen is necessary to overcome phases of negative nutrient balance typical for high-yielding dairy cows during the periparturient period. Skeletal muscle, the largest internal organ in mammals, plays a crucial role in maintaining metabolic homeostasis. However, unlike in liver and adipose tissue, the metabolic and regulatory role of skeletal muscle in the adaptation of dairy cows to the physiological needs of pregnancy and lactation has not been studied extensively. The functional integrity and quality of skeletal muscle are maintained through a constant turnover of protein, resulting from both protein breakdown and protein synthesis. Thus, muscle protein breakdown (MPB) and synthesis are intimately connected and tightly controlled to ensure proper protein homeostasis. Understanding the regulation of MPB, the catabolic component of muscle turnover, and its assessment are therefore important considerations to provide information about the timing and extent of tissue mobilization in periparturient dairy cows. Based on animal models and human studies, it is now evident that MPB occurs via the integration of 3 main systems: autophagy-lysosomal, calpain Ca²⁺-dependent cysteine proteases, and the ubiquitin-proteasome system. These 3 main systems are interconnected and do not work separately, and the regulation is complex. The ubiquitin-proteasomal system is the most well-known cellular proteolytic system and plays a fundamental role in muscle physiology. Complete degradation of a protein often requires a combination of the systems, depending on the physiological situation. Determination of MPB in dairy cows is technically challenging, resulting in a relative dearth of information. The methods for assessing MPB can be divided into either direct or indirect measurements, both having their strengths and limitations. Available information on the direct measures of MPB primarily comes from stable isotopic tracer methods and those of indirect measurements from assessing expression and activity measures of the components of the 3 MPB systems in muscle biopsy samples. Other indirect approaches (i.e., potential indicators of MPB), including ultrasound imaging and measuring metabolites from muscle degradation (i.e., 3-methylhistidine and creatinine), seem to be applicable methods and can provide useful information about the extent and timing of MPB. This review presents our current understanding, including methodological considerations, of the process of MPB in periparturient dairy cows.

Skeletal muscle and adipose tissue reserves and mobilisation in transition Holstein cows: Part 2 association with postpartum health, reproductive performance and milk production

The aim of this study was, for the first time, to simultaneously assess the association of skeletal muscle and subcutaneous fat reserves and their mobilisation, measured by ultrasonography, with the incidence of specific postparturient health, reproduction, and milk production traits. For this purpose, ultrasound measurements of longissimus dorsi thickness (LDT) and backfat thickness (BFT) from 238 multiparous cows from 6 dairy farms were obtained at 6 time points during the transition period (from 21 days pre- to 28 days postpartum). In each case, LDT and BFT measurements at each time point and LDT and BFT mobilisation variables at each study period were assessed simultaneously. Cases of specific clinical postparturient diseases and subclinical ketosis were recorded. An additional disease trait was used, defined as the presence or absence of at least one clinical condition after calving (CD_1-28). The associated disease odds with LDT/BFT variables were assessed with binary logistic regression models. The associated hazard for 1st artificial insemination (AI) and for pregnancy by 150 days-in-milk (PREG_150DIM) was assessed with Cox proportional hazard models. Moreover, binary logistic models were used to assess the associated odds for pregnancy to 1^stAI (PREG_1^stAI). Finally, association with 30d, 100d and 305d milk yield was assessed with linear regression models. Increased muscle depth during transition was negatively associated with odds for metritis and CD_1-28, while associations with odds for subclinical ketosis were inconclusive. Moreover, increased LDT reserves were associated with greater hazard for 1st AI by 150 days-in-milk, but results were inconclusive regarding odds for PREG_1^stAI. Increased LDT mobilisation was associated with increased odds for metritis. Increased BFT reserves were positively associated with odds for metritis, CD_1-28 and subclinical ketosis and with decreased hazard for PREG_150DIM. Increased BFT mobilisation was associated with increased odds for subclinical ketosis and with decreased odds for PREG_1^stAI and decreased hazard for PREG_150DIM. Cows with moderate BFT reserves performed better. Finally, increased BFT mobilisation during -21d to -7d from parturition was associated with less milk by 30d and 100d. On the contrary, increased BFT mobilisation during -7d to 7d was associated with more milk by 305d. Metabolism of muscle and fat tissue during transition period was differently associated with different postparturient health, reproduction and milk production traits. In general, greater muscle mass and moderate fat reserves with limited muscle and fat mobilisation were associated with better performance.

Impact of Exposure to Chronic Light-Dark Phase Shifting Circadian Rhythm Disruption on Muscle Proteome in Periparturient Dairy Cows

Muscle tissue serves as a key nutrient reservoir that dairy cows utilize to meet energy and amino acid requirements for fetal growth and milk production. Circadian clocks act as homeostatic regulators so that organisms can anticipate regular environmental changes. The objective of this study was to use liquid chromatography tandem mass spectrometry (LC-MS/MS) to determine how chronic circadian disruption in late gestation affected the muscle tissue proteome. At five weeks before expected calving (BEC), multiparous Holstein cows were assigned to either a control (CON, n = 8) or a 6 h forward phase shift (PS, n = 8) of the light-dark cycle every 3 days. At calving, all animals were exposed to CON light-dark cycles. Muscle biopsies were collected from longissimus dorsi muscles at 21 days BEC and at 21 days postpartum (PP). At p < 0.1, 116 and 121 proteins were differentially abundant between PS and CON at 21 days BEC and 21 days PP, respectively. These proteins regulate beta oxidation and glycolysis. Between pregnancy and lactation, 134 and 145 proteins were differentially abundant in CON and PS cows, respectively (p < 0.1). At both timepoints, PS cows exhibited an oxidative stress signature. Thus, dairy cattle management strategies that minimize circadian disruptions may ensure optimal health and production performance.