Lactation performance and rumen fermentation in dairy cows fed a diet with alfalfa hay replaced by corn stover and supplemented with molasses.

OBJECTIVE: The objective of current study was to investigate the lactation performance and rumen fermentation characteristics of dairy cows fed a diet with alfalfa hay replaced by corn stover but supplemented with molasses. METHODS: Sixteen Holstein cows in mid-lactation were randomly assigned to 1 of 2 dietary treatments: i) alfalfa based diet (AH), and ii) corn stover based diet supplemented with molasses (CSM). The experiment was conducted according to a 2×2 crossover design with 22-d each period, consisting of 17 d for adaptation and 5 d for data and samples collection. RESULTS: Dry matter intake and milk yield were higher for cows fed AH than CSM (p<0.01). Milk protein content and nitrogen conversion were higher (p<0.05), while milk urea nitrogen was lower (p<0.01) for cows fed AH than CSM-fed cows. Contents of milk total solids, fat and lactose were not different between two groups (p>0.10). Total rumen volatile fatty acid concentration tended to be higher (p = 0.06) for cows fed AH than CSM-fed cows. Molar proportion of acetate was lower (p = 0.04), but valerate was higher (p = 0.02) in cows fed AH than CSM-fed cows. Rumen concentration of propionate, and isobutyrate, and ratio of acetate to propionate tended to be different (p<0.10) between two groups. The feed cost per kilogram of milk was lower in CSM than AH (p<0.01). No differences were found in feed efficiency and most plasma parameters tested (p>0.10). CONCLUSION: In comparison with AH diet, CSM diet could be fed to dairy cows without negative effect on feed efficiency, ruminal fermentation, but economically beneficial, indicating that CSM could be an alternative choice for dairy farms instead of AH to feed mid-lactation dairy cows.

Lactation-related metabolic mechanism investigated based on mammary gland metabolomics and 4 biofluids' metabolomics relationships in dairy cows.

BACKGROUND: Lactation is extremely important for dairy cows; however, the understanding of the underlying metabolic mechanisms is very limited. This study was conducted to investigate the inherent metabolic patterns during lactation using the overall biofluid metabolomics and the metabolic differences from non-lactation periods, as determined using partial tissue-metabolomics. We analyzed the metabolomic profiles of four biofluids (rumen fluid, serum, milk and urine) and their relationships in six mid-lactation Holstein cows and compared their mammary gland (MG) metabolomic profiles with those of six non-lactating cows by using gas chromatography-time of flight/mass spectrometry. RESULTS: In total, 33 metabolites were shared among the four biofluids, and 274 metabolites were identified in the MG tissues. The sub-clusters of the hierarchical clustering analysis revealed that the rumen fluid and serum metabolomics profiles were grouped together and highly correlated but were separate from those for milk. Urine had the most different profile compared to the other three biofluids. Creatine was identified as the most different metabolite among the four biofluids (VIP = 1.537). Five metabolic pathways, including gluconeogenesis, pyruvate metabolism, the tricarboxylic acid cycle (TCA cycle), glycerolipid metabolism, and aspartate metabolism, showed the most functional enrichment among the four biofluids (false discovery rate < 0.05, fold enrichment >2). Clear discriminations were observed in the MG metabolomics profiles between the lactating and non-lactating cows, with 54 metabolites having a significantly higher abundance (P < 0.05, VIP > 1) in the lactation group. Lactobionic acid, citric acid, orotic acid and oxamide were extracted by the S-plot as potential biomarkers of the metabolic difference between lactation and non-lactation. The TCA cycle, glyoxylate and dicarboxylate metabolism, glutamate metabolism and glycine metabolism were determined to be pathways that were significantly impacted (P < 0.01, impact value >0.1) in the lactation group. Among them, the TCA cycle was the most up-regulated pathway (P < 0.0001), with 7 of the 10 related metabolites increased in the MG tissues of the lactating cows. CONCLUSIONS: The overall biofluid and MG tissue metabolic mechanisms in the lactating cows were interpreted in this study. Our findings are the first to provide an integrated insight and a better understanding of the metabolic mechanism of lactation, which is beneficial for developing regulated strategies to improve the metabolic status of lactating dairy cows.

Comparative studies of two methods for miRNA isolation from milk whey.

MicroRNAs (miRNAs) from milk whey have been considered for their potential as noninvasive biomarkers for milk quality control and disease diagnosis. However, standard protocols for miRNA isolation and quantification from milk whey are not well established. The objective of this study was to compare two methods for the isolation of miRNAs from milk whey. These two methods were modified phenol-based technique (Trizol LS(®) followed by phenol precipitation, the TP method) and combined phenol and column-based approach (Trizol LS(®) followed by cleanup using the miRNeasy kit, the TM method). Yield and quality of RNA were rigorously measured using a NanoDrop ND-1000 spectrophotometer and then the distribution of RNA was precisely detected in a Bioanalyzer 2100 instrument by microchip gel electrophoresis. Several endogenous miRNAs (bta-miR-141, bta-miR-146a, bta-miR-148a, bta-miR-200c, bta-miR-362, and bta-miR-375) and an exogenous spike-in synthetic control miRNA (cel-miR-39) were quantified by real-time polymerase chain reaction (PCR) to examine the apparent recovery efficiency of milk whey miRNAs. Both methods could successfully isolate sufficient small RNA (<200 nt) from milk whey, and their yields were quite similar. However, the quantification results show that the total miRNA recovery efficiency by the TM method is superior to that by the TP method. The TM method performed better than the TP for recovery of milk whey miRNA due to its consistency and good repeatability in endogenous and spike-in miRNA recovery. Additionally, quantitative recovery analysis of a spike-in miRNA may be more accurate to reflect the milk whey miRNA recovery efficiency than using traditional RNA quality analysis instruments (NanoDrop or Bioanalyzer 2100).