Circadian disruption increased insulin resistance and decreased mammary development in late gestation, non-lactating (dry) cows. The objective was to measure the effect of circadian disruption on transcriptomes of the liver and mammary gland. At 35 d before expected calving (BEC) multiparous dry cows were assigned to either control (CON) or phase-shifted treatments (PS). CON was exposed to 16 h light and 8 h of dark. PS was exposed to 16 h light to 8 h dark, but phase of the light-dark cycle was shifted 6 h every 3 d. On d 21 BEC, liver and mammary were biopsied. RNA was isolated (n=6 CON, n=6 PS per tissue), libraries prepared and sequenced using paired end reads. Reads mapping to bovine genome averaged 27 M ± 2 M, and aligned to 14,222 protein coding genes in liver and 15,480 in mammary analysis. In the liver, 834 genes, and in the mammary gland, 862 genes were different (nominal P < 0.05) between PS and CON. In the liver, genes upregulated in PS functioned in cholesterol biosynthesis, endoplasmic reticulum stress, wound healing, and inflammation. Genes downregulated in liver function in cholesterol efflux. In the mammary gland, genes upregulated functioned in mRNA processing and transcription, downregulated genes encoded extracellular matrix proteins and proteases, cathepsins and lysosomal proteases, lipid transporters and regulated oxidative phosphorylation. Increased cholesterol synthesis and decreased efflux suggests circadian disruption potentially increases the risk of fatty liver in cows. Decreased remodeling and lipid transport in mammary may decrease milk production capacity during lactation.
The objective of these studies was to determine the effects of feeding a novel rumen-protected Lys (RP-Lys) product on plasma AA, lactational performance, and Lys bioavailability. To evaluate RP-Lys on lactation performance a corn-based diet (42.5% of corn silage and 21.9% of corn and corn by-products, on DM basis) was formulated to be Lys deficient but adequate in Met, energy, and metabolizable protein. Thirty-six lactating Holstein cows were fed either a Lys-deficient control diet (CON) with no added RP-Lys, or diets containing 0.3% of RP-Lys (0.3RP-Lys) or 0.6% of RP-Lys (0.6RP-Lys) for 8 wk. There were no effects on dry matter intake (mean ± SD; 26.1 ± 0.58 kg/d), milk yield (37.9 ± 0.72 kg/d), or milk composition to the RP-Lys supplementation. No effect was observed on plasma AA concentrations except for His. Plasma His was linearly reduced by Lys feeding (42.6, 41.2, 30.0 ± 4.09 μM, for CON, 0.3RP-Lys, and 0.6RP-Lys, respectively). Calculated efficiency of Lys utilization decreased linearly with RP-Lys supplementation. In the companion study, 3 rumen-cannulated lactating dairy cows were used in a 3 × 3 Latin square design to assess the bioavailability of the RP-Lys. Free Lys (HCl-Lys), RP-Lys, and water were administered separately by postruminal bolus dosing. The Lys bioavailability was assessed by the ratio of area under the curve of Lys plasma concentration for RP-Lys compared with HCl-Lys and discounted for the area under the curve for water bolus dose. The estimated bioavailability of the RP-Lys was 24.4% ± 4.61. In summary, increased supplemental doses of Lys had no effect on Lys plasma concentration and lactational performance when fed to dairy cows on a corn-based diet, although altered Lys as % of essential AA was observed. However, the lack of effects should be considered in light of the lower-thanexpected bioavailability of the RP-Lys.
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