Effects of increased doses of lysine in a rumen-protected form on plasma amino acid concentration and lactational performance of dairy cows fed a lysine-deficient diet

Abstract

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.

Production of rumen- and gastrointestinal-resistant nanoparticles to deliver lysine to dairy cows

“…To address this issue, several rumen protection technologies were developed, which aimed at producing delivery systems capable of protection AA from the ruminal microbiota 3 – 6 . However, adequate AA supplementation remains a dauting task in ruminants where limitations regarding poor protection and release issues 3 , 7 are further complicated by difficulties in correctly measuring the true bioavailability of rumen-protected AA technologies 4 . The former usually leads to inadequate dietary formulations that, in turn, cause unbalanced AA levels in the plasma.…”

“…Most of the existing rumen-protection systems have been developed to be degraded, thus releasing their cargo, in one or across several of the former organs, which will ultimately be absorbed into the bloodstream at the intestine. However this can lead to reduced bioavailability mainly due to poor release 3 , 7 , 13 . The development of delivery systems that are themselves up-taken into the blood may reduce this loss, assuming that these systems are herein destroyed and their contents made available to the animal 10 , 14 , 15 , even if the degradation occurs after phagocytosis 16 .…”

The functional and regulatory entities underlying free and peptide-bound amino acid transporters in the bovine mammary gland

“…Growth hormone and insulin, individually or the combination of hydrocortisone, insulin, and prolactin, supplemented to dairy cows in pregnancy or mid-lactation periods improved lactation performance, showing higher mammary AA uptake and milk protein synthesis ( Menzies et al, 2009 ; Burgos et al, 2010 ; Sciascia et al, 2015 ). Measuring the differences between arteriovenous/venous AA concentrations and blood flow rate has been considered as a reliable indicator for determining the net uptake of AA by bovine MEC and their utilization for milk protein synthesis ( Wang et al, 2010 ; Cant et al, 2018 ; Malacco et al, 2022 ; Smith et al, 2022 ). As the requirement for AA precursor changes during the lactation cycle, dairy cows during late gestation and early lactation initiate muscle mobilization to provide AA for body maintenance and colostrogenesis ( McCabe and Boerman, 2020 ).…”