Rumen lysine escape, rumen fermentation, and productivity of early lactation dairy cows fed free lysine

The primary objective was to quantitate forestomach escape of lysine fed to cows in a free form. However, since it was expected that a large proportion of the lysine would be degraded in the rumen, other objectives were to determine if lysine impacted ruminal fermentation as well as determine effects on performance of the cows. Four multiparous Holstein cows, fitted with large diameter rumen cannulae between 6 and 8 weeks prior to their projected calving date, were assigned in a 4 × 4 Latin square design experiment between 2 and 4 weeks post-partum. All cows were fed the same total mixed ration (TMR) and treatment differences were achieved by manually incorporating l-lysine HCl into each cowʹs individually weighed allocation of TMR at the time of feeding to deliver 0, 1, 2 or 3 g of l-lysine from l-lysine HCl/kg of dry matter (DM) intake, although actually delivered lysine values were about 16% higher. As expected, average rumen free lysine concentrations increased linearly (P=0.05) due to increased feeding levels of lysine. Rumen pH, N and volatile fatty acid concentrations, as well as other organic components of rumen ingesta, including those of isolated rumen bacteria, were unaffected by lysine feeding. Intake of DM, neutral detergent fibre and crude protein were not influenced by increased feeding of l-lysine, as were production of milk and its components. Feeding increasing levels of free lysine to lactating dairy cows, in three levels up to 71 g/day, resulted in an estimated forestomach escape of lysine of 35 g/kg of lysine fed, a level that is only about 1/6 of those reported in previous studies based upon short term pulse dosing and/or feeding studies.