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1、21Rumen lysine escape, rumen fermentation and productivity ofearly lactation dairy cows fed free lysineP.H. Robinsona,*, E.J. DePetersa, I. Shinzatob, H. SatobaDepartment of Animal Science, University of California, Davis, CA, 95616, USA, andAtlantic Dairy & Forage Institute, Fredericton Junction, N
2、B, E0G 1T0, Canada bAjinomoto Co., Inc., 5-8 Kyobashi I-Chome, Chuo-Ku, Tokyo 104, Japan* Corresponding author. Tel: 530-754-7565; Fax: 530-752-0175; EM: phrobinsonucdavis.eduSubmitted to Animal Feed Science and Technology in June 2005Revised and re-submitted in August 2005.Revised and re-submitted
3、in September 2005.AbstractThe 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
4、 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 x 4 Latin square design experiment between 2 and 4 weeks post-partum. All cows were fed t
5、he same total mixed ration (TMR) and treatment differences were achieved by manually incorporating L-lysine HCl into each cows 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 deliver
6、ed 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
7、 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
8、g/d, 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.Keywords: lysine, forestomach, escape, rumenAbbreviations: AA, amino acids; ADF, acid de
9、tergent fibre; BCS, body condition score; BW, body weight; DM, dry matter; RP, ruminally protected, TMR, totally mixed ration; NDF, neutral detergent fibre1. IntroductionIt is widely accepted that dairy cows have requirements for amino acids (AA) that must be provided in the diet as a supplement to
10、the AA in microbial protein that passes from the rumen. However due to the lack of commercial availability of ruminally protected (RP) lysine that escapes the forestomach undigested, thereby making it available for absorption in the small intestine, there is little experimental data to support produ
11、ctive benefits to supplementation of dairy rations with lysine. Previous researchers (Velle et al., 1997, 1998; Volden et al., 1998) have reported ruminal escape of lysine that varied from about 100 to 291 g/kg of the lysine dosed, dependent upon the level of lysine dosed to the rumen. Such levels,
12、particularly the higher ones, make the use of free lysine a potentially economical source of intestinally available lysine. However, the method of administration of lysine in all three of these studies, as a pulse dose, may have resulted in a relatively high estimate of ruminal lysine escape due to
13、transitorily high concentrations of lysine in rumen fluid, which then washed out of the rumen at high levels due to the high passage rates of rumen liquids. The objective of this study was to feed cows unprotected L-lysine HCl, at levels similar to Volden et al. (1998), but mixed into the diet, in o
14、rder to estimate ruminal lysine escape under conditions similar to those used in commercial situations. However other objectives were to determine if feeding free lysine impacted rumen fermentation and function, forestomach NDF digestion, forestomach escape of microbial biomass, and productivity of
15、the cows. This study differed from Robinson et al. (2005) only in that the cows were not the same and the corn grain fed was fine ground as opposed to coarse cracked. However a second study was deemed to be worthwhile in order to increase confidence in all the results obtained.2. Materials and metho
16、dsThe study was completed simultaneous with Robinson et al. (2005) and so only a brief summary of the materials and methods are presented here.2.1. Cows and DesignFive multiparous Holstein cows, due to calve within a 4 week period, were fitted with large diameter rumen cannulae (Bar Diamond, Parma, ID, USA) between 6 and 8 weeks prior to their projected calving date. Du
