HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Interpretive Summary Alert me when this article is cited Alert me if a correction is posted Services Related articles in JDS Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Vanhatalo, A. Articles by Rinne, M. PubMed PubMed Citation Articles by Vanhatalo, A. Articles by Rinne, M.

Effects of feeding grass or red clover silage cut at two maturity stages in dairy cows. 1. Nitrogen metabolism and supply of amino acids

A. Vanhatalo^*,1, K. Kuoppala, S. Ahvenjärvi and M. Rinne

^* Department of Animal Science, University of Helsinki, PO Box 28, FI-00014 Helsinki, Finland
MTT Agrifood Research Finland, Animal Production Research, FI-31600 Jokioinen, Finland

¹ Corresponding author: aila.vanhatalo{at}helsinki.fi

This study investigated the effects of plant species (red clover vs. timothy-meadow fescue) and forage maturity at primary harvest (early vs. late cut silage) on rumen fermentation, nutrient digestion, and nitrogen metabolism including omasal canal AA flow and plasma AA concentration in lactating cows. Five dairy cows equipped with rumen cannulas were used in a study designed as a 5 x 5 Latin square with 21-d periods. The diets consisted of early-cut and late-cut grass and red clover silage, respectively, and a mixture of late-cut grass and early-cut red clover silages given ad libitum with 9 kg/d of a standard concentrate. Grass silage dry matter intake tended to decrease but that of red clover silages tended to increase with advancing maturity. Milk yields were unchanged among treatments, milk protein and fat concentrations being lower for red clover than for grass silage diets. Rumen fluid pH was unchanged but volatile fatty acid and ammonia concentrations were higher for red clover than for grass silage diets. Intake of N, and omasal canal flows of total nonammonia N (NAN), microbial NAN, and dietary NAN were higher for red clover than for grass silage diets but were not affected by forage maturity. However, microbial NAN flow and amount of N excreted in the feces decreased with advancing maturity for grass diets but increased for red clover diets. Apparent ruminal N degradability of the diets was unchanged, but true ruminal N degradability decreased and efficiency of microbial synthesis increased with red clover diets compared with grass silage diets. Omasal canal flows of AA, except those for Met and Cys, were on average 20% higher for red clover than grass silage diets. Omasal canal digesta concentrations of Leu, Phe, branched-chain, and essential AA were higher but those of Met lower for red clover than for grass silage diets. Plasma AA concentrations, except for His (unchanged) and Met (lower), were higher for red clover than for grass diets. However, none of these AA-related variables were affected by forage maturity. Total digestibility of N and excretion of N in the urine were higher for red clover than for grass diets and decreased with advancing maturity. It was concluded that despite the higher total AA supply of cows fed red clover versus grass silage diets, further milk production responses on red clover diets were compromised by an inadequate supply of Met as evidenced by lower Met concentration in the AA profile of omasal digesta and plasma.

Key Words: dairy cow • red clover silage • nitrogen metabolism • amino acid supply

Related articles in JDS:

Effects of feeding grass or red clover silage cut at two maturity stages in dairy cows. 2. Dry matter intake and cell wall digestion kinetics

K. Kuoppala, S. Ahvenjärvi, M. Rinne, and A. Vanhatalo
JDS 2009 92: 5634-5644. [Abstract] [Full Text]