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The effect of supplementary carbohydrate composition on lactational performance in dairy cows grazing alfalfa pasture

Published online by Cambridge University Press:  05 November 2021

A.R. Castillo
Affiliation:
EEA Rafaela INTA, Casilla de correo 22, 2300 Rafaela, Santa Fe, Argentina
D.E Beever
Affiliation:
CEDAR, Department of Agriculture, The University of Reading, Reading RG6 6AT
R.F. Gregoret
Affiliation:
EEA Rafaela INTA, Casilla de correo 22, 2300 Rafaela, Santa Fe, Argentina
S.G. Onetti
Affiliation:
EEA Rafaela INTA, Casilla de correo 22, 2300 Rafaela, Santa Fe, Argentina
O.R. Quaino
Affiliation:
EEA Rafaela INTA, Casilla de correo 22, 2300 Rafaela, Santa Fe, Argentina
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Extract

The rate of disimilation of the dietary protein fraction of fresh forages, especially fresh legumes, is rapid and often exceeds microbial requirements for ammonia [Beever, 1993]. Consequently total dietary nitrogen [N] utilisation is impaired due to increased absorption of ammonia from the rumen and excretion of urea via the kidneys. This experiment, as part of a larger co-ordinated study to examine N utilisation in alfalfa swards for milk production, considered the evaluation of different isoenergetic supplements formulated to contain contrasting carbohydrate components with respect to starch and fibre level and type, and water soluble carbohydrate content.

Forty multiparous Holstein cows in immediately post peak lactation were randomnly allocated to one of four alfalfa paddocks, and provided fresh daily allowances [13kg Dry matter (DM)/cow/d] by means of electric fencing. Cows were milked twice daily [0600&1500h] when 3.5kg DM concentrate was offered at each milking. At all other times cows were at pasture and intakes were estimated by measuring pasture DM on offer to and refused by the cows.

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Copyright
Copyright © The British Society of Animal Science 1998

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References

Beever, D.E. [1993]. Rumen function. In ‘ Quantitative Aspects of Ruminant Digestion & Metabolism’ Eds. Forbes, J.M. & France, J.. CAB International, Wallingford Oxon.Google Scholar