Comparison of grass and legume silages for milk production. 2. In vivo and in sacco evaluations of rumen function

RJ Dewhurst, RT Evans, ND Scollan, JM Moorby, RJ Merry, RJ Wilkins

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126 Citations (Scopus)

Abstract

Two experiments were conducted to investigate the basis for higher voluntary intakes and increased α-linolenic acid content in milk from cows offered clover silages. Six cows with rumen and duodenal cannulae were used in a four-period changeover-design experiment. Cows received 8 kg/d of dairy concentrate and had ad libitum access to one of six silage treatments: grass, red clover, white clover, alfalfa, and 50/50 (dry matter basis) mixtures of grass with red clover or white clover. The rumen fermentability of grass, red clover, white clover, and grass/red clover silages was also evaluated in a nylon bag study. Legume silages led to increased dry matter intake and milk production in comparison with grass silage. There was no significant effect of legume silages on rumen pH and volatile fatty acid concentrations, but a significant increase in rumen ammonia concentration with the legume silages, reflecting their higher protein content. The inclusion of white clover or alfalfa silage, but not red clover silage, in diets led to an increase in molar proportions of iso-butyric, iso-valeric, and n-valeric acids in comparison with diets based on grass silage. Rumen fill was significantly lower, and rumen passage rates were significantly higher for cows offered alfalfa or white clover silages. However, the markedly different particle size distribution of rumen contents with these feeds suggests very different mechanisms for the high intake characteristics: high rates of particle breakdown and passage with alfalfa, and high rates of fermentation and passage with white clover. Microbial energetic efficiency (grams microbial N per kilogram organic matter apparently digested in the rumen) was highest for cows offered alfalfa silage, intermediate for clover silage, and lowest for cows offered grass silage. These differences reflect the higher rumen outflow rates for legume silages in comparison with grass silage. However, the effect of these differences on N-use efficiency (feed to milk) was probably quite small in comparison with effects of N intake. Although the biohydrogenation of α-linolenic acid was still high for red clover silage (86.1% compared with 94.3% for grass silage), there was a 240% increase in the proportion of α-linolenic acid passing through the rumen. This explains the increased recovery of α-linolenic acid from feed into milk with diets based on red clover silage.
Original languageEnglish
Pages (from-to)2612-2621
JournalJournal of Dairy Science
Volume86
Issue number8
Publication statusPrint publication - Aug 2003

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rumen fermentation
silage
milk production
legumes
rumen
grasses
Trifolium pratense
Trifolium repens
grass silage
linolenic acid
cows
alfalfa
alfalfa silage
milk
diet
valeric acid
biohydrogenation
voluntary intake
energy efficiency
particle size distribution

Cite this

Dewhurst, RJ ; Evans, RT ; Scollan, ND ; Moorby, JM ; Merry, RJ ; Wilkins, RJ. / Comparison of grass and legume silages for milk production. 2. In vivo and in sacco evaluations of rumen function. In: Journal of Dairy Science. 2003 ; Vol. 86, No. 8. pp. 2612-2621.
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title = "Comparison of grass and legume silages for milk production. 2. In vivo and in sacco evaluations of rumen function",
abstract = "Two experiments were conducted to investigate the basis for higher voluntary intakes and increased α-linolenic acid content in milk from cows offered clover silages. Six cows with rumen and duodenal cannulae were used in a four-period changeover-design experiment. Cows received 8 kg/d of dairy concentrate and had ad libitum access to one of six silage treatments: grass, red clover, white clover, alfalfa, and 50/50 (dry matter basis) mixtures of grass with red clover or white clover. The rumen fermentability of grass, red clover, white clover, and grass/red clover silages was also evaluated in a nylon bag study. Legume silages led to increased dry matter intake and milk production in comparison with grass silage. There was no significant effect of legume silages on rumen pH and volatile fatty acid concentrations, but a significant increase in rumen ammonia concentration with the legume silages, reflecting their higher protein content. The inclusion of white clover or alfalfa silage, but not red clover silage, in diets led to an increase in molar proportions of iso-butyric, iso-valeric, and n-valeric acids in comparison with diets based on grass silage. Rumen fill was significantly lower, and rumen passage rates were significantly higher for cows offered alfalfa or white clover silages. However, the markedly different particle size distribution of rumen contents with these feeds suggests very different mechanisms for the high intake characteristics: high rates of particle breakdown and passage with alfalfa, and high rates of fermentation and passage with white clover. Microbial energetic efficiency (grams microbial N per kilogram organic matter apparently digested in the rumen) was highest for cows offered alfalfa silage, intermediate for clover silage, and lowest for cows offered grass silage. These differences reflect the higher rumen outflow rates for legume silages in comparison with grass silage. However, the effect of these differences on N-use efficiency (feed to milk) was probably quite small in comparison with effects of N intake. Although the biohydrogenation of α-linolenic acid was still high for red clover silage (86.1{\%} compared with 94.3{\%} for grass silage), there was a 240{\%} increase in the proportion of α-linolenic acid passing through the rumen. This explains the increased recovery of α-linolenic acid from feed into milk with diets based on red clover silage.",
author = "RJ Dewhurst and RT Evans and ND Scollan and JM Moorby and RJ Merry and RJ Wilkins",
year = "2003",
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Dewhurst, RJ, Evans, RT, Scollan, ND, Moorby, JM, Merry, RJ & Wilkins, RJ 2003, 'Comparison of grass and legume silages for milk production. 2. In vivo and in sacco evaluations of rumen function', Journal of Dairy Science, vol. 86, no. 8, pp. 2612-2621.

Comparison of grass and legume silages for milk production. 2. In vivo and in sacco evaluations of rumen function. / Dewhurst, RJ; Evans, RT; Scollan, ND; Moorby, JM; Merry, RJ; Wilkins, RJ.

In: Journal of Dairy Science, Vol. 86, No. 8, 08.2003, p. 2612-2621.

Research output: Contribution to journalArticleResearchpeer-review

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T1 - Comparison of grass and legume silages for milk production. 2. In vivo and in sacco evaluations of rumen function

AU - Dewhurst, RJ

AU - Evans, RT

AU - Scollan, ND

AU - Moorby, JM

AU - Merry, RJ

AU - Wilkins, RJ

PY - 2003/8

Y1 - 2003/8

N2 - Two experiments were conducted to investigate the basis for higher voluntary intakes and increased α-linolenic acid content in milk from cows offered clover silages. Six cows with rumen and duodenal cannulae were used in a four-period changeover-design experiment. Cows received 8 kg/d of dairy concentrate and had ad libitum access to one of six silage treatments: grass, red clover, white clover, alfalfa, and 50/50 (dry matter basis) mixtures of grass with red clover or white clover. The rumen fermentability of grass, red clover, white clover, and grass/red clover silages was also evaluated in a nylon bag study. Legume silages led to increased dry matter intake and milk production in comparison with grass silage. There was no significant effect of legume silages on rumen pH and volatile fatty acid concentrations, but a significant increase in rumen ammonia concentration with the legume silages, reflecting their higher protein content. The inclusion of white clover or alfalfa silage, but not red clover silage, in diets led to an increase in molar proportions of iso-butyric, iso-valeric, and n-valeric acids in comparison with diets based on grass silage. Rumen fill was significantly lower, and rumen passage rates were significantly higher for cows offered alfalfa or white clover silages. However, the markedly different particle size distribution of rumen contents with these feeds suggests very different mechanisms for the high intake characteristics: high rates of particle breakdown and passage with alfalfa, and high rates of fermentation and passage with white clover. Microbial energetic efficiency (grams microbial N per kilogram organic matter apparently digested in the rumen) was highest for cows offered alfalfa silage, intermediate for clover silage, and lowest for cows offered grass silage. These differences reflect the higher rumen outflow rates for legume silages in comparison with grass silage. However, the effect of these differences on N-use efficiency (feed to milk) was probably quite small in comparison with effects of N intake. Although the biohydrogenation of α-linolenic acid was still high for red clover silage (86.1% compared with 94.3% for grass silage), there was a 240% increase in the proportion of α-linolenic acid passing through the rumen. This explains the increased recovery of α-linolenic acid from feed into milk with diets based on red clover silage.

AB - Two experiments were conducted to investigate the basis for higher voluntary intakes and increased α-linolenic acid content in milk from cows offered clover silages. Six cows with rumen and duodenal cannulae were used in a four-period changeover-design experiment. Cows received 8 kg/d of dairy concentrate and had ad libitum access to one of six silage treatments: grass, red clover, white clover, alfalfa, and 50/50 (dry matter basis) mixtures of grass with red clover or white clover. The rumen fermentability of grass, red clover, white clover, and grass/red clover silages was also evaluated in a nylon bag study. Legume silages led to increased dry matter intake and milk production in comparison with grass silage. There was no significant effect of legume silages on rumen pH and volatile fatty acid concentrations, but a significant increase in rumen ammonia concentration with the legume silages, reflecting their higher protein content. The inclusion of white clover or alfalfa silage, but not red clover silage, in diets led to an increase in molar proportions of iso-butyric, iso-valeric, and n-valeric acids in comparison with diets based on grass silage. Rumen fill was significantly lower, and rumen passage rates were significantly higher for cows offered alfalfa or white clover silages. However, the markedly different particle size distribution of rumen contents with these feeds suggests very different mechanisms for the high intake characteristics: high rates of particle breakdown and passage with alfalfa, and high rates of fermentation and passage with white clover. Microbial energetic efficiency (grams microbial N per kilogram organic matter apparently digested in the rumen) was highest for cows offered alfalfa silage, intermediate for clover silage, and lowest for cows offered grass silage. These differences reflect the higher rumen outflow rates for legume silages in comparison with grass silage. However, the effect of these differences on N-use efficiency (feed to milk) was probably quite small in comparison with effects of N intake. Although the biohydrogenation of α-linolenic acid was still high for red clover silage (86.1% compared with 94.3% for grass silage), there was a 240% increase in the proportion of α-linolenic acid passing through the rumen. This explains the increased recovery of α-linolenic acid from feed into milk with diets based on red clover silage.

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JO - Journal of Dairy Science

JF - Journal of Dairy Science

SN - 0022-0302

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ER -