Evaluation of physically effective fibre in forages and its interaction with concentrate supplementation on rumen function, performance and health of UK dairy cows

Tayyab, U. (2019) Evaluation of physically effective fibre in forages and its interaction with concentrate supplementation on rumen function, performance and health of UK dairy cows. Doctoral thesis, Harper Adams University.

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It is important to feed lactating dairy cows a diet with the correct particle size distribution: too long a particle length can reduce milk yield and increase diet selection whereas too short a particle length can reduce milk fat content and possibly lead to sub-clinical acidosis. In order to characterise the particle distribution of UK rations in study 1, the Penn State Particle Separator was modified to include an additional 26.9 mm hole sieve. The majority (58%) of UK dairy farms were found to have sub-optimal or poorly mixed rations. This resulted in a different diet being available along the feed face, which could affect the performance and/or health of individual cows. There was also significant diet selection on many (66%) of herds, with cows selecting for shorter material on some farms and longer material on others. There was little evidence of an effect of mixer wagon type on particle size distribution, but there was considerable variation between farms in mixing protocol. In study 2, a short and long chop length grass silage was fed alone or mixed with maize silage (40:60 DM basis) to 16 cows in 4 periods of 28 days duration. A short chop length (31 mm) grass silage increased the intake of early lactating cows on grass or grass/maize silage-based diets compared to a longer chop grass silage (44 mm). A short chop length grass silage also increased milk production in cows fed grass silage as the sole forage, and improved body condition score and live weight gain in cows when fed as a mixed grass/maize silage-based diet. A short chop length grass silage also decreased DM digestibility and reduced milk fat concentration, but milk fat yield was unaffected. Chop length had little effect on reticulo-rumen pH, whereas the inclusion of maize silage reduced mean and minimum reticulo-rumen pH, although minimum values were above those considered to represent sub-acute ruminal acidosis. Intake, milk production, milk protein concentration and live weight gain were higher when cows were fed diets that contained a mixture of grass and maize silage than grass silage alone. In study 3, feeding cows a high maize silage based diet increased intake, milk yield, nitrogen efficiency, and acute phase proteins but decreased milk fat concentration, rumen passage rate and fibre digestibility compared to when fed a high grass based diet (with 23.6 mm mean particle size). The use of a high starch supplement increased the milk fat concentration compared to a high fibre supplementation in grass and maize silage based diets. The source of concentrate had little effect on intake, milk yield and composition, rumen pH, rumen passage kinetics, nitrogen balance and eating behaviour. In conclusion, the current particle size of UK dairy rations based on grass silage/maize silage on commercial dairy farms in the UK in longer than North American recommendations and will reduce intake and could promote diet sorting. A short chop length grass silage increases intake and milk performance when fed as the sole forage and milk production and cow performance can benefit from replacing a proportion of grass silage with maize silage, irrespective of the chop length of the grass silage that had a minimal effect on rumen pH. Feeding a high starch diet tends to reduce the length of time ruminating but has no effect on rumen pH and no detrimental short-term effect on the immune response associated with rumen epithelial damage. Consistency of diet mixing, and reduce diet selection may have more of an impact on rumen fermentation than diet composition.

Item Type: Thesis (Doctoral)
Divisions: Animal Production, Welfare and Veterinary Sciences (to 31.07.20)
Depositing User: Ms Kath Osborn
Date Deposited: 23 Aug 2019 15:22
Last Modified: 19 Feb 2020 08:37
URI: https://hau.repository.guildhe.ac.uk/id/eprint/17440

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