Effects of sward characteristics and concentrate supplementation on herbage intake and performance of lactating dairy cows at pasture

Wilson, Lynn Alice (2003) Effects of sward characteristics and concentrate supplementation on herbage intake and performance of lactating dairy cows at pasture. PhD thesis, University of Glasgow.

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Sward characteristics have a major effect on intake and performance of dairy cows at pasture. Milk production from grazing cows however can be restricted by herbage intake, and concentrate supplementation can allow them to perform closer to their production potential. This study investigates effects of sward characteristics and concentrate supplementation on intake and performance of grazing dairy cows. Grazing cows yielding on average 36.8 kg milk day (d)-1 were offered high levels of concentrates in late summer. Milk yield response was 1.01 kg milk kg-1 concentrate dry matter (DM) d-1 when concentrate was increased from 5.2 to 7.7 kg DM d-1. Milk yield response declined to 0.83 kg milk kg-1 DM when concentrate was increased from 7.7 to 10.2 kg DM d-1. Grazing time and herbage intake were reduced at higher levels of supplementation. Increasing concentrate level by 1.7 kg DM d-1 when cows were housed overnight had no effect on animal performance. In another experiment, there was no significant difference in animal performance between cows offered either a high starch or high fibre concentrate at a rate of 5.3 kg concentrate DM d-1. Supplementation with an additive formulated to reduce dietary protein degradability however had a positive effect on milk yield, which was on average 34.4 and 32.9 kg d-1 for additive and control treatments respectively. Inclusion of the additive also increased milk protein yield and herbage intake. Interactions between sward characteristics and intake were examined. Bite mass was predicted from estimates of bite dimensions and measurements of vertical distribution of herbage mass in cut swards. A general relationship observed between sward height and vertical distribution of mass could be used to predict bite mass from sward height and total herbage mass. Methods to make detailed measurements of intake and grazing activity within patches of a sward using grazing cows were developed and demonstrated an effect of time of day on bite mass. Research to quantify interactions between sward structure, supplementation and grazing activity, focusing on bite mass, should enable development of strategies to exploit the potential of grazed grass and provide appropriate supplementation, which will ultimately contribute to improved profitability of milk production.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Animal sciences, range management.
Colleges/Schools: College of Medical Veterinary and Life Sciences
Supervisor's Name: Swain, Dr. David and Roberts, Dr. David
Date of Award: 2003
Depositing User: Enlighten Team
Unique ID: glathesis:2003-71214
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 10 May 2019 10:49
Last Modified: 27 May 2021 09:15
URI: http://theses.gla.ac.uk/id/eprint/71214

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