Pattern of concentrate allocation for dairy cows offered silage ad libitum

Taylor, William (1983) Pattern of concentrate allocation for dairy cows offered silage ad libitum. PhD thesis, University of Glasgow.

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Abstract

The literature review studies the effects which concentrates have on silage intake, milk yield, milk composition and partition of energy. The inter-relationships with forage quality, concentrate type, stage of lactation and milk yield potential as also discussed. Some of the main effects are quantified. The final review chapter discusses experiments where different patterns of concentrate allocation have been compared using the same total quantity of concentrate. Five experiments were carried out: The first three were of continuous design and 20 to 25 weeks duration beginning 3 weeks post-calving. They compared different patterns of concentrate allocation to autumn- calving dairy cows offered silage ad libitum. The effects of forage quality and total level of concentrate were included within this framework. Two changeover experiments studied silage and milk yield responses, to different levels of concentrate supplementation with autumn-calving dairy cows in mid-lactation offered moderate quality silage ad libitum. In Experiment 1; Three groups of cows and heifers were offered high quality grass silage ad libitum and an average of 1.26 tonnes cow-1 of concentrate from weeks 3-22 of lactation. Concentrates were either offered: at a flat rate to all animals, in steps to all animals, or a flat rate per cow based on milk yield potential. Feeding proportionately more concentrates in early lactation or to higher yielding cows gave similar levels of performance to where concentrates were offered at a flat rate to all cows. 4. Experiment 2. From weeks 3-27 of lactation silages of 65 and 59 DOMD were offered ad libitum to two groups of dairy cows. Within each group two patterns of concentrate allocation were compared: a flat rate for all cows or a variable rate for individuals. The total quantity of concentrate given to each group averaged 1.58 tonnes cow-1. With both high and low DOMD silages, feeding proportionately more concentrates in early lactation and to individuals of higher milk yield did not result in any better performance than a simple flat rate to all cows. 5. Experiment 3. From weeks 3-27 of lactation two levels of concentrate 1.925 tonnes cow-1 or 1.225 tonnes cow-1 were fed to two groups of cows offered high quality silage ad libitum. Within each group two patterns of concentrate allocation were compared: a flat rate to all cows or a variable rate for individuals. Pattern of concentrate allocation had no effects on average performance within the low level of concentrate. Within the high level of concentrate over the first 25 weeks the flat rate pattern had significantly better average milk fat yields and solids-corrected milk yields and a non-significant increase in 305-day yield of 570 kg compared with the variable pattern to individuals. 6. Moderate quality silage was offered ad libitum and either 8, 7, 6 or 5 kg day-1 (fresh weight) in experiment 4 and 11, 9, 7 or 5 kg day-1 of concentrate in experiment 5, to dairy cows in mid-lactation using changeover experiments with 3 week periods. Silage intakes were only increased by an average of 0.17 and 0.22 kg DM kg-1 decrease in concentrate DM and milk yields were decreased by an average of 0.84 and 0.76 kg kg-1 reduction in concentrate DM in experiments 4 and 5 respectively. These results indicate that reducing concentrate levels between 5 and 9 kg day-1 (fresh weight) with moderate quality silage offered ad libitum will lead to accelerated declines in milk yield and composition in mid-lactation. Considerable attention has been given in the past to feeding proportionately more concentrates in early lactation and to higher yielding individuals. This series of experiments and others reviewed from the literature have failed to show any significant advantages of complex individual feeding to yield patterns of concentrate allocation, compared with a simple flat rate to all cows.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J D Leaver
Keywords: Animal sciences
Date of Award: 1983
Depositing User: Enlighten Team
Unique ID: glathesis:1983-73419
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56
URI: http://theses.gla.ac.uk/id/eprint/73419

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