Effects of amino acid nutrition on milk production responses of the dairy cow to more frequent milking

Yeo, Joon-Mo (2002) Effects of amino acid nutrition on milk production responses of the dairy cow to more frequent milking. PhD thesis, University of Glasgow.

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Printed Thesis Information: https://eleanor.lib.gla.ac.uk/record=b2100204


1. This thesis focuses on the influence of amino acid nutrition on the response of lactating dairy cows to increasing the frequency of milking from twice to thrice daily. Two diets were chosen to represent extremes of amino acid balance. A basal diet of grass silage was supplemented with a cereal-based concentrate containing either fish meal or feather meal. Fish meal and feather meal have a similar, high content of rumen-undegradable protein (UDP) but differ widely in amino acid composition. Compared with fish meal, feather meal contains low concentrations of histidine, methionine and lysine. Both diets were given in amounts calculated to supply metabolizable energy (ME) well in excess of requirement (at least 15 %).

2. As a starting point, two experiments were conducted to examine the pattern of response of milk production and mammary function (total DNA, cell proliferation rate, activities of key enzymes) to differences in amino acid supply in two stages of lactation. A control group received the fish meal diet throughout the experiments whereas cows in the treatment group received the fish meal diet until week 6 of lactation when they were changed to the feather meal diet for 6 weeks and then returned to the fish meal diet for 4 weeks (Experiment 1). After a break of 5 weeks, the experimental procedure was repeated using the same cows (Experiment 2). Although milk yield fell as lactation advanced, the differences in milk yield between the feather meal and the fish meal treatments in the two stages of lactation remained similar (21 % and 16 % in Experiments 1 and 2, respectively). However, despite the markedly lower milk yield in cows given the feather meal diet, no clear differences between the treatments were detected in the measurements of mammary function. 3 A series of three experiments was conducted to test the hypothesis that cows are unable to fuel an increase of milk production in response to an increase of milking frequency when milk production is limited by deficiencies in the supply of specific amino acids (His Met and Lys). The first two experiments were conducted in late (Experiment 3) and early (Experiment 4) lactation to examine the effect of stage of lactation on the response to thrice-daily milking in cows consuming a diet containing feather meal as the only protein supplement. In addition, in Experiment 4, half-udder milking was adopted to examine compensatory responses in milk yield between the two halves of the udder in response to thrice-daily milking. In the third experiment (Experiment 5), fish meal, a positive control, was included against feather meal and the response of thrice-daily milking to an increase of ME supply was also investigated.

The results of Experiment 3 and 4 show that, in cows fed a diet containing feather meal as the only protein supplement, thrice-daily milking had little or no effect on milk secretion in the two stages of lactation.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: S Agriculture > SF Animal culture
Colleges/Schools: College of Medical Veterinary and Life Sciences
Supervisor's Name: Chamberlain, Dr. D.G.
Date of Award: 2002
Depositing User: Ms Anikó Szilágyi
Unique ID: glathesis:2002-5902
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 12 Jan 2015 10:24
Last Modified: 12 Jan 2015 10:27
URI: http://theses.gla.ac.uk/id/eprint/5902

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