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Title: Feeding methionine to laying hens in drinking water
Author: Cadirci, Sahin
ISNI:       0000 0001 3513 6029
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 2001
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The present study intended to demonstrate the appetite of laying hens for methionine when offered as a choice in drinking water. Methionine, the first limiting amino acid in practical layer diets is currently provided in the feed in constant amounts. In contrast to this arguable practice, its addition to the drinking water would enable the birds to consume amounts according to their actual methionine requirements. Ten experiments were performed to investigate the conditions of this way of delivery. For the first 5 experiments ISA Brown, for the second 5 Lohmann layers were used. 1) Two preliminary tests determined that a minimum of 140 g/kg dietary crude protein (CP) is necessary for normal egg production of at least 90% of commercial target values, and that the typical feed intake/water intake ratio is 1:1.44. 2) Initially, the appetite of layers for methionine in drinking water was investigated by subjecting them to the combinations of feed adequate or deficient in methionine, and plain or methionine-treated water. Neither cues nor training were used. In the choice situation, the birds could not express an appetite for treated water. 4) Colour cues and training of the birds were introduced to enable birds to express an appetite for methionine-treated water. The choices made in favour of treated water were 98.9% in a period of 5 days, and 93.9% when the position of the bottles was swapped. 5) Methionine deficiency resulted in decreased feed and water intake which were restored when methionine was added to the diet. The way of delivery (in water or feed) was insignificant in this effect, indicating that the source of methionine does not influence normal appetite. 6) Next, the birds' ability to regulate their intake of methionine was investigated. The introduction of an additional colour was expected to avoid the association of plain water with the effects of methionine deficiency, thus in the choice situation, neither the treated nor the plain water had a "history" of causing discomfort to the birds previously. Yet, the birds did not stop the consumption of the treated water even when they had satisfied their methionine requirements, indicating that they can not regulate methionine intake. 7) The detection threshold for methionine was investigated by using different levels of methionine in the drinking water in combination with methionine- deficient feed. It was found that the minimum level of methionine in drinking water for which birds can express appetite is at least 0.025%. 8) The investigations on the metabolic effects of methionine deficiency showed that the birds respond to the deficiency by reducing their feed intake, which decrease becomes significant after eight hours. 9) The hypothesis was examined that giving a methionine-deficient diet in the last 5 hours of the feeding period, the birds will reduce their feed intake in the following morning even if they are fed on an adequate diet that time. It is indicated that the time of receiving a methionine-deficient diet is closely associated with the time of feed intake depression. 10) Determination of the threshold period of training of the birds showed that the using of an 8-hours exposure time resulted in a more than 90% of choices for methionine-treated water. 11) The memory of the birds was tested once after a period of 15 days and again after a period of 45 days on commercial diet. In the subsequent choice situation, birds receiving the 8-hours treatment showed a strong preference for methionine indicating that birds memory last at least 45 days. 12) It was shown that 2.1 g/kg methionine in the feed was deficient for almost all the birds. Birds receiving adequate or nearly adequate amounts of methionine do not feel the physiological effects of deficiency. These birds do not select methionine treated water in a choice situation. The main conclusions of the study are that the source of methionine is insignificant in terms of feed intake, and that layers can express an appetite for methionine in drinking water with the aid of a cue and adequate training.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Appetite; Feed intake