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Phosphorus and the dairy cow

influence of intake level, source and stage of lactation on apparent digestibility and bone turnover

Ekelund, Adrienne (2003). Phosphorus and the dairy cow. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae. Agraria, 1401-6249 ; 412
ISBN 91-576-6435-8
[Doctoral thesis]

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The general aim of the present work was to investigate phosphorus balance in the dairy cow, with reference to the amount and source of phosphorus. Furthermore, biochemical bone markers were used to study the bone turnover during the lactation and dry period. Phosphorus is located in every cell of the body and has more known functions than any other mineral element in the animal body. Phosphorus is also an important constituent of milk, and is therefore required in large amounts in a high yielding dairy cow. It is of great nutritional, but also environmental and economical importance, to meet the animals’ phosphorus requirement, and yet to neither feed more or less than necessary is a complicated balance. Three experiments were included in this thesis. In the first experiment five cows received, at different times, five levels of P intake, from 44 to 142 g/day, in a Latin Square Design. In the second experiment four cows received four different concentrates with various phosphorus sources; rapeseed, sunflower seed/palm kernel, wheat middlings/bran and monosodium phosphate, also in a Latin Square Design. The third study included 21 cows and covered a dry period, a lactation, and the following dry period. Two different levels of phosphorus, 0.32% and 0.43% of DM, were fed during the first four months of the lactation. From the fifth month until the end of the lactation one level, 0.43% of DM, were fed. In all studies, total collections of faeces were conducted for five consecutive days during each collection period. Milk yield and feed intake were also recorded. During the third experiment blood samples were taken and analysed for osteocalcin and CTx. Osteocalcin is a specific product of the osteoblast and was therefore used as a measurement of bone formation. CTx is a specific product of the osteoclast and was therefore used as a measurement of bone resorption. The results presented here show that increased phosphorus intake decreased the apparent digestibility of phosphorus linearly. There was a considerable variation in faecal P excretion between days, mostly due to differences in the daily amounts of faecal DM. The apparent digestibility of phosphorus did not differ between the P sources investigated. Cows receiving 0.32% phosphorus of DM excreted less phosphorus in the faeces and had a higher apparent digestibility of phosphorus than cows receiving 0.43%, but there were no differences in phosphorus retention between the groups. The bone markers showed an appreciable increase in bone resorption immediately after parturition, whilst bone formation was highest during mid lactation. Phosphorus fed in excess of the requirements was excreted in the faeces, showing the pointlessness of feeding phosphorus above the needs of the cow. The large variation in faecal phosphorus output between days showed the necessity of total faeces collections when studying phosphorus balance. It was suggested that the naturally occurring bone resorption in early lactation could be taken into account in diet calculations, leading to lower P intake during this time, and consequently less P excretion in faeces.

Authors/Creators:Ekelund, Adrienne
Title:Phosphorus and the dairy cow
Subtitle:influence of intake level, source and stage of lactation on apparent digestibility and bone turnover
Series Name/Journal:Acta Universitatis Agriculturae Sueciae. Agraria
Year of publishing :August 2003
Number of Pages:44
ALLI. Ekelund, A., Spörndly, R., Valk, H. & Murphy, M. 2003. Effects of varying monosodium phosphate intake on phosphorus excretion in dairy cows. Submitted. II. Ekelund, A., Spörndly, R., Valk, H. & Murphy, M. 2003. Influence of feeding various phosphorus sources on apparent digestibility of phosphorus in dairy cows. Animal Feed Science and Technology 109 (In press). III. Holtenius, K. & Ekelund, A. 2003. Biochemical markers of bone turnover in the dairy cow during lactation and in the dry period. Submitted. IV. Ekelund, A., Spörndly, R. & Holtenius, K. 2003. Influence of low phosphorus intake during early lactation on apparent digestibility of phosphorus and bone metabolism in dairy cows. Manuscript.
Place of Publication:Uppsala
Publisher:Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences
ISBN for printed version:91-576-6435-8
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:L Animal production > L51 Animal physiology - Nutrition
Subjects:Not in use, please see Agris categories
Agrovoc terms:dairy cows, digestibility, bones, feeds, phosphorus, animal nutrition, nutrition physiology
Keywords:apparent digestibility, biochemical bone marker, bone turnover, dairy cow, feed stuff, inorganic phosphorus, phosphorus excretion, phosphorus requirement
Permanent URL:
ID Code:318
Department:(VH) > Dept. of Animal Nutrition and Management
Deposited By: Adrienne Ekelund
Deposited On:14 Aug 2003 00:00
Metadata Last Modified:19 Mar 2015 10:21

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