Renal and mammary PD excretion in Holstein/Friesian dairy cows: Its potential as a non-invasive index of protein metabolism

Shingfield, Kevin John (1996) Renal and mammary PD excretion in Holstein/Friesian dairy cows: Its potential as a non-invasive index of protein metabolism. PhD thesis, University of Glasgow.

Abstract

The significance and contribution of rumen synthesised MCP (MCP) in the context of current metabolisable protein (MP) systems and variations in the energetic efficiency of MCP synthesis reported in the literature are reviewed. The estimation of MCP supply from urinary PD (PD) excretion is discussed and reviewed in detail, with the conclusion that it is a reliable non-invasive technique. HPLC methodologies were developed to determine PD, pseudouridine and creatinine in bovine urine and allantoin in bovine milk. A series of experiments were conducted to evaluate the potential of the PD technique using spot urine samples or measurements of allantoin in milk as on-farm diagnostics of MCP supply. Prediction of daily mean urinary molar ratios of PDs to creatinine (PD/c) ratios from spot urine samples was poor due to diurnal variations, the extent of which was influenced by feeding regimen. Furthermore, prediction of urinary PD excretion from daily mean PD/c ratios was poor due to between-cow variations in urinary creatinine excretion. On this basis the spot urine sampling technique was considered unreliable and a total urine collection proved necessary. Variabilty of urinary creatinine excretion precludes its use as a urinary output marker for individual cows. Urinary pseudouridine excretion was independent of nutrient supply but appeared to be influenced by metabolic changes occurring during lactation. In two experiments, dietary fermentable metabolisable energy (FME) supply was manipulated during early and late lactation. For both experiments, individual cow urinary PD excretion was poorly predicted from calculated FME intake or MCP supply. Based on mean treatment values, urinary PD excretion was accurately predicted from calculated MCP. Individual cow milk allantoin excretion or concentration were poorly correlated with urinary PD excretion, calculated FME intake or MCP. Relationships derived using mean treatment values indicated that milk allantoin excretion or concentration were strongly correlated with urinary PD excretion or calculated MCP. Variability precludes the use of milk allantoin as an index of MCP supply for individual cows, but it appears as reliable as urinary PD excretion when used on a herd or group feeding basis.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Supported by funding from the Ministry of Fisheries and Food.
• Keywords: Animal sciences.
• Colleges/Schools: College of Medical Veterinary and Life Sciences
• Supervisor's Name: Offer, Dr. N.W., Dewhurst, Dr. R.J. and Roberts, Dr. D.J.
• Date of Award: 1996
• Depositing User: Enlighten Team
• Unique ID: glathesis:1996-71720
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 17 May 2019 09:31
• Last Modified: 05 Aug 2022 14:30
• Thesis DOI: 10.5525/gla.thesis.71720
• URI: https://theses.gla.ac.uk/id/eprint/71720