List of references :

6.1. Essential books (text books)

• Veterinary Hygiene (1921): R.G. Linton, W. Green and Sons, LTD Ediburgh.
• Livestock health and Housing (1982): David Sainsbury and peter Sainsbury and peter Sainsbury. Butler and tanner LTD, Frome and London.
• Pollution in Livestock production systems (1994): I.A.P. Dewi, R.F.E. Axford, I. Fayez M. Marai and H. Omed. CAB International. UK. 

6.3. Recommended books

• Animal Welfare (1989): Mahmoud A. Metwally, Zagazig University.
• Farm animal health (1991): Patrick T. Cullen, Pregamon Press. PLC. UK.
• Farm animal and the environment (1992): Clive Philips and David Piggs. CAB International. UK.