Effect of dietary energy and protein contents on buffalo milk yield and quality during advanced lactation period

Among Italian buffalo farmers, it is widely held that administering diets with high energy and protein concentrations is an effective way to increase milk production. In order to assess the validity of this opinion, we verified milk yield and physico-chemical characteristics from buffaloes that, from the 5th month of lactation, were fed two total mixed rations (TMRs) which, given the same intake, should have led to satisfaction of protein requirements though with a slight energy deficit (diet A) or excessive amounts of energy and protein (diet B). Estimate of the energy and protein value of the diets and that of the corresponding requirements was carried out both by using two software programs derived from the Cornell Net Carbohydrate and Protein System (1992), and with the method set up by INRA researchers (1988). The results obtained show that the two diets administered did not result in significant changes to the quantity of milk produced. However, with Diet B the protein concentration in the milk was significantly (p<0.01) higher, although this was partly offset by the higher concentration (p<0.05) of non-protein nitrogen (NNP). The Group B buffaloes also showed significantly higher blood urea levels (p<0.01), with concentrations exceeding those considered physiological for lactating buffaloes. Finally, while administering Diet A the Body Condition Score (BCS) was close to 6.5 (Wagner et al., 1988), whereas in buffaloes which used Diet B it sometimes increased by over 0.5 points. As regards which of the two methods compared is more suitable for expressing dietary energy and protein value and corresponding requirements, we feel that due to the high variability in the Italian Mediterranean buffalo's milk production aptitude, it would be premature to express a judgement on methods which rest on a common scientific base and do not differ substantially.