Effect of feeding regime on the nutritional status and purine derivative excretion of milking cows Livestock Research for Rural Development 23 (6) 2011 Notes to Authors LRRD Newsletter Citation of this paper Effect of feeding regime on the nutritional status and purine derivative excretion of milking cows T Seresinhe Department of Animal Science, Faculty of Agriculture, University of Ruhuna, Mapalana, Kamburupitiya, Sri Lanka thakshas@ansci.ruh.ac. lk ; profthakshala@yaho.com Abstract Daily excretion of purine derivatives (PD), milk yield and composition by lactating cows under two different nutritional regimes were examined to determine the validity of their use as indicators of nitrogen (N) and nutritional status. Ten crossbred (Sindhi x Sahiwal) milking cows between 2 nd – 4 th lactation (230 ± 11 kg of live weight, 119 ± 10 days in lactation) were fed on a traditional ‘on farm’ diet with 115g of crude protein (CP)/ kg of feed on a dry matter (DM) basis for 20 days followed by an experimental diet (137.5 g of CP/kg of feed) for another 20 days. Intake of organic matter, N, milk yields, fat and total solids were higher (P< 0.05) with the experimental diet due to higher (P< 0.05) dry matter intake, however, the “Nitrogen Use Efficiency” (NUE) of milk was reduced in this period. The estimated microbial nitrogen yields were 28 and 33 g/day for the ‘on farm’ and ‘experimental ’ diets, respectively. PDC Index or allantoin/PD ratios were not affected (P> 0.05) by dietary treatments. However, the PDC Index and PD output showed a positive correlation (r 2 = 0.74). It can be concluded that allantoin alone or PD could be used as indicators of microbial nitrogen production and the nutritional status of Sindhi x Sahiwal milking cows. Keywords: Allantoin, Creatinine, Dry matter intake, Microbial nitrogen, Nitrogen use efficiency I ntroduction Dairying is exclusively a small holder activity in Sri Lanka but produces only marginal profits for farmers. Poor breeding, scarcity and low quality of feed, improper management practices etc. result in low productivity levels of dairying mainly based on indigenous cross-bred cattle. Therefore, one http://www.lrrd.org/lrrd23/6/sere23129.htm (1 of 10) [6/29/2012 9:49:54 AM]