Milk yield and milk composition of lactating dairy cows fed on paddy straw based complete rations containing different levels of neutral detergent fibre (NDF)

Abstract

ABSTRACT

            A study of six months duration was conducted to assess the milk yield and milk composition of lactating dairy cows fed on paddy straw based complete rations containing different levels of NDF, in two phases, viz., early and mid lactation. Three isonitrogenous and isocaloric complete rations, T1, T2 and T3 with 25, 30 and 35 per cent NDF, respectively were formulated with paddy straw was the sole source of roughage NDF. 18 dairy cows yielding approximately 10 kg of milk per day were divided into three groups of six each and allotted to the three experimental rations. The average daily milk yield of cows fed on the experimental rations, T1, T2 and T3, in phases I and II were similar (P>0.05), even though the milk yield of the animals tended to increase with increase in NDF content of the ration. The cows fed on ration T3 attained peak milk yield earlier and had greater persistency of milk yield than cows fed on rations T2 and T1.

            There was no significant difference (P>0.05) in milk composition parameters such as fat, total solids, solids not fat and protein, between the three dietary treatments. The milk urea nitrogen (MUN) content of cows decreased linearly and significantly (P<0.05), with increase in NDF content of the ration. The yield of four per cent fat corrected milk, fat and protein yield of cows in both the phases as well as the total experiment was highest in cows of T3, followed by T2 and T1, in descending order.  

            Evaluation of the results obtained in the present study, reveal that the animals in all the three dietary treatments performed well, with the complete rations T3 with 35 per cent NDF and T2 with 30 per cent NDF, showing better performance than T1 with 25 per cent NDF. Among T2 and T3 which were more or less comparable in milk yield, fat, TS, SNF and protein percentage, the cows fed on diet T3 remained in peak milk yield for longer period than T2. The cows fed on diet T3 had a significantly lower (P<0.05) MUN throughout the lactation and a significantly higher (P<0.05) FCM, fat and protein yield in the mid as well as total lactation than those fed on the diet T2, indicating that T3 was better than T2. These results suggest that complete rations with 25 to 35 per cent NDF, containing paddy straw as the sole source of roughage NDF, can be recommended for use among early and mid lactation dairy cows, with 35 per cent being the ideal NDF level.