Abstract:
A study was conducted with crossbred cows to assess the effect of urea as a source of rumen degradable protein on the milk production in early lactation. Eight crossbred cows within 20 days of lactation were selected as uniformly as possible with regard to their age, parity, weight and milk yield. They were allotted to the four dietary treatments in a switch over design. The four concentrate mixtures contained 16.93, 17.37, 19.92 and 19.92 per cent crude protein (CP) and 70.60, 69.24, 70.26 and 68.98 per cent TDN, respectively. The levels of rumen undegradable protein (UDP) and rumen degradable protein (RDP) in the four concentrate mixtures were 28, 39.15, 26.46 and 40 per cent of CP as UDP and 72, 61.85, 73.54 and 60 per cent of CP as RDP, respectively, on DM basis.
There was no significant effect (P>0.05) of dietary CP or UDP levels on the body weight, dry matter intake and milk production of animals. The inclusion of urea at different CP or UDP levels did not show any marked influence on the production performance of the animals. There was no significant difference in any of milk composition parameters except MUN which was significantly higher (P<0.05) with 20 per cent concentrate mixtures compared to17 per cent concentrate mixtures at both levels of degradability.
The haematological and biochemical parameters such as haemoglobin, plasma glucose, plasma urea nitrogen, plasma creatinine, plasma calcium, plasma phosphorus, plasma total protein and albumin estimated at the end of each feeding period were not significantly affected (P>0.05) by the four dietary treatments. There was no significant effect (P>0.05) of four dietary combinations on rumen fermentation parameters such as rumen pH, total volatile fatty acids and (TVFA) and rumen ammonia nitrogen (NH3–N) concentration. The cost of production per kg milk produced was Rs.7.25, 8.10, 8.05 and 9.09, respectively, for the four dietary treatments.
From the overall results obtained in the present study, it could be concluded that a 17 per cent CP concentrate mixture with 28 per cent UDP was sufficient for meeting the protein requirement of early lactating crossbred cows producing about 10 kg milk per day. The study also revealed that one per cent urea can be added in the concentrate mixture of early lactating cows as a source of RDP without any deleterious effect.
