ABSTRACT
Performance, digestibility of nutrients, microbial nitrogen flow [MNF] and nitrogen efficiency [NE] in early lactating Holstein cows were investigated by diet supplementation with sodium caseinate [CN]
Multiparous lactating Holstein cows [n = 15] with an average body weight of 638 kg and 21 days in milk were assigned to a completely randomized design [five cows per treatment] and fed a basal diet with different CN levels [treatments 1, 2, and 3, contained 0, 50, and 100, g/d/head CN, respectively]. The study lasted 49 days [first 14 days for adaptation and the last 35 days for collection of data]
There were no statistical differences in dry matter intake, milk yield, milk lactose yield, and protein yield with CN supplementation
3.5% fat corrected milk yield was increased by CN supplementation [P<0.05] Digestibility of ADF was increased by CN supplementation [P<0.05]
The higher level of CN affected MNF was estimated by spot urine sampling technique [P<0.05]
Predicted N excretion through urine was affected [P<0.05]; however, there was no effect of CN supply on predicted N excretion through faeces. In conclusion, the results indicated that although supplementation with CN improved MNF, negligible effects on performance of the cows were observed. Furthermore, increased milk urea nitrogen [MUN] concentration and predicted urine N excretion revealed the lower NE in early lactating dairy cows supplemented with CN compared with control treatment?