Effects of including NaOH-treated corn straw as a substitute for wheat hay in the ration of lactating cows on performance, digestibility, and rumen microbial profile

This study measured the effects of including 5% NaOH-treated corn straw (T-CS) as a substitute for 15% wheat hay in the control total mixed ration (TMR) of lactating cows on performance, digestibility, and rumen microbial profile. Two groups of 21 cows each, similar in initial performance, were fed individually 1 of the 2 TMR examined. Voluntary dry matter intake of cows fed the control TMR was 4.3% higher than that of the T-CS cows, but in vivo dry matter and organic matter digestibilities of both groups were similar. Crude protein digestibility was higher in the control cows but digestibility of neutral detergent fiber polysaccharides (cellulose and hemicelluloses) was higher in the T-CS TMR. This was followed by 4.6% reduction in rumination time of the T-CS group. A slightly higher milk yield was observed in the control cows compared with the T-CS group; however, milk fat and milk protein content were higher in cows fed the T-CS TMR. This was reflected in 1.3% increase in energy-corrected milk yield and 5.34% increase in production efficiency (energy-corrected milk yield/intake) of the T-CS cows compared with the control. Welfare of the cows, as assessed by length of daily recumbence time, was improved by feeding the T-CS TMR relative to the control group. As a whole, the rumen bacterial community was significantly modulated in the T-CS group in the experimental period compared with the preexperimental period, whereas the bacterial community of the control group remained unchanged during this period. Out of the 8 bacterial species that were quantified using real-time PCR, a notable decrease in cellulolytic bacteria was observed in the T-CS group, as well as an increase in lactic acid-utilizing bacteria. These results illustrate the effect of T-CS on the composition of rumen microbiota, which may play a role in improving the performance of the lactating cow.