Abstract #M251

# M251
Undigested NDF (uNDF240h) excretion in feces of lactating cows: A comparison of multiple time-points, diurnal and 24-hour composite collections.
E. Bonfante*1, D. Cavallini1, A. Palmonari1, M. Fustini1, L. Mammi1, G. Canestrari1, A. Formigoni1, 1DIMEVET, Dipartimento di Scienze Mediche Veterinarie, Ozzano dell'Emilia, BO, Italy.

The aim of the study was to evaluate the pattern of undigested NDF (uNDF240h, %DM) excretion in feces and to compare the singular time points with a 24h composite. Four dairy cows, paired for lactation number (2), days in milk (184 ± 38d), milk production (35 ± 2kg), weight (664 ± 50kg), and daily rumination time (564 ± 50 min), were housed in tie-stalls for individual dry matter intake (DMI) determination. The feed was delivered once a day (0800h). After an adaptation period the feces collection started. The feces were collected every 2h (12 time points in total) for 3d; all samples were divided in 3 aliquots: one was kept separate, one was composited to create a 4 time points sample (c08–14h, c16–22, c00–06), representative for the morning, afternoon, and night excretion; the latter aliquot was used to create a composite of the whole day (c24h). During the study, the DMI, rumination time, milk production, were recorded daily, and the total mixed ration (TMR) sampled every day. The chemical composition of feeds and feces were determined.The data were analyzed using JMP-12 (SAS Institute Inc., Cary NC). A mixed model was used; the time points and the day were considered as fixed effect, the cow as random. The TMR during the experimental period was uniform in its physical and chemical composition. The DMI was 24.5 ± 2.9kg, the rumination time 452 ± 87min, the milk production 34.0 ± 4.0L. The mean uNDF240h excretion during the day was 32.4 ± 1.0%DM; the higher excretion was at 18h (33.9 ± 0.9%DM) and the lower at 8h (feed delivery; 30.9 ± 0.9). Some significant differences were detected comparing the 12 time points, most of all between the morning (10 and 12h) and the night (18, 20, 22, 2, 4h; P < 0.05) samples. No difference were detected comparing the 12 time points with the c08–14h, c16–22, c00–06, and c24h, except for the c24h and 18h (32.1vs33.9%DM; P = 0.048). We can concluded that the uNDF240h excretion isn’t linear, with a min reached at feed delivery and a max reached 10h after. However, except for the difference between max excretion time point and c24h, the multiple time points are not different from the composites.

Key Words: feces collection, undigested NDF (uNDF240h)