Abstract #T242

# T242
Amount of milk replacer offered to female Holstein calves during first eight weeks of life: Effect on ruminal pH and diet digestibility in pre and post weaning weeks.
G. Antúnez1, C. Cajarville*1, C. M. Fernández1, J. E. Dayuto1, L. M. Artús1, M. Fernández1, L. Hornos1, F. Correa1, R. Biasiolo2, A. Vicente3, J. L. Repetto1, 1Instituto de Producción Animal de Veterinaria, Facultad de Veterinaria, Universidad de la República, Libertad, San José, Uruguay, 2Centro de Ciências Agroveterinárias Universidade do Estado de Santa Catarina, Lages, Santa Catarina, Brazil, 3Facultad de Ciencias Veterinarias de la Universidad del Nordeste, Cabral, Corrientes, Argentina.

The aim of this study was to evaluate whether amount of milk replacer (MR) offered to female Holstein calves during first 8 weeks of life affects ruminal pH and diet digestibility in pre and post weaning weeks. Thirty-two newborn female Holstein calves (41 ± 4.3 kg BW) were housed individually. From 2nd to 7th week of life, calves were distributed in 2 feeding programs: 24 g (AR, n = 16) or 12 g (CR, n = 16) of MR powder per kg of initial BW (25% CP, 20% fat, prepared at 12.5% solid and offered at 0800 and 1630 h). In both treatments, calves had free access to a pelleted starter (PS, 21% CP, 15% NDF) and water. Weaning process was during 8th weeks and in this period calves received decreasing amounts of MR, free access to PS and 0.2 kg of chopped hay (CH, 18% CP, 40% NDF) in a separated bucket. In 9th week, all calves received 2.0 kg of PS and 0.4 kg of CH per day. In 7th and 9th week feed intake was recorded daily and feces were collected during 6 consecutive days to determinate diet dry matter digestibility [(g DM intake- g DM excreted)/g DM intake]. In the same weeks ruminal fluid samples was taken through a stomach tube at 0800, 1200, 1630 and 2000 h and ruminal pH was measured. Feed intake, digestibility and daily average ruminal pH were analyzed using a mixed model including the fixed effect of treatment and the random effect of block. During the 7th week, calves fed the AR treatment had a lower intake of PS (695 vs. 1160 ± 86.0 g DM/d, P < 0.01) but digestible dry matter intake was higher (1592 vs. 1198 ± 73.7 g DM/d, P < 0.01). Their digestibility and daily average ruminal pH were higher (0.92 vs. 0.87 ± 0.01 g DM, P < 0.01 and 5.56 vs. 5.38 ± 0.06, P = 0.04, respectively). However, during the week after weaning (9th week) no significant differences were found in diet dry matter digestibility, digestible dry matter intake or ruminal pH (P > 0.05). In conclusion, offering greater amounts of MR affected feed intake, diet digestibility and ruminal pH before weaning, but did not affect intake and digestion immediately after weaning.

Key Words: dairy calf, digestibility, ruminal pH