A Study to Predict Impact of Atmospheric Temperature and Carbon dioxide Increase on Digestibility (in vitro and in vivo) of Maize Fodder in Ram Lambs

Abstract

Present study was conducted to assess the impact of increasing temperature and carbon dioxide on maize fodder (stems and leaves) digestibility in ram lambs. The maize fodder was grown with recommended package of practices in the CTGC chambers under four set of environmental conditions (a) Reference (ambient temperature and carbon dioxide i.e., 27±0.5ºC and 380 ± 25 ppm CO₂), (b) Chamber with temperature gradient of 5±0.5°C over  reference and referred as elevated temperature (eTemp), (c) Chamber with elevated CO₂ concentration of 550± 50 ppm with temperature gradient 5±0.5°C over reference  referred as elevated carbon dioxide and temperature (eCO₂+ eTemp) and (d) Chamber with elevated CO₂ concentration of 550± 50ppm referred as elevated carbon dioxide (eCO₂). Leaf and stem portion of maize fodder at milking stage were screened , in vitro dry matter digestibility (IVDMD) by ankom technology, in vitro gas production technique by ankom gas production system and digestibility of nutrients through a digestibility trial on Nellore Ram lambs.  In vitro dry matter degradability (IVDMD) of stem and leaf portion in the maize fodder grown under carbon dioxide and temperature gradient chambers (CTGC) differed significantly (P<0.05). Highest IVDMD (%) in maize stem was found in the maize fodder grown in eCO₂ (51.1±0.12), whereas lowest (43.6±0.84) under eTemp environmental chamber conditions.  Leaf of maize fodder grown at ambient (reference) (55.3±0.12) had highest IVDMD, whereas lowest (50.1±0.43) under eTemp environmental chamber conditions. Among different chambers, highest (P<0.05) DE (MJ/kg DM) was found in the stem and leaf of the maize fodder grown in eCO₂ chamber. DE in maize stem and leaf decreased (P<0.05) from G1 to G5 as temperature increased in both the eTemp and eCO₂+e Temp chambers.  A similar trend was observed in Metabolizable energy (ME) content of maize stem. Cumulative gas production (ml/g^-1DM) from stem and leaf of maize fodder grown in carbon dioxide and temperature gradient chambers (CTGC) differed significantly (P<0.05). A similar trend was observed in leaf portion of maize fodder grown in CTGC. Average dry matter (DM) digestibility coefficients (P < 0.05) of 68.40 ± 0.93, 64.26 ±1.04, 66.92 ±1.14 and 65.58 ± 0.76 per cent were recorded for ambient, e Temp, eCO₂ and eCO₂+e Temp, respectively, respectively for the maize fodder grown in CTGC under different environmental conditions. Similarly, crude protein (CP) digestibility coefficients were 71.46 ± 0.42, 66.32 ± 0.62, 68.06 ± 0.48 and 69.22 ± 0.56 per cent and crude fibre (CF) digestibility coefficients were 60.43 ± 0.52, 58.12 ± 0.74, 59.26 ± 0.43 and 58.54 ± 0.65 per cent for ambient, e Temp, eCO₂ and eCO₂+e Temp, respectively for the maize fodder grown in CTGC under different environmental conditions. The study indicated that nutritive value of maize fodder in terms of CP and DE/ME would decrease under elevated temperature and elevated carbon dioxide & temperature environmental conditions. Further, growing maize fodder under elevated temperature and elevated carbon dioxide & temperature would results in lower digestibility in small ruminants.