Use of chromium oxide and alkane indicator methods for determination of feed intake and digestibility at grazing sheep on pasture

This experiment was carried out to feed intake and digestibility at grazing sheep on pasture. A total of 14 animals, 7 animals within two groups were used in the experiment. Digestibility of pastures was determined using two types of markers (alkane (C32-C36) and chromium oxide). Moreover, energy contents of pasture were also calculated using digestibility values obtained from both methods. Nutrient contents of pasture as wet basis were 40.13, 11.19, 88.81, 14.14, 1.83, 36.86, 54.89, 31.67 and 5.63% for DM, ash, OM, CP, EE, CF, NDF, ADF and ADL, respectively. Dry matter intake were 717.22 g/d; digestibilities of DM, OM, CP, EE, NDF, and ADF were 65.20, 69.59, 66.08, 24.30, 62.38 and 57.80%; GE, DE, ME and NEL energy values were 3.90, 3.07, 2.52 and 1.58 Mcal/kg DM, respectively based on chromium oxide method in the experiment. Alkane contents of pasture were 9.96, 41.30 and 3.82 mg/kg DM for C32, C33 and C36 for alkanes, respectively. According to alkane method, dry matter intakes were 965.93 and 1051.07 g/d for C32 and C36, respectively. Digestibilities of DM, OM, CP, EE, NDF, and ADF using C32 were 68.40, 72.48, 69.02, 26.21, 66.71 and 65.76%, whereas digestibilities of DM, OM, CP, EE, NDF, and ADF using C36 were 65.13, 69.63, 65.82, 26.95, 63.26 and 62.21%, respectively. GE, DE, ME and NEL energy values determined with same method were 3.90, 3.20, 2.62 and 1.66 Mcal/kg DM for C32; 3.90, 3.07, 2.52 and 1.59 Mcal/kg DM for C36, respectively. Digestibility and energy values were not significantly different between chromium oxide and alkane methods (P>0.05). According to time of sampling, nutrient digestibilities determined by alkane methods of C32 at morning samples were 69.63, 73.54, 70.23, 25.58, %68.01 and 67.10% while they were 67.17, 71.41, 67.81, 27.10, 65.41 and 64.42% for DM, OM, CP, EE, NDF, and ADF, respectively at night sampling. These parameters for C36 were 66.49, 70.81, 67.17, 29.55, 64.71 and 63.69% at morning sampling; 63.77, 68.45, 64.48, 24.34, 61.81 and 60.72% at night sampling, respectively. Energy contents of feedstuffs determined by same method for C32 were 3.90, 3.24, 2.66 and 1.68 Mcal/kg DM at morning sampling; and 3.90, 3.02, 2.47 and 1.56 Mcal/kg DM at night sampling. Effects of sampling time on parameters determined by alkane methods were not significant (P>0.05). In conclusion, pastures met 74-81% of CP and 57-61% of energy requirements of lambs grazing on Yuzuncu Yıl University pasture that is mid-quality and 4-7 month-old with a 275 g/d expected daily gain. It was calculated that when 628 g - 693 g/d of barley is given, both CP and ME requirements of animals can be met.