Abstract :

Twelve lactating Friesian cows with the average body weight of 435-570 kg were used in this study. All animals in this study were in the 2^nd to 4^th lactation season were randomly distributed into four similar groups (three cows for each group). All groups were individually fed according to NRC (2001) recommendations. The four experimental rations were formulated as follows: control: 52% concentrate feed mixture (CFM) (40% corn grain, 30% wheat bran, 23% undecorticated cottonseed meal, 5% molasses, 0.5% salt and 1.5% limestone) + 20% corn silage (CS) + 28% rice straw (RS), experimental ration 1 (Exp.1): 52% CFM (35% corn grain, 30% wheat bran, 10% corn gluten feed (CG), 18% undecorticated cottonseed meal, 5% molasses, 0.5% salt and 1.5% limestone) + 20% CS + 28% RS, experimental ration 2 (Exp.2): 52% CFM ( 32.5% corn grain, 30% wheat bran, 15% CG, 15.5% undecorticated cottonseed meal, 5% molass, 0.5% salt and 1.5% limestone) + 20% CS + 28% RS and experimental ration 3 (Exp.3): 52% CFM (30% corn grain, 30% wheat bran, 20% CG, 13% undecorticated cottonseed meal, 5% molasses, 0.5% salt and 1.5% limestone) + 20% CS + 28% RS. Four digestibility trials were conducted to determine nutrients digestibility coefficients and nutritive values of the experimental rations. Each digestibility trial consisted of 15 days preliminary period followed by 7 days collected period. Results showed that the dry matter intakes (% body weight) were higher with feeding on Exp.1 or Exp.2 (3.38 and 3.51, respectively) than feeding on control or Exp.3 (3.25 and 3.26, respectively). The apparent digestibility of CP was significantly (P<0.05) higher with feeding on control (74.60%) than feeding on Exp.1, Exp.2, and Exp.3 (67.88, 62.12 and 64.57% respectively). The TDN% values were 72.74, 70.18, 66.45 and 68.8% with feeding on control; Exp.1, Exp.2 and Exp.3 ,respectively, and the same trends were also with ME (Mcal/ kg), ME (Mj/ kg) and NE_L (Mcal/kg). Total tract digestibility (%) of starch was lower for the low starch diets, but ruminal digestion (%) of starch was not affected by starch concentration. The pH values were ranged from 6.16 to 7.59 with different treatments and at all measuring times. The mean value was higher (P<0.05) with feeding on control (6.97) and lower with feeding on Exp.1 (6.51), while there were no significant differences when feeding on Exp.2 (6.73) and Exp.3 (6.73) or among Exp.1 and Exp.2 or Exp.3. The mean values showed that the TVFA’s concentration was significantly (P<0.05) higher in control group (4.43 ml eq. /100 ml RL) than feeding on Exp.1 or Exp.2 or Exp.3 (4.08, 4.01 and 4.18 ml eq. /100 ml RL, respectively), but there was no significant effect among Exp.1, Exp.2 and Exp.3. Ruminal NH₃-N   concentration was higher (P<0.05) with feeding on the control or Exp.1 (10.50 and 10.25 mg /100 ml, respectively) than feeding on Exp.2 (8.42), but there was no significant effect with feeding on Exp.3 (9.58 mg /100 ml) or control or Exp.1 or Exp.2. The effective neutral detergent fiber (eNDF) values ranged from 25.58 to 36.63%, the eNDF was higher (P<0.05) with feeding on control (36.63%) than feeding on Exp.1 or Exp.2 or Exp.3 (25.58, 30.92 and 30.78 % respectively). The mean value of fibrolytic bacteria was higher (P<0.05) with feeding on Exp.2 (14.7x 10⁵ CFU/ml) than feeding on control or Exp.1 or Exp.3 (7.75, 8.12 and 9.65x 10⁵ CFU/ ml, respectively). On the other hand, the amylolytic bacteria count was ranged from 1.93 to 8.47x 10⁵ CFU/ ml with different treatments. The mean value was the highest (P<0.05) with feeding on the control (6.25 x 10⁵ CFU/ ml) than feeding on Exp.1 or Exp.2 or Exp.3 (3.93, 2.89 and 4.11x 10⁵ CFU/ ml respectively). The insulin concentration was higher (P<0.05) with feeding on Exp.3 (0.25 ng/ ml) than feeding on control or Exp.1 or Exp.2 which were have similar concentration (0.23 ng/ ml). The triglycerides concentrations were ranged from 106.06 to 343.73 mg /100ml with different treatments at all times, the mean values were higher (P<0.05) with feeding on control and Exp.1 (246.44 and 231.39 mg/ 100ml, respectively) than feeding on Exp.2 and Exp.3 (196.21 and 209.13 mg/ 100ml, respectively). The total protein concentrations were ranged from 4.19 to 8.01 g/ 100ml with feeding on the experimental rations at all times. The urea concentrations were increased with Exp.1 or Exp.2 or Exp.3 than feeding on control at all times. The mean values were higher (P<0.05) with feeding on Exp.2 or Exp.3 (21.68 and 23.24 g/ 100ml, respectively) than feeding on control or Exp.1 (16.6 and 18.67 g/ 100ml respectively). Corn grain and undecorticated cottonseed meal can be replaced by 15% corn gluten feed are often considered providing the proper amounts of ruminally fermentable carbohydrates.

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Research :