ABSTRACT
A total of 30 Zaraibi does aged 2-4 years and weighed 35-40 kg were used to define the influence of oral administration of L-tyrosine on milk yield and composition, some blood metabolites during breeding period in pregnant and non-pregnant doe as indicator for the physiological status of animals are also studied. Does were randomly assigned to three equal groups (10 each). The first group (G1): was kept as a control (without L-tyrosine treatment). The second (G2) and third (G3) groups were received orally two doses of L-tyrosine at levels 1.0 and 1.5gm / 10 kg live body weight, respectively. L-tyrosine was given as two doses, one single dose before one week from the beginning of breeding period and the other dose three days post kidding.
Results indicated that milk yield and 4% fat correct milk (FCM) of does treated with 1.5 g L-tyrosine (G3) were significantly (P≤0.05) higher than those of does treated with 1.0g L-tyrosine (G2) and control (G1) groups. Fat, protein and lactose percentages in milk from does treated with L-tyrosine groups were significantly (P≤0.05) higher as compared to the control group (G1).
L-tyrosine administration significantly (P ≤ 0.05) increased blood albumin and glucose concentration compared to the control does. Meanwhile, blood globulin was decreased significantly due to L-tyrosine administration. The concentrations of urea-N and creatinine decreased as a result of L-tyrosine treatments compared to the untreated does.
Total protein, globulin and urea –N decreased (P ≤ 0.05) till 8 days after mating where it increased gradually up to 18 days after mating and decreased again at the end breeding period. The effect of breeding period on albumin and A/G ratio were not significant. Values of glucose were significantly (P ≤ 0.05) increased at 8 days after mating and then decrease (P ≤ 0.05) in estrous period. While, obtained values of blood plasma creatinine were higher in estrous period as compared to other breeding period. In pregnant does, there were significantly (P ≤ 0.05) lower concentrations of total protein, urea, glucose, triglyceride, calcium and Phosphorus and significantly (P ≤ 0.05) higher concentrations of total lipids and cholesterol in relation to non pregnant does. The changes of Plasma albumin, creatinine, AST, ALT, alkaline phosphates and zinc between pregnant and non pregnant does were not significant.