ABSTRACT
Sixty Zaraibi does aged 2-4 years and weighed 35-40 kg were used to define the oral administration influence of L-tyrosine on ovarian activities and reproductive performance. Does were randomly assigned to three equal groups (20 each). The first group (G1): was kept as a control (without L-tyrosine treatment). The second (G2) and third (G3) groups were received oral dose of L-tyrosine at levels 1.0 and 1.5gm / 10 kg live body weight, respectively. L-tyrosine was given one week before the beginning of breeding season.
Results show that  Does treated with L- tyrosine at level 1.0 gm (G2) had significantly (P≤ 0.05) higher oestrus (95.0%), while those treated with 1.5 gm (G3) had insignificant increase in oestrus (90%) compared to the control group (80%). The duration of oestrus showed the longest time (41.94 hr) with does on G2 (1.0 mg) and the shortest (13.73 hr) in G1 (control) (P < 0.05). While G3 (1.5 gm) had a medium duration (20.43 hr) which represent the normal duration. The interval from treatment to onset of oestrus (time to oestrus) was significantly (P≤ 0.05) shorter with does in G 3 and G2 than those in control group (G1). The non-return to oestrus of the does was significantly (P≤ 0.05) higher in G3 than G1.
The does treated with .L-tyrosine at level 1.5 gm (G3) increased (P≤ 0.05) total number of ovulatory cycle and number of oestrus ovulatory cycles compared to the control does. The number of anoestrus ovulatory cycles / doe was  insignificantly decrease in G2 compared to the other groups (G1 and G3). Anoestrus ovulatory cycle (%) showed insignificant lowering in the does in G3 than G1 and G2.
At pre-oestrus period, progesterone (P4) concentration in blood plasma was significantly (P≤ 0.05) higher in G2 does followed by G3 compared with control does (G1). At 4, 8 and 30 days post mating, P4 concentration was higher in does of G2 and G3 than that of G1.
The pregnancy rate was significantly (P≤ 0.05) higher in G3 does than the control (G1). The interval from buck exposure to kidding was decreased in the does of G2 and G3 compared to G1. Gestation length was insignificantly shorter in does of G3 and G2 than does of G1. The does in G3 attained higher (P≤ 0.05) kidding percentage (200%) followed by G2 (190 %) compared to control group (150%). Number of kids born per doe kidded was higher with G2 and G3 does compared to control group. The percentage of does kidded twins and triplets were higher among does treated with L-tyrosine (G2 and G3) than control group (G1). Litter weight at birth was insignificantly higher for does treated with L-tyrosine (G2 and G3) than control does. Mortality rate was significantly (P≤ 0.05) lower in the does treated with L-tyrosine (G2 and G3) compared with control group (G1).