Effect of l-tyrosine on growth performance and some blood constituents of suckling friesian calves during winter and summer seasons

الملخص EN

Thirty two newly born Friesian calves during winter season, 16 male with average body weight (BW) of 30.69 kg and 16 female with BW of 30.94 kg and twenty nine newly born Friesian calves during summer season, 14 male with BW of 30.43 kg and 15 female with BW of 29.40 kg were divided into three similar groups.

The first group (G1) was served as a control, while the second group (G2) was received orally a dose of 0.1 g L-tyrosine/kg BW at the first week and the third group (G3) was received orally with two dose of 0.1 g L-tyrosine/kg BW at the first and eight weeks of age.

Results revealed that total dry matter (DM) intake tended to increase during winter compared to summer season.

The red blood cells (RBC) count and plasma glucose and creatinine concentrations were higher (P<0.05), however, PCV value was lower (P<0.05) for both G2 and G3 compared to G1.

Concentrations of plasma protein (TP), globulin (GL) and cholesterol (CHD) were higher (P<0.05) for both G1 and G3 than that for G2.

Count of white blood cells (WBC), hemoglobin (HB) concentration and plasma albumin (AL) and urea (UR) concentrations were nearly similar for the three studied groups.

The blood RBC count, HB concentration, PCV value and plasma glucose concentration were higher (P<0.05), however plasma UR and creatinine concentrations were lower (P<0.05) for winter than summer season.

Only, WBC and PCV values were lower (P<0.05) for female than male calves.

BW at 5, 10 weeks and weaning and average daily gain (ADG) from birth to 5, 6 to 10, 11 week to weaning and during the whole suckling period from birth to weaning were higher (P<0.05) forG2 and G3 compared with G1.

Treatment of G2 and G3 improved weaning weight by 9.66 and 13.11 kg or 10.49 and 14.23% compared to G1, respectively.

Moreover, ADG during the whole suckling period from birth to weaning increased by 15.25 and 20.34% for G2 and G3 compared withG1, respectively.

ADG during the period from 11 week to weaning was higher (P<0.05) for winter than summer season.

BW at 10 week and weaning and ADG from 6 to 10 weeks were higher (P<0.05) for male than female calves.

The amounts of whole milk, starter, fresh berseem, berseem hay and total DM required per kg gain were lower (P<0.05) for G2 and G3 compared withG1.

The feed cost per kg gain was lower (P<0.05), however, the price of daily gain and economic efficiency were higher (P<0.05) forG2 and G3 compared toG1.