الفهرس 
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Abstract
The experimental work of this study was carried out on Ossimi and Ossimi—Rahmani crossbred male lambs. These lambs belonged to the herd raised in the, Experimental Farm of the Faculty of Agriculture at Moshtohor, Banha University.
Twenty-four pure Ossimi and thirty crossbred male lambs (resulting from mating between Ossimi and Rahmani sheep) produced during the period of the study were fattened for three months. Fattening started when male lambs reached five, seven and nine months of age, lambs of fattening groups was assigned form all the weaned lambs at random. Wheat straw and Egyptian clover were offered ad libitum while the concentrate mixture was allowed according to National Research Council N.R.C. (1985) recommendation based on the animal live body weight. Body dimensions measured were body length, height at withers, heart girth, chest width, chest depth and width at hind quarter. At the end of the fattening period six (three Ossimi and three crossbred) male lambs from each of the fattened groups (i.e. five, seven and nine months of age) were slaughtered for carcass evaluation. Blood samples were taken when the lambs reached five, seven and nine months of age.The results obtained in this study can be summarized as follows:
1. Fattening period
Body weight: the differences between means of male lambs body weight, due to breed group, type of birth and parity effect was in-significant. While, the differences between means of male lambs body weight, due to age at start of fattening period effect, was highly significant (P<0.001) at first, second and third month of fattening period.
Daily gain: the differences between means of male lambs daily gain, due to breed group, type of birth and parity effect, was not significant. While, the differences between means of male lambs daily gain, due to age at start of fattening effect, was significant at second (P<0.05) and third ( P<0.01) month of fattening period.
Economical efficiency: the differences between means of male lambs economical efficiency, due to breed group, type of birth, parity and age at start of fattening period effect, were not significant.
Total feed intake: the differences between means of male lambs total feed intake, due to breed group, type of birth and parity effect, was insignificant. While, the differences between means of male lambs total feed intake, due to age at start of fattening period effect, was significant at first, second and third (P<0.01) month of fattening period.Feed conversion: the differences between means of male lambs feed conversion, due to breed group, type of birth and parity effect, was not significant. While, the differences between means of male lambs feed conversion, due to age at start of fattening effect, was significant at first, second and third (P<0.01) months of fattening period.
2. Live body dimensions and score
Body length: the differences between means of lamb live condition score and body length, due to breed group effect, were in-significant for live condition score but it was significant for body length (P<0.05). While, the differences between means of male lambs live body dimensions and score, due to its age at slaughter effect , were in-significant for live condition score but it were highly significant for body length (P<0.001).
Height at withers: differences between means of male lambs height at withers, due to breed group effect, were in-significant while, due to age at slaughter effect, were highly significant (P<0.001).
Heart girth: differences between means of male lambs heart girth, due to breed group effect, were highly significant (P<0.001) while, for age at slaughter effect, were highly significant (P<0.001).
Shoulder width: the differences between means of male lambs shoulder width, due to breed group effect, weresignificant (P<0.05) while, for age at slaughter effect, were highly significant (P<0.001).
Chest depth: the differences between means of male lambs chest depth, due to breed group effect, were not significant while, for age at slaughter, were highly significant (P<0.001).
Width at hind quarter: the differences between means of male lambs width at hind quarter, due to breed group effect, were significant (P<0.05) while, for age at slaughter effect, were highly significant (P<0.001).
3. Carcass traits
Carcass measurements and scores: the differences between means of carcass measurements and scores, due to breed group effect, were insignificant except for carcass width (P<0.01) and hind quarter circumference (P<0.05) while, for age at slaughter effect, were highly significant for carcass length (P<0.01), carcass width (P<0.001) and hind quarter circumference (P<0.01) but it were not significant for carcass conformation score and subcutaneous fat score traits.
Hot carcass and dressing percentages: the differences between means of hot carcass weight and dressing percentages, due to breed group effect, were insignificant while, for Age at slaughter showed a highly significant (P<0.001) differences between means of hot carcass weight and dressing percentage.Prime and second cuts: the differences between means of carcass prime and second cuts weight, due to breed group effect, were not significant while, for age at slaughter effect , was significant for average weight of round , loin (P<0.01) , rack , shoulder , total prime cuts (P<0.001) , neck , brisket (P<0.05) , flank (P<0.01) , tail (P<0.05) and total second cuts (P<0.01) weight.
Physical component of the lean on 9, 10 and 11th ribs
cut: the differences between means of physical component of 9, 10 and 111h ribs cut, due to breed group effect, were insignificant except for fat thickness on ribs was highly significant (P<0.001) while, for age at slaughter effect, was insignificant except for fat thickness on ribs since it was significant (P<0.05).
Eye muscle (Longissimus dorsi) Characteristics: the differences between means of L.dorsi characteristics, due to breed group effect, was insignificant except for L. dorsi width (P<0.05) and depth (P<0.001) since they proved highly significant while, for age at slaughter effect, was insignificant except for fat thickness on L.dorsi and width of L.dorsi (P<0.05).
Chemical analysis of lean on the 9, 10 and 11th ribs cut: effect of breed group on differences between means of chemical analysis of lean on the 9,10 and 111h ribs cut, were non-significant while, for age at slaughter effect, were significant for fat percentage (P<0.05) only.
Physical analysis of lean on the 9, 10 and 11th ribs cut: the differences between means of physical analysis of lean on the 9,10 and 111 ribs cut, due to breed group effect, was not significant while, for age at slaughter were insignificant except for PH-value of lean on the 9,10 and 111 ribs cut which proved significant
(P<0.05).
Skin, head, legs and body offals weight: obtained differences between means of skin, head, legs and body offals weights, due to breed group effect, were significant for head (P<0.05) and digestive tract full (P<0.001) weight while, for age at slaughter effect, were highly significant for head (P<0.01), legs and digestive tract full (P<0.001) weight.
Internal organs weight: the differences between means of internal organs weight, due to breed group effect, were highly significant for heart (P<0.01), kidneys (P<0.05), liver, lungs and trachea, spleen and tests (P<0.001) weights while, for age at slaughter effect, were highly significant for heart (P<0.001), kidneys (P<0.01), liver, lungs and trachea, spleen and tests (P<0.001) weights.
4. Concentration of some blood components in lambs during fattening period
Total protein: the differences between means of plasma total protein, due to breed group effect, was not significant except the differences between means at first month of fattening (P<0.01) while, for age at start of fattening effect, was not significant except at second month of fattening which proved significant (P<0.05).Albumin: effects of breed group and age at start of fattening period effect were not significant on differences between means of plasma albumin.
Globulin: the differences between means of plasma globulin, due to breed group and age at start of fattening period effect, were non-significant.
Albumin/Globulin (A/G) ratio: The differences between means of plasma albumin/globulin (A/G) ratio, due to breed group and age at start of fattening period effect, were not significant.
Cholesterol: The differences between means of plasma cholesterol, due to breed group effect, was not significant except between means at the third month of fattening period which proved significant (P<0.05) while, for age at start of fattening period effect, was not significant except the differences between means at second (P<0.01) and third (P<0.05) month of fattening which proved significant.
Total lipids: The difference between means of plasma total lipids, due to breed group and age at start of fattening period effect, were not significant.