كليدواژه :
چربي پشت , گوشت لخم , خصوصيات لاشه , ضريب تبديل خوراك , ماده خشك مصرفي
چكيده لاتين :
Background and objectiv
e
s
:
Fattening lambs is an important source of animal protein in Iran.
The fattening enterprise is performed by rearing livestock on pasture
or
at feedlot or both of
them.
At this time, feedlot system with
feeding high concentrate diet
s is more prevalent t
han
other systems.
This study was conducted to evaluate the effects of using different dietary forage
to concentrate ratios on growth performance, feed intake, feed efficiency, and carcass
characteristics
of fattening
Chall male lambs
in Animal Science Res
earch Institute.
Materials and methods:
Eighty Chall male lambs
breed
, averaging
four to five
months of age
and body weight of 33.5
±
3.9 kg
were randomly assigned to
four
treatments
with
four
replicates
of
five
animals per treatment. F
our diets containing
alfalfa hay
-
to
-
concentrate ratios (DM basis)
of 70:30, 50:50, 30:70, 10:90; Metabolizable
energy of 2.23
, 2.43, 2.58; 2.71 Mcal/kg DM and
CP
contents
of 151
, 158, 164, and 170 g/
kg
were randomly assigned to
four
groups
,
respectively
.
The diets were prepar
ed in pelleted form and lambs were fed three times a day at
8.00, 14.00 and 20.00
for 84 days
ad libitum
.
At the end of the feeding period, all lambs were
weighed after 16 h feed deprivation and one lamb from each replicate was slaughtered. After
complete
bleeding, the bodies were skinned and the internal organs such as head, feet and skin
were weighed. The carcasses were eviscerated, and the internal organs or tissues and di
gestive
tract were separated and weighed.
The hot carcasses were weighed and chille
d at 4
º
C for 24 h.
The cold carcasses were weighed and sawed into two
symmetrical sides along backbone. The
right side carcasses were cut into six wholesale cuts (neck, shoulder, leg, rack
–
loin,
brisket
–
flank, and tail fat) and weighed separately. All cuts
except tail fat were dissected into the main
tissue components (lean, subcutaneous and inter
-
muscular fat, and bone) and the weight of each
tissue was recorded.
Results:
Dry matter intake and feed conversion ratio (P<0.01) decreased linearly as concentr
ate
level increased in the diet. However, average daily gain improved (P<0.01) with increasing
dietary concentrate (up to 700 g/kg) and then decreased. Slaughter weight, hot and cold carcass
weight, empty body weight, and weights of lean, bone, subcutaneou
s fat, intramuscular fat, total
fat, neck, shoulder, brisket, loin and leg, and eye muscle area, back
-
fat thickness and lean
-
to
-
fat
ratio were not affected by the experimental diets. However, as dietary concentrate increased, a
linear increase for dressing
percentage, and a linear decrease for digestive contents were
observed.
Conclusion:
In conclusion the results of this study indicated that the increase of dietary
concentrate (up to 700 g/kg) improves growth rate, FCR and dressing percentage without
neg
ative effect on carcass lean
-
to
-
fat ratio of Chall lambs.
