3 linda majdoub mathlouthi 2013 meat science

Effect of concentrate level and slaughter body weight on growth performances,
carcass traits and meat quality of Barbarine lambs fed oat hay based diet
L. Majdoub-Mathlouthi ⁎, B. Saïd, A. Say, K. Kraiem
Department of Animal Production, Institut Supérieur Agronomique de Chott-Mariem, University of Sousse, 4042, Tunisia
a b s t r a c ta r t i c l e i n f o
Article history:
Received 2 February 2012
Received in revised form 22 October 2012
Accepted 26 October 2012
Available online 8 November 2012
Keywords:
Barbarine lamb
Concentrate level
Slaughter weight
Growth
Carcass quality
Meat fatty acids
This study was conducted to evaluate concentrate level (CL) and slaughter body weight (SW) effects on
growth performances, carcass traits and meat quality of Barbarine lambs. Twenty-four weaned male lambs
(23.1 kg), receiving an oat-hay based diet, were allotted into two groups. The LCL group received low concen-
trate level (300 g) and the HCL group received high concentrate level (600 g). Lambs were slaughtered at
two prefixed weights (35 and 42 kg). For each group and each weight, six lambs were slaughtered. Lambs
from HCL group had higher ADG, carcass yields, carcass compactness and subcutaneous fat thickness, and
lower carcass meat proportion. CL increase did not affect meat pH, meat and fat color, chemical and fatty
acid composition. Late slaughtering improved carcass yields and increased carcass adiposity. However, it
did not affect carcass meat proportion and shoulder tissue composition. SW had effect on meat color and
fatty acid composition.
© 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Barbarine is the predominant sheep breed in Tunisia. It is a fat-tailed
sheep breed raised traditionally on natural pasture, in an extensive
system. Actually, some of these grasslands used for pasture are
transformed for field crop. In the semi-arid and arid areas of Tunisia,
feed available from natural pasture is becoming limited and of a very
poor quality, especially when rainfall is scarce. For these reasons,
farmers are adopting more and more the semi-intensive and intensive
systems for growing and fattening lambs. Those systems, based mainly
on oat hay and concentrate are considered expensive. In fact, the price
of oat hay is very fluctuant and affected by rainfall. Main feed compo-
nents in concentrate are frequently imported and with ever increasing
prices. Increasing concentrate level and energy supply for growing
and fattening lambs improved growth performances and eventually
carcass yield (Dixon & Stockdale, 1999; Papi, Mostafa-Tehrani,
Amanlou, & Memarian, 2011). However, high-energy supply could af-
fect negatively the carcass fatness and nutritional meat quality (Papi
et al., 2011). Carcass quality was also associated to slaughter body
weight (Abdullah & Qudsieh, 2008). Sheep producers need to know
the optimal slaughter weight, in relation to production cost, carcass
weight and quality. Consumers need also to know the optimal slaughter
weight for carcass and meat quality, especially fat content and fatty acid
composition. Santos-Silva and Portugal (2001) and Abdullah and
Qudsieh (2008) reported that increasing slaughter body weight (SW)
above 35 kg could improve dressing percentage without having detri-
mental effects on carcass and meat quality. Barbarine lambs are mainly
slaughtered at a body weight below 35 kg. It could be better to increase
the SW up to 40–45 kg. This last SW is essentially preferred for festivi-
ties. Therefore, in our study, we aimed to determine the effects of two
concentrate levels and two slaughter body weights on growth, carcass
traits and meat fat composition in Barbarine lambs receiving oat hay
based diet.
2. Materials and methods
2.1. Experimental design and animal management
The experiment was conducted at the experimental farm of the
Institut Supérieur Agronomique de Chott Mariem, Tunisia. Twenty
four, 6 month old, weaned Barbarine lambs of an average body
weight of 23.1±0.4 kg were used. Prior to weaning, lambs grazed
with their mothers on natural pasture. They were allotted into eight
pens (3 lambs per pen). The eight pens were assigned randomly to
two treatments. All animals received chopped oat hay ad libitum
and a commercial concentrate composed of 16.5% of soybean meal,
25% of wheat bran, 53.5% of corn grain and 5% of mineral vitamin sup-
plement. The chemical composition of the feeds is shown in Table 1.
For the first treatment, animals received a low concentrate level
(200 to 300 g/d, LCL) and for the second treatment, lambs received
a high concentrate level (400 to 600 g/d, HCL). Concentrate quantity
was adjusted to lamb body weight increase and was determined
based on French feeding system (INRA, 1988). Concentrate was
allowed twice a day. Lambs had free access to water. To determine
Meat Science 93 (2013) 557–563
⁎ Corresponding author. Tel.: +216 73 327 546; fax: +216 73 327 591.
E-mail addresses: lmajdoub@lycos.com (L. Majdoub-Mathlouthi),
bessem.said@live.fr (B. Saïd), khkraiem@yahoo.com (K. Kraiem).
0309-1740/$ – see front matter © 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.meatsci.2012.10.012
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Meat Science
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intake, allowed and refused feed were weighed daily for each pen.
Lambs were weighed in the beginning of the trial, each 15 days and
before slaughter. Linear regression was used to determine individual
average daily gain (ADG) and feed conversion rate was calculated
for each pen.
2.2. Slaughter procedure, carcass measurements and dissection
Two slaughter body weights were predetermined: 35 (SW1) and
42 kg (SW2). The day before slaughtering, lambs were weighed in
the experimental farm. They were then fasted for 12 h, with free ac-
cess to water. They were transported to a commercial slaughterhouse,
where they were re-weighed just before slaughtering. Lambs were
slaughtered according to the Muslim rite and under veterinarian con-
trol. Hot carcass, viscera (liver, heart, lungs, and empty digestive
tract) and gastro-intestinal content were weighed. Dressing percent-
age was determined as the rate of hot carcass weight over empty
body weight. Viscera proportions were expressed in relation to
pre-slaughter body weight. Carcasses were then chilled at 4 °C for
24 h. They were then re-weighed. Commercial dressing percentage
was calculated as the rate between cold carcass and pre-slaughter
body weight. Kidney, kidney fat, testis and tail were removed and
weighed. Carcasses were split along the midline. The left sides were
separated into seven joints, as described by Fisher and De Boer
(1994). The different joints were weighed to estimate their propor-
tions based on the cold carcass. Proportions of higher-priced joints
(leg+shoulder+loin) were also determined. All the joints were
deboned to evaluate meat dressing. Shoulder and tail were dissected
into fat, muscle and bone. In fact, according to Rodriguez et al. (2008)
shoulder was considered as the best joint to predict carcass tissue
composition.
Carcass length (C1), internal carcass length (C2), chest or thoracic
depth (T1) and rump circumference (B1) were recorded based on
Fisher and De Boer (1994) measures. Leg length (L1) and leg circum-
ference were measured as presented by Laville et al. (2002). These
measurements were used to evaluate carcass compactness (cold car-
cass weight/C2), leg compactness (leg weight/L1), based on the work
of Carrasco et al. (2009). Subcutaneous fat thickness was measured
using a digital calibrator at 4 cm from the spinal column and at the
level of the 13th rib (Fisher & De Boer, 1994).
Meat and fat color was determined 24 h after slaughter with a
chromameter (Minolta CR-401, Ltd Japan), using the L* (Lightness),
a* (redness) and b* (yellowness) system and the D65 illuminant.
Meat color was measured in the m. longissimus lumborum. Muscles
were maintained at 4 °C and exposed to air for 10 min before mea-
suring color. Fat color was measured in the tail and in the subcutane-
ous fat over the lumbar region. The pH of the m. longissimus thoracis
was recorded 1 h and 24 h after slaughter using a pH-meter
WTW-340, equipped with penetrating electrode (pH senTix 6, sp).
Longissimus lumborum was dissected to eliminate subcutaneous
fat, ground and frozen at −20 °C for chemical analyses. Dry matter,
crude protein and total ash were analyzed according to AOAC
(1995). Fat was determined using the Folch method (Folch, Lees, &
Sloane Stanley, 1957). Fatty acid were converted to methyl esters by
transesterification and then analyzed by gas chromatography on an
omega wax 320 capillary column; 30 m×0.32 m. Injector and detec-
tor temperatures were of 230 °C and 250 °C, respectively. Tempera-
ture increased by 5 °C/min. For each fatty acid, results were
expressed as a percentage of the total fatty acids.
2.3. Statistical analyses
The GLM procedure of Statistica (2000) was used. The model in-
cluded concentrate level (2), slaughter body weight (2) and their in-
teractions (2×2) as fixed factors. Individual lamb was considered as
the experimental unit. Values were given as means. Residual mean
squares were used as error term. Differences among means were de-
termined using the Fisher test and were considered significant when
P≤0.05.
3. Results and discussion
3.1. Growth and feed intake
Oat hay voluntary intake decreased when increasing concentrate
level (CL, Pb0.001). This could be associated with inhibitory effect of
concentrate on voluntary intake of forages (Table 2). ADG was 57%
higher (Pb0.001) for the HCL group than the LCL group (Table 2),
while feed conversion rate (FCR) was 41% lower (Pb0.001) for the
HCL group. Final weight increase from 35 to 42 kg did not affect ADG.
However, it increased (Pb0.001) oat hay voluntary intake and FCR by
14% and 13%, respectively.
3.2. Carcass and offal proportions
At fixed slaughter weights, hot and cold carcass weights increased
(Pb0.05) by 12 and 11%, dressing percentage increased (Pb0.05) by
1.5% and commercial dressing percentage increased (Pb0.01,
Table 3) by 2.7% when CL increased. Papi et al. (2011) reported a
4 kg and 4.9% increase in carcass weight and dressing percentage, re-
spectively, when concentrate proportion went from 30 to 50%. Those
results confirmed those reported previously in other studies when in-
creasing dietary energy concentration or concentrate level in the ra-
tion (Jacques, Berthiaume, & Cinq-Mars, 2011; Mahgoub, Lu, & Early,
2000, Mushi, Safari, Mtenga, Kifaro, & Eik, 2009). Higher percentage
of empty gut (Pb0.05) and liver (Pb0.001) with HCL resulted in a
higher offal percentage (Pb0.05). The weight of empty gut (3.18
and 2.86 kg for HCl and LCL groups, respectively) was also higher
with HCL (Pb0.05) and could be associated to higher visceral fat.
Fluharty and McClure (1997) reported higher gut and visceral fat
weight for lambs fed ad libitum than for lambs fed at 85% of the ad
libitum. Jacques et al. (2011) showed also an increase of digestive
tract weight when concentrate was fed ad libitum than when it rep-
resented 40% of DMI. However, Papi et al. (2011) reported no effect
of CL on empty gut weight for lambs slaughtered at 60 kg. Moreover,
testis and kidney percentage were lower for HCL group (Pb0.001).
Table 1
Chemical composition of experimental feeds (g/kg DM).
DM (g/kg) Ash Crude fiber Crude protein
Oat hay 957.4 62.9 369.8 37.5
Concentrate 892.9 43.8 52.00 185.6
Table 2
Effects of concentrate level and slaughter weight on voluntary hay intake, concentrate
intake, ADG and feed conversion rate (FCR) in Barbarine lambs.
Concentrate
level
Slaughter
weight
Level of
significance
LCL HCL SW1 SW2 SEM CL SW CL∗SW
Initial weight (kg) 23.1 23.1 22.7 23.4 0.45 NS NS NS
Final weight (kg) 37.4 39.2 34.8 41.7 1.00 NS *** NS
Slaughter weight (kg) 36.4 38.2 33.9 40.7 1.00 NS *** NS
ADG (g) 77.2 121.7 100.2 98.7 5.88 *** NS NS
Hay intake (kg/d) 0.9 0.6 0.7 0.8 0.03 *** *** NS
Concentrate intake (kg/d) 0.3 0.5 0.3 0.4 0.09 *** *** NS
FCR (g DM/g ADG) 15.8 9.3 10.9 12.3 0.9 *** *** NS
Fattening period (day) 186 124 121 185
LCL: low concentrate level (200–300 g); HCL: high concentrate level (400–600 g);
SW1: slaughter weight of 34 kg; SW2: slaughter weight of 41 kg. CL*SW: interaction
between slaughter weight and concentrate level.
***Pb0.001; NS: P>0.05.
558 L. Majdoub-Mathlouthi et al. / Meat Science 93 (2013) 557–563

When SW increased, hot and cold carcass weights increased by 25%
and 24.5%, respectively (Pb0.001, Table 3). Dressing percentages
(Pb0.01), as well as the commercial dressing percentage (Pb0.05)
were higher for lambs slaughtered at 41 kg than for lambs slaughtered
at 34 kg. In fact, for the same slaughter weights, Solomon, Kemp,
Moody, Ely, and Fox (1980) reported an increase of 2% for dressing
percentage. Galvani et al. (2008) indicated that lambs slaughtered at
weights growing from 17 to 35 kg showed a linear effect of SW on dress-
ing percentage. The same effects were reported for rams slaughtered
between 50 and 80 kg (Sents, Whiteman, & Walters, 1981). However,
for Abdullah and Qudsieh (2008), dressing percentage increased only
between 20 and 30 kg, and was not altered between 30 and 40 kg.
Offal percentages decreased with increasing SW (Pb0.001). In fact, the
increase of SW reduced empty gut (Pb0.05) and liver (Pb0.001) per-
centages. The effect of SW on liver percentage was more important for
LCL group (Pb0.001). A higher percentage of testis (Pb0.001) was
observed for heavy lambs, particularly those from the HCL group (0.28
vs. 0.76% for SW1 and SW2, respectively). This result confirms the effect
of age and puberty on testis percentage. Lambs from HCL group and
slaughtered at 34 kg were 8 months old whereas those slaughtered at
41 kg were 11 months old and were pubescent. For the LCL group,
lambs were older and were pubescent for the two slaughter weights,
so the effect of age was less important on testis development.
3.3. Carcass cut weights and proportions
CL in the ration increased (Pb0.05, Table 4) tail, loin region and
shoulder weights (distal and proximal thoracic limb weights). The
effect of CL on tail weight was higher for heavy lambs. In fact, tail
weight increased by 21% for heavy lambs, while it did not change
for lighter ones. This result was coherent with an increase of fat
development with high-energy diet. Jacques et al. (2011) reported a
better loin classification for lambs receiving ad libitum concentrate
compared to those on restricted quantity of concentrate (40% DMI).
Leg, abdominal region and neck–thorax weights were not altered.
However, when expressed as percentage of carcass weight, leg,
abdominal region and neck–thorax were lower for HCL group
(Pb0.001). Significant interaction (Pb0.05) was observed for the ab-
dominal region percentage (6.1 vs. 5.3% for light and heavy lambs, re-
spectively). On the opposite, lumbar or loin region was higher for HCL
(Pb0.001). Borton, Loerch, McClure, and Wulf (2005) indicated that
loin proportion was higher for lambs finished on concentrate than
those finished on forages. According to Preziuso et al. (1999) and
Abdullah and Qudsieh (2008), leg had probably an allometric coeffi-
cient lower than 1, while lumbar region had probably an allometric
coefficient higher than 1. This could explain why leg proportion was
lower and loin proportion was higher for HCL group.
Table 3
Effects of concentrate level and slaughter weight on carcass weights, dressing percentages and offal percentages of Barbarine lambs.
Concentrate level Slaughter weight Level of significance
Hot carcass weight (kg) 16.4 18.3 15.4 19.3 0.60 * *** NS
Cold carcass weight (kg) 16.0 17.8 15.1 18.8 0.58 * *** NS
Dressing percentage (%) 53.1 54.6 52.8 54.8 0.42 * ** NS
Commercial dressing percentage (%) 43.9 46.6 44.4 46.0 0.52 ** * NS
Offals (%) 11.5 12.3 12.4 11.4 0.20 * *** NS
Empty gut 7.9 8.4 8.5 7.8 0.16 * * NS
Lungs and trachea 1.5 1.3 1.3 1.5 0.05 *** NS NS
Heart 0.3 0.3 0.4 0.3 0.01 NS NS NS
Liver 1.1 1.3 1.3 1.1 0.04 *** *** ***
Kidney 0.2 0.2 0.2 0.2 0.01 *** NS ***
Testis 0.8 0.5 0.5 0.8 0.05 *** *** ***
LCL: low concentrate level (200–300 g); HCL: high concentrate level (400–600 g); SW1: fixed slaughter weight of 34 kg; SW2: fixed slaughter weight of 41 kg. CL∗SW: interaction
*Pb0.05; **Pb0.01; ***Pb0.001; NS: P>0.05.
Table 4
Effects of concentrate level and slaughter weight on carcass cut weights and their percentages in Barbarine lambs.
Leg weight (kg) 2.6 2.3 2.3 2.6 0.07 NS *** NS
Distal pelvic limb (kg) 0.5 0.6 0.5 0.6 0.02 *** *** ***
Proximal pelvic limb (kg) 2.1 1.7 1.8 2.0 0.06 *** * NS
Lumbar region (kg) 0.5 0.9 0.6 0.8 0.06 *** * NS
Abdominal region (kg) 0.4 0.4 0.4 0.5 0.02 NS * NS
Neck and thorax (kg) 2.5 2.6 2.2 2.8 0.08 NS *** NS
Shoulder (kg) 1.3 1.4 1.2 1.4 0.04 * *** NS
Distal thoracic limb (kg) 1.0 1.1 0.9 1.1 0.03 * * NS
Proximal thoracic limb (kg) 0.2 0.3 0.2 0.3 0.01 *** NS NS
Tail weight (kg) 1.5 1.9 1.3 2.0 0.11 ** *** **
Leg (%) 32.5 26.7 30.6 28.5 0.80 *** * NS
Lumber region (%) 5.7 10.4 8.1 8.0 0.51 *** NS NS
Abdominal region (%) 5.7 4.0 4.9 4.8 0.24 *** NS *
Neck and thorax (%) 31.0 28.7 29.8 30.0 0.42 *** NS NS
Shoulder (%) 15.7 15.2 15.5 15.5 0.19 NS NS NS
High priced joints (%) 53.9 52.2 54.2 52.0 0.61 NS NS NS
Tail (% carcass weight) 9.2 10.2 8.6 10.9 0.40 NS *** NS
*Pb0.05; **Pb0.01; ***Pb0.001; NS: P>0.05.
559L. Majdoub-Mathlouthi et al. / Meat Science 93 (2013) 557–563

SW affected essentially carcass cut weights, which increased sig-
nificantly with increasing SW (Pb0.05). Except for leg and tail pro-
portions, carcass cut percentages were not affected by increasing
SW. Leg proportion was 2.1% lower (Pb0.05) and tail proportion
was 2.3% higher (Pb0.001) for heavy lambs. Abdullah and Qudsieh
(2008) reported the same trend for Awassi lambs slaughtered be-
tween 30 kg and 40 kg. In addition, Solomon et al. (1980) and Zgur,
Cividini, Kompan, and Birtic (2003) also found a decrease in leg pro-
portion for thin tailed lambs. This result confirmed the hypothesis of
an allometric coefficient of leg lower than 1 (Preziuso et al., 1999).
3.4. Meat and tissue composition
Despite the increase of meat proportions in the lumbar region and
the distal pelvic limb, meat proportion in the untailed carcass decreased
with increasing CL (Pb0.001, Table 5). This was explained by a higher
untailed carcass weight for the HCL group (15.97 vs. 14.52 kg for HCL
and LCL groups, respectively) and to a lower percentage of leg. Leg is
considered as having the higher percentage of meat. CL did not affect
shoulder composition (P>0.05).
When whole carcass is considered, SW did not affect meat percent-
age in the whole carcass. Nevertheless, we observed lower percentage
in the leg (Pb0.001) and higher percentages in lumbar region
(Pb0.001) and shoulder (Pb0.001) for heavy lambs. Higher fat deposi-
tion could explain these higher percentages. In fact, fat percentage in the
shoulder tended to be higher for heavy lambs (15.6 vs. 17.8%, Pb0.1),
while bone percentage was lower (Pb0.001). Abdullah and Qudsieh
(2008) showed a significant increase in fat proportion in the shoulder
and in the loin, when SW increased from 20 to 40 kg. This increase
was essentially associated to higher inter muscular fat proportion.
3.5. Carcass linear measurements
HCL diet influenced carcass lamb conformation (Table 6). In fact,
thoracic depth and rump circumference were higher for HCL group
than LCL group (Pb0.001). Carcass compactness was 19% higher for
HCL, while leg compactness was 10% lower (Pb0.05). Mushi et al.
(2009) reported an increase in carcass compactness of kids when
concentrate proportion increased from 33% to 66%. Carcass fatness in-
creased with increasing concentrate level. Subcutaneous fat thickness
was 3.1 and 5 mm for HCL and LCL group, respectively (Pb0.001).
These results confirmed those reported by Carrasco et al. (2009),
Mushi et al. (2009) and Jacques et al. (2011). Nevertheless, fat thick-
ness for the two concentrate levels was acceptable and did not depre-
ciate the carcass quality. According to Abdullah and Qudsieh (2008),
fat tailed lambs seem to stock the fat particularly in tail and not on
the carcass. According to our results, CL increased (Pb0.01) tail fat
by 21.4%, whereas it did not affect kidney fat. In fact, Carrasco et al.
(2009) reported a clear effect of feeding system on intramuscular
and subcutaneous fat but not on internal fat.
Table 5
Effect of concentrate level and slaughter weight on meat proportion (%) in the different joints and in the no-tailed carcass and on the tissue composition of shoulder in Barbarine
lambs.
Leg 85.3 85.3 86.0 84.6 0.34 NS *** NS
Distal pelvic limb 70.6 73.5 71.5 72.7 0.60 * NS NS
Proximal pelvic limb 88.3 88.7 89.4 87.5 0.50 NS * NS
Lumbar region 78.8 83.3 77.1 85.0 1.39 *** *** NS
Neck and thorax 79.7 79.7 79.0 80.3 0.52 NS * NS
Shoulder 82.1 82.8 81.6 83.2 0.32 NS *** NS
Distal thoracic limb 85.4 86.2 85.1 86.6 0.32 NS *** NS
Proximal thoracic limb 63.9 65.9 63.5 66.2 0.71 NS * NS
Carcass 82.9 78.6 80.3 81.2 0.70 *** NS NS
Shoulder composition
Muscle (%) 63.6 62.6 63.4 62.8 0.66 NS NS NS
Bone (%) 18.9 18.1 19.3 17.6 0.32 NS *** NS
Fat (%) 15.9 17.5 15.6 17.8 0.24 NS NS NS
*Pb0.05; ***Pb0.001; NS: P>0.05.
Table 6
Effects of concentrate level and slaughter weight on carcass linear dimensions (cm) and carcass fatness in Barbarine lambs.
Carcass length 67.7 68.4 63.3 72.8 1.24 NS *** NS
Internal carcass length 61.9 58.0 55.6 64.3 1.27 ** *** ***
Thoracic depth 25.7 27.4 26.3 26.7 0.33 *** NS NS
Rump circumference 58.8 61.8 59.4 61.2 1.39 *** * NS
Leg circumference 37.3 38.5 38.0 37.8 0.51 NS NS NS
Leg length 37.8 38.4 36.9 39.3 0.49 NS ** NS
Carcass compactness (g/cm) 257.8 307.1 273.5 291.4 7.53 *** NS NS
Leg compactness (g/cm) 68.4 61.3 62.4 67.3 1.68 * * NS
Subcutaneous fat thickness (mm) 3.1 5.0 2.5 5.6 0.5 *** *** ***
Kidney fat (g) 149.0 121.4 102.9 167.5 11.8 NS ** NS
Tail fat (g) 1.4 1.7 1.2 1.3 0.11 ** *** *
*Pb0.05; **Pb0.01; ***Pb0.001 LCL: low concentrate level (200–300 g); HCL: high concentrate level (400–600 g); SW1: fixed slaughter weight of 34 kg; SW2: fixed slaughter
weight of 41 kg. CL∗SW: interaction between slaughter weight and concentrate level.
*Pb0.05; **Pb0.01; ***Pb0.001; NS: P>0.05.

The increase of SW from 34 to 41 kg increased carcass length
(Pb0.001), leg length (Pb0.01), rump circumference (Pb0.05) and
leg compactness (Pb0.05). Moreover, the increase of SW increased
subcutaneous fat thickness (Pb0.001), tail fat (Pb0.001) and kidney
fat (Pb0.01) by 124%, 8.3% and 62.8%, respectively. The effect of SW
on fat tail was higher for lambs receiving 600 g of concentrate
(Pb0.05). These results confirmed those reported by Abdullah and
Qudsieh (2008).
3.6. Meat pH, meat and fat color
CL and SW did not affect the meat pH (Table 7). The ultimate pH
was within the acceptable range (5.6–6.4) reported for lamb meat
(Dragomir, 2005). Abdullah and Qudsieh (2009) reported that SW
had no effect on the ultimate pH of longissimus thoracis when SW
went from 20 to 40 kg. Interaction between CL and SW (Pb0.05)
was observed for the ultimate pH. Heavy lambs receiving the HCL
ration had lower pH than light ones receiving the same ration (5.89
vs. 6.18). This effect could be explained by a higher muscle glycogen
reserve for heavy lambs receiving HCL (Beriain et al., 2000).
CL and SW had no effect on subcutaneous fat color in the loin
region and the tail (Table 7).
Meat color was not altered with increasing CL. Lightness (L*) of
the longissimus lumborum decreased with increasing SW (Pb0.01).
This confirms previous results reported by Sanudo, Santolaria,
Maria, Osorio, and Sierra (1996), Martinez-Cerezo et al. (2005) and
Abdullah and Qudsieh (2009). Redness (a*) and yellowness (b*) of
the longissimus lumborum were not affected.
3.7. Lean chemical composition and fatty acid composition
CL and SW had no significant effect on chemical composition of the
longissimus lumborum. DM, crude protein and total ash averaged
26.82%, 81.01% and 5.58% DM, respectively. Intramuscular fat was not
affected by CL or SW (Table 8), except a higher intramuscular fat
(Pb0.05) for the heavy lambs receiving HCL ration (12.81 vs. 10.10%
DM). Mushi et al. (2009) noted an increase in the longissimus dorsalis
fat content with increasing concentrate. Abdullah and Qudsieh (2008)
did not report a modification in protein percentage but an increase in
intramuscular fat when slaughter weight went from 20 kg to 40 kg.
Wood et al. (2003) recommended for human health a PUFA to SFA
ratio of 0.4. Low PUFA/SFA rates are partially responsible in
cholesterolaemia. Table 8 shows the fatty acid composition of
longissimus lumborum intramuscular fat. In this study, meat PUFA/SFA
ratio (0.24) was higher than the one (0.15) reported by Wood et al.
(2003) for meat lamb. But, it was similar to ratios reported by other
works (Caneque et al., 2003; Rhee, Lupton, Ziprin, & Rhee, 2003;
Santos-Silva, Bessa, & Santos-Silva, 2002) for lambs assigned to different
feeding systems (pasture; grazing with concentrate supplement; in
confinement with concentrate…). Omega 6/omega 3 ratio (9.28) was
higher than values recommended for human nutrition (4) and reported
by many authors (Aurousseau, Bauchart, Calichon, Micol, & Priolo,
2004; Nuernberg, Fischer, Nuernberg, Ender, & Dannenberger, 2008;
Santos-Silva et al., 2002 ; Wood et al., 2003) for lambs receiving differ-
ent diets and slaughtered at different weights. However, it was compa-
rable to ratio reported by Nasri et al. (2011) for Barbarine lambs
receiving oat hay plus concentrate and by Demirel, Ozpinar, Nazli, and
Keser (2006) for Turkish breeds. Nasri et al. (2011) suggested that
breed effect could partially explain higher omega 6 proportions. In
fact, Demirel et al. (2006) and Juarez et al. (2008) showed a significant
effect of breed on fatty acid composition. Our results showed no effects
of CL or SW on PUFA/SFA and Omega 6/Omega 3 ratios. Nevertheless,
the increase of CL increased C18:2n-6/C18:3n-3 rate (Pb0.05). Lower
C18:3n-3 concentration for HCL group can explain the lower stearic
acid proportion observed for this group (Pb0.05). Demirel et al.
(2006) reported an increase of PUFA/SFA, omega 6/omega 3 and
C18:2/C18:3 when concentrate proportion increased from 25% to 75%.
Same results were also shown by Aurousseau et al. (2007). The increase
in CL decreased CLA proportion (Pb0.05). Troegeler-Meynadier and
Enjalbert (2005) reported a decrease of CLA level when crude fiber in
the diet decreased from 42.8 to 19.5% or when starch level increase
from 12.2% to 35.7%. In these conditions, ruminal pH could decrease
and biohydrogenation in the rumen could drop.
CL had also a significant effect on odd saturated acid (C15:0 and
C17:0) and on branched acids (isoC15 and antéisoC15) percentages.
They were lower for HCL group. This result contrasts with the findings
of Caneque et al. (2003) and Velasco, Caneque, Lauzurica, Perez, and
Huidobro (2004). This effect could be attributed to a modification in
the microbial composition in the rumen, with increasing concentrate
level. Nevertheless, branched chain fatty acids concentration was
Table 7
Effects of concentrate level and slaughter weight on muscle pH and meat and fat color in Barbarine lambs.
pH1h longissimus thoracis 6.48 6.33 6.53 6.29 0.07 NS * **
pH24h longissimus thoracis 6.19 6.04 6.12 6.11 0.05 NS NS *
Fat color
Lumbar region
L* 79.84 79.11 80.81 78.14 0.76 NS NS NS
a* 6.37 8.64 6.51 8.51 0.68 NS NS NS
b* 10.06 10.39 10.45 10.00 0.40 NS NS *
Tail
L* 80.72 80.57 80.66 80.64 0.48 NS NS **
a* 7.89 6.92 7.39 7.42 0.41 NS NS NS
b* 10.45 10.06 10.57 9.94 0.36 NS NS *
Meat color
Longissimus lumborum
L* 39.64 40.67 41.44 38.87 0.53 NS ** NS
a* 21.81 22.67 22.13 22.36 0.29 NS NS NS
b* 3.36 3.87 3.54 3.69 0.26 NS NS NS
*Pb0.05; **Pb0.01; NS: P>0.05.

reported to be higher for lambs receiving concentrate than those
raised on pasture (Schreurs, Lane, Tavendale, Barry, & McNabb, 2008).
SW affected only long polyunsaturated fatty acids. The long n-6
PUFA proportions were higher for heavy lambs (Pb0.05). This could
be attributed to a higher but not significant C18:2n-6 proportion for
heavy lambs and could explain the higher omega 6 level (9.07 vs.
7.74% for light and heavy lambs, respectively).
4. Conclusion
In conclusion, Barbarine lambs reared indoor, in semi-intensive sys-
tem seemed to have moderate performances. Increasing concentrate
supply improved ADG, carcass yields, carcass compactness and adipos-
ity. Delaying slaughtering improved carcass yields, without modifying
meat yields and shoulder composition. However, it increased carcass
fatness while maintaining its quality. Increasing concentrate level or
slaughter weight influenced meat color and fatty acid composition.
Acknowledgments
The authors would like to thank the World Bank for financial
support and the company “Général Viandes” for the technical support
in slaughtering and preparing carcass.
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C20: 5n-3 (EPA) 0.10 0.09 0.09 0.10 0.01 NS NS *
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C22:5n-4 0.18 0.27 0.26 0.19 0.04 NS NS NS
C22:6n-3 (DHA) 0.05 0.07 0.04 0.07 0.01 * * NS
SFA 45.85 44.48 45.73 44.60 0.73 NS NS NS
UFA 52.02 53.32 52.02 53.33 0.78 NS NS NS
MUFA 40.84 42.68 41.79 41.74 0.67 NS NS NS
PUFA 11.19 10.63 10.23 11.59 0.60 NS NS NS
Omega 6 8.58 8.23 7.74 9.07 0.53 NS * NS
Omega 3 1.03 0.88 0.89 1.10 0.09 NS NS NS
UFA/SFA 1.14 1.21 1.15 1.20 0.03 NS NS NS
PUFA/SFA 0.24 0.24 0.23 0.26 0.01 NS NS NS
Omega 6/omega 3 8.84 9.73 9.28 9.29 0.78 NS NS NS
C18:2n-6/C18:3n-3 9.95 12.38 10.96 11.37 0.61 * NS NS
SFA: saturated fatty acid; UFA: unsaturated fatty acid; PUFA: polyunsaturated fatty acid; omega 3 (C18 : 3n-3+C20 : 5n-3+C22 : 5n-3+C22 : 6n-3); omega 6 (C18 : 2 n-6+C20 :
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*Pb0.05; **Pb0.01; NS: P>0.05.

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