Effects of genotype and dietary forage to concentrate ratio during the finishing period on carcass characteristics and meat quality of lambs from hill sheep systems
Af. Carson et al., Effects of genotype and dietary forage to concentrate ratio during the finishing period on carcass characteristics and meat quality of lambs from hill sheep systems, J AGR SCI, 137, 2001, pp. 205-220
The study investigated the effects of lamb genotype produced from hill floc
ks on feed efficiency, carcass characteristics and meat quality in animals
finished on either a high forage: concentrate ratio diet (HFC) or a low for
age: concentrate ratio diet (LFC). Purebred Scottish Blackface (BXB) lambs
were compared with Blue-Faced Leicester x Scottish Blackface (BLXB) and Tex
el x Scottish Blackface (TXB) lambs. Purebred Cheviot (CXC), Suffolk x Chev
iot (SXC) and Texel x Cheviot (TXC) lambs were also investigated. Lambs on
the LFC diet were offered grass silage and concentrates mixed in the propor
tion of 0.80 silage and 0.20 concentrates on a dry matter basis. The LFC di
et consisted of 0.20 grass silage and 0.80 concentrates on a dry matter bas
is. Representative lambs were slaughtered at the start of the experiment an
d on reaching 38 and 46 kg live weight. Averaged over the two slaughter wei
ghts, within the Blackface cross lambs, BXB had a lower liveweight gain (P
< 0.01) than either BLXB or TXB (138,207 and 203 (S.E. 11.1) g/day, respect
ively). Within the Cheviot cross lambs, CXC had a lower liveweight gain (P
< 0.05) than SXC (188 v. 220 (S.E. 11.1) g/day), while SXC and TXC (204 g/d
ay) had similar liveweight gains. Lambs on the LFC diet had a higher dressi
ng proportion (P < 0.001) compared with lambs finished on the HFC diet (0.4
66 v. 0.434 (S.E. 0.0018) kg carcass per kg live weight). Averaged over the
two slaughter weights BXB lambs had a lower (P < 0.05) dressing proportion
than the other genotypes. Carcass conformation classification (assessed on
a five-point scale) was higher (P < 0.001) in lambs finished on the LFC di
et (3.0 v. 2.4 (S.E. 0.04)). Conformation classification was higher in lamb
s produced from Cheviot compared with Blackface ewes (P < 0.05). Within the
Blackface cross lambs, BXB and BLXB lambs had a lower conformation classif
ication (P < 0.001) than TXB lambs (2.4, 2.4 and 2.9 (S.E. 0.08) respective
ly). Within the Cheviot ewes, TXC lambs had a higher (P < 0.001) classifica
tion than either CXC or SXC (3.1, 2.7 and 2.7 (S.E. 0.08) respectively). La
mbs finished on the LFC diet had a higher fat classification score compared
with lambs on the HFC diet (P < 0.001) (3.4 v. 2.8 (S.E. 0.04)). Fat class
ification was similar across all genotypes. Lambs finished on the LFC diet
had a lower ash content in the carcass than lambs finished on a HFC diet (P
< 0.01) (44 v. 47 (S.E. 0.8) g/kg). Lamb genotype and dietary forage: conc
entrate ratio had no significant effect on cooking loss, sarcomere length,
Warner-Bratzler shear force and L* values. Ultimate pH (pH(U)) was not infl
uenced by dietary forage: concentrate ratio, but was significantly (P < 0.0
1) higher in BXB lambs compared with BLXB, TXB, CXC and TXC lambs. Lambs of
fered the LFC diet during the finishing period had significantly higher val
ues for a* (P < 0.05), b* (P < 0.001), C* (P < 0.001) and HI (P < 0.05) tha
n lambs offered a HFC diet. Of these parameters only b* was significantly a
ffected by lamb genotype, with BXB lambs having a lower value (P < 0.05) th
an the other genotypes.