G. Bozzolo et M. Bouillieroudot, EFFECT OF FAT SUPPLY TO FATTENING DIET ON GROWTH AND CARCASS QUALITIES OF EARLY WEANED MALE LAMBS FED INDOORS DURING WINTER, Annales de zootechnie, 44(1), 1995, pp. 59-72
The effect of dietary fat supplies was investigated for growth and car
cass characteristics on 270 Lacaune male-lambs randomized and fattened
in 3 pens indoors during winter. Two treatments were compared with cl
assical starter and fattening diets: i) 21 kg commercial starter then
a commercial 'growing-fattening' diet; ii) 21 kg starter supplemented
with coconut oil then the 'growing-fattening' diet supplemented with l
ard; iii) 17 kg starter supplemented with coconut oil then the referen
ce commercial 'growing-fattening' diet. The 2 starling diets were isoc
aloric and isonitrogenous (ME = 10.9 MJ/kg DM; CP = 189 g/kg DM). One
was supplemented with 5% coconut oil (fat (F) = 74 g/kg DM) and fed at
2 levels (21 kg/lamb during 29 d vs 17 kg/lamb for 21 d). The second
was a reference commercial starter diet (F = 31.6 g/kg DM) issued at 2
1 kq/lamb level. The 2 succeeding growing-finishing diets were also bo
th isocaloric and isonitrogenous (ME = 10.7 MJ/kg DM; CP = 176 g/kg DM
). One was supplemented with 3% lard (F = 50.4 g/kg DM) and the other
was a reference commercial diet (F = 37.5 g/kg DM). All diets were giv
en ad libitum and straw was freely accessible. The lambs were weaned e
arly (3-5 weeks old) and were slaughtered at a fixed body weight (BW =
39 kg) in one slaughterhouse. Carcasses were scored by the same skill
ed operator. From these, and for statistical purposes owing the discre
pancy in the frequency distribution of initial parameters of lambs, 2
sub-samples were made and standardized according to a normal distribut
ion and in respect to the weight at weaning (12 kg; 3 x [n = 58]), the
relative growth between 0-20 d (16.2 g/d/g BW; 3 x [n = 64]). Concern
ing growth, feeding with starter diet over an extended time produced a
higher growth rate on final fattening stage (+5%, P < 0.04). Coconut
oil did not promote growth during the starting stage. However, through
a remaining effect, it improved the conversion food ratio in the last
fattening stage when lard diet was associated (CFR = 3.6 for treatmen
t a vs 3.0 kg DM/kg gain; P < 0.05). Supplementing with lard in the 'g
rowing-finishing' diet did not modify the lamb growth. in the 3 lots,
the conversion food ratio increased until the lambs reached about 32%
of their mature weight. The relative growth came close to a maximum wh
en lambs weighed about 22% of BW at maturity (17.5 g/kg BW), then it r
egularly decreased to 10 g/kg BW at the end. Concerning the characteri
stics of carcasses, only coconut oil supplementation during the starti
ng stage induced a greater proportion of carcasses with very firm subc
utaneous fat (27 vs 13%, P < 0.03) and reduced the proportion of soft
and oily class of disqualitative carcasses (17 vs 33% P < 0.02). Howev
er the colours of the layer ro, fat were not affected.