پديد آورندگان :
دزفوليان، اميرحسين دانشگاه بوعلي سينا همدان - دانشكده كشاورزي - گروه علوم دامي , علي عربي، حسن دانشگاه بوعلي سينا همدان - دانشكده كشاورزي - گروه علوم دامي , بهاري، علي اصغر دانشگاه بوعلي سينا همدان - دانشكده پيرادامپزشكي
كليدواژه :
بز , كبالت , گلوكوهپتونات , گوارش پذيري , ويتامين 12B
چكيده لاتين :
Introduction:
The essentiality of cobalt (Co) in ruminant nutrition and its key function in ruminal
vitamin B
12
synthesis has been clearly demonstrated by previ
ous literature (Russell, 1944; Marston,
1952; Smith and Loosli, 1957; Smith and Marston, 1970). The National Research Council (NRC,
2007) lists the dietary Co requirement of goat kids with 20kg body weight to be 0.07 mg Co/d;
However, in lambs Bishehsari
e
t al.
(2010) demonstrated that supplementing the diet with more than
twice the NRC recommendations with cobalt
-
sulphate increased plasma vitamin B
12
concentration,
final body weight, average daily gain and gain efficiency. It has also been demonstrated tha
t
increasing amounts of dietary cobalt supplementation causes elevated serum and liver vitamin B
12
concentrations in sheep, however no benefits in animal performance were observed (Kawashima
et
al.
, 1997a). The NRC (2007) recommendations of 0.1
-
0.2 mg Co/k
g dry matter (DM) in sheep are
based on observations in grazing animals (Wang
et al.
, 2007)
.
For a long time, mineral requirements
of goats have been considered as a halfway between those of cattle and sheep (Meschy, 2000).
However, based on several report
s (Kišidayová
et al.
, 2001; Johnson
et al.
, 2004; Wang
et al.
, 2007;
Bishehsari
et al.
, 2010), the levels of 0.1
-
0.2 mg Co/kg DM do not meet rumen microbial Co
requirements for vitamin B
12
synthesis in sheep or goats.
Material and
m
ethods:
Thirty weaned m
ale goat kids, with an average body weight of 17.8 kg were
randomly assigned to five treatments including: 1) Basal diet containing 0.076 mg Co/kg DM
(Control); 2
and 3
) basal diet + 0.25
and 0.5
mg Co/kg DM as Co
-
sulphate (sulphate 0.25
and sulphate
0.5
);
4
and 5
) basal diet + 0.25
and 0.5
mg Co/kg DM as Co
-
glucoheptonate (glucoheptonate 0.25
and glucoheptonate 0.5)
.
T
his study was conducted in two trials. The first and second trials were
carried out in 75 and 14 days, respectively, as a 2×2+1 factorial ex
periment based on a completely
randomized design.
Blood samples were collectedo
n days 0, 35 and 75 of the first trial. And during
the second trial, feces, urine and feed orts samples were collected. Result
s
and
d
iscussions:
Serum vitamin B
12
was elevated
during the trial in the Co supplemented
groups as compared to control. Although the differences between treatments were not statistically
significant on day 35, the 0.5ppm levels (sulfate and glucoheptonate) had numerically higher vitamin
B
12
concentratio
ns. On d 75, differences between organic and inorganic supplements were more
pronounced as the two organic treatments regardless of level had higher serum vitamin B
12
concentrations (P<0.0001). Even though inorganic Co treatments were not significantly dif
ferent
from the control, they had numerically higher vitamin B
12
values. The effect of source and level of
Co were both significant on d 75 as the organic source and higher level of Co supplementation led to
higher vitamin B
12
values (P<0.05). In general,
Co
-
glucoheptonate supplements were more effective
in increasing serum vitamin B
12
levels. There were no significant interactions between level and
source of Co.
In ruminants, the efficiency of vitamin B
12
production from Co is low, only about 3%
(Smith an
d Marston, 1970). There have been few reports of comparisons
between different sources
of Co
in animal studies. The carbonate, chloride, sulphate, nitrate and glucoheptonate forms of Co
have been indicated to be effective supplemental sources of Co for rum
inants but these are not always
supported by comparative data (Henry, 1995). The increase in Vitamin B
12
from day 0 to day 35 in the control group, is believed to be related to the previous diet the goats had received before the onset
of the study, which p
robably had been cobalt deficient. The greater vitamin B
12
values observed in
the Co
-
glucoheptonate treatments in our study demonstrates that this source of Co may be more
available to ruminal metabolism of vitamin B
12
.
There were no significant differen
ces between
treatments for DFI, with the exception of the 0.5mg/kg Co
-
G group which had significantly higher
feed intake compared to control but not compared to other Co treated groups. The effect of Co
concentration was significant as the 0.5 mg Co/kg DM
had higher feed intakes compared to 0.25mg
Co/kg DM groups. The effect of Co concentration was also significant for ADG. The Co
-
S 0.5 and
Co
-
G 0.5 groups showed higher weight gains compared to other Co receiving treatments and control.
The greater Co treat
ed groups, although having better feed conversion ratios compared to other
treatments, failed to show a significant difference in the statistical analysis and the differences were
only numerical.
Cobalt supplements affected DM, OM and NDF digestibility. Th
e effect of Co source
was significant and the 0.5 ppm level caused higher DM, OM and NDF digestibility in goat kids. It
seems the level of 0.25 mg Co/kg DM was not sufficient in improving nutrient digestibility.
Conclusion:
The overall data obtained by co
mparing the Co treatments show
ed
that the
concentration of 0.076 mg Co/kg dry matter of the basal diet seems to be marginally
insufficient
for goats and additional Co
may be required
.
