Resumen:
This study determined the chemical composition and metabolizable
energy (ME) value for ruminants of seeds and pulps from
grape pomaces (GP), which were produced from white and red
Vitis vinifera cultivars in Italy and California (USA). Six Italian (i.e.,
three white and three red) and five California red cultivarswere collected
after the crush of grape juice had been completed and were
ensiled in micro-silos for 45 d. Fresh and ensiled sampleswere manually
sieved to separate seeds from the pulp plus skin fraction and
an overall inventory of 44 samples was obtained from the 24 Italian
and 20 California samples (i.e., seeds and pulp fractions, fresh
or ensiled from 6 or 5 cultivars, respectively). Both in seeds and
pulp, the red Italian samples had higher organic matter (P<0.01),
ether extract (P<0.05), neutral detergent fiber (aNDF, P<0.01), acid
detergent fiber (ADF, P<0.01), lignin(sa, P<0.01) and Cu (P=0.02 and
P<0.01, respectively) relative to the California red samples. In addition,
K (P<0.01), Fe (P<0.01) and Zn (P=0.03 and P<0.01, respectively
in seeds and pulps) were higher in red samples from California
versus those from Italy. Italian white samples had higher saponins
in pulp (SAP, P<0.05) and tended to have higher total extractable
phenolics both in seeds and pulps (P=0.07 and P=0.10, respectively) than did Italian reds. Both in seeds and pulps, ensiling increased
concentrations of aNDF (P<0.01 and P=0.08, respectively), ADF
(P<0.01) and lignin(sa) (P<0.01 and P=0.03, respectively), had no
impact on mineral levels and decreased concentrations anthocyanins
(P=0.05) and SAP (P=0.01), respectively in seeds and pulp.
Samples were fermented in diluted rumen fluid to measure in vitro
rumen fermentability in terms of gas production, which was used
to predict ME. Gas production from seeds of different origin were
similar, with the exception of higher values at 48 h in red California
cultivars with respect to those from Italy (19.2 ml versus 18.0 ml,
P<0.05). In pulps, Italian reds did not differ from Italian whites, but
had lower gas production than the red California samples (9.2 ml
versus 12.2 ml, 16.6 ml versus 21.3 ml, 26.3 versus 32.7, P<0.01, at 4,
24 and 48 h respectively). Ensiling reduced gas production in seeds
at 24 and 48 h of incubation (P<0.01) and in pulps at 48 h (P=0.09).
Seeds from Italian red samples were lower (P<0.01) in ME than
Italian whites (6.23 MJ/kg DM versus 6.89 MJ/kg DM, P<0.01) and
higher (P<0.01) than the California samples (5.58 MJ/kg DM). There
were no differences between ME of the groups of pulps, but ensiling
reduced estimated ME content in seeds (5.94 MJ/kg DM versus
6.54 MJ/kg DM, P<0.01), but not in pulps. On the basis of our results,
and in agreement with other recent papers and/or textbook data,
the potential to use de-seededGP as a feed in diets of high producing
ruminants is limited.