262
is 66% of ad libitum intake. The higher proportion of SFA observed in OF from T0
and T33 could be linked to the higher extent of biohydrogenation due to relatively
higher retention time of feed in the rumen caused by higher forage intake (Diaz et al.
2002; Marinova et al. 2001). Incidence of coronary diseases has been linked with
intake of meat with high ratios of n-6/n-3 PUFA or SFA (Avilés et al. 2016).
4.4 Distribution of Fatty Acids in MM, LD and OF
The separation of intramuscular fat (LD) from other fat depots observed in the present study partly corroborates the findings of Aldai et al. (2007) whereby LD displayed different fatty acid composition (higher PUFA, lower SFA and MUFA) from
that of both intermuscular and subcutaneous depots. On the other hand, the higher
proportion of MUFA and CLA in MM may partly be due to the higher activity of
Δ-9 desaturase in subcutaneous fat (Daniel et al. 2004; Aldai et al. 2007). This is an
endoplasmic reticulum enzyme that is not only responsible for the conversion of
SFA into MUFA but is also involved in the desaturation of trans-vaccenic acid into
CLA (Avilés et al. 2016). Monounsaturated fatty acids of cis-configuration are
hypocholesterolemic and do not reduce HDL cholesterol, which protects against
coronary heart diseases (Webb et al. 1998).
The observed strong association between OF and SFA indicates that internal fats
are more saturated than external fat depots. This might indicate effects of genetic
programming that dictate a lower expression of Δ-9 desaturase in this depot. A
higher level of saturation in internal fat might be an adaptation to the higher temperature in the core of the body than in the periphery (Monziols et al. 2007; Barton
et al. 2007). Similar results were reported by Webb et al. (1998), who found that the
level of saturation increases from external fat depots towards internal depots, with
kidney and intermuscular fat depots being the most saturated while intramuscular
and subcutaneous fat are the least saturated. Webb et al. (1998) noted significant
effects of anatomical location on the proportion of C14:0, C16:0 and C18:1 in fat
depots of Belgium Blue bulls, but there are limited reports on the effects of the same
factor on fat acid composition of fat depots in goats.
5 Conclusion
It is concluded that feeding crossbred goats with concentrate diets increases the
overall content of DFA, n-6 PUFA, trans-MUFA and CLA but lowers the proportion
of n-3 PUFA in meat. Reasonable amounts of fresh forage should thus be offered to
such goats with access to concentrate diets to balance for the proportion of n-3
PUFA, with known health-promoting benefits. Concentrate supplementation beyond
66% of ad libitum feeding has limited effects on fatty acid composition, as depicted
by similarity between T66 and T100 goats in the proportions of oleic acid, CLA,
D. E. Mushi and L. O. Eik
is 66% of ad libitum intake. The higher proportion of SFA observed in OF from T0
and T33 could be linked to the higher extent of biohydrogenation due to relatively
higher retention time of feed in the rumen caused by higher forage intake (Diaz et al.
2002; Marinova et al. 2001). Incidence of coronary diseases has been linked with
intake of meat with high ratios of n-6/n-3 PUFA or SFA (Avilés et al. 2016).
4.4 Distribution of Fatty Acids in MM, LD and OF
The separation of intramuscular fat (LD) from other fat depots observed in the present study partly corroborates the findings of Aldai et al. (2007) whereby LD displayed different fatty acid composition (higher PUFA, lower SFA and MUFA) from
that of both intermuscular and subcutaneous depots. On the other hand, the higher
proportion of MUFA and CLA in MM may partly be due to the higher activity of
Δ-9 desaturase in subcutaneous fat (Daniel et al. 2004; Aldai et al. 2007). This is an
endoplasmic reticulum enzyme that is not only responsible for the conversion of
SFA into MUFA but is also involved in the desaturation of trans-vaccenic acid into
CLA (Avilés et al. 2016). Monounsaturated fatty acids of cis-configuration are
hypocholesterolemic and do not reduce HDL cholesterol, which protects against
coronary heart diseases (Webb et al. 1998).
The observed strong association between OF and SFA indicates that internal fats
are more saturated than external fat depots. This might indicate effects of genetic
programming that dictate a lower expression of Δ-9 desaturase in this depot. A
higher level of saturation in internal fat might be an adaptation to the higher temperature in the core of the body than in the periphery (Monziols et al. 2007; Barton
et al. 2007). Similar results were reported by Webb et al. (1998), who found that the
level of saturation increases from external fat depots towards internal depots, with
kidney and intermuscular fat depots being the most saturated while intramuscular
and subcutaneous fat are the least saturated. Webb et al. (1998) noted significant
effects of anatomical location on the proportion of C14:0, C16:0 and C18:1 in fat
depots of Belgium Blue bulls, but there are limited reports on the effects of the same
factor on fat acid composition of fat depots in goats.
5 Conclusion
It is concluded that feeding crossbred goats with concentrate diets increases the
overall content of DFA, n-6 PUFA, trans-MUFA and CLA but lowers the proportion
of n-3 PUFA in meat. Reasonable amounts of fresh forage should thus be offered to
such goats with access to concentrate diets to balance for the proportion of n-3
PUFA, with known health-promoting benefits. Concentrate supplementation beyond
66% of ad libitum feeding has limited effects on fatty acid composition, as depicted
by similarity between T66 and T100 goats in the proportions of oleic acid, CLA,
D. E. Mushi and L. O. Eik