Animal Science Abstract
Effect of rumen-protected supplements of fish oil on intake, digestibility and nitrogen balance of growing goats
J. R. Fernández, M. RodrÃguez Osorio, E. Ramos, G. de la Torre, F. Gil Extremera and M. R. Sanz SampelayoA
ACorresponding author e-mail: rsanz@eez.csic.es
Abstract
Two groups of six male goats were used to assess the effects of rumen-protected supplements of fish oil on intake, digestibility and nitrogen (N) balance. The animals were offered a diet consisting of forage and concentrate, the latter fraction supplemented with 0 (control) or 100 g/kg of rumen-protected fish oil supplement (PFO), containing a high proportion of the n-3 series (whole diet contained 0 or 60 g PFO per kg dry matter). No significant differences (P > 0.05) were found between the two groups concerning live-weight gain, food intake, digestibility of DM, organic matter, N, neutral-detergent fibre and energy. In contrast, there were differences (P < 0.05) regarding the digestibility of fat and of acid-detergent fibre, which were higher among the animals given the PFO diet. With respect to the individual fatty acids, we observed higher digestibility (P < 0.05) of C14 : 0, C16 : 0, C18 : 0 and C20 : 0 among the animals given the PFO diet. The digestibility of C14 : 0, C18 : 0 and C20 : 0 was found to be negative among the animals given the control diet. No significant differences (P > 0.05) were found regarding digestibility of total C18 : 1. In contrast, the coefficients for C18 : 2 (n-6) and C18 : 3 (n-3) were higher (P < 0.05) among the non-supplemented animals. The intake and faecal flow values of C18 : 0 suggest that the mono- and polyunsaturated fatty acids with 18 atoms of carbon may, in both cases, undergo partial hydrogenation, which would be greater among the control group. The utilization of C20 : 5 (n-3) and, especially, of C22 : 6 (n-3), which were consumed only by the animals given the PFO diet, was estimated at 1.000. The PFO diet also produced lower levels of urinary-N excretion (P < 0.05), giving rise to higher N balances (P < 0.05).
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