EFFECT OF DRY ROASTING ON COMPOSITION, DIGESTIBILITY AND DEGRADABILITY OF FIBER FRACTIONS OF MESQUITE PODS (PROSOPIS LAEVIGATA) AS FEED SUPPLEMENT IN GOATS

Abstract

Two studies were performed to analize the roasting effects (150º C/45 min) in the composition, in vivo digestibility and in situ degradability of fiber fractions (NDF and ADF) of mesquite pods. In the first test, eight Nubian goats (37.6 + 3.4 kg), fistulated and cannulated of rumen were used, in two periods with four goats/treatment, each. Roasted pods (150ºC/45 min) (RMP) and Raw pods (RP) were milled in a 2 mm sieve, and placed into porous bags; two bags were used as sample, one of them without sample for each degradation time and for each animal. Tested degradation times were 1, 3, 6, 9, 12, 24, 48 and 72 hours. A cross-over design was used, with two periods, considering the treatments (raw or roasted pods), periods and interactions in question. The kinetics of degradation for the fibrous fractions were valued with a non-lineal model (Deg= a + b* (1 – e(-c*t) ) and the effective degradation (E.Deg) (a + b* [c/c + kp*]), being kp the fractional rate of passage (kp 0.6/hr). During the second experiment, in vivo digestibility of the fiber fractions was studied, using ten male goats (32.68 + 4.5 kg) for two periods of twenty-two days each, including fifteen days for adaptation and seven days for sampling in a metabolic cage. The food administered and rejected in addition to excrements were weighed and measured and the NDF and ADF contents were analyzed. With this information the digestibility coefficient was calculated (Cdig). The experimental rations were control (CTR); raw mesquite pods (RP)= 80% CTR+ 20% of RP; Roasted mesquite pods (RMP)= 80% CTR+20% RMP. Roasting process modified the mesquite pods composition (P< 0.05), increasing the content of crude protein (CP), ADF, crude protein linked to NDF and ADF (CP-NDF and CP-ADF) as well as ashes. The treatment did not modify (P>0.05) both, NDF and ADF degadation. Nevertheless, soluble fraction decreased (P<0.05), whereas slow degradation fraction (b) and degradation fraccional rate (c) increased, resulting in a major E.Deg (P<0.05). Roasting caused an increment (P<0.05) in ADF slow degradation fraction (b), which caused a minor D.efect (P<0.05). A 20 % inclution of RP or RMP did not affected (P>0.05) the consumption (g/d) of NDF and ADF. Nevertheless, ADF consumption (g/kg of PV0.75 per day) was higher in the RMP. Otherwise, the RP or RMP inclusion increased the NDF and ADF digestible content (%of the DM), without Cdig modification. In conclusion, roasted mesquite pods can modify their nutrimental content, as it can modify the NDF kinetic degradation increasing the fractional degradation rate and the effective degradation, thus, RP or RMP inclusion in the rations improved the Cdig of the ADF.