Effect of season on chemical composition and in situ degradability in cows and in adapted and unadapted goats of three Mexican browse species

Abstract

Browse foliages from Lysiloma acapulcencis, Quercus laeta and Pithecellobium dulce, native to the subtropical region of southern México, were harvested during the dry season (DS) and rainy season (RS) to determine in situ degradability using ruminal inoculum from fistulated cows as well as goats previously adapted (AG) or not adapted (UG) to browse species fed in their daily diet. Browse leaf samples were incubated in the rumen of each group for 48 h. The crude protein (CP) content of browse was considerably higher in RS (P<0.001). P. dulce had the lowest neutral detergent fiber (NDFom) and acid detergent fiber (ADFom) in the two seasons; L. acapulcencis had the highest values and Q. laeta values were intermediate, with an overall increase in fiber fractions in DS browse foliage (P<0.001). The lowest in situ degradability values were in L. acapulcencis and Q. laeta had intermediate values during both seasons. Season of harvest (RS or DS), and ruminal inoculum (cows, UG, and AG) affected (P<0.001) dry matter degradability (DMD), crude protein degradability (CPD) and fiber fractions of browse. Nutrient degradabilities in all species were higher (P<0.001) in DS than RS. Goats previously exposed to these browse species (AG) had higher (P<0.001) in situ degradability of the browse species than cows or goats in UG fed diets without browse. Overall, goats had higher (P<0.001) nutrient in situ degradability than cows. Our results suggest higher potential of these browse species as forages for ruminants during the dry period in semi-arid regions, but goats previously exposed to diets supplemented with the browse species had a better ability to degrade them than cows or goats in UG. P. dulce has the highest potential as a feed protein source in small ruminants during the dry period.