Seasonal variation in ruminant digestibility of nutrients from 10 shrubs indigenous to northeastern Mexico

Leaves from 10 native shrubs from NE Mexico were collected in 1995/6 to est imate and compare seasonally, the extent and rate of cell wall (PC) degrada tion in the rumen of fistulated Pelibuey sheep. The in situ technique was u sed to estimate the non linear parameters: a) soluble PC fraction; b) PC fr action slowly degraded in the rumen; a+b) potentially degradable PC fractio n; c) rate of PC degradation; lag phase (time that microbes took to initiat e PC degradation), and effective degradability of PC (DEPC). Nylon bags, co ntaining 3 g of ground leaves were incubated in the rumen of sheep. In gene ral, in winter the non linear parameters of PC digestion were higher than i n the other seasons. The DEPC of Pithecellobium pallens, Celtis pallida, Be rnardia myricaefolia, Helietta parvifolia, Eysenhardtia polystachya, Gymnos perma glutinosum, Diospyros texana, Caesalpinia mexicana, Pithecellobium eb ano and Parkinsonia aculeata were different (P<0.01) among and within seaso ns. High lignin levels in P. ebano and P. aculeata may account for their ve ry low DEPC (lower than alfalfa's, while the rest of the shrubs had higher DEPC than alfalfa). Most shrubs showed PC components easily accessible to microbial attack and degradation in the rumen of sheep. Thus, they may be considered good forage , for grazing ruminants in northeastern Mexico.