Diet selection of Raramuri Criollo and Angus x Hereford crossbred cattle in the Chihuahuan Desert

摘要

Strategies to help producers cope with unpredictable forage production associated with low and variable pre-cipitation patterns on arid rangelands are needed, particularly if global warming trends continue as projected. One option is to identify cattle biotypes compatible with less productive shrubby landscapes. One such biotype is the Raramuri Criollo (RC) from the Copper Canyon of northern Mexico. This small-framed animal exhibits travelling behaviors that allow it to exploit vegetation at a greater distance from water, although it is unknown whether RC have dietary preferences that differ from European breeds typically raised in the southwestern U.S.A. We examined diet selection of RC vs. desert adapted Angus x Hereford (AH) crossbreds typical of the region using DNA metabarcoding to determine the proportion of plant species in fecal samples. Fecal samples were collected from 10 cows of each breed in two adjacent pastures during two seasons (growing and dormancy; four weeks per season) for three consecutive years. Dominant plant species in fecal samples of both cattle breeds were Atriplex canescens (four-wing saltbush), Hoffmannseggia glauca (hog potato), Hopia obtusa (vine mesquite), Setaria leucopila (plains bristlegrass), Sporobolus spp. (S. contractus , S. flexuosus , and S. giganteus), Pleuraphis mutica (tobosa), and Bouteloua eriopoda (black grama), which is consistent with previous studies in the region using different tech-niques for assessing dietary plant composition of other breeds of cattle. Only a few differences were detected between breeds. Compared to AH, fecal samples from RC tended to contain a higher proportion of mesquite and Yucca spp. (P < 0.07) and less Ephedra spp. (P < 0.06). The only grass species that differed between breeds was black grama (P < 0.05), with AH fecal samples containing about twice as much as RC cows (~8 vs. 4). This finding could have important implications for conservation of black grama in the Chihuahuan Desert.