Comparison of Diet Selection By Raramuri Criollo and Angus Crossbreds in the Chihuahuan Desert

Raramuri Criollo (RC) is a cattle biotype that has undergone natural selection for the past 500 years in northern Mexico. No information exists on diet selection for this biotype. The objective of this study was to compare diet selection of RC and Angus x Hereford crossbreds (AH) typically found in the arid southwestern United States. We examined dietary composition of RC and AH cattle using DNA metabarcoding of fecal samples. Ten mature cows of each breed grazed two adjacent pastures (1190 ha, 1165 ha) for 28 days in July-August 2015 and January-February 2016 in a crossover design. Each breed grazed each pasture 14 days per period and cows were then switched to the reciprocal pasture. Fecal samples were collected on day 14 in each pasture in both seasons. Dominant species present in fecal samples included black grama (Bouteloua eriopoda), tobosa (Pleuraphis mutica), plains bristlegrass (Setaria leucopila), hog potato (Hoffmannseggia glauca), and four-wing saltbush (Atriplex canescens). Black grama was present in higher concentration in AH than RC fecal samples (P < 0.0001) and was greater during winter dormancy than during the summer growing season (P < 0.0001). Hog potato was not affected by breed (P = 0.137) but was greater in fecal samples during the growing season than during winter dormancy (P < 0.001). Four-wing saltbush was marginally greater in AH than RC fecal samples (P = 0.053) and greater during dormancy than in the growing season (P < 0.0001). These results suggest that RC cattle select diets that differ from AH cows and that differences are affected by plant growth phenology.