Mesquite seed density in fecal samples of Raramuri Criollo vs. Angus x Hereford cows grazing Chihuahuan Desert Rangeland

TitleMesquite seed density in fecal samples of Raramuri Criollo vs. Angus x Hereford cows grazing Chihuahuan Desert Rangeland
Publication TypeConference Paper
Year of Publication2016
AuthorsMercado T.J., Cibils AF, Nyamuryekung'e S., Estell R.E., Gonzalez AL
Conference Name69th Annual Meeting of the Society for Range Management
Date Published01/31/2016
PublisherSociety of Range Management
Conference LocationCorpus Christi, Texas
ARIS Log Number332024
Abstract

This study was part of a larger project investigating breed-related differences in feeding habits of Raramuri Criollo (RC) versus Angus x Hereford (AH) cows. Seed densities in fecal samples collected in July and August 2015 were analyzed to compare presumed mesquite bean consumption of RC and AH cows grazing Chihuahuan Desert rangeland in summer. Two groups of 11 nursing RC or AH cows grazed separately in large adjacent pastures for four weeks. After the first two weeks, groups switched pastures to insure that both breeds were exposed to the same grazing environment. Five cows in each group were fitted with GPS collars configured to log animal location at 10 minute intervals. Weekly rectal fecal samples were collected from all 22 cows. Fecal samples were frozen and later thawed at 40oC. All seeds were recovered, surface sterilized, identified, counted, weighed, and placed in petri dishes at room temperature. Seedless thawed fecal samples were then dried at 60oC for 72 h and weighed. A mixed effects repeated measures analysis of variance was used to determine the influence of breed and pasture on mesquite seed density in fecal samples of RC and AH cows.  Mesquite seed density in feces was significantly higher in RC vs. AH cows (Mean ± SEM RC: 0.21 ± 0.01 vs. AH: 0.09 ± 0.03 seeds/g seedless fecal DM; P = 0.03). Mesquite seed density in RC fecal samples was similar regardless of pasture grazed (P=0.32). Conversely, seed density for AH cows differed significantly among pastures (P = 0.03). Despite their apparent higher consumption of mesquite beans, GPS data revealed that RC spent detectably less time (P= 0.05) in mesquite-dominated plant communities than their AH counterparts. Our preliminary results suggest that during summer months, RC cows included higher amounts of mesquite seed pods in their diet compared to AH counterparts. The fact that AH cows spent more time than their RC counterparts in mesquite-dominated areas suggests that AH possibly seek mesquite shrubs for both forage and shade.