Range cattle grazing in semi-arid regions are commonly limited by lack of nutrients from low-quality forage. Due to this, ranchers are faced with the challenge of monitoring diet quality in order to address nutrient limitations. Near infrared spectroscopy (NIRS) of fecal samples is a method used to determine diet quality values like crude protein (CP) and digestible organic matter (DOM) in grazing animals. When combined with a nutritional balance analyzer such as the NUTBAL system, fecal NIRS can be used to monitor diet quality and project animal performance. Our research aimed to test the ability of NUTBAL to project animal performance as represented by body condition score (BCS) in cattle (n=82 Animal Units) grazing on the Santa Rita Experimental Range (SRER) in southern Arizona. Previous work conducted on other Arizona rangelands led to the hypothesis that fecal NIRS coupled with NUTBAL can be used to monitor diet quality and project BCS in a southern Arizona commercial grazing operation. Data collection occurred between June 2016 and June 2017. Standing biomass and botanical composition were measured before each grazing period, and relative utilization was measured following each grazing period. During the midpoint of grazing in each pasture, 30 body condition scores and a fecal composite of 15 samples were collected. Fecal derived diet quality varied between a maximum of 10.75% CP and 61.25% DOM in early August 2016, to a minimum value of 4.00 % CP and 58.40 % DOM in March 2017. This study confirmed the ability of fecal NIRS paired with NUTBAL to project future BCS within 0.5 a score point more than 80% of the time in cattle grazing on the SRER. With this information, cattle managers in southern Arizona can better address animal performance needs and nutrient deficiencies.

The impact of undesirable plant communities (Cymbopogon afronardus and woody species dominated by Acacia species) on livestock carrying capacity and performance was investigated on 15 farms in an Acacia/Cymbopogon dominated pastoral system of south-western Uganda. Species prevalence based on basal cover for grasses, frequency for forbs and effective canopy cover for trees/shrubs were determined on farms. The PHYGROW model was used to predict forage productivity for computation of carrying capacity. The NIRS/NUTBAL nutritional management system was used to determine cattle dietary CP and DOM through fecal scans and to estimate animal performance. Cymbopogon afronardus had a prevalence of 10.29% among the grasses while Acacia gerrardii (34.37%) and Acacia hockii (33.66%) were the most prevalent woody species. Forage productivity differed significantly among the farms with a mean long-term annual forage yield of 4560(SE+41) kg/ha. Farms infested with Cymbopogon and woody species produced the least amount of forage and therefore had the lowest carrying capacities (0.38 -0.39 AU/ha) while improved farms had comparatively higher forage yields with higher carrying capacities (0.49 - 0.52 AU/ha). A mean carrying capacity for the system was estimated at 0.44 AU/ha using a 25% harvest efficiency for ANPP. All the farms were overstocked, on average by 3.2 times. Livestock BCS, diet CP and DOM were significantly different (P<0.0001) among the different farm types. BCS were highest on improved farms and lowest on Cymbopogon infested farms while dietary CP and DOM values were lowest on improved farms and highest on farms with a high woody component. Farms with a relatively high woody component exhibited intermediate BCS despite the high dietary CP values. Cattle on Cymbopogon infested farms had consistently lower body weights over the months although there were no significant differences in daily live weight gains among farms. Recommendations included need for research into appropriate control measures for both Cymbopogon afronardus and woody species, farmer sensitization about overstocking, research to improve forage quality on improved farms and need for feed supplementation for improved breeds on improved farms. Integration of NIRS/NUTBAL and PHYGROW models into the research and management systems was desirable. The observed increase in Sporobolus spp. required investigation.