Changes In Forage Availability Research Articles

Local resource reliance of juvenile fish in small lakes

AbstractJuvenile stages of fishes are frequently bottlenecks to recruitment. Habitat use of early life stages and the extent to which fish rely on local resources may affect how they respond to habitat loss and alterations, with important implications for habitat management. To investigate the potential for prolonged reliance on local resources, we quantified stable isotope ratios (δ13 carbon, δ15 nitrogen, δ18 oxygen and δ2 hydrogen) of young‐of‐year (YOY) largemouth bass Micropterus salmoides and isotope ratios of locally collected water and potential prey across three study components, a controlled pond experiment, a multi‐lake survey and a detailed single‐lake survey. Across study components, we observed habitat and site fidelity of YOY largemouth bass in mid‐summer, demonstrated by distinct spatial differences in young bass stable isotope ratios. Additionally, we observed significant, positive correlations between δ13C of YOY largemouth bass and δ13C of locally collected invertebrates and small bluegill Lepomis macrochirus in the single lake survey, suggesting localised foraging. Later in summer, spatial differences in largemouth bass stable isotope ratios were not apparent, indicating a transition to more spatially integrated foraging. Prior to switch to piscivory, YOY largemouth bass rely on local resources indicating that they may be more susceptible, both positively and negatively, to hyper‐local changes in forage availability or disturbances. This study demonstrates that stable isotope ratios allow for differentiating environmental experiences among young fish in relatively close proximity in small freshwater systems. Moreover, high spatial variation of consumer stable isotope ratios demonstrates the importance of considering spatial heterogeneity in stable isotope studies.

Forage Availability and Quality, and Feeding Behaviour of Indigenous Goats Grazing in a Mediterranean Silvopastoral System

The aim of this study was to evaluate the feeding behaviour of indigenous goats and the selection drivers of different plant species in a Mediterranean forest rangeland. To achieve this goal, the seasonal variations in terms of forage availability and quality of ingested plant species were studied during three grazing seasons. In the same period, eight indigenous goats of Beni Arouss breed were selected to explore the seasonal changes in their browsing behaviour. Forage quality was determined by the hand-plucking technique. The results showed a wide seasonal variation in forage availability and quality, and feeding behaviour. Woody species were more selected independently of the season (p < 0.001). The crude protein content varied from 53.3 g/kg of dry mater (DM) for Erica arborea in summer to 197 g/kg DM for Calicotome villosa in autumn (p < 0.001). Despite the high condensed tannins content in selected shrubs, they were highly consumed. In vitro organic matter digestibility (IVOMD) and metabolizable energy (ME) had recorded the highest contents in herbaceous during spring. Shrubs and trees contain the lowest levels of IVOMD (<500 g/kg) and ME (<7.2 MJ/kg) during autumn and summer. It is concluded that seasonal changes in forage availability and quality did not necessarily affect the indigenous goats’ preference. These findings could help goat herders to develop feeding and grazing systems while increasing the performance of goats in the Mediterranean silvopastoral system.

Diet composition of the African manatee: Spatial and temporal variation within the Sanaga River Watershed, Cameroon.

The present study aimed to investigate the diet of African manatees in Cameroon to better inform conservation decisions within protected areas. A large knowledge gap on diet and seasonal changes in forage availability limits the ability to develop informed local management plans for the African manatee in much of its range. This research took place in the Sanaga River Watershed, which includes two protected areas in the Littoral Region of Cameroon: the Douala‐Edea National Park and the Lake Ossa Wildlife Reserve. We analyzed 113 manatee fecal samples and surveyed shoreline emergent and submerged vegetation within the Sanaga River Watershed. We used microhistological analyses to determine the relative contribution of each plant species to African manatee diets and compared across locations and across seasons (wet vs. dry season). We found that the shoreline vegetation is diverse with over 160 plant species, unevenly distributed across space and season, and dominated by emergent vegetation mostly represented by the antelope grass (Echinochloa pyramidalis). We recorded a total of 36 plant species from fecal samples with a spatial and temporal distribution mostly reflecting that of the corresponding shoreline vegetation. African manatees appear to be primarily opportunistically feeding on available vegetation across the seasons and habitat. This work documents the current, but changing, state of plant availability in the Sanaga River Watershed and reports the African manatee diet in Cameroon for the first time. This information can play a critical role in successfully managing the species and these protected areas. If we wish to protect the African manatee and the aquatic ecosystems within the Sanaga River Watershed, we must understand how forage availability changes over time, especially as its waters become nutrient enriched, eutrophic, and exposed to invasive species of plants in a changing world.

Snowier winters extend autumn availability of high‐quality forage for caribou in Arctic Alaska

AbstractCaribou (Rangifer tarandus) rely on the short Arctic growing season to restore body condition, support the demands of lactation, and prepare for the long arctic winter, making them susceptible to even small changes in forage availability or quality. Body condition in the summer and autumn is linked to winter survival rates and fecundity in cows, critical factors in the productivity of caribou populations. Climate change predictions of warmer and wetter northern winters suggest increased snowfall over Alaska's North Slope, which has recently been verified between 1995 and 2017. However, a comprehensive analysis of how deeper snow will affect caribou forage quality is absent across Alaska. In this study, we quantify how snow depth alters the quality and seasonality of caribou forage using a long‐term (24 yr) International Tundra Experiment snow depth manipulation to evaluate how winter climate change scenarios may affect tussock tundra systems in northern Alaska. Deeper snow in prior winters leads to increases in growing season leaf N and digestible protein (DP) in deciduous shrubs (Salix spp. and Betula spp.) and graminoids (Carex spp. and Eriophorum spp.), but not evergreen dwarf shrubs (Rhododendron spp. and Vaccinium spp.). Dry matter digestibility varied among species with small differences (<5%) associated with snow depth. Most striking was the discovery that deeper snow in the prior winter increased the duration of DP levels above the minimum threshold for protein gain in caribou by as much as 25 d in Salix pulchra and 6–9 d in Betula nana and Carex bigelowii in late summer and early autumn. Consequently, deeper winter snow may provide an extended window of opportunity for foraging and the accumulation of lean body mass and fat reserves which promote winter survival and successful calving the following spring and potentially improve the productivity of caribou in northern Alaska.

Ungulate distributions in a rangeland with competitors, predators and pastoralists

Summary African rangelands support diverse ungulate communities whose member species exhibit unique combinations of body morphology and behaviour that have evolved over millions of years to limit the effects of competition and predation on fitness, and more recently, to cope with people and livestock. The mechanisms by which native ungulates cope with the combined effects of competition, predation and human disturbance are poorly understood. Addressing this knowledge gap will help guide management and conservation plans for large mammal communities outside of strictly protected areas. We conducted animal counts on line transects and used a spatially explicit distance sampling model to test the influence of bottom–up effects (vegetation), top–down effects from African lion Panthera leo and spotted hyena Crocuta crocuta and human disturbance (livestock density, occupied human settlements) on native ungulate densities and distributions across a multiple‐use rangeland in Kenya. We examined five species that varied in body morphology and foraging strategy, including two large‐bodied grazers (zebra Equus quagga; wildebeest Connochaetes taurinus), two medium‐bodied, mixed‐feeders (Grant's gazelle Nanger granti; impala Aepyceros melampus) and one very large‐bodied browser (giraffe Giraffa camelopardalis tippelskirchi). Densities and distributions of all species varied across available land‐use types, with bottom–up effects (vegetation) and human disturbance having the strongest overall effects. Responses varied by ungulate foraging strategy. Distributions of grazers and the browser (giraffe) changed seasonally, while distributions of mixed‐feeders and a grazer (zebra) changed diurnally. At broad spatial scales, ungulates did not respond to long‐term variation in predation risk though they have been shown to respond behaviourally to short‐term variation in risk. Synthesis and applications. Our results revealed that native ungulates in this multiple‐use rangeland occur at densities comparable to many flagship protected area populations. We attribute observed densities to spatial heterogeneity across this landscape that included variation in human land use (community conservation area, seasonal settlements and livestock grazing, permanent settlements) and vegetation (grassland, bushland, woodland) that changed through time (seasonally, diurnally). This variation allowed ungulates to carve out ecological niches while reducing exposure to the potential limiting effects of competition and human disturbance. For some species, securing access to forage resources and avoiding human disturbance may be associated with costs through increased risk of predation. Our research reveals the trade‐offs native ungulates make to cope with changes in forage availability, human disturbance and predation risk, providing important insights to help guide native ungulate conservation efforts in multiple‐use rangelands.

Selective behavior of Creole goats in response to the functional heterogeneity of native forage species in the central Monte desert, Argentina

The changes in forage availability and the physicochemical variability of plants influence the diet selection by herbivores. In this study, the foraging behavior of Creole goats was studied in terms of botanical composition of the diet, food availability and physicochemical properties of vegetation. The study was performed in a desert rangeland in the northeast (NE) Mendoza region in Argentina. Experiments with grazing goats were made in dry (winter) and wet (summer) seasons and cafeteria experiments (feeding trial) were performed during the summer. Food availability was estimated from forage species cover. Botanical composition of the goat's diet was determined by microhistological analysis of fecal samples. Morphological parts of forage species consumed by goats were sampled and analyzed to determine chemical traits (plant nutrients and secondary metabolites) in both seasons. Also, during summer, the two morphological traits of browse species stem specific density (SSD) and specific leaf area (SLA) were evaluated. In the experiments with grazing goats, diet selection was evaluated based on Ivlev's electivity index (Iˆ) and, in cafeteria experiments, preference was estimated based on the number of bites. Diet selection varied between the two seasons. Grazing goats showed differences in the patterns of diet selection related to changes in forage availability. The botanical composition of the diet had a greater (p<0.001) participation of woody species in relation to grass species in both seasons, but the herbaceous stratum was more utilized by goats during the summer according to their higher availability. Correlations between diet and availability were positive in both seasons, but not significant in summer. The models including crude protein (CP), neutral detergent fiber (NDF) and total phenols (TP) had substantial support for predicting variation in diet selection in summer and winter. In both seasons the preference increased as the concentrations of CP, NDF and TP increased, but the effect of CP was significant only in winter. Thus, goats selected supplementary food mixtures (mixed diet) and tannins were not considered dissuasive but, rather, were maintained below a certain threshold. In summer, SSD was negatively and significantly related to diet selection by grazing goats. This morphological trait allowed explaining a greater percentage of the variation in Iˆ (36%) with regard to the variation explained by the chemical variables (16%). In cafeteria experiments, in summer, the optimization of nutrient intake rate through consumption of species with low SSD values represented a best explanation for the preferences observed, whereas the hypotheses of minimization of secondary metabolites and maximization of nutrients were not able to fully explain the preferences observed in cafeteria experiments. To conclude, dietary decisions by goats in desert rangelands could be interpreted in terms of intake rate optimization and complementation of nutrients and secondary compounds, rather than by explanations involving the isolated effects of nutrient intake maximization or tannin intake minimization.

Seasonal habitat selection of the red deer (Cervus elaphus alxaicus) in the Helan Mountains, China

We studied the seasonal habitat selection of the red deer, Cervus elaphus alxaicus Bobrinskii & Flerov, 1935, in the Helan Mountains, China, from December 2007 to December 2008. Habitat selection varied widely by season. Seasonal movements between high and low elevations were attributed to changes in forage availability, alpine topography, the arid climate of the Helan Mountains, and potential competition with blue sheep, Pseudois nayaur (Hodgson, 1833). The use of vegetation types varied seasonally according to food availability and ambient temperature. Red deer used montane coniferous forest and alpine shrub and meadow zones distributed above 2,000 m and 3,000 m in summer, alpine shrub and meadows above 3,000 m in autumn, being restricted to lower elevation habitats in spring and winter. The winter habitat of C. elaphus alxaicus was dominated by Ulmus glaucescens Franch. and Juglans regia Linnaeus, deciduous trees, and differed from the habitats selected by other subspecies of red deer. Cervus elaphus alxaicus preferred habitats with abundant vegetation coverage to open habitats in winter, but the reverse pattern was observed in summer and autumn. Red deer preferred gentle slopes (<10°) but the use of slope gradient categories varied seasonally. Red deer avoidance of human disturbance in the Helan Mountains varied significantly by season. Information on red deer habitat selection can help understand the factors affecting seasonal movements and also support decision making in the management and conservation of red deer and their habitats.

Systematic management of stocking rates improves performance of northern Australian cattle properties in a variable climate

The risks for extensive cattle properties in the rangelands of northern Australia arising from high inter-annual rainfall variability are predominantly managed through adjustments in stocking rates (SR). This modeling study compared the performance of SR strategies that varied considerably in the extent that they adjusted SR annually at 3 locations in northern Australia. At all locations, land types and pasture condition states, the SR strategies that achieved the best pasture condition were those that least increased and most decreased SR annually in response to changes in forage availability. At Donors Hill (Qld), these conservative strategies also achieved the highest cattle liveweight gains per hectare (LWG/ha). While conservative strategies produced the highest percent perennial pasture species at Fitzroy Crossing (WA), strategies which allowed larger increases and decreases in SR also performed well, enabling them to also achieve high LWG/ha with little deterioration of pasture condition. A similar trend occurred at Alice Springs (NT), although at this location the strategies with even larger annual increases and decreases in SR achieved relatively high percent perennials and the highest LWG/ha. While systematic management of SR appears to perform better than a constant SR strategy when rainfall variability is high, it is unclear if the magnitude of annual adjustments in SR needs to increase with increasing rainfall variability.

Economically Optimal Stocking Rates: A Bioeconomic Grazing Model

A dynamic bioeconomic model that examines economically optimal stocking rate decisions while taking into account changes in forage availability is presented. The model presented here focuses on economically optimal stocking decisions while taking into account changes in the forage resource. The model is parameterized for a stocker operation in central Wyoming. Regardless of the scenario analyzed, the general rule of 50% utilization is determined to be an economically sound management strategy. The factors most heavily influencing economically optimal stocking rate decisions are forage growth rates and the Michaelis Constant. Both grain prices and cattle prices impact financial returns yet do not directly impact optimal stocking decisions by cattle producers. Se presenta un modelo bioeconómico dinámico que examina decisiones de carga animal económicamente óptimas tomando en cuenta al mismo tiempo cambios en la disponibilidad forrajera. El modelo que aquí se presenta se enfoca en decisiones de carga animal económicamente óptimas tomando en cuenta al mismo tiempo cambios en la disponibilidad forrajera. El modelo se configuró para un establecimiento de engorde en el centro del estado de Wyoming. Independientemente del escenario analizado, se determinó que la regla general del 50% de uso es una estrategia de manejo económicamente sólida. Los factores que ejercen mayor influencia en la decisión de carga animal económicamente óptima son las tasas de crecimiento del forraje y la Constante de Michaelis. Los precios de granos y del ganado ejercen un impacto en el retorno financiero, pero no influyen de modo directo las decisiones de carga animal óptima de los productores ganaderos.

Fatal Pneumonia Epizootic in Musk Ox (Ovibos moschatus) in a Period of Extraordinary Weather Conditions

The musk ox is adapted to extreme cold and regarded as vulnerable to the impacts of climate change. Population decline is proposed to occur due to changes in forage availability, insect harassment, parasite load, and habitat availability, while the possible role of infectious diseases has not been emphasized. The goal of the present article is to describe an outbreak of fatal pasteurellosis that occurred in the introduced musk ox population of Dovrefjell, Norway in 2006, causing the death of a large proportion of the animals. The epizootic coincided with extraordinary warm and humid weather, conditions that often are associated with outbreaks of pasteurellosis. The description is based on long series of data from the surveillance of the musk ox population, weather data from a closely located meteorological station, and pathoanatomical investigation of the diseased animals. It is concluded that the weather conditions likely were the decisive factors for the outbreak. It is suggested that such epizootics may occur increasingly among cold-adapted animals if global warming results in increased occurrence of heat waves and associated extreme weather events, thereby causing population declines and possibly extinctions.

Climate‐driven fluctuations in surface‐water availability and the buffering role of artificial pumping in an African savanna: Potential implication for herbivore dynamics

Abstract In arid and semiarid environments surface‐water strongly constrains the distribution and abundance of large herbivores during the dry season. Surprisingly, we know very little about its variability in natural ecosystems. Here we used long‐term data on the dry‐season occurrence of water at individual waterholes to model the surface‐water availability across Hwange National Park, Zimbabwe, under contrasted climatic and management scenarios. Without artificial pumping only 19.6% of the park occurred within 5 km of water under average climatic conditions. However surface‐water availability was strongly influenced by annual rainfall, and over 20 years the variability of the surface area of the park occurring within 5 km of water was slightly larger than the variability of rainfall. This contrasts with the usual buffered response of vegetation production to rainfall fluctuations, and suggests that the variability in dry‐season foraging range determined by surface‐water availability could be the main mechanism regulating the population dynamics of large herbivores in this environment. Artificial pumping increased surface‐water availability and reduced its variability over time. Because changes in surface‐water availability could cause the greatest changes in forage availability for large herbivores, we urge ecologists to investigate and report on the variability of surface‐water in natural ecosystems, particularly where rapid climate changes are expected.

Seasonal variations in physiological and behavioural parameters in a bachelor group of stallion ponies (Equus caballus)

AbstractAnimals living in temperate climates are continually adapting to seasonal demands of reproduction and survival. Whilst it is well documented that ruminants show seasonal changes in both reproductive and non-reproductive physiological and behavioural characteristics (reduction of metabolic rate and appetite during the winter with respective increases during spring and summer), this information has not been fully established in the non-ruminating ungulate species of Equidae. This may be important information from a practical management perspective since groups of equids are increasingly being kept in natural conditions for the purposes of conservation grazing.The aim of this study, therefore, was to document the behavioural and physiological adaptive changes made by ponies during a 12-month period and to relate these to changes in forage availability and environment. Five mature pony stallions were kept in west Wales (4°5′W, 52°25′N) and monitored for 12 months. A range of physiological (testis size, body weight, condition score (CS), hoof growth, moult (M), pelage fibre length, depth and density) and behavioural measurements (foraging and non-foraging activities) were recorded along with monthly forage analysis (crude protein (CP), water-soluble carbohydrates (WSC)), dry matter (DM)) and environmental conditions (day length and minimum ambient temperature). All physiological measurements were significantly (P&lt;0·001 to P&lt;0·05, r2=0·16 to 0·69) related to day length and all except testis size, body weight and M were significantly related to minimum temperature, CS (P&lt;0·001; r2=0·583), hoof growth (P&lt;0·001; r2=0·457), pelage fibre length (P&lt;0·001; r2=0·61), pelage fibre depth (P&lt;0·001; r2=0·489) and pelage density (P&lt;0·05; r2=0·192). Fewer significant relationships were observed in relation to forage characteristics; significances only obtained between CP and CS (P&lt;0·001; r2=0·854), fibre length (P&lt;0·01; r2=0·625) and pelage fibre depth (P&lt;0·01; r2=0·624); between DM and CS (P&lt;0·05; r2=0·352) and pelage fibre depth (P&lt;0·05; r2=0·343); between WSC and pelage fibre depth (P&lt;0·01; r2=0·55) and pelage fibre depth (P&lt;0·05; r2=0·34). Behaviour results showed a significant relationship between time spent alert and day-length (P&lt;0·05; r2=0·35) and between minimum ambient temperature and time spent eating (P&lt;0·05; r2=0·37), locomotory behaviour (P&lt;0·01; r2=0·53) and passive interaction (P=0·001; r2=0·63). A significant relationship was also reported between eating and CP (P&lt;0·01; r2=0·53) as well as DM (P=0·01; r2=0·43). The ponies in this study demonstrated a series of adaptive changes during winter concomitant with energy conservation, however, forage availability and intake also decreased indicating lower energy input. Despite energy conserving adaptations it is unlikely that nutrient intake was adequate to account for the limited winter decline in CS and weight. In conclusion, it was considered that: (a) ponies demonstrated physiological and behavioural adaptation in response to environmental demands, (b) during winter ponies demonstrated behaviours indicative of a cost benefit analysis of expending energy in the pursuit of poor quality forage, (c) despite energy conserving adaptations, intake is unlikely to have been adequate to maintain the CS observed, and (d) reduction in metabolic rate and increased food conversion efficiency may be additional adaptations made during times of environmental challenge.

Photoperiodic entrainment of seasonal changes in appetite and growth in pony colts

During winter, voluntary food intake (VFI) and growth decreased in light horse weanlings given ad libitum access to a forage/concentrate diet (Cymbaluk et al, 1989). These changes were attributed to decreased ambient temperatures. However, photoperiodically entrained seasonal changes in VFI and growth are documented in other Northern ungulates (Moen, 1978) and may comprise an adaptation to changes in forage availability. Throughout their evolution, horses experienced similar environmental pressures and may demonstrate similar photoperiodic adaptations. This study characterised changes in VFI and growth in pony colts maintained under an artificial photoperiodic regime.Seven, 2 year-old pony colts of Welsh Mountain type (182.4 ± 5.4 kg), were obtained from pasture (53°N). Animals were individually housed in loose-boxes, within a light-proof building. Measured quantities of a complete pelleted diet (gross energy = 16.7 MJ.kgDM-1), calculated to exceed appetite by at least 1 kg, were offered daily.

Photoperiodic entrainment of seasonal changes in appetite and growth in pony colts

During winter, voluntary food intake (VFI) and growth decreased in light horse weanlings given ad libitum access to a forage/concentrate diet (Cymbaluk et al, 1989). These changes were attributed to decreased ambient temperatures. However, photoperiodically entrained seasonal changes in VFI and growth are documented in other Northern ungulates (Moen, 1978) and may comprise an adaptation to changes in forage availability. Throughout their evolution, horses experienced similar environmental pressures and may demonstrate similar photoperiodic adaptations. This study characterised changes in VFI and growth in pony colts maintained under an artificial photoperiodic regime.Seven, 2 year-old pony colts of Welsh Mountain type (182.4 ± 5.4 kg), were obtained from pasture (53°N). Animals were individually housed in loose-boxes, within a light-proof building. Measured quantities of a complete pelleted diet (gross energy = 16.7 MJ.kgDM-1), calculated to exceed appetite by at least 1 kg, were offered daily.

Spatial and behavioral response of white-tailed deer to forage depletion

We tested predictions regarding the effects of forage depletion on patterns of foraging effort, diet selection and quality, and patch selection by white-tailed deer (Odocoileus virginianus). Two deer were allowed access to four 150-m2 enclosures (patches) for 8, 16, 24, and 32 days, resulting in the exposure of the patches to deer for 16, 32, 48, and 64 animal-days and different levels of forage depletion. When the deer were given simultaneous access to all four enclosures, feeding patch selection was markedly skewed toward heavily and lightly grazed environments, while moderately depleted patches were selected least. Deer primarily consumed woody browse in patches with low (16 days) and high (64 days) forage depletion, and forbs in patches that were moderately depleted (32 and 48 days). Deer responded to forage depletion by foraging less selectively, reducing movement rates, and increasing average bite size. During the last phase of the trial, biting rates on forbs declined but increased on woody browse in response to declining forage availability. Diel foraging times remained unaffected by changes in forage availability. The behavior of deer foraging in experimental patches appeared to be consistent with predictions based on the maximization of nutrient (protein) gain, although use of the most depleted patch was greater than expected. We conclude that vegetative biomass alone is a poor indicator of foraging rewards for highly selective herbivores.

Colony Defense in the African Honey Bee in Africa (Hymenoptera: Apidae)

Defensive behavior was investigated in a naturally occurring population of Apis mellifera scutellata (Lepeletier) colonies in the Okavango River Delta, Botswana. In general, colonies exhibited low levels of stinging activity during nest dissection. However, positive associations were observed between defensiveness and increasing colony size (inferred from total comb area) and swarming activity. The lower stinging activity of the smaller colonies and the increased defensiveness of the larger and swarming colonies may have reflected relative levels of investment in colony growth and reproductive potential. Seasonal patterns of colony defensiveness were not associated with fluctuations in resource abundance, although some changes in forage availability may have influenced aggressive behavior. Colony defensiveness was not associated with nest entrance location and orientation; the proportions of comb area devoted to brood rearing, food storage, or the area that was empty, or any of three weather parameters measured.

Perennial Irrigated Pastures. III. Beef Calf Production from Irrigated Pasture and Winter Annual Range1

AbstractIrrigated pastures in the Western arid and semi‐arid regions provide support to the beef cattle industry through the maintenance of beef cow herds and the production of calves. Increasingly unfavorable production economics, including the rising cost and logistical difficulty of seasonally moving cattle from seasonal range to other pastures (e.g., high mountain Federal grazing allotments), necessitate evaluation of management options which permit increased stocking rate and year‐around home ranch operation.The objective of this study was to compare simple (range‐only, yearlong) and complex [improved range and irrigated pasture plus winter supplementation with alfalfa (Medicago sativa L.) cubes] systems for beef calf production using a fall calving (November‐December), early summer weaning (May‐June) reproduction cycle.In the complex system, cleared and reseeded range was used (winter) an average (4 years) of 6 months per year at a stocking rate of 2.2 ha/cow (2.8 AUM/ha). Irrigated pasture was used (summer) an average of 6 months per year at a stocking rate of 0.5 ha/cow (10.3 AUM/ha). Alfalfa cube supplement was fed (about 1 kg/ha per day) during fall and winter. In the simple system, cleared range was used yearlong at an average stocking rate of 5 ha/cow (2.4 AUM/ha). No supplements were fed except during the last year when drought prevailed. An average of 70 kg calf/ha was produced in the complex system. Average birth weight was 34 kg and average daily gain (ADG) to 205 days was 0.76 kg. In the simple system, comparable values were 37.5 kg calf/ha, 32 kg birth weight, and 0.75 ADG. Birth weights and ADGs were not significantly different between systems. Average cow weights reflected seasonal changes in forage availability and quality. Cows in the simple system tended to lose weight more consistently during the months July. October than did those in the complex system, which, instead, more consistently lost weight during the months November‐March. Economic return was similar but low in both systems. While total land per cow/calf unit was less for the complex system and total investment higher for the simple system, operating costs, depreciation, and interest were higher for the complex system.It appeared that second and third trimester cow stresses, as evidenced by negative bodyweight changes, did not adversely affect calf birth weights and ADG, at least at the levels found under these experimental conditions.