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A total of 188 yearling steers of predominantly Angus and Hereford breeds, with mean body weight of 299 kg, were used in this study, which started on 8 April and finished on 3 October, to assess the effects of environmental factors on feed intake of steers in various housing systems. Housing consisted of outside lots with access to overhead shelter, outside lots with no overhead shelter and a cold confinement building. Ad libitum corn, 2.27 kg of 35% dry matter whole plant sorghum silage and 0.68 kg of a 61% protein-vitamin-mineral supplement was offered. Feed that was not consumed was measured to determine feed intake. The temperature data were recorded by hygro-thermographs. Hourly temperatures and humidity were used to develop weather variables. Regression analysis was used and weather variables were regressed on dry matter intake (DMI). When addition of a new variable did not improve R (2) more than one unit, then the number of variables in the model was truncated. Cattle in confinement had lower DMI than those in open lots and those in open lots with access to an overhead shelter (P < 0.05). Cattle in outside lots with access to overhead shelter had similar DMI compared to those in open lots (P = 0.065). Effect of heat was predominantly displayed in August in the three housing systems. In terms of explaining variation in DMI, in outside lots with access to overhead shelter, average and daytime temperatures were important factors, whereas in open lots, nocturnal, peak and average temperatures were important factors. In confinement buildings, the previous day's temperature and humidity index were the most important factors explaining variation in DMI. Results show the effect of housing and weather variables on DMI in summer and when considering these results, cattle producers wishing to improve cattle feedlot performance should consider housing conditions providing less stress or more comfort.

Data from a three-year study conducted to integrate pasturing systems with drylot feeding systems were used to assess cultural energy analysis of the cattle production systems. Each year, 84 fall-born and 28 spring-born calves of similar genotypes were brought from Oklahoma and used in the experiment. Fall-born and spring-born calves were started on test in May and October, respectively. Seven treatments were imposed: (1) fall-born calves directly into feedlot; (2) and (3) fall-born H.

Data obtained from 4 different capacity houses were evaluated to analyse the cultural energy and perfor- mance of broilers. Capacities of housings were 20,000, 25,000, 30,000 and 60,000 birds per production peri- od and they were assigned as HI, HII, HIII and HIV, respectively. The study was conducted in 2005 in which there were 6 production periods of 45 days. Data collected for each period were: date of starting and finish- ing; number of chicks entered and broilers sold; live weight at slaughter; carcass weight; feed consumption for starting, growing and finishing phase; labour; medication, vaccination and disinfectant; electricity con- sumption; heating and cooling methods and amount spent; distance for transportation of feed, chicks, broil- ers, wood shaving, limestone; and other miscellaneous expenditures. Ross 308 chickens in all houses received the same commercial feed and water ad libitum. Chicks were reared under a conventional temper- ature regimen. Chicks were fed starter, grower and finisher diets according to their ages. Even though capac- ities for houses were different their stocking densities were 16.36, 16.00, 16.38 and 16.54 birds/m2 for HI, HII, HIII and HIV, respectively. For cultural energy analysis, feed, transportation, labour, machinery, electric- ity, brooding, and other inputs were calculated and corresponding energy values for each input were obtained from literature. For the analysis it was assumed that carcasses would have 18.2% protein and 15.2% fat. Total cultural energy invested in broilers in HIII was lower than that of broilers in HI (P< 0.05). Energy input per kg live weight gain and per kg carcass of HIII were lower than that of HI (P< 0.05, P< 0.01, respective- ly). The HIII had lower cultural energy ratio for protein energy output than HI (0.01). Energy efficiency (kcal input/kcal output) of HIII was better than that of HI (P< 0.01). Results of the study showed that increasing capacity of housings decreases cultural energy input up to certain capacity and indicated that increasing housing capacity without interfering with performance could be a means for energy conservation in sustain- able agriculture