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Feeding cattle in intensified settings allows cow-calf producers to decrease their reliance on grazed forage and utilize alternative feedstuffs. Under intensification diet type may alter energy utilization. Fourteen pregnant MARC III (1/4 Angus, 1/4 Hereford, 1/4 Red poll, and 1/4 Pinzgauer) heifers (405 ± 44 kg BW) were used to determine effects of diet type on nutrient and energy utilization. Heifers were randomly assigned to 1 of 2 treatments, a forage diet (FORAGE; 2.16 Mcal ME/kg) or a concentrate diet (CONC; 1.98 Mcal ME/ kg), and individually fed to meet maintenance energy requirements (0.135 Mcal ME/kg BW0.75). The CONC diet contained corn stalks (15%), dry-rolled corn (78%), soybean meal (4%) and a premix pellet (3%); FORAGE contained corn stalks (82%), corn silage (10%), soybean meal (4%) and a premix pellet (4%). Measurements of intake and digestion were measured over a 96-h period after approximately 21 d of adaptation. Using portable headbox calorimeters, measurements of O2, CO2, and CH4 gases were collected over a period of 24 h to determine individual heifer oxygen consumption, carbon dioxide production, and methane production. Data were analyzed as a RCBD with diet as fixed effect and measurement group as a random block. Intake of OM was greater for CONC (74.6 g/kg BW0.75) than FORAGE (68.0 g/kg BW0.75; P < 0.01), but NDF intake was greater in FORAGE (57.4 vs 27.2 g/kg BW0.75). Digestion of OM and NDF were greater (P ≤ 0.03) for CONC (78.5 and 56.2%, respectively) than FORAGE (53.4 and 47.3%, respectively). Intake of DE and ME were greater for CONC (15.84 vs 9.37 Mcal and 13.54 vs 7.38 Mcal; P < 0.01). The ratio of ME to DE was greater for CONC (0.85 vs 0.79; P = 0.01). Although methane production and heat production relative to GE were not different between treatments (6.2 and 57.5%; P ≥ 0.15), the methane production as % of DE was greater (P < 0.01) for FORAGE than CONC (12.6 vs 8.0 % of DE). Retained energy was 1.61 Mcal/d for CONC compared to -3.17 Mcal/d for FORAGE; P < 0.01). Similarly, retained nitrogen was greater in CONC than FORAGE (-1.59 vs -35.68 g/d; P < 0.01). Feeding concentrate-based rather than forage-based diets improved energy efficiency. The ratio of ME to DE may be dependent upon diet and more dynamic than previously thought. [ABSTRACT FROM AUTHOR]

Weather risk and land values challenge the economic sustainability of cow-calf systems. Intensified systems reduce a producer's dependence on forage production and (or) allows them to more efficiently use forage resources. However, delivery of limit-fed, total mixed rations brings greater fixed costs and creates logistical challenges, preventing smaller producers from capturing benefits associated with intensified systems. Therefore, we evaluated three management scenarios: 1) ad libitum hay (HAY), representing conventional drought management in Southeast Texas; 2) a limit-fed total mixed ration (TMR) requiring significant investment in equipment; and 3) a management system where forage and concentrate in the TMR are not mixed but rather fed separately (SEP), decreasing need for investment in equipment. Within TMR and SEP systems four feeding levels to provide 70, 85, 100, and 115% of requirements (NRC, 1996) were considered. Net returns were estimated using a stochastic simulation model based on a 200 cow operation. Stochastic variables included weaning weights, calf prices, and feed ingredient prices. Production responses were based on empirical data from studies evaluating feeding strategy or level. Ingredient and calf prices were estimated from multivariate empirical distributions, which incorporates historical variability and correlation in stochastic forecasted prices. Enterprise budgets for each system were developed and simulated 500 times, drawing stochastic variables from their respective distributions to estimate a distribution of net returns for each strategy and feeding level combination. Net returns for limit-fed systems at intake levels of 70, 85 and 100% ranged from $93.00 to $155.30 per cow and were greater than HAY ($72.41 per cow). However, HAY had greater net returns than TMR at 115% intake level ($62.95 per cow), but HAY had lower net returns compared to SEP at 115% intake level ($95.58 per cow). Reductions in feed costs for limit-fed systems ranged from $29.90 to $116.59 per cow compared to HAY, offsetting increases in other costs. Probability of a negative net return was 0.35 for HAY, slightly less than the negative net return probability observed for TMR at 115% (0.37). All other probabilities for negative returns ranged from 0.13 (SEP at 70%) to 0.30 (SEP at 115%). The CV of net return for HAY (272) was greater than that of any limit-fed system (mean CV = 144). Limit-feeding is preferred to ad libitum hay feeding, and separate delivery of forage and concentrates is the most profitable and least risky of the intensive cow-calf strategies tested. [ABSTRACT FROM AUTHOR]