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Cool-season annuals may fill gaps in seasonal forage availability and reduce stored feed needs for beef cattle producers in the Southeast. These forages can be established during the autumn via sod-seeding or broadcasting on warm-season perennial grass pastures such as bermudagrass and bahiagrass or planted into a prepared seedbed. Opportunity exists to use small grains that vary in their individual growth distribution to extend the grazing season. Small grains adapted to the region include cereal rye (Secale cereale), wheat (Triticum aestivum), oats (Avena sativa), and triticale (x Triticosecale). These species provide bimodal forage dry matter (DM) production during the autumn and early winter months, and can be grown in monocultures or mixtures. Cereal rye generally provides forage DM earliest in the season, followed by triticale, wheat, and oats. Fall production potential of these species is primarily dependent on planting method, seeding date, fertility, and variety selection. These species provide high quality forage DM that may support animal performance in stocker and cow-calf operations with minimal supplementation, and can be grown in combination with annual ryegrass and/or legumes to further lengthen the window of grazing. Annual ryegrass and legumes in the Southeast includes coldtolerant and rust-resistant diploid and tetraploid varieties of ryegrass, and adapted true clover (Trifolium sp.) varieties. Autumn-planted ryegrass and/or clovers including primarily crimson, arrowleaf, ball, and white clover, provide minimum to nonexistent forage mass for grazing during the fall. Naturally reseeding ryegrass or clovers will often provide earlier forage mass; however, DM is usually not adequate for stocking until late-January through May. With appropriate levels of N fertilization, ryegrass produces more forage DM, and thus allows for earlier stocking and greater stocking rates compared to clovers. Tetraploid varieties of ryegrass, when seeded into prepared seedbed, can provide adequate forage mass for fall grazing. Earliness of forage mass for stocking of clover ranges from crimson (earliest), to arrowleaf and ball (mid), to white clover (latest). White clover, however, in adapted soils and with adequate spring-summer rainfall and proper stocking rate, can provide grazing during early to mid-summer months. From the first frost event in late fall through the early spring months, cool-season annual forages provide actively growing forage to extend fall and spring grazing for cow-calf and/or stockers during winter dormancy of perennial grass pastures. [ABSTRACT FROM AUTHOR]

Cool-season annuals may fill gaps in seasonal forage availability and reduce stored feed needs for beef cattle producers in the Southeast. These forages can be established during the autumn via sod-seeding or broadcasting on warm-season perennial grass pastures such as bermudagrass and bahiagrass or planted into a prepared seedbed. Opportunity exists to use small grains that vary in their individual growth distribution to extend the grazing season. Small grains adapted to the region include cereal rye (Secale cereale), wheat (Triticum aestivum), oats (Avena sativa), and triticale (×Triticosecale). These species provide bimodal forage dry matter (DM) production during the autumn and early winter months, and can be grown in monocultures or mixtures. Cereal rye generally provides forage DM earliest in the season, followed by triticale, wheat, and oats. Fall production potential of these species is primarily dependent on planting method, seeding date, fertility, and variety selection. These species provide high quality forage DM that may support animal performance in stocker and cow-calf operations with minimal supplementation, and can be grown in combination with annual ryegrass and/or legumes to further lengthen the window of grazing. Annual ryegrass and legumes in the Southeast includes coldtolerant and rust-resistant diploid and tetraploid varieties of ryegrass, and adapted true clover (Trifolium sp.) varieties. Autumn-planted ryegrass and/or clovers including primarily crimson, arrowleaf, ball, and white clover, provide minimum to nonexistent forage mass for grazing during the fall. Naturally reseeding ryegrass or clovers will often provide earlier forage mass; however, DM is usually not adequate for stocking until late-January through May. With appropriate levels of N fertilization, ryegrass produces more forage DM, and thus allows for earlier stocking and greater stocking rates compared to clovers. Tetraploid varieties of ryegrass, when seeded into prepared seedbed, can provide adequate forage mass for fall grazing. Earliness of forage mass for stocking of clover ranges from crimson (earliest), to arrowleaf and ball (mid), to white clover (latest). White clover, however, in adapted soils and with adequate spring-summer rainfall and proper stocking rate, can provide grazing during early to mid-summer months. From the first frost event in late fall through the early spring months, cool-season annual forages provide actively growing forage to extend fall and spring grazing for cow-calf and/or stockers during winter dormancy of perennial grass pastures. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the effect of residual feed intake (RFI), residual average daily gain (RADG), feed to gain (F:G) on productivity in Brahman heifers (n=242). Following a 56-d post-weaning period for six calf crops, Brahman heifers were individually fed for periods of 60-d at 2.8% of their body weight in a Calan gate system. Rations were adjusted at weekly intervals. For each contemporary group, the mean and standard deviation of RFI, RADG, and F:G was calculated. Based on the mean plus or minus ½ standard deviation for each group, heifers with the lowest RFI and F:G were classified as efficient (E), while higher RFI and F:G heifers were classified as moderately efficient (ME) or inefficient (I). For RADG, heifers with the highest RADG were classified E, while lower RADG heifers were classified as ME or I. Cow records for age at first calving (AFC), interval from the first to second calf (CI) and calf records for birth weight (BW) and 180-d adjusted weaning weight (AWW) were recorded. Data were analyzed using mixed linear models. The additive genetic effects were modeled as random in all analyses. In analyses of calf traits, maternal additive genetic effects were also random effects. For all traits, cow year of birth was investigated as a fixed effect. For calf traits, calving interval, the calf birth year was a fixed effect. Calf breed, season of birth, and sex were fixed effects in analyses of calf traits. The effects of interest were 3-level classification variables created using the upper and lower quartiles and the two middle quartiles combined of RFI, RADG, and FG. These were modeled in distinct analyses. In analyses of RADG, the high (inefficient) and low (efficient) RFI groups of heifers differed (0.03 ± 0.018 and -0.04 ± 0.02, respectively; P=0.03). In analyses of F:G all RADG groups differed (P<0.01) as expected; that is E (8.0 ± 0.25) < ME (9.5 ± 0.24) < I (12.6 ± 0.25; P< 0.01). Heifer AFC and CI were not significantly influenced by efficiency classifications for RFI, RADG, or F:G (P>0.10). As expected, male calves had greater BW (P<0.05). Classification for efficiency group did not influence either BW or AWW. RFI, RADG, or F:G did not affect reproductive or calf performance in young Brahman cows. Selection for RFI will result in selecting against RADG or F:G. [ABSTRACT FROM AUTHOR]

The forage-animal interface is a vital component of agricultural systems that is often overlooked by both agronomy and animal science programs. As such, current grazing models do not always provide a satisfactory understanding of how forage species and/or cultivars respond to livestock interaction in both production and physiology, how forage can influence the animal, and how the nexus of these two entities may affect the environment. The objective of this effort was to develop a conceptual framework of a dynamic model that combined the forage and ruminant livestock interactions, and to provide the initial parameterization of a model for bermudagrass pastures. The systems dynamic methodology was used. The causal loop diagram (CLD) was first envisioned based on the hypothesis that not only can forage factors affect performance and behavior of the grazing animal, but the grazing animal, through its herbivorous behavior and selective intake, can affect and alter the physiology, growth, and performance of the forage and the pasture. Generation of a preliminary stock-and-flow diagram (SFD) with variable flight simulators was also performed. The main CLD was a composite of four sub-models that represented the agronomic, animal, atmospheric, and soil subsystems. The limitations of this model existed in the lack of meta-analytical publications in which necessary equations have been summarized that could be used in model programming. The parameterization of the model suggested that forage allowance was the driving factor in animal ADG, and forage growth rate was governed by a combination of evapotranspiration, defoliation, soil N, and precipitation. Our simulation of the bermudagrass scenario suggested that under these production conditions, most portions of the model operated in a traditional goal-seeking fashion. The initial results provided the documentation of the interface concept for the benefit of forage agronomy and animal nutrition programs as well as the foundation for advancements of the model to eventually serve as potential decision aid in production-economic strategies. [ABSTRACT FROM AUTHOR]

The forage-animal interface is a vital component of agricultural systems that is often overlooked by both agronomy and animal science programs. As such, current grazing models do not always provide a satisfactory understanding of how forage species and/or cultivars respond to livestock interaction in both production and physiology, how forage can influence the animal, and how the nexus of these two entities may affect the environment. The objective of this effort was to develop a conceptual framework of a dynamic model that combined the forage and ruminant livestock interactions, and to provide the initial parameterization of a model for bermudagrass pastures. The systems dynamic methodology was used. The causal loop diagram (CLD) was first envisioned based on the hypothesis that not only can forage factors affect performance and behavior of the grazing animal, but the grazing animal, through its herbivorous behavior and selective intake, can affect and alter the physiology, growth, and performance of the forage and the pasture. Generation of a preliminary stock-and-flow diagram (SFD) with variable flight simulators was also performed. The main CLD was a composite of four sub-models that represented the agronomic, animal, atmospheric, and soil subsystems. The limitations of this model existed in the lack of meta-analytical publications in which necessary equations have been summarized that could be used in model programming. The parameterization of the model suggested that forage allowance was the driving factor in animal ADG, and forage growth rate was governed by a combination of evapotranspiration, defoliation, soil N, and precipitation. Our simulation of the bermudagrass scenario suggested that under these production conditions, most portions of the model operated in a traditional goal-seeking fashion. The initial results provided the documentation of the interface concept for the benefit of forage agronomy and animal nutrition programs as well as the foundation for advancements of the model to eventually serve as potential decision aid in production-economic strategies. [ABSTRACT FROM AUTHOR]

Preweaning growth data were obtained during 4 yr on 349 Braford-sired calves from Brahman-Hereford F1 first-calf females. These females were allotted to either semiarid rangeland (Uvalde) or humid improved pasture (Overton) as weanlings and to one of four herbage allowance levels at each location as yearlings. Females were wintered on systems in local industry practice and maintained on various allotted herbage levels both as yearlings and during first lactation. The desired range in herbage allowance (400 to 2,800 kg of DM per 100 kg of BW at Uvalde and 80 to 460 kg of DM per 100 kg of BW at Overton) was accomplished by adjusting stocking rate monthly from April to weaning (October). Herbage allowance and yearling heifer characteristics (hook height, condition score, or weight) were treated as continuous, independent variables in regression analyses. Preweaning daily gain responded to increased herbage allowance differently for the two locations. Generally, at Overton, herbage allowance influenced suckling calf growth to a greater extent than for the F1 yearling variables, but at Uvalde this trend was reversed. Heifers with larger yearling heights had first calves that grew faster to weaning for both locations and all herbage allowances, although the relationship was stronger for greater herbage allowances at Overton (herbage allowance x yearling weight interaction, P < .07). This interaction was not detected (P > .15) at Uvalde. Interactions between herbage allowance and yearling condition score were detected (P < .05) at both Overton and Uvalde, but these interactions were different (P < .15) at the two locations.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth data were collected over 4 yr from 349 Brahman-Hereford F1, first-calf, lactating females that had been allotted as weanlings to either semiarid extensive rangeland (Uvalde) or humid improved Bermudagrass pasture (Overton) and to one of four herbage allowance levels at each location as yearlings. Heifers were wintered according to systems in local practice and maintained on allotted forage levels both as yearlings and during their first lactation. Heifers were bred to Braford bulls to calve as 2-yr-olds in January to March. Herbage allowance (400 to 2,800 kg of DM/100 kg BW at Uvalde and 80 to 460 kg of DM/100 kg BW at Overton) was maintained by adjusting stocking density monthly from April to weaning (October). Herbage allowance and yearling heifer hook height, condition score, or weight (taken on April 15) were continuous independent variables in regression analyses. Final heifer weight, height, and condition responses to increased herbage allowances were related to yearling phenotypes differently (P < .01) for the two locations. At Uvalde, yearling condition score interactions were especially important in that heifers that had more condition (especially those > 5 for 1 to 10 with 10 = fattest) as yearlings retained more (P < .05) weight and condition and grew more (P < .05) in height than did those of lower yearling condition. These females also responded to increased herbage allowance by gaining advantage (P < .05) in these variables, whereas those of lower yearling condition made smaller advances. At Overton, yearling condition played little role in subsequent growth. The yearling variable that had the greatest interactive effect was height. Shorter yearling heifers (< 123 cm) responded (P < .07) to increased herbage allowance so that they had greater final condition and grew more rapidly in height than those taller as yearlings.

Yearling heifer growth data were obtained during 4 yr for 524 heifers allotted to either humid bermuda grass pastures (Overton) or semiarid rangeland (Uvalde). Each year, heifers were allotted on April 15 to four forage availability levels (400 to 2,800 kg of DM per 100 kg of BW at Uvalde and 80 to 260 kg of DM per 100 kg of BW at Overton) maintained by varying the stocking rate monthly until mid-October of each year. Forage availability and yearling heifer characteristics (weight, condition score, and height at hooks, taken on April 15) were treated as continuous variables in regression analyses. Final heifer weight, height, and condition responses to increased forage allowance were related to yearling phenotypes differently for the two locations. Generally, at Overton, forage availability influenced final characteristics to a greater extent than did yearling variables, whereas the trend was the opposite at Uvalde. At Uvalde, the yearling characteristic that had the largest effect on performance was height at hooks. Yearlings with large frames benefited from increased forage allowance by accumulating body fat at a faster rate than those with small frames. In contrast, at Overton, the yearling characteristic that had the largest effect on performance was condition. Fat heifers responded to increased forage availability to gain even greater advantages in fatness at the expense of potential growth in height and, thus, achieved early maturation. Yearling phenotypes were more broadly adapted to arrays of forage availability for humid, improved pastures than for semiarid rangeland.

The Texas A & M Cattle Production Systems Model was used to study herd productivity under several management plans open to cow-calf producers in the southeastern United States. An east Texas farm herd was simulated as a self-contained unit where all hay fed in the winter months was harvested from hay pastures or as surplus forage from grazed pastures. Management options examined involved (1) variation in the amount of forage fed as hay, and (2) spring vs fall calving. All forage was produced on well fertilized, intensively managed Coastal bermudagrass pastures. The winter feed options consisted of hay fed (1) ad libitum, and at (2) 80, (3) 60 and (4) 40% of the ad libitum level. The hay feeding period was November 15 through April 15. Overall herd productivity decreased as level of winter feeding decreased. Higher levels of hay feeding resulted in fewer cattle/unit land area but higher production/breeding cow. Herd size increased by 2.9, 11.9 and 32.5% as winter hay levels were reduced from ad libitum to 80, 60 and 40% of ad libitum, respectively, under spring calving management, whereas herd productivity measured as total live weight sold/herd (fixed land area) declined by 2.2, 9.4 and 10.3% with the respective feed levels. Spring-calving herds were approximately 3.2% larger in number than corresponding fall-calving herds on the same land area, but fall-calving herds produced an average of 3.6% more live weight sales.