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In the Gulf Costal Plain adapted summer annual forages such as pearl millet [Pennisetum typhoides(Burm.) Stapf and C. E. Hubb] are generally higher in energy content than perennial grasses and are capable of producing higher rates of gain. However, practically no data are available which define animal performance at different levels of forage utilization. The lack of definitive data on which to base a grazing program with pearl millet prompted this study which determined liveweight gains of weanling cattle grazing ]pearl millet and evaluated the relationships between gain, forage yield, forage quality, grazing pressure, and profitability. A hybrid pearl millet ‘Millex 23’ was seeded at the rate of 15 kg/ha on Thenas (Fluvaquentic Eutrochrept; coarse, loamy, mixed, thermic) soil and fertilized with 112 kg/ha each of N, P2O5, and K2O in each of 2 years. Weanling crossbred beef calves were used as tester animals and grazed at stocking rates ranging from 3.73 to 11.35 animals/ha. Liveweight average daily gains (ADG) from 0.27 to 1.01 kg were shown to be a non‐linear function of forage availability and a positive linear function of percent in vitro dry matter disappearance (IVDMD) available forage. Percent IVDMD of available forage varied from 36.29 to 63.57% and was inversely related to length of trial. Neutral detergent fiber values for available forage were negatively correlated with ADG (r= −0.84). Maximum profitability, expressed as return per ha, was found at intermediate grazing pressure and was dependent upon the magnitude of positive or negative margin between the time of purchase and the time of selling. Maximum profit occurred at greater grazing pressures as the positive margin between selling and purchase price increased. The most important factor affecting the profitability of grazing pearl millet was the differential between buying and selling price of the cattle. Aside from this factor, which the farmer seldom controls, grazing pressure is the most important determinant of profit. It was concluded that the greatest profit or least loss occurs at medium grazing pressures which, in this study, was approximately 2 kg of available forage per kg of animal liveweight.

Yearling heifer growth data were obtained during 4 yr for 524 heifers allotted to either humid bermudagrass 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.

Two trials were conducted to determine the influence of monensin on live weight gain and efficiency of forage utilization of calves grazing Bermudagrass. In trial 1, 32 calves, weaned at an average age of 238 days and 250 kg, were grazed on “Coastcross I” Bermudagrass from July 20 to October 13. Eight steers and eight heifers were randomly assigned to one of two treatments: 200 mg monensin/head/day or 0 mg monensin/head/day fed in a .91 kg/head/ day diet of pelletized 14% protein feed. Both groups were stocked at 15.3 head/ha. Monensin-fed calves gained .52 kg/head/day, while the control-fed calves gained .42 kg/head/day (P<.10). Average daily gains (ADG) of steers (.54 kg) were greater (P<.05) than those of heifers (.40 kg). Forage to gain ratio estimates were 15:1 and 19:1 for calves on monensin and control paddocks, respectively. In trial 2, 48 steer calves, averaging 265 days of age and 260 kg, were randomly assigned to each of two replicates of the following grazing treatments: common Bermudagrass only (P), Bermudagrass + .91 kg/head/day 14% protein feed (PF) or Bermudagrass + .91 kg/head/day feed + 200 mg monensin/head/day (PFM). ADG were .45, .47 and .68 kg for steers fed P, PF and PFM, respectively. The monensin-fed calves showed a 45% improvement in ADG (P<.05). Estimated forage to gain ratios for calves fed P, PF and PFM were 20.5:1, 19:1 and 13:1, respectively. The use of 200 mg monensin/head/day improved calf gains by 23 to 45% and increased estimated feed efficiencies by 21 to 36% on Bermudagrass pastures. The improvement in gain for heifers fed monensin was 28.6%, while steers gained 18.4% more when fed monensin.

Two groups of eight first-cross Brahman-Hereford cows of equal parity within groups were fed monensin and no monensin, respectively, from day 246 ± .4 of gestation. The cows were group fed Coastal bermudagrass hay ad libitumand either 0 (group NMON) or 200 mg (group MON) of monensin incorporated in 1.8 kg of standard range cube (daily per cow). The experimental purpose was to study concentration profiles of sex steroids prepartum. Blood was sampled via tail vein or artery on alternate days through day 270 of gestation and at least daily thereafter until 3 days postpartum as well as within 1 hr after calving (day 0). Progesterone (P4), estrone (E1) and estradiol-17β (Eβ) and -17α (Eα) were measured in blood serum by radioimmunoassay. The data were analyzed by least-squares and split-plot analysis of variance and by stepwise-addition multiple regression. Diet did not affect body weight and length, wither height, heart girth or condition score of cows, calving traits or birthweight and vigor of calves. Periparturiently, concentration profiles of the serum steroids were characteristic of other published data. Concentrations of the serum steroids were not different (P>.25) between groups initially, but serum P4increased (P<.01) about 3 ng/ml in cows of group NMON during the first 22 days of the feeding trial and serum P4was higher (P<.01) on day 22 than in cows of group MON. In contrast, concentrations of serum estrogens did not differ significantly between diet groups until days 2 to 0 prepartum when concentrations of serum E1and Eβ were higher (P<.05) in cows of group NMON than in cows of group MON. Concentrations of serum Eα started to decrease on either day −4 (group MON) or day −1 (group NMON). Cows carrying a female calf had higher concentrations of serum P4(P<.05) and lower concentrations of serum estrogens [E1, P>.10; Eβ and Eα, P<10] prepartum than cows carrying a male calf. Differences in concentrations of the serum estrogens associated with calf sex were most evident during the last 18 days before calving.

Previously selected plants for improved lines of kleingrass (Panicum coloratumL.) were evaluated for growth and seed production characteristics. At the initiation of this test, 13 experimental synthetic varieties were available for chemical comparisons of forage quality. This study was conducted to determine if differences existed in percent of neutral detergent fiber (NDF) and NDF components within the available synthetic varieties of kleingrass. The effects of five stages of plant maturity on NDF and its components were also evaluated for each variety. Since kleingrass has an indeterminate type of growth form, plants collected as initial and regrowth forage were harvested when a certain percent of the seed on the most mature kleingrass tillers reached the soft dough stage, but prior to the time of seed maturation. Previously nonharvested cumulative forage was collected at the same chronological age as the regrowth forage. At each of the maturity‐stage dates, plant samples were separated into leaf laminae and stems. Each plant part was analyzed for its neutral detergent solubles:neutral detergent fiber ratio (NDS:NDF). The NDF was then sequentially partitioned into hemicelluloses (HEM), cellulose (CEL), lignin (LIG), and ash. The hemicelluloses were further divided into easily hydrolyzable (EHH) and difficulty hydrolyzable hemicelluloses (DHH). Kleingrass varieties differed in NDS:NDF and NDF components. Leaf:stem ratios ranged from 1:1 to 1:4. By harvesting at a morphological stage prior to seed maturation, the NDS: NDF ratio of leaves and stems in regrowth forage did not vary throughout the study period. Leaf laminae contained approximately 34% HEM and 24% CEL; whereas, stems contained approximately 34% HEM and 34% CEL. With advancing maturity, HEM of leaf laminae increased at the expense of CEL. However, the HEM: CEL ratio of stems remained at approximately 1:1 throughout the collection period. The EHH:DHH ratio changed significantly with plant age as percent EHH increased and DHH decreased. The percent of LIG in both leaves (3.2%) and stems (6.6%) changed with plant age but the buildup of LIG was greatest in stems. Acid‐insoluble ash was influenced by the stage of growth only in leaf laminae and the leaves, with an average of 2.4%, contained four to eight times more ash than did stem sections.

Recent studies have shown that differences in neutral detergent fiber:neutral detergent solubles ratios (NDF:NDS) exist within experimental synthetic varieties of kleingrass (Panicum coloratumL.), and those varieties which had the highest NDF content were genetically closely related. This investigation was initiated to determine if selected varieties which differed in NDF:NDS also differed in in vitroand in vivodigestibility. The relationships between NDF, components of NDF, and various NDF component ratios vs. in vitroand in vivodigestibility were also studied using three synthetic varieties harvested at four stages of plant growth. Initial and subsequent regrowth forage was harvested as a certain percent of seed reached the soft dough stage, but before seed maturation had occurred. Cumulative growth forage was collected at the same chronological time as the final regrowth harvest date. At each harvest date, analyses were obtained for in vivodigestible dry matter (DDM), in vitrotrue digestible dry matter (IVDDM), neutral detergent fiber (NDF), digestibility of NDF (DNDF), and NDF components (hemicelluloses, cellulose, lignin, and ash). Percent DDM, IVDDM, and DNDF declined from 62, 74, and 60%, respectively, to 51, 65, and 47%, respectively, with plant maturity. NDF increased from 64% to 71% with plant age and accounted for approximately 92% (r = −0.96**) of the variability associated with DDM. The regression of DDM vs. DNDF resulted in a positive relationship (r = 0.99**). NDF vs. DNDF gave a highly significant negative relationship (r = −0.93**). Cellulose, lignin, and lignin:acid detergent fiber ratio were negatively related to DNDF; whereas, hemicellulose:NDF and hemicelluloses:cellulose ratios were positively related to DNDF. Regression with IVDDM and NDF components and component ratios were of the same magnitude as those relationships with DDM. The level of NDF showed a closer relationship to its digestibility than did any NDF component ratio with DNDF. NDF and DDM showed no difference between varieties, but the IVDMM analyses proved one of the varieties to be superior to the other two.