Genotype x environment interactions for postweaning performance in crossbred calves grazing winter wheat pasture or dormant native prairie.

Data from 403 calves from Angus, Brahman, and reciprocal-cross cows sired by Polled Hereford bulls were used to evaluate the impact of postweaning backgrounding forages on postweaning BW, gains, and carcass traits. Calves were born (spring of 1991 through 1994) and reared on either endophyte-infected tall fescue or common bermudagrass pastures. After weaning, calves were transported 360 km to the Grazinglands Research Laboratory, west of El Reno, OK, and, within breed and preweaning forage, were assigned to one of the following winter stocker treatments: 1) winter wheat pasture or 2) dormant native prairie plus supplemental CP. In March, winter stocker treatments were ended and calves were grazed as a single group on cool-season grasses until early July (1992, 1993, and 1994) or late May (1995), when the feedlot phase began. In the feedlot, calves were fed a high concentrate diet for an average of 120 d until a backfat thickness of > 10 mm was reached. Calves were shipped in truck load lots to Amarillo, TX (350 km), for processing and collection of carcass data. Averaged over calf breed group, calves wintered on wheat pasture gained faster (P < 0.01) during the stocker phase (0.71 vs 0.43 kg); had heavier (P < 0.01) final feedlot weights (535 vs 512 kg); lower feedlot (P < 0.01) ADG (1.37 vs 1.53 kg); heavier (P < 0.01) carcass weights (337 vs 315 kg); larger (P < 0.01) longissimus muscle (84.9 vs 81.8 cm2); higher percentage (P < 0.01) of kidney, heart, and pelvic fat (2.32 vs 2.26); and higher (P < 0.01) dressing percentage (62.2 vs 61.3) than calves backgrounded on native prairie. Maternal heterosis for stocker ADG was evident in calves backgrounded on native prairie but not on winter wheat (P < 0.10), but the two environments were similar in maternal heterosis for feedlot ADG and carcass traits. Calves wintered on native prairie were restricted in growth and expressed compensatory gain during the feedlot phase but not during the spring stocker phase. Dormant native grasses can be used to winter stocker calves excess to the winter wheat pasture needs, but ownership of these calves would have to be retained through the feedlot phase to realize any advantage of built-in compensatory gain. Finally, these data suggest that expression of maternal heterosis for weight gain is more likely in calves backgrounded on native prairie than in calves grazed on winter wheat.     

An evaluation of production and economic efficiency of two beef systems from calving to slaughter

A 3-yr experiment was conducted with cows and their calves to evaluate resource inputs, animal performance, and carcass characteristics of two production systems. In the control system, cows (CON; n = 99/yr) grazed pasture and were fed hay during the winter, and CON steer calves were finished in the feedlot for 211 d after weaning. In the treatment system (TRT; n = 100/yr), cows grazed pasture and crop residue during the winter and were fed hay. Treatment steer calves grazed crop residue after weaning, grazed pasture in the spring and summer, and were finished in the feedlot for 90 d. Body condition scores after TRT cows returned from crop residue grazing were greater (P < 0.01) for CON than for TRT cows. Calving rates were similar for both groups (CON = 91%; TRT = 93%). In the feedlot, CON steers had lower (P < 0.05) ADG and DMI, but were more efficient (P < 0.01) than TRT steers. Treatment steers had greater (P < 0.05) final weight, hot carcass weight and longissimus muscle area, and decreased marbling score. The cost per weaned calf and weaning breakeven were greater (P = 0.07) for the CON system than for the TRT system (CON = 455.12 dollars, 0.91 dollar/0.45 kg; TRT = 421.43 dollars, 0.84 dollar/0.45 kg). When steers were priced into the postweaning phase on an economic basis, slaughter breakeven was lower (P = 0.01), and profit potential tended (P = 0.14) to be greater for TRT steers when they were sold on a live basis. When steers were priced into the postweaning phase on a financial basis, slaughter breakeven was lower (P = 0.03) and profit potential from the sale of steers on a live basis was greater (P = 0.07) for TRT than for CON steers. Economic evaluation of the total system resulted in greater (P = 0.06) profit potential for the TRT system when steers were priced into the system on either an economic or a financial basis and when steers were sold on a live basis, but no differences were observed when steers were sold on a grid basis. Despite differences in cow weight and body condition, calving rates did not differ between systems. Although calves were herdmates, feedlot performance and carcass characteristics differed between systems. The TRT system had lower weaning and slaughter breakeven, lower cost per weaned calf, and greater profit potential when finished steers were sold on a live basis.     

Effects of pre- and postpartum nutrition on reproduction in spring calving cows and calf feedlot performance

Crossbred, spring-calving cows (yr 1, n = 136; yr 2, n = 113; yr 3, n = 113) were used in a 3-yr experiment to evaluate the influence of supplemental protein prepartum and grazing subirrigated meadow postpartum on pregnancy rates and calf feedlot performance. A 2 x 2 factorial arrangement of treatments was used in a switchback design. From December 1 to February 28, cows grazed dormant upland range in 8 pastures (32 +/- 2 ha each). The equivalent of 0.45 kg of supplement/cow per d (42% CP) was provided to half of the cows on a pasture basis 3 d/wk. For 30 d before the beginning of breeding (May 1 to May 31), half of the cows grazed a common subirrigated meadow (58 ha), and the remainder was fed grass hay in a drylot. Cow BW and BCS were monitored throughout the year, and steer calf performance was determined until slaughter. Feeding supplement prepartum improved (P = 0.01 to P < 0.001) BCS precalving (5.1 vs. 4.7) and prebreeding (5.1 vs. 4.9) and increased (P = 0.02) the percentage of live calves at weaning (98.5 vs. 93.6%) but did not affect (P = 0.46) pregnancy rate (93 vs. 90%). Calves born to dams fed supplement prepartum had similar (P = 0.29) birth weight (37 vs. 36 kg) but greater (P = 0.02) weaning weight (218 vs. 211 kg). However, steer feedlot DMI (8.53 vs. 8.48 kg), ADG (1.6 vs. 1.6 kg), and carcass weight (369 vs. 363 kg) were not affected (P = 0.23 to P = 0.89) by prepartum supplementation. Allowing cows to graze subirrigated meadow postpartum improved (P < 0.001) BCS prebreeding (5.2 vs. 4.9) but did not affect (P = 0.88) pregnancy rate (92 vs. 91%). Allowing cows to graze subirrigated meadow increased (P = 0.01) calf weaning weight (218 vs. 211 kg) but not (P = 0.62 to P = 0.91) feedlot DMI (8.4 vs. 8.3 kg), ADG (1.6 vs. 1.6 kg), or carcass weight (363 vs. 362 kg) of their steer calves. Increased percentage of live calves at weaning as a result of feeding supplemental protein increased net returns at weaning and after finishing in the feedlot. Net returns were increased by allowing cows to graze subirrigated meadow postpartum regardless of whether calves were marketed at weaning or after finishing in the feedlot.     

Effects of interval-feeding whole sunflower seeds during mid to late gestation on performance of beef cows and their progeny

This experiment was conducted to determine the effects of interval feeding of whole sunflower seeds on the performance of beef cows and their progeny. During mid to late gestation, 144 multiparous, spring-calving beef cows (588 kg of initial BW; 5.6 initial BCS; 4 to 13 yr old) were individually fed 1 of 3 supplements 4 d/wk for a 76-d period. Supplements (DM basis) included: 1) 0.68 kg of soybean meal/feeding (NCON); 2) 3.01 kg of a soybean hull-based supplement/feeding (PCON); and 3) 1.66 kg of whole sunflower seeds high in linoleic acid/feeding (WSUN). Supplements were formulated to provide similar amounts of CP and ruminally degraded intake protein; PCON and WSUN were also formulated to be isocaloric. During the supplementation period, cows had free-choice access to bermudagrass (Cynodon dactylon) and tall-grass prairie hay. By the end of the 76-d supplementation period, cows fed PCON (P < 0.01) and NCON (P < 0.01) had gained more BW than cows fed WSUN (33, 23, and 10 kg, respectively). However, from the end of this supplementation period to the beginning of the breeding season 84 d later, cows supplemented with PCON had lost more (P < 0.01) BW than cows supplemented with WSUN (-123 kg vs. -111 kg). Cow BW change through weaning (-50 kg, P = 0.43) and final cow BW (536 kg, P = 0.70) at weaning were not different among supplement groups. Furthermore, cow BCS was similar among supplement treatment groups at the end of the supplementation period (5.3, P = 0.09), at the beginning of the breeding season (4.8, P = 0.38), and at weaning (4.7, P = 0.08). No difference among treatments was detected for calf birth weight (36 kg, P = 0.42), calf weaning weight (235 kg, P = 0.67), percentage of cows exhibiting luteal activity at the beginning of the breeding season (57%, P = 0.29), or pregnancy rate (88%, P = 0.44). However, first service conception rate was greater (P = 0.01) for cows fed PCON (79%) and tended (P = 0.07) to be greater for cows fed WSUN (74%) than for cows fed NCON (53%). After weaning, all steer calves were placed in a feedlot and fed a high-concentrate finishing diet for an average of 188 d. Supplements fed to dams during gestation did not influence feedlot performance or carcass characteristics. Prepartum energy supplementation, regardless of energy source or prepartum energy balance, resulted in improved conception rate, but other measures of reproduction, calf and feedlot performance, and carcass characteristics were not affected.     

Age of calf at weaning of spring-calving beef cows and the effect on cow and calf performance and production economics

Over a 5-yr period, spring-calving cows were used in a carry-over design experiment to evaluate effects of calf age at weaning on cow and calf performance and production economics. Weaning management groups were early (n = 60, calf age 150 d, EW), traditional (n = 60, calf age 210 d, NW), and late (n = 60, calf age 270 d, LW). Cow body condition score (BCS) and weights at the last weaning date were different (P < .05) for EW (5.8, 583 kg), NW (5.5, 560 kg), and LW (5.2, 541 kg) management groups. Pregnancy rates among groups were similar. Days on feed for groups differed (P = .001) and was 247 for EW, 204 for NW, and 164 d for LW steers. Average daily gain in the feedlot differed (P = .01) among groups and averaged 1.5 kg for LW, 1.4 kg for NW, and 1.3 kg for EW steers. Dry matter intake while steers were in the feedlot was greater (P = .001) for LW than for NW and EW calves. Hot carcass weight was greater (P = .01) for EW (328 kg) and NW (332 kg) calves than for LW (321 kg) steers, and fat depth was greater (P = .05) for EW and NW steers than for LW steers. When carcass data for the NW and LW steers were adjusted to the fat depth of EW steers, carcass characteristics among groups were similar. Net income per steer at slaughter for the feedlot phase was greater (P < .001) for the EW ($75.36) and NW ($62.16) steers than for the LW ($10.09) steers. Again, when carcass data for the NW and LW steers were adjusted to the same fat depth of the EW steers, net income differences among groups were reduced. Replacement heifers were developed in a drylot and costs were higher (P < .001) for the EW than for NW and LW heifers. Annual cow costs were greater (P < .10) for the LW ($443.45) than for the EW ($410.09) and NW ($421.35) groups. Break-even for each system on a steer financial basis was not different between the NW and LW groups, and both the NW and LW groups had lower (P = .08) break-evens than the EW group. Age of the calf at weaning affects cow weight and BCS. Net income in each system is influenced by cow costs, month of the year that steer calves are purchased into the feedlot and finished steers are sold, month of the year cull cows are marketed, and replacement heifer development costs.     

Comparison of Charolais and Limousin as terminal cross sire breeds

Birth, weaning, feedlot and carcass traits were evaluated on 1,181 calves sired by Charolais and Limousin bulls out of eight crossbred dam groups (Hereford X Angus, Angus X Hereford, Simmental X Angus, Simmental X Hereford, Brown Swiss X Angus, Brown Swiss X Hereford, Jersey X Angus, Jersey X Hereford). Calves were born in the spring over a 4-yr period during which dams ranged from 3 to 8 yr of age. Charolais-cross calves were 2.7 kg heavier (P less than .01) at birth and had a 9.9% higher (P less than .01) incidence of difficult calvings and 4.6% greater (P less than .05) preweaning death loss than did Limousin crosses. Charolais-sired calves out-gained Limousin-sired calves by 31 g/d (P less than .01) from birth to weaning and were 9 kg heavier (P less than .01) at weaning. After weaning, calves were self-fed a finishing diet and slaughtered as each animal attained an estimated carcass grade of low Choice. Charolais-cross calves gained 60 g/d faster (P less than .01) than Limousin crosses, were fed 6.8 fewer d and were 17.3 kg heavier (P less than .01) at slaughter. Feed efficiency was similar for both sire breeds. On a grade-equivalent basis, Charolais crosses produced 7 kg heavier (P less than .01) carcass and had 22 g more carcass weight per day of age (P less than .01). Charolais crosses had slightly less internal and external fat. Dressing percentage was higher for Limousin cross calves (64.6 vs 63.9%, P less than .01). Longissimus muscle area and carcass cutability were similar for crosses of both sire breeds.     

Evaluations of genotypexenvironment interactions of beef bulls performance-tested in feedlot or pasture

Purebred Angus (n = 96) and Polled Hereford (n = 96) bull calves sired by bulls of either low or high yearling weight performance lines were assigned to either creep-fed or non-creep-fed treatment before weaning for four calf crops. For each breed, after weaning in the fall, half of the calves within each of the four groups were fed a high concentrate diet for 189 d after weaning in a feedlot and the remainder were put on winter temporary pastures (rye or ryegrass) followed by summer grazing on pearl millet and bermudagrass pastures for 329 d after weaning. Dependent variables were ADG for various intervals and the complete test period, weight, height and scrotal circumference at periodic intervals, and weight per day of age at regular intervals during the test. The model included breed, performance line, sire nested within breed and line, year, age of dam, preweaning treatment, postweaning treatment, and two- and three-factor interactions. Age of calf was included as a covariate for weight, height, and scrotal circumference measurements. Line and breed differences generally were significant for weight but not for height. The interaction of primary interest (line by preweaning treatment by postweaning treatment) was not significant. The high growth performance line gained faster than low growth performance line for all intervals and were 45 kg heavier by 189 d after weaning. Preweaning treatment did not affect postweaning ADG but did affect weight per day of age. Creep-fed calves were heavier than non-creep-fed calves and maintained this advantage during the postweaning treatment periods in both the feedlot and pasture. Both preweaning treatment groups had similar ADG after weaning. Angus were 23 kg heavier at weaning than Polled Herefords; however, breed weight means were similar by 16 mo of age. In summary, bulls from different selection lines for growth were identified in feedlot and pasture when adjustments were made for prior management effects. The lack of significant interactions in these data indicates that central test station data, appropriately adjusted, are useful for ranking bulls on genetic merit for growth in feedlot and on pasture.     

Productivity and profitability of twin births in beef cattle

Data from 1,277 single and 85 twin calvings, occurring in both spring and fall from 1980 through 1987, were used to examine the productivity and profitability associated with twin births in beef cattle. Pregnancies in pure and crossbred cattle resulted from both AI and embryo transfer. Cows and calves were confinement-housed. Cows were individually fed to specification. Calves were given ad libitum access to creep feed and those born in 1986 and 1987 were fed to slaughter. The influence of birth number of gestation length, total calf birth and weaning weights, lactation yield, and cow fed intake during both the dry and lactating periods were examined. Twin-bearing cows had their gestation length shortened by 6.4 d (2%); yielded 25.5 (59) and 186.0 kg (73%) more weight of calf at birth and weaning, respectively; had lactation yield and lactation feed intake increased by 25 and 20%, respectively; and had precalving (dry) period feed intake no different from their single-bearing counterparts (P = .12). Postweaning growth was not different for single and twin calves (P = .50); twin gain, relative to initial size, was higher. Feedlot feed intake of twins was 85% of that for singletons (P = .20). Twins were 90% of singleton live weight at slaughter and yielded 93% of singleton hot carcass weight (P = .12). Twins were slightly older and significantly leaner at slaughter. Returns less feed costs showed twin births to be associated with increased profit for cow-calf programs. Returns less feed and overhead costs were higher for twin calves than for singles in the feedlot.     

Evaluation of tropically adapted straightbred and crossbred cattle: postweaning gain and feed efficiency when finished in a temperate climate

Beef cows in the subtropical USA must be adapted to the stressors of the environment, typically supplied by using Brahman (Br) breeding. Calves produced in the region, however, are usually grown and finished in more temperate regions, and have a perceived reputation for poor ADG and feed efficiency during finishing. Compromised fertility and carcass quality often associated with the Br have increased interest in tropically adapted Bos taurus breed types. The objective of this study was to evaluate 3 breeds [An = Angus (Bos taurus, temperate); Br (B. indicus, tropical); and Ro = Romosinuano (B. taurus, tropical)] and all possible crosses during various segments of post-weaning growth, and for feed efficiency during the finishing phase. Steer calves (n = 473) born over 3 yr were weaned in late September, backgrounded for at least 21 d (BKG), shipped 2,025 km to El Reno, OK, in October, fed a preconditioning diet for 28 d (RCV), grazed wheat (Triticum aestivum L.) pasture from November to May (WHT), finished on a conventional feedlot diet (FIN), and serially harvested after approximately 95, 125, and 150 d on feed. Body weight and ADG during each segment were tested using a mixed model that included calf age at weaning, year (Y), breed of sire (SB), breed of dam (DB), and interactions. In addition, winter treatment (continuous wheat or reduced grazing of wheat with supplement) was included for the wheat and feedlot phases. Sire within SB × SB [and pen (barn × year) for feedlot phase] were considered random. The SB × DB interaction was significant for all traits (P < 0.01) except exit velocity taken at weaning and ADG during FIN, but both traits were affected by 3-way interactions with Y or harvest group. Tropically-adapted purebred steers had greater (P < 0.01) ADG than AnAn through weaning and BKG in FL but the reverse was true during the RCV and WHT segments. Similar, but less pronounced results were noted for F(1) steers with 100% tropical influence compared with those with only 50%. Heterosis was numerically greater for most traits for An × Br (11 to 64%) compared with An × Ro and Br × Ro (3 to 42%), which were similar. In a subset of the steers (n = 261), G:F was not influenced by level of tropical breeding, but tropically adapted steers were more efficient (P < 0.05) by residual feed intake. No heterosis was evident. These data show that in temperate zones, winter is the period when productivity of tropically adapted cattle is compromised.     

Productivity and hay requirements of beef cattle in a Midwestern year-round grazing system

Our objective was to evaluate a replicated (n = 2) Midwestern year-round grazing system's hay needs and animal production compared with a replicated (n = 2) conventional (minimal land) system over 3 yr. Because extended grazing systems have decreased hay needs for the beef herd, it was hypothesized that this year-round system would decrease hay needs without penalizing animal production. In the minimal land (ML) system, two replicated 8.1-ha smooth bromegrass-orchardgrass-birdsfoot trefoil (SB-OG-BFT) pastures were rotationally stocked with six mature April-calving cows and calves and harvested as hay for winter feeding in a drylot. After weaning, calves were finished on a high-concentrate diet. Six mature April-calving cows, six mature August-calving cows, and their calves were used in the year-round (YR) grazing system. During the early and late summer, cattle grazed two replicated 8.1-ha SB-OG-BFT pastures by rotational stocking. In mid-summer and winter, April- and August-calving cows grazed two replicated 6.1-ha, endophyte-free tall fescue-red clover (TF-RC) and smooth bromegrass-red clover (SB-RC) pastures, respectively, by strip-stocking. In late autumn, spring-calving cows grazed 6.1-ha corn crop residue fields by strip-stocking. Calves were fed hay with corn gluten feed or corn grain over winter and used as stocker cattle to graze SB-OG-BFT pastures with cows until early August the following summer. First-harvest forage from the TF-RC and SB-RC pastures was harvested as hay. Body condition scores of April-calving cows did not differ between grazing systems, but were lower (P < or = 0.03) than those of August-calving cows from mid-gestation through breeding. Preweaning calf BW gains were 47 kg/ha of perennial pasture (P < 0.01) and 32 kg/cow (P = 0.01) lower in the YR grazing system than in the ML system. Total BW gains ofpreweaning calf and grazing stocker cattle were 12 kg/ha of perennial pasture less (P = 0.07), but 27 kg/cow greater (P = 0.02) in pastures in the YR grazing system than in the ML system. Amounts of hay fed to cows in the ML system were 1,701 kg DM/cow and 896 kg DM/cow-stocker pair greater (P < 0.05) than in the YR grazing system. Extended grazing systems in the Midwest that include grazing of stocker cattle to utilize excess forage growth will decrease stored feed needs, while maintaining growing animal production per cow in April- and August-calving herds.     

Effects of different grazing and feeding periods on performance and carcass traits of beef steers

Over three consecutive years, 180 (60/yr) fall-born steer calves were weaned in May (average initial BW = 238 kg, SD = 36.2 kg) and allocated to one of three groups: 1) calf-fed steers that entered the feedlot at weaning; 2) short yearlings that grazed irrigated pasture for another 4 mo and entered the feedlot in September; and 3) long yearlings that grazed with short yearlings during the summer, remained on annual California foothills range through the fall, winter, and spring, and entered the feedlot the following May. All steers were fed until the average group backfat (BF), determined by ultrasound, reached 11 to 12 mm. On pasture, short- and long-yearling steers gained weight in the summer; long yearlings then slightly lost weight in the fall and winter, and then gained weight again the following spring. Average days in the feedlot were 188, 158, and 94 (P < 0.10) for calves, short yearlings, and long yearlings, respectively. Feedlot DMI increased with age (and weight) at feedlot entry, with no difference among groups in gain:feed ratio. The gain of BF was nil on pasture, even when animals were gaining weight, and then increased rapidly when animals were placed on a high-energy diet. Final body weights were heaviest (P < 0.10) in long yearlings, followed by short yearlings and then calves, indicating that a prolonged growing period increases the apparent mature size of the animal. Moreover, total carcass fat contents and percentage of Choice or above were all lower (P < 0.10) in cattle that were older at feedlot entry (i.e., long yearlings) compared with the other groups. In conclusion, increasing the backgrounding period decreased time and total concentrate requirements in the feedlot of Angus-Hereford steers. Older cattle reached 10 mm of BF at heavier weights. Grazing animals gained weight without increasing BF; however, BF increased rapidly in the feedlot. Prolonged grazing may decrease quality grade, either by impairing the ability of the animal to deposit intramuscular fat or by decreasing the time during which dietary energy supply is adequate for intramuscular fat deposition to occur.     

Postweaning performance of calves from Angus, Brahman, and reciprocal-cross cows grazing endophyte-infected tall fescue or common bermudagrass

Data from 403 Polled Hereford-sired calves from Angus, Brahman, and reciprocal-cross cows were used to evaluate the effects of preweaning forage environment on postweaning performance. Calves were spring-born in 1991 to 1994 and managed on either endophyte-infected tall fescue (E+) or common bermudagrass (BG) during the preweaning phase. After weaning, calves were shipped to the Grazinglands Research Laboratory, El Reno, OK and stratified to one of two winter stocker treatments by breed and preweaning forage; stocker treatments were winter wheat pasture (WW) or native range plus supplemental CP (NR). Each stocker treatment was terminated in March, calves grazed cool-season grasses, and calves were then moved to a feedlot phase in June. In the feedlot phase, calves were fed to approximately 10 mm fat over the 12th rib and averaged approximately 115 d on feed. When finished, calves were weighed and shipped to Amarillo, TX for slaughter. Averaged over calf breed group, calves from E+ gained faster during the stocker phase (P<.10), had lighter starting and finished weights on feed (P< .01), lighter carcass weights (P<.01), and smaller longissimus muscle areas (P<.05) than calves from BG. Calves from E+ were similar to calves from BG in feedlot ADG, percentage kidney, heart, and pelvic fat, fat thickness over 12th rib, yield grade, marbling score, and dressing percentage. Maternal heterosis was larger in calves from E+ for starting weight on feed (P<.01), finished weight (P<.10), and carcass weight (P<.16). These data suggest that few carryover effects from tall fescue preweaning environments exist, other than lighter, but acceptable, weights through slaughter. These data further suggest that the tolerance to E+ in calves from reciprocal-cross cows, expressed in weaning weights, moderated postweaning weight differences between E+ and BG compared to similar comparisons in calves from purebred cows.     

Growth Performance by Stocker Steers Fed Magnesium-Mica During a Grazing and Feedlot Period

Two experiments were conducted to determine the effects of Mg-mica supplementation on grazing and feedlot performance of stocker steers. In Exp. 1, eight groups of six steers were fed a basal diet of 80% ground grain sorghum, 15% corn silage, and 5% control protein supplement (DM basis) or a supplement containing Mg-mica (9% of supplement; 4.5 mg/kg diet DM) for 141 d. Marbling scores tended (P<0.10) to be greater, and the percentage of carcasses grading USDA Choice or higher was greater (P<0.05), from steers fed Mg-mica than from those fed the control supplement. In Exp. 2, eight groups of nine head each were offered either a control grain sorghum-based supplement or one containing 34 g/d of Mg-mica (2.7 g Mg) while grazing smooth bromegrass pastures for 112 d. Pasture groups were then placed in feedlot pens for 120 d and fed a basal diet similar to that described above. Two groups fed each pasture supplement received a control supplement, and two received a supplement containing Mg-mica (10% of supplement; 5 mg/kg diet DM). Steers fed Mg-mica during the pasture phase tended to have heavier (P=0.11) hot carcass weights, higher (P<0.05) dressing percentages, numerically (P>0.10) higher marbling scores, and a higher percentage of carcasses grading USDA Choice than steers fed the control supplement during the pasture phase. Therefore, adding Mg-mica to pasture supplements or feedlot diets appears to have no impact on grazing or feedlot performance, but may improve carcass quality.     

Effect of calf weaning age and cow supplementation on cow productivity

Five years of data were collected on 124 Brangus-type cows to evaluate weaning calves at 8.5 or 10.5 mo of age and winter supplementation of the brood cow with 2.25 kg of molasses daily. Cows with calves weaned at 10.5 mg of age gained 14 kg less weight (P less than .01) during the late nursing period than did cows from which calves were earlier weaned. Age of calf at weaning had no effect on cow reproduction, but calves weaned at 10.5 mo were 2 to 3 d younger (P less than .06) and 5.3 kg lighter (P less than .05) at 8.5 mo of age. During the last 2 mo of nursing, calves weaned at 10.5 mo of age gained 37.2 kg and had a 31.9-kg heavier weaning weight than calves weaned at 8.5 mo of age. Molasses supplementation resulted in differences (P less than .01) in cow weight changes. Cows fed molasses had calving percentages 5 to 7 units higher (P less than .30) than cows not fed molasses. Feeding cows molasses for 145 d throughout the calving and breeding season increased calf weaning weight 7.7 (P less than .02) and 11.2 (P less than .03) kg, respectively, at 8.5 and 10.5 mo of age over the nonsupplemented controls.     

Winter grazing system and supplementation during late gestation influence performance of beef cows and steer progeny

A 2 x 2 factorial study evaluated effects of cow wintering system and last trimester CP supplementation on performance of beef cows and steer progeny over a 3-yr period. Pregnant composite cows (Red Angus x Simmental) grazed winter range (WR; n = 4/yr) or corn residue (CR; n = 4/yr) during winter and within grazing treatment received 0.45 kg/d (DM) 28% CP cubes (PS; n = 4/yr) or no supplement (NS; n = 4/yr). Offspring steer calves entered the feedlot 14 d postweaning and were slaughtered 222 d later. Precalving BW was greater (P = 0.02) for PS than NS cows grazing WR, whereas precalving BCS was greater (P < 0.001) for cows grazing CR compared with WR. Calf birth BW was greater (P = 0.02) for CR than WR and tended to be greater (P = 0.11) for PS than NS cows. Prebreeding BW and BCS were greater (P 0.32) by PS. Calf weaning BW was less (P = 0.01) for calves from NS cows grazing WR compared with all other treatments. Pregnancy rate was unaffected by treatment (P > 0.39). Steer ADG, 12th-rib fat, yield grade, and LM area (P > 0.10) were similar among all treatments. However, final BW and HCW (P = 0.02) were greater for steers from PS-WR than NS-WR cows. Compared with steers from NS cows, steers from PS cows had greater marbling scores (P = 0.004) and a greater (P = 0.04) proportion graded USDA Choice or greater. Protein supplementation of dams increased the value of calves at weaning (P = 0.03) and of steers at slaughter regardless of winter grazing treatment (P = 0.005). Calf birth and weaning BW were increased by grazing CR during the winter. Calf weaning BW was increased by PS of the dam if the dam grazed WR. Compared with steers from NS cows, steer progeny from PS cows had a greater quality grade with no (P = 0.26) effect on yield grade. These data support a late gestation dam nutrition effect on calf production via fetal programming.     

Effect of weaning status and implant regimen on growth, performance, and carcass characteristics of steers

One hundred forty-three Angus x Simmental crossbred steers (initial BW = 155.1 +/- 4.5 kg) were used in a 2-yr study (yr 1, n = 67; yr 2, n = 76) to determine the effects of weaning age, implant regimen, and the weaning age x implant regimen interaction on steer growth and performance, organ mass, carcass characteristics, and cooked beef palatability. Steers were early-weaned at an average age of 108 d (EW) or normally weaned at an average age of 202 d (NW) and allotted by weight to an aggressive or nonaggressive implant regimen. On their respective weaning dates, EW and NW steers were penned individually and fed a grain-based diet until they were slaughtered at a final BW of 546 kg. A subsample of steers (n = 2 per treatment) were slaughtered at 254 kg. At 254 kg, EW steers implanted with the aggressive implant regimen had 64% greater backfat depth than those implanted with the nonaggressive implant regimen; conversely, NW steers implanted with the aggressive implant regimen had 52% lower backfat depth than those implanted with the nonaggressive implant regimen (weaning status x implant regimen interaction; P < 0.01). A similar interaction was observed for empty visceral organ weights. Early-weaned steers were younger (354.7 vs 372.4 d; P < 0.01) at final slaughter but were in the feedlot longer (246.5 vs 169.6 d; P < 0.01) than NW steers, whereas the aggressive implant regimen decreased days fed (203.3 vs 212.7; P < 0.07) compared to the nonaggressive implant regimen. Overall ADG was greater for EW than for NW steers (1.61 vs 1.50 kg/d; P < 0.01) and for the aggressive compared with the nonaggressive implant regimen (1.59 vs 1.52 kg/d; P < 0.02). Early-weaned steers consumed less DM per day (7.4 vs 8.5 kg/d; P < 0.01) and were more efficient (0.217 vs 0.208 kg/kg; P < 0.02) but consumed more total DM (1,817 vs 1,429 kg; P < 0.01) than NW steers while in the feedlot. Implant regimen did not affect DMI (P > 0.37) or feed efficiency (P > 0.15). Weaning status did not affect carcass characteristics (P > 0.14), final empty body composition (P > 0.25), or final longissimus muscle composition (P > 0.18); however, steaks from EW steers had higher (P < 0.05) taste panel tenderness and juiciness ratings than steaks from NW steers. The aggressive implant regimen decreased yield grade (P < 0.02), but did not affect quality grade (P > 0.86) compared to the nonaggressive implant regimen. Placing early-weaned steers on an aggressive implant regimen is a viable management option.     

Effect of age at feedlot entry on performance and carcass characteristics of bulls and steers

Seventy Angus x Simmental calves (BW = 166.3 +/- 4.2 kg) were used in a 3 x 2 factorial arrangement to determine the effect of age at feedlot entry and castration on growth, performance, and carcass characteristics. At 82 d of age, steers were castrated. Calves were placed in the feedlot at 111 (early-weaned), 202, or 371 (yearling) d of age. Steers were implanted with Synovex-S followed 93 d later with Revalor-S. Calves were harvested on an individual basis when fat thickness was estimated to be 1.27 cm. During the feedlot phase, yearlings gained faster (P < 0.01) than calves placed in the feedlot at 202 or 111 d of age (1.88, 1.68, and 1.62 kg/d, respectively); however, from 111 d of age until harvest, ADG was greatest for early-weaned calves, intermediate for cattle placed in the feedlot at 202 d of age, and lowest for yearlings (1.62, 1.47, and 1.21 kg/d, respectively; P < 0.01). Early-weaned calves spent the most days in the feedlot, followed by calves placed in the feedlot at 202 d of age; yearlings spent the fewest days in the feedlot (221, 190, and 163 d, respectively; P < 0.01). Total DMI when in the feedlot was similar (P = 0.22) among age groups; however, daily DMI was lowest for early-weaned calves, intermediate for calves placed in the feedlot at 202 d of age, and the highest for yearlings (7.1, 8.1, 10.5 kg/ d, respectively; P < 0.01). Early-weaned calves were the most efficient, followed by calves placed in the feedlot at 202 d of age; yearlings were the least efficient (227, 207, 180 g gain/kg feed, respectively; P < 0.01). Weight at harvest (682, 582, 517 kg, respectively; P < 0.01) and hot carcass weight (413, 358, 314 kg, respectively; P < 0.01) were greatest for yearlings, intermediate for cattle placed in the feedlot at 202 d of age, and lowest for early-weaned calves. Early-weaned calves had the smallest longissimus area, followed by calves placed in the feed-lot at 202 d of age; yearlings had the largest longissimus area (77, 86, 88 cm2, respectively; P < 0.01). Calves placed in the feedlot at 111 and 202 d of age had lower yield grades (3.2, 3.1, 3.5, respectively; P < 0.04), and produced fewer select carcasses than yearlings (25, 13, 48%, respectively; P < 0.01). Bulls and implanted steers both had an ADG of 1.7 kg/d when in the feedlot; however, bulls had a greater (P < 0.09) hot carcass weight (370 vs 354 kg) and a larger (P < 0.01) longissimus area (85.8 vs 81.3 cm2) than steers. Earlier feedlot placement resulted in greater quality grades but lower carcass weights.     

Use of dried distillers grains throughout a beef production system: effects on stocker and finishing performance, carcass characteristics, and fatty acid composition of beef

A 2-yr study was conducted using a 3 × 2 factorial arrangement of treatments to evaluate the effects of feeding dried distillers grains throughout a beef production system on performance, carcass characteristics, and fatty acid profile of beef. Factors were wheat pasture supplement [no supplement (CON), dry-rolled corn (DRC), and dried distillers grains (DDG)] fed at 0.5% BW daily and finishing diet [steam-flaked corn based diet containing 0 (SFC) or 35% (35DDG) DDG]. Each year, 60 preconditioned Hereford steers (initial BW = 198 kg ± 3) grazed winter wheat pasture with or without supplement. Body weight gain was 8% greater for steers consuming DDG supplement compared with CON and DRC steers (P < 0.01). After the grazing period, pastures within supplement treatment were randomly assigned to SFC or 35DDG. There was no supplement by finishing diet interaction for any performance or carcass variable of interest (P ≥ 0.41). Previous supplementation on winter wheat affected BW at feedlot entry and adjusted G:F (P ≤ 0.05) but had no effect on finishing ADG or carcass traits (P ≥ 0.12). On a carcass-adjusted basis, steers consuming 35DDG had reduced final BW, ADG, G:F, and total BW gain throughout the system (P ≤ 0.04) compared with SFC. Additionally, steers consuming 35DDG had reduced HCW, dressing percent, and fat thickness (P ≤ 0.03) compared with SFC. There was a supplement by finishing diet interaction (P = 0.02) for 18:0, in which cattle supplemented with DRC and fed the SFC finishing diet had the lowest concentration of 18:0 but DRC supplemented steers fed the 35DDG diet had the greatest concentration. The interaction was not significant (P ≥ 0.18) for other fatty acids. Main effects of supplement and finishing diet affected (P ≤ 0.05) several other fatty acids of interest, particularly 18:2, which is associated with reduced flavor-stability of beef. The use of DDG as a supplement to wheat pasture resulted in greater ADG during wheat grazing and heavier BW at feedlot entry, but final BW was not different from CON or DRC groups. Feeding DDG at 35% DM in steam-flaked corn-based finishing diets reduced ADG, G:F, and HCW, and affected the fatty acid composition of beef.     

Influence of Bos indicus crossbreeding and cattle age on apparent utilization of a high-grain diet

Ten Bos indicus x MARC III (initial BW = 303 +/- 25 kg) and 10 MARC III (initial BW = 322 +/- 16 kg) steers were used in a 2 x 2 factorial design to determine whether cattle age or Bos indicus crossbreeding influence site of digestion of a high-grain diet. Initially, five Bos indicus x MARC III and five MARC III steers were fitted with duodenal cannulas and adapted to a 95% concentrate diet that was offered for ad libitum consumption for a 237-d feeding period (calves). During the feeding period, duodenal and fecal samples were collected during 4-d periods beginning on d 14, 67, 137, and 228. The remaining 10 steers were fed a forage-based diet for a targeted daily gain of .6 to .7 kg for 210 d (yearlings). Following this period, yearling steers were duodenally cannulated and adapted to the 95% concentrate diet. Yearling steers had ad libitum access to feed for 165 d, and samples were collected during 4-d periods beginning on d 13, 42, 102, and 159. Dry matter intake was 9.8 and 7.6 kg/d and daily gain was 1.35 and 1.16 kg in yearlings and calves, respectively. Apparent OM digestion in the stomach was greater (P < .01) in yearlings than in calves. In contrast, postruminal disappearance as a percentage of OM intake was greater (P = .05) in calves than in yearlings. Duodenal flows of total N, microbial N, nonmicrobial N, and total amino acids and total tract N digestibility were not affected (P > .05) by age or Bos indicus crossbreeding. Fecal N excretion was greater (P < .01) in yearlings than in calves. Results of this experiment suggest little effect of Bos indicus influence on utilization of a high-grain diet. However, more feed is digested in the rumen of yearlings than of calves consuming a high-grain diet.     

Comparison of an early and normal weaning management system on cow and calf performance while grazing endophyte-infected tall fescue pastures

A 3-yr study used 16 cows and their spring-born calves (yr 1) and 48 first-calf heifers (yr 2, n = 24; yr 3, n = 24) and their spring-born calves in a completely randomized design. All cows and heifers were Angus x Beefmaster, and calves were sired by Angus bulls. Cow-calf pairs were assigned randomly to one of two management systems: 1) an early-weaning system, in which steer and heifer calves were weaned at 108 d of age and fed a postweaning growing diet (EW), or 2) a normal weaning system, in which calves were weaned at 205 d without supplementation (NW). Before early weaning and within each management system, calves and their dams were maintained in two 1.4-ha, endophyte-infected tall fescue pastures for 35 d (yr 1) or 14 d (yr 2 and 3). Early-weaned calves and cow-calf pairs were then randomly allotted to 1.4-ha, endophyte-infected tall fescue pastures with two (yr 1) or three (yr 2 and 3) calves or cow-calf pairs per pasture (four pastures per management system). Cow weights and BCS changes and calf gains were measured from early to normal weaning. Dietary intakes and nutrient digestibilities by EW and NW calves were determined during two periods of yr 1 and three periods of yr 2 and 3. Total gains and BCS changes were greater (P < 0.01) for cows that produced EW calves in all years. Calf ADG from early to normal weaning did not differ (P = 0.32). Similar to ADG, BW of calves at normal weaning were not different (P = 0.11). Forage intake was greater (P < 0.01) by NW calves during Periods 2 and 3 of yr 1 and Periods 1 and 2 of yr 2 and 3; however, total DM and CP intakes were greater (P < 0.01) for EW calves in Periods 2 and 3 of each year. Intakes of NDF tended (P = 0.11) to be greater by EW calves across all years. Estimates of CP and NDF digestibilities were higher (P < 0.01) for EW calves during yr 1 and 2; however, all components of the diet consumed by NW calves in yr 3 were more digestible (P < 0.05) than those consumed by EW calves. These results show the condition of cows with EW calves was improved by early weaning and gains by calves weaned at 108 d to pasture plus a commercial grower diet were comparable to those by calves continuing to nurse dams until weaned at 205 d.