Comparison of wet brewers' grains or dried distillers' grains as supplements to conserved bermudagrass forage as winter feeding options for beef cows.

The objective of this study was to examine the use of 2 byproduct supplements and conserved warm-season forage as winter feeding options for primiparous beef cows. Gestating Angus ( = 48) and Brangus ( = 24) 2-yr-old cows were stratified by BW and breed to 1 of 12 pens. Pens were randomly assigned 1 of 2 supplements, wet brewers' grains (WBG) or dried distillers' grains (DDG). Coastal bermudagrass hay or round bale silage (RBS) was fed free choice (6 pens each) and cows received WBG or DDG supplements at a daily rate of 0.05% BW (DM basis) prorated for feeding 3 d/wk. Total BW and BCS changes did not differ ( = 0.65 and = 0.93, respectively) between DDG- and WBG-supplemented cows. Total amount of forage DM offered and mean calculated daily forage DM offered did not differ ( = 0.59 and = 0.20, respectively) between supplement treatments. Estimated daily mean and total supplement DM offered was greater ( < 0.001) for WBG than for DDG treatments. The same 2 supplements and forage sources were used in an unbalanced 6 × 4 design to measure intake, digestibility, and rumen parameters in ruminally fistulated steers. Supplement did not affect forage DMI of hay ( = 0.31) or RBS ( = 0.63). Total DMI was not different ( = 0.37 and = 0.73) for hay-based and RBS-based diets, respectively. Total tract digestibility tended to be greater ( = 0.06) for DDG than for WBG in hay diets but was not different ( = 0.76) for RBS diets. Daily mean ruminal pH was greater ( = 0.03) for WBG than for DDG when supplemented to hay-based diets. In RBS diets, a supplement × hour interaction ( = 0.05) existed for ruminal pH. Daily mean ruminal ammonia N concentration was greater ( < 0.001) for WBG-supplemented diets compared with DDG-supplemented diets. A supplement × hour interaction existed for ruminal ammonia in hay- ( < 0.001) and RBS- ( = 0.09) based diets. Ruminal pH and ammonia N concentrations stayed in ranges adequate to support ruminal metabolism and cattle performance. Marginal differences in ruminal measures between high-moisture and dry byproduct supplements resulted in no differences in cow performance when offered with hay or high-moisture forage. High-moisture forage sources can be coupled with high-moisture byproduct supplements.

Assessment of serum 25-hydroxyvitamin D concentrations of beef cows and calves across seasons and geographical locations.

Vitamin D is critical for the growth and development of calves and positively contributes to immune function of cattle. Serum 25-hydroxyvitamin D (25(OH)D) concentrations above 20 ng/mL have traditionally been considered adequate for growth and development of cattle, but recent evidence has indicated that concentrations below 30 ng/mL are insufficient for immunity. Because little information is available regarding vitamin D status of beef cattle, the objective of this study was to evaluate vitamin D status of beef cow-calf herds on pasture as affected by season and location. Serum samples were collected from 43 cow-calf pairs plus an additional 54 calves in herds located in Florida, Idaho, and Minnesota in the spring calving season. Samples were collected again over the summer months from animals in the Florida and Minnesota herds. Effects of subcutaneous injection of vitamins A, D, and E also were investigated in a subset of calves from the Idaho herd. All cows sampled had serum 25(OH)D concentrations above 30 ng/mL at the time of calving in the spring. The average serum 25(OH)D concentrations of cows rose from near 60 ng/mL in the spring to 75 ng/mL in the summer ( < 0.001). Most calves, on the other hand, had serum 25(OH)D concentrations below 20 ng/mL. The calves in the Florida and Minnesota herds similarly rose from averages of 10 to 15 ng/mL at birth to near 50 ng/mL by the end of summer. Serum 25(OH)D of severely deficient calves increased from 3 ng/mL in nonsupplemented calves to 11 ng/mL at 48 h after birth if given a bolus supplementation of 40,000 IU of vitamin D via subcutaneous injection of a vitamin A, D, and E supplement at birth ( < 0.001). Vitamin D supplementation of cows late in pregnancy has been shown to increase serum 25(OH)D of calves; however, beef cattle generally receive very little supplemental vitamin D, as was the case for the cows studied here. The lower serum 25(OH)D of cows in spring compared with summer and the prevalence of vitamin D deficiency of calves observed here indicate that increased vitamin D supplementation of cows over the winter months or vitamin D supplementation of newborn calves would be beneficial.

Performance of beef cows and calves fed different sources of rumen-degradable protein when grazing stockpiled limpograss pastures.

Two experiments evaluated the effects of different sources of RDP on forage characteristics, animal performance, and ruminal and blood parameters of beef cattle grazing stockpiled limpograss (Hemarthria altissima) from January to May 2011 and 2012. In Exp. 1, 24 mature lactating beef cows and their respective calves were allocated to 8 stockpiled limpograss pastures (3 pairs/pasture). Treatments were 2 different sources of RDP, urea or cottonseed (Gossypium spp.) meal (CSM), distributed in a completely randomized design with 4 replicates. Feather meal and corn (Zea mays) meal were added to the urea treatments to balance RUP and energy. Treatments were mixed in sugarcane (Saccharum officinarum) molasses, which resulted in 3 kg DM/cow per day of supplement. There were no differences (P > 0.10) in herbage mass (HM; 3,200 ± 400 kg DM/ha), herbage allowance (HA; 1.9 ± 0.2 kg DM/kg of BW), CP (5.2 ± 0.2%), and in vitro digestible organic matter (IVDOM; 47 ± 0.5%) concentrations. There was a decrease (P < 0.10) in HM (from 4,100 to 2,600 kg/ha), IVDOM (from 46 to 39.9%), and HA (from 2.5 to 1.4 kg DM/kg BW) from January to March. Cow ADG (0.23 ± 0.08 kg/d), BCS (4.6 ± 0.2), milk yield (7.0 ± 0.4 kg/d), and plasma urea nitrogen (PUN; 16.1 ± 0.8 mg/dL) and calf ADG (0.71 ± 0.05 kg/d) were similar (P > 0.10) among treatments. Sixteen cow-calf pairs were moved to 8 drylot pens after Exp. 1, maintained on the same treatment, and evaluated for forage and total DMI. There was no difference in forage (P = 0.16; 2.1 ± 0.1% BW) and total DMI (P = 0.12; 2.5 ± 0.1% BW) between treatments. In Exp. 2, 2 rumen-cannulated steers were used in a 2 × 2 Latin square design, replicated in 2011 and 2012, to test the effects of the same treatments on rumen fluid and blood parameters. There was no difference (P > 0.10) in ruminal NH3-N (12.9 ± 0.3 mg/dL), pH (6.5 ± 0.1), propionic acid (25 ± 2.2 mol/100 mol), acetic acid (69.2 ± 2.9 mol/100 mol), and butyric acid (4.5 ± 0.5 mol/100 mol) as well as branched-chain VFA (1.3 ± 2.2 mol/100 mol) concentrations in the rumen. In addition, there was no difference (P = 0.91) in PUN (7.9 ± 0.3 mg/dL) concentration between treatments. Therefore, urea can be as effective as CSM as the main source of RDP in the molasses-based supplement offered to mature lactating beef cows grazing stockpiled limpograss pastures.

Effects of calf weaning age and subsequent management systems on growth performance and carcass characteristics of beef steers.

Brahman × British crossbred steers (n = 40 and 38 in yr 1 and 2, respectively) were used to evaluate the effects of calf management systems following early weaning (EW) on growth performance, muscle gene expression, and carcass characteristics. On the day of EW (d 0), steers were stratified by BW and age (95 ± 14 kg; 74 ± 14 d) and randomly assigned to a control treatment that was normally weaned (NW) on d 180 (n = 10 steers/yr) or to 1 of 3 EW treatments: 1) EW and limit fed a high-concentrate diet at 3.5% of BW (as-fed basis) in drylot until d 180 (EW180; n = 10 steers/yr), 2) EW and limit fed a high-concentrate diet at 3.5% of BW (as-fed basis) in drylot until d 90 and then grazed on bahiagrass pastures until d 180 (EW90; n = 10 steers/yr), or 3) EW and grazed on annual ryegrass pastures until d 60 (yr 1; n = 10 steers) or 90 (yr 2; n = 8 steers) and then on bahiagrass pastures until d 180 (EWRG). Early-weaned steers on ryegrass and bahiagrass pastures were supplemented with high-concentrate diet at 1.0% of BW (as-fed basis) until d 180. From d 180 to 270 (yr 1), all EW steers remained in their respective treatments, whereas NW steers were provided high-concentrate diet at 1.0% of BW (as-fed basis) on bahiagrass pastures. In yr 1, feedlot finishing period began on d 270. In yr 2, the study was terminated on d 180. In both years, EW180 steers were heaviest (P < 0.0001) on d 180. On d 180 of yr 1, EWRG steers were lightest (P < 0.0001) and EW90 steers were heavier (P = 0.05) than NW steers, whereas EW90, EWRG, and NW steers had similar BW on d 180 of yr 2 (P ≥ 0.14). On d 90, muscle PPARγ mRNA expression tended (P = 0.07) to be greater for EW180 steers and was greater (P = 0.008) for EW90 vs. EWRG steers but similar (P = 0.25) between EW180 and NW steers. On d 180, PPARγ mRNA was greater (P ≤ 0.06) for EW180 vs. NW, EW90, and EWRG steers. From d 274 to 302, EW180 steers had the least ADG (P ≤ 0.09), whereas EW90 steers had similar (P = 0.19) ADG compared with EWRG steers but greater (P = 0.03) ADG than NW steers. At slaughter, carcass characteristics did not differ (P ≥ 0.22) among treatments. In summary, EW steers provided a high-concentrate diet in drylot for at least 90 d were heavier at the time of normal weaning than NW steers and EW steers grazed on ryegrass pastures for 60 to 90 d and supplemented with concentrate at 1.0% of BW. Feeding a high-concentrate diet immediately after EW enhanced the muscle PPARγ expression but did not enhance marbling at slaughter.

Effects of calf weaning age and subsequent management system on growth and reproductive performance of beef heifers.

Brahman × British crossbred heifers (n = 40 and 38 heifers in yr 1 and 2, respectively) were used to evaluate the effects of calf weaning age and subsequent management system on growth and reproductive performance. On d 0, heifers were ranked by BW (89 ± 16 kg) and age (72 ± 13 d) and randomly assigned to a conventional management group that was normally weaned on d 180 (NW; n = 10 heifers annually) or early weaned (EW) on d 0 and 1) limit fed a high-concentrate diet at 3.5% of BW (as fed) in drylot until d 180 (EW180; n = 10 heifers annually), 2) limit fed a high-concentrate diet at 3.5% of BW (as fed) in drylot until d 90, then grazed on Bahiagrass pastures until d 180 (EW90; n = 10 heifers annually), or 3) grazed on annual ryegrass pastures until d 60 (yr 1; n = 10 heifers) or 90 (yr 2; n = 8 heifers), then on Bahiagrass pastures until d 180 (EWRG). On d 180, all heifers were grouped by treatment and rotated on Bahiagrass pastures until d 390. Grazing heifers were supplemented at 1.0% BW until d 180 and at 1.5% BW from d 180 to 390. From d 0 to 90, EW180 and EW90 heifers were heavier (P ≤ 0.02) than NW and EWRG heifers, whereas NW heifers tended (P = 0.09) to be heavier on d 90 than EWRG heifers. In yr 1 and 2, EW180 heifers were heaviest (P < 0.0001) on d 180. In yr 1, EWRG heifers were lightest (P < 0.0001), whereas EW90 and NW heifers had similar BW (P = 0.58). Conversely, EW90, EWRG, and NW heifers achieved similar BW on d 180 of yr 2 (P ≥ 0.18). Positive correlations were detected (P ≤ 0.05) between liver IGF-1 mRNA abundance on d 90 and ADG from d 0 to 90 and between liver IGF-1 mRNA abundance on d 180 and ADG from d 90 to 180. The EW180 heifers were youngest (P ≤ 0.01) at puberty. From d 260 to 340, the percentage of pubertal heifers was greater (P ≤ 0.03) for EW90 vs. NW heifers but did not differ (P ≥ 0.15) between EWRG and NW heifers. The ADG from d 0 to 90 and the plasma IGF-1 on d 90 and 180 explained approximately 34% of the variability in age at puberty. In summary, the EW90 and EW180 heifer management systems evaluated in this study altered the BW at the time of NW and were good alternatives for anticipating puberty achievement compared to NW heifers.

Effect of castration technique on beef calf performance, feed efficiency, and inflammatory response.

The objective of this experiment was to examine the effect of castration technique on daily feed intake (DFI), daily water intake (DWI), growth performance, residual feed intake (RFI), and inflammatory response in weaned beef calves. Seventy-five beef calves (214 ± 3.2 kg; 200 ± 26 d of age) were housed in a GrowSafe 4000 feed intake facility 7 d post weaning (15 calves/pen). Calves were offered a total mixed ration (TDN = 67.3% and CP = 12.2%, DM = 89%) for ad libitum consumption. On d 0, calves were assigned to 1 of 5 treatments (n = 15 calves/treatment): 1) steers castrated surgically pre-weaning (52 d of age; CON); 2) intact bulls (BULL); 3) bulls castrated by the Callicrate Bander on d 0 (No-Bull Enterprises LLC.; BAN); 4) bulls castrated by the Henderson Castrating Tool on d 0 (Stone Mfg & Supply Co.; HEN); and 5) bulls castrated surgically utilizing an emasculator on d 0 (SUR). Average daily gain, DFI, and DWI were recorded over 84 d. Blood was collected from a sub-sample of calves (n = 45) on d 0, 2, 6, 9, 12, and 15 relative to castration. Castration decreased (P = 0.06) ADG for castrates compared with CON from d 0 to 14 but not d 0 to 84. Daily feed intake and DWI were similar (P > 0.10) among treatments during d 0 to 84. Gain:feed was not affected by castration technique; however, RFI tended (P = 0.09) to be negative for CON and BULL compared with castrates on d 0 to 14 but not d 0 to 84. Acute phase protein analyses indicated that surgical castration (SUR or HEN) elicited a short-term inflammatory response in calves, whereas calves castrated with BAN elicited a delayed response. Calves castrated pre-weaning had improved d 0 to 14 ADG, feed intake, and inflammation response compared with calves castrated at weaning. Banding elicited a delayed negative response in ADG, DWI, and inflammation. In weaned calves, castration method did not affect performance, DFI, DWI, or inflammatory response during the 84-d trial.

Evaluation of two progestogen-based estrous synchronization protocols in yearling heifers of Bos indicus × Bos taurus breeding.

Yearling Bos indicus × Bos taurus heifers (n = 410) from three locations, were synchronized with either the Select Synch/CIDR+timed-AI (SSC+TAI) or 7-11+timed-AI (7-11+TAI) treatments. On Day 0 of the experiment, within each location, heifers were equally distributed to treatments by reproductive tract score (RTS; Scale 1-5: 1 = immature, 5 = estrous cycling) and body condition score. The 7-11+TAI treatment consisted of melengestrol acetate (0.5 mg/head/d) from Days 0 to 7, with PGF(2α) (25 mg im) on Day 7, GnRH (100 µg im) on Day 11, and PGF(2α) (25 mg im) on Day 18. The SSC+TAI heifers received the same carrier supplement (without MGA) from Days 0 to 7, and on Day 11 they were given 100 µg GnRH and an intravaginal CIDR (containing 1.38 g progesterone). The CIDR were removed on Day 18, concurrent with 25 mg PGF(2α) im For both treatments, estrus was visually detected for 1 h twice daily (0700 and 1600 h) for 72 h after PGF(2α), with AI done 6 to 12 h after a detected estrus. Non-responders were timed-AI and received GnRH (100 µg im) 72 to 76 h post PGF(2α). The 7-11+TAI heifers had a greater (P < 0.05) estrous response (55.2 vs 41.9%), conception rate (47.0 vs 31.3%), and synchronized pregnancy rate (33.5 vs 24.8%) compared to SSC+TAI heifers, respectively. Heifers exhibiting estrus at 60 h (61.7%) had a greater (P < 0.05) conception rate compared to heifers that exhibited estrus at ≤ 36 (35.3%), 48 (31.6%), and 72 h (36.2%), which were similar (P > 0.05) to each other. As RTS increased from ≤ 2 to ≥ 3, estrous response, conception rate, synchronized pregnancy rate, and 30 d pregnancy rate all increased (P < 0.05), irrespective of synchronization treatment. In conclusion, the 7-11+TAI treatment yielded greater synchronized pregnancy rates compared to SSC+TAI treatment in yearling Bos indicus × Bos taurus heifers.

Evidence of heterogeneity within bovine satellite cells isolated from young and adult animals.

Satellite cells are a heterogeneous population of myogenic precursors responsible for muscle growth and repair in mammals. The objectives of the experiment were to examine the growth rates and degree of heterogeneity within bovine satellite cells (BSC) isolated from young and adult animals. The BSC were harvested from the semimembranosus of young (4.3 ± 0.5 d) and adult (estimated 24 to 27 mo) cattle and cultured en masse. Young animal BSC re-enter the cell cycle sooner and reach maximal 5-ethynyl-2'-deoxyuridine (EdU) incorporation earlier (P < 0.05) than adult contemporaries. Adult BSC contain fewer (P < 0.05) MyoD and myogenin immunopositive nuclei than BSC isolated from young animals after 3, 4, and 5 d in culture. These results indicate that BSC from young animals activate, proliferate, and differentiate sooner than isolates from adult animals. Lineage heterogeneity within BSC was examined using antibodies specific for Pax7 and Myf5, lineage markers of satellite cells, and myoblasts. Immunocytochemistry revealed the majority of Pax7-expressing BSC also express Myf5; a minor population (~5%) fails to exhibit Myf5 immunoreactivity. The percentage of Pax7:Myf5 BSC from young animals decreases sooner (P < 0.05) in culture than adult BSC, indicating a more rapid rate of muscle fiber formation. A subpopulation immunopositive for Myf5 only was identified in both ages of BSC isolates. The growth kinetics and heterogeneity of young BSC was further evaluated by clonal analysis. Single cell clones were established and analyzed after 10 d. Colonies segregated into 2 groups based upon population doubling time. Immunostaining of the slow-growing colonies (population doubling time ≥ 3 d) revealed that a portion exhibited asymmetric distribution of the lineage markers Pax7 and Myf5, similar to self-renewable mouse muscle stem cells. In summary, these results offer insight into the heterogeneity of BSC and provide evidence for subtle differences between rodent and bovine myogenic precursors.

Effect of dietary cation-anion difference on measures of acid-base physiology and performance in beef cattle.

Dietary constituents can affect cow acid-base physiology and uterine pH. Dietary cation-anion difference (DCAD) has been shown to affect cow acid-base physiology, but the effect on uterine pH has not been demonstrated. The objective of this work was to determine if DCAD [(Na + K + 0.15Ca + 0.15Mg) - (Cl + 0.60S + 0.50P)] could affect cow DMI, acid-base physiology, and uterine pH, and second, to determine if dietary supplements could alleviate any negative effects of DCAD on these variables. In Exp. 1, 21 cows were utilized to determine the effect of a negative DCAD (-0.9 mEq/100 g of DM; low-DCAD) or positive DCAD (+25.0 mEq/100 g of DM; high-DCAD) diet on cow BW, DMI, and pH of blood, urine, and uterine flush fluid. In Exp. 2, 21 cows were randomly allotted to 1 of 3 treatments: control (-3.1 mEq/100 g of DM), molasses (+2.9 mEq/100 g of DM), or molasses+buffer (+25.8 mEq/100 g of DM) to determine if supplemental liquid molasses or liquid molasses with a buffer could alleviate the effects of a negative DCAD, forage-based diet. Cows were individually fed their respective diets for 42 d in both experiments. Cow BW, blood, urine, and uterine flush were collected on d 0, 21, and 42 during both experiments. Cow ADG was not different (P = 0.71) in Exp. 1 or Exp. 2 (P = 0.47). Hay DMI did not differ (P < 0.70) between high-DCAD and low-DCAD cows before d 28, but was greater (P < 0.001) for high-DCAD cows after d 28 in Exp. 1. In Exp. 2, mean hay DMI did not differ (P = 0.39) among treatments. In Exp. 1, a treatment x day interaction (P < 0.05) was apparent for blood, pH, base excess, bicarbonate, pCO(2), and urine pH. Blood gas and pH measures peaked on d 21 for high-DCAD and declined from d 0 to 42 in low-DCAD cows. High-DCAD cows had greater (P = 0.08) uterine flush pH compared with low-DCAD cows. In contrast, during Exp. 2 there were no differences (P > 0.14) among treatments for blood, pH, base excess, pCO(2), or uterine flush pH. Urine pH exhibited a treatment x day interaction (P < 0.0001). On d 21 molasses supplemented cow urine pH was greater (P < 0.0001) than control cows, whereas on d 42 molasses+buffer had greater (P = 0.01) urine pH compared with control and molasses cows. Dietary cation-anion difference and the use of molasses-based supplements had minimal effect on forage-fed beef cow DMI. However, DCAD has the capacity to alter forage-fed beef cow acid-base physiology and potentially affect uterine physiology.

Leucine/glutamic acid/lysine protein 1 is localized to subsets of myonuclei in bovine muscle fibers and satellite cells.

Skeletal muscle growth is accomplished chiefly through the actions of satellite cells, a heterogeneous population that includes the adult muscle stem cell. Located adjacent to a mature muscle fiber, satellite cells typically reside in a quiescent state. Little information exists detailing satellite cell regulation of reversible G(0). One member of the mitosin family of centromere proteins, LEK1 (leucine/glutamic acid/lysine protein 1), is present in the nucleus of nondividing mouse satellite cells. The objective of this study was to evaluate LEK1 as a marker of quiescent bovine satellite cells (BSC) in vitro and in vivo. The BSC were isolated from young bull calves (< or =7 d) and cultured in vitro for up to 9 d before fixation and immunostaining for LEK1. Results demonstrated that all myogenic cells contain the protein, with immunostaining primarily within the nucleus and immediate perinuclear region. Immunocytochemical detection of LEK1 in cryosections of mature cows revealed that the protein was present in a fraction of satellite cells and muscle fiber nuclei. Approximately 20% of Pax7-expressing satellite cells contained LEK1. An equivalent percentage of myonuclei, as defined by nuclei within a dystrophin boundary, contained nuclear LEK1. To gain insight into the functional role of LEK1, BSC were transiently transfected with plasmids coding for putative dominant inhibitory LEK1 proteins [DeltaLEK1(991) and DeltaLEK1(911)] and evaluated for cell proliferation. Both forms of DeltaLEK1 inhibited (P < 0.05) BSC proliferation, as indicated by a decrease in Ki67 immunopositive cells. In C2C12 myoblasts, DeltaLEK1(911) inhibited (P < 0.05) myoblast determination protein 1 (MyoD)-directed muscle gene transcriptional activity; DeltaLEK1(991) had no effect on TnI-Luc transcription. By contrast, both DeltaLEK1 fusion proteins inhibited myogenin expression in BSC without disrupting myoblast fusion. These results provide evidence that LEK1 serves to coordinate proliferation and differentiation in myogenic cells. Coupling the immunostaining pattern and functional data, we propose that LEK1 may serve as a useful marker for satellite cells that are preparing to fuse into adjacent fibers as well as an indicator of recently added myonuclei.

Opportunities to enhance performance and efficiency through nutrient synchrony in forage-fed ruminants.

Increasingly, the need for optimized nutrient utilization to address increasing production costs and environmental considerations will necessitate opportunities to improve nutrient synchrony. Historically, attempts at synchronizing nutrient supply in ruminants, particularly in cattle consuming high-forage diets, have met with variable results. The success of nutrient synchrony has been measured primarily in ruminants by increases in microbial yield, microbial efficiency, nutrient utilization, and to a lesser extent, animal performance. Successful synchrony of nutrient supply to cattle consuming forage-based diets faces several challenges. From a feed supply aspect, the challenges to nutrient synchrony include accurately measuring forage intake and consumed forage chemical composition. The issue of forage intake and chemical composition is perhaps the most daunting for producers grazing cattle. Indeed, for forage-fed cattle, the availability of forage protein and carbohydrate can be the most asynchronous aspect of the diet. In most grazed forages, digestion rates of the carbohydrate fractions are much slower than that of the corresponding protein fractions. Additionally, the forage-supplement interaction exerts a large impact on the synchrony of nutrients. The supplemental feedstuffs compose the component of the nutrient synchrony scenario that is most often manipulated to influence synchrony. The supplement type (e.g., starch vs. fiber, dry vs. liquid), nutrient profile, and degradation rates are often prime considerations associated with nutrient synchrony on high forage diets. Other considerations that warrant attention include temporal intake patterns of the forage and supplement, increased use and types of coproduct supplements, and an assessment of the success of nutrient synchrony. Synchronization of nutrient utilization by forage-fed ruminants has and will continue to encounter challenges for successful outcomes. Ultimately it is the improvement in animal performance and optimization of nutrient utilization efficiency that dictates whether nutrient synchrony is a successful strategy.

Effects of grazing program and subsequent finishing on gene expression in different adipose tissue depots in beef steers.

This experiment was conducted to examine the effects of grazing program and subsequent finishing on gene expression in adipose tissue from steers. Twenty Angus x Angus-Hereford steer calves (initial BW = 231 +/- 25 kg) were allotted randomly to one of two winter grazing treatments: 1) grazing winter wheat pasture to achieve a high rate of BW gain (HGW); or 2) grazing dormant tallgrass native range (NR). Steers in the NR treatment were provided 0.91 kg.steer(-1).d(-1) of a 41% CP (as-fed basis) cottonseed meal supplement. Following the grazing period, steers were assigned randomly to feedlot pens. Steers were fed to a common endpoint of 1.27 cm of backfat between the 12th and 13th rib. Four steers from each treatment were slaughtered at the end of the grazing period, and the remaining steers from each treatment (n = 6) were slaughtered at the predetermined compositional endpoint. Intramuscular and s.c. fat samples were collected from LM sections of each steer at the 12th-/13th-rib interface on the left side. Pools of RNA were prepared for HGW and NR s.c. adipose tissue from steers slaughtered immediately after grazing. Suppression subtractive hybridization was performed followed by dot-blot hybridization screening to confirm differential expression of subtracted transcripts. Transcripts confirmed to be differentially expressed were subjected to dideoxy chain-termination sequencing. Quantitative reverse transcription PCR was performed on three differentially expressed clones: osteonectin, ferritin heavy chain, and decorin. Osteonectin, ferritin heavy chain, and decorin gene expression was greater (P < 0.05) in s.c. than in i.m. adipose tissue of finished steers. A depot x background interaction for osteonectin (P < 0.01) and ferritin heavy chain (P = 0.03) gene expression was observed for steers slaughtered after grazing, indicating that nutritional management can affect gene expression in adipose tissue depots differently. No differences resulting from prefinishing nutritional background (HGW or NR) were noted in osteonectin, ferritin heavy chain, or decorin gene expression in i.m. adipose tissue collected from finished steers, which might have resulted from feeding steers to the same compositional endpoint. Our data suggest that nutritional background alters gene expression in adipose depots, and that depots are influenced differently.

Effect of live weight gain of steers during winter grazing: III. Blood metabolites and hormones during feedlot finishing.

Two experiments were conducted using 48 Angus x Angus-Hereford steers in each experiment to determine the effect of previous winter grazing BW gain on jugular concentrations of metabolites and hormones during feedlot finishing. In each experiment, steers were randomly assigned to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range (NR) with 0.91 kg/d of a 41% CP (DM basis) supplement. Steers grazed for 120 or 144 d in Exp. 1 and 2, respectively. Plasma and serum were collected from all steers before placement into a feedlot, and six or seven times during finishing in Exp. 1 and 2, respectively. In Exp. 1, before steers entered the feedlot, concentrations of insulin, triiodothyronine (T3), and thyroxine (T4) were greater (P < 0.05) in HGW than in LGW or NR steers, and concentrations of IGF-I and plasma urea-N were greater (P < 0.05) in steers that grazed wheat pasture than in NR steers. In Exp. 2, concentrations of glucose, T3, T4, and IGF-I were greater (P < 0.05) in steers that grazed wheat pasture than NR steers. In Exp. 1 (P < 0.19) and 2 (P < 0.86), glucose concentration did not differ among treatments during finishing. In Exp. 1, insulin concentration across days on feed was greater for HGW than LGW steers, which were greater than for NR steers (treatment x day interaction, P < 0.03). In Exp. 2, insulin concentration increased (P < 0.001) as days on feed increased. Concentrations of IGF-I were greater in steers that had grazed wheat pasture, whereas the increase in IGF-I with increasing days on feed was greater for NR steers (treatment x day interaction, P < 0.003). Concentrations of T3 and T4 during finishing were greater (P < 0.001) in HGW and LGW than in NR steers in Exp. 1. In Exp. 2, T4 concentration also differed (P < 0.009) among treatments (HGW > LGW > NR). In Exp. 2, final concentration of glucose was greater (P < 0.01) in NR than in HGW and LGW steers, and serum insulin concentration was greater (P < 0.04) in NR than LGW steers. Final concentrations of T3 (P < 0.01) and T4 (P < 0.004) were greater in NR than in HGW steers. Our data show that previous BW gain can affect blood metabolites and hormones in steers entering the feedlot. However, lower concentrations of T3, T4, and IGF-I in steers when they entered the feedlot did not inhibit the growth response of previously restricted steers.

Effect of live weight gain of steers during winter grazing: II. Visceral organ mass, cellularity, and oxygen consumption.

Two experiments were conducted to examine the effect of BW gain during winter grazing on mass, cellularity, and oxygen consumption of splanchnic tissues before and after the feedlot finishing phase. In each experiment, 48 fall-weaned Angus x Angus-Hereford steer calves were assigned randomly to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range supplemented with 0.91 kg/d of a 41% CP supplement (NR). At the end of winter grazing, four steers were selected randomly from each treatment for initial slaughter to measure organ mass, cellularity, and oxygen consumption. All remaining steers were placed into a feedlot and fed to the same backfat end point (1.27 cm). Six steers were selected randomly from each treatment for final organ mass, cellularity, and oxygen consumption. Initial empty BW (EBW) was greatest (P < 0.001) for HGW, intermediate for LGW, and least for NR steers in both Exp. 1 and 2 (355 > 263 > 207 +/- 6.5 kg and 337 > 274 > 205 +/- 8.7 kg, respectively). For both experiments, the initial total gastrointestinal tract (GIT; g/kg of EBW) proportional weight was greater (P < 0.05) in NR steers than in LGW, and LGW steers had greater (P < 0.05) initial GIT proportional weight than HGW steers. Proportional weight of total splanchnic tissues (TST; g/kg of EBW) did not differ (P < 0.19) among treatments. Initial duodenal RNA concentration and RNA:protein were greater (P < 0.02) in LGW than in HGW steers, and NR steers were intermediate. Initial in vitro liver O2 consumption was greater (P < 0.09) in HGW and LGW than in NR steers (34.5 > 16.9 mL/min), whereas initial small intestinal oxygen consumption was greater (P < 0.01) in LGW than in HGW and NR steers (12.1 > 5.2 mL/min). Ruminal papillae oxygen consumption did not differ (P < 0.55) among treatments. The rate of decrease of GIT (g x g EBW(-1) x d(-1)) during finishing was greater in NR than in HGW and LGW steers in both Exp. 1 and 2, but mesenteric fat (g x g EBW(-1) x d(-1)) increased for NR steers, resulting in a similar (P < 0.75) increase in TST across the finishing period for all treatments. Similar rates of increase in TST across the finishing phase corresponded with similar rates of live and carcass weight gain among treatments. Our data support the hypothesis that increased visceral organ mass increases maintenance energy requirements of growing cattle.

Effect of live weight gain of steers during winter grazing: I. Feedlot performance, carcass characteristics, and body composition of beef steers.

Two experiments were conducted to examine the effect of previous BW gain during winter grazing on subsequent growth, carcass characteristics, and change in body composition during the feedlot finishing phase. In each experiment, 48 fall-weaned Angus x Angus-Hereford steer calves were assigned randomly to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range (NR) supplemented with 0.91 kg/d of cottonseed meal. Winter grazing ADG (kg/d) for HGW, LGW, and NR steers were, respectively, 1.31, 0.54, 0.16 (Exp. 1) and 1.10, 0.68, 0.15 (Exp. 2). At the end of winter grazing, four steers were selected randomly from each treatment to measure initial carcass characteristics and chemical composition of carcass, offal, and empty body. All remaining steers were fed a high-concentrate diet to a common backfat end point. Six steers were selected randomly from each treatment for final chemical composition, and carcass characteristics were measured on all steers. Initial fat mass and proportion in carcass, offal, and empty body were greatest (P < 0.001) for HGW, intermediate for LGW, and least for NR steers in both experiments. Live BW ADG and gain efficiency during the finishing phase did not differ (P = 0.24) among treatments, but DMI (% of mean BW) for NR and LGW was greater (P < 0.003) than for HGW steers. Final empty-body composition did not differ (P = 0.25) among treatments in Exp. 1. In Exp. 2, final carcass and empty-body fat proportion (g/kg) was greater (P < 0.03) for LGW and NR than for HGW steers. Accretion of carcass fat-free organic matter was greater (P < 0.004) for LGW than for HGW and NR steers in Exp. 1, but did not differ (P = 0.22) among treatments in Exp. 2. Fat accretion in carcass, offal, and empty body did not differ (P = 0.19) among treatments in Exp. 1, but was greater (P < 0.05) for LGW and NR than for HGW steers in Exp. 2. Heat production by NR steers during finishing was greater (P < 0.02) than by HGW steers in Exp. 1 and 2. Differences in ADG during winter grazing and initial body fat content did not affect rate of live BW gain or gain efficiency during finishing. Feeding steers to a common backfat thickness end point mitigated initial differences in carcass and empty-body fat content. However, maintenance energy requirements during finishing were increased for nutritionally restricted steers that were wintered on dormant native range.

Effect of the live weight gain of steers during winter grazing on digestibility, acid-base balance, blood flow, and oxygen consumption by splanchnic tissues during adaptation and subsequent feeding of a high-grain diet.

Ten multicatherized steers were used in a completely random design to determine the effect of previous BW gain on blood flow, acid-base balance, and oxygen consumption across portal-drained viscera and liver of growing beef steers fed a high-grain diet. Treatments were high (1.31 +/- 0.09 kg/d) or low (0.68 +/- 0.07 kg/d) daily BW gain during an 82-d winter wheat pasture grazing period and a subsequent 37-d transition period. Blood flow, blood gas measurements, and oxygen consumption were determined on d 0, 14, 28, 42, and 64 of a high-grain finishing period. Compensatory growth was evident in low-gain steers; ADG (1.50 vs. 1.11 kg/d, P < 0.05) and gain efficiency (0.221 vs. 0.109 kg/kg, P < 0.01) were greater from d 14 through 28 than for high-gain steers. Arterial base tended (P < 0.12) to be greater in low-gain than in high-gain steers, whereas calculated HCO3- (mmol/L; P < 0.20) did not differ between treatments. Arterial O2 concentration was not different (P < 0.97) between treatments but increased (P < 0.001) with increasing days on feed. Portal blood flow increased with days on feed (P < 0.001) but did not differ (P < 0.34) between treatments. Hepatic blood flow scaled to metabolic BW was 19.7% greater (P < 0.02) in low-gain than in high-gain steers. Across the feeding period, O2 consumption and CO2 flux by PDV, liver, and total splanchnic tissue (TST) did not differ (P < 0.33) between treatments. However, TST O2 consumption (mmol/[h x kg BW(0.75)]) tended (P < 0.12) to be greater in low- than in high-gain steers. Compensating steers' arterial blood acid-base measurements did not change with days on feed, indicating that they were not more susceptible to metabolic acidosis than high-gain steers. However, steers that had lower BW gain before high-grain feeding exhibited increased hepatic blood flow and TST O2 consumption (metabolic BW basis) during the finishing period compared with high-gain steers. Greater hepatic blood flow and energy expenditure by TST of previously restricted steers might have facilitated compensatory growth.

Evaluation of berseem clover in diets of ruminants consuming corn crop residues.

Berseem clover hay was compared to alfalfa hay provided at 0, 25, and 50% of the diet DM in mixtures with corn crop residues to wether lambs. Berseem clover hay had lower (P < .05) concentrations of NDF, ADF, and CP than alfalfa hay. The digestibility of DM, DMI, and N balance did not differ (P > .05) between diets containing alfalfa hay or berseem clover hay. To evaluate stockpiled berseem clover as a supplement for grazed corn crop residues, berseem clover and oats were incorporated into a corn-corn-oat/berseem clover crop rotation for 3 yr in replicated 6.1-ha fields. Two cuttings of oat-berseem clover hay were harvested each summer before forage was stockpiled for winter grazing. After corn grain harvest, multiparous and primiparous crossbred cows in midgestation were allotted to each field at 1.01 ha/cow to strip-graze corn crop residues with or without stockpiled berseem clover or allocated to replicated drylots for 98 to 140 d. Each group was offered alfalfa-grass hay as large bales to maintain a mean body condition score of 5 on a 9-point scale. Mean rates of total and digestible OM disappearance from grazed and ungrazed field areas of berseem clover and corn crop residues did not differ over the 3 yr. In vitro organic matter disappearance (IVOMD) tended to decrease more rapidly (P = .13) and NDF and ADF concentrations increased more rapidly (P < .05) in berseem clover than in corn crop residues. Seasonal BW change did not differ (P > .05) between winter management systems in any year, and seasonal body condition score changes did not differ (P > .05) between cows grazing corn crop residues and berseem clover and those maintained in a drylot in yr 2 and 3. Cows grazing corn crop residues with or without berseem clover required less (P < .05) hay than those maintained in drylot. Although the effects of berseem clover hay supplementation on the intake and digestibility of corn crop residues do not differ from alfalfa hay, the nutritional value of stockpiled berseem clover decreases rapidly during winter, limiting its value as a standing supplement for corn crop residues in late winter.