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This study examined effects of stage of gestation and nutrient restriction with subsequent realimentation on maternal and foetal bovine pancreatic function. Dietary treatments were assigned on day 30 of pregnancy and included: control (CON; 100% requirements; n = 18) and restricted (R; 60% requirements; n = 30). On day 85, cows were slaughtered (CON, n = 6; R, n = 6), remained on control (CC; n = 12) and restricted (RR; n = 12), or realimented to control (RC; n = 11). On day 140, cows were slaughtered (CC, n = 6; RR, n = 6; RC, n = 5), remained on control (CCC, n = 6; RCC, n = 5) or realimented to control (RRC, n = 6). On day 254, the remaining cows were slaughtered and serum samples were collected from the maternal jugular vein and umbilical cord to determine insulin and glucose concentrations. Pancreases from cows and foetuses were removed, weighed, and subsampled for enzyme and histological analysis. As gestation progressed, maternal pancreatic α-amylase activity decreased and serum insulin concentrations increased (p ≤ 0.03). Foetal pancreatic trypsin activity increased (p

We hypothesized that maternal nutrition and day of gestation would impact utero-placental mRNA expression of the nutrient transporters GLUT1, GLUT5, CAT-1, CAT-2, and CAT-3 in beef heifers. Crossbred Angus heifers (n = 49) were estrous synchronized, bred via AI, assigned to nutritional treatment (CON = 100% of NRC requirements for 0.45 kg/d gain and RES = 60% of CON) and ovariohysterectomized on d 16, 34, or 50 of gestation (n = 6 to 9/d); Non-bred, non-pregnant (NB-NP) controls were fed the CON diet, not bred, and were ovariohysterectomized on d 16 of the synchronized estrous cycle (n = 6). The resulting arrangement of treatments was a 2 × 3 factorial + 1 (CON vs. RES × d 16, 34, or 50 + NB-NP controls). Caruncle (CAR), intercaruncular endometrium (ICAR), and fetal membranes (FM [chorioallantois]), were obtained from the pregnant uterine horn (the uterine horn containing the conceptus) immediately after ovariohysterectomy. On d 50 cotyledons (COT), intercotyledonary placenta (ICOT) and amnion (AMN) were also collected. Relative expression of nutrient transporters was determined for each tissue utilizing NB-NP-CAR and NB-NP-ICAR tissues as the baseline. For FM, NB-NP endometrium served as the baseline. There was no interaction of day × treatment (P ≥ 0.20) for any genes in CAR. However, CAR expression of GLUT1 was greater (P < 0.01) on d 16 compared with d 34 and 50, and GLUT5, CAT-1, and CAT-2 were greater (P ≤ 0.05) on d 34 compared with d 16 and 50. In ICAR, CAT-2 was the only gene to be influenced by the day × treatment interaction (P = 0.01), being greater in d 50 CON compared with d 34 CON and d 16 and 50 RES. In ICAR, expression of GLUT1 was greater (P < 0.01) on d 16 compared with d 34, and expression of CAT-1 was greater (P < 0.01) on d 34 and 50 compared with d 16. In FM, expression of GLUT5 was greater (P = 0.04) on d 16 compared with d 50 of gestation, and expression of CAT-1 was greater (P < 0.01) on d 34 and 50 compared with d 16. On d 50, expression of GLUT1, CAT-1, and CAT-3 expression were all greater (P < 0.05) in AMN compared with COT and ICOT, and expression of GLUT5 was greater (P < 0.01) in ICOT compared with COT and AMN. These data indicate that day was a more influential factor for mRNA expression of utero-placental glucose and cationic AA transporters than maternal nutritional status in heifers during early pregnancy.

We hypothesized that both day of gestation and maternal nutrition would alter the relative mRNA expression of neutral and acid AA transporters , , , , and . Crossbred Angus heifers ( = 49) were synchronized, bred via AI, assigned to nutritional treatment (100% of NRC requirements for 0.45 kg/d gain [control heifers {CON}] and 60% of CON [restricted heifers {RES}]), and ovariohysterectomized on d 16, 34, or 50 of gestation ( = 6 to 9/d). Nonbred, nonpregnant (NB-NP) controls were ovariohysterectomized on d 16 of the estrous cycle ( = 6) after synchronization. The resulting arrangement was a 2 × 3 factorial + 1 (CON vs. RES × d 16, 34, or 50 + NB-NP controls). Tissues collected included caruncular endometrium (CAR), intercaruncular endometrium (ICAR), fetal membranes (FM; chorioallantois; d 16 and 34), cotyledonary placenta (COT; d 50 only), intercotyledonary placenta (ICOT; d 50 only), and amnion (AMN; d 50 only]). Relative expression of , , , , and was determined for each tissue using NB-NP CAR and NB-NP ICAR tissues for the baseline; for FM, endometrium from NB-NP controls served as the baseline. In CAR, no day × treatment interaction was observed (0.05). However, day of gestation affected relative expression of , where expression on d 16 was greater (0.01) than expression on d 34 and 50. Additionally, relative expression of and was greater ( ≤ 0.05) in pregnant heifers compared with NB-NP heifers. For ICAR, was influenced by a day × treatment interaction (0.01), where expression in d 16 RES was greater ( ≤ 0.05) than that of any other day or nutritional treatment. Furthermore, expression in d 16 CON was greater ( ≤ 0.05) than that in d 50 RES, with those in d 34 CON and RES and d 50 CON being intermediate. In addition, was affected by day of gestation, where expression on d 16 was greater (0.01) than that on d 34 and 50. A day × treatment interaction was not observed (0.05) in FM; however, expression on d 34 was greater ( = 0.02) than on d 50, with that on d 16 being intermediate. Day of gestation also affected expression of , where expression on d 34 and 50 was greater (0.01) than that on d 16. These data support our hypothesis in that both day of gestation and maternal nutrition affected the relative mRNA expression of AA transporter in ICAR, whereas day of gestation has a greater effect on the relative mRNA expression of other neutral and acidic AA transporters in the various tissues studied.

We hypothesized that a standing flank ovariohysterectomy procedure could be developed in beef heifers that would provide high quality tissues for addressing critical questions during early pregnancy, while concomitantly keeping livestock stewardship a high priority. To test the hypothesis, we: 1) developed a standing flank ovariohysterectomy procedure for use in beef heifers, and 2) implemented this procedure in a cohort of heifers up to d 50 of pregnancy for tissue collections, documentation of post-surgical recovery, and assessment of feedlot finishing performance. Ovariectomy and cesarean section protocols are well established in research and veterinary medicine and were used as starting points for procedural development. Crossbred Angus heifers ( = 46; ∼ 15 mo of age; BW = 362.3 ± 34.7 kg) were used to develop this new surgical tissue collection technique. Heifers were subjected to the 5-d CO-Synch + CIDR estrous synchronization protocol so ovariohysterectomy occurred at d 16, 22, 28, 34, 40, and 50 of gestation. Key aspects of the standing flank ovariohysterectomy technique included 1) use of local anesthetic for a standing flank incision, 2) locate the uterine and ovarian arteries via blind palpation and ligate them through the broad ligament via an improved clinch knot, 3) cut the ovaries and uterus free from the broad ligament, 4) ligate the cervix and uterine branch of the vaginal artery, and 5) cut through the cervix and remove the reproductive tract. Surgical times, from skin incision to placement of the last suture, were influenced ( = 0.04) by stage of gestation. In pregnant heifers, time decreased from d 22 (120.0 ± 12.0 min) of gestation to d 40 (79.5 ± 12.0 min) of gestation; then increased at d 50 (90.5 ± 14.7 min) of gestation. Using this procedure, we obtained uterine, placental, and embryo/fetal tissues that had experienced limited hypoxia, little or no trauma, and thus were excellent quality for scientific study. All heifers recovered from surgery quickly and were moved to a finishing period. During the finishing period, ovariohysterectomized heifers had a DMI of 13.8 kg, gained 1.99 ± 0.35 kg/d, and had a G:F of 0.145 over 132-d. The standing flank ovariohysterectomy technique represents a new and viable model to economically obtain high quality tissues for investigating critical biological mechanisms during early pregnancy in beef heifers.

Glucose transporter solute carrier family 2 member 14 () is a duplicon of glucose transporter solute carrier family 2 member 3 () with a 95% shared homology to and has not previously been isolated in ruminant uteroplacental tissues. The transporter has been previously isolated in Holstein heifer uterine epithelium but not in ovine epithelium. We hypothesized that and its duplicon would be found in bovine uteroplacental tissues and that maternal nutrition and day of gestation would impact mRNA expression of and . Crossbred Angus heifers ( = 49) were estrus synchronized, bred via AI, and assigned to nutritional treatment (CON = 100% of requirements to gain 0.45 kg/d; RES = 60% of CON) at breeding. Ovariohysterectomy was performed on d 16, 34, or 50 of gestation ( = 6 to 9/d); nonpregnant (NP) controls were not bred and ovariohysterectomized on d 16 of the synchronized estrous cycle ( = 6). The resulting treatment arrangement was a 2 × 3 factorial + 1. Uteroplacental tissues (caruncle, CAR; intercaruncular endometrium, ICAR; and fetal membrane [chorioallantois], FM) were obtained from the pregnant uterine horn immediately after ovariohysterectomy. For NP controls, only CAR and ICAR were obtained. There were no day × treatment interactions for or gene expression in CAR, ICAR, or FM. Expression of in CAR was greater ( = 0.03) on d 50 compared with d 16. In ICAR, was greatest ( = 0.02) on d 50 compared with d 16 and 34 of gestation. In FM, was greater ( = 0.04) on d 16 compared with d 50. Expression of was greater ( = 0.05) in pregnant compared with nonpregnant heifers. Additionally, expression of was greater ( = 0.01) on d 34 and 50 compared with d 16. Expression of in CAR was greater ( = 0.03) on d 50 compared to d 16 and 34. In CAR, tended ( = 0.07) to be greater on d 34 and 50 than on d 16 and was greater ( = 0.02) on d 50 than on d 34. There was no effect of treatment for either or in CAR, ICAR, or FM. These data demonstrate that glucose transporters and are expressed in beef heifer uteroplacental tissues and that they are expressed differentially by day of gestation in bovine uteroplacental tissues.

During early gestation, nutrients are transported to the developing embryo via transporters in the uterine endometrium and chorioallantois. In the present study, we examined glucose transporters and and the cationic AA transporters , , and to test the hypotheses that 1) relative mRNA expression of transporters would be different among uteroplacental tissue type as gestation progresses and 2) concentrations of glucose and cationic AA would be different among target sites (placental compartments, serum, and histotrophic) and days of gestation. To test these hypotheses, crossbred Angus heifers ( = 46) were synchronized, bred via AI, and then ovariohysterectomized on d 16, 22, 28, 34, 40, or 50 of gestation (5 to 9/d) or not bred and ovariohysterectomized on d 16 of the synchronized estrous cycle ( = 7) to serve as nonpregnant (NP) controls. Uteroplacental tissues (maternal caruncle [CAR], intercaruncular endometrium [ICAR], and fetal membranes [FM; chorioallantois, d 22 and later]) were collected from the uterine horn ipsilateral to the corpus luteum immediately following ovariohysterectomy. Relative mRNA expression of the glucose transporters and cationic AA transporters was determined for each tissue from d 16 to 50 of gestation and from NP controls. Chorioallantoic, amniotic, and plasma fluids were collected from heifers on d 40 and 50 of gestation to determine concentrations of glucose and cationic AA. Expression of and showed a tendency (0.10) toward being greater in d 16 ICAR and d 34 ICAR, respectively. Day × tissue interactions (0.05) were present for , , and . Expression of was greater in d 50 CAR, expression of was greater on d 34 in ICAR, and expression of was greater in CAR tissue on d 34 compared with all other tissues and days of gestation. Glucose concentrations tended ( = 0.10) to be impacted by a day × fluid interaction. A day × fluid interaction ( = 0.01) for arginine concentration was observed, with greater concentrations in allantoic fluid on d 40 compared with all other days and fluid types. These data support our hypothesis that glucose and cationic AA transporters differ in their level of mRNA expression due to day of gestation and uteroplacental tissue type. In addition, concentrations of nutrients were differentially impacted by day, target site, and/or their respective interaction.

Endogenous retroviral gene elements have been implicated in development and formation of the feto-maternal interface. A variant of the syncytin endogenous retroviral envelope gene family, , was recently found in ruminants. We hypothesized that mRNA would be differentially expressed in utero-placental tissues and would fluctuate during key time points of early gestation in beef heifers. Commercial Angus crossbred heifers ( = 46; ∼15 mo of age; BW = 362.3 ± 34.7kg) housed in 6-animal pens were fed daily with native grass hay and supplemented with cracked corn to gain 0.3 kg/d. The heifers were estrus synchronized, artificially inseminated, (d of breeding= d 0) and ovariohysterectomized on d 16, 22, 28, 34, 40, and 50 ( = 9, 6, 6, 7, 6, and 5, respectively) of gestation and at d 16 of the estrous cycle for non-bred, non-pregnant controls (NP; = 7). Harvested tissues were separated into maternal caruncle (CAR), intercarunclar endometrium (ICAR), and fetal membranes, (FM; chorioallantois, d 22 and later). All tissues were obtained from the ipsilateral uterine horn to the CL. Statistical analyses were conducted via the GLM procedure of SAS. Maternal CAR expression of was greater ( = 0.003) on d 50 by 81.5-fold compared to NP controls. At d 50 expression of in CAR was 190.3-fold greater than (0.0001) ICAR. Fetal membranes had greater (0.002) expression of from d 22 until d 50 of gestation compared to maternal ICAR (d 16 not analyzed). Expression of in FM was greater (0.004) than in CAR until d 40 of gestation. Therefore, we conclude that is differentially expressed in utero-placental tissues and may be involved in the establishment of pregnancy. The expression of in maternal tissues is completely novel and indicates unique functions of syncytin in ruminant pregnancy.

Four ruminally and duodenally cannulated Holstein steers (BW = 449 ± 7.3 kg) were used to examine the effects of feeding either dried distiller's grains plus solubles (DG) or grass hay on alternate days (every other day) on intake, ruminal fermentation and passage rates, and serum NEFA in forage-fed steers. Steers were assigned to 1 of 4 dietary treatments in a 4 × 4 Latin square: 1) only hay (CON), 2) hay and 0.4% of BW as DG DM daily (DG7), 3) hay daily and 0.8% BW DG every other day (DG2), and 4) alternate day feeding of hay and 0.8% of BW as DG (DGA). Treatment periods consisted of 13 d of adaptation and 8 d of collecting digesta and blood. Over the entire collection period, DMI was decreased ( = 0.004) for DGA compared with other treatments (13.0 ± 0.8, 12.7 ± 0.8, 13.3 ± 0.8, and 10.9 ± 0.8 kg/d for CON, DG7, DG2, and DGA, respectively). Immediately after feeding on days supplement was fed to DG2 and DGA (supplemented days [SUP]), ruminal pH of DGA was less than other treatments but by the end of the day was greater than other treatments (treatment × time,0.001). At feeding time on nonsupplemented days (NSUP), ruminal pH of DGA steers was greater than other treatments but was similar (treatment × time,0.001) to DG2 and CON by 5 h after feeding. Total concentrations of VFA were similar ( = 0.09) among treatments on SUP; however, on NSUP, total VFA concentrations were least in DGA from feeding until 4 h after feeding (treatment × time, = 0.02). No differences ( ≥ 0.06) were observed among treatments for apparent ruminal, total intestinal, and total tract DM, OM, or CP digestibility. There were no differences ( = 0.36) in serum NEFA among treatments on SUP; however, on NSUP, steers fed DGA (209.5 ± 12.7 m) had greater (0.01) NEFA compared with other treatments (84.4 ± 12.7, 88.0 ± 12.7, and 77.7 ± 12.7 m for CON, DG7, and DG2, respectively). The DGA feeding strategy influenced DMI and ruminal kinetics and circulating NEFA without impacting total tract digestibility.

Four ruminally and duodenally cannulated crossbred beef steers (397+/-55 kg initial BW) were used in a 4 x 4 Latin square to evaluate the effects of increasing level of field pea supplementation on intake, digestion, microbial efficiency, ruminal fermentation, and in situ disappearance in steers fed moderate-quality (8.0% CP, DM basis) grass hay. Basal diets, offered ad libitum twice daily, consisted of chopped (15.2-cm screen) grass hay. Supplements were 0, 0.81, 1.62, and 2.43 kg (DM basis) per steer daily of rolled field pea (23.4% CP, DM basis) offered in equal proportions twice daily. Steers were adapted to diets on d 1 to 9; on d 10 to 14, DMI were measured. Field pea and grass hay were incubated in situ, beginning on d 10, for 0, 2, 4, 8, 12, 16, 24, 36, 48, 72, and 96 h. Ruminal fluid was collected and pH recorded at -2, 0, 2, 4, 6, 8, 10, and 12 h after feeding on d 13. Duodenal samples were taken for three consecutive days beginning on d 10 in a manner that allowed for a collection to take place every other hour over a 24-h period. Linear, quadratic, and cubic contrasts were used to evaluate the effects of increasing field pea level. Total DMI and OMI increased quadratically (P = 0.09), whereas forage DMI decreased quadratically (P = 0.09) with increasing field pea supplementation. There was a cubic effect (P0.001) for ruminal pH. Ruminal (P = 0.02) and apparent total-tract (P = 0.09) NDF disappearance decreased linearly with increasing field pea supplementation. Total ruminal VFA concentrations responded cubically (P = 0.008). Bacterial N flow (P = 0.002) and true ruminal N disappearance (P = 0.003) increased linearly, and apparent total-tract N disappearance increased quadratically (P = 0.09) with increasing field pea supplementation. No treatment effects were observed for ruminal DM fill (P = 0.82), true ruminal OM disappearance (P = 0.38), apparent intestinal OM digestion (P = 0.50), ruminal ADF disappearance (P = 0.17), apparent total-tract ADF disappearance (P = 0.35), or in situ DM disappearance of forage (P = 0.33). Because of effects on forage intake and ruminal pH, field peas seem to act like cereal grain supplements when used as supplements for forage-based diets. Supplementing field peas seems to effectively increase OM and N intakes of moderate-quality grass hay diets.

We hypothesized that gestational nutrition would affect calf feed efficiency and small intestinal biology, which would be correlated with feed efficiency. Multiparous beef cows (n = 36) were individually fed 1 of 3 diets from d 45 to 185 of gestation: native grass hay and supplement to meet NRC recommendations (control [CON]), 70% of CON NEm (nutrient restricted [NR]), or a NR diet with a RUP supplement (NR+RUP) to provide similar essential AA as CON. After d 185 of gestation, cows were managed as a single group, and calf individual feed intake was measured with the GrowSafe System during finishing. At slaughter, the small intestine was dissected and sampled. Data were analyzed with calf sex as a block. There was no effect (P ≥ 0.33) of maternal treatment on residual feed intake, G:F, DMI, ADG, or final BW. Small intestinal mass did not differ (P ≥ 0.38) among treatments, although calf small intestinal length tended (P = 0.07) to be greater for NR than NR+RUP. There were no differences (P ≥ 0.20) in calf small intestinal density or jejunal cellularity, proliferation, or vascularity among treatments. Jejunal soluble guanylate cyclase mRNA was greater (P0.03) for NR+RUP than CON and NR. Residual feed intake was positively correlated (P ≤ 0.09) with small intestinal mass and relative mass and jejunal RNA content but was negatively correlated (P ≤ 0.09) with jejunal mucosal density and DNA concentration. Gain:feed was positively correlated (P ≤ 0.09) with jejunal mucosal density, DNA, protein, and total cells and was negatively correlated (P ≤ 0.05) with small intestinal relative mass, jejunal RNA, and RNA:DNA. Dry matter intake was positively correlated (P ≤ 0.09) with small intestinal mass, relative mass, length, and density as well as jejunal DNA and protein content, total cells, total vascularity, and kinase insert domain receptor and endothelial nitric oxide synthase 3 mRNA and was negatively correlated (P = 0.02) with relative small intestinal length. In this study, calf performance and efficiency during finishing as well as most measures of small intestinal growth were not affected by maternal nutrient restriction during early and midgestation. Results indicate that offspring small intestinal gene expression may be affected by gestational nutrition even when apparent tissue growth is unchanged. Furthermore, small intestinal size and growth may explain some variation in efficiency of nutrient utilization in feedlot cattle.

The objectives were to evaluate the effects of nutrient restriction during early to midgestation followed by realimentation on maternal performance and organ mass in pregnant beef cows. On d 30 of pregnancy, multiparous, nonlactating cows (initial BW = 620.5 ± 11.3 kg and BCS = 5.1 ± 0.1) were assigned to 1 of 3 dietary treatments: control (CON; 100% NRC; n = 18) and restricted (RES; 60% NRC; n = 30). On d 85, cows were slaughtered (CON, n = 6; R, n = 6), remained on control (CC; n = 12) and restricted (RR; n = 12), or were realimented to control (RC; n = 11). On d 140, cows were slaughtered (CC, n = 6; RR, n = 6; RC, n = 5), remained on control (CCC, n = 6; RCC, n = 5), or were realimented to control (RRC, n = 6). On d 254, all remaining cows were slaughtered. Cows were weighed before slaughter and all maternal organs were dissected and weighed. The diet consisted of grass hay to meet 100 or 60% NEm recommendations for fetal growth and to meet or exceed recommendations for other nutrients. At d 85 slaughters, BW and empty BW (EBW) were not affected (P ≥ 0.84) by maternal nutrition. However back fat was decreased (P = 0.05) in RES vs. CON cows. Large intestine and abomasum mass were increased (P ≤ 0.05) in RES cows vs. CON. At d 140, BW was decreased (P = 0.05) and EBW tended to be decreased (P = 0.10) in RRC cows vs. CCC and RCC being intermediate. Liver mass was decreased (P = 0.02) in RR vs. CC with RC being intermediate. Ruminal mass was decreased (P = 0.003) in RR vs. CC and RC cows. At d 254, BW and EBW were similar (P ≥ 0.78) across treatments. We observed partial changes in maternal weight and organ masses due to different lengths of maternal nutrient restriction followed by realimentation. It appears that the dam undergoes some adaptations during an early to midgestation nutrient restriction and becomes more efficient in the utilization of nutrients after being realimented and as gestation advances.

Interannual variation of forage quantity and quality driven by precipitation events influence beef livestock production systems within the Southern and Northern Plains and Pacific West, which combined represent 60% (approximately 17.5 million) of the total beef cows in the United States. The beef cattle requirements published by the NRC are an important tool and excellent resource for both professionals and producers to use when implementing feeding practices and nutritional programs within the various production systems. The objectives of this paper include evaluation of the 1996 Beef NRC model in terms of effectiveness in predicting extensive range beef cow performance within arid and semiarid environments using available data sets, identifying model inefficiencies that could be refined to improve the precision of predicting protein supply and demand for range beef cows, and last, providing recommendations for future areas of research. An important addition to the current Beef NRC model would be to allow users to provide region-specific forage characteristics and the ability to describe supplement composition, amount, and delivery frequency. Beef NRC models would then need to be modified to account for the N recycling that occurs throughout a supplementation interval and the impact that this would have on microbial efficiency and microbial protein supply. The Beef NRC should also consider the role of ruminal and postruminal supply and demand of specific limiting AA. Additional considerations should include the partitioning effects of nitrogenous compounds under different physiological production stages (e.g., lactation, pregnancy, and periods of BW loss). The intent of information provided is to aid revision of the Beef NRC by providing supporting material for changes and identifying gaps in existing scientific literature where future research is needed to enhance the predictive precision and application of the Beef NRC models.

Three studies were conducted to evaluate the feasibility of field peas as a protein source in diets for beef cattle. In the first study, 4 cultivars of field pea were incubated in situ to determine rate and extent of CP disappearance. Results indicate that field pea cultivars vary in CP content (22.6, 26.1, 22.6, and 19.4%, DM basis for Profi, Arvika, Carneval, and Trapper, respectively). Soluble protein fraction ranged from 34.9% for Trapper to 54.9% for Profi. Degradable CP fraction was greater (P = 0.01) for Trapper compared with the other cultivars, and no differences (P ≥ 0.25) were observed among Profi, Arvika, and Carneval. Rate of CP degradation differed (P ≤ 0.03) for all cultivars, with Profi being the greatest and Trapper the smallest (10.8, 10.0, 8.1, and 6.3 ± 1.4%/h for Profi, Carneval, Arvika, and Trapper, respectively). Estimated RDP was not different (P = 0.21) for all 4 cultivars. In the second study, 30 crossbred beef steers (301 ± 15 kg) were individually fed and used to evaluate effects of field pea processing (whole, rolled, or ground) on steer performance. Diets contained 40% field pea grain. Growing steers consuming whole field pea had greater ADG (P = 0.08) than those consuming processed field pea (1.69, 1.52, and 1.63 ± 0.05 kg/d, for whole, rolled, and ground, respectively). However, DMI (kg/d and as % of BW) and G:F were not different (P ≥ 0.24). In the third study, 35 individually fed gestating beef cows (694 ± 17 kg) were used to evaluate the use of field pea as a protein supplement for medium quality grass hay (9.3% CP). Treatments consisted of whole field peas at 1) 0 g (CON), 2) 680 g (FP680), 3) 1,360 g (FP1360), and 4) 2,040 g (FP2040), and 5) 1,360 g of 74% barley and 26% canola meal (BCM). Total intake (forage + supplement) of gestating beef cows increased with increasing field pea level (linear, P = 0.01; supplemented vs. nonsupplemented, P = 0.01). In summary, protein quantity and rate of ruminal protein degradation vary across sources of field peas used in this study. Additionally, because of source variability, nutrient analysis and animal requirements should be considered when field pea is incorporated into beef cattle diets. Processing field pea does not improve performance of growing steers. Supplementation of field pea to gestating cows consuming medium-quality grass hay increased total DMI. Overall, our data indicate field pea can be used in a wide variety of beef cattle diets.

Eight ruminally and duodenally cannulated beef steers (374 +/- 11 kg) were used to evaluate effects of advancing season and grazing treatment (season-long; SL or twice-over rotation; TOR) on dietary composition (Exp. 1 and 2), intake, site and extent of digestion, and microbial efficiency (Exp. 2) of native range. In Exp. 1, six 11-d sample collections were conducted from early June to mid-November 2000 and 2001. In vitro OM disappearance decreased (Por = 0.04) for both years and both treatments with advancing season. Dietary N declined (Por = 0.07), whereas fiber content increased (Por = 0.05) during both years in both treatments, with the exception of NDF (P = 0.55) during yr 2 (YR2) on the TOR, as season advanced. In Exp. 2, three 11-d sample collections were conducted from late July to mid-September 2000 on SL and TOR. Organic matter intake (g/kg of BW) was not altered (P = 0.28) by grazing treatments or advancing season. Total tract OM and apparent ruminal OM digestion were not different (Por = 0.12) between treatment and decreased (Por = 0.04) with advancing season. Grazing treatment x season interactions (P = 0.06) were present for true ruminal OM digestibility with TOR being greater (Por = 0.10) than SL in late August and mid-September but not late July. Microbial efficiency was greater (P = 0.07; 15.1 vs. 10.8 +/- 1.6 g of microbial N/kg of OM truly fermented) in SL than TOR, respectively. Degradable intake protein (g/d) was less (P = 0.05) in TOR than SL during late July to early August and not affected by treatment in late August or mid-September. However, undegradable intake protein was unchanged (Por = 0.54) between treatment and across season. These data suggest that mixed-grass range forage consumed by cattle after late September is deficient in N, particularly degradable intake protein, and that forage intake may be insufficient to support adequate performance in lactating cows independent of grazing management strategies evaluated. Knowledge of diet quality and forage intake should aid producers in meeting the nutritional needs of livestock grazing these forages.

The objectives were to evaluate effects of maternal nutrient restriction and stage of gestation on maternal and fetal visceral organ mass and indices of jejunal growth and vascularity in beef cows. Thirty multiparous beef cows (BW = 571 +/- 63 kg; BCS = 5.4 +/- 0.7) carrying female fetuses (d 30 of gestation) were allocated to receive a diet of native grass hay (CON; 12.1% CP, 70.7% IVDMD, DM basis) to meet NRC recommendations for BW gain during early gestation or a nutrient-restricted diet of millet straw (NR; 9.9% CP, 54.5% IVDMD, DM basis) to provide 68.1% of NE(m) and 86.7% of MP estimated requirements. On d 125 of gestation, 10 CON and 10 NR cows were killed and necropsied. Five remaining CON cows received the CON diet, and 5 NR cows were realimented with a concentrate supplement (13.2% CP, 77.6% IVDMD, DM basis) and the CON hay to achieve a BCS similar to CON cows by d 220 of gestation. Remaining cows were necropsied on d 245 of gestation. Cow BW and eviscerated BW (EBW) were less (P0.01) for NR than CON at d 125 but did not differ (P0.63) at d 245. Cows fed the CON diet had greater (P0.09) total gastrointestinal (GI) tract, omasal, and pancreatic weights. Stomach complex, ruminal, and liver weights were greater for CON than NR cows (P0.09) on d 125. Total GI, stomach complex, and pancreatic weights increased (P0.001) with day of gestation. Restricted cows had decreased (P = 0.09) duodenal RNA:DNA compared with CON. Duodenal DNA was less (P = 0.01) and jejunal RNA:DNA (P = 0.09) was greater for cows at d 125 vs. 245. Cow jejunal capillary area density increased with day of gestation (P = 0.02). Fetal BW and EBW were unaffected by dietary treatment (Por = 0.32). Total GI tract and all components increased in mass with day of gestation (P0.001). Fetuses from NR dams had greater (P = 0.003) reticular mass at d 245 than CON fetuses. Fetuses from NR cows had greater (P = 0.02) percent jejunal proliferation at d 125 and greater (P = 0.03) total intestinal vascularity (mL) at d 245. Fetal jejunal DNA decreased (P = 0.09), RNA:DNA increased (P = 0.05), and total jejunal proliferating cells increased (P0.001) with day of gestation. Jejunal capillary area density, number density, and surface density were greater (P0.008) during late gestation. Results indicate that maternal and fetal intestines undergo changes during gestation, which can be affected by nutrient restriction and may partially explain differences observed in fetal development and postnatal performance.

Developmental programming refers to the programming of various bodily systems and processes by a stressor of the maternal system during pregnancy or during the neonatal period. Such stressors include nutritional stress, multiple pregnancy (i.e., increased numbers of fetuses in the gravid uterus), environmental stress (e.g., high environmental temperature, high altitude, prenatal steroid exposure), gynecological immaturity, and maternal or fetal genotype. Programming refers to impaired function of numerous bodily systems or processes, leading to poor growth, altered body composition, metabolic dysfunction, and poor productivity (e.g., poor growth, reproductive dysfunction) of the offspring throughout their lifespan and even across generations. A key component of developmental programming seems to be placental dysfunction, leading to altered fetal growth and development. We discuss various large animal models of developmental programming and how they have and will continue to contribute to our understanding of the mechanisms underlying altered placental function and developmental programming, and, further, how large animal models also will be critical to the identification and application of therapeutic strategies that will alleviate the negative consequences of developmental programming to improve offspring performance in livestock production and human medicine.

Seventy-two crossbred and purebred beef steers (296 +/- 9 kg initial BW) were used in a completely randomized design to determine effects of 30% distillers dried grains with solubles (DDGS; 29.2% CP, 9.7% fat, DM basis) inclusion during the growing or finishing period on DMI, performance, carcass, and meat quality traits. The resulting treatments were 0:0, 30:0, 0:30, and 30:30 (diet DDGS percentage fed during growing and finishing periods, respectively). Steers were individually fed a growing diet (65% concentrate) for 57 d, then acclimated to and fed a finishing diet (90% concentrate) for 80 or 145 d. Dietary ingredients included dry-rolled corn, corn silage, grass hay, concentrated separator by-product, and supplement. Diets included 27.5 mg/kg of monensin and 11 mg/kg of tylosin and were formulated to contain a minimum of 12.5% CP, 0.70% Ca, and 0.30% P. During the growing period, DMI was not different (Por= 0.63; 10.22 +/- 0.23 kg/d; 2.42 +/- 0.06% of BW). Steer performance, including ADG (1.75 +/- 0.05 kg/d) and G:F (174.1 +/- 6.8 g/kg), was not affected (Por= 0.14) by treatment during the growing period, and final BW at the end of the growing period was not different (425 +/- 7 kg; P = 0.99). During the finishing period, DMI was not different (Por= 0.54; 8.47 +/- 0.66 kg/d; 1.57 +/- 0.09% BW). During the finishing period, no differences (Por= 0.22) were observed for ADG (1.54 +/- 0.07 kg/d) or G:F (202.4 +/- 28.3 g/kg). As a result, final BW was not different (Por= 0.28; 551 +/- 15 kg). Longissimus muscle area (77.8 +/- 3.3 cm(2)), 12th-rib fat thickness (1.26 +/- 0.10 cm), and KPH (2.48 +/- 0.16%) were not different (Por= 0.16). There were no differences (Por= 0.35) in yield grade (3.33 +/- 0.17) or marbling (431 +/- 21; Small(0) = 400). Results from the trained panel indicated no differences (Por= 0.16) in tenderness, which averaged 6.03 +/- 0.16 (8-point hedonic scale); however, steaks from steers fed 0:30 or 30:30 tended (P = 0.10) to be juicier and more flavorful than steaks from steers fed 0:0 or 30:0 (6.01 vs. 5.83 +/- 0.11; 6.02 vs. 5.89 +/- 0.08, respectively). Inclusion of 30% DDGS in the growing period tended to reduce L (P = 0.08; 48.6 vs. 48.9 +/- 0.2) and b (P = 0.01; 8.24 vs. 8.65 +/- 0.18) of steaks. Feeding DDGS during growing or finishing reduced b (P = 0.02; 8.35 vs. 8.74 +/- 0.18) compared with 0:0. Feeding DDGS during the finishing period reduced a (P0.001; 20.1 vs. 22.0 +/- 0.24) of steaks. Furthermore, feeding DDGS during growing or finishing reduced a (P0.001; 20.9 vs. 21.7 +/- 0.24) compared with 0:0. Feeding 30% DDGS did not affect any performance or carcass characteristics but did influence steak sensory attributes and color.

Five ruminally and duodenally cannulated steers (500 +/- 5 kg of initial BW) were used in a 5 x 5 Latin square to evaluate effects of increasing level of corn distillers dried grains with solubles (DDGS) in growing diets (70% concentrate) on OM intake, site of digestion, ruminal fermentation, and microbial efficiency. Diets consisted of 30% grass hay, 6% concentrated separator by-product, 4% supplement, and 60% dry-rolled corn, sunflower meal, urea, or DDGS (DM basis). Treatments consisted of increasing DDGS at 0, 15, 30, 45, or 60% of diet DM replacing a combination of dry-rolled corn, sunflower meal, and urea. Diets were balanced for growing steers gaining 1.22 kg/d and included 0.25% (DM basis) chromic oxide as a digesta flow marker. Diets were offered to the steers for ad libitum intake each day (10% above the intake of the previous day). Each period consisted of 14 d for adaptation and 7 d for collections. Intake of OM responded quadratically (P = 0.004) with greatest intakes at 15% DDGS and least at 60% DDGS. No differences (Por= 0.14) were observed in CP intake or duodenal flow of OM, CP, and NDF. Apparent and true ruminal OM digestibilities decreased (linear; Por= 0.009) with increasing DDGS inclusion. Total tract CP digestibility increased (linear; P0.001) with increasing DDGS, but total tract OM digestibility was not different (P = 0.74). Microbial efficiency (g of microbial N/kg of OM truly fermented) was not affected (P = 0.22) by treatment. As DDGS increased, ruminal pH increased (linear; P = 0.004), whereas ammonia concentration remained unchanged (P = 0.42). Acetate proportions decreased (linear; P0.001) with increasing DDGS, whereas propionate and butyrate were not affected (Por= 0.19). A cubic (P = 0.02) effect was observed for total ruminal fill (as is basis) with the greatest fill at 0% DDGS and the least fill at 45% inclusion. Replacing dry-rolled corn with up to 60% DDGS in 70% concentrate diets resulted in no adverse effects on total tract OM digestion, although OM intake was reduced at 60% DDGS inclusion.

Twelve ruminally, duodenally, and ileallycannulated Hereford heifers (average initial BW 313 f 20 kg) were used in a replicated experiment to evaluate dairy food processing wash water solids (WWS) as a protein source. Heifers were fed 2.8 kg of chopped (7.6 cm) hay and one of three supplements (1.5 kg/d, DM basis). Supplements were formulated to be similar in energy and contained 1.0 (control), 23.2 (WWS), and 21.6% (soybean meal, SBM) CP on an OM basis. Total N and nonammonia N entering the duodenum (gld) were greater (P c .lo) for heifers fed WWS and SBM supplements than for controls. Bacterial N flow (g/d) at the duodenum was less (P < .lo) for controls (43.9) than for WS- (63.9) and SBM- (69.9) supplemented heifers. Feed escape N (g/d) was greater (P e .lo) for WWS-fed heifers than for those fed SBM (32.1 vs 20.7 gld, respectively). Total tract N digestion (g/d) was greatest (P < .lo) for SBM, intermediate for WWS, and least for control heifers. Microbial protein synthesis (g/kg of OM intake) was enhanced (P < .lo) by WWS and SBM supplementation, but efficiency of synthesis @/kg of OM fermented) did not differ among treatments. Essential amino acid (AA) disappearance in the small intestine (g/d) was less (P < .lo) for control than for the other two treatments. Nonessential AA disappearance was greatest (P < .lo) for the WWS and least (P c .lo) for the control treatment. Based on our short-term feeding data, WWS can be used as a protein source for ruminants, but N availability of WWS seems less than that of soybean meal.

Four ruminally and duodenally cannulated beef steers (388 +/- 12 kg) were used to evaluate effects of advancing season on forage quality, intake, site of digestion, and microbial efficiency while grazing mixed-grass prairie in western North Dakota. Five 11-d sample collections were conducted from late June to mid-November. Chromic oxide (8 g) was dosed twice daily at 0700 and 1900 h via gelatin capsule from d 2 to 11 of each collection period, and duodenal and fecal collections were performed on d 7 to 11. Masticate samples were collected for each sampling period. Dietary N declined linearly (P = 0.01), from 1.95% in June to 1.15% in November, whereas NDF increased linearly (P = 0.01), 72.4% in June to 85.1% in November. Total OM intake (g/kg of BW) decreased linearly (Por= 0.01) from June to November, from 26.2 to 11.4 +/- 2.7 g/kg of BW, respectively, and ruminal fill increased linearly (Por= 0.01) from June to November, from 45.4 to 65.9 +/- 3.3 kg, respectively. True ruminal OM and N digestion declined linearly (Por= 0.01) with advancing season. Total tract OM, N, and NDF digestion declined linearly (Por= 0.01). Microbial efficiency (g of microbial N/kg of OM truly fermented) increased linearly (P = 0.02) from late June to late November. Undegradable intake protein (UIP) intake (g/d) declined (Por= 0.06) linearly and cubically from 374.4 in June to 215.9 g in November. Degradable intake protein (DIP) intake was 735.5 g/d in June and declined linearly (Por= 0.01) to 99.5 g/d with advancing season. Likewise, microbial CP supply at the duodenum (g/d) declined linearly (Por= 0.01) as season advanced. As expected, DIP (% of CP) decreased (Por= 0.01; 66.1 to 31.9 +/- 5.8% for June to November, respectively), whereas percentage of UIP increased (Por= 0.01; 33.9 to 68.1 +/- 5.8% for June to November, respectively) with advancing season. The portions of DIP and UIP (% of CP) were not different in late August and mid-September. These data imply that mixed-grass range forage consumed by cattle after late September is deficient in N, particularly DIP, and that forage intake may decrease and may be too low to support adequate cow performance. Supplementation could be implemented to overcome these deficiencies; however, additional research is needed to determine supplemental type and frequency needed to optimize nutritional and economic efficiency.

Sodium chlorate effectively reduces or eliminates gram-negative pathogenic bacteria in the gastrointestinal tracts of live cattle. Limitations to the in vivo efficacy of chlorate are its rapid absorption from the gastrointestinal tract and its presumed reduction to chloride within the gastrointestinal tract. We hypothesized that chlorate would be reduced via ruminal bacteria in a ruminal in vitro system and that the reduction of chlorate would be influenced by the dietary for-age:concentrate ratio; thus, 4 ruminally cannulated steers were fed 20 or 80% concentrate diets in a crossover design. Ruminal fluid was collected in 2 periods and dispensed into in vitro tubes containing sodium [36Cl]chlorate, which was sufficient for 100 or 300 mg/L final chlorate concentrations. The tubes were incubated for 0, 1, 4, 8, 16, or 24 h; autoclaved, control ruminal fluid, fortified with sodium [36Cl]chlorate, was incubated for 24 h. Chlorate remaining in each sample was measured by liquid scintillation counting after [36Cl]chloride was precipitated with silver nitrate. A preliminary study indicated that chlorite, a possible intermediate in the reduction of chlorate, had a half-life of approximately 4.5 min in freshly collected (live) ruminal fluid; chlorite was, therefore, not specifically measured in ruminal incubations. The chlorate dose did not affect in vitro DM digestion (Por = 0.11), whereas in vitro DM digestibility was decreased (Por = 0.05) by 80% forage content. By 24 h, 57.5 +/- 2.6% of the chlorate remained in 100-mg/L incubations, whereas 78.2 +/- 2.6% of the chlorate remained in the 300-mg/L incubations. When the data were expressed on a concentration basis (mg/L), diet had no effect (Por = 0.18) on chlorate reduction; however, when chlorate reduction was expressed on a percentage basis, chlorate reduction tended to be greater (Por = 0.09) at 8 and 16 h in the incubations containing the low-concentrate diet. Chlorate remaining in autoclaved controls at 24 h was intermediate (P0.01) between chlorate remaining in live ruminal fluid samples incubated for 0 or 24 h. Attempts to isolate chlorate-respiring bacteria from 2 sources of ruminal fluid were not successful. These data indicate that microbial-dependent or chemical-dependent, or both, reduction of chlorate occurs in bovine ruminal fluid and that dietary concentrate had a negligible effect on chlorate reduction.

Four ruminally and duodenally cannulated beef steers (492 +/- 30 kg) were used in a 4 x 4 Latin square design to evaluate the effect of undegradable intake protein (UIP) supplementation on intake, digestion, microbial efficiency, in situ disappearance, and plasma hormones and metabolites in steers fed low-quality grass hay. The steers were offered chopped (10.2 cm in length) grass hay (6.0% CP) ad libitum and 1 of 4 supplements. Supplemental treatments (1,040 g of DM daily), offered daily at 0800, were control (no supplement) or low, medium, or high levels of UIP (the supplements provided 8.3, 203.8, and 422.2 g of UIP/ d, respectively). The supplements were formulated to provide similar amounts of degradable intake protein (22%) and energy (1.77 Mcal of NE(m)/kg). Blood samples were taken at -2, -0.5, 1, 2, 4, 8, 12, and 24 h after supplementation on d 1 (intensive sampling) and at -0.5 h before supplementation on d 2, 3, 4, and 5 (daily sampling) of each collection period. Contrasts comparing control vs. low, medium, and high; low vs. medium and high; and medium vs. high levels of UIP were conducted. Apparent and true ruminal OM and N digestion increased (P0.03) in steers fed supplemental protein compared with controls, but there were no differences (P0.26) among supplemental protein treatments. There were no differences (P0.11) among treatments for NDF or ADF digestion, or total ruminal VFA or microbial protein synthesis. Ruminal pH was not different (P = 0.32) between control and protein-supplemented treatments; however, ruminal pH was greater (P = 0.02) for supplementation with medium and high compared with low UIP. Daily plasma insulin concentrations were increased (P = 0.004) in protein-supplemented steers compared with controls and were reduced (P = 0.003) in steers fed low UIP compared with steers fed greater levels of UIP. Intensive and daily plasma urea N concentrations were increased (P0.01) in protein-supplemented steers compared with controls and increased (P0.02) for intensive and daily sampling, respectively, in steers supplemented with medium and high UIP compared with low UIP. Supplemental protein increased apparent and true ruminal OM and N digestion, and medium and high levels of UIP increased ruminal pH compared with the low level. An increasing level of UIP increases urea N and baseline plasma insulin concentrations in steers fed low-quality hay.

In Exp. 1, 4 ruminally and duodenally cannulated beef steers (444.0 +/- 9.8 kg) were used in a 4 x 4 Latin square with a 2 x 2 factorial treatment arrangement to evaluate the effects of forage type (alfalfa or corn stover) and concentrated separator byproduct (CSB) supplementation (0 or 10% of dietary DM) on intake, site of digestion, and microbial efficiency. In Exp. 2, 5 wethers (44 +/- 1.5 kg) were used in a 5 x 5 Latin square to evaluate the effects of CSB on intake, digestion, and N balance. Treatments were 0, 10, and 20% CSB (DM basis) mixed with forage; 10% CSB offered separately from the forage; and a urea control, in which urea was added to the forage at equal N compared with the 10% CSB treatment. In Exp. 1, intakes of OM and N (g/kg of BW) were greater (P0.01) for steers fed alfalfa compared with corn stover. Steers fed 10% CSB had greater (P0.08) OM and N intakes (g/kg of BW) compared with 0% CSB-fed steers. Total duodenal, microbial, and nonmicrobial flows of OM and N were greater (P0.01) for steers fed alfalfa compared with corn stover. Steers fed 10% CSB had increased (P = 0.02) duodenal microbial flow (N and OM) compared with 0% CSB-fed steers. Forage x CSB interactions (P0.01) existed for total tract N digestibility; alfalfa with or without CSB was similar (67.4 vs. 69.5), whereas corn stover with CSB was greater than corn stover without CSB (31.9 vs. -23.9%). True ruminal OM digestion was greater (P0.09) in steers fed alfalfa vs. corn stover (73.0 vs. 63.1%) and in steers fed 10 vs. 0% CSB (70.3 vs. 65.8%). Microbial efficiency was unaffected (P0.25) by forage type or CSB supplementation. In Exp. 2, forage and total intake increased (linear; P0.01) as CSB increased and were greater (P0.04) in 10% CSB mixed with forage compared with 10% CSB fed separately. Feeding 10% CSB separately resulted in similar DM and OM apparent total tract digestibility compared with 10% CSB fed mixed. Increasing CSB led to an increase (linear; P0.02) in DM, OM, apparent N digestion, and water intake. Nitrogen balance (g and percentage of N intake) increased (linear; P0.08) with CSB addition. Feeding 10% CSB separately resulted in greater (P0.01) N balance compared with 10% CSB fed mixed. Using urea resulted in similar (P = 0.30) N balance compared with 10% CSB fed mixed. Inclusion of CSB improves intake, digestion, and increases microbial N production in ruminants fed forage-based diets.

Concentrated separator by-product (CSB) is produced when beet molasses goes through an industrial desugaring process. To investigate the nutritional value of CSB as a supplement for grass hay diets (12.5% CP; DM basis), 4 ruminally and duodenally cannulated beef steers (332 +/- 2.3 kg) were used in a 4 x 4 Latin square with a 2 x 2 factorial arrangement of treatments. Factors were intake level: ad libitum (AL) vs. restricted (RE; 1.25% of BW, DM basis) and dietary CSB addition (0 vs. 10%; DM basis). Experimental periods were 21 d in length, with the last 7 d used for collections. By design, intakes of both DM and OM (g/kg of BW) were greater (P0.01; 18.8 vs. 13.1 +/- 0.69 and 16.8 vs. 11.7 +/- 0.62, respectively) for animals consuming AL compared with RE diets. Main effect means for intake were not affected by CSB (P = 0.59). However, within AL-fed steers, CSB tended (P = 0.12) to improve DMI (6,018 vs. 6,585 +/- 185 g for 0 and 10% CSB, respectively). Feeding CSB resulted in similar total tract DM and OM digestion compared with controls (P = 0.50 and 0.87, respectively). There were no effects of CSB on apparent total tract NDF (P = 0.27) or ADF (P = 0.35) digestion; however, apparent N absorption increased (P = 0.10) with CSB addition. Total tract NDF, ADF, or N digestion coefficients were not different between AL- and RE-fed steers. Nitrogen intake (P = 0.02), total duodenal N flow (P = 0.02), and feed N escaping to the small intestine (P = 0.02) were increased with CSB addition. Microbial efficiency was unaffected by treatment (P = 0.17). Supplementation with CSB increased the rate of DM disappearance (P = 0.001; 4.9 vs. 6.9 +/- 0.33 %/h). Restricted intake increased the rate of in situ DM disappearance (P = 0.03; 6.4 vs. 5.3 +/- 0.33 %/h) compared with AL-fed steers. Ruminal DM fill was greater (P = 0.01) in AL compared with RE. Total VFA concentrations were greater (P = 0.04) for CSB compared with controls; however, ammonia concentrations were reduced (P = 0.03) with CSB addition. At different levels of dietary intake, supplementing medium-quality forage with 10% CSB increased N intake, small intestinal protein supply, and total ruminal VFA.

Two metabolism (4 x 4 Latin square design) experiments were conducted to evaluate the effects of corn condensed distillers solubles (CCDS) supplementation on intake, ruminal fermentation, site of digestion, and the in situ disappearance rate of forage in beef steers fed low-quality switchgrass hay (Panicum virgatum L.). Experimental periods for both trials consisted of a 9-d diet adaptation and 5 d of collection. In Exp. 1, 4 ruminally and duodenally cannulated steers (561 +/- 53 kg of initial BW) were fed low-quality switchgrass hay (5.1% CP, 40.3% ADF, 7.5% ash; DM basis) and supplemented with CCDS (15.4% CP, 4.2% fat; DM basis). Treatments included 1) no CCDS; 2) 5% CCDS; 3) 10% CCDS; and 4) 15% CCDS (DM basis), which was offered separately from the hay. In Exp. 2, 4 ruminally and duodenally cannulated steers (266.7 +/- 9.5 kg of initial BW) were assigned to treatments similar to Exp. 1, except forage (Panicum virgatum L.; 3.3% CP, 42.5% ADF, 5.9% ash; DM basis) and CCDS (21.6% CP, 17.4% fat; DM basis) were fed as a mixed ration, using a forage mixer to blend the CCDS with the hay. In Exp. 1, ruminal, postruminal, and total tract OM digestibilities were not affected (P = 0.21 to 0.59) by treatment. Crude protein intake and total tract CP digestibility increased linearly with increasing CCDS (P = 0.001 and 0.009, respectively). Microbial CP synthesis tended (P = 0.11) to increase linearly with increasing CCDS, whereas microbial efficiency was not different (P = 0.38). Supplementation of CCDS to low-quality hay-based diets tended to increase total DM and OM intakes (P = 0.11 and 0.13, respectively) without affecting hay DMI (P = 0.70). In Exp. 2, ruminal OM digestion increased linearly (P = 0.003) with increasing CCDS, whereas postruminal and total tract OM digestibilities were not affected (Por = 0.37) by treatment. Crude protein intake, total tract CP digestibility, and microbial CP synthesis increased (Por = 0.06) with increasing level of CCDS supplementation, whereas microbial efficiency did not change (P = 0.43). Ruminal digestion of ADF and NDF increased (P = 0.02 and 0.008, respectively) with CCDS supplementation. Based on this data, CCDS used in Exp. 2 was 86.7% rumen degradable protein. The results indicate that CCDS supplementation improves nutrient availability and use of low-quality forages.

Fourteen Holstein steers (446 +/- 4.4 kg of initial BW) with ruminal, duodenal, and ileal cannulas were used in a completely randomized design to evaluate effects of whole or ground canola seed (23.3% CP and 39.6% ether extract; DM basis) on intake, digestion, duodenal protein supply, and microbial efficiency in steers fed low-quality hay. Our hypothesis was that processing would be necessary to optimize canola use in diets based on low-quality forage. The basal diet consisted of ad libitum access to switchgrass hay (5.8% CP; DM basis) offered at 0700 daily. Treatments consisted of hay only (control), hay plus whole canola (8% of dietary DM), or hay plus ground canola (8% of dietary DM). Supplemental canola was provided based on the hay intake of the previous day. Steers were adapted to diets for 14 d followed by a 7-d collection period. Total DMI, OM intake, and OM digestibility were not affected (Por = 0.31) by treatment. Similarly, no differences (Por = 0.62) were observed for NDF or ADF total tract digestion. Bacterial OM at the duodenum increased (P = 0.01) with canola-containing diets compared with the control diet and increased (P = 0.08) in steers consuming ground canola compared with whole canola. Apparent and true ruminal CP digestibilities were increased (P = 0.01) with canola supplementation compared with the control diet. Canola supplementation decreased ruminal pH (P = 0.03) compared with the control diet. The molar proportion of acetate in the rumen tended (P = 0.10) to decrease with canola supplementation. The molar proportion of acetate in ruminal fluid decreased (P = 0.01), and the proportion of propionate increased (P = 0.01), with ground canola compared with whole canola. In situ disappearance rate of hay DM, NDF, and ADF were not altered by treatment (Por = 0.32). In situ disappearance rate of canola DM, NDF, and ADF increased (P = 0.01) for ground canola compared with whole canola. Similarly, ground canola had greater (P = 0.01) soluble CP fraction and CP disappearance rate compared with whole canola. No treatment effects were observed for ruminal fill, fluid dilution rate, or microbial efficiency (Por = 0.60). The results suggest that canola processing enhanced in situ degradation but had minimal effects on ruminal or total tract digestibility in low-quality, forage-based diets.

Nine ruminally and duodenally cannulated (172 +/- 23 kg of initial BW; Exp. 1) and 16 intact (153 +/- 28 kg of initial BW; Exp. 2) crossbred nursing steer calves were used to evaluate the effects of creep feed supplementation and advancing season on intake, digestion, microbial efficiency, ruminal fermentation, and performance while grazing native rangeland. Treatments in both experiments were no supplement or supplement fed at 0.45% of BW (DM basis) daily. Supplement consisted of 55% wheat middlings, 38.67% soyhulls, 5% molasses, and 1.33% limestone. Three 15-d collection periods occurred in June, July, and August. In Exp. 1, ruminal evacuations were performed and masticate samples were collected for diet quality analysis on d 1. Duodenal and fecal samples were collected from cannulated calves on d 7 to 12 at 0, 4, 8, and 12 h after supplementation. Ruminal fluid was drawn on d 9 and used as the inoculate for in vitro digestibility. On d 11, ruminal fluid was collected, and the pH was recorded at -1, 1, 2, 4, 8, 12, and 24 h postsupplementation. In Exp. 1 and 2, milk intake was estimated using weigh-suckle-weigh on d 15. Steers in Exp. 2 were fitted with fecal bags on d 6 to 11 to estimate forage intake. In Exp. 1, supplementation had no effect (P = 0.22 to 0.99) on grazed diet or milk composition. Apparent total tract OM disappearance increased (P = 0.03), and apparent total tract N disappearance tended (P = 0.11) to increase in supplemented calves. Microbial efficiency was not affected (P = 0.50) by supplementation. There were no differences in ruminal pH (P = 0.40) or total VFA concentration (P = 0.21) between treatments, whereas ruminal NH3 concentration increased (P = 0.03) in supplemented compared with control calves. In Exp. 2, supplementation decreased (P = 0.02) forage OM intake (OMI; % of BW) and increased (P = 0.06) total OMI (% of BW). Supplementation had no effect on ADG (P = 0.94) or G:F (P = 0.35). Supplementation with a wheat middlings and soybean hull-based creep feed reduced forage OMI but improved total tract OM and N digestion and had minimal effects on ruminal fermentation or performance. Supplementation with a wheat middlings and soybean hulls-based creep feed might improve OM and N digestion, but might not produce significantly greater BW gains compared with no supplementation.

Seventy-two (36 in each of two consecutive years) lactating, British-crossbred cows (609 +/- 19 kg) were used to evaluate effects of feeding a feather meal-blood meal combination on performance by beef cows fed grass hay. Bromegrass hay (9.6% CP, DM basis) was offered ad libitum and intake was measured daily in individual Calan electronic headgates. Acclimation to Calan gates began approximately 20 d after parturition, and treatments were initiated 21 d later. Cows were assigned randomly to one of four treatments (DM basis) for 60 d: 1) nonsupplemented control (CON), 2) energy control (ENG; 790 g/d; 100% beet pulp), 3) degradable intake protein (DIP; 870 g/d; 22% beet pulp and 78% sunflower meal), or 4) undegradable intake protein (UIP; 800 g/d; 62.5% sunflower meal, 30% hydrolyzed feather meal, and 7.5% blood meal). Net energy concentrations of supplements were formulated to provide similar NE(m) intakes (1.36 Mcal/d). The DIP and UIP supplements were calculated to supply similar amounts of DIP (168 g/d) and to supply 64 and 224 g/d of UIP, respectively. Forage DMI (kg/d) decreased in supplemented vs. nonsupplemented (P = 0.03) and DIP vs. UIP (P = 0.001); however, when expressed as a percentage of BW, forage DMI was not different (P = 0.23). Supplemented cows tended (P = 0.17) to lose less BW than CON. Body condition change was not affected (P = 0.60) by postpartum supplementation. No differences were noted in milk production (P = 0.29) or in calf gain during the supplementation period (P = 0.74). Circulating insulin concentrations were not affected by treatment (P = 0.42). In addition, supplementation did not affect circulating concentrations of NEFA (P = 0.18) or plasma urea nitrogen (P = 0.38). Results of the current study indicate that supplementation had little effect on BW, BCS, milk production, or calf BW when a moderate-quality forage (9.6% CP) was fed to postpartum, winter-calving cows in optimal body condition (BCS5). Supplemental UIP did not enhance cow performance during lactation. Forage UIP and microbial protein supply were adequate to meet the metabolizable protein requirements of lactating beef cows under the conditions of this study.

Six Angus crossbred cow-calf pairs (653 +/- 35 kg and 157 +/- 10 kg initial BW for cows and calves, respectively) were used to evaluate the influence of a fiber-based creep feed on intake, ruminal fermentation, digestion characteristics, and microbial efficiency in nursing beef calves. Cow-calf pairs were stratified by calf age and assigned randomly to one of two treatments: control (no supplement) or supplemented. Supplemented calves received 0.9 kg of a 49% soy hulls, 44% wheat middlings, 6% molasses, and 1% limestone supplement (DM basis) daily. All calves were cannulated in the rumen and duodenum and given ad libitum access to chopped brome hay (Bromus inermus L; 7.43% CP, 40.96% ADF, and 63.99% NDF; DM basis). Supplementation was initiated on May 1 (88 +/- 10.3 d calf age). Three sampling periods were conducted throughout the study (June 14 to 25, July 5 to 16, and August 9 to 20). Supplement and forage were offered at 0800 daily. Total, hay, and milk OM intakes of nursing calves were not affected by supplementation (2,014 vs. 2,328 +/- 288.8, 1,486 vs. 1,029 +/- 3,06.9, and 528 vs. 575 +/- 87.0 g/d, respectively). Milk OM intake was less (P0.09) in August than in June and July (635, 691, and 345 +/- 110.6 g/d for June, July, and August, respectively). A supplementation x month interaction occurred (P0.10) for total-tract OM digestion. Supplementation did not affect (P0.40) total-tract OM digestibility during June and August; however, during July, total-tract OM digestibility was lower (P = 0.03) for the control calves. Ruminal ammonia concentration, total VFA, and butyrate molar proportion increased (P0.05), whereas acetate proportion decreased (P = 0.01) in supplemented calves. Microbial efficiency was not influenced by supplementation (11.8 vs. 12.0 g/kg of OM truly fermented for control and supplemented calves, respectively). These data indicate that fiber-based supplements can be used as creep feed without negative effects on OM intake, total-tract OM digestibility, and ruminal fermentation characteristics in nursing beef calves.

Objectives of this research were to evaluate effects of increasing level of barley supplementation on forage intake, digestibility, and ruminal fermentation in beef steers fed medium-quality forage. Four crossbred ruminally cannulated steers (average initial BW = 200 +/- 10 kg) were used in a 4 x 4 Latin square design. Chopped (5 cm) grass hay (10% CP) was offered ad libitum with one of four supplements. Supplements included 0, 0.8, 1.6, or 2.4 kg of barley (DM basis) and were fed in two equal portions at 0700 and 1600. Supplements were fed at levels to provide for equal intake of supplemental protein with the addition of soybean meal. Forage intake (kg and g/kg BW) decreased linearly (P0.01), and total intake increased linearly (P0.03) with increasing level of barley supplementation. Digestible OM intake (g/kg BW) increased linearly (P0.01) with increasing level of barley supplementation; however, the majority of this response was observed with 0.8 kg of barley supplementation. Treatments had only minor effects on ruminal pH, with decreases occurring at 15 h after feeding in steers receiving 2.4 kg of barley supplementation. Total-tract digestibility of DM, OM, NDF, and CP were increased (P0.04) with barley supplementation; however, ADF digestibility was decreased by 1.6 and 2.4 kg of barley supplementation compared with controls. Ruminal ammonia concentrations decreased linearly (P0.01) at 1 through 15 h after feeding. Total ruminal VFA concentrations were not altered by dietary treatments. Ruminal proportions of acetate and butyrate decreased (P0.10) in response to supplementation. Rate, lag, and extent (72 h) of in situ forage degradability were unaffected by treatment. Generally, these data are interpreted to indicate that increasing levels of barley supplementation decrease forage intake, increase DM, OM, and NDF digestibility, and indicate alteration of the ruminal environment and fermentation patterns.

Two experiments evaluated digestive and performance effects of field pea-based creep feed in nursing calf diets. In Exp.1, eight nursing steer calves (145 +/- 27 kg initial BW) with ruminal cannulas were used to evaluate effects of supplementation and advancing season on dietary composition, intake, digestion, and ruminal fermentation characteristics. Treatments were unsupplemented control (CON) and field pea-based creep (SUP; 19.1% CP, DM basis) fed at 0.45% BW (DM basis) daily. Calves grazed native range with their dams from early July through early November. Periods were 24 d long and occurred in July (JUL), August (AUG), September (SEP), and October (OCT). Experiment 2 used 80 crossbred nursing calves, 48 calves in yr 1 and 32 calves in yr 2 (yr 1 = 144 +/- 24 kg; yr 2 = 121 +/- 20 kg initial BW), to evaluate effects of field pea-based creep on calf performance. Treatments included unsupplemented control (CON); field pea-based creep feeds containing either 8% (LS); or 16% (HS) salt; and soybean meal/field pea-based creep containing (as-fed basis) 16% salt (HIPRO). Masticate samples from SUP calves in Exp.1 had greater CP (P = 0.05) than those from CON calves. Forage CP and ADIN decreased linearly with advancing season (P = 0.01 and 0.03, respectively). In vitro OM digestibility of diet masticate decreased from JUL to OCT (P0.01; 58.5 to 41.3%). Forage intake did not differ (P = 0.33) between treatments but increased linearly with advancing season (1.67, 1.90, 3.12, 3.38 kg/d for JUL, AUG, SEP, and OCT, respectively; P0.01). Milk intake (percentage of BW) did not differ (P = 0.56) between CON and SUP calves but decreased linearly (P0.01) with advancing season. Supplemented calves had greater (P = 0.03) total intake (g/kg of BW; forage + milk + creep) compared with CON calves. Treatment did not affect (P0.30) rate of in situ disappearance of forage or creep. Forage DM, CP, and creep DM disappearance rate decreased linearly (Por = 0.02) with advancing season. Supplementation decreased (P = 0.05) ruminal pH, whereas ruminal ammonia and VFA concentrations were greater (Por = 0.02) in SUP calves. In Exp. 2, creep-fed calves had greater ADG and final BW than CON calves (P0.01). Calves offered HS tended (P = 0.07) to have increased gain efficiency above CON than LS calves. Field peas can be used as an ingredient in creep feed to increase calf weight gain without negatively affecting ruminal fermentation and digestion.

Two trials were conducted to determine the effect of energy source (ENG) and ruminally degradable protein (RDP) on lactating cow performance and intake and digestion in beef steers. In Trial 1, 78 cow-calf pairs were used in a 2 x 2 factorial design to determine the effect of ENG (corn or soyhulls; SH) and RDP (with our without sunflower meal) to a forage diet for lactating beef cows. The basal diet consisted of 75% grass hay (11.5% CP) and 25% wheat straw (7.4% CP). Supplement treatments and predicted RDP balances were corn (-415 g of RDP/d); SH (-260 g of RDP/d); corn plus RDP (0 g of RDP/d); or SH plus RDP (0 g of RDP/d). Data were analyzed as a split-plot in time, with pen as the experimental unit (two pens per treatment). No interaction between ENG and RDP was present (P0.08) for any response variable. No differences (P0.39) due to ENG or RDP were noted for BW, BCS, or milk yield; however, final calf weight tended to increase with ENG (P = 0.06). In Trial 2, a 5 x 5 Latin square was used to determine effects of ENG and RDP on intake and digestion in steers (686 +/- 51 kg BW). Treatments were arranged as a 2 x 2 plus one factorial and comprised a control (CON; grass hay, 7% CP), grass hay plus 0.4% BW SH, grass hay plus 0.4% BW SH and 0.15% BW sunflower meal, grass hay plus 0.4% BW corn, and grass hay plus 0.4% BW corn and 0.2% BW sunflower meal. Preplanned contrasts included main effects of ENG and RDP, ENG x RDP interaction, and CON vs. supplemented (SUP) treatments. Supplementation increased total DMI compared with CON (P = 0.001), but forage DMI was greater (P = 0.001) for CON than for SUP. An ENG x RDP interaction occurred for forage DMI (P = 0.02); addition of RDP to corn decreased forage intake, whereas addition of RDP to SH had no effect. There was an ENG x RDP interaction (P = 0.001) for ruminal pH; pH tended to increase with RDP addition to SH (P = 0.07), but decreased with RDP addition to corn (P = 0.001). Supplementation increased ruminal ammonia compared with CON (P = 0.001). Likewise, RDP increased ruminal ammonia (P = 0.001). An interaction occurred for OM disappearance (OMD; P = 0.01). The RDP addition to SH numerically decreased OMD (P = 0.23), whereas RDP addition to corn numerically increased OMD (P = 0.14). Intake and digestion seem to respond differently to RDP addition depending on supplemental energy source. Both corn or SH seem to be suitable supplements for the quality of forage used in this trial. Addition of supplemental protein did not improve cow or calf performance.

Twelve crossbred steers (351 +/- 24 kg initial BW) were used to determine effects of high-Se wheat on visceral tissue mass, intestinal cell growth, and intestinal cellularity and vascularity. Steers were allotted randomly by BW to one of two treatments consisting of 75% concentrate diets that supplied 1) adequate Se concentration (7 to 12 microg x kg x BW(-1) x d(-1)) or 2) high-Se concentration (60 to 70 microg x kg x BW(-1) x d(-1)). Diets were similar in composition, including 25% grass hay, 25% wheat, 39% corn, 5% desugared molasses, and 6% wheat middlings supplement on a DM basis. In the Se treatment, high-Se wheat (10 ppm Se, DM basis) was replaced with low-Se wheat (0.35 ppm Se, DM basis). Diets were formulated to be similar in CP and energy (14.0% CP, 2.12 Mcal of NEm/kg, and 1.26 Mcal NEg/kg of DM) and were offered daily (1500) to individual steers in an electronic feeding system. Diets were fed at 2.38% BW. After 126 d, steers were slaughtered, and individual visceral tissue weights determined. Concentrations of DNA, RNA, and protein of duodenum, ileum, and total small intestine were not affected (Por = 0.33) by treatment. Similarly, RNA:DNA and protein:DNA ratios in duodenum, jejunum, ileum, and whole small intestine were not (Por = 0.33) affected by feeding high-Se wheat. Conversely, jejunal weight was greater (P0.002) in steers fed high-Se wheat than in controls (916 vs. 1,427 +/- 84 g). Jejunal DNA was increased (P0.04) in steers fed high-Se wheat (2.95 vs. 3.56 +/- 0.19 mg/g), suggesting increased cell number. Concentrations of jejunal RNA and protein were not altered by treatment; however, because the jejunal weight increased in high-Se steers, DNA, RNA, and protein contents (grams) were greater than in control steers (P0.05). Vascularity of jejunal tissue decreased (P0.10) with high-Se wheat; however, because jejunal mass was greater for the high-Se wheat treatment, total microvascular volume was not affected by treatment. Percentage of jejunal crypt cell proliferation was not affected (P = 0.48) by treatment; however, total number of cells proliferating within the jejunum was increased in steers fed high-Se wheat. Data indicate that the lower jejunal vascularity in the diet high in Se (provided from wheat) may have resulted in increased jejunal mass to meet physiological nutrient demand. Therefore, negative effects of Se level used in this study on productive performance of feedlot steers are not expected.

Four ruminally and duodenally cannulated steers (703.4 +/- 41 kg initial BW) were used in a 4 x 4 Latin square to evaluate the effects of field pea inclusion level on intake and site of digestion in beef steers fed medium-concentrate diets. Steers were offered feed ad libitum at 0700 and 1900 daily and were allowed free access to water. Diets consisted of 45% grass hay and 55% by-products based concentrate mixture and were formulated to contain a minimum of 12% CP (DM basis). Treatments consisted of (DM basis) 1) control, no pea; 2) 15% pea; 3) 30% pea; and 4) 45% pea in the total diet, with pea replacing wheat middlings, soybean hulls, and barley malt sprouts in the concentrate mixture. Experimental periods consisted of a 9-d dietary adjustment period followed by a 5-d collection period. Grass hay was incubated in situ, beginning on d 10, for 0, 2, 5, 9, 14, 24, 36, 72, and 98 h; and field pea and soybean hulls for 0, 2, 5, 9, 14, 24, 36, 48, and 72 h. Total DMI (15.0, 13.5, 14.1, 13.5 +/- 0.65 kg/d) and OM intake (13.4, 12.0, 12.6, 12.0 +/- 0.58 kg/d) decreased linearly (P = 0.10) with field pea inclusion. Apparent ruminal (17.5, 12.0, 0.6, 6.5 +/- 4.31%) and true ruminal CP digestibility (53.5, 48.7, 37.8, 46.2 +/- 3.83) decreased linearly (P0.10) with increasing field pea. Neutral detergent fiber intake (8.9, 7.9, 7.8, 7.0 +/- 0.3 kg/d) and fecal NDF output (3.1, 2.9, 2.6, 2.3 +/- 0.2 k/d) decreased linearly (P0.03) with increasing field pea. No effects were observed for microbial efficiency or total-tract digestibility of OM, CP, NDF, and ADF (Por = 0.16). In situ DM and NDF disappearance rates of grass hay and soybean hulls decreased linearly (P0.05) with increasing field pea. Field pea in situ DM disappearance rate responded quadratically (P0.01; 5.9, 8.4, 5.5, and 4.9 +/- 0.52%/h, for 0, 15, 30, and 45% field pea level, respectively). Rate of in situ CP disappearance of grass hay decreased linearly (P0.01) with increasing field pea level. Field pea is a suitable ingredient for beef cattle consuming medium-concentrate diets, and the inclusion of up to 45% pea in by-products-based medium-concentrate growing diets decreased DMI, increased dietary UIP, and did not alter OM, NDF, or ADF digestibility.

Dietary selenium influences the Se content in edible muscle of beef cattle. Limited data are available to describe the effects that feeds naturally high in Se have on production, carcass characteristics, and Se distribution in terminal tissues. Therefore, 43 crossbred steers (BW = 351 +/- 24 kg) were stratified by BW and assigned to one of four dietary treatments: Se adequate (CON; n = 12), Se provided as high-Se wheat (WHT; n = 9), high-Se hay (HAY; n = 11), or sodium selenate (SEO; n = 11). Daily selenium intake for WHT, HAY, and SEO diets was 65 microg/kg BW, whereas it was 9.5 microg/kg BW for CON. Diets were similar in ingredient composition (25% wheat, 39% corn, 25% grass hay, 5% desugared molasses, and 6% wheat middling-based supplement; DM basis), isonitrogenous and isocaloric (14.0% CP, 2.12 Mcal NEm/kg DM and 1.26 Mcal NEg/ kg DM), and offered once daily (1500) individually to steers in a Calan gate system for 126 d. At the end of the trial, steers were slaughtered; carcass data were recorded; and samples of the liver, kidney, spleen, semitendinosus, and hair were collected for Se analysis. Intake of DM, G:F, and ADG did not differ (P0.13). No differences (P0.12) were noted for hot carcass weight, organ weights, longissimus muscle area, back-fat thickness, marbling scores, or quality and yield grade. Kidney, pelvic, and heart fat tended to be higher (P = 0.06) in CON and WHT compared with SEO and HAY steers (2.9, 2.4, 2.5, 2.9 +/- 0.2% for CON, SEO, HAY, and WHT, respectively). Selenium concentrations in all tissues collected differed (P0.003) due to treatment. Distribution of Se to the kidney, spleen, and hair were similar with CONSEOHAYWHT (8.40, 10.05, 10.86, 12.89 +/- 0.26 ppm for kidney; 2.00, 2.60, 3.82, 5.16 +/- 0.09 ppm for spleen; 1.80, 4.00, 5.93, 10.54 +/- 0.56 ppm for hair; P0.01). The distribution of Se in liver and muscle (DM basis) differed from that in other tissues, with CONHAYSEO = WHT (2.33, 6.56, 9.91, 10.79 +/- 0.80 ppm; P0.01) and CON = SEOHAYWHT (1.33, 1.55, 3.32, 4.41 +/- 0.18 ppm; P0.01), respectively. When providing dietary Se at supranutritional levels, source of Se did not affect production or carcass characteristics, but it altered the distribution and concentration of Se throughout the tissues of finishing beef steers.

Beef heifers (24 mo; 378 +/- 32 kg of BW; 22 pregnant, PR; 17 nonpregnant, NP) were grouped in common pens and fed corn silage- and hay-based diets formulated to provide an ADG of 0.45 kg in NP heifers. Both PR and NP heifers were slaughtered on d 40, 120, 200, and 270 of the study. Intestinal and hepatic tissues were analyzed for protein, DNA, RNA (mg/g of fresh tissue), and in vitro oxygen use. Jejunal samples were analyzed for cellular proliferation via immunohistochemical analysis. For ileum, DNA, which provides an estimate of cell number per unit of tissue, revealed an interaction (P = 0.06) between pregnancy and slaughter day; both PR and NP decreased with time, but NP increased on d 270 (P = 0.09). Cell number in the ileum was reduced at d 200 and 270 in the PR heifers (P0.09). Liver protein concentration was less (P = 0.07) in PR than in NP heifers (NP = 291.1 vs. PR = 210.5 +/- 33.9 mg/g). Hepatic protein:DNA ratio was not affected (P0.10) by pregnancy or day. Energy use (kcal/d) of duodenum and jejunum, calculated from in vitro oxygen consumption, increased linearly (P0.02) with time for both PR and NP. Pregnant and NP ileal energy use increased linearly (P0.01), but ileal energy use by PR was less throughout gestation (P = 0.07) than ileal energy use by NP. Cellular proliferation in the crypt region of the jejunum was decreased on d 120 and 200 (P0.02). These data indicate that the small intestine and liver of PR heifers may conserve energy expenditure compared with NP heifers. Energy conservation can partially be explained by differences in growth and cell proliferation and by energy use of the liver and small intestine.

Four ruminally and duodenally cannulated beef steers (558 +/- 37 kg) were arranged in a 4 x 4 Latin square to evaluate the influence of crambe meal as a protein source on intake, digestion, and microbial efficiency. Steers were offered chopped (10.2 cm) brome hay (6.2% CP) for ad libitum consumption and one of four supplements. Protein sources used were soybean and crambe meals (CM). Protein sources were blended to provide four levels of supplemental CM protein (0, 33, 67, and 100%). Protein supplements were fed to provide similar amounts of protein and energy. Amounts of supplements fed were 831, 885, 950, and 996 g of DM/steer daily for 0, 33, 67, and 100% CM treatments, respectively. Crambe meal represented 0, 2.00, 3.83, and 5.88% of the DM intake for respective treatments. Steers were allowed a 21-d adaptation to diets before each collection period. Supplements were offered at 0800 and forage at 0830. Crambe meal had no influence (P.10) on forage and total DM intake (grams/kilogram of BW). Apparent total tract, ruminal, and postruminal digestion of OM, NDF, ADF, and N were unaffected (P.10) by CM supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)

Twelve ruminally and duodenally cannulated beef steers (initial BW 368 +/- 25.3 kg) and four ruminally cannulated beef heifers (initial BW 559 +/- 79.5 kg) were used to evaluate the effects of yeast culture (YC) and advancing season on ruminal fermentation, microbial protein synthesis, ruminal fluid kinetics, and site of digestion. Treatments were control and YC supplementation (28.4 g.steer-1.d-1 dosed ruminally). Steers grazed from late June to early November 1991 on mixed-grass prairie. Ruminal pH decreased (P.10) from late July to early October. Fluid dilution rate decreased (P.10) as the grazing season advanced, whereas ruminal fluid volume and flow rate increased (P.10) from late July to early October. Ruminal ammonia concentration (milligrams/deciliter) was lower (P.10) during late July and late August than during late June and early October at 4, 8, 12, and 16 h after sunrise in YC-supplemented steers. Molar proportions of propionate and butyrate were greater (P.10) in control than in YC-supplemented steers at 0, 4, 12, and 24 h and 0, 4, and 12 h after sunrise, respectively, during late July. Acetate (mol/100 mol) was greater (P.10) during late July and late August than in late June and early October for YC-supplemented steers at 0, 4, and 8 h after sunrise. True ruminal OM digestion was greatest (P.10) in late June, intermediate in late July and late August, and least in early October. Supplementation with YC increased (P.04) true ruminal OM digestion in late June and late July. Steers receiving YC had greater (P.07) duodenal bacterial N flow in late July. These data indicate that yeast culture supplementation can increase true OM digestibility early in the grazing season. Advancing season seems to result in increased ruminal fluid volume, lower true ruminal OM digestion, and greater microbial efficiency.

Twelve beef steers (368 +/- 25.3 kg) and four beef heifers (559 +/- 79.5 kg) fitted with ruminal cannulas were used to evaluate effects of yeast culture (YC) and advancing season on dietary chemical composition, intake, and in situ CP and NDF degradation. Treatments were control and YC supplementation (28.4 g.steer-1.d-1 dosed ruminally). Steers grazed from late June to early November 1991 on mixed-grass prairie. Experimental periods consisted of 10 d for adaptation and a 13-d collection phase. Forage samples collected from YC-supplemented steers had greater (P.10) soluble N and in vitro OM disappearance than forage from controls throughout the grazing season. Organic matter intake was greater (P.10) by YC-supplemented steers during June. Fecal output and OM intake increased (P.10) from June to September. Increases (P.10) in in situ NDF disappearance were noted at 8, 16, and 24 h in June, at 8, 48, and 72 h in July, and at 8 h in August for the YC treatment group. Supplemental YC did not affect (P.10) rate or lag time of NDF disappearance. In situ CP disappearance (ISCPD) was greater (P.10) at all times except 48 h in June, at 48 and 72 h in July, and at 0, 4, 8, and 12 h in August for YC-supplemented steers. Steers supplemented with YC had an increased extent (P.10) of ISCPD in July and an increase in CP degradation rate in June; however, total CP degradation was greater (P.10) during June for control than for YC steers.(ABSTRACT TRUNCATED AT 250 WORDS)

Eight multicannulated heifers (average BW 415 +/- 34 kg) were used in a replicated 4 x 4 Latin square to evaluate fluid milk processing wash water solids (WWS) as a dietary N source. Heifers were fed corn/cottonseed hull-based diets containing soybean meal (control, 0% WWS N) or WWS replacing soybean meal at 33, 67, or 100% of supplemental dietary N. Total tract and ruminal DM and OM digestibilities decreased linearly or cubically (P less than .05) as dietary WWS N increased. Total ruminal VFA concentration (P less than .05) and propionic acid molar proportion (P less than .10) were greater in heifers fed 0 vs 100% WWS N. Heifers fed 0% WWS N had the greatest (P less than .05) ruminal ammonia concentration at all sampling times. Dietary WWS did not affect (P greater than .10) ruminal pH, fluid dilution rate, fluid flow, fluid volume, or turnover time. Total tract N digestibility decreased quadratically (P less than .10) with increasing WWS N in the diet. Supplemental WWS N did not affect (P greater than .10) flow of duodenal ammonia N or bacterial N, or efficiency of microbial N synthesis. Diets containing WWS N resulted in a cubic increase (P less than .10) in duodenal flow of essential amino acids compared with 0% WWS N; however, there were no differences in small intestinal amino acid disappearance. Data indicate that WWS can replace 33% of the soybean meal N in a corn/cottonseed hull-based diet without decreasing ruminal fermentation, fluid digesta kinetics, microbial efficiency, or small intestinal amino acid utilization.

Twelve ruminally, duodenally, and ileally cannulated (average initial BW 313 +/- 20 kg) and 27 intact Hereford heifers (average initial BW 256 +/- 17 kg) were used in two experiments to evaluate dairy food wash water solids (WWS) as a protein source in medium-quality hay diets. Heifers received a basal diet of orchardgrass hay (7.4% CP) and were assigned to one of three supplement treatments: control (C; .9% CP), WWS (18.8% CP)-, and soybean meal (SBM; 19.1% CP)-based supplements (fed at 1.5 kg of DM/d). Supplements were formulated to have similar ME concentrations. Ruminal ammonia concentrations were greater (P less than .10) for WWS- and SBM-supplemented heifers than for C heifers at most sampling times. Moreover, WWS and SBM increased (P less than .10) total VFA (mM) and acetate (mol/100 mol) and lowered propionate (mol/100 mol) at several sampling times. Ruminal fluid volume (liters) was unchanged (P greater than .10) by treatment; however, fluid dilution and flow rate (liters/h) were less (P less than .10) in C heifers than in heifers fed SBM or WWS supplements. Wash water solids and SBM supplementation increased (P less than .10) OM, NDF, and ADF digestibilities compared with C heifers. Feeding WWS and SBM supplements increased BW at 84 d (P less than .10) compared with C-supplemented heifers. Forage intake at 54 and 84 d by heifers supplemented with SBM or WWS was greater (P less than .10) than by C heifers. Control-supplemented heifers had the least, WWS intermediate, and SBM the greatest ADG at 84 d (P less than .10; .14 vs .35 vs .48 kg/d, respectively). These data indicate that WWS may be used as a protein source without serious adverse effects in heifers consuming medium-quality hay for 84 d.