Doctor of Philosophy / Department of Animal Sciences and Industry / Bradley J. Johnson / Research regarding rumen epithelial adaptation and potential mechanisms during the transition period of the dairy cow is lacking. The rumen epithelium has a tremendous capacity for the absorption of volatile fatty acids (VFA) produced from microbial fermentation in the rumen. Absorption of VFA from the rumen pool delivers energy substrates to the animal and provides stability to the rumen environment. Increased epithelial surface area from the development and adaptation of rumen papillae facilitates VFA absorption. Manipulation of the diet to alter rumen fermentation can have positive effects upon the rumen papillae development supporting VFA absorption. We hypothesized that enhancing rumen epithelial surface area through dietary alterations could lead to greater VFA absorption and improve rumen stability. Experiments were conducted to determine the effects of diets formulated with cane molasses to stimulate the production of ruminal butyrate and thereby increase rumen epithelial surface area and to investigate a potential mechanism for glucagon-like peptide-2 (GLP-2) to impact epithelial development. Feeding cane molasses in the dry period improved dry matter intake during the close-up period and during lactation. Milk production was increased for cows that were fed cane molasses during the dry period. Ruminal absorption of valerate was greater during the close-up period than the far-off period but was not influenced by the addition of cane molasses. Total VFA concentration measured during the dry period was not affected by the addition of cane molasses to the diet. The presence of glucagon-like peptide receptor (GLP-2R) mRNA was confirmed in bovine tissue obtained from rumen epithelium, omasum, abomasum, duodenum, jejunum, ileum, large intestine, and pancreas. The greatest level of expression of mRNA for GLP-2R was in the small intestine and large intestine. Expression of GLP-2R mRNA during the prepartum period tended to be increased with the addition of cane molasses. Postpartum expression of GLP-2R was not increased by supplementing cane molasses in the dry cow diet. Results from these experiments indicate that dry cow diets formulated to contain cane molasses can positively influence transition cow performance and that the presence of glucagonlike peptide-2 receptor could play a pivotal role in rumen epithelial development.

Doctor of Philosophy / Department of Animal Sciences and Industry / James S. Drouillard / Four studies evaluated effects of dry distillers grains with solubles (DDGS) containing high S concentrations on feedlot performance, ruminal fermentation, and diet digestibility by finishing cattle. Trial 1 used finishing steers fed diets based on steam-flaked corn (SFC) or dry-rolled corn (DRC), and containing 30% DDGS (DM) with 0.42% S (0.42S) or 0.65% S (0.65S). No interaction (P ≥ 0.15) between dietary S and grain processing occurred, but feeding 0.65S decreased DMI (P < 0.001) and ADG (P = 0.006) by 8.9% and 12.9%, respectively, whereas G:F was unaffected by S concentration (P = 0.25). Steers fed 0.65S had 4.3% lighter HCW (P = 0.006), lower KPH (P = 0.009), and lower yield grades (P = 0.04) than steers fed 0.42S. Concentration of H2S was inversely related (P ≤ 0.01) to ADG (r = -0.58) and DMI (r = -0.67) in cattle fed SFC, and DMI (r = -0.40) in cattle fed DRC. Trial 2 used the same treatments as in the first stud, and investigated ruminal fermentation characteristics and diet digestibility by feedlot cattle. Feeding 0.65S increased ruminal pH (P < 0.05), but decreased total VFA concentrations (P = 0.05). Steers fed 0.65S had greater ruminal NH3 concentrations (P < 0.01) than steers fed 0.42S. The magnitudes of these effects were greater in steers fed DRC than in steers fed SFC (interaction, P < 0.01). Feeding 0.65S yielded greater apparent total tract digestibilities of DM (P = 0.04) and ether extract (P = 0.03). The 3rd study evaluated effects of in vitro S titration (0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6% of DM) in substrates based on ground corn and DDGS (GC-DDGS) or ground corn with urea and soybean meal (GC-SBM). Concentrations of NH3, total VFA, IVDMD, in vitro gas production, and gas composition were unaffected by S (P > 0.05) or by the S × substrate interaction (P > 0.05). Study 4 evaluated cattle feedlot performance when exposed to DDGS containing high S levels, either continuously or intermittently. Treatments were chronic high S (CHS; 0.60% DM), chronic intermediate S (CIS; 0.50% DM), and sporadic intermediate S (SIS; oscillating from 0.40 or 0.60% S DM basis). Steers fed CHS had 11.2 and 6.1% less (P < 0.05) DMI than steers fed CIS and SIS, respectively, but there were no treatment effects on ADG, G:F, or carcass characteristics (P > 0.10). These studies suggest that changes in cattle performance and digestibility associated with high S are primarily attributable to decreased DMI, but infrequent exposure to high levels is no more harmful than continuous exposure.

Master of Science / Department of Animal Sciences and Industry / Michael E. Dikeman / The CVap steam generation oven was compared to a Blodgett forced-air, convection oven to examine effects of cooking method on yields, cooked color, tenderness, and sensory traits of beef Longissimus lumborum (LL), Deep pectoralis (DP), and Biceps femoris (BF) muscles cooked to three endpoint temperatures (65.6, 71.1, and 76.7°C). For each cooking treatment, four roasts were cooked in the CVap oven for a pre-determined, average amount of time, and two roasts were cooked in the Blodgett oven until they reached desired internal endpoint temperature. Cooking yields were higher (P ≤ 0.05) for BF and LL roasts cooked in the CVap. Slice shear force (SSF) for BF roasts cooked in the CVap were lower (P ≤ 0.05), whereas, SSF values for DP roasts cooked in the Blodgett were lower (P ≤ 0.05). No oven difference (P > 0.05) was found for LL roasts. Sensory tenderness scores for BF roasts cooked in the CVap were slightly higher (P ≤ 0.05) than roasts cooked in the Blodgett. Sensory scores for LL roasts cooked in the CVap were slightly higher but were also drier (both P ≤ 0.05). The CVap oven offers tenderization and cooking yield advantages for certain muscles.

Doctor of Philosophy / Department of Animal Sciences and Industry / KC Olson / We evaluated effects of preconditioning on performance and health of beef calves raised and finished in the Great Plains. In experiment 1, calves were preconditioned for 0, 15, or 45 d and vaccinated against BRD-causing pathogens 14 d before maternal separation or after feedlot arrival. During receiving and finishing, preconditioned calves had greater DMI and ADG than non-preconditioned calves; however, timing of BRD vaccination did not affect animal health. In experiment 2, calves were vaccinated against BRD pathogens 0, 1, 2, or 3 times during a 30-d preconditioning program. Vaccination for BRD, regardless of degree, improved health during preconditioning; however, DMI, ADG, and G:F during preconditioning, receiving, and finishing were unaffected by degree of vaccination. In experiment 3, calves were preconditioned for 30 d, shipped 4 h to an auction facility, commingled for 12 h, and transported 4, 8, or 12 h to a feedlot. Feedlot performance and health of beef calves were not affected by transport of up to 12 h following auction-market commingling. In experiment 4, beef calves were subjected to 1 of 3 ranch-of-origin preconditioning programs: drylot weaning + abrupt dam separation, pasture weaning + fence-line contact with dams, and pasture weaning + fence-line contact with dams + supplemental feed delivered in a bunk. Drylot-weaned calves gained more weight during preconditioning. Unsupplemented, pasture-weaned calves had the least ADG during receiving but had greater ADG during finishing and had carcass characteristics similar to other treatments. In experiment 5, we evaluated performance of early-weaned beef calves fed grain-based diets with DMI adjusted to achieve ADG of 0.45, 0.91, or 1.36 kg/d during an 84-d growing period. Calves fed at restricted rates did not exhibit improved G:F relative to full-fed counterparts. In addition, there appeared to be limitations associated with predicting DMI and ADG of light-weight, early-weaned calves fed a grain-based diet.

Master of Science / Department of Animal Sciences and Industry / James S. Drouillard / Exogenous growth promotants, such as the synthetic beta agonist zilpaterol hydrochloride (ZH), have been shown to increase carcass weight by repartitioning energy toward increased skeletal muscle at the expense of adipose tissue, which is associated with a decline in tenderness. More recently, essential oils such as menthol have been observed to have growth promoting properties in livestock. The objectives of this research were to determine effects of ZH on blood parameters and long chain fatty acids in plasma and adipose tissue, to determine if the decline in tenderness can be negated by temporary depletion of calcium during ZH supplementation, and to determine effects of crystalline menthol on blood parameters. Blood samples were collected in 7-d intervals during ZH administration. Zilpaterol hydrochloride decreased concentrations of plasma urea nitrogen and whole blood glucose (P < 0.10), but had no effects on concentrations of plasma glucose, lactate, beta-hydroxybutyrate, NEFA, or whole blood lactate (P > 0.10). Total long chain fatty acids of plasma and adipose tissue were unaffected (P > 0.10); however, ZH supplementation increased HCW, dressing percentage, and LM area (P < 0.10). Calcium was temporarily depleted during ZH supplementation in an attempt to increase tenderness of meat. No differences (P > 0.10) were observed for Warner-Bratzler shear force values, live animal performance, or carcass measurements. Addition of 0, 0.003, 0.03, 0.3% menthol (diet DM) to diets of steers resulted in a menthol × time within day interaction (P < 0.01) for IGF-1 concentration and BW; however, glucose, lactate, and PUN concentrations were unaffected (P > 0.05). Furthermore, concentrations of VFA were not different (P > 0.05), but production of fermentative gas was decreased (P < 0.01) when menthol was added at 0, 0.003, 0.03, 0.3% of substrate DM in a 24 h in vitro fermentation trial. Results from these studies suggest ZH improved efficiency of nutrient utilization for increased skeletal muscle growth; however, the decline in tenderness was not negated by the temporary depletion of calcium in the diet. Overall, ZH affected components related to increased skeletal muscle growth, but menthol did not affect blood parameters associated with growth.

Doctor of Philosophy / Department of Animal Sciences and Industry / Jim Nelssen / A total of 701 pigs were used to evaluate effects of natural vitamin E relative to synthetic vitamin E in sow diets, late gestation feeding level on sow reproductive performance, dietary L-carnitine and chromium on sow reproductive performance, and experimental design on nursery pig trial interpretation. As D-α-tocopheryl acetate increased in the sow’s diet, concentrations of α-tocopherol increased (P < 0.03) in sow plasma, colostrum, milk, pig plasma, and pig heart. Regression analysis indicated that the bioavailability coefficients for D-α-tocopheryl acetate relative to DL-α-tocopheryl acetate ranged from 2.1 to 4.2 for sow and pig plasma α-tocopherol, 2.9 to 3.0 for colostrum α-tocopherol, 1.6 for milk α-tocopherol, 1.8 for heart α-tocopherol, and 2.0 for liver α-tocopherol. Overall, this study indicates that the relative bioavailability for D-α-tocopheryl acetate relative to DL-α-tocopheryl acetate varies depending on the response criteria but is greater than the standard potency value of 1.36. Increasing sow gestation feeding level by 0.9 kg from d 90 of gestation through farrowing reduced (P = 0.001) daily lactation feed intake in gilts, but also resulted in improved conception rate in gilts, whereas increasing late gestation feeding level decreased conception rate in sows (interaction; P = 0.03). Increasing late gestation feed intake in gilts also increased (P < 0.02) pig weaning weights during the second parity. Increasing late gestation feeding levels did not improve performance of older sows. Adding L-carnitine and chromium from chromium picolinate to sow gestation and lactation diets reduced (P = 0.01) the amount of sow weight loss during lactation, however, did not improve (P > 0.05) litter size, pig birth weight, or the variation in pig birth weight. Blocking pens of nursery pigs by BW in a randomized complete block design (RCBD) did not improve the estimates for σ2error compared to a completely randomized design (CRD) where all pens were allotted to have similar means and variations of body weight. Therefore, the added degrees of freedom for the error term in the CRD allowed more power to detect treatment differences for the CRD compared to the RCBD.

Doctor of Philosophy / Department of Animal Sciences and Industry / Jeffrey S. Stevenson / Two experiments assessed pregnancy outcomes (pregnancy per AI; P/AI) after 5-d Ovsynch-56 Resynch (RES; GnRH injection 5 d before [GnRH-1; d 0] and 56 h (GnRH-2) after the last PGF2α [PGF] injection on d 6 given 24 h after first PGF injection on d 5, and TAI on d 8) with and without a 5-d progesterone insert. In Exp. 1, only 76% of 1,023 nonpregnant cows enrolled on d 34 post-AI had high (≥1 ng/mL) progesterone. The RES-CIDR cows with low progesterone at treatment initiation had greater P/AI than RES-CON (37.7 vs. 29.4%), whereas RES-CIDR cows with high progesterone had lesser P/AI than RES-CON (27.4 vs. 34.3%) suggesting that supplemental progesterone is progesterone-dependent. In Exp. 2, 381 cows were enrolled in similar treatments on d 31 with RES on d 41post-AI plus a third treatment including PG-3-G (Pre-PGF on d 31, Pre-GnRH on d 34, and RES on d 41. The P/AI was similar among treatments but was greater in cows starting RES on d 41 when progesterone was low (44%) than high (33%).Experiment 3 determined LH and ovulatory responses in cows enrolled in two treatments before AI: 1) Pre10 (n = 37): PGF-1 and PGF-2 given 14 d apart (Presynch); or PG3G (n = 33): PGF given concurrent with the PGF-2, 3 d before GnRH-1 followed in 7 d by Ovsynch [injection of GnRH (GnRH-2) 7 d before PGF (PGF-3) and GnRH-3 at either 56 or 72 h after PGF-3] that was initiated 10 d after PGF-2 for Pre10 or 7 d after GnRH-1 of PG3G. The GnRH- 1 increased incidences of LH surges and ovulation in PG3G compared with Pre10. The LH in serum of Pre10 was greater than that of cows receiving PG3G after GnRH-2. Following GnRH- 3, cows receiving GnRH at 72 h had increased incidence of spontaneous LH surges before GnRH-3. The P/AI for PG3G vs. Pre10 and for 56 vs. 72 h was similar, but the Pre10-72 h treatment combination was less than all other treatment combinations. Release of LH is protocol dependent and flexibility of GnRH timing is an advantage for PG3G before first-service TAI.

Master of Science / Department of Animal Science and Industry / David M. Grieger / Controlling reproductive cycles during active cyclicity and seasonal anestrous in small ruminants is critical for profitability. The objective of this study was to evaluate the effect on estrous response and interval to estrus of two CIDR protocols in sheep and goats during breeding and non-breeding seasons. In experiment 1, 133 ewes were randomly assigned to 1 of 3 treatments during the breeding season. In the CIDR-7 group, ewes received a CIDR insert for 7 d. In the CIDR-7 + PGF treatment, ewes received a CIDR insert for 7 d and 20 mg of prostaglandin-F[subscript]2[subscript]α (PGF[subscript]2[subscript]α) upon CIDR removal. Ewes in the CIDR-14 treatment received a CIDR insert for 14 d. Following CIDR removal all ewes were exposed to a ram every 12 h until breeding. There was a shorter interval from CIDR removal to estrus in the CIDR-14 treatment compared to the CIDR-7 and CIDR-7 + PGF treatments (P<0.05). There was no difference in number of ewes per treatment displaying estrus. In experiment 2, 54 ewes were randomly assigned to one of two treatment groups during the anestrous season. Ewes in CIDR-7 and CIDR-14 treatments received a CIDR insert for 7 d and 14 d, respectively. Upon CIDR removal ewes were exposed to a ram every 12 h until breeding. There was a significantly shorter interval from CIDR removal to estrus in CIDR-14 ewes when compared with CIDR-7 ewes (P<0.05). For experiment 3, 37 Boer does were randomly assigned to one of two treatments. In the CIDR-10 treatment, does received a CIDR insert for 10 d and 20 mg of PGF[subscript]2[subscript]α at time of CIDR removal. In the CIDR-19 treatment, does received a CIDR insert for 19 d. Upon CIDR removal, does were exposed to a buck fitted with a marking harness and chalk marks were recorded every 12 h. The number of does displaying estrus was not different (CIDR-7, 85%; CIDR-14, 95%). There was no difference in interval from CIDR removal to estrus between treatments. Results from experiments 1 and 2 supported the hypothesis that long-term protocols yield a shorter interval to estrus when compared with short-term protocols.

Master of Science / Animal Sciences and Industry / Jennifer M. Bormann / Feed is the single most expensive cost related to beef cattle production. Currently a 70 d performance test is recommended for accurate calculation of efficiency. Previous research has suggested intake tests can be limited to 35 d. Objectives of this study were to estimate genetic parameters for growth and intake traits, compare two alternative indices for feed efficiency, and quantify the genetic response to selection for feed efficiency combining an intake test with two types of gain data. On–test average daily feed intake (ADFI), on-test average daily gain (ADG), and postweaning gain (PWG) records on 5,606 growing steers and heifers were obtained from the U.S. Meat Animal Research Center in Clay Center, NE. On-test ADFI and ADG data were collected from a minimum of 62 to 148 d testing days. Independent quadratic regressions were fitted for body weight on time, and on-test ADG was predicted from the resulting equations. PWG was calculated by subtracting adjusted 205-d weights from 365-d weights and dividing by 160. Genetic correlations were estimated using multiple trait animal mixed models with ADG, ADFI, and PWG for both sexes as dependent variables. The genetic correlations between ADG and PWG for both steers (0.81) and heifers (0.65) were strong. This indicates PWG is a strong proxy for ADG on-test and long test periods may not be necessary. Indices combining EBVs for ADFI and ADG and for ADFI and PWG were evaluated. For each index, the weighting of gain was arbitrarily set to 1.0 and the weighting for ADFI was the negative of the average of the intra-contemporary group ratio of mean gain divided by mean ADFI. Values were combined with EBV to compute two index values per animal. Pearson correlations for steers (0.96) and heifers (0.45) indicated a strong relationship for steers between the indices. Because more animals can be measured for intake, using PWG increases genetic progress of selection for feed efficiency by 15-17% per year. These findings support using PWG data in combination with ADFI to determine efficient animals, lessen costs, and increase annual feed efficiency genetic change.

Doctor of Philosophy / Department of Animal Sciences and Industry / Joel M. DeRouchey / A total of 7,061 finishing pigs were used in 7 experiments. Experiment 1 investigated the effects of withdrawing high-fiber ingredients prior to marketing to optimize growth performance, carcass yield, and carcass fat quality. Switching pigs from a high-fiber to a low-fiber corn-soy diet approximately 15 to 19 d before slaughter restored carcass yield and partially decreased carcass fat IV compared to pigs fed the high-fiber diet until slaughter. Experiment 2 studied 30% distillers dried grains with solubles (DDGS) and 5% added fat prior to slaughter on growth performance and carcass characteristics. Adding 5% fat to finishing pig diets containing 30% DDGS approximately 20 d before slaughter improved ADG and G:F but did not overcome the reduction in carcass yield from feeding DDGS. Experiment 3 investigated the Cu source on growth performance and carcass characteristics. Increasing dietary Cu in high byproduct diets improved growth and feed intake, resulting in increased final BW and HCW for pigs fed both Cu sources. Experiment 4 examined added Cu and standardized ileal digestible (SID) lysine (Lys) level on growth performance, carcass characteristics, and carcass fat quality. Feeding 150 mg/kg Cu to pigs in the 100% SID Lys requirement diet had improved growth but in the 85 or 92.5% SID Lys requirement diet no response to added Cu was found. Furthermore, increasing SID Lys increased ADG and HCW, but added Cu did not influence growth when feeding low SID Lys. Experiment 5 investigated diet ingredient type and added Cu on growth performance, carcass characteristics, gross energy digestibility, and small intestine histology and gene expression. When comparing diet type and added Cu, pigs fed a byproduct diet with DDGS and bakery meal tended to have lower G:F and reduced HCW compared to pigs fed a corn-soy diet. Adding Cu did not influence growth or carcass characteristics. However, adding Cu to the byproduct diet improved gross energy digestibility and decreased the crypt depth in the distal small intestine. Finally, a linear programming model was developed as a decision tool for commercial swine producers to help guide pig flow decisions to maximize the return to the operation.