Egg white contains many functionally important proteins: ovalbumin (54%), ovotransferrin (12%), ovomucoid (11%), ovoglobulin (G2 and G3, 8%), ovomucin (3.5%), and lysozyme (3.5%) are major proteins, while ovoinhibitors, ovomacroglobulin, ovoglycoprotein, ovoflavoprotein, thiamine-binding proteins, and avidin are minor proteins present in egg white. These proteins, as well as the peptides derived from the proteins, have been recognized for their functional importance as antioxidant, antimicrobial, metal-chelating, anti-viral, anti-tumour, and angiotensin-converting enzyme (ACE)-inhibitory activities. Among the functional properties of the peptides, antioxidant and antimicrobial activities are important characteristics for food processing while other properties such as ACE-inhibitory activity of the peptides can have important health-related functionalities. Bioactive peptides can be produced from egg white proteins by enzyme hydrolysis, chemical treatments, or thermal treatments at different pH conditions. The effective functional peptides produced from egg white proteins are usually smaller than 2 kDa in molecular size. However, these peptides are known for their beneficial activities in vitro only, and little work has been done to prove their beneficial effects in vivo. Therefore, further studies are needed to see if the bioactive peptides derived from egg white proteins are helpful for humans in the future.

Carbohydrates represent the largest components of swine diets in the U.S. due to the different chemical and physical characteristics among sources; carbohydrates can exert different effects in the gastrointestinal tract of pigs. The primary purpose of this dissertation was to improve our understanding of the role of simple and complex carbohydrates on various nutritional interventions for nursery and growing pigs. To achieve this objective 5 experiments were conducted. A set of three experiments were designed to determine the effect of a prototype Lactobacillus acidophilus fermentation product (FP). The first experiment evaluated the FP with and without dietary antibiotics on growth performance. Second, a similar experiment was performed to determine the effect of the FP and lactose (LA) level on growth performance in an antibiotic-free diet scenario. A more mechanistic experiment was conducted to determine the effects of LA and the FP, on diet digestibility, N balance and intestinal function of weaned pigs. A set of- two experiments were designed to investigate the role of insoluble in two scenarios. The first experiment evaluated the effect of insoluble fiber on the efficacy of the phytase enzyme in nursery pigs when fed diets limiting in P content. The second was designed to determine if the impact of increasing insoluble fiber level on the digestibility of energy and nutrients- differs when diets are adjusted to constant nutrient (CN) or to constant ingredient composition (CI). Results of Exp 1 supported the positive role of dietary antibiotics on the growth performance of nursery pigs. However, the addition of FP or increasing the level of LA (from 7.5 to 15%) were not effective strategies to improve these growth variables (Exp 1 and Exp 2). Results of Exp 3 showed that LA benefits the weaned pig by improving nutrient utilization rather than by improving gut function and structure. Results also showed a little benefit of using FP alone or in combination with LA and that there were no additive effects between the two (LA and FP), at least under the conditions of this study. Results of Exp 4 clearly showed that the efficacy of

phytase to release P from phytate is not impaired by insoluble fiber. Results of Exp 5 showed that increasing the insoluble fiber level in the form of DDGS decreased the digestibility of most dietary components. Results also showed that the use of the CI method for formulating diets resulted in a lower digestibility of insoluble fiber compared with diets formulated using the CN method. This demonstrated the bias that can be introduced into this type of experiment by the formulation method.

Feed grains are processed to improve their value in pig diets by exposing kernel contents to enzymatic and microbial action. The objective of this study was to quantify the effect of reducing mean particle size (PS) of wheat grain ground with two different grinding methods (GMs) on the apparent total tract digestibility (ATTD) of nutrients and energy in growing and finishing pigs. Forty-eight barrows were housed in individual pens for 11 d for two periods. Pigs were randomly assigned to a 3 × 2 × 2 factorial experimental design: three target mean PS of wheat grain (300, 500, and 700 µm), two GMs (roller mill and hammermill), and two body weight (BW) periods (growing period; initial BW of 54.9 ± 0.6 kg and finishing period; initial BW of 110.7 ± 1.4 kg). Diets contained one of six hard red wheat grain samples, vitamins, minerals, and titanium dioxide as an indigestible marker. Feed allowance provided 2.5 (for the two lightest pigs in each treatment) or 2.7 (for the remaining six pigs in each treatment) times the estimated daily maintenance energy requirement for each growth stage. Fecal samples were collected for the last 3 d of each period. Data were analyzed as a linear mixed model with pig as a random effect and PS, GM, and BW period and their interactions as fixed effects utilizing the MIXED procedure of SAS. Growing pigs had greater (P < 0.05) ATTD of dry matter (DM), gross energy (GE), N, acid hydrolyzed ether extract (AEE), and neutral detergent fiber (NDF) by lowering mean PS from 700 to 500 μm using either a roller mill or a hammermill. However, digestibility did not increase when PS was reduced from 500 to 300 μm, except for AEE (P < 0.05). Finishing pigs had greater ATTD of DM, GE, N, AEE, and NDF by lowering mean PS with a hammermill from 700 to 500 μm (P < 0.05), but it was greater for 500 μm than for 300 μm (P < 0.05). Using a roller mill reduced the ATTD of DM and NDF by lowering PS from 700 to 300 μm (P < 0.05). The ATTD of GE decreased by lowering PS from 700 to 500 μm with a roller mill (P < 0.05) for finishing pigs. The ATTD of N and AEE for finishing pigs were similar from 700 to 300 μm when ground by a roller mill. These data suggest that the PS that maximized digestibility for a hammermill is 500 μm for both growing and finishing pigs. However, for the roller mill, the PS resulting in the best digestibility were 500 and 700 μm for growing and finishing pigs, respectively.

The experimental objective was to determine the role of mean particle size (PS), grinding method, and body weight (BW) category on nutrient, fiber, and energy digestibility of corn. A total of 48 barrows were housed in individual pens and randomly assigned to one of six dietary treatments for 11 d at two BW categories (55 kg and 110 kg). The six treatments consisted of corn ground at three different targeted mean PSs (300, 500, and 700 µm) using either a roller mill or a hammermill. Fecal samples were collected for the last 3 d of each feeding period. Titanium dioxide was used as an indigestible marker. Digestibility data were analyzed as a linear mixed model using the MIXED procedure of SAS. Finishing pigs had greater apparent total tract digestibility (ATTD) of dry matter (DM), gross energy (GE), and N than growing pigs (P = 0.02, P = 0.01, and P <0.01, respectively). The ATTD of DM, GE, and N was similar in pigs fed hammermilled corn across all PS treatments. However, in roller-milled corn, they increased as PS was reduced (P < 0.05). The ATTD of acid-hydrolyzed ether extract (AEE) in growing pigs was similar between corn ground at 700 and 500 µm, but it was increased by further reducing PS to 300 µm (P < 0.05). In finishing pigs, the ATTD of AEE increased as mean PS decreased from 700 to 300 µm (P < 0.05). The ATTD of AEE was similar in hammermilled corn at all three PS treatments. On the other hand, the ATTD of AEE was similar in corn ground in a roller mill to 700 and 500 µm, but it increased when PS was reduced to 300 µm (P < 0.05). In conclusion, reducing PS of corn with a roller mill increased digestibility of energy and nutrients, but there was less effect using a hammermill. It is possible that differences in SD, distribution, chemical composition, and the shape of the particles resulting from the two grinding processes help to explain the different response.

Ovomucoid is well known as a “trypsin inhibitor” and is considered to be the main food allergen in egg. However, the negative functions of ovomucoid can be eliminated if the protein is cut into small peptides. The objectives of this study were to hydrolyze ovomucoid using various enzyme combinations, and compare the functional properties of the hydrolysates. Purified ovomucoid was dissolved in distilled water (20 mg/mL) and treated with 1% of pepsin, α-chymotrypsin, papain, and alcalase, singly or in combinations. Sodium sodium dodecyl sulfate-polyacrylamide (SDS-PAGE) results of the hydrolysates indicated that pepsin (OMP), alcalase (OMAl), alcalase + trypsin (OMAlTr), and alcalase + papain (OMAlPa) treatments best hydrolyzed the ovomucoid, and the 4 treatments were selected to determine their functional characteristics. Among the 4 enzyme treatments, hydrolysate from OMAlTr showed the highest iron-chelating and antioxidant activities, while OMP showed higher ACE-inhibitory activity, but lower Fe-chelating activity than the other treatments. However, no difference in the copper-chelating activity among the treatments was found. MS/MS analysis identified numerous peptides from the hydrolysates of OMAlPa and OMAlTr, and majority of the peptides produced were <2 kDa. Pepsin treatment (OMP), however, hydrolyzed ovomucoid almost completely and produced only amino acid monomers, di- and tri-peptides. The ACE-inhibitory, antioxidant and iron-chelating activities of the enzyme hydrolysates were not consistent with the number and size of peptides in the hydrolysates, but we do not have information about the quantity of each peptide present in the hydrolysates at this point.

The net energy (NE) system describes the useful energy available for growth better than the metabolizable energy (ME) system. The use of NE in diet formulation should maintain growth performance and carcass parameters when diets contain a diversity of ingredients. This study compared the growth performance of pigs on diets formulated using either the ME or NE system. A total of 944 gilts and 1,110 castrates (initial BW = 40.8 ± 2.0 kg) were allotted to group pens and assigned to one of 5 different feeding programs according to a randomized complete block design. A simple corn-soybean meal control (CTL) established baseline levels of ME or NE concentrations for the other dietary treatments. Thus, for two of the treatments, corn DDGS were added at 25% and formulated to achieve a constant ME or constant NE relative to the CTL (ME-D and NE-D). For the other two treatments, corn DDGS and corn germ meal were added at 15% and 20%, respectively, formulated to achieve a constant ME or a constant NE diet (ME-DC and NE-DC). When required, fat was added as an energy source. Pigs were harvested at an average BW of 130.3 ± 4.0 kg. Growth performance was not affected by treatment (P = 0.581, P = 0. 177 and P = 0.187 for ADG, ADFI and G: F ratio respectively). However, carcass growth decreased with the addition of co-products except for the NE-D treatment (P=0.016, P = 0.001, P = 0.018, P = 0.010 and P = 0.010 for dressing percentage, HCW, carcass ADG, back fat and loin depth respectively). Carcass G:F and lean percentage did not differ among treatments (P = 0.109 and P = 0.433). On the other hand, NE intake decreased (P = 0.035) similarly to that of carcass gain, suggesting a relationship between NE intake and energy retention. Calculations of NE per kg of BW gain differed among treatments (P = 0.010), but NE per kg of carcass was similar among treatments (P = 0.640) This suggests that NE may be better than ME at explaining the carcass results. Finally, ME intake and ME per kg of BW gain were not different among treatments (P = 0.112), but ME per kg of carcass gain was different among treatments (P = 0.048). In conclusion, the sequential addition of co-products in diets formulated on an NE or ME basis can result in similar growth performance, but carcass parameters may be affected independently of the energy system used. However, formulating diets based on NE tended to improve predictability of growth, especially carcass parameters.

The objective of this study was to determine the differences in response to distillers dried grains with solubles (DDGS) level under constant nutrient or floating nutrient concentrations. A total of 21 ileal-cannulated gilts (33.1 ± 0.4 kg body weight) were randomly allotted to one of seven dietary treatments in a 3-period incomplete Latin square design (n = 9). Treatments consisted of a 0% DDGS basal diet, plus diets containing 15%, 30%, or 45% DDGS. Diets were formulated using one of two different formulation methods: 1) constant nutrient (CNU) where nutrients were held equal to the basal diet or 2) constant ingredients (CIN) where DDGS were added at the expense of corn and all other ingredients remained constant, so nutrient levels were allowed to “float.” Chromic oxide was added to the diets at 0.5% as an indigestible marker. Increasing the level of DDGS decreased the apparent ileal digestibility (AID) of dry matter (DM), gross energy (GE), starch, dispensable amino acids (AA), and fiber components (P < 0.050). The decrease in the AID of Lys, Met, Thr, and Trp was more pronounced under CNU compared with the CIN formulation method (P < 0.050). The decrease in the AID of hemicellulose was less pronounced under CNU compared with the CIN formulation method (P = 0.045). There was a DDGS level × formulation method interaction for the AID of acid hydrolyzed ether extract (AEE; P = 0.015); for the CNU formulation method, increasing level of DDGS decreased the AID of AEE from 0% to 30% and remained similar from 30% to 45% DDGS, whereas the CIN had no effect on the AID of AEE. Increasing the level of DDGS decreased the apparent total tract digestibility (ATTD) of DM, GE, and fiber components (P < 0.050), except for acid detergent fiber, which was not affected. The decrease in the ATTD of insoluble dietary fiber and total dietary fiber was less pronounced under CNU compared with CIN (P < 0.050). The ATTD of AEE decreased for CNU compared with CIN (P < 0.010). In conclusion, increasing the insoluble fiber level in the form of DDGS decreased the digestibility of most dietary components, including DM, GE, starch, insoluble fiber, and AA. The CNU and CIN formulation methods are equivalent when evaluating the digestibilities of DM, GE, starch, crude protein, and AA (when they were not added in purified synthetic forms). Differences between CNU and CIN formulation methods were detected for the digestibility of insoluble fiber, fat, and essential AA (when added as crystalline AA).

There are several constraints to of the sustainability of the livestock industries in different areas of the world. The two most obvious hurdles to high dairy production are diseases during the transition period and heat stress (HS). Despite decades of research, the actual pathologies of ketosis and HS remain poorly understood. In the US, it was estimated that the economic losses from ketosis is $360/cow/cycle, and to HS was ~ $900 million per year. Thus, both severely jeopardize the competitiveness of animal agriculture. Regardless of the herd size, HS and ketosis affect every dairy region in the country. The biological investigations of ketosis and HS have been studied for more than 50 years, but the negative impacts of both are as severe today as they were 30 years ago.

In the current dissertation, ketosis in dairy cows and HS in pigs and steers were investigated to better understand the biology and etiology of both disorders. Study 1 (Chapter 2) was conducted to characterize biomarkers of inflammation during the transition period in healthy and clinically diagnosed ketotic cows. The results indicated that circulating NEFA and BHBA were increased and milk yield was decreased in ketotic relative to healthy cows. In addition, pre-calving circulating LPS was increased twofold in cows that were diagnosed with ketosis post-calving compared to healthy cows, but no LPS differences were detected post-partum. Post-calving LPB, SAA and Hp were increased when compared with their healthy counterparts. Our data suggest the development of ketosis may be intimately linked to inflammation and our selection criteria suggest that intestinal permeability may be the origin of maladaptation to lactation.

In Study 2 (Chapter 3) we investigated the effects of a mineral supplement (zinc amino acid complex) on temporal biomarkers of intestinal integrity and intestinal morphology in heat-stressed steers. As expected, HS increased thermal indices and decreased feed intake. However, steers supplemented with zinc amino acid complex had decreased rectal temperature, improved biomarkers of leaky gut (haptoglobin, and LBP), altered intestinal morphology (decreasing duodenum villi width, increasing jejunum villi height and jejunum and ileum villi height:crypt depth), and improvement in some of the blood gas variables relative to steers supplemented with zinc sulfate. Altogether, the findings of Study 2 demonstrated that a Zn-amino acid complex may mediate some of the negative effects of HS in a growing ruminant model.

Study 3 (Chapter 4) investigated the temporal pattern of metabolic variables and biomarkers associated with intestinal barrier dysfunction during recovery from HS in pigs. Similar to Study 2, HS increased thermal indices and decreased feed intake. Circulating glucose decreased during HS and remained low for 3 d following HS. The insulin:feed intake tended to be increased during HS, and LBP increased linearly during HS recovery. In addition, HS decreased villous height in both jejunum and ileum but intestinal morphology mostly returned to normal following 3 days of recovery. The results of this study confirmed the negative effects of HS on thermal indices, inflammatory biomarkers, and intestinal morphology; however, it suggests that intestinal integrity was restored fairly quickly, but the acute phase protein response increased with time following HS exposure.

In conclusion, the results of the aforementioned studies indicate a negative association of impaired gut integrity with the incidence of ketosis in transitioning dairy cows and performance in heat-stressed steers and pigs. A better understanding of the relative contribution of the intestinal barrier dysfunction to ketosis and heat-induced effects on metabolism and gut morphology is a prerequisite for designing targeted strategies to alleviate the negative consequences of ketosis and HS on farm animals’ productivity.

Rising feed expenditures demand that our industry pursues strategies to lower the cost of production. One option is the adoption of the net energy system (NE), although many producers are hesitant to proceed without proof that NE estimates are reliable. The objective of this experiment was to compare the apparent total tract digestibility (ATTD) of energy and nutrients and the N retention (NR) of diets formulated using the NE system with increasing quantities of co-product ingredients. The 5 dietary treatments included a control corn-soybean meal diet (CTL), the CTL diet plus 6% each of corn distiller’s dried grains with solubles (DDGS), corn germ meal, and wheat middlings, and NE equal to the CTL diet by adding soybean oil (CONS- 18), the CONS-18 diet, without oil added, with NE content lower than CTL (DECL-18), CTL plus 12% each of corn DDGS, corn germ meal, and wheat middlings, and NE equal to CTL by adding soybean oil (CONS-36), the CONS-36, without oil added, with NE content lower than the CTL diet (DECL-36). Diets were formulated for both growing (40 to 70 kg; GP) and finishing (70 to 110 kg; FP) periods. Forty gilts (PIC 337 × C22 or C29; initial BW=38.5 ± 0.4 kg) were randomly assigned to treatment and received feed and water ad-libitum (8 pigs per treatment). For the last 13 d of the GP and FP, pigs were transferred to metabolism crates, where two total urine and fecal collections (d 4 to 6; d 11 to 13) were performed. The GP fed diets with coproduct ingredients had lower ATTD of DM, N and GE than those fed the CTL diet (P < 0.050). The ATTD of N and GE decreased progressively as co-product inclusion increased from 0 to 18 to 36% in the FP (P < 0.010). In the GP and FP, there were no differences in ATTD of DM, N or GE between the pairs of CONS and DECL-NE treatments (P > 0.050). The NR declined on all co-product diets on the GP (P = 0.010) and tended to decline in the FP (P = 0.079). There were no differences in NR between CONS and DECL diets with the same level of co-product inclusion (P > 0.050). In conclusion, digestion of diets containing up to 36% co-products and formulated using NE resulted in expected DE and ME values; NR of diets with coproducts was lower than on the simple corn-soybean meal CTL diet, which is not related to the accuracy of the energy estimations, but rather to other factors such as imbalances in the AA concentrations or to post-absorptive energy metabolism, factors not accounted by the current energy systems approach.

The approach of this experiment was to apply the regression method for the estimation of endogenous intestinal losses of ether extract (EEE) when pigs are fed complete diets ad libitum and using dietary levels of fat typical of those employed in commercial situations. A total of 40 gilts (PIC 337 sires × C22 or C29) were allotted to individual pens and randomly assigned to diets (8 pigs per treatment) with 5 different levels of acid hydrolyzed ether extract (AEE). The dietary treatments consisted of a corn-soybean meal diet with no added fat (L1); a corn-soy diet with 6% each of corn distiller’s dried grains with solubles (DDGS), corn germ meal, and wheat middlings (L2); the L2 diet but with 12% each of corn DDGS, corn germ meal, and wheat middlings (L3); the L2 diet plus soybean oil to equalize the NE concentration of the L2 diet with L1 (L4); and the L3 diet plus soybean oil to equalize the NE concentration of the L3 diet with L1 (L5). Pigs received feed and water ad libitum for the growing period (initial BW = 38.5 ± 1.2 kg) and the finishing period (initial BW = 73.82 ± 2.9 kg). A quadratic broken-line model was employed to estimate the response of apparent total tract digestibility (ATTD) of AEE to dietary AEE level. The average true total tract digestibility (TTTD) of AEE and endogenous losses of AEE were estimated using regression analysis of dietary AEE intake (g/kg of DM) against apparent digested AEE (g/kg of DMI). The ATTD of AEE increased in curvilinear fashion as dietary AEE level increased in growing and in finishing pigs (P < 0.001). This suggests an influence of EEE on the ATTD of AEE estimates. The linear regression of apparent digested AEE against dietary AEE intake (L1–L5; P < 0.001, R2 = 0.99 for growing pigs and P < 0.001, R2 = 0.99 for finishing pigs) estimated greater EEE (P < 0.05) and TTTD of AEE (P < 0.05) for growing than finishing pigs. Estimated EEE from growing pigs ranged between 18.1 and 20.2 g/kg of DMI, while TTTD of AEE ranged between 96.40% and 100.70%. In finishing pigs, EEE ranged between 21.6 and 23.8 g/kg of DMI and TTTD of AEE ranged between 91.30% and 95.25%. In conclusion, EEE under practical conditions is estimated to be 19.2 g/kg of DMI in growing and 22.7 g/kg of DMI in finishing pigs.