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<p>Gastrointestinal health in the young pig is a constant challenge for the swine industry. Weaning introduces many stressors such as a new solid diet, being separated from their mother, new pen mates, transportation, and an entirely new environment. Therefore, this dissertation primarily focuses on research aiding the pig immediately post-weaning. In chapter 2, a developmental bacillus direct fed microbial (DFM) was added to nursery pig diets to evaluate its effects on pig growth and health in two 35-d experiments, both randomized complete block designs based on initial BW and sex. Experiment 1 used 376 weaned pigs (17.8 d of age; 5.99±0.18 kg initial BW) allotted to one of four diets. 1) Negative Control (NC; no antibiotics with pharmacological Zn or Cu), 2) NC+DFM 0.275x109 CFU, 3) NC+DFM 0.55x109 CFU, 4) NC+DFM 1.1x109 CFU. Experiment 2 used 420 weaned pigs (20.1 d of age; 6.11±0.34 kg initial BW) allotted to one of four diets: 1) Negative Control (NC; no antibiotics with pharmacological Zn or Cu), 2) NC+DFM 0.55x109 CFU, 3) NC+DFM 1.1x109 CFU, 4) NC+BioPlus 2B 1.1x109 CFU. Experiment 1; during week 1 there were no treatment effects. During week 3 ADFI (P=0.053) quadratically increased while G:F (P=0.028) quadratically decreased as DFM increased in the diet. During d21-35 of experiment 2, ADG (P=0.092) quadratically increased and G:F (P=0.014) quadratically decreased as DFM increased.  Overall, for Experiment 1, ADFI numerically increased (4.3%) with no increase in ADG, resulting in a quadratic decrease in G:F (P=0.010) as the DFM increased in the diet.  For Experiment 2, during week 1, DFM fed pigs tended to have linearly decreased ADFI (P=0.092) and linearly increase G:F (P=0.072). Pigs fed the Bioplus2B bacillus had greater ADFI (P=0.018) than the same dose of the experimental bacillus. During week 2 pigs fed the experimental bacillus at 1.1x109 CFU tended to have improved G:F (P=0.084) than the similar DFM concentration from, the Bioplus 2B. During week 4 ADG tended to linearly (P=0.057) improve with increasing DFM in the diet and the average of all DFMs tended to have improved ADG (P=0.075) over the NC. During week 5 ADFI linearly increased (P=0.029) as DFM increased in the diet and all DFM treatments had greater ADFI (P=0.009) than the NC.  During d 21-35 of experiment 2, DFM fed pigs had linearly increased ADG (P=0.04) and ADFI (0.090). All pigs fed DFM had improved ADG (P=0.068) and ADFI (P=0.032) compared to NC fed pigs. Summarizing these two studies, the DFM product had its greatest effect improving gain feed intake and efficiency during late nursery when simplest diets are fed.</p> <p>In chapter 3, Dacitic tuff breccia (DTB) and poultry by-products (PBP) were added to nursery pig diets to evaluate their effects on growth performance and jejunal characteristics in a 35 d experiment. PBP were added as a replacement for fishmeal and was expected to provide an increased immune challenge to the newly weaned pigs. DTB was added as a functional trace element source and was hypothesized to ameliorate some of the negative impacts of PBP on the gut. A randomized complete block design based on BW and sex was used. Newly weaned pigs (N=564, 20.1±1.2 d of age, 6.18±1.13 kg initial BW). allotted to four diets (15 replicates/treatment; 9 or 10 pigs/pen): 1) Control (C; no DTB or PBP), 2) C+DTB (0.5% inclusion), 3) C+PBP (4% chicken by-product meal + 2% feather meal – replacing fishmeal, corn, and synthetic amino acids in the C), 4) C+DTB+PBP. Phase 1-3 were each 7-d and Phase 4 was from d 21-35. One barrow/pen was harvested 11d post-weaning. Jejunal tissue and mucosa were collected for histological measures and gene expression. In week 2, pigs fed DTB tended to increase ADG (323 vs. 303 g/d; P=0.068) and ADFI (376 vs. 356 g/d; P=0.055) compared to pigs not fed DTB and pigs fed PBP tended to have increased ADG (P=0.093). In week 3 pigs fed PBP had reduced ADG (460 vs 483 g/d; P=0.011) and G:F (0.689 vs. 0.723; P<0.001), and there tended to be an interaction for G:F (P=0.083) with DTB improving G:F when fed in combination with PBP but reducing G:F in the control diet.  In week 4, feeding PBP decreased ADG (384 vs 415 g/d; P<0.01) and ADFI (629 vs 666 g/d; P<0.01) compared to pigs fed no PBP.  For Phase 4 (d21-35) pigs fed PBP had decreased ADG (479 vs 497 g/d; P=0.041) and tended to have reduced ADFI (P=0.092) compared to pigs fed no PBP. Overall (d 0-35), there were no significant differences among treatments in pig growth performance.   Pigs fed PBP had increased jejunal expression of interferon-alpha (P=0.041) and interleukin-10 (P=0.037) and tended to have increased expression of claudin-1 (P=0.076).  Pigs fed DTB tended to have decreased jejunal expression of interferon-gamma (P=0.079).  Jejunal gene expression of tumor necrosis factor-alpha and nuclear factor kappa-beta did not differ among treatments. In conclusion, DTB improved nursery pig growth performance early and pigs fed PBP had decreased ADG and feed efficiency late in the nursery period. Feeding PBP had minimal effects on jejunum architecture but increased the gut immune response.</p> <p>Chapter 4 focuses on weaning age in addition to dietary treatments. Changes in weaning age and diet complexity can impact pig growth post-weaning. 432 weanling gilts and barrows (Topigs Duroc Ⅹ (US York X Landrace)) from the same farrowing group were utilized for a 30 or 35 d growth trial to compare early (EW) versus late weaning (LW) and high or low levels of specialty proteins in nursery diets. 216 pigs were EW (18 or 19 d, avg. age=18.4 days, avg. BW=5.96 kg) and 216 pigs were LW 5 days later (24, 25 or 26 d, avg. age=24.6 d, avg. BW=7.50 kg). At weaning pigs were blocked by weaning age, BW, sex and litter, and randomly allotted to 48 pens with 9 pigs/pen. Pigs at each weaning age were fed a High Complexity (HC) or a Low Complexity (LC) diet. The trial was conducted as a 2X2 factorial design: 1) EW+HC; 2) EW+LC; 3) LW+HC; 4) LW+LC. Pigs and feeders were weighed on d 0, 7, 14, 21, 28, and 35 for EW, and on d 0, 7, 14, 21, 28, and 30 for LW.  LW pigs had improved ADG and ADFI from d 0-7, 7-14, 14-21, and the final week of the nursery (P<0.05). G:F decreased for LW pigs from d 21-28 (P<0.01) compared to EW pigs, however for the overall nursery trial LW pigs had increased G:F (P=0.01). LW pigs had increased overall nursery ADG vs EW pigs (452.5 g/d vs 400 g/d; P<0.01). End of nursery BW was greater for LW vs EW pigs (21.70 kg vs 20.74 kg; P=0.001).  There was a weight block by weaning age interaction, EW heavy pigs had lower ADG compared to LW heavy pigs, however when comparing light weight pigs, the EW light pigs had improved ADG compared to LW light weight pigs (P=0.017). EW pigs were lighter at market (approximately d146 of age) compared to LW pigs (120.78 vs 124.16 kg; P=0.014). An interaction between weaning age, nursery diet, and sex (P<0.07) was observed for market weight, EW barrows fed LC diets were lighter at market (120.77 kg) than EW barrows fed HC diets (126.54 kg).  Whereas for LW barrows fed LC had higher market weights (130.04 kg) than LW barrows fed HC diets (127.59 kg). A similar, but non-significant pattern was observed for gilts. Weaning age and feeding pigs the correct diet for their age in the nursery can have a lifelong effect on the pig. </p> <p>In conclusion, feeding a DFM containing bacillus licheniformis did not impact nursery pig growth performance early in the nursery period. From d21-35 ADG and ADFI was improved in both experiments 1 and experiment 2. While the growth results were sporadically improved throughout the nursery period, the DFM’s greatest effect was it ability to improve ADFI. The improvement in the late nursery phase may be due to the need for the DFM to establish itself in the GIT. DTB tended to improve ADG and ADFI in week 2 of the nursery period, however there were no differences for growth overall. PBP reduced ADG in week 3 of the nursery period, as well as reduced ADG and ADFI in week 4 of the nursery. While there were differences in individual weeks of the trial there were no overall differences in growth performance. However, when looking at gene expression in the jejunum at d11 post-weaning, there was an increase in IFN-α and IL-10 in pigs fed PBP. In pigs fed DTB there was a decrease in IFN-γ jejunal gene expression as well. Feeding a high complexity and low complexity diet had no impact on the nursery pigs growth performance, in hindsight the low complexity diet was perhaps not low enough in specialty proteins. When comparing weaning age, pigs weaned later had increased ADG and ADFI from d0-21 post-weaning. For the overall nursery performance, LW pigs had a higher ADG, and ended the nursery period 0.96 kg heavier than the EW pigs. Comparing pigs of similar bodyweight at weaning, EW pigs were 1.5 kg heavier than LW pigs at the end of the nursery period, but the LW pigs were more feed efficient. There was a weight block by weaning interaction in this trial, as the heaviest LW pigs had higher ADG compared to the heaviest EW pigs. However, when looking at the lightest pigs, the EW pigs outperformed the LW pigs. Looking at market weights of each age group, LW pigs were 3.5 kg heavier on average at d146 of age. Although there was not a difference in diet found in the nursery phase, interestingly there were interactions discovered between treatments at market weight. Barrows are more sensitive to nursery diet compared to gilts, as LW barrows fed the low complexity diet performed better than the LW high complexity fed barrows. EW barrows were heavier at market when fed the high complexity diet, compared to EW barrows fed the low complexity diet. This shows that while the diet didn’t appear to have an impact in the nursery, feeding the pig the proper diet for their age has a lifelong impact on the pig.</p>

Researchers have investigated several factors that could alter fetal growth, including nutrient restriction (Valiente et al., 2021), hair shedding (Gray et al., 2011), and extreme hot and cold temperatures (Davidson et al., 2022). Hot temperatures and increased humidity percentages in the southeast United States caused researchers to investigate the hair coats of Angus cattle in the commercial production setting. An improvement in fiber digestibility and calf birth and weaning weights has been observed in Angus dams that shed 50% of the winter hair coat by May (Gray et al., 2011; Burnett et al., 2021). Our objective of this experiment was to investigate the nutrient digestibility of Angus calves born to cows that on average, shed early compared to calves from cows that shed later. Newly weaned, purebred Angus bull calves (early; n = 6, late; n = 6) were housed in metabolism crates for 10 d. Prior to the trial, calves had a 14 d adaption period to a 14% CP textured feed (CPC 14% Developer, CPC Commodities, Fountain Run, KY) and offered ad libitum Cynodon dactlyon hay and water. After 3 d crate acclimation period, urine, feces, orts, and hay samples were collected for 7 d. Concentrate was offered at 0.25% of average BW. Approximately 5% samples were taken of feces, and urine samples had 1-1.5% of 25% metaphosphoric acid added to prevent ammonia volatilization, and both collections were composited by animal. Orts were collected at 0600 h daily, dried, and composited by animal. Laboratory analysis included dry matter (DM), organic matter (OM), Ash, neutral detergent fiber (NDF), acid detergent fiber (ADF), Kjeldahl N (CP), and fat. Data were analyzed using the GLM procedure of SAS 9.4 in a completely randomized design with calf as the experimental unit. Significant (P ≤ 0.05) means were separated using Fischer’s protected LSD. The model for intake included average daily DM and OM (kg) and adjusted by body weight (BW%). For digestibility analysis, the model included: DM, OM, ash, NDF, ADF, hemi-cellulose (HC), CP, and fat. The N retention model included: N retained (g/d), N retained/consumed (%), and N retained/DM intake (%). There were no differences between early or late calves for DM intake (5.502 ± 0.2774 kg/d; 2.251 ± 0.1247 %BW), or OM intake (5.199 ± 0.2591 kg/d; 2.128 ± 0.1166 %BW). There were no differences in digestibility for either group for DM, OM, Ash, NDF, ADF, HC, CP, or fat (Table 1.). There were also no differences in N retention in either group of calves (3.686 ± 2.0242 g/d; 4.366 ± 2.3964 %; 0.064 ± 0.0355 %). Replication and further research are needed in this area to adequately understand factors influencing nutrient digestibility in calves born from early and late shedding dams.

This study took place in Bolivia with the purpose of using thermally treated Capinota phosphate rock as a phosphorous supplement in balanced feed diets. The objective was to produce a natural phosphate substance that would be more easily accessible to the local population than commercial feed supplements. An additional objective of this study was to increase the availability of the low-fluoride phosphorous. The biological assays indicated that the diet with the added burned phosphoric rock produced similar yields to those using a commercial feed supplement (dicalcium phosphate). This indicates that the locally manufactured product, by partial acidification, can compete with similar commercial products.

<p dir="ltr">The objective of this thesis was to evaluate the nutrient digestibility in alternative animal and plant sources of feed ingredients for chickens and pigs. Therefore, 5 studies were carried out to determine the nutrient utilization in poultry meal (<b>PM</b>), faba beans (<b>FB</b>), and 3 cultivars field peas (<b>FP</b>).</p><p dir="ltr">In the first study, 2 experiments investigated the energy and phosphorus utilization of PM for broiler chickens. Poultry meal was used to substitute corn and soybean meal in the reference diet at 0, 80, or 160 g/kg in Experiment 1. Whereas PM was included in the diet at 0, 50, or 100 g/kg in Experiment 2. A total of 192 birds were allotted to 3 experimental diets in both experiments. The estimated ileal digestible energy (<b>IDE</b>), metabolizable energy (<b>ME</b>), and nitrogen-corrected metabolizable energy (<b>MEn</b>) for PM were 4,002, 3,756, and 3,430 kcal/kg DM, respectively. In Experiment 2, the true ileal digestibility (<b>TID</b>) and true total tract utilization (<b>TTTU</b>) of P in PM were 77.5 and 79.0%, respectively.</p><p dir="ltr">The second study consisted of 3 experiments. In the first experiment, 240 birds were assigned to 5 diets to determine the energy values of FB and DS admiral FP (<b>FPD</b>). In Experiment 1, the test ingredients were incorporated into a corn-soybean meal-based diet at 0, 150 or 300 g/kg. The IDE, ME, and MEn for FB were 2,541, 2,628, and 2,394 kcal/kg, respectively. The respective values for FPD were 2,254, 2,540, and 2,331 kcal/kg DM. In each of Experiments 2 and 3, 162 birds were assigned to 3 diets. Faba beans was included at 21, 42, or 63% and FPD at 16, 32, or 48% in Experiments 2 and 3, respectively. The TID and TTTU of P in FB were 66.5 and 66.7%, respectively. The corresponding values for FPD were 73.4 and 73.8%.</p><p dir="ltr">The third study consisted of 3 experiments. In Experiment 1, the energy values for Hampton FP (<b>FPH</b>) and 4010 FP (<b>FP4</b>) fed to broiler chickens were estimated. Two hundred and forty birds were assigned to 5 diets. The test ingredients were included at 0, 150 or 300 g/kg into a corn-soybean meal-based reference diet. With regression analysis, the determined IDE, ME, and MEn were 3,274, 3,033, and 2,850 kcal/kg DM in FPH, respectively, in FP4 the energy values were 3,019, 3,155, and 2,991 kcal/kg DM, respectively. The P utilization in FPH and FP4 were determined in Experiments 2 and 3, respectively. The corresponding TID and TTTU of P in FPH were 74.6% and 68.3%, and 74.3 and 61.7% in FP4.</p><p dir="ltr">Two experiments were conducted in the fourth study to estimate the digestible energy (<b>DE</b>) and ME in FB and FP fed to pigs. Twenty-four barrows were assigned to 3 dietary treatments in each of the experiments. Faba beans or FPD in Experiment 1 and FPH or FP4 in Experiment 2 were included in the diet at 0 or 300 g/kg. The determined DE and ME values for FB using the total collection method were 3,772 and 3,606 kcal/kg DM and in FPD were 3,683 and 3,589 kcal/kg DM, respectively. In Exp. 2, the respective DE and ME for FPH were 4,164 and 4,014 kcal/kg DM and for FP4 were 3,574 and 3,467 kcal/kg DM.</p><p dir="ltr">In the last study, standardized ileal digestibility (<b>SID</b>) of amino acids (<b>AA</b>) in faba beans and three cultivars of FP between broiler chickens and pigs were compared. The test ingredients were the only source of protein providing 160 g/kg crude protein and a nitrogen-free diet was prepared to estimate the basal endogenous losses of AA. The same set of five diets was used across both species. The SID of Lys in FB, FPD, and FPH exceeded 90% but in FP4 it was 85.1% for broiler chickens. Whereas for pigs the SID of Lys in FB, FPD, and FPH exceeded 80% but for FP4 it was 89.8%. The SID of Met in the test ingredients ranged from 72.1 to 89.8% and 68.1 to 81.8% for broiler chickens and pigs, respectively. In general, the SID of AA in the test ingredients were greater compared with chickens. The energy, P, and AA digestibility of the test ingredients determined in the five studies could be used in diet formulation for chickens and pigs.</p>

<p>Two experimentswere  conducted  using  pigs  at different  life stages to  determine  the  effects  of dietary  tryptophan  and  water  delivered  oregano  essential  oil  on growth performance, rectal temperature, water use,intestinal integrity and gene expression of biomarkers in the face heat or transport stress. In the first experiment, 192 grow-finish pigs were used to investigate the effects of  water  supplementation  of  oregano  essential  oil  (OEO)  on  growth  performance,  water  intake, rectal temperature, intestinal integrity, and expression of genetic biomarkers during an acute heat challenge. Pigs were randomly allotted to 2 X 2 factorial arrangement of treatments with pigs being heat  stressed  or  not  and  being  supplemented  with  OEO  or  not with 8  replicate  pens  of  each treatment  with  6  pigs/pen  (4  barrows,  2  gilts  per  pen).  Water  treatments  were administered immediately, with  dosing at  47 μL/L of OEO. One-half  of  the  pigs  on  each  water  treatment remained under thermoneutral conditions (TN; 21.1C), while the other half was subjected to a 3 d diurnal, acute heat stress (HS) with 12 hours at 33.3 oC (7AM-7PM) and 12 hours at 26.7oC (7PM-7AM). Three days post-HS, temperatures were reduced back to TN for the rest of the study, and pigs remained on their water treatments. Rectal temperatures were collected in the morning and evening  of  the  heat  stress  period  on  one  barrow  and  one  gilt  in  each  pen. Jejunal  tissue was collected for subsequent histological examination and determination of gene expression. All data were  analyzed  using  the  GLM  procedure  of  SAS  (ver.  9.4).  Pigs  subjected  to  heat  stress  had reduced ADG (P < 0.003) and G:F (P < 0.008) during the 3d heat stress compared to pigs reared under thermoneutral conditions. However, post-heatstress, heat stressed pigs had compensatory gain resulting in increased ADG (P < 0.001) and G:F (P < 0.001) compared to thermoneutral reared pigs.   Overall,  there  was an  interaction  (P  <  0.006)  observed  between  water  and  heat  treatment with  OEO  increasing  ADG  in  thermoneutral  pigs  but  not  in  heat  stressed  pigs.  Similarly, interactions  between  water  and  heat  treatment  were  observed  for  ADFI  during  heat  stress  (P  < 0.004),  post  heat  stress  (P  <  0.01),  and  overall  (P  <  0.004)  from  increasing  OEO  intake  in thermoneutral pigs but not in heat stressed pigs. Rectal temperatures were higher (P < 0.001) for heat stressed pigs at the end of d 1 and 2 of the acute heat challenge compared to TN housed pigs. Pigs exposed to HS also used more water than pigs housed in a thermoneutral environment (P < 0.002). There were no differences between villi height, crypt depth or VH:CD between treatment groups  (P  >0.05).  There  was  also  no  difference  in  TP53  and  CDKNA1  gene  expression  among treatments (P > 0.10). In the second experiment, 36 barrows were used in an 18d experiment to investigate the effects of pre-weaning tryptophan supplementation on performance and intestinal integrity following  weaning  with  or  without  transport  stress  at  weaning.  Pigs  were  randomly allotted to 2 X 2 factorial arrangement of treatments of pre-weaning tryptophan supplementation or not and weaning transport or not. Pigs on the tryptophan treatment received 0.35, 0.45, and 0.55 g Trp/d in 5 day intervals, beginning 15 d prior to weaning.Tryptophan was dissolved in chocolate milk and administered by oral gavage with control pigs receiving milk only. At weaning, 4 pigs from each pre-weaning treatmentwere euthanized for collection of jejunal tissue.  Of the remaining pigs, half the pigs oneach treatment were transported for 12 h, and half were moved into individual pens  with  no  transport.  Following  transport,  all  pigs  were  individually  housed  and  provided  ad libitum  access  towater  andfeed  from  a  common  diet.  On  d  3  post-weaning,  all  pigswere euthanized for collection of jejunal tissue. Jejunal tissue was used for histological examination and for determination of gene expression. All data were analyzed using the GLM procedure of SAS (9.4).  No  effects  of  Trp  supplementation  were  observed  on  pre-weaning  (P  >  0.10)  growth. Pig BW and ADFI were unaffected (P > 0.10) by Trp supplementation and transport at weaning. Post-weaning, there was a tendency (P < 0.06) for an effect of transport on ADG as transported pigs lost weight in the 3 d post-weaning period while non-transported pigs gained slightly. Gain:Feed post-weaning  was  lower  (P  <  0.04)  for  transported  pigs  compared  to  non-transported  pigs.  No differences  were  observed  for villus base  and  mid  width,  villus  height,  crypt  depth  or  villus height:crypt   depth.   There   was   a   tendency   for   an   interaction   of   transportation   and   Trp supplementation  (P  <  0.06)  on  villi  base  width  driven  by  an  increased  villus  width  in  non-transported pigs given supplemental Trp but a decrease in villus width in transported pigs given supplemental Trp.These results conclude that these alleviating agents had minimal effects when pigs  were  stressed, however TN grow-finish pigs  benefitted  from  OEO  water  supplementation among growth performance.</p>

In the present study the effect of diets restricted in either zinc or pyridoxine upon estrogen directed gene expression in the mature rat uterus was tested. Sexually mature female rats were maintained on zinc-adequate (40 mg/kg diet) <i>ad libitum</i> or restricted-fed, pyridoxine-deficient, or zinc-deficient ( < 1 mg/kg diet or 3mg/kg diet) <i>ad libitum</i>-fed diets for 35 days. All animals were bilaterally ovariectomized and used for experimentation at 14 days post ovariectomy. On day 35 each rat was injected intraperitoneally with estrogen. They were killed at different times post injection and thymidine kinase (TK, EC 2.7.1.21) or creatine kinase (CK, EC 2.7.3.2) activity was assayed in uteri cytosol fractions. In addition the steady state level of <i>ckb</i> mRNA in uteri cytosol fractions was measured following estrogen administration. The weight gain of the rats fed the low zinc and low pyridoxine diets was significantly lower than those fed the zinc-adequate diet ad libitum. The consumption of the zinc-deficient diet resulted in a significant decrease in plasma zinc while a pyridoxine deficient diet produced a significant reduction in plasma pyridoxine. Vehicle-injected uterine TK activity was 2-3 pmoles of d-TMP/min/mg protein. The TK activity was significantly increased (p < 0.05) 42 h post estrogen injection on the zinc-adequate diet <i>ad libitum</i> and pair-wt fed rats. This activity was sustained at 48 h post injection prior to declining to control values within 60 h. The maximum (4-fold) increase occurred at 36 h post estrogen injection in pyridoxine-deficient rats which was sustained at 42 & 48 h. The increase in uterine TK activity was 3-fold at 42 hand 48 h post injection. However this increase was not significantly different from the peak value seen in zinc-adequate and pyridoxine-deficient diet fed rats. No measurable effect of estrogen on CK activity was observed on the zinc adequate or zinc-deficient diet fed rats using a coupled enzyme assay. However the time course of ckb mRNA induction on the zinc-adequate pair-wt fed rats following estrogen administration paralleled the time course of estrogen induced protein (IP) synthesis previously observed by Gorski et al. (1970). IP is now known to be the brain type isoenzyme of creatine kinase. An induction of <i>ckb</i> mRNA between 0-3 h post estrogen injection was not observed on the zinc-deficient diet fed rats. However in a subsequent experiment an induction of uterine ckb mRNA 2 h following estrogen administration was observed in zinc-deficient rats. The possible reasons for this discrepancy are discussed. Zinc ions are known to be required to enable the estrogen receptor complex to bind to DNA and initiate transcription. It has been hypothesized that inadequate provision of dietary zinc may therefore reduce compliance to estrogen directed gene expression by limiting the efficiency of recruitment of zinc ions for stabilization of the zinc finger of the steroid receptor. The results of the present study failed to support this hypothesis at this moderate level of zinc depletion. / Ph. D.

Plasma and erythrocyte (RBC) free amino acids and plasma peptide and serum protein amino acid concentrations and arteriovenous (A/V) differences across the hindlimbs were determined on growing Holstein steer calves (130 kg) fed purified diets containing scy protein or urea as the sole source of dietary nitrogen. Animals were fed at hourly intervals in a constantly lighted environment in order to achieve near ‘steady-state’ metabolic conditions. Experimental trials lasted 30 days with blood samples collected on day 10 and day 30 of each trial. Plasma and Plasma and RBC free amino acids were determined from filtrates obtained by deproteinization with sulfosalicylic acid. Peptide amino acids were determined from filtrates obtained by deproteinization with sulfosalicylic acid. Peptide amino acids were determined from 4N methanesulfonic acid hydrolyzed plasma filtrates. Serum proteins were grossly separated by ion-exchange chromatography. Specific protein fractions were then hydrolyzed and analyzed for amino acid concentrations. Urea resulted in the reduction of plasma free amino acid levels due to a 30% decrease in EAA and a 16% decrease in NEAA. All EAA except MET and HIS were significantly depressed. Concentrations of amino acids in blood from the RBC were generally lower of amino acids in blood from the RBC were generally lower than from plasma for all amino acids, however, HIS and ASP were always more concentrated in the RBC. Urea significantly depressed RBC concentration of THR, VAL, MET, ILE, LEU AND PHE, however, most NEAA in the RBC were unaffected by dietary treatment. Exceptions were a large increase in GLY and decrease of ALA in the RBC of urea-fed animals. Net A/V differences across the hindlimb of soy-fed animals was positive for most plasma free amino acids. GLU, GLY and CYS accounted for all of the amino acid release. Urea feeding resulted in a small negative amino acid net A/V difference due to decreased uptakes and/or increased outputs by the hindlimb of several amino acids relative to soy-fed animals. The RBC hindlimb fluxes of several amino acids were altered by dietary treatment. The BCAA changed from large outputs in soy-fed animals so essentially a zero flux in urea-fed animals. In contrast, GLY changed from a large uptake in soy treatments to a large output when urea was fed. The free amino acid data from this experiment indicate that the urea-fed calves were subject to diets deficient in total protein and amino acids rather than specific amino acid differences. Negative A/V fluxes in urea-fed calves indicate muscle protein breakdown. Time effects were generally nonsignificant although a trend towards increased amino acid output across the hindlimb in urea-fed calves was apparent at 30 days. This implies that adaptation under these conditions was not occurring but rather a more severe deficiency state was encountered over time. These data also show further interrelationships between GLY and the neutral SCAA in altered nutritional states. Plasma peptides exhibited amino acid concentrations approximately 30% greater than whole blood free amino acids. HIS was significantly depressed and a tendency for lower levels of most other amino acids was noted in urea treatments. Peptide hindlimb exchanges were variable and nonsignificant with the exceptions of GLU, LYS, HIS and VAL uptakes in soy-fed animals and ILE in urea-fed animals. Peptides may, thus, be acting as a supplemental source of several amino acids to muscle tissue. Diet had little effect on amino acid composition of blood protein fraction I (primarily globulins) and fraction II (primarily albumin). Hindlimb amino acid exchanges of both fractions in soy-fed animals were inconsistent and non-significant. In contrast, the hindlimb of urea-fed animals removed large quantities of amino acids from both fractions with fractions II making the greatest contribution. Patterns of amino acid uptake closely resemble molar ratio within each fraction indicating whole protein uptake. These data show striking evidence of increased uptake of amino acids from blood proteins in calves fed urea purified diets. This may represent adaptation by muscle tissue of the animal to protein-deficient diets. / Ph. D.

Forty four first-calf heifers were randomly selected to determine lactational and metabolic responses to high fat diets and isoacids. All heifers were allowed ad libitum consumption of a control diet for the first 2 weeks of lactation and then offered experimental diets Eor the next 4 weeks. Each 6 cows of twenty four were randomly assigned to 1) a control diet (C) with 35.2% corn silage, 14.4% alfalfa haylage and 50.4% concentrate (dry matter basis), 2) C with 2% calcium stearate (S) substituted for corn grain, 3) C with 2% tallow (T) for corn grain, and 4) C with 10% whole cottonseed (W) for corn grain, cottonseed meal and cottonseed hulls. The remaining 20 heifers were randomly assigned to diets C, S, T, and W, each with 4g/kg isoacids added (CI, SI, TI, and WI). Fat supplementation or isoacid addition did not affect milk production. Addition cf isoacid increased milk fat percentage, 4% fat-corrected milk, milk fat production (kg/day) and dry matter intake. Differences due tc isoacid were greatest when added to W. Increased milk lactose percentage and weight gain were evident in animal receiving WI compared to W ration. Fat supplementation depressed percentages cf milk fat, milk lactose and milk solids-not-fat. Milk protein percentage and somatic cell count were not affected by treatments. Plasma glucose,and glucose and epinephrine challenge parameters were not affected by diet. Peak plasma non-esterified fatty acid response to epinephrine injection, detected at 10 to 12 minites, was similar for C, S, T, and W. Concentrations of individual volatile fatty acids (VFA) and total VFA in rumen fluid were increased by fat supplements. Isoacid addition increased the amounts of isobutyrate and isovalerate; however, acetate and total VFA concentrations were decreased compared to CI when isoacids were added to high fat diets. The ratio of acetate to propionate was similar for all diets. Digestibilities cf dry matter, crude protein, and acid detergent fiber were not influenced by diet. The efficiency of energy utilization was highest for control diet. In conclusion, lactational, metabolic, and physiological responses to S, CI, and WI were favorable. Responses to W were lowest. / M.S.

Six Angus steers were used in a series of three metabolism trials to study the effect of energy concentration on nitrogen metabolism and digestibility. The experimental design consisted of two randomly selected 3 x 3 Latin squares. Three fattening rations were ted which contained 1133, 1164 and 1222 kcal. digestible energy per lb. feed and 12.18, 12.51 and 12.29% crude protein, respectively. The rations were composed of 10% grass hay, shelled corn, corn cobs and cottonseed meal. An attempt was made to equalize calcium and phosphorus contents. Vitamins A and D were added at the rate or 30,000 I.U. and 3750 I.U. per steer per day, respectively. Energy concentration was varied by changing the proportions of shelled corn and corn cobs. Digestible and metabolizable energy and TDN were all significantly increased with each increase in energy concentration. Digestible energy concentration of feed had no significant effect on nitrogen retention. Biological value waa higher for the medium energy ration than for the low or high energy rations. The quadratic effect was significant (P < .05). The apparent digestibilities of crude protein and ether extract were not influenced by energy concentration. Digestibility of' dry matter, organic matter and NPE significantly increased and digestibility of crude fiber significantly decreased with each increase in energy concentration. / Master of Science