<p dir="ltr">Organizational newcomers strive to adjust when they start new jobs, yet little is known about how remote and hybrid work structures influence this process. Previous research has adopted variable-centered approaches to explore the frequency with which newcomers engage in dozens of proactive behaviors in traditional, face-to-face work environments. The current study builds upon this work to capture the socialization process in modern work environments. Adopting a person-centered approach, this study 1.) identifies profiles of newcomers’ perceptions of their work environments, 2.) identifies profiles of newcomer proactive behaviors, 3.) examines the effect of virtuality on these two sets of profiles, and 4.) explores which behavior profiles are associated with the most favorable changes in adjustment.</p>

Two consecutive experiments were conducted to test a hypothesis that mixed grazing outcome is influenced by the type of stocking system applied. The objective of both experiments was to investigate the influence of co-grazing with sheep on cattle liveweight gain (LWG) under continuous (C) and rotational (R) stocking, where sheep weekly liveweight change under the two stocking systems was kept similar. In experiment I nine yearling heifers (266 ± 4.5 kg liveweight) and 27 ewe hoggets (54±0.9 kg liveweight) were continuously stocked for 19 weeks on an irrigated perennial ryegrass-white clover pasture (2.95 ha) maintained at a sward surface height (SSH) of 5cm by adding or removing additional animals in a fixed ratio (1: 1 W⁰.⁷⁵ cattle:sheep). An equal area of pasture was rotationally stocked by a similar group of animals where they received a new area of pasture daily and also had access to the grazed area over the previous 2 days. The size of the new area provided daily was such that the weekly liveweight change of rotationally co-grazed sheep was equal to that of those continuously co-grazed with cattle. Similar groups of animals were used in the second experiment with additional group of 9 heifers grazed alone on C and R pastures. Liveweight of animals was recorded weekly and final fasted weight was determined after 24-hour total feed restriction. SSH on both treatment swards was recorded daily. There were three intake measurement periods spread over the trial period. Organic matter intake (OMI) was predicted from the ratio of N-alkanes in faeces and herbage. Diet composition was determined by dissecting oesophageal extrusa samples. Grazing behaviour (bite rates and grazing time) were also recorded. The mean SSH for C pasture was 5.1±0.09 cm. Overall pre- and post-grazing SSH for R pasture was 15.9 ±0.12 and 5.6 ±0.07 cm, respectively. As determined by the protocol average daily LWG of sheep was similar between C and R (147 (±5.8) vs 138 (±6.7) g day⁻¹; (P>0.05). In contrast, cattle continuously stocked with sheep grew 200 g day⁻¹ slower than those rotationally stocked with sheep (800 (±41.6) vs 1040 (±47.7) g day⁻¹, P<0.0l). R heifers achieved 30 kg higher final fasted liveweight than C heifers (350 vs 381 kg; P<0.01). Overall LWG per ha was also 6 % higher under R than C stocking (674 vs 634 kg ha⁻¹). The OMD of both sheep (73.5 vs 75.8 %) and cattle (75.8 vs 78.0 %) diets was similar under continuous and rotational stocking. There was no significant difference OMI data also concurred with the L WG data (Cattle: 7.94 vs 6.31 (±0.32) kg day⁻¹ (P<0.05); sheep: 1.40 vs 1.44 (±0.04) kg day⁻¹ for Rand C treatments, respectively). There was no difference in clover content of cattle diet under C and R treatments. C heifers had higher number of bites per minute than R heifers (62 vs 56; P<0.05). Proportion of heifers seen grazing (every 15-minute) during four 24-hour observations was greater on C than R pasture (0.44 vs 0.31 (±0.03); P<0.05). The similarity coefficient between sheep and cattle diet was 0.61 and 0.76 under C and R stocking, respectively. The lower daily LWG of C heifers was attributed to (a) the lower SSH under C than R stocking and/or (b) the inability of cattle to compete well with sheep where there is small, continual renewal of resources (C) in contrast to a large periodic renewal under R stocking. This experiment showed that the outcome of mixed gruing can be influenced by the stocking system chosen. But it was not possible to apportion the difference in LWG of cattle between mixed grazing per se and the difference in mean grazed sward height (5.1 for C vs 10.8 cm for R). A second experiment was conducted to determine the relative performance of cattle co-grazed with sheep (CS) and grazed alone (CA) under each stocking system. Hence, there were four treatments. CA- continuous stocking (CA-C), CS- continuous stocking (CS-C), CA- rotational stocking (CAR) and CS- rotational stocking (CS-R). A total area of 4.42 ha was allocated to each stocking system. Under C stocking, 2.95 ha (2/3) was assigned to CS-C and 1.47 ha (1/3) to CA-C, and SSH on both treatments was kept at 4 cm by adding or removing extra animals. Under R stocking, CA-R and CS-R grazed side by side separated by an electric fence. They were given a fresh area daily, the size of which was varied such that the weekly LW change of R sheep was equal to that of the C sheep. CA-R received one-third of the new area though the size was adjusted regularly to achieve the same post-grazing SSH with CS-R. Measurements included: weekly liveweight change, OMI (two periods) and diet composition (using N-alkanes). The mean SSH of CA-C and CS-C swards was 4.27 and 4.26 (±0.02) cm, respectively. CA-R and CS-R swards had mean pre-grazing SSH of 14.9 and 15.2 (±0.08) cm and post-grazing heights of 4.87 and 4.82 cm (±0.03), respectively. The proportion of areas infrequently grazed was higher for CA-C than CS-C swards (0.22 vs 0.17, respectively). C and R sheep daily LWG: 155 (±0.6) and 147 (±0.7) g, and OMI: 1.96 and 2.04 (±0.ll) kg, respectively, were not significantly different. They also had similar diet composition. In comparison, CS-C heifers grew only at 69 % of the daily LWG achieved by CS-R heifers (706 vs 1028 (±72) g; P<0.05). LWG of CA-C and CA-R was 916 and 1022 (±72) g day⁻¹, respectively. The difference in LWG between CS-R and CS-C (D₁) heifers was due to difference in mean sward height, stocking system and mixed grazing, while D₂ (difference in LWG between CA-R and CAC) was due to difference in mean sward height and stocking system. D₁-D₂ (the effect of stocking system on mixed grazing) was 216 g and made up 67 % of the total difference between CS-R and CS-C. There was a significant stocking system-species mixture interaction in the final fasted LW achieved by heifers. Final fasted LW was significantly lower for CS-C than CA-C heifers (283 vs 323 (±9.7) kg), but did not differ between CS-R and CA-R (332 vs 330 (±9.7) kg, respectively). The digestibility of diet OM was similar for both continuously and rotationally stocked sheep (84.4 vs 83.2 %, respectively). Cattle diet OMO was 76.5, 74.7, 79.4 and 77.8 for CA-C, CS-C, CA-R and CS-R respectively (P>0.05). Differences in OMI followed a similar pattern to daily LWG. Mean daily OMI was 8.98, 6.24, 8.80 and 9.45 (±0.40) kg for CA-C, CS-C, CA-R and CS-R, respectively. Clover content of the diet of CA-C heifers was three times higher than that of CS-C heifers (30.7 vs 10.4 % OM; P<0.05); there was no difference in clover content of diets of CS-R and CA-R heifers (21.5 vs 23.9 % OM, respectively). In both stocking systems LWG per ha was higher on CA than CS treatments. These results suggested that the disadvantage of selective clover grazing by sheep outweighed the advantages of sheep grazing around cattle dung patches under continuous stocking. Under rotational stocking, rapid diurnal changes in sward conditions probably limited selective grazing by both sheep and cattle such that there was no disadvantage to CS cattle. The results do not provide a basis for recommending grazing cattle with sheep rather than cattle alone, but do provide some basis for recommending co-grazing of sheep and cattle using rotational rather than continuous stocking.

This thesis describes two approaches for studying of lipoprotein metabolism in sheep. The first approach involves the assay of lipoprotein lipase (LPL) activity to determine the role of lipoprotein-triacylglycerol fatty acids in fat deposition in sheep. This enzyme is the rate limiting enzyme in the hydrolysis of fatty acids from lipoprotein-triacylglycerol. The second approach was to characterize and quantify in vivo lipoprotein metabolism using iodinated very low density lipoprotein (¹²⁵I-VLDL) and low density lipoprotein (¹³¹I-LDL). Cross-bred lambs were divided into two treatment groups and either weaned early at 5 weeks of age or remained suckling. Lambs were slaughtered at 12 or 23 weeks at which time the body composition and adipose tissue LPL activity were determined. The differences in rearing led to differences in body composition. The suckled lambs were larger and fatter than weaned lambs. The increased fatness in the suckled lambs was associated with increased LPL activity (U/mg protein) in subcutaneous adipose tissue and was reflected in higher LPL activity in post-heparin plasma (PHP) taken 2 days prior to slaughter. The role of insulin in the regulation of LPL activity was investigated by either infusing a subset of the weaned and suckled lambs with insulin for 7 or 18 weeks or using the euglycemic clamp technique to study the effect of short insulin infusions. The long term infusion of insulin had no significant effect on PHP LPL or on adipose tissue LPL (U/g tissue). However, after infusing insulin for 6h at 6.3 mU.kg⁻·⁷⁵.h⁻¹ during the euglycemic clamps, a two fold increase in LPL activity in biopsied subcutaneous adipose tissue was observed. In the second approach, in vivo lipoprotein metabolism was investigated in 4 lambs using apolipoprotein B as a marker. Following the simultaneous injection of ¹²⁵I VLDL and ¹³¹I VLDL, the specific activities of apoB in VLDL, IDL and LDL fractions were determined. ApoB specific activity curves demonstrated that VLDL is metabolised to IDL and subsequently to LDL. The turnover of VLDL-B (3.45mg.d⁻¹.kg⁻¹) and LDL-B (4.8mg.d⁻¹.kg⁻¹) was calculated by fitting the VLDL-¹²⁵I-B and LDL-¹³¹I-B specific activity data to a mono-exponential equation. The metabolism of lipoproteins, inferred from the study of apoB, was shown to be similar in sheep to that reported in other animals although the amount of lipoprotein synthesised was low. A model to describe the kinetics of apoB metabolism in sheep was developed using SAAM. The proposed model features a three pool delipidation chain for VLDL, and subsystems containing two pools for IDL and LDL. IDL may be catabolised to LDL or cleared directly from the plasma. The developed model can now be used to compare the metabolism of lipoproteins in different physiological states and to design new experiments to study lipoprotein metabolism further.

<p dir="ltr">Newborn animals undergo a lot of early-life stress that heavily impact on their long-term growth, performance, and welfare. Typically, the stress would indirectly interfere with the capacity of these neonates to utilize dietary nutrients and consequently impact tissue growth and development. In piglets, weaning is a stressful situation characterized by disruption of intestinal epithelial cell development which causes poor digestion of solid feed and a negative impact on absorption of nutrients especially in the post-gastric region. In addition, weaning in piglets could cause an increase in cellular assault by reactive oxygen species thereby potentially causing gut leakiness and paracellular loss of nutrients along the intestinal tract. In broiler chickens, access to feed may take up to 72 h following hatching which may affect their gut development as well as their gut microbiota. After the first feed ingestion, there is a sharp increase in the gut microbiota which triggers an increase in the development of the immune system as well as the gut. There is continuous attention on the strategies and nutritional interventions to mitigate or ameliorate the adverse effects of early life stressors in these food animals, especially in broiler chickens and piglets. In the studies described in this dissertation, myo-inositol (purely supplemented or phytase-induced) and luteolin were tested as nutritional strategies to mitigate the effects of early-life stressors on growth and the potential mechanisms by which myo-inositol and luteolin regulate growth were investigated.</p><p dir="ltr">In study I, the effect of myo-inositol on growth in 128 postweaning piglets fed protein-deficient corn-soy diets was tested. There were 4 dietary treatments in a randomized complete block design with body weight as the blocking factor. The treatments consisted of 1 positive control (PC) diet formulated to meet all the nutrient requirements of the piglets with a 20% crude protein (CP); the remaining 3 diets were the negative control (NC) diets with a 3% reduction in CP, a 2 g/kg myo-inositol supplemented negative control diet (NC+INO), and phytase (3,000 FTU/kg) supplemented negative control (NC+PHY) diet. The results showed that phytase enhanced the apparent total tract digestibility (ATTD) of P in the weanling pigs. Myo-inositol supplementation in a protein-deficient diet improved (P < 0.05) porcine plasma myo-inositol concentration while an in vitro myo-inositol incubation with intestinal epithelial cells increased the expression of genes that encode for Claudin-1, Claudin-3, Claudin-4, ZO-1, NaPiIIb, GLUT2, and SLC7A2. The in vitro analysis of tight junction integrity in the IPEC-J2 cells indicated by the transepithelial electrical resistance and FITC-Dextran permeability showed an enhancement in response to myo-inositol treatment. Although the in vivo study found that myo-inositol did not improve growth performance or ATTD, the in vitro myo-inositol enhanced markers of gut health and function.</p><p dir="ltr">In study II, the effect of myo-inositol on the growth of broiler chickens was tested. In this study, there were 6 experimental treatments based on two dietary protein levels (PC and NC) and three supplement types (BASAL, INO, and PHY) resulting in a 2 x 3 factorial arrangement in a completely randomized design. A total of 384 broiler chickens comprising 6 treatments with eight replicates per treatment and 8 birds per replicate were used. The birds were fed a common starter diet for the initial 7 days after they arrived at the poultry unit followed by a 14-day trial. The protein-deficient diet decreased the feed efficiency of the birds. Phytase addition increased (P < 0.05) the apparent ileal digestibility (AID) and ATTD of P and Ca in both PC and NC groups. The jejunal gut morphology was enhanced by supplemental phytase as indicated by an increase in villus height and the ratio of the villus height-to-crypt depth, coupled with an increase in serum myo-inositol concentration caused by both myo-inositol and phytase. In conclusion, myo-inositol showed a differential influence on growth performance, nutrient digestibility, and gut morphology.</p><p dir="ltr">In study III, the effects of luteolin on weanling pigs and IPEC-J2 cells were examined. A total of 48 piglets were randomly allotted to two dietary treatments consisting of a control group and a luteolin (LUT)-supplemented dietary group for a 4-week trial. A weekly assessment of the growth performance and expression of specific proteins in the jejunal mucosa was performed. In each dietary group, 8 piglets were slaughtered at weeks 1, 2, and 4 postweaning to collect blood, jejunal and ileal mucosa, and tissues. Luteolin supplementation numerically improved the ADG and G:F of the pigs. Luteolin feeding altered the jejunal and ileal gut morphology with increased villi height (P < 0.05) and villus height-to-crypt depth ratio (VCR, P < 0.05) in the jejunum and decreased crypt depth in the ileum. The effect of luteolin on IPEC-J2 global proteome and phosphor-proteome showed that luteolin could potentially improve intestinal barrier integrity by enhancing the abundance of proteins important in cell growth and survival. </p><p dir="ltr">In summary, dietary supplementation with myo-inositol and luteolin could regulate growth and nutrient digestibility in broiler chickens and weanling pigs by enhancing the integrity of intestinal cells and facilitating the expression of nutrient transporters that are significant in the uptake of nutrients across the lining of the gastrointestinal tract. Phytase supplementation improves the P release from phytate in the diets thereby alleviating its loss.</p>

<p dir="ltr">Nulliparous replacement beef heifers represent an opportunity to improve both genetic potential and lifetime production within the herd. However, advances in reproductive efficiency and synchrony in the herd require heifers to conceive earlier than multiparous cows in order to account for the extended postpartum interval following first-time parturition. Further, those heifers that achieve early calving dates continue to calve early throughout their lifetime. This early calving results in increased weaning weights and better synchrony in subsequent years. One obstacle producers face when breeding nulliparous heifers is the ability to identify which animals have reached puberty at the initiation of the breeding season. This results in the variation observed in synchronization success within a group of heifers. In Chapter 2 our laboratory formulated a study to analyze the efficacy of the 7-d CO-synch + CIDR protocol when utilizing short-term exposure to a progestin (melengestrol acetate, MGA) as a pre-synchronization protocol. Our hypothesis was that the heifers may respond more efficiently to an orally fed progestin as the increase in serum progesterone is less pronounced, when compared to the CIDR. This first study resulted in a protocol application error, in which MGA was fed an extra day (8 vs. 7). This additional day of treatment with MGA following the administration of a prostaglandin eliminated our laboratory’s opportunity to collect meaningful data from this first attempt. Thus, it was pertinent to restart the experiment in an attempt to obtain data for analysis. In order to avoid confounding data, half of the heifers in each treatment received a new treatment, while the other half remained on the treatment assigned during the first attempt. After completing the second round of experiments it was observed that at the first pregnancy check (study day 30), the heifers that were originally assigned to MGA, but were switched to a CIDR for the second attempt numerically outperformed their counterparts in the other three formulated treatment groups. In an attempt to replicate these results, a second study was formulated (Chapter 3), to mimic the timeline from the preliminary study. This resulted in a pre-synchronization treatment protocol prior to the initiation of the breeding season synchronization protocol. Previous studies that have been conducted with similar protocols were designed to provide heifers with a pre-synchronization period that would aid in the attainment of puberty prior to their first attempt at breeding through exposure to progesterone. The purpose of the Chapter 3 experiment was to evaluate the effects of feeding melengestrol acetate (MGA®) as a pre-synchronization for 10 days immediately prior to estrous synchronization and fixed-timed artificial insemination (FTAI). The ten days were chosen as this was a novel protocol that was the result of the preliminary study and the subsequent restart. Ninety-three crossbred heifers (395.67 ± 5.37 kg) were blocked by BW, genetics, and reproductive tract scores and allotted to 3 treatments. The 3 treatment groups were: 7-day CO-synch + CIDR without pre-synchronization (CON, n=31); 25 mg PGF2α (Lutalyse®) followed immediately by MGA feeding for 7 d prior to the start of the 7-day CO-synch + CIDR program (PRE, n=31); and 25 mg PGF2α followed immediately by MGA feeding for 7d followed 10 d later by the start of the 7-day CO-synch + CIDR program (PRE+10, n=31). The 7-day Co-synch + CIDR protocol in all three treatments was initiated on d 0 by administering a 2 cc IM injection of GnRH (Cystorelin®) and placing a CIDR into the vagina. The CIDRs were removed 7 days later and accompanied by 25 mg IM injection of PGF2α. An injection of GnRH occurred 60-66 hours following PGF2α at FTAI with frozen semen from a single bull. Ten days after FTAI, heifers were exposed to a bull. Estrotect® patches were applied throughout the study to assess estrous behavior. Ovaries were visualized by transrectal ultrasonography 24 hours post-FTAI to determine whether ovulation occurred. Pregnancy was determined on days 40, 64, and 109 post-FTAI via transrectal ultrasonography. Blood was collected via jugular venipuncture (d -19 and -12, MGA initiation and termination, days 0, 7, and 9) and serum progesterone determined. Performance data were analyzed using the MIXED procedure and conception data were analyzed using the GLIMMIX procedure of SAS. Heifers in the PRE+10 treatment group had higher levels of progesterone (P=0.04) at d 0 compared to PRE heifers. At d 7 (CIDR removal) there was a tendency (P=0.07) for PRE+10 heifers to have higher levels of progesterone than PRE, but did not differ by d 9 (FTAI, P=0.36). FTAI conception rates in heifers in the PRE treatment group (63%) tended (P = 0.09) to be higher compared to the controls (35%), but not different from PRE+10 (43%), with no differences in season-long pregnancy rates (P > 0.15). Pre-synchronization with MGA immediately prior to FTAI synchronization appears to increase conception rates early in the breeding season in beef heifers. In Chapter 4, our laboratory analyzed the efficacy of supplementation strategies post-insemination. Unlike the first two experiments, the third study focused on reproductive failure that occurs after insemination. The overarching goal remained the same, increasing the reproductive efficiency within our nulliparous heifer herd. A common practice for beef producers in the United States is to use estrous synchronization, and immediately turn heifers out to lush spring pasture immediately following FTAI. The fresh forage is high in water content which lowers dry matter intake (DMI) and creates a negative energy balance. Ultimately, this reduced energy intake can result in a reduction in reproductive performance. In the Chapter 4 our laboratory formulated a supplementation strategy utilizing the SmartFeed™ technology to deliver soybean hulls to our treatment group following insemination for 45 days. The utilization of the SmartFeed® technology provided the opportunity to analyze the efficacy of the supplementation strategy using each individual animal as an experimental unit. Sixty-two nulliparous crossbred heifers were fed in drylot to obtain moderate body condition prior to breeding at d 0 via FTAI and trained to utilize the SmartFeed™ system.Heifers were blocked by weight and body condition score to either the soybean hull supplementation group (SOY) or the non-supplemented control group (CON). . Heifers in the treatment group received their supplementation by entering the SmartFeed™ system, allowing for RFID controlled release of 2.27 kg. per head each day for 45 days. Scales located beneath each feed pan sent real time weight data for regulation and analysis on individual animal feeding behavior. On study d 6, a subset of the nulliparous crossbred heifers (n = 12; n = 6/ treatment) were transported by trailer from the Feldun Purdue Agricultural Center to Purdue West Lafayette main campus (approximately 217.74 km.). The subset of heifers had embryos flushed and evaluated for embryo quality and number of live/dead cells. Ultrasonography was utilized to monitor ovarian activity throughout the duration of the study and to determine pregnancy status 30 days after FTAI and 30 days after the 45-day breeding season. Though conception rates were not statistically (P=0.17) different (SOY 16/25; 64% vs. CON 11/25; 44%) when comparing treatment groups, the numerical differences suggest there is potential in pursuing a similar supplementation strategy following breeding in nulliparous beef heifers. The supplementation of SBH resulted in greater weight gain over time (P = 0.04), potentially explaining the numeric improvement in conception rate. The two pre-synchronization studies from Chapters 2 and 3 resulted in numerical improvements in conception rate as a result of exposing replacement heifers to a source of progestin prior to the initiation of their synchronization protocol. The implementation of progesterone priming mitigates the occurrence of short cycles and immature oocyte maturation at the time of ovulation. Based on results from previous studies conducted by our laboratory, the source of progestin greatly determines the timing and concentration of P4 circulating in replacement heifers immediately following treatment. Additionally, the 7 & 7 estrous synchronization protocol has grown in popularity and implementation. This protocol when broken down is very similar to the pre-synchronization protocol our laboratory utilized for the first two studies. Several studies have been conducted to analyze the efficacy of the 7 & 7 and the conception data was comparable to the MGA derived protocol. Thus, one potential direction for the future would be to formulate a research study that compares the two protocols. Since the conception rates were similar, it may be hypothesized that the MGA protocol could be more widely accepted as there is a reduction number of times animals are handled.</p>

<p dir="ltr">Porcine reproductive and respiratory syndrome virus (PRRSV) is a devastating virus that is endemic to the swine industry. This virus has little direct effect on the dam but results in abortions, stillborn, and delivery of viremic piglets. PRRSV is unable to cross the swine placenta in early gestation but as gestation progresses, the placenta becomes permissible during late gestation. The mechanisms that allow the virus to cross the late gestation placenta are not well understood, but several theories have been presented regarding changes in placental morphology or enzymatic changes. Additionally, piglets who experience IUGR due to uterine crowding have been found to be more resistant to PRRSV infection, having lower viral levels than their normal litter mates. When vertical transmission from the dam to fetus occurs not only can the effects previously mentioned occur, but PRRSV is also known to cause suppression of maternal and fetal thyroid hormone. Thyroid hormone plays numerous roles in fetal development such as accretion of fetal mass, appetite regulation, and coincidently follows a similar increase trajectory to that of fetal growth during mid- to late-gestation. Consequently, any dysregulation of thyroid hormone has the potential to cause severe side-effects and may alter fetal growth. The relationship between thyroid hormone and fetal growth and development is not well understood. Chapter 2 investigates the potential cause-and-effect relationship between fetal growth and thyroid hormone through the induction of fetal hypothyroidism. Pregnant gilts (n=24) were given a sham treatment (CON; n=12) or treated with methimazole (MMI; n=12), a goitrogen capable of crossing the placenta. These gilts were then further subdivided across four gestational timepoints spanning mid- to late-gestation, these being days 55, 66, 76, and 86. Treatment started 21 days prior to these desired dates. Upon completion of treatment the gilts were humanely euthanized, and fetuses were extracted (resulting populations of n=174 MMI and n=166 CON) and fetal body and organ weights were recorded. Collected tissues included heart, liver, lung, kidneys, spleen, brain and thyroid. Fetuses were imaged in the left and right lateral recumbency for phenotypic analysis, including novel head measurements. Placental sample were also taken. Additionally fore- and hind limbs were taken from the centermost male and female from each litter so that radiographs could be taken to analyze bone growth. Statistical analysis of all phenotypic differences was carried out using a linear mixed effect model including gestational age and treatment as fixed effects and gilt as a random effect. The data revealed that the left and right phenotypic parameters are highly correlated (R2>0.9). Upon extraction, goiters were present in the MMI fetuses and there was a significant increase in both absolute and relative thyroid weights. Thus, the use of MMI during this period of gestation was successful in inducing hypothyroidism. Additionally, the MMI treated thyroids had a significant treatment by time interaction with 0.014g and 0.21g increase at day 55 and 66 respectively indicating reduced compensatory action within the fetal hypothalamic-pituitary-thyroid axis during this earliest period. Liver weight as a percentage of body weight decreased from 6.06% to 2.56% between days 55 and 86 in the CON group but, was significantly increased at all time points in response to MMI induced hypothyroidism (P<0.01). Thus, the in brain to liver weight ratio decreases over time, in MMI fetuses (P<0.05). While all other phenotypic parameters were significantly altered by gestation age, there was no significant impact of fetal hypothyroidism. This indicates that fetal thyroid hormone is not the driving factor for the exponential fetal growth seen in mid- to late-gestation. PRRSV virus is a complex and devastating virus to the swine industry, especially when it infects pregnant gilts and sows. PRRSV is unable to cross the swine placenta during mid-gestation but as gestation progresses the virus readily crosses the placenta and is able to infect piglets during this late gestation period. The mechanisms by which PRRSV crosses the highly restrictive porcine placenta are not clear. Additionally, piglets who experience intrauterine growth retardation experience lower virus levels than their normal counterparts. Chapter 3 investigates the changes in three genes of interest that we hypothesized, had the potential to fluctuate throughout gestation and facilitate PRRSV transfer, as well as the morphological changes that occur in the maternal-fetal interface through mid- to late-gestation and how these aspects may vary between IUGR and normal piglets. Placental samples were collected from pregnant gilts (n=12) equally divided across days 55, 66, 76, and 86 of gestation. Samples were taken of each fetus’s placenta adjacent to the umbilical cord. A portion of the sample was cut into 1 cm2 and placed into a mold with optimal cutting temperature media (OCT) for later cryo-sectioning and histology. The remaining portion had the fetal placenta peeled from the endometrium and flash frozen in liquid nitrogen for RNA extraction. A subset of samples was chosen based on fetus’s brain to liver weight ratios (n=96). From each litter two males and two females with the most extreme case of IUGR, based on z-scores, were chosen and the same was done for the two males and females with lowest brain to liver weight ratios, the later were classified as large for gestational age (LGA). 56 of the original 64 had acceptable levels of placental RNA for analysis. A total of 3 genes were chosen for analysis based on their function and previous literature. These included CD163, SIGLEC1 and IL-10. No significant up or down regulation was seen in any of the selected genes and there was no variation between IUGR and LGA fetuses. Additionally, placenta histology was conducted to evaluate populations of CD163 positive macrophages throughout the maternal fetal interface across mid- to late-gestation. Populations of CD163 positive macrophages were found on both the maternal and fetal sides of the maternal fetal interface at all timepoints. Collectively these results show there is no fluctuation in CD163, SIGLEC1, or IL-10 among timepoints or between IUGR and LGA fetuses. Additionally, the histology samples confirm the presence of resident populations of CD163 positive macrophages on maternal and fetal sides of the MFI. Collectively these results indicate that more research needs to be done to determine the underlying mechanisms of PRRSV transmission during late gestation.</p>

Prolificacy in sheep, under most types of flock management, may exert an overwhelming influence on profitability. Three major classes of sheep farming are found in New Zealand, namely Extensive farming, on high country and droughty areas where wool is the chief product, Store sheep farming, on harder hill country, where income is derived from sales of both wool and surplus stock, and Fat lamb farming, in the easier and improved areas, where sales of fat stock almost exclusively dictate the size of the income. In all three types, ewe fertility is of paramount importance. This investigation was undertaken as a pilot attempt to demonstrate, with more accuracy, the source of, or reason for, the additional lambs which result from flushing ewes, in as far as this practice may increase both ovulation rate and subsequent mortality or merely reduce mortality in developing ova at some as yet underdefined stage of early pregnancy. The nature of the experiment was such that a study of the time-relationships of ovum loss and embryo mortality at various stages in early pregnancy could be made. Thus the matings of 225 ewes in two separate mobs were observed and slaughter dates were measured for individual ewes from mating times. By this means a considerable collection of both field and laboratory data was made available for a study of comparative individual and group reactions to the flushing treatment applied.