Effects of prenatal maternal TRH stimulation on the postnatal ability of neonatal piglets to cope with a cold challenge.

The effect of administering thyrotropin-releasing hormone (TRH) before farrowing on the ability of their newborn piglets to withstand a cold challenge was studied. Sows received intravenous infusions of TRH (5 microg kg(-1); TRH group) or physiological saline (0.9% NaCl; control group) from day 105 of gestation until farrowing. The plasma concentrations of thyroxine and triiodothyronine increased in sows treated with TRH. There were no differences in thyroxine and triiodothyronine between pigs born to sows in the TRH group and those of the control group. The rectal temperature of piglets born to TRH-treated sows decreased less than that of piglets born to controls as a consequence of a 1-hour cold challenge. Piglets born to sows in the TRH group had higher body weights at birth, and by day 28 they were an average 600 g heavier than those born to sows in the control group. Summarizing, prenatal maternal treatment with TRH appears to increase piglets' resistance to cold as well as to have beneficial effects on birth and weaning weights.

Responses of pulmonary intravascular macrophages to 915-MHz microwave radiation: ultrastructural and cytochemical study.

BACKGROUND: Microwave (MW) radiation is being increasingly used as a source of heat supplementation during early postnatal development of pigs. Although MW radiation does not cause deleterious physiological effects, no specific information exists regarding its impact on immune cells such as macrophages. Pulmonary intravascular macrophages (PIMs) are emerging as important inflammatory cells due to their endocytic and secretory potential. An in vivo study was conducted to evaluate the effects of infrared, and low and high power MW radiation on the PIMs of pigs. METHODS: Pigs were exposed to infrared (IR), low MW (LMW; 6.1mW cm-2), and high MW (HMW; 11.4mW cm-2) radiation at 915 MHz (n = 2 for each treatment) for 24 hr. The controls (n = 2) were exposed to natural light for the same period of time. Lung tissues were processed for ultrastructural examination and acid phosphatase (AcPase) cytochemistry. In addition, rough endoplasmic reticulum (RER) as a fraction of cytosol of the PIMs was counted. RESULTS: Ultrastructural and numerical data suggested enhanced secretory activity in the PIMs of LMW-treated pigs as indicated by the increased RER:cytoplasm ratio, prominent Golgi complex profiles, and accumulation of secretory vesicles in conjunction with microtubules as compared with the control, IR, and HMW-exposed pigs. High MW treatment induced some damage to pulmonary interstitium as deduced from the presence of extracellular AcPase precipitates and disrupted collagen matrix. Intracellular globules were noticed in the PIMs of IR and LMW-treated pigs but not in the control and HMW-radiated animals. CONCLUSIONS: Elaboration of structural signs of secretory activity in the PIMs by LMW radiation in the absence of pulmonary pathological changes indicates its potential for cell activation in addition to the already established role of LMW in heat supplementation. This activation could be due to either increased core body temperature or initiation of intracellular signaling by the LMW radiation. This study also shows that the HMW radiation is capable of inducing pathology in the form of changes in the pulmonary interstitial matrix and may not be a good source of supplementary heat.

Morphological changes in the small intestine of the fetal pig after prenatal stimulation of the sow with ACTH.

Twelve pregnant primiparous sows were catheterized on day 102 of gestation and randomly allocated to receive ACTH (days 112-113 of gestation [2d], days 105-parturition [10d]) or saline. At parturition the 3rd, 4th, 6th and 7th piglet born alive were sacrificed either at birth or at 6 h. The later group was fed bovine colostrum through a stomach tube at 30 min, 2 and 4 h of life. Following sacrifice, the small intestine of each piglet was excised, extended and measured. Piglets from sows in the 2d group tended to be heavier with longer small intestines than either the control or 10d groups. When the small intestine length was expressed as a function of body weight, the 10d group had the greatest ratio, suggesting that the pre-parturition maintenance of elevated cortisol levels either enhanced small intestine growth or attenuated overall weight gain. Two types of enterocyte granules were described at the level of the electron microscope: granular and opaque. Opaque granules from piglets born to sows in the 2d treatment group had both a lower volume fraction and were fewer per unit area when compared to those of either the saline or 10d treatments. The process of macromolecule uptake from the intestinal lumen appeared to have been interfered with as a result of an acute prenatal stimulation with ACTH. The above results suggest that in piglets, the level of circulating cortisol differentially controls the processes of IgG absorption, enterocyte replacement and small intestine growth through separate mechanisms. Further, these processes can be manipulated in the prenatal piglet.

Development of the small intestine of piglets in response to prenatal elevation of glucocorticoids.

The effects of prenatal adrenal stimulation and synthetic glucocorticoid supplementation on development of the gastro-intestinal tract of the piglet were investigated. Twelve pregnant sows were treated with either ACTH infusion, Isoflupredone injection or Saline between days 105 and 112 of gestation. Neonatal pigs were weighed, bled and sacrificed at 0 or at 6 h. Piglets sacrificed at 6 h were fed bovine colostrum. Transverse sections were prepared from the duodenum, jejunum and ileum for measurement of the villus amplification factor (VAF) and basal membrane circumference. Sows in the ACTH group showed an elevation in cortisol in response to infusion; this decreased after infusion and then rose again at parturition. Piglets from both the ACTH and Saline groups had more villus surface area per unit of body weight (BW) than those born to Isoflupredone-treated animals. The BW of the ACTH piglets was lower (P less than 0.05) than those of piglets in the other groups. When the weight of the stomach and the Small Intestine (SI) was expressed as a function of the body weight, the stomach and SI:BW ratio was larger (p less than 0.05) in pigs born to ACTH-treated sows. The circumference of the ileum was larger at 6 h than at 0 h. Control pigs had a higher concentration of bovine IgG at 4 and 6 h (P less than 0.05). Observations of the light microscopic preparations indicated a less organized epithelium in both ACTH and isoflupredone pigs sacrificed at 0 h. Light and EM preparations of ileum from ACTH pigs sacrificed at 6 h, showed an abundance of dark-stained vacuoles, characteristic of IgG-containing structures. These became less evident in piglets from the Isoflupredone group and even less so in the control groups. The consequences of these phenomena in terms of absorptive capacity are discussed.

Production of oestrone and oestradiol-17 beta by different regions of the filamentous pig blastocyst.

Pig blastocysts aged 14, 16 and 18 days were divided into 15 cm segments representing tissue adjacent to the embryonic disc, an intermediate section and the tip region. Whenever total blastocyst length allowed, the intermediate segment was divided into proximal and distal portions for separate culture. All were rinsed with buffer and incubated with dehydroepiandrosterone for 3 h. Rinsing buffer and incubation medium were subsequently assayed for concentrations of oestrone and oestradiol-17 beta. The highest production of oestrogen was found in the embryonic disc region. The intermediate regions had the lowest synthetic ability, while the tip region produced more oestrogens than the intermediate regions but less than the disc region. The production of oestrone was higher (P less than 0.05) in 18-day-old blastocysts than in younger ones while oestradiol-17 beta production was lower (P less than 0.05) on Day 16. The proportional role of the embryonic disc region as oestrogen-producing tissue increased over time. On Day 14, each intermediate region produced over 70% as much oestrogen as the disc region. These proportions declined on Days 16 and 18 to about 50 and 30% respectively. The regional variation in the ability of blastocysts to produce oestrogens may have some influence on the ability of the blastocyst to create an adequate microenvironment within the uterus which permits successful differentiation and placentation.

Performance of large groups of chicks using operant conditioning to control the thermal environment.

In four trials, 408, 320, 160, and 400 chicks were housed on litter in pens 1.8 x 2.4 m. Eight pens were used for each trial. For the first 6 days the environmental temperature was maintained at 28 C; on Day 7 the temperature was reduced to 16 C. Four pens were equipped with microswitches; the remaining four pens were each heated by two infrared lamps in constant operation. When chicks struck the microswitch, infrared lamps were turned on for 1 min during the learning phase when chicks were being conditioned to the experimental setup and 4 min during the experimental phase during which data were collected for analysis. Feed intake, gain, and mortality were recorded. Trials 1 and 2 were concluded at 28 days and Trials 3 and 4 concluded at 21 days. At the conclusion of the trials protein, fat, and water content of the birds were determined. Additional analysis for ash content was performed for Trials 1 and 2 only. No significant differences (P greater than .05) in gain, feed conversion, body composition, and mortality rate were found between treatments. Chicks provided with continuous heat were exposed to three times as much supplemental heat as operant conditioned groups yet feed efficiency was unaffected.

Effect of air movement on operant heat demand of chicks.

Chicks, 8 days of age, were housed in a wind tunnel at temperatures from 12 to 28 C in increments of 4 C. The tunnel was equipped with a microswitch, an infrared bulb located above the switch, and a small electric fan controlled by a rheostat. Following learning, chicks were exposed at each temperature to air speeds of 0, .5, 1.0, and 1.5 m/s according to a Latin-square design. Chicks readily responded to air speed and temperature changes. For each increase of .1 m/s the effective environmental temperature dropped .6 C.

Behavioral observations and operant procedures using microwaves as a heat source for young chicks.

Four trials, using operant conditioning procedures, were conducted to study the response of chicks, housed at 16 C, to microwave or infrared heat. Microwave power density was 26 mW/cm2 in Trial 1, 13 mW/cm2 in Trial 2, and 10 mW/cm2 in Trials 3 and 4. Chicks voluntarily demanded between 28 and 63% as much heat (min heat/hr) from microwave source as from infrared source at all power densities. There was no correlation, however, between the ratio of heat demanded and the power density used. There were no significant differences in growth between infrared- or microwave-heated chicks. It is evident from these studies that 8-day-old broiler chicks are capable of associating the performance of a task with a thermal reward provided by the microwaves. They are also able to utilize these microwaves through operant conditioning without any visible detrimental effect to their health or behavior.

Estrogens and piglet viability. I. Serum estrogen concentrations in piglets.

An experiment was conducted to establish estrogen (Es) levels in piglet serum up to 13 h after birth. Treated piglets were given an injection of estradiol benzoate into the vena cava immediately after birth. Control piglets were similarly injected with saline solution. Blood samples were obtained frequently for monitoring Es levels. Each sample was analyzed for estrone (E1), estrone sulphate (E1SO4) and estradiol-17 beta (E2) by radioimmunoassay. Immediately after birth, Es declined at a very fast rate for 4 h and thereafter declined slowly until 9 h, when a small recovery occurred. There were no differences (P greater than .05) in the initial concentrations of Es between the control and treated groups. Injected estradiol benzoate did not significantly increase serum Es concentration (P greater than .05) by 5 min postinjection in treated animals, but sustained a trend showing higher level of Es than the control until 4 h. At birth, E1SO4 was the Es with the highest concentration in piglet serum, followed by E1 and E2. The sharpest decline after birth occurred in E1SO4, which fell to lower values than E1 by 3 h. We conclude that an undetermined catabolic system for Es allows the piglet to eliminate or transform Es to other compounds.

Estrogens and piglet viability. II. Effect of estrogen on piglet viability.

The effect of estrogens (Es) on piglet viability was determined as measured by birth to suckling intervals. Starting on d 109 postbreeding daily blood samples were obtained from 15 Yorkshire sows, Immediately after birth, blood samples were taken from the umbilical cord (UC) and the vena cava (VC) of piglets, followed by injections via the VC of either estradiol benzoate (EB) or a saline solution. The interval from birth to suckling (BTS), and body weight gain until 96 h was recorded. Total estrone concentration in the sows' serum rose until the day before parturition and declined sharply by d 2 postpartum. Piglets given EB injections had a shorter interval from BTS (P less than .05) and females suckled sooner than males in both the control and treated groups. No significant differences in weight gain were detected between control and treated groups at 2, 24 or 96 h. Higher (P less than .001) levels of estrone and estrone sulphate were found in the UC than in VC samples, but no correlation existed between levels of Es in the UC and VC (P greater than .05). We concluded that Es or other hydroxylated compounds could be acting upon a high control center of the newborn piglet to cause hyperactivity with a consequent reduction in BTS interval.