Influence of the environmental temperature on the metabolic use of dietary energy and nitrogen in the growing rat

Sixty-seven male rats of the Wistar CF strain were used in two trials to study the effect of ambient temperature on nitrogen and energy balances (experiment 1) and on the variations of certain biochemical parameters of metabolism (experiment 2). In both cases, the rats, housed individually in metal cages and fed ad libitum, were kept under three different temperatures : 21 degrees C (control), 3 degrees C (cold), 31 degrees C (hot). Compared to the controls, the rats at 3 degrees C showed a significant increase (P less than 0.01) in food intake and a significant decrease (P less than 0.01) in daily growth rate and feed efficiency ratio; body fat content was unchanged. Compared to the controls, the rats at 31 degrees C showed a decrease (P less than 0.01) in food intake and growth rate, a better feed efficiency ratio (P less than 0.01) and a significant increase in carcass lipid content. When compared to rats at 21 degrees C, those at 3 degrees C had a much lower nitrogen retention; at 31 degrees C this retention was only slightly lower. The urinary nitrogen excretion, increased by the cold temperature, reflected higher nitrogen catabolism, while its increase at a high temperature was probably due to a decrease in protein synthesis, and a subsequent degradation of excess ingested nitrogen. Energy retention increased (P less than 0.01) as the ambient temperature increased from 3 to 31 degrees C, and wide variations in the amounts of fixed energy in the form of proteins or lipids were observed. The balance results obtained have been discussed in relation to the variations of some biochemical parameters of metabolism such as free fatty acids, free glycerol, lipoprotein-lipase activity and in vitro utilization of labelled glucose.     

Effects of a bovine colostrum-supplemented diet on some gut parameters in weaned piglets

The present study investigated the effects of a bovine colostrum-supplemented diet on gut post-weaning adaptation and health in piglets. Thirty-six 21-d-old piglets were allocated to one of the three following dietary treatments: sow-reared (SR), weaned on a control starter diet (WCtrl) or on a starter diet supplemented with bovine colostrum (WCol) until slaughter at 28 d or 35 d of age. Gastric pH and intestinal bacteriological, structural and functional parameters were determined. Compared to WCtrl, the gastric pH was lower (P < 0.05) and the duodenal lactobacilli:coliform ratio was higher (P = 0.05) in WCol piglets. The relative small intestine weight was 18% (P < 0.05) higher in WCol piglets than in SR piglets. Duodenal villous height was lower (P < 0.01) in WCtrl than in SR piglets, whereas the value for WCol piglets was intermediate. The weaning-increased crypt cell proliferation was not affected by bovine colostrum supplementation. The mucosal ribosomal capacity was higher (P < 0.05) in W than in SR piglets. In conclusion, a diet supplemented with colostrum induced, although not always significantly, variations of gut parameters, suggesting that globally, colostrum may limit weaning-induced gut structural and microbial alterations. The observed effects occurred early and were maintained throughout the post-weaning adaptive phase.     

Insulin and glucose concentration changes in newborn piglets after suckling the colostrum from insulin administered sows

Immunoreactive insulin (IRI) concentration in sows colostrum has been previously proven to be much higher than that in blood. The experiment was carried out to show the influence of endogenous and added insulin in sows colostrum on insulinaemia and glycaemia of newborn piglets. In colostrum collected from 3 control and 5 experimental sows before loading, basal insulin concentration were 1.595 and 1.365 nM-1, respectively, and calculated for all 8 sows together were 1.451 nM-1 (SEM +/- 0.289). Basal plasma insulin concentrations calculated for 68 healthy piglets before sucking were little differentiated (mean 0.318 +/- 0.044 nM l-1), whereas glucose initial concentrations for those piglets (mean 3.581 +/- 0.275 nM l-1) were highly differentiated. Intramuscular loading of 5 experimental sows with insulin (80 I.U. per animal) caused an increase in the concentration of insulin in colostrum from 1.365 to 3.449 nM l-1 (0.01, P less than 0.02). The mean insulin level (0.313 +/- 0.04 nM l-1) in experimental piglets blood plasma (n = 42) increased significantly to 1.234 +/- 0.07 (P less than 0.001) after suckling by sows loaded with exogenous insulin. Glycaemic response of those two piglets litters was poor but showed a statistically significant increase (P less than 0.001). The glucose concentrations in blood plasma samples of the other three litters did not changes after sucking. The experiment excluded the hypothesis that high level of insulin in colostrum could be the cause of hypoglycaemia in healthy piglets after sucking.     

Effects of high temperature on body temperature and hormonal adjustments in piglets

Effects of a high (33 degrees C) or thermoneutral (23 degrees C) temperature on body temperature and endocrine parameters were studied in weaned piglets. Rectal and skin temperatures were measured in four ad libitum fed animals per temperature during three weeks. After this acclimation period, 11 blood samples were withdrawn on a 24-h period. Over the acclimation period, rectal and skin temperatures were 0.6 and 2.9 degrees C higher, respectively, at 33 degrees C than at 23 degrees C (P < 0.01), this change occurring from the 1st day at 23 or 33 degrees C. A tendency of serum leptin concentrations to be lower after meals at 33 degrees C than at 23 degrees C was also displayed (P = 0.09). Plasmatic concentrations in Insulin-like growth factor I and thyroxine were decreased at 33 degrees C relative to 23 degrees C (P < 0.01 and P < 0.06, respectively), and triiodothyronine concentrations tended to be lower at 33 degrees C than at 23 degrees C (P = 0.1), which could account for the lower heat production and growth observed in pigs exposed to high temperatures.     

Effects of warm exposure on adipose tissue and muscle metabolism in growing pigs.

1. Forty-eight pigs weaned at 3 weeks old and acclimated to the experimental temperatures for 2 weeks before the start of the experiment, were fed ad lib and used between 9 and 33 kg live weight to determine the effects of warm exposure (31.5 vs 18.5 degrees C) on adipose tissue and muscle metabolism. 2. Warm exposure induced a decline in the lipid content (P less than 0.01) of backfat whereas degree of saturation (P less than 0.05) and adipocytes size were increased (P less than 0.05). 3. At 31.5 degrees C, as compared to 18.5 degrees C, activities of malic enzyme and glucose-6-phosphate dehydrogenase were depressed by an average 33% in backfat (P less than 0.01) and 23% in leaf fat (P less than 0.05) while lipoprotein-lipase activity was stimulated by 60% (P less than 0.01) in leaf fat. 4. In warm conditions, the activities of the enzymes indicative of oxidative and glycolytic metabolism in muscle, i.e. lactate dehydrogenase, beta-hydroxyacyl coenzyme-A dehydrogenase, citrate synthase and cytochrome oxidase, were reduced in the longissimus dorsi muscle (P less than 0.05) and to a lesser extent in the trapezius muscle. 5. At 31.5 degrees C, pigs exhibit lower average plasma levels of insulin, T3 and T4 than those maintained at 18.5 degrees C.     

Dietary supplementation with maize distillers dried grains with solubles during late gestation and lactation: Effects on sow and litter performance,and on colostrum and milk composition

The objectives of this study were to determine the effects of maize distillers dried grains with solubles (DDGS) during late gestation and lactation on sow and piglet performance, and on colostrum and milk composition. Thirty-six second- and third-parity (2.43 parity) sows (Yorkshire) were allotted to 1 of 3 groups and fed diets containing 0 (control), 200 or 400 g DDGS/kg during the last 20 d of gestation and throughout a 21 d of lactation. Experimental diets contained 12.9 MJ metabolizable energy/kg and 9.7 g lysine/kg. The colostrum and milk samples were obtained on d 0 (farrowing) and d 21 (weaning). There were no differences (P>0.05) in the sows’ average gestation lengths, weaning-to-estrus interval, average daily feed intake, and the lactation backfat and body weight change between dietary treatments. There were no dietary effects (P>0.05) of DDGS on the numbers of total, born alive piglets, average birth weights, piglets per litter at weaning or piglets average daily gain during lactation. No differences (P>0.05) were observed in total solids, protein, fat and lactose among the sows fed the DDGS diets compared with the control. The composition of total solids and protein of sows colostrum and milk were higher at farrowing (d 0) than at weaning (d 21) (P<0.001). However, the fat and lactose content of sows colostrum and milk were increased (P<0.001) from d 0 (farrowing) to d 21 (weaning). In conclusion, the results suggest that 400 g DDGS/kg (87 g lysine/kg) supplemented with 5.2 g lysine/kg included in late gestation and lactation diets is sufficient to replace all the dietary soybean meal without significantly affecting sow and litter performance or colostrum and milk composition.     

In a hypergravity environment neonatal survival is adversely affected by alterations in dam tissue metabolism rather than reduced food intake.

Exposure of rat dams to hypergravity during pregnancy is associated with increased pup mortality, reduced food intake, and decreased rates of glucose oxidation and lipogenesis in mammary tissue. We hypothesized that increased pup mortality is due to changes in maternal metabolism and not to reduced food intake of dams. Effects of hypergravity on rate of glucose oxidation and lipogenesis in mammary, liver, and adipose tissue were measured in rat dams centrifuged at 2.0 G [hypergravity (HG)], kept at 1.0 G (control), or fed to match the intake of HG rats (pair fed) from gestation day 11 (G11) until G21 or postpartum day 3 (P3). Body weight, percent body fat, metabolizable energy, and nitrogen balance were significantly less in HG dams compared with controls (P<0.05); however, these factors were not different between HG and pair-fed dams. By P3, 100% of control and pair-fed pups survived, while only 49% of HG pups survived. At G21, rates of glucose oxidation and lipogenesis in mammary and adipose tissue were less in HG than in control and pair-fed dams (P<0.1 and P<0.05). In liver, at G21, the rate of lipogenesis was greater in HG than control and pair-fed dams (P<0.01); at P3, lipogenesis was greater in control than HG and pair-fed dams (P<0.05). Gene expression of ATP citrate lyase, acetyl-CoA carboxylase, and fatty acid synthase increased in liver from pregnancy to lactation in control and pair-fed dams but not HG dams. Thus reduced food intake and body mass due to hypergravity exposure cannot explain the dramatic decrease in HG pup survival.     

Late gestation diet supplementation of resin acid-enriched composition increases sow colostrum immunoglobulin G content,piglet colostrum intake and improve sow gut microbiota

Resin acid-enriched composition (RAC) mainly containing tall oil fatty acid with an active component of resin acid (RA) can improve the microbial population in the digestive system, change the microbial fermentation, and improve the feed conversion ratio. We investigated the effects of dietary supplementation of RAC on sow colostrum yield (CY), colostrum composition and gut microbiota. Tall oil fatty acid and RA are commonly termed RAC and CLA, pinolenic, abietic, dehydrobiotic acids are characteristic components of RAC. The experiment was conducted in three trials in three respective herds. Sows were fed with a control diet and the same diet supplemented with 5 g RAC/day per sow during the last week of gestation. The 16S ribosomal RNA gene sequencing technique was used to assess sows’ faecal microbiota populations at farrowing. Colostrum nutritional composition, acute phase proteins (APPs) and immunoglobulin (Ig) content were also assessed. Individual piglets were weighed at birth and 24 h after the birth of first piglets in order to calculate CY and later at 3 to 4 weeks to calculate average daily gain. The RAC-fed sows had significantly higher IgG levels (P<0.05) in all three herds but treatment did not influence colostrum IgA and IgM concentration. There were no significant differences in colostrum protein, lactose and fat content in sows of the two diet groups (P>0.05), but those fed RAC had higher levels of colostrum serum amyloid A. Colostrum yield was significantly higher in RAC-fed sows in herds 2 and 3 with heavier piglets between 3 and 4 weeks of age (P<0.05), but not in herd 1 (P>0.05). Resin acid-enriched composition supplementation significantly increased some beneficial and fermentative bacteria (Romboutsia and Clostridium sensu stricto) than the control diet (P<0.01) while some opportunistic pathogens (Barnesiella, Sporobacter, Intestinimonas and Campylobacter), including Proteobacteria, were suppressed. Therefore, RAC added to the sow diet at late pregnancy increases colostrum IgG, colostrum availability for neonate piglets, and seems to promote better maternal intestinal microbial sources.     

Complement Titres of Naturally and Artificially Raised Piglets: I. In piglets of different birth weights

Titrations of haemolytic complement, C(1), activity have been carried out on serial weekly bleedings from four litters of piglets, a total of 39 animals. One of these litters was raised naturally on the sow, the other three litters were removed by hysterectomy and fed artificially without colostrum supplement. At one day of age the nursing piglets had considerably higher C(1) titres than the colostrum-deprived animals, owing presumably to their ingestion of maternal complement components from the colostrum. The naturally-raised piglets grew more rapidly and continued to have higher C titres during the first three weeks. After that time, although the artificially-raised piglets were still gaining weight more slowly, their C(1) titres began to compare favourably with those of the naturally-raised animals. Considerable variation was noted in the complement activity of sera of littermates. Deaths occurred among animals with high or with low C(1) titres.     

Coordinate induction of peroxisomal acyl-CoA oxidase and UCP-3 by dietary fish oil: a mechanism for decreased body fat deposition

Rats fed dietary fats rich in 20- and 22-carbon polyenoic fatty acids deposit less fat and expend more energy at rest than rats fed other types of fats. We hypothesized that this decrease in energetic efficiency was the product of: (a) enhanced peroxisomal fatty acid oxidation and/or (b) the up-regulation of genes encoding proteins that were involved with enhanced heat production, i.e. mitochondrial uncoupling proteins (UCP-2, UCP-3) and peroxisomal fatty acid oxidation proteins. Two groups of male Fisher 344 rats 3-4 week old (n=5 per group) were pair fed for 6 weeks a diet containing 40% of its energy fat derived from either fish oil or corn oil. Epididymal fat pads from rats fed the fish oil diet weighed 25% (P < 0.05) less than those found in rats fed corn oil. The decrease in fat deposition associated with fish oil ingestion was accompanied by a significant increase in the abundance of skeletal muscle UCP-3 mRNA. The level of UCP-2 mRNA skeletal muscle was unaffected by the type of dietary oil, but the abundance of UCP-2 mRNA in the liver and heart were significantly lower (P < 0.05) in rats fed fish oil than in rats fed corn oil. In addition to inducing UCP-3 expression, dietary fish oil induced peroxisomal acyl-CoA oxidase gene expression 2-3 fold in liver, skeletal muscle and heart. These data support the hypothesis that dietary fish oil reduces fat deposition by increasing the expression of mitochondrial uncoupling proteins and increasing fatty acid oxidation by the less efficient peroxisomal pathway.     

Dietary fat saturation and gender/hormonal status modulate plasma lipids and lipoprotein composition(1)

Male, female and ovariectomized (to mimic menopause) guinea pigs were fed a saturated (SFA) or a polyunsaturated (PUFA) fat diet for 4 weeks to determine the effects of dietary fat saturation on lipoprotein levels and composition and to assess whether gender and hormonal status modulate the cholesterolemic response. Both diets contained 15g/100 g fat and 0.04 g/100 g cholesterol and were identical in composition except for the type of fat. The SFA diet contained 50% saturated fat (25% lauric + myristic fatty acids), 25% PUFA and 25% monounsaturated fatty acids while the PUFA diet had 50% PUFA (linoleic acid), 25% monounsaturated and 25% SFA fatty acids. Plasma LDL cholesterol (LDL-C) was an average 21% lower in guinea pigs fed PUFA compared to those fed SFA (P < 0.05). In addition, ovariectomized guinea pigs, both in the SFA and PUFA groups, had 20–33% higher LDL-C than either males or females (P < 0.01). VLDL cholesterol was 70% higher in the PUFA-fed animals (P < 0.0001). A gender effect was observed in plasma HDL cholesterol (HDL-C) with females and ovariectomized guinea pigs having 30–42% higher HDL-C than males (P < 0.01). LDL susceptibility to oxidation was not affected by dietary fat saturation or gender. In contrast, VLDL and LDL composition were significantly influenced by diet and gender. VLDL particles were larger in size in guinea pigs fed the SFA diets (P < 0.01) while LDL particles were larger in female guinea pigs (P < 0.001). Hepatic lipids were influenced by the interaction between diet and group. Hepatic cholesterol (P < 0.01) and TAG concentrations (P < 0.0001) were highest in female guinea pigs fed the PUFA diet. Since the liver is the major site of lipoprotein synthesis and catabolism, these results suggest that not only diet but also gender may play a major role in determining the composition and size of lipoproteins.     

Some regulatory aspects of thermogenesis in cold-exposed piglets

1. Thermoregulatory mechanisms were studied in weaned piglets fed ad libitum for 3 weeks at 12 or 23 degrees C. 2. Cold-adapted pigs maintained a growth rate and a carcass composition similar to the control ones, while increasing food intake by 20% (P less than 0.05). 3. Lipoprotein lipase activity was increased (P less than 0.05) by cold exposure in white adipose tissue (WAT) and heart. A large enhancement of lipogenesis was observed in WAT and to a lesser extent in the liver while WAT composition did not change significantly in the cold. 4. Cytochrome oxydase activity was increased in liver (30%), perirenal fat (40%) and interscapular muscle (75%) of cold-exposed pigs. 5. Plasma levels of thyroid hormones (TSH, T3, T4) were increased in the cold. 6. Mechanisms and locations of heat production are discussed.     

Effect of organic and inorganic selenium sources in sow diets on colostrum production and piglet response to a poor sanitary environment after weaning

The objectives of this study were to determine the effect of the chemical form of selenium (Se) fed to sows (1) on production and immune quality of colostrum and (2) on piglet response to a deterioration of sanitary conditions after weaning. Twenty-two pregnant sows were assigned to receive a diet supplemented with 0.3 ppm Se from either sodium selenite (inorganic Se) or Se-enriched yeast (organic Se as Sel-Plex®; Alltech Inc., Nicholasville, KY, USA). Dietary treatments were applied during the last month of pregnancy and lactation. Blood samples were collected on sows before dietary treatment, on the day of weaning and 6 weeks later, and on three to five piglets within litters at birth, at weaning and 6 weeks post weaning. Whole blood was analysed for Se concentration. Colostrum samples were collected at 0, 3, 6 and 24 h post partum and milk samples on days 14 and 27 of lactation. Colostrum and milk were analysed for Se and immunoglobulin G (IgG) concentrations. At weaning, 40 pairs of littermate piglets were moved to rooms where sanitary conditions were good or purposely deteriorated. Piglets were reared individually and fed ad libitum. After 15 days, piglets and feed refusals were weighed and a blood sample was collected to measure plasma haptoglobin concentration. When sows were fed organic Se, Se concentrations were increased by 33% in colostrum (P < 0.05), 89% in milk (P < 0.001) and by 28% in whole blood of piglets at weaning (P < 0.001). Colostrum production during the 24 h after the onset of farrowing and IgG concentrations in colostrum and milk did not significantly differ between the two groups of sows. Weaned piglets reared in good sanitary conditions grew faster (P < 0.001) than piglets housed in poor conditions. Sanitary conditions did not influence mean plasma haptoglobin concentrations of piglets (P > 0.1). The source of Se fed to the dams did not influence piglet performance or haptoglobin concentrations after weaning. These findings confirm that, compared with inorganic Se, organic Se fed to the dam is better transferred to colostrum and milk, and consequently to piglets. They indicate that the Se source influences neither colostrum production nor IgG concentrations in colostrum, and that the higher Se contents of piglets does not limit the reduction of growth performance when weaning occurs in experimentally deteriorated sanitary conditions.     

Effect of gut active carbohydrates on plasma IgG concentrations in piglets and calves

Improving immune status in neonates is crucial to health and production. Gut active carbohydrates (GAC) have been associated with increasing immunoglobin levels and immonucompetence development in mammals. The objective of the following studies was to evaluate whether GAC (mannan-oligosaccharides) applied orally to progeny immediately following parturition, improved blood plasma immunoglobulin (Ig) type G concentrations in piglets and calves. Three trials were conducted comparing control groups with those receiving GAC orally. The first two trials used piglets that were monitored for blood IgG at 2 days of age and for changes in body weight (BW), and the third trial monitored calf IgG from birth to 21 days of age. Piglets in the experimental group received 0.75 g GAC in 10 ml saline at birth and 24 h of age. The calf trial compared the control group against calves that received 22.5 g GAC mixed into 4.5 l of colostrum (to give 5 g/l) in the first 24 h after parturition. Blood serum samples were taken at 2 days post partum in piglets, and at several time points from 6 h to 21 days of age in calves, and were analysed for IgG levels by radial immunodiffusion. In the first piglet trial, significantly higher levels (32%) of IgG were observed for piglets fed GAC (P < 0.001), and in the second, IgG concentration was elevated by 23% (P < 0.01) and BW increased by 9% (P = 0.023) with GAC supplementation. Significant improvements for calves were recorded at all time points in those fed GAC (P < 0.05), with an increase in serum IgG observed after the first day, which was maintained throughout the sampling period, resulting in a difference of 39% at the end of the trial (21 d). These findings form a basis for further studies, which are required to investigate possible modes of action involved in enhancing blood immunoglobulin concentrations in young animals, and the longer-term effects this may have on the development of the immune response.     

Heat production and substrate oxidation in rats fed at maintenance level and during fasting

A total of 36 Wistar rats were fed a commercial diet to a stipulated live weight of 75 g (Group A), 100 g (Group B) and 225 g (Group C). All rats were measured in energy balance experiments, in which the animals were fed near maintenance level, followed by a period of fasting with measurements of the gas exchange. The rats in Group A, B and C were fasted for 2, 3 and 4 days, respectively. The minimum heat production on the last day of fasting for all groups was proportional to metabolic body weight (kg0.75) with a regression: heat production, kJ day-1 = 321 x kg0.75 (R2 = 0.994). In rats fed near maintenance level, heat production was provided by oxidation of carbohydrates in 80-85%, oxidation of protein was 10-15%, while oxidation of fat contributed less than 10%. It is suggested that in the fasting period, the contribution to the total heat production from oxidized carbohydrate and fat depended on the size of the fat depots, a large fat depot giving rise to fat oxidation. On the last day of fasting, 24, 51 and 90% of the total heat originated from fat oxidation in Group A, B and C, respectively.     

Comparative physiological responses of normotensive and essentially hypertensive men to exercise in the heat

Six essentially hypertensive men (average resting arterial pressure of 150/97 mm Hg) and eight normotensive controls (average resting arterial pressure of 115/73 mm Hg) were tested during 1 h of dynamic leg exercise in a warm environment. The groups were well matched for age, VO2 max, body surface area, weight, and body fat. Environmental conditions were 38 degrees C dry-bulb, 28 degrees C wet-bulb; exercise intensity was approximately 40% VO2 max (85-90 W). There were no significant intergroup differences in core or mean skin temperatures, calculated heat exchange variables, heart, or sweat rates. Blood pressure differences between the groups were maintained (P less than 0.01). The hypertensive group responded with a significantly lower stroke index (P less than 0.01) and cardiac index (P less than 0.01), and a decreased slope of the rise in forearm blood flow (P less than 0.01) due to an higher vascular resistance (P less than 0.01). The combined heat load (M + R + C) presented was not sufficient to override the hypertensives' higher cutaneous vasoconstrictor tone. However, on a practical basis, the hypertensives were able to tolerate exercise in the heat as well as their normotensive counterparts.     

Rates of energy substrates utilization during human cold exposure

Although it is well established in animals that acute cold exposure markedly increases the oxidation of energy substrates, the absolute quality and quantity of substrate oxidation is poorly understood in humans. This study compared the rates of substrate utilization in seven healthy young men exposed to both the warm (control exposure at 29 degrees C; semi-nude, 14 h fasted) and to the cold for 2 h (10 degrees C, 1 m.s-1 wind velocity). Substrate utilization was calculated using indirect calorimetry and the nonprotein respiratory exchange ratio, which was derived from the urinary urea nitrogen output. Cold exposure induced a 3.1 +/- 0.2 degrees C drop in mean body temperature and a body heat debt of 825.9 +/- 63.3 kJ (p less than 0.01). These parameters remained essentially unchanged in the warm. Cold exposure elevated the 2 h energy expenditure 2.46-fold in comparison to the warm (p less than 0.01). This cold-induced thermogenesis was accompanied by increases of 588% in carbohydrate oxidation (p less than 0.01) and 63% in fat oxidation (p less than 0.05), whereas protein oxidation remained unchanged. Although the greatest proportion of the energy expenditure in the warm was derived from lipid (59%), carbohydrate oxidation represented the major fuel for thermogenesis in the cold, since it accounted for 51% of the corresponding total energy expenditure. The results demonstrate that cold exposure causes a much greater increase in the utilization of carbohydrate than lipid. It is suggested that these substrates are directly utilized for thermogenesis in the shivering skeletal muscles.     

Neonatal piglet survival: impact of sow nutrition around parturition on fetal glycogen deposition and production and composition of colostrum and transient milk

Piglet survival is a major problem, especially during the first 3 days after birth. Piglets are born deficient of energy, but at the same time they have a very high energy requirement because of high physical activity, high need for thermoregulation (because of their lean body with low insulation) and high heat production in muscle tissues. To be able to survive, newborn piglets may rely upon three different sources of energy, namely, glycogen, colostrum and transient milk, which orchestrate to cover their energy requirements. Piglets are born with limited amounts of energy in glycogen depots in the liver and muscle tissues and these depots are sufficient for normal activity for ∼16 h. Intake and oxidation of fat and lactose from colostrum must supply sufficient amount of energy to cover at least another 18 h until transient milk becomes available in the sow udder ∼34 h after the first piglet is born. Selection for large litters during the last two decades has challenged piglets even further during the critical neonatal phase because the selection programs indirectly decreased birth weight of piglets and because increased litter size has increased the competition between littermates. Different attempts have been made to increase the short-term survival of piglets, that is, survival until day 3 of lactation, by focusing on improving transfer of vital maternal energy to the offspring, either in utero or via mammary secretions. Thus, the present review addresses how sow nutrition in late gestation may favor survival of newborn piglets by increasing glycogen depots, improving colostrum yield or colostrum composition, or by increasing production of transient milk.     

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.     

Body composition at vaginal opening in mice as influenced by food intake and photoperiod: tests of critical body weight and composition hypotheses for puberty onset

To determine if photoperiod and food intake influenced age and body composition at vaginal opening (VO), 80 mice were exposed to either 18L:6D (LL) or 6L:18D (SL) and fed either 3.64 g/mouse per day (HIGH) or 2.73 g/mouse per day (LOW) of Wayne Lab-Blox. Treatments began at weaning (21 to 23 days of age). Mice were killed at VO and analyzed for fat, water and protein content. Mice fed the HIGH ration were younger (P less than 0.01; 35.9 vs. 41.1 days) and heavier (P less than 0.001; 17.8 vs. 15.4 g) at VO than mice fed the LOW ration. Neither age nor weight at VO were affected by photoperiod. Fat content at VO was greater (P less than 0.001) for HIGH than LOW. Differences in fat percentage at VO between diet groups were greater for LL (9.7 vs. 7.0%) than for SL (9.1 vs. 8.6%), resulting in a photoperiod X ration interaction (P less than 0.01). Percent water and protein at VO were not significantly affected by photoperiod or diet. Within-group correlations between body weight and age at VO were not significant. Body water/body weight was inversely proportional to age at VO. This resulted from increased fat deposition in older animals of the LL-LOW group and increased percent protein in older animals of other groups. We concluded that dietary intake did not influence age at VO by affecting age at which a critical body weight or fat content were attained. A photoperiod of 18L:6D did not affect age at VO relative to 6L:18D.