Reproduction, nutrition, developpement最新文献

Changes in the blood and the behaviour of 14 growing pigs from 4 different litters were evaluated under different experimental conditions of blood sampling, grouping and adrenal stimulation. The results showed that the different techniques of blood sampling influenced lactic dehydrogenase (LDH) and creatine kinase (CK) activities. Cortisol, proteins and CK levels were negatively correlated with social hierarchy after regrouping. Cortisol was also correlated with total activity levels. Adrenal stimulation by adrenocorticotropic hormone (ACTH) administration caused a sharp increase in plasma cortisol levels. However, plasma glucose, plasma proteins and total leukocyte counts were not affected by the ACTH treatment.

The skeletal muscle contains fibers with various contractile and metabolic properties. These populations of muscle fibers differ in their sensitivity and their response to circulating hormones which also affect the muscular differentiation (multiplication and fusion of myoblasts into myotubes). This review deals with the regulations of energy metabolism and of protein synthesis in muscles by several hormones acting either directly, or in association with other hormones, or by induction of growth factors. In most cases, hormonal effects seem to depend on the type and level of activity of the constitutive muscle fibers. The muscle fiber types involved in the anabolic properties of estrogens have not yet been clearly described. In the case of growth hormone and insulin, the slow fiber type is mainly affected; their effects are partially mediated through an increased secretion of somatomedins (IGFs) or by interaction on IGF receptors. The other reported hormones or factors induce a shift toward a more potent fast contracting activity, ultimately increasing the percentage of fast glycolytic fibers. Androgens, catecholamines and beta-agonists are anabolic and produce an enlargement of these fibers, whereas thyroid hormones or glucocorticoids in excess increase their catabolism.

The effect of Ca++ and Mg++ upon intestinal absorption of oleic acid was investigated using two in vitro models: rat isolated jejunal loops at 30 degrees C and 37 degrees C and mouse jejunal explants at 37 degrees C. At 30 degrees C or at 37 degrees C, Ca++ significantly increased 14C oleic acid uptake by rat isolated jejunal loops or mouse jejunal explants; at 37 degrees C, Ca++ significantly enhanced lipid exocytosis in rat intestinal loops but not in mouse jejunal explants; in both models, in the presence of Ca++ and at 37 degrees C, Mg++ significantly improved the esterification of oleic acid phospholipids and triacylglycerols, as shown by the increase in triacyglycerol synthesis in rat isolated intestinal loops or by the increase in triacylglycerols recovered from the incubation media of mouse jejunal explants; experiments carried out with rat isolated jejunal loops highlighted the determinant role of temperature in oleic acid absorption processes. The present work shows that the simultaneous presence of Ca++ and Mg++ did not impede oleic acid absorption processes but, on the contrary, enhanced them.

Localization of the somatotropic activity of growth hormones from several species and from different organs was attempted using different approaches. Sequences were compared in order to detect one or several regions with a common homology. The technique of peptide recombinants as well as chemical changes affecting some amino acids was applied to these hormones; the biological function in vivo of growth or binding to somatotropic receptors was then estimated. The few data available on biosynthetic molecules and secondary structures of natural growth hormones are reported. This study indicates the somatotropic function of particular sites.

Ovaries from decapitated, sham-operated and intact 18-day-old chick embryos were cultured in Medium 199 for 6 h, and the amount of 17 beta-estradiol released into the culture media was determined by radioimmunoassay. Ovaries from decapitated embryos secreted significantly lower amounts of 17 beta-estradiol than those from intact embryos, but there was no difference when they were compared to ovaries from sham-operated embryos in this respect. On an ovarian weight basis, 17 beta-oestradiol production was significantly different between the 3 groups of embryos, the ratio being highest in the decapitates. 17 beta-Estradiol concentration was the same in serum from both decapitated and intact female embryos. Considering these results, it is concluded that the hypophysis does not control 17 beta-estradiol secretion by the chick embryo ovary even near hatching time.

In 10 bulls, changes in blood plasma concentrations of insulin-like growth factor I (IGF1) were studied during rearing and during the ensuing growth period. IGF1 continuously increased from 32 micrograms/l at the age of 15 d to 194 micrograms/l at the age of 307 d together with body weight. However, IGF1 was not related to daily rate of gain, which remained fairly constant during the growth period. An age-dependent increase was also observed for blood levels of insulin, thyroxine and triiodothyronine. The data suggest that insulin and thyroid hormones may be causally related to the age-dependent increase in IGF1 levels.

In a first experiment, 2 groups of 46 and 47 multiparous ewes received diets which provided an iodine intake of 0.36 and 0.26 mg/kg dry matter (group C) and, 2.01 and 1.94 mg/kg (group D), respectively, for pregnancy and lactation. In a second experiment, 3 groups of 10 nulliparous ewes received diets which provided an I intake of 0.13 and 0.12 mg/kg dry matter (group A), 0.22 and 0.20 mg/kg dry matter (group B), and 10.77 and 8.88 mg/kg dry matter (group E), respectively, for pregnancy and lactation. Observations and sampling were carried out on the ewes from the first third of pregnancy to the 2nd and the 6th week of lactation. The diets provided adequate nutrition for pregnant and lactating ewes. Dietary I content had no effect on the dry matter intake, the size or the weight of the litter and the length of pregnancy. Plasma inorganic iodine (PII) was less affected by the I intake during lactation than during pregnancy. The excretion of I in milk induced a decrease in PII between pregnancy and lactation. The I in urine expressed as microgram I/g creatinine was largely affected by the intake. Colostrum I was 6.7, 4.0, 1.2, 1.3 and 1.5 times higher in groups A, B, C, D and E than the I in milk collected 1 week postpartum. Milk iodine (MI) content and the ratio MI/PII were markedly dependent on the I intake. During pregnancy, plasma T4 concentration decreased for each group. Plasma T4 concentration remained low during lactation in the low I intake group, whereas it increased at the same time in the other groups. The plasma T3 concentration decreased at the 6th week of lactation in the highest I intake group. Experimental values showed that 0.12 mg I/kg dry matter induced depletion in the I stocks of pregnant and lactating ewes, whereas an I intake above 10 mg I/mg dry matter disturbed the metabolism of thyroid hormones.

Nuclear magnetic resonance (NMR) was used to study the metabolism of the rumen bacterial ecosystem. The fermentation of 1-13C-glucose was investigated. This system showed a transient build-up and decay of lactate labelled at the C3 position. The degradation of lactate gave rise to volatile fatty acids. These results agree with in vivo data on diets rich in available carbohydrates.

Twenty first-liter sows were used to investigate the relationship between plasma lactose concentrations following weaning and milk production, total milk content of lactose, post-weaning plasma oestradiol-17beta (E2) concentration and weaning to mating interval. Milk production was estimated from 6 out of 8 hourly successive "weighing-suckling-weighing" of piglets on day 21 of a 28-day lactation. Sows were cannulated in the jugular vein and sampled at 8-h intervals from 2 h to 66 h after weaning. Plasma lactose concentrations (means +/- SE) after weaning increased from 52 +/- 4 microM at the beginning of sampling to a peak value of 183 +/- 23 microM 40 h later and then decreased to 91 +/- 11 microM 66 h after weaning (P less than 0.001). Milk production on day 21 (7.5 +/- 0.3 kg) and the corresponding milk content of lactose (400.5 +/- 0.2 g) were not related (P greater than 0.10) to area under the curve, timing, amplitude and spreading of the lactose peak in plasma. Similarly, none of the characteristics of the lactose peak were related (P greater than 0.10) to weaning to mating interval. There was a linear increase (P less than 0.0001) in mean plasma E2 concentrations (means +/- SE) from 5.6 +/- 0.3 pg/ml, 2 h after weaning, to 12.9 +/- 1.2 pg/ml at the end of the sampling period. On a within-sow basis, there was a correlation (r = 0.28; P less than 0.01) between post-weaning plasma lactose and E2 concentrations. Results showed the existence of the post-weaning peak of plasma lactose in sows.(ABSTRACT TRUNCATED AT 250 WORDS)

Five adult rabbits (New Zealand White x Californian) were fed ad libitum for 10 days a pelleted feed compound containing dehydrated lucerne whose particles (0.05-0.5 mm in size) were marked with a rare earth, i.e. ytterbium (Yb). In order to estimate the proportion of marker liable to leave its initial site of binding, we measured the amount of ytterbium present on faeces particles larger than 0.5 mm. The total amount of faeces was collected during the following 3 days. The faeces screening technique used in this study was adapted from that applied to feed. However, the repeatability was low for the large particles (greater than 1 mm), whose number was small. Half of the digesta particles (52%) exhibited a smaller size than 0.05 mm. The proportion of large particles (greater than 1 mm) in the faeces was low (1.5%) while that of the other particle classes ranged from 20-33.5%. After pelleting, more than 40% Yb initially bound to lucerne particles measuring 0.5 to 0.05 mm, was present on fine particles (less than 0.05 mm). Accordingly, only minima and maxima amounts of Yb having migrated on large particles (greater than 0.5 mm) could be measured, i.e. 2.5 and 8.9%, respectively of the ingested Yb. Taking also into account a migration towards small particles, about 10% Yb was liable to leave its initial site during its passage through the digestive tract of the rabbit.