Hervé Michels

Incubation temperature as a management tool: a review

Temperature as one of the most important single physical factors determining or influencing embryo development and hatchability is reviewed and possible temperature manipulations are discussed as a...

Energy and protein metabolism between 3 and 6 weeks of age of male broiler chickens selected for growth rate or for improved food efficiency.

1. A new open-circuit respiration unit consisting of 6 respiration chambers, gas analysis unit and data-acquisition system is briefly described. 2. Energy and protein metabolism in broiler lines selected for improved food efficiency (FC) or for growth rate (GL) were measured weekly from 3 to 6 weeks of age. 3. Gross and apparent metabolisable energy intake per kg W0.75 was on average higher for GL than for FC chickens without differences in metabolisability. Fed and fasted heat production per kg W0.75 did not differ between the lines. FC chickens retained less energy per kg W0.75 than GL chickens. 4. FC chickens deposited much less of the retained energy as fat than their GL counterparts and also showed greater protein conversion efficiency. The leaner composition of the body weight gain in FC chickens was confirmed by the estimated lower fat deposition per kg W0.75 and by the lower fat: protein ratio.

Differences in serum iodohormone concentration between chick embryos with and without the bill in the air chamber at different incubation temperatures.

Serum levels of triiodothyronine (T3) and thyroxine (T4) were measured, by RIA, in developing chick embryos of the Rhode Island Red strain incubated at different temperatures in a forced-draught laboratory incubator. A low incubation temperature resulted in a longer incubation period, whereas eggs incubated at a higher temperature hatched sooner. In all temperature groups serum levels of T3 and T4 increased during the incubation period studied. Whatever the total duration of incubation within the experimental conditions, maximal T3 and T4 serum levels were always obtained on the day of “pipping”. Embryos having perforated the air space membrane the day before pipping showed elevated serum levels of T3, but not of T4, compared with embryos that had not perforated the air space. The presence of high levels of T3 in serum, in chick embryos after perforation of the air space membrane, and the sharp increase in ratio before the event of “pipping”, appear to suggest that T3 has an important role in the processes of “pipping” and hatching.

Litter size, ovulation rate and prenatal survival in relation to ewe body weight: genetics review.

Lambs birth weight and litter weight were found to be related to ewe weight. Deviations from generally applicable formulae indicated an interaction between the genotype of the lamb and the maternal environment, as suggested in egg transfer experiments. Lands (1977) hypothesis on the spare conceptus capacity, when comparing large and small breeds within a species, with respect to prolificacy, was more applicable to genetically homogeneous groups within a breed than between breeds and lines within a breed. A hypothesis suggests that variation in the within breed genetic correlation between ewe weight and prolificacy may largely depend on the relative uniformity of selection criteria applied. It can further be argued whether selection based on body weight or growth rate, compared to selection on reproductive performance, could be important sources of within breed as well as among breed variations in the genetic correlation estimates between ewe weight and prolificacy. The dynamics of the genetic correlation between ewe weight and prolificacy has an effect of long-term selection for body weight, growth rate and reproduction traits. This leads to the problem of the relative incompatibility of selection of an association between body proportions with reproductive traits, especially in meat type breeds. There is a parallellism or antagonism in the genetic correlations between ewe weight and prolificacy as compared to those between ewe weight and other reproduction traits. The within breed relationship between ewe weight and ovulation rate was found to be positive in some breeds. The effects of body condition at mating were contradictory. Genotypexenvironment interactions were observed in certain cases. Among most breeds, differences in ewe weight were unrelated to differences in ovulation rate. There were no relationships between ewe weight and prenatal survival within breeds or in lines within a breed. However, there exists a differential relationship between ovulation rates and prenatal survival rates in relation to ewe weight, depending on the selection criteria applied. A clearcut relationship between litter weight components and ewe weight cannot be generalized but may vary among differentially selected breeds and lines within them. This is a final, unifying and unresolved question.

The presence of vasotocin and mesotocin in serum and the hypothalamo-neurohypophyseal axis of chick embryos before hatching and in posthatch chicks.

Decreasing hematocrit values were observed in chick embryos, from Day 17 to 1 day posthatching. Arginine vasotocin (AVT) and mesotocin (MT) were determined radioimmunologically in serum, neural lobe, and hypothalamic tissue. Serum levels of AVT and MT were significantly increased on Day 18 of incubation compared to Day 17. Thereafter AVT levels decreased, reaching at hatching levels even below Day 17. Serum MT remained elevated on Day 19, but decreased thereafter to the concentration values of Day 17. The amount of AVT in the preoptic hypothalamus and infundibulum was maximal on Day 19, whereas in the neural lobe the maximum was attained on Day 20. The MT content of the infundibulum and neural lobe reached a maximum plateau on Day 18. These results suggest that a stimulation of the hypothalamo-neurohypophyseal axis in the chick embryo occurs at the end of incubation. A possible causal relation with the observed decreasing hematocrit values is discussed.

THERMOREGULATORY RESPONSE AND THYROID HORMONE CONCENTRATION AFTER COLD EXPOSURE OF YOUNG CHICKS TREATED WITH IOPANOIC ACID OR SALINE

Publisher Summary This chapter discusses thermoregulatory response and thyroid hormone concentration after cold exposure of young chicks treated with iopanoic acid (IOP) or saline. Some evidence has been obtained that the thyroid gland has a role in thermoregulatory mechanisms in chickens. There is a larger amount of evidence about the role of thyroid hormones in thermoregulation in different mammals. The injection of IOP at a dose of 5 mg/100 g of body weight in young chickens did decrease the serum T 3 -concentrations, whereas serum T 4 concentration rose. The lag observed between T 4 and T 3 peaks after TRH injection suggests that in the domestic fowl, T 3 partly derived from T 4 by peripheral deiodination. An opposite effect on serum rT 3 was observed in mammals after the administration of radiographic contrast agents such as IOP. In the experiment, no rT 3 was found in the serum of young chickens even after IOP-treatment, but only after the combined effect of IOP and cold, and the amounts were nevertheless very small and reached only 5 % of T 3 levels in serum.

Light-dark variations of oxygen consumption and subcutaneous temperature in young Gallus domesticus: influence of ambient temperature and depilation

Abstract 1. 1.|With lower ambient temperatures (Ta): (a) subcutaneous temperature (Tsc) was subject to large individual variations and to a higher variation of instability between depilated chicks; and (b) depilated chicks compared to controls, showed a larger increase in O2 consumption; during darkness their increase in Tsc was lower, but during light hours to fall in Tsc was the same. 2. 2.|Lower light-dark variation of Tsc and O2consumption at lower Ta in young chicks can be put in parallel with lower circadian variations at higher Tas, as found in adult animals.

Early prenatal survival in relation to the parental environment in sheep: A review

Abstract After multiple egg transfer litter size (LS) in recipient ewes from some breeds was greater than their potential natural size; Finnish Landrace, not Booroola Merino recipients, tended to be superior to recipient ewes from other breeds with a lower natural ovulation rate (OR). In Finnish Landrace and Merino ewes the difference in prenatal survival (PS) between purebred and crossbred litters was small. In Berrichone and Romanov breeds PS was higher in crossbred than in purebred ewes. A significant variation in PS was found between eggs from Finnish Landrace donors. A dam–embryo interaction on PS was present in high and low twinning Merino ewes. Embryos from Romney ewes selected against lamb faecal egg count (LFEC) were more likely to survive than embryos from Romney ewes selected for LFEC. Various translocation types in heterozygous and homozygous combinations in rams and ewes did not influence their overall fertility, probably because of prezygotic selection of gametes. Scrotal heating in Merino rams caused an increased loss of fetuses. Fetal survival in Merino ewes increased as both the number of spermatozoa and feeding level were higher. Lower service activity was linked to lower pregnancy rates (PR) and PS in 1.5-year-old Merino ewes, interacting with the mean duration of oestrus as compared to that in adult Merino ewes. Service activity per ewe, PR and PS in Merino flocks were lower as ram: ewe ratio decreased from 1.0 to 0.5 and 0.25%. In Merino flocks selected for skin folds the percentage of twin births per ewe lambing was lower in hot weather than in Merino flocks selected against skin folds. PR and PS tended to be higher in ewes exposed to Rambouillet rams selected for high prolificacy, compared to Rambouillet rams selected for low prolificacy. PR and PS were lower in Clun Forest ewe lambs than in Clun Forest ewes. Survival of ova from Galway and Romney ewes was greater than that of ewe lamb ova. Conditions in the uteri of both ages were equally favourable. In Galway ewe lambs plasma estrogen concentration 12–36 h after sponge removal was more than 100% greater than in adults. Progesterone levels were similar, also on day 12 of pregnancy. After day 13 progesterone concentration increased at a slower rate and remained lower on day 28 in Clun Forest ewe lambs than in Clun Forest adults. The smaller and more variable preovulatory LH surge in Clun Forest ewe lambs was considered to be evidence of inadequate progesterone priming. These and other data support the suggestion that conditions in the developing follicle and in the reproductive tract between ovulation and the 8–16 cell stage are related to the reduced fertility and PS in very young ewes. It is concluded that endogenous, paragenous and exogenous factors can have similar and interacting effects on PS in sheep.

Prenatal survival in relation to peri-ovulatory phenomena and the site of ovulation in sheep: A review

Abstract Differences in ovarian follicular dynamics between ewe breeds and between lines within breeds were shown to result from a different follicle recruitment and selection process. Synchrony and asynchrony of embryos were shown to depend largely on luteinizing hormone (LH), progesterone and oestrogen levels in ewes before, during and post-mating. GnRH therapy suggested that the endocrine environment prior to ovulation has a fundamental influence on luteal function and hence on prenatal survival (PS). The decreasing effect of multiple ovulation on uterine efficiency was higher in androstenedione-immune Border Leicester×Merino (BL×M) than in immunized BL×Booroola Merino (BM) ewes. Exogenous progesterone increased lambing rate in Polypay (P) but not in Targhee ewes. The 200% of maintenance feeding level reduced plasma progesterone concentrations on day 12 near the threshold critical for embryo survival in M ewes but not in BL×Scottish Blackface ewes. The latter maintained pregnancy rate (PR) and PS at the same levels as the controls. In unilaterally twin ovulating ewes, foetal mortality was significantly lower in ewes in which distributive embryo migration occurred. Within this ovarian class, survival was lower in the Cheviot, probably because of a lower migration frequency, than in the Blackface breed. More embryos migrated in unilaterally twin ovulating M ewes in autumn than in summer mating, with a higher incidence of loss of one embryo in the latter season. A higher incidence of successful migration was observed in unilaterally twin ovulating BL×M than in M ewes. The higher mortality of a migrating embryo, compared with the nonmigrating, was attributed to an asynchronous environment in the contralateral horn, since ovine trophoblastine (oTP-1) might have preferentially altered the uterine environment of the ipsilateral horn. Studies on oTP-1 and protein in uterine flushings and on conceptus development at day 13 in ewes that displayed short or long oestrous cycles, as well as further studies on unilaterally ovariectomized ewes with two or three conceptuses, suggest that the ovine embryo stimulates the migratory process locally, in interaction with the dam. This review raises the question whether and to what degree pre-, peri-, as well as, post-ovulatory phenomena and the site of ovulation can be interacting factors for determining PS, especially in multiple ovulating sheep as a function of breed and breed–environment interactions.

Gene-specific pituitary gland responsiveness of ovariectomized FecB or FecC carrier and non-carrier ewe crosses with German Mutton Merino, Texel and Suffolk breeds to LHRH before and after oestradiol or progesterone treatments

Abstract These studies were undertaken to establish whether there are gene-specific differences in FSH and LH concentrations in the plasma of ovariectomized ewes that are crosses between local breeds (German Mutton Merino, Texel or Suffolk) and carriers and non-carriers of Booroola (FecB) or Cambridge (FecC) genes for prolificacy. The relationships of FSH or LH levels to ovulation rates, predetermined over two oestrus cycles before ovariectomy, were also determined. Ewes that were carriers (F + ) or non-carriers (F ++ ) of Booroola or Cambridge genes included in the studies were: Booroola × German Merino (BM), Booroola × Texel (BT), Cambridge × Cambridge (CC), Cambridge × Suffolk (CS) and Cambridge × Texel (CT). Ovulation rates were significantly higher in the F + genotypes than in the F ++ genotypes. Basal and LHRH-induced FSH and LH secretion in ovariectomized ewes were measured in plasma of blood collected by venipuncture. The effects of oestradiol-17β (E2) or progesterone (P4) implants for 8 days, acting as ovarian feedback hormone, on basal FSH and LH secretion and on pituitary responsiveness to LHRH were also determined. Basal and peak levels of FSH, LH and % responsiveness to LHRH were compared between fecundity genotypes within breeds and between breeds. Basal concentrations of FSH or LH were similar in genotypes within breeds. Both genotypes showed similar responsiveness to LHRH by a significant increase in both FSH and LH secretion. E2 treatment significantly depressed basal FSH and LH secretion; the effect being similar in genotypes within breeds. However, E2 significantly increased pituitary responsiveness to LHRH. P4 only marginally increased basal and LHRH-induced FSH secretion but had no effect on basal LH levels. It significantly increased LHRH-induced LH secretion in FecB but not in FecC ewes. The effect was similar in both genotypes within breeds. No relationships could be established between the concentrations of FSH or LH at basal or peak levels and ovulation rates of the genotypes. BT ewes (F + and F ++ ) had lower FSH levels than the BM (F + and F ++ ) as a result of greater sensitivity to E2 and lower responsiveness to LHRH. Consequently, the BT tended to have a lower ovulation rate than the BM. The Cambridge breeds (within genotypes) showed no differences in the levels of basal or LHRH-induced FSH or LH secretion and sensitivities to E2 or P4 were not significantly different. Their ovulation rates were not different either. In conclusion, although both FSH and LH play important roles in follicular development and ovulation, it seems unlikely that the pituitary is a major site for the effects of the FecB and FecC fecundity genes in regulating ovulation rates in heterozygous carriers and in homozygous non-carriers taken from sheep crosses, since there were no gene-specific differences in FSH or LH between fecundity genotypes.