Structural rearrangements of chromosomes in the domestic chicken: experimental production by X-irradiation of spermatozoa

Cryopreservation of poultry sperm: the enigma of glycerol

This review summarizes recent data for cryopreservation of poultry sperm and data establishing the contraceptive effect of glycerol. Successful cryopreservation protocols for bovine sperm are compared to the requirements for rooster sperm, with emphasis on glycerol-induced alterations in avian reproductive systems. It has been shown that molar concentrations of glycerol can affect (a) physical features of the cytoplasm (cytoplasmic organization and viscosity), (b) permeability and stability of the membrane bilayer(s), and (c) noncovalent attachment of proteins to the sperm surface. Perturbing effects of glycerol on sperm metabolism and the essentiality of maintaining bioenergetic balance during the temperature changes associated with any cryopreservation protocol are discussed. Emphasis is placed on the processes in avian reproduction that may be altered by interactions with glycerol. Finally, we discuss the potential value of using available genetic models (lines of roosters differing in the capacity of their sperm to survive a freeze-thaw cycle) to clarify and overcome damage to poultry sperm induced by cryopreservation.

Effect of the MN t(1;4) translocation on some economic traits of the chicken

The F2 progeny from an original mating between chickens that were carriers of the MN t(1;4) chromosome translocation and the inbred WI-ES line were compared to determine if the translocation had any effect on selected economic traits. Homozygous translocation (TT), heterozygous translocation (TN), and karyotypically normal (NN) individuals were compared. Traits analyzed were body weight at 8, 18, 39, and 55 wk of age; shell deformation; Haugh units; egg weights at 32 and 55 wk of age; sexual maturity; egg production; and male fecundity. The TT group had greater body weights at 39 and 55 wk than the TN and NN groups, and at 55 wk the TN group was heavier than NN group. Shell deformation was greater for TT birds at 32 wk. At 32 wk, Haugh units of the TT and TN birds, and the TN and NN birds were not significantly different. The TT eggs were heavier than the TN eggs at 32 wk, which in turn were heavier than the NN eggs. Sexual maturity was reached in the order NN, TN, then TT. Eggs from TT males had the lowest fertility and highest percentage of late dead embryos. There were increased early deaths among embryos from heterozygous males. An unexplained higher number of pips among embryos from normal males was noted. No differences were noted among any other traits in either sex. Results suggest that this translocation may have some effect on production traits.

Cryopreservation of semen from unique lines of chicken germ plasm

Frozen semen is a practical means of preserving valuable germ plasm. Monitored samples of semen cryopreserved with glycerol for heterozygous, dominant marker stocks and for nine chromosomal rearrangement lines had sufficiently high fertility for germ-line retrieval. The results also indicated a potential for the genetic selection of certain lines for the freezability of spermatozoa, since stock and line differences in fertility occurred when previously frozen semen was used for insemination. Freezing the semen of stocks routinely reproduced provides insurance against possible disasters.

Studies of the pirouette mutation. 1. Lack of linkage association with marked regions of chromosomes 1 and 2

The pirouette mutation was tested for possible genetic linkage with naked neck, tardy feathering, the MN t(Z;1) chromosome rearrangement, all assigned to distinctly different regions of Chromosome 1, and the OH inv(2) chromosome rearrangement and shankless (associated with the OH inv(2) rearrangement). No linkage associations were found in any of these tests. This eliminates specific regions of Chromosomes 1 and 2 as possible locations for the pirouette mutation.

Gonosome-autosome translocations in fowl: the development of chromosomally unbalanced embryos sired by singly and doubly heterozygous cockerels

Cockerels singly or doubly heterozygous (t1/ +, t2/ + and tl/t2, respectively; collectively heterokaryotypic, HTK) for two different Z-autosome translocations (t1, t2) produce an array of chromosomally balanced and unbalanced spermatozoa owing to adjacent segregation and nondisjunction at the first meiotic division. This study addresses the developmental capacity of embryos derived from matings of control ( + / + ) and HTK (tl/ +, t2/ +, tl/t2) cockerels with hens bearing normal chromosome complements (+ /W).

Estimates of the hatchability of fertile eggs sired by + / +, tl/ +, t2/ + and tl/t2 cockerels were 82·8%, 43·0%, 41·3% and 10·9%, respectively. Approximately 75% of the mortality observed in embryos sired by HTK cockerels occurred by four days of incubation. Developmental arrest generally occurred earlier in embryos sired by t2/+ and tl/t2 cockerels than in those by tl/ + cockerels. These differences reflect variation in the degree of embryonic chromosome unbalance expected among embryos of the different sire groups. The pattern of mortality after three days was similar in embryos sired by HTK cockerels. In control embryos, mortality was highest on days 20–21 of incubation.

Chromosome analysis of 16/18 h embryos, day 1/5 embryos and hatched chicks sired by HTK cockerels revealed that most, if not all, chromosomally unbalanced embryos died during development; the majority before three days of incubation. Partial monosomy for chromosome one was found to be more deleterious to embryonic development than partial trisomy.

Gonosome-autosome translocations in fowl: meiotic configurations and chiasma counts from singly and doubly heterozygous cockerels

Many X-ray or chemical mutagen-induced chromosome translocations in domestic fowl (Gallus domesticus) are thought to involve microchromosomes as centromere donors to acentric macrochromosomal fragments. In order to study the involvement of microchromosomes in such translocations, and to investigate the possibility that such translocations are reciprocal, meiotic chromosomes from cockerels singly or doubly heterozygous for two different Z-autosome translocations were analyzed. Ring multivalents were observed in 74.94% of cells from cockerels bearing the different translocations, and the presence of microchromosomes in certain multivalents was apparent after C-banding. The results indicate that both Z-autosome translocations involve reciprocal exchange and that a microchromosome is indeed involved in one translocation. Chain multivalents at frequencies of 6% to 26% do not inferfere with spermatogenesis in domestic fowl.