Warren C. Foote

Translocations of acrocentric chromosomes and their implications in the evolution of sheep (Ovis).

Cytogenetic evidence suggests that the caprids (sheep and goats) evolved from a common ancestor with a 2n=60 karyotype. Although goats (Capra) retained the primitive 2n=60 karyotype, sheep (Ovis) underwent a sequential reduction in the number of chromosomes by means of acrocentric translocation. The formation of the first metacentric autosome (M1) occurred in the aoudad (Ammotragus) and urial (O. vignei), resulting in a 2n=58 karyotype. The G-bands are homologous, which implies both genotypes arose from a common ancestor, possibly a rupicaprid. Based on G-bands, acrocentric chromosomes 1 and 7 of the 2n=60 karyotype formed the M1. The X chromosome, which is the second longest acrocentric in the 2n=60 karyotype, became the longest acrocentric in Ammotragus and Ovis (2n=58). The second pair of metacentrics to evolve, which is ranked in the M3 position of the 2n=54 karotype, resulted from the translocations of acrocentric chromosomes 4 and 14 or 15 in the 2n=60 karyotype. The M2 was the third pair of metacentrics to be formed and resulted from the translocations of acrocentric chromosomes 3 and 12 or 13 in the 2n=60 karyotype. The G-bands of all 2n=54 karyotypes are homologous, which indicates origin from a common ancestor. Evidence is presented that suggests a prezygotic selection is bringing about a reduction in diploid chromosome numbers. The possible roles of fission and fusion in the karyotypic evolution of Ovis are discussed.

INTERSPECIES OVUM TRANSFER TO PROPAGATE WILD SHEEP

Ovarian responses to intramuscularly administered pregnant mare serum gonadotropin (PMSG) were measured in 23 mouflon ewes (Ovis musimon). Ovulation rates increased significantly with 1,000 i.u. PMSG or higher. PMSG at 1,200 i.u. also produced a significant increase in follicles !10 mm. Ova flushes showed recovery rates lower than for controls. Fertility rates were also lower, with zero fertility at 1,100 and 1,200 i.u. PMSG. Ten fertilized ova were transferred from mouflon to domestic sheep, re- sulting in 3 pregnancies, and 2 births. Pregnancies were established only with 16-32 cell ova and when estrous synchrony of donor and recipient was within 4 hours.

Comparison of three methods of pregnancy diagnosis in alpacas and llamas

Abstract This study was conducted at the La Raya Research Station of IVITA (15° South latitude and 71° West longitude, 4250 m elevation) with 50 alpacas and 20 llamas, 3 to 8 y of age and having at least one previous pregnancy. The alpacas were bred to fertile males for 20 min twice in the same day. The llamas were selected at random from a flock bred to fertile males for 32 d. Accuracy of the following three methods of pregnancy diagnosis were compared: ultrasound, palpation per rectum, and estrous behaviour using teaser males. The same animals were used to test all three methods. Using teaser males with alpacas 84 and 88% accurate diagnoses were obtained at 70 and 125 d of pregnancy, respectively. With llamas, 85 and 95% accuracy was obtained at 75 and 125 d of pregnancy, respectively. Using the ultrasound method, the accuracy of pregnancy diagnosis was 92 and 100% at 80 and 75 d of gestation in alpacas and llamas, respectively. This rate of accuracy fell to 60% as the stage of pregnancy advanced in both species. When palpation per rectum was performed, 100% of pregnancies were diagnosed accurately. In alpacas, palpation was statistically more accurate (P 0.05) were found among animal species in any one of the methods tested.

Circannual estrous variations and ovulation rate in Pelibuey ewes

Abstract Twelve cycling, mature ewes were kept with two vasectomized rams under constant nutrition maintenance conditions to study annual estrous activity and ovulation. Mean ovulation rate per month was 1.2 corpora lutea (CL) /ewe and 1.72 CL/ewe ovulating, mean proportion of ewes ovulating per month was 69%; proportions of ewes ovulating varied significantly ( P P P P 22 d), proportions for each class were 4, 70 and 26%, respectively. Results indicated that Pelibuey ewes exhibit estrous cycles regularly from May through December, and the frequency of estrous cycles declines significantly from February through April, due perhaps to factors such as temperature or humidity.

Preventing experimental vertical transmission of scrapie by embryo transfer

This study investigated whether the transmission of naturally occurring scrapie in sheep can be prevented using embryo transfer. Embryos were collected from 38 donor ewes in a Suffolk sheep flock with a high incidence of naturally occurring scrapie, treated with a sanitary procedure (embryo washing) recommended by the International Embryo Transfer Society and then transferred to 58 scrapie-free recipient ewes. Ninety-four offspring were produced. None of the offspring or the recipient ewes developed scrapie. Furthermore, offspring derived from embryos collected from donor ewes bred to the immunohistochemically positive ram did not develop scrapie. We conclude that scrapie was not transmitted to offspring via the embryo nor was the infective agent transmitted to recipient ewes during embryo transfer procedures.

Polymorphic distribution of the ovine prion protein (PrP) gene in scrapie-infected sheep flocks in which embryo transfer was used to circumvent the transmissions of scrapie.

The genetic sequence of the ovine prion protein (PrP) gene between codons 102 and 175 with emphasis on ovine PrP gene codons 136 and 171 was determined, and the polymorphic distribution of the ovine PrP gene in the scrapie-exposed Suffolk embryo donors and offspring from these donors that were transferred to scrapie-free recipient ewes was investigated in this study. The most common genotype was AA(136)QQ(171) (70% and 63% in the donor and offspring flocks, respectively), which is considered a high risk genotype in US Suffolk sheep. Although embryos were collected from scrapie-positive donors and many embryos had the high risk genotype, no scrapie occurred in the resulting offspring. Based upon the results of this study, we conclude that vertical transmission of scrapie can be circumvented using embryo transfer procedures even when the offspring have the high risk genotype.

Contemporary comparisons between progeny by Finnish Landrace and Romanov rams out of Mutton Merino and Awassi ewes

Results based on contemporary comparisons of F1 progeny by Finnish Landrace and Romanov rams out of Mutton Merino and Awassi ewes are given. Within the four genotypes thus produced, the F1 females were mated to F1 males to produce F2 progeny. Mutton Merino crosses were carried through the first lambing and the Awassi crosses through two lambings. All animals were housed and lambs reared on ad lib. concentrates and hay. There were no significant differences between sire breeds in the performance of their F1 progeny except for wool traits. Awassi crossbred females at 1 year old exceeded the Mutton Merino crosses in proportion lambing (74 vs 65%); lambs born per ewe mated (1.15 vs 0.95); birth weight (5.1 kg vs 4.2) and 150-day weight (46 kg vs 43). Lamb mortality up to 150 days was similar at around 24%. For the Awassi crossbreds at the second lambing the F2 progeny with finn blood were heavier at birth and grew faster to weaning than those with Romanov blood (4.1 kg and 233 g/day vs 3.6 kg and 198 g/day). Romanov rams either introduced or greatly increased the incidence of pigmented and kemp-like fibres in the wool of their progeny; in the cross with Mutton Merinos they also adversely affected breed type, character and handle.

Evolutionary implications of haemoglobin polymorphism in domesticated and wild sheep

Abstract The distribution of haemoglobin polymorphism was investigated in 11 breeds of domesticated and three genetic groups of wild sheep in the USA. HbβB was more frequent than HbβA in most of the domesticated breeds with a pooled frequency of 0.71. The HbβB gene frequencies were: 0.95 (Barbados), 0.45 (Booroola), 0.77 (Columbia), 0.40 (Finnsheep), 0.87 (Hampshire), 0.88 (Karakul), 0.98 (Rambouillet flock 1), 0.93 (Rambouillet flock 2), 0.12 (Romanov), 0.50 (St. Croix flock 1), 0.63 (St. Croix flock 2), 1.00 (Suffolk flock 1), 0.86 (Suffolk flock 2) and 0.86 (Targhee). All the wild sheep tested [Argali × European Mouflon cross (Ovis ammon × Ovis musimon), Asiatic Mouflon × European Mouflon cross (Ovis orientalis × Ovis musimon) and Desert Bighorn (Ovis canadensis)] were monomorphic for HbβB. The monomorphism of HbβB of wild sheep and the higher frequency of HbβB than HbβA in domesticated sheep indicates that HbβA probably occurred after sheep were domesticated. The wide variation in haemoglobin polymorphism within and between breeds may have resulted from a combination of genetic drift and selection.

Protein polymorphism in sheep pedigree testing.

Four polymorphic proteins (transferrin, serum arylesterase, hemoglobin and a red-blood-cell lysate protein) were used as genetic markers in a sheep parentage test. It was found that errors in parentage records occurred in a minimum (9.2%) of the progeny. The efficacy of protein genetic markers in solving questionable parentage cases was estimated to be 67.2%. Among all cases, 58.3% were solved on the basis of genetic incompatibility involving transferrin alone. The results of this study demonstrate that the occurrence of errors in pedigrees can be identified by the use of protein polymorphic characters as genetic markers.

Seasonal variations in circulating testosterone and luteinizing hormone in Pelibuey lambs

Abstract This study was carried out to determine seasonal variations in circulating testosterone and luteinizing hormone levels in ram and castrate male Pelibuey lambs. Body weights at the end of the study were 36.9 ± 1.2 kg for the intact and 38.8 ± 1.6 kg for the castrate lambs. Ram lambs showed greater (P