Influence of exogenous melatonin and altered day length on reproductive performance of Polypay ewes

Two experiments were designed to evaluate postlight treatment use of melatonin as a method of overcoming photorefractory response by measuring the lambing percentage of early-postpartum Polypay ewes bred either late in the breeding season or during anestrus. In Trial 1, pregnant ewes (n = 140) were assigned to one of three groups: 1) ambient photoperiod (control), 2) extended light (20 h) from October 21 to December 27, and 3) extended light as in Group 2, followed by supplemental feeding of 10 mg melatonin/head (hd) daily until April 6. Breeding started on February 3 and ended April 9. A greater percentage of ewes given extended light plus melatonin (54%) and extended light alone (45%) lambed than controls (24%) (P = 0.06). In Trial 2, pregnant ewes (n = 158) were assigned to groups as in Trial 1, except extended light was given to Groups 2 and 3 from January 1 to March 11, and Group 3 ewes were supplemented with 10 mg melatonin daily from March 12 to June 10. Breeding started April 18 and ended June 10. Lambing percentage was increased (P < 0.01) by extended light plus melatonin (54%) compared to controls (6%) or ewes given only extended light (10%). The shift from artificially extended light to the shorter ambient light with or without melatonin enhanced the lambing percentage of early postpartum ewes on an accelerated lambing program during breeding late in the season. However, only the more pronounced shift from long days to short days, accomplished with extended light plus melatonin, was effective in inducing out-of-season breeding in Polypay ewes.     

Electroejaculation of the coyote

Two electroejaculators were used to collect semen from 40 adult male coyotes. The most effective apparatus used a two-ring rectal probe and an AC voltage of 18 (Vrms) at 1000 Hz. With this ejaculator, 11 of 15 coyotes produced a satisfactory semen sample, which averaged 0.9 ml in volume and 70 million spermatozoa per ml.     

Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

Analysis of plastid DNA-like sequences within the nuclear genomes of higher plants

A wide-ranging examination of plastid (pt)DNA sequence homologies within higher plant nuclear genomes (promiscuous DNA) was undertaken. Digestion with methylation-sensitive restriction enzymes and Southern analysis was used to distinguish plastid and nuclear DNA in order to assess the extent of variability of promiscuous sequences within and between plant species. Some species, such as Gossypium hirsutum (cotton), Nicotiana tabacum (tobacco), and Chenopodium quinoa, showed homogenity of these sequences, while intraspecific sequence variation was observed among different cultivars of Pisum sativum (pea), Hordeum vulgare (barley), and Triticum aestivum (wheat). Hypervariability of plastid sequence homologies was identified in the nuclear genomes of Spinacea oleracea (spinach) and Beta vulgaris (beet), in which individual plants were shown to possess a unique spectrum of nuclear sequences with ptDNA homology. This hypervariability apparently extended to somatic variation in B. vulgaris. No sequences with ptDNA homology were identified by this method in the nuclear genome of Arabidopsis thaliana.      

Use of naloxone challenge to predict sexual performance of rams before the fall breeding season

Serving capacity tests (SCT) identify rams as sexually active, sexually inactive, or low sexual performers. Labor and time requirements make SCT impractical and expensive. Therefore, a hormone-based test for libido was developed using the responses of LH and testosterone (T) after naloxone. This test effectively identified sexually active and inactive rams during the breeding season (November and December). The current study evaluated the effectiveness of this method at a different time of the year. Objectives were to determine if the blood test can detect differences in libido during late July and August, and to characterize LH and T profiles up to 120 min postnaloxone treatments at this time of year. Two experiments were conducted using i.v. naloxone at 0.75 mg/kg BW. Sexually active (SA) and sexually inactive (SIA) rams were identified using SCT. In Experiment 1, 16 SA and 18 SIA rams of several breeds were identified based on SCT conducted before naloxone tests. In Experiment 2, 72 Suffolk x white face rams were given SCT after naloxone tests and were of unknown sexual activity at the time of the naloxone tests. Mixed model analyses for repeated measures with repeated factors (month and sample time) and a covariate for mean LH or T before naloxone treatment were used for LH and T data. Proc Logistics modeled probabilities that rams were sexually active. The LH response to naloxone increased but did not differ (P > 0.09) by ram class (SA or SIA) or month. The T response peaked 75-90 min after naloxone treatment and was still elevated at 120 min. Testosterone differed (P < 0.03) for ram class by month by time in Experiment I and differed (P < 0.01) between months in Experiment 2. Proc Logistics incorrectly indicated that SA and SIA rams were all sexually active. This study indicates that the naloxone challenge test cannot discriminate between SA and SIA rams during July and August. Further research is required to determine the time of year when this sire identification test for libido has significant accuracy.     

Late immature mortality is the major influence on reproductive success of African black beetle, Heteronychus arator (Fabricius) (Coleoptera: Scarabaeidae), in a Mediterranean-climate region of Australia

In field and laboratory studies, mortality of African black beetle, Heteronychus arator, in the winter-rainfall, Mediterranean-type climate region of south-western Australia was higher in the late immature stages during summer than in the early immature stages that occur during spring, a contrast to summer-rainfall climatic regions. Greatest mortality occurred around the pupal stage in contrasting soil types, despite drying differences in summer and supplementary watering in some plots. Sampling of natural populations confirmed experimental results that mortality in late immature stages is the major factor limiting H. arator populations under a Mediterranean-type climate. Inter-generation increase in H. arator abundance was uncommon, explaining the consistent abundance typically observed between years in south-western Australia. Random dispersal of newly emerged adults in autumn was inferred to restore uniformity in adult abundance between areas of varying favourability for immature survival.     

Antitesticular activity of DL-6-(N-2-Pipecolinomethyl)-5-Hydroxy-Indane maleate (PMHI) in coyotes (canis latrans)

The ban on toxicants for coyote control has created a need for alternative control methods. Reproductive inhibitors may provide a means of maintaining coyote populations at levels where impact on live-stock is acceptable. Therefore, the effects of PMHI on testicular activity of coyotes were evaluated. Twelve mature, male coyotes were weighed and allotted randomly to 1 of 4 treatment groups: (1) controls, (2) 5, (3) 10, and (4) 20 mg PMHI/kg body weight (BW). PMHI was dissolved in 2 ml distilled water and ethanol (1:1) and administered as a single sc injection. All coyotes were observed for 1 hr after treatment and any adverse effects recorded. Fifteen days after treatment, a testicle and epididymis from each coyote was selected at random, ablated, weighed, fixed in formalin, and prepared for histologic examination. The remaining testicle was prepared similarly 30 days post-treatment. Data were analyzed by a balanced factorial in a split-plot arrangement. Unlike controls, coyotes given PMHI exhibited signs of nausea and diarrhea within 15 to 30 min, which subsided after 45 to 60 min. PMHI temporarily increased (P<.01) serum glutamic-pyruvate transaminase (SGPT) but did not alter other blood chemistry or hematologic values. PMHI reduced (P<.01) testicular weights (wet weights) from 10±1.0 g (controls) to 6.3±0.2 g after 5 mg, 4.4±0.2 g after 10 mg, and 6.0±0.5 g after 20 mg/kg BW. Testicular weights were not different among the 3 treatments of PMHI. Histological changes in seminiferous tubules were consistent with absence of spermatogenesis at 15 and 30 days after all treatment levels of PMHI. Only occasional intact spermatozoa were present in sections of epididymis at 15 and 30 days after PMHI treatment. We conclude that PMHI may cause infertility in the male coyote from 15 to at least 82 days after treatment without apparent chronic damage to vital organs.     

Effect of early and late exposure to estrual ewes on ram sexual performance classifications

This study was conducted to determine whether exposure of ram lambs to estrual ewes during their first autumn and again as adults just before serving capacity tests (SCT) affected the outcome of the sexual performance tests. Treatments were either early exposure of Polypay ram lambs (i.e., 7-8-mo-old rams with ewes for 17 d [n=30] or no early exposure [n=30]), and late exposure (i.e., 16-19-mo-old rams with estrual ewes for 3 d) or no exposure to estrual ewes in a 2x2 factorial arrangement. Three serving capacity tests were conducted immediately after the early exposure period for individual ram lambs that were exposed to ewes early. Three sham sexual performance tests (i.e., four ram lambs placed in test pens for 30-min without ewes) were conducted with ram lambs that were not exposed to ewes early. All rams were evaluated during nine 30-min serving capacity tests over a 2-mo period at 16-19 mo of age to determine sexual performance. Prior to serving capacity tests, one half of the rams from each early exposure treatment were exposed to estrual-induced ewes for 3 d. Specific sexual behaviors (e.g., sniffs, flehmens, foreleg kicks, vocalizations, mount attempts, mounts, and ejaculations) were recorded during serving capacity tests. Number of sniffs, flehmens, foreleg kicks, vocalizations, and mount attempts were summed without estimating the value of importance and analyzed as courtship behaviors. Sexual performance data were analyzed with Mixed model procedures for repeated measures. During serving capacity tests, the early exposed rams exhibited more courtships (40.3+/-8.0 versus 23.4+/-4.6; P<0.05; LSM+/-estimated SE), mounts (11.3+/-1.0 versus 7.7+/-0.9; P<0.01), and ejaculations (3.3+/-0.2 or 2.4+/-0.2; P<0.01) than rams not exposed to ewes as ram lambs, respectively. We conclude that early exposure of 7-8-mo-old ram lambs to estrual ewes improves sexual performance in serving capacity tests at 16-19 mo of age in most rams whereas, late exposure to estrual ewes for 3 d prior to serving capacity tests did not improve sexual performance scores.     

Luteolysis, estrus and ovulation, and blood prostaglandin F after intramuscular administration of 15, 30 or 60 mg prostaglandin F2α

During diestrus in three consecutive estrous cycles, each of six heifers was given (im) 30 mg, 15 mg (twice at 6-hr intervals) and 60 mg prostaglandin F_2α (PGF_2α) tham salt. Neither the decline in blood progesterone, the increase in blood estradiol, the duration or the peak of the LH surge, the interval to onset of estrus, nor the interval to ovulation was affected significantly by dose of PGF_2α. Thus, relative to that after 30 mg PGF_2α im, two injections of 15 mg at 6-hr intervals or 60 mg PGF_2α did not hasten luteolysis. Thirty mg was an ample im dose of PGF_2α to cause luteolysis. Regardless of im dose of PGF_2α, blood PGF peaked at about 6.0 ng/ml within 10 minutes and returned to basal values (<1.0 ng/ml) within 90 minutes. In another trial, after a single iv injection of 5 mg PGF_2α, blood PGF peaked (25 ng/ml) within 5 minutes and returned to basal values within 15 minutes. During a 30-minute infusion (0.5 mg/minute) of PGF_2α, blood PGF plateaued at 29.5 ng/ml with a metabolic clearance rate of 17.0 liters per minute.