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PubMed1991

Effects of breed, heterosis, age of dam, litter size, and birth weight on lamb mortality.

Sources of individual plus maternal effects on lamb mortality were studied in data collected at the U.S. Meat Animal Research Center from 1980 to 1985 for paternal and maternal breeds lambing yearly and for maternal breeds lambing at 8-mo intervals. Records included 16,881 lambs born. Breeds included were Finnsheep (F), Dorset (D), Rambouillet (R), Suffolk (S), Targhee (T), Composite 1 (C1 = F/2, D/4, R/4), Composite 2 (C2 = F/2, S/4, T/4), and Composite 3 (C3 = Columbia/2, S/4, Hampshire/4), Traits analyzed were perinatal, postnatal, and total mortality to 60 d of age and postnatal respiratory, digestive, starvation, injury, and other or unknown causes of mortality. The least squares analyses included breed, year, sire within breed-year, sex, linear and quadratic season and age of dam covariates (Model 1), plus litter size (Model 2), plus birth weight (Model 3), and significant two-way interactions. Age of dam, litter size, and birth weight all had important, often quadratic, effects that differed among breeds. Models 1, 2, and 3, respectively, reduced variation by 8, 10, and 16% for perinatal, 7, 8, and 12% for postnatal, and 9, 11, and 20% for total mortality. In Model 1, breed means ranged from 3.5 to 16.2% for perinatal, 7.2 to 21.1% for postnatal, and 16.7 to 32.8% for total mortality. Respiratory and starvation problems were major causes of postnatal mortality. Heterosis for lamb survival retained in composites was 9% for C1 and 18% for C2. Mortality was 1 to 5% higher for males than for females.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1992

Evaluation of mating systems involving five breeds for integrated beef production systems: II. Feedlot segment.

Computer models were used to simulate the feedlot segment of an integrated beef production system. Five breeds, Angus (A), Charolais (C), Hereford (H), Limousin (L), and Simmental (S), in three mating systems, pure-breeding and two- and three-breed rotational crossbreeding, were evaluated for feedlot and carcass performance. Breed data were taken from the literature. Feeder calves (steers and non-replacement heifers) entered the feedlot at 205 d of age. After a 35-d adjustment period, calves were custom-fed to four slaughter end points: 440 d, 457 d, 288-kg carcass weight, or low Choice. Cattle were fed to requirements (megacalories of ME). Input costs included feed and nonfeed expenses (purchase prices, transportation, yardage, and medicinal fees). Carcass values were $2.65 and $2.54/kg of carcass weight for steer and heifers, respectively, between 272 to 318 kg. Over- or underweight carcasses were discounted $.60/kg. At the 440-d end point, Select grade steer and heifer carcasses were discounted an additional $.22 and $17/kg, respectively. Biological efficiency was measured as megacalories of ME/kg of gain, and economic efficiencies were measured as input costs per kilogram of carcass weight, input costs per kilogram of lean weight, and input costs per carcass value. Continental breed combinations (C and S) were most efficient at age- and weight-constant end points for megacalories of ME per kilogram of gain and for input costs per carcass value and most efficient at all end points for input costs per kilogram of carcass weight and input costs per kilogram of lean weight. British breed combinations (A) were most efficient at a fat-constant end point for megacalories of ME per kilogram of gain and input costs per carcass value. Therefore, choosing breed combinations for feedlots depends on slaughter end point and measures of efficiency.

Adipose Tissue↗

PubMed1993

Breed and environmental effects on postweaning growth of rabbits.

Growth records of 4,270 weanling rabbits born between March 1985 and December 1989 were studied to evaluate the effects of breed and month of birth on postweaning growth performance of four medium-sized breeds. Californian (CAL), New Zealand White (NZW), Palomino (PAL), and White Satin (WS). Traits examined were 28-d weaning weight (WW), postweaning gain (GAIN), attainment of 1,600-g market weight by 76 d of age (MKT), and approximate age at 1,600 g (AGE). Least squares models included breed, month of birth, sex, and year of birth as fixed effects and litter within breed by month and by year and the residual as random variables. The NZW had significantly higher GAIN and MKT and lower AGE than the other three breeds. White Satin had the highest WW, followed by CAL, NZW, and PAL. White Satin had higher GAIN and lower AGE than PAL or CAL but did not differ for MKT. Poorer performance was seen during the summer, but the NZW tended to be less affected by the environmental extremes than the other breeds. The effects on GAIN of mean monthly temperature and daylength and the interrelationships of these with estimated milk production and litter size at weaning were evaluated by regression methods for the 2,100 NZW fryers. Temperature and daylength had significant effects on GAIN, with lowest GAIN in the summer, but the individual contributions to the variance were small because of some redundancy when month, temperature, and (or) light were included in the same model. Curvilinear trends were observed that favored GAIN as estimated milk production increased but decreased GAIN as litter size at weaning increased. In the hot, humid climate of southern Louisiana important breed differences were noted. There were also indications that daylength may be an important factor in postweaning fryer performance.

Animals↗

PubMed1994

Effect of dietary chlortetracycline during breeding and(or) farrowing and lactation on reproductive performance of sows: a cooperative study. S-145 Committee on Nutritional Systems for Swine to Increase Reproductive Efficiency.

A cooperative regional study involving 850 litters was conducted at five experiment stations (Arizona, Florida, Oklahoma, Texas, and Virginia) to assess the effects of feeding 220 mg/kg of chlortetracycline (CTC) from 1 wk before to the initiation of the breeding season to 15 d after the breeding season and(or) from 110 d of gestation through lactation on reproductive performance of sows (2 x 2 factorial). Sows were fed 1.82 kg/d (2.27 kg during December, January, and February) during the breeding period and before farrowing. Feed was consumed on an ad libitum basis during lactation. Feeding CTC during the breeding season increased litter size at birth (10.8 vs 10.3; P < .05) and decreased feed consumption (5.4 vs 5.5 kg/d; P < .05) in the subsequent lactation period. Feeding CTC during lactation reduced lactation weight loss in sows (4.3 vs 6.1 kg; P < .07). Feeding the antibiotic at breeding had no effect on conception rate; however, feeding the antibiotic during lactation improved subsequent conception rate at the first service (80 vs 73%; P < .10) and overall conception rate (89 vs 84%; P < .05). This indicates that some carryover effect of feeding CTC during lactation occurred during the subsequent breeding period. Station x treatment interactions were observed for survival rate to 21 d (P < .05) and to weaning (P < .06). Overall, survival rates were not greatly affected by antibiotic feeding. No treatment interaction was observed for any trait measured, indicating that the effects of CTC during the breeding and lactation periods were independent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Breed effects, retained heterosis, and estimates of genetic and phenotypic parameters for carcass and meat traits of beef cattle.

Retained heterosis for meat traits was estimated in F3 generation castrate males in three composite populations of beef cattle finished on two levels of dietary energy density (2.82 Mcal of ME and 3.07 Mcal of ME and 11.50% CP) and serially slaughtered at four end points at intervals of 20 to 22 d. Breed effects were evaluated in nine parental breeds (Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 B, 1/4 C, 1/4 L, 1/8 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, and 1/4 A). Breed effects were important (P < .01) for all carcass and meat traits evaluated. Dietary energy density and slaughter group affected (P < .05) most traits evaluated. The effects of retained heterosis were not consistent among composites. For the mean of the three composites, retained heterosis was significant only for percentage of 9-10-11th rib fat and for percentage of retail product. Phenotypic correlations indicated that marbling score was a poor predictor of palatability attributes of individual carcasses. Estimates of heritability were intermediate to high for measures of fatness but were generally low for palatability attributes. The high negative genetic correlation (-.56) between percentage of retail product and marbling score and the relatively low genetic correlations between percentage of retail product and palatability attributes suggests the need for simultaneous attention to percentage of retail product and palatability attributes rather than to marbling score. Correlations among breed group means were generally high for measures of fatness with palatability attributes and were high and negative for percentage of retail product with marbling score and with other measures of fatness. Limited opportunity exists for selecting among breeds to achieve high levels of marbling in the longissimus muscle simultaneously with a high percentage of retail product. These results suggest that the most logical approach to resolution of the genetic antagonism between favorable carcass composition and less favorable palatability attributes is to form composite breeds with breed contributions organized to achieve an optimum balance between favorable carcass composition and desirable palatability attributes at optimum slaughter weights.

Analysis of Variance↗

PubMed1995

Influence of maternal and service-sire breed on serum progesterone and estrogen before calving and plasma 13,14-dihydro-15-keto-prostaglandin F2 alpha after calving.

Effects of breed of service sire and cow on birth weight and prepartum and postpartum endocrine function were studied in multiparous Brahman (n = 20) and Angus (n = 20) cows bred to Brahman or Angus bulls. Before calving, blood samples were collected on d 34 to 28, 27 to 21, 20 to 14, and 13 to 7, and after calving, samples were collected from d 0 to 7. Progesterone (P4), estrogen (E2), and 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) were quantified with RIA. Calves born to Brahman were smaller (P < .05) than calves born to Angus cows. Prepartum concentrations of P4 were greater in Angus cows and decreased more rapidly near parturition than in Brahman cows (breed of dam x period; P < .03). Cows bearing bull calves had greater concentrations of P4 on d 20 to 14 before calving than cows bearing heifer calves (sex of calf x period; P < .04). Prepartum E2 was influenced (P < .05) by the breed of dam x breed of sire x period interaction. The ratio of P4:E2 tended to decrease more in Angus than in Brahman cows near parturition (breed of dam x period; P < .09). Postpartum PGFM tended to be influenced (P < .08) by breed of dam x breed of sire; from d 3 to 5, Brahman cows bred to Angus bulls tended (P < .08) to have greater PGFM than Brahman cows bred to Brahman bulls or than Angus cows bred to Brahman or Angus bulls.2+ f1p4

Animals↗

PubMed1998

Heterosis and breed additive effects for Hereford, Tarentaise, and the reciprocal crosses for calf traits.

Records from 595 straightbred Hereford (HH), straightbred Tarentaise (TT), and reciprocal-cross (HT) females, randomly mated to HH, TT, or HT bulls, were analyzed for estimates of heterosis and breed additive effects for calf traits that included birth weight (BWT), calving difficulty (DIFF), prebreeding (PRE) and postbreeding (PST) weight, weaning weight (WWT), weaning condition score (WCS), weaning hip height (WHH), and preweaning average daily gain (ADG). The statistical model included year, age of dam, sex, regression on age at time of measurement, and regressions for the genetic effects of breed individual, breed maternal, breed grandmaternal, individual heterosis, and maternal heterosis. Breed effects were coded to reflect TT- HH differences. Age at the time of measurement, year, age of dam, and sex were significant for most traits. Individual breed effects were important (P < .05) for BWT, PRE, PST, WCS, and WHH but not for WWT, resulting in lower weights, less condition, and taller animals for TT. Maternal breed effects did not influence BWT, but they were important ( P < .05) for PRE, PST, WWT, WCS, WHH, and ADG. Grandmaternal effects were only important for BWT and ADG. Individual and maternal heterosis were important (P < .05) for most traits measured, resulting in increased calf size, weight, and body condition.

Animal Feed↗

PubMed2000

Definition of animal breeding goals for sustainable production systems.

What we do is determined by the way we "view" a complex issue and what sample of issues or events we choose to deal with. In this paper, a model based on a communal, cultural, or people-centered worldview, informed by a subjective epistemology and a holistic ontology, is considered. Definitions and interpretations of sustainable agriculture are reviewed. Common elements in published definitions of sustainable agriculture and animal production among those who seek long-term and equitable solutions for food production are resource efficiency, profitability, productivity, environmental soundness, biodiversity, social viability, and ethical aspects. Possible characteristics of future sustainable production systems and further development are presented. The impact of these characteristics on animal breeding goals is reviewed. The need for long-term biologically, ecologically, and sociologically sound breeding goals is emphasized, because animal breeding determined only by short-term market forces leads to unwanted side effects. Hence, a procedure for defining animal breeding goals with ethical priorities and weighing of market and non-market values is suggested. Implementation of non-market as well as market economic trait values in the aggregate genotype, as suggested, may allow for breeding programs that contribute to sustainable production systems. Examples of breeding goals in salmon, cattle, and pigs are given, and the resulting genetic responses are evaluated with respect to economic profit (or costs) and other criteria of sustainability. Important prerequisites for breeding programs for sustainable production are appropriate governmental policies, awareness of our way of thinking, and a more communal worldview informed by a subjective epistemology and a holistic ontology.

Animal Husbandry↗

PubMed2000

Carcass traits and retail display-life of chops from different goat breed types.

Four groups of goats, Boer x Spanish, straightbred Spanish, Spanish x Angora, and straightbred Angora were slaughtered at a constant age according to accepted industry procedures. At 24 h postmortem, various carcass yield and quality measurements were taken. At 48 h postmortem, one side from each carcass was fabricated into major wholesale cuts for dissection into percentage lean, bone, and fat. Rib chops from the opposite side were fabricated, packaged, and displayed in a retail case. Trained panelists evaluated the rib chops over 4 d of retail display for lean color, surface discoloration, and overall appearance; packages were opened and analyzed for off-odor on d 4. When slaughtered at constant ages, Angora goats had lighter (P < .05) live and hot carcass weights than all other breed types, and Boer x Spanish goats had heavier (P < .05) live and carcass weights than Spanish goats. Live and carcass weights for Boer x Spanish and Spanish x Angora goats did not differ (P > .05). Carcasses from Angora goats had considerably smaller (P < .05) longissimus muscle areas than all other breed types. Carcasses from Spanish goats had lower (P < .05) carcass conformation scores than carcasses from Boer x Spanish goats but did not differ (P > .05) from carcasses of the other two breed types. Carcasses from Angora goats had smaller (P < .05) leg circumferences than the carcasses from Boer x Spanish and Spanish x Angora breed types. In general, carcasses from Boer x Spanish and Spanish goats possessed higher (P < .05) percentages of lean and lower (P < .05) percentages of fat for the side than did carcasses from Spanish x Angora and Angora goats. When the Spanish x Angora carcasses were compared to the Angora carcasses, it seemed that the addition of the Spanish breeding tended to increase lean and decrease fatness for most side or primal comparisons. There were no (P > .05) breed type or breed type x day effects for lean color, surface discoloration, overall appearance or off-odor; however, day of display did influence (P < .05) these traits. Crossing Spanish with Angora goats may be an option to improve carcass characteristics over that of straightbred Angora.

Animals↗

PubMed2005

Additive, dominance, and epistatic loss effects on preweaning weight gain of crossbred beef cattle from different Bos taurus breeds.

(Co)variance components, direct and maternal breed additive, dominance, and epistatic loss effects on preweaning weight gain of beef cattle were estimated. Data were from 478,466 animals in Ontario, Canada, from 1986 to 1999, including records of both purebred and crossbred animals from Angus, Blonde d'Aquitaine, Charolais, Gelbvieh, Hereford, Limousin, Maine-Anjou, Salers, Shorthorn, and Simmental breeds. The genetic model included fixed direct and maternal breed additive, dominance, and epistatic loss effects, fixed environmental effects of age of the calf, contemporary group, and age of the dam x sex of the calf, random additive direct and maternal genetic effects, and random maternal permanent environment effects. Estimates of direct and maternal additive genetic, maternal permanent environmental and residual variances, expressed as proportions of the phenotypic variance, were 0.32, 0.20, 0.12, and 0.52, respectively. Correlation between direct and maternal additive genetic effects was -0.63. Breed ranking was similar to previous studies, but estimates showed large SE. The favorable effects of direct and maternal dominance (P < 0.05) on preweaning gain were equivalent to 1.3 and 2.3% of the phenotypic mean of purebred calves, respectively. The same features for direct and maternal epistatic loss effects were -2.2% (P < 0.05) and -0.1% (P > 0.05). The large SE of breed effects were likely due to multicollinearity among predictor variables and deficiencies in the dataset to separate direct and maternal effects and may result in a less reliable ranking of the animals for across breed comparisons. Further research to identify the causes of the instability of estimates of breed additive, dominance, and epistatic loss genetic effects, and application of alternative statistical methods is recommended.

Animals↗

PubMed2006

Impacts of chronic stress and social status on various physiological and performance measures in pigs of different breeds.

Pigs typically experience various environmental stressors, which can negatively affect performance. Cortisol concentrations and various immune and performance measures are influenced by breed, but few data exist describing the impact of breed on stress responsiveness in pigs. The objective of this experiment was to determine if certain physiological responses to chronic stressors differed among 3 breeds and 2 commercial lines of pigs. The pigs were Landrace (n = 36), Meishan (n = 30), Yorkshire (n = 32), or 1 of 2 commercial lines (Line-A and Line-B; both n = 36). All pigs were weaned at 17 to 21 d and kept in a common nursery. At 49 d of age, pigs were assigned to 1 of 2 treatments: stress (heat, crowding, and mixing) or control (no stress treatment). Pigs were allocated to groups of 3 pigs per pen of the same sex. Control pigs were kept with their littermates. At the onset of the experiment, stressed pigs were mixed with 2 unfamiliar pigs once, and heat and crowding stressors were implemented simultaneously for 14 d. Pigs allocated to the stress treatment were video-recorded for 24 h following initiation of mixing to determine social status: dominant, intermediate, or submissive. Blood samples were taken at d 0 (baseline), 1, 7, and 14 to assess cortisol concentrations and immune measures. Breed and treatment affected cortisol, immune, and performance measures, but no significant breed x treatment interactions were found. In general, pigs subjected to the chronic stressor had lower (P < 0.001) BW and ADG (P < 0.001) than did control pigs. Plasma cortisol was lower (P < 0.001) among stressed pigs at d 7 and 14. Regardless of breed, lipopolysaccharide-induced proliferation (P < 0.01) and natural killer (NK; P < 0.005) cytotoxicity were greater in stressed pigs compared with controls. Furthermore, among stressed pigs, dominant pigs had a greater total white blood cell count (P < 0.005), NK (P < 0.05), and phagocytosis (P < 0.05) than the subordinate pigs. The results indicate that pig breed did not influence the physiological responses to the chronic concurrent stressors imposed for 14 d in this study, but social status did influence the immune responsiveness of these pigs to heat, crowding, and mixing.

Animals↗

PubMed1987

Periodic rotational crosses. I. Breed and heterosis utilization.

Periodic rotational crosses differ from conventional rotations by using sire breeds an unequal number of generations but in a regular sequence. Formulas for breed composition and heterosis in offspring from periodic rotations at equilibrium averaged over all generations of a cycle and for each generation of the cycle are presented. Coefficients of squares and products of breed differences and heterosis used to calculate inter-generational variance are also derived. Several specific periodic rotations utilizing a range of breed proportions were found to use from 70 to 95% as much heterosis as conventional rotations using the same number of breeds equally. Estimates of swine and cattle additive breed and heterosis effects taken from the literature were applied to the formulas. In both the swine and cattle examples, periodic rotations were found that equaled or exceeded the conventional rotations using the same number of breeds and also had lower inter-generational variance.

Animal Husbandry↗

PubMed1987

Periodic rotational crosses. II. Optimizing breed and heterosis use.

Choice of the optimal number and sequence of breeds in a periodic cross was determined by comparing the trade-off between increased utilization of breed differences and decreased utilization of heterosis. It was shown that the change in mean efficiency resulting from adding the next best breed to the best conventional n-breed rotation is always less than the change in efficiency predicted from the increase in heterosis. Periodic rotations were generally optimized by decreasing the proportion of poorer performing breeds in the rotation. However, efficiency of periodic rotations can exceed that of the better breed even when the difference in additive breed effects for efficiency is almost twice the effect of heterosis on efficiency. The periodic rotation that was optimal also tended to have the lowest inter-generational variance. It was suggested that inter-generational variances of component traits, which are not necessarily minimized when crosses are selected on a combined efficiency trait, can be considered by including inter-generational variance in an index or by introducing maximum thresholds.

Animal Husbandry↗

PubMed1989

Crossbreeding among British and continental European dual-purpose breeds in the coastal Pacific Northwest.

From 1979 through 1987, British breed and crossbred cows were mated to Simmental, Pinzgauer or Tarentaise bulls or to Hereford-Angus crossbred bulls. Beginning in 1982, continental European crossbred females also entered the herd, to be mated for first calving to Hereford-Angus or Angus bulls and as cows to continental European or Hereford-Angus bulls. In progeny of British breed and crossbred cows, dam breed effects on birth and weaning weight were not important, but continental European crossbred calves were heavier than British crossbred contemporaries at birth and weaning. Pinzgauer- and Simmental-sired calves were heavier at birth than Tarentaise crosses, but calves sired by each of the continental breeds had similar weaning weights. Maternal heterosis was greater than direct heterosis effects on weaning weight (8% vs 5%), but only direct heterosis (13%) influenced birth weight. Within progeny of continental European crossbred cows, calves with a Tarentaise maternal grandsire were lighter at birth, with no significant difference among other maternal grandsire breeds. Maternal breed effects on weaning weight were not significant. Nevertheless, in contemporary years, continental European crossbred cows reared calves that were 10% heavier than calves reared by British crossbred cows. Pacific Northwestern cattle producers could achieve substantial increases in weaning weight from introducing inheritance from continental European dual-purpose breeds into cow herds and calf crops of British ancestry.

Animals↗

PubMed2001

Influence of litter size and breed on the duration of gestation in dogs.

The variation in the duration of gestation, defined as the period from mating to parturition, was studied in 113 bitches of six breeds (31 Dobermans, 31 Labrador retrievers, 14 German shepherds, 13 Bernese mountain dogs, 12 golden retrievers and 12 West Highland white terriers). The bitches were mated once on the optimal day for mating, which was established by measuring the plasma concentration of progesterone. The duration of gestation varied between 58 and 65 days with a mean of 61.4 +/- 1.5 days (+/- SD). The mean duration of gestation in West Highland white terriers (62.8 +/- 1.2 days) was significantly longer than that of German shepherds (60.4 +/- 1.7; P < 0.001), Labrador retrievers (60.9 +/- 1.5; P < 0.001) and Dobermans (61.4 +/- 1.0; P < 0.025). The variation in the duration of gestation in any one of the six breeds was low, ranging from 4 to 7 days, or less when litters of one pup (n = 4) were excluded. The number of pups per litter varied between one and 15 with a median of eight pups. In the total population, the duration of gestation was negatively correlated with litter size (r = -0.73; P = 0.005) for litters (n = 112) containing < or = 13 pups. However, within each breed multiple regression analysis failed to show any influence of litter size on the duration of gestation. The median litter size of different breeds and the mean duration of gestation were negatively correlated (r = -0.78; P = 0.03; n = 6). Therefore, although it was not conclusively proven, the results indicate that the breed is a major determinant of the duration of gestation in bitches and that the influence of breed may be ascribed to breed-related differences in litter size.

Animals↗

PubMedDate not supplied

[Population genetic analysis of the new dog breed Elo].

The breeding of the dog breed Elo was started in 1987. This dog breed was established by using 16 dogs of nine different breeds. All pedigree information of the dogs from 1987 to 2002 was included for the analysis of the proportion of genes of the different founder breeds, of the inbreeding coefficient, and relationship coefficients. Additionally, the number of died puppies per litter were investigated. The Eurasian dog breed contributed about 48% of the genes in the whole Elo dog population. Old English sheepdog and Chow Chow contributed about 23% and 10% of the genes. The other dog breeds were of minor importance. The mean inbreeding and relationship coefficients of the whole Elo dog population were 12.04% and 19.22%, respectively. With the exception of 3.5% of animals, all Elo dogs were related to each other. The mean litter size was 6.39 puppies. The percentage of stillborn puppies per litter averaged at 9.47%. The inbreeding coefficients of the puppies and of their dams, the age of the sire and the dam at the time of birth of the puppies, the litter size, the puppies' year of birth and the proportion of genes of the Chow Chow showed a significant effect on the number of stillborn puppies per litter. The heritability for the frequency of stillborn puppies was estimated using a linear animal model. After transformation of the linear estimates to the underlying liability scale, the heritability amounted to h2 = 0.15.

Animals↗

PubMed2005

Some characteristics of the larval breeding sites of Anopheles culicifacies species B and E in Sri Lanka.

BACKGROUND & OBJECTIVES: Anopheles culicifacies Giles, the major malaria vector in Sri Lanka, exists as a species complex comprising two sympatric sibling species--species B and E. Species E is reported to be the major vector of Plasmodium vivax and P. falciparum parasites in Sri Lanka, whilst species B is a poor or nonvector as in India. Knowledge of the breeding habits of the two sibling species can help in designing optimal vector control strategies. Hence, a survey was conducted in Sri Lanka to study the preferential breeding habitats of An. culicifacies species B and E. METHODS: Immature forms of An. culicifacies were collected from identified breeding sites in malarious districts. Collected larvae were typed for their sibling species status based on mitotic Y-chromosome structure. Data was analysed using Statistical Package for Social Science version 10.0. RESULTS: An. culicifacies immature forms were found in 23 collection sites. Among these samples 19 were found to have species E and four to have species B. All species B larvae were collected from Tonigala village in the Puttalam district. None of the 23 sites was found to have both species B and E. Species E, the major vector of malaria, appears to breed in variety of breeding sites which can be of an indication of its adaptive variation to exploit breeding sites with varying limnological characteristics. INTERPRETATION & CONCLUSION: The present findings have to be taken into account when formulating more effective larval control measures. They also show the need for a detailed study of possible different preferences for larval breeding sites between species B and E.

Animals↗

PubMed2005

[Analysis of genetic diversity of Sichuan indigenous chicken breeds using microsatellite markers].

Thirty microsatellite markers with medium or high polymorphisms were selected to detect the genetic diversity of 8 indigenous chicken breeds in Sichuan. According to the allele frequencies of 30 microsatellite sites, mean heterozygosity (H), polymorphism information content (PIC) and DA genetic distances were calculated for each breeds. The results showed that 24 of 30 microsatellite sites were highly polymorphic, so the 24 microsatellite markers were effective markers for analysis of genetic relationship among chicken breeds. The mean heterozygosity of 8 chicken breeds was all over 0.5. The highest was the Luning chicken (0.681), and the lowest was the Jiuyuan Dark chicken. The high diversity of 8 chicken breeds might be caused by the traffic obstruction(geographic isolation). The results of the heterozygosity were consistent with that of PIC. UPGMA tree was completed through analysis of DA genetic distances. Emei Dark chicken, Miyi chicken, Luning chicken and Jiuyuan Dark chicken were the first group: Miyi chicken and Luning chicken were grouped firstly, then Emei Dark chicken were grouped with them in shorter time distances, and Jiuyuan Dark chicken were grouped with them at last. Shimiancao Ke chicken Xingwen Silky chicken and Muchuan Silky were the second group: Xingwen Silky chicken and Muchuan Silky were grouped firstly, and then Shimiancao Ke chicken was grouped with them. Liangshangya Ying chicken had its own branch. The result of UPGM was consistent with the genesis, breeding history, differentiation and location of 8 chicken breeds.

Animals↗