Population dynamics and production effects of sheep lice (Bovicola ovis Schrank) in extensively grazed flocks

2011 ◽  
Vol 51 (8) ◽  
pp. 753 ◽  
Author(s):  
P. J. James ◽  
B. J. Horton ◽  
N. J. Campbell ◽  
D. L. Evans ◽  
J. Winkleman ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Logistic Models ◽  
Economic Loss ◽  
First Year ◽  
Associated Production ◽  
High Solar Radiation ◽  
Apparent Source ◽  
Fleece Weight ◽  
Carry Over ◽  
Production Effects

An experiment was conducted to characterise population dynamics of lice and associated production loss in extensively grazed flocks infested at different times after shearing. Merino wethers were allocated to six groups of 31 sheep. In the first year (Y1), one sheep in each of two groups was infested with 2500 lice at 6 weeks after shearing (September), sheep in two groups were infested at 4 months (December) and two groups remained uninfested. In year 2 (Y2), infestations carried over from Y1, but a lousy sheep was added to each 6-week infestation mob. In year 3 (Y3), the infested mobs were treated and remained lice free, while lousy donor sheep were added to the two previously uninfested mobs. In Y1, lice appeared to die out in one 6-week-infestation group and were found on only two sheep before next shearing in the other. Lice persisted and spread in the two 4-month-infestation flocks, reaching mean counts (±s.e.) of 0.5 (±0.2) and 0.2 (±0.1) per part before shearing. In Y2 and Y3, lice persisted and increased in all infested flocks, reaching mean counts of 2.3 (±0.6), 8.5 (±1.5), 3.6 (±0.6) and 2.8 (±0.7) per part in Y2 and 1.0 (±0.2) and 1.2 (±0.4) per part in Y3. The count of 8.5 was in the flock with both a carry-over infestation and an infestor sheep. Exponential and logistic models were fitted to describe lice increase; differences in fleece derangement reflected louse numbers. Clean fleece weight was higher in flocks without lice in all years (0.12 kg/head in Y1; 0.22 kg/head in Y2 and Y3; P < 0.05). Classer-assigned colour scores (although not measured colour), cott score and line into which the wool was classed also differed significantly (P < 0.05) between infested and non-infested flocks and there was an indication that staple length was reduced in more heavily infested flocks. In spring-shorn flocks in environments with high solar radiation and no lice present at shearing, even if lice subsequently enter the mob, it appears unlikely that they will increase to levels where serious economic loss will be experienced before next shearing. The study also indicated that lice could persist in flocks at levels unlikely to be detected by most commercial wool producers for extended periods, possibly through one season, which may help to explain reports of new infestations with no apparent source.

Effect of selenium supplementation on survival, liveweight and wool weight of young sheep on Kangaroo Island, South Australia

1979 ◽  
Vol 19 (101) ◽  
pp. 689 ◽  
Author(s):  
SK Walker ◽  
GP Hall ◽  
DH Smith ◽  
RW Ponzoni ◽  
GJ Judson
Keyword(s):  
Total Dose ◽  
Whole Blood ◽  
Sodium Selenite ◽  
South Australia ◽  
Selenium Concentration ◽  
Mortality Rates ◽  
Selenium Supplementation ◽  
First Year ◽  
Weaning Weight ◽  
Fleece Weight

The responses in liveweight, wool weight and survival, to selenium supplementation, were studied in young sheep from weaning to yearling age. The experiment was conducted over three years. In the first year, one sodium selenite supplementation rate was used (total dose 46.5 mg). During the following two years two supplementation rates were administered (total doses 46.5 mg and 93 mg). Mean concentrations of selenium in whole blood in unsupplemented sheep varied from 0.19-0.56 pmol l-l and from 0.20-0.44 pmol l-1 in the two years in which concentrations were measured. Supplementation, which commenced at lamb marking, increased the selenium concentration in sheep at weaning and thereafter. Selenium supplementation improved the break-of-season weight (P < 0.01) and yearling weight (P < 0.01 ) but not weaning weight (0.05 < P < 0.1 ). Hogget fleece weight was improved (P < 0.01 ) and mortality reduced (P < 0.01) by selenium supplementation. There was a treatment x year interaction in mortality rates (P < 0.01 ). There were no significant differences between the two supplementation rates

scholarly journals Migratory connectivity in the context of differential migration

2018 ◽  
Vol 14 (12) ◽  
pp. 20180679 ◽  
Author(s):  
Martins Briedis ◽  
Silke Bauer
Keyword(s):  
Population Dynamics ◽  
Differential Mortality ◽  
Breeding Period ◽  
Migratory Connectivity ◽  
Differential Migration ◽  
Relative Contribution ◽  
Breeding Populations ◽  
Conservation Actions ◽  
Carry Over ◽  
The Times

Understanding how breeding populations are spatially and temporarily associated with one another over the annual cycle has important implications for population dynamics. Migratory connectivity typically assumes that populations mix randomly; yet, in many species and populations, sex-, age- or other subgroups migrate separately, and/or spend the non-breeding period separated from each other—a phenomenon coined differential migration. These subgroups likely experience varying environmental conditions, which may carry-over to affect body condition, reproductive success and survival. We argue that environmental or habitat changes can have disproportional effects on a population's demographic rates under differential migration compared to random mixing. Depending on the relative contribution of each of these subgroups to population growth, environmental perturbations may be buffered (under-proportional) or amplified (over-proportional). Thus, differential migration may result in differential mortality and carry-over effects that can have concomitant consequences for dynamics and resilience of the populations. Recognizing the role of differential migration in migratory connectivity and its consequences on population dynamics can assist in developing conservation actions that are tailored to the most influential demographic group(s) and the times and places where they are at peril.

Population Dynamics of Percids in Lake IJssel and some Smaller Lakes in The Netherlands

1977 ◽  
Vol 34 (10) ◽  
pp. 1710-1719 ◽  
Author(s):  
J. Willemsen
Keyword(s):  
Population Dynamics ◽  
Perca Fluviatilis ◽  
First Year ◽  
Homing Behavior ◽  
Perch Perca Fluviatilis ◽  
Class Strength ◽  
High Summer Temperature ◽  
Dependent Growth ◽  
First Year Of Life ◽  
Slow Growing

Pikeperch (Stizostedion lucioperca) and Eurasian perch (Perca fluviatilis) in Lake IJssel both prey mainly upon the very abundant smelt (Osmerus eperlanus). But competition for food is of little or no importance and growth is not density-dependent. Growth rates for perch and ruffe (Gymnocephalus cernua) in some lakes are exceptionally rapid, mean lengths after 3 yr being 24 and 18 cm, respectively. Very intensive fishing for pikeperch (total annual mortality 81%) in the season before first spawning removes particularly the fast-growing fish from the population, thus restricting reproduction mainly to the slow-growing pikeperch. Year-class strength of pikeperch is strongly favored by a high summer temperature during the first year of life. Strong year-classes of pikeperch in Lake IJssel are characterized by a mean length of the young-of-the-year of 14.5 cm or more. Migration of pikeperch and perch in Lake IJssel is restricted. When transported to other areas of the lake, both species showed a distinct homing behavior. Key words: Percidae, population dynamics, Stizostedion, Perca, Gymnocephalus

Yield responses of oats and alfalfa to common hemp-nettle (Galeopsis tetrahit) interference

1991 ◽  
Vol 71 (1) ◽  
pp. 141-147 ◽  
Author(s):  
Anne Légère ◽  
Jean-Marc Deschênes
Keyword(s):  
Field Experiments ◽  
First Year ◽  
Weed Competition ◽  
Yield Losses ◽  
Weed Interference ◽  
Medicago Sativa L ◽  
Lower Height ◽  
Carry Over ◽  
Yield Responses ◽  
Early Harvest

Effects of various densities of hemp-nettle (Galeopsis tetrahit L.) on yields of oats (Avena sativa L.) and first year alfalfa (Medicago sativa L.) were investigated in field experiments. In both crops, emergence of hemp-nettle seedlings occurred after plot establishment such that final densities were generally greater than initial densities. Hemp-nettle plants within a stand were distributed normally over no more than seven 15-cm height classes. Very few plants were found in the lower height classes. Weight distribution according to the same height classes showed that average to tall individuals produced a large proportion of the weed biomass. Oat yields decreased as hemp-nettle density increased. In the density range of 28–248 hemp-nettle plants m−2, oat grain yield losses varied between 12 and 50%. Alfalfa was cut according to either a two-cut regime, or a three-cut regime which included an early harvest. Alfalfa yields decreased with increase in hemp-nettle density regardless of cutting regime, whereas effects of cutting regime on alfalfa yield varied with year of experiment. In each regime, timing of first harvest determined the duration of hemp-nettle interference and may have affected the degree of carry-over effects to later harvests. Key words: Hemp-nettle, Galeopsis tetrahit, weed competition, weed interference, crop losses

The effect of predation on the life histories of Littorina obtusata and Littorina mariae

1992 ◽  
Vol 72 (2) ◽  
pp. 403-416 ◽  
Author(s):  
Gray A. Williams
Keyword(s):  
Population Dynamics ◽  
Brown Alga ◽  
Life Histories ◽  
Size Range ◽  
Ascophyllum Nodosum ◽  
First Year ◽  
Littorina Obtusata ◽  
Fucus Serratus ◽  
Second Year

Littorina obtusata is an epiphytic gastropod which lives for three to four years on its host Ascophyllum nodosum, a long-lived brown alga. Most of the population consists of adults, present throughout the year in the size range 14 to 17 mm. Newly hatched individuals appear between April and October with a peak in July; the immature winkles grow to merge with the adult cohort in May.In contrast Littorina mariae is an annual; newly hatched individuals grow to maturity by the winter of their first year. Those reaching maturity overwinter as adults but very few live beyond spring of their second year. The population dynamics of L. mariae are closely linked with changes in the biomass of the alga Fucus serratus on which it lives.

scholarly journals Dietary Fiber for Gestating Sows During Heat Stress: Effects on Reproductive Performance and Stress Level

2021 ◽  
Author(s):  
SeungMin Oh ◽  
Abdolreza Hosseindoust ◽  
SangHun Ha ◽  
Joseph Moturi ◽  
JunYoung Mun ◽  
...  
Keyword(s):  
Gene Expression ◽  
Heat Stress ◽  
Dietary Fiber ◽  
Stress Level ◽  
Reproductive Performance ◽  
Glucose Transporter ◽  
Economic Loss ◽  
Lactation Period ◽  
Ileal Digestibility ◽  
Carry Over

Abstract Background: Heat stress is an important issue in swine farms, which causes economic loss and compromises sows health. The addition of fiber to the diet is an option in modifying intestinal health. This study was designed to evaluate the effect of fiber level on reproductive performance, intestinal microbiota and integrity, and metabolism of gestating sows, and its carry-over effect on the lactation period during heat stress. Methods: A total of 36 gestating sows (90 day-pregnant) were allotted to three treatments with 12 replicates. The diets included 3% (LF), 4.5% (MF), and 6% (HF) crude fiber. All gestating sows fed 2.5 kg of diet daily and diets contained 3150 kcal/kg of ME, 14% crude protein (CP), and 0.58% standardized ileal digestibility of lysine. Results: Sows fed the HF diet showed a lower respiratory rate and hair cortisol concentration compared with the LF treatment. The HF diet increased the feed intake of sows compared with the LF diet, while it decreased the farrowing duration. The HF diet increased the constipation index compared with the MF and LF diets. Sows in the HF treatment showed a greater piglet weight and litter weight compared with the LF treatment at weaning. Sows in the LF treatment showed the highest digestibility of CP and the greatest digestibility of acid detergent fiber was observed in sows fed HF diet. The HF diet increased lying and decreased standing, and sham chewing behavior compared with the LF diet. The concentration of acetate and total short-chain fatty acid were increased in sows fed the HF diet. The gene expression of glucose transporter 3 and 4 was increased in the HF treatment. The gene expression of heat shock protein70 was decreased in the HF treatment.Conclusion: Increasing dietary fiber level decreased stress level and improved farrowing duration and reproductive performance.

scholarly journals Impact of abiotic factors on population dynamics of Bactrocera dorsalis Hendel and Bactrocera zonata (Saunders) at different ecological zones in NW Plains of India

2021 ◽  
Vol 22 (3) ◽  
pp. 250-257
Author(s):  
REENA ◽  
AMANDEEP KAUR ◽  
MAHENDER SINGH ◽  
BHAV KUMAR SINHA ◽  
ANIL KUMAR ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Fruits And Vegetables ◽  
Abiotic Factors ◽  
Economic Loss ◽  
Fruit Flies ◽  
Bactrocera Dorsalis ◽  
North West ◽  
Ecological Zones ◽  
Bactrocera Zonata ◽  
Trap Catches

In India, fruit flies have been identified as one of the ten most serious problems of agriculture because of their polyphagous nature and the huge economic loss it causes to the fruits and vegetables (2.5 to 100%). Study was carried to determine the population dynamics of fruit flies (Bactrocera dorsalis and Bactrocera zonata) and establish the correlation with abiotic factors in guava and citrus fruits crops in two agro ecological zones of North West India. Fruit flies population was recorded by installation of pheromone traps in different fruit crop ecosystems during the fruiting season of this zone. The data of trap catches of both the locations was correlated with the significantly influencing abiotic parameters. The peak fruit fly incidence varied between 31st to 34th standard weeks in guava ecosystem at both the locations. In citrus ecosystem, the incidence was highest during 35th and 39th standard weeks coinciding with the ripening of the fruits. At both the locations, trap catches of guava ecosystem were positively correlated with all the weather parameters, while under citrus ecosystem minimum temperature and rainfall showed negative correlation, but relative humidity was positively correlated. Information may be utilized in targeting suitable pest management techniques for respective zones.

scholarly journals Population Dynamics of Acromyrmex crassispinus (Forel) (Hymenoptera: Formicidae) and Attacks on Pinus taeda Linnaeus (Pinaceae) plantations

Sociobiology ◽  
2015 ◽  
Vol 62 (3) ◽  
pp. 340 ◽  
Author(s):  
Mariane Aparecida Nickele ◽  
Wilson Reis Filho
Keyword(s):  
Population Dynamics ◽  
Spatial Distribution ◽  
Pinus Taeda ◽  
Forest Canopy ◽  
First Year ◽  
Nest Density ◽  
Nuptial Flight ◽  
The Third ◽  
Leaf Cutting ◽  
Pinus Taeda L

This work aimed to study the population dynamics of Acromyrmex crassispinus (Forel) in Pinus taeda L. plantations, evaluating the density and spatial distribution of nests over time, inferring about the period of the first nuptial flight of A. crassispinus colonies, and evaluating the levels of attack of this leaf-cutting ant on P. taeda plants. Assessments were performed monthly in the first year after planting, every three months until the third year and every six months until the plantation was six years old. The presence of nests was observed only after 15 months after planting. The nest density gradually increased until the planting completed 30 months, and decreased when the forest canopy began to close (after 54 months). Spatial distribution of A. crassispinus nests was random. Probably, the first nuptial flight of an A. crassispinus colony occurs after the third year of the colony foundation. Pinus taeda plants were not attacked by A. crassispinus throughout the evaluation period. Then, when dealing with a replanting area of Pinus plantation, where the previous forest has not been subject to pruning nor thinning, the problem with A. crassispinus is almost null if the clearcutting and the new planting occur during the winter. In this case, leaf-cutting ants control can be alleviated and it is not necessary to carry out systematic control of ants where A. crassispinus is the predominant leaf cutting ant species. Acromyrmex crassispinus control should be done only if nests are located or if attacked plants by ants are detected.

scholarly journals Cold Tolerance and Population Dynamics of Leptoglossus zonatus (Hemiptera: Coreidae)

Insects ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 351 ◽  
Author(s):  
Kristen E. Tollerup
Keyword(s):  
Population Dynamics ◽  
Late Summer ◽  
Economic Loss ◽  
San Joaquin Valley ◽  
Destructive Sampling ◽  
Fresno County ◽  
Winter Temperatures ◽  
Early Fall ◽  
Aggregation Size ◽  
Considerable Economic Loss

In California’s San Joaquin Valley, feeding by the coreid pest, Leptoglossus zonatus, can cause considerable economic loss on almond and pistachio. This research was conducted to improve understanding of how winter temperatures affect mortality of overwintering adult L. zonatus and to develop a better understanding of the role pomegranate plays in the species’ life-history. We exposed 7410 field-collected adult L. zonatus to temperatures between −2 and −10 °C for a period of three, four, or six hours using insect incubators. At six hours of exposure, the, LD50 and LD95 occur at −5.8 and −9.7 °C, respectively. We classified L. zonatus as chill-intolerant. Temperatures cold enough to affect substantial mortality of overwintering L. zonatus rarely occur in the San Joaquin Valley. Whole aggregation destructive sampling from a pomegranate hedgerow in Fresno County was conducted to determine population dynamics. At late summer to early fall, aggregations consisted of >90% immature stages. By early to mid-winter, mean aggregation size decreased, consisting of only three to 12 late-instars and adults. During years one and two of the experiment, L. zonatus produced a generation on pomegranate, mostly between September and mid-November. Overwintering did not occur on pomegranate, rather the majority of adults emigrated to other overwintering locations by mid-winter.

CARRY-OVER EFFECTS OF HIGH FERTILIZER RATES ON NATIVE SEDGE BOG VEGETATION IN INTERIOR BRITISH COLUMBIA

1968 ◽  
Vol 48 (1) ◽  
pp. 49-55 ◽  
Author(s):  
W. L. Pringle ◽  
A. L. van Ryswyk
Keyword(s):  
British Columbia ◽  
Application Rate ◽  
First Year ◽  
Fertilizer Treatment ◽  
Monthly Precipitation ◽  
Fertilizer Response ◽  
Equal Importance ◽  
Carry Over ◽  
Complete Fertilizer ◽  
Fertilizer Rates

A factorial fertilizer trial using rates of 0, 224 and 448 kg/ha of N, P2O5 and K2O in all combinations, was established on a sedge bog in the Cariboo area of British Columbia. Yields taken in the subsequent 5 years showed that a complete fertilizer in a 1:1:2 ratio was most efficient. The most limiting of the three elements was P, followed by K. Nitrogen had an effect in the first year only. Yearly fluctuations in yields and certain fertilizer response could be related to monthly precipitation. Tissue analysis revealed that, where supplied, N and P were increased in the first year only while K was increased in all years by the higher application rate. Presumably, it was taken up in luxury amounts in the first year. Digestibility of the forage was not affected by fertilizer treatment. It was concluded that hay quantity increased through the use of complete fertilizers and that elemental ratio is of equal importance to the rate. The entire picture was not complete as the test was still giving significant carry–over responses 5 years after the initial harvest.

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