Herd Units Research Articles

Duration of Mycoplasma hyopneumoniae detection in pigs following purposeful aerosol exposure

Swine disease elimination programs for Mycoplasma hyopneumoniae are commonly applied in the North American swine industry and may include the aerosolization of medium containing lung tissue to achieve population exposure prior to start. Field data has indicated M. hyopneumoniae PCR detection in pigs beyond 240 days post-herd closure (dphc; planned end of an elimination program) and is thought to contribute to disease elimination programs’ failure. Here, the duration of M. hyopneumoniae detection in sows and replacement gilts following aerosolized lung homogenate exposure, as part of a dual disease elimination program, was determined. A subset of sows and gilts from a commercial sow herd and off-site gilt development unit were longitudinally sampled to collect deep tracheal catheter secretions at various times post-exposure. Samples were tested for M. hyopneumoniae using a species-specific real-time PCR. A proportion of 58, 51, 52, 19, and 2% females were detected positive at 30, 60, 120, 180 and 240 dphc, respectively. Noteworthy, a greater proportion of gilts exposed at the off-site GDU were detected PCR positive for M. hyopneumoniae at each sampling event, compared to sows. In this study, assaying for genetic material in live female pigs showed extended detection of M. hyopneumoniae until at least 240 dphc. This data suggests persistence of M. hyopneumoniae longer than previously reported and highlights the importance of performing diagnostic testing to confirm negativity to the bacterium, prior to opening sow herds, especially late in the herd closure timeline.

The association between measurements of antimicrobial use and resistance in the faeces microbiota of finisher batches

The objectives were to present three approaches for calculating antimicrobial (AM) use in pigs that take into account the rearing period and rearing site, and to study the association between these measurements and phenotypical resistance and abundance of resistance genes in faeces samples from 10 finisher batches. The AM use was calculated relative to the rearing period of the batches as (i) 'Finisher Unit Exposure' at unit level, (ii) 'Lifetime Exposure' at batch level and (iii) 'Herd Exposure' at herd level. A significant effect on the occurrence of tetracycline resistance measured by cultivation was identified for Lifetime Exposure for the AM class: tetracycline. Furthermore, for Lifetime Exposure for the AM classes: macrolide, broad-spectrum penicillin, sulfonamide and tetracycline use as well as Herd Unit Exposure for the AM classes: aminoglycoside, lincosamide and tetracycline use, a significant effect was observed on the occurrence of genes coding for the AM resistance classes: aminoglycoside, lincosamide, macrolide, β-lactam, sulfonamide and tetracycline. No effect was observed for Finisher Unit Exposure. Overall, the study shows that Lifetime Exposure is an efficient measurement of AM use in finisher batches, and has a significant effect on the occurrence of resistance, measured either by cultivation or metagenomics.

Energy development and hunter success for mule deer and pronghorn in Wyoming

ABSTRACTInfrastructure associated with energy development influences hunter access and introduces disturbance activities to landscapes that can influence habitat selection and behavior of ungulates. Consequently, habitat loss and hunter access concerns must be addressed by wildlife managers as they consider management of populations of western big game species including mule deer (Odocoileus hemionus) and pronghorn (Antilocapra americana). We evaluated whether increased energy development, as quantified through change in well pad density, has affected hunter success of mule deer and pronghorn. Ungulates tend to avoid energy development; therefore, we also evaluated whether hunting statistics can be used to identify potential effects of energy development on mule deer and pronghorn. We included data from 22 of 39 mule deer and 34 of 46 pronghorn Herd Units across Wyoming, USA, from 1980 to 2012. On average, well pad densities across mule deer Herd Units increased from 0.01 km2in 1980 to 0.06 km2in 2012, and well pads in pronghorn Herd Units increased from 0.01 km2to 0.12 km2during the same period. Our results indicated that hunter success for mule deer in Wyoming was positively associated with hunter effort, whereas pronghorn hunter success was negatively associated with hunter effort. Hunter success for both species was unaffected by well pad density. We identified a change in mule deer and pronghorn harvest success associated with hunter numbers and effort; however, harvest statistics were not informative in identifying impacts from energy development on mule deer or pronghorn populations. © 2017 The Wildlife Society.

Oil and gas development influences big‐game hunting in Wyoming

ABSTRACTDevelopment from extracting oil and gas resources can have unintended effects on multiple ecosystem functions, with cascading effects on wildlife, ecosystem services, and local economies. Big‐game hunting opportunities may be closely related to these effects, but empirical analyses of impacts of energy development on hunting are limited. We examined the influence of oil and gas development density on harvest efficiency, or harvest per unit of hunter effort, within all hunt areas in Wyoming, USA, from 2008 to 2014 for 3 big‐game species: elk (Cervus canadensis), mule deer (Odocoileus hemionus), and pronghorn (Antilocapra americana). Using harvest/hunter day as the response variable, we compared linear mixed‐effects models for each species that included total well density (i.e., all wells constructed up to the year of record), active well density (i.e., only those wells currently producing oil or gas in that year), or neither as a predictor variable. We used well densities as indicators of development in the absence of data specifying the locations of other oil and gas infrastructure (e.g., roads, well pads). Models also accounted for the fixed effects of road density, hunter density, proportion of the area that is public land with unrestricted hunter access, proportion of the area that is forested, year of observation, and random effects of variation among hunt areas nested within associated game herd units. Presence of oil and gas wells had a positive influence on harvest efficiency for elk and mule deer. Although there was no overall effect to pronghorn, there was a negative influence of wells on juvenile pronghorn harvest efficiency. Changes in harvest efficiency due to expanding oil and gas development could alter the time spent hunting by hunters and their chances of harvesting an animal. This could have subsequent impacts on hunter satisfaction, game populations, and economic revenue generated from recreational hunters. © 2016 The Wildlife Society.

Influences of supplemental feeding on winter elk calf:cow ratios in the southern Greater Yellowstone Ecosystem

Several elk herds in the Greater Yellowstone Ecosystem are fed during winter to alleviate interactions with livestock, reduce damage to stored crops, and to manage for high elk numbers. The effects of supplemental feeding on ungulate population dynamics has rarely been examined, despite the fact that supplemental feeding is partially justified as necessary for maintaining or enhancing population growth rates. We used linear regression to assess how the presence of feedgrounds, snowpack, summer rainfall, indices of grizzly bear density and wolves per elk, elk population trend counts, brucellosis seroprevalence, and survey date were correlated with midwinter calf:cow ratios, a metric correlated with population growth, from 1983–2010 from 12 ecologically similar elk herd units (7 fed and 5 unfed) in Wyoming, USA. Our statistical approach allowed for rigorous tests of the hypotheses that supplemental feeding had positive effects on calf:cow ratios and reduced sensitivity of calf:cow ratios to bottom-up limitation relative to top-down limitation from native predators. Calf:cow ratios generally declined across all herd units over the study period and varied widely among units with feedgrounds. We found no evidence that the presence of feedgrounds had positive effects on midwinter calf:cow ratios in Wyoming. Further, fed elk showed stronger correlations with environmental factors, whereas calf:cow ratios for unfed elk showed stronger correlations with predator indices. Although we found no consistent association between winter feeding and higher calf:cow ratios, we did not assess late winter mortality and differences in human offtake between fed and unfed regions, which remain a priority for future research. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

The optimal number of heifer calves to be reared as dairy replacements

Dairy farmers often keep almost all their newborn heifer calves despite the high cost of rearing. By rearing all heifer calves, farmers have more security and retain flexibility to cope with the uncertainty in the availability of replacement heifers in time. This uncertainty is due to mortality or infertility during the rearing period and the variation in culling rate of lactating cows. The objective of this study is to provide insight in the economically optimal number of heifer calves to be reared as replacements. A herd-level stochastic simulation model was developed specific for this purpose with a herd of 100 dairy cows; the biological part of the model consisted of a dairy herd unit and rearing unit for replacement heifers. The dairy herd unit included variation in the number of culled dairy cows. The rearing unit incorporated variation in the number of heifers present in the herd by including uncertainty in mortality and variation in fertility. The dairy herd unit and rearing unit were linked by the number of replacement heifers and culled dairy cows. When not enough replacement heifers were available to replace culled dairy cows, the herd size was temporarily reduced, resulting in an additional cost for the empty slots. When the herd size reached 100 dairy cows, the available replacement heifers that were not needed were sold. It was assumed that no purchase of cows and calves occurred. The optimal percentage of 2-wk-old heifer calves to be retained was defined as the percentage of heifer calves that minimized the average net costs of rearing replacement heifers. In the default scenario, the optimal retention was 73% and the total net cost of rearing was estimated at €40,939 per herd per year. This total net cost was 6.5% lower than when all heifer calves were kept. An earlier first-calving age resulted in an optimal retention of 75%, and the net costs of rearing were €581 per herd per year lower than in the default scenario. For herds with a lower or higher culling rate of dairy cows (10 or 40% instead of 25% in the default scenario), it was optimal to retain 35 or 100% of the heifer calves per year. Herds that had a lower or higher cost of empty slots (€50 or €120 per month instead of €82 in the default scenario) had an optimal retention of 49 or 83% per year; the optimal retention percentage was dependent on farm and herd characteristics. For Dutch dairy farming conditions, it was not optimal to keep all heifer calves.

STATUS OF BRUCELLOSIS IN FREE-RANGING ELK AND BISON IN WYOMING

Brucella abortus is the causative agent of brucellosis, a disease enzootic in populations of free-ranging elk (Cervus elaphus) and bison (Bison bison) in the Greater Yellowstone Ecosystem, USA. We define the distribution of the disease in elk throughout Wyoming, USA, using three epidemiologic/geographic classifications based on winter-foraging opportunity. Antibody prevalence for >3,300 yearling and adult, female elk, sampled from supplemental feedgrounds in western Wyoming, USA, since 1985, was 21.9%. Surveillance of nearly 3,800 winter free-ranging, adult, female elk, sampled from herd units adjacent to feedgrounds from 1991 to 2008, indicated a total antibody prevalence of 3.7%. In contrast, none of the 1,930 male and female elk sampled from 1991 to 2008 in herd units distant from feedgrounds in Wyoming, USA, demonstrated exposure to B. abortus. In comparison to elk, bison had a higher incidence of brucellosis. Surveillance of 321 cow bison harvested within the Absaroka and Jackson bison herds in western Wyoming, USA, from 1992 to 2008 yielded an antibody prevalence of 63.9%.

Probable causes of increasing brucellosis in free‐ranging elk of the Greater Yellowstone Ecosystem

While many wildlife species are threatened, some populations have recovered from previous overexploitation, and data linking these population increases with disease dynamics are limited. We present data suggesting that free-ranging elk (Cervus elaphus) are a maintenance host for Brucella abortus in new areas of the Greater Yellowstone Ecosystem (GYE). Brucellosis seroprevalence in free-ranging elk increased from 0-7% in 1991-1992 to 8-20% in 2006-2007 in four of six herd units around the GYE. These levels of brucellosis are comparable to some herd units where elk are artificially aggregated on supplemental feeding grounds. There are several possible mechanisms for this increase that we evaluated using statistical and population modeling approaches. Simulations of an age-structured population model suggest that the observed levels of seroprevalence are unlikely to be sustained by dispersal from supplemental feeding areas with relatively high seroprevalence or an older age structure. Increases in brucellosis seroprevalence and the total elk population size in areas with feeding grounds have not been statistically detectable. Meanwhile, the rate of seroprevalence increase outside the feeding grounds was related to the population size and density of each herd unit. Therefore, the data suggest that enhanced elk-to-elk transmission in free-ranging populations may be occurring due to larger winter elk aggregations. Elk populations inside and outside of the GYE that traditionally did not maintain brucellosis may now be at risk due to recent population increases. In particular, some neighboring populations of Montana elk were 5-9 times larger in 2007 than in the 1970s, with some aggregations comparable to the Wyoming feeding-ground populations. Addressing the unintended consequences of these increasing populations is complicated by limited hunter access to private lands, which places many ungulate populations out of administrative control. Agency-landowner hunting access partnerships and the protection of large predators are two management strategies that may be used to target high ungulate densities in private refuges and reduce the current and future burden of disease.

Comparison of the reproductive performance of sows kept outdoors in Croatia with that of sows kept indoors

In this Eastern-European study the reproductive lifetime performance of indoor or outdoor kept sows were compared. Twenty-one indoor (280–952 sows per herd) and 12 outdoor (35–251 sows per herd) units of identical feeding, similar genetics and health status were evaluated. Indoor sows were kept in identical crates and outdoor sows were kept in uninsulated huts. Indoor kept sows were significantly ( P<0.01) older at culling, had a lower percentage of unproductive days ( P<0.001), lower culling rate but a higher mortality rate ( P<0.05). As a consequence of the lower number of farrowings in the herd outdoor sows produced less piglets born ( P<0.01), liveborn ( P<0.01) and weaned ( P<0.001). The present results indicate that outdoor production systems under unfavorable climatic and environmental condition may be associated with lower reproduction performance. Continental climate with high temperature fluctuations may present a risk factor for successful low-investment outdoor sow systems.

Crossbreeding cattle for dairy production in the tropics: effects of genetic and environmental factors on the performance of improved genotypes on the Cameroon highlands

Abstract Three hundred and thirty (330) records from 363 lactations and 104 cows born between 1979 and 1991 from crossbreeding Holstein-Friesian (H) bulls with H, Ngaoundere Gudali (G) and Holstein × Gudali F1 (H1G1) cows, Montbeliard (M) bulls with G and Montbeliard × Gudali Fl (M1G1) cows and M1G1 bulls with M1G1 cows and raised in the Dairy Herd Unit of the Wakwa Animal and Veterinary Research Station in the sub-humid highlands of Cameroon were analysed to investigate the effects of genotype and environment on lactation and reproductive traits. Fixed effects of genotype season and year of calving parity and age of cow at calving were studied. Lactation milk yield (LMY), lactation length (LL), annualized milk production (AMP), calving interval (C1), dry period (DP) and age at first calving (AFC) were amongst the traits analysed. F1 crosses (H1G1, M1G1), backcrosses (¾ Holstein — ¼ Gudali; ¾ Montbeliard — ¼ Gudali) (H3G1, M3G1) and F2 crosses (MGF2) were compared. Results showed that H1G1 cows were proportionately 0·49 and 0·23 better than their corresponding backcross in LMY and AMP, respectively, while M1G1 cows were proportionately 0·12 and 0·24 inferior to M3G1 in these traits. M1G1 were proportionately superior to MGF2 in LMY (0·05), AMP (-0·04) and AFC (-0·14). M3G1 were superior (0·18 to 0·19) to MGF2 in LMY and AMP. H1G1 were consistently superior to M1G1 for most traits, suggesting that H1G1 may be better than M1G1 for dairy production.

Efficiency of beef production systems: Description and preliminary evaluation of a model

A deterministic beef efficiency model (BEM) was developed for investigating production efficiency. Efficiency was defined, over the lifetime of the herd, as a ratio of total output (lean meat equivalent) from the herd to total input (feed equivalent in Mcal metabolizable energy, ME) to the herd, and has units of g lean meat Mcal −1 ME. The model combines three tandem submodels describing: (1) growth and feed intake, (2) herd structure, and (3) enterprise efficiency. It is capable of investigating efficiency of production in traditional cow-calf systems, dairy-beef systems as well as systems where an offspring's sex-ratio at birth is controlled. It treats the female and her offspring as the basic herd unit and evaluates efficiency in relation to how long the cow stays in the herd (age at culling) and the degree of maturity of her offspring when marketed. Procedures for validating and evaluating behaviour of a beef efficiency model are described. The model was most sensitive to the degree of maturity of the dam. Increasing the dam's maturity by 10% resulted in a large (up to 35%, depending on breed group) decline in efficiency. The model was moderately sensitive to maturing rate and carcass lean content but was not sensitive to mature size or the inflection parameter. Increasing the maturing rate or lean content by 10% results in up to 8·7% increase in efficiency.

HERD SIZE AND UNIT COSTS OF PRODUCTION IN THE ENGLAND AND WALES DAIRY SECTOR

This paper examines the relationship between herd size and unit costs of production in the England and Wales dairy sector. Following the two‐stage estimation procedure of Dawson &amp; Hubbard (1987), longrun average cost (LAC) functions are estimated from cross‐section data for five separate years between 1976/7 and 1986/7. Results show that the LAC curves are U‐shaped but highly skewed, implying that considerable economies of size are present at low output levels but diseconomies at larger levels are much less marked. Over time, technological change in particular has been shifting the LAC curves downward and to the right and away from the sector's long‐run equilibrium. The differential shift of cost curves, depending on the size of production, implies that technological change has been biased in favour of larger herds.

Estimating pregnancy rates from the number of embryos collected and those of transferable quality for Holstein donor females from a single herd unit

Estimating pregnancy rates from the number of embryos collected and those of transferable quality for Holstein donor females from a single herd unit

Comments

In this Eastern-European study the reproductive lifetime performance of indoor or outdoor kept sows were compared. Twenty-one indoor (280–952 sows per herd) and 12 outdoor (35–251 sows per herd) units of identical feeding, similar genetics and health status were evaluated. Indoor sows were kept in identical crates and outdoor sows were kept in uninsulated huts. Indoor kept sows were significantly (P<0.01) older at culling, had a lower percentage of unproductive days (P<0.001), lower culling rate but a higher mortality rate (P<0.05). As a consequence of the lower number of farrowings in the herd outdoor sows produced less piglets born (P<0.01), liveborn (P<0.01) and weaned (P<0.001). The present results indicate that outdoor production systems under unfavorable climatic and environmental condition may be associated with lower reproduction performance. Continental climate with high temperature fluctuations may present a risk factor for successful low-investment outdoor sow systems.

Does Summer Range Quality Influence Sex Ratios among Mule Deer Fawns in Utah?

Larger ratios of males to females were found among fawns from herd units where forage production on the summer ranges was low and the forage base was dominated by browse. Summer ranges where forage production was high and domhted by forbs produced even or female dominated sex ratios. The number of deer harvested per unit area was correlated with sex ratio of the fawn crop: harvests were lower where males were significantly overrep resented in the fawn crop and higher where sex ratios were even or female biased. We previously reported the comparative productivity of mule deer on 2 southeastern Utah mountains that differed markedly in summer range condition but had winter ranges of comparable quality (Pederson and Harper 1978, 1979). The La Sal Mountain mule deer herd was shown to consistently produce about 40% more fawns per doe than the Henry Mountain herd. Deer from the La Sals were also larger than animals of the same age and sex from the Henrys (Pederson and Harper 1978). We could detect no difference in either disease incidence or predation between the 2 herds, but the La Sal Mountain summer range was in good to excellent condition, and the forage base for deer was dominated by forbs. In contrast, the Henry Mountains summer range was in poor to fair condition, and the forage base was heavily dominated by shrubs (Pederson and Harper 1978). Since considerable evidence suggests that nutrition may influence the sex ratio of offspring born to a variety of cervid (deer) species (Julander et al. 1961; Verme 1965, 1967, 1969; Bannikov 1967; Robinette et al. 1973, 1977; McCullough 1979), we expanded our previous study to include a comparison of sex ratios in mule deer herds on 7 ranges known to vary among themselves in respect to vegetative condition. Sex ratio statistics have many implications for management. Medin and Anderson (1979) found that a 4% shift toward females in the ratio resulted in a 16% increase in fawn production. If range condition can be shown to be correlated with herd sex ratios, managers may be able to manipulate sex ratios through management of the forage base. Managers may also be better able to anticipate herd growth potential and prescribe more suitable management and harvest programs through a knowledge of range conditions coupled with inexpensive demographic studies.

Seasonal Movements and Home Ranges of Feral Horse Bands in Wyoming's Red Desert

Feral horses have seasonal movement patterns which correspond to their use of water sources and areas near ridges. Home ranges of horse bands varied in size from 73 to 303 km2. Some bands shared use of a common home range. Those bands having a common range followed similar movement patterns within their home ranges. A herd is defined as a structured social unit made up of bands following movement patterns within a common home range. Movements of feral horses can be important to managers in determining the effects of the horses on the range and in setting boundaries of herd management units. Previously reported feral horse home ranges have varied from 0.9 km2 on Sable Island (Welsh 1975) to 78 km2 for a spring and summer home range in Stone Cabin Valley, Nev. (Green and Green 1977). As part of a general study of feral horses in Wyoming's Red Desert (Miller and Denniston 1979, Boyd 1980, Miller 1980, Miller 1981, Miller 1983), movements and home ranges of the horses were determined. The objectives of this portion of the study were to determine the size of band use areas and to determine if a pattern existed in time of use for any one area.

Factors Influencing Productivity of Two Mule Deer Herds in Utah

Highlight: Doe-fawn counts show that the mule deer herd on the LaSal Mountains of southeastern Utah produced over 38% more fawns per doe than the Henry Mountain herd over a 9-year period. Carcass weights of animals from the LaSal herd were generally greater for all age classes. Observed reproductive differences appear to be unrelated to the incidence of diseases, parasites, or predation. Furthermore, winter ranges are nearly equal in forage quantity and quality on the two ranges. Summer range vegetation on the LaSal Mountains, however, produced more forage of better quality than did similar community types on the Henry Mountains. LaSal summer ranges produced 2,149 kg/ha fresh weight of available forage while similar ranges on the Henrys produced only 1,314 kg/ha. Forbs account for 52% of the forage on LaSal summer ranges but only 12% of the forage on ranges of comparable elevation on the Henrys. The data suggest that the characteristics of the forage found on the summer range, especially the quantity and quality of forbs, exert important influences on productivity of these herds. During the 1950’s, Utah experienced high populations of mule deer (Odocoileus hemiorzus), and a general deterioration of habitat results. In an attempt to correct this condition, the Utah State Division of Wildlife Resources and federal land management agencies embarked on a program to reduce mule deer and livestock numbers to the carrying capacity of the range. Management tools implemented to reduce deer numbers included building access roads, issuing permits for special hunts, and extending hunting seasons. The effect of that program on herd size varied by herd unit. Some herds maintained a high reproductive rate and special controls are still being used to keep such herds in balance with their ranges. Other herds have not responded to reduced hunting pressure; production of fawns appears to be low and herd size has remained static. Because of such apparent differences in productivity, this study was initiated to quantify reproductive differences between two herds and identify factors that might be responsible for observed differences. The LaSal and Henry Mountain deer herds were selected for their apparent differences in fawn production. Both areas are geologically similar, and each is an isolated mountain system rising from the surrounding desert. There is little movement of deer into or out of either herd unit. Research objectives were to determine: (1) fawn production for the two herds; (2) carcass

Tests for the study of pheromones in cows: Akhlebininskii, K. S. & A. A. Ishutov. Zhivotnovodstvo. Mosc., [formula omitted]: 78, 1974. School for Command Improvement of the Ministry of Transport of the USSR (no further details on address available)

In this Eastern-European study the reproductive lifetime performance of indoor or outdoor kept sows were compared. Twenty-one indoor (280–952 sows per herd) and 12 outdoor (35–251 sows per herd) units of identical feeding, similar genetics and health status were evaluated. Indoor sows were kept in identical crates and outdoor sows were kept in uninsulated huts. Indoor kept sows were significantly (P<0.01) older at culling, had a lower percentage of unproductive days (P<0.001), lower culling rate but a higher mortality rate (P<0.05). As a consequence of the lower number of farrowings in the herd outdoor sows produced less piglets born (P<0.01), liveborn (P<0.01) and weaned (P<0.001). The present results indicate that outdoor production systems under unfavorable climatic and environmental condition may be associated with lower reproduction performance. Continental climate with high temperature fluctuations may present a risk factor for successful low-investment outdoor sow systems.