Multiplicative Adjustment Factors Research Articles

Genetic evaluation to design a reference cow population for the Holstein breed in Tunisia: a first step toward genomic selection

Context There is a large gap between developed and developing countries in the field of genetic evaluation of livestock animals. Introduction of genomic evaluation procedures and methods could contribute to reducing this gap. Aims The goal of this study was to select a reference cow population for the Holstein breed in Tunisia. Specific objectives were to update adjustments for non-genetic factors affecting milk yield, estimate genetic parameters for milk yield, and predict cow breeding values. Methods A BLUP animal model was used for 11 175 lactations recorded between 2012 and 2017 from 6251 dairy cattle raised in 33 Holstein dairy herds from three types of herds or production sectors. A pedigree file of 16 211 males and females was included in the genetic evaluation. Multiplicative adjustment factors were computed for age and month of calving, using adjusted 305 days in milk. Key results Month of calving, age at calving and farm ownership were significant sources of variation for milk yield. Cows calving in autumn and early winter (September–January) yielded more milk than those calving in spring (February–May) by 430 kg, and summer (June–August) by 455 kg. Holstein cows in Tunisia reached their maximum milk yield during the fourth lactation. Average adjusted milk yield for days in milk, month and age of calving was 6621 ± 2883 kg. Heritability estimates of adjusted milk yield were 0.14 ± 0.02 for all seven lactations and 0.16 ± 0.03 for the three first lactations. Phenotypic correlations among lactations were all positive, ranging from 0.25 to 0.43. On the basis of two main traditional designs (extreme yield and top accuracy), 1000 cows were selected to form the Tunisian female reference population. Conclusion The first step of genomic evaluation has been realised by forming a reference population from cows selected for adjusted milk yield production, based on their predicted breeding values and accuracies, using a BLUP animal model. Implication In the absence of progeny testing and sufficient proven sires, a cow reference population could represent the alternative for implementing genomic selection in developing countries.

Adjustment Factors for Month of Calving, Age at Calving and Days in Milk for Holteins in Tunisia

Multiplicative adjustment factors for month of calving, age at calving and lactation length were computed for complete lactation records (n= 11’175) recorded between 2012 and 2017 from 6251 dairy cattle raised in 33 Holstein dairy herds. An animal model was used with fixed effects for herd-year-sector, month of calving and age at calving and random and the residual random error. The objectives of this study were: 1) to examine the effect of the non-genetic factors on the milk yield production, 2) to adjust milk yield for non-genetic sources of variation and 3) to examine the effect of milk yield adjustments on estimates of the genetic trend. Main results showed that month of calving, age at calving and lactation length were significant sources of variation for milk yield. Cows calving in the fall and early winter yielded 430 kg and 455 kg more milk than cows calving in spring and summer, respectively. Holsteins in Tunisia reached their maximum milk yield between 68 and 70 months of age. Average adjusted milk yield for days in milk, month and age of calving was 6621±2883 kg. An overall rate of increase in milk yield was found to be 22.68 kg/year over the 15 years period.

Calibrating HCM model for roundabout entry capacity under heterogeneous traffic

Roundabout is a channelized intersection where traffic moves around a central island, clockwise for left-side driving and anti-clockwise for right-side driving. Efficiently designed roundabouts can handle traffic very smoothly without causing any delay. The capacity of roundabouts used to be calculated by the weaving theory in India. However, calculation of the entry capacity in the recent literature is based on critical gaps and follow-up times, and the Highway Capacity Manual of US (HCM 2010) provides an equation to estimate the entry capacity of a roundabout by using the flow in passenger car unit per hour (PCU/h), critical gaps and follow-up times at the entry section. In order to examine whether the HCM equation applies to Indian traffic condition or not, we collected data from five roundabouts in India in this study. Relevant data were extracted/estimated to calibrate parameters of the HCM equation. The PCU for a vehicle was estimated on the basis of lagging headway and width of the vehicle, and the critical gap value for a vehicle was estimated by minimizing the sum of absolute difference in a gap with respect to the highest rejected and accepted gaps. Results show that the critical gap values obtained under heterogeneous traffic conditions are much lower than those given in the literature for homogeneous traffic conditions. In addition, the modified HCM equation based on the critical gap values was verified using the field data taken during the formation of a continuous and stable queue at the entry of a roundabout. It was found that a multiplicative adjustment factor needs to be calculated for different sizes of roundabouts to ensure the adjusted HCM equation represents well the traffic condition prevailing in developing countries like India. A test conducted at another roundabout validated that the entry capacity estimated from the calibrated and adjusted HCM model was consistent with the field entry capacity, and the calibrated and adjusted HCM model could predict the entry capacity of an approach to a roundabout quite accurately.

Refined Use of Satellite Aerosol Optical Depth Snapshots to Constrain Biomass Burning Emissions in the GOCART Model

AbstractSimulations of biomass burning (BB) emissions in global chemistry and aerosol transport models depend on external inventories, which provide location and strength for BB aerosol sources. Our previous work shows that to first order, satellite snapshots of aerosol optical depth (AOD) near the emitted smoke plume can be used to constrain model‐simulated AOD, and effectively, the smoke source strength. We now refine the satellite‐snapshot method and investigate where applying simple multiplicative emission adjustment factors alone to the widely used Global Fire Emission Database version 3 emission inventory can achieve regional‐scale consistency between Moderate Resolution Imaging Spectroradiometer (MODIS) AOD snapshots and the Goddard Chemistry Aerosol Radiation and Transport model. The model and satellite AOD are compared globally, over a set of BB cases observed by the MODIS instrument during the 2004, and 2006–2008 biomass burning seasons. Regional discrepancies between the model and satellite are diverse around the globe yet quite consistent within most ecosystems. We refine our approach to address physically based limitations of our earlier work (1) by expanding the number of fire cases from 124 to almost 900, (2) by using scaled reanalysis‐model simulations to fill missing AOD retrievals in the MODIS observations, (3) by distinguishing the BB components of the total aerosol load from background aerosol in the near‐source regions, and (4) by including emissions from fires too small to be identified explicitly in the satellite observations. The small‐fire emission adjustment shows the complimentary nature of correcting for source strength and adding geographically distinct missing sources. Our analysis indicates that the method works best for fire cases where the BB fraction of total AOD is high, primarily evergreen or deciduous forests. In heavily polluted or agricultural burning regions, where smoke and background AOD values tend to be comparable, this approach encounters large uncertainties, and in some regions, other model‐ or measurement‐related factors might contribute significantly to model‐satellite discrepancies. This work sets the stage for a larger study within the Aerosol Comparison between Observations and Models (AeroCOM) multimodel biomass burning experiment. By comparing multiple model results using the refined technique presented here, we aim to separate BB inventory from model‐specific contributions to the remaining discrepancies.

Multi-rate cubature Kalman filter based data fusion method with residual compensation to adapt to sampling rate discrepancy in attitude measurement system.

This paper investigates the multi-rate inertial and vision data fusion problem in nonlinear attitude measurement systems, where the sampling rate of the inertial sensor is much faster than that of the vision sensor. To fully exploit the high frequency inertial data and obtain favorable fusion results, a multi-rate CKF (Cubature Kalman Filter) algorithm with estimated residual compensation is proposed in order to adapt to the problem of sampling rate discrepancy. During inter-sampling of slow observation data, observation noise can be regarded as infinite. The Kalman gain is unknown and approaches zero. The residual is also unknown. Therefore, the filter estimated state cannot be compensated. To obtain compensation at these moments, state error and residual formulas are modified when compared with the observation data available moments. Self-propagation equation of the state error is established to propagate the quantity from the moments with observation to the moments without observation. Besides, a multiplicative adjustment factor is introduced as Kalman gain, which acts on the residual. Then the filter estimated state can be compensated even when there are no visual observation data. The proposed method is tested and verified in a practical setup. Compared with multi-rate CKF without residual compensation and single-rate CKF, a significant improvement is obtained on attitude measurement by using the proposed multi-rate CKF with inter-sampling residual compensation. The experiment results with superior precision and reliability show the effectiveness of the proposed method.

Effects of Rain on Freeway Traffic in Southern California

A number of studies in the past quantified the effect of rain on traffic parameters but were limited to wet areas. This research expands the literature by studying the effect of rain in a dry area such as Southern California and considering regional differences in the impact. Traffic data (loop detectors) and precipitation data (rain gauges) from the Los Angeles, California, metropolitan area were analyzed to access the effect of rain on traffic stream parameters such as free-flow speed, speed at capacity, and capacity. Rainfall events were categorized as light, medium, and heavy as discussed in the 2010 Highway Capacity Manual. Density plots and fundamental diagrams for rain types proved that free-flow speed, speed at capacity, and capacity were reduced by 5.7%, 6.91%, and 8.65%, respectively, for light rain; 11.71%, 12.34%, and 17.4%, respectively, for medium rain; and 10.22%, 11.85%, and 15.34%, respectively, for heavy rain. The reductions for free-flow speed were lower, whereas for speed at capacity and for capacity, they were higher than those reported in the 2010 manual. Moreover, headway increased during rain; this finding shows cautious driving behavior. Multiplicative weather adjustment factors were computed to compensate for the loss of speed and capacity. Also demonstrated was the spatial and temporal effect of rain on traffic. Downstream traffic was not much affected by a rainfall event, whereas the upstream traffic was negatively affected. This study is expected to support weather-responsive traffic management strategies for dry areas.

Roundabout Capacity in Heterogeneous Traffic Condition: Modification of HCM Equation and Calibration

Abstract The highway capacity manual (HCM-2010) is widely referred document around the globe for planning and design of roads. However, the transferability of HCM recommendations for heterogenous traffic condition represents a significant research issue as they are often not suitable to adequately explain the traffic complexities of a mixed-traffic state. This research investigates the suitability of HCM equations for determining the entry capacity of a four-legged roundabout under mixed traffic condition and proposes a methodology for validating and calibrating HCM equations for performance evaluation. Data corresponding to traffic composition, traffic volume, critical gap and follow-up time have been extracted from the video records collected at two roundabouts. The relationship between entry flow and circulatory flow has been plotted from the observed data when there is a complete saturation in the approach leg and depicted that it follows a negative exponential behavior. It implies that the entry capacity reduces exponentially with the increase in circulating flow. The critical gap has been estimated by various methods such as Maximum Likelihood Method (MLM), Root Mean Square (RMS) method and Probability Equilibrium Method (PEM). Further, a stream equivalent critical gap of 1.60 seconds and stream equivalent follow-up time of 1.24 seconds have been derived due to the mixed traffic scenario at the study location. A multiplicative adjustment factor of 1.1 is suggested for the use of HCM 2010 equation directly to estimate entry capacity under heterogeneous traffic condition. The study results may use for planning and designing of roundabout under mixed-traffic flow condition.

Time occupancy as measure of PCU at four legged roundabouts

This study is carried out to estimate the passenger car unit (PCU) values of different vehicle categories at a typical four-legged roundabout based on the concept of time occupancy. A stream equivalency factor (k) has also been developed based on the estimated PCU to convert the heterogeneous traffic flow into a homogenous stream equivalent without making use of PCU factors. Relationship between entry flow and circulatory flow has been plotted based on the observed data corresponding to the time period in which there was queue formation in the approach. Further, estimated critical gap and follow-up time have been used to derive the capacity by HCM 2010 equation. A multiplicative adjustment factor is suggested for the use of HCM 2010 equation directly in the field to estimate entry flow under heterogeneous traffic condition. The study results may be suitable for revising the code of practice, named IRC 65–1976, and useful for ongoing national-level efforts of developing Indian Highway Capacity Manual.

Effects of birth-rearing type on weaning weights in meat sheep are systematically associated with differences in mean performance among flocks.

BackgroundAdjustment of body weights for systematic environmental effects such as dam age and litter size is essential for accurate prediction of breeding values in meat sheep and often accomplished by pre-adjusting records using simple multiplicative adjustment factors, which are derived as ratios of least-squares means of weights of lambs in target and reference classes. However, increasing use of multibreed genetic evaluations that incorporate data from both purebred and commercial flocks has generated concerns regarding the ability of simple additive or multiplicative adjustment factors to properly correct for environmental effects in flocks that differ widely in mean performance. Thus, consistency of adjustment factors across flocks and systematic effects of the level of flock performance on these factors were evaluated using data from the US National Sheep Improvement Program.MethodsWe used birth and weaning weights of lambs from 29 flocks that had at least 500 records per flock and represented several terminal-sire sheep breeds. Effects of lamb sex, dam age class and litter size on birth weights, and of dam age class and combined effects of type of birth and rearing on weaning weights were evaluated. Interactions between these effects and flock were assessed. Bias associated with different adjustment protocols was evaluated for high- and low-performance flocks.ResultsEffects of litter size and differences between yearling and adult dams varied (P < 0.001) among flocks. For weaning weights, additive adjustment factors were not associated with the level of flock performance, but multiplicative adjustment factors were strongly and inversely related to flock means for weaning weights (W). Flock-specific adjustment factors (F = αWβ) reduced bias in adjusted weaning weights associated with differences in flock performance. By contrast, simple multiplicative adjustment factors were appropriate to adjust birth weights.ConclusionsDifferences in weaning weights among single, twin, and triplet lambs were inversely related to the level of flock performance. Use of simple multiplicative adjustment factors led to adjustment bias when applied across flocks with large differences in mean performance. This bias was reduced by using additive adjustment factors or multiplicative factors that were derived as simple exponential functions of flock means for weaning weight.

Adjustment of Lactation Number and Stage on Informal Linear Type Traits of Holstein Dairy Cattle

A total of 4,323,781 records for informal 16 primary linear descriptive traits of dairy cows in Holstein breed from 1988 to 2007 in USA were analyzed to estimate adjustment factors for lactation number and stage. While all factors in the model were highly significant (P < 0.01), major influences on linear type traits were due to lactation number and stage. The frequencies of lactation number 1 through 6 were 58.6, 22.0, 11.8, 4.8, 2.1, and 0.8%, respectively. Further, the frequencies of lactation stage were 0.7, 76.9, 15.3, 4.9, and 2.1%, respectively, for springing, early, medium, late, and dry. To adjust 16 linear traits (stature, dairy form, strength, body depth, rump width, rump angle, legs rear view, leg set, foot angle, fore udder, rear udder height, rear udder width, udder support, udder depth, and front teat placement), additive and multiplicative adjustment factors of lactation number (lactations 2 to 4) and stage (springing, medium, late and dry) were estimated with the solutions in the generalized linear model, assigning lactation 1 and stage early as base class. Additive adjustment factors of lactation number ranged from 1.23 to 2.908, while multiplicative factors ranged from 0.853 to 2.207. Further, additive and multiplicative adjustment factors for lactation stage ranged from 0.668 to 0.785, and from 0.891 to 1.154. Application of adjustment factors to 20 randomly sampled sub-data sets produced the results that additive adjustment factors for both lactation number and stage reduced more mean square of lactation number and stage over 16 linear traits than any combination of adjustments, and leaded additive adjustment factors for both lactation number and stage as a choice of methods for adjustment of informal 16 primary linear type traits collected by classifiers of AI studs.

Comparison of multiplicative age adjustment factors calculated for milk yield for the Mediterranean Italian Buffalo Breed for two base ages: a first lactation average age base (34 months, parity 1) and a mature age base (55 months, parity 2)

This study was carried out to compare multiplicative age adjustment factors calculated for milk yield for the Mediterranean Italian Buffalo Breed for two different base ages: a mature age base (55 months, parity 2), and a first lactation average age base (34 months, parity 1) using a mixed model procedure. Fixed effects of age-parity classes and random effects of contemporary group, genetic and permanent environmental effects of cows were included in the model. Two data sets were formed: Data Set I consisted of 83,810 lactation records and was used to develop separate multiplicative factors for each base age. Data Set II consisted of 115,242 lactation records and was used to examine the effectiveness of the multiplicative age factors and especially to compare the factors with different base ages. Factors were larger for milk yield adjusted to a mature age than to a first lactation average age. However, age factors followed the same trend and effectively adjusted milk yields for the effect of age at calving for all of the two base ages. The only difference among the two base ages was that the adjusted average milk yields to a first lactation average age base (34 months, parity 1), as expected, were smaller than the adjusted average milk yields to a mature age base (55 months, parity 2).

Estimate of multiplicative and additive age adjustment factors for milk yield for the Mediterranean Italian Buffalo Breed

This study was carried out to estimate multiplicative and additive age adjustment factors for milk yield for the Mediterranean Italian Buffalo Breed for a mature age base (55 months, parity 2) with a mixed model procedure. Fixed effects of age-parity classes and random effects of contemporary group, genetic and permanent environmental effects of cows were included in the model. Two data sets were formed: Data Set I consisted of 83,810 lactation records and was used to develop the age factors. Data Set II consisted of 115,242 lactation records and was used for validation of the age factors estimated from Data Set I. Additive and multiplicative factors followed the same trend within the three parities (parity 1, parity 2, and parity ≥ 3). Averages of milk yield by age class for Data Set II pre-adjusted with multiplicative and additive factors from Data Set I were similar and tended to follow a straight line as expected. However, multiplicative factors might be preferred to additive factors because they would be affected less by an increase of the average milk yield due to selection or management. Age factors were smoothed to reduce differences among factors for similar age-parity classes. The smoothed age factors showed only slight differences among averages for similar age-parity classes, which suggests that the smoothed age factors may be more appropriate than the original factors.

Adjustment of lamb birth and weaning weights for continuous effects of ewe age

AbstractProcedures for continuous adjustment of lamb birth and weaning weights for effects of ewe age were developed using 18 747 birth and 13 139 weaning weight records of Polypay sheep enrolled in the US National Sheep Improvement Program. Changes in birth and weaning weights across ewe age groups were modelled using hybrid curves that combined asymptotic regression models to describe initial increases in lamb weight as ewes moved into adulthood with secondorder polynomials to describe declines in lamb weights in older ewes. Lamb birth and weaning weights were highest (and the asymptotic and polynomial forms comprising the hybrid curves intersected) at ewe ages of 76 and 52 months, respectively. Across all ewe ages, hybrid curves were superior to second- and third-order polynomials in goodness of fit, producing a parabolic form with a flat top and different decay rates on either side of the ewe ages corresponding to maximum lamb weights. Fourth- and fifth-degree polynomials were equivalent to hybrid curves in goodness of fit, but generally did not produce reasonable predictions for the oldest ewes. Adjustment factors derived from the hybrid curve predicted that lamb birth weight would increase from 76% of maximum in 11-month-old ewes to 90 and 96% of maximum in 24- and 36-month-old ewes, respectively, and then decline to 97% of maximum at 105 months. For weaning weight, 83, 95, 99, and 93% of maximum lamb weight were attained at ewe ages of 11, 24, 36, and 105 months, respectively. Resulting multiplicative adjustment factors avoid discontinuities at boundaries between ewe age categories and are particularly useful in accelerated or other multiple-season lambing systems.

Adjustment for non-genetic effects on body weight and size in Angora goats

Data on 864 Angora goats, collected from 1988 to 2000, were used to study non-genetic effects on body weight and daily gain from birth to 24 months of age and body size at different ages. Non-genetic factors included birth year, birth month, sex, age of kids, age of dam, type of birth and rearing. Birth year, sex and type of birth and rearing were the major factors affecting growth of Angora goats. Age of dam influenced body weights at birth and weaning, early growth rate and height at withers. The unfavorable effects of young dams on their kids suggested that it was essential to strengthen the feeding and management of kids, especially in maintaining the body weight during mating and pregnancy. Growth rate of kids born from November to February was relatively slower during sucking period but more rapid after weaning than those born between March and July. This can result from seasonal change and suggests that it is necessary to plan the kidding season rationally by controlling the estrus and mating time. The kids born as twin had lower birth weight and slower early growth rate than those born as single, but had a higher post-weaning growth rate. The general trend was the differences between singles and twins decreased as the kids became older, possibly due to a decreasing maternal effect and a growth compensation of twin kids. Additive and multiplicative adjustment factors for body weights and growth rates were derived from least squares means of subclasses for birth month, sex, age of dam, type of birth and rearing. Subclass variances were tested for heterogeneity with Levene's test. The results were used to determine appropriate adjustment for non-genetic effects.

Real-Time Variational Assimilation of Hydrologic and Hydrometeorological Data into Operational Hydrologic Forecasting

Variational assimilation (VAR) of hydrologic and hydrometeorological data into operational hydrologic forecasting is explored. The data assimilated are the hourly real-time observations of streamflow and precipitation, and climatological estimates of potential evaporation (PE). The hydrologic system considered is a single headwater basin for which soil moisture accounting and routing are carried out in a lumped fashion via the Sacramento model (SAC) and the unit hydrograph (UH), respectively. The control variables in the VAR formulation are the fast-varying SAC soil moisture states at the beginning of the assimilation window and the multiplicative adjustment factors to the estimates of mean areal precipitation (MAP) and mean areal potential evaporation (MAPE) for each hour in the assimilation window. In a separate application of VAR as a parameter estimation tool, the estimation of empirical UH is also explored by treating its ordinates as the control variables. To evaluate the assimilation procedure thus developed, streamflow was forecast with and without the aid of VAR for three basins in the southern plains under the assumption of perfectly forecast future mean areal precipitation (FMAP). The streamflow forecasts were then compared with each other and with those based on persistence and the state space-based state-updating procedure, the state-space Sacramento model (SS-SAC). The results indicate that the VAR procedure significantly improves the accuracy of the basic forecast at short lead times and compares favorably with SS-SAC.

Real-Time Adjustment of Range-Dependent Biases in WSR-88D Rainfall Estimates due to Nonuniform Vertical Profile of Reflectivity

Abstract A procedure for real-time adjustment of range-dependent biases in Weather Surveillance Radar-1988 Doppler version (WSR-88D) rainfall estimates due to nonuniform vertical profile of reflectivity is proposed. Using volume-scan measurements of effective reflectivity, the procedure estimates conditional mean and variance profiles of point reflectivity in the vertical and calculates, as a function of elevation angle and slant range, a multiplicative adjustment factor to be applied to the apparent radar rain rate. As a by-product, the maximum effective coverage of radar is also delineated, outside of which radar rainfall estimates are subject to beam overshooting. To evaluate the procedure, unadjusted and adjusted radar rainfall estimates from a Pacific Northwest winter storm are examined and compared with rain gauge data.

Efeito do ajustamento para os períodos de serviço anterior e corrente sobre os valores genéticos de touros para produção de leite na raça Holandesa

Os períodos de serviço anterior e corrente foram considerados, simultaneamente, como efeitos fixos em um modelo de touro para produção de leite até 305 dias (L305), contendo ainda os efeitos fixos rebanho-ano-estação e grau de sangue, idade da vaca como covariável (até 3º grau) e os efeitos aleatórios de touro e vaca. Foi usada uma matriz de parentesco que incluiu o touro, seu pai e sua mãe. O mesmo modelo, excluindo-se idade da vaca, foi usado para produção de leite até 305 dias ajustada para idade à maturidade (PROAJU). O método da máxima verossimilhança restrita (REML) foi usado para resolução das equações por meio do programa MTDFREML. Pelas soluções, concluiu-se que a PROAJU aumentou 902 kg, quando o período de serviço anterior variou de 20 a 300 dias. Este aumento foi de 813 kg para a mesma variação no período de serviço corrente. Os valores genéticos dos touros para PROAJU foram obtidos em quatro conjuntos de dados, usando-se o mesmo modelo anterior com exclusão dos períodos de serviço anterior e corrente. Os registros de produção foram ajustados com os fatores multiplicativos obtidos para período de serviço anterior e corrente e os touros foram reavaliados. Correlações de ordem entre valores genéticos dos touros para produção de leite ajustada e não-ajustada foram próximas de 1. As médias das diferenças entre valores genéticos dos touros com as produções de leite ajustadas e não-ajustadas para os períodos de serviço foram aproximadamente zero, indicando que os fatores para período de serviço foram adequados para os dados.

Influência dos períodos de serviço anterior e corrente e do período seco anterior sobre a produção de leite na raça holandesa

O objetivo deste trabalho foi avaliar os efeitos dos períodos de serviço anterior e corrente e do período seco anterior ajustados simultaneamente como efeitos fixos em modelo de touro para produção de leite até 305 dias, contendo ainda os efeitos fixos de rebanho-ano-estação, grupo genético e idade da vaca e os efeitos aleatórios de touro e vaca. Foi usada matriz de parentesco, que incluiu o touro, o seu pai e sua mãe. O mesmo modelo com exclusão da idade da vaca foi usado para produção de leite até 305 dias ajustada à maturidade. As soluções nas análises foram obtidas usando-se o método da máxima verossimilhança restrita e o algoritmo livre de derivada. Polinômios ortogonais foram ajustados para suavização das soluções. Soluções e valores previstos para produção até 305 dias não foram apresentados, por terem seguido mesma tendência da produção até 305 dias ajustada à maturidade. A produção até 305 dias ajustada à maturidade aumentou 950 kg, quando o período de serviço anterior variou de 20 a 300 dias. Este aumento foi de 802 kg para a mesma variação do período de serviço corrente. Vacas com período seco de 60 a 80 dias obtiveram a produção de leite mais alta na lactação seguinte. Valores estimados da heritabilidade foram 0,02 para o período de serviço e 0,08 para o período seco, quando a produção total foi considerada no modelo, e 0,12 quando foi excluída. Fatores multiplicativos foram estimados para o ajustamento da produção de leite para os efeitos de período de serviço e seco.

A comparison of thermospheric [O] derived at EISCAT with [O] predicted by MSIS

In recent years aeronomic considerations of the value of the O+−O collision cross‐section (QO+−O) in the ionospheric F‐region have resulted in many values of a multiplicative adjustment factor (F) to the standard value of QO+−O which had been in use from the mid sixties to the late eighties. QO+−O and oxygen concentration ([O]) appear as a product in aeronomic calculations, so F can also be considered a multiplicative factor for the oxygen. [O] derived at EISCAT for data from 1984 to 1997 is compared to oxygen predicted by MSIS and values of F are calculated as a function of solar cycle and year. There is a solar cycle variation, with F varying from .65 at solar minimum to 1.18 at solar maximum. For solar fluxes between 100 and 160 solar flux units F at EISCAT is in good agreement with a value of F calculated for MSIS. No long term trend in the relationship between EISCAT [O] and MSIS [O] was found.

Environmental effects on growth traits and fleece weights in Baluchi sheep

SummaryData from 20 249 Baluchi lambs, recorded from 1966 to 1989 in the Abbasabad Sheep Breeding Station located in the north‐east of Iran (Mashhad), were used to investigate the influences of environmental factors, multiplicative and additive adjustment factors for lamb weights at birth (BW), weaning (WW), six month (W6) and 12 months (YW) of age, preweaning (WG) and postweaning (PWG) gains, lamb fleece weight (LFW) and ewe fleece weight before first mating (FW1). Significant effects of flock, year, sex, birth‐rearing type and parity of ewe were observed for lamb weight at different ages and weight gains. Male lambs were heavier than females and the difference between them increased with age of lamb. The ratio of single lamb weight (S–S) to twin birth and single rearing (Tw–S) and twin birth and twin rearing (Tw–Tw) decreased with advancing age of lamb. Lambs born at parity 4–6 were heavier than lambs of younger or older ewes. Weight gain declined in all subclasses from weaning to 12 months of age. The effects of flock and year were significant for lamb and ewe fleece weights. In addition the effect of sex was significant for LFW. Based on a test of heterogeneity of variance among class levels of fixed effects, multiplicative adjustment of sex, type of birth and parity of ewe for BW, and the effects of sex and parity of ewe for lamb weight at other ages were recommended. For LFW the effect of sex should be considered for multiplicative adjustment. Due to homogeneous variances, the additive adjustment for effect of birth‐rearing type should be considered for WW, W6 and YW.