Effects of dalfampridine on multi-dimensional aspects of gait and dexterity in multiple sclerosis among timed walk responders and non-responders.

BACKGROUND: Dalfampridine extended release 10mg tablets (D-ER) have demonstrated improvement in walking for ambulatory persons with multiple sclerosis (pwMS), termed "responders." OBJECTIVE: This study examined the extent additional aspects of gait and dexterity change for patients prescribed D-ER. METHODS: Over 14-weeks, walking endurance, dynamic gait, self-report walking ability and fine and gross dexterity were examined in pwMS prescribed D-ER as a part of routine clinical care. RESULTS: The final results (n=39) validate that a subset of pwMS improve walking speed (Time 25-Foot Walk Test, p<0.0001). Significant improvements in gait and dexterity were observed even among participants who did not improve walking speed. Improvements were evident in gait and dexterity domains including Six Minute Walk Test, p=0.007, Six-Spot Step Test, p<0.0001, Multiple Sclerosis Walking Scale-12, p<0.0001, Nine Hole Peg Test, p<0.0001 dominant and non-dominant sides, and Box and Blocks Test, p=0.005 and 0.002, dominant and non-dominant sides, respectively. CONCLUSIONS: These findings suggest that D-ER may be a potential treatment for gait impairments, beyond walking speed and dexterity in pwMS. Further investigation regarding D-ER response is warranted.

Use of residual feed intake in Holsteins during early lactation shows potential to improve feed efficiency through genetic selection.

Improved feed efficiency is a primary goal in dairy production to reduce feed costs and negative impacts of production on the environment. Estimates for efficiency of feed conversion to milk production based on residual feed intake (RFI) in dairy cattle are limited, primarily due to a lack of individual feed intake measurements for lactating cows. Feed intake was measured in Holstein cows during the first 90 d of lactation to estimate the heritability and repeatability of RFI, minimum test duration for evaluating RFI in early lactation, and its association with other production traits. Data were obtained from 453 lactations (214 heifers and 239 multiparous cows) from 292 individual cows from September 2007 to December 2011. Cows were housed in a free-stall barn and monitored for individual daily feed consumption using the GrowSafe 4000 System (GrowSafe Systems, Ltd., Airdrie, AB, Canada). Animals were fed a total mixed ration 3 times daily, milked twice daily, and weighed every 10 to 14 d. Milk yield was measured at each milking. Feed DM percentage was measured daily, and nutrient composition was analyzed from a weekly composite. Milk composition was analyzed weekly, alternating between morning and evening milking periods. Estimates of RFI were determined as the difference between actual energy intake and predicted intake based on a linear model with fixed effects of parity (1, 2, ≥ 3) and regressions on metabolic BW, ADG, and energy-corrected milk yield. Heritability was estimated to be moderate (0.36 ± 0.06), and repeatability was estimated at 0.56 across lactations. A test period through 53 d in milk (DIM) explained 81% of the variation provided by a test through 90 DIM. Multiple regression analysis indicated that high efficiency was associated with less time feeding per day and slower feeding rate, which may contribute to differences in RFI among cows. The heritability and repeatability of RFI suggest an opportunity to improve feed efficiency through genetic selection, which could reduce feed costs, manure output, and greenhouse gas emissions associated with dairy production.

Multibreed genomic evaluations using purebred Holsteins, Jerseys, and Brown Swiss.

Multibreed models are currently used in traditional US Department of Agriculture (USDA) dairy cattle genetic evaluations of yield and health traits, but within-breed models are used in genomic evaluations. Multibreed genomic models were developed and tested using the 19,686 genotyped bulls and cows included in the official August 2009 USDA genomic evaluation. The data were divided into training and validation sets. The training data set comprised bulls that were daughter proven and cows that had records as of November 2004, totaling 5,331 Holstein, 1,361 Jersey, and 506 Brown Swiss. The validation data set had 2,508 Holstein, 413 Jersey, and 185 Brown Swiss bulls that were unproven (no daughter information) in November 2004 and proven by August 2009. A common set of 43,385 single nucleotide polymorphisms (SNP) was used for all breeds. Three methods of multibreed evaluation were investigated. Method 1 estimated SNP effects separately within breed and then applied those breed-specific SNP estimates to the other breeds. Method 2 estimated a common set of SNP effects from combined genotypes and phenotypes of all breeds. Method 3 solved for correlated SNP effects within each breed estimated jointly using a multitrait model where breeds were treated as different traits. Across-breed genomic predicted transmitting ability (GPTA) and within-breed GPTA were compared using regressions to predict the deregressed validation data. Method 1 worked poorly, and coefficients of determination (R(2)) were much lower using training data from a different breed to estimate SNP effects. Correlations between direct genomic values computed using training data from different breeds were less than 30% and sometimes negative. Across-breed GPTA from method 2 had higher R(2) values than parent average alone but typically produced lower R(2) values than the within-breed GPTA. The across-breed R(2) exceeded the within-breed R(2) for a few traits in the Brown Swiss breed, probably because information from the other breeds compensated for the small numbers of Brown Swiss training animals. Correlations between within-breed GPTA and across-breed GPTA ranged from 0.91 to 0.93. The multibreed GPTA from method 3 were significantly better than the current within-breed GPTA, and adjusted R(2) for protein yield (the only trait tested for method 3) were highest of all methods for all breeds. However, method 3 increased the adjusted R(2) by only 0.01 for Holsteins, ≤0.01 for Jerseys, and 0.01 for Brown Swiss compared with within-breed predictions.

Factors associated with frequency of abortions recorded through Dairy Herd Improvement test plans.

Frequency of abortions recorded through Dairy Herd Improvement (DHI) testing was summarized for cows with lactations completed from 2001 through 2009. For 8.5 million DHI lactations of cows that had recorded breeding dates and were >151 d pregnant at lactation termination, the frequency of recorded abortions was 1.31%. Effects of year, herd-year, month, and pregnancy stage at lactation termination; parity; breed; milk yield; herd size; geographic region; and state within region associated with DHI-recorded abortion were examined. Abortions recorded through DHI (minimum gestation of 152 d required) were more frequent during early gestation; least squares means (LSM) were 4.38, 3.27, 1.19, and 0.59% for 152 to 175, 176 to 200, 201 to 225, and 226 to 250 d pregnant, respectively. Frequency of DHI-recorded abortions was 1.40% for parity 1 and 1.01% for parity ≥ 8. Abortion frequency was highest from May through August (1.42 to 1.53%) and lowest from October through February (1.09 to 1.21%). Frequency of DHI-recorded abortions was higher for Holsteins (1.32%) than for Jerseys (1.10%) and other breeds (1.27%). Little relationship was found between DHI-recorded abortions and herd size. Abortion frequencies for effects should be considered to be underestimated because many abortions, especially those caused by genetic recessives, go undetected. Therefore, various nonreturn rates (NRR; 60, 80, …, 200 d) were calculated to document pregnancy loss confirmed by the absence of homozygotes in the population. Breeding records for April 2011 US Department of Agriculture sire conception rate evaluations were analyzed with the model used for official evaluations with the addition of an interaction between carrier status of the service sire (embryo's sire) and cow sire (embryo's maternal grandsire). Over 13 million matings were examined using various NRR for Holstein lethal recessive traits (brachyspina and complex vertebral malformation) and undesirable recessive haplotypes (HH1, HH2, and HH3) as well as >61,000 matings for a Brown Swiss haplotype (BH1), and 670,000 matings for a Jersey haplotype (JH1). Over 80% of fertility loss occurred by 60 d after breeding for BH1, HH3, and JH1, by 80 d for HH2, by 100 d for BY, and by 180 d for HH1. For complex vertebral malformation, fertility loss increased from 40 to 74% across gestation. Association of undesirable recessives with DHI-recorded abortions ranged from 0.0% for Jerseys to 2.4% for Holsteins.

Use of the Illumina Bovine3K BeadChip in dairy genomic evaluation.

Genomic evaluations using genotypes from the Illumina Bovine3K BeadChip (3K) became available in September 2010 and were made official in December 2010. The majority of 3K-genotyped animals have been Holstein females. Approximately 5% of male 3K genotypes and between 3.7 and 13.9%, depending on registry status, of female genotypes had sire conflicts. The chemistry used for the 3K is different from that of the Illumina BovineSNP50 BeadChip (50K) and causes greater variability in the accuracy of the genotypes. Approximately 2% of genotypes were rejected due to this inaccuracy. A single nucleotide polymorphism (SNP) was determined to be not usable for genomic evaluation based on percentage missing, percentage of parent-progeny conflicts, and Hardy-Weinberg equilibrium discrepancies. Those edits left 2,683 of the 2,900 3K SNP for use in genomic evaluations. The mean minor allele frequencies (MAF) for Holstein, Jersey, and Brown Swiss were 0.32, 0.28, and 0.29, respectively. Eighty-one SNP had both a large number of missing genotypes and a large number of parent-progeny conflicts, suggesting a correlation between call rate and accuracy. To calculate a genomic predicted transmitting ability (GPTA) the genotype of an animal tested on a 3K is imputed to the 45,187 SNP included in the current genomic evaluation based on the 50K. The accuracy of imputation increases as the number of genotyped parents increases from none to 1 to both. The average percentage of imputed genotypes that matched the corresponding actual 50K genotypes was 96.3%. The correlation of a GPTA calculated from a 3K genotype that had been imputed to 50K and GPTA from its actual 50K genotype averaged 0.959 across traits for Holsteins and was slightly higher for Jerseys at 0.963. The average difference in GPTA from the 50K- and 3K-based genotypes across trait was close to 0. The evaluation system has been modified to accommodate the characteristics of the 3K. The low cost of the 3K has greatly increased genotyping of females. Prior to the availability of the 3K (August 2010), female genotyping accounted for 38.7% of the genotyped animals. In the past year, the portion of total genotypes from females across all chip types rose to 59.0%.

Triennial Lactation Symposium: Opportunities for improving milk production efficiency in dairy cattle.

Increasing feed costs and the desire to improve environmental stewardship have stimulated renewed interest in improving feed efficiency of livestock, including that of US dairy herds. For instance, USDA cost projections for corn and soybean meal suggest a 20% increase over 2010 pricing for a 16% protein mixed dairy cow ration in 2011, which may lead to a reduction in cow numbers to maintain profitability of dairy production. Furthermore, an October 2010 study by The Innovation Center for US Dairy to assess the carbon footprint of fluid milk found that the efficiency of feed conversion is the single greatest factor contributing to variation in the carbon footprint because of its effects on methane release during enteric fermentation and from manure. Thus, we are conducting research in contemporary US Holsteins to identify cows most efficient at converting feed to milk in temperate climates using residual feed intake (RFI), a measure used successfully to identify the beef cattle most efficient at converting feed to gain. Residual feed intake is calculated as the difference between predicted and actual feed intake to support maintenance and production (e.g., growth in beef cattle, or milk in dairy cattle). Heritability estimates for RFI in dairy cattle reported in the literature range from 0.01 to 0.38. Selection for a decreased RFI phenotype can reduce feed intake, methane production, nutrient losses in manure, and visceral organ weights substantially in beef cattle. We have estimated RFI during early lactation (i.e., to 90 d in milk) in the Beltsville Agricultural Research Center Holstein herd and observed a mean difference of 3.7 kg/d (P < 0.0001) in actual DMI between the efficient and inefficient groups (±0.5 SD from the mean RFI of 0), with no evidence of differences (P > 0.20) in mean BW, ADG, or energy-corrected milk exhibited between the 2 groups. These results indicate promise for using RFI in dairy cattle to improve feed conversion to milk. Previous and current research on the use of RFI in lactating dairy cattle are discussed, as well as opportunities to improve production efficiency of dairy cattle using RFI for milk production.

Harmful recessive effects on fertility detected by absence of homozygous haplotypes.

Five new recessive defects were discovered in Holsteins, Jerseys, and Brown Swiss by examining haplotypes that had a high population frequency but were never homozygous. The method required genotypes only from apparently normal individuals and not from affected embryos. Genotypes from the BovineSNP50 BeadChip (Illumina, San Diego, CA) were examined for 58,453 Holsteins, 5,288 Jerseys, and 1,991 Brown Swiss with genotypes in the North American database. Haplotypes with a length of ≤ 75 markers were obtained. Eleven candidate haplotypes were identified, with the earliest carrier born before 1980; 7 to 90 homozygous haplotypes were expected, but none were observed in the genomic data. Expected numbers were calculated using either the actual mating pattern or assuming random mating. Probability of observing no homozygotes ranged from 0.0002 for 7 to 10⁻45 for 90 expected homozygotes. Phenotypic effects were confirmed for 5 of the 11 candidate haplotypes using 14,911,387 Holstein, 830,391 Jersey, and 68,443 Brown Swiss records for conception rate. Estimated effect for interaction of carrier service sire with carrier maternal grandsire ranged from -3.0 to -3.7 percentage points, which was slightly smaller than the -3.9 to -4.6 percentage points expected for lethal recessives but slightly larger than estimated effects for previously known lethal alleles of -2.5 percentage points for brachyspina and -2.9 percentage points for complex vertebral malformation. Conception rate was coded as a success only if the gestation went to term or the cow was confirmed to be pregnant. Estimated effect of carrier interaction for stillbirth rate based on 10,876,597 Holstein and 25,456 Jersey records was small. Thus, lethal effects may include conception, gestation, and stillbirth losses. Carrier frequency has been >20% for many years for the confirmed defect in Jerseys and is currently 16% for the defect in Brown Swiss. The 3 defects discovered in Holsteins have carrier frequencies of 2.7 to 6.4% in the current population. For previously known defects, map locations and lack of homozygotes were consistent with the literature and lethal recessive inheritance, but numbers of expected homozygotes for some were small because of low frequency. Very large genotypic and phenotypic data sets allow efficient detection of smaller and less frequent effects. Haplotype tests can help breeders avoid carrier matings for such defects and reduce future frequencies.

Genomic inbreeding and relationships among Holsteins, Jerseys, and Brown Swiss.

Genomic measures of relationship and inbreeding within and across breeds were compared with pedigree measures using genotypes for 43,385 loci of 25,219 Holsteins, 3,068 Jerseys, and 872 Brown Swiss. Adjustment factors allow genomic and pedigree relationships to match more closely within breeds and in multibreed populations and were estimated using means and regressions of genomic on pedigree relationships and allele frequencies in base populations. Correlations of genomic relationships with pedigree inbreeding were higher within each breed when an allele frequency of 0.5, rather than base population frequencies, was used, whereas correlations of average genomic relationships with average pedigree relationships and also reliabilities of genomic evaluations were higher using base population frequencies. Allele frequencies differed in the 3 breeds and were correlated by 0.65 to 0.67 when estimated from genotyped animals compared with 0.72 to 0.74 when estimated from breed base populations. The largest difference in allele frequency was between Holstein and the other breeds on chromosome Bos taurus autosome 4 near a gene affecting appearance of white skin patches (vitiligo) in humans. Each animal's breed composition was predicted very accurately with a standard deviation of <3% using regressions on genotypes at all loci or less accurately with a standard deviation of <6% using subsets of loci. Genomic future inbreeding (half an animal's mean genomic relationship to current animals of the same breed) was correlated by 0.75 to 0.94 with expected future inbreeding (half the average pedigree relationship). Correlations of both were slightly higher with parent averages than with genomic evaluations for net merit of young Holstein bulls. Thus, rates of increase in genomic and pedigree inbreeding per generation should be slightly reduced with genomic selection, in agreement with previous simulations. Genomic inbreeding and future inbreeding have been provided with individual genomic predictions since 2008. New methods to adjust pedigree and genomic relationship matrices so that they match may provide an improved basis for multibreed genomic evaluation. Positive definite matrices can be obtained by adjusting pedigree relationships for covariances among base animals within breed, whereas adjusting genomic relationships to match pedigree relationships can introduce negative eigenvalues. Pedigree relationship matrices ignore common ancestry shared by base animals within breed and may not approximate genomic relationships well in multibreed populations.

Differences among methods to validate genomic evaluations for dairy cattle.

Two methods of testing predictions from genomic evaluations were investigated. Data used were from the August 2006 and April 2010 official USDA genetic evaluations of dairy cattle. The training data set consisted of both cows and bulls that were proven (had own or daughter information) as of August 2006 and included 8,022, 1,959, and 1,056 Holsteins, Jerseys, and Brown Swiss, respectively. The validation data set consisted of bulls that were unproven as of August 2006 and were proven by April 2010 with 2,653, 411, and 132 Holsteins, Jerseys, and Brown Swiss for the production traits. Method 1 used the training animal's predicted transmitting ability (PTA) from August of 2006. Method 2 used the training animal's April 2010 PTA to estimate single nucleotide polymorphism effects. Both methods were tested using several regressions with the same validation animals. In both cases, the validation animals were tested using the deregressed April 2010 PTA. All traits that had genomic evaluations from the official USDA April 2010 genetic evaluations were tested. Results included bias, differences from expected regressions (calculated using selection intensities), and the coefficients of determination. The genomic information increased the predictive ability for most of the traits in all of the breeds. The 2 methods of testing resulted in some differences that would affect interpretation of results. The coefficient of determination was higher for all traits using method 2. This was the expected result as the data were not independent because evaluations of the validation bulls contributed to their sires' evaluations. The regression coefficients from method 2 were often higher than the regression coefficients from method 1. Many traits had regression coefficients that were higher than 2 standard deviations from the expected regressions when using method 2. This was partially due to the lack of independence of the training and validation data sets. Most traits did have some level of bias in the prediction equations, regardless of breed. The use of method 1 made it possible to evaluate the increased accuracy in proven first-crop bull evaluations by using genomic information. Proven first-crop bulls had an increase in accuracy from the addition of genomic information. It is advised to use method 1 for validation of genomic evaluations.

Interaction of energy balance, feed efficiency, early lactation health events, and fertility in first-lactation Holstein, Jersey, and reciprocal F1 crossbred cows.

First-lactation Holstein (HH), Jersey (JJ), and crossbred cows (HJ and JH, with sire breed listed first, followed by dam breed) were observed for cumulative energy intake (CEI15) and energy used for milk production (CEL15) at wk 15 of lactation in addition to recordings of health problems and pregnancy. Cumulative energy balance (CEB15) was calculated from CEI15 and estimates of expenditures at wk 15 of lactation. Feed efficiency (FE15) was calculated by dividing CEL15 by CEI15. Data included 140 cows with 43, 34, 41, and 22 in the HH, HJ, JH, and JJ groups, respectively. The first incidence of displaced abomasum (DA), ketosis (KET), mastitis (MAST), and metritis (MET) was recorded in the first 100 d of lactation with an incidence of the disease coded as 1 and no incidence coded as 0. Pregnancy (PREG) at d 150 was recorded as 1 if a cow had conceived by d 150 and 0 if she had not. Logistic regression was used to analyze health and fertility with fixed effects in the model including genetic group, linear and quadratic effects for age at calving, and year-season of freshening group. Pregnancy was analyzed with the same variables and the addition of CEB15. In other analyses, CEB15, CEI15, CEL15, and FE15 were response variables with the same explanatory variables plus health events (MAST, DA, MET, and KET), where each health event was a separate analysis. Genetic group effects were significant in the occurrence of MAST and a trend for MET, but were not significant for PREG, DA, and KET. Significant odds ratio for MAST was 19.6 for HJ cows when compared with that for HH cows. Thus, HJ cows were 19.6 times more likely than HH cows to have an incidence of MAST. The trend was for HJ and JH to have a lower odds ratio of MET than that of HH. No other genetic group effects were significant in any of the disease and PREG models. The linear and quadratic terms for age at calving were not significant. An occurrence of MAST decreased FE15 by 5.2±2.2%. Mastitis also decreased CEI15 and CEL15, but the compensatory reductions left the CEB15 unaffected. An occurrence of a DA decreased CEI15 and an incidence of KET decreased CEB15.

Energy balance in first-lactation Holstein, Jersey, and reciprocal F1 crossbred cows in a planned crossbreeding experiment.

The Virginia Tech crossbreeding project began in the fall of 2002 by mating Holstein (H) and Jersey (J) foundation females to Holstein and Jersey bulls to create HH, HJ, JH, and JJ genetic groups, where the sire breed is listed first followed by dam breed. Collection of individual daily feed intakes began in September 2005 and continued through November 2008, resulting in observations on 43, 34, 41, and 22 HH, HJ, JH, and JJ cows, respectively. Intakes were measured for 2 wk out of every 6-wk period for first-lactation cows less than 310 d in milk. The ration was analyzed for dry matter and nutrient content, which was used to calculate net energy of lactation (NEL, Mcal/kg). Body and milk weights were collected daily with milk components measured monthly. The NEL requirements for maintenance, growth (in the form of retained energy), pregnancy, and production were calculated using National Research Council (2001) equations. Random regression models were used to predict consumed NEL and NEL required for production, maintenance, and body weight at every week in lactation. Energy required for growth was calculated for each cow at each stage of lactation using five 2-mo stages. Energy balance was estimated by subtracting the predicted energy required for production, maintenance, growth, and pregnancy from the predicted NEL consumed. A linear model with fixed effects of genetic group, year-season of calving group, and a linear and quadratic effect of age at calving was used to analyze the energy terms. The HJ and JH groups were not different in any of the analyses for energy terms. The HH cows consumed more energy than did HJ and JJ cows. There were no genetic group differences for total energy for pregnancy. The HH, HJ, and JH groups were not different from each other for energy required for production but required more energy for production than the JJ. The JH allocated a lower percentage of their energy intake to maintenance than the HH (25.7 to 27.4%) and the JJ allocated less energy to growth than the HH and HJ. Genetic group explained significant variation for percentage of energy partitioned to production with the JJ allocating more energy to production than the HH (66.3 vs. 60.9%). Genetic group differences in characterization of energy balance warrant further study.

Dystocia, stillbirth, gestation length, and birth weight in Holstein, Jersey, and reciprocal crosses from a planned experiment.

Holstein and Jersey cows were mated to 4 Holstein (H) bulls and 4 Jersey (J) bulls to create HH, HJ, JH, and JJ genetic groups (sire breed listed first) in a diallele crossbreeding scheme. Calvings (n = 756) occurred in research herds in Virginia, Kentucky, and North Carolina with 243, 166, 194, and 153 calvings in the HH, HJ, JH, and JJ groups, respectively. Birth weights (BW), dystocia scores (0 for unassisted and 1 for assisted), and stillbirth (0 for alive or 1 for dead within 48 h) were recorded at calving. Gestation lengths (GL) were determined from breeding dates. An animal model was used to analyze BW and GL, and an animal model with logistic regression was used for dystocia and stillbirth. Fixed effects considered for model inclusion were genetic group, herd-year-season, sex, parity (primiparous or multiparous), twin status, and gestation length. Genetic group and effects significant in the model building process were kept in the final model for each trait. Heifer calves had lower BW, shorter GL, and had a lower odds ratio (0.53) for dystocia than bull calves. Twins had lower BW, shorter GL, were 3.86 times more likely to experience dystocia, and 7.80 times more likely to be stillborn than single births. Primiparous cows had calves with lower BW, shorter GL, were 2.50 times more likely to require assistance at birth, and were 2.35 times more likely to produce stillborns than calves from multiparous cows. Genetic group did not affect GL. Least squares means (kg) for BW were 37.7 +/- 1.1, 29.1 +/- 1.1, 30.3 +/- 1.0, and 22.5 +/- 1.3 for HH, HJ, JH, and JJ, respectively. Animals in HH weighed more than animals of other genetic groups; the JJ group had the smallest BW, with no differences for BW between HJ and JH. Probability of dystocia in JJ and JH were 5.73% and 18.98% of HH. Calves in HJ and HH were not different for dystocia. Calves in HJ were 3.38 times more likely to be stillborn than calves in JH, but no other genetic group differences were significant for probability of stillbirth. Groups HJ and JH differed for calving traits, with JH crosses experiencing less dystocia than HJ; JJ showed no indication of dystocia. No differences were observed between HH and JJ for stillbirths. Additional investigation of stillbirths in Jerseys is justified.

Predicting breeding values and accuracies from group in comparison to individual observations.

Individual observations are routinely used in livestock evaluations. In some cases, pooled data representing the joint but not individual performance of a group of animals may be available. For example, pooled feed intake may be measured on a pen of livestock. The usual mixed model approach to genetic evaluation can still be applied as an exact method in this setting, provided incidence and residual variance-covariance matrices are suitably modified to account for the pooling. Approximate evaluations may be achieved by treating average performance as if it pertained to each individual in the pool. Theoretical accuracies can be obtained as a function of elements of the inverse coefficient matrix. A 3-generation data set representing 1,000 animals with feed intake observations from 49 sires and 200 maternal grand sires was simulated with heritability of 0.34. Individual records were pooled to represent circumstances in which animals with records were collectively measured. Animals were allocated into pens at random, by sire, or by maternal grand sire. Simulation was replicated with unique fixed effects for each pen. Following evaluation from each method, the empirical accuracy or product-moment correlation between true (simulated) and estimated merit could be quantified. The analysis of individual observations resulted in empirical accuracy of 0.63 for animals on test and 0.77 for their sires. Pooling the observations in pens of 2, 4, or 12 animals reduced empirical accuracies for animals on test to 0.50, 0.41, and 0.21 when pooling was at random and 0.53, 0.47, and 0.34 when pooling was by sire. Simulating a fixed pen effect representing 10% phenotypic variation, but ignoring that effect in the evaluation minimally reduced empirical accuracies to 0.52, 0.46, and 0.33 when pooling by sire. Theoretical accuracies were in close agreement with empirical accuracies when the exact method was used. The approximate method that treated averages of pooled data as if they were individually observed overstated accuracy and should not be used. Selection on the basis of pooled observations can be almost as effective as using individual observations when pool sizes are small. The exact method to account for pooled data is no more complex than conventional procedures.

Computerized morphometric quantitation of cellular features in splenocytes from normal and nutrient-restricted mice.

The morphometric analysis of splenocytes reveals quantitative changes in the chromatin and cytoplasm that may be used to distinguish between cells from normally fed animals and cells from subjects fed restricted diets. Analysis of Feulgen-stained and Papanicolaou-stained cells from mice fed normal diets and mice fed either calorie-restricted diets or isocaloric but protein-restricted diets showed an approximately 10% reduction in the nuclear area and in the total optical density (TOD) of stained chromatin in cells from diet-restricted mice. Some changes in chromatin texture features were also observed. Utilization of nuclear area, TOD and one textural feature in a linear discriminant analysis produced a distinct separation of the cells from dietary-restricted mice and the cells from normally fed subjects; this was observed with both Feulgen-stained and Papanicolaou-stained cells. The cellular effect of dietary restriction was more noticeable in the cytoplasm than in the nucleoplasm; Papanicolaou-stained cells from diet-restricted animals showed a 23% reduction in the cytoplasmic TOD and a 10% reduction in the nuclear TOD. This study shows that computerized morphometric analysis may be used in place of or in conjunction with other measurement procedures and chemical tests to quantitate and differentiate cells subjected to different types and levels of nutritional stress.

Computerized morphometric differentiation of chromatin changes in splenocytes from normal and calorie-restricted mice.

Morphometric image analysis of splenocytes obtained from mice fed calorie-restricted diets for periods of up to three weeks revealed slight but significant changes in nuclear size, nuclear texture and total amounts of stainable Feulgen-positive DNA as compared to age-and-sex-matched control cells. The cellular changes were associated with body weight loss and changes in the distribution of splenic T cells and B cells during the three weeks of dietary restriction. The reduced nuclear area and Feulgen-stained DNA may reflect an altered susceptibility of cells from nutrient-restricted sources toward acid hydrolysis. This in turn may be indicative of a temporarily altered synthesis of subcellular components, as these phenomena seem to lessen by the third week of dietary restriction.