The importance of mRNA structure in determining the pathogenicity of synonymous and non-synonymous mutations in haemophilia.

INTRODUCTION: Mutational analysis is commonly used to support the diagnosis and management of haemophilia. This has allowed for the generation of large mutation databases which provide unparalleled insight into genotype-phenotype relationships. Haemophilia is associated with inversions, deletions, insertions, nonsense and missense mutations. Both synonymous and non-synonymous mutations influence the base pairing of messenger RNA (mRNA), which can alter mRNA structure, cellular half-life and ribosome processivity/elongation. However, the role of mRNA structure in determining the pathogenicity of point mutations in haemophilia has not been evaluated. AIM: To evaluate mRNA thermodynamic stability and associated RNA prediction software as a means to distinguish between neutral and disease-associated mutations in haemophilia. METHODS: Five mRNA structure prediction software programs were used to assess the thermodynamic stability of mRNA fragments carrying neutral vs. disease-associated and synonymous vs. non-synonymous point mutations in F8, F9 and a third X-linked gene, DMD (dystrophin). RESULTS: In F8 and DMD, disease-associated mutations tend to occur in more structurally stable mRNA regions, represented by lower MFE (minimum free energy) levels. In comparing multiple software packages for mRNA structure prediction, a 101-151 nucleotide fragment length appears to be a feasible range for structuring future studies. CONCLUSION: mRNA thermodynamic stability is one predictive characteristic, which when combined with other RNA and protein features, may offer significant insight when screening sequencing data for novel disease-associated mutations. Our results also suggest potential utility in evaluating the mRNA thermodynamic stability profile of a gene when determining the viability of interchanging codons for biological and therapeutic applications.

Reproductive aging in Japanese quail, Coturnix japonica is associated with changes in central opioid receptors.

Quantitative in vitro autoradiography was used to measure specific mu and delta opioid receptor densities in regions of the Japanese quail, Coturnix japonica, brain that regulates reproductive endocrine and behavioral responses to determine the possible involvement of the opioid system in reproductive decline seen during aging. Densities were measured in selected brain regions of young sexually active (YAM), young photoregressed (YPM), old reproductively senescent (OIM) male, young active (YF), and old senescent female (OF) Japanese quail. Medial and lateral septum (SM, SL), medial preoptic area (POM), and n. intercollicularis (ICo) were of particular interest for reproductive responses. Similar to previous observations, mu and delta opioid receptors showed differential distributions in the areas measured. Some age-related changes were observed, with lower SM mu receptor densities in aged males (OIM) than females or young males (YAM). Densities of mu receptors in the POM and in other areas examined did not vary with sex or age. Similarly, OIM males had lower densities of delta receptors in the SM than young males (YAM and YPM); POM delta receptor densities were also low in OIM males compared to the YPM males, and YAM males were intermediate. Interestingly, photoregressed males (YPM) had higher SL delta receptor densities than any other group. Thus there were age-related differences detected in mu receptor densities among groups in the SM of OIM relative to other groups; and the mu and delta receptor densities did not differ in females with brain region. Additionally for delta receptors specifically, YF and OF did not differ from OIM for any brain region and similarly had lower densities of delta receptors compared to YAM males. These data provide support for regional differences in opioid receptor distribution and for age- and sex-related differences in delta opioid receptor densities. The direction of change presents an interesting dichotomy in that, compared to young active males, delta opioid receptor densities increased with loss of reproductive function in the YPM, whereas receptor densities decreased in the OIM. Plasma androgen levels were relatively low in both these groups compared to the young active males. This observation suggests that there is an age-related loss in the ability of this receptor system to respond to circulating and centrally produced steroid hormones in the POM and in some septal regions, compared to young animals that are responding to environmental cues. Furthermore, these data support an active role of the opioid peptide system in the inhibition of the reproductive axis in photoregression.

Reproductive success of broiler breeders in natural mating systems: the effect of male-male competition, sperm quality, and morphological characteristics.

In natural mating systems in which broiler breeder males compete for females, reproductive behavior plays an important role in male fertility, along with sperm competition and morphological and physiological characteristics. We investigated the effect of male-male competition compared with a noncompetitive situation on fertility, sperm quality, and morphological traits. Six groups of 3 males and 12 females were housed in mixed-sex pens. Their frequency of mating was recorded, and progeny of each male was determined through DNA fingerprinting. Males with the highest and the lowest mating frequencies were later placed into groups of 1 male and 4 females, their behavior was recorded, and their fertility was calculated. We collected data on semen quality (semen volume, sperm concentration, and mobility) and morphometrical characters. Finally, females were artificially inseminated with sperm from highest frequency, lowest frequency, or a mix, paternity and fertility were estimated. Our results indicate that heavier males had higher frequency of matings without cloacal contact, and males with smaller combs had more mating attempts. We also detected that males with high sperm concentration had lower fertility. However, we found an overall lack of association between mating behavior, morphometrical traits, sperm quality, and fertility. This, together with the discrepancy of results in fertility when compared with artificial insemination conditions, suggest a multifactorial nature of the fertility of broiler breeder males in natural mating systems. In addition we observed a high male fertility when housed individually, suggesting that male fertility is a relative parameter that depends upon the reproductive quality of the other male competitors within the group.

Using blood urea nitrogen to predict nitrogen excretion and efficiency of nitrogen utilization in cattle, sheep, goats, horses, pigs, and rats.

The objectives of this study were to evaluate the potential for using blood urea N concentration to predict urinary N excretion rate, and to develop a mathematical model to estimate important variables of N utilization for several different species of farm animals and for rats. Treatment means (n = 251) from 41 research publications were used to develop mathematical relationships. There was a strong linear relationship between blood urea N concentration (mg/100 mL) and rate of N excretion (g x d(-1) x kg BW(-1)) for all animal species investigated. The N clearance rate of the kidney (L of blood cleared of urea x d(-1) x kg BW(-1)) was greater for pigs and rats than for herbivores (cattle, sheep, goats, horses). A model was developed to estimate parameters of N utilization. Driving variables for the model included blood urea N concentration (mg/100 mL), BW (kg), milk production rate (kg/d), and ADG (kg/d), and response variables included urinary N excretion rate (g/d), fecal N excretion rate (g/d), rate of N intake (g/d), and N utilization efficiency (N in milk and gain per unit of N intake). Prediction errors varied widely depending on the variable and species of animal, with most of the variation attributed to study differences. Blood urea N concentration (mg/100 mL) can be used to predict relative differences in urinary N excretion rate (g/d) for animals of a similar type and stage of production within a study, but is less reliable across animal types or studies. Blood urea N concentration (mg/100 mL) can be further integrated with estimates of N digestibility (g/g) and N retention (g/d) to predict fecal N (g/d), N intake (g/d), and N utilization efficiency (grams of N in milk and meat per gram of N intake). Target values of blood urea N concentration (mg/100 mL) can be backcalculated from required dietary N (g/d) and expected protein digestibility. Blood urea N can be used in various animal species to quantify N utilization and excretion rates.

Comparison of analytical methods and the influence of milk components on milk urea nitrogen recovery.

The objectives of this study were to compare analytical instruments used in independent laboratories to measure milk urea nitrogen (MUN) and determine whether any components in milk affect the recovery of MUN. Milk samples were collected from 100 Holstein cows fed one ration in a commercial dairy herd with a rolling herd average of 9500 kg. Half of each sample was spiked with 4 mg/dL of urea N, while the other half was not, to determine recovery. Both milk samples (spiked and not spiked) were sent to 14 independent laboratories involved in the MUN Quality Control Program through National Dairy Herd Improvement Association and analyzed for MUN, fat, protein, lactose, somatic cell count (SCC), and total solids. The laboratories analyzed MUN using CL-10 (n = 3), Skalar (n = 2), Bentley (n = 3), Foss 4000 (n = 3) or Foss 6000 (n = 3) systems. When recovery of MUN was evaluated among the 5 analytical methods, the mean recoveries for the Bentley, Foss 6000, and Skalar systems were 92.1 (SE = 2.76%), 95.4 (SE = 10.1%), and 95.1% (SE = 7.61%), respectively, and did not differ from each other. However, MUN recovery was 85.0% (SE = 2.8%) for the CL-10 system and 47.1% (SE = 9.9%) for the Foss 4000 system, both of which differed from the other 3 systems. Recoveries from Foss 4000, Foss 6000, and Skalar varied among laboratories using the same instrument. As initial MUN concentration increased, recovery decreased using the Bentley and CL-10 systems. Increasing milk fat resulted in a decrease in recovery using the Foss 6000 system. For 4 of the 5 methods, recovery of MUN was not associated with specific milk components. Recovery of MUN was inconsistent for laboratories using the Foss 4000 and the Foss 6000 method and using these systems may result in an overestimation or underestimation of MUN.

A comparison of instruments and laboratories used to measure milk urea nitrogen in bulk-tank milk samples.

The objective of this study was to compare the instruments and laboratories that are currently used for analysis of milk urea nitrogen (MUN) for bulk-tank milk samples. Two replicate samples from each bulk tank on 10 different dairy farms were sent to 12 Dairy Herd Improvement Association (DHIA) laboratories throughout the US for MUN analysis. Two laboratories used 2 different methods for MUN analysis for a total of 14 analyses on 20 samples (n = 280). Values of MUN were analyzed using a random effects model with farm, laboratory, and farm x laboratory variance components. Greater than 98% of the variance in measured MUN was attributed to farm-to-farm variance for analysis of MUN by the Bentley, CL 10, Foss 6000, and Skalar instruments. However, for the laboratories using the Foss 4000 system, <60% of the variance in MUN was attributed to farm-to-farm variance. Laboratories using the Bentley, CL 10, Foss 6000, and Skalar instruments provided slightly different results for MUN analysis, but >95% of sample measurements fell within 1.75 mg/ dL of each other. The laboratories using Foss 4000 differed from each other, and 95% of samples fell within 5 mg/dL of the CL 10 measurement. Laboratories using the Foss 4000 instrument did not consistently provide measurements of MUN that were similar to each other or to the measurements of the other instruments.

Effects of milk urea nitrogen and other factors on probability of conception of dairy cows.

The objective of this study was to evaluate the relationships between milk urea nitrogen (MUN) and other factors and the probability of conception in dairy cows. Data were retrieved from the Lancaster Dairy Herd Improvement Association (DHIA). A total of 713 dairy herds and 10,271 dairy cows were included in the study. Logistic regression was used to determine the within-herd effects of MUN, milk production, lactation number, and breeding season on the probability of conception for each of 3 services. Within herds, MUN displayed a slight negative association with probability of conception at first service. For example, there was a 2- to 4-percentage unit decrease in conception rate at first service with a 10-mg/dL increase in MUN. In among-herd regression analysis, there was no effect of MUN on probability of conception. These results suggest that MUN may be related to conditions affecting reproduction of individual cows within a herd. Diet formulation usually would affect MUN equally among all cows at a similar stage of lactation in a herd. Because there was no effect of MUN among herds, diet formulation did not appear to affect conception rate.

Reduction of cholera in Bangladeshi villages by simple filtration.

Based on results of ecological studies demonstrating that Vibrio cholerae, the etiological agent of epidemic cholera, is commensal to zooplankton, notably copepods, a simple filtration procedure was developed whereby zooplankton, most phytoplankton, and particulates >20 microm were removed from water before use. Effective deployment of this filtration procedure, from September 1999 through July 2002 in 65 villages of rural Bangladesh, of which the total population for the entire study comprised approximately 133,000 individuals, yielded a 48% reduction in cholera (P < 0.005) compared with the control.

Effects of density and perch availability on the immune status of broilers.

This study attempted to evaluate the effect of various housing densities and perch availability on the immune status of commercial broilers. Birds were raised from hatch to 42 d of age with 10, 15, and 20 birds/m2 in pens, with and without the availability of horizontal perches. The immune parameters that were assessed were lymphoid organ weights, antibody response to SRBC in the last 10 d of growth, heterophil:lymphocyte ratios at 32 and 42 d of age, and lymphocyte blastogenesis of peripheral blood lymphocytes collected at 32 and 42 d of age. As density increased, bursa weight and bursa/body weight ratios decreased significantly (P < 0.05). Addition of perches to the pens also significantly decreased the bursa weights and bursa/body weight index (P < 0.01). No other significant effects were observed for the flock performance, morphometric data, or immunological tests between treatments. We concluded that under the conditions of this study, which tried to simulate commercial conditions, the bursal weight was the best indicator of stress that was related to housing density. Addition of perches appeared to increase this level of stress because the birds used the perches infrequently, and therefore there might have been a further reduction in the availability of floor space to the birds.

Evaluation of models to estimate urinary nitrogen and expected milk urea nitrogen.

Milk urea nitrogen (MUN) has been introduced as a means to estimate urinary nitrogen (N) excretion and protein status of dairy cattle. For Holstein cows, the amount of urinary N excreted (g/d) was originally reported to be 12.54 x MUN (mg/dl), but recently urinary N (g/d) was reported to equal 17.64 x MUN (mg/dl). The objectives of the present study were to evaluate models to predict urinary N and expected MUN, by using older and newer data sets, and to quantify changes that may have occurred in MUN measurements over time. Two data sets were used for model evaluation. Data set 1 was from the spring of 1998 and data set 2 was from the spring of 1999. Similar cows and diets were used in both studies. By using data set 1, the newer model underestimated MUN by an average of 3.8 mg/dl, whereas the older model was accurate. By using data set 2, the older model overestimated MUN by 4.8 mg/ dl, but the newer model was accurate. In the period between the two studies, the MUN measured appeared to decrease by an average of 4.0 mg/dl. By using current wet chemistry methods to analyze for MUN, urinary N (mg/dl) can be predicted as 0.026 x MUN (mg/dl) x body weight (kg). Because of changes in methodology that occurred in the fall of 1998, target MUN concentrations have decreased to 8.5 to 11.5 mg/dl for most dairy herds compared with previous target concentrations of 12 to 16 mg/dl.

Effect of sampling method on the representative recovery of microorganisms from the surfaces of aquacultured finfish.

The objective of this study was to determine if a gentle rinse procedure was equivalent to the combination of excision and homogenization with a stomacher for the relative removal of various microorganisms from finfish fillets. Fillets of hybrid striped bass and rainbow trout were obtained from local markets and sampled using three methods: rinse (R), excision followed by homogenization in a stomacher (S), and homogenization of fillets following a rinse (RS). Microorganisms were enumerated on selective and nonselective media, and randomly selected colonies from aerobic plate counts were identified using MIDI Sherlock and BIOLOG microbial identification systems. Enrichments and selective media were used for the isolation of Listeria monocytogenes, Salmonella spp., and Yersinia enterocolitica. This study confirms previous reports that stomaching is superior to rinsing for enumerating total microbial populations from fish fillets. Rinsing was more effective for rainbow trout than for striped bass. Sampling method did not affect the relative magnitude of plate counts on media selective for aeromonads, pseudomonads, Shewanella, lactic acid bacteria, enterics, and gram-positive cocci. In the compositional analysis of random isolates, R recovered significantly lower fractions of aeromonads than did S or RS, but sampling method did not affect the percent recovery of lactic acid bacteria, pseudomonads, Shewanella, Moraxellaceae, or Cytophaga/Flavobacterium. However, observations suggest that with increased replication, differences among Moraxellaceae, Pseudomonas, and gram positives might be significant. Only one L. monocytogenes colony was isolated, and no Salmonella or Y. enterocolitica, so the effect of sampling method could not be determined for these organisms. Differences in predominant bacterial populations were seen between fish species.

Modified atmosphere packaged cheddar cheese shreds: influence of fluorescent light exposure and gas type on color and production of volatile compounds.

The influences of fluorescent light exposure and packaging atmosphere on the headspace volatiles and color of Cheddar cheese shreds were evaluated using gas chromatography-mass spectrometry and spectrocolorimetry, respectively. Cheddar cheeses were packaged under atmospheres of 100% carbon dioxide or 100% nitrogen and stored at 4 degrees C under fluorescent light for 6 weeks. Cheeses stored under carbon dioxide contained higher concentrations of aldehydes and fatty acids and lower concentrations of alcohols and esters than cheeses stored under nitrogen. Carbon dioxide atmospheres potentiated light-induced oxidation in shredded Cheddar cheeses, as evidenced by aldehyde and fatty acid headspace volatiles measured following storage. Color bleaching occurred only in cheeses packaged under carbon dioxide and exposed to light. The shift in color is proposed to be due to an interaction between carbon dioxide and high-intensity light, leading to the oxidation of the pigment molecule, bixin. The results have significant implications for procedures used to handle and store pigmented cheeses to ensure desirable flavor and consumer acceptability.

Intact soil-core microcosms compared with multi-site field releases for pre-release testing of microbes in diverse soils and climates.

Intact soil-core microcosms were used to compare persistence of Pseudomonas chlororaphis 3732RN-L11 in fallow soil and on wheat roots with field releases at diverse sites. Parallel field and microcosm releases at four sites in 1996 were repeated with addition of one site in 1997. Microcosms were obtained fresh and maintained at 60% soil water holding capacity in a growth chamber at 70% relative humidity, a 12-hour photoperiod, and constant temperature. Persistence of 3732RN-L11 was measured at each site in field plots and microcosms at 7-21 day intervals, and in duplicate microcosms sampled at an independent laboratory. Linear regression slopes of field plot and microcosm persistence were compared for each site, and between identical microcosms sampled at different sites, using log10 transformed plate counts. Microcosm persistence closely matched field plots for wheat roots, but persistence in fallow soil differed significantly in several instances where persistence in field plots was lower than in microcosms. Analysis of weather variations at each site indicated that rainfall events of 30-40 mm caused decreased persistence in fallow soil. Cooler temperatures enhanced persistence in field plots at later time points. Inter-laboratory comparison of regression slopes showed good agreement for data generated at different sites, though in two instances, longer sampling periods at one site caused significant differences between the sites. Soil characteristics were compared and it was found that fertility, namely the carbon to nitrogen ratio, and the presence of expanding clays, were related to persistence. These microcosm protocols produced reliable data at low cost, and were useable for pre-release risk analyses for microorganisms.

Stature as a prognostic factor in cystic fibrosis survival.

OBJECTIVE/DESIGN: This study provides a longitudinal analysis of the National Cystic Fibrosis Patient Registry to determine if height-for-age percentile would be a useful predictor of survival. SUBJECTS: All patients were selected from the national registry (n = 19,000) maintained by the Cystic Fibrosis Foundation's 115 accredited Cystic Fibrosis Care Centers in the United States. Inclusion in our analysis required that subjects were born between 1980 and 1989; had a minimum of 4 records each; the subject was alive at age 7; and the subject had a recorded height measurement at age 7 to 8 (n = 2,773). STATISTICAL ANALYSIS: The Cox proportional hazards model was used to compare height-for-age with survival. We recorded whether a subject was less than the 5th National Center for Health Statistics (NCHS) percentile at age 5 and then in a separate analysis at age 7. Cohort effect was coded as "1" if they were born before 1982 and "0" otherwise. RESULTS: Stature is a significant prognostic indicator of survival. The relative hazard associated with height below the 5th NCHS percentile for age was significant for both males and females. In males at age 5 the relative hazard was 2.9, [95% confidence interval (CI) 1.23, 6.91; P < .02] and at age 7 it was 6.3 (95% CI 2.1, 18.8; P < .001). The relative hazard in females at age 5 was 4.3 (95% CI 2.4, 7.3; P < .0001) and at age 7 was 5.8 (95% CI 2.5, 13.1; P < .0001). APPLICATION: These highly significant relative hazard values strongly suggest that shorter patients are much more likely to die before taller patients. The dietetic professional should consider using height-for-age as an effective screening tool to identify patients at risk. Based on these data, short stature should not be considered benign to patients with cystic fibrosis. The CF team, clinicians, family, and patients need work together to maximize linear growth through medical and nutritional intervention.

Analysis of fungal communities by sole carbon source utilization profiles.

A simple method for characterization of fungal communities in environmental samples was developed. Dilute suspensions of samples in 0.2% agar containing three different antibiotics were pipetted into 96-well plates (Biolog SF-N) containing a diverse collection of 95 different carbon sources. The plates were incubated for 4-12 days at 22 degrees C and the absorbance measured at 650 nm. Canonical variates analysis was then used to analyze the multivariate data. This method allowed fungal communities in rhizosphere soil of corn and soybean to be distinguished according to soil and plant type. Data taken at a single time-point, which varied greatly in total absorbance of the plate, separated rhizosphere samples primarily by soil type. When multiple time-points were combined to keep the total absorbance constant, differences in substrate utilization patterns due to different plant types could be distinguished. The method was also applicable to analysis of phylloplane and compost fungal communities. This method is readily applied to large numbers of samples and should be useful for community analysis in a variety of agricultural and ecological studies.

Postpartum iron status in nonlactating participants and nonparticipants in the special supplemental nutrition program for women, infants, and children.

BACKGROUND: Iron deficiency, a pervasive problem among low-income women of childbearing age, threatens maternal health and pregnancy outcomes. The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) was designed to alleviate health problems and provides supplemental nutritious foods, nutrition education, and health care referrals. OBJECTIVES: The aim of this study was to examine the benefits associated with participation in WIC in terms of biochemical tests of postpartum iron status in nonlactating women. DESIGN: WIC participants (n = 57) and eligible nonparticipants (n = 53), matched by race and age, were followed bimonthly over 6 mo postpartum. Finger stick blood samples (500 microL) were collected for measurement of plasma ferritin, transferrin receptor (TfR), and hemoglobin (Hb). RESULTS: The mean (+/-SE) Hb concentration of participants exceeded that of nonparticipants from months 2 through 6. At 6 mo, the mean Hb concentration of participants was significantly higher than that of nonparticipants (8.01+/-0.12 and 7.63+/-0.12 mmol/L, respectively; P< 0.05) and the prevalence of anemia was significantly lower (17% and 51%, respectively; P<0.05). TfR and ferritin concentrations (consistently within the reference ranges) and dietary iron intakes did not differ significantly between participants and nonparticipants and were not correlated with Hb concentrations. CONCLUSIONS: Our results suggest that WIC participants were significantly less likely to become anemic if uninterrupted postpartum participation lasted for 6 mo. The lack of correlation among iron status indicators suggests that the lower mean Hb concentration in nonparticipants at 6 mo may not have been related to improved iron status in participants but to other nutrient deficiencies or differences in access to health care and health and nutrition education.

A two-sample method for assessing growth hormone response to growth hormone-releasing hormone challenge: use as a predictor of gain in beef bulls.

In two experiments, Black Angus bulls were challenged at weaning with GHRH analog and evaluated for their GH response to determine whether GH response can predict subsequent growth characteristics. The GH response was determined by measuring GH in blood serum collected 0 and 10 min after GHRH injection (Exp. 1: 1.5 microg/100 kg BW human GHRH, n = 34; Exp. 2: 1.5 and 4.5 microg/100 kg BW bovine GHRH [treatments LGHRH and HGHRH, respectively] administered 3 h after a 4.5 microg/100 kg BW "clearance dose" of GHRH, n = 38]. In Exp. 1, GH response did not predict growth or carcass measurements. In Exp. 2, GH response to LGHRH was positively related to ADG (R2 = .18; P = .007) during a 112-d controlled feeding trial. In addition, there was a tendency for bulls with a greater GH response to HGHRH to exhibit greater ADG than animals with a low response. However, GH response to GHRH was not related to changes in hip height (HH) or carcass ultrasound measurements at d 112 of the growth performance trial. Response of GH to repeated GHRH challenges was consistent within animal over time (r = .47; P = .003). The use of a clearance dose 3 h prior to GHRH challenge improved the relationship between GH response and ADG. Results of this study suggest that GH response to GHRH challenge is a useful tool for identifying beef bulls with superior growth potential.

Endocrine patterns during aging in the common tern (Sterna hirundo).

Blood samples were taken from breeding common terns (Sterna hirundo) of known age during two successive breeding seasons to determine if plasma concentrations of estradiol, progesterone, androgen, and luteinizing hormone (LH) reflect the process of aging. Males and females were trapped and sampled once between laying of the first and the second eggs in the clutch. The transient capture and sampling did not disrupt incubation or the timing of the subsequent oviposition. Ages ranged from 2 to 21 years, with most in the range 4-11 years. There was a strong inverse correlation (P < 0.0001) between age and laying date in both females and males, with older birds nesting earlier in the season. Plasma LH levels increased (P < 0.005) among mature (>5 year) females. Plasma progesterone and E2 were positively correlated with each other among mature females, but did not change in an age-dependent manner. In males, plasma progesterone levels showed no age-related changes. However, maturing (3-5 year) males showed increasing plasma androgen levels (P < 0.01); mature males showed no change with age. Plasma LH levels were correlated with androgen levels in both maturing and mature males. Plasma progesterone declined with age in maturing males (P < 0.001). These data provide evidence for changing endocrine status with age, but the patterns differ for younger individuals (

Effects of dietary crude protein concentration and degradability on milk production responses of early, mid, and late lactation diary cows.

Three experiments were conducted to investigate the effect of crude protein (CP) concentration and ruminally undegraded protein (RUP) concentration on milk production and composition of dairy cows at three different stages of lactation. Experiments 1, 2, and 3 using 39, 40, and 39 Holstein cows were conducted for cows in early (wk 4 to 14 postpartum), mid (wk 19 to 29), and late (wk 34 to 44) lactation, respectively. Cows were assigned to one of four corn-based diets: high CP, medium RUP (control); low CP, low RUP; low CP, medium RUP; and low CP, high RUP. Percentages of CP in the high and low CP diets were, respectively, 17.4 and 15.2 for Experiment 1, 15.3 and 13.3 for Experiment 2, and 14.2 and 12.6 for Experiment 3. The RUP concentrations (percentages of CP) for low, medium, and high diets averaged 35.5, 41.4, and 46.5%, respectively. For Experiment 1, production of milk, 4% fat-corrected milk, milk fat, and milk protein was increased by the high protein diets versus the low protein diets. Production of milk and fat-corrected milk increased linearly as RUP in the diet increased. During Experiment 2, lactational responses were not affected by treatment. During Experiment 3, dry matter intake, body weight, and body weight change increased for cows fed the high protein diets versus those same measurements for cows fed the low protein diets. Milk fat and milk protein percentage decreased linearly as RUP in the diet increased. Because there was no effect of diet on milk production, decreasing CP in diets fed to cows in mid or late lactation can reduce the cost of the diet and waste N excreted from the cow.

Evaluating treatments when a gender by treatment interaction may exist.

We propose a two-stage procedure for investigating whether males and females respond differently to treatment. The size of the first stage is based on the assumption of homogeneity of treatment effects across genders. Using stage I, we test for a gender by treatment interaction. If non-significant, we compute an overall average treatment effect and terminate the study. If we find an apparent interaction at the end of the first stage, we consider each gender separately. Because we now need to estimate treatment effects separately for each gender, we may have a need to collect additional information in a second stage. We consider the performance of our procedure for a normally distributed endpoint as well as for a survival model.