Effects of the timolol-dorzolamide fixed combination and latanoprost on circadian diastolic ocular perfusion pressure in glaucoma.

PURPOSE. To evaluate the effect of the timolol-dorzolamide fixed combination (TDFC) and latanoprost 0.005% on 24-hour intraocular pressure (IOP), systolic (SBP) and diastolic (DBP) blood pressure, and diastolic ocular perfusion pressure (DOPP) in patients with primary open-angle glaucoma (POAG). METHODS. This was an institutional, randomized clinical trial. After a 24-hour assessment without treatment, 27 previously untreated patients with POAG were randomized to 6 weeks’ treatment with twice-daily TDFC (8 AM and 8 PM) followed by once-daily latanoprost 0.005% (8 PM), or vice versa. One eye was analyzed per patient. The mean values of IOP, DBP, SBP, and DOPP (difference between DBP and IOP) were recorded at each time point, and the 24-hour data are the mean values of each patient’s measurements over the 24-hour period. The differences between the values of the first treatment period and the baseline and the second treatment period and washout were calculated and analyzed by means of an analysis of variance model that tested the effects of sequence and treatment. RESULTS. Both treatments significantly reduced 24-hour IOP (P <0.0001), but TDFC led to lower 24-hour pressure (mean ±SD: 15.4 ±1.9 vs. 16.7± 1.7 mm Hg; P=0.004). Latanoprost did not lead to any significant reduction in mean 24-hour SBP and DBP (SBP: P =0.952; DBP: P=0.831), but TDFC did (SBP and DBP: P < 0.0001). Both treatments significantly increased 24-hour DOPP (P < 0.0001), with no difference between the two medications (P=0.09). CONCLUSIONS. In previously untreated patients with POAG, TDFC, and latanoprost equally enhanced 24-hour DOPP: the former by counteracting the decrease in DBP with a substantial reduction in IOP and the latter by not affecting DBP and significantly reducing IO

Investigating the potential for genetic selection of dairy calf disease traits using management data.

Genetic selection could be a tool to help improve the health and welfare of calves, however, to date, there is limited research on the genetics of calfhood diseases. This study aimed to understand the current impact of calf diseases, by investigating incidence rates, estimating genetic parameters, and providing industry recommendations to improve calf disease recording practices on farms. Available calf disease data comprised of 69,695 Holstein calf disease records for respiratory problems (RESP) and diarrhea (DIAR), from 62,361 calves collected on 1,617 Canadian dairy herds from 2006 to 2021. Single and multiple trait analysis using both a threshold and linear animal model for each trait were evaluated. Furthermore, each trait was analyzed using 2 scenarios with respect to minimum disease incidence threshold criterion (herd-year incidence of at least 1% and 5%) to highlight the impact of different filtering thresholds on selection potential. Observed scale heritability estimates for RESP and DIAR ranged from 0.02 to 0.07 across analyses, while estimated genetic correlations between the traits ranged from 0.50 to 0.62. Sires were compared based on their estimated breeding value and their diseased daughter incidence rates. On average, calves born to the bottom 10% of sires were 1.8 times more likely to develop RESP and 1.9 times to develop DIAR compared with daughters born to the top 10% of sires. Results from the current study are promising for the inclusion of both DIAR and RESP in Canadian genetic evaluations. However, for effective genetic evaluation we require standardized approaches on data collection and industry outreach to highlight the importance of collecting and uploading this information to herd management software. In particular, it is important that the herd management software is accessible to the national milk recording system to allow for use in national genetic evaluation

Review: Opportunities and challenges for the genetic selection of dairy calf disease traits.

Interest in dairy cow health continues to grow as we better understand health's relationship with production potential and animal welfare. Over the past decade, efforts have been made to incorporate health traits into national genetic evaluations. However, they have focused on the mature cow, with calf health largely being neglected. Diarrhoea and respiratory disease comprise the main illnesses with regard to calf health. Conventional methods to control calf disease involve early separation of calves from the dam and housing calves individually. However, public concern regarding these methods, and growing evidence that these methods may negatively impact calf development, mean the dairy industry may move away from these practices. Genetic selection may be a promising tool to address these major disease issues. In this review, we examined current literature for enhancing calf health through genetics and discussed alternative approaches to improve calf health via the use of epidemiological modelling approaches, and the potential of indirectly selecting for improved calf health through improving colostrum quality. Heritability estimates on the observed scale for diarrhoea ranged from 0.03 to 0.20, while for respiratory disease, estimates ranged from 0.02 to 0.24. The breadth in these ranges is due, at least in part, to differences in disease prevalence, population structure, data editing and models, as well as data collection practices, which should be all considered when comparing literature values. Incorporation of epidemiological theory into quantitative genetics provides an opportunity to better determine the level of genetic variation in disease traits, as it accounts for disease transmission among contemporaries. Colostrum intake is a major determinant of whether a calf develops either respiratory disease or diarrhoea. Colostrum traits have the advantage of being measured and reported on a continuous scale, which removes the issues classically associated with binary disease traits. Overall, genetic selection for improved calf health is feasible. However, to ensure the maximum response, first steps by any industry members should focus efforts on standardising recording practices and encouragement of uploading information to genetic evaluation centres through herd management software, as high-quality phenotypes are the backbone of any successful breeding programme

Phenotypic analysis of heat stress in Holsteins using test-day production records and NASA POWER meteorological data.

Weather station data and test-day production records can be combined to quantify the effects of heat stress on production traits in dairy cattle. However, meteorological data sets that are retrieved from ground-based weather stations can be limited by spatial and temporal data gaps. The National Aeronautics and Space Administration Prediction of Worldwide Energy Resources (NASA POWER) database provides meteorological data over regions where surface measurements are sparse or nonexistent. The first aim of this study was to determine whether NASA POWER data are a viable alternative resource of weather data for studying heat stress in Canadian Holsteins. The results showed that average, minima, and maxima ambient temperature and dewpoint temperature as well as 4 different types of temperature-humidity index (THI) values from NASA POWER were highly correlated to the corresponding values from weather stations (regression R2 > 0.80). However, the NASA POWER values for the daily average, minima, and maxima wind speed and relative humidity were poorly correlated to the corresponding weather station values (regression R2 = 0.10 to 0.49). The second aim of this study was to quantify the influence of heat stress on Canadian dairy cattle. This was achieved by determining the THI values at which milk, protein, and fat yield started to decline due to heat stress as well as the rates of decline in these traits after the respective thresholds, using segmented polynomial regression models. This was completed for both primiparous and multiparous cows from 5 regions in Canada (Ontario, Quebec, British Columbia, the Prairies, and the Atlantic Maritime). The results showed that all production traits were negatively affected by heat stress and that the patterns of responses for milk, fat, and protein yields to increasing THI differed from each other. We found 3 THI thresholds for milk yield, 1 for fat yield, and 2 for protein yield. All thresholds marked a change in rate of decrease in production yield per unit THI, except for the first milk yield threshold, which marked a greater rate of increase. The first thresholds for milk yield ranged between 47 and 50, the second thresholds ranged between 61 and 69, and the third thresholds ranged between 72 and 76 THI units. The single THI threshold for fat yield ranged between 48 and 55 THI units. Finally, the first and second thresholds ranged between 58 and 62 THI units and 72 and 73 THI units for protein yield, respectively

Predictive value of heidelberg retina tomograph parameters for the development of glaucoma in the European glaucoma prevention study

PURPOSE: To determine whether baseline Heidelberg Retina Tomograph (HRT) measurements of the optic disc are associated with the development of open-angle glaucoma (OAG) in individuals with ocular hypertension in the European Glaucoma Prevention Study (EGPS). DESIGN: Retrospective analysis of a prospective, randomized, multicenter, double-masked, controlled clinical trial. METHODS: There were 489 participants in the HRT Ancillary Study to the EGPS. Each baseline HRT parameter was assessed in univariate and multivariate proportional hazards models to determine its association with the development of OAG. Proportional hazards models were used to identify HRT variables that predicted which participants in the EGPS had developed OAG. Development of OAG was based on visual field and/or optic disc changes. RESULTS: At a median follow-up time of about 5 years, 61 participants developed OAG. In multivariate analyses, adjusting for randomization arm, age, baseline IOP, central corneal thickness, pattern standard deviation, and HRT disc area, the following HRT parameters were associated with the development of OAG: the "outside normal limits" classification of the Frederick Mikelberg (FSM) discriminant function (hazard ratio [HR] 2.51, 95% confidence interval [CI]: 1.45-4.35), larger mean cup depth (HR 1.64, 95% CI: 1.21-2.23), cup-to-disc area ratio (HR 1.43, 95% CI: 1.14-1.80), linear cup-to-disc ratio (HR 1.43, 95% CI: 1.13-1.80), cup area (HR 1.33, 95% CI: 1.08-1.64), smaller rim area (HR 1.33, 95% CI: 1.07-1.64), larger cup volume (HR 1.30, 95% CI: 1.05-1.61), smaller rim volume (HR 1.25, 95% CI: 1.01-1.54), larger maximum cup depth (HR 1.18, 95% CI: 1.01-1.36), and cup shape measure (HR 1.18, 95% CI: 1.01-1.36). CONCLUSIONS: Several baseline HRT parameters, alone or in combination with baseline clinical and demographic factors, were significantly associated with the development of OAG among the EGPS participants

Identification of unique ROH regions with unfavorable effects on production and fertility traits in Canadian Holsteins

Background: The advent of genomic information and the reduction in the cost of genotyping have led to the use of genomic information to estimate genomic inbreeding as an alternative to pedigree inbreeding. Using genomic measures, effects of genomic inbreeding on production and fertility traits have been observed. However, there have been limited studies on the specific genomic regions causing the observed negative association with the trait of interest. Our aim was to identify unique run of homozygosity (ROH) genotypes present within a given genomic window that display negative associations with production and fertility traits and to quantify the effects of these identified ROH genotypes. Methods: In total, 50,575 genotypes based on a 50K single nucleotide polymorphism (SNP) array and 259,871 pedigree records were available. Of these 50,575 genotypes, 46,430 cows with phenotypic records for production and fertility traits and having a first calving date between 2008 and 2018 were available. Unique ROH genotypes identified using a sliding-window approach were fitted into an animal mixed model as fixed effects to determine their effect on production and fertility traits. Results: In total, 133 and 34 unique ROH genotypes with unfavorable effects were identified for production and fertility traits, respectively, at a 1% genome-wise false discovery rate. Most of these ROH regions were located on bovine chromosomes 8, 13, 14 and 19 for both production and fertility traits. For production traits, the average of all the unfavorably identified unique ROH genotypes effects were estimated to decrease milk yield by 247.30 kg, fat yield by 11.46 kg and protein yield by 8.11 kg. Similarly, for fertility traits, an average 4.81-day extension in first service to conception, a 0.16 increase in number of services, and a - 0.07 incidence in 56-day non-return rate were observed. Furthermore, a ROH region located on bovine chromosome 19 was identified that, when homozygous, had a negative effect on production traits. Signatures of selection proximate to this region have implicated GH1 as a potential candidate gene, which encodes the growth hormone that binds the growth hormone receptor. This observed negative effect could be a consequence of unfavorable alleles in linkage disequilibrium with favorable alleles. Conclusions: ROH genotypes with unfavorable effects on production and fertility traits were identified within and across multiple traits on most chromosomes. These identified ROH genotypes could be included in mate selection programs to minimize their frequency in future generations

Associations between feed efficiency and aspects of lactation curves in primiparous Holstein dairy cattle.

Genetic selection for improved feed efficiency in dairy cattle has received renewed attention over the last decade to address the needs of a growing global population. As milk yield is a critical component of feed efficiency metrics in dairy animals, our objective was to evaluate the associations between feed efficiency in primiparous Holstein cattle and parameters of a mathematical model describing individual lactation curves. The Dijkstra lactation curve model was fit to individual lactation records from 34 Holstein heifers with previously estimated measures of feed efficiency. We found that the optimal fit of the Dijkstra model was achieved using daily milk yield records up to 21 d in milk to capture the rise to peak milk yield and using monthly dairy herd improvement records for the remainder of lactation to accurately characterize lactation persistency. In the period of lactation before peak milk yield, improved feed efficiency was associated with a faster increase in daily milk yield over a shorter period of time at the expense of increased mobilization of body reserves; this serves to reinforce the concept that dairy cattle are primarily capital breeders versus income breeders. Feed efficiency in the period following peak lactation, as measured by gross feed efficiency, return over feed costs, and net energy efficiency of lactation, was positively associated with higher peak milk yield. The findings in early lactation suggest that estimates of feed efficiency could be improved by evaluating feed efficiency relative to conception, rather than parturition and lactation, to better account for the energy stored and released from body reserves in capital breeding