Full model selection using regression trees for numeric predictions of biomarkers for metabolic challenges in dairy cows

Dairy cows suffer poor metabolic adaptation syndrome (PMAS)¹ during early post-calving periods caused by negative energy balance. Measurement of blood beta-hydroxy butyric acid (BHBA)² and blood non-esterified fatty acids (NEFA)³ allow early and accurate detection of negative energy balance. Machine learning prediction of blood BHBA and blood NEFA using milk testing samples represents an opportunity to identify at-risk animals, using less labor than direct blood testing methods. Routine milk testing on modern dairies and computer record keeping provide an immense amount of data which can then be used in machine learning models. Previous research for predicting blood metabolites using Fourier-transform infrared spectroscopy (FTIR)⁴ milk data has focused mainly on individual models rather than a comparison among the models. Full model selection is the process of comparing different combinations of pre-processing methods, variable selection, and statistical learning algorithms to determine which model results in the lowest prediction error for a given dataset. For this project we used a full model selection approach with regression trees (rtFMS)⁵ . rtFMS uses the cross-validated performance of different model configurations to feed a regression tree for selecting a final model. A total of 384 possible model configurations (algorithms, predictors and data preprocessing options) for each outcome (blood BHBA and blood NEFA) were considered in the rtFMS technique. rtFMS allows direct comparison of multiple modeling approaches reducing bias due to empirical knowledge, modeling habits, or preferences, identifying the model with minimal root mean squared prediction error (RMSE)⁶ . An elastic net regression model was selected as the best performing model for both biomarkers. The input data for blood BHBA predictions were FTIR milk spectra, with a second derivative pre-processing, and a filter with 212 wave numbers, obtaining RMSE = 0.354 (0.328-0.392). The best performing model for blood NEFA had input data of FTIR milk spectra, with a second derivative pre-processing, and a filter with 212 wave numbers filter along with the time of milking, obtaining RMSE = 0.601 (0.564-0.654). The comparison of multiple modeling strategies, conducted by rtFMS, present an option for improved FTIR prediction models of blood BHBA and blood NEFA by reducing error due to human bias. The implementation of rtFMS to design future prediction models can guide model inputs and features. Our prediction models have the potential to increase early detection of metabolic disorders in dairy cows during the transition period.

Auswirkungen der Länge der Trockenstehzeit bei Milchkühen auf Leistung, Gesundheit, Fruchtbarkeit und Kolostrumqualität

In Bezug auf die Milchproduktion ist die Trockenperiode eine unproduktive Zeit. Ferner steigt das Mastitisrisiko, wenn Kühe mit einer Tagesmilchleistung > 12,5 kg trockengestellt werden, was bei Trockenstehzeiten (TZ) von 55–60 Tagen häufig der Fall ist. Hinweise auf positive Auswirkungen einer verkürzten TZ auch auf die Stoffwechselgesundheit zu Beginn der Laktation und das Reproduktionsgeschehen waren der Anlass für diese Übersichtsarbeit. Durch Verzicht auf eine TZ oder deren Verkürzung sinkt die Milchleistung (ML) in der Folgelaktation, besonders ausgeprägt zu Beginn der zweiten Laktation. Es wird angenommen, dass dies unter anderem auf unterschiedlichen Involutions- und Proliferationsprozessen der Milchdrüsen primi- und multiparer Tiere beruht. Die Mehrzahl der Untersuchungsergebnisse spricht dafür, dass eine TZ-Verkürzung die Eutergesundheit nicht negativ, sondern eher positiv beeinflusst. Auch die Kolostrumqualität wird nicht beeinträchtigt. Bei Verzicht auf ein Trockenstellen kommt es lediglich zu einem Verdünnungseffekt. Nach einem Teil der Untersuchungen wird durch Verkürzung der TZ oder einen Verzicht darauf der Energiestoffwechsel zu Beginn der Laktation entlastet. Die eindeutig positiven Auswirkungen zeigten sich jedoch nur für multipare Tiere. Zudem werden die Ergebnisse durch weitere Faktoren (z. B. Melkfrequenz vor und nach dem Kalben) beeinflusst. In verschiedenen Studien wurden positive Auswirkungen einer Verkürzung der TZ auf das Reproduktionsgeschehen nachgewiesen. Die Zeit von der Kalbung bis zur ersten Ovulation wie auch Indikatoren zur Beurteilung des Besamungserfolgs und der Reproduktionsleistung zeigten bei Tieren ohne oder mit verkürzter TZ die besseren Ergebnisse, wobei auch diese vor allem für multipare Kühe zutrafen, während sich für primipare Tiere zum Teil sogar Verschlechterungen ergaben. Insgesamt ist festzustellen, dass sich die Frage nach einer optimalen Länge der TZ nicht allgemeingültig beantworten lässt. Die Festlegung der TZ sollte als betriebsspezifisch und bedarfsorientiert anzuwendendes Managementwerkzeug genutzt werden.

Verlauf einer Herdeninfektion mit BVDV-2

Gegenstand und Ziel: In der Fallstudie werden die klinischen Erkrankungen einer schweren akuten BVDV-2-Infektion mit hohen wirtschaftlichen Verlusten in einer Milchviehherde beschrieben und der Infektionsverlauf labordiagnostisch nachvollzogen. Material und Methoden: In dem Betrieb wurden 25 Kühe plus Nachzucht der Rasse Deutsch Fleckvieh gehalten. Der Betrieb war BHV-1-frei, die durchschnittliche Jahresmilchleistung pro Kuh lag bei 6500 kg. Erkrankungen und Befunde von September 2002 bis April 2003 wurden erfasst und ausgewertet. Der Nachweis von BVDVAntikörpern erfolgte mittels indirektem Antikörper-ELISA. BVDV-Antigene wurden mittels Antigen-ELISA und in der Immunfluoreszenz-Durchflusszytometrie nachgewiesen. Die Zuordnung der isolierten Viren zu BVDV-2 erfolgte mithilfe eines monoklonalen Antikörpers sowie der PCR. Ergebnisse: Sechs Kühe und eine Kalbin erkrankten an hämorrhagischen Enteritiden. Zwei dieser Kühe mussten euthanasiert werden, eine Kuh verendete. Sechs Tiere abortierten oder hatten eine Frühgeburt. Vier Kälber starben und drei lebensschwach geborene oder in den ersten Lebenswochen an profusem Durchfall erkrankte Kälber mussten euthanasiert werden. Zwei Kälber wurden persistent infiziert. Als Ursache der Erkrankungen wurde eine Bestandsinfektion mit BVDV-2 diagnostiziert. Schlussfolgerung und klinische Relevanz: Die Ergebnisse weisen darauf hin, dass die Herde zum Zeitpunkt der Bestandsinfektion BVDV-naiv war. Das Virus muss auch ohne die Anwesenheit eines persistent infizierten Tieres über längere Zeit im Bestand zirkuliert sein.

[The intradermal tuberculin test: literature, directive and implementation in practice]

OBJECTIVE

Because of an increase in the number of cases of bovine tuberculosis in southern Germany (Allgäu region, mainly in the administrative district Swabia) during recent years, blanket tuberculosis testing was resumed in this region. The aim of this study was to review the veterinarians' current knowledge regarding the technique of the intradermal tuberculin test. As a consequence, a guide with precise instructions for the execution and interpretation of intradermal tuberculin testing in cattle based on the current legislation should be created.

MATERIAL AND METHODS

Using a questionnaire, farm-animal practitioners' knowledge and experiences of intradermal tuberculin testing were surveyed, collected and evaluated. Legislative texts on tuberculosis (particularly testing of tuberculosis) were evaluated in their current and previous versions, and compared with the experiences reported by the veterinarians.

RESULTS

A total of 137 veterinarians participated and 130 returned questionnaires could be evaluated. Forty-four of the 130 participants were involved in tuberculosis testing when the survey was performed. Of these 44 questionnaires, 42 were incorporated in the final evaluation. The majority of the veterinarians perform the intradermal tuberculosis test as laid down in the Commission Regulation (EC) no. 1226/2002 of 8 July 2002 amending Annex B to Council Directive 64/432/EEC. However, many practitioners do not comply with the requirements of the Commission Regulation (EC) no. 1226/2002 when evaluating the results of the intradermal tuberculosis test. Veterinarians showing the least accordance with required standards only test single animals or work in areas other than Swabia.

CONCLUSIONS

In areas severely affected by tuberculosis, the technique of intradermal tuberculosis testing is performed almost as demanded by the Commission Regulation (EC) no. 1226/2002. However, a more uniform and careful approach should be sought when monitoring the results. The guide designed in the context of this study can help to improve the performance of the intradermal tuberculosis test. The information from the literature review also shows that there is currently no standardized method of intradermal tuberculosis testing.

Occurrence of zoonotic clostridia and Yersinia in healthy cattle

Zoonotic pathogens are a frequent cause of disease worldwide. This study was designed to determine the occurrence of Clostridium difficile, Clostridium botulinum, and Yersinia enterocolitica in cattle in southern Bavaria, Germany. The study population included 49 farms; 34 were dairy farms (30 also fattening beef cattle) and 15 were solely beef cattle farms. Fecal and dust samples were collected from summer 2011 to summer 2012 and analyzed using a combination of enrichment procedures and real-time PCR. For the detection of C. difficile, samples were screened for the presence of the tpi gene and toxin genes tcdA, tcdB, and cdtA. Samples also were screened for genes for C. botulinum toxins A through F and for the ail gene of Y. enterocolitica. Of 506 samples, C. difficile genes were found in 29 samples (5.7%): 25 samples from dairy farms and 4 samples from beef cattle farms. Toxin genes were identified in 17 samples, with toxigenic profiles of A(+)B(+)CDT(-), A(+)B(-)CDT(+), and A(+)B(+)CDT(+). C. botulinum toxin genes were not detected in fecal samples from cattle, but the gene for toxin B was detected in 1 (0.8%) of 125 dust samples. Y. enterocolitica genes were found in 6 (1.6%) of 382 fecal samples from three dairy farms and one beef cattle farm. This study revealed that C. difficile and Y. enterocolitica are rare on cattle farms in Bavaria, Germany. In contrast to results of previous studies, C. botulinum was not detected in fecal samples but was found very rarely in dust samples from the cattle environment.

[Relationships between different parameters for the evaluation of the energy balance and the differential cell count in milk from cows with healthy udders]

OBJECTIVE

The aim of the study was to investigate possible associations between the energy balance of dairy cows and the differential cell count in milk. Such associations could be used for the assessment of the mastitis risk due to metabolic stress.

MATERIAL AND METHODS

In 15 red Holstein cows, samples were collected in the 2nd, 6th and 12th week post partum. To reflect the energy balance of the cows, the following parameters were evaluated: β-hydroxybutyric acid (BHB) in serum, fat-protein-ratio (FEQ) in milk at times of examination and difference of the body condition score (DBCS) between times of examination. The overall somatic cell count (SCC) and the differential cell count were determined. Measuring the differential cell count, comprising fractions of lymphocytes (LYM), macrophages (MAK), polymorphonuclear leucocytes (PMN) and epithelial cells (EPI), was carried out using indirect immune fluorescent staining in combination with propidium iodide staining. The interrelationships between parameters of energy status and milk cells were statistically assessed using correlation analysis. Data which were not normally distributed were transformed using logarithms (log). A mixed model was used to test the associations between milk cell parameters and the parameters of energy balance, using the animal as a random effect.

RESULTS

There was a significant correlation between FEQ and SCClog as well as between DBCS and SCClog (FEQ: r=0.459, p<0.01; DBCS: r=-0.301, p<0.05). Similarly directed correlations were found between both parameters of energy balance and LYMlog (FEQ: r=0.530, p<0.01; DBCS: r=-0.318, p<0.05) and MAKlog (FEQ: r=0.520, p<0.01; DBCS: r=-0.299, p<0.05). Univariate analysis provided the highest correlations between LYMlog and FEQ and between MAKlog and FEQ (LYMlog: F=17.36, p<0.01; MAKlog: F=14.46, p<0.01).

CONCLUSION

The results of the study indicate associations between energy balance and the differential cell count in milk.

Zusammenhänge zwischen verschiedenen Parametern zur Beurteilung der Energiebilanz und Zellsubpopulationen in der Milch eutergesunder Kühe

Ziel der Arbeit war festzustellen, ob bei eutergesunden Kühen Zusammenhänge zwischen verschiedenen Parametern zur Beurteilung der Energiebilanz der Tiere und dem Differenzialzellbild in der Milch bestehen. Diese Zusammenhänge könnten nach weiteren Untersuchungen zur Beurteilung des stoffwechselbedingten Mastitisrisikos dienen.Material und Methoden: Bei 15 Red-Holstein-Kühen wurden in der 2., 6. und 12. Woche post partum die β-Hydroxy-Buttersäure-(BHBA-)Konzentration im Blutserum, der Fett-Eiweiß-Quotient (FEQ) in der Milch sowie die Körperkonditionsveränderungen (DBCS) im Zeitraum zwischen Kalbung und erster Probenentnahme bzw. zwischen den weiteren Probenentnahmezeitpunkten bestimmt. Ferner erfolgte mittels indirekter Immunfluoreszenzfärbung in Kombination mit einer Propidiumjodidfärbung eine Messung des Differenzialzellbildes der Milch (Lymphozyten [LYM], Makrophagen [MAK], polymorphkernige Granulozyten [PMN] und Epithelzellen [EPI]). Zur statistischen Analyse wurden Korrelationen zwischen allen Zellparametern und den Parametern zur Beurteilung der Energiebilanz berechnet. Lag keine Normalverteilung der Daten vor, erfolgte eine Logarithmierung (log). Zur weiteren Bearbeitung wurde in einem Mixed Model die Abhängigkeit der Zellparameter von den Parametern zur Beurteilung der Energiebilanz geprüft, wobei der Parameter Tier als zufälliger Effekt fungierte. Ergebnisse: Es bestanden signifikante Korrelationen zwischen FEQ und SCClog sowie zwischen DBCS und SCClog (FEQ: r = 0,459, p < 0,01; DBCS: r = –0,301, p < 0,05). Gleichgerichtete Korrelationen ergaben sich für die beiden Parameter zur Beurteilung der Energiebilanz und LYMlog (FEQ: r = 0,530, p < 0,01; DBCS: r = –0,318, p < 0,05) sowie MAKlog (FEQ: r = 0,520, p < 0,01; DBCS: r = –0,299, p < 0,05). LYMlog und MAKlog wiesen im Mixed Model univariat die höchste Abhängigkeit vom FEQ auf (LYMlog: F = 17,36, p < 0,01; MAKlog: F = 14,46, p < 0,01). Schlussfolgerung: Die Ergebnisse weisen auf Zusammenhänge zwischen Energiebilanz und dem Differenzialzellbild der Milch hin.

[Effects of dry period length on milk production, health, fertility, and quality of colostrum in dairy cows. Invited review]

In terms of milk production, the dry period (DP) is a non-productive time. In addition, the risk of mastitis increases when cows with daily milk yield >12.5kg are dried off, which is often the case when the DP is set to 55-60 days. References on the positive effects of a shortened DP on the metabolic health at the start of lactation and the subsequent reproductive performance were the motive of this review. Completely foregoing or shortening the DP produces a decrease in milk yield during the following lactation. This decrease is particularly pronounced for cows at the beginning of the second lactation. It is thought that this may be due in part to different involution and proliferation processes of the mammary glands in primiparous and multiparous animals. The majority of the scientific papers suggest that shortening the DP has a positive rather than a negative effect on udder health. The quality of the colostrum is also unaffected; but if there is no drying off, the colostrum will be diluted. When considered overall, the literature, with support from metabolic profile studies, appears to favour a reduced impact on energy metabolism in early lactation in circumstances when the DP is shortened or waived. Clear positive effects on parameters relevant to energy metabolism however only apply to multiparous animals, and other factors, such as milking frequency before and after calving, exert an influence. Positive effects of shortening the DP on the reproductive performance were shown in several studies. Time from calving to first ovulation as well as indicators for assessing the success of artificial insemination and reproductive performance showed better results in animals with no or shortened drying off periods. Again, this only applied to multiparous animals. Overall, there is no single clear answer to the question of an optimal length of the DP, but conversely it is abundantly clear that a dry period of 55-60 days is not necessary in all cases and does not make sense under certain circumstances. Based on the study findings from recent years, the determination of dry periods should be used as a farm-specific and needs-oriented applied management decision.

Die Behandlung metabolischer Azidosen bei Kälbern mittels Gabe von Natriumbikarbonat per Schlundsonde

Ziel der Studie war zu überprüfen, inwieweit eine einmalige intraruminale Verabreichung einer zuvor festgelegten Menge an Natriumbikarbonat mittels Schlundsonde geeignet ist, den Säuren-Basen-Haushalt von an Durchfall erkrankten Kälbern mit Anzeichen einer gering- bis mittelgradigen Azidose auszugleichen, ohne dass Nebenwirkungen auftreten. Material und Methoden: 32 an Durchfall erkrankte Kälber mit einer metabolischen Azidose (BE –3 bis –15 mmol/l) wurden nach Blut- und Pansensaftentnahme ihrem Pansensaft-pH-Wert entsprechend in zwei Gruppen (> bzw. < pH 6) eingeteilt. Nach vollständiger Rehydrierung mit einer standardisierten Infusionslösung (5 Liter 0,9%ige NaCl-Lösung, 2 Liter 5%ige Glukoselösung) erhielten alle Kälber 50 g Natriumbikarbonat per Schlundsonde. In regelmäßigen Abständen wurden die Tiere klinisch untersucht und Blut-, Harn- und Pansensaftproben genommen. Ergebnisse: Bei 87,5% der Kälber konnte die metabolische Azidose durch die Natriumbikarbonatgabe mittels Schlundsonde ausgeglichen werden. 56,7% der Patienten wurden für mindestens weitere 48 Stunden erfolgreich therapiert. Je weniger Milch ein Tier nach der Therapie mit Natriumbikarbonat trank, desto wahrscheinlicher war ein Azidoserückfall. Ein Einfluss des Pansensaft-pH-Werts auf die Resorption des Natriumbikarbonats im Pansen war nicht festzustellen. Offensichtliche Nebenwirkungen der intraruminalen Bikarbonateingabe wie Pansentympanie oder zentralnervöse Störungen infolge Hypernatriämie traten nicht auf. Schlussfolgerung und klinische Relevanz: Die intraruminale Gabe von 50 g Natriumbikarbonat per Schlundsonde ist eine geeignete Azidosetherapie bei selbstständig trinkenden Kälbern sowie bei vorbehandelten und somit rehydrierten Kälbern.

Computer based instruction is effective to teach dairy reproductive management

This paper describes a classroom experiment in a German College of Veterinary Medicine (Tieraerztliche Hochschule Hannover) using an instructional software package designed to increase dairy reproductive problem-solving skills. A pre-test/post-test experimental design demonstrated that learning occurred in an enjoyable environment when 21 4th year veterinary students used the program. Students' perception in respect to content, design, and usability criteria of the program were excellent to good.

Endometritis in cattle experimentally induced by Chlamydia psittaci

On the day of estrus, eight virgin heifers received intrauterine inoculations of yolk sac propagated Chlamydia psittaci strain BovEnd 11/88 isolated from the uterus of a slaughter cow. All heifers developed purulent vaginal discharge which persisted for 3 to 7 weeks. Chlamydiae or chlamydial antigen were detected in vaginal and uterine discharges of infected animals by culture or Capture ELISA, while other bacterial pathogens were not found. In sera of the chlamydia-infected heifers marked increases in antibody titres against the chlamydial genus-specific LPS-antigen were found by ELISA and complement fixation test. Six heifers were artificially inseminated in 5 successive cycles beginning at the first estrus following intrauterine inoculation. In two of the infected heifers spontaneous healing of endometritis occurred after 5 estrus cycles. Only these animals conceived after the 5th breeding, whereas in the remaining four animals a chlamydia-associated chronic endometritis was recognized as the cause of infertility in the 19th and 26th week p.i. at slaughter. Two control heifers which remained clinically normal after intrauterine exposure to sterile yolk sac-suspensions conceived at the 1st and 2nd service, respectively.

[Model of an information system for veterinary fertility monitoring as part of an integrated herd management system]

The requirements of the veterinarian's work are changing by reason of an increasing intensity of dairy industry. The model of an information system for monitoring and managing dairy herd health and management system is described. General and special requirements are illustrated. The program requires urgent development for the use of veterinarians and herd owners, including the provision of a data communication link to a veterinary-agricultural information system. The system should integrate the veterinarians into the animal production in order to improve herd health and to secure the veterinarian's role in, and facilitate the development of novel scientific approaches to, dairy herd health and management.

[The effect of gonadotropin releasing hormone (GnRH) and analogs on the conception rate in cattle. A critical literature review]

The objective of this article was to review the current literature of the influence of gonadotropin releasing hormone (GnRH) and GnRH agonists on conception rate in dairy cattle. The application of GnRH or agonists at artificial insemination (first and subsequent) and between days 7 and 34 after parturition were considered. The variations between studies were discussed as well as different mechanisms concerning the influence of GnRH for establishing pregnancy. From a critical point of view the routine use of GnRH or agonists at the time of first or subsequent breeding or during the postpartum period cannot be supported.