Roczniki Naukowe Polskiego Towarzystwa Zootechnicznego, t. 5 (2009), nr 3 Thoroughbred foals' mortality causes during first six months of life. Part II. Diseases and injuries Maria Kulisa, Katarzyna Makieła, Bogusława Długosz, Magdalena Gaj University of Agriculture in Kraków, Department of Horse Breeding, al. Mickiewicza 24/28, 30-059 Kraków The aim of the study was to analyze Thoroughbred mortality caused by diseases or injuries during the first six months of life. Causes of foals' deaths from birth until weaning were analyzed. Data were collected at one of Polish Thoroughbred National Studs. Twelve breeding seasons were analyzed during which 395 foals were live-born. Data were collected from broodmare cards, foaling notes and direct information was received from the generał farm manager. Colts and fillies were divided into two groups. One of them we re foals dead until third day of life and another groups were foals dead from fourth day of life until weaning, which had place around 6 month of life. Causes of foals' death were diseases of the following systems: digestive, circulatory, nervous, respiratory and musculoskeletal. Injuries were also considered. Because of incomplete data in broodmare cards, a group of foals dead from unknown causes was created. It was found that 4.55 % of foals died until third day of life and 15.19% died until sixth months of life. Main causes of foals' deaths up to third day of life were diseases of circulatory system (16.16%) and from fourth day of life Rhodococcus equi pneumonia (58.97 %). KEY WORDS: foals / mortality / Thoroughbred horses Highly specialized breeding has made Thoroughbreds the fastest horses in the world, yet such a rigid selection for speed has also produced its negative effects. Intensive rising and training exert significant influence on young organisms, particularly on their nervous excitability, which in tum affects the endocrine system and finally reproductive functions. Thoroughbred mares are less fertile than other breeds; they suffer from infertility more frequently or abort their foals. In addition, they are more prone to multiple pregnancies [5, 8]. A high inbreeding coefficient is also a significant factor here, as it conditions strong genetic feature transmission. Along with the desired feature, which is speed, certain other flaws, such as reduced immunity, are transmitted [6]. Immunological deficits are particularly dangerous in the case of diseases such as Rhodococcus equi pneumonia [1]. 79
The aim of the study was to analyze Thoroughbred mortality caused by diseases or injuries during the first six months of life. Materiał and methods Data was collected at one of Polish Thoroughbred National Studs. It was based on broodmare cards, foaling notes and direct information received from the general farm manager. Twelve breeding seasons during which 395 foals were bom, were analyzed. Dead colts and fillies were divided into two groups: de ad foals until the third day of life and dead foals from the fourth day of life up to weaning (around the sixth month of life). Foals' deaths were caused by diseases of the following systems: digestive, circulatory, nervous, respiratory and musculoskeletal. Injuries were also tak en into consideration. The influence of prenatal factors has been already discussed in Part l of this study. Because of incomplete data in certain broodmare cards, a group of foals dead from unknown causes was created. Results and discussion Due to relatively significant difficulties in breeding and raising Thoroughbred horses, identifying causes of foals' deaths becomes a very serious challenge. Table l presents numbers and percentages of live-bom and dead foals. It can be seen that 4.55% of foals died up to the third day of life, while no difference between the number of dead fillies or colts was noted. On the other hand, many more colts than fillies died from day forth up to weaning. Generally, 19.74% of all live-born foals died prior to their weaning age. Most deaths, taking into consideration after birth diseases (until the third day of life), were caused by impaired functioning of the circulatory system (16.66%). In individual cases, colts died as a result of nervous system disorders, neonatal isoerythrolysis and joint deformation; whilst the causes of filiies' deaths included circulatory system disorders (neonatal isoerythrolysis and eongenital heart defects) - Table 2. Rhodococcus equi pneumonia was the most frequent cause of foal losses from the fourth day of life; it was more often suffered by colts (81.81 %) than fillies (70.37%). In three cases, no cause of filly's death was provided, whilst five other deaths were cause by the following: volvulus, e1eft palate, cerebral symptoms, fracture and septicemia. For two colts, the cause of death has not been given, while single animals died as a result of congenitallung defect, peritonitis, croup paresis and joint deformation (Table 2). Rhodococcus equi pneumonia was the cause of more than half of deaths (58.97%); prenatal factors analyzed in Part l of this study foliowed - Table 2. No cause of death was recorded in 6.4% cases (5 animals). Two foals (2.56%) died due to each of the following: neonatal isoerythrolysis, cerebral symptoms and deformation. Single deaths were caused by volvulus, peritonitis, e1eft palate, eongenital heart defect, eongenital lung defect, croup paresis, contractures, fracture and septicemia. The percentage value in each of the above categories equalled 1.28%. I I.J 1 j I 80
Table 1 - Tabela 1 Number and percentage of live-born and dead foals Liczba i procent źrebiąt żywo urodzonych i padłych Live-born Dead foals - Źrebięta padłe foals up to third day of life after fourth day of life until weaning total Źrebięta do trzeciego dnia życia po czwartym dniu życia do odsadzenia ogólem żywo fillies colts subtotal fillies colts subtotal urodzone klaczki ogierki suma klaczki ogierki suma n % n % n % n % n % n % n % n % 395 100.0 8 2.02 10 2.53 18 4.55 27 683 33 8.35 60 15.19 78 19.74 00...
00 Table 2 - Tabela 2 tv Foals mortality causes Przyczyny upadków źrebiąt Foals de ad up to third day of life Foals dead from fourth day of life Dead foals Foals monality causes Źrebięta padle do 3. dnia życia Źrebięta padle od 4. dnia życia - total Przyczyny upadków fillies colt s subtotal fillies colts subtotal Źrebięta padle klaczki ogierki suma klaczki ogierki suma - ogólem n % n % n % n % n % n % n % Oigestive system 2 7.40 3.03 3 4.98 3 3.84 pokarmowy Circulatory system 2 25 10 3 16.66 3 3.84 (neonatal isoerythrolysis included) (2) (2.56) krwionośny (w tym konflikt serologiczny) Nervous system 10 5.55 3.70 1.66 2 2.56 Uklad nerwowy Respiratory system 19 70.37 28 8484 47 78.32 47 60.25 (Rhodococcus equi pneumonia included) (19) (70.37) (27) (81.81) (46) (76.66) (46) (58.97) oddechowy (w tym rodokokoza) Musculoskeletal system 10 5.55 3.70 2 6.06 3 4.98 4 5.12 (joint deformation incjuded) (2) (2.56) mięśniowo-szkieletowy (w tym deformacja stawu) Injuries 3.70 1.66 1.28 Urazy mechaniczne Preriatal factors 6 75 7 70 13 72.22 13 16.66 Czynniki prenatalne Unknown reason 3 11.10 2 6.06 5 8.32 6.40 Brak podanej przyczyny Total - Razem 8 100 10 100 18 100 27 100 33 100 60 100 78 100 ""--...~~L -----..&.._J-, -----I.~ '-- l..~
Owing to an insignificant amount of other causes of foal death, Rhodococcus equi pneumonia will be discussed in more details here. It is a bacterial disease affecting the respiratory system brought about by Rhodococcus equi [3]. In foals up to the sixth month of age, this microorganism causes pneumonia and sometimes also endoenteritis [2, 7]. Rhodococcus equi pneumonia can threaten breeding significantly as, according to Frymus [1] and previous research, 5-7% offoals suffer from it. Mortality rate amounts to 80%. Rhodococcus equi pneumonia is a cause of 5-17% of al! foal losses globally, which confirms an incredible scale of the problem [1]. The observed high mortality rate due to Rhodococcus equi pneumonia is, as Max says [6], a result of its being an enzootie herd disease with difficulties in early diagnosis. That is why it would be important to draw particular attention to the prevention of Rhodococcus equi infections. As Grądzki et al. [4] points out, successful active measures for Rhodococcus equi pneumonia prevention have not been developed so far. Early diagnosis makes it possible to select appropriate treatment and increases its effectiveness. The study revealed Rhodococcus equi pneumonia to be a more common cause of death among colts than filiies. It can be presumed therefore that colts are more vulnerabie to this disease. No incident of Rhodococcus equi pneumonia among foals up to the third day of life was noted, which can be explained by higher immunity at this stage provided by colostrum. Due to relatively high losses in Thoroughbred breeding, caused by infertility, foal abortion or multiple pregnancies, it is necessary to take all measures aiming at the elimination of factors conditioning foals' deaths. The conducted study revealed that 4.55% of foals died until the third day of life and 15.19% died prior to weaning. Rhodococcus equi pneumonia was the most common cause of death in foals from the fourth day of life - 58.97% of al! deaths. The number confirms the incredible scale of the problem and the need for further research aiming at the improvement of diagnostics and successful preventive measures. BIBLIOGRAPHY l. FRYMUS T., 1994 - Zwalczanie rodokokozy źrebiąt. Życie Weterynaryjne 2, 52-54. 2. GIGUERE S., PRESCOTT J.F., 1997 - Clinical manifestations, diagnosis, treatment, and prevention of Rhodococcus equi infections in foals. Vet. Microbiol. 56, 313-334. 3. GRĄDZKI Z., ZIĘTEK A., BOGUTA L., WINIARCZYK S., WOŁOSZYN S., 2002 - Rodokokoza źrebiąt. Medycyna Wet. 58 (12), 915-920. 4. GRĄDZKI Z., ŻIĘTEK A., BOGUTA L., WINIARCZYK S., 2003 - Aktualne możliwości przyżyciowej diagnostyki Rodococus equi u źrebiąt. Medycyna Wet. 59 (9), 773-777. 5. KULISA M., PIESZKA M., FRYBES 0.,1999 - Ciąże bliźniacze w hodowli koni pełnej krwi angielskiej w Polsce w latach 1987-1996. Medycyna Wet. 55 (l O), 13. 6. MAX A., 2003 - Niewydolność oddechowa i zapalenie płuc u źrebiąt. Kall Polski 2 (225), 36-38. 7. MElJER W.G., PRESCOTT r.r.. 2004 - Rhodococcus equi. Vet. Res. 35,383-396. 8. PRUSKI W., 1960 - Hodowla koni. T. 1. PWRiL, Warszawa. 83
I 1 j ~, J Maria Kulisa, Katarzyna Makieła, Bogusława Długosz, Magdalena Gaj Przyczyny śmiertelności źrebiąt pełnej krwi angielskiej w okresie pierwszych sześciu miesięcy życia. Cz. II. Schorzenia i urazy mechaniczne Streszczenie Celem badań była analiza przyczyn śmiertelności źrebiąt pełnej krwi angielskiej w okresie pierwszych sześciu miesięcy życia. Materiał do pracy zebrano w państwowej stadninie koni pełnej krwi angielskiej. Dane uzyskano z kart klaczy matek, zeszytów porodowych oraz bezpośrednich informacji udzielonych przez dyrektora stadniny. Przeanalizowano 12 sezonów rozrodczych, w których urodziło się 395 źrebiąt. Klaczki i ogierki padłe podzielono na dwie grupy. Pierwszą grupę stanowiły osobniki padłe do trzeciego dnia życia, drugą grupę - od czwartego dnia życia do odsadzenia, tj. do szóstego miesiąca. Powodem strat źrebiąt były choroby układu pokarmowego, krwionośnego, nerwowego, oddechowego i mięśniowo-szkieletowego. Uwzględniono również u- razy mechaniczne. Ze względu na braki w niektórych kartach klaczy matek wyłoniono grupę źrebiąt bez podanej przyczyny upadku. Stwierdzono, że w okresie do trzeciego dnia życia padło 4,55% źrebiąt, a do czasu odsadzenia - 15,19%. Najczęstszą przyczyną upadków źrebiąt w pierwszych dniach po porodzie były schorzenia układu krwionośnego (16,16%), a w późniejszym czasie - schorzenia układu oddechowego (76,66%). i l.j 84