Introduction
Osteodystrophia fibrosa also known as bran disease was first described in 400 A.D., it is known as nutritional secondary hyperparathyroidism [1]. It has been reported in horses in Australia, Canada, Ethiopia, Hawaii, Hong Kong, South Africa, and the United States of America [2–7]. There is a paucity of literature reports on the condition in Nigeria. The condition has been reported to be induced by a persistent imbalance of calcium and phosphorus in the diet of horses and grazing horses on very low-quality pastures [5,8]. Horses in Nigeria are used for polo, racing, leisure, traditional ceremonies, and local sugar production [9,10]. In many situations, horses are also confronted with diseases that adversely affect their uses [11,12]. Some of these diseases include O. fibrosa, equine influenza, African horse sickness, equine piroplasmosis, brucellosis, ulcerative lymphangitis, and colic [12–14]. In horses with chronically low levels of calcium, the parathyroid glands respond by releasing excessive levels of parathyroid hormone. This hormone causes calcium to be released from bones into the blood, potentially leading to brittle bones over time. The condition can also result in a swollen face, hence the name Big Head Disease [15].
The poor disease reporting along with the poor surveillance network could also add to the seeming poor records on the disease in Nigeria. Horse keeping in Nigeria is becoming a big business, especially through racing, weekend riding by youths, and marriage processions [16]. If this condition is present in these horses, they may not be available to perform for these activities. O. fibrosa is a preventable disease with appropriate horse diet balancing. Knowing the causes, symptoms, and treatment is important for all horse owners. This study was aimed at confirming the occurrence of this disease in the selected local Government in Kaduna State.
Materials and Methods
Study Area
This study was carried out in three Local Government Areas (LGAs) of Kaduna State, namely, Igabi, Sabon-gari, and Zaria. The state is located within the geographical coordinates of latitude 10°20’N and longitude 7°45’E.
Ethical clearance
Approval for the use of horses was obtained from the Ahmadu Bello University, Zaria Committee on Animal Use and Care with the approval number ABUCAUC/2020/73.
Horses studied
A purposive sampling technique was used to select the LGAs with the highest population of polo, racing, and traditional ceremonial horses. Furthermore, a convenience sampling technique was used to select horse stables with the agreement of horse owners to participate in the study. A total of 59 horses were sampled for the study. Nineteen of the horses were from Igabi LGA while 20 horses each were from Zaria and Sabon Gari LGA. The reproductive status of the horses showed that 26 were stallions, 31 mares, and 2 geldings, respectively. The breed distribution of the horses sampled showed 25 Argentine, 21 Sudanese, and 13 West African Barb horses. The estimated age distribution of the horses indicated that 13 horses were of the ages 1–5 years, while 19, 15, and 12 horses were of the ages of 6–10 years old, 11–15 years old, and 16–20 years of age, respectively. The guideline by Payne [17], was used to determine the breed of the horses while the reproductive status of sampled horses was determined using the presence of the various sex organs for males and females. The approximated age of the horses was determined by using dentition [18].
Feeding
Some horses in the study area (Sudanese and West African Barb, n=34) were fed twice daily in their stable (Morning and evening), while the more organized farms (farms with Argentine horses, n=25) provided feed for the horses and allowed them to go out on the paddock to graze. They were fed with Bracheria decumbens 6 kg (60% of forage), Vossia cuspidate 3 kg (30% of forage), Soya bean hull 0.5 kg (20% of concentrate), and corn bran 0.5 kg (20% of concentrate). For each feeding session, the total daily intake was divided into multiple feedings to avoid digestive issues. The horses were monitored and adequately fed to avoid overfeeding or obesity by visual assessments of body condition, and nutritional analysis of feed samples.
Physical examination
The vital parameters (respiratory rate, pulse rate, and rectal temperature) of all animals under study were taken as a routine for clinical examination of the horses. Rectal temperature was taken in degrees Celsius (°C) using a digital thermometer while pulse rate was taken in beats per minute at the external maxillary artery while the respiratory rate was taken in cycles per minute by observing the caudal thoracic movement for inspiration and expiration through the flank area of the sampled horses. A complete physical examination of the entire body of the horse, starting from the head was carried out. For those showing swollen heads (bilateral), palpation of the facial bones and percussion of the sinuses were done for evidence of malformations, along with an examination of the long bones for possible signs of the condition. Furthermore, the horses were allowed to walk to ascertain the degree of lameness. Horses with swollen, soft, and painful facial bones, lameness or reluctance to move due to pain or fractures, weight loss despite adequate food intake, and poor coat condition were classified as clinically diseased. Halter head restraint was used to restrain the horses.
Blood sampling
Early in the morning before feed administration, 5 ml of whole blood was collected through venipuncture of the jugular vein using a disposable sterile 10 ml syringe and 18-gauge needle after disinfecting the site using chlorhexidine-soaked cotton wool. Before blood collection, each horse was restrained using a head restraint by an assistant. The collected blood samples were placed in a labeled sample bottle without ethylene diamine tetra acetic acid, they were transported to the DNA Laboratory, Kinkino Government Reservation Area (G.R.A) Kaduna in cold packs for serum biochemical analysis. In the Laboratory, each blood sample was centrifuged at 800 × g for 15 minutes. Serum was harvested and used for analysis of calcium, phosphorous, and parathyroid hormone levels (PTH).
Fecal samples collection
About 5 g of fecal samples were collected from the rectum of each horse and kept in polythene bags and transported to the Institute of Agricultural Research (IAR), Ahmadu Bello University, Zaria laboratory where they were refrigerated at 4°C used for analysis.
Serum biochemical and parathyroid hormone determination
The serum calcium and phosphorous levels were determined with the modified Clark-collip (1925) procedure, using an automated Mindray Bs 230 machine. PTH were determined with the automated Chemiluminescent Technique, using the Mindray cli 1,000i machine for the analysis [19].
Fecal calcium and phosphorous levels determination
The calcium and phosphorous levels were determined in feces using the method described by Henry [20]. Briefly, a fecal sample weighing 2–6 g was heated at 60°C for 6 hours in a platinum dish. To the ash in the dish, 2 g of anhydrous sodium carbonate was added and further heated to 90°C. When the dish and its content cooled, diluted hydrochloric acid (HCl) (1:1) was added to dissolve it. After the mixture was completely dissolved, it was transferred into a beaker and dehydrated using silica by evaporating to dryness in a steam bath. One drop of concentrated HCl was then added, filtered, and washed then precipitated several times with hot water. The clear solution was neutralized with NH4OH, and then 10 ml each of 0.5 HCl and 2.5 % oxalic acid solution were added. The mixture was heated by boiling in a steam bath, and 30 ml of 3 % solution of ammonium oxalate was added, with constant stirring. After cooling to room temperature, 8 ml of 20 % sodium acetate solution was added slowly, with constant stirring. The precipitate was allowed to stand overnight, filtered through asbestos previously treated with H2S04 and KMnO4, and washed with cold water. The oxalate and the asbestos were washed into a 250 ml Erlenmeyer flask, and 5 ml of concentrated H2S04 was added.
Feed sample analysis
Oxalate level was determined by titration method [21]. Exactly 2 g of the sample was dispensed in 190 ml of distilled water in a 250 ml volumetric flask. Ten milliliters of 6M HCl were added after which it was digested at 100°C for 1 hour then cooled and made to volume before filtration. The filtrate was precipitated with ammonium hydroxide and the precipitate was dissolved in 10.0 ml of 20 % sulphuric acid. The solution was titrated with 0.05 M potassium permanganate. Phytate level was determined using the method of Reddy and Love [22]. Four grams of the ground sample was soaked in 100 ml of 2 % HCl for 5 hours and then filtered. To 25 ml of the filtrate, 5 ml 0.3 % ammonium thiocyanate solution was added. The mixture was then titrated with Iron III chloride solution until a brownish-yellow color that persisted for 5 minutes was obtained.
Data analysis
Data obtained were expressed as means ± standard errors of means (SEM). Independent t-test was used to compare data from clinically and non-clinically diseased horses. Analysis was computed with a statistical package for social sciences (SPSS for Windows, Version 26, Chicago). Values of p ≤ 0.05 were considered statistically significant.
Results
Distribution of clinically diseased and non-diseased horses by sex, age, and breed
In this study, 17 horses were clinically healthy, and 42 were clinically diseased. Male horses had the highest number of clinically diseased horses, while horses between 6 and 10 years and Sudanese breeds had the highest number (Table 1).
Table 1.
Distribution of clinically diseased and non-diseased horses by sex, age, and breed.
| Igabi (N=19) | Zaria (N=20) | Sabon Gari (N=20) | ||||
| Clinically diseased | Non-clinically diseased | clinically diseased | Non-clinically diseased | Clinically diseased | Non-clinically diseased | |
| Male | 5 | 1 | 11 | 3 | 6 | 2 |
| Female | 10 | 3 | 3 | 3 | 7 | 5 |
| 1–5 years | 3 | 0 | 4 | 1 | 4 | 1 |
| 6–10 years | 2 | 1 | 6 | 2 | 5 | 3 |
| 11–15 years | 4 | 2 | 3 | 2 | 2 | 2 |
| 16–20 years | 6 | 1 | 1 | 1 | 2 | 1 |
| Argentine | 4 | 15 | 3 | 2 | 1 | 0 |
| Sudanese | 0 | 0 | 8 | 3 | 6 | 4 |
| West African Barb | 0 | 0 | 3 | 1 | 6 | 3 |
Clinical findings
The vital parameters of the 59 horses examined during the study were within the normal ranges. The overall mean pulse rates for clinically diseased horses were 37.5 ± 0.22 beats per minute while for the non-clinically diseased horses, the respiratory rate was 37.4 ± 0.40 which was not significant (p > 0.05) when compared. The mean respiratory rates were 10.55 ± 0.74 cycles per minute and 10.53 ± 0.74 cycles per minute for the clinically and non-clinically diseased horses which was not significant (p > 0.05) when compared and the overall mean rectal temperatures were 37.4°C ± 0.05°C and 37.6°C ± 0.67°C for clinically and non-clinically diseased horses which was not significant (p > 0.05) when compared (Table 2). The clinical signs observed were enlarged bilateral facial bones, pain while chewing, stiff gait, and the average body condition score of 2/5 in clinically diseased horses and 4/5 in non-clinically diseased (Fig. 1).
Figure 1.
(A) Enlarged facial soft tissue (Arrow), (B) Bilateral enlargement of facial bones (mandibula and maxilla) in a horse with Osteodystrophia fibrosa (Arrow), and (C) Body condition score of 2/5 in a horse with Osteodystrophia fibrosa (arrow).
Table 2.
Mean values of vital parameters of sampled horses.
| Vital parameters | Clinically diseased | Non-clinically diseased | Reference value |
|---|---|---|---|
| Pulse rate (cpm) | 37.5 ± 0. 22 | 37.4 ± 0.40 | 36—40 |
| Respiratory rate (bpm) | 10.55 ± 0.74 | 10.53 ± 0.74 | 8—15 |
| Temperature (°C) | 37.4 ± 0.05 | 37.6 ± 0.67 | 37.5—38.5 |
Key: cpm: cycles per minute, bpm: beats per minute, °C: degree celsius, p > 0.05.
Biochemical parameters of sampled horses
The horses in Zaria LGA had the highest calcium value for the non-clinically diseased horses (2.82 ± 0.02 mmol/l), while clinically diseased in Igabi LGA was 2.71 ± 0.03 mmol/l though not significant (p > 0.05) when compared to non-clinically diseased. Also, for the non-clinically diseased horses, phosphorous levels were highest in horses in Sabon Gari (1.20 ± 0.11 mmol/l) while horses in Zaria had the highest (1.26 ± 0.08 mmol/l) in the clinically diseased horses. The serum calcium of clinically diseased horses was significantly (p < 0.05) decreased in Zaria (2.47 ± 0.03) and Sabon gari (2.24 ± 0.02) when compared to non-clinically diseased. Phosphorus levels were not significantly different (p > 0.05) (Fig. 2). The serum PTH for horses under the study were highest in Igabi LGA for the non-clinically diseased horses (38.9 ± 3.50 pg/ml) while parathyroid hormones of clinically diseased horses were significantly (p < 0.05) higher in Zaria (93.01 ± 6.44) and Sabon gari (81.01 ± 6.34) when compared to non-clinically diseased (Fig. 3A). Parathyroid hormones of clinically diseased horses were significantly (p < 0.05) higher in male and female when compared to non-clinically diseased horses (Fig. 3B). The West African Barb and Sudanese breeds of horses had lower calcium levels and higher PTH in the diseased horses. Based on age group, the clinically diseased horses within the age brackets of 1–5 years and 6–10 years had slightly lower calcium levels (Fig. 4A, B, C).
Figure 2.
Levels of calcium and phosphorus in clinically and non-clinically bran diseased horses in the three selected local government areas in Kaduna State. *Significantly different at p < 0.05.
Figure 3A, B.
Levels of parathyroid hormones in clinically and non -clinically bran diseased horses in the three selected local government areas in Kaduna state. *Significantly different at p < 0.05.
Figure 4A, B, C.
Levels of calcium and phosphorus in clinically and non-clinically diseased horses by sex, breed, and age.
Fecal calcium and phosphorous levels in sampled horses
The fecal calcium value was highest in horses in Igabi (75.89 ± 6.55 mg/kg) for the non-clinically diseased horses and (82.85 ± 4.17 mg/kg) for the clinically diseased horses. Similarly, the fecal phosphorous values for the clinically diseased horses were highest in horses in Igabi (2801.76 ± 212.51 mg/kg) while the lowest phosphorus level (2554.5 ± 207.38 mg/kg) was recorded in Sabon Gari. The fecal calcium and phosphorous level were not significantly different (p > 0.05) (Fig. 5A, B).
Figure 5A, B.
Fecal calcium and phosphorus levels in clinically and non -clinically bran diseased horses in the three selected Local Government Areas of Kaduna State.
Level of oxalate and phytate in horse feeds
The grasses identified to be fed to the horses during the time of sampling were Bracheria decumbens and Vossia cuspidate, while the concentrates were pelleted processed feed, corn bran and soya bean hull (Fig. 6). The oxalate levels were as follows Bracheria decumbens (0 mg/100 kg) Vossia cuspidate (0.02 mg/100 kg), corn bran (0 mg/100 kg), soya beans hull (0 mg/100 kg) while the phytate level were Bracheria decumbens (0 mg/100 kg), Vossia cuspidate (0 mg/100 kg), corn bran (0.77 mg/100 kg), and soya beans hull (0.51 mg/100 kg) (Table 3).
ureFigure 6.
Various Horse feeds in the Local Government Area of study.
Table 3.
Analysis of horse feeds for oxalate and phytate in selected Local Government Areas of Kaduna State.
| Feed | Oxalate mg/100 kg | Phytate mg/100 kg |
|---|---|---|
| Soya bean hull | 0 | 0.51 |
| Corn bran | 0 | 0.77 |
| Vossia cuspidate | 0.02 | 0 |
| Bracheria decumbens | 0 | 0 |
Discussion
From the study, the vital parameters (respiratory rate, pulse rate, and rectal temperature) of the horses under study were within normal ranges when compared with previous reports [23,24]. This seems to indicate that O. fibrosa does not significantly influence vital parameters of affected horses at this level of the disease. This has been similarly observed in previous research [25]. It could be that the condition, being non-infectious, does not affect these parameters. There was a marked difference in calcium levels of the clinically diseased and non-clinically diseased horses. This could be a result of the type of feed, general management practice in the stables under study, and other reasons like soil and forage types which could have an important impact on the etiology of this disease. It has been reported that calcium from soil accumulates in several plants and when fed to these horses, calcium builds up over time in the system. Previous research reported that feeds high in oxalate tend to result in net losses in calcium and phosphorus levels and are excreted through feces [26]. However, in a situation where horse owners provide salt licks to their horses may tend to alleviate the condition, if present. The PTH were also statistically significant. This may be ascribed to the fact that PTH is responsible for the minute-to-minute regulation of extracellular calcium (Ca2+) concentrations. The relationship between serum Ca2+ concentrations and PTH is inverse and sigmoidal in horses [27,28]. This enables the parathyroid gland to respond rapidly to minimal changes in Ca2+ concentrations. In O. fibrosa, elevated levels of PTH often lead to increased bone resorption (breakdown) to release calcium into the bloodstream. This results in the replacement of bone tissue with fibrous tissue and the formation of cysts [29]. The difference in the calcium and phosphorous levels had no statistical significance based on the sex of the horses in this study. However, the diseased male and female horses had slightly lower calcium levels. The PTH levels were also higher in the diseased male and female horses but that of the male was higher. It could be that the male horses were more active, judging by their roles in polo and racing [11]. The West African Barb and Sudanese breeds of horses had lower calcium levels and higher PTH in the diseased horses and this could also be ascribed to the fact that these breeds were not adequately fed when compared with the Argentine breed of horses that were managed and owned by more organized farm. Based on age group, the clinically diseased horses within the age brackets of 1–5 years and 6–10 years had slightly lower calcium levels. This could be associated with the fact that the younger horses were most susceptible to the condition with more pronounced lesions compared to the adults. This may be because of their need for more calcium required for growth development. This agrees with the report that the condition is seen more in horses of 2–8 years of age [29]. It could also be that the owners were not particular in caring for them as they might have been more interested in feeding the older ones that could be used immediately for racing or polo as reported horse owners in Kano Metropolis being more particular in feeding those horses in active service [11]. The PTH for the clinically diseased horses of age groups 1–5 years, 6–10 years, and 11–15 years were high. This could be accounted for due to the decrease in the calcium level. Previous reports showed that increasing age does not affect the condition [29]. The higher levels of phosphorus in this study could be a result of grains and bran being the most common food fed to horses in the study. Grains and bran block the absorption of calcium and eventually lead to a severe calcium deficiency. Grains and bran are high in phosphorus, low in calcium, and also contain chemicals called phytates, which bind to calcium in the gut, forming calcium-phytate compounds that cannot be absorbed by the horse [30]. Elevated fecal phosphorus levels in clinically diseased horses are indicative of dietary imbalances and are consistent with O. fibrosa while elevated fecal calcium levels in clinically diseased horses suggest a metabolic response to excess phosphorus or poor calcium absorption [7].
Conclusion
The study has shown that O. fibrosa exists in the study area. Also, there seems not to be an age predisposition for the occurrence of the condition. The parathyroid hormone of clinically diseased horses was found to be higher than that of non-clinically diseased horses. The fecal calcium and phosphorous levels were highest in Igabi LGA. The haematological parameters as seen in this study were within normal ranges.
Acknowledgment
The authors appreciate the laboratory staff for their technical expertise in carrying out this research.
Conflict of interest
The authors declare no potential conflict of interest.
Authors’ contributions
RAN, SS, KKB, and PWM designed the study, supervised the research, and edited the manuscript; RAN, KOJ, RE, and PWM performed the research and analyzed the data; RAN and KOJ drafted the manuscript. All authors have read and agreed to the published version of the manuscript.
