In view of the task of the Animal Health Service in the Netherlands there is a need to know the parameters by which diseases on farms can be traced and treated. The variables should be measured at central places such as slaughterhouses and feed mills. Here one can use existing systems so that the collection of data will only require some additional costs. Moreover the data can be collected independent of the farmers.
For many years the Animal Health Service in the Province of North Brabant has paid much attention tot the general health. of fattening pigs on farms. This care was instigated by the Coöperatieve Vee en Vleescentrale (Co-operative Cattle and Meat Organization) of the Noord-Brabantse Christelijke Boerenbond (NCB) (North Brabant Christian Farmers Union) and the association of pig farmers of the NCB to improve the general health for pig production. Two very frequent pig affections are of lung and liver.
This study was concerned with whether it is possible to distinguish between pigfattening farms on the basis of differences in incidence of lung and liver affections in slaughtered pigs. The influence of environment on frequency and on the severity of affection was also investigated. The study was done on farms tot include the influence of a set of factors related to commercial farms.
The aim of the study was to answer the following questions:
1. What is the frequency of lung- and liver affections in pigs at slaughtering?
2. Are there differences in frequency of affected lungs and livers between sexes, between breeding farms, between offspring of boars, between farms, between piggeries on the farms and between the seasons?
3. Does the climate inside the piggery influence the frequency of lungand liver affections?
4. Are there other environmental and management factors that influence lungand liver affections?
5. What is the effect of an affected lung or liver on bodyweight gain per day and slaughter quality of pigs?
Chapter 2 reviews the literature on the etiology and frequency of lungand liver affections, the influence of the environment upon these frequency and the consequences for productivity.
Chapter 3 describes the material and methods. The investigation was carried out on 18 pig-fattening farms in North Brabant. These 18 farms had 31 piggeries in which the fattening pigs were housed. All pigs were slaughtered at one slaughterhouse. All farmers were participants of the Asten Integration Group of the Coöperatieve Vee- en Vleescentrale of the NCB.
For each pig, data on pedigree, farm of origin and growth and slaughter quality were collected by the integration administration. Every pig was checked at the slaughterhouse for lung- or liver affection: the extent of the affection if present was estimated.
On the basis of this estimation the lungs and the livers were classified: not affected (0), small macroscopic lesions or scars (1), moderately affected (2), severely affected (3). The affected livers that were discarded belonged to Class 3. From 1 October 1969 to 1 October 1970, in total 5741 lungs and 5756 livers were examined and assessed according to this classification.
To investigate the influence of some environmental factors on incidence of affected lungs and livers, 11 farms were chosen out of the 31 according to the frequency of affected lungs and livers per piggery. On these 11 farms 17 piggeries were selected to study the influence of climatic factors. From April 1971 until April 1972 in 10 different months the following were measured: the temperature and relative humidity inside and outside the piggery, air velocity at 4 locations in the piggery, the katavalue (cooling rate) and the ammonia- and carbon dioxide contents. At each measurement the hygiene was evaluated with a score of 0 to 9. Also the number of pigs as a percentage of the total capacity of the piggery was recorded. Furthermore data were collected on the volume per pig, floor surface per pig, capacity, heating and ventilation system, number of times the pig are shifted, cleaning measures, deworming and system of removing dung. Once the degree of temperature fluctation (TSG) was determined (Section 3.4.l.).
The relation between the mean value of these variables per piggery and the incidence of lung- and liver affections from each piggery were computed. From the data collected by the Integration Group the bodyweight gain per day and slaughter weight and quality were known for each pig.
By correlation and regression analyses the relation between these production characteristics and the degree of lung- and liver affection (0 to 3) was calculated.
The results of the research are described in Chapter 4. In Section 4.1 the frequencies of lung- and liver affections were analysed. The main conclusions are:
- Of the lungs examined 49,2% were unaffected, 38,5% had small lesions, 9,2% were moderately affected and 3,1% were severely affected.
- Of the livers that were examined 34,5% were unaffected, 50,1% had small lesions, 7,8% were moderately affected and 7,6% severely (discarded).
- There were differences in percentage of lung affections and also in the severity of the lesions between gilts and barrows. No differences were found in liver affections between these sexes.
- From the results given in Chapter 4 it can be concluded that the frequency of lung and liver affections is significantly influenced by the farm on which the pigs are fattened, the piggery in which they are housed, the breeding farms within fattening farms and the offspring within breeding farms.
Thus it is possible to distinguish between farms on the basis of frequency of lung- and liver affection. Between the pig-fattening houses the percentage of affected lungs ranged between 30 and 72%; the percentage of affected livers ranged from 21 to 79% and that of discared livers (Class 3) between 1 and 29%. When the frequency of the affected lungs increased so did the severity of the affection.
- The frequency of lung- and liver affections was influenced by the month of slaughtering. The degree of the lung affection (LoA) at the slaughterhouse was also influenced by the day of the year (ti) on which the pigs entered the fattening house. This influence was found to be a sine function:
barrow: LoA = 0.746 + 0.109 sin (ti + 43°05')
gilt: LoA = 0.578 + 0.156 sin (ti + 50°07')
Piglets put in the fattening houses between December and April had severer lesions on the lungs at the slaughterhouse than those of other months.
Some of the results given in Chapter 4 deal with the climate inside the fattening house and with general management. From the data given in the tables and graphs it can be concluded that:
- The climate inside a piggery is mainly influenced by the climate outside. There is a positive relation between temperature inside and outside and between relative humidity inside and outside the piggery.
- In the periode with a low temperature inside, the r.h. and CO 2
content of the air inside increased by decreasing the ventilation rate. The cooling rate in these periods were higher than at other periods.
- The piggeries with a higher temperature have a lower r.h. but also a high CO 2
content and a smaller cooling rate. It can be concluded that with a high temperature inside there is a reduction in ventilation rate. The differences in temperature and r.h. inside the piggery are especially due to differences in the periods with low temperatures.
- A rise in air velocity caused a decrease in r.h. and NH 3
and CO 2
contents; moreover the kata value is higher. Hence the increased air velocity is probably due to an increased ventilation rate.
- In piggeries with a high percentage of occupied fattening places the temperature is higher. Piggeries with more available places have a higher percentage of occupied places.
The results of the study of the influence of the environment upon the incidence of affected lungs and livers are described in sector 4.2.5. and 4.2.6. From the data it can be concluded that:
- The influence of climatic factors on the frequency of lung- and liver affections is mostly via temperature and air velocity. Temperature and air velocity measurements were compared with two indices: the degree of temperature fluctuation inside a piggery (TSG), and a draughtiness index (TW) which is obtained by multiplying the temperature differences inside and outside the piggery with mean air velocity inside. The frequency of affected lungs was increased when both TW and TSG were also increased. Especially in periods with low temperature the TW strongly influences the number of affected lungs.
- A decrease in the area per pig increased the number of affected lungs; the probability of infection may be increased.
- A lower percentage of affected lungs was found in piggeries with central heating.
- Climate in the piggery had hardly any influence on frequency of affected livers.
- Hygienic factors were negatively correlated with the number of affected and discarded livers. It seems to be possible to reduce the percentage of affected livers bij efficient cleaning-out measures.
In Section 4.3 the results of the influence of the affected lungs and livers on bodyweight gain per day and slaughter quality are given.
The results show that the bodyweight gain per day was reduced by 11,3 g (2,5%) when the lungs were affected. The reduction in bodyweight gain per day increased with the severity of the lung affection.
Pigs with affected livers had a reduction of 7,5 g gain per day (1,5%) in compared with the pigs with unaffected livers.
Contrary to the effect of the severity of affected lungs on gain, the pigs whose livers were discarded had less reduction in gain than pigs with moderately affected livers.
Both affected lungs and livers in the same pig caused a greater reduction in bodyweight gain per day than when one of these organs was affected. Pigs with severely affected lungs and livers gained 26 g per day less (5%) than pigs without lung and liver lesions.
Slaughter quality is hardly influenced by lung and liver affections.
In the discussion the results of this study are compared with those reported in literature. This study shows that it is possible to distinguish between pigfarms on the basis of frequence of lung- and liver affections. Moreover it has been shown that some environmental and climatic factors can influence the incidence of the affection. A method has been described of how to organize veterinary measures for the reduction in lung and liver affections. By using a routine in the slaughterhouse for the detection of affected lungs and livers, incidence of affection on the fattening farms can be assessed. Because of the existing facilities the detection will only require some additional costs. On the basis of the frequency found the organizations involved can set up an efficient veterinary survey on the pertinent farms.