Investigation of Early Mortality in Piglets - Coursework Example

Investigation of Early Mortality in Piglets 1.0 Introduction The high rate of neonatal deaths in piglets remains a key concern for pig producers across the world (1, 2). Consequently, many studies have been conducted to determine the cause of mortality in piglets in their early stages (3, 4). Various conclusions have been made based on the findings of the various studies. For instance, according to Kirkden et al. (5), in North American and European countries that produce pigs, the mean mortality rate of pre-weaned piglets is typically at the level of 11 percent to 13 percent, with an additional seven to eight percent of piglets that are stillborn. The same source also notes that the rate of mortality varies significantly among herds, in that a live-born mortality rate of five to seven percent as well as a stillbirth rate of less than 5 percent can be achieved. The variations in early deaths of piglets are caused by many factors, including differences between farms, housing, genotype, management and nutrition (5). Against this background, this review will discuss some of the factors that are related to the early mortality of piglets. The review will start by discussing the causes of death in piglets, focusing on non-infectious causes and infectious causes. This will be followed by review of the methods that are used to determine the cause of piglet deaths, other than histopathological techniques. Next will be a comparison of early mortality in piglets with mortality in young ones of a few other domestic animals. The last part of the review will be an analysis of the measures that are used to prevent piglet deaths, followed by a conclusion to wrap up the entire discussion. 2.0 Common causes of death in piglets 2.1 Non-infectious causes 2.1.1 Crushing Crushing or overlying of piglets by the mother sow has been identified in several studies as the most common cause of early death among piglets that are born alive (6,7). For example, Vrbanaca et al. (6) conducted an analysis of data pertaining to 354,094 piglets born alive from 34,648 litters in a pig farm in Bosnia Herzegovina between June 1985 and May 1988. The data were gathered by monitoring the piglets on a daily basis during the stated period, and the authors found out that overlying was the most common cause of death, at six percent. Along the same line, Andersen et al. (7) have argued that about 50 percent of the deaths that occur after piglets are born are as a result of crushing by the mother sow when the sow and the piglets are kept in a farrowing pen that is loose. Deaths due to crushing occur mainly during instances when sows that have farrowed change their position, especially when they roll over or when they lie down after being in a standing position (5). It so happens that when a change of position occurs, some of the piglets can be trapped by the sow’s body and may be crushed to death. Crushing is said to have occurred when no movement of a trapped piglet occurs after a change of position by the sow (1). 2.1.2 Starvation Starvation is also one of the underlying causes of mortality of piglets at an early age [4]. According to Kirkden et al. (5), starvation can occur due to reasons such as the sow failing to produce adequate colostrum or individual piglets failing to suckle enough. Failure by piglets to consume adequate colostrum can be as a result of a poor competitive capability or an inadequate number of the piglets’ mother’s teats (5). The strong competition among the piglets for milk and colostrum (2) may lead to those piglets that are not competitive enough dying at an early stage. The piglets that are most affected are those with low body weight since they take longer to get to the teat and suckle, and are also less competitive for suckling compared with their heavier counterparts (4). In one study, 72 percent of piglets that were born alive but later died had failed to consume colostrum (3). 2.1.3 Suffocation Piglet death by suffocation is closely related to crushing of the piglets by their mother when she changes position as explained in section 2.1.1 above. McOrist (8), a consultant pig veterinarian in China, has observed that the largest percentage of live-born piglets’ deaths in normal farm conditions is caused by suffocation as a result of the piglets being overlain by the sow. 2.1.4 Poor housing and environmental causes The housing conditions in which piglets are raised soon after birth determine whether the piglets will growth or die at an early age. For instance, farrowing pens that do not have suitable sleeping areas or dry floors expose the piglets to very cold conditions (8). When piglets are exposed to such conditions, chilling can result. Piglet chilling means that the piglets become very cold due to the cold or wet conditions to which they are exposed in the pen (8). When this happens, the piglets, unable to generate enough heat on their own, may lie on their side on the cold surfaces and die due to hypothermia and starvation (4, 8, 9). Hypothermia in piglets occurs because the surrounding temperature of the farrowing pen is usually less than the critical temperature of the newly born piglets (5). As such, the piglets must at first use their innate energy reserves to sustain the body temperature (5). When the surrounding environment temperature is below the recommended level, this causes significant mobilisation of the piglets’ energy stores (9). This has negative ramifications on other aspects of the piglets such as increasing susceptibility to diseases and hindering mobility (9). When piglets’ mobility is hindered, or when the piglets lie too close to the sow to stay warm, the probability of them being crushed by the sow also increases (8). Another issue that is related to housing is the manner in which sows and piglets are housed. A study conducted by Thomsson et al. (10) found out that in general, overall piglet mortality was positively associated with mortality in pens housing several sows that have litters, especially where piglets aged less than one week are involved. This is because such piglets are more likely to be overlain or crushed by sows (10). 2.2 Infectious causes 2.2.1 Bacterial infections Some of the bacterial pathogens that cause deaths of piglets at an early stage include Leptospira spp., Erysipelothrix rhusiopathiae, Chlamydia spp., and Mycoplasma suis (11, 12). These pathogens cause different diseases and have different effects on piglets. For example, E. rhusiopathiae is a gram-positive bacterium that causes erysipelas (11). The pathogen spreads via oronasal exposure, after which there is septicaemia in both adult pigs and piglets. M. suis, which causes eperythrozoonosis, attaches itself to red bold cells and replicates on them (11). It results in anorexia, anaemia, immune suppression, icterus and fever. The resultant frailty in piglets can result in death. 2.2.2 Viral Infections The viral diseases that are known to cause death in piglets include African swine fever, Teschen disease, hog cholera (also known as swine fever), Talfan disease, transmissible gastroenteritis, epizootic diarrhoea, toxoplasmosis, porcine parvovirus infection, and Aujeszky's disease (pseudorabies) (11, 13-15). These diseases occur in different regions of the world and have different effects that may culminate in death in piglets. For example, according to Peter et al. (15), Teschen disease, which causes acute polioencephalomyelitis, is found in the USA, Europe and Scandinavia. On the other hand, Talfan disease, which occurs occasionally in Denmark and the UK, causes sub-acute encephalomyelitis. Talfan disease is mostly seen in piglets that are aged below two weeks (15). Both diseases (Talfan disease and Teschen disease) are characterised by higher mortality in younger pigs (15). 2.2.3 Other diseases There are also some fungal infections that cause piglet mortality. For example, the fungus Claviceps fusiformis that is commonly found on Pennisetum typhoides (pearl millet) has been associated with deaths of newborn piglets (16, 17). 3.0 Other methods that are used to determine the cause of piglet deaths (apart from histopathological techniques) Apart from histopathological techniques, other methods that are used to determine the cause of death in piglets include virological and bacteriological examinations of piglets that die suddenly, as noted by Lavoue et al. (18). Such examinations are conducted if the piglets show some clinical signs before they die (19). For instance, if there are symptoms such as diarrhoea, distended abdomen, tarry faeces or any other clinical symptom in dead piglets, then the various appropriate examination techniques will be applied to determine the cause of death (19). To determine non-infectious causes of piglet mortality such as crushing, starvation, and deaths that can be attributed to poor environmental conditions such as chilling, individual piglet examination can be done (20). This may involve visual examination to check for signs of being overlain, cold bodies to suggest chilling, and smaller or emaciated bodies to suggest starvation among other examination techniques (20). 4.0 Comparison of early mortality in piglets with early mortality in other animals Some of the deaths in piglets can be related to deaths in the young ones of other kinds of livestock while others tend to be more unique to pigs. Most of the mortalities that are comparable in both pigs and other animals include those caused by infectious diseases such as leptospirosis, which is caused by the Leptospira spp. bacteria and affects pigs, cattle, goats, sheep and horses (11, 21, 22). This implies that infections that affect livestock may lead to the death of nearly all young ones in the different farm animals. The problem is particularly likely to be exacerbated when the young ones are unable to suckle due to infection or other problems such as chilling. Hypothermia also affects nearly all types of livestock if the temperature of the pen in which young ones are kept is not regulated, especially in very cold areas (23). Since hypothermia impairs the ability of the young ones to suckle colostrum and milk, this may lead to death due to starvation. Death by crushing on the other hand appears to be more frequent among piglets than in the young ones of other types of livestock. According to Gordon (24), piglets are the most susceptible to crushing, especially during the first 24 hours of life. This is because at this time, they spend much of their time near the udder and have considerably poor mobility (24). This, coupled with the fact that there are many piglets in any given litter competing for a small number of teats, means that some of the piglets are likely to be killed when the sow changes its position. This is unlike cows, sheep and goats, which have fewer offspring at a go. 5.0 Measures that are used to prevent piglet deaths 5.1 Crushing It has been found that most crushing incidents in loose house pens occur when sows lie down without wall support (25). In a study, it was also noted that piglet crushing was just 0.5 percent when the sow lied down against a wall, but it was 14 percent when the sow lied down without wall support (25). Thus, a wall may support the process of lying down and make it slow and controlled (25). As such, pens that have walls designed in such a way as to provide support to the sow when lying down can help reduce piglet mortality due to crushing (5, 25). An example of this is shown in Figure 1. Provision of straw and other related bedding stuff in the pen may also lower the risk of crushing (5). Figure 1: A sleeping zone with an escape zone for piglets (25: p. 101). The wall attracts the pig to make use of the support when lying down. The double wall ensures that piglets are not crushed by the sow as its body goes down. 5.2 Starvation Piglets need to be assisted in their attempts to suckle, and supplementary feeding may be necessary to ensure that weak piglets get adequate colostrum and milk (2, 5). Also, fostering piglets as soon as they are born is necessary to make sure that the number of piglets born does not surpass the sow’s accessible and functional teats (2, 5). 5.3 Housing and environmental control measures To prevent chilling and cold floors, there is need to ensure that farrowing pens have bedding materials such as saw dust or straw to keep the piglets warm (5, 7). As well, there is need provide heat during cold seasons to ensure that the pen does not get very cold (7). 5.4 Diseases Diseases can be prevented by measures such as keeping the pen clean and disinfected, fostering the piglets to reduce litter size, and monitoring diseases within the pig herd (5, 7). 6.0 Conclusion This review of literature has analysed several issues pertaining to early death of piglets. The issues that have been reviewed include the common causes of piglet mortality, the methods used to assess causes of death other than histopathological techniques, comparison of causes of early mortality in piglets with early mortality in other types of livestock, and measures that are used to prevent early mortality in piglets. References (1) Vieuille C, Berger F, Le Pape G, Bellanger, D. Sow behaviour involved in the crushing of piglets in outdoor farrowing huts – a brief report. Applied Animal Behaviour Science. 2003; 80: 109–115. (2) Bowman GL, Ott SL, Bush EJ. Management effects on preweaning mortality: A report of the NAHMS National Swine Survey. Swine Health and Production. 1996; 4(1): 25-32. (3) Le Devidich J, Rook J. Piglets survival: importance for efficient productivity. In: Taylor-Pickard JA, Nollet L. (eds.) Nutritional approaches to arresting the decline in fertility of pigs and poultry. Wageningen, The Netherlands: Wageningen Academic Publishers; 2006. p. 53-72. 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