Perinatal mortality in the pig: environmental or physiological solutions?

Posted in: Pork Insight Articles, Welfare by admin on September 25, 2013 | No Comments

The evolutionary strategy adopted by the pig is to produce a large number of relatively undeveloped offspring. Such a strategy demands that relatively little investment is made in each individual piglet pre-natally, and that piglets which are surplus to resources should die at an early stage with least prejudice to their littermates. Thus, inherent variation in neonatal competitiveness is an advantage and survival of the strongest is promoted. Genetic selection strategies resulting in increased litter size and reduced physiological maturity at birth have compounded these effects, making piglet mortality an intractable problem. Records of piglet mortality in commercial units indicate that most deaths of liveborn piglets are attributed to crushing and starvation, but these ultimate causes are often secondary to the effects of perinatal hypothermia. Piglet survival is the outcome of complex interactions between the sow, the piglet and the environment. Commercial strategy has focused on improving the farrowing environment to modify sow behaviour and increase human intervention. However, concerns about the welfare implications of confining sows in farrowing crates may limit the use of such approaches in the future and change the focus towards genetic selection for characteristics in both the dam and offspring which promote survival. Methods of improving the inherent viability of the piglet, for example by increasing birth weight, neonatal vigour and thermoregulatory ability, have been commercially less effective to date, with intra-partum hypoxia exerting an overwhelming influence. A better understanding of neonatal and maternal physiology in relation to placental transfer of nutrients, regulation of the parturition process, colostrum transfer and expression of appropriate maternal behaviour is required for the development of effective future solutions.

Sandra Edwards

Identification of risk factors associated with poor lifetime growth performance in pigs

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During the production period from birth to slaughter there are some pigs that grow markedly slower, despite conditions that seem to support the growth of their contemporaries. This reduction in growth inevitably leads to weight variation within a group, causes difficulties with management, and results in system inefficiencies. By understanding the factors that contribute to poor growth, the performance of these slow growing pigs might be improved, thereby decreasing the overall variability at slaughter. The aim of this paper was to analyze the factors associated with poor growth performance in pigs from birth to slaughter, determine the effect of piglet birth weight (BiW) and weaning weight (WW) on lifetime growth, and investigate the capacity of small piglets to compensate for any BW deficit. Two industry databases, with individual data for approximately 40,000 and 90,000 pigs, respectively, and containing BW profiles and relevant variables, were analyzed. Body weight at birth, weaning, intermediate, and finishing stages were available as well as sex, month of birth, litter size information (number born alive and total born including still born), sow parity number, and length of gestation. Absolute and relative growth rates, based on adjusted BW for age, were calculated for each time interval and 3 types of analysis were performed: a logistic regression, a continuous linear plateau model, and a weight category analysis. For both datasets poor absolute and relative growth from birth to final BW was associated with low BiW (P < 0.001), low WW (P < 0.001), sex (P < 0.001), breed code (P < 0.001), and month of birth (P < 0.001). The linear plateau model suggested that the relationship between BiW and lifetime growth was not linear beyond 1.91 (database 1) or 1.84 (database 2) kg; the same applied to the relationship between WW at 21 d and final BW (FW) growth, which was not linear beyond 7.53 kg. Finally, the weight category analysis revealed that piglets with the lightest BiW were able to exhibit compensatory growth from BiW to FW with 74 (database 1) and 82% (database 2) moving at least 1 BW category. It is concluded that growth performance to slaughter is not solely reliant on pig BiW, with WW also playing a critical role. Additionally, piglets with BiW below the average are capable of some degree of compensatory growth; this provides the opportunity for managing them so as to improve their lifetime growth.

Sandra Edwards

Social rank and feeding behaviour of group-housed sows fed competitively or ad libitum

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Animals living in a group generally establish a dominance hierarchy which enables the group to function without the necessity of fights whenever group members encounter each other (Beilharz and Cox, 1967). A stable dominance hierarchy can be maintained by subtle signals and give high-ranking animals priority of access to resources in limited availability (Banks et al., 1979). In intensive housing systems this can have serious consequences for low-ranking animals (Csermely and Wood-Gush, 1990), owing to close proximity of high-ranking sows and, in some cases, limitation of resources.

A restricted feeding regimen is adopted in commercial practice to maintain an almost constant body-condition of the sow throughout the reproductive cycle. Depending on the manner of distribution of this limited amount of food between sows in a group-housing situation, competition can result in unequal distribution of food and loss of condition of low-ranking sows (Brouns and Edwards, 1992 ). This kind of competition is likely to occur in feeding systems where the food is distributed once or twice daily on the floor (floor-feeding) and is aggravated by a low feeding level (McBride et al., 1964; Baxter, 1983 ). A  conventional diet is concentrated in nutrients and although it is sufficient for good health and performance, it might not fulfil other needs of the sow, since the small amount of food is unlikely to give a feeling of satiety (Lawrence et al., 1988 ). Provision of
a diet ad libitum should, in theory, obviate the need for competition and eliminate negative consequences for low-ranking sows.
In this experiment, the consequences of food available, in limited quantities once daily or ad libitum, on live weight gain and feeding behaviour of sows of different social rank in a group-housing situation, were investigated.

Sandra Edwards

The welfare implications of large litter size in the domestic pig II: management factors

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Increasing litter size has long been a goal of pig breeders and producers in many countries. Whilst this has economic and environmental benefits for the pig industry, there are also implications for pig welfare. Certain management interventions
are used when litter size routinely exceeds the ability of individual sows to successfully rear all the piglets (ie viable piglets
outnumber functional teats). Such interventions include: tooth reduction; split suckling; cross-fostering; use of nurse sow systems and early weaning, including split weaning; and use of artificial rearing systems. These practices raise welfare questions for both the piglets and sow and are described and discussed in this review. In addition, possible management approaches which might mitigate health and welfare issues associated with large litters are identified. These include early intervention to provide increased care for vulnerable neonates and improvements to farrowing accommodation to mitigate negative effects, particularly for nurse sows. An important concept is that management at all stages of the reproductive cycle, not simply in the farrowing accommodation, can impact on piglet outcomes. For example, poor stockhandling at earlier stages of the reproductive cycle can create fearful animals with increased likelihood of showing poor maternal behaviour. Benefits of good sow and litter management, including positive human-animal relationships, are discussed. Such practices apply to all production situations, not just those involving large litters. However, given that interventions for large litters involve increased handling of piglets and increased interaction with sows, there are likely to be even greater benefits for management of hyper-prolific herds.

Sandra Edwards

Alternative farrowing accommodation: welfare and economic aspects of existing farrowing and lactation systems for pigs

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From the evaluation of welfare and economic performance of systems described in this paper, the designed pen appears to offer the best indoor alternative to conventional farrowing crates. However, it is important to make efforts to refine these systems as there are still concerns, particularly regarding safety and ease of operation, and robustness to variability in maternal behaviour. Research into physical attributes of the systems that can facilitate the former and biological strategies (e.g. breeding for better maternal behaviour) to target the latter are important on-going objectives. In addition, to futureproof systems for a developing pig industry and uncertain market, additional research is needed to determine the environmental impact of certain systems and their economic feasibility in a national and international market place.

Sandra Edwards

Factors influencing aggression between sows after mixing and the consequences for welfare and production

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Hierarchy positions in groups of sows are settled relatively quickly, though long term stability can be affected by several factors including method of feeding. Fighting is less intense between pigs of unequal sizes, may be reduced by previous exposure but is less affected by the presence of a boar. Larger groups have more hierarchy positions to resolve and therefore more fighting. Greater space allowance appears to have little effect on fighting at mixing but can reduce aggression in the longer term. Barriers can limit aggression by allowing losers to escape more easily. Provision of ad libitum feed has been shown to reduce aggression over the short term. Straw bedding has no effect on fighting. Chemical intervention techniques would appear to delay rather than reduce fighting. Newly mixed sows should be supervised to reduce fighting. The fighting which occurs during mixing results in physiological stress responses which can have detrimental effects on reproductive parameters. However, the short-term nature of this response means that detrimental effects can be avoided by careful timing of regrouping. It is therefore possible to achieve equally good reproductive performance in group-housing systems as in systems with individual housing, provided that good management is practised.

Sandra Edwards

Positive handling in late pregnancy and the consequences for maternal behaviour and production in sows

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Fear of humans is an important welfare indicator for many reasons. First of all, fear reactions are the most immediate responses that the animals show to potentially dangerous stimuli in the environment. Secondly, it is associated with physiological stress and has negative effects on growth, food intake (performance), important health parameters (immune status) and, not least, reproductive performance (Gonyou et al., 1986; Hemsworth
et al., 1981, 1986, 1987, 1989, 1994, 1999; Boissy, 1995; Jones, 1997; Janczak et al., 2003a). Fear responses to humans show great similarities between different species of farm animals, and can be easily monitored both under experimental conditions (e.g. Janczak et al., 2003b), and on commercial farms (e.g. Hemsworth et al., 1994). Furthermore, fear responses are fairly consistent over time (i.e. represent a part of personality; Janczak et al.,
2003b). Because of the many negative effects of fear of humans, this is an important measure of welfare as well as of great economic interest to the farmer. Even in larger herds, where handling may be minimised by increased technology and more effective handling facilities, there will still be situations where direct contact with the animals is necessary. Positive and consistent handling should therefore be of great importance in any production
system.

Sandra Edwards

The Effect of Rubber Flooring and Social Grouping on the Utilisation of Free Space for Sows in Walk-In/Lock-In Stalls

Posted in: Pork Insight Articles, Welfare by admin on June 11, 2013 | No Comments

The abstract for a study looking at flooring type to increase time spent in communal areas in group housing with free access stalls. The addition of rubber floors, and using the T configuration of housing increase time spent in communal areas by sows of all parities.

Assessment of Gilt Temperament: Are the Tests Reliable & Related to Stress Responses?

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The abstract for a study examining the relationship between temperament and stress-susceptibility, and whether temperament traits are heritable. Four tests measured introversion/extroversion and fear/confidence traits in gilts 12 and 18 weeks old.

Lessons Learned From a Decade of Transitioning Sow Farms from Stalls to Pens

Posted in: Pork Insight Articles, Welfare by admin on June 10, 2013 | No Comments

As the end of gestation stalls seems to be occurring, it is important to consider different setup options and management needs. Gestation stalls were initially used to ensure individual animals received nutrition and care, and to avoid negative social interactions. One thing to consider when switching to group housing is group size. Small groups can be best if similar age and size sows are together, whereas large groups can avoid strict social hierarchy from occurring. Group structure can be static or dynamic. Static structure is all-in all-out and may not utilize space efficiently, and dynamic structure utilizes space, but works better in a large group without social hierarchy. The timing of formation of the group can be pre-implantation, and will result in most of the gestating sows housed in groups. Post-implantation minimizes the effect of negative social interactions on pregnancy, and results in fewer sows being in groups at any one time. Feeding system has a large impact on competition between sows, and can result in varying body conditions if the non-dominant sows are not able to eat their full amount. Systems that can be used include floor feeding with or without stalls, trickle feeding, cafeteria style, free access stalls, or electronic sow feeding (ESF). Electronic sow feeding has a lot of potential since it will allow individual sow nutrition to be determined. Some considerations to have if switching to ESF include parity segregation, group structure, timing, pen design, training both of sows and stockpeople, and how to provide individual animal care. ESF can be an effective feeding system in group housing, but retraining and proper management are essential for its success.