Dry Sows Looking for Satisfaction
The modern gestating sow has a problem we can all identify with - she really likes to eat but, at the same time, has to watch her weight. Restricting feed intake in gestating sows is necessary to limit excessive weight gain and fat deposition, stimulate lactation feed intake and increase overall sow productivity. However, limit feeding does not allow the sow the chance to feel full or satisfied after eating and can lead to frustration and, ultimately, stereotypic behaviours. Given the opportunity, a sow would voluntarily eat almost twice the amount of feed that she receives.
Normally a hormone, cholecystokinin, signals the end to feeding behaviour. However, when meal size is small, this hormone may not reach high enough levels to trigger. Without this trigger, the sow has the motivation to continue eating after the feed is gone. In response, she will often engage in stereotypic feeding activities such as rubbing the feeder, biting bars, chewing, playing with the water nipple, or drinking in an attempt to get that satisfaction.
Skip-a-day feeding is a common practice in modern swine production that may help address this situation. Recent research in Iowa has taken this idea one step further and looked at feeding once every third day. Researchers compared sows being fed a 12% corn-soybean meal ration either 2 kg daily or 6 kg once every third day. The weight gain of sows on the 2 regimens did not differ.
Table 1 summarizes some of the more interesting results from the experiment. Overall, behaviour observations suggested the large meal fed to interval-fed sows decreased feeding motivation and arousal substantially. Despite the length of time between feedings, the interval-fed sows did not compensate for the lack of feed on non-feed days with excessive water consumption. In contrast, daily-fed sows spent more time exhibiting a wide range of behaviours, such as sham chewing, drinking or playing with the drinker. The researchers suggested that these behaviours can result in increased energy expenditure by a magnitude of 40%, which likely increases the nutrient requirements needed to maintain body weight and condition.
Based on this research, it is clear that interval feeding is one management practice that can be used to increase the sow's level of satisfaction after feeding. Another option is the inclusion of low-energy nutrients or roughage to increase satiety without the risk of increasing weight gain during gestation.
Researchers in France have shown that feeding fibrous diets can reduce feeding motivation and the resulting behaviours. Sows were fed wheat-barley-soybean meal diets containing increasing levels of sunflower meal, wheat bran, sugar beet pulp, soybean hulls and corn gluten feed to achieve crude fiber levels of 3.3, 10.6 and 18.14%. Sows fed high levels of fiber ate slower, taking three times longer to eat their meals, and were quieter between meals.
Regardless of the diet received, overall the sows were engaged in oral activity (feeding and non-feeding) for the same length of time. For sows fed the low fiber diet, this meant that they spent more time exhibiting stereotypic feeding behaviours, such as licking and bar biting. The researchers did note that substrates in the sow's environment, such as straw bedding, can provide a supplementary source of fiber and potentially alter the nature of the behaviours exhibited.
Research has clearly shown that feeding regimen has a strong impact on feeding motivation in dry sows. Although it remains to be confirmed, it is assumed that this reduction in feeding motivation improves animal welfare. This is definitely a step in the right direction for the sow in search of satisfaction. However, the consequences of interval-feeding and fibrous feeding regimens need to be evaluated further to assess impacts on reproductive parameters and subsequent litters, as well as possible environmental consequences.
Douglas, M.W., Cunnick, J.E., Pekas, J.C., Zimmerman, D.R., and
von Borell, E.H. 1998. Impact of feeding regimen on behavioral
and physiological indicators for feeding motivation and satiety,
immune function, and performance of gestating sows. J. Anim.
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