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Monogastric Nutritionist, Grand Valley Fortifiers

It has been reported by PigChamp that the culling rate in Canada is approximately 40%, as shown in Figure 1. Sows are removed from their herd through voluntary or/and involuntary culling or sudden death. Lameness is one of the major issues when it comes to sow longevity, since it can result in removal of the sow, and impaired animal health and welfare. In addition, the pain and uncomfortableness from lameness affects sow mobility, which can negatively effect their feed intake (FI) and fertility causing an economic challenge to pig farmers. There are more concerns surrounding lameness as sow housing systems are being switched to loose housing systems that require more movement and interaction with other sows. Loose housing is related to higher incidents of lameness compared to individual stall systems due to the need by sows to establish a dominance hierarchy.

Figure 1. Culling rate from 2017 to current (data adapted from PigChamp).

Lameness can be caused by many reasons. One of the main reasons is concrete flooring. In general, solid concrete, slatted concrete, or a combination of the two are used as a flooring material, and the abrasive concrete can cause hoof and leg injuries leading to lameness. Using bedding can lessen the frequency and severity of the injuries; however, more effort is required to maintain floor hygiene

Group size is another reason for injuries that can result in lameness. More fighting and aggressive behavior have been seen in larger groups compared to smaller groups of sows. Fighting can cause hooves to get stuck in the slats causing injuries to the leg and hooves.

In general, two types of housing systems can be seen; static group and dynamic group. A static group system keeps gestating sows together in the same group for the entire gestation. A dynamic group, on the other hand, is a larger group where sows are constantly introduced to new sows during gestation.

Keeping sows in a smaller group or in a static group can reduce this issue. However, even in a static group system, aggressive behavior can be a challenge early on when grouping until their hierarchy is set.

Yet, there are many farms running a dynamic housing system as it can be more flexible for space requirements and locating animals. In dynamic group systems, keeping the weekly mixing number small can reduce the incidence of fighting. If space allows, it has been found that grouping sows by their parities can help lessen the aggressiveness in the group. Nevertheless, in static or dynamic group, sow aggressiveness is inevitable as they must set their hierarchy overtime.

To reduce the incident of fighting, fiber can be added to the diets. In general, sows in gestation are restricted fed to prevent them from getting too fat or skinny. This is because under or over-conditioned sows will have many issues (fertility, milk yield, piglet quality etc.) in the future. However, restricted feeding results in sows getting hungry, which makes them feel frustrated, making them more aggressive and competitive. Adding fiber sources can improve this as dietary fiber makes them feel more satiated for a prolonged time due to the better gut fill effect and delayed gastric transition.

But it should be noted that different types of fiber (soluble vs insoluble) can act differently. In short, soluble fiber increases digesta viscosity, hydration properties, and digesta retention time, while insoluble fiber increases fecal bulk and decreases digesta retention time. This topic can be talked about in more detail in a later article.

Sows that have long hooves have a greater risk of getting their hooves damaged or ripped off which can lead to infections causing a severe lameness. Hoof trimming can be beneficial, however, proper training, equipment and care is required when hoof trimming is attempted.

In order to understand the importance of nutrition in reducing lameness, it is important to understand the structure and the regenerating mechanisms of bones and hooves. However, that will not be discussed in detail in this article. Briefly, the hoof is composed of rigid keratin surrounding the wall and a sole/heel, although it is much more complex. In harder keratins of the wall, calcium (Ca), phosphorus (P) and zinc (Zn) levels are greater than in the softer keratins found on the heels.

To develop and maintain healthy bones and hooves, nutrients must be adequately supplied. When the supply of nutrients is not properly provided, legs and hooves will suffer as they will be more susceptible to getting damaged from physical, chemical, and microbial activities.

Zinc, copper (Cu), and manganese (Mn) have been known to play a key role in the process of keratinization. But other minerals and vitamins such as selenium (Se), vitamin A, D, E and biotin have been a great contributor in producing and preserving healthy keratinized tissues which translate to healthy hooves.

Nowadays, sows are hyper-prolific, and therefore they require much more minerals and vitamins than older genotypes. Consequently, these nutrients must be well provided. It is important to understand that nutrients can interact with each other, making them insoluble and unavailable for the animal to absorb. Chelated minerals are more likely to be soluble and have a greater digestibility than inorganic minerals. Thus, using chelated minerals in feed can ensure that the animals are absorbing adequate amounts.

Calcium, phosphorus and vitamin D are critical when it comes to healthy bones. Insufficient amounts of Ca, P and vitamin D can result in poor bone quality. Deficiency in these can even result in bone fractures, rickets and osteomalacia which is a condition where bones become soft and weak. The availability of Ca in diets is fairly high, whereas P availability can vary depending on the ingredients used. This can be managed by using phytase, an enzyme which breaks down phytate P, making P more available. Vitamin D is also important as it regulates Ca absorption for bone formation and maintenance. Therefore, making sure that the sows are getting an adequate amount of these nutrients is essential.

The requirements for Ca and P is highest during the late gestation and during lactation. Especially in lactation, as sows use their body reserves to mobilize Ca for milk production, it is important to make sure enough Ca and P is being provided to the animal. Checking their feed intake is also crucial during lactation. There may be enough nutrients in the feed, but if the sow does not eat, she will not get those nutrients. To have your sows eating during lactation, monitoring body condition during gestation is crucial.

However, we must keep in mind that not just minerals, but also other nutrients such as proteins (amino acids) are also important. When protein (amino acids) is short, developing hooves may result in inefficient protein synthesis causing lameness. Among the amino acids, cysteine specifically has been found to play an important role in keratinisation. Hence, amino acid balance should also be looked at.

Clearly nutrition plays a significant role in maintaining sows’ leg and hoof health. However, it is important to understand that lameness can be caused by many other factors as mentioned above. Simply walking the barn and monitoring the sows everyday can reduce the number of sows becoming lame as they can be treated before its too late.

This article was written for the Fall 2022 Swine Eastern Dairy Grist. To read the whole Swine Grist, click the button below.