Our questions are answered by Dr. Michael Lütke-Dörhoff from Osnabrück University of Applied Sciences
- Dr. Lütke-Dörhoff, as a research assistant in the animal nutrition department at Osnabrück University of Applied Sciences, you examined the influence of different vitamin supplements on the fundamental health of sows, piglets and fattening pigs. What is it about?
Lameness can quickly lead to serious health and animal welfare problems in sows, but also in growing pigs. In addition to infectious causes, one possible trigger for this is disturbed bone mineralization. If the mineral supply is inadequately balanced and other general stress factors, such as intestinal diseases or suboptimal housing conditions, the risk of lameness could increase.
- Where does vitamin supply come into play here?
Vitamin D promotes the absorption of phosphorus and calcium from the small intestine. Adequate vitamin D status is therefore necessary for maintaining bone mineralization, immune function, muscle strength and other physiological processes. However, since pigs in closed stables only produce vitamin D themselves to a very limited extent, the feed rations are usually supplemented with up to 2000 international units (IU) of vitamin D3 (cholecalciferol) per kilogram of feed. As an alternative to this classic form of supplement, 25-hydroxycholecalciferol (25-OHD3), a vitamin D metabolite, has been available for some time. This is approved in the EU as a feed additive for poultry and pigs and can partially or completely replace vitamin D3. The direct supply of 25-OHD3 has two main advantages. First, 25-OHD3 is absorbed at a higher rate. It also bypasses the hydroxylation step in the liver. The animal’s vitamin D status – measured by the 25-OHD3 serum level – can be increased more effectively by direct supplementation of the metabolite than by administering “classic” vitamin D3.
- And you examined this in more detail in an experiment…
Correct: As part of a cooperative doctoral project from several universities, the influence of 25-OHD3 supplementation instead of the usual vitamin D3 supplement in N-/P-reduced feed of sows and growing pigs on the prevalence of leg swelling, gait changes and lameness was examined. To do this, we randomly divided 49 sows of Topig origin into two groups of 25 and 24 animals on a practical farm in Lower Saxony before insemination. While the diet of the control group (VD) was supplemented with 2000 IU/kg vitamin D3 in the form of cholecalciferol, in the experimental group (25D) we mixed 25-OHD3 instead at a dose of 50 μg/kg diet. The addition took place throughout the entire pregnancy and 28 days of suckling. And because we wanted to research the vitamin D effects not only in the sows, but also in their offspring (Topigs 20 × Pietráin), the piglets were divided into the following four groups:
– VD/VD: These piglets from vitamin D3 sows also received feed supplemented with vitamin D3 during rearing and fattening.
– VD/25D: Vitamin D3 in sows – rearing and fattening with 25-OHD3,
– 25D/VD: 25-OHD3 for sows – rearing and fattening with vitamin D3,
– 25D/25D: 25-OHD3 in sows and 25-OHD3 in rearing and fattening.
The groups were allocated equally according to initial body weight and gender. Due to operational conditions, each rearing group consisted of 96 piglets. During fattening, 72 animals per test group were examined. The vitamin D3 and 25-OHD3 used (product name “Rovimix Hy-D”) were provided by the company DSM Nutritional Products GmbH.
- What characteristics did you use to measure the effect of the different forms of vitamin D?
Leg swelling and gait changes were recorded on an individual animal basis. For this purpose, the legs (carpal/tarsal joints) of all sows at insemination, stalling and weaning as well as all offspring at the age of 6, 8, 10, 14, 18, 20 and 22 weeks were examined for swelling using a three-stage score (0 = no lesion; 1 = at least one lesion with a diameter <2 cm; 2 = at least one lesion with a diameter ≥2 cm). We assessed any gait changes for each animal at the same time points. For this purpose, the pigs were assessed on a 16 m long corridor according to the following key: 0 = no changes in gait/even steps; 1 = gait changes (asymmetrical walking), 2 = mild lameness (shortened stride/reduced weight bearing on the affected limb); 3 = severe lameness (minimal weight bearing on an affected limb).
- Have you found any differences in the sows’ fundamental health?
Yes, definitely and clearly: As can be seen in Overview 1, there were fewer problems with gait changes in the sows in the 25D group.
79% of these animals had no noticeable movement before birth, while gait changes and slight lameness were noticeable in almost two thirds of the sows from the VD group. At weaning, 67% of the sows in the 25D group but only 28% in the VD group showed no signs of gait changes and mild lameness. Overall, the effects were highly significant both before birth and at weaning. Severe lameness did not occur in the study and the prevalence of leg swelling in the sows in our trial was not influenced by the dietary form of vitamin D.
- And what about the piglets or fattening pigs?
The study produced several results here:
In piglets from sows that received 25-OHD3 in their diet (groups 25D/25D and 25D/VD), leg swelling was observed less frequently during rearing than in the experimental groups in which the sows received “conventional” vitamin D3 (Overview 2 ). Direct supplementation of the offspring with 25-OHD3 instead of vitamin D3 (group VD/25D and 25D/25D), on the other hand, did not bring such clear advantages for leg health during rearing. In fattening, a positive effect of 25-OHD3 could only be partially observed. At 14 weeks, for example, only 15% leg swelling was recorded in the 25D/25D group. In contrast, for the VD/VD pigs it was 56%. For the characteristic gait changes, we found, among other things, a significantly lower prevalence in the offspring of 25D sows in the 6th week (25D/VD group 8%, VD/VD piglets 21%). And direct supplementation of the offspring with 25-OHD3 also seems to have a positive effect on gait stability.
- What conclusions do you draw from the experiments?
The frequency and severity of leg swelling and gait changes generally increase with age. However, our results show that this health problem can at least be reduced by supplementing with 25-OHD3. A comparable study on the influence of the form of vitamin D on lameness and gait changes was not found in the literature reviewed. Sows whose feed was supplemented with 25-OHD3 also remained standing longer after feeding. This indicates a healthy musculoskeletal system. The severity of leg swelling and gait changes may also be positively influenced by longer standing times and shorter lying times. Since we did not analyze standing and lying times in the growing pigs in the study, these hypotheses should be tested in further studies.
First, however, we note that replacing classic vitamin D3 with 25-OHD3 leads to a reduced prevalence of leg swelling in growing pigs, few gait changes and mild lameness in sows and growing pigs, and increased standing time in sows. These are clear effects with potential for practical use.
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