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It is well known that starting June 2022 all European pig producers are no longer allowed to use medical zinc after weaning. This has led to several attempts in recent years aiming to find good alternatives that make it possible to wean piglets without medical zinc and at the same time without increasing the use of antibiotics for these young animals. There has gradually been agreement that not one single ingredient can replace medical zinc and to obtain a successful weaning several practical issues, i.e., hygiene, climate, feeding system etc. must be optimized in the weaning sections. Yet, an optimized weaning diet may be one of the most important tools in obtaining a successful weaning.
Earlier this year the pig nutritionists at the Danish Pig Advisory Center (SR) decided to formulate and test a diet that was optimized especially for the very small piglets after weaning. The aim was to formulate the best possible diet (SR-Elite) and unlike other diet formulations the price was not taken into consideration. The success criterium was to make a diet that resulted in a similar performance level (especially with regards to post weaning diarrhea) as a standard diet with medical doses of zinc from zinc oxide (Control). The choice of feed stuffs and additives was based on personal practical experiences combined with knowledge from the literature.
At weaning the feed intake is very low, the intestinal tract is not fully developed or ready to digest nutrients not originating from sow milk. At the same time the stressful change of environment for these young animals demands a very robust immune system. Hence, the SR-Elite diet was formulated to contain feed ingredients that are known to be easily digestible in the immature pig intestine. Furthermore, the diet contained feed stuffs and additives that are expected to provide the most optimal conditions for digestion, intestinal health, and pig immunity. The ingredients and principles used to obtain these optimal conditions are presented in Table 1.
Table 1. The SR-Elite diet was formulated from the following ingredients and principles, to optimize digestibility, intestinal health as well as piglet immunity.
| Expected to improve: | |||
|---|---|---|---|
| Digestibility | Intestinal health | Pig immunity | |
| Heat treated and gelatinized wheat and barley | + | ||
| Soy protein concentrate | + | ||
| Milk powder | + | ||
| Blood plasma | + | + | |
| Unsoluble fibers | + | ||
| Calcium formate | + | ||
| Citric acid | + | + | |
| Benzoic acid | + | + | |
| Low protein content | + | ||
| Amino acid content was increased relative to standard recommendations | + | ||
| Lysine-choloride was used instead of Lysine-sulphate (reduces pH) | + | ||
| Increased vitamin dosing | + | ||
| The supplemented zinc and iron were organically bound | + | ||
| Total iron content was kept below standard recommendations | + | ||
| A probiotic source of Bacillus Subtilis was included | + | ||
| Finally, 0.2% of an acid blend was given through the drinking water | + | + | |
A trial where the SR-Elite diet was compared with the Control diet was performed by TestPig. In addition, the SR-Elite diet was tested in three commercial herds. The main objective was to study if the SR-Elite diet could keep post weaning diarrhea at the same low level as a Control diet that contained medical doses of zinc from ZnO (3 kg/ton).
Testing the pigs
The piglets were weaned at 25 ± 3 days of age and the average initial body weight was 4.2 and 4.1 kg for the Control and the SR-Elite diets, respectively. The study included 20 pens per dietary treatment and the total number of pigs was 538 and 534 in the Control and the SR-Elite group, respectively. The piglets were kept in baby-pig rooms for the first two weeks after weaning before being transferred to the standard weaning rooms.
Every day, the proportion of manure of liquid consistency was registered. The result of these registrations is presented in Table 2, which shows that the number of days with liquid feces on the manure-area was very limited in both groups. The statistical analysis revealed no differences between the two diets.
Table 2. Average number of days in which liquid manure amounted to <1/3-part, 1/3-part, 2/3-part, or 3/3-part of the manure on the manure area of the pen during the first 2 weeks of the trial.
| Control | SR-Elite | P-value | |
|---|---|---|---|
| Less than 1/3 liquid manure, days | 13.0 | 11.9 | - |
| 1/3 liquid manure, days | 0.9 | 1.7 | 0.28 |
| 2/3 liquid manure, days | 0.1 | 0.4 | 0.30 |
| 3/3 liquid manure, days | 0 | 0 | - |
Our experience from the baby-pig rooms at this test facility, is that antibiotic treatments for diarrhea are required the first days after weaning, when the pigs do not receive medical zinc in the feed. It was therefore surprising that there was no need for medical treatment for diarrhea in either of the dietary groups. When this study was completed, and a new batch of pigs was weaned, it turned out that diarrhea occurred again. This observation suggests that the SR Elite diet prevented post weaning diarrhea for these small pigs.
The performance results in terms of average daily gain (ADG), Feed Intake (FI) and Feed Conversion Ratio (FCR) from the first two weeks after weaning is shown in Table 3. The SR Elite group had a slightly higher ADG, although not statistically significant, compared to the control group. Feed utilization, on the other hand, was significantly more efficient in the SR Elite group compared with the Control group (1.78 FUpig/kg vs. 1.96 FUpig/kg gain, respectively).
Table 3. Average Daily Gain (ADG), Feed Intake (FI) and Feed Conversion Rate (FCR) the first 2 weeks after weaning. Different letters indicate significant differences.
| Control | SR-Elite | P-value | |
|---|---|---|---|
| ADG (g/day) | 173 | 198 | 0.13 |
| FI (g/day) | 265 | 275 | 0.53 |
| FCR (FUpig/kg weight gain) | 1.96a | 1.78b | 0.007 |
When the pigs left the baby-pig room, they weighed an average of 6.6 and 6.9 kg in the Control and SR-Elite group, respectively. In the standard weaning section, the growth averaged 549 and 533 g/day in the Control and the SR Elite group, respectively. Consequently, the final weight on day 43 of the trial was almost identical for the two groups, with 22.8 and 22.6 kg for the Control and the SR Elite group, respectively. Feed utilization over the entire trial period was better for the SR Elite group (1.38 kg feed/kg gain) compared to the Control group (1.44 kg feed/kg gain).
When you look a little closer at the figures behind the results shown in Table 3, it turns out that it was especially the smallest of the pigs (<4.0 kg) that utilized the SR-Elite diet very efficiently, which indicates that the SR-Elite diet was particularly beneficial for the very small pigs after weaning.
Experience collections
The three commercial farms, that replaced their standard weaning diet (incl. medical zinc) with the SR-Elite diet, generally had positive experiences. The herds experienced the same or higher growth and slightly more diarrhea when using the SR-Elite diet, but in general the incidence of diarrhea was low for both mixtures.
Conclusion and perspectives
The results from the project show that SR's Nutritionists have grasped something right with the SR-Elite diet. The good feed utilization (especially in the very small pigs) and the low incidence of diarrhea is what is necessary to get the pigs well through the weaning period without the use of medical zinc and without increasing use of antibiotics.
In this study, it was not possible to point out exactly which ingredient or which combinations of ingredients that were significant to obtain the positive effect on post weaning diarrhea and feed utilization. However, currently it is essential to develop solutions that ease the post weaning period without using medical zinc and without antibiotics. The next step is to optimize on these solutions in order to find the most effective and economical solutions.
