The study was conducted between January and June 2018 at a commercial breeding farm in Brandenburg, Germany. The production was set to a 1-week-rhythm for the 1200 sows of the farm of the Danish genetic. All sows were vaccinated against the porcine parvovirus and Erysipelothrix rhusiopathiae (Parvoruvac®, IDT Biologica GmbH, Dessau-Roßlau, Germany). As prophylaxis against clinical E. coli and Clostridia infection of sucking pigs, the pregnant sows received a protective maternity vaccination (Clostricol®, IDT Biologica GmbH, Dessau-Roßlau, Germany). About 1 week before farrowing, the sows were moved to the farrowing compartments and treated against endoparasites (Fenbendatat® 5%, aniMedica GmbH, Senden-Bösensell, Germany; Dosage: 5 mg fenbendazole/kg KM oral).
A total of 114 pregnant Danish genetic sows (second to eleventh parity) were included in this study, and divided into two differently designed compartments, hereinafter referred to as experimental system (with 56 focus sows) and standard system (with 58 focus sows). The experimental system sows were kept in large dynamic groups of 105 sows on average. New groups of around 40 sows were admitted on the 74th (first batch) and the 73rd and 107th (second batch) day of gestation, while 40 sows were brought to the farrowing compartments. In the standard system, sows were kept in a stable group of 44 sows on average divided by the trough in the middle into two groups of 17 to 24 sows. The study was carried out in two successive batches. In the first and second batch, 31 and 25 focus sows from the experimental system, and 31 and 27 focus sows from the standard system, respectively, were semi-randomly selected (i.e., taking into account the sows’ parity number).
The experimental system was composed of an activity and lying area and two ad libitum liquid feeding areas enabling access to an either low- (area A) or high-energy diet (area B). Sows were assigned to one of the two feeding areas based on their weight in relation to their parity, and could enter the feeding area passing through a sorting gate (Hölscher + Leuschner GmbH & Co. KG®, Emsbüren, Germany). Sows could return to the activity and resting areas via a reverse door. This ensured a synchronized feed intake of a maximum of 18 sows in the allocated feeding compartment at all times.
The liquid feed was calculated on the basis of whole plant wheat silage (WPWS). The wheat was sown in 2015 (winter wheat) and harvested as WPWS in July 2016, before being ground and ensiled in a tubular silo. In autumn 2017, the tubular silo was cut, and the WPWS was mixed with water in an external mixing tank. The resulting WPWS-water mixture was pumped into the liquid feed mixing tank in the barn building. In the mixing tank, the feed was mixed with other supplemented feed components (Table 10).
Table 10. Botanical composition of ad libitum feeding (% of DM).
Components
|
Low-energy diet
|
High-energy diet
|
Barley
|
30.93
|
48.54
|
WPWS
|
51.55
|
25.89
|
Soya extraction meal
|
13.40
|
21.04
|
Mineral feed
|
4.12
|
4.53
|
The mineral feed and a feed mix of 30.23% soya extraction meal and 69.77% barley meal were purchased by the farm. Table 11 presents the chemical composition of the low-energy and high-energy feed under ad libitum feeding, as well as conventional pellet feed under restrictive feeding.
Table 11. Chemical composition of the rationed diet (standard system) and ad libitum diets (experimental system) (% of DM).
Analytical components
|
Rationed diet
|
Low-energy diet
|
High-energy diet
|
Crude protein
|
17.2
|
18.5
|
22.5
|
Crude fat
|
4.18
|
2.18
|
2.38
|
Crude fibre
|
8.48
|
12.7
|
9.34
|
Raw ash
|
5.9
|
5.3
|
5.16
|
Calcium
|
0.79
|
0.76
|
0.81
|
Phosphorus
|
0.8
|
0.41
|
0.46
|
Natrium
|
0.25
|
0.15
|
0.13
|
Energy (MJ ME/kg TS)
|
13.31
|
11.54
|
13.15
|
In the experimental system, the diets were pumped via stub lines to the troughs in the respective feeding areas (Hölscher + Leuschner GmbH & Co. KG®, Emsbüren, Germany). Two longitudinal troughs in each feeding area were attached to the wall. The length per trough was 4.5 m without feeding place dividers. A sensor was installed in each trough to measure the filling level: if the level was low, the feed was automatically re-filled. Contrary to the standard system, the floor of the experimental system was visibly soiled with food. The experimental compartment was equipped with negative pressure ventilation with three exhaust air ducts (Stienen Bedrijfselektronica B.V., RT Nederweert, Netherlands), and a partially slatted floor. In the lying area of the sows, as well as in the middle of the compartment in front of the sorting gate, a plain concrete floor was available (Fig. 2). The slatted floor has a slot width of 20 mm.
Figure 2. Floor plan of the experimental system with ad libitum liquid feeding.
Sows under standard restrictive feeding were fed a dry diet (for the chemical composition see Table 11) provided by feed dispensers at a long trough. The amount of feed delivered by the feeders was considered as the amount of feed consumed by the sows, since food was completely eaten on all study days. The standard compartment was equipped with negative pressure ventilation with one exhaust air duct (Stienen Bedrijfselektronica B.V., Ort, Netherlands), and a fully slatted floor with a slot width of 20 mm (Fig. 3).
Figure 3. Floor plan of the standard system with restrictive feeding.
Table 12 presents the main characteristics of the two feeding systems being compared in the study.
Table 12: Main characteristics of the standard and experimental system studied.
|
Standard system
|
Experimental system
|
Feed type
|
dry
|
liquid
|
Feed access
|
restricted
|
ad libitum and group-adapted
|
Animal-feeding-place-ratio
|
1:1
|
4:1
4:1
|
Group size (average)
|
44 sows
|
105 sows
|
Group management
Animal-place-ratio
|
Stable group
2.9 m2 / sow
|
Dynamic group
3.0 m2 / sow
|
The following indicators were assessed on the focus sows (ntotal = 114) in the experimental system (n = 56) and in the standard system (n = 58). The body weight was measured at the 31st, 71st, and 109th day of gestation with a mobile animal scale (T.E.L.L. control systems GmbH & Co.KG, Vreden, Germany; weighing range: 65–500 kg).
Scoring of sows’ integument was performed at the 31st, 38th, 45th, 52nd, 71st, 94th, and 109th day of gestation. Integument injuries were documented on both sides of the head, neck (from the ears to the back of the shoulders), lateral abdominal wall (from the back of the shoulders to hind-quarters), and hindquarters (according to the Welfare Quality® Protocol, 2009). Depending on the injuries’ number and depth, they were classified into four categories:
0, no injuries; 1, low number of superficial injuries (< 5 injuries); 2, medium number of superficial injuries (5–10 injuries) or a low number of deep injuries (< 5 deep injuries); 3, high number of superficial injuries (> 10 injuries) or medium to high number of deep injuries (> 5 deep injuries). For each sow, eight marks (0–3) were thus documented, and from these, an averaged value of the whole body was calculated to represent the animal degree of injury. This was included in the statistical analysis as “injury index” characteristic feature.
Evaluation of lameness in pregnant sows was performed simultaneously to the integument’s assessment. Depending on the affected limbs, one of the following scores was assigned (according to the Welfare Quality® Protocol, 2009): 0 = physiological gait pattern or small impurities when walking; 1 = asymmetric gait pattern with distinct lameness, with only a minimum of weight on the affected limb; and 2 = distinct lameness with no weight on the affected limb or sow no longer able to walk. When sows were moved to the farrowing compartments, vulva injuries (existent or non-existent) and litter performance (i.e., number of piglets alive, dead and mummified, and litter weight) were recorded.
To record the sows’ behavior (i.e., displacements at the trough and feed intake rhythm), the activity area and the two feeding areas of the experimental system were each equipped with two cameras (Monacor HDCAM-630, Monacor International GmbH & Co. KG, Bremen, Germany; a 2-megapixel HD-SDI color camera with day/night function and 2.8–12 mm varifocal lens). In the standard system with restrictive feeding, a total of three in the first batch and four cameras in the second batch were placed throughout the compartment. After the integument and lameness assessments (31st, 38th, 45th, 52nd, 71st, 94th, and 109th day of gestation), video material was collected for 1 or 2 days of the three following days. The video material was evaluated in both systems with focal sampling between 6:00 and 10:00 (during the feed intake) each day regarding the displacements at troughs between sows. Displacements were considered only when at least one focus animal was involved. Furthermore, in the experimental system, the video material was evaluated with a 20-min time sampling over 24 h regarding the feed intake rhythm. All sows in the system that showed visible chewing movements or had their head above the trough were included in the evaluation.
Data were prepared in Excel 2016 (Microsoft Deutschland GmbH, Munich, Germany), and statistical analyses were carried out with Statistical Analysis System 9.4 (SAS Institute Inc., Cary, USA). The percentage distribution of lameness of the sows in the experimental and standard systems was calculated using the FREQ Procedure. The MIXED procedure was used to examine how the feeding systems affected the body weight, integument injuries (summed as injury index), and litter performance characteristics. The body weight and injury index models included the feeding system (factor with two levels: experimental, standard), batch (factor with two levels: 1, 2), parity class (factor with four levels: 1–4), measurement time-point (factor with seven levels: 1–7), and their interactions as fixed effects. Because of repeated measurements for sows, the sows’ effect was included as a random effect. Since sows from the two feeding systems showed very different initial weights and integument injuries, the weight and injury rate was corrected at the beginning of the study and included as co-variables. The litter performance characteristics contained five models. The litter weight model included the feeding system, batch, and parity class as fixed effects and numbers of weighed piglets as a co-variable. The number of born/born alive/stillborn/mummified piglets’ models included the feeding system, batch, and parity class as fixed effects, and the residuals as random effects. The number of born piglets was additionally included as co-variable (except for the number of born piglets’ model). The GLIMMIX procedure was used for the binary traits lameness, vulva injuries, and displacements at a trough. The lameness model included the feeding system, batch, parity class, measurement time-point, and the interaction between the feeding system and time-point as fixed effects. The vulva injuries model included the feeding system, batch, and parity class as fixed effects. The sow body weight, sow initial body weight, and the number of weighed piglets were additionally included as co-variables. The displacements at the trough model included the feeding system, time of day (factor with five levels: 6, 7, 8, 9, 10 h), and their interaction as fixed effects. Due to the small number of sows in higher parities, the focus animals were categorized into four parity classes: 1, second pregnancy (n = 22); 2, third pregnancy (n = 23); 3, fourth pregnancy (n = 19); 4, fifth to eleventh pregnancy (n = 50). Since sows showed very different initial weights and integument injuries in the experimental and standard systems, the weight and injury rate were corrected at the beginning of the study. Since repeated observations were available for the sows for all binary traits, the sow effect was always included as a random effect in the respective model.