Over 90% of EU pigs are tail docked to minimise tail biting which causes reduced welfare and production [1]. Although tail biting is a multifactorial, lack of long straw has been identified as the largest risk factor for tail biting [2]. Several studies have investigated the amount of straw needed to keep tail biting at an acceptable level on both research farms [3, 4] and in commercial settings [5, 6]. Actual implementation of straw has however largely not taken place and there are still lack of management routines on how to provide straw.
One reason why straw provision has not been implemented is the farmer opinion that straw may block the slatted flooring, manure handling system and stack mired straw in pens, disturbing the pen environment [7–9]. A survey among Swedish farmers using straw it was considered that blockage of slats and manure handling was the most common reason for not increasing straw rations although problems in the manure handling system were quite rarely reported [6]. Furthermore, in practice straw was not reported to be associated with increased need of manual cleaning [5] which has previously been proposed by e.g. Tuyttens [10]. Previous studies show that pig hygiene was worse in straw-based compared to fully slatted systems [11]. However, fully slatted pens substantially reduce the possibility to provide straw on the floor since most straw will quickly pass through the slats and reduces the behavioural benefits for the pigs. Pigs in straw-based systems may purposely soil their lying area to enabling wallowing during hot conditions, which may impair pig hygiene [11] but may also be an indication of poor indoor environment.
There is lack of knowledge of how straw provision impact hygiene under commercial conditions. The aim of this study was to investigate the pig and pen hygiene in systems with partly slatted flooring in farms that are providing increased straw ration compare to standard level. The gained knowledge may be used for facilitating straw usage in commercial production in partly slatted flooring systems.
Methods
Animals and housing
The study was conducted in five commercial Swedish pig farms from November 2015 to June 2017. All pigs were progenies of crossbred sows (Landrace and Yorkshire sows; either Norwegian Landrace*Swedish Yorkshire or Norwegian Landrace*Topigs Large White, that were inseminated with Duroc (G1, G2, F2, F3, G5, F5) or Hampshire boars (F4). One batch each of growing pigs (10 to 30 kg) was investigated on three grower farms: one specialized piglet producing farm (G1), and two farrow-to-finish farms (G2, G4). One batch each of finishing pigs (30 kg – 120 kg) was investigated on four farrow-to finish farms (F2, F3, F4, F5). On F2 and F4 the same batch of pigs was observed in the grower finishing pig stable. The experiment started as the pigs moved in to the grower/finisher unit and finished as the pigs were moved from the grower unit to the first pig was sent to slaughter, respectively. Detailed information about farms and housing is found in Table 1.
Table 1
Information on participating farms, studied animals and straw provisions. Identical Farm number (within farm id) indicates that the farm produced both grower and finisher pigs. C indicates Control treatment and ES Extra Straw treatment (Wallgren et al. 2018).
Farm | Age category | No. pigs produced /year | No. of days in experiment | No. pigs in experiment | No. of pens | Pen Size (m2) | No. of pigs / pen | Area/pig (m2) | Mean straw length (range).cm | Straw ration. g/pen | Straw ration. g/pig | No. of missing daily obs. |
C | ES | Total | Slatted | C | ES | C | ES | (%) |
G1 | Growers | 18 000 | 35 | 286 | 12 | 12 | 4.98 | 1.19 | 12 | 0.41 | 6.6(1-40.5) | 100 (day 1–15) 200 (day 16–24) 600(day 25–35) | 200 500 1000 | 8.3 16.7 50.0 | 16.7 41.7 83.3 | 0 (0) |
G2 | Growers | 7000–7500 | 34 | 427 | 22 | 17 | 5.39 | 1.06 | 10–11 | 0.49–0.54 | 11.9 (7.5–88.5) | 47 | 94 | 4.3–4.7 | 8.5–9.4 | 1 (3) |
F2 | Finishers | 74 | 444 | 21 | 21 | 10.49 | 2.68 | 11 | 0.95 | 11.9 (7.5–88.5) | 132 | 264 | 12 | 24 | 112 (15) |
F3 | Finishers | 2300 | 70 | 195 | 11 | 9 | 9.7 | 1.8 | 11 | 0.88 | 10.4 (1–44) | 100 | 200 | 9.1 | 18.2 | 2 (3) |
G4 | Growers | 7500 | 43 | 360 | 12 | 12 | 4.01 | 1.08 | 12(9)1 | 0.33–0.45 | 5.3(1–31) | 46 | 92 | 3.8–5.11 | 7.6-10.21 | 2 (5) |
F4 | Finishers | 74 | 209 | 12 | 12 | 9.05 | 2.25 | 9 | 1.00 | 6.9(5.5–51.5) | 110 | 220 | 12.2 | 24.4 | 103 (14) |
F5 | Finishers | 10 000 | 68 | 408 | 20 | 20 | 10.49 | 2.68 | 10 | 0.95 | 8.4(1.5–44.5) | 58 | 115 | 5.8 | 11.5 | 144 (21) |
1In farm 4. three pigs per pen were removed after 5 weeks to comply with national legislation according to Swedish board of Agriculture regulations and general advice (SJVFS 2017:25) on the holding of pigs in agriculture, case no. L 106 |
22 weekends and one week |
33 weekends |
47 weekends |
The pigs had daily straw provision and supervision according to normal farm routines. All pens consisted of both solid and slatted flooring (Table 1). The pigs were mixed in pens with gilts and castrates and sorted by size; housing the heaviest and the lightest pigs together respectively. Intact litters was practices when possible. This study was part of a larger study investigating the impact of increased straw ration on pig behaviour and prevalence of tail lesions (see [5]).
Experimental design and treatments
The studied pens was divided in two treatments per farm: Control (C), receiving the farm normal straw ration; and Extra Straw (ES), receiving a double C-ration (Table 1). The C-ration was determined and standardized before the experiment by measuring the daily straw ration provided by the herdsmen (Table 1). All pens of the same treatment were located in the same row of the stable unit, to ease for the animal caretaker. Except for straw ration, all pens in the stable unit were managed in the same way on farm level. Any exceptions from the straw provision routine were recorded by the caretaker (Table 2). If there was blockage in the slatted flooring, and more than 50% of the slatted area was no longer visible, the daily straw provision could be paused until blockage was cleared.
Table 2
Interruption in provision of daily straw, %. Identical Farm number indicates that the farm produces both grower and finisher pigs. C indicates Control treatment and ES Extra Straw treatment.
Grower Farm | C | ES | Finisher Farm | C | ES |
G1 | 0 | 0 | | | |
G2 | 0 | 0 | F2 | 11 | 11 |
| | | F3 | 1 | 6 |
G4 | 0 | 0 | F4 | 6 | 6 |
| | | F5 | 0.3 | 0.08 |
Observations
The pig and pen hygiene was scored every second week, including the first and last week of the experiment by two observers (taking turns scoring C or ES treatment, no intra-observer reliability was measured) (Table 3). The recordings were conducted at least one hour after the daily cleaning and straw provision.
Table 3
Production length and number of observations specified per participating farm. Identical Farm number indicates that the farm produces both grower and finisher pigs. WIP indicates weeks in production.
Farm | WIP | Number of scorings |
G1 | 5 | 4 |
G2 | 5 | 3 |
G5 | 3 | 4 |
F2 | 13 | 7 |
F3 | 9 | 5 |
F4 | 11 | 7 |
F5 | 10 | 6 |
Pig hygiene
Pig hygiene was scored according to the Welfare Quality® protocol applied to growing and finishing pigs manure on the body (Welfare Quality 2009). All pigs were individually assessed for manure on the body, on the side that was visible towards the observer according to a three point scale; 1 if a maximum of 20% of the pig was covered in manure; 2: >20–50% of manure coverage; 3: >50 of manure coverage.
Pen hygiene
The solid and slatted floor of the pen were each divided in to four separate parts (Fig. 1). The solid floor part was considered dirty when at least 50% of the area was covered by faeces, mired straw or was wet. The slatted floor area was considered as blocked, when the slats was covered and no space between the slats was visible for at least 50% of the assessed area. For each past assessed as dirty/blocked, the pen was scored with one point. Subsequently the scores were added to receive the final hygiene score of the solid and slatted area respectively. A pen could have a maximum of four points (all parts ≥ 50% dirty/blocked) and a minimum of 0 points (all parts < 50% dirty/blocked) per solid/slatted area.
Statistical analysis
All data was recorded in Microsoft Excel 2016 and analysed through SAS 9.4 (SAS Institute Inc., Cary, NC, USA). The descriptive statistics were calculated through means and frequencies on both farm and age category (grower/finisher) level. Pig and pen hygiene data was ordinal and data had repeated measurements on pen level.
Pig hygiene
The low variability made analysis of variance on age level impossible. To enable analysis the data was rearranged into binomial traits; hygiene score 1 (i.e. maximum 20% soiled body surface) were considered clean while pigs with score 2–3 (> 20% soiled body surface) were considered dirty. Data was then analysed using Fisher’s exact test, investigating impact of Treatment (C or ES) on Pig hygiene on pig level for each Farm and observation occasion separately.
Pen hygiene
The low variability made analysis of variance on age level impossible. To enable analysis of variation, the data was rearranged into binomial traits on the solid/slatted floor separately. Pens with the score 0 (no soling/blockage of the floor) were considered clean while pens with score 1–4 (soling/blockage of 25–100% of the Solid/Slatted area) were considered dirty. Data was then analysed using Fisher’s exact test, investigating the impact of Treatment (C or ES) on pen hygiene on pen level for each Farm and observation occasion separately.
Correlation between Pig and Pen hygiene
Spearman rank correlation was used to investigate the correlation between pig hygiene and solid/slatted floor hygiene. Pig hygiene was converted into a mean score per pen instead of the initial pig level value. Solid and slatted hygiene was kept as the initial values ranging from 0–4 for each occasion. Thus, the correlations were estimated based on pen level scores, for each scoring occasion, both on Farm and Treatment level.