An experiment with slaughter pigs from weaning to slaughter including five treatments and five replicates was carried out at the Danish organic experimental station, Rugballegård. Treatments included full or partial outdoor rearing of the pigs, and the replicates covered the seasonal effects. Pigs fed ad libitum indoors had a significantly lower feed consumption (5 MJ ME /kg gain), a lower lean percentage (2.3% points), and a higher backfat depth (1.1 mm, P < 0.05) than pigs fed ad libitum outdoors. Compared with outdoor pigs fed ad libitum, restricted feeding outdoors resulted in a significantly lower daily gain (107 g), a lower feed consumption (6.3 MJ ME/kg gain), higher lean percentage (2.1% points), and a reduced backfat (1.8 mm) (P <0.001). The content of soil nitrogen was considerably higher than for the soil outside the paddocks. Despite a considerable variation within the paddocks, N was distributed throughout the paddock. The present investigation highlights the fact that outdoor rearing of organic finishers may be a competitive option even in a temperate climate and all year round

Eriksen, Jørgen

Hermansen, John E.

Strudsholm, Karin

English

Organic Eprints

FULL OR PARTIAL OUTDOOR REARING OF SLAUGHTER PIGS – EFFECTS ON PERFORMANCE, CARCASS QUALITY AND NUTRIENT LOAD  John E. Hermansen, Jørgen Eriksen & Karin Strudsholm Danish Institute of Agricultural Sciences, Department of Agroecology, Research Centre Foulum, PO Box 50, DK-8830 Tjele, Tel. +45 8999 1236, E-mail John.Hermansen@agrsci.dk, Homepage: http://www.agrsci.org/jpm     Key Words: grazing, N-leaching, production strategy  Abstract An experiment with slaughter pigs from weaning to slaughter including five treatments and five replicates was carried out at the Danish organic experimental station, Rugballegård. Treatments included full or partial outdoor rearing of the pigs, and the replicates covered the seasonal effects. Pigs fed ad libitum indoors had a significantly lower feed consumption (5 MJ ME /kg gain), a lower lean percentage (2.3% points), and a higher backfat depth (1.1 mm, P < 0.05) than pigs fed ad libitum outdoors. Compared with outdoor pigs fed ad libitum, restricted feeding outdoors resulted in a significantly lower daily gain (107 g), a lower feed consumption (6.3 MJ ME/kg gain), higher lean percentage (2.1% points), and a reduced backfat (1.8 mm) (P <0.001). The content of soil nitrogen was considerably higher than for the soil outside the paddocks. Despite a considerable variation within the paddocks, N was distributed throughout the paddock. The present investigation highlights the fact that outdoor rearing of organic finishers may be a competitive option even in a temperate climate and all year round.  Introduction In many countries, including Denmark, organic pork production takes place in barns where the pigs have free access to a limited outdoor area. However, such housing is often very expensive and it may be questioned whether pigs reared under such conditions comply with consumer expectations of organic farming.  Alternatively, slaughter pigs can be reared outdoors. However, data on production results obtained from outdoor rearing are limited. In addition, in relation to the deposition of manure in the outdoor paddocks, outdoor rearing may have drawbacks such as an increased risk of nitrate leaching. Strategies that combine indoor and outdoor rearing may be preferable from an overall perspective.  The purposes of this investigation were to quantify differences in performance and carcass quality traits of pigs reared outdoors or indoors, and to highlight the risk of N-leaching from grass paddocks in such systems.  Methodology The experimental design comprised five rearing strategies in five replicates using a group size of ten pigs that were balanced in terms of live weight and sex. Upon weaning at age 7-8 weeks (approx. 19 kg live weight) piglets born in an outdoor system were distributed over the five rearing strategies as follows:   1.   Piglets were moved indoors at weaning and fed ad libitum until slaughter. 2.   Piglets stayed on pasture and were fed restrictively with concentrates until 40 kg live weight, followed by ad libitum feeding in an indoor pen. 3.   Piglets stayed on pasture and were fed restrictively with concentrates until 80 kg live weight, followed by ad libitum feeding in an indoor pen. 4.   Piglets stayed on pasture until slaughter and were fed restrictively during the whole period. 5.   As treatment 4, but the growers were fed ad libitum until slaughter.  The first replicate started in January 2002 and the fifth and last replicate was completed in April 2003, so that the seasonal variation was covered by the design.  C:\Dokumente und Einstellungen\Jens Unrath\Desktop\Jasmin\Orgprints\ISOFAR\4368-Hermansen_etal_4p_revised-ed.doc In the field each experimental unit (group of ten pigs) was allocated to a ‘new’ piece of land, differing in size according to the expected nutrient load from the pigs. The stocking rate in the field was calculated to cause a level of excretion of 280 kg N per hectare. To ensure a good distribution of the manure and thereby the environmental load from the pigs on the pasture, the huts, troughs and water supply were moved on a regular basis.   All pigs were individually weighed at weaning, at transfer, and at slaughter. Soil samples where collected and grass cover evaluated each time pigs were transferred from the field to housing or slaughterhouse. Grid points were established for every 5x5 m in the 10 m wide paddocks and similarly points were established outside the paddocks for every 5 m as a reference. At each point soil samples were collected to 40 cm by pooling 8 soil cores. A total of 948 soil samples have been analysed for content of mineral N, exchangeable K and extractable P to determine the level and the distribution of nutrients within the paddocks.  Results The content of soil nitrogen was considerably higher than for the soil outside the paddocks. Despite considerable variation within the paddocks, increased N levels were found throughout the paddock (Figure 1). Generally, it was difficult to maintain a grass cover in the paddocks. The nitrogen use efficiency in the paddocks (feed N input relative to animal N output) decreased the longer pigs were kept on the pasture. Thus, N in piglets kept outside until 40 kg accounted for 38% of feed N input, whereas N in piglets on pasture until slaughter accounted for only 30% of feed N input.  100 kg/ha200    -300    -N-min 0-40 cmCol 17 vs Col 18 Col 45 vs Col 46 Col 47 vs Col 48 Distance (m)02 5 5 0 7 5 1 0 040 kg80 kg99 kg94 kgPig exit weight: Fig.1. Bubble plot of inorganic soil nitrogen (0-40 cm) in and outside the four paddocks in replicate 4 of the experiment on growing pigs. Each paddock contained one hut (▲) and one feeding trough (■) that were moved every four weeks (from right to left). All positions throughout the experiment have been shown.   Performance traits of the pigs achieved in the five rearing strategies are given in Table 1.   The daily gain and age at slaughter were significantly affected by the weight/age at transfer indoors. The length of the pasture period with restricted feeding seemed directly related to a decrease in the overall daily gain in treatments IA, I40A, I80A and OR. However, the feed conversion rate was not significantly different among these treatments. Restrictively fed pigs had a higher age at slaughter (17 days), a lower daily gain (133 g), and an improved feed conversion rate (-6.3 MJ ME/kg gain). C:\Dokumente und Einstellungen\Jens Unrath\Desktop\Jasmin\Orgprints\ISOFAR\4368-Hermansen_etal_4p_revised-ed.doc C:\Dokumente und Einstellungen\Jens Unrath\Desktop\Jasmin\Orgprints\ISOFAR\4368-Hermansen_etal_4p_revised-ed.doc Compared to the indoor-reared pigs (IA) the outdoor-reared pigs (OA) had a small numerically lower daily gain and a higher age at slaughter, while the feed conversion was significantly poorer (13.4%).   Pigs that were transferred at a live weight of 40 kg to indoor facilities with free access to feed compensated almost completely in overall daily gain before slaughter, while pigs transferred at 80 kg live weight only compensated a little.   The pigs reared on pasture had a significantly higher intake of roughage compared with indoor pigs. Although they had the possibility to graze and root, pigs reared outdoors with free access to concentrates consumed 85% more roughage than indoor pigs. This indicates a synergy between foraging and access to a variety of feeds in an enriched environment, as discussed by Andresen (2000).    Table 1. Performance traits achieved in five rearing strategies compared at the same live weight at slaughter; Least square means, SEM and P values for significance of differences between treatments. Treatment Indoor ad lib (IA) Transfer to barn at 40kg (I40A)  Transfer to barn at 80 kg (I80A) Outdoor restricted (OR) Outdoor ad lib (OA) SEM  P value Age at slaughter, days 1) 156 a 161 a 170 b 177 b 160 a 2.2  <  0.0001 Daily gain,   g/day 1) 767 a 728 a 672 b 634 b 737 a 14  <  0.0001 Concentrate,          kg per kg gain 2.81 a 3.03 ab 2.95 ab 2.64 a 3.15 b 0.12  <  0.05 Roughage,             kg per kg gain 0.21 a 0.23 a 0.43 b 0.46 b 0.39 b  0.06   < 0.05 Feed conversion,   MJ ME/kg gain 37.3 a 40.2 ab 39.9 ab 36.0 a 42.3 b 1.7  <  0.05 Different letters within each row indicates a significant difference (P < 0.05) 1) Adjusted to a final live weight of 97 kg   The carcass characteristics are given in Table 2.   Table 2. Carcass characteristics of pigs as a result of five rearing strategies; Least square means, SEM and P values for significance of differences between treatments. Treatment Indoor   ad lib  (IA) Transfer to barn at 40 kg(I40A)  Transfer to barn at 80 kg (I80A) Outdoor restricted (OR) Outdoor ad lib  (OA) SEM  P value Lean in total carcass, % 57.5 a 57.6 a 60.4 b 61.9 c 59.8 b 0.39  <  0.0001Backfat depth, mm  17.6 a 18.4 ab 15.9 d 14.7 e 16.5 ac 0.51  <  0.001 Lean in central piece, % 61.9 a 61.4 a 65.4 d 67.3 e 64.2 d 0.57  <  0.0001Different letters within a row indicate a significant difference (P < 0.05)   Rearing strategy had a significant effect on carcass traits (Table 2). Pigs reared outdoors throughout their life or until 80 kg live weight had a significantly higher meat content than pigs reared indoors. Backfat depth showed the opposite results. There were no significant differences in the lean percentage between I80A and OA pigs.  C:\Dokumente und Einstellungen\Jens Unrath\Desktop\Jasmin\Orgprints\ISOFAR\4368-Hermansen_etal_4p_revised-ed.doc  The effects on lean percentage and backfat corresponds to findings by Guy et al. (2002) and Stern et al. (2001).  Gustafson & Stern (2003) and Gentry et al. (2002), however, found no such difference between indoor and outdoor pigs during the summer. An explanation could be that pigs on pasture use more energy during cold periods to maintain body temperature than indoor pigs with access to an outdoor pen.   Conclusion The recorded differences in carcass characteristics in the present investigation resulting from the different rearing strategies can be very important in organic production. In some situations, such as in Danish organic production, the price achieved for a slaughter pig depends very much on whether the carcass fulfils certain quality threshold values, i.e. a minimum lean percentage and a maximum depth of backfat. The effect of this can turn out to be more important for the financial return in pig production than the achieved weight gain and cost of the feed. The present investigation highlights the fact that outdoor rearing of organic finishers may be a competitive option even in a temperate climate and all year round.   A risk of nitrogen leaching commensurate with stocking rate is inevitable. It is important to focus on a lowering of the level of dietary N to increase N use efficiency in outdoor slaughter pig production. However it was demonstrated that carefully planned movements of huts and feeding troughs made it possible to have an acceptable distribution of the nutrient load.  References Andresen, N. (2000) The Foraging Pig. Resource utilisation, interaction, performance and behaviour of pigs in cropping systems. Agraria 227. Swedish University of Agricultural Sciences, 40 pp. Gentry, J.G., McGlone, J.J., Blanton, J.R.Jr. & Miller, M.F. (2002) Alternative housing systems for pigs: Influences on growth, composition, and pork quality. Anim. Sci. 80, 1781-1790. Gustafson, G. & Stern, S. (2003) Two strategies for meeting energy demands of growing pigs on pasture. Livest. Prod. Sci. 80, 167-174. Guy, J.H., Rowlinson, P., Chadwick, J.P. & Ellis, M. (2002) Growth performance and carcass characteristics of two genotypes of growing-finishing pig in three different housing systems. Animal Science 74, 493-502. Stern, S., Heyer, A., Andersson, K., Lundström, K. & Rydhmer, L. (2001) Ekologisk slaktsvinproduktion - ska smågrisar födda ute födas upp till slakt ute eller inne? Ekologiskt lantbruk 262-265.  

Full or partial outdoor rearing of slaughter pigs – effects on performance, carcass quality and nutrient load

Abstract

Similar works

Full text

Available Versions

Organic Eprints