Predicting the consequences of social stressors on pig food intake and performance - I. J. Wellock, G. C. Emmans and I. Kyriazakis Animal Nutrition and Health Department, Scottish Agricultural College, West Mains Road, Edinburgh, EH9 3JG Scotland J. Anim. Sci. 2003. 81:2995-3007

The influence of social stressors on pig performance, although undeniable, is frequently underestimated, and in pig growth modeling is generally ignored. The aims here were to quantify the effects of the main social stressors (i.e., group size, space allowance, feeder space allowance, and mixing) on the performance of growing pigs and to incorporate these relationships into a general growth simulation model. Effects of the individual stressors were described by conceptual equations derived on biological grounds. Parameter values were estimated from experimental data, while taking steps to avoid the problems of using a strictly empirical approach. It was assumed that social stress decreases the capacity of the animal to attain its potential. This is equivalent to lowering the maximum rate of daily gain (ADGp, kg/d). Because it is generally assumed that animals eat to attain their potential, a decrease in ADGp necessarily leads to a decrease in intake. Genetic variation among genotypes in their ability to cope with social stressors was accounted for by introducing an extra genetic parameter (EX) into the model. The value of EX adjusts both the intensity of stressor at which the animal becomes effectively stressed and the extent to which stress decreases performance and increases energy expenditure at a given stressor intensity. Rather than using an empirical adjustment to predict values for the model output variables, such as intake and gain, the chosen functional forms were integrated into a general growth model as mechanistic equations. This allowed the effects of interactions that exist between social stressors and the other variables, such as the genotype, feed composition, and environment on pig intake and growth, to be explored and, at least in principle, predicted. The adapted model is able to predict the performance of pigs differing in both the potential and ability to cope with environmental stressors when raised under given dietary, physical, and social environmental conditions. The social stressor equations developed here can be incorporated into other pig growth simulation models.
http://jas.fass.org/cgi/content/full/81/12/2995



Effect of group size on performance of growing-finishing pigs - Schmolke SA, Li YZ, Gonyou HW. Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5A8, Canada. J Anim Sci. 2003 Apr;81(4):874-8.

Six hundred forty growing-finishing pigs (initial BW = 23.2 +/- 4.8 kg) were used in a 12-wk study (final BW = 95.5 +/- 10.2 kg) to quantify the effects of group size (10, 20, 40, and 80 pigs/pen) on performance, tail biting, and use of widely distributed feed resources. One single-space wet/dry feeder was provided for every 10 pigs, and floor allowance was 0.76 m2/pig in all treatment groups. Weight gain and feed intake were measured every 2 wk. At weighing, a tail-biting injury score was given to each pig. Blood samples were collected and analyzed for neutrophil:lymphocyte ratio before regrouping at the beginning of the experiment, 24 to 48 h after regrouping, and on the last day of each trial. The use of feeders by individual pigs was assessed by behavioral observations. Average daily gain for the entire 12-wk trial did not differ among group sizes (861, 873, 854, and 845 g/d for groups of 10, 20, 40, and 80, respectively; P > 0.10). During the first 2 wk, ADG was lower for pigs in groups of 40 (554 g/d) than pigs in groups of 10 (632 g/d; P < 0.05), but not pigs in groups of 20 or 80 (602 and 605 g/d, respectively). Average daily feed intake, feed efficiency, and variability in final BW within a pen also did not differ among group sizes. Tail-biting injury scores increased throughout the study, but did not differ among group sizes. Similar proportions of pigs were removed from the trial for health reasons, primarily due to tail biting, in all treatments. Individual pigs in each group size ate from most, if not all, of the feeders in the pen. There was no evidence of spatial subgrouping within the larger groups. The results suggest that housing growing-finishing pigs in groups of up to 80 pigs is not detrimental to productivity and health if space allowance is adequate and feed resources are evenly distributed.
http://jas.fass.org/cgi/content/full/81/4/874



Effect of stocking arrangement on pig performance - Chapple, R. P. 1993. Pages 87–97 in Manipulating Pig Production IV. E. S Batterham, ed. Australian Pig Science Association, Victoria.



Effects of floor area allowance on performance of growing pigs kept on fully slatted floors - Edwards, S. A., A. W. Armsby, and H. H. Spechter. 1988. Anim. Prod. 46:453–459.



Metabolic consequences of stress - Elsasser, T. H., K. C. Klasing, N. Filipov, and F. Thompson. 2000. Pages 77–110 in the Biology of Animal Stress. Basic Principles and Implications for Animal Welfare. G. P. Moberg and J. A. Mench, ed. CABI, Wallingford, U.K.



Consequences of repeated early isolation in domestic piglets (Sus scrofa) on their behavioural, neuroendocrine, and immunological responses - Kanitz E, Tuchscherer M, Puppe B, Tuchscherer A, Stabenow B. Research Unit Behavioural Physiology, Research Institute for the Biology of Farm Animals, Dummerstorf, Germany Brain Behav Immun. 2004 Jan;18(1):35-45.

Stress in the form of intermittent maternal deprivation and social isolation during early postnatal life in rats and monkeys produces persistent changes in physiology and behaviour. In farm animals physiological consequences of disrupting mother-infant interactions with respect to health and animal welfare are relatively unknown. Therefore, the aim of the present study was to investigate the behavioural, neuroendocrine and immunological consequences of a 2h daily social isolation from day 3 to day 11 of age in domestic piglets as well as potential long-term effects on the brain-endocrine-immune regulation. Repeated social isolation resulted in significantly decreased open-field activity (locomotion, vocalization) during the isolation period, increased basal cortisol concentrations and decreased lymphocyte proliferation in response to concanavalin A and pokeweed mitogen one day after the isolation. There was also a significant increase of interleukin-1beta (IL-1beta) concentration in hippocampus in isolated piglets compared to controls at this time. Six weeks after isolation significant enhanced basal ACTH concentrations as well as higher IL-1beta content and glucocorticoid receptor (GR) binding in hippocampus were found. These endocrine and immune responses were associated with decreased CRH levels in the hypothalamus and increased CRH content in the amygdala. The present data indicate that early social isolation in pigs may cause changes in behavioural, neuroendocrine, and immune regulation and produce long-term effects not only on the activity of the hypothalamic-pituitary-adrenal (HPA) system, but also on the immune-brain circuitry with possible negative consequences in health and welfare of commercial pigs. Using the pig as a suitable animal model, the finding of this study may also have some implications for the etiology of anxiety and depression in humans.



Individual behavioural characteristics in pigs--influences of group composition but no differences in cortisol responses - van Erp-van der Kooij E, Kuijpers AH, van Eerdenburg FJ, Dieleman SJ, Blankenstein DM, Tielen MJ. Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL, Utrecht, Netherlands. Physiol Behav. 2003 Mar;78(3):479-88.

To determine the effect of group composition on backtest (Bt) responses and to determine the predictive value of the Bt for the physiological stress response to weaning and mixing, 814 pigs were backtested at 3, 10 and 17 days of age. Twenty-nine percent of all pigs were cross-fostered at 3 days according to Bt responses and groups were formed of animals with high responses (HR) only, low responses (LR) only or mixed groups of animals with high, intermediate and low responses (MISC). Original litters (OR, no cross-fostering) were used as controls. Cortisol responses were measured in saliva after weaning at 4 weeks of age and after moving and mixing at 9 weeks of age.In HR groups, mean Bt responses decreased after cross-fostering while in LR groups, mean Bt scores increased. In both groups, Bt responses of individual animals before and after cross-fostering were not correlated. In MISC and OR groups, all Bt scores were correlated. Weaning and mixing caused a significant rise in cortisol in all animals while moving or weighing did not. No relations were found between Bt scores and cortisol levels.We conclude that Bt behaviour can change according to the social environment between 3 and 10 days. This could be intentional, to form a varied group, or it might be caused by a change in the hypothalamic-pituitary-adrenal (HPA) function due to social stress. At an older age, this ability is lost and common farm practises such as regrouping, weaning and mixing of piglets at ages >10 days might have a negative effect on the piglets.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T0P-47RS0S0-1&_coverDate=03%2F31%2F2003&_alid=134967650&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=4868&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=9d735169a4fb98f0ae90054f0c33e271



Adaptation to social isolation. Acute and long-term stress responses of growing gilts with different coping characteristics - Ruis MA, te Brake JH, Engel B, Buist WG, Blokhuis HJ, Koolhaas JM. Department of Behaviour, Stress Physiology and Management, Institute for Animal Science and Health (ID-Lelystad), PO Box 65, 8200 AB, Lelystad, Netherlands Physiol Behav. 2001 Jul;73(4):541-51.

The present experiment studied the acute and long-term stress responses of reactive and proactive prepubertal gilts to social isolation. Gilts with either reactive or proactive features were identified according to behavioral resistance in a backtest at a young age (2-4 days), respectively being low (LR) and high resistant (HR) in this test. At 7 weeks of age, 12 gilts of each type were socially isolated. Initially, isolation was stressful for both types of gilts, as shown by increased cortisol concentrations and decreased body temperatures. Moreover, both types reacted with increases in exploration and vocalizations. Stress responses to isolation, however, differed in magnitude and/or duration between LR and HR gilts, which was in line with expected reaction patterns on the basis of preferred ways of coping. The cortisol response to isolation was higher in LR gilts, and they generally showed more explorative behavior. HR gilts seemed to be more engaged in walking/running behavior in the first hour after isolation, they generally vocalized more and their noradrenaline excretion in urine was higher at 3 weeks after the start of isolation. Several responses to isolation in the longer term pointed to a prolonged higher general state of stress of HR gilts. Body temperature in HR gilts, for instance, did not recover during 3 weeks of isolation, but values returned to "normal" within 1 day in LR gilts. At 1 week of isolation, relatively high parasympathetic responsivity to novelty was observed in HR gilts, probably due to stress-related high sympathetic reactivity. A shift in percentages of leucocyte subsets, typically occurring under conditions of stress, only developed in HR gilts during isolation. Finally, gastric ulceration was found in one HR gilt, but did not occur in LR gilts. To conclude, LR and HR gilts differed in their strategies to adapt to social isolation, and especially for HR gilts, this procedure seemed to become a chronic stressor.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T0P-43N2XRM-C&_coverDate=07%2F31%2F2001&_alid=134967901&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=4868&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=312de92060e5cafc4b65dec158ab3964



Long-term effects of social stress on antiviral immunity in pigs - de Groot J, Ruis MA, Scholten JW, Koolhaas JM, Boersma WJ. Department of Immunology, Pathobiology and Epidemiology (ID-Lelystad), Institute for Animal Science and Health, University of Groningen, P.O. Box 65, 8200 AB Lelystad, Netherlands. Physiol Behav. 2001 May;73(1-2):145-58.

Mixing of unfamiliar pigs is common practice in intensive pig husbandry. Since pigs maintain a dominance hierarchy, mixing often leads to vigorous fighting. Apart from the negative impact that fighting has on welfare, there is evidence that the social stress associated with fighting suppresses immune function. In the present experiment, we investigated the impact of mixing on specific long-term immune responses and protection against challenge infection after vaccination with pseudorabies virus (PRV). Specific pathogen-free (SPF) pigs were mixed pairwise with an unfamiliar same-gender conspecific or left undisturbed with a same-gender littermate at 3 days after vaccination with PRV. Half of the pigs were females (gilts) and half were castrated males (barrows). Mixing increased agonistic behavior to the same degree in gilts and barrows. Cortisol concentrations in saliva and catecholamine excretion in urine were increased in mixed pigs, and these effects were independent of dominance status and gender. Subsequently, the effects of mixing, gender, dominance status and interactions between these factors on immune response parameters were studied. The main result was that mixed barrows showed suppressed immune responses after vaccination and increased clinical symptoms after challenge infection compared to control barrows. Mixed gilts however did not differ from control gilts. It also appeared that mixed dominants were more seriously affected than mixed subordinates were. We conclude that, in some pigs, social stress after mixing suppresses the immune response to a viral vaccine and consequently impairs protection against challenge infection.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T0P-436F9NT-N&_coverDate=05%2F31%2F2001&_alid=134967993&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=4868&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=3b57032645c9fcf30e8928ca2aceec39



Behavioural and physiological consequences of acute social defeat in growing gilts: effects of the social environment - Ruis MA, de Groot J, te Brake JH, Dinand Ekkel E, van de Burgwal JA, Erkens JH, Engel B, Buist WG, Blokhuis HJ, Koolhaas JM. Department of Behaviour, Stress Physiology and Management, Institute for Animal Science and Health, P.O. Box 65, 8200 AB, Lelystad, Netherlands Appl Anim Behav Sci. 2001 Jan 6;70(3):201-225.

Endocrine, behavioural and immunologic processes, together with body growth, were evaluated in gilts that were defeated at 10 weeks of age in resident-intruder tests. Immediately after defeat, gilts were either separated from or reunited with a familiar conspecific (litter-mate; always a barrow). Gilts were assigned to one of four treatments: (a) DI: defeat, followed by isolation (separation from original litter-mate; n=8); (b) I: no defeat, isolation (control group; n=9); (c) DP; defeat, followed by pair-housing (reunion with original litter-mate; n=8); and (d) P: no defeat, pair-housing (control group; n=8). The following general conclusions were derived: (1) social defeat caused pronounced short-term elevations in hypothalamic-pituitary-adrenal (HPA) and sympathetic-adrenal medullary activities, and of prolactin levels. Moreover, as soon as 1h after defeat, percentages of blood lymphocytes and neutrophilic granulocytes were, respectively, decreased and increased; (2) social defeat had some long-lasting influence on behaviour and physiology, but isolation predominantly determined responses in the longer term. Defeat, as well as isolation, resulted in increased cardiovascular activities compared to P controls, as observed in a novel object test (NOT: +7 days) and an aversion test (AVT: +14 days). Moreover, defeated as well as isolated gilts did not habituate to a repeated novel environment test (NET: -7, +2 and +7 days) in terms of frequencies of vocalising, whereas P controls did. Isolation, through the separation from any other pig, was responsible for the other observed long-term characteristics, which developed progressively. Isolated gilts showed high mobilities and high cortisol responses in the repeated NET (+7 days), not being habituated. This contrasted the reactions of pair-housed gilts, which were much reduced. In addition to their high cardiovascular activities in the NOT and the AVT, isolated gilts also displayed higher heart rates in the repeated NET and during human presence following the NOT, compared to pair-housed gilts. Finally, isolated gilts were more inhibited to approach a novel object (in the NOT) than pair-housed pigs; and (3) stress responses of defeated gilts were modulated by the subsequent social environment. Stimulation of the HPA-axis (plasma- and salivary cortisol) was prolonged in those defeated gilts which were isolated (observed in the first hour). Changes in leucocyte subsets were still observed after 3 days in DI, but were 'normalised' within 1 day in DP gilts. Two days after defeat, habituation to the repeated NET in terms of mobility and salivary cortisol responses occurred in control and DP gilts, but not in DI gilts. We argue that these effects of the social environment shortly after defeat were related to a stress-reducing effect of a stable social relationship, i.e. social support.



The effect of group housing on feeding patterns and social behaviour of previously individually housed growing pigs - Bornett HL, Morgan CA, Lawrence AB, Mann J. Institiute of Ecology and Resource Management, University of Edinburgh, West Mains Road, EH9 3JG, Edinburgh, UK Appl Anim Behav Sci. 2000 Dec 1;70(2):127-141.

Group housed pigs make less frequent feeder visits of longer duration, and eat at a faster rate than pigs housed individually. They also have lower growth rates which may be due to elevated stress levels resulting from changes in the concentrations of hormones, such as cortisol and adrenaline associated with aggression and social stress. The aim of this experiment was to investigate the effects of grouping on feeding pattern, time budgeting and the social behaviour of pigs kept as individuals from weaning until grouping. In total, 12 Large WhitexLandrace male pigs (four pigs per block) mean (+/-S.E.) start weight 22.5+/-0.7kg were housed individually for 3 weeks (Period 1) after which in two replicates (Blocks 1 and 3), pigs were combined into a group of four (Period 2) before being returned to individual housing for a further 3 weeks (Period 3). In Block 2, the four pigs remained as individuals across periods but were moved between pens at the end of Periods 1 and 2 to account for any pen effects. Feeding pattern and food intake were recorded throughout and pigs were weighed three times a week. Video recordings and live behavioural observations were made to record time budgets and social behaviour. Grouped pigs made less visits to the feeder in Period 2 than when they were housed individually in Periods 1 (P<0.001) and 3 (P<0.01). Visit duration was longer in Period 2 than in Periods 1 (P<0.01) and 3 (P<0.05). Food intake and weight gain were greater in Period 3 than in Periods 1 and 2 (P<0.001 and P<0.01, respectively). There were no significant effects of moving pigs between pens in Block 2 on feeding behaviour and timebudgets. In Period 2, grouped pigs slept more (P<0.01) and spent less time feeding (P<0.01) and rooting (P<0.01) than in Periods 1 and 3. The frequency of aggression decreased over time from mixing (P<0.001). Possible explanations for the changes in feeding behaviour when pigs are moved from individual to group housing are competition, group cohesion, or that the high frequency of feeder visits when the pigs are housed individually is a consequence of a lack of social stimulation. Of these different possibilities, the results suggest that group cohesion is most likely to have been causal in the observed changes in feeding behaviour.




Relationships between individual behavioural traits and post-weaning growth in segregated early-weaned piglets - Giroux S, Martineau G, Robert S. College of Veterinary Medicine, University of Montreal, P.O. Box 5000, Que., J2S 7C6, St-Hyacinthe, Canada Appl Anim Behav Sci. 2000 Nov 1;70(1):41-48.

Piglets' individual behavioural traits have been studied in the last decade but no report has linked these traits with growth. This experiment was conducted to determine if behavioural traits of segregated early-weaned piglets could be good predictors of their post-weaning growth and, thus, help to predict their adaptation to early weaning. Following segregated early weaning at 17+/-1 days old, 252 piglets were submitted to three tests between 20 and 25 days of age: open-field, reaction to humans and rank order based on competition for a restricted-access feeder. The body weight of each piglet was measured the day before weaning and once a week for the next 4 weeks. A principal component analysis yielded five factors with an Eigenvalue higher than 0.90 that accounted for 81% of the total variation between individuals: reaction to humans (25%), active response to stress (21%), passive response to stress (14%), feeding behaviour (10%) and rank order (9%). Passive reaction to stress was associated with better weight gain during the first week post-weaning (r=0.18; P=0.01), and a positive correlation was found between social status and weight gain during the 4 weeks following weaning (-0.15


Effects of social status after mixing on immune, metabolic, and endocrine responses in pigs - Tuchscherer M, Puppe B, Tuchscherer A, Kanitz E. Forschungsbereich Physiologische Grundlagen der Tierhaltung, Forschungsinstitut fur die Biologie landwirtschaftlicher Nutztiere, Dummerstorf, Germany. Physiol Behav. 1998 Jun 1;64(3):353-60.

The effects of social rank on immune, metabolic, and endocrine responses were studied in 10 newly mixed groups of German Landrace pigs (9 individuals each) at an age of 12 weeks. Immediately after mixing, the agonistic interactions (AI) of all group members were continuously recorded over 3 days (10 h daily). An individual dominance value (DV) was calculated by the number of wins minus defeats in relation to all decisive fights (DV < or = 0, subordinate; DV > 0, dominant). Blood samples were taken 24 h before and 3 days after mixing. The data showed that the social status had a significant effect on lymphocyte proliferation in responses to different mitogens: socially dominant pigs had higher proliferative response than subordinate pigs. In addition, during the observation period the lymphocyte activation by mitogens increased in the dominant animals and decreased in the subordinate animals with increasing number of agonistic interactions. The rise in total serum IgG concentration 3 days after mixing was higher in dominant pigs compared with subordinates. The dominance status did not significantly affect plasma metabolic levels nor cortisol concentrations. However, mixing appeared to increase glucose and total protein values and to decrease alkaline phosphatase and cortisol levels in both, dominant and subordinate pigs. In conclusion, mitogen induced cell proliferation seems to be a valuable marker for acute social stress in pigs.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T0P-3V7T7VH-P&_coverDate=06%2F01%2F1998&_alid=134968553&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=4868&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ab363cb138543fb91c408a6cd65193e2



Energy metabolism in young pigs as affected by mixing - Heetkamp MJ, Schrama JW, de Jong L, Swinkels JW, Schouten WG, Bosch MW. Department of Animal Husbandry, Agricultural University, Wageningen, The Netherlands. J Anim Sci. 1995 Dec;73(12):3562-9.

The effect of mixing on energy metabolism was studied in 8-wk-old pigs. In each of two trials, two clusters of 20 pigs (two litters of 10 pigs) were randomly assigned to one of two treatments: control or mixing. Each cluster was housed in two pens. In each trial, after a preliminary period od 2 wk, the two litters within the mixing treatment were mixed at the start of a 2-wk experimental period. During mixing, the five heaviest pigs of each litter were put together in one pen, and the five lightest pigs of each litter were put together in the other pen. In the control treatment, the social structure of both litters in one climatic chamber was not altered. After mixing, a short-term effect on total heat production and activity-related heat production was present. Both were increased (P < .01) only during the 1st h after mixing. Only 57.3% of this increased total heat production was caused by an increased activity. However, no long-term effects of mixing on energy partitioning were present during the total experimental period. The absence of a long-term mixing effect might be caused by the optimal conditions at the moment of mixing. In the preliminary period the transposition of GE into ME increased 1.3% (P < .05), and ME for maintenance decreased 80 kJ.kg(-.75).d(-1) (P < .01) between wk 1 and 2. These large alterations in energy metabolism are probably a carry-over effect of the transportation of the pigs and (or) the changes in housing environment.
http://jas.fass.org/cgi/reprint/73/12/3562.pdf



Effect of group size and feeder type on growth performance and feeding patterns in finishing pigs - Hyun Y, Ellis M. Department of Animal Sciences, University of Illinois, Urbana 61801, USA. J Anim Sci. 2002 Mar;80(3):568-74.

The effects of four group sizes (2, 4, 8, and 12 pigs per pen) and two single-space feeder types (conventional and electronic feed intake recording equipment FIRE) on feed intake, growth performance, and feeding patterns were determined in 208 crossbred finishing pigs (equal numbers of barrows and gilts) between 84.4 (SD = 0.81) to 112.8 (SD = 1.08) kg BW over a 4-wk period. Pigs were given ad libitum access to a corn-soybean meal-based diet (15.9% CP; 0.79% lysine; 3,328 kcal ME/kg). The floor space allowance was 0.9 m2/pig for all treatments. Growth rates were not different for the two feeder types; however, feed intake was lower and gain:feed ratio higher for pigs on the FIRE feeders (P < 0.01). Feed intake, growth rate, and gain:feed ratio were not different (P > 0.05) among the group sizes. Number of feeder visits per day decreased and feed intake per visit, feeder occupation time per visit, feed consumption rate, and percentage of time the feeder was occupied increased with group size (P < 0.05). Feed intake per visit had the strongest correlation with daily feed intake (r = 0.54; P < 0.01) and was negatively correlated with gain:feed ratio (r = -0.38; P < 0.01). However, the correlations between growth performance and other feeding pattern traits were relatively weak (r < or = 0.30). As group size increased, diurnal variation in number of feeder visits and feed consumed per hour decreased. There was no difference in time spent sitting and standing between the two feeder types. The proportion of time spent eating was generally lower for the larger groups on both feeders. The proportion of time spent lying was similar across group sizes for pigs on the conventional feeders but was greater for pigs in the larger groups on the FIRE feeders. This study suggests that finishing pigs can maintain feed intake and growth rate by changing feeding behavior as group size increases from 2 to 12.
http://jas.fass.org/cgi/reprint/80/3/568.pdf



Social behavior and growth of pigs following mixing during the growing-finishing period - Graves, H.B., Graves, K.L., Sherritt, G.W. 1978. Appl. Anim. Ethol. 4: 169-
180.


Applications:

Recognizing Stress Factors - Brian Cotton, Swine Specialist
Stress in pigs can be caused by many factors. Depending on how the pig adapts to stress, it may have a deleterious effect or it could be an instrument of training and hardening. Stress has three stages: mobilization (alarm reaction), resistance or adaptation, and exhaustion.
http://www.gov.mb.ca/agriculture/livestock/pork/swine/bab02s07.html



Concepts of Pig Growth and Composition - A.P. Schinckel and M.E. Einstein
Department of Animal Sciences
Pork producers have economic incentives based on consumer demand and carcass-value marketing programs to produce lean pork as efficiently as possible. Changes in the absolute and relative rates of lean and fat gain determine the efficiency of lean gain and, ultimately, carcass composition. Thus, pork producers must increase lean growth rates by implementing genetic and management improvements.
Pig growth results from a multitude of biological processes. The genotype of an animal determines the maximum level at which these processes can occur, whereas environmental factors such as health status, nutrition, ambient temperature, social hierarchy and pen density determine the degree to which genetic potential is expressed. Thus, in order to evaluate and implement genetic and management strategies which potentially enhance pig growth, an understanding of the relationships between pig genotype and environmental factors is essential.
http://www.ansc.purdue.edu/swine/porkpage/growth/pubs/aps95-5.htm



Modeling Genetic and Environmental Effects on Pig Lean Growth - A.P. Schinckel, B.T. Richert, L.K. Clark, J.W. Frank and J.T. Turek, Purdue University
Environmental factors including disease exposure, social stress and less than optimal stocking density limit growth such that pigs managed under commercial conditions are unlikely to express their maximum potential protein accretion, even when allowed ad libitum access to a high quality nutrient dense diet. For this reason, the term operational protein accretion was introduced. The operational protein accretion is the maximum protein accretion rate that pigs can achieve under specified commercial conditions. This definition implies that, for a given genotype, the maximum achievable protein accretion potentials are limited by environmental conditions under which it is determined.
http://mark.asci.ncsu.edu/nsif/97proc/schinckel.htm

Assessing Feed Intake in Your Finisher Barn - Nadine Funk, Non-Ruminants
Tawnya MacNeil and Sara Murphy, Resource Contact Centre, Agri-Point International Fact Sheet, November 2002
Social Factors
Space Allocation
Restricting space allowances for pigs negatively impacts FI and ADG. Studies indicate that limiting space for pigs, causes a chronic stress that eventually reduces the efficiency of feed utilization. Additionally, space restriction can cause behavioural changes, including increased aggression, which further decreases feed efficiency.
http://www.agrapoint.ca/publications/Assessing%20Feed%20Intake%20Factsheet%20Porkfolio.pdf


Aggression and feeding behavior of group-housed male pigs - Greg Cronin, Animal Welfare Centre, Department of Primary Industries, Werribee, Victoria, Australia
Finisher pigs, i.e. pigs from about 50 kg to slaughter weight, are housed in single-sex groups because the dietary requirements for optimal growth are different between the sexes. In addition, in many countries male pigs not required for breeding are surgically castrated; typically this occurs early in life. Research in the 1970s showed that surgical castration reduced growth efficiency. Specifically, conversion of feed to lean meat was less efficient and body fat content increased. Consequently, the Australian pig industry ceased castration of pigs about 25 years ago. However pig nutritionists have recently found that growth efficiency of group-housed entire male pigs declined during the last weeks of growth for older/heavier pigs. It was suspected that increased sexual behavior and aggression was reducing feed intake and thus impairing growth in entire males.
http://www.noldus.com/applications/zoology/cronin.html



Effects of Housing on Feed Intake of the Growing Pig - Gerard McCutcheon, Teagasc, Bagenalstown , Irish Agriculture and Food Development Authority
Over-crowding/Stocking Rates
High stocking rate is a “disease” on many Irish pig farms. A mismatch exists between sow numbers (determined by number of farrowing pens) and the number of places for the growing pigs (weaners and finishers). Pigs should be stocked at the rates shown in Table 2.
http://www.teagasc.ie/publications/2003/pigconf/paper03.htm


Assessment of Multiple Concurrent Stressor Effects in Swine - Y. Hyun, M. Ellis, G. Riskowski, and R.W. Johnson
The effects of many single stressors have been reported, but how pigs perform when subjected to more than one or two stressors at a time, as is common in commercial swine production, has not. To study this, 256 Yorkshire H Hampshire or purebred Duroc pigs (34.7 " 0.5 kg) were subjected to one of the eight treatment combinations (2 H 2 H 2 factorial) of ambient temperature consant thermoneutral (24° C) or high cycling temperature (28-34° C), stocking density (.56 m² or .25 m²/pig) and social group (static group or regrouped at the start of wk 1 and 3) during a 4-wk experiment. The stress of high temperature, high stocking density and regrouping depressed 4-wk ADG by 12%, 16% and 10% (P<.05); and ADFI by 7%, 6% and 5%, respectively (P<.05). Out of a possible 60 stressor interactions for ADG, ADFI and G:F, there were no significant three-way interactions and only six two-way interactions, suggesting the effects of the individual stressors were additive (i.e., the stressors' effects on performance were similar regardless of whether they were imposed singly or in combination). Thus, when pigs were subjected to all three stressors simultaneously ADG, ADFI, and G:F were depressed by 31%, 15%, and 18%, respectively. Stressor additivity was further corroborated by examining the effect of "stressor order," or the number of stressors imposed simultaneously. As the number of stressors increased from 0 to 3, ADG, ADFI and G:F decreased linearly. These data suggest that multiple concurrent stressors affect growth performance of pigs in a predictable fashion (i.e., additively) and indicate that avoidance or removal of a given stressor is advantagous even when other uncontrollable stressors persist.
http://www.traill.uiuc.edu/porknet/paperDisplay.cfm?ContentID=415