The role of breeding and genetics in animal welfare

Transcription

1 The role of breeding and genetics in animal welfare T. Bas Rodenburg, Animal Breeding & Genomics Centre Simon P. Turner, Scottish Agricultural College (SAC)

2 Introduction Domestication started thousands of years ago Past years: intensive selection for increased production Genetic selection Contributed to welfare issues: lameness broilers Can also be used to alleviate welfare issues (Rauw et al., 1998)

3 Variation between species Domestic species vary greatly in: Traits under selection Selection intensity Application of breeding technologies Intensive versus extensive systems Differences in genetic progress

4 Focus on intensive sectors Breeding-related welfare challenges Mainly associated with the highly selected poultry, dairy and pig sectors Also play a role in the extensively managed breeds Increased lambing rate: reduction in lamb survival Calving difficulties in beef cattle

5 Variation within species Breeds and hybrids Generalist- versus specialist-type Intensive production: generalist-type Rare breeds: specialist-type Rare breeds more hardy in specific environments Easy care sheep

6 High-yield crosses Pigs and poultry: pure-bred lines used for selection Commercial product is a hybrid cross (4 lines) Female lines: reproductive traits Male line: fast growth, low feed conversion Sheep production: low-maintenance ewes Mated to less hardy, but more productive sires Crossbreds for fattening on lower ground

7 Selection for increased growth in broilers Extremely successful: 25 to 100 grams/day Increased incidences of Lameness Ascites Sudden death syndrome (Knowles et al., 2008)

8 Suboptimal conditions 40 Temperature Control Test Age (days) Van Horne et al., 2004 (van Horne et al., 2004)

9 Mortality Slow growing A B C Fast growing Sudden Death Heart Failure Ascites Total Heart + circulation Van Horne et al., 2004 (van Horne et al., 2004)

10 Slower growing broilers Grow to slaughter weight in 56 rather than 42 days Much less welfare issues Reduced mortality Reduced lameness Reduced footpad dermatitis Limited feed restriction required in parent stock (dwarf mothers)

11 Dairy cows Selection for increased milk yield Decreased fertility and longevity Increased lameness Increased metabolic problems A higher incidence of mastitis Future: automatic collection of data in/around milking parlour Incorporate information in breeding program (Oltenacu and Broom, 2010)

12 Selection enhancing undesired behaviour Genetic correlation tail biting with (Breuer et al., 2005): Lean tissue growth rate (0.27) Backfat thickness (-0.28) Selection for early sexual maturation laying hens Correlated to increased feather pecking (Jensen et al., 2005)

13 Selection for improved welfare Direct selection against undesired behaviours feasible Aggression in pigs (Turner, 2011) Feather pecking in laying hens (Kjaer et al., 2001) 5 Helpful in understanding behaviours Unravel underlying mechanisms Frequency of feather pecking High feather pecking Low feather pecking Generation

14 Breeding for improved group performance Traditional: focus on individual performance Risk to select animals that are harmful for group performance Alternative methods needed that take group performance into account

15 Group selection (Muir, 1996) Per cage Eggs Per individual Group Selected Individual Selected

16 Cumulative mortality (Muir, 1996) CONTROL GROUP SELECTED 7 COMMERCIAL AGE (WEEKS)

17 New methods Kin selection method Combine individual performance with information from sisters in group housing (Ellen et al., 2007) Social breeding values Estimate the genetic effect an animal has on the performance of its group mates (Muir, 2005; Bijma et al., 2007)

18 Kin selection on low mortality White leghorn line Control line: Selection candidate individual Selection on production Non-beak trimmed in cages: mortality due to cannibalism Low mortality line Selection candidate individual Selection on production Full sisters in group (4) Selection on low mortality (Ellen et al., 2007)

19 Results after one generation Generation 1 50 Mortality % Control Low

20 Effects on behaviour Birds selected on low mortality: Less fearful Young age Adult age Reduced stress response Less cannibalistic pecking Changes in the serotonergic system compared with control birds (Bolhuis et al., 2009; Rodenburg et al, 2009ab; Nordquist et al., 2011)

21 Role of the serotonergic system Feather pecking is redirected foraging In response to fear and stress inducing stimuli The serotonergic (5-HT) system central role: Involved in coping with fear and stress, Involved in foraging and in feather pecking (van Hierden et al., 2004) Selection for low mortality: changes in the peripheral serotonergic (5-HT) system (Bolhuis et al., 2009)

22 FP and the serotonergic system Associations between feather pecking and genes involved in the serotonergic system Comparison of lines selected for high an low FP Frequency difference DEAF1 polymorphisms Regulatory gene serotonergic system (Flisikowski et al., 2009)

23 FP and the serotonergic system Association study on feather damage Nine different lines of laying hens Allele frequency Brown and white lines 0 Brown White Association between feather damage and HTR2C Receptor gene serotonergic system (after Biscarini et al., 2010)

24 Plumage condition 5.5 Plumage condition Brown White (after Uitdehaag et al., 2008)

25 Fearfulness 0.4 Probability of showing a fearful response Age (weeks) Brown White (after Uitdehaag et al., 2008)

26 Coherent with selection experiment Birds selected on low mortality Less fearful Reduced stress response Less cannibalistic pecking Changes in the serotonergic system compared with control birds Further developing genetic fingerprint associated with FP will enhance possibilities for genetic selection (Bolhuis et al., 2009; Rodenburg et al, 2009ab; Nordquist et al., 2011)

27 Aggression in pigs Observed after mixing but also under stable conditions Mixing is a routine procedure Results in skin lesions Aggression can negatively affect performance (Turner et al., 2006)

28 Breeding against aggression Technically possible Fighting and bullying have moderate heritabilities in pigs (between 0.17 and 0.43) Number of resulting skin lesions (between 0.21 and 0.26) (Lovendahl et al., 2005; Turner et al., 2006; 2009) Genetic correlations indicate that skin lesions can be used as an indicator of being aggressive (Turner et al., 2006)

29 Effects of selection Genetic correlation between aggression around mixing and under stable conditions: selection reduces both Associated changes in: Genes involved in coping with stress (HPA-axis) Brain gene expression vasopressin and serotonin Altered cholesterol metabolism (Murani et al., 2010, 2011; D Eath et al., 2005)

30 Effects of selection Selection might alter basic pathways that govern a range of biological functions Aggressive animals also faster to enter weighing scale (D Eath et al., 2009) No differences in general activity levels to underlie reduced aggressiveness No adverse effects on lean tissue growth (Turner et al., 2006)

31 Social breeding values Traditional selection methods lack attention for social interactions Social genetic effects contribute profoundly to genetic variance in growth rate in pigs (Bergsma et al. 2008)

32 Number of lesions Similar results found by Canario et al. (2008) Post mixing High SBV Steady situation Low SBV High SBV Low SBV Anterior a b ** Middle Rear Back a 1.63 b * * p < 0.05, ** p < 0.01 De Vries, unpublished results (Rodenburg et al. 2010, Canario et al. 2008)

33 Effects on manipulative behaviour High SBV pigs showed: Showed 15% more comfort behaviour Spent 14% less time on ear biting Spent 35% less time on chewing objects Had less tail damage This may indicate that low SBV pigs have a stronger tendency to perform oral manipulation (Camerlink et al. 2012, Ursinus et al. 2012)

34 Conclusion selection experiments Scope to use novel selection methods to improve welfare of group-housed animals Kin selection laying hens Social breeding value pigs Progress may be slower than expected Hens: easier to select for increased damage Pigs: realised genetic progress relatively small Increased understanding of genetics of social behaviour

35 General conclusion Breeding and genetics: important role in the welfare of domestic animals If focused only on increasing production: Clear risk of increasing welfare problems Wider perspective is needed that encompasses both production and welfare traits

36 General conclusion Genomics era could offer opportunities More precise information on the biological impact of certain breeding decisions Help breeders to make more informed choices in their selection programs Facilitate selection for complex behavioural traits: 5-HT polymorphisms Genetic fingerprint: targeted genomic selection approaches

37 Open to collaboration! Main topic: Improving social behaviour in group-housed animals by genetic selection and improving early-life conditions Future position (from 1 August): Assistant Professor Behavioural Ecology at WUR Focus on research + teaching applied animal behaviour and welfare Centre of Animal Welfare and Adaptation (CAWA)

38 Thank you! This paper will be published in the July 2012 issue of Animal Frontiers (special issue on Animal Welfare, edited by Don Lay)