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Intermittent fasting in chickens: Physiological mechanisms and welfare implications for broiler breeders
(AVIAN Behavioural Genomics and Physiology group)ORCID iD: 0000-0001-8961-3193
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Broiler breeder chickens are the parent stock used to produce broiler chickens raised for human consumption and have long been caught in a welfare dilemma. The immensely successful selection of fast-growing meat-type chickens over the last 80 years has created a remarkably efficient meat-producer and given us access to cheap chicken meat but has also created health problems for the animals. These problems especially affect the breeder generation, which must be raised with strict feed restriction to limit weight gain and thus maintain physical health and normal fertility. At the same time, however, feed restriction causes chronic hunger and feeding frustration with reduced animal welfare as a result. In the EU alone 60 million breeders are affected annually and although the problem is well-known within the industry, there is financial incentive to keep selecting for even higher growth potential in broilers, further increasing the problems for broiler breeders.

Many strategies for reducing the impact of growth restriction on breeder welfare have been suggested and are usually aimed at somehow increasing the amount of feed given at feeding times. This can be done either through adding bulky fibers to the diet or by reducing feeding frequency. In this thesis, focus is on the latter as we explore the effects of intermittent fasting (IF) on the welfare of young broiler breeders as well as wild-type Red Junglefowl. Intermittent fasting, or “skip-a-day” feeding, is supposedly the most common feeding strategy for broiler breeders worldwide but is perceived as welfare-reducing and thus illegal in Sweden and several other European countries. In spite of this, the scientific knowledge of how this type of feeding affects chicken welfare is scarce.

Assessing the overall effect of IF on breeder welfare is complicated by large variations in both physiological and behavioral parameters between feeding and fasting days, but it does appear that chicken welfare is improved at least on the feeding days of IF regimens. It also seems that some of the health benefits reported from mammalian studies of IF may apply to chickens as well, although behavioral indicators still point to welfare issues unless the level of feed restriction can be relaxed. In comparison with daily feed restriction, IF appears to increase the motivation for feed consumption but to reduce the motivation for appetitive behaviors such as foraging, which may explain why birds fed on this type of schedule are often reported as calmer.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. , p. 54
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 2005
National Category
Zoology
Identifiers
URN: urn:nbn:se:liu:diva-160814DOI: 10.3384/diss.diva-160814ISBN: 9789176850183 (print)OAI: oai:DiVA.org:liu-160814DiVA, id: diva2:1359720
Public defence
2019-11-22, Planck, Physics building, Campus Valla, Linköping, 09:15 (English)
Opponent
Supervisors
Available from: 2019-10-16 Created: 2019-10-10 Last updated: 2019-10-16Bibliographically approved
List of papers
1. Slow and steady wins the race? No signs of reduced welfare in smallerbroiler breeder hens at four weeks of age
Open this publication in new window or tab >>Slow and steady wins the race? No signs of reduced welfare in smallerbroiler breeder hens at four weeks of age
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2015 (English)In: Animal Welfare, ISSN 0962-7286, Vol. 24, no 4, p. 447-454Article in journal (Refereed) Published
Abstract [en]

Broiler breeder chickens are commonly reared under strict feed-restriction regimes to reduce obesity-induced health and fertilityproblems during adult life, and are assumed to experience a reduced welfare due to the resulting hunger. In these conditions, feedcompetition could influence the growth rate, so that the individuals falling behind in growth would experience more stress and hunger.We hypothesised that these chickens are poor competitors due to a reactive coping style and experience a further reduced welfaresituation before size-sorting (‘grading’) at four weeks of age. Our results from open field, tonic immobility and home pen activity monitoringshow signs of lower fear and higher home-pen activity levels in smaller hens and do not support the idea of reactive coping.H/L ratios of smaller hens were also found to be lower, indicating less stress in these birds. Dissections of smaller and larger fourweekbreeder hens may offer an explanation in the form of a relatively larger gastrointestinal tract in smaller birds. We argue thatthis is a form of habituation to restricted feeding, offering these birds a physiological stress coping mechanism, and that low earlygrowth rate may not always be a sign of poorer welfare in broiler breeders.

Place, publisher, year, edition, pages
Universities Federation for Animal Welfare, 2015
Keywords
animal welfare, broiler breeders, chicken, feed restriction, growth, stress
National Category
Zoology
Identifiers
urn:nbn:se:liu:diva-122024 (URN)10.7120/09627286.24.4.447 (DOI)000363898500009 ()
Note

Funding agencies: Swedish research council Formas [2013-293]

Available from: 2015-10-16 Created: 2015-10-16 Last updated: 2019-10-10
2. Growth heterogeneity in broiler breeder pullets is settled before the onset of feed restriction but is not predicted by size at hatch
Open this publication in new window or tab >>Growth heterogeneity in broiler breeder pullets is settled before the onset of feed restriction but is not predicted by size at hatch
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2017 (English)In: Journal of Animal Science, ISSN 0021-8812, E-ISSN 1525-3163, Vol. 95, no 1, p. 182-193, article id 2017.95Article in journal (Refereed) Published
Abstract [en]

Uniform growth is a desirable trait in  all large-scale animal production systems because it  simplifies animal management and increases profitability.  In parental broiler flocks, so-called broiler  breeders, low growth uniformity is largely attributed  to the feed competition that arises from quantitatively  restricted feeding. As feed restriction is crucial to  maintaining healthy and fertile breeders, several practices  for reducing feed competition and the associated  growth heterogeneity have been suggested and range  from nutrient dilution by increasing fiber content in  feed to intermittent fasting with increased portion size  (“skip a day”), but no practice appears to be entirely  effective. The fact that a large part of the heterogeneity  remains even when feed competition is minimized  suggests that some growth variation is caused by other  factors. We investigated whether this variation arises  during embryonic development (as measured by size at  hatch) or during posthatch development by following  the growth and body composition of birds of varying  hatch sizes. Our results support the posthatch alternative,  with animals that later grow to be small or large  (here defined as >1 SD lighter or heavier than mean  BW of the flock) being significantly different in size as  early as 1 d after gaining access to feed (P < 0.05). We  then investigated 2 possible causes for different postnatal  growth: that high growth performance is linked 1) to  interindividual variations in metabolism (as measured  by cloacal temperature and verified by respirometry)  or 2) to higher levels of social motivation (as measured  in a social reinstatement T-maze), which should reduce  the stress of being reared in large-scale commercial  flocks. Neither of these follow-up hypotheses could  account for the observed heterogeneity in growth. We  suggest that the basis of growth heterogeneity in broiler  breeder pullets may already be determined at the time  of hatch in the form of qualitatively different maternal  investments or immediately thereafter as an indirect  result of differences in incubation conditions, hatching  time, and resulting fasting time. Although this potential  difference in maternal investment is not seen in body  mass, tarsometatarsal length, or full body length of  day-old chicks arriving at the farm, it may influence  the development of differential feed and water intake  during the first day of feeding, which in turn has direct  effects on growth heterogeneity.

Place, publisher, year, edition, pages
Champaign, IL, United States: American Society of Animal Science, 2017
Keywords
broiler breeders, feed restriction
National Category
Ecology
Identifiers
urn:nbn:se:liu:diva-133189 (URN)10.2527/jas.2016.0929 (DOI)000397115100019 ()28177396 (PubMedID)
Available from: 2016-12-13 Created: 2016-12-13 Last updated: 2019-10-10Bibliographically approved
3. The physiological and neuroendocrine correlates of hunger in the Red Junglefowl (Gallus gallus)
Open this publication in new window or tab >>The physiological and neuroendocrine correlates of hunger in the Red Junglefowl (Gallus gallus)
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2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 17984Article in journal (Refereed) Published
Abstract [en]

The ability to regulate food intake is critical to survival. The hypothalamus is central to this regulation, integrating peripheral signals of energy availability. Although our understanding of hunger in rodents is advanced, an equivalent understanding in birds is lacking. In particular, the relationship between peripheral energy indices and hypothalamic hunger peptides, agouti-related protein (AgRP), proopiomelanocortin (POMC) and neuropeptide Y (NPY) is poorly understood. Here, we compare AgRP, POMC and NPY RNA levels in the hypothalamus of Red Junglefowl chicks raised under ad libitum, chronic restriction and intermittent feeding regimens. Hypothalamic gene expression differed between chronically and intermittently restricted birds, confirming that different restriction regimens elicit different patterns of hunger. By assessing the relationship between hypothalamic gene expression and carcass traits, we show for the first time in birds that AgRP and POMC are responsive to fat-related measures and therefore represent long-term energy status. Chronically restricted birds, having lower indices of fat, show elevated hunger according to AgRP and POMC. NPY was elevated in intermittently fasted birds during fasting, suggesting a role as a short-term index of hunger. The different physiological and neuroendocrine responses to quantitative versus temporal feed restriction provide novel insights into the divergent roles of avian hunger neuropeptides.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2017
National Category
Other Biological Topics
Identifiers
urn:nbn:se:liu:diva-144265 (URN)10.1038/s41598-017-17922-w (DOI)000418562100024 ()29269733 (PubMedID)
Note

Funding Agencies|Swedish research council Formas [2013-293]; Swedish Centre of Excellence in Animal Welfare Science; Carl Tryggers Stiftelse for Vetenskaplig Forskning

Available from: 2018-01-12 Created: 2018-01-12 Last updated: 2019-10-10
4. Measuring ketones in the field: rapid and reliable measures of beta-hydroxybutyrate in birds
Open this publication in new window or tab >>Measuring ketones in the field: rapid and reliable measures of beta-hydroxybutyrate in birds
2019 (English)In: Ibis, ISSN 0019-1019, E-ISSN 1474-919X, Vol. 161, no 1, p. 205-210Article in journal (Refereed) Published
Abstract [en]

Ketone bodies such as beta-hydroxybutyrate are important indicators of metabolic condition in birds and are linked to a suite of ecologically relevant factors including migratory decision-making, hunger level and ectoparasite load. Portable point-of-care (POC) devices designed to measure ketones in humans offer a cheap and easy solution to field physiologists in comparison with previous laboratory methods; however, their accuracy for use in birds has received scant attention. Here, we assessed the accuracy of a POC ketone meter (FreeStyle Precision Neo, Abbott, IL, USA) using samples from intermittently fed Red Junglefowl Gallus gallus. Although the device overestimated ketone levels in comparison with laboratory-derived values, random error was low and laboratory vs. device values correlated well, indicating that the Precision Neo is of sufficient accuracy for use in the field and is a pragmatic choice for avian physiologists.

Place, publisher, year, edition, pages
WILEY, 2019
Keywords
intermittent feeding; ketosis; point-of-care; Red Junglefowl
National Category
Ecology
Identifiers
urn:nbn:se:liu:diva-153969 (URN)10.1111/ibi.12643 (DOI)000454604400018 ()
Note

Funding Agencies|Swedish research council Formas [2013-293]; Swedish Centre of Excellence in Animal Welfare Science; Carl Tryggers Stiftelse for Vetenskaplig Forsknin

Available from: 2019-01-22 Created: 2019-01-22 Last updated: 2019-10-10
5. The Quest for Welfare-Friendly Feeding of Broiler Breeders: Effects of Daily vs. 5:2 Feed Restriction Schedules
Open this publication in new window or tab >>The Quest for Welfare-Friendly Feeding of Broiler Breeders: Effects of Daily vs. 5:2 Feed Restriction Schedules
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2018 (English)In: Poultry Science, ISSN 0032-5791, E-ISSN 1525-3171, Vol. 97, no 2, p. 368-377Article in journal (Refereed) Published
Abstract [en]

Restricted feeding of broiler breeders is required for improved long-term health and welfare. Because feeding frustration and hunger are major welfare concerns during rearing, many suggestions have been made to decrease the negative feelings of hunger while maintaining suitable growth rates and reproductive health. Non-daily ("skip-a-day") feeding schedules are commonly used around the world to increase portion sizes at meal times while restricting intake but these practices are prohibited in many countries due to welfare concerns on fasting days. We compared birds raised on a non-daily feeding schedule (2 non-consecutive fasting days per week, 5:2), previously suggested as a welfare-friendlier non-daily alternative, to birds raised on daily feed restriction. We found signs of increased physiological stress levels in 5:2 birds, including elevated heterophil to lymphocyte ratios (1.00 for 5:2 vs. 0.75 for daily fed at 12 weeks of age), increased adiposity (0.21% lean body weight [LBW] for 5:2 vs. 0.13% LBW for daily fed), and reduced muscle growth (pectoral muscle 5.94% LBW for 5: 2 vs. 6.52% LBW for daily fed). At the same time, 5:2 birds showed signs of lower anxiety before feeding times (activity was reduced from 10.30 in daily fed to 4.85) which may be a result of the lower feed competition associated with larger portion sizes. Although we found no difference in latency to first head movement in tonic immobility between the treatments (136.5 s on average for both groups), 5:2 birds generally showed more interest in a novel object in the home pen which indicated increased risk taking and reduced fear while fasting. The 5:2 birds in this study showed no signs of learning the feeding schedule, and this unpredictability may also increase stress. Taken together, the effects of 5:2 vs. daily feed restriction on the welfare of broiler breeder pullets remain inconclusive and differ between feeding and fasting days. In addition to reducing stress by minimizing the number of fasting days, we suggest that a shift to more predictable schedules may help improve the welfare of broiler breeder pullets.

Place, publisher, year, edition, pages
OXFORD UNIV PRESS, 2018
Keywords
animal welfare; broiler breeders; feed restriction; intermittent fasting; skip-a-day
National Category
Zoology
Identifiers
urn:nbn:se:liu:diva-145242 (URN)10.3382/ps/pex326 (DOI)000424248600003 ()29182752 (PubMedID)
Note

Funding Agencies|Swedish research council Formas [2013-293]; Swedish Centre of Excellence in Animal Welfare Science

Available from: 2018-02-21 Created: 2018-02-21 Last updated: 2019-10-10

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  • nn-NO
  • nn-NB
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Output format
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