Seasonality, food and design

Seasonality in food is often addressed with reference to vegetables and fruits and their natural growing seasons. In this post I will look at seasonality in relation to a processed food, namely beer. I will start by looking briefly into the history of beer, and try to track signs of seasonality. I will then turn to the present, and explore whether and how beer consumption and production still fluctuates throughout the year. Next, I will describe typical seasonal beers that are well-known in the Netherlands and explore what makes such beers ‘seasonal’ – are they seasonal because they rely on the growing seasons of particular ingredients, or does seasonality have a different meaning in contemporary seasonal beers? Finally, I will briefly touch upon the ongoing ‘craft beer revolution’, which has also created new interest in seasonal beers, and where seasonality appears to have a strategic value for small brewers. Beer’s history in relation to the seasons Not much has been written about the history of beer with a focus on seasonality. For what I describe below, I make use of several sources on the history of beer and its production, each of them offering sparse insights about seasonal aspects of beer. I organise these insights around three topics: the seasonality of cereals, the seasonality of the fermentation process for producing beer, and some reflections on how hop contributed to ‘de-seasoning’ beer. De-seasoning refers to the process of how production and consumption become less and less dependent on the conditions that the natural seasons create. Seasonality of cereals – In Prehistoric times there were no ‘beer’ and ‘wine’ traditions yet, but a wide variety of fermented beverages were available. What was used in the brewing of these beverages depended on what fermentable products were available³. Such beverages were likely to be seasonally dependent. The brewing of beer, which came to be a tradition much later, was dependent on the availability of cereals, which was and still is the main ingredient of beer. Cereals became broadly available with the agricultural revolution. While cereals had their particular harvest seasons, and there were techniques available to dry and store the them, little seems to be written about to what extend these stored cereals were available throughout the seasons for the purpose of brewing beer. Seasonality of the fermentation process – Another historical aspect of seasonality of beer concerns the fermentation process. Fermentation is a process of transforming sugars into alcohol, carbon dioxide and other components. The yeast that is used in beer brewing has a long history, going back thousands of years. Modern yeast populations are a result of admixture between different domesticated populations that were transferred via the Silk Route¹⁴. A general distinction is often made between bottom- and top fermentation, or bottom- and top yeast. Top fermentation was, for a long time, the dominant fermentation process and the resulting beer is currently known as ‘ales’. The use of bottom fermentation, now used to produce ‘pilsner’ and ‘lager’, while known in the Middle Ages, was mostly restricted to the region in and around Bohemia (now the eastern part of Czech Republic). Unger, p.6: “Bottom yeast requires a lower and more consistent temperature to function than the other type of yeast, and until mechanical refrigeration became practical in the 1870s, its use was restricted to colder seasons of the year and regions where cooler temperatures could be expected.” Hop as a strategy for de-seasoning – While hop was already cultivated in the early middle ages, its use appears to have been mainly medicinal. There is some evidence for sparse use of hop in beer in the 9th century. Only in the 13th century, its use became more popular, as described by  Unger² (p55): “it is possible to say that by the thirteenth century [hops] were widely cultivated throughout northern Europe and had different uses, among them replacing gruit or other herbs in the making of beer.” One of the main reasons for hop’s success was that it made beer last longer (i.e. resulting in a more reliable product) and thus also travel further and being better ‘marketable’. Unger elaborates: “Preservation of foods was one of the greatest problems of pre-nineteenth-century Europe. The addition of hops in the brewing process made for a significant change in beer. It now joined the few foods that would keep for months with- out becoming inedible.” Through its improved durability, hop made the consumption of beer less reliant on the seasons. Production-side seasonality of beer at present Barley is the most commonly used cereal in beer. In current barley production, a clear distinction is made between animal feed barley and malting barley. This distinction has some history: already in the 1940s these were two genetically distinct types of grain. Barley used in beer production was a more carefully selected grain than barley used for animal feed and other purposes.⁴ Compared to feed barley, malting barley has genetic qualities that benefit brewing – qualities that result in lower levels of protein and beta glucan, and higher levels of enzymes. This genetic difference also has implications for the the growing of barley: malting barley requires relatively well-managed growing conditions compared to animal feed barley. Barley is a cool season crop, for which ultimate conditions for germination and growing are between 12 – 24 ̊C. This means that barley is either sown in spring or fall, and there are different cultivars for both seasons. Particular to winter cultivars is that they undergo a period of vernalisation (cold exposure) before they can flower in the spring. Barley is a short-season crop: after emerging, plants need 60-90 days to grow mature. Planting barley needs good timing. For the spring cultivars, early planting reduces the risk from drought stress, high temperatures, diseases and insect infestations, while delayed planting increases the risk of high protein content (which is undesirable for malting) and decreased yields⁵. The choice for a spring or fall cultivar may depend on the climatic zone: in colder climates, barley is more easily grown over the summer, while in warmer climates it is better grown over the winter⁶. Strategic decisions may also relate to the timing of the harvest: In Europe, barley grows over the winter is harvested in the early summer, while barley that grows over the spring and summer, is harvest in the fall. The brewing of beer ultimately depends on the harvests of barley, as illustrated by recent history in the Netherlands. Barley harvests in Germany and France were low in 2016, and provided too little barley for Dutch brewers. The main reason for the low harvests was a very wet early season (first half of 2016). This led brewers, such as Gulpener in the Netherlands, to also buy barley from external suppliers outside Europe. While production was maintained, Gulpener had to make do with grains that didn’t comply with the sustainability standards that their internal suppliers of the farmers cooperative Triligran guaranteed. The bad harvests were also seen from a positive point of view. On Gulpener’s website it is written: “For the farmers as well as Gulpener this was a disappointment on the one hand. On the other hand, it is remarkable to conclude that since the founding of Triligran in 1994, this cooperative was able to meet Gulpener’s needs”⁷. The brewing of beer with particular standards or qualities is thus dependent on successful harvests of particular farms, but a globalised market allows to compensate for bad harvests. Does the seasonality of barley –i.e. it being a spring and winter crop with particular harvest times – affect beer brewing and consumption in any way? To answer this question we need to consider storage time. When dried and stored properly, barley can be stored up to 18 months. Thus, the supply of barley for the production process is managed through proper storage facilities, and has no effect on the availability of (regular) beer throughout the seasons. Furthermore, the shelf life of beer ranges from several months up to several years, depending on the type of beer – for example, the higher the percentage of alcohol, the longer the shelf life. Added up, the maximum storage time of barley, together with the shelf life of beer, means that the seasonality of barley production is compensated for and not necessarily reflected in consumption patterns. Demand-side seasonality of beer at present While the seasonality of beer production generally does not affect the seasonality of consumption, this does not mean there are no seasonal patterns in when we drink beer, or particular kinds of beer. A study in Estonia (1999-2002) on alcohol use and seasonality clearly shows a peak of beer consumption in the summer months. Their data show a strong correlation between air temperature and beer consumption (and the number traffic accidents, but let’s stay on topic)⁸.  While there seems not much to be published on this topic, similar patterns were found in a study in Montana, US (1969-1975)⁹. Other ways in which seasonality of beer consumption (or alcohol consumption more generally) may occur, is through festivities like New Year’s eve or St. Patrick’s day. In a study with college students consumption peaks were found at these days, as well as a pattern of increased consumption early in the semesters and decreased consumption during the exam periods.¹⁰ The numbers of these studies are about total beer consumption, but one can imagine that there are also nuances to be found in what kinds of beers are consumed when. I couldn’t find any data or studies that address such seasonality. Traditional seasonal beers: ‘Herfstbok’ in autumn and ‘Lentebok’ in spring While most modern beers are available throughout the year and don’t have a specific seasonal character, there are also several seasonal beers that are brewed and bought in particular times of the year. What makes these beers ‘seasonal’? I will look into ‘bokbier’ particularly, which is a beer now brewed in the autumn (i.e. ‘herfstbok’) and in spring (i.e. ‘lentebok’) – the Dutch names explicitly refer to these seasons. While bokbier originates from Germany, where they produced ‘bockbier’, Dutch brewers started brewing bokbier around 1870-1880. The timing of its availability has shifted throughout history: “for a very long time February was the traditional bokbier month. Around 1920, the annual bokbier launch date was advanced to December and later put back still further into the autumn. In recent years the date has been set on or around 21 September”¹¹. The reason for this timing does not become clear from the scarce historical documentation that is available. Explanations I could find refer to the times before mechanical refrigeration. Brewing during the summer was unproductive and sometimes prohibited, as the fermenting process required low temperatures. The first brews could start right after the summer, to eventually deliver the beer in winter. These first brews were extra strong and became to be known as ‘bokbier’, and in particular the ‘herfstbok’.¹¹ Some suggest that Lentebok has a different history¹². It was the last brew before the summer, which was made extra strong (in terms of alcohol and the use of hop) to improve its shelf life. The typical beer that resulted from this way of brewing came to be known as ‘meibok’ and then ‘lentebok’ only in the last couple of decades. Both ‘lentebok’ and ‘herfstbok’ have lost their ‘natural seasonality’ so to speak, as they do not rely on temperatures imposed by the natural seasons anymore. The seasonality that remains is of a cultural kind. The flavours and colour can also be said to be ‘seasonally appropriate’, and can be expected to have been designed that way: while herfstbok is typically described as ‘ruby red’, ‘dark’, with a ‘malty caramel flavour’, lentebok is described as a ‘bright’ and ‘fresh’ beer, with a ‘hoppy’ and sometimes ‘fruity’ flavour. In a future post I hope to learn more about seasonal flavours: To what extent are particular flavours and colours ‘imposed’ by natural seasons, either in the past or present? Or are they designed that way without reference to what’s naturally available? Seasonality and the ‘craft beer revolution’ Over the last decades we have witnessed, what has been described as a ‘craft beer revolution’ in many parts of the world. This revolution has meant a strong increase in the number of breweries currently out there. Without elaborating too much, let the following graphs speak for themselves – one describing the number of breweries in the US since 1873 and the other in the Netherlands since 1350 (only in Dutch). With the growing popularity of craft beers also comes an increasing interest in seasonality. This seasonality has value from both a supply-side and a demand-side point of view. For brewers it can have strategic value¹³. The continuous introduction of new beers as a result of a seasonal product strategy can keep consumer interest high over the year. An example is the ‘Dogfish Head’ brewery, which brews 5 major brands but also 18 seasonal brands, each sufficiently distinct from one another. Each of the seasonal beers is only available for two specific months. The seasonal beers bring opportunities for connecting with seasonal events, and also their limited availability can work positively: “Strangely, the “loss” of the chance to buy it tends to increase brand retention and intention to purchase.”¹³ From the consumers’ point of view, the seasonality of craft beers can bring unique qualities to the ‘beer experience’. The coming and going of seasonal beers brings continuous novelty, eliciting curiosity to ‘try something new’. Also the limited availability of seasonal craft beers may increase their perceived value – knowing that the very special ‘pumpkin ale’ that you bought is a limited edition might make you savor your ownership of it and the moment you drink it even more. I can imagine a similar experience may occur as with seasonal vegetables and fruits, which is an experience of a more cyclical nature: each year, we have a brief period in which we get to enjoy, for example, asperges or a particular apple cultivar (e.g., Elstar is my favorite). Besides enjoying these temporary treats, their limited availability also brings a sense of anticipation. Can seasonal beers, or any ‘seasonal processed food’ for that matter, offer a similar experience? If so, this allows us to consider seasonality not only as something relevant in terms of environmental sustainability or health, but also in terms of its potential to elicit rich experiences. In this post many questions still remain open that might be of interest for this blog: For example, what makes these seasonal craft beers actually seasonal? Is it because the flavours are specifically attuned to the seasons in a similar way that herfstbok and lentebok are promoted? Or do some brewers choose their ingredients based on what is actually seasonally available? Or are their techniques of brewing somehow seasonally dependent? And besides the potential rich experience of seasonal beers described above: what are additional reasons to choose a seasonal craft beer? Are they a form of supporting a local economy? Does the small scale production and seasonality of seasonal craft beers tell us anything about their environmental sustainability?  Is the rich diversity that these smaller brewers represent something valuable in its own right? References

1. Nelson, M. (2005). The barbarian’s beverage: a history of beer in ancient Europe. Routledge.
2. Unger, R. W. (2004). Beer in the Middle Ages and the Renaissance. University of Pennsylvania Press.
3. Nelsen (2005) writes: “The picture sketched so far seems to contradict the theory that already in prehistoric times there were two general drinking traditions in Europe, a wine-drinking tradition in the south and a beer-drinking tradition in the north, as attested much later. This seems far too simplistic. Rather in both areas there was, no doubt, an ancient tradition of making and drinking fermented beverages, but the only thing ostensibly determining what was used in these beverages seems to have been the availability of fermentable products.”
4. Weaver, J. C. (1944). United States malting barley production. Annals of the Association of American Geographers, 34(2), 97-131.
5. Oser, H. H. (2015). Producing quality barley for the malting industry. PhD thesis. The University of Nebraska-Lincoln.
6. Pržulj, N., Dragović, S., Malešević, M. et al. (1998) Comparative performance of winter and spring malting barleys in semiarid growing conditions. Euphytica 101, 377–382. https://doi.org/10.1023/A:1018388430317
7. https://www.gulpener.nl/gevolgen-tegenvallende-gerstoogst-2016/
8. Silm, S., & Ahas, R. (2005). Seasonality of alcohol-related phenomena in Estonia. International Journal of Biometeorology, 49(4), 215-223.
9. Lovett, C. K. (1977). A study of beer consumption trends in Montana.
10. Tremblay, P. F., Graham, K., Wells, S., Harris, R., Pulford, R., & Roberts, S. E. (2010). When do first-year college students drink most during the academic year? An internet-based study of daily and weekly drinking. Journal of American College Health, 58(5), 401-411.
11. Flissebaalje (2013) Bokbier in the Netherlands: a historical overview. Brewery History 152, 33-42
12. https://www.gall.nl/ontdek/bier/lentebok/#:~:text=Herfstbok%20is%20de%20tegenhanger%20van,Vandaar%20de%20naam%20’herfstbok’.
13. Pitta, D. A., & Scherr, B. G. (2009). The product strategy for seasonal products. Journal of Product & Brand Management.
14. Fay JC, Liu P, Ong GT, Dunham MJ, Cromie GA, et al. (2019) A polyploid admixed origin of beer yeasts derived from European and Asian wine populations. PLOS Biology 17(3): e3000147. https://doi.org/10.1371/journal.pbio.3000147

   

At present time, the seasonality of animal products such as meat, dairy and eggs seems either hidden to us, or non-existing. There is a seeming abundance of these products available throughout the year¹. In this post I’m asking several questions in relation to meat and its production and consumption in relation to seasonality (i.e. ‘the fact that something changes according to the seasons’). How has seasonality played a role in our meat production and consumption in the past? Is there still seasonality to be found in the present abundance, for example, when looking at particular animal products? Is it relevant to consider seasonality of meat in terms of the nutritional and sustainability challenges of our time? This post shares some preliminary answers to these questions. Seasonality of meat in the past Hunter-gatherer societies Animal foods were a major component in hunter-gatherer societies, such as the Aboriginals before European settlement of Australia² and the Ache hunter gatherers that used to live in Eastern Paraguay³. Animal foods were often the primary source of energy for hunter-gatherers – an analysis of 13 quantitative dietary studies concluded that hunter-gatherer diets consisted of about 65% of animal foods and 35% plant-based foods as a source of energy⁷. What can we say about the seasonality of animal foods in hunter gatherer societies? Making general statements is difficult, as the ecological settings in which these societies were based differ a lot. In communities such as the Ache hunter gatherers, meat consumption did not vary significantly throughout the year, whereas other hunter gatherer societies are / were likely to have periods of meat scarcity. For example, present-day communities in the Congo Basin face an annual seasonal scarcity in available bushmeat (i.e. meat from wildlife species), although the intensity of this scarcity fluctuates throughout the years⁴. Also the Tanzanian Hadza people are known for mainly eating meat in the dry season, when hunting is easier, while in the wet season berries and honey become a more important part of their diet⁵. The specific reasons for these dietary shifts are different for each specific ecological setting, and they are difficult to unravel within the scope of this post – I hope to return to this topic in a future post. Acknowledging that the specifics of seasonality in different ecological settings vary, what are some of the important factors related to seasonality that affect meat consumption? Fluctuations in rainfall and temperature appear to be important, which in turn influence the availability of certain animal species, the rate of encounters with these animals, and the difficulty of hunting, as well as the availability and quality of plant foods. So as the environment of hunter-gatherers changes throughout the seasons, animal availability tends to fluctuate as well, as well as the availability of other food sources. The ways in which hunter gatherers have responded to these fluctuations vary – some communities were mobile and moved away when meat sources turned scarce, while other communities shifted their diet to more plant foods such as tubers. Generally speaking, people’s strategies with respect to seasonal changes appear to be characterised by adaptation – i.e., hunter-gatherers organised themselves by flexibly adapting to the changing availability of different foods. Early agricultural societies Patterns of meat consumption changed during the Neolithic revolution, in which a lifestyle of hunting and gathering slowly got replaced by a lifestyle of agriculture and settlement. In this period, starting around 13.000 BC, animals were first domesticated, driven by the need to have food when hunting was unproductive. Animals were kept not only for their meat, but also came to serve as a valuable source of nutrition through the milk that they produced. They also provided other useful products and services – for example, sheep provided wool and other animals were used for transporting goods or pulling the plow. Returning to our focus on meat, how did seasonality affect its availability throughout the year in early agricultural societies? And how did farmers relate to this seasonality? In his book Seasonal Food ⁹, Paul Waddington describes how pigs in Britain used to be more than just the meat that they produced. Rather, pigs were an integral part of the annual cycle of a homestead and played an important role in the peasant economy: “Traditionally, they were fattened through the year and killed in the autumn to provide a supply of protein, flavour and fat through the winter” (p. 29). Specific techniques were required to get the most out of the pig, resulting in products as black puddings, sausages, chitterlings (i.e. cooked intestines) and faggots (i.e. meatballs made from minced off-cuts and offal). From this example we get a picture that the seasonality of meat in early agriculture often had a specific timing – a timing that was connected to other functions of the animals (i.e. turning food waste into manure) as well as to the preparations that people made for the leaner winter months (i.e. the techniques of turning the pig into various products that could be stored for later consumption). Besides pigs, other animals occupied roles in peasant households. A distinction can be made between animals that yield products only upon death (i.e. pigs), and animals that also provide secondary products (i.e. sheep, goats and cattle, which also provide wool, milk or animal traction)¹⁰. In terms of meat seasonality, sheep and goat often served as an ‘insurance’ for periods of scarcity. Often multiple sheep or goats were kept, allowing some of them to be killed while the herd would remain. Pigs were also commonly used for these purposes, as they ate almost anything and had no by-products that peasants relied upon¹⁰. Several archeological studies have shown that in the Neolithic period, pig slaughter often took place in the first winter after birth, and this is often explained as a preparation for winter, as well as preventing the loss of body mass of the big during winter. Another explanation is that pig slaughter had a ceremonial function, being associated with feasting activities in the fall or winter¹². From the above, we understand that meat was a valuable source of nutrition, particularly during the winter months. Compared to hunter gatherers, early farmers responded differently to seasonal changes in terms of meat consumption. Having animals such as pigs and sheep by their side throughout the year, they could strategically make use of the ‘products and services’ that these animals offered. Furthermore, keeping animals throughout the year allowed peasants to decide to eat meat at particular times, for example, during periods of food scarcity. Rather than ‘flexibly adapting’ to the seasons, early peasants had strategies to deal with seasonal fluctuation that are more characterised by planning and control. Such planning and control also appears to have served the purpose of facilitating feasting activities. Seasonality of meat in the present For hunter gatherers and early farmers, seasonality had implications for what could be hunted, raised or grown in specific seasons, which affected the ways in which people organised themselves over the year in a direct way. With respect to animal husbandry, this meant that there were certain predictive cycles, for example,  when parts of the herd were needed for consumption to get through the winter months. Another example of seasonality, not described above, is how herds were expanded through newborn calves or lambs, particularly during spring.  People organised themselves according these natural cycles. Our current agricultural system, however, does not always take these natural cycles as a starting point. Much more is possible in terms of ‘when to do what’ and this plays out in both production and consumption of meat. On the production side, can we still consider meat as a seasonal product? For this, let’s take a look at breeding, which is one of the most important elements of animal husbandry upon which many other things depend. It turns out that the ‘natural breeding season’ still has an important role to play in animal husbandry, although farmers have the possibility to manage the timing. Take for example sheep, and the timing of lambing. On the website of the Western Australian Government we read: “Sheep fertility increases as daylight decreases, that is, after 22 December. Pregnancy rates from joining [i.e., when ewes and rams are joined] in January and February can be up to 20% better compared to a joining in October and November from ewes of equal condition”¹⁵. Many other factors need consideration. For example, ewes’ energy demand increases significantly when pregnant, and increases further during lactation. The farmer needs to respond to this by offering sufficient nutrition, which in turn depends on pasture availability, which in turn may seasonally fluctuate. There are also ways to breed out of season – several techniques have been developed such as altering the light conditions, using hormones, or stimulating ewes to ovulate through the use of fertile rams or so-called ‘teaser rams’^{15, 16}. Seasonality also takes place on the consumer side of meat production – consumer demand for certain meat products fluctuates throughout the year. There are various examples of consumer-driven seasonality in meat. Summer is a season in which many people get out their barbecue to grill meat¹⁴. Also religious traditions create a certain seasonality in meat consumption, such as the Muslim Festival of Sacrifice, which causes an increase in demand for beef, sheep and other meats in spring¹³, and Thanksgiving, which causes an annual peak in demand for turkey in the november month. In Time magazine I read that “more than 18 percent of all the 244.5 million turkeys raised on American farms” was consumed during Thanksgiving in 2017¹⁷. From the above we learn that the seasonality of meat in our current agricultural system is not always something resulting directly from natural cycles. More dominant in meat seasonality seem to be the ‘cultural cycles’ on the consumer side – these have a strong influence on what is eaten when. I am curious how certain techniques, such as enforced breeding at ‘unnatural’ times, are related to these cultural cycles. Furthermore, to what extent are these cultural cycles connected or disconnected to natural cycles? I have an intuition, based on earlier readings¹⁸, that the ‘disconnect’ between natural and cultural cycles may be part of the explanation of many health- and sustainability-related issues we are currently facing as a society and as individuals. Notes and references:

1. The abundant availability of animal products is a relatively recent phenomenon – for example, milk production has doubled and meat production has quadrupled over the past 50 years¹. See: Ritchie, H. & Roser M. (2019) Meat and Dairy Production. Published online at OurWorldInData.org. Retrieved from: https://ourworldindata.org/meat-production
2. O’Dea, K. (1991). Traditional diet and food preferences of Australian Aboriginal hunter-gatherers. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 334(1270), 233-241.
3. Hill, K., Hawkes, K., Hurtado, M. et al. Seasonal variance in the diet of Ache hunter-gatherers in Eastern Paraguay. Hum Ecol 12, 101–135 (1984). https://doi.org/10.1007/BF01531269
4. Dounias, E., & Ichikawa, M. (2017). Seasonal bushmeat hunger in the Congo basin. EcoHealth, 14(3), 575-590.
5. Smits, S. A., Leach, J., Sonnenburg, E. D., Gonzalez, C. G., Lichtman, J. S., Reid, G., Knight, R., Manjurano, A., Changalucha, J., Elias, J. E., Dominguez-Bello, M. G., & Sonnenburg, J. L. (2017). Seasonal cycling in the gut microbiome of the Hadza hunter-gatherers of Tanzania. Science, 357(6353), 802–806. https://doi.org/10.1126/science.aan4834
6. Heim, A., & Pyhälä, A. (2020). Changing food preferences among a former hunter-gatherer group in Namibia. Appetite, 104709.
7. Cordain, L., Eaton, S. B., Miller, J. B., Mann, N., & Hill, K. (2002). The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic. European Journal of Clinical Nutrition, 56(1), S42-S52.
8. Reyes-García, V., Powell, B., Díaz-Reviriego, I., Fernández-Llamazares, Á., Gallois, S., & Gueze, M. (2019). Dietary transitions among three contemporary hunter-gatherers across the tropics. Food Security, 11(1), 109-122.
9. Waddington, P. (2004) Seasonal Food: A guide to what’s in season when and why. Transworld publishers, London.
10. Bogucki, P. (1993). Animal traction and household economies in Neolithic Europe. Antiquity, 67(256), 492–503. doi:10.1017/s0003598x00045713
11. Vigne, J.-D. (2011). The origins of animal domestication and husbandry: A major change in the history of humanity and the biosphere. Comptes Rendus Biologies, 334(3), 171–181. https://doi.org/https://doi.org/10.1016/j.crvi.2010.12.009
12. Wright, E., Viner-Daniels, S., Parker Pearson, M., & Albarella, U. (2014). Age and season of pig slaughter at Late Neolithic Durrington Walls (Wiltshire, UK) as detected through a new system for recording tooth wear. Journal of Archaeological Science, 52, 497–514. https://doi.org/https://doi.org/10.1016/j.jas.2014.09.009
13. Fidan, H., & Klasra, M. A. (2006). Seasonality in household demand for meat and fish: Evidence from an urban area. Turkish Journal of Veterinary and Animal Sciences, 29(6), 1217-1224.
14. Peng, Y., McCann-Hiltz, D., & Goddard, E. W. (2004). Consumer demand for meat in Alberta, Canada: Impact of BSE (No. 377-2016-20604).
15. https://www.agric.wa.gov.au/management-reproduction/time-lambing
16. http://www.omafra.gov.on.ca/english/livestock/sheep/facts/08-065.htm#1
17. https://time.com/5022315/turkeys-killed-thanksgiving/
18. Princen, T. (2010) Treading Softly: Paths to Ecological Order. Cambridge, The MIT Press