Animals receive feedback via their organs and organ systems – digestive system, lungs, heart, and so forth. The feedback comes from the forages they learn to eat that help them to become locally adapted and in tune with need. A palate in tune with the landscapes it inhabits.
This is the second principle identified by Fred Provenza and that I discussed with him and wrote of in an introduction to the topic of animal behaviour and feeding a few weeks back. In a diverse pasture or native plant diverse area, animals have access to a huge variety of phytochemicals in the grasses, trees, forbs and shrubs that they feed and browse on. The levels and type of primary compounds of energy, protein, minerals and vitamins and secondary compounds of alkaloids, polyphenols and terpenes will vary from one species to the next – while also varying depending on the age of the plant and the part of the plant. This creates a need for animals to be experienced about these feedtypes, as some of these compounds can be nutritious, while others can be toxic. The likelihood of toxicity will depend on many variables of the plant, like soil, age, season etc., as well as variables of the animal, such as age, experience with eating that plant and the combination of plants it has consumed with the toxin.1
How then, do animals select what they need for both safe consumption and for optimal health?
Last week I talked about the social and in utero influence of the mother/offspring interactions in teaching the offspring how and what to feed on. Many of the examples I gave highlighted the social interactions. What also exists in animals, is internal flavour feedback mechanisms that aid the animals in their food choices.
Animals use flavour feedback associations to determine the outcomes of eating different feed types in a meal or feeding session. These flavour feedback systems, and the associated positive or less positive feedback can influence the plant selection choice of animals in both the short and long term.
The primary and secondary compounds consumed in feedstuffs interact with the body’s cells and organs which give feedback as to the consequences of that eaten, which then influences future food selection. This is really amazing stuff. Nerves, neurotransmitters, peptides and hormones all link the aroma and taste receptors of the animal to the organ system of its body. Such systems allow the animals to meet their dietary requirements, as well as self-medicating through nutrition – as long as the diversity in plants will allow this.
The animals’ needs will vary with time and circumstance. Examples include that “they eat less protein as they age and their needs for protein decline. Conversely, sheep increase intake of protein relative to energy as their needs for protein increase during the last trimester of gestation.”2
A great example of animals self-medicating through nutrition is a study where “Sheep on a P-deficient diet increased intake of a P supplement when given a choice between a P or calcium (Ca) supplement. Conversely, sheep eating a Ca-deficient diet ate more of a Ca supplement than sheep fed a diet high in Ca. During the trial… lambs licked and chewed the dirt not only in their own pens but also in their neighbours’ pens. Lambs were observed eating soil, faeces and licking urine of their neighbours. Lambs in the study were randomly assigned to pens, so lambs on high P and low Ca diets were often penned next to lambs on a low P and high Ca. They were apparently alleviating their mineral deficiency by licking urine and eating faeces from their neighbours. Blood mineral levels remained normal even though lambs were fed deficient diets. When animals were separated, blood mineral levels dropped. Evidently, lambs were able to solve their mineral deficit as long as they had a source of minerals even if their solution was pretty disgusting.”3
“Mammals have mechanisms to digest foods, to assimilate nutrients, and to counter toxins. The capacity of these systems is seldom exceeded because animals quickly experience internal malaise and limit intake before toxicosis ensues. Blood flow through the ruminal artery increases within 30 to 60 seconds after feeding begins, and peaks about 15 min later. Thus, ruminants probably sense many toxins (and nutrients) in the cardiovascular system early in a meal.”4
So, these findings that animals are able to self-regulate nutrition (and toxicities) through their internal feedback systems and subsequent feed intake, “support the practice of offering minerals free-choice so animals can select for particular minerals that are low in forages”5. I know that this is something that graziers have had differing levels of success with. Perhaps though, it is about the feedback systems of the animal AS WELL AS the early life social experiences, then this would mean animals were familiar with this kind of supplementary feed system. If we extrapolate what we learnt last week from examples with grain – without experiencing a free choice mineral lick trailer as a young animal, with mother, they are much less likely to feed from this successfully as an adult.
Perhaps this helps to explain what appeared to be completely random consumption when we have provided animals with free choice mineral supplements over the years on our farm. Derek has at times been perplexed at how much mineral supplement such as sulphur, dolomite, salt and even copper sulfate could be consumed in one week, only to then all but cease not long after. There seemed to be no clear pattern to the rates of consumption of the different supplements on offer, with kelp meal being the exception.
How to use feedback systems for bettering production
We can actually use these feedback systems to our advantage to have animals consume low value feedstuffs. Given that the animal’s feedback systems allow them to meet their dietary requirements, as well as self-medicating through nutrition, we can use these to our advantage. We can offer supplements that provide the nutrition and balance that allow animals to then consume feedstuffs that they otherwise would not due to nutrient imbalances or toxin levels.
Animals can also be trained via their feedback systems and their social experiences, to eat weeds.7 (Clearly we would only want to do this if the weeds are non-toxic). Cattle can then be used in the management of certain weed species, and can be used strategically – like goats often are, but cattle seldom do without training. Many weeds have valuable attributes – saffron thistle (or distaff thistle in the US) has a protein content of 17%.8 This could prove quite a handy feedstuff with such a protein content. I will talk more about training animals to eat weeds another week.
The greatest way to utilise the animals’ feedback systems for the purpose of health and self-medication however is by offering them a diverse pasture on which to choose their diets. This brings me to the third principle of Fred Provenza’s observations of animal behaviour and management – ensuring a diversity of plants is available from which animals can choose their feeds. I will expand on this third principle next week.
As a final note, you may be interested to know that humans also possess such taste feedback systems and organ receptors. This is why when someone has a heart transplant, they may take on the eating preferences of the donor.6 If only we were more in tune with these feedback systems. Unfortunately, they have been hijacked by highly processed food companies who understand these loops and play on them by adding flavours to foods that trick the brain into thinking it may be getting the nutritious food and nutrients in need.
References
1, 2, 5 & 6. Provenza, F.D., M. Meuret, and P. Gregorini. 2015. What humans can learn from herbivores about nourishing links between palates and landscapes. Appetite, submitted.
3. ‘Can animals rectify mineral deficiencies’? 19th April 1015. https://extension.usu.edu/behave/htm/past-projects/minerals/
4. Provenza F. (1995) ‘Postingestive feedback as an elementary determinant of food preference and intake in ruminants’. Journal of Range Management, 48 (1) Jan 1995.
7. Voth, K. (2010) Educated Cows eat Weeds. 20th April 2015. http://www.livestockforlandscapes.com/cowmanagers.htm
8. Cows Eat Weeds Introduction. https://www.youtube.com/user/KathyVoth#p/u/1/dANLnHEi19A