Voisin Rational Grazing and Its Four Principles: Comparison
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Please note this is a comparison between Version 2 by Jessie Wu and Version 1 by Luiz Carlos Pinheiro Machado Filho.

This enote, based on our full review [1], try briefly describes the need to promote sustainable agriculture, proposing Voisin Rational Grazing (VRG) as an alternative livestock production system as a way to address sustainability in all its dimensions. WeIt describes the four VRG principles that allows this livestock production system to attain high productive standards while boosting social, cultural and environmental characteristics within the pastoral ecosystem.

  • voisin rational grazing
  • multispecies pasture
  • biodiversity
  • sustanaible livestock production
  • pasture management

 1. Background

Countries around the world have faced limitations in using the planet’s biophysical resources to meet basic needs. Achieving a high standard of living for all would require the use of biophysical resources two to six times greater than the level considered sustainable [1], depleting our resources and threatening life on the planet. Agriculture plays a central role in providing food resources, but the current agricultural model has caused serious negative environmental and social impacts [2].
According to the UNCCD (United Nations Convention to Combat Desertification; https://www.unccd.int/message-land-and-soil), the planet loses 28–75 billion tons of fertile soil to erosion annually. Livestock has been considered responsible for 14.5% of anthropogenic greenhouse gases (GHG) emitted, of which meat and dairy products represent 41% and 21%, respectively [3]. The current agricultural model, which is based on the “Green Revolution”, has also promoted massive rural exodus, changing the rural landscape from its cultural richness and biodiversity to the monotony of monocultures in large farms [4].
Promoting sustainable livestock production systems is imperative, and the current challenge is to combine intensification of animal production and maintenance of ecosystem services [5]. Well-managed pastureland provides a range of ecosystem services [6,7][6][7]. A key aspect of sustainable livestock production is to identify the best management practices to optimize environmental services while supporting farmers’ profitability [8]. Maintaining high animal productivity is in line with farmers’ motivations [9,10][9][10] and may help bridge the gap between the trade-offs of confinement and extensive systems. Ecologically based systems require a paradigm that focuses on agroecological processes involving soil, plants, and animals in order to optimise the use of renewable resources [10,11][10][11]. This means shifting away from agriculture heavily based on fossil fuel inputs and moving toward intensification based on pasture management and clean energy [12].
Permanent meadows and pastures encompass about 67% (33.6 million km2) of the world’s agricultural land [13]. This large area is probably sufficient to sustain not only wildlife, but also the current livestock population of ruminants: 1.5 billion head of cattle, 204 million head of buffaloes, 1.24 billion sheep, and 1.09 billion goats [13] in sustainable, regenerative systems. Many types of systems are considered ecologically-based or regenerative: holistic grazing management [14], adaptive multi-paddock grazing management (AMP; [15]), management intensive grazing (MIG; [16]) and Voisin Rational Grazing (VRG; [12,17][12][17]). All these systems rely on pastoral ecosystems and share the basis of agroecological reasoning, notwithstanding there are different reasons for applying one system instead of another. While some systems are applied mostly with the aim of land recovery, others focus on increased animal productivity.
Another agriculture is possible and necessary, with sustainability as a fundamental guide. For ruminants, in particular, Voisin Rational Grazing (VRG) [12,17][12][17] addresses sustainability in all its dimensions: economic, energetic, productive, social, cultural, environmental, and animal welfare, bolstering the pastoral ecosystem. VRG is part of an agricultural system based on ecology, compatible with the integration of livestock and agriculture, through the rotation of pasture and crop areas, the use of cover crops without disturbing the soil and without the use of pesticides. It optimises the use of endogenous resources and minimises external dependence, reducing costs and increasing profitability.

 2. Voisin Rational Grazing and Its Four Principles

VRG can be defined as a rational method for managing the soil–plant–animal complex through direct grazing and well-planned pasture rotation. The system was first described in André Voisin’s book entitled Productivité de l’herbe (1957; [17]). Among other works, he later published Dynamique des herbages (1960; [18]) to complement the concept of pasture management. Voisin’s work was first implemented in South America in 1964 by the agronomist Nilo Ferreira Romero on his farm called Conquista located in Bagé, southern Brazil [12,19,20][12][19][20].
Further, the Brazilian agronomist and professor, Luiz Carlos Pinheiro Machado, coined the term “Pastoreio Racional Voisin” (Voisin Rational Grazing) and introduced advances in the system, such as the concept of bringing water to the animal and not the animal to the water, the need for shade in the paddocks and the concept of dividing the area with square paddocks and internal and external corridors designed to facilitate the flow of animals and prevent soil erosion. Pinheiro Machado left his book Pastoreio Racional Voisin (2004; [12]) as his main legacy. Developed in Brazil in the 1970s and 1980s, VRG spread to other countries in the Americas. The American professor Bill Murphy brought VRG to the USA from Brazil and began to teach and research the method at the University of Vermont, USA. In his work, professor Murphy used the term “MIG” (Management Intensive Grazing; [16]). More recently, in December 2020, the French Academy of Agriculture acknowledged and recognized the work of Andre Marcel Voisin in a Webinar promoted by the Association pour l’étude de l’histoire de l’agriculture (https://www.academie-agriculture.fr/actualites/academie/seance/academie/seance-organisee-par-laeha-andre-voisin-controverses-autour-de; 3 August 2021).
The VRG system follows four “laws” (principles) of rational grazing, as first enunciated by Voisin (1957; [17]) and summarized below:
(I) “First Law”—recovery period principle: Before a sward, sheared with the animal’s teeth, can achieve its maximum productivity, a sufficient interval must have elapsed between two successive shearings to allow the grass (1) to accumulate in its roots the reserves necessary for a vigorous spurt of regrowth and (2) to produce its “blaze of growth” (or highest daily yield per hectare).
Time of recovery period is always variable and should provide an optimum post-grazing period that enables full plant recovery after the following grazing bout. This optimum recovery period (ORP; Figure 1) can be defined as the moment when the acceleration of pasture growth curve is equal to zero; the moment of maximum herbage growth rate [21], which has been related to the regrowth moment when light interception reaches 95% [19]. The ORP coincides with the maximum accumulation rate of protein, energy, and organic matter digestibility in herbage [20,22,23][20][22][23]. On the other hand, after the plant has reached its ORP, it rapidly redirects nutrients and energy to enter into the reproductive stages, followed by the decline of herbage mass growth rate, drop in leaf to stem ratio, and severe reduction of herbage quality [23,24,25][23][24][25]. The ORP can be determined by the plant’s phenological stages, right before it directs its energies towards flowering. For instance, at the paddock level, ORP occurs when (i) plants begin stem elongation, (ii) the flag leaf emerges [26], (iii) boot stages occur, which is common in most grass species, and/or (iv) the first emerged leaves become senescent in grasses or when 30 to 50% of plants are in flowering stage for temperate legumes [12].
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Figure 1. Plant growth curve (adapted from Voisin, [17]).
For the first principle to be achieved, VRG does not follow a pre-established sequential pasture rotation scheme. Instead, it uses each paddock at the moment its ORP has been reached by the targeted pasture species within the paddock or field to be grazed. Species growth is dependent on soil characteristics and environmental conditions, particularly the lack of adequate soil moisture or precipitation [27]. Therefore, ORP for a given species is site-specific and varies along the grazing season [17]. In order to attain ORP for a given species at any moment of the season, it is necessary to determine a set number of paddocks according to the longest ORP of the intended species. The number of paddocks is key to allow for a high degree of control over the timing of occupancy of a grazed area [12,15][12][15]. Most commonly, a paddock is grazed using a mean ORP when most of the desired species have attained their ORP. However, the ORP of a particular species can be targeted to allow it to increase its presence in the paddock [12]. Moreover, targeting the ORP of the most productive and/or best nutritive value plant species may promote ideal conditions to maximise overall annual herbage production and nutritive value [11], in turn hampering the survival of undesirable species or weeds [26,27,28][26][27][28]. Such effects are related to the fact that when the plant is cut at its ORP, there is the best combination of accumulated reserves and the lowest fibre content in the plant tissue [28]. Thus, when cut at this point, it will have a faster and more vigorous regrowth than other plants that have not attained their ORP and will have fewer reserves to promote vigorous regrowth. More mature plants that have passed their ORP will have already redirected some of the accumulated reserves to the flower and seed formation and will be less palatable to animals due to a higher fibre content. As a consequence, the grazed plant will have a higher senescent residue, with greater respiration and lower photosynthetic rate during the regrowth [29], reducing their competitiveness compared with plants cut at their ORP. Pratensis plants, as Voisin (1957) called them, or plants growing in meadows that co-evolved with ruminants, have a high tolerance to grazing. Compared with a 60-day cutting interval, frequent defoliation reduced root and shoot biomass in species with high tolerance to grazing, but not in species with low grazing tolerance [30]. Thus, it is expected that in a multispecies pasture cut at its ORP, this characteristic would favour the presence of high-tolerance grazing species and reduce the participation of non-grazing species.
(II) “Second Law”—occupation principle: The total occupation period on one paddock should be sufficiently short for a grass sheared on the first day (or at the beginning) of occupation not to be cut again by the teeth of these animals before they leave the paddock.
This principle is tightly related to the first law in order to prevent grazing of plant regrowth in a shorter time scale. In this sense and as a rule of thumb, the animals should not stay more than 3 days grazing the same paddock, ideally allocating one or even two paddocks per day [15,31][15][31]. However, this period is site-specific. For example, in tropical areas where herbage growth rates are high, the period to avoid grazing of herbage regrowth should be shorter. On the other hand, in conditions where herbage growth is slow or dormant, as in summer in Mediterranean climates or winter in temperate climates, these periods can be extended [32]. To obtain short occupation times, it is necessary to use high stocking densities, which results in concentrated manure deposits [10], promoting large flows of readily available organic matter to activate soil biocenosis [33] that will provide the required nutrients to ultimately guarantee a fast growth rate of herbage after defoliation and during the growing season [12].
(III) “Third Law”—maximum performance principle: The animals with the greatest nutritional requirements must be helped to harvest the greatest quantity of grass of the best possible quality.
To achieve maximum herd performance, animals of higher nutritional demand should be allowed the herbage of greatest nutritive value. Herbage nutritional value is greatest at the top fraction of the canopy and lowest at the lower fractions [31,32][31][32]. Thus, to follow this rationale one may separate groups of animals by their nutritional requirements. For example, lactating animals (higher nutritional demand) may enter a fresh paddock while non-lactating animals (lower nutritional demand) may enter that same paddock shortly after the lactating herd has left to a new fresh paddock. This management is deemed first and second or leader-follower grazing groups  [34].
(IV) “Fourth Law”—regular performance principle: If a cow is to give regular milk yields she must not stay any longer than three days on the same paddock. Yields will be at their maximum if the cow stays on one paddock for only one day.
Animals should be offered herbage of consistent quality to maximise their performance and avoid unstable productivity. Although ruminant animals are resilient to irregular feed offering, it does decrease overall productivity and promote irregular performance [35]. Thus, in line with the second principle, to achieve the best and most consistent performance, lactating dairy cows, for example, should be moved to a fresh pasture after each milking (e.g., twice a day). Likewise, finishing steers should not stay more than one day grazing the same paddock. Tight grazing regime is essential to promote herbage regrowth of new photosynthetically active tissue with higher leaf to tiller rates. Thus, increased grazing severity maintains high-nutritive value grass [36]. Therefore, to ensure proper tight grazing, following the first grazing group, a category of animals with lower requirements should occupy the paddock for similar length of time [12]. 
The dynamic and complete observance of VRG principles is key to attaining maximum system production efficiency, including positive responses in the quality of food produced [17]. The application of the four principles must be dynamic, dialectic, and constantly evaluated, but without fixed rules, fixed times, or fixed stocking densities. However, this requires good planning. It is a dynamic management process of the soil–plant–animal complex with holistic evaluation throughout the pastoral ecosystems. The key aspect to achieving such management is time. ORP should be assessed regularly since it never has the same length, therefore the sequence of paddocks’ use is not repeated in consecutive grazing seasons. Likewise, occupation time varies with pasture productivity over the season. In the first–second group dynamic, the first group will leave to a fresh paddock when all pasture of the second group´s paddock is consumed. Therefore, the second group defines the moment of paddock change for both groups. These management principles (Table 1) are oriented toward satisfying both herbage and animal requirements [17].
Table 1. The four “laws” (principles) of Voisin Rational Grazing.
Principle (Law) Goal(s) Description/Management
(1) Recovery period Maximum pasture productivity and restoration of reserves Observe the correct ORP 1 in order to allow maximum herbage productivity, high forage quality and reserve storage for the following regrowth. The period of rest of the grass between two successive cuts will be variable according to the plant species, the season of the year, climatic conditions, soil potential, and other environmental factors.
(2) Occupation Avoid cutting early regrowth, promote soil biocenosis and grazing efficiency Observe high stocking densities for a short period of time to prevent grazing of plants in early regrowth and to deposit large amounts of manure. Apart from exceptional situations, occupation time should not exceed 3 days, and ideally, it would be 12 h for dairy or 1 day for beef.
(3) Maximum performance Increase animal productivity Allow animals to graze pastures of nutritive value that match their nutritional needs. Split the herd according to the nutritional needs of the animals into 2 or 3 groups, moving firsts, seconds, and thirds in sequence in all paddocks.
(4) Regular performance Ensure regularity in animal productivity Observe short periods of occupation per group to provide regular pasture allowance according to the animals' needs and constant nutrient intake.
1 OPR: optimum recovery period.
Among different grassland management systems that have been described, we see close similarities between VRG and the adaptive multi-paddock system (AMP; [15]), as well as management-intensive grazing (MIG) or management-intensive rotational grazing (MIRG) [16]. These management methods follow principles very similar to the four previously described for VRG. To read more about how VRG responds to global challenges see the full publication [1].

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