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The Charolaise breed shows excellent qualities, among which stand out its adaptation to different environments, good feed conversion even in grasses with low nutritional value, its recognized maternal ability and achieving weight gains higher than 650g.animal.day-1 (González 2016).
This breed is used in Empresa de Genética y Cría "Manuel Fajardo" and its weight gain is 200 g.animal.day-1 and the incorporation age to reproduction is above 30 months, unfavorable productive indicators, determined due to the productive system where imbalances were found in the DM availability, as well as deficient water supply, among other aspects (Vega et al. 2016).
The above determined the need to change the management and feeding system of this breed, introduce new technologies for the use of grasses that take into account trees and legumes (Vega et al. 2019) and promote better productive indicators evaluated through multivariate statistical analysis. (Torres et al. 2008).
The objective of this study was to study the grass-legume silvopastoral system compared with the grass monoculture in the productive indicators of the replacement female Charolaise, using the impact index methodology.
Materials and Methods
The experiment was developed for three years at “San José del Retiro” farm belonging to Empresa de Genética y Cría “Manuel Fajardo”, Granma province, Cuba, located at 115 m o.s.l. with slightly flat relief. Table 1 shows the chemical composition of the soil with neutral pH and the rest of the indicators evidenced the presence of a soil of medium to low fertility, classified as brown with carbonates according to Hernández et al. (1999).
Table 1 Chemical characterization of the soil
| Indicator | Mean |
|---|---|
| pH | 7.00 |
| OM (%) | 6.70 |
| P2O5 (mg. 100 g-1) | 0.36 |
| K2O (mg. 100 g-1) | 65.6 |
The performance of the climatic variables was: annual mean temperature of 25.4 °C, with mean of 23.9 °C and 26.8 °C in the dry and rainy season, respectively, annual mean precipitation of 939 mm and relative humidity of 81.7 %. These values are within the historical range of the region.
In a total area of 26.40 ha, 12 ha were distributed for each treatment in 24 paddocks of similar size and two treatments were established: silvopastoral system of Leucaena leucocephala-Cynodon nlemfuensis and monoculture of Cynodon nlemfuensis, 2.4 ha were destined for pens where the animals remained during the night and for the access ways to the paddocks.
For the establishment of silvopastoral system, the botanical composition of the area in which the species were: 25 % Star grass (C. nlemfuensis), 25 % Romerillo (Bidens alba Lin.), 3 % Guinea grass (Megagthrysus maximus) and the rest was without pastures. Later, the soil was prepared in a conventional way by plowing, two harrow passes and furrowing with oxen, the furrows spaced 5m apart. Leucaena was sown at a distance of 3 m between plants with seed with 85 % germination and an average density of 500 plants ha-1 was achieved. During the establishment, weeds were manually removed and Leucaena was considered to be established when it reached 2 m in height at 15 months.
The monoculture (C. nlemfuensis) was sown by plowing method and it was considered established after 100 days of sowing with a botanical composition higher than 98 % of the grass.
During the experimental period, the Leucaena was pruned due to the height reached (2.6m) and it coincided with the entry of the animals in cycle II. In addition, the presence of Clitoria ternatea was observed in 2%.
A total of 30 Cuban Charolaise heifers were used, 15 per treatment, repeated in two productive cycles (I and II) for a total of 60 animals. They were grouped into homogeneous lots according to weight (168 kg in cycle I and 155 kg in cycle II) and 8 months of age, they were dewormed before the experimental period with 1mL Levamisol per 100 kg of live weight. They had free access to the mineral salt composed of dicalcium phosphate, 50 %; common salt, 40 %; MT3, 10 % (corn, 19 %; iron oxide, 27.50 %; manganese sulfate, 23 %; copper oxide, 10 %; zinc oxide, 20 %; sodium selenite, 0.02 % and cobalt sulfate, 0.10 %). The animals grazed 14 hours a day and were in the pens overnight with water, but without food. A stocking rate of 1.1 animals.ha-1 was used. The resting times were 77 and 110 days per paddock in the rainy and dry season, respectively within the silvopastoral system, with an occupation time of 3 days and in monoculture it depended on the grass availability where in dry season it only allowed 6 hours daily.
The following indicators were quantified: live weight of all fasting animals every 28 days using a 500 kg balance, calculation of the mean daily weight gain (MDG) between weighing and the accumulated gain of the period by initial and final weight difference of each cycle according to Preston and Willis (1970) and Menéndez (1984).
Grass availability was estimated according to Martínez et al. (1990) by taking 80 samples per replication at the beginning of each rotation and in parallel with the availability samplings, but with a bimonthly frequency, grass samples were taken at 10 cm above soil level (300 g) simulating with the hand the selection made by the grazing animal.
The availability of L. leucocephala cv. Peru was quantified in 10 random trees in each replication, simulating the browsing carried out by the animals in the tender parts of the plants, leaves and stems up to approximately 2 mm in diameter (Lamela 1998).
The statistical analysis was performed using the Impact Index measurement methodology developed by Torres et al. (2008). In the selection of the Principal Components, it was taken into account that the eigenvalue was higher than unity; it was assumed that the variables had a preponderance factor higher than 0.60 and, according to the characteristics of each component, they were assigned a denomination (Torres et al. 2007).
For the economic analysis of the rearing of developing cattle (females), a herd of 120 animals was taken as a scale, simulating a productive herd, with a stocking rate of 1.1 animal.ha-1 and it was started from primary data detailed in two cycles with Cuban Charolaise cattle evaluating the two productive alternatives. The financial analysis included the calculation of the gross margin.ha-1 (net income. ha-1- direct costs.ha-1) with a view to evaluating the feasibility of each of the technologies and the economic profitability (gross margin.ha-1/ net income.ha-1) for each of the treatments according to Gargano et al. (1997) methodology. The equilibrium point was also estimated to determine both the volume to be produced (kg) and the number of animals to be reared, equaling the level of gains in production (neither losses nor gains) according to Reyes (2006).
Results
Four main components were obtained with eigenvalues higher than the unit and explain 82.22 % of the variability (table 2).
Table 2 Components, eigenvalues, and partial and cumulative variance
| Components | Eigen values | Variance (%) | |
|---|---|---|---|
| Partial | Cumulative | ||
| 1 | 3.05 | 33.83 | 33.83 |
| 2 | 1.68 | 18.72 | 52.56 |
| 3 | 1.42 | 15.81 | 68.37 |
| 4 | 1.25 | 13.86 | 82.22 |
The studied variables (table 3) were distributed in four main components. The weight, gain per animal and MDG were located in MC 1; in MC 2 are the availability and the incorporation age; temperature and rainfall are in MC 3, and the starting age in MC 4. All these variables with a preponderance index higher than 0.60.
Table 3 Matrix of preponderance factors in the main components
| Variables | Preponderance factors | |||
|---|---|---|---|---|
|
|
|
|
|
|
| Weight, kg | 0.67 | -0.13 | -0.39 | -0.06 |
| Gain, kg. animal-1 | 0.93 | 0.28 | 0.02 | -0.02 |
| Gain, kg. animal. day-1 | 0.92 | 0.28 | 0.01 | -0.02 |
| Availability, kg | 0.17 | 0.95 | 0.03 | 0.15 |
| Starting age, months | 0.01 | -0.17 | 0.24 | 0.89 |
| Incorporation age, months | -0.20 | -0.92 | 0.07 | 0.22 |
| Rainfalls, mm | -0.03 | 0.00 | 0.71 | -0.06 |
| Temperature, ºC | -0.17 | -0.02 | 0.89 | 0.22 |
| Evaporation, mm | 0.13 | -0.28 | 0.51 | -0.64 |
Taking into account the previous results, a cluster analysis was carried out that allows forming similar groups of animals through hierarchical clusters, using the inter-group link method and the Eucliadian distance interval squared measure. Three groups were obtained, made up of animals in silvopastoral system (1), in monoculture (3) and those that lost weight (2). Figure 1 shows the cluster analysis where these groups were formed.
Group 1 was the one with the best performance in weight gain, availability and incorporation age to reproduction (table 4). The analysis did not show relevance for the variable climate evaporation.
Table 4 Groups formed from the cluster analysis between the variables and the different technologies
| Group 1 | SD | Group 2 | SD | Group 3 | SD | |
|---|---|---|---|---|---|---|
| Mean | Mean | Mean | ||||
| Weight | 228.61 | 48.46 | 166.90 | 1.98 | 234.07 | 47.73 |
| Gain, kg.ani-1 | 16.72 | 5.24 | -21.25 | 9.12 | 9.22 | 2.99 |
| Gain, kg.ani.day-1 | 0.55 | 0.18 | -0.71 | 0.26 | 0.31 | 0.10 |
| Availability , kg | 119.10 | 2.47 | 98.95 | 26.23 | 92.92 | 12.00 |
| Starting age, m | 8.47 | 0.92 | 9.00 | 0.00 | 7.84 | 1.00 |
| Incorporation age, m | 19.93 | 1.83 | 24.50 | 4.95 | 25.58 | 3.62 |
| Rainfall, mm | 103.35 | 87.63 | 111.95 | 33.59 | 87.74 | 72.21 |
| Temperature, ºC | 25.85 | 1.51 | 26.35 | 1.20 | 24.80 | 1.78 |
| Evaporation , mm | 182.13 | 42.51 | 157.50 | 12.02 | 197.14 | 43.21 |
m: months
ani: animal
Stocking rates of 1.1 animals.ha-1 were managed and mineral salt was offered ad libitum for both technologies (silvopastoral system and monoculture), where silvopastoral system exceeded 500 g. animal-1 MDG of LW. However, at the beginning of the productive cycle I, due to temporary water stress, only 69 g.animal-1 of MDG was reached. Nevertheless, the Cynodon monoculture did not exceed 350 g.animal-1 of MDG.
The incorporation of the animals to reproduction was with weights higher than 300 kg of LW and ages between 19 - 17 months, with stays in the silvopastoral system of 273 and 366 days, reaching a total MDG of 416 and 567 g.animal- 1 in each productive cycle, which was not possible to achieve in those that grazed in Cynodon which were between 25 and 28 months, with longer days of permanence (578 and 548) and total MDG lower than 241 and 278 g.animal-1 in each productive cycle.
The starting age did not show marked variation (figure 2) but the lowest weight was for group three (monoculture). However, the lowest incorporation age was obtained in group 1 consisting of the silvopastoral system.
When determining the starting age impact index, the silvopastoral system showed positive impact (higher than zero) compared to the star grass monoculture during the experimental period (figure 3).
Figure 4 shows the impact of food and the incorporation age to reproduction, performance above zero only with silvopastoral technology, in the monoculture only the October month occupied a value of 0.09, the rest with negative values, similar was the performance at the incorporation age to reproduction of both treatments.
The most represented variables for animal impact were the gains kg.animal.month-1, kg.animal.day-1 and weight, with values of 0.93, 0.92 and 0.67, respectively it only reached values below zero with the introduction of the silvopastoral system in the system (figure 5) in the months of April to July, value which coincided with the lack of water in cycle I (silvopastoral system and monoculture), highlighting that for the rainy season and the beginning of the dry season in both cycles of the introduction of silvopastoral technology they were higher than those obtained with monoculture.
A similar situation occurred in the monoculture with the weight and gains, specifying that they were not higher than those of the silvopastoral cycles, that is, 8 of cycle I were below zero, the remaining between 0 and 1, the highest values in both cycles were in silvopastoral system, which was consistent with the food availability.
The analysis of financial indicators in the case of silvopastoral technology shows that: the gross margin exceeds by 210.70 and 150.33 Cuban pesos in cycles I and II, respectively, than those obtained in monoculture; net income increases.ha-1; direct costs decrease and the equilibrium point is reached with fewer animals (table 5).
Table 5 Financial indicators (Cuban pesos) in developing female rearing systems
| Indicators | Silvopastoral system | Monoculture | ||
|---|---|---|---|---|
| Cycle I | Cycle II | Cycle I | Cycle II | |
| Direct costs. ha-1 | 814.61 | 710.12 | 903.37 | 840.92 |
| Net incomes. ha-1 | 2179.51 | 2077.00 | 2057.57 | 2057.57 |
| Gross margin. ha-1 | 1364.90 | 1366.88 | 1154.20 | 1216.55 |
| Profitability, % | 62.00 | 66.00 | 56.00 | 59.00 |
| Equilibrium point, animals | 47.00 | 43.00 | 58.00 | 54.00 |
| Equilibrium point, kg | 15492.00 | 13298.00 | 17866.50 | 16574.90 |
Discussion
Regarding the results found between the technologies, table 1 shows the main components, as well as the particular and accumulated variance of each one of them. A total of nine variables distributed in four main components were studied, whose eigenvalues were higher than the unit. These four components explain 82.2 % of the variability of the systems.
Of the nine studied variables (table 3), six are related to the animals and three of them are located in the first component (weight, weight gain and mean daily gain). This is an indicator of the preponderant influence of the animal in the conditions where the studies were conducted. This first component, called “animal factor”, explained 33.3 % of variability.
The three variables mentioned above show the urgent need to pay attention to animal behavior, related to the need to meet their nutritional requirements (Preston and Willis 1970) and to avoid stress due to environmental or management factors (Enríquez and Álvarez 2020).
The second component, “food-age”, showed the inverse relation between food and the incorporation age to reproduction of the animals. This explained 18.72 % of variability.
In the third component, “climate”, rainfall and temperature highlighted as the most preponderance in a direct relation that is easy to explain, since as higher rainfall the food availability increased ( Herrera 2020) and with it the gains, weight and decreased the incorporation age to reproduction of the animals. On the other hand, Ramírez et al. (2018) showed that the elements of the climate play an important role in biomass production, while Enríquez and Álvarez (2020) when studying the temperature-humidity index (THI) showed the role that humidity plays in animal behavior.
The fourth component, “starting age”, showed only the starting age that explained 13.86 % of the variability linked to the growth processes of the animals, which, in turn, are determined by the performance of the variables that make up the components previous described.
The fact that in the cycles the variables related to animal production, food, climate and starting age have high factorial loads, is an important element in measuring the impact, because the factor loads are the correlations between each variable and the main component. Therefore, they show the degree of correspondence between them, making a variable with a higher load representative of the main component. It was showed that most of the variables contribute to the explanation of the variability of the cycles of the studied animals and that the Varimax rotation achieved simpler factorial solutions and eliminated some of the ambiguities that enclose the initially rotated factorial solutions.
The application of this model allows, through the matrix of rotated components, according to Varimax method, to identify the variables that contribute the most to the variability of the system in each cycle and show the changes that occur in the different treatments.
These variables are important because they inform about aspects of capital importance in the adoption of technologies, such as silvopastoral systems, a strategy to achieve that replacement females are incorporated into reproduction with more than 300 kg of live weight and age between 15 and 20 months, as occurred in this research.
The groups in the cluster analysis (figure 1) were three: animals in sylvopastoral system (1), those that lost weight due to lack of water (2) and those that represented monoculture grazing (3). Group 1 was the one with the best performance in weight gain and incorporation age to reproduction, since the food availability (29.8 kg DM.animal-1) was higher due to the introduction of the tree legume and as a consequence decreased the incorporation age in this group to 19.93 months, obtaining the highest gains with 0.55 kg.animal.day-1 (table 4). The literature that reports on this is extensive, but the greatest importance lies in the results obtained in this research correspond to a climatic zone with high temperatures, low rainfalls and soils with several limiting factors. In addition, another favorable element was the lower number of plants of the tree used in the system (Leucaena-star grass) compared to other silvopastoral systems (Lok et al. 2013).
The analysis carried out with the groups that originated in the cluster study shows that group 2, represented by the animals that lost weight due to the lack of drinking water, were the ones with the lowest weight, even when the biomass availability was 24.7 kg. DM and in group 3 corresponding to the monoculture, the weight gain was only 0.31 kg.animal.day1. This shows that, despite the value of availability, the presence of water is essential for animal intake, an aspect previously mentioned by Vega et al. (2015).
It is known that animals are more sensitive to lack of water than food. The first sign of the effect of moderate water restriction is the food intake reduction. As a consequence of a more severe restriction of water intake, weight loss is rapid as the body becomes dehydrated and of course there are no weight gains (Galeno 2005), as occurred in this research with Charolaise cattle. The dehydration associated with a loss of 10 % of body water content is considered severe and a 20 % loss results in death, while animals are able to live even after a loss of 40 % of their body weight due to hunger (García-Trejo 2011).
When comparing the starting age, it did not reveal a marked variation with the incorporation age to reproduction (figure 2), but group 1 represented by the silvopastoral system with the highest weight of the animals according to the daily gain, reached the younger initiation age to reproductive life (19 months). Conversely, in group 3 with the lowest weight and gains, the incorporation age to reproduction was 25 months (six months more), which could be explained by the development and growth of the animals caused by the nutritional improvement of the diet provided by the silvopastoral system. In addition, the beneficial effect and the environmental improvement that Leucaena produces in the silvopastoral system by lowering the temperature, providing greater ventilation and providing shade for the animals is unquestionable.
When applying the impact index in the starting age it was similar to those previously described, because only in the silvopastoral system was positive impact achieved with values higher than zero, not being the case in the animals that grazed in the star grass monoculture. According to the impact index, in both systems it was found that the starting age coincides with the weaning of Charolaise females (figure 3).
This methodology confirmed that when the animals are weaned at approximately nine months, they reach positive values in both treatments, showing the impact of this stage on the animals (figure 3). Although the introduction of silvopastoral system was decisive in the incorporation age, gain and weight, since it showed that by covering the nutritional requirements of the animals, better productive indicators can be achieved according to the animals age (Benítez et al. 2009).
At present, the incorporation age to reproduction requires special attention, since the necessary resources are not available for the correct animals feeding due to the lack of improved grasses of higher nutritional value than natural species and the limitations for acquisition of imported concentrated foods able of substituting to some extent breast milk. Therefore, the introduction of legumes could be an economically viable and environmentally friendly alternative to solve this problem.
The benefits of legumes trees caused the weight gains of the animals to increase in favor of silvopastoral system in both cycles with higher productive indicators, which corresponds to the growth and development reached by the animals (figure 5). However, it is necessary to consider the influence of temperature, since it is probably that it had a negative influence on the voluntary intake of animals where the trees were not found, due to the high temperatures to which they were exposed due to the lack of shade that does not occur in the silvopastoral system (Vega 2012).
According to Matías and Parreño (2011), the main objectives of efficient replacement animal rearing are: to achieve satisfactory growth and development and good health at the lowest possible cost. A similar result was obtained in this study with the introduction of silvopastoral system.
In group 3 (Cynodon monoculture) the mean daily weight gains did not exceed 350 g. animal-1 in both productive cycles (I and II), which reiterates the need that for the replacement female Charolaise it is necessary to use feeding systems that cover their nutritional requirements, which was not possible in the monoculture system and was possible when legumes trees were used.
In this research, it was achieved in the silvopastoral system to incorporate the animals to reproduction with average weights higher than 300 kg, average ages of 21 and 17 months, in times of 273 and 366 days of duration in the system and a total MDG of 416 and 567 g. animal-1 in each productive cycle. Result that was more relevant if it is taken into account that concentrated food, irrigation or fertilizers were not used. However, the animals that only grazed in Cynodon the incorporation age was 25 and 28 months, at 578 and 548 days, with a lower total MDG of 241 and 278 g. animal-1 in each productive cycle.
The animals can enter the system between seven and nine months of age and weights between 155 to 170 kg, they are able to incorporate into the reproduction with 17 months of age and more than 300 kg of LW, performance reported for the first time in Cuba for the replacement female Charolaise with feeding based on grasses and tree legumes that make up a silvopastoral system. This reaffirms what was stated by Aubriot et al. (2012) on the need to use foods of high nutritional value.
The gross margin in the case of silvopastoral technology exceeds 210.70 and 150.33 Cuban pesos in cycles I and II, respectively, than those obtained in the Cynodon monoculture (table 5). In addition, the increase in net income .ha-1 must be highlighted because it was possible to reduce the cycle of incorporation to reproduction from 25 to 19 months, which corresponds to the increase in the gains and weight of the animals, and represents a decrease in the cost of 146.66 and 206.83 Cuban pesos per animal in each month that the incorporation for cycles I and II is decreased, respectively in favor of the silvopastoral system.
To achieve economic balance in monoculture production, more than 56 animals and 17220.70 kg are necessary, while in silvopastoral system only 45 animals and 16679.25 kg are required. However, it is important to point out the positive balance that is achieved in animal production when the minimum necessary inputs are ensured, the adequate food base, the favorable changes that occur in the soil and in the environment (Vega et al. 2014), the increase in production and productivity, and the reduction of the time of incorporation to reproduction of the female.
The analysis of the information of this research by means of the measurement methodology of the impact index defined with clarity, accuracy and scientific rigor the elements that most influence to reach replacement females with higher weight and lower incorporation age, aspects that were not previous dealed in the national scientific literature and especially for the eastern region of the country.
Conclusions
It is concluded that the mathematical methods used (impact index measurement) were adequate to establish the superiority of the silvopastoral system compared to the grass monoculture when obtaining higher weight, lower incorporation age and satisfactory economic balance of the Charolaise female. In addition, it is recommended to develop this system with other cattle breeds in commercial production units and under other environmental conditions.
