ORIGINAL ARTICLE

Performance of male bovines under intensive grazing of pasture and shrub legumes during dry period in Valle del Cauto, Cuba

Conducta de machos bovinos en pastoreo intensivo de gramíneas y leguminosas arbustivas en época poco lluviosa en el Valle del Cauto, Cuba

J.L. Ledea,^I J. V. Ray,^I Y. Cabrera,^II Y. Nuviola,^I D. G. Benítez,^I

ABSTRACT

The effect of improved pastures, combined and associated with shrub legumes, on the performance of Charolais males and ⅜ Charolais x ⅝ Zebu was studied in a representative area of Valle del Cauto during dry season. A completely randomized design and an intensive rotational grazing system were applied. Two grazing areas were established: 1) association of Megathyrsus + Leucaena and 2) combination of Megathyrsus + Cenchrus. Grazing was conducted during daylight hours, from 7:00 am to 5:00 pm, in paddocks of 0.28 ha with long periods of rotation. An amount of 10 animals were used in each treatment. The results showed that, in the association, the habit of grazing and lying varied according to genotype (P≥0.10). Only the habit of grazing herbaceous plants had significant effect (P ≤ 0.05). In the combination, all the activities showed significant effects for different confidence levels. Crossbred animals tended to spend less time consuming plants (P ≥ 0.10), while the time for resting was significantly superior compared to Charolais (P ≤ 0.05). Shrub component of associations had a compensatory effect on the performance of males in evaluation because there were no significant differences at a confidence level of 95%. The animals of both genotypes concentrated the highest time for grazing in the initial period of the morning and at the end of the afternoon. The applied grazing system maintained the performance pattern of meat-producer males during dry season.

Key words: grasses, intensive grazing, associations, genotypes.

RESUMEN

Se estudió el efecto de pastos mejorados, combinados y asociados con leguminosas arbustivas, en la conducta de machos Charolais y ⅜ Charolais x ⅝ Cebú en una zona representativa del Valle del Cauto durante el período poco lluvioso. Se aplicó un diseño completamente aleatorizado y un sistema basado en el pastoreo rotacional intensivo. Se establecieron dos áreas de pastoreo: 1) asociación de Megathyrsus + Leucaena y 2) combinación de Megathyrsus + Cenchrus. El pastoreo se condujo en horario diurno, desde las 7:00 a.m. a 5:00 p.m., en potreros de 0.28 ha con intervalos prolongados de rotación. Se utilizaron 10 animales en cada tratamiento. Los resultados mostraron que en la asociación el hábito de pastar y echarse  varió según el genotipo (P ≥ 0.10). Solo el hábito de pastar herbáceas tuvo efecto significativo (P ≤ 0.05). En la combinación, todas las actividades mostraron efectos significativos para diferentes niveles de confianza. Los animales cruzados tendieron  a dedicar menos tiempo al consumo de pastos (P ≥ 0.10), mientras que el destinado al descanso fue significativamente superior con respecto a los Charolais (P ≤ 0.05). El componente arbustivo de las asociaciones tuvo un efecto compensatorio en la conducta de los machos en evaluación, al no encontrarse diferencias significativas a un nivel de confianza de 95 %. Los animales de ambos genotipos concentraron el mayor tiempo para el pastoreo en el período inicial de la mañana y al final de la tarde. El sistema de pastoreo aplicado mantuvo el patrón de conducta de machos de carne durante la época poco lluviosa.

Palabras clave: gramíneas, pastoreo intensivo, asociaciones, genotipos.

INTRODUCTION

Valle del Cauto is a plain dominated by the Cauto river basin in the eastern region of Cuba. It covers an area of 4.5 thousands km² (Benitez et al. 2007) and occupies areas from four eastern provinces (Holguín, Las Tunas, Granma and Santiago de Cuba).

Due to the characteristics of this region, the practice of cattle rearing in the Valle del Cauto is one of its main economic source, representing 90% of cattle rearing in the eastern territory (Fajardo 2008), in an area of 167.103 ha. However, the high risk of drought, deterioration of ecosystems and inappropriate agricultural practices cause, in general, a low productive efficiency and that the full productive potential of herds is not expressed, which base their feeding on pasture and forages.

There are several technologies for the diet based on pasture and forage. One of them is the intensive grazing, which requires more advanced feeding techniques and soils with better conditions for cattle rearing use (Ray 2000). Currently, great efforts are destined to increase productivity by increasing animal production (Cabrera 2012). These may include the introduction of silvopastoral systems with high density of tree legumes.

Pastoral systems were designed to increase weight gain and productivity of meat and milk herd, respectively. However, this productivity and increase of liveweight are directly associated with production systems that use pasture as a basic feed on the diet (Mannetje and Haydock 1963).

It is known that animals modify substantially their performance when kept in grazing systems of high density, unlike those raised under extensive conditions (Ray 2000), so changes should expect when management of intensive grazing is combined with high tree densities.

In Latin America, the factors that determine the productivity of cattle grazing have studied (Senra 2005). However, the problems that determine their performance are rarely discussed. It is important to know the processes of selection and intake of diet intended for grazing cattle, because it will help specialists and producers to optimize management and improve productive performance of animals.

 In Cuba, since the 90s, the use of trees for the production of ruminants has been developed and researches have been conducted, focused on improving feeding and animal productivity (Simón 1996, Simón and Francisco 2000). Studies on densities up to 555 plants/ha (Iglesias 2003) in association with Megathyrsus maximum have also been developed. However, there are only few studies carried out with densities superior to 5,000 shrubs per hectare.

MATERIALS AND METHODS

This study was developed during dry season (November-May) in the cattle farm from the Estación Experimental de Pastos y Forrajes of the Instituto de Investigaciones Agropecuarias "Jorge Dimitrov", representative ecosystem of Valle del Cauto, located at 10½ km far from the city of Bayamo, at 20º 18 '13''  N and 76° 39 '48'' West. The climate of this region is classified as relatively humid tropical (Barranco and Díaz 1989) and is the most extense of the plains of Cuba. It is characterized by presenting two well-defined rainy seasons. Annual rains vary from 630 to 1,025 mm, with periods of severe drought in dry season, representing 15.3% of the total per year. The mean annual temperature is 26 °C, maximum of 19.7 °C and minimum of 33 °C, with relative humidity of 77%. Prevailing winds are from East-West and North-Northeast, and reach an average speed of 11 km.h^-1 (Rosell et al. 2003).

Animals, treatments and design. Castrated male bovines from nested Charolais and ⅜ Charolais x ⅝ Zebu genotypes were used, which were considered as the two treatments, distributed in a completely randomized design.

Experimental procedure. A system for growth and fattening was used, based on the intensive grazing in areas of improved grasses, combined and associated with shrub legumes, without the use of concentrated supplement.

The system had two grazing areas, which had a rotational intensive management: a) association of Megathyrsus maximum (Guinea Likoni) + Leucaena leucocephala (Megathyrsus + Leucaena), and b) combination of Megathyrsus maximum (Guinea Likoni) + Cenchrus ciliaris (Megathyrsus + Cenchrus). Ten animals were used in each treatment.

 Grazing was conducted during daytime (10 h), in paddocks of 0.28 ha. Each area had 10 paddocks with permanent access to water during grazing. Grazing intensity was variable depending on the availability of dry matter in each rotation, which determined the time for occupying each paddock.

The system was characterized by including long periods of rest: 70 d in the associations and 80 d in the combination.

Botanic composition was determined at the beginning of dry season composition, by the method of dry weight ranges (Mannetje and Haydock 1963) (Table 1).

The performance of grazing animals was followed by visual observation every 15 min. for 10 h of day grazing for three consecutive days. The time used for grazing (herbaceous and shrubs), walking, lying, standing and drinking, was calculated by the formula described by Petit (1972). These observations were carried out in an area of association and another of combination. The animals grazed from 7:00 am to 5:00 pm. After grazing, they were confined to a pen where king grass forage (Pennisetum purpureum) of low quality (6% CP) was provided, at the rate of 10 kg .animal.d^-1.

Statistical analysis. In order to test data normality, the test of Kolmogorov-Smirnov was applied, and the test of Bartle was used for determining homogeneity of variance. Descriptive statistic was performed to all grass indicators and the analysis of variance was applied to each of the activities of animal performance (grazing, walking, lying, standing and drinking), in which the effect of genotype (two) was controlled in each grazing area. The activity of grazing was characterized, considering effects of genotype and time of the day (three) on each grazing area. For mean comparison, the test of Newman-Keuls (Steel and Torrie 1992) was applied.

RESULTS AND DISCUSSION

There are many interesting results from analysis of variance carried out to the activities of performance of bovine males in an association area and other of combination during day time in dry season (table 3). In the grazing area of the association of Megathyrsus + Leucaena, there was only effect of the genotype (P < 0.05) on the activity of grazing herbaceous plants. Grazing and lying showed a tendency (P < 0.01) to change, according to genotype. In the rest of the activities, the performance of the two genotypes was similar (P < 0.05).

In the grazing area with the combination of Megathyrsus + Cenchrus, the significant effect of genotype influenced on the performance of males, because there were values lower than P < 0.05 in all the observed activities.

These results suggest that shrub component and high availability of dry matter modify, at a certain degree, the performance of grazing males, when systems of associations and combinations of improved and associated grasses are used. This criteria coincide with López et al. (2010), who stated that grasses provide a coarse food and dry matter, while legumes, due to their high content of proteins, may be used as supplement or complement of diet for grazing animals.

Table 4 shows that animals of Charolais genotype had a tendency to spend more time grazing (P < 0.10), a significantly higher time (P < 0.05) for grazing herbaceous plants and a tendency to dedicate less time (P < 0.10) to be lying, regarding those from ⅜ Charolais x ⅝ Zebu genotype. This information indicates that crossed animals obtained the feed in less time, which allowed to dedicate more time to rest.   

In the area of combination of Megathyrsus + Cenchrus, as it is evident in table 4, the performance per genotype had a similar tendency, although with highly significant differences. Charolais animals dedicated significantly more time to grazing (P ≤ 0.001) and less to walking (P ≤ 0.01), to lying (P≤0.05) and to drinking (P ≤ 0.01) than Charolais x Zebu animals.

Table 5 presents mean values of walking, standing and lying for both genotypes in the association area.  

The averages obtained from the activities of each area (table 4 and 5) are similar to the performance pattern of animals under intensive grazing  (Ray et al. 2000). This is different form the other grazing systems due to the low times used for walking, increase of time in resting (lying and standing) and the regulation of the increase of grazing time (grass intake), due to the high availability of dry matter that characterizes these systems. It is significant the time animals used for walking in the area of combination of grasses, where crossed animals completed 0.8 h, and Charolais (P ≤ 0.01) used 0.5 h, which indicates higher time for selection. Pérez et al. (2008) stated similar times for walking in animals grazing in a system of eight paddocks with high availability of dry matter.

After characterizing the habit of grazing in the areas of association and combination during different day times, there was only effect of the period (P ≤ 0.05), without considering the animal genotype, so the performance of both genotypes was similar in each period. Figure 1 shows the habits of grazing shrubs and herbaceous plants in the association of Megathyrsus + Leucaena in the different moments of the day.

The percentage of animals grazing shrubs was similar (P ≥ 0.05) between 7:00 a.m. and 5:00 p.m. (17.4-18.8%). However, animals grazing herbaceous plants were characterized by concentrate their grazing during the times of the lowest temperature (7:00 a.m. -11:00 a.m. and 3:00 p.m. - 5:00 p.m.), so their best meals are carried out at the beginning of the day and at the end of the afternoon. From 11:00 a.m. to 3:00 p.m., time of the maximum heat in Cuba, even though when the association with shrubs of leucaena favors the welfare of animals, the percentage of those grazing herbaceous was reduced (P ≤ 0.05), from more than 70 % in the extreme periods up to 50.8 % in this intermediate stage.

In the combination of grasses (figure 2), grazing habits had a similar tendency to that shown in the area of association. Values ranged between 83.2 and 85.3% in the extreme periods, versus 67.5 % of animals grazing in the intermediate (noon). This performance could be caused by high temperatures present during these times that provoke an endocrine unbalance in animals. They, before the effect of caloric stress, show a adrenocortical response, with a marked increase of cortisol levels that increase rectal temperature and respiratory frequency (López et al. 2010). Besides, digestive processes produce metabolic heat that should be balanced by the animal with their environment in order to achieve a comfort zone. On the contrary, it will be necessary to carry out considerable physiological adjustments (Simón et al. 2010), stopping or reducing food intake as compensatory mechanisms on heat production during the times of heat stress, as it is evident in the associations and combination.

This performance of animals during grazing coincides with reports of Ray et al. (2000) in dairy cows under intensive grazing. In addition, it is similar to the statements about animals concentrated in two large grazing, one at the sunrise and the other at the sunset.

In general, the performance of males coincides with the statements for meat-producer animals under grazing conditions with concentrated supplementation (Benítez et al. 1993), demonstrating the potential of areas with improved, combined and associated grasses, with high density of shrub legumes, to maintain an appropriate performance pattern of growth-fattening animals, due to the high availability that favors selection and nutritional quality.

It is concluded that the system of intensive grazing of improved, combined and associated grasses, and high density of shrub legumes and prolonged periods of rest by the animals during the dry season, maintains the performance pattern of Charolais and Charolais x Zebu males. The superior shrub component within the associations corrects for differences in the times dedicated to grazing and resting by the genotypes.

Thanks to José Cruz Tejeda, engineer in Agronomy, for the support provided during all the evaluation and data collection period.

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Received: 3/7/2015
Accepted: 18/7/2016

J.L. Ledea, Instituto de Investigaciones Agropecuarias “Jorge Dimitrov”, Carretera de Manzanillo, km. 16½. Apartado Postal 2140. Bayamo, Granma, Cuba. Email: ledea@dimitrov.cu