Silvopastoral systems, an alternative for rearing young cattle under low-input conditions


Jesús Manuel Iglesias Gómez
Estación Experimental de Pastos y Forrajes Indio Hatuey Central España Republicana 44280, Matanzas, Cuba

 

ABSTRACT
The main results obtained in studies about silvopastoral production systems of low external inputs, with male and female growing cattle.
The soil on which the research was conducted was of plain topography, classified as lixiviated Ferralitic Red and belonging to the Pastures and Forages Research Station “Indio Hatuey”, Matanzas province, Cuba. The research work was divided into four experiments and a stage of validation of results: A) Fattening of commercial Zebu bulls in a Protein Bank System and/or Association System in 100 % of the area, compared with a control of fertilized grasses; B) Rearing of crossbred replacement yearling heifers (5/8 Holstein x 3/8 Zebu) in Protein Bank and/or Associated System; C) Fattening of bulls of different racial genotypes (Zebu, F1 Holstein x Zebu and 5/8 Holstein x 3/8 Zebu) in Associated System; D) Rearing of females of different racial genotypes (5/8 Holstein x 3/8 Zebu and F1 Holstein x Zebu) in Associated System; and E) Validation of this last system under commercial production conditions with 5/8 Holstein x 3/8 Zebu heifers. The animals were not supplemented in any of the studied systems and only nitrogen fertilization was applied, at a rate of 80 kg N/ha/year, in the traditional system without trees and in 75 % of the area of the Protein Bank systems. The basis pasture of the systems was Panicum maximum, although the natural pastures of the region and other cultivated varieties were maintained. The tree used was the legume Leucaena leucocephala cv. Cunningham, with a population of 555 plants/ha in the Association system and 1 250 in the Protein Bank. The exploitation always started when they reached 2 m of height as average. In all the cases, for the statistical analysis completely randomized designs were used, with simple classification variance analysis, while the means were compared according to Duncan (1955).
The Association system in 100 % of the area produced accumulated individual gains higher than 620 g per day in the Zebu bulls and more than 490 g in the dairy genotypes, with final weights over 400 kg in the former, and between 376 and 357 kg for genotypes F1 and 5/8 x 3/8 Zebu, respectively. The other evaluated systems also obtained satisfactory individual gains (more than 530 g/animal/day), although in them external inputs were used, as fertilizers in the grass areas.
In the case of replacement heifers, the accumulated daily gains of the animals that grazed the Association (524 g for F1 and 493-441 g for the 5/8 Holstein x 3/8 Zebu cows), were satisfactory for this type of system of low external inputs, as well as the weights of incorporation to reproduction which varied between 280 and 310 kg. The gains of the Protein Bank system were also close to 455 g/animal/day, with an incorporation weight higher than 290 kg. The age of incorporation to reproduction was high in all the studied systems, caused by the low weight/age shown by the experimental animals before the beginning of the studies.
In all the trials a high biomass production was observed, with yields in the dry season that fluctuated between 7,37 and 14,58 kg DM/100 kg LW/day.
The daily offer of leucaena in the studied Silvopastoral Systems was very variable, depending on the size and weight of the animals and the management to which the trees were subject (browsing or pruning). Thus, values were found between 0,115 and 2,40 kg DM/100 kg LW/day in the dry season and 0,284-2,50 kg for the rainy season. The protein quality of the offered biomass was high, with crude protein contents in leucaena and the companion pastures of more than 20 and 9 %, respectively.
It is concluded that the fattening of bulls and the rearing of replacement heifers with the use of low-input Silvopastoral Systems are feasible, because no weight losses occur during the year and average gains were obtained between 400 and 600 g/animal/day. Their use under production conditions is recommended.