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RESEARCH WORK

Dairy performance of Holstein x Zebu genotypes under silvopastoral system conditions

L. Simón y O. López

Estación Experimental de Pastos y Forrajes "Indio Hatuey". Central España Republicana, CP 44280, Matanzas, Cuba.

ABSTRACT

With the objective of evaluating the bioproductive and economic potential of herds from different double purpose racial genotypes (Holstein x Zebu) in associations of legume trees with grasses, three dairy units were selected with 80 cows each, including the genotypes Mambí (3/4 H x ¼ Z), Siboney (5/8 H x 3/8 Z) and F1 (1/2 H x ½ Z), respectively. Dry matter availability of the pastures and intake of complementary feedstuffs were determined, as well as the productive indicators of the herds and the incomes. No remarkable differences were found among herds regarding DM availability and contribution of pasture to the diet. Values of whole milk production of 7,2; 6,8 and 6,7 and corrected milk values of 9,1; 9,3 and 9,8 kg/cow/day were obtained for the breeds Mambí, Siboney and F1, respectively. Milk sale prices were higher than 90 cents in the three herds, with profits higher than 10 000 pesos. It is concluded that there were no noticeable differences, in terms of milk production, among genotypes; the economic differences in favor of genotype F1 are given by its rusticity and adaptation to the grazing environment. On the other hand, the productive sustainability of the rational silvopastoral system technology during 10 years of exploitation was proven.

Key words: Milk production, silvopastoral systems

INTRODUCTION

Cattle production was based, for many years, on the use of high inputs (concentrates, fertilizers, machinery and fuel) and on the use of animals with high dairy potential, but adapted to tropical conditions; in addition, there was a solid feeding basis.

Currently, cattle production enterprises face the challenge to provide the market with the dairy and meat products that are so necessary for the population and which production has decreased.

In this context, the renewal and recovery of pasturelands, together with the strategic reincorporation of trees and shrubs in grazing areas, appear as a technological alternative that contributes to improve the production of the livestock sector and decrease the impact of cattle production on the ecosystems on which it is developed.

On the other hand, the bioclimatic conditions of the tropic impose on animal production systems limitations which effect should be reduced, partially, with the use of animals that show tolerance to them and a good productive potential (Osorio, 2001). In this sense, double purpose production systems have been affected due to their poor productive efficiency (Galina et al., 2001).

López and Mejía (1994) claim that the applied management is not feasible at commercial scale under tropical conditions, and that crossbred genotypes do not show a better performance in growth traits due to environmental limitations and not genetic ones.

For such reason, the objective of this work was to evaluate the bioproductive and economic potential of herds from different double-purpose racial genotypes (Holstein x Zebu) in associations of tree legumes with grasses.

MATERIALS AND METHODS

Three dairy herds that applied successfully the rational silvopastoral system technology described by Simón (1999) were selected, after making a general diagnosis of the units, in which the degree of similarity regarding the utilization of areas, soil characteristics, floristic composition of the pasturelands, integral
management and the complementation and supplementation of the available feedstuffs could be proven. The management and feeding were adjusted to be similar in the three herds during the experimental period.

The silvopastoral systems had been planted for nine years and were evaluated from the eighth to the tenth year of exploitation with the objective of learning their technical and productive possibilities.

Animals. The herds were composed by 80 cows each, from the double-purpose racial genotypes Mambí, Siboney and F1, which contain different proportions of Holstein x Zebu blood: Mambí ¾ H x ¼ Z, Siboney 5/8 H x 3/8 Z and F1 ½ H x ½ Z. The stocking rate used was 1,6 animals/ha.

Soil. The soil is classified as Brown with Carbonates and, according to the National Agrochemical Service of Cuba, does not show limitations in its fertility for plant growth.

Floristic composition of the pastureland. It was determined by the method of steps (Anon, 1980). The prevailing cultivated pastures were Panicum maximum cv. Común and Cynodon nlemfuensis (star grass), with more than 60%; the rest was constituted by natural pastures, mostly by Paspalum notatum (tejana or alpargata) without remarkable differences among the units; Leucaena leucocephala showed a density of around 1 000 plants/ha.

Measurements. Pasture samplings to determine dry matter availability and nutrients were monthly conducted, according to Martínez et al. (1990); likewise, feed (pastures, sugarcane and North gold) samples were taken and sent to the laboratory for determining DM, CP, CF, Ca and P, according to the techniques proposed by the AOAC (1995), to find their contribution in the daily rations of the animals, in the dry season (December to May) and the rainy season (June to November).

The milk production indicators were determined by the records existing in the units, in which two to three controls of production and lactation duration were monthly performed. The body condition of the animals was estimated monthly (Álvarez, 1997). The economic data were calculated using the program Microsoft Excel Office of 2003.

In milk production and the economic indicators a simple variance analysis was applied by means of the statistical pack SPSS, version 10.0 for Windows XP®. Duncan's multiple range comparison test was used to determine differences among means.

RESULTS AND DISCUSSION

In general, no remarkable differences were found among the systems regarding dry matter availability and the contribution made by pasture to the diet (table 1).

Although DM availability behaved similarly among herds, differences were found between seasons, because production in the rainy season exceeded in approximately 25% that of the dry season, which is in agreement with previous results (Simón et al., 2000) in which the contribution of silvopastoral systems in the increase of biomass production during the dry season is reported; with that the difference in production between both seasons could be reduced and seasonal balance was improved, which was shown in the daily contribution of DM, CP and CF per cow. Similar performance was found when analyzing an association of P. maximum and L. leucocephala for milk production (Sánchez, 2007).

The contribution of calcium in the daily ration of the animals stood out as contribution of the silvopastoral system, while phosphorus turned out to be insufficient to achieve an adequate calcium:phosphorus relationship, which was compensated with the supply of 20 kg of sugarcane forage per milking cow (daily) during the dry season and the supplementation with residue from corn distillery (north gold) from the second kilogram of milk throughout the year; this guaranteed acceptable production in moderate production animals, in a system with neither irrigation nor fertilization.

Table 2 shows the daily production of whole milk and 3%-fat corrected milk, of the herds formed by the different Holstein x Zebu racial genotypes.

Whole milk was significantly higher in the Mambí herd in both seasons, but it had lower values of 3%-fat corrected milk, favoring the genotype F1 due to a higher content of milk fat, which values were 3,8; 4,1 and 4,4% for Mambí, Siboney and F1, respectively.

The absence of significant differences in milk production among herds which was in correspondence with DM availability and the contribution of nutrients to the system, proving that the grazing conditions were similar for the three herds and this was confirmed with the body condition (BC) of the cows, which was around 3 (of a scale from 1 to 5) an it is considered acceptable for dairy cows. Similar BC values were obtained by López et al. (2003) in Holstein x Zebu cows, in an association of improved grasses and leucaena under commercial conditions.

The values of this indicator were related to the feed availability during the evaluation stage, which together with the pasture contribution favored milk production and allowed to maintain a stable body condition.

Berry et al. (2003) and López and Álvarez (2005) claimed that BC constitutes an accurate indicator of the available energy reserves for the animal to face any productive process. It is a demonstration of the nutritional level to which it is exposed in a given time period.

Table 3 shows, briefly, the milk production per lactation, annual production and milk production per area in the triennium 2004-2006. As can be observed, there were no differences among the racial genotypes for any of the analyzed indicators.

The milk production per lactation, per year and per area were similar to the productions of the first years of exploitation of these herds with the same technology, when they averaged 3 147 kg/ha/year (Simón et al., 1997); with this the rational silvopastoral system proved that its productive sustainability still remained after 10 years of exploitation.

The percentage of milking cows in the triennium was 65,6; 64,7 and 67,5% for Mambí, Siboney and F1, respectively, with high similarity in the three units.

The quantity of milking cows, as percentage of the total cows present in the unit, constitutes an indicator of the satisfactory reproductive status of these herds, which influences favorably total milk production.

Menéndez et al. (2004), when quantifying the effect of the percentage of milking cows on total milk production of the herd in 19 dairy units, through mixed lineal models, found that for every 1% increase in such percentage, there was an increase of 138,3; 2,16 and 4,54 kg for total monthly milk production, total monthly milk production per hectare and total daily milk production, respectively. This proves the importance of the percentage of milking cows in the productive performance of the herd, because the decrease in this indicator leads to the reduction of total production and production per hectare.

The economic results, according to the income balance for milk sale, are shown in table 4. The milk production of the genotypes Mambí and Siboney was slightly higher, just like total incomes; however, the profits obtained by genotype F1 were higher in more than 40% due to a higher sale price according to milk quality and the lower costs per peso produced and per kilogram of milk.

Other indicators had influence too, such as the losses for death and sanitary slaughter, expenses for drugs and services of artificial insemination, which were lower in the herd of the genotype F1, due to the higher rusticity and adaptation of these animals to the environmental conditions of the tropic, because they contain a higher proportion of Zebu genes.

The values of total incomes in the experimental stage were higher than the one found by Cruz (2002) in a commercial dairy unit of 87 ha (52 172,32 pesos), where neither irrigation nor fertilization was applied and the prevailing species were natural pastures and 26% C. nlemfuensis.

According to the results, no noticeable differences were concluded to be found among the three genotypes, in terms of milk production; the economic differences in favor of genotype F1 are given for its rusticity and adaptation to the grazing environment, which make it less demanding regarding its nutritional requirements and attention to maintain health.

On the other hand, the results proved the productive sustainability of the rational silvopastoral system technology during 10 years of exploitation.