RESEARCH WORK

Evaluation of double purpose Holstein x Zebu cows in grazing systems with trees. II. Biparous

L. Simón, O. López y D. Álvarez

Estación Experimental de Pastos y Forrajes "Indio Hatuey"Central España Republicana CP 44280, Matanzas, Cuba.
E-mail: lsimon@indio.atenas.inf.cu

ABSTRACT

In order to evaluate the productive and reproductive performance of biparous double-purpose Holstein x Zebu cows, 75 cows were used in a completely randomized design, 25 per group, from genotypes Siboney (5/8 Holstein x 3/8 Zebu), Mambí (3/4 H x ¼ Z) and crossbred Siboney (5/8 H x 3/8 Z), which integrated a common herd with access to the same management and feeding, in a production dairy unit of the Supervaca farm, Genetic Livestock Production Firm of Matanzas. The stocking rate was 1,6 animals/ha and they rotated in 28 paddocks. Pasture availability and daily offer of forages and supplements were monthly measured. The body condition was estimated at the beginning and end of each season, milk production per cow was fortnightly measured, and the duration and production per lactation and the reproduction indicators were determined. The best body condition (3,97) favored crossbred Siboney (P<0,01); while no significant differences were found in the duration and production of milk per lactation. Likewise, crossbred Siboney was significantly higher (P<0,01) in the reproductive indicators parturition-first insemination (51,9), parturition-pregnancy (81) and parturition-parturition (363 days). The crossbred Siboney genotype was concluded to have the best performance in body condition and reproductive indicators, excelling Siboney and Mambí under the same management and feeding conditions, which shows higher adaptation to tropical grazing conditions.

Key words: Genotypes, performance, silvopastoral systems

INTRODUCTION

The livestock production firms of the country currently face the challenge of providing the market with milk and meat products so necessary for human feeding, of which there is shortage.

In order to face this challenge it is necessary to propose technological strategies which allow to decrease the effect of seasonality on rain distribution, pasture availability in the paddocks and degradation of ecosystems, particularly soil productivity. 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 in the ecosystems where it is developed.

On the other hand, the milk and meat production of ruminants fed diets based mainly on cellulose-rich biomass is much less dependent on the prices of fuel and other inputs, and in the future the cost of ruminant meat should be much more competitive than the meat of monogastric animals (Leng and Preston, 2003). However, the milk production of specialized breeds in the tropic has proven to be an unsatisfactory solution, because double-purpose production systems have been limited due to their low reproductive efficiency (Galina et al., 2001); while reproduction constitutes the primary and decisive event to reach higher milk production (Menéndez, 1993), because the more fertile a cow is in its productive period, the higher its daily production, considered in the stage of permanence in the herd (Cappa, 1993). For such reasons, the objective of this work was to continue evaluating the productive and reproductive performance of different double-purpose genotypes of the Holstein x Zebu crossings, with biparous cows in grazing systems with trees.

MATERIALS AND METHODS

Location. The trial was conducted in a dairy unit with trees (number 98 of the Supervaca farm, Genetic Livestock Production Firm, Matanzas, on a Ferralitic Red soil (Hernández et al., 2003).

Characteristics of the pastureland with trees. It was composed by 22,4% Cynodon nlemfuensis; 23,9% Paspalum notatum; 29,4% Dichanthium annulatum; 8,3% Sporolobus indicus; 12,3% other grasses; 3,0% Mimosa pudica and 0,7% herbaceous legumes. The tree count indicated the presence of 25 trees of Leucaena leucocephala, 14 of guava (Psidium guajava); six of Albizia lebbeck and 13 belonging to other species, for a total of 58 trees per hectare.

Animals, feeding and experimental design. Seventy-five biparous cows were used, 25 per group of genotypes Siboney (5/8 H x 3/8 Z), Mambí (3/4 H x ¼ Z) and crossbred Siboney (5/8 H x 3/8 Z), which integrated a common herd with access to the same management and feeding. A completely randomized design was used. The pasture availability and roughage supply are described by Simón et al. (2010) and only the supply form of the supplements varied, which was adjusted to the new milk production levels of the cows in their second lactation, which consumed 1,4 kg of concentrate and 2,5 kg of distillery residues (Northgold) per milking cow.

Management. The unit had a grazing area of 52 ha, divided into 28 paddocks for animal rotation and two small areas of sugarcane (5 ha) and King grass (2 ha) for forage. The stocking rate was 1,6 animals/ha; occupation and resting in the paddocks were managed according to pasture availability and season.
Measurements. The body condition was estimated in a scale from 1 to 5 points to determine the physical status of the cows at the beginning and end of lactation (Anon, 2004).

Milk production and reproduction. The milk production of each cow was controlled by weighing fortnightly and the duration and production of the first lactation was determined; while the reproductive performance was evaluated from the control cards. A variance analysis (ANOVA) was applied, and Duncan's multiple range comparison test was used to detect inequalities among the means. It was used the statistical program SPSS in its version 10.0 for Windows XP.

RESULTS AND DISCUSSION

The body condition of the biparous cows is shown in table 1. Crossbred Siboney reached the highest score and differed significantly from Siboney; no differences were obtained between it and Mambí.

The fact that all genotypes improved their body condition during lactation shows that this indicator is adequate to determine the available energy reserves by the animals to face any productive process, and constitutes a proof of the nutritional aspect (López and Álvarez, 2005; López, 2006). This confirms that the feeding used not only contributed to maintain milk production, but it also improved the physical status, just like during the first lactation (Simón et al., 2010).

The production and duration of the second lactation in biparous cows is shown in table 2. Significant differences were found (P<0,05) in favor of the Mambí genotype with regards to crossbred Siboney in daily milk production per cow; however, no differences were recorded in the duration or milk production per lactation.

Individual production as well as production per lactation of the cows in the second parturition was in correspondence with the report made by Reinoso and Simón (2000) in the Siboney genotype under silvopastoral system conditions, and they were higher than the ones reported by Lamela et al. (2009) with Holstein cows in an association of L. leucocephala and C. nlemfuensis, which showed low productive yield in correspondence with their milk production potential.

Crossbred Siboney significantly excelled Siboney and Mambí in all the reproductive indicators (table 3), although in general the three genotypes improved such indicators as compared to first lactation and the reports made by DNG (2006) for multiparous cows from these genotypes under commercial production conditions; likewise, they are considered adequate according to Blanco (2000), who recommended 120 days for PPI. In this study the PPI was lower (81 days) for crossbred Siboney, as well as the number of matings per pregnancy (1,5), which coincides with Caballero et al. (2002).

On the other hand, no remarkable differences were found in the live weights of calves at birth (table 3), which were similar as the calves in the first parturition and slightly lower than the ones obtained by López et al. (2004) in Mambí calves, and by Lamela et al. (2009) in Holstein calves which mothers were managed under silvopastoral system conditions.

The performance of crossbred Siboney seems to be related to its genetic origin when receiving an injection of new blood through backcrossing, which improves its heterozygosis and allows it to stand out as a double-purpose animal (milk and beef producer).

Crossbred Siboney was concluded to show the best performance in body condition and reproductive indicators, and it excelled Siboney and Mambí under similar feeding and management conditions, which shows higher adaptation to tropical grazing conditions.