RESEARCH WORK

Study of a fattening cycle with an integral diet based on forage and citrus pulp. I. Effect of forage quality

F. Ojeda¹, Bárbara N. Pino², L. Lamela¹, H. Santana¹ e I. Montejo<sup>1

1</sup>Estación Experimental de Pastos y Forrajes «Indio Hatuey». Central España Republicana CP 44280, Matanzas, Cuba

E-mail: felix.ojeda@indio.atenas.inf.cu

²Empresa Citrícola «Victoria de Girón», Matanzas, Cuba

ABSTRACT

The objective of this study was to evaluate a fattening cycle with an integral diet based on forage, citrus pulp, hay, non conventional concentrate (40% corn and 60% wheat bran) and salt, which was developed at the Citrus Fruit Production Firm «Victoria de Girón» in areas of the Livestock Production Farm No. 1, located in Torriente, Jagüey Grande municipality. Four hundred and fifty two animals were used, backcross of F1 (Holstein x Zebu) with Zebu, F2, which started the cycle with 190 kg average weight under semi-confinement conditions, during 324 days, divided into three consecutive stages. In September-December, the gain was 0,390 kg/animal/day. When the forage quality decreased (from January to April), its ingestion was decreased and the gain was lower (0,370 kg/animal/day). In the rainy season (May-August) the intake increased and the highest gain was achieved (0,450 kg/animal/day). It was proven that by increasing forage quality its contributions of DM, CP and ME are also increased and a relative decrease in the contribution of these nutrients by the citrus pulp and the concentrate is induced, although the feeding balances indicated the need to use urea to cover the protein needs. The feed efficiency (kg ingested DM/kg LW cattle) of the diets in each stage was: September-December, 14,0; January-April, 17,3; May-August, 16,3. This evaluation proved the importance of the quality of the forage and concentrate supplied to improve the feeding efficiency of the diets.

Key words: Quality, Citrus, beef cattle

INTRODUCTION

Animal production is a complex chain of interactions that are linked to results, through the genetic capacity of the animals and the health conditions. However, all that potential can only be expressed if the feed needs are covered by means of adequate nutrition. For that purpose it is essential to perform, appropriately, the management, feeding and supplementation (Mancilla, 2002).

In the countries where there are citrus fruit plantations the use of high pulp proportions is usual in diets, although it is known that the crude protein percentages it supplies are low with regards to the nutritional needs of fattening bulls, and that in order to achieve good productive results it is necessary to use other feedstuffs such as forage, hay, mineral salts and protein supplementation (Coppo and Mussart, 2006).

The objective of this study was to determine the effect of the integral diets based on forage and citrus pulp, on the weight gain of bulls during a fattening cycle.

MATERIALS AND METHODS

The study was conducted at the Citrus Fruit Production Firm «Victoria de Girón» in areas of the Livestock Production Farm No. 1, located in Torriente, Jagüey Grande municipality.

The study area averages 1 549 annual rainfall, distributed from May to October (rainy season) with 81%, and from November to April (dry season). Mean annual temperature is 24,7ºC, with maximum temperatures of 35ºC and minimum, 19ºC.

The soil, according to the cartographic map of the Firm, is classified as Ferralitic Red, typical, rocky and deep (Hernández et al., 1999).

Four hundred and fifty two animals were used, between 12 and 18 months old, which began the cycle with 190 kg average weight. The prevailing breed was dairy crossbred, consisting in a backcrossing of F1 (Holstein x Zebu) with Zebu, F2.

In order to facilitate the analysis of the results three consecutive stages were defined: September-December, January-April and May-August.

The diets consisted in: forage, fresh citrus pulp, grass hay, mineral salt, nitrogen contribution in the form of urea and non conventional protein supplement (40% corn and 60% wheat bran).

Exploitation and management system. A semi-confined system was used, with four hours of grazing (from 6:00 a.m. to 10:00 a.m.) and twenty hours of confinement (from 10:00 a.m. to 6:00 a.m. the next day).

This unit had a one-hectare barnyard for the permanence of the animals (limited by stone fences) and a grazing area of 50 ha, divided into four paddocks, which were subject to stocking rates that fluctuated between five and eight animals per hectare.

The prevailing pastures were Dichanthium annulatum and Dichanthium caricosum, with very low average availability (5 kg DM/animal/day during the rainy season and 3 kg DM/animal/day in the dry season), without trees for shade.

A feeding trough space of 0,5 m/animal was guaranteed and there was a water drinking trough with reserve tanks permanently supplied by a wind mill. The installation also had two sheds of 260 and 300 m² and an input storehouse.

The feed distribution and cleaning of the feeding and drinking troughs and adjacent areas were performed while the animals were grazing.

The forage, hay, citrus pulp, protein supplement and mineral salts were supplied in separate feeding troughs.

The fresh citrus pulp was obtained directly from the juice factory and it was deposited in feeding troughs 3 m wide, 5 m long and 1,5 m deep. Before depositing the product, the distributing trucks were weighed and no new deliveries were made until its total consumption.

The urea was sprinkled over the hay, diluted at a rate of 2 kg in 6 L water, according to the quantities established in the diets.

In the case of forage, fresh citrus pulp and hay, periodical bromatological analysis of dry matter (DM), crude protein (CP) and crude fiber were made once a month, by the analytical techniques of the AOAC (1991); their objective was to determine, among the feedstuffs that are shown in the feeding balance tables, those that were closer to the experimental conditions, to take their metabolizable energy values, elaborate the diets that would be supplied and, afterwards, make the retrospective balances according to the average weight and mean gain in the analyzed periods.

The forage was obtained from an area where king grass (Pennisetum purpureum) prevailed, which received two fertilizations of 40 kg N/ha. No irrigation was used during the dry season.

The average composition of the forage supplied is shown in table 1.

Table 2 shows the bromatological composition of the other feedstuffs used.

The feeding balances were made by means of the CALRAC program (1996), version 1.0, elaborated by the Institute of Animal Science (Havana, Cuba).

Because of the scarce pasture availability in the paddocks, the brief permanence time of the animals and the high stocking rates used, the possible nutrient contributions obtained by them during their permanence in grazing were not taken into consideration in the feeding balances.

The diets supplied were regularly recorded in the fattening farm to control the daily input of the feedstuffs, and the intake was measured through the method of supply and rejection.

In order to guarantee that the forage was offered at will it was weighed weekly, guaranteeing an excess lower than 10% of the consumption.

The average weight of the hay bales was calculated dividing the total number of bales between the net weight of the truck before their entrance to the storehouse.

The quantities of fresh citrus pulp consumed were determined according to the time the animals took to ingest it.

In this evaluation a fixed quantity of commercial concentrate was used, in order to know how the different components of the diet interacted, mainly forage quality.

The mineral salt and urea were supplied according to the quantities calculated by the previous feeding balances that were made to elaborate the diets, every two weeks, taking into consideration the intake of roughages and their bromatological composition.

The animals were weighed in a commercial scale, per group, at the beginning and end of each evaluation period; a monthly follow-up of the weight gain, estimated from the thoracic perimeter, was made in 15% of the stock, taking the precaution that it responded to a representative sample.

Simple classification analysis was performed on all the data to determine the mean and standard error of each measurement, using the statistical pack Windows SPSS version 10.0.

In order to compare the diet efficiency the feeding conversion rate was determined, dividing the total consumed dry matter between daily gain.

RESULTS AND DISCUSSION

During a fattening cycle the progressive change of weight of the animals in time implies variations in their ingestion capacity and their nutritional requirements, for which it is essential to conduct evaluations by growth stages.

In addition, in the case of the diets which include forage it is necessary to take into consideration the differences in their nutritive value, because it has repercussions on the animal response as well as on the intake of the other feedstuffs present in it.

The ingestion of the different feedstuffs, the average live weight and daily gain during the studied stages are shown in table 3. Important variations were found in the intakes of forage, fresh citrus pulp, hay and urea.

Among the factors that most affect forage quality are age and season. With age the main nutritional indicators decrease, due to a sustained increase in lignocellulose components; while the action of season is more linked to yields and the decrease in nutritive value when the plant flowers (Cáceres and Santana, 1989).

Peruchena (2007) considers that in tropical pastures the responses are much more complex, given the interaction of each climate component, and that this is the reason for which a gradual differentiation of the nutritive value occurs, because of the effects of solar radiation, rainfall and ambient temperature.

In September-December the forage supplied maintained the positive effect exerted by the rainy season on bromatological composition, and the animals obtained gains of 0,390 kg/animal/day.

From January to April, forage quality (as it came from a forage area without irrigation) decreased as the dry season advanced, which caused a reduction in its ingestion and made it essential to increase hay quantities to satisfy the dry matter needs of the animals. The gains were the lowest of the cycle (0,370 kg/ha/day).

According to the report made by Pirela (2005), forge intake decreases rapidly when the CP content of the forage decreases below 7%, as a consequence of a nitrogen deficiency in the rumen, which limits microbial activity.

With the beginning of the rainy season (May-August) a remarkable increase occurred in forage intake, by improving its quality, and it was feasible to decrease the hay quantity.

The gains obtained were the highest of the whole study (0,450 kg/animal/day), in which the nutrient contribution combined with the compensatory growth, which occurs in ruminants as long as the diet allows it (Bavera et al., 2005).

The retrospective balances indicated that the diets allowed to cover the requirements of the animals, according to their live weight and gain (table 4).

In the three evaluations a protein unbalance was found solved by using the urea, which is essential in this type of diet because it provides the ammonia necessary for the rumen bacteria, and in turn maintains the levels of ruminal pH close to neutrality, considered as a desirable value for cellulose and hemicellulose digestion in forages (Owens, 1978).

This beneficial action encourages the animal to consume more forage, by improving the efficacy of microorganism multiplication within the rumen (Araque, 2006).

The intake increases found in citrus pulp and urea, were in correspondence with the weight increase of the animals.

The percentage analysis of the ingested nutrients allowed to define that the forage quality had repercussions on the nutritional contribution of each feedstuffs to the diet, and that the intake increase augmented the DM, CP and ME and induced a relative decrease in the contribution of concentrate regarding those nutrients (table 5).

Likewise, when the forage intake decreased, the citrus pulp and hay contribution in the diets increased.

The feeding conversion in each period showed proper values, according to the nutritional value of forage, season and physical status of the animals (table 6).

In the period September-December, when the animals from areas with less feeding possibilities entered the fattening farm, they showed a good response to the diet and reached the best conversion values; in the second period, when decreasing the forage quality, the efficiency decreased, to improve again during May-August because of the compensatory effect.

The feeding conversion of the diets was higher than the one found by De León et al. (2004) for rations based on sorghum and corn silages (10,3 and 7,5 DM/kg live weight), and the one obtained by Di Marco (2007) in evaluations with supplemented pastures (8,3 and 7,8 DM/kg live weight).

In these evaluations the authors used feedstuffs under temperate climate conditions, where the nutritional quality of the forages and supplements is better than the ones used in Cuba, in addition to the fact that they worked with breeds specialized in beef production.

Nevertheless, when supplementation with low nutritional quality feedstuffs is used in such latitudes similar values as the ones in this study are obtained (Villanueva and San Martín, 1997).

In this research the importance of forage quality in the diet and the need to improve the quantity and quality of the concentrate supplied were proven. Nevertheless, the values obtained can be considered as reference for later studies.