RESEARCH WORK

Bull fattening with diets based on fresh or preserved citrus pulp

F. Ojeda1, Bárbara N. Pino2, L. Lamela1, H. Santana1 e I. Montejo1

1Estación Experimental de Pastos y Forrajes «Indio Hatuey». Central España Republicana, CP 44280, Matanzas, Cuba
2 Empresa Citrícola «Victoria de Girón», Matanzas, Cuba
E-mail:f.ojeda@indio.atenas.inf.cu

ABSTRACT

At the «Victoria de Girón» Citrus Fruit Production Enterprise, Matanzas province, Cuba, a study was conducted for 138 days with 433 crossbred bulls of dairy breeds (Holstein x Zebu), in which a diet based on restricted grazing (four hours in the morning), green forage and citrus fruit pulp ad libitum, was evaluated, supplemented with grass hay, mineral salt and North gold. The citrus fruit pulp was supplied as silage since August 8 until October 31, and fresh since November 1st until December 24. The latter was enriched with urea, at a rate of 0,04 kg per 5 kg of citrus fruit pulp. In the rainy season, the forage showed the lowest DM percentages and the highest ME and PDIN values, with little variation between periods for PDIE. The fresh and ensiled citrus pulp maintained analogous values to other studies; the hay had low quality and forage intake was similar in both periods; preserved citrus pulp was less consumed than the fresh one. The gain was higher with preserved citrus pulp (0,593 vs. 0,556 kg/animal/day). Nutritional balances indicated that the DM and ME requirements were covered, although in nitrogen compounds inefficient utilization was made because there was excess of PDIE, which was not corrected through urea incorporation. In both periods the highest percentages of nutrient contributions corresponded to forage and citrus fruit pulp in its two modalities. The conversion values had a better response with silage (13,3 vs. 15,5 kg DM/kg of gain). The feasibility of using fresh or ensiled citrus fruit pulp is concluded; although, to increase gains and feeding conversion, it is necessary to increase protein supplementation and have feedstuffs which balance the quantities of PDIN and PDIE in the diets.

Key words: fattening, citrus pulp.

INTRODUCTION

The «Victoria de Girón» Citrus Fruit Production Enterprise has developed a productive diversification program which intends, among other objectives, to utilize the residues of juice elaboration for feeding fattening bulls, to decrease the environmental contamination caused by these residues and, in turn, obtain a foodstuff of high social demand. For beef production semi-intensive systems have been adopted, which allow achieving acceptable individual gains, in feedlots with a large number of animals (Rodríguez et al., 2009; Gil, 2010).

In preceding studies the utilization alternatives of fresh as well as ensiled citrus fruit pulp, and different complementation and supplementation choices in the diets, were reported, with encouraging results (Ojeda et al., 2009). The objective of this study was to evaluate a final cycle of cattle fattening, using fresh or preserved citrus fruit pulp as main diet component.

MATERIALS AND METHODS

Location. The study was conducted in the livestock production farm No. 1-Torriente, of the «Victoria de Girón» Citrus Fruit Production Enterprise, located in the Jagüey Grande municipality, Matanzas, Cuba.

Climate and soil. The area shows average annual rainfall of 1 549 mm, 81% of the rainfall occurs between May and October (rainy season), and the other, from November to April (dry season). Mean annual temperature is 24,7ºC, with maximum values of 35ºC and minimum temperatures of 19ºC; while the soil is classified as typical, rocky and deep Ferralitic Red (Hernández et al., 1999).

Animals. As the harvest of citrus fruits starts in late September, the study was divided into two periods: the first one, from August 8 to October 31, in which the citrus fruit pulp was supplied as silage, from a reserve of this product stored since the previous year; and a second period, from November 1st to December 24, in which the citrus fruit pulp was supplied fresh, directly brought from the factory to the livestock production facilities.

The feedlot had 433 crossbred animals of dairy breeds (Holstein x Zebu), which began fattening with an initial weight of 305 kg and were slaughtered with 385 kg. The study period comprised a total time of 138 days.

Management system. A semi-confined system was used, with restricted grazing during four hours per day, from 6:00 a.m. to 10:00 a.m., and 20 hours of confinement, since 10:00 a.m. until 6:00 a.m. of the next day. The unit had a one-hectare pen (delimited by stone fences) for the animals to stay and rest, as well as a grazing area of 50 ha, which was divided into four paddocks, for a total stocking rate of 8,7 animals/ha.

The feedlot had several feeding troughs, 3 m wide, 5 m long and 1,5 m deep, which guaranteed a feeding trough front of 0,5 m/animal. There were also drinking troughs with reserve water tanks, permanently supplied by a windmill. The facility also had two sheds of 260 and 300 m2, and an input storehouse.

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

The citrus pulp silages were elaborated in surface silos, with a proportion of 86% fresh citrus fruit pulp, 10% grass hay and 4% urea. The elaboration technology was by layers, and a tractor with front shovel was used for the introduction of roughages and compaction. Urea was manually added on the citrus fruit pulp. Once the silo was filled, it was covered with additional 20-cm layers of citrus fruit pulp and hay. The fermentation period of the silage was 120 days, before using it.

The forage was daily harvested with a SPKZ silage harvester, in an area where king grass (Penniseum purpureum) prevailed; it had a regrowth age between 70 and 80 days, and had received fertilization of 60 kg N/ha in July.

The pasture for hay consisted in a mixture of natural grasses, from areas near the enterprise, which were dried for two days and packed in rectangular bales, with an average weight of 20 kg. They were immediately collected from the field and placed in a roofed storehouse until their later distribution in the feedlots.

Feeding. In the grazing area the prevailing pastures were: Dichanthium annulatum and Dichanthium caricosum, with an average availability of 5 and 3 kg DM/animal/day, during the rainy and dry season, respectively.

The rest of the diet was supplied as cake and consisted in green forage and ensiled or fresh citrus fruit pulp, besides additional supplementation. This procedure consisted in placing a hay layer on the bottom of the feeding trough, at a rate of 0,7 kg/animal; next, a layer of fresh or ensiled citrus fruit pulp, 5 kg/animal; and then, another layer of forage and 0,04 kg of urea sprayed over the feedstuffs, when the citrus fruit pulp was supplied fresh. On top of these feedstuffs 1 kg of North gold and 0,05 kg of whole mineral salts were incorporated per animal.

Feed intake. The supplied diets were quantified and recorded in the feedlot, through the control of daily feed supply. Intake was determined through the offer and rejection method. The forage and silage were weighed every week, to guarantee they were supplied ad libitum, and that the animals received 10% over the intake of the previous week.

Live weight. The animals were weighed, by groups, on a commercial scale, at the beginning and the end of the evaluation period. During the intermediate periods, the live weight was estimated through measurements of the thoracic perimeter in 10% of the animals in the feedlot.

Bromatological analysis. Samples of forage, fresh citrus fruit pulp, silage and hay were taken once a month, to determine dry matter (DM), crude protein (CP), crude fiber (CF), calcium (Ca) and phosphorus (P), through the analytical techniques established by the AOAC (1991); while metabolizable energy (ME), protein digestible in the intestine from energy (PDIE) and protein digestible in the intestine from nitrogen (PDIN) of the feedstuffs were estimated through the formulas and chemical composition tables in the CALRAC program (1996).

Feeding balance. The feeding balance was made every two weeks, to adjust the forage and silage offer during the evaluation period. At the end of the study, the balances were retrospectively made. The CALRAC program (1996), version 1.0, elaborated by the Institute of Animal Science (ICA), was used.

Conversion rate. To compare diet efficiency, the feed conversion rate was determined, by means of the division of total dry matter consumed by the daily live weight gain.

Data analysis. The forage and fresh citrus fruit pulp intakes, as well as the initial and final weights of the animals, were analyzed through descriptive statistics (mean and standard deviation), using the SPSS pack, version 10.0 for Windows.

RESULTS AND DISCUSSIONS

The bromatological composition of the forages showed variations according to the season in which the study was conducted. In the first evaluation period, which coincided with the months of the rainy season, the lowest DM percentages and Ca concentrations were found; however, the highest ME, PDIN and P values were recorded, with little variation between both periods for PDIE (table 1). This performance coincides with the report by García-Trujillo and Cáceres (1981), when they evaluated king grass as forage in different seasons of the year.

Fresh as well as ensiled citrus fruit pulp, maintained its values within the range obtained in other similar studies, where it was used in diets for fattening cattle (Pino, 2008). In this sense, the fresh citrus fruit pulp showed lower DM, CP and P percentages, but higher ME values, than the preserved citrus fruit pulp.

Concerning the PDI components, the inclusion of urea in the elaboration of the silages favored a more balanced composition between PDIN and PDIE, with regards to fresh citrus fruit pulp.

The hay used had low quality, with CP values lower than 4%. This classification is based on the nutritional indicators established by Ojeda et al. (2006). On the other hand, the nutritional value of North gold remained within the ranges reported in literature (Trenkle, 2004).

Fresh forage intake was similar in both periods, which did not occur in the case of fresh and preserved citrus fruit pulp, because the silage was less consumed than fresh citrus fruit pulp; these differences could have occurred due to the effect of their DM contents (table 2). In the other supplied feedstuffs no variations appeared in intake, as they were predetermined in the diets. Regarding the live weight gain, a trend was found towards obtaining higher values when the diet with preserved citrus fruit pulp was used (first evaluation period); although in both diets they were lower than the ones reported by Ojeda et al. (2010), when simultaneously evaluating these forms of inclusion in fattening diets. Such differences are ascribed to the fact that in this evaluation there was lower contribution of protein supplement.

The importance of supplementation in the productive results was corroborated with the study conducted by Rodríguez et al. (2007), who obtained gains of 1,305 kg/animal/day in Siboney bulls, in a feeding system which also included restricted grazing and supplementation with 2 kg of molasses, 2 kg of wheat bran, 5 kg of fresh citrus fruit pulp and 2 kg of North gold.

The retrospective feeding balances corroborated that the diets covered the DM and ME requirements, according to the average live weight in each period and the weight increase (tables 3 and 4). Nevertheless, regarding the digestible nitrogen compounds contributed by the diets (PDIN and PDIE), it was shown that it was not possible to make an efficient use of their nutritional potential, because in both cases there was excess of PDIE and PDIN values higher than and close to the requirements, with predominance in the PDIE contributions over the supplied quantities of PDIN. In an optimum diet, the contributions of digestible nitrogen compounds should be equal or very close (García-Trujillo and Cáceres, 1984).

These results indicate the need to conceive, for later evaluations, the use of feeding components which are capable of guaranteeing an adequate balance among the digestible nitrogen compounds in the intestine, but taking into consideration that there is correspondence between the contributed nutrients and the ingestion capacity of the animals. In this sense, a solution could have been provided by the incorporation of a supplement with better PDIN contributions, such as the yeast Saccharomyces cerevisiae (Cáceres et al., 2006); but it was not possible because the enterprise did not have these complements.

The analysis of the percentage contributions of nutrients contributed by the feedstuffs (table 5) allows characterizing the diets more accurately. In both periods, the highest ingested DM percentage corresponded to forage, followed, in order of importance, by citrus fruit pulp in its two forms. Such results indicate the importance of these feedstuffs to cover the DM requirements of the animals, but especially that they constitute viable and utilizable feeding sources for this type of production.

The contribution of the other feedstuffs to DM intake was below 30%, as a whole, without evident differences among the diets, for which it may be stated that supplementation did not exert a substitutive effect. Regarding the ME, forage participation was higher during the first period, because it corresponded to the rainy season in which the values of this indicator were higher.

The energy contribution of fresh citrus fruit pulp was slightly higher as compared to the silage, because of the decrease induced by fermentation processes on this nutritional component. The hay had little contribution in all nutrients, although with a slightly higher energy supplementation in the second period, due to the higher contribution made by the forage. Regarding North gold, its energy contribution was relatively important.

The highest differences were found in the contribution of feedstuffs with regards to the components related to the protein digestible in the intestine. The forage in the diet with silage covered the PDIE to a higher extent (40,3 vs. 34,8), although in both diets the contribution was similar for the PDIN. The preserved citrus fruit pulp contributed higher PDIN percentages; yet, its contribution in PDIE was lower with regards to its fresh form.

In the case of hay and North gold no large differences were found among the diets, although the latter greatly contributed, with PDIN values very close to that of citrus fruit pulp preserved as silage, and higher than that of fresh citrus fruit pulp.

The feeding conversion rate (table 6) showed better response with the combination of forage and citrus pulp silage. In this sense, at the beginning of the experiment the animals showed low weight and body condition, for which when receiving the diet based on citrus fruit pulp silage and forage better structured from the nutritional point of view than the previous one- they could have compensatory growth (Parnell, 1996), which did not occur afterwards when they received the fresh citrus fruit pulp.

In general, both rates were less efficient than the ones found in previous evaluations, which is mainly ascribed to the low inclusion of protein supplement (Pino, 2008). The conversion values also differed from the ones reported for similar fattening systems in temperate countries, where diets were used with low grain percentage (25-20%) and higher quality forages, in which the conversion rates oscillated between 9 and 11 (Gil, 2002).

The results in this evaluation allowed concluding that it is possible to obtain gains higher than 550 g per day in bull fattening, under production conditions, from animal feeding with a diet based on forages and residues of the citrus fruit juice production in the form of fresh as well as ensiled citrus fruit pulp. To increase protein supplementation, in order to raise the feeding conversion efficiency of diets and to balance the adequate quantities of PDIN and PDIE, is recommended.