Effect of the inclusion of mixed silage on the productive performance of grazing Pelibuey ewes
Y. López1, J. Arece1, E. León2, N. Aróstica1 y F. Ojeda1
1Estación Experimental de Pastos y Forrajes "Indio Hatuey". Central España Republicana, CP 44280, Matanzas, Cuba
2 Centro de Estudios de Producción Animal (CEPA). Universidad de Granma. Cuba
With the objective of evaluating feeding variants with mixed silage of pig excreta and citrus pulp (MSPECP) in a system with naturalized pastures and leucaena forage, a trial was developed with 48 Pelibuey ewes, in areas of the EEPF "Indio Hatuey", Matanzas province. A completely randomized design was used and the animals were distributed in four groups, in which the inclusion of MSPECP in 10% (TII), 20% (TIII) and 30% (TIV) of the total dry matter intake (DMI) was evaluated, with the presence of a control group 0% (TI). The bromatological composition and nutrient intake of the MSPECP, live weight and body condition of the ewes, live weight at birth and mean daily gain (MDG) of the lambs were determined. The CP values of the silage varied between 13,4 and 14,6%. The CP intake was related to the inclusion percentage of silage (23,7; 49,0 and 70,2 g/day for TII, TIII and TIV, respectively). The live weight of the ewes did not show significant differences among treatments, with values higher than 30 kg in the whole campaign. The body condition showed values higher than 3,3 in the four experimental groups and remained over 2,4 at 30 days postpartum. The weight of the lambs at birth showed significant differences (p<0,05), with the best performance for treatments II, III and IV; while the weight gain of the lambs at 30 days did not differ.
Key words: Silage, excreta, reproduction
Among the alternatives in Cuba to increase the supply of protein from animal origin to the population is the development of sheep rearing, because in it a group of advantages are gathered that make it ideal for these purposes under the current conditions (Marshall, 2000).
The incomes are based mainly on the sale of lambs for consumption; nevertheless, their low numeric productivity, as a consequence of poor fertility and survival of the offspring, increases the production costs and decreases income for the producers (González-Stagnaro, 1997). That is why reproduction constitutes an important element for the achievement of good productive and economic results in the systems. This statement is valid for all species and for any type of management and feeding system. As it is known, a large part of sheep production in the country is under critical or intermediate conditions regarding management and feeding (Herrera and Pulgarón, 2005).
The current systems demand changes, due to the need to develop strategies that lead to sustainable production, progressively decreasing contamination of the environment, with a better utilization of the availability of local resources and the livestock production wastes that are generated.
The utilization of mixed silage of pig excreta and citrus pulp, as supplement for feeding the ewe, can constitute an alternative for the moments of higher nutritive demand. The objective of the work was to evaluate this type of mixed silage in diets for ewes, during the covering campaign and the first postpartum weeks.
MATERIALS AND METHODS
Location. The study was carried out in the production areas of the small livestock facility of the Experimental Station of Pastures and Forages "Indio Hatuey", in the Matanzas province, Cuba.
Animals. For the study 48 Pelibuey ewes were used, between four and five years old and good apparent health conditions. Before the research they were subject to a selection process, regarding their general condition.
Experimental procedure. The experiment comprised two main stages of the productive cycle in the ewes: covering campaign (May-June) and the last third of pregnancy (August-September), applying a feeding system based on leucaena (Leucaena leucocephala) forage and different proportions of mixed silage of pig excreta and citrus pulp (MSPECP). A 15-day adaptation phase was established previous to the experiment, in which the animals were fed leucaena forage at a rate of 30% and MSPECP in 20% of the dry matter consumed in the experimental groups.
The animals had an individual identification that allowed separation by groups. A directed grazing was established since 9:00 a.m. until 3:00 p.m., in an area of 4,86 ha divided in 18 paddocks of 0,27 ha each, covered by naturalized pastures (Dichantium-Botriochloa). The ewes were transferred in the evening to the tenancy shed, with excellent hygienic-sanitary conditions, in which they were supplied water and mineral salts ad libitum.
Feedstuffs. For the elaboration of the mixed silage the pig excreta were collected in the morning, in a facility for intensive fattening; they were deposited on cement floor to increase their dry matter content and they were mixed afterwards with the citrus pulp in a proportion of 60% excreta and 40% citrus pulp. They were pre-dried under sunlight for eight hours; before being put in the tanks 3% of Sorbial® ferment (Sorbial, France) was added and they were placed in airtight metallic tanks with capacity for 200 kg. The bottom of the tanks was filled up with 3 kg of well-compacted hay for gathering the effluents that could be produced during the conservation.
The estimated intake of pasture was 2,4 kg/animal/day as average. The leucaena forage was cut in the morning, in a plantation of the production areas of the facility. The leaves and fresh stems were selected for the supplementation, considering a diameter of 10 mm utilizable by these animals.
Measurements. During the trial the live weight and body condition of the ewes were determined (Russel, Doney and Gunn, 1969) at the beginning of the campaign, at the moment of parturition and 30 days after parturition; in turn, the lambs were weighed at birth and after 30 days the mean daily gain of live weight (MDG) in the stage was measured. The animals were weighed with a scale of 50 kg ± 0,2 and a dynamometer of 10 kg ± 0,02.
Fifteen days before the campaign and the parturition of the animals, samples of the MSPECP were taken for determining DM (%), CP (%), P (%) and ash (%), according to the norms of the AOAC (1995).
Experimental design and treatments. A completely randomized design was used, with 12 animals per treatment. The treatments were: TI) 6 hours of grazing plus leucaena; TII) 6 hours of grazing plus leucaena plus MSPECP (10%); TIII) 6 hours of grazing plus leucaena plus MSPECP (20%); TIV) 6 hours of grazing plus leucaena plus MSPECP (30%).
Statistical analysis. The data were processed using the SPSS® program version 15.0 for Windows®. The effect of the treatments on each of the variables analyzed was evaluated through a variance analysis (ANOVA) with a factor of four levels. The mean comparison test was performed.
RESULTS AND DISCUSSION
The chemical composition of the mixed silage and the nutrient intake in the different treatments (table 1), showed dry matter and crude protein values (35,8 and 42% DM; 13,4 and 14,6% CP) that are considered adequate for the diets of the ewes under grazing conditions; however, it must be considered that the quantity and quality of the dung is variable, because there is influence of factors related to the feedstuff, characteristics of the pig and productive management system. Padilla, Emperatriz, Castellanos, Cantón and Monquel (2000) found values of 73,5% DM; 27,5% CP and 12,6% mineral matter; while Aguilar, Valencia and Santos (2002) reported values in the fresh pig excreta of 21% DM and 23% CP. On the other hand, Salazar and Cuarón (2002) found 24% CP; 12,6% ash; 2,2% Ca and 1,4% P; while Gutiérrez (2003) reported ranges of 50% DM; 16,1% CP; 5,02 MJ/kg ME; 2,0% Ca and 1,5% phosphorus.
This suggests that there can be a contribution of the excreta in the variability of the chemical composition of the citrus pulp, because in a study carried out by Cáceres, Ojeda, González, Arece, Simón, Lamela, Milera, Iglesias, Esperance, Montejo and Soca (2006), the crude protein values were 7,7; 7,7 and 8,7% for the fresh, dehydrated and ensiled pulp, respectively.
The crude protein values of the mixed silage in this work (13,4 and 14,6) are higher than those of other feedstuffs considered as high, middle and low quality feedstuffs (10,28; 7,10 and 6,70%) for diets of sheep, reported by Rojas, Chávez and Fernández (1984). However, they are lower than the ones reported by Padilla et al. (2000); Aguilar et al. (2002); Salazar and Cuarón (2002) and Gutierrez (2003), for fresh pig excreta. An element that could have influenced the results of this work was that the excreta were pre-dried, mixed with citrus pulp, lactic ferments and presented as silage.
In the case of the intake of nutrients contributed by the silage, values were reached of 37,6 g of dry matter/kg P0,75 and 70,2 g of crude protein per day, when the mixed silage was used in 30% of the total DM intake, with differences among the treatments (p<0,05). Something similar occurred in the calcium and phosphorus intake. These results suggest the possibility of supplementing with mixed silage the ewes during the moments of higher nutritive demand: the covering campaign, the last third of pregnancy and the first weeks of lactation, coinciding with the statements made by Acevedo (1999), López (2004) and León, López, Olmos, Rodríguez, Fonseca and Labrada (2006).
Figure 1 shows the live weight of the ewes during the campaign, the parturition and the first 30 days postpartum, which did not present significant differences among the evaluated treatments. The values were higher than those indicated by López, León, Fonseca and Ramírez (2004) and León et al. (2006) in studies of supplementation with leucaena foliage and molasses-urea to ewes, in a system with natural pastures.
On the other hand, a decrease of live weight was observed 30 days postpartum with regards to the weight at parturition, which is due to the increase of the metabolic demands because of lactation (López, 2004). The cause of the increase of the needs is attributed to milk production for lamb rearing, which in most of the sheep breeds reaches high values (1,5-3,0 L/day), regarding the number and vigor of the lambs. Nevertheless, this increase is not in correspondence with an increase of the ingestion capacity, because in the first days postpartum the rumen in the ewes has not reached the normal size, for which in practice they are forced to mobilize their body reserves (Acevedo, 1999; Yzaguirre and Combellas, 2002); especially if the base feed has low quality, as occurs usually with natural pastures under the conditions described in the work.
The body condition (table 2) showed little variation among treatments and was higher than the one obtained by Olmos (2001) and León et al. (2006) under conditions of supplementation with molasses-urea and leucaena, in a grazing system with natural pastures. In these works the dams conserved their body condition, because when including leucaena in 30% the animal does not mobilize its reserves due to the high nutritive value of the diet, which increases the nutrient contribution as the intake increases. Something similar occurred in this work, because in the treatment with the highest inclusion of silage (T IV) the body condition was higher than 3 units at the moment of parturition and it was maintained over 2,7 units in the first 30 days of lactation; this suggests a remarkable nutrient contribution for the ewes, without needing to mobilize their body reserves. This shows the need to supplement the animals in pasture feeding systems, mainly if the pastures have very low quality.
Table 3 shows the weight of the lambs at birth and 30 days postpartum, as well as the mean daily gain for this period. The weight at birth was within the range proposed by Rodríguez (1990) for Cuban conditions; this indicator allows to make an evaluation of the animals' productivity and constitutes one of the most important factors to be considered when evaluating their productive potential (Fonseca, Costa, La O, Ponce, Vázquez, Miranda, Sánchez and Liranza, 2001; Herrera and Pulgarón, 2005). It is known that the low weight of lambs at birth is related to nutritional deficiencies, bad animal management and to the environment; in addition, they have more possibilities of dying than those that are over the general mean of the herd (Fonseca, 2003).
The highest live weight increases of the lambs were observed in the treatments in which the ewes consumed mixed silage with regards to the control group. A similar performance occurred 30 days after parturition, which can be attributed to the consumption of good nutritive quality silage, propitiating a better assimilation of the nutrients in the diet, an increase of milk production for the consumption of the lambs and, hence, a better conversion of kilograms of milk per grams of live weight, which coincides with the reports by López et al. (2004).
The weight of the lambs at birth was higher than the ones obtained by Rodríguez (2001), López et al. (2004) and León et al. (2006) under grazing conditions and supplementation with leucaena and molasses-urea, in zones of the Granma province. It must be stated that these studies were carried out in a region with very different edaphoclimatic characteristics, that cause variations in the chemical composition of the feedstuff fed to the ewes and thus the milk contribution for the consumption of the lambs is affected, which could account for the weight differences; however, when the performance of the weights at birth and in the first 30 days postpartum is analyzed, they were similar to the ones obtained in this study.
Under the conditions of this work the lambs reached mean daily gains of more than 90 g/animal/day, which means an adequate milk production of the dams, that can be attributed to the nutrient contributions of the experimental diets in systems with natural pastures, without discarding the positive effect of leucaena on the balance of the ration for all the groups under study; the effect of the pregnancy season could also be considered, because it is a determining factor in the weight at birth of sheep, especially if pasture is the feeding base of the system (Herrera and Pulgarón, 2005).
The season exerts a direct influence on the fluctuations of the feed availability, which justifies that pregnancies that are developed in the rainy season originate a higher weight of the lambs at birth (Fonseca et al., 2001), and it is a positive response of the mother and the fetus to the improvement of the nutritional aspect produced in this period. These authors describe a better performance of all the reproductive indicators in coarse hair sheep for the rainy season, in the systems developed under the conditions of plains as well as mountains.
The mixed silage of pig excreta and citrus pulp shows good nutritive characteristics, which allow its inclusion in the diets for grazing ewes.
Adequate crude protein intakes were obtained with the use of mixed silage in 30 % of the total dry matter intake, for ewes under grazing conditions.
With the supplementation of mixed silage good results can be obtained in the body condition, live weight of the ewes and weight of the lambs at birth, as well as adequate gains in the lambs at the first month after birth.