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Introduction
One of the cattle practices in Cuba for male cattle under grazing, due to objective issues, related to the safety and protection of animals, consists on the diurnal grazing and night enclosure throughout the year (Iraola et al. 2013, 2016a). This situation can be critical during the dry season, framed between November- May, when the availability of grasses is reduced. Thus, feeding alternatives are needed to supplement the dry matter deficit and provide adequate stability in the animals weight gain.
In order to deal with this shortage of grasses during the dry season, the conservation of king grass (Cenchrus purpureus) and moringa (Moringa oleifera) forages by means of the silage technique, would allow the conservation of forages with nutritional value similar to the silage for beef production (Zea and Díaz 2011). However, the nutritional value of these silage materials could be increased using starchy sources, such as sweet potato (Ipomoea batata) and the addition of the microbial additive VITAFERT® (Rodríguez et al. 2017). In relation to the mentioned antecedent, a research was carried out to evaluate the effect of supplementing silage composed of CT-115, moringa, sweet potato and VITAFERT® in the live weight change of fattening cattle in diurnal grazing and night enclosure during the dry season.
Materials and Methods
The research was carried out during 60 d in an experimental farm "Cebadero Ayala", belonging to the Instituto de Ciencia Animal (ICA) during the dry season, between November - May. Sixteen non-castrated male bovines were used, with an initial live weight of 324 ± 7.50 kg, from a crossbred dairy genetic group (5/8 Holstein x 3/8 Cebu) in the completion phase.
The management variant used was diurnal grazing and night enclosure, with supplementation of fresh forage or silage composed of CT-115, moringa, sweet potato and the VITAFERT® microbial additive (1 L per 100 kg of fresh matter). The animals were distributed in two groups of eight, according to a completely randomized design with the following treatments: I) grazing and 4 kg.animal-1.d-1 of fresh forage, II) grazing and 4 kg.animal-1.d-1 of silage.
Silage production. The silage process was carried out prior to the study in experimental areas of ICA, according to the inclusion percentages fitted by Rodríguez et al. (2017). These were manually mixed with the help of shovels and were deposited in independent plastic bags with a capacity of 300 kg, where the process of compaction and extraction of air was manually performed with the help of a tamper. The bags were ready for use after 60 d.
Management of animals. A period of adaptation to the management of 21 d was performed. The animals grazed during the daytime between 6 and 8 h, in six hectares of a mixture of improved grasses, associated with herbaceous legumes. The hectares were divided into eight paddocks of 0.75 ha, where the animals had free access to water. In the afternoon, they moved to independent pens, according to treatment. In the pens, it was offered, forage and silage in a single feeder, both products were mixed with distillery vinasse of Havana Club rum, at a rate of 0.5 L.animal-1.d-1 and corn meal (1 kg.animal-1).A total of 80 g of mineralized salts were daily offered per animal and water ad libitum. The weighing of the animals was carried out monthly on a digital scale (CEMA model of Cuban manufacture of 1 500 kg).
Measurements. The dry matter (DM) availability of the grass was estimated, for which the methodology described by Haydock and Shaw (1975) was used and 80 representative points were taken per paddock, with the help of a 0.25 m2 frame. The chemical composition analyzes of crude protein (CP), dry matter of the foods (DM) and silage acidity were performed according to AOAC (1995), while the metabolizable energy was estimated by the prediction equations, proposed by García- Trujillo and Pedroso (1989).
To samples taken at random, in each bag of silage the temperature was determined with the help of a digital thermometer (Infrarot-Thermometer ScanTemp 333, TFA), the odor and texture. By means of offer - rejection, the DM intake was determined. The average daily gain (ADG) and the weight gain in (WG) were calculated. For the calculation of food balance exercises, DM intake was estimated, for which the tables showed by Martín (1981) and the energy and protein requirements, according to Martín and Palma (1999, 2017) for an estimated average gain 700 g were used. The ratio crude protein (CP): metabolizable energy (ME) of the contribution was also estimated, according to the ADG achieved in each treatment.
Analysis of variance was carried out and a multiple comparison test was applied for the differences between means, according to Duncan's test (1955). The processing of the data was developed with the help of SAS software (2013).
Results and Discussion
With respect to the silage bags used during the experiment, the temperature data oscillated between 30- 32 °C and the acidity maintained values close to 4, which are among the parameters suitable for forages silage (García-Trujillo and Esperance 1979 and Reyes et al. 2008). The silage bags showed pleasant odors (never odor of tobacco, vinegar, ammonia or rot) and a firm texture. This allowed an adequate conformation of the obtained silage, with average CP values of 10 %, unlike the control treatment. In this, the forage offered did not exceed 7 % of CP. Regarding the control group and silage, the average intake values were 95 % during the research.
Table 2 shows the productive indicators evaluated for live weight, ADG and WG. There was not difference for the live weight indicators and neither for the WG. However, a difference was observed (P <0.01) between treatments for ADG. The animals that had access to the silage reached an average 703g of individual gain. Everything indicates that the adaptation period influenced on the initial live weight in both treatments, which conditioned, according to the ADG, the weight gain and the final live weight during the research.
The results of ADG in the treatment with silage composed of CT-115, moringa, sweet potato and VITAFERT®, are the first productive indicators that are referred to in Cuba with crossbred dairy bulls. In this study, an ADG higher than that reported by Díaz et al. (2013), who reported 589 g during the growth stage with crossbred Holstein x Cebu animals, 24 h grazing in grasses associated with herbaceous legumes and a ruminal activator. They were also higher than the ADG reported by Iraola et al. (2016 a), of 573 g and 622g, in the final phase of crossbred dairy males during the dry season, with management variant consisting of diurnal grazing (8 h) of grasses associated with herbaceous legumes and nocturnal enclosure with energy supplementation ( fresh whole sugar cane and corn meal). Likewise, the ADG was lower than the one obtained by Zea and Díaz (2011) in regions from Spain, where they evaluated the capacity of some silages of different forages with minimal supplementation of concentrates, for the production of beef with different genotypes.
Table 2 Productive indicators of male crossbred dairy cattle in diurnal grazing and nocturnal enclosure.
ADG: average daily gain; WG: weight gain
Therefore, the ADG obtained with the management variant showed above and this type of silage, mixed with corn meal and vinasse, seems to be viable for cattle males from dairy herds (Holstein x Cebu) under production conditions. However, higher ADG cannot be achieved without higher energy- protein supplementation in their diet. This is due, among many factors, to the grazing time, the grasses availability, the percent of grass use and the caloric stress to which these genetic groups could be subjected with different management conditions, which differ between production systems. The obtained results from ADG in the silage treatment could also be associated with the DM availability in the grasslands of 29 kg.day-1, the quality and the DM intake of the silage.
Table 3 shows the energetic - protein food balances and the total N ratio: ME of the contribution and conversion of the ME and CP by treatment. The SDG of LW in the silage treatment allowed covering the nutritional requirements of CP and ME for an estimated gain of 0.700 kg. However, in the control treatment it was not possible to meet the requirements.
Table 3 Results of the food balance and the total N ratio: ME of the contribution and conversion of the ME and CP in the diet of crossbred dairy bulls.
The difference in the contribution of ME and CP of the diets, in both treatments, could affect the total N: DM (g Mcal-1) in the intake. A better ratio of 0.35 of difference was observed in the silage treatment. This also caused a lower total N ratio: ME of the contribution, and could affect the conversion of the ME and CP, which was observed in the control treatment, and could have a direct impact on the obtained ADG.
These results confirm that in order to achieve daily gains more than 700 g with grass grazing variants associated with herbaceous legumes and nocturnal enclosure, the nutritional balance of ME and CP with a higher supplementation level should be considered, which would allow a higher energy-protein synchronization and a higher productive response. Other factors that support the supplementation are the short time of grazing that the animals have and the energy expenditure in the search of grass during the dry season, where the growth of tropical grasses was affected and the availability of grasses was reduced (Iraola et al. 2016b). However, it is necessary to continue other studies to deepen the nutritional aspects of different silages, which can increase the nutritional quality and achieve a greater productive response in animals, so that Cuban commercial livestock can benefit.
It is concluded that the animals which intake silage of CT-115, moringa, sweet potato and VITAFERT® showed a favorable productive performance during the evaluated period, with average daily gain of 703 g.
