Abstract

The objective of this study was to evaluate the effects of different sealing strategies on aerobic stability and feed value of corn silage supplied to finishing lambs. The treatments were set up according to the silo sealing strategy: BP (black polyethylene film), BP + Bagasse (black polyethylene film + sugarcane bagasse) and BP + Silostop (Silostop® Orange oxygen barrier film + black polyethylene film). Six lambs per treatment were used, totaling 18 animals in an experimental period of 63 days. The silage from LP treatment presented the highest aerobic stability, however with lower dry matter digestibility coefficients. No significant differences were detected among treatments for intake and performance of lambs. But for final body weight, weight gain, daily average gain, feed efficiency and dry matter intake, the best results, in absolute value, were found for lambs fed with silage from LP + Bagasse treatment. The silage sealed exclusively with black polyethylene film showed greater aerobic stability. The different sealing strategies used in this experiment did not influence the performance of finishing Dorper x Santa Inês lambs.

Keywords:
aerobic deterioration; carcass; digestibility; weight gain

Resumo

Objetivou-se avaliar os efeitos de differentes estratégias de vedação sobre a estabilidade aeróbia e o valor alimentício da silagem de milho fornecida para cordeiros em terminação. Os tratamentos foram definidos de acordo com a estratégia de vedação do silo: LP (lona preta de polietileno), LP + Bagaço (lona preta de polietileno + bagaço de cana) e LP + Silostop (lona preta de polietileno + filme de barreira de oxigênio Silostop® Orange). Foram utilizados seis cordeiros por tratamento, totalizando 18 animais, em um período experimental de 63 dias. A silagem do tratamento LP apresentou maior estabilidade aeróbia, porém proporcionou menor coeficiente de digestibilidade da matéria seca. Não foi observada diferença significativa entre os tratamentos para o consumo e desempenho dos cordeiros. Todavia, para o peso corporal final, ganho de peso, ganho médio diário, eficiência alimentar e consumo de matéria seca, os melhores resultados, em valor absoluto, foram encontrados para os cordeiros alimentados com dieta à base da silagem coberta com LP + Bagaço. A silagem vedada exclusivamente com a lona preta de polietileno apresentou maior estabilidade aeróbia. As diferentes estratégias de vedação utilizadas nesse experimento não influenciaram o desempenho de cordeiros Dorper x Santa Inês em terminação.

Palavras-chave:
carcaça; deterioração aeróbia; digestibilidade; ganho de peso

1. Introduction

Whole-plant corn silage has been widely used in ruminant feeding,(¹1 Liu Y, Wang G, Wu H, Meng Q, Khan MZ, Zhou Z. Effect of hybrid type on fermentation and nutritional parameters of whole plant corn silage. Animals. 2021;11(1587):1-9. Available from: https://doi.org/10.3390/ani11061587
https://doi.org/10.3390/ani11061587... ) mainly because it provides a high content of total digestible nutrients and high voluntary intake, consisting of a good option for roughage feed for finishing lambs.(²2 Pereira OG, Obeid JÁ, Gomide JA, Queiroz AC. Produtividade de uma variedade de milho (Zea mays L.) e de três variedades de sorgo (Shorgum bicolor (L.) Moench) e o valor nutritivo de suas silagens. Revista da Sociedade Brasileira de Zootecnia. 1993; 22 (1):31-38.) However, processes that lead to nutrient losses may occur in the most diverse magnitudes during the forage fermentation period, and the degree of anaerobiosis that occurs inside the silo is the factor that has a direct influence on silage preservation.(³3 Borreani G, Dolci P, Tabacco E, Cocolin L. Aerobic deterioration stimulates outgrowth of spore-forming Paenibacillus in corn silage stored under oxygen-barrier or polyethylene films. Journal of Dairy Science. 2013; 96(8):5206- 5216. Available from: http://dx.doi.org/10.3168/jds.2013-6649
http://dx.doi.org/10.3168/jds.2013-6649... , ⁴4 Tabacco E, Righi F, QuarantelliA, Borreani G. Dry matter and nutritional losses during aerobic deterioration of corn and sorghum silages as influenced by different lactic acid bacteria inocula. Journal of Dairy Science. 2011; 94(3):1409–1419. Available from: https://doi.org/10.3168/jds.2010-3538
https://doi.org/10.3168/jds.2010-3538... ) The presence of oxygen favors the development of undesirable microorganisms, resulting in nutrient losses, a decrease in hygienic quality, a reduction in the silage feed value,(⁵5 Lindgren S, Pettersson K, Jonsson A, Lingvall P, Kaspersson A. Silage inoculation. Selected strains, temperature, wilting and practical application [Pediococcus acidilactici, Lactobacillus plantarum, Streptococcus faecium]. Swedish Journal of Agricultural. 1985; 15(1): 9-18., ⁶6 Borreani G, Tabacco E, Schmidt RJ, Holmes BJ, Muck RE. Silage review: Factors affecting dry matter and quality losses in silages. Journal of Dairy Science. 2018; 101: 3952-3979. Available from: https://doi.org/10.3168/jds.2017-13837
https://doi.org/10.3168/jds.2017-13837... ) and a reduction of intake by animals.(⁷7 Pahlow G, Muck RE, Driehuis F, Oude Elferink SJWH, Spoelstra SF. Microbiology of ensiling. In: Buxton DR, Muck RE, Harrison JH. Silage science and technology. 1.ed. Madison: American Society of Agronomy. 2003; 31-94. Available from: https://doi.org/10.2134/agronmonogr42.c2
https://doi.org/10.2134/agronmonogr42.c2... )

In this context, the plastic film used to seal silos makes a significant contribution, as it is used to reduce the penetration of air from the external environment into the silo. Traditionally, polyethylene film has been the most used material for sealing horizontal silos,(⁸8 Amaral RC, Santos MC, Daniel JLP, Sá Neto A, Bispo ÁW, Cabezas-Garcia EH, Bernardes TF, Nussio LG. The influence of covering methods on the nutritive value of corn silage for lactating dairy cows. Revista Brasileira de Zootecnia. 2014; 43(9): 471–478. Available from: https://doi.org/10.1590/S151635982014000900003
https://doi.org/10.1590/S151635982014000... ) mainly due to its low cost and mechanical characteristics.(⁹9 Borreani G, Tabacco E. Low permeability to oxygen of a new barrier film prevents butyric acid bacteria spore formation in farm corn silage. Journal of Dairy Science. 2008, 91(11): 4272-4281. Available from: https://doi.org/10.3168/jds.2008-1151
https://doi.org/10.3168/jds.2008-1151... ) However, the polyethylene polymer is not a material totally impermeable to oxygen diffusion, and, therefore, it does not completely prevent the entrance of oxygen into the silo.(¹⁰10 Bernardes TF. Advances in Silage Sealing. In: Advances in Silage Production and Utilization. 2016; 1(cap. 3): 53-62. Available from: http://dx.doi.org/10.5772/65445
http://dx.doi.org/10.5772/65445... , ¹¹11 Borreani G, Piano S, Tabacco E. Aerobic stability of maize silage stored under plastic films with different oxygen permeability. Journal of the Science of Food and Agriculture. 2014; 94(13): 2684-2690. Available from: https://doi.org/10.1002/jsfa.6609
https://doi.org/10.1002/jsfa.6609... ) Thus, even with good sealing conditions, the use of polyethylene films may not prevent the penetration of oxygen into the peripheral areas of the silo, and these regions may be exposed to deterioration.

Therefore, alternatives have been sought in recent years to contain losses during silage storage through the use of plastic films with lower oxygen permeability.(¹²12 Borreani G, Tabacco E. Charter 9: Plastics in Animal Production. In: A Guide to the Manufacture, Performance, and Potential of Plastics in Agriculture. Elsevier. 2017; 145–185. Available from: https://doi.org/10.1016/B978-0-08-1021705.00009-9
https://doi.org/10.1016/B978-0-08-102170... ) Amaral et al.(⁸8 Amaral RC, Santos MC, Daniel JLP, Sá Neto A, Bispo ÁW, Cabezas-Garcia EH, Bernardes TF, Nussio LG. The influence of covering methods on the nutritive value of corn silage for lactating dairy cows. Revista Brasileira de Zootecnia. 2014; 43(9): 471–478. Available from: https://doi.org/10.1590/S151635982014000900003
https://doi.org/10.1590/S151635982014000... ) point out the importance of plastic film quality but its protection with some other material can bring benefits, reducing the incidence of sunlight and gas exchange with the environment, in addition to causing adhesion between the film and ensiled mass, making it difficult for oxygen to move through the mass.

However, although several studies have been developed(⁹9 Borreani G, Tabacco E. Low permeability to oxygen of a new barrier film prevents butyric acid bacteria spore formation in farm corn silage. Journal of Dairy Science. 2008, 91(11): 4272-4281. Available from: https://doi.org/10.3168/jds.2008-1151
https://doi.org/10.3168/jds.2008-1151... , ¹¹11 Borreani G, Piano S, Tabacco E. Aerobic stability of maize silage stored under plastic films with different oxygen permeability. Journal of the Science of Food and Agriculture. 2014; 94(13): 2684-2690. Available from: https://doi.org/10.1002/jsfa.6609
https://doi.org/10.1002/jsfa.6609... , ¹³13 Cristo FB, Neumann M, Sidor FS, Seller MEC, Plodoviski DC, Carneiro EL, Cesar PVP, Savoldi LS, Costa L. Efeitos de differentes filmes plásticos dupla face sobre características químico-fermentativas da silagem de milho. Ciência Animal Brasileira. 2021; 22(e-66770). Available from: https://doi.org/10.1590/1809-6891v22e-66770
https://doi.org/10.1590/1809-6891v22e-66... ) aiming to evaluate different plastic films in the sealing stage, few evaluations have been directed to the effects generated in the performance of animals fed these silages. Most studies aim to evaluate the qualitative and quantitative losses of silages in terms of storage time. In this context, this study was developed to evaluate the effects of different sealing strategies on silage aerobic stability and the performance of finishing lambs.

2. Material and methods

The experiment was conducted on the Experimental Farm of Iguatemi (FEI) (23°25′38″ South; 51°56′15″ West) and the Laboratory of Food Analysis and Animal Nutrition (LANA), both belonging to the State University of Maringá, Maringá, Paraná, Brazil. The corn crop (hybrid DKB 177) was sown on FEI and ensiled when it reached 29% dry matter, on average. The plants were harvested with a JF92 Z10 forage harvester set to cut with a theoretical particle size of 10 mm. The forage was compacted in a trench-type horizontal silo, with dimensions of 4.85 m wide x 18 m long and 1.6 m deep (volume of 139.68 m³). Immediately after the supply and compaction stages, the silo was divided transversely into three equal parts (46.56 m³) and three different sealing strategies were used, consisting of the following treatments:

1. 200-µm black polyethylene film (BP).

2. 200-µm black polyethylene film with the addition of a ~10 cm high layer of sugarcane bagasse along its entire length (BP + Bagasse).

3. 45-µm oxygen barrier film (Silostop® Orange), covered with a 200-µm black polyethylene film (BP + Silostop).

The silo was opened after 200 days of storage and the upper stratum material (depth of 0–50 cm) from the different sealing strategies was relocated into plastic barrel silos with a capacity of approximately 150 L (seven barrels for each treatment). The silage was compacted in the silos by human trampling to reach a density of approximately 600 kg/m³. Subsequently, the silos were sealed using films and adhesive tapes and remained in a covered shed for 20 days. After this procedure, the silage from the plastic barrels began to be used to feed the finishing lambs.

Animal performance was evaluated using 18 Dorper x Santa Inês crossbred lambs (12 males and 6 females) with an average initial live weight (ILW) of 21.4 kg (±2.27 kg), distributed in complete blocks according to ILW and sex (n = 6 animals/treatment). Thus, 4 blocks were composed of males and 2 blocks were composed of females, and the animals of each block presented homogeneous ILW. The animals were housed in individual suspended covered stalls (0.60 x 0.90 m) with a slatted foor and provided with individual feeding and drinking troughs. The use of animals in the research complied with the specifications and precautions imposed by the Council for Ethics and Animal Protection (CEUA/UEM No. 4411180917).

The animals remained in the experimental period for 63 days until they reached an average slaughter weight of ~35 kg. Diets were composed of corn silage (CS), rehydrated corn + soybean (20%) high-moisture grain silage (CSHMGS), rehydrated corn grain silage (CHMGS), and mineral supplement (Table 1), formulated according to NRC (2007)(¹⁴14 National Research Council - NRC. Nutrient Requirements Of Small Ruminants: Sheep, Goats, Cervids and New World Camelids. Washington, DC: The National Academies Press. 2007; 384 p. Available from: https://doi.org/10.17226/11654
https://doi.org/10.17226/11654... ) for a daily average weight gain of 200 g, considering a roughage to concentrate ratio of 40:60, based on dry matter (DM) (Table 2).

The diet was provided twice a day, at 8:00 am and 4:00 pm, and leftovers were collected before the morning feeding to quantify the material consumed individually by the animals. The amount of diet provided was calculated to allow approximately 10% leftovers, and water was provided ad libitum. Weekly, samples of feed and leftovers were collected and stored at –20 °C for further chemical analyses. The animals were weighed at the beginning of the experimental period, every 21 days, and on the day of slaughter, always preceded by a solid diet fasting for 16 hours. Weight gain (WG) assessment was calculated as the difference between ILW and final live weight (FLW); the daily average gain was obtained by the difference between FLW and ILW divided by the number of days of the experimental period; and feeding efficiency was obtained through the relationship between the WG and DM intake.

The animals were slaughtered in accordance with the rules of the Regulation of Industrial and Sanitary Inspection for Products of Animal Origin– RIISPOA.(¹⁵15 Brasil - Ministério da Agricultura. R.I.I.S.P.O.A. Regulamento da Inspeção Industrial e Sanitária de Produtos de Origem Animal (Aprovado pelo decreto nº 30690, de 20.03.52, alterado pelo decreto nº 1255, de 25.06.52). Brasília. 1980; 66p.) After evisceration, the hot carcass was weighed to obtain the hot carcass yield (HCY), where HCY = ((hot carcass weight/live weight at slaughter) x100). The carcasses were then refrigerated at a temperature of 4 °C for 24 hours. Subsequently, they were weighed again to determine the cold carcass yield (CCY), where CCY = ((cold carcass weight/live weight at slaughter) x 100). Feces were collected from the 29th to 31st experimental days directly from the rectal ampulla of the animals to determine the in vivo digestibility of nutrients, according to Huhtanen et al.(¹⁶16 Huhtanen P, Kaustell K, Jaakkola S. The use of internal markers to predict total digestibility and duodenal fow of nutrients in cattle given six different diets. Animal Feed Science and Technology. 1994; 48: 211-227. Available from: https://doi.org/10.1016/0377-8401(94)90173-2
https://doi.org/10.1016/0377-8401(94)901... ) In addition, samples of feed and leftovers were collected and stored at –20 °C for further laboratory analysis. Fecal output estimation was performed using indigestible neutral detergent fiber (iNDF) as an internal indicator.(¹⁷17 Casalli AO, Detmann E, Filho SCV, Pereira JC, Henriques LT, Freitas SG, Paulino MF. Infuência do tempo de incubação e do tamanho de partículas sobre os teores de compostos indigestíveis em alimentos e fezes bovinas obtidos por procedimentos in situ. Revista Brasileira de Zootecnia. 2008; 37(2): 335-342. Available from: https://doi.org/10.1590/S151635982008000200021
https://doi.org/10.1590/S151635982008000... )

At the end of the experiment, all samples (feed, leftovers, and feces) were pre-dried in a forced-air circulation oven at 55 °C for approximately 72 hours and then ground in a Willey mill with a 1-mm opening sieve. Subsequently, the contents of dry matter (DM), mineral matter (MM), crude protein (CP), and ether extract (EE) were determined according to AOAC.(¹⁸18 Association Of Official Analytical Chemists – AOAC. Official methods of analysis. 15. ed. Arlington: AOAC International, 1990; 1117p.) Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined according to Van Soest et al.(¹⁹19 Van Soest PJ, Robertson JB, Lewis BA. Methods for Dietary Fiber, Neutral Detergent Fiber, and Nonstarch Polysaccharides in Relation to Animal Nutrition. Journal of Dairy Science. 1991; 74: 3583-3597. DOI: 10.3168/jds.S0022-0302(91)78551-2
https://doi.org/10.3168/jds.S0022-0302(9... ) and total digestible nutrients (TDN) were estimated using the equation TDN = 88.9 – (0.779 x %ADF).(²⁰20 Patterson T, Klopfenstein TJ, Milton T, Brink DR. Evaluation of the 1996 beef cattle NRC model predictions of intake and gain for calves fed low or medium energy density diets. Nebraska Beef Cattle Reports: 2000; 76: 26-29. Available from: https://digitalcommons.unl.edu/animalscinbcr
https://digitalcommons.unl.edu/animalsci... ) Total carbohydrates (TC) were calculated according to the methodology described by Snifen et al.,(²¹21 Snifen CJ, O’Connor JD, Van Soest PJ, Fox DG, Russel JB. A net carbohydrate and protein system for evaluating cattle diets: II. Carbohydrate and protein availability. Journal of Animal Science. 1992; 70(11): 3562-3577. Available from: https://doi.org/10.2527/1992.70113562x
https://doi.org/10.2527/1992.70113562x... ) in which TC = 100 – (%CP + %EE + %MM), and non-fibrous carbohydrates (NFC) were obtained by subtracting NDF (corrected for its MM and PB content) – TC. The equation proposed by Merchen(²²22 Merchen NR. Digestión, absorción y excreción em los rumiantes. In: Church DC. El rumiante. Fisiología digestiva y nutrición. Zaragoza: Acríbia, 1988; Cap.9: 191–224.) was used to calculate nutrient digestibility: Digestibility (%) = [(Ni – Nf) / Ni] x 100, where Ni is the ingested nutrient and Nf is the fecal nutrient.

Samples of 2.5 kg of silages were collected from each treatment, with four replications, packed without compaction in plastic buckets without lids, and randomly distributed in a room with controlled temperature (24 °C ± 1 °C) for 144 hours to evaluate some parameters of aerobic stability. Silage temperatures were measured every 15 minutes using data loggers (Novus Tagtemp®) inserted in the center of mass of each bucket. The room temperature was measured using data loggers placed next to the buckets. Samples were collected on the first day of the aerobic stability study to determine lactic acid and ammonia. The lactic acid concentration was determined using the spectrophotometric method (565 nm) of Pryce(²³23 Pryce JD. A modification of Barker-Summerson method for the determination of lactic acid. Analyst. 1969; 94: 1151-1152. Available from: https://doi.org/10.1039/AN9699401151
https://doi.org/10.1039/AN9699401151... ) and ammonia according to Chaney and Marbach. (²⁴24 Chaney AL, Marbach EP. Modified reagents for determination of urea and ammonia. Journal: Clinical Chemistry. 1962; 8(2): 130-132. Available from: https://doi.org/10.1093/clinchem/8.2.130
https://doi.org/10.1093/clinchem/8.2.130... )

The variables assessed during the aerobic stability test were aerobic stability, calculated as the time, in hours, for the silages to present a temperature 2 °C higher than the room temperature after opening the silo;(²⁵25 Jobim CC, Nussio LG, Reis RA, Schmidt P. Avanços metodológicos na avaliação da qualidade da forragem conservada. Revista Brasileira de Zootecnia. 2007; 36 (Supl. Esp.): 101-119. Available from: https://doi.org/10.1590/S151635982007001000013
https://doi.org/10.1590/S151635982007001... ) maximum temperature reached by the mass, in °C; and temperature accumulation in 6 days of aerobic exposure (Σ6d). Another parameter used to evaluate the aerobic stability of silages was pH, through a daily collection of samples from buckets. The readings were performed using a digital pH meter, calibrated with pH 4.0 and 7.0 buffer solutions, with the pH reading being performed via infusion of 10 g of silage sample in 100 mL of distilled water. A complete block design with randomized treatment was used to evaluate animal performance. The experimental data were subjected to analysis of variance and their means compared by the Tukey’s test (α = 0.05), using the PROC MIXED of SAS.(²⁶26 Statistical Analysis Software [SAS]. SAS/STAT User guide, Version 9.4. Cary, NC: SAS Institute Inc. 2013.) The experimental design used in the assessment of aerobic stability was completely randomized and the experimental data were subjected to analysis of variance and their means compared by the Tukey’s test (α = 0.05), using the PROC MIXED of the SAS software.(²⁶26 Statistical Analysis Software [SAS]. SAS/STAT User guide, Version 9.4. Cary, NC: SAS Institute Inc. 2013.)

3. Results and discussion

The silage sealed with BP showed a higher N–NH₃ value (P<0.05), while the silage sealed with BP + Bagasse and BP + Silostop showed similarity between their values. In turn, lactic acid contents were lower in the silage sealed with BP (Table 3).

According to McDonald et al.,(²⁷27 McDonald P. Biochemistry of silage. Marlow: Chalcombe Publication, 1991: 340 p.) poorly preserved silages have N–NH₃ contents higher than 10%. Thus, the values observed in the present study are characteristic of the typical fermentation profile of good-quality corn silages, indicating low proteolytic activity of clostridia. Kung et al.(²⁸28 Kung Junior L, Stokes MR, Lin CJ. Silage additives. In: Buxton DR, Muck RE, Harrison JH. Silage Science and Tecnology. 2003; 42 (Cap.7): 305-360.) pointed out that the desirable fermentation profile does not always avoid losses after opening the silos but increases them in some cases. According to Weinberg and Muck,(²⁹29 Weiberg ZG, Muck RE. New trends and opportunities in the development and use of inoculants for silage. FEMS Microbiology Reviews. 1996; 19(1): 53-68. Available from: https://doi.org/10.1111/j.1574-6976.1996.tb00253.x
https://doi.org/10.1111/j.1574-6976.1996... ) silages that present better fermentation patterns, characterized by high concentration and predominance of lactic acid, as well as the presence of residual sugars, are more affected by aerobic deterioration. The results observed in the present study corroborate that mentioned literature, as silages sealed with BP + Bagasse and BP + Silostop, which showed higher contents of lactic acid, thus providing higher amounts of substrates available for consumption by microorganisms in the aerobic phase, resulted in lower aerobic stability (Table 3).

The silage sealed with BP + Silostop showed a higher maximum temperature (38.10 °C) than the other silages, resulting in a higher temperature accumulation for 144 hours (27.25 °C) (P<0.05), which is an indication of greater microbial activity (Table 3). On the other hand, the silage sealed only with BP showed lower temperature values over the time of aerobic exposure (Figure 1A). The increase in silage temperature is the result of the balance between the rate of heat produced by microbial activity and heat losses by conduction, radiation, evaporation, and convection and is directly related to DM oxidation, which causes losses in the form of carbon dioxide (CO₂).(³⁰30 Hill J.; Leaver JD. Changes in chemical composition and nutritive value of urea treated whole crop wheat during exposure to air. Animal Feed Science and Technology. 2002; 102 (1-4):181-195. Available from: https://doi.org/10.1016/S03778401(02)00258-4
https://doi.org/10.1016/S03778401(02)002... )

Figure 1
Temporal behavior of silages under aerobic conditions regarding temperature (A) and pH (B).

All average pH values were similar to each other (P>0.05) and showed a pH below 4.2 at the beginning of the period of exposure to air regardless of the type of seal used, demonstrating good acidification for corn silage. The silages presented an increase in pH values with the advancement in aerobic exposure time (Figure 1B), probably due to the lactic acid degradation by aerobic microorganisms, especially yeasts, to obtain energy,(³¹31 Woolford MK. The detrimental effects of air on silage. Journal of Applied Bacteriology. 1990; 68 (2): 101-116. Available from: https://doi.org/10.1111/j.1365-2672.1990.tb02554.x
https://doi.org/10.1111/j.1365-2672.1990... ) and the loss of other organic acids by volatilization,(³²32 Amaral RC, Bernardes TF, Siqueira GR, Reis RA. Estabilidade aeróbia de silagens do capim-marandu submetidas a diferentes intensidades de compactação na ensilagem. Revista Brasileira de Zootecnia. 2008; 37(6): 977-983. Available from: https://doi.org/10.1590/S1516-35982008000600004
https://doi.org/10.1590/S1516-3598200800... ) intensifying the silage deterioration process.

Regarding lamb performance (Table 4), the variables were not influenced (P>0.05) by the type of sealing. The similarity between the animal responses can be attributed, among other factors, to the similarity regarding the chemical composition of the experimental diets (Table 2). Thus, the magnitude of changes in the chemical composition of the evaluated silages (Table 1) was not enough to change the lamb performance.

The DAG reached with the three diets was 251 g/day, which is higher than the 200 g/day predicted in the diet formulation. Lambs fed silage from the BP + Bagasse treatment showed a higher DAG of 21 and 17 g/day than lambs fed diets with silage from treatments with BP and BP + Silostop, respectively (Table 4), although there was no statistical difference, which can guarantee a better economic return. This behavior may have been a consequence of the higher DMI by animals in the BP + Bagasse treatment (Table 5) than animals fed silages of the other treatments although without statistical difference.

There was a trend towards lower FE for animals fed silage sealed with BP alone and it can be explained by the lower apparent digestibility coefficients of DM (P<0.05; Table 5), influencing the use of nutrients by the animals. In short, this would be the result of higher nutrient losses in the silage covered only with BP. Likewise, carcass yield (Table 4) was not influenced by the type of sealing on the silages (P>0.05), with mean values of 49.27% for HCY and 48.63% for CCY.

Intake variables were not influenced by experimental diets (P>0.05). However, lambs fed silage sealed with BP + Bagasse tended to intake more of all nutrients (P>0.05; Table 5). DMI is important in the performance of feedlot ruminants, as it is considered a determinant of the supply of nutrients needed to meet the maintenance and weight gain requirements of animals.(³³33 Snifen CJ, Black JR. Nutrient requirement versus supply in dairy cow: Strategies to account for variability. Journal of Dairy Science. 1993; 76(10): 3160-3178. Available from: https://doi.org/10.3168/jds.S0022-0302(93)77655-9
https://doi.org/10.3168/jds.S0022-0302(9... ) According to Mertens,(³⁴34 Mertens DR. Chapter 11: Regulation of Forage Intake. In: Fahey Junior GC, Collins M, Mertens DR, Moser LE. Forage Quality, Evaluation and Utilization. Madison: American Society of Agronomy, 1994; 450-493. Available from: https://doi.org/10.2134/1994.foragequality.c11
https://doi.org/10.2134/1994.foragequali... ) 60 to 90% of differences in animal performance are a function of intake. The present study showed that although there was no significant difference, lambs fed silage sealed with BP + Bagasse had higher absolute values of DMI, FBW, WG, DAG, and FE, corroborating the authors’ assertion.

Regarding the apparent digestibility coefficients of nutrients, only dry matter digestibility coefficient (DMDC) was influenced by the type of seal used in the silages. DMDC was lower (P<0.05; Table 5) when BP was used alone, which may be associated with a higher ADF content and lower NFC content of the silage sealed with BP (Table 1). DMDC was superior for silages sealed with BP associated with bagasse or Silostop® (Table 5), but it was not enough to significantly influence animal performance (Table 4).

4. Conclusion

Silage sealed exclusively with black polyethylene film showed higher aerobic stability. The different sealing strategies used in this experiment did not influence the performance of Dorper x Santa Inês lambs under finishing. Thus, the choice of the best sealing strategy should be based on the production costs incurred at the time of ensiling.

Acknowledgments

The authors would like to thank the Coordination for the Improvement of Higher Education Personnel (CAPES) for granting the scholarship to the first author.

References

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