Consumo e produção de leite em vacas alimentadas com cana de açúcar e níveis de óleo de soja
Laís Pereira Rocha1, Ricardo Marostegan de Paula2, João Paulo Pacheco Rodrigues3, Luciana Navajas Rennó4, Marcos Inácio Marcondes5, Andreia Ferreira Machado6, Ariane Silveira e Silva7, Vanessa do Carmo Eleto Hamade8
1 - Universidade Federal de Viçosa
2 - Universidade Federal de Viçosa
3 - Universidade Federal de Viçosa
4 - Universidade Federal de Viçosa
5 - Universidade Federal de Viçosa
6 - Universidade Federal de Viçosa
7 - Universidade Federal de Viçosa
8 - Universidade Federal de Viçosa
2 - Universidade Federal de Viçosa
3 - Universidade Federal de Viçosa
4 - Universidade Federal de Viçosa
5 - Universidade Federal de Viçosa
6 - Universidade Federal de Viçosa
7 - Universidade Federal de Viçosa
8 - Universidade Federal de Viçosa
RESUMO -
A cana de açúcar é uma importante forragem para vacas leiteiras em países tropicais. Contudo, estudos que avaliam a suplementação de gordura como uma estratégia para aumentar a ingestão de energia usando esta forragem são escassos. Oito vacas holandesas fistuladas no rúmen em média lactação (peso corporal=574±19.1 kg e 122±6.9 dias em lactação), produzindo 22.5±1.22 kg/d de leite foram distribuídas em quadrados latino 4 × 4 replicados. O período experimental durou 21 dias, sendo: 14 dias para adaptação, seguido de um período de amostragem de 15 a 21 dias. As dietas foram formuladas com concentrações crescentes de SBO (% de matéria seca (DM)): controle (0%), baixa (LSBO, 1,57%), média (MSBO, 4,43%) e alta (HSBO, 7,34%). A inclusão de SBO a 7,34% DM diminuiu a ingestão de DM e a produção de leite. A suplementação com óleo de soja em 1,57% DM demonstrou ser uma concentração segura. No entanto, nenhuma das concentrações de SBO avaliadas aumentou a ingestão de energia e o desempenho.
Palavras-chave: óleo de soja, cana-de-açúcar, suplementação
Intake and milk production in cows fed sugarcane and levels of soybean oil
ABSTRACT - Sugarcane is an important forage for dairy cows in tropical countries. However, studies evaluating fat supplementation as a strategy to increase energy intake using this forage are scarce. Eight rumen-cannulated multiparous Holstein cows in mid-lactation (body weight = 574 ± 19.1 kg and 122 ± 6.9 days in milk), averaging 22.5 ± 1.22 kg/d of milk were assigned to replicated 4 × 4 Latin squares. The experimental period lasted 21 d, being: 14 d for adaptation, followed by a sampling period from d 15 to 21. The diets were formulated with increasing concentrations of SBO (% of dry matter (DM)): control (0%), low (LSBO; 1.57%), medium (MSBO; 4.43%) and high (HSBO; 7.34%). We observed that SBO inclusion at 7.34% DM decreased DM intake and milk production. Soybean oil supplementation at 1.57% DM proved to be a safe concentration. However, none of the evaluated SBO concentrations increased energy intake and performance.Keywords: soybean oil, sugarcane, supplementation
Introdução
Sugarcane is a forage frequently used as the main source of fiber for cattle in tropical environments. Due to its high indigestible fiber content, it is associated with a low dry matter intake (DMI) and, consequently, it needs more concentrate, leading to high levels of non-fibrous carbohydrates (NFC) in the diet. Supplementation with soybean oil (SBO) may be an alternative to increase energy intake and reduce NFC levels in the diet. We hypothesized that SBO supplementation would increase energy intake and milk production in cows fed high concentrate diets with sugarcane. Based on this hypothesis, our objective was to quantify the productive responses of dairy cows fed different levels of SBO in high concentrate diets with sugarcane as the main forage.Revisão Bibliográfica
Sugarcane is a forage commonly fed to cattle in tropical environments and often used as the main dietary fiber source. It has excellent feeding potential for dairy cows because of its high productivity and wide harvesting window (Daniel et al., 2014). However, its use for high yielding dairy cows is usually associated with feeding high amounts of concentrates, leading to a high proportion of NFC in the diet (Oliveira et al., 2011). Furthermore, sugarcane fiber contains a high proportion of indigestible neutral detergent fiber (iNDF) and low potentially digestible neutral detergent fiber (pdNDF) at about 25 and 27% DM, respectively (Daniel et al., 2014) that is associated with a low DMI. Consequently, more concentrate is needed compared to corn silage-based diets (Oliveira et al., 2011). Under these feeding situations, fat supplementation can be an alternative to increasing energy intake while reducing dietary NFC concentration. However, the optimal inclusion rate of added fat, in diets with sugarcane as the sole forage, needs to be defined. Previous research has indicated that the forage source can determine the response of fat supplementation on fiber digestion (Ueda et al., 2003). For instance, adding rapeseed oil at 6.6% DM, Salem et al. (1993) observed a lower reduction in grass hay NDF digestibility when compared with corn silage. Incorporating linseed oil at 4% DM, Benchaar et al. (2015) observed a reduction in NDF digestibility in corn silage diets, without effects in red clover silage diets. Bateman and Jenkins (1998) included soybean oil (SBO) until 8% DM in diets with Bermuda grass hay and did not observe any effects on fiber digestibility. Data with tropical forages are scarce and, in such instances, the diets are formulated based on the recommendations of maximum supplementary fat levels at 4 - 5% DM (Lewis et al., 1999) or 6 - 7% ether extract (EE) in the diet DM (NRC, 2001) to minimize deleterious effects on fiber digestibility.Materiais e Métodos
Eight, rumen-cannulated, multiparous, Holstein cows (574 ± 19.1 kg of BW and 122 ± 6.9 DIM) were used. The milk production of the cows was 22.5 ± 1.22 kg/d at the beginning of the study. Cows were grouped in a replicated 4 × 4 Latin square design balanced for residual effects. The experimental period lasted 21d, comprising of 14d for adaptation followed by a sampling period from d15 to 21. Four diets were formulated with increasing concentrations of SBO (%DM): control (0%), low (LSBO; 1.57%), medium (MSBO; 4.43%) and high (HSBO; 7.34%) (Table 1). The cows were milked twice daily and fed diets as a TMR individually after each milking session. Intake was calculated by manually weighing the offered TMR and collected refusals. Diets were offered on an ad libitum basis. Samples of sugarcane and diet refusals were taken from d15 to 19 of each experimental period. Milk production was measured and samples were collected from d16 to 18 of each experimental period. Samples were analyzed according to AOAC (2005). Total tract digestibility was estimated by collecting eight spot fecal samples at 9 h intervals starting at 09:00 h on d 16. To estimate fecal excretion iNDF was used as marker. The digestible organic matter intake (dOMI) was estimated by multiplying the OM intake by the OM digestibility. Digestible energy (DE) intake was estimated according to NRC (2001). The energy corrected milk (ECM) production was calculated as described by Sjauna et al. (1990). The statistical analysis was performed using the SAS MIXED procedure (SAS Institute Inc., Cary, NC, version 9.3). The significance was declared at P < 0.05 and P-values from 0.05-0.10 were considered to indicate a trend.Resultados e Discussão
Soybean oil inclusion quadratically decreased DMI, dOM and DE intake (P < 0.01). The HSBO diet corresponded to the lowest DE intake. SBO quadratically affected the milk and ECM production (P < 0.01 and P = 0.04); both decreasing slightly from the LSBO to MSBO diet, then decreasing considerably in the HSBO diet. Increasing the SBO decrease linearly milk fat concentration and yield (P = 0.04 and P < 0.01). Milk protein concentration had a quadratic trend (P = 0.06), with the lowest concentration (3.05%) in the MSBO diet (Table 2). SBO supplementation did not affect (P > 0.10) the concentration of milk urea nitrogen (MUN) and feed efficiency. As previously reported, SBO inclusion up to 8% DM negatively affects the DMI (Bateman and Jenkins, 1998). The uptake of unsaturated fatty acids (UFA) in the gut can decrease the DMI, either by increasing the hepatic oxidation or the activity of proximal gut peptides, like cholecystokinin (Choi and Palmquist, 1996; Allen et al., 2009). The quadratic decrease in DMI, dOM and DE intake indicates that the adverse effects of SBO on intake are greatest between the MSBO and HSBO diets. The high standard error of the mean (SEM) in DMI, milk production and ECM can be a consequence of the greater variation between cows fed the HSBO diet. Huhtanen and Nousiainen (2012) observed that increments in diet fat concentration up to 3.5% DM, can improve ECM production by increasing energy intake. However, in our study, the increase in dietary fat did not increase ECM, even at the LSBO diet. Also, although not statistically significant, the feed efficiency decreased numerically. The reduction in milk protein up to the MSBO diet was probably associated with the reduction in nitrogen intake. A reduction in milk protein as a consequence of increased dietary fat is mainly associated with a reduction in DM and nitrogen intake. However, the increase in milk protein from the MSBO to HSBO diet may be a consequence of the reduction in milk production.Conclusões
We concluded that the SBO supplementation at up to 4.43% of the diet DM in sugarcane-based diets with high levels of concentrate, do not improve energy intake and feed efficiency. Soybean oil supplemented at 7.34% of the diet DM had a greater adverse effect on energy intake and milk production than SBO supplemented at up to 4.43% of the diet DM. We concluded that the SBO supplementation at up to 4.43% of the diet DM in sugarcane-based diets with high levels of concentrate, do not improve energy intake and feed efficiency. Soybean oil supplemented at 7.34% of the diet DM had a greater adverse effect on energy intake and milk production than SBO supplemented at up to 4.43% of the diet DM.Gráficos e Tabelas
