Nutritional evaluation of sugarcane treated with calcium oxide at different times of exposure to cattle / Avaliação nutricional da cana-de-açúcar acrescida de óxido de cálcio em diferentes tempos de amazenamento para bovinos

Douglas dos Santos Pina

Were performed 4 experiments aiming evaluate the chemical composition and in vitro and in situ digestive kinetics of sugarcane treated with calcium oxide at different exposure times under nutrients intake and digestibility, performance, and ruminal parameters of Nellore heifers. The first experiment aimed to evaluate the effects of levels of inclusion and exposing duration of sugarcane to calcium oxide on the digestive parameters and performance of Nellore heifers. In addition, titanium dioxide (Ti) and chromium oxide (Cr) were compared as external markers to estimate the concentrate intake and digestibility of all nutrients. Thirty Nellore heifers with mean body weight of 285 31 kg and age of 24 months were fed in 6 pens (50 m2 approximately) containing 5 animals in each pen (feeding group). The treatments were allocated in a factorial arrangement 3 x 2, containing three levels of calcium oxide (0; 0.5 and 1.0 in the sugarcane fresh matter) and two levels of exposing duration (0 and 3 days) of the sugarcane to the calcium oxide. The trial was carrying out in 3 periods of 28 days after 14 days of adaptation. Mean comparisons were performed by orthogonal contrast and the t test. There were no effects (P >0.05) of calcium oxide exposing duration on the intake of DM, OM, CP and TDN, but, it affected (P <0.05) the intake of EE, NDFcp, and NFC. The levels of calcium oxide decreased linearly (P<0.05) the intake of DM, OM, CP and TDN. However, no effects were found (P >0.05) for markers (titanium and chromium) or interactions among treatments on the intake of nutrients. Significant interactions were observed between the calcium oxide exposing duration and levels on the total tract apparent digestibility of DM, OM, CP, NDFcp and TDN. As exposing duration increased from 0 to 3 days, there was a positive effect on the total tract apparent digestibility coefficient for DM, OM, CP, NDF and TDN within the calcium oxide levels of 0.5 and 1.0%. According to the sugarcane hydrolysis with calcium oxide after three days of exposing time results on improvement on the digestibility of some nutrients but decreased the TDN intake and consequently the animal performance, the use of sugarcane treated with calcium oxide is not recommended. It is also concluded that the external markers Ti and Cr produced similar estimative of intake and total tract apparent digestibility to all nutrients to cattle group feeding, and that 3 days of sugarcane exposing time with 0% of calcium oxide do not affect the Nellore Heifers performance. The second experiment was conducted to evaluate the effect of calcium oxide inclusion levels and exposition time on sugarcane base diets under the partial or total tract digestibility, ruminal parameters and nutrient intakes. The titanium dioxide and chromium oxide also were evaluated as a marker to estimate the fecal (FDMF) and abomasal (ADMF) dry matter flux. Six Nellore heifers with mean body weight at 250 19 kg rumen and abomasum cannulated were allocated in 6 × 6 Incomplete Latin Square design fitted by carryover effect. The trial was carrying out in 4 periods each period had 12 days, such 7 days for dietary adaptation and 5 days to sample colleting. The treatments were allocated in a factorial arrangement 3 x 2, containing three levels of calcium oxide (0; 0.5 and 1.0 in the sugarcane fresh matter) and two levels of exposing duration (0 and 3 days) of the sugarcane to the calcium oxide. There were not effects (P>0.05) of calcium oxide exposing time neither interactions between treatments (P>0.05) on the intake of DM, OM, CP, EE, NDF and NFC. However, the levels of calcium oxide inclusion linearly affected (P<0.05) the intake of DM (kg/ day or % BW), OM and NFC, but did not affect (P>0.05) the intake of CP, EE and NDF. The calcium oxide exposing time decreased (P<0.05) the total tract apparent digestibility of DM, OM and NDF. However, the ruminal apparent digestibilities of all nutrients were not affecting by the calcium oxide exposing time. The level of calcium oxide inclusion increased (P<0.05) the intake of TDN (kg/ day). Nevertheless, any effects (P>0.05) on the digestibility of all nutrients were observed. The markers yielded similar (P>0.05) estimates to ruminal and total tract apparent digestibility of all nutrients. The ruminal pH was affected by treatments (P<0.01) and interactions between treatments (P<0.05) were observed. On the other hand, the ruminal NH3-N concentration was affected only by the time over sampling (P<0.001). In conclusion, the addition of calcium oxide did not have effect on the sugar cane preservation, but had a positively influence on the intake of DM, OM and TDN by the animals. The markers produced similar estimative to total tract and ruminal apparent digestibility of all nutrients. The third experiment was performed to evaluate the effect of calcium oxide inclusion level (0, 0.5 and 1.0% fresh matter of sugarcane) and the exposing time (0 or 3 days) under sugarcane based diets on the microbial protein (MCP) synthesis and efficiency of synthesis using the data set obtained at two previous experiment. The urinary purine derivatives excretion (UPD) obtained through urinary spot sampling or abomasum purine bases determined using titanium dioxide (PBTi) or chromic oxide (PBCr) as a maker to estimate the abomasum DM flux, were used to determine the MCP synthesis and efficiency of synthesis. In the first, 6 Nellore heifers with mean body weight of 250 19 kg, ruminally and abomasally cannulated, were allocated in one uncompleted Latin Square design fitted to carry-over effects, constituted by 6 treatments and 4 periods. In the second, 30 Nellore heifers with mean body weight of 315 37 kg were fed in 6 pens (50 m2 approximately). The experiment was carried out in three periods of 28 days, after 12 days of adaptation. The treatments were allocated in a 3 x 2 factorial arrangement and the means comparisons were performed by orthogonal contrasts. The abomasum sampling were performed in intervals of 22 hours during 5 consecutive days, rather than urinary spot samples were take 4 hours after feeding. The amount of MCP ruminally synthesized was not affect (P>0.05) by the calcium oxide exposing time (0 or 3 days) or inclusion level (0, 0.5 and 1.0% fresh matter of sugarcane) in both experiments. The microbial markers yielded similar (P>0.05) estimates of synthesis or efficiency of synthesis of MCP. Therefore, we concluded that all markers were adequate to estimate the MCP synthesis and efficiency of synthesis. And the urinary purine derivatives excretion obtained through the urinary spot samples are as efficient as the methods based on the purine bases in the abomasum to determine the ruminal microbial synthesis and efficiency of synthesis. The fourth experiment was carried out to evaluate the effects of 3 inclusion levels of calcium oxide (0, 5, and 10 g/kg of sugarcane fresh matter) and 4 exposure times (0, 24, 48, and 72 h) of sugarcane to calcium oxide on the chemical composition and digestive kinetic parameters of sugarcane using in vitro and in situ techniques. The treatments were arranged in a 3 by 4 factorial design. Freshly-cut sugarcane (whole plant) was treated with calcium oxide and separated into twelve piles inside a barn to prevent direct exposure to sunlight, rain, and wind. Every day, before and after animal feeding, the calcium oxide was proportionally hand-mixed with approximately 150 kg of freshly-cut sugarcane to make up the dietary treatments. The inferior (Ti) and superior (Ts) temperature and pH of the treated sugarcane piles were measured immediately before and after sampling. The ether extract (EE) and DM were not affected (P >0.05) by either exposure time or inclusion level. However, CP increased linearly (P = 0.01) and OM decreased linearly (P <0.0001) as the exposure time and calcium oxide inclusion level increased. Interactions between inclusion level and exposure time on DM, OM, CP, EE, Ti, and Ts were not observed. However, significant interactions were detected for non-fiber carbohydrate (NFC), neutral detergent fiber (NDF), and pH. Quadratic effects of exposure time on the Ti [Ti = 24.5297 (1.8258) + 1.1874 (0.1241)×T 0.0116 (0.0017)×T2; R2= 82.3; RMSE= 5.612] and Ts [Ts = 24.1717 (1.9307) + 1.2065 (0.1292)×T 0.0119 (0.0017)×T2; R2= 80.7; RMSE= 5.942] were observed. The maximum temperature was reached with approximately 51 h of exposure time. Calcium oxide affected the insoluble potentially digestible fraction of sugarcane DM and NDF (P = 0.001 and P = 0.001, respectively), and the undegradable fraction of sugarcane NDF (P = 0.001). Interactions between inclusion level and exposure time on soluble and undegradable fractions of sugarcane DM (P = 0.0001 and P = 0.01, respectively) were found. However, no interactions (P >0.27) were found between inclusion level and exposure time on NDF digestive kinetic parameters. The fractional digestion rate (kd) of sugarcane DM and NDF was not influenced by treatments (P >0.05). The mean values of kd for sugarcane DM and NDF were 0.0235 and 0.0215 h-1, respectively. The gas production kinetics parameters were not affected (P >0.05) by treatments. In summary, the inclusion of calcium oxide improved the in situ potentially digestible fraction of sugarcane DM and NDF; however, it did not influence the fractional digestion rate. No effects were observed on the in vitro digestive kinetic parameters.

Nutritional evaluation of sugarcane treated with calcium oxide at different times of exposure to cattle / Avaliação nutricional da cana-de-açúcar acrescida de óxido de cálcio em diferentes tempos de amazenamento para bovinos

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