Effect of the replacement of steam treated sugarcane bagasse by milo upon performance of finishing cattle

Effect of the replacement of steam treated sugarcane bagasse by milo upon performance of finishing cattle

The trial was conducted to determine the effects of substituting milo for steam-treated sugarcane bagasse (STB) on performance of finishing cattle as well as to compare these results with results obtained from similar diets, in which STB was replaced by raw sugarcane bagasse (RSB). The following basal diets were fed : 26% RSB + 47% milo, 38% RSB + 34% milo, 26% STB + 47% milo, 38% STB + 34% milo and 52% STB + 20% milo (dry matter basis). These diets represented the treatments called RB26, RB38, SB26, SB38 and SB52, in the same order. They were completed with: yeast (15%), molasses (6%), cottonseed meal (3%), sodium bicarbonate (0.8%) and minerals (1.7%). There was one more treatment, which half the experimental period was given diet SB52 and the other half diet SB38, named SB52/38. All diets were given to feedlot cattle. Each treatment was given to each of six groups of 10 animals. Treatments SB38 and SB26 resulted in higher daily gain (p<0.05) than treatment RB38. Dry matter intake was higher (p<0.05%) in treatment RB26 than in treatments SB52, SB38, SB26 and RB38. By replacing STB with milo, the daily gain tended to increase, but since dry matter consumption was probably limited by energy intake, those increase were not significant. Comparison data among diets provide clear evidence that the steam treatment improved the sugarcane bagasse utilization.

KEY WORDS: Bagasse, cattle, daily gain, finishing, intake, performance, steam treatment, sugar cane

Several researchers demonstrate that the use of raw sugarcane bagasse (RSB) in ruminant diets is limited if it is expected to achieve good daily gains (Randel 1966, Paccola et al 1977, Burgi 1985). The objective of the steam treatment is to decrease the fibrous portion resistance to ruminal degradation in order to improve its utilization by the animal. The resultant steam treated bagasse (STB) has its usage restricted to farms near the sugar and alcohol factory and the sugar and alcohol factory itself. The use of this unconventional roughage has shown satisfactory results. However, the positive results obtained with STB have been attributed to the higher concentrate intake determined by the higher intake of the diets with STB rather than by the effect of treatment itself. Another remaining answer is what is the worthwhile roughage:concentrate ratio range. In order to attain high levels of production the diets need to contain high energy concentration that is accomplished by the use of large proportions of concentrate. The roughage importance is diminished in this situation, not only for its amount, but also because this type of diet determines low fibre degradation rate. Consequently, there must be a minimum proportion of RSB bellow which the steam treatment is ineffective. The objective of this trial was to determine the effect of the replacement of the STB by milo in order to conclude if there is advantage in steam treating the bagasse among the levels studied. The results complement those on ruminal fermentation and digestibility presented by Medeiros & Machado (1993).

The diets utilized are in Table 1. There was an additional treatment in which half the time the animals were fed diet SB52 and the other half they were fed diet SB38. This treatment was named SB52/38.

Table 1: Composition of the diets (DM basis)

	T r e a t m e n t e s
Ingredients	RB26	SB26	RB38	SB38	SB52

	%
STB	-	26.3	-	38.9	52.5
RSB	26.3	-	38.9	-	-
MILO	47.0	47.0	34.0	34.0	20.0
UREA	0.2	0.2	0.6	0.6	1.0
MOLASSES	6.0	6.0	6.0	6.0	6.0
YEAST	15.0	15.0	15.0	15.O	15.0
COTTON SEED MEAL	3.0	3.0	3.0	3.0	3.0
SODIUM BICARBONATE	0.8	0.8	0.8	0.8	0.8
MINERALS	1.7	1.7	1.7	1.7	1.7

This trial was conducted at the Feedlot Cattle Experimental Facilities, the Sao Martinho sugar and alcohol mill in Pradopolis, Sao Paulo state, Brazil, from July 9 to October 10, 1990. Seventy- two female Nelore breed animals were selected, vaccinated and dewormed. For an adaptation period they were allocated in collective corrals and fed diet SB52 three times a day at 10:00 am, 4:00 pm and 10:00 pm. They were weighted for 3 consecutive days and this procedure was repeated 3 weeks later. The average daily gain (ADG) of each animal was recorded along with the final weight, and used to select 60 animals. The animals were allotted to groups of 10 in order that the ADG and weight of the groups were similar. Each treatment was assigned to one of the groups. The diets were fed as in the adaptation period in quantities to allow daily orts of 20%. The orts were weighted daily to calculate the average intake of each group. Chemical analyses of the diets and orts were performed to determine dry matter (DM), crude protein (CP), crude fiber (CF), ether extract (EE), ash, Ca, P, K, Mg, S, Cu, Fe, Mn, I and Zn. The diets were also analyzed for ADF according to Goering & Van Soest (1970). The other analyzes were made according to A.O.A.C. (1965). The diets were formulated to attend these recommended daily requirements for energy, protein, vitamins and minerals from NRC (1984). CP content was above NRC requirements because the biological value of yeast is not known. After 90 days the animals were weighted again as in the beginning of the experiment and the ADG was calculated. It was used a fully randomized statistical design. All gain and intake data were subjected to analysis of variance using the PROC ANOVA procedure of SAS (1986). Treatment was the main source of variation. Differences between treatments were performed by Tukey's test (p<0.05).

Chemical composition of the diets are in Table 2. Analysis were carried out at the Water Treatment Laboratory of the Sao Martinho sugar and alcohol factory.

Table 2. Chemical composition of the diets (DM basis)

	Treatments
	RB 26	RB 38	SB 26	SB 38	SB 52

	%
DM	58.73	57.58	52.87	49.54	46.66
CP	12.73	11.89	13.55	13.07	11.83
CF	14.72	18.38	12.29	14.21	17.37
ADF	25.05	30.93	23.17	28.36	34.14
ASH	5.46	5.58	5.29	5.51	5.73

Table 3. Average (Avg.) and standard deviation (sd) of variables from treatments in the finishing cattle performance

	ADG (kg/d)		Intake (kg)		Intake (%LW)		FCE
	Avg	sd	Avg	sd	Avg	sd	Avg

RB 26	0.917	0.119ab	11.13	0.75a	2.91	0.02a	12.14
SB 26	0.985	0.175a	9.33	0.29c	2.46	0.24ab	9.47
SB 38	1.012	0.216a	9.84	0.38bc	2.59	0.12b	9.72
SB 52	0.866	0.214ab	10.01	0.75bc	2.67	0.04a	11.56
SB 52/38	0.927	0.119ab	10.42	0.36ab	2.79	0.09b	11.24
RB 38	0.740	0.174b	9.99	1.08bc	2.71	0.15ab	13.50

The ADG (kg/d), intake (kg) and as live weight percentage, and feed conversion efficiency (FCE) are shown in Table 3.

The ADG values obtained were satisfactory and are similar to values reported by other experiments (Lacorte 1987, Lanna and Boin 1990, Santos 1991), especially taking in account the animals were females that usually have lower intake and lower ADG. The high intake was also in accordance with the literature. ADG was higher for diets SB38 and SB26 than diet RB38 (p<0.05). The later, however, presented ADG similar to treatments RB26, SB52 and SB52/38, even though it has been numerically inferior. As the proportion of milo increases there was a tendency to improve daily gains. In the case of STB diets, diet SB38 presented slightly superior ADG than SB26. In the digestibility experiment from the complementary work by Medeiros and Machado (1993), these two diets presented similar DM and organic matter digestibility. As the intake of diet SB38 was greater than SB26, assuming that the digestibility did not change considerably, the higher ADG for diet SB38 would have been caused by the greater intake of digestible energy. As milo proportions increases the intake tend to diminish, improving the feed conversion efficiency. Thus, besides the slightly greater ADG for diet SB38, the diet SB26 presented better efficiency in the energy transformation. Probably the reason for this result was the greater proportion of propionic acid (C3) determined for diet SB26 in the evaluation of ruminal fermentation of the concurrent work (Medeiros and Machado 1993). The higher proportion of C3 results in greater metabolizable energy available for the animal (Preston & Leng 1987). The higher proportion of concentrate for diet SB26 determines lower heat of fermentation (Van Soest 1982) than diet SB38, which higher proportion of roughage determines just the opposite, therefore diet SB26 might have had more net energy than diet SB38. Results for diet RB26 showed the greatest intake superior to diet SB52, SB38, SB26 and RB38 (p<0.05). Diet SB52/38 had intake similar to diet RB26 and was greater only than diet SB26 (p<0.05). For the RSB diets, as the proportion of milo increased the intake also increased, demonstrating that physical space limited intake. For STB diets, oppositely, as the proportion of milo increased, intake diminished. This result indicates that what might be controlling intake was the chemostatic control of ingestion. Probably diet SB38 is in a less defined range of the chemostatic control of ingestion that would allow higher energy intake than diet SB26. This could explain the higher intake and consequently the higher ADG presented by diet SB38. These results demonstrate that the animals lack genetic potential for more energetic diets, hence comparison between diets was impaired because the animals response to the greater energetic concentration from diet SB26 has not been the expected higher gain but lower intake.

The effect of the steam treatment is clearly demonstrated in the comparison between diets SB38 and RB38. The intake of these two diets were very similar but they presented the highest and lowest ADG values, respectively. The highest value for feed conversion efficiency was for diet SB38 and the worst was for diet RB38. The comparison between diets SB26 and RB26, which resulted in the lowest and highest intake respectively, but similar ADG, confirms the advantage of the steam-treatment effect when the feed conversion efficiency is analysed. If the milo conversion efficiency is analysed (milo kg/ kg ADG) diet SB26 was better than diet RB26 (4.45 vs 5.70, respectively) and diet SB38 was better than diet RB38 (3.50 vs 4.59, respectively).

Literature data on steam treatment effect shows that one of the great advantages is greater intake. That was not the case of this work. Results from the parallel work (Medeiros and Machado 1993) were in accordance with data from literature. One explanation for this difference in intake could be the fact that the RSB used in this trial was offered just after its production, while in the parallel experiment it was fed to the animals even one week after its production and, therefore, the organic acids produced by the fermentation of the residual sugar and the probable microorganisms development could be responsible for the diminished intake.

The replacement of STB by milo tend to increase the ADG by the greater digestive energy provided. The steam treatment effectively improves energy availability. Diets SB26 and SB38 had similar ADG demonstrating that the steam treatment is questionable when low proportions of RSB are used, however feed conversion efficiency for diet SB26 was better, which can justify the steam treatment even in this situation. RSB intake may be affected by factors related to conservation.

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