The experiment was conducted at Palmares farm, located in Iaçu, a semi-arid region in Bahia, Brazil (15º31'0"S, 40º14'1"W). According to Köppen climate classification, the climate of the region is tropical and wet, mesothermic, hot and rainy during the summer and cold and dry in the winter. The study was conducted during the rainy season, from January to April (Table 1).
Table 1
Rainfall (mm), average minimum temperature (Tmin) and maximum temperature (Tmax) during the experimental period
Month
|
Rainfall (mm)
|
Tmin (°C)
|
Tmax (°C)
|
January
|
36.0
|
17.5
|
32.5
|
February
|
40.0
|
21.1
|
38.2
|
March
|
42.0
|
21.4
|
38.8
|
April
|
40.0
|
17.1
|
38.5
|
Mean
|
39.5
|
19.2
|
37.0
|
Total
|
158.0
|
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|
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|
Twenty-four Santa Inês intact male lambs of four months of age and average initial body weight (BW) of 32 ± 2 kg were used in this study. A completely randomized design was carried out, with 4 treatments, six replicates for each treatment, and each animal within the treatment representing a replicate. Ground energy source was used to comprise the multiple supplements: mesquite pod meal (MPM), wheat bran (WB) or sorghum grain (SG) and a control group was kept just in the pasture and receiving mineral mix (MM) to supply mineral requirements. The MM was provided to all treatments ad libitum to avoid a mineral deficiency. Ground corn, soybean meal and urea were added to the energy sources to make the multiple supplements with 210.0 g/kg of CP and 602.2 g/kg of total digestible nutrients (TDN) on a DM basis (Table 2). Therefore, lambs were distributed to receive only the mineral mix (MM), MPM supplement, WB supplement, and SG supplement. The chemical composition of the treatments and pasture is given below (Table 3).
Table 2
Proportion of ingredients of the mineral mix (MM) and multiples supplements (g/kg), expressed on the fresh matter basis
Ingredients
|
MM1
|
Treatments2
|
MPM
|
WB
|
SG
|
Ground corn grain
|
|
411.5
|
420.0
|
411.5
|
Soybean meal
|
|
207.9
|
200.0
|
208.0
|
MPM
|
|
353.2
|
0.0
|
0.0
|
WB
|
|
0.0
|
352.6
|
0.0
|
SG
|
|
0.0
|
0.0
|
353.1
|
Urea
|
|
9.7
|
9.7
|
9.7
|
MM1
|
100.0
|
-
|
-
|
-
|
1MM (control group): calcium 120.00 g, phosphorus 87.00 g, sodium 147.00 g, sulfur 18.00 g, copper 590.00 mg, cobalt 40.00 mg, chromium 20.00 mg, iron 1,800.00 mg, iodine 80.00 mg, manganese 1,300.00 mg, selenium 15.00 mg, zinc 3,800.00 mg, molybdenum 300.00 mg and fluorine (max) 870.00 mg, per kg of the product; |
2Treatments: mineral mix (MM), mesquite pod meal (MPM), wheat bran (WB), sorghum grain (SG). |
Table 3
Chemical composition of the urochloa grass and the multiple supplements
|
|
|
Treatments3
|
|
Item 1
|
Urochloa grass
|
MPM
|
WB
|
SG
|
DM, g/kg
|
266.0
|
896.6
|
892.4
|
888.3
|
CP, g/kg DM
|
115.2
|
218.7
|
243.0
|
219.6
|
NDF, g/kg DM
|
678.4
|
321.3
|
409.9
|
296.8
|
ADF, g/kg DM
|
351.0
|
163.5
|
152.5
|
177.0
|
EE, g/kg DM
|
29.1
|
23.3
|
36.6
|
26.3
|
Ash, g/kg DM
|
148.4
|
57.1
|
67.4
|
54.1
|
Lig, g/kg DM
|
77.1
|
25.0
|
17.0
|
19.0
|
TCHO, g/kg DM
|
707.3
|
700.9
|
653.0
|
700.0
|
1Item: dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), ether extract (EE), lignin (Lig), total carbohydrates (TCHO). |
3Treatments: mesquite pod meal (MPM), wheat bran (WB), sorghum grain (SG). |
The experimental area was comprised of seven paddocks of 4.0-ha of urochloa grass (Urochloa mosambicensis), equipped with drink and food troughs, and an availability of 3213.45 kg/ha of DM, 482.01 kg/ha of leaves, 2262.27 kg/ha of stems and 754.93 kg/ha of dead material (dry matter basis). To estimate the total forage availability, eight points were randomly chosen per paddock and cuts were made at each point using metal squares (0.5 × 0.5 m). All material within the square was cut at 15 cm above the ground, as described by Boswell (1977). These samples were taken to the laboratory, where they were weighed and homogenized, and two subsamples were obtained from each sample. An aliquot was used to determine the total DM content, and another one was divided into leaf, stem, and dead material components. The estimation of the quality of the consumed forage was done with the plucking-hand technique (De Vries, 1995).
According to each treatment, lambs were identified with different ear and collar tags, and all lambs belonging to each treatment were put together in a group in one paddock of 4.0-ha. Aiming to reduce the influence of a variation of forage DM availability, the animals were moved to another paddock every five days to remove the effect of the pasture in the treatments. Lambs were allowed to access the paddocks from 7:00 am to 5:00 pm and then they were taken to the pens to be supplemented in feeders. Collective pens had 1 m2/lamb, with 6 animals each. They had access to the supplementation provided in the trough at a ratio of 10 g/kg body weight, based on the mean body weight of the group, with no leftovers.
The experimental period lasted 95 days: 15 days of adaptation, 70 days for performance evaluation and 10 days for intake and digestibility evaluations.
The animals were weighed at the beginning and at the end of the experiment. Lambs were weighed on the 15th of every month to adjust the quantity of the supplement provided, and also to make up the average daily gain during this evaluation period (the fifteenth day of every month). The average daily gain (ADG) was estimated by the following equation:
where ADG is the average daily gain; FBW is the final body weight considering the total gain, during 15 days; IBW is the initial body weight and N is the number of days of weighing (every 15 days) in the experiment.
Fecal output data was determined by using chromium oxide (Cr2O3) at 2 g/animal.day (Hill and Anderson, 1958) as an external marker, in the morning and in the afternoon. The external marker was packed in bags, and introduced in the esophagus of the lambs by using a PVC (Polyvinyl chloride) apparatus. Fecal samples were collected during five days from the 6th to the 10th day after starting the supply of the marker, every 3 hours directly from the animal's rectum, making up eight samples during the 24 hours of the day. Then, compound samples were made per day and frozen at -20°C. Fecal recovery was measured by the ratio of the amount of marker excreted and the ingested amount. The fecal dry matter was estimated by the marker through the equation as follows:
where: IM is the ingestion of the marker (mg/g; DM basis); FM is the fecal marker (mg/day; DM basis)
For the determination of the indigestible acid detergent fiber (iADF), 0.5 g of the feces were taken, supplements, and hand-plucked samples were packed in non-woven fabric (NWF-100 g/m2) of 4 × 5 cm and they were inserted in the rumen in the proportion of 20 mg of DM/cm2 of the surface. The samples were triplicated and inserted in lingerie bags for each treatment, and were incubated for 264 hours (Casali et al., 2008). After removing the bags from the rumen, they were washed in running water and immediately transferred to a forced ventilation oven (60°C) for 72 hours. DM determination was done according to the method 930.14 of AOAC (AOAC, 2005). The voluntary forage intake was estimated as described by Arthington and Spears (2007). The DM intake was determined by the ratio between the fecal excretion and the internal indicator indigestibility, as described earlier, using the equation proposed by Detmann et al. (2001):
DMI = [(FE xMCF) – CIS)/CIFOR] + DMIS
where: DMI = dry matter intake (kg/day); FE = fecal excretion (kg/day); MCF = marker concentration in the animal feces (kg/kg); CIS = concentration of iADF in the supplement (kg/day); CIFOR = concentration of iADF in forage (kg/kg); and DMIS = intake of supplement DM (kg/day). Supplement intake was measured by the quantity supplied minus the refusals and then divided by the number of animals of the treatment.
The substitution rate (SR) was calculated according to Kellaway and Porta (1993) and describes the rate of substitution of forage for the supplement.
SR=(Forage intake when unsupplemented)-(Forage intake when supplemented)/Supplement intake
To calculate the SR, the average of forage intake of the unsupplemented animals was used.
Total carbohydrates (TCHO) were calculated according to Sniffen et al. (1992) using the equation TCHO = 100 – (%CP + %EE + %ash).
The NDF and ADF contents were determined according to Van Soest et al. (1991). Evaluations of DM, CP (N x 6.25) and ether extract (EE) contents were estimated by the methods 930.15, 984.13 and 920.39 of the AOAC (AOAC, 2005), whereas ash content was calculated as 100-organic matter. The lignin content was analyzed by the sulfuric acid solubilization method following the procedures described by Gomes et al. (2011).
The data was analyzed using the Statistical Analysis System (SAS, 2001), after verification of the normality by the PROC UNIVARIATE statement. The data was analyzed using the PROC GLM procedure, according to the completely randomized design model:
where Yijk is the dependent variable, µ is the overall mean, SUPi is the fixed effect of supplements and εijk is the random error.
The model considers the supplements as fixed effect and animals were the experimental units. The statistical analysis of the substitution rate (SR) was performed by just using the supplemented animals, because there was no effect of substitution in the animals unsupplemented. The comparisons between means were performed by Tukey’s range test. In all models, the statistical significance between means was declared to be P < 0.05.