RESULTS

Nutrient composition of feed ingredients

The chemical composition analyses of each feed ingredient revealed substantial variation in nutrient profiles, reflecting the distinct functional contributions of forage and concentrate components to the overall ration (Table 2).

Ingredients | DM | OM* | CP* | EE* | CF* | NFE | TDN* | ADF* | NDF*
Native grass | 30.27 | 93.56 | 6.44 | 2.21 | 34.07 | 45.82 | 62.6 | 29.78 | 68.85
Rice bran | 90.41 | 88.22 | 7.57 | 12.79 | 19.09 | 48.77 | 74.1 | 13.20 | 10.26
Cassava waste | 87.30 | 87.93 | 2.14 | 3.23 | 0.57 | 81.99 | 84.1 | 21.23 | 55.88
Cracked corn | 89.23 | 94.91 | 10.10 | 5.24 | 2.50 | 67.15 | 83.8 | 32.45 | 59.34
Tofu waste | 87.12 | 92.48 | 18.56 | 23.89 | 13.59 | 36.44 | 76.3 | 18.06 | 38.76
Copra meal | 88.17 | 92.40 | 25.63 | 10.74 | 20.79 | 44.68 | 67.3 | 36.50 | 54.70
Mineral mix | – | – | – | – | – | – | – | – | –

Native grass, which served as the basal forage across all treatments, exhibited a low CP content of only 6.44%. These values indicate limited nutritive value, particularly when compared with concentrate ingredients. The grass also contained high CF (34.07%) and elevated ADF (29.78%) and NDF (68.85%) fractions, indicating substantial structural fiber content that is likely to restrict intake. These characteristics are consistent with previous assessments of forage quality in Bangkalan Regency [19], where high-fiber native grasses commonly limit voluntary consumption and contribute minimally to growth performance.

In contrast, rice bran exhibited relatively favorable nutrient characteristics, and its EE (12.79%) and TDN (74.1%) contents reflect its function as a readily available source of digestible energy. The ingredient's low ADF (13.20%) and very low NDF (10.26%) indicate high digestibility with minimal structural fiber load, thereby enhancing energy supply without substantial ruminal fill constraints. Cassava waste emerged as a highly fermentable energy source, as indicated by its high NFE (81.99%) and TDN value (84.1%). Although the CP content was low (2.14%), the ingredient provided considerable digestible energy potential. Cassava waste contained a moderate ADF (21.23%) and a higher NDF (55.88%), suggesting abundant structural fiber but a sufficiently low proportion of lignified material to support moderate digestibility. The presence of rapidly fermentable carbohydrates, together with moderate fiber levels, necessitated complementary inclusion of protein-rich ingredients or rumen-degradable nitrogen sources.

Tofu waste and copra meal supplied most of the CP within the concentrate mixtures. Tofu waste contained 18.56% CP and a substantial EE fraction of 23.89%, highlighting its dual role in supplying protein and lipid-derived energy. Copra meal provided an even higher CP (25.63%) but was accompanied by elevated CF (20.79%) and ADF (36.50%), thereby moderating its digestibility. Nevertheless, copra meal remained a valuable protein source within appropriate inclusion levels. Cracked corn provided additional digestible energy through its high NFE (67.15%) and TDN (83.8%), although its relatively high NDF content (59.34%) indicated appreciable fiber content.

Nutrient composition of concentrate mixtures

The varying proportions of cassava waste and tofu waste in concentrate treatments C1–C4 resulted in predictable nutrient shifts (Table 3).

Chemical composition | C1 | C2 | C3 | C4
DM (%) | 87.44 | 87.45 | 87.46 | 83.70
OM* | 91.62 | 91.20 | 90.78 | 90.09
CP* | 14.10 | 13.28 | 12.48 | 11.33
EE* | 16.05 | 15.02 | 13.99 | 11.93
CF* | 9.03 | 8.38 | 7.73 | 6.49
NFE* | 50.38 | 52.44 | 54.50 | 54.83
TDN* | 75.37 | 75.76 | 76.16 | 73.27
ADF* | 45.55 | 46.40 | 47.25 | 48.53
NDF* | 24.62 | 24.77 | 24.93 | 25.41

DM content ranged from 87.46% in C3 to 83.70% in C4, with the reduction in C4 attributable to the higher moisture content of cassava waste. OM content decreased slightly from C1 to C4, reflecting the influence of ingredient moisture and mineral fractions. CP decreased progressively from 14.10% in C1 to 11.33% in C4 as the contribution of tofu waste declined. EE exhibited a similar pattern, decreasing from 16.05% in C1 to 11.93% in C4, consistent with the replacement of high-fat tofu waste by low-fat cassava waste.

CF decreased from 9.03% to 6.49% as tofu waste levels decreased, whereas ADF and NDF exhibited slight increases because of the additional structural carbohydrates supplied by cassava waste. The NFE value increased from 50.38% in C1 to 54.83% in C4, indicating a progressive increase in readily available carbohydrates as cassava inclusion increased. TDN values remained relatively stable (73.27%–76.16%), suggesting that changes in ingredient composition did not compromise dietary energy density. These findings demonstrate that despite variations in nutrient contributions, the four concentrate formulations provided comparable metabolizable energy.

DMI and nutrient intake

Statistical analysis demonstrated significant effects of treatment and breed on total DMI (p < 0.05; Table 4).

Variables | Breeds | T1 | T2 | T3 | T4 | SEM | p (T) | p (B) | p (T × B)
Total DMI (kg/day) | Madura | 4.08 | 4.63 | 5.08 | 5.06 | 0.243 | * | * | ns
 | Madrasin | 5.91 | 6.82 | 6.86 | 7.19 |  |  |  | 
Native grass (kg/day) | Madura | 0.98 | 1.12 | 1.19 | 1.17 | 0.663 | ns | ns | ns
 | Madrasin | 1.15 | 1.25 | 1.21 | 1.35 |  |  |  | 
Concentrate (kg/day) | Madura | 3.10 | 3.51 | 3.89 | 3.89 | 0.191 | ** | ** | ns
 | Madrasin | 4.76 | 5.67 | 5.65 | 5.84 |  |  |  | 
Total DMI (% LW) | Madura | 1.75 | 1.92 | 1.81 | 1.87 | 0.070 | ns | ns | ns
 | Madrasin | 1.83 | 2.01 | 1.82 | 2.00 |  |  |  | 
Native grass (% LW) | Madura | 0.33 | 0.36 | 0.35 | 0.36 | 0.021 | ns | ns | ns
 | Madrasin | 0.35 | 0.37 | 0.32 | 0.38 |  |  |  | 
Concentrate (% LW) | Madura | 1.42 | 1.56 | 1.46 | 1.51 | 0.054 | ns | ns | ns
 | Madrasin | 1.47 | 1.64 | 1.50 | 1.62 |  |  |  | 
DMI (g/kg LW0.75) | Madura | 72.89 | 80.45 | 80.42 | 79.23 | 2.947 | ns | ns | ns
 | Madrasin | 77.47 | 86.41 | 83.61 | 87.01 |  |  |  | 
OM intake (kg/day) | Madura | 4.03 | 4.27 | 5.03 | 5.02 | 0.207 | ** | ** | ns
 | Madrasin | 5.25 | 6.14 | 6.06 | 6.31 |  |  |  | 
CP intake (kg/day) | Madura | 0.67 | 0.71 | 0.68 | 0.62 | 0.268 | ** | ** | ns
 | Madrasin | 0.74 | 0.82 | 0.77 | 0.74 |  |  |  | 
ADF intake (kg/day) | Madura | 1.45 | 1.63 | 1.69 | 1.69 | 0.006 | ** | ** | ns
 | Madrasin | 1.62 | 1.89 | 1.88 | 2.01 |  |  |  | 
NDF intake (kg/day) | Madura | 2.58 | 2.93 | 3.85 | 3.09 | 0.117 | ** | ** | ns
 | Madrasin | 2.88 | 3.40 | 3.42 | 3.67 |  |  |  | 

Bulls receiving T2, T3, and T4 exhibited greater DMI than those receiving T1, indicating that diets containing higher proportions of cassava waste supported increased feed intake. For example, Madrasin bulls receiving T4 consumed 7.19 kg/day, representing the highest value among all treatments. This increased consumption may be attributed to improved palatability and enhanced ruminal fermentation, both associated with higher concentrations of soluble carbohydrates.

Breed exerted a consistent effect, with Madrasin bulls consuming significantly more feed than Madura bulls across all treatments. This pattern was observed for total intake (kg/day), percentage of LW, and metabolic LW. For example, Madrasin bulls receiving T2 consumed 86.41 g/kg LW0.75 compared with 80.45 g/kg LW0.75 in Madura bulls. These differences in feed intake were attributable to the larger body size and higher metabolic requirements of Madrasin bulls.

DMI from native grass was not significantly affected by treatment or breed (p > 0.05), indicating that forage intake remained relatively constant regardless of concentrate composition. This finding highlights the limited nutritional adaptability of native grass under the feeding conditions used. In contrast, concentrate intake differed significantly among treatments and breeds (p < 0.01). Madrasin bulls consistently consumed more concentrate than Madura bulls, particularly in T2–T4, indicating that concentrate composition rather than forage intake was the principal determinant of nutrient intake variation.

Nutrient intake

Statistical analysis showed that treatment and breed significantly affected OM, CP, ADF, and NDF intake (p < 0.05; Table 4). OM and CP intake increased with increasing DMI, with Madrasin bulls exhibiting greater OM intake across all treatments and the highest value observed in T4 (6.31 kg/day). ADF and NDF intake were significantly affected by treatment and breed (p < 0.01). Madrasin bulls consistently consumed more ADF and NDF, with the highest values recorded under T4. These findings highlight the greater ruminal capacity of Madrasin cattle and their ability to utilize diets with higher concentrations of structural fiber.

Nutrient digestibility

Digestibility results indicated significant treatment effects for DM and OM digestibility (p < 0.05; Table 5).

Variables | Breeds | T1 | T2 | T3 | T4 | SEM | p (T) | p (B) | p (T × B)
Digestibility coefficients (%) |  |  |  |  |  |  |  |  | 
DM digestibility | Madura | 77.90 | 76.97 | 75.06 | 77.76 | 0.602 | ns | ** | ns
 | Madrasin | 79.77 | 77.58 | 75.52 | 76.84 |  |  |  | 
OM digestibility | Madura | 78.23 | 77.26 | 76.77 | 78.67 | 0.847 | ns | ** | ns
 | Madrasin | 81.21 | 78.02 | 76.80 | 77.80 |  |  |  | 
CP digestibility | Madura | 76.85 | 77.37 | 76.81 | 78.78 | 0.803 | ns | ** | ns
 | Madrasin | 78.38 | 77.28 | 78.18 | 79.10 |  |  |  | 
ADF digestibility | Madura | 68.81 | 69.21 | 68.99 | 68.91 | 0.632 | * | * | ns
 | Madrasin | 71.00 | 69.98 | 70.93 | 70.20 |  |  |  | 
NDF digestibility | Madura | 75.34 | 74.91 | 75.14 | 73.38 | 1.134 | ns | ns | ns
 | Madrasin | 77.38 | 76.79 | 76.27 | 77.23 |  |  |  | 
Digestible nutrient intake (g/kg LW0.75) |  |  |  |  |  |  |  |  | 
Digestible DMI | Madura | 56.78 | 61.92 | 62.80 | 61.61 | 2.873 | * | * | ns
 | Madrasin | 61.80 | 67.04 | 63.14 | 66.89 |  |  |  | 
Digestible OMI | Madura | 50.78 | 54.99 | 52.54 | 54.55 | 2.513 | * | * | ns
 | Madrasin | 55.92 | 59.82 | 54.57 | 57.68 |  |  |  | 
Digestible CPI | Madura | 6.99 | 7.42 | 6.64 | 6.40 | 0.343 | ** | ** | ns
 | Madrasin | 7.61 | 7.91 | 7.06 | 6.88 |  |  |  | 
Digestible ADF intake | Madura | 13.48 | 15.24 | 14.83 | 15.27 | 0.824 | ** | ** | ns
 | Madrasin | 15.09 | 16.52 | 15.64 | 16.58 |  |  |  | 
Digestible NDF intake | Madura | 26.26 | 29.65 | 36.80 | 29.72 | 0.344 | ** | ** | ns
 | Madrasin | 29.23 | 32.60 | 30.59 | 33.30 |  |  |  | 

Bulls receiving T1 exhibited the highest DM and OM digestibility values, probably because of the greater inclusion of tofu waste, which contributed to higher CP and EE concentrations and promoted improved microbial fermentation. Madrasin bulls generally exhibited numerically greater digestibility values than Madura bulls. However, breed effects were significant only for ADF digestibility, whereas DM, OM, CP, and NDF digestibility were not significantly affected by breed.

CP digestibility remained relatively stable across treatments (76.81%–79.10%), indicating adequate protein supply for ruminal microbial activity in all diets. Similarly, ADF and NDF digestibility were not significantly affected by treatment despite slight increases in fiber fractions in C3 and C4.

Breed effects were observed for ADF digestibility, with Madrasin bulls exhibiting significantly higher values (p < 0.05). This finding suggests superior utilization of structural carbohydrates and is consistent with previous studies demonstrating greater ruminal degradation efficiency of fibrous feedstuffs in crossbred cattle [24].

Digestible nutrient intake

Digestible DMI was significantly affected by treatment and breed (p < 0.05). T2 resulted in the highest digestible DMI (67.04 g/kg LW0.75) in Madrasin bulls, followed by T4, T3, and T1. Similar patterns were observed for digestible OM intake.

Digestible CP, ADF, and NDF intake were significantly influenced by treatment and breed (p < 0.01), with consistently higher values observed in Madrasin bulls. These findings highlight the interaction between intake capacity and digestibility coefficients. Although digestibility remained relatively stable across treatments, the greater DMI observed in Madrasin cattle resulted in higher overall digestible nutrient intake.

LWG and FCR

Statistical analysis showed that LWG was not significantly affected by breed, treatment, or their interaction (p > 0.05; Table 6), although numerically greater gains were observed in Madrasin bulls, particularly those receiving T4.

Variables | Breeds | T1 | T2 | T3 | T4 | SEM | p (T) | p (B) | p (T × B)
Initial LW (kg) | Madura | 278.6 | 282.0 | 307.3 | 294.4 | 7.781 |  |  | 
 | Madrasin | 290.5 | 314.0 | 345.0 | 325.5 |  |  |  | 
Final LW (kg) | Madura | 330.7 | 339.8 | 366.3 | 352.9 | 7.480 |  |  | 
 | Madrasin | 356.2 | 375.8 | 406.0 | 395.2 |  |  |  | 
LWG (kg/day) | Madura | 0.62 | 0.69 | 0.70 | 0.70 | 0.029 | ns | ns | ns
 | Madrasin | 0.78 | 0.75 | 0.73 | 0.83 |  |  |  | 
FCR | Madura | 8.64 | 8.79 | 9.36 | 8.70 | 0.497 | ns | ns | ns
 | Madrasin | 7.58 | 9.64 | 9.64 | 8.64 |  |  |  | 
IOFC (IDR/day) | Madura | 35,745 | 36,357 | 37,651 | 35,581 | 2.307 | * | * | ns
 | Madrasin | 42,156 | 44,456 | 41,346 | 40,376 |  |  |  | 

All four diets supported comparable growth, indicating that variations in the proportions of cassava waste and tofu waste did not compromise nutrient adequacy. This observation is consistent with previous findings showing that appropriately balanced cassava-based diets can support efficient growth [18]. Madrasin bulls tended to exhibit higher average daily gain (0.77 kg/day) than Madura bulls (0.68 kg/day), reflecting their superior growth potential, enhanced intake, and greater nutrient utilization efficiency.

Similarly, FCR was not significantly affected by treatment or breed (p > 0.05), indicating that feed efficiency remained stable among treatments. Both Madrasin and Madura bulls converted feed into body weight with comparable efficiency despite differences in absolute weight gain.