Energy balance and methane emission prediction in Simmental Cross-breed Cattle Feeding different types of forages and concentrates

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Introduction
The feed aspect plays an important role in fattening cattle, so attention must be paid to aspects of the availability and adequacy as well as the nutritional content of the feed.Apart from that, the economic efficiency aspect of farmers must be considered.This is because almost 70% of the costs incurred to increase livestock productivity are mostly for procuring animal feed.The use of quality and sufficient feed to meet livestock requirements will increase beef cattle production parameters such as daily weight gain, carcass and meat production, feed intake, feed conversion and feed efficiency can be maximized.Feed plays an important role in livestock fattening sector.One important factor that influences daily weight gain of livestock is feed energy intake.
Traditional farmers generally use natural resources for feed that is nearby.One of the food resources that easy to reach is kolonjono grass.Kolonjono grass has several advantages such as high productivity, sufficient nutritional content and a palatable [1].However, the growth area for kolonjono grass is getting narrower, so replacement feed ingredients are needed which are cheap and easy to obtain.One substitute feed ingredient that can be used by farmers is fermented rice straw [2].The use of fermented rice straw is due to the increase in feed quality due to the involvement of microorganisms in degrading crude fiber, reducing lignin levels and anti-nutritional compounds, so that the digestibility value of feed from waste can increase [2] [3].The rice straw used for feeding livestock in single form cannot meet the nutritional requirements of livestock.So additional feed in the form of concentrate is needed.The concentrate can be formulated from pollard bran, rice bran or commercial concentrate.However, when using these feed, it is necessary to have the proper proportions.Based on the description above, research was carried out to obtain energy balance in simmental crossbreed cattle given different types of forage and different proportion of concentrates.

Materials and methods
This research was conducted from September-December 2022 in Izzah Farm, Sambi District, Boyolali Regency, Central Java.Chemical analysis of feed ingredients was carried out at the Animal Feed and Nutrition Laboratory, Faculty of Animal Science, Sebelas Maret University.Energy test analysis at the Faculty of Animal Husbandry, Gadjah Mada University.
The materials used in this study included nine Simmental cross-breed cattle with initial body weight of 506 ± 80.09 kg, kolonjono (Brachiaria mutica) grass, calfeed C-130 commercial concentrate, fermented rice straw, rice bran and wheat bran.
The research design used a completely randomized design (CRD) with three types of treatment (T1, T2, T3) and three replications each treatments.
T1: C1 (rice bran+wheat bran) 70%+ kalanjana grass 30% T2: C2 (rice bran+wheat bran) 70%+ fermented rice straw 30% T3: C3 (commercial concentrate+wheat bran) 70%+ fermented rice straw 30% The preparation stage consists of pen preparation, cattle preparation, forage preparation and concentrate feed preparation.The pen preparation stages include cleaning and repairing.The next preparation stage is the cattle procurement stage, this stage includes administering medicine and vitamins, providing adapted feed for 14 days.The forage preparation stage includes providing forage in the form of kolonjono grass.The concentrate preparation stage includes mixing pollard bran and rice bran until homogeneous and commercial concentrate and rice bran until homogeneous.The nutritional content of feed ingredients is presented in Table 1 and the proportion content of concentrate rations is presented in Table 2.The next stage includes weighing the cattle first to determine the body weight of the cattle.This stage includes feeding, 3% of body weight, carrying out the total collection model, and collecting data.Feeding was carried out according to the treatment, which can be seen in Table 3. Data collection or total collection of faeces and urine was carried out for 7 days.Faeces were collected in the morning and then weighed.The last day of the total collection, all samples were mixed per animal and then 500 grams of samples were taken.The faeces were then dried and ground for proximate analysis.Urine is collected every morning and then weighed.All urine that has been collected for seven days is then mixed evenly per cattle, then a sample of 250 ml is taken.The methane emission was calculated according to Blaxter and Clapperton [7].The data obtained were analyzed using analysis of variance (ANOVA).If there are differences between treatments or groups, they will be tested further using the Duncan Multiple Range Test (DMRT) to determine the differences between treatments.All data obtained were analyzed using R studio software version R 4.2.0.

Result and discussion
Based on the research that has been carried out, data obtained in the form of average energy consumption, digested energy, energy digestibility, metabolized energy and methane energy are presented in Table 4.

Gross Energy intake
Energy consumption is the amount of energy consumed by livestock through dry matter consumption.The more rations consumed, the greater the energy consumed by livestock [8].Energy consumption among treatments was found to be different (P<0.05).This is because the energy content in the ration among the treatments was found to be different, namely 3622.6,3579.19, and 3395.78kcal for T1, T2, T3, respectively.This research is in line with [9] statement which states that the high or low energy content in feed influences the amount of feed consumed.Thus, the energy content of the three feeds causes relatively different feed consumption.The highest energy consumption in this study was at T3.It is suspected that feed T3 has a higher palatability than T2.High palatability can increase feed intake which can increase energy consumption.

Digestible Energy
Digestible energy is energy obtained from digested nutrients [10].Digestible energy is obtained by calculating the difference between the energy consumed by livestock and the energy released through the faeces.The digested energy in this study shows that there is no difference (P>0.05) and has a positive value, which means that there is digested energy that is used for production.The factor causing no significant difference in digested energy was caused by the equation of the speed of the digesta flow.The speed of digesta flow is influenced by several factors, namely the type of feed given, the amount of feed consumed, and the physical ability of the rumen to consume the ration.T1 used forage kolonjono grass while T2 and T3 used fermented rice straw.It is suspected that although the energy consumption at T2 and T3 is high, the digestibility is low.So as to produce the same digestible energy in the three treatments.The digestible energy in Kacang goat fed different composition of concentrate did not show differences [11].

Energy Digestibility
Energy digestibility is the percentage of feed consumed by livestock and not excreted in the faeces.Energy digestibility in cattle between treatments showed significantly different results (P<0.05).This is presumably due to relatively high energy consumption and energy expended from faeces.This assumption is strengthened by the opinion of [12] who states that high digestibility reflects the large contribution of certain nutrients to livestock, while feed with low digestibility indicates that the feed is less able to supply nutrients for basic living and livestock production purposes.The average result of the energy digestibility analysis in this study was 60.22%.The results of this study are lower than the results of [13] with an average energy digestibility of 81.6%.
The low digestibility value of fermented rice straw can cause energy digestibility to also be lower than the digestibility value of kolonjono grass.This is because fermented rice straw contains lignin and silica which makes this feed ingredient of low quality [14].

Table 1 .
Nutrition content of ration ingredients.

Table 2 .
Feed proportion of concentrate.

Table 3 .
Energy content of feed ration for cattle.
Source: Laboratory analysis.

Table 4 .
Energy balance of Simmental Crossbreed.