Feed intake, digestibility and growth performance of Dorper-Menz cross bred sheep fed local brewery by-product (atella) and concentrate mixture at different levels of combination

© 2021 Kokeb, M. et al. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Abstract The aim of this experiment was to evaluate the effect of graded level of local brewery by-product (atella) replacement to concentrate mixture on feed intake; digestibility and body weight change of Dorper-Menz crossbred lambs fed hay basal diet. The feeding period of 90 days was preceded by 15 days of acclimatization period. The experimental design was Randomized Complete Block Design (RCBD) with five treatments: T1 [Control, hay ad libtium]; T2 [25% atella + 75% concentrate mix]; T3 [50% atella + 50% concentrate mix]; T4 [75% atella + 25% concentrate mix]; and T5 [100% atella]. Body weight changes were monitored fortnightly for 112 days. Data on feed intake, body weight change, and digestibility were subjected to Analysis of Variance (ANOVA) using the General Linear Model procedure. Partial budget analysis was performed to evaluate profitability of treatments. The crude protein content of atella was above 20% and can be used as a supplement. Atella alone or at different level with commercial concentrate mixture has significantly increased body weight gain of crossbred sheep. The positive weight gain results of atella supplemented group clearly indicate the potential of atella. Based on partial budget analysis, supplementation of dried atella could be recommended for fattening Dorper-Menz crossbred male lamb.


Introduction
In Ethiopia there are six indigenous sheep breed groups and nine breeds (Solomon, 2008). Among those breeds, Menz sheep is well adapted to the cool highlands of Ethiopia and has slow growth rate. In the past efforts have been made to improve the performance of this breed through selection and cross breeding (Solomon, 2008). These days, pure Dorper rams have been distributed to farmers so as to overcome the slow growth rate of Menz sheep. Currently, selected farmers and small scale private investors are producing 50% Dorper-Menz crosses. Though, sheep feeding with low quality feed resources is a common practice at farmers level in Ethiopia, improved feeding of Dorper-Menz crosses seems inevitable. Therefore, looking for local protein sources from the available feed resources is vital and commendable. In this regard, locally available agroindustrial by-products seem proper choice in a country where commercial concentrate is scarce and costly. The traditional agro-industrial brewery by-product (locally called atella) is used widely by smallholder livestock farmers in Ethiopia due to its CP content (21-22%) and abundance in most households' localities (Mekasha et al., 2003). However, local brewery by-product (Atella) as replacement for concentrate mixture in crossbred sheep ration was not well documented. Therefore, the objective of this experiment was to evaluate the effect of graded level replacement of concentrate mixture with local brewery by-product (atella) on feed intake, digestibility and performance of 50% Dorper-Menz crossbred lambs fed natural pasture hay basal feed.

Experimental site
The experiment was conducted at Debre Birhan Agricultural Research Center. Debre Birhan is located in the central highlands of Ethiopia at about 120 km North East of Addis Ababa and 10 km from Debre Birhan town, at an altitude of 2,800 meter above sea level. The geographical location of the area is 09º 35' 45'' to 09º 36' 45'' North latitude and from 39º 29' 40" to 39º 31' 30" East longitude. The mean annual rainfall of the area is 897.8 mm. The mean annual maximum and minimum temperature is 19.9 and 6.5 ºC

Experimental animals and their management
Twenty five yearlings intact male Dorper with Menz crossbred sheep were obtained from Debre Birhan agricultural research center and identified by using ear tags. The age of animals was determined based on the available records of the research center. Before start of the experiment, sheep were de-wormed with Albendazol bolus and dipping using Diazinol 60% following manufacturer's recommendation. Animals were vaccinated against Anthrax and Pasteurelosis. To fully acquaint sheep with their experimental diets, the actual feeding trial period of 90 consecutive days was preceded by acclimatization period of 15 days. Sheep were kept in door in a well ventilated individual pens equipped with watering and feeding troughs. Animals' were continuously observed for incidence of any ill health and disorders during the experimental period.

Experimental feeds preparation and feeding management
Natural pasture hay (mostly Andropogon abynicus) was harvested from Debre Birhan agricultural research center and dry under the shade. Grass hay was chopped in to smaller size ( ≈ 5 cm) and fed ad libtium (allowing ≈ 20% refusal). Atella was purchased from local breweries in Debre-Birhan town having similar ingredient (barley, maize, wheat and buckthorn) and fermentation period of seven days. Commercial concentrate mixture was bought from Akaki feed processing plant. Hay and supplement (mixture of concentrate and dried atella ) were offered separately in two equal portions at 08:00 and 16:00 h daily. Feed offered and corresponding refusal was recorded daily once in the morning before the next feeding throughout the experimental period. Water and salt lick were freely accessed to animals during experimental period. Ingredients of the commercial concentrate mixture are Noug (Guizotia Abyssinica) seed cake, wheat bran, graded maize and salt.

Experimental design and treatment
The experimental design was Randomized Complete Block Design (RCBD). Treatment diets were randomly assigned to each animal within each block in (Table 1). The total daily offer of atella with concentrate mixture was 400 g. Treatment 1 was the control, where animals received only hay basal diet ad libtium. The remaining treatments involved are atella and concentrate mixture at different levels of combination on top of natural pasture hay basal diet.

Data collection
Feed offer and refusal of each animal were weighed daily to calculate the daily feed intake. Animals were fasted overnight before taking body weight measurement. The initial and final weights were taken twice on two consecutive days and the average of the two was taken as initial and final weights, respectively. Weight gain was calculated as the difference between final and initial body weights. Average daily weight gain was calculated as a weight gain divided by the number of feeding days. Feed conversion efficiency was estimated as a ratio of average daily weight gain per units of dry matter feed consumed daily. Feed intake was recorded daily whereas body weight of animals had been taken every ten days interval (before the morning feeding) with a Salter balance (50 kg capacity of 200 g. precision). At the end of the feeding trial period, animals' were fitted with feces collection bags for digestibility trial and daily feces excretion was collected for seven days. Fecal bags were emptied daily just after the morning meal, and the daily fecal output was weighed and recorded for each animal. Afterwards, the fecal output of each animal was thoroughly mixed and 20% of the voided feces were sampled to make a composite of fecal samples for each animal over the collection period. The fecal samples were stored frozen at -20 ºC until processing for chemical analysis. Apparent DM and nutrients digestibility were determined as the difference between nutrients intake and that recovered in feces expressed as a proportion of nutrient intake (McDonald et al., 2002).

Chemical analysis
Feed and feces sample were analyzed at DBARC. Sample of feed offered, refusals and feces were dried at 65 °C in forced draft oven for about 72 h and ground to pass 1 mm mesh screen size. The ground samples were stored in airtight plastic containers pending chemical analysis. The DM was determined according to the standard methods of association of analytical chemists (AOAC, 1990). Nitrogen was determined by the Kjeldahl procedure. Crude protein was estimated as N ×6.25. Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF) and Acid Detergent Lignin (ADL) were analyzed according to the procedures of Van Soest and Robertson (1985). Hemi cellulose and cellulose contents were calculated as NDF minus ADF and ADF minus ADL, respectively.

Statistical analysis
Data on feed intake, body weight change, and digestibility were subjected to Analysis of Variance (ANOVA) using the General Linear Model (GLM) procedure of SAS (2002). Treatment means were separated using Least Significant Difference (LSD).The model used for this study was Y ij =  + T i + B j + e ij Where;Y ij = the response variable (feed intake, body weight change, and digestibility); = the overall mean; T i = the treatment effect; B j = the block effect; e ij = the random error.

Partial budget analysis
Partial budget analysis was performed using the procedure of Shapiro et. al. (1994). Labor cost was assumed to be constant for all treatments. The initial and final market prices of target animals were estimated by traders. The price differences of target animals in each treatment before and after the experiment was considered as gross/total return (TR). The cost of supplementary feeds was computed by multiplying the actual intake for the entire feeding period with the prevailing prices.
The marginal rate of return (MRR) measures the increase in net return (NR) associated with each additional unit of expenditure (TVC) after arranging total variable cost (TVC) in ascending order. MRR = (NR/TVC) × 100

Chemical composition of treatment feeds
The chemical composition of experimental feeds and refusals is shown in Table 1. The CP content of treatment mixture was much higher than hay, whereas the fiber fraction (NDF, ADF and ADL) in treatment mixture was clearly lower than the basal feed. The hay refusals in all treatments had lower CP and higher NDF, ADF and ADL as compared to the hay offered, which was an indication for the selectivity of animals for the better nutritious parts of the plant. The CP content of atella found in this study is similar with Solomon (2007), Almaz (2008) and Hagos (2014). According to Lonsdale (1989) feeds that have <12%, 12-20% and >20% CP are classified as low, medium and high protein sources, respectively. Therefore, dried atella in the present study could be categorized among the medium upper limit protein source feed that can serve as a protein supplement for low quality hay and in agreement with Susan (2003).

Feed and nutrients intake
The mean daily DM and nutrient intake of 50% Dorper-Menz crossbred sheep is presented in Table 2.  The total DM intake of sheep in this study was comparable with 25% Dorper-Menz crossbred sheep [12]. The lowest total DMI of the control group was attributed to the low CP content of hay, because protein have great role to facilitate the rumen microorganisms and increase the DMI. Replacement rate has not influenced the total DMI. Total NDF and ADF intake was in the order of T1 > T5 > T4 > T3 > T2 which appeared to be associated with the level of NDF and ADF in the supplemental diets. Increatment in the replacement rate of atella has increased NDF and ADF, but decreased CP intake. The OM and CP intake of feed replaced with sole atella was similar to its lowest replacement rate.

Body weight change
The body weight gain and feed conversion efficiency of 50% Dorper-Menz crossbred sheep fed natural pasture hay basal diet supplemented with different proportion of atella and commercial concentrate mix is presented in Table 3. Atella alone or at different level of mixture with commercial concentrate has significantly (p < 0.05) increased the body weight gain of 50% Dorper-Menz crossbred sheep. Weight gain results of atella supplemented group clearly indicate the potential of atella to be supplement for Dorper-Menz crossbred sheep. When the level of atella has increased in the ration there was a decrease in the body weight change. Similar trend has been also observed in final body weight, total body weight change and average daily weight gain. It can be speculated that atella might contain rumen undegradable protein and if consumed in higher amount it might not be efficiently utilized by rumen microbes and may resulted in removal of the excess protein through feces (urine) which is in agreement with the findings of Almaz (2008). Body weight loss in the control group is attributed to the poor quality of natural pasture hay (low CP and higher fiber) that could not satisfy the nutrient requirement of growing Dorper-Menz crossbred sheep.

Nutrient digestibility
Apparent DM and nutrient digestibility and correlation of intake, digestibility and BWG is presented in Tables 4 and 5.  Average daily gain is strongly and positively correlated (p < 0.001) with DMI, OMI, ADFI, ADFD and CPD. The increase in nutrient intake would create a favorable ruminal environment for microorganism in the rumen to increase digestibility and passage rate of the digesta with a subsequent increase in the overall DMI and Body weight gain/kg Experimental Days improves body weight gain. Total DMI is negatively correlated with NDFI and positively correlated (p < 0.001) with CPI, CPD, ADFI and NDFD.  The negative correlation of fiber component NDF with feed intake is in agreement with Van Soest (1965). The non significant (p > 0.05) difference in apparent digestibility of CP among the treatments confirmed the comparable quality of atella with that of concentrate mixture. Feeds rich in protein promote high microbial population which in turn facilitates rumen fermentation and the fermentative activity is usually responsible for the increased digestibility McDonald et.al. (2002). Therefore, the current finding is in agreement with Mekonnen et al. (2014) denoting that lambs with higher growth potential has higher nutritional needs.

Partial budget analysis
Economic analysis of the experiment is computed and described for each treatment (Table 6).  The major cost that determined profitability of sheep feeding was the initial price of animals and the feed cost. Sheep received T5 (atella alone) returned higher net income followed by sheep fed T4 (75 % atella + 25% CM). The differences in total return, net return and marginal ret of return among treatments is mainly associated with the differences in selling price of the sheep, differences in intake and cost of feed. The marginal rate of return analysis reveals what farmers can expect to gain on the average in return for their investment. Considering the net return and MRR, sheep supplemented with dried atella is economically profitable and in agreement with the recommendation of Hagos (2014).

Conclusion
Result of this study shows that traditional brewery by-product (atella) can be used as a protein source. Based on partial budget analysis, different levels of atella with concentrate mixture could be recommended as profitable supplement for 50% Dorper-Menz crossbred male lamb fattening. Atella may lose some volatile nutrients during drying process and further research is needed to compare wet atella with dried one.