​Use of Corn Dried Distillers Grains to Improve Feed Diets for Intensive Lamb Fattening

The rising price of raw materials used to produce animal feed is compelling nutritionists to look for new and cheaper feedstuff that can replace the more expensive traditional energy and protein ingredients such as corn and groats. In recent times, the by-products in animal feed for fattening have come back to use, including corn dried distillers grain, a by-product resulting from the ethyl alcohol preparation from corn kernels (Abdelrahim et al., 2014; Pecka-Kiełb et al., 2017; Crane et al., 2018; Neville et al., 2021).

This by-product is considered to have a high content of protein, energy and phosphorus due to the remaining nutrients (protein, fat, fiber) which are concentrated about 3-fold when the starch in corn is fermented to produce ethyl alcohol (Klopfenstein et al., 2008; Kim et al., 2015).

Protein and amino acid utilization of corn dried distillers grains has been evaluated in growing lambs and the results indicated that this by-product represents an excellent source of protein (Archibeque et al., 2008). Moreover, the high supply and corn price has made dried corn distillers grains a very attractive source of energy for ruminants (Klopfenstein et al., 2008; Hodges et al., 2020).

When used as feed for raising or finishing lambs, corn dried distillers grain can be used at a level of inclusion of up to 60% of the dry matter in the diet, being both a source of energy and a source of protein (Neville et al., 2021). The inclusion of corn dried distillers grains in lamb diets has tended to be more economical for producers, being generally a practical, cost-effective source of protein, which is usually beneficial as protein represents the most expensive fraction of the diet (Sahin et al., 2013).

In general, corn dried distillers grains can be used as a source of protein or energy in lambs’ rearing and finishing diets, according to the nutritional needs, type of food used and cost concerns (Curzaynz-Leyva et al., 2019).

The aim of this study was to investigate the effect of including corn dried distillers grains as a single source of protein and energy in the compound feed of the fattening lambs diet up to 30 kg live weight and as a substitute for sunflower meal over this body weight.

Location, animals and feeding
 
The animals in this experiment have been cared for in accordance with the Romanian Law 43/2014 on protection of experimental animals, as well as with EU Council Directive 98/58/EC on protection of farm animals. The experiment took place in the National Research-Development Institute for Animal Nutrition and Biology, Balotesti, Romania (IBNA-Balotesti), in 2021, in accordance with the provisions on the animal study protocol approved by the Ethics Committee of IBNA-Balotesti (approval No. 146/12.07.2020). During the experiment, all animals remained healthy and no veterinary drugs were used.

The research work was carried out on 30 lambs, which were randomly divided into two batches (15 lambs/group) for a total fattening period of 110 days, until reaching a body weight of about 40 kg. The fattening period was divided into two phases (the former phase - of 50 days, the latter - 60 days) and the rations of the lambs were formulated in according to the feed requirements of the French system (INRA, 2010).

The batches were fed with meals consisting of compound feed, barley hay and corn silage. The structure of the compound feed (CF) given during the two fattening phases (Table 1) made the difference between the batches. Thus, group T1 (control group) received compound feed consisting in corn, sunflower meal, mineral salts and premix in both fattening phases, while group T2 (experimental group) received compound feed formed in the first fattening phase of corn dried distillers grains (95%) and mineral salts plus premix (5%) and in the second phase compound feed consisting of corn (46%), corn dried distillers grains (49%), mineral salts and premix (5%).



Corn dried distillers grains (DDG) completely replaced corn and sunflower meal in the first fattening phase (43% of the total dry matter of the ration) and in the second fattening phase completely replaced sunflower meal (20% of the total dry matter of the ration). All diets were isoprotein and isoenergetic.

The structure of the CF recipes was established taking into account the energy and nutrient requirements of lambs in the two fattening stages. The compound feeds as well as the bulk feeds (barley hay and corn silage) were administered ad libitum, according to the daily feed diets as established for each batch according to the fattening phases.   

The calculation for the nutritional value (Table 1 and Table 2) of feeds and fodder was based on the French system (INRA, 2010). The biological material investigated consisted of lambs belonging to the Palas Merino breed. Only female lambs from single births were chosen for the experiment, lambs that were weaned at the age of 3 months and had an average body weight at the beginning of the experiment of 19.87±0.36 kg for group T1 and 19.93±0.29 kg for group T2. All lambs were housed in collective pens (15 lambs/pen) during the experimental period and the pen was equipped with a suitable drinker and feeder for all 15 lambs (each pen had an area of 24 m2).

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Feed consumption, growth performance and meat parameters
 
Chemical analysis of lamb fodder was carried out using official methods of feed analysis (EC Regulation No 152/2009). The corn dried distillers grains used in this study was purchased from a single source and a single production batch, while the other fodder was prepared in IBNA-Balotesti. Feeds were administered twice a day (at 08.00 AM and 04.30 PM) and the control of their consumption was done by weighing them at the moment of distribution and the refusals at every morning before feeding. The animals had ad libitum access to water throughout the study. Consumption of UFV (net energy value for meat maintenance and production), DM (dry matter), PDIN (protein digestible in the intestine allowed by the nitrogen content of the ration) and PDIE (protein digestible at the intestinal level allowed by the energy content of the ration)/ per kg gain were calculated for the entire fattening period.

In order to highlight the dynamics of lamb growth and fattening, the individual weighing of the lambs was performed in different stages of fattening. Based on these data, the evolution of body weight (BW) and average daily gain (ADG) was established throughout the entire fattening period.

At the end of the fattening period, five lambs from each group were slaughtered and slaughter weight, carcass weight, slaughter yield, muscle surface area and carcass tissue structure were established. The slaughter of the animals was done after 12 hours of fasting and the weight of the carcass was determined after a cooling period of 24 hours at a temperature from 0 to + 4°C (cold carcass). Based on the ratio between carcass weight and live weight were calculated the slaughter yield. The surface of muscle (section of Longissimus dorsi muscle at the level between the 12th and 13th ribs) was determined using the planimetric method.
 
Statistical analysis
 
The results were presented as mean values±standard errors of mean. Microsoft Office Excel 2016 was used to calculate all statistical parameters (mean, standard deviation, coefficient of variability and standard error of average values) and t-test (Student) to determine the significance of the difference between the mean values. The differences were considered statistically significant at P<0.05 and indicated by superscripts.

Feed consumption
 
Pursuant the results obtained (Table 3) it was found that over the entire fattening period the average amount of daily dry matter intake (DMI) expressed in kg/head/day was 2.3% lower in group T2 compared to group T1, the differences being insignificant (P>0.05).

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Regarding feeding efficiency, the lambs from the T2 group had at all analyzed parameters (consumption of compound feed, DM, UFV, PDIN and PDIE/kg of gain) superior values of conversion into gain (between 5.5 and 8.3%) compared with lambs from T1 group. In addition, the feed conversion ratio (FCR), was better in group T2 compared to group T1 and the feed cost was 19.4% lower for the T2 group of lambs fed with DDG.

These results allowed us to conclude that DDG is an efficient and economical feed ingredient that can be used successfully by farmers in lambs fattening diets as a single source of protein and energy in the compound feed up to 30 kg live weight and as a substitute for sunflower meal, over this body weight.

The results of our study agree with previous literature (Gabr et al., 2010; Felix et al., 2012; Van Emon et al., 2012; Abdelrahim et al., 2014) which showed that DDGS inclusion in fattening diets of lambs had not increased DMI or feed conversion rates. Contrary to our findings, other studies found a significant increase in DMI consumption when growing lambs received diets with different levels of DDGS (Schauer et al., 2008; Curzaynz-Leyva et al., 2019).

In a complex analysis of the impact of the inclusion of DDGS in fattening lamb diets (Neville et al., 2021) showed that the consumption of DMI improves when DDGS is included at rates less than 30% of the ration dry matter, while the inclusion of DDGS at greater than or equal to 30% seems to decrease DMI. Decreased DMI can be attributed to increased dietary crude protein in DDGS - fed lambs (Van Emon et al., 2012).
 
Growth performance
 
As regards the evolution of the body weight of the lambs during fattening (Table 4), it was found that at the end of the fattening period (110 days) there were no statistical differences (P>0.05) between groups T1 and T2 regarding the average body weight of lambs (39.71±0.45 kg vs. 40.38 ±0.32). No statistical differences (P>0.05) were found either for the average daily gain (180.9±4.4 g for T1 and 186.3± 3.7 g for T2).

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The higher weight gain of lambs in group T2 compared to those in group T1 could be explained by the fact that corn dried distillers grain contains 15 to 20% undegradable intake protein (UIP) and 8 to 12% fat which makes possible this additional increase in weight gain (Abdelrahim et al., 2014). In general, the average daily gain increases most when DDGS is included at rates between 20-30% of the dry matter of the ration and less when it is included at rates above 40% (Neville et al., 2021).

Similarly to the results recorded in this study, previous research (Schauer et al., 2008; Gabr et al., 2010; Van Emon et al., 2012; Sahin et al., 2013) showed that including DDGS in fattening diets of lambs have not negatively influenced ADG and BW.

In contrast to the present study, (Klopfenstein et al., 2008) noticed a quadratic response in ADG as the level of DDGS in the beef cattle diet increased from 0 to 40%. Also, (Curzaynz-Leyva et al., 2019) found significantly higher values (P<0.05) for ADG and BW in the groups of lambs fed with levels of 15, 30 and 45% DDGS (% of the DM ration) compared to the control group (0% DDGS).

According to the results obtained in the present study, BW and ADG had higher values in group T2 than group T1, which led to the conclusion that the inclusion of corn dried distillers grain in feed diets had a beneficial effect on lamb growth performance.
 
Meat parameters
 
As regards the carcass parameters observed in the present study (live slaughter weight, carcass weight, slaughter yield and Longissimus dorsi muscle area), it was found that they had higher values in group T2 compared to group T1 (Table 5), yet such differences are not statistically different (P>0.05).

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In general, the results reported in the specialty literature showed that the inclusion of DDG in the lambs fattening diets led to no significant differences and no negative effects on carcass parameters, which are in accord with the results obtained in our study (Schauer et al., 2008; Van Emon et al., 2012; Abdelrahim et al., 2014; Hodges et al., 2020).

Contrary to the results obtained in the present study, (Curzaynz-Leyva et al., 2019) found that the inclusion of DDGS at 30 and 45% from DM levels of ration in lamb feed significantly improves (P<0.05) slaughter yield and carcass weight.

Based on the results of this study, it can be concluded that the inclusion of DDG in the lamb diet improved the consumption of dry matter intake, feed conversion rate, body weight, average daily gain and carcass parameters such that it can be recommended to be used in the lambs fattening diets as a single source of protein and energy in the compound feed up to 30 kg live weight and as a substitute for sunflower meal over this body weight. In addition, the feed cost is 19.4% lower for the batch of lambs fed with this by-product. Thus, the decision to include DDG as a feed ingredient in lambs fattening diets depends on the price and availability of cereals and groats on the market.

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