Influence of particle size of barley and wheat grain on performance, feeding behavior, nutrient digestibility, and blood parameters in Dalagh fattening lambs

Introduction: Wheat grain is normally used for animal feed in some regions, but is seldom used in others. Its nutritional composition is very similar to that of the barley grain commonly used, but there are concerns about its effects on the performance and health of the animals. Wheat seed is one of the grain varieties with the highest amount of protein available for animal feed, exceeding corn. Furthermore, it has a high energy value of 3.0 to 3.5 Mcal of ME (metabolizable energy), which is an important source of energy for animal feed. The most abundant carbohydrate in wheat is starch, a digestible polysaccharide. On the other hand, it is recommended that wheat has a moisture content of less than 14% to avoid problems with digestibility and contamination by mycotoxigenic fungi. Barley is an important grain which is widely used as a source of feed for ruminants. Feed deliveries during the fattening period are the physical processing of the feed. It has been demonstrated that barley starch ferments rapidly in the rumen. The high digestibility of barley has raised concerns regarding acidosis, lameness, liver abscesses, and gastrointestinal abnormalities in ruminants. It is generally considered that the processing of barley grain may be used in the feed industry to adjust the rate of digestion of its nutrients to avoid acidosis. Consequently, the distribution of particle sizes after processing is one of the main factors influencing the rate and extent of digestion of barley (feeding of livestock accounts for 65-70% of the cost of raising livestock). Wheat and barley are used as the predominant source of energy for animal nutrition in most parts of the world. Wheat seed has been used for a long time because of the extensive cultivation and livestock rearing in Iran. The most common way of processing barley and wheat grain in the country is by grinding. Farmers prefer to use whole grains in the production of concentrates, as the concentrate involves the use of crushed grains, but the farmer's wish to use whole grains in the concentrate requires a study and field investigation. The purpose of this study is therefore to examine the effects of the grain size of barley and wheat on the diet of lambs fattening and to compare their effects on growth performance, digestibility, rumination and blood parameters. Materials and methods: This experiment was carried out in the form of a completely randomized design with a factorial arrangement of 3×2 with six treatments including 1. Finely milled barley grain with sieve number two, 2. Coarsely milled barley grain with sieve number eight, 3. Unmilled barley grain, 4. Finely milled wheat grain with sieve number two, 5. Coarsely milled wheat grain with sieve number eight, and 6. Unmilled wheat grain. Five fattening lambs aged 4-5 months with almost the same starting weight were allocated to each treatment and a total of 30 male lambs were individually tested for 98 days, including two weeks for acclimatization and 84 days for the remainder of the main test period. The performance of lambs was assessed in this experiment, including average daily feed consumption, daily weight gain, final weight, and feed conversion ratio. Nutrient digestibility was measured by the acid-insoluble ash (AIA) method from day 80 for four days. The digestibility of dry matter organic matter, crude protein, ether extract, and neutral detergent fiber was evaluated. Blood parameters were measured including blood glucose, blood cholesterol (LDL-c, HDL-c), and blood urea nitrogen (BUN). Results and discussion: The results showed that daily weight gain was significant throughout the treatment period and daily weight gain was greater in the treatment group that consumed barley than in the treatment group that consumed wheat (P<0.05). The impact of the grain, the type of processing, and their interaction on feed consumption in all three experimental periods was not significant. Total feed consumption was not significant, but it was significant during the last month of fattening (P<0.05). Lambs consuming barley and wheat milled with sieve number eight had the highest feed consumption compared with the treatment of wheat and barley with sieve number two and whole grains (P<0.05). The feed conversion ratio in treatments receiving wheat was higher than that in those receiving barley (P<0.05). The type of processing had no significant impact on the feed conversion rate (P>0.05). In the study of nutritional behavior, the results showed that the parameters of eating and rumination were higher in the treatments receiving wheat compared to barley (P<0.05). Also, the treatments receiving unmilled barley and wheat (whole grain) showed the highest levels of eating and rumination (P<0.05). The treatments receiving barley and wheat grains with sieve number two also showed the lowest levels of eating and rumination. There were no significant differences in nutrient digestibility, rumination parameters, and blood parameters (P>0.05). Contrary to the view of the farmers that whole grains are better than milled grains, the results showed that overall the use of ground or whole grains did not show a significant difference. Conclusions: Overall, the results showed that there was no significant difference between whole grain and milled grain, and even from the point of view of palatability, milled grain with a sieve number 8 had a higher consumption rate than the other treatments. These findings indicate that milled barley grain with a sieve number 8 may be used as a substitute for whole barley grain in the feeding of lambs.