Effects of different levels of corn steep liquor on performance, milk composition, digestibility of nutrients, rumination behavior and blood parameters of Dalagh ewes

Abstract
Introduction: In today's society, where we are facing an increase in the price of grains, the use of agricultural by-products in animal husbandry is very important. Corn is widely used in industry. The nutritional value of corn industrial products is very important and it is one of the cheapest and purest sources of production of organic materials for industrial consumption. Starch, animal feed, sugar syrup and oil are extracted from this plant in starch factories. Residues from food industries are among the industrial wastes that can be consumed by animals. In extracting starch and preparing glucose from corn, by-products are obtained which are suitable for animal feeding. Among these products, we can mention the corn steep liquor. Corn steep liquor, which is produced during the wet milling process of corn kernels to extract corn starch and oil, is a relatively cheap, tasty and easily available product for animals and it has potential to be used as a feed material in ruminants due to its relatively high energy and protein content and low fiber concentration. Materials and Methods: This research was conducted in order to investigate the effect of different levels of corn steep liquor on performance, milk composition, digestibility of nutrients, rumen and blood parameters and rumination behavior of Dalagh ewes. In order to perform this experiment, 21 dairy ewes with three bellies of the Dalagh breed with an average weight of 36±3.7 kg were used in 3 treatments and 7 repetitions in the form of a completely randomized design. The treatments included: control treatment (diet without adding corn steep liquor), second treatment (ration containing 100 grams of corn steep liquor per kilogram of dry matter consumed), third treatment (ration containing 200 grams of corn steep liquor per kilogram of dry matter consumed). The duration of the experiment was 42 days of main course. The rations used in this experiment were prepared and adjusted according to the tables of the National Sheep Research Society and were given to the ewes at two times in the morning (8 o'clock) and in the evening (16 o'clock).The daily feed was thoroughly mixed with livestock. During the whole experiment, the animals had free access to clean drinking water. On the 38th day of milk test all ewes were milked and samples were taken to measure milk composition. The ewes were weighed weekly before feeding in the morning. Feed was also given, and feed was then recorded daily to calculate the dry matter consumed. Stool and feed samples were collected from days 41 to 45 for 5 days to perform digestibility tests. Blood sampling were performed on days 42, respectively. In order to perform this experiment, 21 dairy ewes with three bellies of the Dalagh breed with an average weight of 36±3.7 kg were used in 3 treatments and 7 repetitions in the form of a completely randomized design. The treatments included: control treatment (diet without adding corn steep liquor), second treatment (ration containing 100 grams of corn steep liquor per kilogram of dry matter consumed), third treatment (ration containing 200 grams of corn steep liquor per kilogram of dry matter consumed). The duration of the experiment was 42 days of main course. The rations used in this experiment were prepared and adjusted according to the tables of the National Sheep Research Society and were given to the ewes at two times in the morning (8 o'clock) and in the evening (16 o'clock).The daily feed was thoroughly mixed with livestock. During the whole experiment, the animals had free access to clean drinking water. On the 38th day of milk test all ewes were milked and samples were taken to measure milk composition. The ewes were weighed weekly before feeding in the morning. Feed was also given, and feed was then recorded daily to calculate the dry matter consumed. Stool and feed samples were collected from days 41 to 45 for 5 days to perform digestibility tests. Blood sampling were performed on days 42, respectively. During the 39th and 40th days of the experiment, feed intake behavior was recorded as activity record for 24 h. Results and Discussion: The results showed that there was no significant difference in the final weight of ewes, daily weight gain and food conversion ratio in receiving different amounts of corn steep liquor (P<0.05), but the dry matter consumption increased with the increase in the level of corn steep liquor in the diet. Among the different treatments, no significant difference was observed in terms of the amount of milk produced, milk fat, total solids and milk lactose, but the percentage of protein and milk ash was affected by the experimental treatments, so that with the increase in the levels of corn steep liquor, this Milk compounds also increased (P<0.05). There was no significant difference between the treatments for dry nutrients, organic matter, crude protein, acid detergent fiber, neutral detergent fiber and ether extract. By increasing the level of corn steep liquor in the diet, the rumination behavior including eating, ruminating, chewing increases and naturally the resting behavior decreases (P<0.05). There is no significant difference in albumin, globulin and the ratio of albumin to blood globulin among the treatments receiving different amounts of corn steep liquor. However, total protein was affected by the experimental treatments, so that the concentration of these parameters increased with the increase in the level of corn steep liquor (P<0.05). Conclusion: According to the results, it can be recommended to add corn steep liquor to animal rations up to the level of 200 grams per kilogram of dry matter consumed.