An Assessment of Differences in the Ruminal Degradability and Intestinal Digestibility of Crude Protein in Brewer’s Grains and Maize Draff

MAJER, V., VESELÝ, P.: An assessment of diff erences in the ruminal degradability and intestinal digestibility of crude protein in brewer’s grains and maize draff . Acta univ. agric. et silvic. Mendel. Brun., 2012, LX, No. 1, pp. 97–104 The submitted thesis aims to assess the diff erences between the ruminal degradability and intestinal digestibility of crude protein contained in brewer’s grains (BG) and maize draff (AMG). The eff ectiveness of ruminal degradability was tested using the “in sacco” method on 3 dry Holstain cows fi tted with rumen cannulas. The dynamics of ruminal degradability of crude protein (CP) was detected a er 0, 4, 8, 16, and 24 hours of samples incubation in the rumen. The intestinal digestibility of crude protein undegradable in the rumen was determined using the “mobile bag” method on 3 dry Holstain cows fi tted with duodenal cannulas. The crude protein degradability of BG was detected in the abovementioned hours (%): 4.06; 18.16; 32.40; 38.56, and 50.70; crude protein degradability of AMG: 42.04; 63.56; 84.47; 85.16, and 87.19. The eff ectiveness of rumen degradability of BG crude protein at the rate of passage of rumen content 6 % per hour was calculated at 35.33 % and that of AMG, at 76.29 %. Intestinal digestibility of BG crude protein and dry matter at the rate of passage of intestinal content 6 % per hour was calculated at 79.41 % and 22.84 %, respectively, and that of AMG, at 57.01 % and 11.33 %, respectively. The diff erences between the indicators of both feedstuff s were signifi cant (P < 0.05). The results show that BG are mostly a source of crude protein with higher intestinal digestibility than AMG. fresh brewer’s grains, fresh maize draff , “in sacco” method, ruminal degradability, “mobile bag” method, intestinal digestibility The increasing worldwide demand for raw materials for food production and the increasing pressure of food producers on improving the quality of raw cow milk and decreasing its price, require from breeders, not only in European Union countries, to pay greater attention to breeding from the view of both keeping the principles of free stabling and reaching the appropriate nutrition of animals. The aim of achieving the maximum sign of genetic potential through optimizing nutrition o en makes dairy cow breeders increase the concentration of nutrients in feed rations. The most frequently used feedstuff s with a high concentration of nutrients are cereals. Apart from cereals, also byproducts from industrial production are included in feed rations. Besides the nutritional value, also the price and local availability of nutrients are important criteria decisive for their utilization. Traditional by-products from industrial production include a locally and easily available intermediate product of the brewing industry – brewer’s grains (DACCORD et al., 1997). Fresh brewer’s grains (BG) are produced as an intermediate product in beer-making a er the separation of sweetwort (desugarization) from deslimed output (i.e. the suspension of grains in a water solution of extractive substances – sweetwort). They are insoluble parts of barley caryopsis endosperm with starch residues, glumes, and fl akes of substances coagulated during malt fermentation (gluten fl akes, other coagulated 98 V. Majer, P. Veselý proteins, dead yeast etc.). BG are considered a cheap source of crude protein into which up to 75 % of the content of all crude protein of malting barley is transformed. The biological value of Crude protein contained in grains is high. This is given, among others, by the presence of dead organism residues, mainly yeast, which proliferated in the substrate during fermentation. Fresh BG have a high digestibility of organic matter – 64 %, and they can be considered a good source of protein un-degradable in rumen, preferentially for dairy cows of specialized milk breeds (COSTA et al., 1995). Grains contain 15.25 % of proteins in dry matter on average. Mainly glucose and maltose are represented in fresh BG from monosaccharides and mainly hemicellulose from polysaccharides – 28.4 % and cellulose – 16.8 % in dry matter (LOHNERT et al., 1996). The average content of lignin in brewer’s grains is about 27.8 % in dry matter. BG are also an important source of calcium, sodium, potassium, magnesium, aluminium, iron, copper, zinc, phosphorus, and sulphur (MUSSATTO and ROBERTO, 2006). Its appropriate inclusion in feed has a positive eff ect on increasing the effi ciency and quality of milk – the content of fat, proteins and casein (GOLECKY, 2004). Another suitable source of nutrients for livestock is maize draff (AMG) produced in the process of maize starch production (BATAJOO and SHAVER, 1998). It is a by-product produced a er the grinding, washing and steeping of maize grain in water while adding sulphuric acid. The principle of solubility and insolubility, diff erent specifi c weight and size of individual fractions contained in maize grain processed in this way causes separation and, by the subsequent fi ltration, separating starch and draff , i.e. residues of the endosperm and glumes of maize grains. AMG is a suitable feed for livestock as it has a high value of ruminal degradability of dry matter – 56.9 %, crude protein – 70.3 % (BATAJOO and SHAVER, 1998). The aim of the submitted thesis was to identify diff erences between the ruminal degradability and intestinal digestibility of crude protein contained in fresh BG and fresh AMG. MATERIAL AND METHODS The submitted thesis assessed the ruminal degradability and intestinal digestibility of crude protein in samples of fresh BG and fresh AMG. The eff ectiveness of ruminal degradability was tested using the “in sacco” method on 3 dry Holstain cows fi tted with rumen cannulas. The cows were fed twice a day at 6 a.m. and 4 p.m. The feed ration was comprised of 4 kg of lucerne hay, 10 kg of maize silage and 1 kg of a mixture of barley meal with mineral and vitamin supplements. The samples of BG and AMG were dried at 60 °C for a period of 24 hours and then milled in a laboratory mill with a 1mm sieve. The contents of dry matter, crude protein, fi bre and ash matter (ANONYM, 2001), and neutral detergent fi bre (ISO 16472, 2009) were determined for the samples taken. According to TŘÍNÁCTÝ et al. (2009), the acquired samples were put, in the amount of 2 g of dry matter, in nylon bags 90 x 150 mm, i.e. 15 mg/cm2 of the bag area with pore size 42 μm (VAZANT et al., 1998), and these fi xed into a cylindrical carrier. The nylon bags with samples were incubated in the rumens of cannulated dairy cows standing dry for periods of 2, 4, 8, 16, and 24 hours. The eff ective ruminal degradability was calculated using the method according to ØRSKOV and McDONALD (1979) at the anticipated rate of rumen content passage 6 % per hour. The intestinal digestibility of crude protein undegradable in the rumen was determined using the technique “mobile bag” according to HOMOLKA et al. (1996) on 3 dry Holstain cows fi tted with intestinal cannulas. The cows were fed twice a day at 6 a.m. and 4 p.m. The feed ration was comprised of 4 kg of lucerne hay, 10 kg of maize silage and 1 kg of a mixture of barley meal with mineral and vitamin supplements. The samples of undegradable spent grains acquired a er its 16-hour incubation in the rumens of dairy cows were placed in a solution of pepsin and hydrochloric acid (0,1 N solution) in an artifi cial maw. A er 2.5 hours of incubation, they were inserted in the duodenums of 3 cannulated dry Holstain cows, 20 bags to each of them. The bags with samples found a er 24 hours from insertion in the duodenums in the faeces of the cannulated dairy cows were washed 30 minnutes in water, weighted, dried (lyophilized) and their contents were combined. Then the content of dry matter and nitrogen was determined for the composite samples (ANONYM, 2001). The measured values of ruminal degradability and the calculated values of eff ective ruminal degradability and intestinal digestibility were tested using a twofactor variance analysis by using the Scheff e correction method against exceeding the total experimental error in the program STATISTICA 6 (2001).