Effect of feeding mixtures of high moisture corn and dry-rolled grain sorghum on ruminal fermentation and starch digestion

Starch and Cellulose Degradation in the Rumen and Applications of Metagenomics on Ruminal Microorganisms

Carbohydrates (e.g., starch and cellulose) are the main energy source in the diets of dairy cows. The ruminal digestion of starch and cellulose is achieved by microorganisms and digestive enzymes. In order to improve their digestibility, the microbes and enzymes involved in starch and cellulose degradation should be identified and their role(s) and activity known. As existing and new analytical techniques are continuously being developed, our knowledge of the amylolytic and cellulolytic microbial community in the rumen of dairy cows has been evolving rapidly. Using traditional culture-based methods, the main amylolytic and cellulolytic bacteria, fungi and protozoa in the rumen of dairy cows have been isolated. These culturable microbes have been found to only account for a small fraction of the total population of microorganisms present in the rumen. A more recent application of the culture-independent approach of metagenomics has acquired a more complete genetic structure and functional composition of the rumen microbial community. Metagenomics can be divided into functional metagenomics and sequencing-based computational metagenomics. Both approaches have been applied in determining the microbial composition and function in the rumen. With these approaches, novel microbial species as well as enzymes, especially glycosyl hydrolases, have been discovered. This review summarizes the current state of knowledge regarding the major amylolytic and cellulolytic microorganisms present in the rumen of dairy cows. The ruminal amylases and cellulases are briefly discussed. The application of metagenomics technology in investigating glycosyl hydrolases is provided and the novel enzymes are compared in terms of glycosyl hydrolase families related to amylolytic and cellulolytic activities.

Effects of substituting corn with steam-flaked sorghum on growth, digestion and blood metabolites in young cattle fed feedlot diets

The objective of the present study was to evaluate the effects of substituting ground corn grain with steam-flaked sorghum (SFS) grain on growth performance, nutrient utilisation and blood metabolites in beef bulls. Fifty-six Simmental beef bulls averaging 12 months of age and 356.4 ± 2.6 kg of bodyweight were randomly assigned to four groups. The treatments were control, low-SFS, medium-SFS and high–SFS, with 0, 1/3, 2/3 and 3/3 SFS grain, respectively, substituting ground corn grain of diets(dry matter (DM) basis). Diets consisted of 50% corn silage and 50% concentrate (DM basis). The average daily gain and feed conversion rate improved quadratically with increasing the proportion of SFS grain. Ruminal pH and ammonia-nitrogen (N) concentration decreased quadratically, whereas ruminal total volatile fatty acid concentration increased quadratically. Ratio of acetate to propionate decreased quadratically (P = 0.027) due to the quadratic decrease in acetate production and the quadratic increase in propionate production. Digestibilities of DM, organic matter and crude protein increased quadratically, whereas that of neutral detergent fibre and acid detergent fibre decreased quadratically. The digestible N, retention N and the retention N to digestible N ratio improved quadratically. Inclusion of SFS grain in diets quadratically increased blood concentrations of glucose, total protein, albumin and triglyceride, but quadratically decreased the concentration of urea N. The results indicated that partly substituting ground corn grain with SFS grain could improve growth performance by improving ruminal fermentation and N utilisation; the optimum substitution rate was 2/3 (DM basis).

Effect of replacing barley with corn or sorghum grain on rumen fermentation characteristics and performance of Iranian Baluchi lamb fed high concentrate rations

The present study, conducted in Iran, was aimed to evaluate the effects of partial substitution of barley with corn or sorghum (slowly fermenting grains) on in situ dry matter (DM) and starch degradability and in vivo digestion characteristics and performance in finishing Iranian Baluchi lambs. In the first experiment, samples of ground barley (B), corn (C), sorghum (S) and their combinations [%: 70 barley : 30 corn (LC), 70 barley : 30 sorghum (LS), 30 barley : 70 corn (HC) and 30 barley : 70 sorghum (HS)] were incubated in nylon bags in rumen of three fistulated Holstein steers. Effective degradability (ED) for DM and starch were different (P < 0.05) among treatments. In both cases, ED was higher (P < 0.05) for B than that for C, S, HC and HS. Results of the present study confirmed previous reports that ruminal degradability of barley is higher than that of corn and sorghum, and further suggested that there may be benefits in replacing barley with ~70% of corn or sorghum. In Experiment 2, 30 Iranian Baluchi male lambs weaned at 65 days of age (BW 32 ± 2.3 kg) were divided into five equal weight groups (6 animals per group) in a complete randomised design. Lambs received a mixed diet in the form of total mixed rations (TMR), consisting of 32.5% alfalfa hay [89% DM, 43% natural detergent fibre (NDF) and 16% crude protein (CP) in diet DM basis] and 67.5% of the respective concentrates. The five iso-caloric (10.73 MJ ME/kg) and iso-nitrogenous (14% CP/kg DM) concentrates with different sources of starch used in the study were (1) barley, as the control cereal source for starch, and in the other treatments barley substituted with (2) 30% corn (LC), (3) 30% sorghum (LS), (4) 70% corn (HC) and (5) 70% sorghum (HS). Lambs in HC and HS diets recorded increases of 20 and 50 g/day in average daily gain, respectively, compared with lambs in B. Substitution of B with 70% C and S significantly (P < 0.01) improved ruminal pH and, presumably, resulted in higher starch outflow for post-ruminal digestion, as reflected by a higher blood glucose concentration, particularly for lambs in the HS diet. Results of the present study reaffirmed the advantages of feeding a mixture of grains with differing fermentation rates and, as previously reported, also suggested that the inclusion rate of slowly degradable grains should be ~70% so as to enhance animal performance.