Ensiling Total Mixed Ration for Ruminants: A Review

The interest of ensiling total mixed rations (TMR) for ruminants reemerged in the last decades. In many situations, ensiling TMR has been a sustainable alternative to efficiently handle wet byproducts in ruminant diets. An ensiled TMR typically has a markedly higher aerobic stability than its respective fresh TMR. Ensiling a TMR increases ruminal protein degradability due to proteolysis during storage. An increase of feed efficiency by ruminants fed ensiled rations have been reported, due to the improved starch digestibility in TMR silages containing cereal grains. This manuscript brings an overview of the main nutrient transformations during the ensiling of TMR and their feeding value for ruminants.

Protein degradability of grassland forage under simulated rotational spring grazing

A cutting experiment was conducted to analyze the changes in the crude protein (CP) fraction content and in the estimated ruminal protein degradability of forage, obtained in conditions of simulated rotational spring grazing on permanent grassland. The field trial was conducted on permanent pasture during 2015 and included three cuttings as a simulated rotational spring grazing. For determination of protein degradability of pasture forage, the fractionation of the CP according to Cornell Net Carbohydrate and Protein System (CNCPS v6.5) and the Streptomyces griseus protease assay were used. Relative to CP, no significant differences were found among cuts for ammonia N content (A1 fraction) and for protein fraction C which is completely unavailable to the animals. Values for soluble true protein (A2 fraction) and cell wall-associated protein, which is acid detergent soluble (B2), were significantly increased (p<0.05) while a significant reduction (p<0.05) of the moderately degradable protein (B1) content was determined during the growing season. The lower rumen degradable protein (RDP) content of grassland herbage was obtained in the second cut which was significant (p<0.05) according to the CNCPS procedure. Obtained high solubility and degradability of CP in pasture require adequate content of readily available carbohydrates in rations for grazing ruminants to provide efficient utilization of consumed protein.

In situ ruminal digestibility of red osier dogwood in finishing beef heifers

An in situ study was conducted to determine the effect of feeding red osier dogwood (ROD) on ruminal digestion of barley, ROD, and barley silage in beef heifers. Heifers were fed diets that varied by substituting ROD for barley silage at 0%, 3%, 7%, or 10%. Slowly degradable fraction and effective degradability (ED) of ROD crude protein (CP) linearly (P < 0.02) increased with increasing ROD. The ED of CP of barley and barley silage was reduced (P < 0.01) by feeding ROD. These results indicate that feeding ROD potentially reduces ruminal protein degradability, thereby improving protein efficiency.

In vitro degradability of feed proteins in the rumen: use of non-rumen proteases

Various feed proteins were incubated independently with bacterial protease from Streptomyces griseus (SGP), papain (Corica papaya), and ficin (Ficus glabrata) in a simple laboratory assay to predict ruminal protein degradability. The estimates obtained from in vitro assays were compared with those obtained from an in situ analysis using synthetic fibre bags. The rate and extent of degradation in vitro using proteases from non-rumen sources differed among substrates used. A high correlation coefficient (r2 = 0.99) was observed between N-degradability from the in vitro method using SGP and in situ estimates when soybean meal was the substrate. Soybean meal nitrogen (N) was almost completely hydrolysed (0.99) in vitro. The correlation coefficients were low and variable with assays using other enzymes. The correlation coefficient was also high (r2 = 0.77–0.84) with in vitro methods using either SGP, papain, or ficin when incubated with fish meal. The N disappearance from barley in vitro was slow to moderate. The ‘b’ estimate of barley obtained with the in vitro assay was significantly (P < 0.01) lower than that observed in situ. Slower proteolysis observed in barley may possibly be linked to poor accessibility of structural proteins rather than the degradability of N per se. None of the enzymes could rank barley in the same order as the in situ method.