Degradation parameters and modelling of degradation rate in the rumen of cattle fed non-supplemented roughages.

Master of Science in Agriculture (Animal and poultry science)

Feeding of animal has become increasingly a big challenge in livestock production systems as it is the most costly input. Ruminants are very important to mankind because they can convert fibre-rich vegetation into high quality protein sources for human consumption. The objective of this study was to determine roughage intake in ruminants using data. The study was conducted using two fistulated jersey cows and data from several literature records with feed properties, diet properties and in sacco degradation parameters. An in sacco degradation study was conducted at Ukulinga Research farm. Ten different roughages were used, namely; (MS) maize stover (Zea Mays), maize leaves (ML), (WS) wheat straw (Tritium sativa), (KK) kikuyu (Pennisetum clandenstinum), (EC) weeping love grass (Erograstis curvula), (ECC) weeping love grass at bloom stage (Erograstis curvula), veld grass hays (VGHA, VGHD, VGHC & VGHP) from Airport at Pietermaritzburg, Dundee, Camperdown and Ukulinga Research Farm, respectively. All collected data for both experimental and from the literature were used to determine correlations and build regression models based on degradation parameters, diet and incubated feed properties. Also, intake and total digestibility were predicted based on degradation rate and particle passage rate. In the study to determine degradation properties of roughages and their interaction with three different rumen environments, roughages in rumen environments supplemented with lucerne had increased (P<0.0001) insoluble but potential degradable fraction (b), potential degradability (PD) and effective degradability (ED) of dry matter. Rate of degradation (c), the potential and effective degradability differed (P<0.0001) amongst roughages in three different rumen environments but the DM solubility (a) did not. The outcome of the study to establish a regression model for degradation rate of roughages in non-supplemented diets produced six regression models & there were strong correlations (P<0.0001) between degradation parameters, diet properties and feed properties. In the study to use a model to simulate intake and digestibility, results showed small chances of predicting intake pertaining relationships in all observations with values of coefficient of determination (R2) ranging from 10% to 24%, suggesting that some factor may not have been fully appreciated. The best coefficient of determination (R2) for the digestibility relationship were 82% and 44% for two studies out of four meaning that there are possible chances that digestibility can be predicted. Significant variations of in sacco degradability parameters were reported among roughages incubated in different rumen environments. Therefore, these results may be linked with other studies and be used to find a relationship between degradation rates of low quality roughages. In conclusion, the inclusion of variables like retention time and other factors that significantly affects intake in addition to diet and incubated feed properties, may improve simulation of intake and total digestibility of non- supplemented low quality roughages.