Effect of Feed Digestibility and Milk Yield on Feed Intake and Daily Methane Production
The Kenyan cattle industry relies on beef as well as dairy cattle. The population currently being 120 million heads. These are raised in the relatively dry agroecological zones or the crop-livestock production systems where poor-quality forages are used. This study was based in the medium agricultural zone where grazing natural pastures are used as Nandi County is located in the western part of the Rift Valley of Kenya. The study sampled farms across the three agro-ecological zones (AEZs) (Lower highland1, Lower highland 2 and Upper midlands) and four seasons in the County following a sampling protocol. The number of sampling points in each AEZ was based on the total sample size (127 households) weighted by the total area of each AEZ, and 487 dairy cows and data collection spanned one year, from November 2015 to October 2016.. In total, 36 GPS points across the three AEZs were selected, restricted by proximity to roads of 2 km (<2 km distant). GPS points were allocated across the three AEZs (LH1: 22, LH2: 8 and UM: 6) and then used to navigate to the nearest village, and household. Feed intake, nutrient composition, milk yield and quality were determined as well as body condition and activities of the cows. Milk yield, live weight, live weight changes, total metabolizable energy, dry matter intake and daily methane production for each season and agro-ecological zone (AEZ) were assessed. Analysis of variance (ANOVA); linear regression and correlation test was carried out to test the relationship between DMD and DMP. This was done using the R i386 3.4.1 statistical package. Results revealed that feed differed among the agroecological zones and feed types. A higher feed dry matter digestibility led to significant daily methane production. There were differences in DMP between AEZs (p = 0.0002), 39.97% of which was influenced levels of daily milk yield, and seasons (p-value=0.048) and this only between short rains and hot dry season (p<0.000). It is concluded that enteric methane emissions increase with rising levels of milk production and lower feed quality and digestibility.
Key words: Agro-ecological zone, Dairy cows, Digestibility, Feed quality, Methane production, Milk yield
