An evaluation of Brachiaria grass cultivars productivity in semi arid Kenya

Abstract

The scarce and low nutritive livestock forage resource base in semi arid Kenya limits livestock production in these regions. The major factor contributing to this situation is inadequate and erratic rainfall patterns accompanied by long dry spells often culminating into drought. To exploit the full potential of the ASALs for livestock production there is need to expand the forage resource base through introduction of climate smart forage species. This study was carried out to evaluate the growth of Brachiaria grass cultivars, seasonal herbage yield and quality in semi arid regions of Eastern Kenya. It was conducted at Kenya Agricultural Research Institute, (now Kenya Agricultural and Livestock Research Organisation) Katumani, Machakos. Brachiaria cultivars namely B. decumbens cv. Basilisk, Brachiaria hybrid Mulato II, four Brachiaria brizantha cultivars Marandu, Xaraes, BRS Piata, MG4 and two Brachiaria humidicola cultivars Humidicola and Llanero were assessed in their performance with reference to establishment rates ,dry matter yields, chemical and nutritive composition. Rhodes grass (Chloris gayana KAT R3) and Napier grass (P. pupureum cv. Kakamega I) were included as controls. In the first experiment germination percentages of the cultivars under controlled conditions in the laboratory over a period of 14 days were established alongside seedling vigour. The experimental set up involved soaking seed in concentrated sulphuric acid (> 95%) for 10 minutes and another set of the same seed in water only as controls. The second experiment involved two phases namely field establishment phase and production phase. Field establishment of the cultivars was carried out in a randomized complete block design with four replications. Plant production parameters and attributes which include plant numbers, heights, spread, plant tiller number and plant cover were monitored up to 16 weeks post seedling emergence. A standardization cut was carried out on all the plots at the end of this period and dry matter yields determined. The production phase involved measuring of the same plant attributes and chemical analysis of forage samples harvested at 6, 8 and 12 weeks regrowths after standardization. Treatment of the seeds with Concentrated sulphuric acid (> 95%) had no significant effect (p>0.05) on germination percentage. Cultivars Marandu, MG4 and Brachiaria hybrid Mulato II had similar germination percentage and were superior to the rest of the cultivars. Brachiaria brizantha cultivars Marandu, MG4 and Piata demonstrated superior seedling vigour. All the growth parameters measured varied significantly (p<0.05) among the grass cultivars during the establishment phase. Chloris gayana KATR3 recorded the highest plant numbers (48 plants /m2) and Napier grass the highest plant height (103.8cm), plot cover (94.9%) and average dry matter yields (5430kg /ha). Llanero recorded highest plant spread (146.9 cm) and tiller recruitment (31/plant). At the production phase nutritive value and chemical composition of the cultivars varied significantly (p<0.05). Piata recorded highest dry matter yields (8,867kg/ha), IVDMD (52.3%) at week 12 harvest interval. The metabolizable energy of the grasses declined with maturity and at the week 12, there was no significant difference among the cultivars for this variable. Mean crude protein content of the grasses decreased by 4.8% during the harvest intervals and only MG4, Mulato II and Xaraes were able to meet minimum CP requirement for rumen microbial function during this period. There was a general decrease in ash and phosphorus content and increase in calcium content of the cultivars during the harvest intervals. Mulato II maintained high ash content (15%) ash content during this period. Phosphorus content was low. Mulato II, MG4 and Marandu recorded higher phosphorus content than the rest of the cultivars ranging from 0.81% at week 6 to 0.096% at week 12 harvest interval. Chloris gayana KATR3 recorded highest NDF (72.5-73.8%), ADF (45.6-50.2%) and ADL (5.2-6.5%) content throughout the production phase. From the study, Brachiaria grasses cultivars Marandu, MG4 and Mulato II establish well in terms of germination percentages and seedling vigour. Llanero is excellent in plant spread and this attribute can be used to protect soil from erosion alongside being used as forage. MG4, Mulato II and Xaraes are able to supply quality feed for longer periods than the rest of the cultivars. In general the Brachiaria grass species have potential to supply feed in the semi arid regions of Eastern Kenya and can cushion livestock from feed stress in the prolonged dry seasons. It is recommended that the experiment be conducted for a longer period of time to quantify their production in both dry and wet periods. Further research is needed to assess the effect of feeding these grass cultivars on animal performance.