Assessment Of Sweet Potato Cultivars As Protein And Energy Feed Supplements In The Kenyan Highlands

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Date
2013
Authors
James M K
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James M K
Abstract
A common scenano In livestock production in developing countries is shortage and poor feedstuffs. Whereas, dairying is an important economic activity in the highlands of Kenya, the low income accrued from milk is a result of low quantities of milk produced from dairy cows mainly due to lack of sufficient protein and energy supplement to the basal diet. In view of the high cost of commercial supplements, locally available crops of high nutritive value have offered a better alternative. The main objective of this study was to identify and recommend suitable cultivar(s) of sweet potato as a protein and energy supplement for dairy fanners, in the study areas. Six pre-screened sweet potatoes cultivars; 10300 I, Gweri, Kemb23, Kemb36, Naspotl and Wagabolige were planted in three different agro-climatic areas in the highlands under two different management (defoliating and undefoliating of vines at day-75 post planting). Gweri and Kemb23 had highest establishments of95.7 % and 93.0% (P<0.05) respectively. The vine and storage roots DM yield were 6.55 and 2.83 tons/ha (P<0.05) for Kemb36 and 103001, respectively. The CP content of vines was higher (P<0.05) on day 75 compared to day 150 (29.7% versus (vs) 24.0 %). Naspotl (29.7 %) had the highest level of vine CP at day-75 while Gweri (23.2%) and Naspotl (24.0 %) had the highest levels of unratooned and ratooned vine CP, respectively (P<0.05). Wagabolige gave the highest (P<0.05) root storage CP (14.5 vs 14.2 g/Kg) (P<0.05) both when ratooned and unratooned. Storage roots had higher (P<0.05) ME than the vines, Naspot (12.5 MJ/kg) and Gweri (9.6 MJ/kg) being the highest respectively. Naspotl vines had a high degradation extent (P<0.05) while Kemb36 storage roots had a high effective degradation (P<0.05). Supplementing vines and storage roots increased the rumen pH levels 3 hr postfeeding (P<0.05). Increasing supplemental vines fed to steers from 11 to 22 kg (wet weight) did not improve (P>0.05) the in-vivo degradation of Rhodes grass hay. There was improvement (P<0.05) of Rhodes grass hay degradation potential and rate when various levels of vines (5.5. and 11 kg wet weight) and storage roots (1.5 and 3 kg wet weight) were fed. There was a high (P<0.05) concentration of ammonia nitrogen in the rumen of animals 3 hr post-feeding of the vines. Feeding storage roots increased (P<0.05) the molar proportion of propionate in the rumen (28.3 molll00mol) but vines (25 .5 mol/ lOOmol) (P>0.05). Up to 11 kg of fresh vines and 6 kg of storage roots of sweet potato were recommended for supplementation to dairy cattle based on the various parameters which were investigated.
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