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Effects of Kenaf (Hibiscus cannabinus) as a Substitute Feed on Lactating Dairy Cattle
Dissertation Abstract:
Improvement of ruminant feeding system by using locally grown fodder has received much attention in the tropics. Recently, kenaf has been shown to be a valuable fodder for beef cattle and small ruminants, but information on its use for dairy cow is scanty. Hence, the overall objective of the study was to examine the potential of using kenaf as a susbstitute for alfalfa (AH) and soybean meal (SBM) in dairy cow rations. Three experiments were carried out to achieve the above objective.
Experiment 1 consisted of two studies. In the first study, yield and chemical composition of kenaf at different harvesting age were determined. Kenaf showed a favorable potential yield and chemical composition as fodder. Dry matter (DM), crude protein (CP), and amino acid (AA) degradability and digestibility of kenaf were measured and compared to AH and SBM in the second trial. Dry matter, CP, and AA of kenaf were largely degraded in the rumen, resulting in low ruminal undergradable nutrient and absorbable AA. Nutrient degradability and digestibility of six-week-old kenaf were comparable to AH. Nutrient availability of kenaf was less than SBM.
The optimum level of substituting AH and CP from SBM with kenaf in diets and its effect on growth performance and nutrient utilization of growing dairy heifers were examined in experiment 2, which also consisted of two studies. In the first study, four crossbred dairy heifers were randomly fed four diets, in which AH was substituted with kenaf at 0, 33, 66, and 100 percent in a 4 × 4 Latin square design of 21-day periods. Total substituting AH with kenaf had a significant negative impact (p < .05) on feed intake, digestibilities of DM, organic matter (OM), fiber components, and microbial protein synthesis (MPS). In the second trial, another group of four crossbred dairy heifers were used to determine the effect of substitution of CP from SBM with CP of kenaf at 0, 33, 66, and 100 percent in a 4 × 4 Latin square design.
The results showed that nutrient digestibility and MPS were markedly affected (p < .05) when one- to two-thirds of the CP from SBM was substituted with the CP of kenaf. Therefore, kenaf can substitute AH or CP from SBM up to about 66 percent in dairy heifer diets.
Experiment 3 involved substituting AH and/or CP from SBM with kenaf in lactating dairy cow diets. Eight lactating crossbred Sahiwal-Friesians were used in a 4 × 3 incomplete Latin square design with 15-day periods. The diets were T1 = control, T2 = AH substituted with kenaf, and T3 = CP from SBM substituted with CP of kenaf. Feed intake, nutrient digestibility, milk yield, and milk composition were significantly affected (p < 0.05), and AA availability to the mammary gland tended to decrease with substitution of kenaf. Lysine or methionine was the first or second limiting AA for milk protein synthesis. Leucine and phenylalanine ranked third and fourth, respectively, with increasing levels of inclusion of kenaf in the diets of lactating dairy cows.
