AGRONOMIC CHARACTERISTICS AND FEEDING VALUE OF DESHO GRASS (Pennisetum glaucifolium Hochst. Ex A. Rich) FOR LACTATING DAIRY COWS IN ETHIOPIA

Abstract

This study explored agronomic characteristics of desho grass (Pennisetum glaucifolium Hochst. Ex. A. Rich.) and its feeding value for lactating dairy cows in Ethiopia. The study consisted of experiments conducted to generate information on agronomic characteristics of desho grass; effect of fertilizer application on herbage yield and quality; compatibility and effect of growing desho in binary mixtures with potentially compatible forage legumes (Desmodium unicinatum and Stylosanthes guyanensis) on herbage yield, nutrient composition and feeding value of desho grass hay, fed as a basal feed substitute to high-grade dairy cows. The first experiment was aimed to evaluate the effects of nitrogen fertilizer levels on agronomic performance, forage yield and chemical composition of desho grass varieties under rain fed condition during 2018 and 2019 cropping seasons at Assosa, Ethiopia. This field experiment consisted of a two-factor factorial arranged in a randomized complete block design (RCBD) with three replications. The assessed parameters were plant height, number of tillers per plant, leaf-to-stem ratio and dry matter yield (DMY). The majority of the chemical components of desho grass, mainly dry matter (DM) and crude protein (CP) concentration and crude protein yield (CPY) were influenced (p<0.001) by the level of nitrogen fertilizer and genotypic difference among desho grass varieties. The highest CPY (1.60 t/ha) was recorded from Kulumsa-DZF-592, while the lowest (1.21 t/ha) was from Kindokoisha 1-DZF-591. The highest CPY (1.84 t/ha) was recorded from 150 kg/ha fertilizer level while the lowest (1.01 t/ha) CPY was obtained from the control (0 kg/ha level). Overall, the result suggested that the two desho grass varieties (Kulumsa-DZF#592 and Areka-DZF-590) were superior in terms of herbage yield and chemical composition at 150 kg/ha nitrogen fertilizer application rate. There was also interaction effect (p<0.05) of fertilizer level and varieties in one growth variable, number of tillers per plant (NTP), and with CPY and acid detergent fiber (ADF) concentration. The second experiment was designed to determine the herbage yield, chemical composition and in vitro dry matter digestibility of desho grass varieties mixed with stylo (Stylosanthes guyanensis) and silver leaf desmodium (Desmodium unicinatum) at Assosa. Based on the results of the preceding experiment, one of the best performing desho grass variety (Kulumsa-DZF-592) was intercropped with the two legumes. The treatments included two legume species (Stylosanthes guyanensis and Desmodium unicinatum), each mixed with desho grass at four levels (100%, 75%, 50% and 25%) of the recommended seed rates of the two legume forages. The experimental design was randomized complete block design (RCBD) with four replications, and assessed data were as for the first experiment (growth, yield and quality attributes). The data collected include herbage dry matter yield, nutritional quality and biological compatibility of desho grass mixed with Stylo or Desmodium. The highest total dry matter yield (11.05 t ha-1) was obtained from the sole desho XIII grass planted with nitrogen fertilizer (150 kg/ha) followed by sole desho grass planted without fertilizer (10.17 t ha-1). Among the mixed cropping groups, desho grass with 25% stylo gave a higher total dry mater yield (7.44 tha-1). On the other hand, desmodium sown in pure stand (as a pure stand check) had the lowest DMY (3.37 tha-1) compared with legume-grass mixtures. In terms of quality, increasing the seed proportions of both legume species in their respective mixture resulted in higher CP, CPY and IVDMD but lower NDF, ADF and ADL contents. Total yields of desho grass-legume mixtures at 75% desho:25% Stylo (1.43), 50% Desho:50% desmodium (1.39) and 25% desho: 75% Stylo (1.33) were better compared to the other mixtures levels and pure stands. Generally, mixing of desho grass with stylo at seed rates of 25% and 50% resulted better dry matter yield, nutritional quality and compatibility when compared with the other grass-legume mixture levels. The third experiment was conducted based on the outcomes of the second experiment that desho mixed with stylo was more productive and compatible crop when compared with desho mixed with Desmodium unicinatum. Therefore, the aim of the third experiment was to determine the optimum levels of desho-stylo basal feed combination on feed and nutrient intake, apparent digestibility, milk yield, milk composition and body weight change of lactating F2, 75% crossbred dairy cows. Eight high grade (75%) crossbred cows (Holstein Friesian x Boran) in early lactation of different parties were randomly assigned to a basal forage desho grass hay (DGH) treatment sequence in a double 4 x 4 Latin Square Design with 4 treatments and 4 measuring periods of 22 days in each treatment. In each period, the first 15 days were adaptation periods. The four dietary treatments were; control (100% DGH), SG15 (85% DGH: 15% Stylosanthes guyanensis (SG)), SG30 (70 % DGH: 30% SG) and SG45 (55 % DGH: 45% SG). The result was such that with respect to nutrient intake, replacement of DGH with SG linearly increased at increasing level of the legume (p<0.001) for OMI, CPI and MEI. There was a significant (p<0.01) difference in daily milk yield between the SG45 and that of the control groups (100% DGH) (11.55 vs. 10.45 kg, respectively). Similarly, 4% fat corrected milk and fat yield varied (p<0.001) among treatments. There was a tendency of increased milk fat yield with the increasing level of replacement of DGH by SG. The result led to the conclusion that SG can partially (45% Stylo hay) replace desho grass hay in the diet of lactating dairy cow, leading to an improved daily milk yield, milk fat yield, without affecting milk protein content and milk fat percentage. Overall, the study enabled to recommend the two desho varieties (Kulumsa-DZF-592 and Areka-DZF#590) for wider use both for the smallholder and the specialized production systems in Asosa area and similar agro-ecologies elsewhere in Ethiopia. Furthermore, the overall study has enabled to suggest that reclaiming natural pasturelands with selected grass-legume mixed pastures, such as desho grass-plus-legume, as an excellent strategy option to boost productivity of livestock in the country. In order to complement the present study, the agronomic experiment may need to be conducted for some more years at different locations, with some more potentially compatible legumes so as to recommend optional desho grass-plus-legume mixed pastures for Assosa and other environments elsewhere in Ethiopia. Furthermore, conducting animal performance trials involving different breeds of cattle and small ruminants, including XIV assessment of economic feasibility of production and use of desho grass-based pastures is recommended so as to develop fully verified desho grass pasture technology of high popularity and adoption