Abstract
Series of studies were conducted in Animal Nutrition field laboratory, BAU and farmers' fields in order to improve forage production techniques, evaluation of forages using NIRS and developing low-cost forage preservation techniques for improving milk production of crossbred dairy cows. Four experiments were conducted on maize (Zea mays), napier (Pennisetum purpureum) and jumbo (Sorghum bicolor x Sorghum sudanese) forages at varying rates of N and P fertilizer application and their evaluation using NIRS in phase-1. Five levels of N and three levels of P were applied on yield of these forages by 5 x 3 factorial arrangements in randomized complete block design (RCBD). Green biomass and DM yield of maize forage increased (P<0.01) up to 150 kg N/ha and 30 kg P/ha (P<0.05), however, no further significant increase was observed at a level of 200 kg N/ha. Green biomass and DM yield of both napier and jumbo forages were found to be highest at 160 kg N/ha (P<0.01) and 10 kg P/ha (P<0.01). Fresh and DM yield of napier and jumbo forages were not significantly different with the application of 120 to 160 kg N and 10 to 20 kg P/ha. Although, the DM content (g/100 g) of maize forage was unaffected (P>0.05) by different levels of N and P fertilizer it was decreased both in napier (P<0.01) and jumbo forage (P<0.05) with the increasing level of N fertilizer. However, DM content of napier and jumbo forage was unaffected by P fertilizer application. The CP contents (g/100 g) were increased (P<0.01) in maize, napier and jumbo forages with the increasing level of N fertilizer while it was unaffected by different levels of P fertilizer. There was a tendency to decrease ADF of maize (P<0.05), napier (P>0.05) and jumbo (P>0.05) forages with the increasing level of N fertilizer application, however, no significant (P>0.05) difference was observed in NDF with the application of N and P fertilizer. In-vitro OMD (%) of maize, napier and jumbo forage increased (P<0.01) with the increasing level of N fertilizer, however, the difference was insignificant with increasing levels of P fertilizer application. The NEL (Mcal/kg DM) and RFV% of maize, napier and jumbo forages were unaffected by the application of N and P fertilizer application. Calibrations for the evaluation of forages using NIRS (Bruker MPA, Germany) were developed by Partial Least Square (PLS) as regression method. The RMSECV for the prediction of CP, ADF, NDF, IVOMD and NE, by using NIRS of maize forage samples (n = 45) were 0.41, 1.03, 2.37, 1.26 and 0.09% with correlation coefficients (r) were 0.81, 0.85, 0.81, 0.75 and 0.85 respectively. The RMSECV for CP, ADF, NDF, IVOMD and NEL of napier forage samples (n = 90) were 0.60, 1.63, 0.81, 0.73 and 0.20% having correlation coefficients (r) 0.78, 0.71, 0.59, 0.75 and 0.71 respectively. Similarly, the RMSECV for CP, ADF, NDF, IVOMD and NEL of jumbo forage samples (n = 90) were 0.33, 1.63, 0.89, 1.24 and 0.22 having correlation coefficients (r) 0.83, 0.74, 0.67, 0.60 and 0.76 respectively. Three experiments were conducted in the phase-II. Low-cost forage preservation techniques were developed with the use of Bamboo-mat Fenced Chamber (BFC) and Synthetic Fiber Bag (SFB) and compared to high-cost Concrete Tower Silo (CTS) in terms of silage quality. The pH of silage samples preserved in BFC (4.11) and SFB (4.42) indicated good fermentation characteristics compare to the pH of silage from CTS (4.62). The higher level of NH3-N (% of total N) in silage samples from BFC (16.72), SFB (21.22) and CTS (24.18) were observed, however, no mold infestation was recorded. The forage preservation cost (Tk/kg) in BFC, SFB and CTS were 0.62, 5.26 and 18.48 respectively which indicated that BFC as low-cost forage preservation technique. A feeding trial was conducted to compare maize and napier silages from BFC and fresh napier fodder in terms of nutrient intake, digestibility and rumen fermentation characteristics. Total DM and nutrient (OM, CP, ADF and NDF) intake (kg/d) were not significantly (P>0.05) different between cattle fed napier grass and silage-based diets. Apparent digestibility (%) of DM and OM were significantly (P<0.05) higher in maize silage diet than napier grass and napier silage diets. However, digestibility of ADF and NDF were not significantly (P>0.05) changed between napier fodder and napier silage except that of CP, the digestibility of which was significantly (P<0.05) higher in napier fodder than that of maize silage and napier silage. The overall ruminal pH of napier grass, maize silage and napier silage were 6.97, 7.14 and 7.19 respectively which were in normal physiological range (6.4-7.0). The overall NH3-N (mg/l) concentration in the rumen liquor (56.53, 87.73 and 98.33 for napier grass, maize silage and napier silage respectively) were above 50 mg/l which were thought to be optimum for microbial protein synthesis. The average ruminal VFA concentration (mM/I) was not significantly different between napier grass and silage based diets. Low-cost forage preservation technique (BFC) was demonstrated at farmers field to observe the milk production performance of dairy cows fed maize (T1), jumbo (T2) and napier (T3) silage compared to that of conventional straw (To) diet. Milk yield (4% FCM, kg/d) was higher in T, (10.25), T2 (9.37) and T3 (8.96) diets than To (8.24) when straw DM was replaced by maize, jumbo and napier silage. Milk yield (kg/d) per kg DMI in maize and jumbo silage diet significantly increased (P<0.01) compared to control diet. Milk protein and milk fat (kg/cow/d) of crossbred dairy cows fed maize, jumbo and napier silage based diet were higher (P<0.05) than that of control diet. Maize, jumbo and napier silage could replace conventional straw by 50% as well as increased income to Tk 46.26, 27.89 and 17.90 per cow per day with concomitant decreasing feed cost to Tk 1.30, 1.05 and 0.81 per kg of milk production respectively. It may be concluded that the yield and quality of maize forage can be improved through application of 150 kg N and 30 kg P/ha. Again, yield and quality of both napier and jumbo forage can be improved through application of 120 kg N and 10 kg P/ha. Near Infrared Reflectance Spectroscopy may be an effective tool for quick evaluation of forages. Bamboo-mat Fenced Chamber could potentially be used as low-cost silo for forage preservation with increasing milk production and income of the farmers.