Abstract
Studies were conducted to develop an appropriate feeding system for Red Chittagong Cattle (RCC), an important indigenous cattle genetic resource of Bangladesh (Bos indicus). A baseline survey was conducted to study the existing feeding and management practices of RCC in Chittagong district. Available feedstuffs including rice straw, naturally grown grasses (10 species) and concentrates (6 grain and byproducts) fed to RCC were collected from Chittagong region for botanical identification and nutritional evaluation. Proximate components, ADF, NDF and in vitro organic matter digestibility (IVOMD) and metabolizable energy (ME) contents of feedstuffs were estimated. Three feeding experiments were conducted at station supplementing urea molasses straw (UMS) and green grass based diet of RCC heifers with different levels of energy and protein through concentrate feed. In addition, effect of concentrate supplementation on performance of RCC cows was studied at station and on the basis of the findings of this experiment; a validation trial was conducted under farmers' condition. In the initial feeding experiment, 12 RCC heifers having average LW of 76 kg were blocked according to their initial LW and assigned at random to four dietary treatments having three replications in each. The animals were received supplemental concentrate mixture containing, per kg DM, ME of 8.5 MJ or 10.5 MJ and CP of 150g or 200g in a 2 x 2 factorial experiment. In second feeding experiment, 12 RCC heifers (128.88 kg) were blocked according to their initial LW and assigned at random with four dietary treatments: unsupplemented (US) group received UMS and green grass and supplemented groups fed three iso- nitrogenous (200 g CP/kg DM) concentrate feeds containing 8.5, 10.5 and 12.5 MJ ME/kg DM, respectively in addition to UMS and green grass of US group. In third feeding experiment, 12 RCC heifers (127.5 kg) were divided into four treatment groups and UMS and green grass based diet was supplemented with three iso- energetic (10.5 MJ ME/kg DM) concentrate feeds containing 15, 20 and 25% CP on DM basis, respectively where US group fed no concentrate. In fourth feeding experiment, 16 RCC cows were blocked into 4 groups on the basis of their initial milk yield and assigned at random with 4 levels (0, 10, 15 and 20% of total DM) of concentrate having 20% CP and 10.5 MJ ME/kg DM. Based on the finding of feeding experiment with RCC cows at station, best performing three levels of concentrate (0, 10 and 15% concentrate) were supplemented to 12 RCC cows under three treatment groups at farmers' level in Chandanaish Upazila of Chittagong to validate the findings. Findings of baseline survey suggest that rice straw is the basal diet for RCC and in addition to that green grass and concentrate feeds are also allowed in most of the cases. Red Chittagong cattle are adapted well in prevailing feeding and housing systems and resistant to several diseases and parasitic infections. Average CP content (g/100 g DM) of rice straw was recorded 4.06±0.04. Among 10 grasses evaluated in the study, CP contents (g/100g DM) were highest in Malancha (Alternanthera philoxeroides; 17.40±0.96) and lowest in Angta ((Panicum repens; 7.39±0.59). Among six concentrate feeds, CP contents (g/100g) ranges between 42.86±0.59 in soybean meal and 6.21±0.23 in rice bran. Metabolizable energy contents (MJ/kg DM) and IVOMD (%) of rice straw were 5.38±0.08 and 42.00±0.45, respectively. Malancha had highest IVOMD (58.15±0.55%) and ME contents (7.46±0.12 MJ/kg DM) among the grass samples. Organic matter digestibility (%) of six concentrates ranged from 46.76±0.55 in rice bran to 85.64±0.80 in corn. Average ME contents (MJ/kg DM) was highest (13.15±0.05) in corn and lowest (6.28±0.14) in rice bran. The results of first feeding experiment with each of 2 levels of energy and protein revealed that average daily gain (ADG) of heifers responded (P<0.05) to both energy and protein supplementation and highest value (0.39 kg/d) was recorded in heifers fed concentrate having 10.5 MJ ME and 200 g CP/kg DM. Supplementation of UMS and green grass based diet of RCC heifers with different levels of energy (second feeding experiment) indicated that ADG increased with increasing energy supplementation up to 10.5 MJ/kg DM and remain constant thereafter. In third feeding trial, the highest (P<0.01) ADG (kg/d) was observed in treatment group fed 25% CP supplement (0.354) followed by 20% (0.352), 15% (0.222) and US groups (0.109) but supplement having 20% CP was cost effective. Results of concentrate supplementation to RCC cows revealed that milk yield differed (P<0.05) between unsupplemented and supplemented groups but among supplemented groups mean difference was not significant and cost effective milk yield (2.50 kg/d) was recorded in 10% concentrate group. With increased concentrate supplementation fat content of milk decreased (P<0.05) and protein contents increased (P<0.05) and fat and protein contents (g/100g) ranged from 4.29 to 6.13 and 3.25 to 3.44, respectively. Almost similar results were observed in validation trial and supplementation of concentrate at the rate of 10% of total DM was proved cost effective in RCC cows reared farmers' condition. It may be concluded from the present findings that the ad libitum UMS and restricted (20% of total DM) green grass based diet of RCC could be supplemented with concentrate mixture containing 10.5 MJ ME and 200 g CP/kg DM with an amount (fresh basis, % of BW) of 350 g for economic growth of heifers and 400 g for cost effective milk yield of lactating cows (10% of total DM intake).