| The general objectives of this thesis were to evaluate appropriate crude protein (CP) level in concentrate and concentrate level in diet for local fattening cattle in Vietnam. Four studies were conducted.The first study was conducted to investigate feeding system for fattening cattle at smallholder in Central Vietnam including:farming resources, feed resources, feed intake, diet structure and average daily gain (ADG) of cattle. A total of 40 households were randomly selected from 4 provinces in Central Vietnam to collect data by recording daily from beginning to end of fattening cattle process. Results showed that 100% of households used at least two kind of concentrate and more than 65% of households used elephant grass or native grass for cattle. Concentrate included rice bran, maize, cassava powder and rice. Rice straw, native grass and elephant grass were used as roughage feed. The dry matter (DM) intake ranged from 5.54 to 5.89 kg/d. Concentrate and crude protein (CP) proportion in diet was from 24.0 to 37.0%and 8.37 to 9.82%, respectively. The ADG of cattle was from 0.43 to 0.69 kg/d. In conclusion, feed resources for fattening cattle at smallholder were variety, of which included concentrate and roughage feed, however, proportion of concentrate and CP in diet is low. Therefore, the performance of fattening cattle was poor. Further studies are required to develop an appropriate diet system with an optimal level of concentrate and protein to increase performance and to improve economic efficiency in feedlot cattle at smallholder in Central Vietnam.The second study was carried out to determine the effects of CP level in concentrate on performances, ruminal pH and NH3-N concentration, carcass characteristic, meat quality and body composition of Vietnamese local fattening cattle. An experiment was conducted with 24 local (yellow) cattle, initial live weight (LW) were 150.3 ±11.8 kg. The randomized complete block design was used based on LW of cattle. Treatment contained 4 levels of CP in concentrate (10,13,16 and 19%). Cattle were offered a daily concentrate allowance of 1.5% of LW and roughage feed included 5 kg native grass and rice straw was provided ad libitum (fresh basis). The experiment lasted for 74 days. Results showed that the CP level in concentrate significantly affected DM intake (P<0.05), N retention, ADG and ruminal NH3-N concentration (P<0.01), but it had no significant effect on DM, organic matter (OM) and neutral detergent fibre (NDF) digestibility (P>0.05), whereas CP digestibility increased (P<0.001) along with the CP level. Increasing CP level had no significant effect on pH value both at 0 and 4h post feeding concentrate (P>0.05), whereas NH3-N concentration in rumen fluid at 0 and 4h were significantly different among treatments (P<0.01). However, no significant difference was found between 16 and 19% CP in concentrate. CP level in concentrate significantly affected on slaughter weight, hot carcass weight, meat weight and loin muscle area (P<0.05), but had no significant influenced on dressing percentage, fat thickness, drip and cooking loss (P>0.05). Chemical composition and water holding capacity of longissimus muscle no significant difference by increasing CP level (P>0.05). The total internal organs weight were similar among with CP level (P>0.05). The benefit in fattening cattle is the highest in cattle fed concentrate with 16% CP level. In conclusion, these results indicated that in current practice on local cattle production in Vietnam,16% of CP in concentrate during fattening period is recommendable.The aim of the third study was evaluate the effects of concentrate level on performances, ruminal pH and NH3-N concentration, carcass characteristic, meat quality and body composition of Vietnamese local fattening cattle. An experiment was conducted with 24 local (yellow) cattle, initial LW were 145.1 ± 9.8 kg. The randomized complete block design was used based on LW of cattle. Treatment contained 4 levels of concentrate (1.0,1.4,1.8 and 2.2% of LW). Cattle were offered a basal diet of native grass fed 5 kg/d and rice straw was provided ad libitum (fresh basis). The experiment lasted for 60 days. Results showed that, DM intake, N retention and ADG increased (P<0.001) linearly with concentrate intake. DM and CP digestibility were not significantly affected by concentrate intake (P>0.05). OM digestibility and NH3-N concentration increased linearly (P<0.05), whereas NDF digestibility and ruminal pH declined linearly with increased concentrate consumption (P<0.01). Concentrate level significantly affected on slaughter weight, hot carcass weight, meat weight and loin muscle area (P<0.05), but had no significant influenced on dressing percentage, fat thickness, drip and cooking loss (P>0.05). Crude fat and water holding capacity of longissimus muscle increased (P<0.001) along with concentrate level. The total internal organs weight were significantly affected by concentrate level (P=0.02). The benefit in fattening cattle is the highest in cattle fed 2.2% of LW concentrate. In conclusion, these results indicate that in current practice on local cattle production in Vietnam, feeding concentrate at the rate of 2.2% of LW during fattening period is valuable recommendation.In the fourth study, an in vitro gas production trial was conducted to not only evaluate the effect of concentrate mixtures with different CP level (10,13,16 and 19%) and diets with various ratios of roughage to concentrate (80:20,60:40,40:60 and 20:80 w/w), but also to confirm results of in vivo experiments, and determine relationship about DM and OM digestibility between in vivo and in vitro condition. Rumen fluid collected from three fistulated cattle as inoculum. In vitro fermented parameters were measured at 4,24 and 48h after incubation. Results showed that, in vitro DM, OM digestibility and total volatile fatty acid (VFA) increased, pH value decreased as the amount of concentrate in the diet increased (P<0.001), whereas they are similar among CP levels in concentrate (P>0.05). Gas production reduced when CP levels increased, while it increased with increasing concentrate. The NH3-N concentration and microbial CP were significantly affected (P<0.05) by CP levels and ratios of roughage to concentrate, however, no significant difference was found between 16 and 19%CP treatment. In conclusion,16% CP in concentrate and increasing proportion of concentrate up to 80% in diet which high NDF content (above 30%) could be recommended for in vitro microbial fermentation. |
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