Giá trị dinh dưỡng của một số thức ăn thông thường dùng cho bò sữa ở ngoại ô hà nội

Giá trị dinh dưỡng của một số thức ăn thông thường dùng cho bò sữa ở ngoại ô hà nội

Nutritive value of several forage commonly used for dairy cattle in the suburb of Hanoi Paul Pozy, Vu Chi Cuong, Le Van Ban, Doan Thi Khang Armand Deswysen and Daniel Deharen 1. Introduction Giving appropriate diets to dairy cattle, is supplying a well-balanced diet in nutrients such as crude protein, minerals and vitamins in order to meet their requirements for meat and milk production, and foetus development. Providing enough feeds and ensuring good operation of digestive system, reducing production cost of milk, means using useful available feedstuffs in local areas. In order to calculate the quality of nutritients needed by dairy cow, It must be known clearly the nutritive value of available feedstuffs. The nutritive value of a feed is determined throughout the percentage of each nutrients in this feed digested by animal Digestibilities are normally determined by using experiments on sheep (in vivo digestibility) Aerts, et al., 1984; De Boever et al., 1987). With the above target, from April 1999 to May - 2001, different kinds of grass such as natural grass, cultivated grass and other feedstuffs used dairy cattle in Hanoi suburban were implemented to predict the in vivo digestibility and energy value of feeds. 2. Materials and methods Digestibilities and nutritive value of feeds had analysed and determined in Hanoi suburban. Experiments had made on 17 adult rams of Bach thao breed, averaging 25 kg (7 sheeps during April, 1999; 10 sheeps during Oct, 2000). Sheeps were shed in individually and fed ad libitum (at 9h am and 4h p.m.). Grasses were cut and sun-dried for several hours and before giving to sheeps. Grass were harvested at different periods and 6 kinds of grasses were used in the experiments: fresh natural grass, Pennisetum purpureum, ensiled or unensiled corn stover (after harvesting seed) and rice straw. Natural grasses were cut in areas alongside rive dikes. The grasses were mixture of several grasses but mainly: Cynodon dactylon, Panicum repurs, Paspalum conzugatum. Corn stover was harvested at the periods after making young corn seed or adult corn seed. Old corn stover was ensiled before giving to sheeps. There were 13 experiments, each experiment period lasted 31 day: 21 day adaptation to foodstuff and crate and 10 day of measurements of daily voluntary intake and extent of digestion as described by Burns et al., 1994 and Cochran and Galyean, 1994) The nutritive value of a feed is its net nutritive value used by animal for their body weight maintenance and for productionpurpose. The net nutritive value for producing milk is the metabolisable energy multiply with utilisation efficiency of metabolisable energy for milk production (kl). Metabolisable energy (ME, kcal/kg DM) of feed depends on its digestibility in animal and total energy containing in the feed. The protein value of a feed is its an amount of amino acids amin that was adsorbed by the intestine. These amino acids come amin from two sources: undegraged protein in rumen (PDIA) and protein of micro-organism (PDIM). The quantity of micro-organism changes by feedstuff or diets. The quantity of PDIA depens on nitrogen degraded in ruminant (PDIMN) or energy containing in the feed (or diets) (PDIME). Protein values digestible in the intestine: PDIN = PDIA + PDIMN PDIE = PDIA + PDIME 3. Results and discussion Despite the plant composition of grass mix, its changing quality, and quantity of each grass in mix, there is a little change in the chemical composition of natural grass, except percentage of crude protein: high in July and low in January. It is also rich in nutrients in August (in table 1). This results indicated that the harvesting period is very important. The results also show that Pennisetum purpureum grass has similar chemical compositions around year (table 1). Further more, two rice straws have nearly the same chemical composition (table 1) Natural grass harvested in the winter and rice straw have voluntary dry matter intake (g DM/kg W 0.75 ) which is similar or significant higher than that of Setaria sp grass: 57g DM/kg W 0.75 (Pozy et al, 1995). Voluntary dry matter intake (g DM/kg W 0.75 ) of natural grass, harvested from April until Oct, is higher than that of tropical grass (71g DM/ W 0.75 ) (Xande et al, 1989). Pennisetum purpureum grass harvested in 1999 has high quality. The results of dry matter, organic matter, NDF digestibility were shown in table 1. In the case of natural grasses, these data change significantly during each periods around year; digestibilities of organic matter and NDF reduce from March until August (48%, 55%, 56%; respectively) but they increase from June until Oct (59%, 65%, 66%; respectively), and this results indicate that metabolism energy (ME) and net energy value indicated by feed unit for lactating (UFL) of natural grass are lowest in the period from March to August and of highest in the period from June to Oct. Digestibilities of DM, OM, NDF and metabolism energy, net energy value expressed by feed unit for lactation (UFL) of Pennisetum grass are similar to that of natural grass harvested in Oct and of slightly changes during each year. Pennisetum grass is rich in energy, but corn stover and rice straw are poor in energy; and ensiled corn stover has the energy lower than that of hay. Digestibility of nitrogen of Pennisetum grass is approximately 70% (table 2). In general, digestibility of nitrogen of this grass is higher than 65%. Total protein (on DM basis) of natural grass is around 12% (natural grass cut at the time from June to Oct). Digestibility of nitrogenr is lower than 50% if total crude protein is lower than 10%. Ensiled corn stover, rice straw, hay, grass harvested at the time from January to August has digestibility of nitrogen of about 55-58% for dry grass, and about 55-58% for natural grass. 4. Conclusion All grasses contain low level of energy value, natural grass in particularly, so that they need to be added energy by supplying molasses. Addition 1-2 kg molasses/head/day will helps balancing grass based diets. Pennisetum grass can be used as a main roughage feed for dairy cow in order to balance diet in the winter, it is better for getting enough voluntary dry mate intake if ensiled Pennisetum grass was given. Agricultural by-products such as ensiled corn stover or corn stover, can also include in dairy cattle’diets. Rice straw can not be a main roughage in diets given to dairy cattle in areas around Hanoi. If used rice straw replaces grass when lack of grass, it is needed to be added feed rich in nutritients and crude protein. Acknowledgements To achieve this project, we had received useful helps from Dong Anh Station Veterinary and Breeding Dairy Cattle Project of National Institute of Animal Husbandry, as well as many students of Economy Department of HAU. Thanks to the CUL, the Vietnamese and Belgian governments for funding his study. On this occasion, we also would like to give thanks to related organizations and friends. Summary A series of feeding trials on sheep was conducted to determined the nutritive value of several forage commonly used for dairy cattle in the suburb of Hanoi. It is found that there is a little change in the chemical composition of natural grass, except percentage of crude protein: high in July and low in January. It is also rich in nutrients in August. Pennisetum purpureum grass has the similar chemical compositions around year and two rice straws studied have nearly the same chemical composition. All grasses contain low level of energy value, natural grass in particularly, so that they need to be added energy by supplying molasses. Pennisetum grass can be used as a main roughage feed for dairy cow in order to balance diet in the winter Table 1. Chemical compositions of several kinds of grass Foodstuff DM (%) Organic mate (%) NDF (%) CP (%) Natural grass January March April June August Oct Dried grass 22.10 20.40 49.70 27.50 32.30 21.60 86.90 83.30 79.60 88.10 86.80 85.10 83.50 86.50 63.10 66.10 64.70 63.00 70.40 65.80 68.10 10.70 14.80 12.70 19.30 11.10 12.70 10.90 Penniseutum purpureum Experiment in 1999 year Experiment in 2000 year 17.00 15.90 83.20 84.50 64.60 63.20 13.30 14.10 Silaged corn term (after harvested seed) 23.80 93.10 74.10 9.00 Corn term (after harvested young seed) 8.70 87.10 73.00 8.70 Rice straw Experiment in 1999 year Experiment in 2000 year 92.80 85.10 82.30 84.90 71.50 73.20 7.40 5.10 Table 2. Voluntary dry mate intake, digestibilities and nutritive value of several grasses Digestibilities (%) Nutritive value (g/kg DM) Voluntary dry mater intake (gDM/kgW 0.75) Dry mater Organic mater NDF Nitrogen PDIA PDIN PDIE UFL Natural grass January March April June August Oct Dry grass 58.33 52.99 72.79 80.38 75.27 83.16 75.31 57.4 46.7 53.5 61.8 49.3 57.4 57.9 63.2 54.9 58.3 66.2 54.6 64.4 62.4 65.6 57.6 54.1 68.7 55.7 64.4 63.6 55.9 67.7 66.7 74.3 55.5 66.1 58.7 29 47 44 100 26 44 33 59 88 80 126 57 79 63 74 82 85 117 58 89 78 0.67 0.53 0.65 0.76 0.56 0.70 0.69 Penniseutum purpureum 1999 2000 68.2 62.6 65.9 66.1 69.9 70.4 72.9 72.6 70.9 69.2 53 73 90 91 99 102 0.76 0.78 Corn stover After harvesting seed NS 56.8 59.1 62.8 46.9 2 38 51 0.66 After harvesting young seed 63.8 58.3 67.1 70.6 49.4 0.75 Rice straw 1999 2000 40.7 38.9 44.4 43.6 46.5 48.6 53.1 57.8 40.2 - .11 3 32 11 43 33 0.43 0.46