MEKARN MSc 2001-2003

Citation of this paper

Evaluating protein sources for dairy cattle

Chamnanwit Promkot

 

Existing situation of dairy cattle raising in Thailand and role of milk

Dairy Cow is mainly raised for milk production. The commercial production of dairy cow in Thailand began after the establishment of the dairy farm and herd training centre granted by the Danish Government in 1962. Dairy production was then developed through the subsequent establishment of the Dairy Farming Promotion Organization of Thailand, a state-own enterprise under the Ministry of Agriculture and Cooperatives in 1971. Ready-to-consume milk consumption took off in the mid-1970s reaching 40,000 tons in 1984 (de Leeuw et al., 1999) and 609,000 tons in 2001. Local fresh milk deliveries followed the same trend. Fresh milk was produced by about 150 dairy farmers in 1971, increasing in 2001 with a total of 343,679 cows supplying 528,000 tons, while domestic consumption outpaced production to top 1.2 million tons. Of the total consumption, about 609,000 tons, or 50.8%, is used in the production of ready-to-drink milk. In 2002, the government plans to impose more stringent regulations on the quality of ready-to-consume milk products, thereby having a positive effect on the local dairy cow raising.

Practically 95 to 99 % of dairy farms in Thailand can be classified as small scale or smallhoder farm under mixed crop-livestock farming systems (Wanapat,1995; Chantalakhana and Skunmum, 2002). Dairy operation is generally integrated with rice, sugar-cane , cassava (Wanapat ,1995 ), orchards, or some plantation crops (Chantalakhana and Skunmum, 2002).

Practically, all dairy cows in Thailand are crossbreds Holstein-Friesian (HF), most of them produce around 2,500 to 3,000 kg milk /cow/yr .The number of cows ranged from 6 to 30 heads/farm (Chantalakhana and Skunmum, 2002).

The use of crop residues such as rice straw, brocken rice is very common. However, large variations in rainfall and soil fertility, and the long dry season, reduce the availability and quality of feed resource. This adversely affects the productivity of dairy cattle (Wanapat, 1995). Concentrate feeding were at averaged 5-6 kg/d for lactating cow and 2 kg for dry cows. Feed costs were about 70% of total operating costs, the largest being expenditure on concentrates ( 65- 80 %) resulting in increasing of production cost while availability of funds from various agencies is at present relatively limited for smallholder farmers (Wanapat, 1995). So further research development should be undertaken in the areas of animal nutrition and feeding of locally avaiable resources and forage crops in order to alleviate low productivity and increase efficiency.

It has been observed that milk from rural smallholder dairy farm is totally for sale and not being used for home consumption. It has also been observed that rural farmers rarely consume beef or pork from their own production. Fish is a more common source of protein for rural people, and chickens and eggs are less common. (Chantalakhana and Skunmum, 2002). The nutritional health care are provided to community level.

 

Factors affecting voluntary intake and digestibility in dairy cattle.

Voluntary dry intake (VDMI) is fundamentally important in nutrition because it establishes the amount of nutrients available to an animal for health and production. Underfeeding of nutrients restricts production and can affect the health of an animal, overfeeding of nutrients increases feed costs, can result in excessive excretion of nutrients into the environment, and at excessively high amounts could be toxic or cause adverse health effects. Many factors affect VDMI namely the appetite of the animal which varies according to the animal itself (age, physiological stage, former nutritional status,etc.) (NRC, 2001), the environmental conditions (temperature, humidity, etc.) under which the animal is kept( Holter and Urban, 1992; Holter et al., 1997), the specific characteristics of the feed which would limit ruminant feed intake, (NRC, 2001), NDF(Allen, 2000), fat and energy ( Mertens, 1987; NRC, 1989; Smith et al., 1993), CP (Allen, 2000 ) or forage to concentrate ratio (Llamas-Lamas and Cambs, 1991; NRC, 2001).

The voluntary intake of feed depends essentially on the rate of degradation of digestible matter of feed into particles of a size small enough to enable their passage from the reticulo-rumen to the lower gut. Feeds low in digestibility are thought to place constraints on VDMI because of their slow clearance from the rumen and passage through the digestive tract. The reticulorumen and possibly the abomasum have stretch and touch receptors in their walls that negatively impact VDMI as the weight and volume of digesta accumlated (Allen, 1996). The neutral-detergent fiber (NDF) fraction, because of generally low rates of digestion, is considered the primary dietary constituent associated with the fill effect. It was thought that generally, cows would consume about 1.2% of their body weight per day as NDF ( Merck,1991).The result in Paper II showed that DM intake (DMI) were slightly lower than typical intake levels for lactating dairy cows of varying body weights as given by NRC (1989), it could be due to effect of limitation in NDF intake which was achieved to maximum level of 1.2 %NDF intake.Allen (2000) summarized 15 studies and showed a general decline in DMI with increasing NDF concentrations in diets when diets exceeded 25 % NDF.

The CP content of feed is one of many factors on VDMI (Allen, 2000), increasing CP content of the diets which can increase DMI of lactating cows, particularly when the CP content of diets was low. Oldham (1984) and Roffler et al. (1986) noted that the mechanism involved was presumably a reduction in distension as fiber and DM digestibility increased.This was also found in Paper II. The results showed that DMI and DM digestibility tended to linearly increase with increasing dietary CP.

Feeding roughage with low digestibility resulted in slower rate of passage out of the rumen, thus restricting the feed intake (Leng, 1990). Physical form is one of the limitations of bulk feeds on intake, but it may be overcome by mechanical treatment. Jaster and Murphy (1983) found that the intake of hay by dairy heifers increased when it was chopped as compared to long hay. In ruminants, when forages are chopped or ground there is usually an increase in voluntary feed intake (Osafo et al., 1997). Rice straw with low digestibility was used as a roughage in Paper II and chopped, the reason was to improving the VDMI. However, the balance of nutrients for the rumen organisms and the ratio of protein to energy in nutrients that become available to the animal are the major factors.

Recent research(Morrison et al.,2001) is indicating that feed intake regulation is possibly, and mainly controlled through the release of leptin from fat cells that is stimulated by excessively low levels of energy nutrients absorbed relative to amino acids. The reports demonstrate that leptin is an important regulator of the hypothalamic, neuroendocrine, and endocrine processes regulating appetite (Campfield et al.,1995, Halaas et al.,1995, Pelleymounter et al., 1995).

For digestibilty, there are several factors limiting coplete digestion. The most important factor is chemistry of feed, which related to microbial activity espectially in roughage.There is a decrease in the proportion of CP and increase in the concentration of cellulose, hemicelluloses and lignin, which are normally associated with a depression in DM digestibility. The cell wall content and the magnitude and nature of lignification of these cell walls are amongst the most important factors which govern the degradability and the rate of passage of a forage.This was also found in Paper I. The result showed that palm seed meal is low in protein and high in neutral detergent fiber (NDF), which was lowest in DM and CP digestibility. Good microbial activity will require adequate nutrition of the rumen microorganisms (Leng, 1999), energy in the form of ATP released from soluble and structural carbohydrates of the plant, nitrogen in the form of ammonia generated by the hydrolysis of the fermentable nitrogen, minerals and vitamins, good chemical and physico-chemical rumen environment (pH) and a regular outflow from the rumen. These conditions are not only dependent on the properties of the feeds but also on their rationing (number and frequency of meals, physical form of their presentation). Perdok and Leng (1989) showed that higher level of rumen NH3-N (15-30 mg%) improved digestibility.In Paper I. it was found that all protein sources were high in rumen degradable DM and CP in cows fed with urea-treated than untreated rice straw. Rice straw is low in protein and when fed as a main roughage, ruminal ammonia concentration would be low for most rumen microorganisms resulting in low degradability.

Climate influence on feed intake and predictability of the nutritional value of a feed

Ruminants are extremely well adapted to cool environments but appear to have poor adaptation to hot conditions (Blaxter, 1962). A number of studies have demonstrated that animals selected for short shiny hair-coats consistently out-produce similar breeds with rough-hairy coats. This may be related to a low density of sweat glands. As animals progress from cold to hot conditions their needs for protein relative to fat or fatty acid under cold conditions the requirements for oxidisable substrate such as fat and short chain volatile fatty acids is increased totally and relative to the requirements for amino acids for tissue synthesis i.e. the P/E ratio in the nutrients required by the animal is decreased. precursors change as follows:- under hot humid conditions the need for oxidisable substrate for heat production may be close to zero and the P/E ratio in the nutrients required by the animal is increased although total nutrient requirements may be decreased. Animals at the upper level of their ability to control their body temperature in a hot environment, may be heat stressed by the extra heat produced in an inefficient rumen microbial ecosystem or where acetate burn-off is required because of the imbalanced nature of the nutrients absorbed (Leng et al 1993). Heat stress in ruminants, which is indicated by excessive respiration rates in general reduce feed intake. This in turn would reduce the heat increment associated with fermentative digestion and also the heat released in fertile cycles of metabolism or in synthesis (of milk or tissue). In general on a poor quality roughage diet if the rumen of an animal in a hot/humid environment is deficient, in say fermentable N and/or sulphur and/or phosphorus then this will:- 1) reduce digestibility - by as much as 5 to 10 units. 2) Reduce efficiency of microbial cell growth per unit of organic matter digested and therefore lower P/E ratio in the nutrients absorbed. 3) Reduce feed intake both because of the lower digestibility and also because the extra heat from the rumen and the animal. One factor was effect on feed intake and digestibility in Paper II , It was due to Climate influence.

Protein in dairy cattle

Protein in rations

Recommendations for the crude protein concentration in dairy cow rations vary from 12% for a dry cow to 18% for a cow in early lactation (NRC,1989). The goals of ruminant protein nutrition are to provide adequate amounts of rumen-degradable protein (RDP) for optimal ruminal efficiency and to obtain the desired animal productivity with a minimum amount of dietary CP. Optimizing the efficiency of use of dietary CP requires selection of complementary feed proteins and NPN supplements that will provide the types and amounts of RDP that will meet, but not exceed, the N needs of ruminal microorganisms for maximal synthesis of microbial protein (NRC, 2001). For the ration of experimental feeds in Paper II. it contained CP of 10.5 - 14.4 % of DM, this level fitted with requirements for maintenance and production in cow 450 kg of body weight, milk yield and fat at 10-15 kg/d and 3.5 %, respectively (NRC, 1989).

Factors affecting protein degradability

The mechanism of ruminal protein degradation has been reviewed ( Jouany and Ushida,1999; Wallace et al., 1999). Numerous factors affect the amount of CP in feeds that will be degraded in the rumen. The chemistry of feed CP is the single most important factor(NRC, 2001). The two most important considerations of feed CP chemistry are: (1) the proportional concentrations of NPN and true protein, and (2) the physical and chemical characteristics of the proteins that comprise the true protein fraction of the feedstuff. Non-protein N compounds are degraded so quickly in the rumen (>300%/h) that degradation is assumed to be 100 percent (Sniffen et al., 1992). However, this is not an entirely correct assumption because degradability is truly related to rate of passage (NRC, 2001). Highest amount of effective CP degradability of LLM, in Paper I, it could be due to leucaena leaf meal (LLM) containing highest level of rapidly soluble fraction 'a'. As reported by NRC (2001) that grasses and legume forages (hay or silage) contained the higest concentration of non-protein N compounds especially in hay.

Differences in 3-dimensional structure and chemical bonding (i.e., cross-links) that occur both within and between protein molecules and between proteins and carbohydrates are functions of source as well as processing. These aspects of structure affect microbial access to the proteins, which apparently is the most important factor affecting the rate and extent of degradation of proteins in the rumen.Proteins that possess extensive cross-linking, such as the disulfide bonding in albumins and immunoglobulins or cross-links caused by chemical or heat treatment, are less accessible to proteolytic enzymes and are degraded more slowly ( Mahadevan et al., 1980). High level of undegradable protein of cottonseed meal was reported in Paper I, possible factors could be due to heat processing during extraction and its cross-links.

The protein meal contains tannins (2-4%) which binds to make an insoluble tannin - protein complex (Barry, 1985). It is not degraded in the rumen but degraded in the abomasum and small intestine. This was also found in cassava hay with contained condensed tannins( Wanapat, 2001) in Paper I, the results was found that rumen protein degradability was lower in cassava hay.

When a relatively soluble protein meal is fed in very high quantities and is either in a finely ground form or is rapidly fragmented into small particles which move quickly through the rumen (Noland and Leng, 1989). Other factors affecting the ruminal degradability of feed protein include ruminal retention time of the protein, microbial proteolytic activity and ruminal pH. The effect of these factors on the kinetics of ruminal protein degradation have been reviewed ( NRC,1985).

Digestibility of rumen undegradable feed protein

NRC (2001) stated that a constant intestinal digestion of feed proteins value of 80 percent was used for RUP of all feedstuffs. This value was selected because it approximated the average calculated true absorption of both non-ammonia N and RUP as measured in vivo. In Paper I, the result of intestinal digestibility in six protein resources expressed in % of rumen residual portion were varied from 78.7 % for PSM to 96.2 % for SBM. However, other feeding standards have attempted to account for differences in RUP digestibility among feedstuffs (Webster,1987). It is assumed (Webster,1987) that acid-detergent insoluble nitrogen (ADIN) is both undegradable in the rumen and indigestible in the small intestine. The result of difference value of intestinal digestion among feed proteins in Paper I , may be due to differences in ADIN contents among feedstuffs.

Dietary protein , concentration of ruminal ammonia nitrogen (NH3-N), blood urea nitrogen (BUN) and milk- urea nitrogen (MUN) relationships

Feed proteins are degraded by microorganisms in the rumen via amino acids into ammonia and branched chain fatty acids. Non-protein nitrogen from the feed and the urea recycled into the rumen through the saliva or the rumen wall contribute also to the pool of ammonia in the rumen. If ammonia levels in the rumen are too low causes bacteria to grow inefficiently producing a low ratio of absorbed amino acids to volatile fatty acid energy. Digestibility is also reduced by the reduction in pool size of cellulolytic bacteria that occurs when bacteria grow inefficiently.

Too much ammonia (due to excessive intakes of dietary CP ) in the rumen leads to wastage and ammonia toxicity. Excessive ammonia will be absorbed cross the ruminal wall and is transported to the liver. The liver converts the ammonia to urea which is released in the blood. Urea in the blood can follow two routes: 1) It can return to the rumen through the saliva or through the rumen wall. 2) It can be excreted into the urine by the kidneys. Excessive intakes of dietary CP can be monitored by either blood urea nitrogen (BUN) or by milk urea nitrogen (MUN). In recent years, studies on mechanisms behind urea formation from dietary protein was found that the concentration of urea nitrogen in blood is directly related to ruminal ammonia absorption (Hammond, 1983), and MUN is also closely correlated with BUN and dietary CP (Roseler et al., 1993; Baker et al., 1995; Butler et al., 1996 ). Relationship of those were also found in Paper II.

BUN and MUN are indication of the protein to energy ratio in the diet

Recently, Abeni et al.(2000) reported that BUN concentrations were more related to dietary CP to energy ratio of diets. Feeding nitrogen in excess of requirements, feeding excessive amounts of ruminally degradable protein, or feeding diets not properly balanced for ruminally degradable and undegradable protein, amino acid, or energy may increase nitrogen excretion in feces or urine (urine nitrogen,UN) (Kauffman and St-Pierre, 2001). Hammond ( 1983) stated that when energy intake was held constant, increasing dietary protein would increase BUN concentrations.

Since MUN is closely correlated with BUN and UN (Jonker et al., 1998; Kauffman and St-Pierre, 2001), therefore, in healthy ruminants, BUN and MUN concentrations are used to be indicative of the protein to energy ratio in the diet (crude protein :digestible organic matter, CP: DOM ratio). Optimum MUN concentration for individual cows ranges from 8 to 25 mg%, while optimum MUN concentration for a herd ranges from 12 to 17 mg/dl (Roseler et al., 1993; Baker et al., 1995;Hwang et al., 2000), while BUN is at 15 mg% (Roseler et al., 1993). However, the fact that MUN is more representative over time of ruminal ammonia levels, less invasive to the animal, and less variable, most researchers would rather analyze for MUN concentrations. BUN and MUN are lower than this reference and could be due to the insufficiency in CP per unit of energy, On the other hand higher value could be due to excess in CP per unit of energy or low rumen degradable nonfiber carbohydrates. In Paper II , the results were found that dietary CP at 12.5 and 13.7 % of DM resulted in lower range of BUN, MUN. Milk yield was corresponding when dietary CP level increased from 10.5 to 14.4 % and the highest increase (0.82 kg/d) was from 10.5 to 12.5 %, respectively.

Response of lactating dairy cows on protein

Overall, milk yield increased quadratically as dietary CP concentrations increased (NRC, 2001). The regression equation obtained was:

Milk yield = 0.8* DMI + 2.3 * CP-0.05* CP2- 9.8 (R2 = 0.29)

where milk yield and dry matter intake (DMI) are kilograms/d and CP is percent of diet DM. Assuming a fixed DMI (there was no correlation between intake and CP percent in this data set), the maximum milk production was obtained at 23 % CP. From the result in Paper II, it was found that milk yield responsed on increasing dietary CP and tended to linearly increase as level of CP in the diet increased from 10.5 to 14.7 % of DM. Milk yeild was increased from 10.7 to 11.6 kg/h/d, this was lower than expected by the equation above. Milk production could be limited by the physiological state, genetic potential of the cow or by other nutrients than protein alone. Leng (1999) reviewed that an optimal balance between aminogenic, glucogenic as well as lipogenic nutrients is required for maximal efficiency of milk production and prevention of ketosis particularly in highly productive dairy cows.

Recently, a regression equation for milk yield with CP in terms of rumen degradable protein (RDP) and rumen undegradable protein ( RUP) ( both as percent of DM) were calculated using the model described in NRC (2001):

Milk yield = 55.61+ 1.15 * DMI + 8.79 * RDP - 0.36* RDP2 + 1.85 * RUP ( r2= 0.52 )

where DMI and milk yield are kilograms/day, and RDP and RUP are percent of diet DM. So, milk responsed on CP, not to depend only on amount of CP but also on partition of RDP and RUP.

Cottonseed meal (CSM) as a ruminant feed

Cottonseed feed products have been used for feeding of livestock for many years. Cottonseed meal, cottonseed hulls and whole cottonseed meal are natural sources of protein, fiber and energy. Cottonseed meal is the most abundant plant protein feed available in Thailand. Cottonseed hulls are a valuable source of roughage for ruminant and fiber for monogastric rations. Whole and delinted cottonseed are concentrated sources of protein and energy in ruminant rations.

Cottonseed meal is one of two by-products produced when oil is extracted from whole cottonseed. Cottonseed oil can be extracted by using a solvent or a mechanical process. The nutrient content of cottonseed meal varied depending on the process used to extract the oil. The major effect of extraction process on cottonseed meal is on fat content. The meal used in this study was generated using a mechanical extraction process and was guaranteed to have at least 40 % crude protein (Paper I ). Crude protein contents of 41 or 44 % are standard in the reference books for cottonseed meal(NRC, 2001) but with changes that have occurred in the extraction processes, less protein is being left in the meal. Cottonseed meal is an excellent protein supplement for cattle. The limitations on effective utilization of this product in rations for swine and poultry are of minor significance for ruminant animals. Cottonseed meal has a relatively low rumen degradability and is therefore a good source of by-pass protein and especially useful in rations for milking cows (Gohl,1998). In comparison with SBM, CSM has a higher concentration of RUP and is beneficial because it supplies more total AA for absorption in the small intestine (Clark et al.,1987.)

Typical parameter estimates of CP disappearance of cottonseed meal from nylon bag, digestibility at intestinal and total tract are reviewed in the Table 1.

Rumen undregradable protien that shown in Table was ranking from 31.9 to 57.3 % of DM , it was due to difference situation and varities of CSM that effect on nutritive value of CSM.

Cottonseed meal can be used to replace soybean meal ,resulting in similar milk production and composition (Blackwelder et al.,1998).The result from Paper II, cottonseed meal can completely replace soybean meal with similar milk production. While, feed cost was decreased when cottonseed meal completely replaced soybean meal. However , the results from Paper I and report by NRC (2001) that cottonseed meal is an available supplemental protein source that is slightly lower in crude protein than soybean meal, but is higher in rumen undegradable protein. However, it is also higher in acid-detergent fiber and lignin as compared to soybean meal.Cottonseed meal (CSM) contains less available protein and energy than either peanut meal or soybean meal. This is especially true for the available protein component and for this reason rations containing cottonseed meal need to contain a little more protein (one to two percent) to be equal to rations containing soybean or peanut meal. In general, however, CSM is typically a very useful, cost-effective feed ingredient. However, cottonseed products, especially whole cottonseed, contain a toxic pigment called gossypol in the glands of the seeds.

Gossypol is a normal existing pigment compound in cottonseed which can at high levels, have a negative effect on livestock performance, especially those of monogastrics. Gossypol is in two forms: free (hazardous) and bound (total-free gossypol; less hazardous). Free gossypol binds cell constituents and iron, damaging the heart and leading to secondary liver damage and fluid accumulation in body cavities. Some cautions are suggested when using both cottonseed meal and whole cottonseed in dairy rations for high producing cows because of the presence of gossypol, which can be toxic at high levels of intake. However, most gossypol is removed during processing of the seeds. Processing of cottonseed will have a significant impact on the concentration of free gossypol. Cottonseed meal pressed with heat and moisture is less hazardous than other forms of cottonseed. Lindsey et al. (1980) reported that the average of free gossypol contents of the CSM were 0.225 and 0.061 % in solvent and mechanical extraction process, respectively. Ruminants especially in mature animals are able to tolerate higher levels of gossypol due to partial detoxification by the rumen fermentation. However, care should be taken that daily intake does not exceed 1000 parts per million (0.1 %) in diet dry matter (Merk, 1991). It means that cow 500 kg of body weight (DMI = 3 % of body weight) should consume no more than 15 grams of free gossypol per day. In Paper II cottonseed meal intake in dietary treatment 4 with high level of cottonseed meal at 2.21 kg/h/d. It means that free gossypol intake was 1.35 g/h/d. Lindsey et al. (1980) fed diets containing 45% CSM, resulting in an intake of 10.1 kg/h/d of CSM and found no effect on gossypol toxicity.

 

Conclusions and recommendations

Based on the results in this thesis the following points can be made:

However, further researches relating to the balance of energy to protein should also be considered in protein supplementation for dairy cows.

References

Abeni, F., Calamari, L., Stefanini,L., Pirlo,G., 2000. Effects of daily gain in pre- and postpubertal replacement dairy heifers on body condition score, body size, metabolic profile, and future milk production. J. Dairy Sci. 83,1468-1478.

Allen, M.S., 1996. Physical constrains on voluntary intake of forages by ruminants. J. Anim. Sci. 74,3063-3075.

Allen, M.S., 2000. Effects of diet on short-term regulation of feed intake by lactating dairy cattle . J Dairy Sci. 83,1598.

Baker, L.D., Ferguson, J.D., Chalupa, W., 1995. Responses in urea and true protein of milk to different protein feeding schemes for dairy cows, J.Dairy Sci. 78, 2424.

Barry, T.N., 1985. The role of condensed tannins in the nutritional value of Lotus pedunculatus for sheep: Rates of body and wool growth. Brit. J. Nutr. 54, 211 -217.

Blackwelder, J.T., Hopkins, B.A., Diaz, D.E., Whitlow, L.W., Brownie, C., 1998. Milk production and plasma gossypol of cows fed cottonseed and oilseed meals with or without rumen-undegradable protein. J. Dairy Sci. 81, 2934-2941.

Blaxter, K.L. 1962. The energy metabolism of ruminants, Hutchinson, London

Brown, W. F., Pate, F. M., 1997. Cottonseed meal or feather meal supplementation of ammoniated tropical grass hay for yearling cattle. J. Anim. Sci. 75,1666- 1673.

Butler, W. R., Calaman, J. J.,Beam, S. W., 1996. Plasma and milk urea nitrogen in relation to pregnancy rate in lactating dairy cattle. J. Anim. Sci. 74,858-865.

Campfield, L.A., Smith, F.J., Guisez, Y., Devos, R., Burn, P. 1995. Recombinant mouse OB protein: evidence for a peripheral signal linking adiposity and central neural networks. Science. 269, 546-549.

Chantalakhana, C., Skunmum, P., 2002. Dairy development in Thailand In : Sustainable smallholder animal systems in the tropics. Bangkok : Kasetsart University Press. pp. 208-235.

Clark, J. H., Murphy M. R., Crooker, B. A., 1987. Supplying the protein needs of dairy cattle from by-product feeds. J. Dairy Sci. 70,1092-1109.

De Leeuw, P.N., Omore, A., Staal,S.,Thorpe, W., 1999. Dairy production systems in the tropics In : Falvey L., Chantalakhana C. (Eds.) Smallholder Dairying in the Tropics. ILRI (International Livestock Research Institute), Nairobi, Kenya. pp. 462.

DePeters, E. J., Bath, D. L., 1986. Canola meal versus cottonseed meal as the protein supplement in dairy diets. J. Dairy Sci. 69,148- 154.

Grings, E. E., Roffler, R. E., Deitelhoff, D. P., 1991. Response of dairy cows in early lactation to additions of cottonseed meal in alfalfabased diets. J. Dairy Sci. 74, 2580- 2587.

Gohl, B., 1998. Tropical feeds version 8 FAO.

Halaas ,J.L., Gajiwala, K.S., Ma.ei, M., Cohen, S.L., Chait, B.T., Rabinowitz,D., Lallone, R.L., Burley, S.K.,Friedman, J.F., 1995. Weight-reducing e.ects of the plasma protein encoded by the obese gene. Science 269 543-546.

Hammond, A. C., 1983. Effect of dietary protein level, ruminal protein solubility and time after feeding on plasma urea nitrogen and the relationship of plasma urea nitrogen to other ruminal and plasma parameters. J. Anim. Sci. 57(Suppl. 1),435

Holter, J.B., Urban,W.E.Jr., 1992. Water partitioning and intake prediction in dry and lactating Holstein cows. J.Dairy Sci. 75, 1472-1479.

Holter, J.B., West, J.W. , McGillard, M.L., 1997. Predicting ad libitum dry matter intake and yield of Holstein cows. J.Dairy Sci. 80, 2188-2199.

Hwang, S.Y., Mei-Ju, L., Peter, W.C., 2000. Monitoring nutritional status of dairy cows in taiwan using milk protein and milk urea nitrogen. Asian-Aus J. Anim. Sci. 13,1667-1673.

Jaster, E.H. , Murphy, M.R., 1983. Effect of varying particle size of forage on digestion and chewing behaviour of dairy heifer. J. Dairy Sci. 66, 802-810.

Jonker, J. S., Kohn, R. A., Erdman, R. A. 1998. Using milk urea nitrogen to predict nitrogen excretion and utilization efficiency in lactating dairy cows. J. Dairy Sci. 81, 2681-2692.

Jouany, J. P., Ushida, K., 1999. The role of protozoa in feed digestion.

Review. Asian-Australasian J. Anim. Sci. 12,113- 128.

Kalscheur, K.F.,Vandersall, J.H.,Erdman R.A.,Kohn,R.A., Russek-Cohen, E., 1999. Effects of dietary crude protein concentration and degradability on milk production responses of early, mid and late lactation diary cows. J. Dairy Sci. 82, 545-554.

Kauffman, A. J., St-Pierre, N. R., 2001. The Relationship of Milk Urea Nitrogen to Urine Nitrogen Excretion in Holstein and Jersey Cows J. Dairy Sci. 84,2284-2294.

Leng, R.A., Jessop, N.J. and Kanjanapruthipong, J. 1993. Control of feed intake and the efficiency of utilisation of feed byruminants. In: Farrell, D.J. (Ed). Recent Advances in Animal Nutrition in Australia 1993 Published by the Department of Biochemistry, Microbiology and Nutrition, University of New England, Armidale, Australia. pp.70-88.

Leng, R. A., Preston, T. R., 1983. Nutritional stratergies for the utilization and technologies to the small farmer in Asia. In : Proc. Vth World Conference on Animal Production Vol. 1, pp. 310 - 318.

Leng, R.A., 1990. Factors affecting the utilization of poor-quality forage by ruminants particularly under tropical conditions. Nutrition Research Reviews 3, 277-303.

Leng,R.A., 1999. Feeding strategies for impoving milk production In : Falvey L. ,Chantalakhana C. (Eds.) Smallholder Dairying in the Tropics. ILRI (International Livestock Research Institute), Nairobi, Kenya. pp. 462.

Lindsey, T.O.,Hawkins, G.E., Guthrie,L.D., 1980. Physiplogical responses of lactating cows to gossypol from cottonseed meal ration. J. Dairy Sci. 63,562-573.

Llamas-Lamas, G., Combs,D.K., 1991. Effect of forage to concentrate ratio and intake level on utilization of early vegetative alfafa silage by dairy cows. J Dairy Sci. 74,526-536.

Mahadevan, S., Erfle, J. D.,Sauer, F. D., 1980. Degradation of soluble

and insoluble proteins by Bacteroides amylophilus protease and by

rumen microorganisms. J. Anim. Sci. 50, 723- 728.

Merck., 1991. Gossypol poisoning. In: Fraser, C.M.,(Ed.), The Merck Veterinary Manual (seventh edition). Merck, Rahway, U.S.A., pp. 1652-1654.

Merck., 1991. Nutrition Cattle. In: Fraser, C.M.,(Ed.), The Merck Veterinary Manual (seventh edition). Merck, Rahway, U.S.A., pp. 1171-1200.

Mertens, D.R., 1987. Predicting intake and digestibility using mathematical models of ruminal function. . J Dairy Sci. 64, 1548-1558.

Morrison, C. D., Daniel, J. A., Holmberg, B. J., Djiane, J., Raver N., Gertler, A., Keisler,D. H., 2001. Central infusion of leptin into well-fed and undernourished ewe lambs: effects on feed intake and serum concentrations of growth hormone and luteinizing hormone. J. of Endocrin. 168, 317-324

National Research Council., 1985. Ruminant Nitrogen Usage. Washington, DC.

National Research Council (NRC).,1989. Nutrient requirements of dairy cattle. 6th Rev. ed. Nat'l Acad. Sci., Washington, DC.

National Research Council (NRC)., 2001. Nutrient requirements of dairy cattle. 7th Rev. ed. Nat'l Acad. Sci., Washington, DC.

Nolan, J.V., Leng, R.A., 1989. Manipulation of the rumen to increase ruminant production. Proceedings of Combined Consultants and Research Co-ordination Meeting, March, 1989, I.A.E.A., Vienna.

Oldham, J.d., 1984. Protein-energy interrelationships in dairy cows. J. Dairy Sci. 67, 1090-1114.

Osafo, E.L., K., Owen, E., Said,A.N.,Gill,M., Sherington, J., 1997. Effect of amount offered and chopping on intake and selection of sorghum stover by Ethiopian sheep and cattle. British Society of Animal Science 65,55-62.

Pelleymounter., M.A., Cullen, M.J., Baker, M.B., Hecht, R., Winters, D., Boone, T., Collins, F. 1995. E.ects of the obese gene product on body weight regulation in ob/ob mice. Science. 269, 540-543.

Perdok H., Leng, R.A., 1989. Rumen ammonia requirements for efficient digestion and intake of straw by cattle . In :Nolan J.V., Leng,R.A. ,Demeyer (Eds), The Roles of Protozoa and Fungi in ruminant Digestion. Penambul Books, Armidale, Australia.

Pate, F. M., Brown, W. F., Hammond, A.C., 1995. Value of feather meal in a molasses-based liquid supplement fed to yearling cattle consuming a forage diet. J Anim. Sci. 73, 2865-2872.

Roffler,r.e., Wray, J.E., Satter, L.D., 1986. Production responses in early lactation to additions of soybean meal to diets containing predominantly corn silage. J. Dairy Sci. 69,1055-1062.

Roseler, D.K., Ferguson, J.D., Sniffen, C.J., Herrema, J., 1993. Dietary protein degradability effects on plasma and milk urea nitrogen and milk non-protein in holstein cows. J. Dairy. Sci. 76, 525-534.

Sarawish., S., Wanapat M. , Yoderanee, S., 1988. Effects of levels of dried leucaena leaf (Leucaena leucocephala) supplementation in straw based diets on growth performance of native cattle. In: Proc. The 26th Annual Conference, Kasetsart University, Bangkok, Thailand.

Smith, W.A., Harris, B. Jr., Van Horn, H.H. ,Wilcox, C.J., 1993. Effects of forage type on production of dairy cows supplemented with whole cottonseed, tallow and yeast. 76, 205-215.

Sniffen, C. J., O'Connor, J. D., Van Soest , P. J., Fox,D. G., Russell, J. B., 1992. A net carbohydrate and protein system for evaluating cattle diets: II. carbohydrate and protein availability. J. Anim. Sci. 70, 3562-3577.

Wallace, R. J., Atasoglu ,C., Newbold, C. J., 1999. Role of peptides

in rumen microbial metabolism. Review. Asian-Australasian J. Anim. Sci. 12,139-147.

Wanapat, M., Devendra, C., 1992. Feeding and nutrition of dairy cattle and buffaloes in Asia. Sustainable Animal Production. Proceedings 6th AAAP Animal Science Congress, Bangkok, Thailand.

Wanapat, M., Sommart, K., Saardrak, K., 1996. Cottonseed meal supplementation of dairy cattle fed rice straw. Livestock Research for Rural Development. 8, 20-23.

Wanapat, M.,Topark-ngarm,A., Wanapat, S., Luandtong, S.,Taesakun, S., 1989. The nutritive value of cowper (Vigna unguiculata L.) residues and supplementation levels of cowper residues for native cattle fed on rice straw. Proc. 27th Annual Meeting,Kasetsart University, Bangkok, Thailand.

Wanapat, M., 1995. Research priorities for improving animal agriculture by agro-ecological zone in Thailand. In : Devendra, C., Gardiner, P. (Eds) Global Agenda for livestock research, Proceeding of the consultation for the South-East Asia Region. International livestock research institute (IRRI).

Wanapat, M., 1994. Supplementation of straw-based diets for ruminants in Thailand. In: Improving Animal Production Systems based on Local Feed Resources. Proceedings "Sustainable Animal Production and the Environment". The 7th AAAP Animal Science Congress, Bali, Indonesia.

Wanapat, M., 1999. The use of local feed resources for livestock production in Thailand. In: Feeding of Ruminants in the Tropics based on Local Feed Resources, Khon Kaen University, Thailand. pp. 59-78.

Wanapat, M., 2001. Role of cassava hay as animal feed in the topics. In: Preston, T.P., Brian,O.,Wanapat,M. (Eds). International Workshop Current Research and Development on Use of Cassava as Animal Feed. Khon Kaen University, Organized and Sponsored by Sida-SAREC,Swedish International Development Agency, Swedish Agency for Research Cooperation with Developing Countries.

Webster, A. J. F., 1987. Metabolizable protein- the U.K. approach. In:

Alderman,G., Jarrige, R. (Eds.), Feed Evaluation and Protein Requirement System for Ruminants. Commission of European Communities, EUR 10657 EN, Luxembourg, pp. 47-54.


Table 1. Typical parameter estimates of degradable, undegradable,(both assuming rate of passage of 0.05/h-1), intestinal (% of rumen undegradable protein) and total tract (% of original feed) digestibility of CP in cottonseed meal

Item

DePeters and Bath (1986)

Grings et al. (1991)

Pate et al. (1995)

Brown and Pate(1997)

NRC (2001)

Paper I. Ureatreated1

Paper I. Untreated2

a3/.

22.1

20.0

15.9

19.0

25.6

28.0

31.0

b

66.5

58.2

74.0

79.5

55.5

48.9

40.5

c

0.080

0.032

0.120

0.072

0.068

0.058

0.043

Effective degradability, %

63.0

42.7

68.1

66.0

57.6

54.6

49.6

Effective Undegradability, %

37.0

57.3

31.9

34.0

42.4

45.4

50.4

Intestinal digestibility, %

-

83.0

-

-

92.0

88.2

88.1

Total tract digestibility, %

-

90.3

-

-

95.4

94.6

94.0

1 Result from Paper I in cow fed with urea treated rice straw

2 Result from Paper I in cow fed with untreated rice straw

3 a=rapidly solubilized CP fraction (% of tatal CP), b= CP fraction potentially degradable in the rumen (% of tatal CP), c = rate constant for degradation of b fraction (% of of tatal CP h-1 ).