Supplementation of ammoniated wheat straw with hulled cottonseed cake

*Bureau of Animal Husbandry, Zhokou Prefecture 466000, Henan Province,
**Department of Animal Husbandry and Aquatic Products, No 13, Yuhua Mid-Road, Shijiazhuang 050011, Hebei Province, People's Republic of China
***FAO consultants to the Project CPR/88/057.

(This paper was first presented at the 'International Conference on Increasing Livestock Production through Utilization of Local Resources'. CECAT, Beijing, 18-22 October 1993)

Two trials were carried out with the objective to develop response curves to supplements of hulled cottonseed cake (CSC). The basal diets were ammoniated wheat straw offered ad libitum, using either urea or anhydrous ammonia as sources of ammonia. One trial involved 40 growing male cattle of the Chinese Yellow Breed randomly allocated to five groups. A group received either 0, 1, 2, 3, or 4 kg hulled cottonseed cake daily.Another trial used 60 growing cattle of which 12 were females. They were allocated to six groups with 10 animals in each of which two were females and supplemented 0, 0.25, 0.50, 1.50, 2.00 and 2.50 kg/day hulled cottonseed cake. Both trials lasted 90 days. The average daily liveweight change (ADG) in response to 0, 1, 2, 3 and 4 kg/day hulled cottonseed cake were 250, 600, 704, 845 and 883 g, respectively. The regression equation was: Y=249+303X-36X² (R²=0.99) where X=kg/day CSC and Y=ADG (g).

In the trial using 0, 0.25, 0.50, 1.50, 2.00 and 2.50 kg/day hulled cottonseed cake, the daily liveweight change was 63, 370, 529, 781, 829 and 892 g, respectively. The regression equation was: Y=149+697X-166X² (R²=0.93).

From a resource perspective the response in the range of 1 - 2 kg cottonseed cake is particulary interesting, because at that level straw still constitutes 70% or more of the total diet.

KEY WORDS: Supplementation, ammoniated wheat straw, hulled cottonseed cake, response curves, protein, cattle, fattening

Alkali treatment of fibrous crop residues is well researched (Sundstol and Owen 1984; Han and Garrett 1986 and Romney et al 1993) and the possibility of using urea as a source of ammonia (Jackson 1978; Dolberg et al 1981) led to expectations of rapid implementation in many developing countries, which, however, have not been realized (Owen and Jayasuriya 1989) for several reasons (Dolberg 1992). Too much attention to treatment technique per se, and too little to supplementation strategies aimed at employing biologically effective supplements available to the farmers, are some of the explanations. Unsupplemented ammoniated treated straw leads to production improvements far below the level potentially made available by treatment (Preston and Leng 1987). Low levels of production may not earn farmers sufficient income to pay for the ammoniation treatment and, consequently, they lose interest and the technology is not taken up.

Lack of feedback from extension or no communication at all between research and extension can be mentioned as some of the other reasons for lack of impact of new technologies. There has been insufficient research with a farmer's perspective in the area of crop residue utilization although good extension work must be based on precise knowledge.

In the Provinces of Henan and Hebei in the People's Republic of China, cottonseed cake is widely available and the present trials were set up with the objective to determine responses to increasing levels of cottonseed cake in cattle fed basal diets of ammoniated wheat straw ad libitum.

Forty young bulls, 10 - 14 months old, of the Chinese Yellow Breed, bought in the local market were allocated at random to five groups with 8 animals in each. The pre-experimental period was 30 days. In the final calculations one sick animal in group five was excluded.

The basal diet was ammoniated wheat straw (5% urea) fed ad libitum together with a standard mineral supplement. The treatments were hulled cottonseed cake, individually fed twice daily in equal quantities and allocated according to the following design: 0, 1, 2, 3 and 4 kg/day for groups 1, 2, 3, 4 and 5, respectively.

The cattle were stall-fed and kept on a dry earth floor. Straw and supplements were offered twice daily at 09:00 and 17:00 hours. It was ensured that a surplus of straw was on offer at all times. Residues were removed and weighed and recorded once daily before morning feeding. The experiment lasted 90 days from February 11 to May 12, 1992. The initial and final weights were an average of 3 consecutive weighings before morning feeding. During the experiment the animals were weighed once every 15 days.

5 kg urea and 80 kg water were mixed and applied per 100 kg air-dry wheat straw, which was subsequently placed in a cement pit and covered with plastic. The treatment period was 30 days and the ambient temperature range from 15 - 25 ?C. The treated straw was allowed to aerate for one day before it was fed.

As the hulled cottonseed cake levels were high in groups 4 and 5, all the cake was treated with 1 kg iron sulphate (FeSO4) per 100 kg to reduce any possible problems with gossypol toxicity (FAO 1992).

Samples were collected daily of the feeds and stored. Every 15 days subsamples of the stored material were subjected to chemical, and biological analysis using the nylon bag method (Örskov 1992) and cannulated sheep. The dry matter degradabilities of straw and cottonseed cake were measured by incubation of samples, which had passed through a laboratory hammer mill with a 3 mm screen in the rumens of the sheep. The filter cloth was 45 um and had been obtained from United Kingdom. The sheep were fed a 1.25 x maintenance ration of ammoniated wheat straw and cottonseed cake. Apparent digestibility of the diets was measured by collecting total faeces during the last 5 days of the experiment, using 4 animals from each treatment. Straw intake was carefully measured during three 15 day periods in the latter half of the first, second and third 30 day periods of the trial. Average straw dry matter was 82%.

In comparison to the Henan trial, the objective of this trial was to elaborate on the point of inflexion of the response curve by employing smaller intervals (250 g/day at the lower and 500 g/day at the higher extremes of the curve) between the cottonseed cake increments.

Sixty young cattle were used, 48 males and 12 females, of which 5 were crossbred (Shorthorn x Chinese Yellow) cattle. All cattle were brought in from neighbouring Henan Province. Except for the 5 crossbreds all were of the Chinese Yellow Breed. The animals were allocated to 6 groups with 10 animals in each of which two were females. The pre-experimental period was 15 days.

The basal diet was ammoniated (3% anhydrous ammonia straw) wheat straw fed ad libitum. The straw was treated in plastic-covered stacks with a minimum treatment period of 21 days before opening. The treatments were daily supplements of hulled cottonseed cake fed individually in two equal meals, twice daily according to the following schedule: 0.0, 0.25, 0.50, 1.50, 2.0 and 2.5 kg/day to groups 1, 2, 3, 4, 5 and 6, respectively.

The cattle were stall-fed. Straw and supplements were supplied once in the morning and once in the afternoon and it was ensured the animals always had some straw on offer. The initial and final weights were averages of 2 consecutive weighings before morning feeding. During the experiment the animals were weighed at 15 day intervals. The experiment lasted 90 days, starting February 1, 1992.

Logistics made experienced research supervision difficult, resulting in a problem with mineral supplementation. Yet, the trial was well conducted and the consistency of the data very high.

Analogous with Henan, feed samples were subjected to nylon bag analysis (Örskov 1992). Straw dry matter was 88% and intake was measured on a group basis involving all animals the last 10 days of the trial.

The 48 hour values for dry matter degradability obtained by biological (nylon bag) evaluation of untreated, 5% urea-treated straw and cottonseed cake in Henan were 42.9, 55.6 and 66.7, respectively. The cottonseed cake contained 30% N x 6.25 and 6.6% fat on a dry matter basis. These values are within the range of values for hulled cottonseed cake (FAO 1992).

The apparent (in vivo) dry matter digestibility coefficients of diets supplemented with 0, 1, 2, 3 and 4 kg/day cottonseed cake were 58.6, 67.3, 68.7, 70.2 and 69.1, respectively. The corresponding intake and liveweight change values are presented in Table 2.

48 hour degradability of dry matter according to the biological evaluation of the untreated and 3% anhydrous ammonia treated wheat straw in Hebei was 37.8 and 58.2%, respectively. The degradability of the hulled cottonseed cake used in the trial was compared to dehulled cottonseed cake (table 1).

Table 1: Nylon bag degradability of dry matter of hulled and dehulled cottonseed cake (% degraded).

	Time of incubation, hours
	8	16	24	48	72	96

Cottonseed cake
hulled	49	54	66	77	84	85
dehulled	63	72	82	88	92	92

The mean values for animal performance are set out in tables 2a and 2b. Liveweight gain was related curvilinearly to CSC input. The respective regression equations were:

Table 2A: Influence of increasing levels of cottonseed cake (CSC) supplementation on daily gain, straw and total dry matter intake and feed conversion (means and SE for 8 animals/treatment group) (Henan)

	Cottonseed cake (kg/day)
	0	1	2	3	4

Liveweight (kg)
Initial	182±31	183±18	183±24	183±21	183±20
Final	205±36	237±27	246±35	258±18	262±13
Daily gain (g)	250±73	600±151	704±141	845±233	883±268

Dry matter (%of liveweight)
Straw	2.6	2.5	2.1	1.9	1.3
CSC	0.0	0.4	0.8	1.2	1.6
Total	2.6	2.9	2.9	3.1	2.9

Feed conversion (dry
matter/LW gain)	20	10	9	8	7

Both trials met the main objective of identifying animal responses to increasing levels of cottonseed cake supplementation. They clearly demonstrated that feeding of ammoniated straw alone is inadequate in terms of exploiting the nutrients potentially made available for animal production. Growth rates on the control diet of unsupplemented ammoniated straw was 250 g/day in the Henan trial and 63 g/day in Hebei. Less than adequate mineral supplementation in Hebei may have affected this group in particular.

Table 2B: Influence of increasing levels of cottonseed cake (CSC) supplementation on daily gain, straw and total dry matter intake and feed conversion (means and SE for 10 animals/treatment group) (Hebei)

	C o t t o n s e e d c a k e (g/day)
	0	250	500	1500	2000	2500

Liveweight (kg)
Init	137±23	159±18	183±42	192±43	175±33	194±50
Fin	143±21	193±22	231±44	263±47	250±41	274±50
ADG (g)	63±48	370±133	529±150	781±165	829±165	892±76

Intake (dry matter % of liveweight)
Stw	2.7	2.5	2.3	2.0	1.8	1.7
CSC	0.0	0.1	0.2	0.5	0.8	0.9
Ttl	2.7	2.6	2.5	2.5	2.6	2.6

Feed conversion (dry matter/ADG)	60	12	10	7	7	7

In the Henan trial the apparent (in vivo) dry matter digestibility coefficient was 58.6% for the control diet and total dry matter intake 2.6% of animal liveweight. Adding 1 kg of hulled cottonseed cake improved total ration apparent digestibility to 67.3% and the expected increased rumen turn-over rate (Preston and Leng 1987) improved intake to 2.9% with very small, although negative effect on straw intake. Daily liveweight gain improved from 250 to 600 g. At the level of 2 kg/day cottonseed cake, straw constituted 72% of the total diet and substitution, mediated through a change in rumen microbial environment (Örskov and Ryle 1990), of straw by cottonseed cake is likely to have taken place (Jackson 1978). Total dry matter intake was maintained at 2.9% of liveweight but, compared to the control group, straw intake was reduced by 20% from 2.6 to 2.1% of animal liveweight. This trend continued with each extra kg of cottonseed cake and at 4 kg/day of supplement, straw constituted only 45% of the total feed. It is noted that the highest dry matter intake (3.1% of liveweight) was obtained with 3 kg/day cottonseed cake.

The trends concerning the animal parameters measured in Hebei were the same as those observed in Henan. However, it is possible to examine the responses to much smaller quantities of hulled cottonseed cake and it can be noted that even 0.25 kg/day causes a more than fivefold increase in daily liveweight gain and a corresponding improvement in feed conversion rate. The improvement continues to be marked up to 1.5 kg/day cottonseed cake. Going from 1.5 to over 2.0 - 2.5 kg/day cottonseed cake led to much smaller liveweight gain increases (Table 2b).

It is observed that while total dry matter intake across the treatments remained within a very narrow range of from 2.5 to 2.7% of animal liveweight, straw was progressively being replaced by cottonseed cake within the diet.

The trials were not set up to compare these two sources of ammonia and being located at different sites, using different sources of straw, they do not meet the conditions for comparisons. The observed values for nylon bag degradability of treated and untreated straw do, however, correspond well with established norms for treatment effect (SundstÝl and Owen 1984).

The stimulating effect of supplementing small quantities of cottonseed cake to a basal diet of fibrous crop residues was expected as it is in agreement with the results of much recent research on protein supplementation (Preston and Leng 1987; Örskov and Ryle 1990). Very satisfactory levels of milk production were obtained in the work reported by Boodoo et al (1990) in which cottonseed cake was used to supplement traditional smallholder milch cow diets, mainly based on sugarcane tops in Mauritius.

However, the apparent (in vivo) dry matter digestibility values of 68.7, 70.2 and 69.1% for diets containing 2, 3, and 4 kg cottonseed cake observed in Henan were perhaps higher than expected.

Applying the apparent dry matter digestibility of 58.6 % to the straw as found in Henan and assuming 75% for the hulled cottonseed cake (Table 1), the following values for expected and observed apparent dry matter digestibilities can be calculated (table 3).

Table 3: Expected and observed dry matter digestibility (%)

Cottonseed cake kg/day	Expected	Observed	Difference

0	58.6	58.6	0.0
1	60.7	67.3	+6.6
2	63.2	68.7	+5.5
3	65.0	70.2	+5.2
4	67.6	69.1	+2.5

The values presented in table 3 suggest that at all levels the hulled cottonseed cake supplementation has had a stimulatory effect on total diet digestion. The 8-hour values (table 1) imply that the hulled cake contained a rapidly disappearing fraction and it is possible - but the point was not pursued in these trials - that it is due to the hull acting as a readily digestible cellulose and hemicellulose fraction stimulating bacterial colonization and digestion of the total fibrous diet (Silva and Örskov 1988; Preston and Leng 1987; Manyuchi et al 1992) and that the effect was not limited to the extra protein alone. FAO (1992) refers to work indicating stimulatory, but not precisely defined, effects of including hulled cottonseed cake in diets for ruminants. It does therefore seem justified to recommend that this point be studied in greater detail, because - if correct - it renders hulled cottonseed cake an almost perfect supplement providing both protein and easily digestible cellulose and hemicellulose.

312 farmers living in 12 villages in Henan and Hebei Provinces having a total of 1027 cattle were simultaneously involved in on- farm trials feeding treated straw ad libitum and supplementing between 1 to 2 kg cottonseed cake daily. Average daily gain was calculated to be 642 g. Straw treatment using urea as a source of ammonia is now finding rapid uptake among Chinese farmers. More than 2 million farmers were estimated to apply the technology in 1992.

In any situation, the exact amount of supplement to recommend will be subject to local prices as illustrated by Finlayson (1992).

From these two trials it can be concluded that hulled cottonseed cake supplementation at a level of 1.5±0.5 kg/day to a basal diet of ammoniated wheat straw fed to cattle dramatically improves feed conversion rate and liveweight gain.

Straw is an abundant feed resource in many developing countries, which makes the responses from a development perspective to the first 1 to 2 kg/day cottonseed cake the most interesting. At these levels straw still constitutes around 75% or more of the total diet.

The Government of China and FAO provided material and financial support. The contribution and cooperation of Project staff in Zhoukou Prefecture and Baixiang County are acknowledged.

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