Effect of ammonia treatment of wheat straw and level of concentrate on performance of chinese yellow cattle

Effect of ammonia treatment of wheat straw and level of concentrate on performance of chinese yellow cattle

T K Ma, C X Gu, B C Dai,
Hebei Bureau of Animal Husbandry and Aquatic Products, 13 Yuhua Mid-Road, Shijiazhuang, Hebei 050011, China

An experiment was conducted with 16 bulls of the Chinese Yellow Cattle breed. They were 12-18 months of age at the start of the trial and the experiment lasted for 182 days. The experiment was a 2 x 2 factorial trial in which the steers were given either untreated or ammonia treated wheat straw ad libitum, together with a daily allowance of either 0.5 or 1.0 kg/d of a supplement consisting of wheat bran (0.75) and cottonseed meal (0.25). Both the effect of ammonia treatment and level of supplementation were significant. The daily intakes of untreated and treated straw were 5.07 and 5.12 kg and the liveweight gains were 0.18 and 0.57 kg/d respectively. The liveweight gains for the bulls receiving 0.5 and 1.0 kg/d of supplement were 0.30 and 0.45 kg/d respectively. The most economic diet was the ammonia treated straw with 1 kg/d of supplement. At the end of the trial, the cattle on that treatment were sufficiently fat for slaughter.

Key words: straw, ammonia, cattle, fattening, sheep, rumen degradability, supplementation

In many cropping provinces of China, there is a large excess of crop residues, mainly wheat straw, rice straw and maize stover. This is partly due to a reduction in the number of cattle as a result of the reduced demand for draught power and partly to a greater use of coal rather than crop residues for domestic fuel. The use of straw for cattle fattening has been limited by the low intake and consequent requirement for costly supplement. In the present experiment, ammoniation of straw was used to investigate whether this could be used, together with a limited amount of supplement, as a food for fattening.

Sixteen male cattle of the Chinese Yellow Cattle breed were used. They were between 180 and 220 kg liveweight. They were allocated at random to receive one of 4 treatments in a 2 x 2 factorial design. The four treatments were as follows:

Untreated straw ad libitum + 0.5 kg supplement/d
Untreated straw ad libitum + 1.0 kg supplement/d
Treated straw ad libitum + 0.5 kg supplement/d
Treated straw ad libitum + 1.0 kg supplement/d

The feeds were given for 182 days. Prior to that the cattle were adapted to indoor feeding and to the straw diet for a period of 30 days. The experiment was carried out at Baixiang County Ammoniation Station.

The chopped wheat straw was stacked and moistened to give about 70% dry matter. Anhydrous ammonia was then injected into the stack to give 30 g ammonia/kg initial air dry weight of the straw. The stacks were sealed with a plastic film and left for 30 days before being opened. Before the feeds were used, the stack was allowed to aerate for 5 days to allow for the escape of volatile ammonia and for drying.

The supplement consisted of 25% by weight of cottonseed cake and 75% of wheat bran. The chemical composition of the supplement ingredients and of the treated and untreated straw is given in Table 1.

Table 1: Chemical composition dry matter basis of feed

	Untreated	Treated	Cottonseed	Wheat
	straw	straw	cake	bran

Ash	3.39	2.52	5.48	4.97
Nitrogen	0.54	2.05	5.62	3.54
Ether extract	0.71	0.59	4.74	4.49
Neutral detergent fibre	83.80	73.10	37.80	42.10

Three sheep, fitted with cannulae of 40 mm diameter, were used. Nylon bags containing about 2 g of substrate were incubated in the rumen and withdrawn after 8, 16, 24, 48, 72 or 96 h of incubation. The dry matter disappearance was subsequently described by the exponential equation of p = a + b (1-exp(-ct)) of Orskov and McDonald (1979) where a is the intercept or an estimate of solubility at time zero, b is the insoluble but fermentable proportion, a + b the total fermentation potential and c the rate constant.

The 48 h degradability and the constants in the exponential equation are given in Table 2 for all feeds used. It can be seen that the ammonia treatment greatly influenced the degradation characteristics seen in the b value and the 48 h degradability while the rate constant was not markedly changed.

Table 2: The constants of the equation p = a + b (1-exp(-ct)) together with 48 h degradability values of the feeds.

	Untreated straw	Treated straw	Wheat bran	Cottonseed cake

a (%)	10.4	17.4	36.1	36.1
b (%)	42.2	62.0	57.3	57.5
a+b (%)	52.6	79.4	93.4	90.8
c (fraction/hr)	0.0223	0.0207	0.0186	0.0240
RSD*	1.43	0.92	0.40	2.80
48 h degradability (%)	47.3	69.4	89	82.8

The 4 cattle for each treatment were fed in groups but care was taken to see that the supplement was well distributed along the trough to ensure that all animals had an equal share. New straw was introduced twice daily. An allowance was offered to ensure that 10 to 15% of uneaten straw remained before each feeding time and the daily intake of each group was measured. The cattle were cleaned daily and weighed once every 2 weeks.

All animals completed the trial but 2 of the bulls on untreated straw and low level of supplement were in poor condition when the trial ended.

It can be seen from Table 3 that not only did ammoniation result in faster and more efficient growth but it was also cost-effective, according to present prices. The responses in liveweight gain to ammoniation and to levels of supplement were highly significant (P<0.01). The cattle on untreated straw, after completion of the trial, looked rather emaciated and some had lost weight while the cattle which received the ammoniated straw had a very healthy appearance. The cattle on treatment 4 were in a condition fit for slaughter.

Table 3: Live weight gain, straw intake, feed conversion and feed cost of local cattle (Yellow Cattle) during 180-day trial

Supplement (kg/d)	---------------- 0.5 ----------------		------------------ 1.0 ------------------
Straw treatment	None	Ammoniated	None	Ammoniated

Initial liveweight (kg)	187	198	194	213
Daily gain (g)	110±33	485±42	240±27	660±90
Straw dry matter intake (kg/d)	4.3	4.8	3.9	4.3
DM conversion	44.3	10.8	20.6	8.0
Cost of feed/kg gain (Yuan)*	5.0	1.82	3.38	1.74

* Price (yuan/kg), wheat straw 0.06, ammoniated wheat straw 0.12,cottonseed cake 0.56, wheat bran 0.50.

Ammonia treatment markedly improved performance of the animals and also the nutritive value of the straw as indicated by the degradation characteristics. The changes are in agreement with expectations, although the difference in intake of ammonia-treated straw and untreated straw might have been expected to be greater (see Sundstol et al 1978).

The increases in animal performance were exceptional. The change in feed conversion as a result of the straw treatment, particularly with 1 kg/d of supplement, was highly economic while, with untreated straw, the cost of liveweight gain was uneconomic. The mature live weight of the Chinese Yellow Cattle is about 350 kg. The cattle which received the ammonia treated straw with 1 kg/d of supplement were judged to be sufficiently fattened for slaughter. Thus ammonia treatment can, in future, enable straw to be used for fattening of cattle with only small amounts of locally produced feed supplements. The technology is now being used by farmers in the area.

The use of anhydrous ammonia on small farms is difficult when stalks of 1 tonne or less have to be treated and the ammonia has to be provided in commercially available tanks usually with capacities in excess of 1000 kg. Small domestic-type gas bottles are presently produced containing 15, 30 or 60 kg of anhydrous ammonia. These would be eminently suitable for stacks containing 0.5, 1.0 or 2.0 tonnes of straw.

The authors are grateful to the Food and Agriculture Organization (FAO) for their support of the feeding trials reported here.

Orskov E R, Hovell F D DeB and Mould F 1980 The use of the nylon bag technique for the evaluation of feedstuffs. Tropical Animal Production 5:195-213

Sundstol F and Owen E 1984 Straw and other fibrous byproducts as feeds. Elsevier, Amsterdam.