Two trials were carried out to study the effect of urea block (UB) feeding on the performance of young growing Friesian heifers. In another trial with mature, dry Chios ewes the value of UB as supplement to straw offered ad libitum was compared with other supplements (concentrate-C, lucerne hay-LH and urea-treated straw-UTS offered ad libitum). All supplements were offered along with ad libitum untreated straw (US). Treatment of straw was made by spraying the bales of straw with 10% (w/v) urea solution at the rate of 400 littres per tonne of straw while making the stack. The DM degradability of untreated straw incubated (48 h) into the rumen of 3 Chios ewes and 3 Damascus goats fed the five experimental diets ( US, UTS, US+C, US+LH, US+UB) was also determined. In trial 1 with Friesian heifers partial replacement of the concentrate mixture with UB resulted in a non-significant difference in weight gain (C 324 vs UB 269 g/head/day). Feeding Friesian heifers UB ad libitum (trial 2) resulted in a significant (P<0.01) increase in weight gain compared to the control (C 657 vs UB 849 g/head/day) diet. In the trial with Chios ewes all animals were loosing weight (US 99, UTS 64, US+UB 51, US+C 56, US+LH 40 g/head/day); the difference was significant only between US and the other three supplemented groups (US+C, US+LH, US+UB). DM degradability of US incubated into the rumen of sheep and goats on the five diets was: US, no supplement=50%, UTS=52%, US+C=52%, US+UB=55%, US+LH=58% ; goats had greater DM degradability than ewes (55 vs 51%).

Poor quality roughage is the main component of the diet for ruminants in most parts of the world ( Preston and Leng 1987). Animals on such diets suffer significant weight losses (Hadjipanayiotou et al 1975; Sansoucy 1986) and supplementary feeding with nitrogen and energy sources has been attempted ( Preston and Leng 1987; Capper et al 1989). Supplements based on molasses and urea, molasses urea blocks, have been used successfully in different parts of the world (Preston and Leng 1987). In recent studies ( Hadjipanayiotou et al 1993a,b), urea blocks (UB) without any molasses have been successfully used for upgrading the nutritional value of a basal diet based only on straw and/or combination of straw with concentrate. Chemical treatment with urea or ammonia has also been used for upgrading the nutritive value of straw (Sundstol and Coxworth 1984). Data comparing straw treatment with urea and straw supplementation with UB are rather limited. Preston and Leng (1987) concluded that UB feeding is a technology that can be applied by small scale farmers whereas preparation of a urea solution and spraying it onto straw is a demanding and often arduous task making its wider application problematic. The present work reports the performance of Friesian heifers on a control or a UB diet and of Chios ewes without any supplement, on urea treated straw (UTS), on other supplements (UB, Lucerne hay, concentrate), and how a non-supplemented or a supplemented straw diet affects the DM degradability of untreated straw.

Three production studies, one with dry mature Chios ewes and two with growing Friesian heifers were carried out. The animals were weighed on two consecutive days at the beginning and at the end of each trial. In another study with rumen fistulated ewes and goats the effect of diet on the degradability of straw in the rumen was studied. Blocks were made in a 300 litre concrete mixer following the procedure outlined by Hadjipanayiotou (1993a). The composition (%) of UB formula was: urea 3, salt 2, cement 2, slaked lime 4, screened poultry litter 12, wheat bran 11, ground barley grain 11 and brewers grain 55 (18% DM). Representative samples of feed offered and refused were taken routinely and analyzed as outlined by Harris (1970). Digestibility in vitro was determined by the procedure described by Tilley and Terry (1963) as modified by O'Shea and Wilson (1965).

Heifers:

Twenty four and 16 Friesian growing heifers were used in trials 1 and 2, respectively. Animals within trials were divided into two age groups, and animals of each age group were divided into two uniform groups based on their body weight, and randomly allocated to either the control or the UB diet. Heifers were housed in four adjacent yards. Animals on the UB diet had free access to it at all times. Feed offered was routinely sampled and analyzed. The concentrate mixture used was composed (g/kg) of 758 barley grain, 170 soybean meal, 50 wheat bran, 2.5 dicalcium phosphate, 14 limestone, 3.5 sodium chloride and 2 vitamin-trace element mixture (Vita 6, Vita-trace Nutrition, Cyprus). The vitamin-trace element mixture supplied 6000 IU vitamin A, 1000 IU vitamin D3, 8.5 IU vitamin E, 25 mg Mn, 1.75 mg I, 45 mg Zn, 30 mg Fe, 2 mg Co and 60 mg Mg per kg concentrate mixture (as fed basis). The concentrate was offered once daily and straw twice. Feed allowance was increased with advancing age. The test period for trials 1 and 2 was 60 and 80 days, respectively. Data collected were analyzed within trials using a model which accounted for treatments (control, UB), age groups (old, young) and their interaction.

Chios ewes:

Thirty five dry mature Chios ewes were divided into five uniform groups based on their body weight. The five groups were randomly allocated to the following treatment diets: US, untreated straw offered ad libitum; UTS, urea-treated straw offered ad libitum; US+C, US plus limited quantities of concentrate; US+UB, US plus urea block offered ad libitum; US+LH, US plus limited quantities of lucerne hay. Animals were housed in individual pens bedded with shavings and had free access to water. The concentrate mixture used was composed (g/kg) of 821 barley grain, 107 soybean meal, 50 wheat bran, 3 dicalcium phosphate, 13 limestone, 4 salt and 2 "Vita 6". Ewes were weighed at the beginning, at the end and at weekly intervals during the course of the 70-day trial. Feed offered and refused was recorded daily. Data collected were analyzed by one-way analysis of variance.

Rumen degradation:

Table 1: Composition (g/kg) of feedstuffs
	DM	N*6.25	Ash	Fibre	"D"
Concentrate1	919	150	51	61	843
Concentrate2	900	197	96	58	845
Urea treated straw	891	119	87	405	661
Untreated straw	912	56	85	391	501
Lucerne hay	890	197	131	254	578
Urea block	909	225	208	ND	ND

1 Concentrate mixture used for ewes and goats
2 Concentrate mixture used for heifers
"D" In vitro DM digestibility

The effect of the five diets mentioned above on DM degradability of straw incubated (48 h) into the rumen of three Chios ewes and three Damascus goats was examined. Straw samples were incubated twice (3 bags/ replication) in the rumen of animals as outlined by Hadjipanayiotou et al (1988). The mean of the two replications was used for analyses. Pre- and post-incubation processing of samples was as outlined by Hadjipanayiotou et al (1988).

The chemical composition of the feedstuffs and of UB used is in Table 1. Feed intake and body weight changes of the heifers in trials 1 and 2 are in Tables 2 and 3.

There was no difference in weight gain between heifers of trial 1 on the C and UB diets. Heifers on the C diet consumed 0.88 kg per day less concentrates but they consumed 0.914 kg of block. In the second trial, heifers on UB had significantly greater (P<0.013) daily weight gain than those on the C diet. Older heifers consumed more UB than young ones. Similarly, intake of conventional feedstuffs was greater in old than young heifers. Response to UB feeding was similar for the two age groups

Table 2: Performance of two age groups of Friesian heifers on the control (C) or the urea block (UB) diet (Trial 1).
	In Wt	Fin Wt	ADG	Conc	Straw	UB
	(kg)	(kg)	(g)	--------(kg/d)----------
Treatment
Control, C	296	313	324	2.75	3.54	-
Block, UB	296	312	269	1.87	3.54	0.914
Age
Old	351a	366	246	2.5	3.79	0.946
Young	241b	261	347	2.13	3.29	0.881
Control, C
Old	351a	369a	297	3.0	3.79	-
Young	241b	262b	251	2.5	3.29	-
Block, UB
Old	352a	363a	194	2.0	3.79	0.946
Young	240b	261b	343	1.75	3.29	0.881
SD	53.5	59.4	180	-	-	-

In this Table and Table 3: In Wt initial weight; Fin Wt final weight; ADG average daily gain.

On all five treatment diets with the ewes there were losses of body weight (Table 4). Ewes on the US diet suffered the greater weight loss, but the difference was significant (P<0.03) only between US and US+LH diets. Intake of UTS was significantly greater (P<0.04) than that of straw intake by ewes on the US+LH diet only.

DM degradability of untreated straw incubated into the rumen was significantly affected (P<0.03) by the diet fed to ewes and goats (Table 5). DM degradability of straw was the lowest when the animals were offered ad libitum only untreated straw. The difference, however , was significant only between US and US+LH diets. DM degradability of UTS incubated into the rumen of animals offered UTS ad libitum was greater than all values obtained for US. Degradability values in goats' rumen was greater than that of ewes.

Table 3: Performance of two age groups of Friesian heifers on the control (C) or the urea block (UB) diet (Trial 2).
	In Wt	Fin Wt	ADG	Con.	Straw	UB
	(kg)	(kg)	(g)	-------kg/d-----------
Control	270	326	657b	2.63	4.35	-
Block	270	343	849a	2.63	4.35	2.20
Age
Old	315a	382a	791	2.88	4.82	2.42
Young	226b	287b	715	2.38	3.88	1.98
Control
Old	315	373	684	2.88	4.82	-
Young	225	279	629	2.38	3.88	-
Block
Old	314	391	898	2.88	4.82	2.42
Young	226	294	800	2.38	3.88	1.98
SD	34.9	40.8	132	-	-	-

Feeding UB and/or any other supplement did not increase the intake of the basal diet (straw) by Chios ewes. Sansoucy et al (1988) reported that the straw consumption with MUB is about 25-30% higher, but only 5-10% higher when some concentrates are given. The present findings are in line with those of Hadjipanayiotou et al (1993a) and Neric et al (1985) where no significant difference in straw intake between the control and block groups were obtained. The lower straw intake by ewes on the US+LH diet might be due to the fact that these animals were already receiving lucerne hay which is a bulky material. In previous studies with Chios sheep (Hadjipanayiotou et al 1975; Economides et al 1981) supplementary feeding of straw resulted in an increase of straw intake and body weight gain (Hadjipanayiotou et al 1975). The loss in weight in the present study therefore, can be at least partly due to the non increase in straw intake due to supplementation. In the study of Hadjipanayiotou et al (1975), where addition of a supplement improved straw intake and led to a body weight gain, animals were on a negative energy balance for 13 weeks prior to supplementation. At variance with earlier results (Hadjipanayiotou 1982) where urea treatment of straw resulted in a significant increase of straw intake (by about 47%), in the present study the increase in straw intake (17%) as a result of straw treatment with urea was not significant.

Table 4: Performance of dry Chios ewes offered straw ad libitum alone (US) or with a supplement of urea block (US+UB), concentrate (US+C) and lucerne hay (US+LH) and/or urea-treated straw (UTS) alone.
	US	UTS	US+UB	US+C	US+LH	SD
Live weight, kg
Initial	64.1	64.2	63.2	64.5	62.7	±10.0
Final	57.2	59.7	59.6	60.6	59.9	±9.4
Loss	6.9b	4.5ab	3.6a	3.9a	2.8a	±2.3
Intake, g/kg0.75/d
Straw	35ab	41a	35ab	33ab	29b	±6.8
Supplement	-	-	1414a	10b	14a	±3.7

Sansoucy et al (1988) reported that the intake of block (g/100 kg liveweight) varied with the type of animal (lambs, 400; calves, 250; Jersey bulls, 150-185 and Zebu heifers, 110). UB intake in the present study was 451, 301 and 717 g/ 100 kg bodyweight in the trial with ewes and trials 1 and 2 with heifers, respectively. With the exception of trial 2 with heifers, UB intakes obtained in the present study were relatively close to previously reported values (Sansoucy et al 1988; Hadjipanayiotou et al 1993b). The higher intake of UB by heifers of trial 2 could be ascribed to differences in hardness and compactness. It seems that the hardness and compactness of UB is not only affected by the ingredients used, but also by the mixer used. UB made in a concrete mixer (trial 2) were less hard and compact than those made in a "Hobart" mixer (model D-300) with a flat beater.

Table 5: Dry matter degradability of untreated straw incubated in the rumen (48 h) of Chios ewes and Damascus goats offered straw alone, with a supplement and/or urea-treated straw (see Table 3).
	US	UTS	US+UB	US+C	US+LH		SD
Ewes	47	67*	50	53	49	56
Goats	52	69*	54	56	56	59
Mean	50b	68*	52ab	55ab	52ab	58a	±5.89

* DM degradability of UTS incubated (48 h) into the rumen of ewes and goats on UTS
Means in the same line with different letter superscripts differ significantly (P<0.026); species effect significant at P<0.01.

It has been shown by Stritzler et al (1992) that the source of diet affects the degradation of barley straw incubated in the rumen. Iin this work, though there was a trend towards an improvement in straw DM degradability in the rumen through supplementation, the difference was significant only between US and US+LH diets. Differences in the extent of straw degradability associated with the source of supplement were also reported by Silva and Orskov (1988).

It is concluded that UB made of by-products can be used for replacing conventional supplements such as good quality roughage and concentrate feeds. Furthermore, UB feeding can give better results than urea-treated straw.

The author is grateful to his colleagues at the Institute Drs A. P. Mavrogenis and Ch. Papachristoforou, and Dr. Rene Sansoucy, Head, Feed Resources, FAO for reviewing the manuscript, Messrs I. Antoniou, G. Kyprianou, A. Photiou and Mesdames M. Theodoridou, M. Karavia and the staff of the central chemistry for skilled technical assistance.

(Received 10 January 1996)