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Effects of live weight, maturity and genotype of sheep fed a
hay-based diet, on intake, digestion and live weight gain
a a ,
*
b aA.L.G. Lourenc¸o , A.A. Dias-da-Silva
, A.J.M. Fonseca , J.T. Azevedo
a
´
Universidade de Tras-os-Montes e Alto Douro, Department of Animal Production, Apartado 202, 5001 Vila Real Codex, Portugal
b
˜
ˆ ´ ´
Instituto de Ciencias Biomedicas de Abel Salazar, Universidade do Porto, Campus Agrario de Vairao, Rua do Monte, Crasto, 4450 Vila do Conde, Portugal
Received 21 December 1998; received in revised form 3 June 1999; accepted 14 June 1999
Abstract
The effects of initial live weight (LW; 18 and 30 kg), maturity (40 and 65% mature LW) and genotype on dry matter intake (DMI), LW gain (LWG), organic matter digestibility (OMD), rumen outflow rate of solid phase and urinary allantoin-N excretion were examined in 14 and 21 female lambs from the local breed Churra da Terra Quente (CH) and Ile-de-France (IF), respectively. LW at 40 and 65% maturity was 18 and 30 kg and 30 and 49 kg for CH and IF lambs, respectively. Lambs were individually fed coarsely ground meadow hay (4 cm) ad libitum supplemented with a protein
21 0.75
concentrate over a period of 12 weeks. DMI (g kg LW ) and rumen outflow rate were higher and OMD lower
21
(P , 0.01) in CH than in IF lambs, irrespective of LW or degree of maturity. Daily allantoin-N excretion (mg kg LW) was higher in CH than in IF lambs (P , 0.10) at the same degree of maturity. LWG was unaffected by LW or maturity and was
21
higher in IF than in CH lambs (P , 0.001; 92.3 vs. 47.1 g day ). Regression analysis of LWG on digestible organic matter intake suggests that energy requirements for maintenance of CH lambs are higher than for IF lambs. It is suggested that differences between breeds in digestive ability and outflow rate should be confirmed at the same level of intake. Experiments should also be designed to measure energy retention and more closely estimate energy requirements for maintenance of the two breeds. 2000 Elsevier Science B.V. All rights reserved.
Keywords: Sheep; Feed intake; Digestibility; Live weight; Maturity; Genotype
1. Introduction have developed different strategies to achieve this
objective. It is well known that small ruminant Fibrous feeds moderately lignified are an impor- species, if allowed, tend to select a more digestible tant feed resource for ruminant animals. For an diet or eat more, while large ruminants have a efficient utilisation of fibrous resources an anaerobic greater ability to utilise poor diets by prolonging feed microbial fermentation is required and ruminants retention in the forestomach (Van Soest, 1994).
Differences between sheep breeds in their ability to both ingest and digest low quality roughage have
*Corresponding author. Tel.: 320-409; fax:
1351-59-also been reported. Weyreter and Engelhardt (1984)
320-629.
E-mail address: analou@utad.pt (A.A. Dias-da-Silva) found that Heidschnucken sheep, a German
autoch-0301-6226 / 00 / $ – see front matter 2000 Elsevier Science B.V. All rights reserved. P I I : S 0 3 0 1 - 6 2 2 6 ( 9 9 ) 0 0 1 3 4 - 7
Table 2
thonous sheep breed, were better able to adapt to a
21
Chemical composition of the feeds used in the experiment (g kg
fibrous diet than Merino sheep by increasing the a
DM; mean6standard deviation)
volume of the reticulorumen and prolonging the
Feed Ash Crude Neutral-detergent
retention time of fluid and particles, while Blackhead
protein fibre
sheep were not able to make such an adaptation.
Hay 69.665.0 63.963.2 703.2619.2
Givens and Moss (1994) reported that Cheviot sheep
b
Concentrate 96.466.2 313.0616.8 187.467.6
had greater digestive efficiency than Suffolk3Mule
a
Each value is the mean of 10 observations.
sheep, and Ranilla et al. (1997) found that Spanish
b
66% soyabean meal130% ground maize14% of a mineral–
Churra showed a higher rate of in situ roughage
vitamin mixture.
fermentation than Merino.
Churra da Terra Quente (CH) is the most
im-portant sheep breed in the northeast region of was coarsely ground through a 4 cm screen. The Portugal. This breed is well adapted to poor quality concentrate allowance was adjusted weekly accord-Mediterranean pastures and to periods of feed scarci- ing to the total dry matter (DM) intake observed in ty. However, there is no information about its the previous week. The supplement was offered once ingestive and digestive ability. Therefore, a study a day (08.00 h) and was readily eaten in totality. The was designed to compare voluntary intake and hay was offered ad libitum with fresh feed being digestibility of CH sheep with that of a European introduced in the morning after the supplement and improved sheep breed (Ile-de-France, IF), as in- in the afternoon at 16.00 h. The troughs were cleaned fluenced by live weight or degree of maturity. A out each morning and refusals collected and preliminary account of part of the work reported here weighed. They represented 15–20% of the hay
˜
has already been given (Guimaraes et al., 1998). offered.
Voluntary intake and LW gain (LWG) were mea-sured over a period of 12 weeks after an initial
2. Materials and methods period of 2 weeks during which the animals were
adapted to the diet. Lambs were weighed at the 2.1. Animals, design and management beginning of the experimental period and sub-sequently every 2 weeks. Samples of hay and Two groups of CH and three groups of IF lambs supplement were taken twice each week for DM were used in this experiment. The initial live weight determination. Refusals were sampled once each (LW) and degree of maturity of the lambs are shown week for the same purpose. The dried material was in Table 1. All the animals were kept indoors with bulked for later chemical analysis.
18 h light per day in individual pens with slatted In the 6th, 7th, 8th and 9th weeks of the ex-floors and free access to water. The barn was well perimental period one or two lambs from each group ventilated. The experiment was performed between were selected at random and moved to metabolic February and May, 1996. cages to measure the digestibility of the diet by total The lambs were fed grass hay ad libitum sup- collection of faeces over 7 days. In total, six animals plemented with a protein concentrate (75:25 on dry per group were used for this purpose. Samples of matter basis; Table 2). Before being offered, the hay hay, supplement, refusals and faeces were taken
Table 1
Initial live weight (LW; kg), degree of maturity and number of lambs used in the experiment Churra da Terra Quente Ile de France Initial LW
(mean6SD) 18.761.1 30.861.4 19.561.6 30.462.1 45.563.5
Degree of maturity (%) 40 65 25 40 65
Number of lambs 7 7 7 7 7
daily and dried in a forced-air drying oven at 658C Urinary allantoin-N was measured by the manual for 24 h and bulked over the period. Total collection method described by Chen and Gomes (1992). of urine was also made. About 100 ml of 1 M H SO2 4 Faecal Cr concentration was determined by atomic was added to the urine containers to give a final pH absorption spectrophotometry.
value below 3. The daily urine excreted was made up
to 4 l with water, filtered through nylon cloth and 2.3. Statistical analyses sampled (100 ml). Daily samples were stored at
2208C until analysed. Data were subjected to standard analyses of Rumen digesta outflow rate of solid phase was variance procedures (Steel and Torrie, 1980) using also measured in three lambs per group. Chromium the statistical package Systat (Wilkinson et al., (Cr) mordanted hay fibre, prepared as described by 1992). When differences were significant treatment
´
Uden et al. (1980), was used as marker. The animals means were compared by contrasts (Steel and Torrie, were given a dose of 15–20 g of Cr-mordanted fibre 1980). Daily LWG of each animal was calculated by mixed with the concentrate supplement at 08.00 h. linear regression of LW on time (12 weeks). Total faeces were collected at 12, 15, 19, 24, 27, 30,
33, 36, 39, 43, 48, 51, 54, 57, 60, 63, 67, 72, 76, 80,
84, 88, 91, 96, 100, 104, 108, 112, 115, 121, 126 and 3. Results
132 h after the concentrate distribution. Rate
con-stants were calculated as the slope of the straight line The chemical analysis of hay refusals (ash, CP and obtained by plotting the natural logarithm of the Cr NDF; not shown) did not show any significant concentration against time for the descending part of difference between groups. Therefore, it can be the excretion curve (Grovum and Williams, 1973). assumed that selective intake of hay, if any, did not differ between groups. The observed proportion of 2.2. Chemical analysis concentrate in the total intake fell within the range
24.5–25.4 which is very close to the objective. Ground samples (1 mm) of hay, concentrate,
refusals and faeces were analysed for ash and 3.1. Feed intake and live weight gain Kjeldahl nitrogen (AOAC, 1990). Crude protein
(CP) was calculated as Kjeldahl nitrogen36.25. Data on dry matter intake (DMI) and LWG are Neutral-detergent fibre (NDF) was determined as presented in Table 3. DMI per kg of metabolic live
0.75
described by Robertson and Van Soest (1981). weight (LW ) of the whole diet and hay were
Table 3
Effects of breed, initial live weight (LW) and maturity on dry matter intake and live weight gain
Treatment SEM F Contrast
CH18 / 40 CH30 / 65 IF18 / 25 IF30 / 40 IF49 / 65 Breed LW Maturity
Number of animals 7 7 7 7 7 7
Total dry matter intake
21 g day 698 1002 731 881 1143 53.8 *** ns *** *** 21 0.75 g kg LW 69.9 72.1 66.7 61.9 60.7 2.45 * ** ns ns 21 g kg LW 32.5 30.0 30.2 25.5 22.8 0.859 *** *** *** **
Hay dry matter intake
21 g day 524 747 553 665 861 40.5 *** ns *** *** 21 0.75 g kg LW 52.5 53.7 50.4 46.7 45.7 1.85 * ** ns ns 21 g kg LW 24.4 22.4 22.8 19.3 17.2 0.650 *** *** *** ** 21 LW gain (g day ) 57.0 37.3 97.5 93.3 86.2 11.6 ** *** ns ns ns, non-significant; *P , 0.05; **P , 0.01; ***P , 0.001.
Table 4
Effects of breed, initial live weight (LW) and maturity on total organic matter digestibility (OMD), digestible organic matter intake (DOMI), urinary allantoin-N excretion and rumen fibre outflow rate
Treatment SEM F Effects
CH18 / 40 CH30 / 65 IF18 / 25 IF30 / 40 IF49 / 65 Breed LW Maturity Number of animals 6 5 6 6 6 6 21 Total OMD (kg kg ) 0.565 0.577 0.607 0.601 0.599 0.010 * ** ns ns 21 0.75 Total DOMI (g kg LW ) 36.6 38.6 37.3 34.3 33.4 1.40 ns ns ns ns
Urinary allantoin-N excretion
21 mg day 290.5 503.0 377.3 430.1 523.3 40.4 ** ns ** ** 21 mg kg LW 12.9 14.8 14.0 12.0 10.1 1.01 * ns ns ns 21 mg kg DOMI 842.1 970.9 842.1 867.1 833.5 73.8 ns ns ns ns Number of animals 3 3 3 3 3 3 21
Fibre outflow rate (h ) 0.036 0.042 0.022 0.024 0.017 0.003 *** *** ns ns ns, non-significant; *P , 0.05; **P , 0.01; ***P , 0.001.
significantly higher in CH than in IF lambs (P , Under these conditions, it was observed that the DM
0.75
0.01), but were not affected by LW or maturity. intake per kg LW or kg LW of the native CH When expressed per kg LW, the difference between breed was clearly higher than in the improved IF breeds was still higher (P , 0.001) and the effects of breed, particularly when comparisons were made at LW or maturity were also highly significant. LWG the same degree of maturity. Among ruminant was significantly higher for the IF breed (P , 0.001) species, data reviewed by Van Soest (1994) indicate and was unaffected by LW or maturity. that species having lower body weight at maturity exhibit higher DM intake per unit of weight, which 3.2. Digestibility, urinary allantoin-N excretion is in agreement with the present data. However, no
and rumen fibre outflow rate comparisons between sheep breeds were found in the
literature. The decrease in DM intake per kg LW, as CH sheep showed lower organic matter digestibili- LW increased, was expected, since energy require-ty (OMD) values (P , 0.01) and higher fibre outflow ments for maintenance also decrease per unit of LW, rates (P , 0.001) than IF sheep (Table 4). Neither as LW increases (AFRC, 1993).
LW nor maturity affected these parameters. The Data on DM intake are consistent with data on absolute amount of urinary allantoin-N excretion (mg rumen fibre outflow rate. Regardless of LW or
21
day ) was unaffected by breed but was significantly maturity, which did not affect this parameter, CH higher (P , 0.01) in heavier or more mature animals, lambs showed outflow rates 70 to 85% higher than as expected. No difference was observed due to IF lambs. This is contrary to the findings of Weyreter breed, LW or maturity (P . 0.05) when excretion and Engelhardt (1984), who reported that was expressed per kg LW. However, breed effect on Heidschnucken sheep, a German autochthonous this parameter and on digestible organic matter breed, fed ad libitum on heather or straw, were able intake (DOMI) reached significance at P , 0.10. to enlarge rumen capacity and prolong retention time None of the factors affected excretion per kg of of feed particles in the rumen, while Blackhead
DOMI. sheep showed much less of such an adaptation under
the same conditions, the response of Merino sheep being intermediate. However, data on LW of animals
4. Discussion used were not provided in that report. The large
difference in outflow rates between the breeds ob-The particle size of the hay used in the present served in the present study suggests that the CH study was deliberately chosen to force the animals to breed has an inherently higher rate of passage of feed eat the same diet and this was successfully achieved. particles than the IF breed. Assuming that
gastroin-testinal capacity limits the intake and utilisation of feeding could not be made. Given the high cell-wall forage diets and given the fact that, within a species, content of the diet used (57.4% NDF) our data smaller animals require more feed per unit of LW for suggest that the CH breed does not rely on enhanced maintenance than larger adult animals (Van Soest, ability for fibre digestion as an adaptation mecha-1994) as was observed in this study, a higher rate of nism to its natural environment. Differences in passage of feed particles can be seen as an adaptation digestive ability between sheep breeds were also mechanism by smaller animals to cope with their observed by Givens and Moss (1994), who found higher requirement for feed. that OMD of dried grass was higher in Cheviot than
The lack of an effect of LW on digestive ability in Suffolk3Mule wethers.
indicates that all lambs were full ruminants at the As expected, microbial protein supply to the small time the experiment started. Givens and Moss (1994) intestine as assessed by urinary allantoin-N excretion did not find significant effects of age and LW on (Chen et al., 1992) was higher in heavier or more digestibility of dried grass, or any interaction be- mature animals since these animals exhibited higher tween either of these variables and digestibility, DMI. The data of this study suggest that the ef-although the range of weights of the animals they ficiency of microbial protein supply, expressed as mg used was much more limited than in the present allantoin-N excreted per kg DOMI, is similar in the
study. two breeds. The tendency for a higher excretion per
The lower digestive ability of CH lambs observed kg LW observed in CH lambs (P , 0.1) is in in this study is consistent with the higher intake and agreement with the tendency for a higher DOMI also outflow rate values measured in this breed. Regres- observed in these animals (P , 0.1).
sion of OMD on intake did not reach significance Since DOMI was higher and LWG was almost and so breed comparisons at the same level of half in CH than in IF lambs, particularly in those
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Chen, X.B., Gomes, M.J., 1992. Estimation of microbial protein
the two breeds arises. Setting all the individual data supply to sheep and cattle based on urinary excretion of purine of LWG against DOMI (Fig. 1) indicates that derivatives — an overview of the technical details. Occasional
estimates of energy requirements for maintenance of Publication. Rowett Research Institute, Bucksburn, Aberdeen, UK, 20 pp.
the two breeds are different (P , 0.001), the estimate
Chen, X.B., Chen, Y.K., Franklin, M.F., Orskov, E.R., Shand, W.J.,
for the CH breed being considerably higher than for
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the IF breed. However, the variation is large, par- derivate excretion and microbial protein supply in sheep. J. ticularly among CH lambs, and therefore this hy- Anim. Sci. 70, 1534–1542.
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It is suggested that differences in digestive ability
Grovum, W.L., Williams, V.J., 1973. Rate of passage of digesta in
and outflow rate between these breeds should be sheep. Differential rates of passage of water and dry matter confirmed by offering a similar diet at the same level from the reticulo-rumen, abomasum and caecum and proximal
of intake. It is also suggested that ingestive be- colon. Br. J. Nutr. 30, 231–240. ˜
Guimaraes, A., Dias-da-Silva, A.A., Fonseca, A., Azevedo, J.,
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´ ´ ´
closely estimate energy requirements for mainte- Ranilla, M.J., Carro, M., Valdes, C., Giraldez, F., Lopez, S., 1997. A comparative study of ruminal activity in Churra and Merino
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Steel, R.G.D., Torrie, J.H., 1980. Principles and Procedures of
A.L.G. Lourenc¸o gratefully acknowledges the
Statistics. A Biometrical Approach, 2nd ed. McGraw-Hill, New
ˆ ´
receipt of a scholarship from Ministerio da Ciencia e
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