Comparison of hay and silage for pregnant and
lactating Finnish Landrace ewes
R. Sormunen-Cristian
a,*, L. Jauhiainen
baAnimal Production Research, Agricultural Research Centre of Finland, FIN-31600 Jokioinen, Finland bData and Information Services, Agricultural Research Centre of Finland, FIN-31600 Jokioinen, Finland
Accepted 16 June 2000
Abstract
A comparison of conserving timothy/meadow fescue/meadow grass as silage or hay was conducted with Finnish Landrace ewes. Intake of hay (H), silage (S) and hay/silage (HS), and the performance of 30 Finnish Landrace ewes carrying twins, triplets and quadruplets and suckling either twin or triplet lambs was measured during the last 8 weeks of pregnancy and
during the ®rst 6 weeks of lactation. The dry matter (DM) intake of HS was lower (p<0:03) than H during lactation, whereas
there was no difference in DM intake between pregnant and lactating ewes fed either H or S. The intake of metabolisable energy was on an average 12.8, 14.3 and 13.4 MJ per day in pregnancy, and 17.7, 20.2 and 18.1 MJ in lactation for H, S and HS, respectively. Daily intakes of protein assessed in terms of amino acids absorbed in the small intestine (AAT) were on an average 92, 110 and 102 g for H, S and HS during pregnancy and 157, 184 and 165 g during lactation, respectively. Ewes in all treatments were, relative to calculated requirements, de®cient in energy and protein during the last month of pregnancy and early lactation. Ewes performed consistently better when fed silage than hay. Lamb mortality was low for all treatments. The number of arti®cially reared lambs tended to be highest when ewes were fed both hay and silage ad libitum. Lamb growth was
higher on S than H based diet (p<0:005). With respect to winter feeding of ewes, grass silage compared favourably with hay
and indicated that hay could be replaced by well preserved grass silage. During late pregnancy and early lactation, there was
no advantage of supplementing silage with hay, relative to entirely silage based diets.#2001 Elsevier Science B.V. All rights
reserved.
Keywords:Hay; Lactation; Pregnancy; Silage; Sheep
1. Introduction
In northern Europe, pregnancy and lactation of most sheep ¯ocks occurs during winter. For 6±8 months ¯ocks are housed indoors and fed conserved
forages. Climate conditions in Finland offer greater opportunities to make good-quality grass silage than hay. However, hay is widely used for winter feeding on Finnish sheep farms. Hence, silage feeding is not typical, and therefore information concerning the suitability for pregnant and lactating Finnish Landrace ewes under Finnish conditions is limited. Dry matter (DM) intake of ensiled crop has often been reported to be lower in sheep than that of the same crop conserved as hay (Thomas et al., 1969; Orr and Treacher, 1989). However, in Small Ruminant Research 39 (2001) 47±57
*Corresponding author. Fax:358-3-41883661.
E-mail address: riitta.sormunen-cristian@mtt.fi (R. Sormunen-Cristian).
spite of higher intake, animal performance on hay based diets has not always been improved (Thomas et al., 1969). The reasons for inconsistencies between forages remain unclear but may be explained by differences between breed, ewe body weight, number of foetuses and suckling lambs in addition to the often great variations in quality of silage and differences in forage digestibility.
Foetal requirements increase rapidly 6 weeks before lambing (SjoÈdin, 1983), whereas voluntary intake declines particularly in multiparous ewes (Orr and Treacher, 1984). On the other hand, voluntary feed intake, at a minimum just before lambing, increases progressively during lactation reaching a maximum 5±8 weeks post-lambing. However, requirements for energy and protein are highest between the second and third weeks of lactation (Sormunen-Cristian et al., 1997). To meet these greater requirements during the last weeks of pregnancy and early lactation, it is not clear whether multiparous ewes should be fed hay or silage. Silage feeding increases the proli®cacy of ewes (Nedkvitne, 1969). However, adult Finnish Landrace ewes lambing once a year, are very proli®c producing on an average 2.8 lambs per ewe (Savolai-nen, 1999) and therefore an increase of proli®cacy is no longer desirable.
The present study was undertaken to compare hay and grass silage harvested in the typical farm condi-tions as the basal forage for pregnant and lactating multiparous Finnish Landrace ewes supplemented with the same amount of concentrates. Furthermore, the in¯uence of conserved forages on the performance of ewes, on lamb growth and development was assessed.
2. Material and methods
2.1. Conserved forages
Hay was prepared from a timothy (Phleum pratense
L.)/meadow fescue (Festuca pratensis Huds.)/mea-dow grass (Poa pratensisL.) sward at the beginning of July and second cut silage was prepared from the same sward on 23 August. Silage was ensiled using an acid based additive (80% formic acid, 2% ortho -phosphoric acid) at a rate of 4.0 l tÿ1 into a tower silo. The study was carried out at Agricultural
Research Centre of Finland (618400N, 27
8130E, 107 m above sea level).
2.2. Animals, feeding and management
One month before a 4-week mating period (26 October±22 November), 30 mature pure bred Finnish Landrace ewes were randomly selected from the 120 ewe experimental ¯ock. Ewes weighed on an average 59.4 kg (S.D. 7.8) and were between 18 and 30 months of age. Ewes were allocated according to weight and age into 10 blocks of three animals. Ewes within each block were fed one of three experimental rations, which consisted of hay (H), or silage (S), or hay and silage (HS), each offered ad libitum. Forages were offered 15% in excess of the previous day's consumption. For ¯ushing (12 October±22 Novem-ber), ewes were daily supplemented with 0.3 kg of oats. For mating, ewes were exposed to two Finnish Landrace rams equipped with a crayon harness. Marked ewes in heat were recorded daily.
During the last 2 months of pregnancy a mixture of rolled barley and oats (50:50 on an air-dry basis) was offered 0.3±0.4 kg per ewe and 0.4 kg per one suckling lamb during lactation. For 3 weeks before, and 4 weeks after parturition 15% of molassed sugar beet pulp was added into the concentrate mixture. A mineral supplement, salt and water were freely available. In addition to milk, the lambs were offered the same forage as to their respective dam. Lambs also had ad libitum access to a commercial protein concentrate.
Approximately 10 weeks before parturition all ewes were housed in individual wooden pens (each 2.4 m2). Individual intake of ewes was recorded daily for 8 weeks before parturition and during the ®rst 6 weeks of lactation. In the case that ewes were unable to rear all her offspring, lambs were transferred to a nursery facility.
2.3. Analytical methods
Feed samples were collected at each feeding and pooled over a 2-week period. DM content of feeds was determined by oven drying at 1058C for 24 h. Silage DM was corrected for loss of volatiles according to Huida et al. (1986). Samples of forages and concen-trates were analysed according to standard procedures (AOAC, 1980). In addition, silage total and water-soluble nitrogen (Kjeldahl method), ammonium nitro-gen (McCullough, 1967), pH and lactic acid (Barker and Summerson, 1941), volatile fatty acid (Huida, 1973) and water-soluble carbohydrate (Somogyi, 1945) content was determined. Digestibility coef®-cients were taken from in vivo experiments. The net energy value of experimental feeds was calculated as feed units (FFU) according to Salo et al. (1990) and metabolisable energy (ME) according to MAFF (1975). Protein intake was calculated in terms of amino acids absorbed in the small intestine (AAT) and protein balance in the rumen (PBV) (Tuori et al., 1996). In the calculations of PBV and AAT a value of 75, 85, 77 and 79% was assumed for the rumen degradability of hay, silage, barley±oats mixture and commercial concentrate protein, respectively (Tuori et al., 1996).
2.4. Statistical methods
Experimental data were statistically analysed as a randomised complete block design using the restricted maximum likelihood (REML) estimation method within the `mixed procedure' of SAS (SAS, 1992) according to the following model:
YijmAiBjeij (1)
wheremis the intercept,Aithe ®xed effect from theith
treatment,Bjthe random effect from thejth block,eijis
a random variable that represents the error associated with theijth cell. Model (1) assumes that there is no interaction between treatment and block and that the
eij's are independent normal random variables with
zero means and the same unknown variance. When the response variable was ewe daily intake and lamb weight gain, the statistical model included the number of lambs reared by ewe (rearing type) and the rearing typetreatment interaction as covariates.
If rearing typetreatment interaction was not statis-tically signi®cant (p>0:10), the covariate was removed from the model (Littell et al., 1996), whereas rearing type was retained in the model despite being non-signi®cant.
When the response variable was lamb birth weight, the statistical model contained birth type and birth typetreatment interaction as a covariate. Birth type was classi®ed into two categories for analysis: less than or at least three lambs. If birth typetreatment interaction was not statistically signi®cant (p>0:10), the covariate was removed from the model. Birth type was included in the model despite being non-signi®cant.
Measurements of ewe intake and live weight of ewe and lamb were repeated several times for each animal, and were found to be correlated. Consequently this correlation was taken into account in the selected statistical model (2). Covariance structure of the repeated measurements was chosen by comparing potential structures using Akaike's and Schwarz's Bayesian information criterion (Wol®nger, 1996). Compound symmetry (CS) covariance structure proved useful for all data, except lamb live weight for which an unstructured (UN) approach was used. Analysis of variance for repeated measurements was performed according to the following model:
YijmAiBjeijTk ATjk
BTikdijk (2)
wherem,Ai,Bjandeij are equivalent terms to that in
model (1).Tkand (AT)jkare the ®xed effect of time
and treatmenttime interactions, respectively, (BT)ik the random effect of blocktime
interac-tions anddijkrepresents experimental error.
When the response variable was lamb live weight, the statistical model (2) contained rearing type, rear-ing typetreatment interaction, rearing typetime interaction and rearing typetreatmenttime inter-action as a covariate. Rearing type was included in the model despite being non-signi®cant. Interactions between the other terms were removed from model, if they were not statistically signi®cant (p>0:10).
Logistic regression was employed for the analysis of data from birth and rearing type. Data were collected from 10 blocks, and therefore a different constant term was required for each block, while the common logistic regression had only one constant term. Regression analyses were carried out using Log-Xact-software (Mehta and Patel, 1996).
3. Results and discussion
3.1. Forage chemical composition
Chemical composition and feeding value of hay and silage were constant throughout the experiment (Table 1). Hay contained more ®brous constituents, less protein and had a lower digestibility than silage. Due to a late harvest, silage was also found to be too coarse for feeding during lactation. It is recommended that crude ®bre content of silage for lactating ewes should not exceed 20% in the DM (SjoÈdin, 1983).
Fermentation quality of silage was good as assessed by pH, ammonium nitrogen and butyric acid. In May, when the preservation conditions deteriorated as a result of higher ambient temperatures, silage con-tained NH3 just over 8% of total nitrogen, but no butyric acid. Silage fed during mating contained 7.1, 8.3, 2.9% water-soluble carbohydrate, lactic acid and
acetic acid, respectively, with a pH of 4.11 and soluble and ammonium N content of 53.7 and 5.7% of total N, respectively. Silage offered during pregnancy and lactation contained 2.4, 9.1, 2.8% water-soluble car-bohydrate, lactic acid and acetic acid, respectively, with a pH of 4.07 and soluble and ammonium N content of 52.5 and 5.8% of total N, respectively.
3.2. Feed intake
3.2.1. Pre-lambing intake
Intake of concentrates during mating and pregnancy was good. Refusals of molassed sugar beet pulp were observed only on a few occasions. The hypothesis of Andrieu et al. (Dulphy and VanOs, 1996) that ewes consume more DM from hay than silage was not supported by the current study (Table 2). Forage DM intakes were similar between H and S diets (1.03 versus 1.02 kg per ewe per day) during preg-nancy, but lower for HS diets (0.95 kg per ewe per day). Expressed on a metabolic body weight basis DM intakes of H, S and HS during pregnancy were on an average 45, 39 and 37 g (per kg W0.75). Differences in DM intakes between forages were not as large as that reported by Thomas et al. (1969). In this study DM intake of hay was considered to be decreased by a high ®bre and a low protein content due to a late cutting date, which is consistent with the study of
Table 1
Chemical composition, quality and feed values of experimental feeds offered during mating (I), pregnancy (II) and lactation (II) for ewes and during lamb rearing (III)
Hay Silage Concentrate
I (n2) II±III (n4) I (n3) II±III (n8) I (n1) II (n4) III (n1)
Dma(%) 84.7 78.8 21.8 23.2 87.0 85.3 87.2
In DM(%)
Organic matter 93.2 93.4 91.7 91.8 97.3 96.9 89.9
Crude protein 9.5 10.0 16.2 16.7 12.2 12.2 24.2
Ether extract 1.9 1.8 5.9 6.7 7.1 3.7 4.8
Crude fibre 32.2 31.3 26.0 25.1 8.0 7.6 7.7
Nitrogen-free extract 49.6 50.3 43.6 43.3 70.0 73.4 53.2
Digestible organic matter 58.4 58.6 64.9 65.0 75.8 72.1 75.9 Feed values(per kg DM)
NEa(FFU) 0.55 0.56 0.74 0.74 1.12 1.01 1.09
Mea(MJ) 8.8 8.8 10.4 10.4 13.1 12.0 12.6
AATa(g) 62 63 80 80 94 93 110
PBVa(g) ÿ34 ÿ31 25 29 ÿ31 ÿ29 66
aDM: dry matter, NE: net energy, FFU: fattening feed unit (0.7 kg starch equivalent), ME: metabolisable energy, AAT: amino acids
Table 2
Daily nutrient intake by pregnant ewes
Weeks 8±5 pre-partum S.E.M. Significance Weeks 4±1 pre-partum S.E.M. Significance
Hay (n10)
Silage (n10)
Hay/silage (n10)
p1 p2 Hay
(n10)
Silage (n10)
Hay/silage (n10)
p1 p2
Forage (kg Dma) 1.13 1.08 0.98 0.054 0.50 0.04 0.92 0.95 0.92 0.054 0.65 0.95 Total DM intake (kg) 1.39 1.34 1.24 0.054 0.45 0.02 1.27 1.30 1.26 0.054 0.62 0.94 Total Omaintake (kg) 1.31 1.25 1.16 0.051 0.31 0.01 1.19 1.21 1.18 0.051 0.82 0.76 NE (FFU)a 1.23 1.07 1.02 0.044 <0.005 <0.0001 1.13 1.06 1.05 0.044 0.13 0.08 ME (MJ)a 13.20 14.53 13.20 0.557 0.05 0.98 12.32 14.11 13.53 0.557 <0.01 0.07
Crude protein (g) 146 201 176 7.9 <0.0001 <0.001 136 197 184 7.9 <0.0001 <0.005
AAT (g)a 95 111 100 4.2 <0.005 0.28 89 108 103 4.2 <0.0001 <0.005
PBV (g)a ÿ41 13 3 2.0 <0.0001 <0.0001 ÿ37 13 6 2.0 <0.0001 <0.0001
aDM: dry matter, OM: organic matter, NE: net energy, FFU: fattening feed unit (0.7 kg starch equivalent), ME: metabolisable energy, AAT: amino acids absorbed in the small
intestine, PBV: protein balance in the rumen, H: hay, S: silage, HS: hay/silage, S.E.M.: maximum standard error of treatment means,p1: H vs. S andp2: H vs. HS.
R.
Sormunen-C
ristian,
L.
Jauhiainen
/
Small
Ruminant
Resear
ch
39
(2001)
47±57
Dulphy (Bocquier et al., 1987). Barley supplementa-tion (>280 g per ewe per day) during the ®nal 6 weeks of pregnancy did not appear to depress silage intake as reported by Sheehan and Lawlor (1972).
It is generally accepted that the increase of the uterus and uterine contents during the last weeks of pregnancy reduces the volume of the abdominal cavity and causes a decline in forage intake during later stages of pregnancy. Metabolic and hormonal factors may also induce depressed intake (Reid and Hinks, 1962). In this study during the last 8 weeks of preg-nancy, DM intake decreased on all treatments, the extent of which was greatest for hay diets (280, 200 and 120 g per ewe for H, S and HS, respectively). The lowest intakes of H, S and HS ewes occurred during the week before lambing (920, 930 and 880 g DM per ewe per day, respectively).
In the literature the effect of increases in the number of foetuses on DM intake have been generally incon-sistent. Orr and Treacher (1989) found that the mean intake during the last 6 weeks of pregnancy by ewes with twins and multiples were 86 and 81% of ewes with a single lamb. However, in the studies of Foot and Russel (1979) and Newton and Orr (1981) the number of foetuses had no effect on maternal intake. In con-trast to the results of Orr and Treacher (1989), DM intake in the current study tended to be higher for ewes with multiple foetuses than those with twins. Daily DM intake of twin-, triplet- and quadruplet-carrying ewes during the last 2 months of pregnancy averaged 1210, 1320 and 1320 g per ewe, respectively.
3.2.2. Post-lambing intake
There were no differences in feed intake of ewes suckling twins and triplets (Table 3) and therefore the results here are presented by treatments. During the 6-week lactation, ewes consumed a mean DM intake of 1.39, 1.40 and 1.23 kg per day for H, S and HS, respectively, which supplied 17.7, 20.2 and 18.1 MJ ME, and 157, 184 and 165 g AAT, respec-tively. Differences between silage and hay intake in the current study was considerably less than that reported by Bishop and Kentish (1969) (<1 versus 30%). The equal DM intake from hay and silage was inconsistent with the review of six trials reported by Thomas et al. (1969) and to that of Orr and Treacher (1989) who found that intake of silage was lower than that of hay when forage was the sole feed, or supple-mented with small amounts (<300 g per day) of con-centrate. Some factors, e.g. low pH (Shaver et al., 1985) as well as high contents of acetic acids (Wilkins et al., 1971) and lactic acids (Mc Leod et al., 1970) have been attributed to the reduced intake of silage. Since silage pH was regarded as normal and the lactic acid content was not excessively high, these factors were not considered to decrease the intake of silage in the current study. Bocquier et al. (1987) found that the intake of hay increased sharply in the ®rst 2 weeks after lambing and reached a maximum during weeks 5±6, whereas in this study the intake of hay increased gradually to week 6. The highest forage DM intakes of H, S and HS (1.71, 1.59 and 1.64 kg per day, equiva-lent to 80, 68 and 70 g (per kg W0.75), respectively)
Table 3
Daily nutrient intake of ewes suckling twins and triplets during lactation
Twins Triplets S.E.M. Significance
Forage (kg DM)a 1.48 1.49 1.32 1.30 1.31 1.14 0.102 0.88 0.03 0.07 Total DM intake (kg) 2.12 2.15 1.97 2.20 2.22 2.04 0.010 0.78 0.03 0.44 Total OM intakea 2.00 1.99 1.84 2.08 2.07 1.91 0.093 0.91 0.02 0.37
NE (FFU)a 1.89 1.74 1.64 2.01 1.86 1.76 0.079 0.04 <0.0005 0.11
ME (MJ)a 17.24 19.70 17.58 18.20 20.66 18.54 1.137 0.01 0.66 0.35
Crude protein (g) 228 332 283 229 333 284 14.2 <0.0001 <0.0001 0.26
AAT (g)a 153 180 161 161 188 169 7.6 <0.0005 0.13 0.25
PBV (g)a ÿ62 26 6 ÿ71 17 ÿ3 3.7 <0.0001 <0.0001 0.02
aDM: dry matter, OM: organic matter, NE: net energy, FFU: fattening feed unit (0.7 kg starch equivalent), ME: metabolisable energy,
occurred during the sixth week of lactation. Total DM intakes of H, S and HS diets during this period were 2.51, 2.61 and 2.29 kg per ewe per day representing 4.2, 3.9 and 3.4% of body weight, respectively. These values are less than those suggested by Peart (1967) (5.2±6.6%), but higher than reported by Thomas et al. (1969) (1.98±3.05% for silage and 2.41±3.11% for hay).
In agreement with many studies (Newton and Orr, 1981; Bocquier et al., 1987; Gallo and Davies, 1988) there were no differences in intake between ewes carrying twins or triplets during lactation. However, Loerch et al. (1985) reported that ewes rearing triplets tended to consume more feed (g per kg W0.75) than those rearing twins.
3.2.3. Energy and protein nutrition during pregnancy and lactation
A 70 kg ewe with multiple foetuses is considered to require 14.6±20.6 MJ ME and 94±169 g AAT of pro-tein during late pregnancy, and 28.6 MJ ME and 234 g AAT during lactation (Tuori et al., 1996). Dur-ing the fourth month of pregnancy, intakes of energy from H and HS did not totally meet ewe energy requirements. Although low, the protein intake from H diets was suf®cient to meet predicted recommenda-tions (Tuori et al., 1996). During the ®fth month of pregnancy all ewes experienced an energy and protein de®ciency with energy and protein intakes being 32± 40 and 36±47% below recommended levels, respec-tively. Also in early lactation, intakes for energy and protein were 29±39 and 20±33% below recommenda-tions, respectively. In addition, the negative protein balance value (PBV) in the rumen of hay suggests that microbial protein synthesis was constrained by dietary nitrogen supply. Differences in PBV values between treatments were statistically signi®cant (p<0:0001). The recommended PBV intake fell between 0 and ÿ20 g for twin- and triplet-suckled ewes as reported by Havrevoll et al. (1992). Due to the higher nutritive value, ewes fed silage were closer to energy and protein requirements during late pregnancy and early lactation. In contrast to the ®ndings of Nedkvitne (1969) the current study suggests that it may not be desirable to feed pregnant and lactating ewes a hay supplement with silage based diets.
Although it is not recommended to feed pregnant and lactating ewes high amounts of concentrates due
to decreases in forage intake (Sheehan and Lawlor, 1972), a shortage of nutrients could be reduced by feeding more concentrates. Good quality silages sup-plemented with 0.45±0.7 kg of concentrate per day can adequately provide the energy requirements of ewes during the last 8 weeks of pregnancy (Robinson, 1985; Treacher and Orr, 1982; Ledin, 1986). However, it is important to consider the cost of additional concentrate feeding relative to the economic returns from increased animal performance.
3.3. Live weights of the ewes
Ewes were in good condition at mating and there were no differences in average live weight (Table 4). From mating to the beginning of the fourth month of pregnancy H, S and HS treatments resulted in con-siderable differences in live weight. Changes in live weight varied from 6.9 kg (11.1%) to 11.7 kg (18.5%) for H and S treatments, respectively. Also during the entire pregnancy, ewes fed silage had a higher (p<0:0001) live weight gain than those fed hay. Typically ewes gain between 9 and 13.5 kg during pregnancy (Ensminger and Parker, 1986). The effect of herbage intake on animal performance has been variable. Hay has improved or it has not affected animal performance compared with silage (Thomas et al., 1969). In contrast to Bishop and Kentish (1969), the ewes fed hay in the current study did not perform better in terms of live weight than those fed silage. During the last 2 months of pregnancy twin-, triplet-and quadruplet-carrying ewes had live weight gains of 7.0 kg (10.5%), 7.3 kg (10.0%) and 6.3 kg (8.4%), respectively.
According to Finnish recommendations (Tuori et al., 1996), ewes did not satisfy their nutrient requirements during the last 2 months of pregnancy, but were able to gain live weight reasonably (SjoÈdin, 1983). In view of good animal performance in this study, Finnish recom-mendations for late pregnancy were considered to be unnecessarily high.
twins tended to lose more body weight than those with triplets (5.8 versus 3.8%). However, Peart (1967) has shown that ewes need not lose weight if their nutrient intake is suf®ciently high. The effect of a 5% loss in body weight on milk yield is likely to be negligible, whereas that of a 10% loss decreases yield by 10±15% (Kilkenny, 1977).
3.4. Mating and lambing performance
All ewes came into heat and were mated during the ®rst oestrus cycle by Finnish Landrace rams. After joining the ram, ewes conceived on an average in 10.7, 8.3 and 11.0 days (p0:57) for H, S and HS, respectively. Gestation time averaged 143.7 days for all treatments. Proli®cacy of ewes on all treatments was high (Table 5). In total 8 quadruplets were born, but none of the ewes gave birth to single lambs. Seven
ewes fed H and HS and nine ewes fed S gave birth to at least three lambs (p0:62). No differences between treatments on proli®cacy between treatments were found. This is inconsistent with the results of Nedk-vitne (1969) who found that silage had a positive effect on litter size.
Lamb mortality for S treatment was not higher than that for other treatments. This is in accordance with the results of Nedkvitne (1969). Only one lamb fed S diet died and two lambs were transferred to arti®cial rearing at the age of 3 days. Mortality of lambs fed hay was also low (7%) compared to typical average of 10±20% at the Finnish Sheep Research Station. How-ever, 18% of lambs fed hay were transferred to an arti®cial rearing. Arti®cially reared lambs were mainly derived from the sets of quadruplets. Ewes fed S could suckle more triplets than those on other treatments (p<0:005).
3.5. Lamb performance
It is generally agreed that improved nutrition during late pregnancy has a positive effect on lamb birth weight and survival (Holst et al., 1986). Also in this study there was a tendency for ewes on the highest intake of energy and protein to produce lambs with higher birth weights (Table 6), although differences in litter weights between treatments were not signi®cant (p0:26). The mean birth weight was lowest for H treatment, being 87 g lower than for HS treatment. The difference between H and S treatments in birth weights was 328 g (95% con®dence interval (CI): Table 4
Mean live weight of ewes at mating and at selected points of pregnancy and lactation
Hay (n10) Silage (n10) Hay/silage (n10) S.E.M.a Significance
p1a p2a Ewe live weight(kg)
At mating 62.2 63.1 64.2 2.73 0.61 0.25
56 days pre-partum 69.2 74.8 72.9 2.73 <0.005 0.03
28 days pre-partum 72.6 78.7 76.3 2.73 <0.001 0.04
7 days pre-partum 75.4 82.7 79.7 2.73 <0.0001 0.01
Change: mating to day 7 pre-partum(kg) 13.1 19.6 15.4 0.97 <0.0001 0.08
2 days post-partum 64.4 71.3 69.2 2.73 <0.0005 <0.01
28 days post-partum 61.5 68.0 68.9 2.73 <0.0005 <0.0001
56 days post-partum 59.5 67.3 67.4 2.73 <0.0001 <0.0001
Change: lambing to day 56 post-partum(kg) ÿ5.0 ÿ4.0 ÿ1.8 0.97 0.45 0.02
aS.E.M.: standard error of treatment means,p1: hay vs. silage andp2: hay vs. hay/silage.
Table 5
Mean treatment effects on lambing performance and lamb mortality
Hay Silage Hay/silage
Number of ewes 10 10 10
Twin births 3 1 3
Triplet births 4 7 4
Quadruplet births 3 2 3
ÿ176,832) in favour of S. This difference was not statistically signi®cant at the 5% level, but on the basis of CI it was considered that lamb birth weight on silage may be higher than that on hay and this differ-ence is of practical importance. At birth, twins were on an average 900 g heavier (p<0:005) than triplets and quadruplets which is consistent with the results of Orr and Treacher (1994).
Lambs which were moved to the arti®cial rearing were deleted from the data. Differences in lamb live weights between treatments were not similar during successive weeks (p0:02). At weeks 2 and 6, S lambs were 1.57 and 2.48 kg heavier than H lambs, respectively, whereas differences between H and HS lambs were not found. Also differences in live weights of twin and triplet lambs varied over time (p<0:0001) being 2.16 kg (p<0:0001), 3.15 kg (p<0:0001) and 3.83 kg (p<0:0001) higher for twins at weeks 2, 4 and 6, respectively.
Lamb growth from birth until the end of the experi-ment was affected by feeding. Lambs from ewes fed on silage grew better than those on hay (234 versus 188 g per day, p<0:005). The growth rate of HS lambs averaged 183 g per day. Differences in growth rates between H and HS lambs were not signi®cant (p0:67). Silage contained more energy and protein than hay, which contributed to a better ewe and lamb
performance. Total live weight of lambs produced by S ewes was 27% greater than that of HS ewes.
During six experimental weeks, twin lambs on H, S and HS treatments gained 9.34, 11.22 and 9.12 kg, respectively. The individual weight gain of triplets was 2.92 kg less than that of twins (p<0:0001), but the total live weight of lambs produced per ewe was 6% greater for ewes rearing triplets than twins.
4. Conclusions
Good quality grass silage was identi®ed as a suit-able feed for pregnant and lactating ewes, indicating that hay can be replaced by grass silage. Due to the higher nutritive value of silage, ewes performed con-sistently better on silage than hay based diets. Lamb growth and performance was also improved for silage relative to hay based diets. During late pregnancy and early lactation, the current study indicated that sup-plementation of silage based diets with hay was of no value.
Acknowledgements
The authors wish to thank Ms. Helvi Kananen and Mr. Alexandru Cristian for their excellent technical Table 6
Mean treatment effects on live weight and growth rate of twin and triplet lambs
Treatments S.E.M.a Significance
Hay Silage Hay/silage p1a p2a
Litter weight (kg) 7.78 8.54 7.33 0.511 0.31 0.53
Birth weight of twinsb(kg) 3.33 3.66 3.42 0.271 0.19 0.72
Birth weight of tripletsb(kg) 2.43 2.76 2.52 0.182 0.19 0.72
Live weight of twinsc(kg)
At 2 weeks 5.99 7.56 6.05 0.397 <0.005 0.88
At 4 weeks 9.11 11.28 9.25 0.456 <0.0005 0.75
At 6 weeks 12.39 14.87 12.17 0.584 <0.001 0.70
Weight gain of twinsc(g per day) 222 268 217 12.0 <0.005 0.67
Live weight of tripletsc(kg)
At 2 weeks 3.83 5.40 3.89 0.431 <0.005 0.88
At 4 weeks 5.96 8.13 6.11 0.495 <0.0005 0.75
At 6 weeks 8.56 11.04 8.35 0.635 <0.001 0.70
Weight gain of tripletsc(g per day) 153 199 148 13.0 <0.005 0.67
aS.E.M.: maximum standard error of means,p1: hay vs. silage andp2: hay vs. hay/silage. bBirth type of lambs.
cRearing type of lambs.
assistance during the study. Professor George Haen-lein and Dr. Seija Jaakkola are also acknowledged for their valuable comments and criticism of the current manuscript.
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