Production of ewes rearing twin or triplet lambs fed grass silage with a commercial concentrate or a mixture of beet pulp and soybean meal

Production of ewes rearing twin or triplet lambs fed grass silage with a commercial concentrate or a mixture of beet pulp and soybean meal H. V. Petit Sheep Research Farm, Agriculture and Agri-Food Canada, La Pocatière, Québec G0R 1Z0. Contribution number 515 from the Dairy and Swine Research and Development Centre, Agriculture and Agri- Food Canada, PO Box 90, Lennoxville, Québec J1M 1Z3. Received 4 March 1996, accepted 4 September 1996. Petit, H. V. 1997. Production of ewes rearing twin or triplet lambs fed grass silage with a commercial concentrate or a mixture of beet pulp and soybean meal. Can. J. Anim. Sci. 77: 87 93. Forty multiparous Outaouais ewes were used to investigate the effects of number of suckling lambs (2 versus 3) and type of feed supplement in grass silage-based diets on ewe and lamb performance. Treatments were arranged in a 2 2 factorial design. Isonitrogenous and isoenergetic supplements were either a mixture of beet pulp and soybean meal (BP) or a commercial concentrate (CO). Dietary treatments continued from 28 d prepartum until 42 d postpartum. Milk yield was measured weekly. Dietary treatments and number of suckling lambs had no effect (P > 0.10) on DM intake. Feeding BP resulted in similar milk yield for ewes nursing twin (TW) and triplet (TR) lambs, and feeding CO resulted in higher milk yield for ewes nursing TW compared to those nursing TR; this resulted in a significant interaction (P = 0.08) between diet and the number of suckling lambs. Dietary treatments and number of suckling lambs had no effect (P > 0.10) on milk composition. Loss of body weight was greater (P < 0.01) for ewes nursing TR than for those nursing TW, while there was no difference (P > 0.10) between ewes fed BP and those fed CO. Body weight at birth and on day 42, and ADG of TW were greater (P < 0.01) than those of TR, but type of supplement had no effect on lamb performance. Intake of DM was below requirements of ewes nursing TW. These data suggest that DM intake is not responsible for all differences observed in milk yield. Factors such as greater body weight loss could have contributed to increased milk yield. Feeding BP compared to CO may have contributed to maintain similar milk yield for ewes nursing TW and TR, but lamb growth was limited by milk yield as less milk was available per lamb for TR compared to TW. Key words: Ewes, lambs, lactation, beet pulp Petit, H. V. 1997. Production des brebis allaitant des jumeaux ou des triplets et recevant de l ensilage de graminées avec un concentré commercial ou un mélange de pulpe de betterave et de tourteau de soya. Can. J. Anim. Sci. 77: 87 93. Quarante brebis Outaouais multipares ont été utilisées afin de déterminer l effet du nombre d agneaux allaités (2 versus 3) et du type de supplément sur les performances des brebis et des agneaux. Les suppléments isoazotés et isoénergétiques consistaient en un mélange de pulpe de betterave et de tourteau de soya (BP) ou en un concentré commercial (CO). Les suppléments traitements ont commencé à être donnés 28 jours avant l agnelage et jusqu au jour 42 postpartum. La production de lait a été mesurée chaque semaine. Les traitements alimentaires et le nombre d agneaux allaités n ont pas eu d effet (P > 0,01) sur l ingestion de matière sèche. La supplémentation avec BP a donné une production de lait semblable pour les brebis allaitant 2 ou 3 agneaux, alors que CO a donné une production de lait supérieure pour les brebis allaitant 2 plutôt que 3 agneaux (P = 0,08). La composition du lait n a pas été affectée (P > 0,01) par le nombre d agneaux allaités et le type de supplément. La perte de poids vif a été supérieure (P < 0,01) pour les brebis allaitant des triplets que pour celle allaitant des jumeaux, alors que le type de supplément n a eu aucun effet. Le poids à la naissance et au jour 42, et le gain moyen quotidien des agneaux jumeaux ont été supérieurs (P < 0,01) à ceux des triplets; le type de supplément n a eu aucun effet. L ingestion de matière sèche a été sous les exigences recommandées pour les brebis allaitant des jumeaux. Les données suggèrent que l ingestion de matière sèche n est pas le seul facteur responsable pour les différences observées dans la production de lait. Des facteurs telle une plus grande perte de poids des brebis peuvent contribuer à augmenter la production laitière. La supplémentation avec BP comparativement à CO peut contribuer à maintenir une production de lait semblable pour les brebis allaitant 2 ou 3 agneaux, mais la croissance des agneaux pourrait être limitée par la moins grande disponibilité de lait par agneau pour les agneaux triplets comparativement aux jumeaux. Mots clés: Brebis, agneaux, lactation, pulpe de betterave Ewe productivity has recently increased with the introduction of more prolific breeds. Although the ability of ewes to increase milk production according to the number of suckling lambs has been well documented (Gardner and Hogue 1964; Loerch et al. 1985), dietary methods to increase milk production of ewes rearing more than two lambs have not 87 Abbreviations: ADF, acid detergent fibre; ADG, average daily gain; BCS, body condition score; BP, mixture of beef pulp and soybean meal; BW, body weight; CO, commercial concentrate; DM, dry matter; DMI, dry matter intake; FCM, fat corrected milk; NEFA, non esterified fatty acids; TR, triplet; TW, twin

88 CANADIAN JOURNAL OF ANIMAL SCIENCE been extensively investigated. Feeding low ruminally degradable protein increases milk production of ewes nursing single and twin lambs (Loerch et al. 1985), but this may not be an economically favorable alternative. Feeding nonstructural carbohydrates could be another alternative to protein supplements. Generally, production of 4% FCM is increased in dairy cattle when grains are replaced by beet pulp in grass silage-based diets (De Visser et al. 1991; Petit and Tremblay 1995). Microbial protein synthesis also is higher in cows fed beet pulp rather than starch (De Visser et al. 1991), suggesting an improvement in N utilization when nonstructural carbohydrates are fed. Moreover, supplements containing digestible fibre, such as beet pulp, can lead to substantially higher intakes of silage than supplements containing starch (Chamberlain et al. 1989) because starch generally reduces silage DMI (Thomas 1987). Therefore animals with increased DMI of high-quality silage could improve their milk production by being supplied more nutrients. Feeding beet pulp may increase ewe milk production and subsequently growth of triplet lambs. The objective of this experiment was to determine the effects of number of lambs reared (twins vs. triplets) and the type of supplement fed (commercial concentrate vs. a mixture of beet pulp and soybean meal) on DMI and ewe lactation. MATERIALS AND METHODS Ewes and Treatment Diets Forty multiparous Outaouais gestating ewes previously synchronized for breeding within a 48-h period, 89-kg mean BW and 2 to 8 yr old, were used in a 2 2 factorial treatment arrangement. Ewes were selected based on an estimate of fetal numbers determined during mid-gestation using a real-time ultrasound scanning device (Aloka, model SSD- 210DX). During the last month of gestation, ewes were individually fed one of two treatment diets in an indoor, heated sheep barn. After lambing, ewes within diet treatments were divided in two groups by the number of lambs born (TW or TR) and balanced according to BW and BCS. Only two adoptions were performed, one to increase the number of lambs from 1 to 2 and another from 2 to 3. Wood shavings were used for bedding of the pens (2.2 m 2 ). The two treatment diets were either a commercial concentrate (CO) or a mixture of 86% beet pulp and 14% soybean meal (BP). The commercial concentrate contained, on an air-dry basis, 40% rolled barley, 27.5% rolled corn, 27% of a commercial supplement (15% CP: 40% canola meal, 30% soybean meal, 15% oats, 10% wheat, 3% molasses, and 2% mineral mix), 3% molasses, and 2.5% minerals. Daily amounts of supplement fed prepartum were, respectively, 200, 300, 400, and 500 g between d 28 and 25, 24 to 22, 21 to 18, and 17 to lambing. After lambing supplements were offered at a rate of 600 g d 1. The two supplements were isonitrogenous and isoenergetic, and intake averaged 54 g of CP per d 1 and 13.64 MJ d 1 of digestible energy after lambing. Digestible energy content of the concentrates was estimated using tabulated values of the National Research Council (1985). Ewes were fed treatment diets until day 42 postpartum. Grass silage was presented to the ewes on an ad libitum basis. Forage was harvested at the head emergence stage from fields containing at least 95% grasses. Grass was ensiled at approximately 21% DM in a noncompacted heap silo with Super-Sile (Biotal, Inc., Eden Prairie, MN) being added at a rate of 2 g t 1 of silage. Three silos were used with one silo per month being fed. The first silo was fed during gestation and contained approximately 75% bromegrass, 20% orchardgrass, and 5% dandelion; the second silo fed during the first month of lactation contained approximately 95% bromegrass, and 5% dandelion; and the third silo fed from day 31 to day 42 postpartum contained 95% orchardgrass and 5% dandelion. The silage was fed once daily to allow daily orts of 10%. Orts consisted only of silage because the supplements were sprinkled on top of the silage and were consumed readily by the ewes. Samples of feed were taken weekly and frozen for chemical analysis. Each ewe received a mineral-vitamin supplement in order to meet their daily requirements according to the number of suckling lambs (National Research Council 1985). The commercial concentrate and the beet pulp diet provided similar intake of minerals. Lambs were not creep fed. Animals were cared for according to the guidelines of the Canadian Council on Animal Care. Measurements Milk yield was measured on days 7, 8, 17, 18, 27, 28, 37 and 38 postpartum. Lambs were removed from their dams, placed in an adjacent pen and then milk letdown was artificially stimulated before machine-milking (Alfa-Laval) by intrajugular injection with 5 IU of oxytocin (McCance 1959), and the first milk was discarded. The milking machine was adjusted to 90 pulses per minute and 5.9 kg of vacuum. Three hours later, the procedure was repeated, and the milk volume was measured. Lambs were returned to the ewes approximately 1 to 1.5 h after the second milking. Milk samples (60 ml) were collected at the same time milk production was measured. Milk samples were separated into three 20-mL containers, frozen, and stored for later analyses. Milk samples on consecutive days of milk yield measurements were pooled. Three-hour milk production was multiplied by 8 to obtain an estimate of daily production (Doney et al. 1979). Ewes were weighed approximately 30 d prepartum, after lambing, and on day 7, 14, 21, 28, 35, and 42 postpartum. Ewes were fasted overnight before weighing at the beginning and end of the trial. Lambs were weighed within 4 h of birth and on the same days as ewes. Body condition score, and measurement of backfat and muscle thickness of ewes were taken 30 d prepartum, at lambing and on day 42. Body condition scores were determined by subjective appraisal of one person using a scoring system ranging from 1 to 5, with 1 indicating an extremely thin and 5 an extremely fat condition. Blood was collected before feeding from all ewes at lambing, and on days 25 and 42 postpartum. Blood was withdrawn from the jugular vein into vacutainer (Becton Dickinson and Co, Rutherford, NJ) tubes. The serum was separated and frozen at 20 C for subsequent analysis.

PETIT BEET PULP FOR LACTATING EWES 89 Table 1. Chemical composition of feed ingredients Item Grass silage Concentrate Beet pulp Soybean meal ph 4.36 DM (%) 26.5 88.5 90.9 90.7 NH 3 N (% of N) 10.2 (% dry matter) ADF 34.5 6.6 20.8 CP 12.3 16.0 9.1 48.8 Lactic acid 3.6 Acetic acid 1.94 Propionic acid 0.26 Isobutyric acid 0.01 Butyric acid 0.51 Isovaleric acid 0.02 Valeric acid 0.11 Table 2. Feed intake, BW and BCS of ewes nursing twin or triplet lambs and fed silage with either a CO or a BP from 0 to 42 d postpartum Treatment z COTW COTR BPTW BPTR SE DMI (g d 1 ) Silage 2203 2264 2381 2210 31 Total 2735 2795 2935 2765 31 DMI (% of BW) Silage 2.69 2.72 2.92 2.75 0.04 Total 3.35 3.37 3.60 3.44 0.04 DMI (% of total DM) Silage 79.9 80.4 80.4 79.5 0.2 Concentrate 20.1 19.6 19.6 20.5 0.2 Total CP intake (g d 1 ) 352 359 372 351 7 BW (kg) At lambing 84.0 86.3 84.4 85.1 1.3 d 42 80.4 80.7 80.8 76.4 1.4 BW change y (g d 1 ) 84 135 87 205 16 BCS At lambing 3.6 3.6 3.5 3.4 0.1 d 42 3.3 3.5 3.3 2.9 0.1 BCS change 0.27 0.11 0.22 0.44 0.10 z COTW = ewes fed concentrate and nursing twins, COTR = ewes fed concentrate and nursing triplets, BPTW = ewes fed a mixture of beet pulp and soybean meal and nursing twins, and BPTR = ewes fed a mixture of beet pulp and soybean meal and nursing triplets. y Twins vs. triplets (P < 0.05). Chemical Analysis Dry matter of silage was determined by toluene distillation according to the method of Dewar and McDonald (1961). Dry matter of the commercial concentrate, beet pulp and soybean meal was obtained by oven drying at 100 C. Total N of feed ingredients was measured on fresh material by the Kjeldahl method. Liquid was squeezed from weekly samples of silage and used for determination of ph, lactic acid (kit 1112 821, Boeringer Mannheim Canada, Laval, QC), and VFA. Concentration of VFA was determined by gas chromatography (Varian, model 3400, Ville St-Laurent, QC) using valeric acid as the internal standard. Silage samples were dried at 55 C for chemical analysis. Determination of ADF was done with the procedure of Goering and Van Soest (1970) without using sodium sulfite or decalin. Milk fat was analyzed by the Association of Official Analytical Chemists method (1990). Milk lactose was determined with a colorimetric method (lactose/d-glucose test kit catalogue number 986 119; Boehringer Mannheim, Laval, QC) and milk protein as Kjeldahl N 6.38. Serum NEFA (NEFA test kit catalogue number 99075401; Wako Pure Chemical Industries, Osaka, Japan) was determined by enzymatic methods. Statistical Analysis All results were subjected to ANOVA using the GLM procedure of the SAS Institute, Inc. (1985) according to a completely randomized design with a 2 2 factorial arrangement of treatments. Main sources of variation were number of lambs reared, type of supplement, and their interaction. Ewe was the experimental unit. Differences among interaction means were assessed by least squares mean separation using the PDIFF option of the SAS Institute, Inc. (1985) when the F test for the interaction was significant (P < 0.05). Data on production and blood composition were analyzed in a repeated measure design using the REPEATED statement of the

90 CANADIAN JOURNAL OF ANIMAL SCIENCE GLM procedure of the SAS Institute, Inc. (1985). Ewe within number of lambs reared type of supplement fed mean square was the error term for the analysis. The profiles in time were partitioned to determine the differences between time segments. Significance was declared at P < 0.05 unless otherwise stated. RESULTS AND DISCUSSION No two- or three-way interactions of wk of lactation and treatments were detected (P > 0.10) for any dependent variables measured. There were only two exceptions, with an interaction between week and diet for milk fat percentage (P = 0.07) and another one between week and number of suckling lambs for milk protein percentage (P = 0.03). Therefore, results are presented for the whole lactation period. Ewes and lambs had no health problems. Percentage of ADF (Table 1) indicated that forage maturity was close to midbloom stage (National Research Council 1985). Ammonia N percentage, ph and VFA concentrations were similar to those observed for heap grass silage conserved under similar climatic conditions (Petit and Tremblay 1995). Prepartum Measurements Silage DMI, expressed in g d 1 or as a percentage of BW, was similar before lambing for ewes fed CO and those fed BP (data not shown). The BCS 4 wk prepartum and at lambing was not affected by the type of supplement fed. Body weight 4 wk before lambing and at lambing, and BW change before lambing were similar for ewes fed CO and those fed BP. Postpartum Dry Matter Intake Silage DMI, expressed in g d 1 or as a percentage of BW, was similar for ewes fed CO and those fed BP (Table 2); this agrees with results of Petit and Tremblay (1995) who found that feeding low amounts of concentrates based on cereals or beet pulp has no effect on total and silage DMI of lactating dairy cows. Total and silage DMI was similar for ewes Fig. 1. Change of BW of ewes nursing twin (TW) or triplet (TR) lambs and fed silage with either CO or BP from 0 to 42 d postpartum. Pooled standard error = 16. nursing twin and triplet lambs as previously reported by Loerch et al. (1985). Total DMI was slightly lower than values established by the National Research Council (1985) for ewes nursing twin lambs (3.0 kg d 1 and 3.8% of BW), suggesting that energy intake also was below requirements for lactating ewes. Total CP intake was similar among treatments and averaged 358 g d 1. Total CP intake was below the National Research Council (1985) requirements (435 g d 1 ) for lactating ewes nursing twins as DMI was lower than expected. Silage with higher fibre content and lower quality would limit DMI as NDF percentage is inversely correlated with forage intake (Seoane 1982). Restricted intake of nutrients could therefore have resulted in lower milk yield of ewes and, indirectly, performance of lambs. Postpartum Ewe Body Weight and Body Weight Change Type of supplement and number of suckling lambs had no effect on BW at lambing and on day 42 (weaning), BCS at lambing and on day 42, and BCS change (Table 2). However, ewes suckling triplets had greater (P < 0.05) BW loss between lambing and weaning than those nursing twins. Loss of ewe BW was greater on all treatments than the average of 60 g d 1 established by the National Research Council (1985) for ewes nursing twin lambs, which could have resulted from DMI also being lower than recommended values. Loss of BW was greater on weeks 3 (P < 0.01) and 6 (P = 0.07) of lactation for ewes nursing triplets than for those nursing twin lambs (Fig. 1). This is in agreement with Loerch et al. (1985) who observed that ewes rearing twins tend to lose less BW and maintain greater BCS during lactation than do those rearing triplet lambs. Moreover, ewes rearing twins have also been shown to lose more BW during lactation than those rearing singles (Hatfield et al. 1995). Ewes fed CO and BP had similar BW change between lambing and weaning, which agrees with results obtained with lactating dairy cows fed silage and concentrates similar to those of the present experiment (Petit and Tremblay

PETIT BEET PULP FOR LACTATING EWES 91 1995). However, BW loss during week 6 of lactation was greater (P < 0.05) for ewes fed BP than for those fed CO (Fig. 1) with a tendency (P = 0.18) for BPTR ewes to have the greatest BW loss; this was paralleled with a trend (P = 0.18) for ewes fed BP compared with ewes fed CO to maintain higher milk production during wk 6 (data not shown) and significantly higher blood NEFA concentration on day 42 (Fig. 2). This could suggest that ewes fed beet pulp used their energy and protein reserves to maintain higher milk yield at the end of lactation. On average, BW of ewes decreased from lambing to week 2 of lactation (data not shown); BW was similar on weeks 2 and 3, and decreased significantly from weeks 3 to 4, 4 to 5, and 5 to 6 of lactation. Thickness of muscle and fat measured by ultrasound (data not shown) were similar among treatments. Milk Production and Composition Feeding BP resulted in similar milk yield for ewes nursing twin and triplet lambs, while feeding CO resulted in higher milk yield for ewes nursing TW compared with those nursing TR (Table 3); this resulted in a significant interaction (P = 0.08) between diet and number of suckling lambs. Milk yield of BPTW and BPTR ewes was similar to that of COTW ewes. This agrees with results of Fegeros et al. (1995) who reported that the inclusion of dried citrus pulp in rations of limit-fed ewes has no significant effect on milk yield and composition when added at a daily rate of around 565 g in an alfalfa hay-based diet. Ewes fed BP tended (P = 0.18) to maintain higher milk production during wk 6 of lactation (data not shown) than those fed CO. Contrary to the results of the present experiment, milk production has been shown to increase with the number of suckling lambs due to more frequent and more complete emptying of the mammary gland (Gardner and Hogue 1964). Loerch et al. (1985) reported a 12% improvement in milk production for ewes rearing triplets compared with those rearing twins, although the opposite has previously been observed at our Research Farm (A. Roy, personal communication). Fig. 2. Blood NEFA concentration of ewes nursing twin (TW) or triplet (TR) lambs and fed silage with either CO or BP from 0 to 42 d postpartum. Pooled standard error = 27. Ewes nursing twin lambs have been shown to have higher DMI and higher milk production in early lactation than ewes nursing singles (Ramsey et al. 1994). Moreover, Loerch et al. (1985) observed a trend for increased DMI and milk production for ewes nursing triplets compared to those nursing twins, which was not observed in our experiment. Dry matter intake in the present experiment was below the norms (National Research Council 1985) for ewes nursing twins, which would have resulted in nutrient deficiency and restricted milk production. However, BPTR ewes increased milk yield to a level similar to that of ewes nursing twins by increasing body fat reserve mobilization as suggested by higher although not significant (P > 0.10) BW loss for BPTR (205 g d 1 ) than for COTR (135 g d 1 ) ewes. Energy deficiency could have been compensated for by mobilizing body fat as corroborated by higher blood NEFA concentrations for ewes fed BP than for those fed CO (Fig. 2). Higher free fatty acids concentrations have already been related to greater milk yield and greater negative energy balance in ewes (Gonzalez et al. 1982). Percentages of fat, protein, and lactose in milk (Table 3) were similar for ewes nursing triplet and twin lambs in agreement with results of Loerch et al. (1985). In general, average milk composition was similar for ewes fed CO and BP as previously reported for ewes fed dried citrus pulp or cereals (Fegeros et al. 1995) and dairy cows fed concentrates similar to those used in the present experiment (Petit and Tremblay 1995). Differences in yield of milk components depended mainly on differences in milk yield as milk composition was similar among treatments. The milk:feed ratio was significantly higher for COTW than COTR and BPTW. The milk:feed ratio of BPTR was similar to that of other treatments. Differences among treatments in milk yield were mainly responsible for differences in milk:feed ratio. Loerch et al. (1985) found no difference in efficiency of milk production between ewes rearing triplets and those rearing twins and Petit and Tremblay (1995) observed improved milk efficiency in cows when feeding beet pulp compared with cereals.

92 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 3. Milk yield, milk composition and lamb performance of ewes nursing twin or triplet lambs and fed silage with either a CO or a BP from 0 to 42 d postpartum Treatment z Blood Concentration of NEFA On average, blood NEFA concentration was lower (P < 0.001) at lambing than on day 25, and was higher (P = 0.02) on day 25 than 42 (Fig. 2). Increases in NEFA concentration could be related to fat mobilization occurring during lactation as observed for dairy cows (Roberts et al. 1981). After lambing, blood NEFA concentration tended (P = 0.07) to be higher for ewes nursing triplets compared with those nursing twin lambs, suggesting greater fat mobilization for ewes carrying more lambs. Moreover, NEFA concentration was higher for ewes fed BP than for those fed CO, suggesting that fat mobilization was greater with beet pulp than cereals as reported by Miettinen and Huhtanen (1989) for dairy cows. Higher free fatty acids concentrations have been related to grated milk yield and greater negative energy balance in ewes (Gonzalez et al. 1982). In the present experiment, ewes fed BP produced milk with higher fat percentage on week 3 than ewes fed CO, which could have contributed to an increased energy deficit and an increased blood NEFA concentration. Lamb Body Weight Dietary treatments fed to nursing ewes had no effect on lamb weight produced per ewe (kg) at birth, on day 42, and on total BW gain of lamb produced per ewe (Table 3). Birthweights were similar for ewes fed CO and those fed BP. Birthweights and BW on day 42, and ADG of lamb were significantly higher for ewes nursing twin compared with those nursing triplet lambs. Lamb produced per ewe at birth and weaning, and total BW gain between birth and weaning were higher for ewes nursing triplet compared with those nursing twin lambs. This agrees with results of Loerch COTW COTR BPTW BPTR SE Milk yield y (ml d 1 ) 2691a 2280b 2399ab 2548ab 69 Milk composition (%) Fat 8.95 8.01 8.52 9.28 0.26 Protein 5.67 5.63 5.78 5.55 0.06 Lactose 5.13 5.11 5.17 5.10 0.02 Milk components yield (g d 1 ) Fat x 241a 183b 204ab 236a 11 Protein 153 128 139 141 4 Lactose y 138a 117b 124ab 130ab 4 Milk feed 1x (g g 1 ) 1.03a 0.84b 0.85b 0.96ab 0.03 Lamb BW (kg) At birth w 3.78 3.11 3.53 2.93 0.07 d 42 w 13.73 10.18 13.13 10.38 0.28 Lamb ADG w (g d 1 ) 237 168 228 177 5 Lamb produced ewe 1 (kg) At birth w 7.55 9.34 7.07 8.78 0.23 d 42 w 27.46 30.55 26.26 31.14 0.64 BW gain w 19.91 21.21 19.19 22.36 0.47 z COTW = ewes fed concentrate and nursing twins, COTR = ewes fed concentrate and nursing triplets, BPTW = ewes fed a mixture of beet pulp and soybean meal and nursing twins, and BPTR = ewes fed a mixture of beet pulp and soybean meal and nursing triplets. y Interaction between diet and nursing approached significance (P = 0.076). x Significant interaction between diet and nursing (P < 0.05). w Twins versus triplets(p < 0.05). a,bmeans in the same row followed by different letters differ (P < 0.05). et al. (1985) who observed that although triplet-reared lambs have lower final weights and lower ADG than do twinreared lambs, total kilograms of lamb produced per ewe is greater for ewes rearing triplets than for ewes rearing twins. CONCLUSIONS Milk yield was lower for ewes nursing triplets than for those nursing twins when a cereal supplement was fed, which could partially explain the lower ADG of triplet than twin lambs. However, there was no difference in milk yield of ewes nursing triplet and twin lambs when a mixture of beet pulp and soybean meal was fed. These results suggest that ewes fed beet pulp and soybean meal used their energy and protein reserves to maintain higher milk yield at the end of lactation as BW loss per day and blood NEFA concentration at the end of lactation were higher for ewes fed beet pulp and soybean meal than for those fed cereals. ACKNOWLEDGMENTS The author thank D. Paradis, C. Levesque and I. Blanchet for technical assistance and the sheep barn staff at La Pocatière for help in maintaining the ewes. This research was sponsored by the Programme d essais et expérimentation en agro-alimentaire through the Syndicat des Producteurs d agneaux et moutons de la Côte-du-Sud. Association of Official Analytical Chemists. 1990. Official methods of analysis. 15th ed. AOAC, Washington, DC. Chamberlain, D. G., Martin, P. A. and Robertson, S. 1989. Optimizing compound feed use in dairy cows with high intakes of silage. Page 175 in W. Haresign and D. J. A. Cole, eds. Recent advances in animal nutrition. Butterworths, London, UK. De Visser, H., Huisert, H. and Ketelaar, R. S. 1991. Dried beet

pulp, pressed beet pulp and maize silage as substitutes for concentrates in dairy cow rations. 2. Feed intake, fermentation pattern and ruminal degradation characteristics. Neth. J. Agric. Sci. 39: 21 30. Dewar, W. A. and McDonald, P. 1961. Determination of dry matter in silage by distillation with toluene. J. Sci. Food Agric. 12: 790 795. Doney, J. M., Peart, J. N. and Smith, W. F. 1979. A consideration of the techniques for estimation of milk yield by suckled sheep and a comparison of estimates obtained by two methods in relation to the effect of breed, level of production and stage of lactation. J. Agric. Sci. (Camb.) 92: 123 132. Fegeros, K., Zervas, G., Stamouli, S. and Apostolaki, E. 1995. Nutritive value of dried citrus pulp and its effect on milk yield and milk composition of lactating ewes. J. Dairy Sci. 78: 1116 1121. Gardner, R. W. and Hogue, D. E. 1964. Effects of energy intake and number of lambs suckled on milk yield, milk composition and energetic efficiency of lactating ewes. J. Anim. Sci. 23: 935 942. Goering, H. K. and Van Soest, P. J. 1970. Forage fiber analyses. ARS, USDA, Agr. Handbook No 379, Washington, DC. Gonzalez, J. S., Robinson, J. J., McHattie, I. and Fraser, C. 1982. The effect in ewes of source and level of dietary protein on milk yield, and the relationship between the intestinal supply of non-ammonia nitrogen and the production of milk protein. Anim. Prod. 34: 31 40. Hatfield, P. G., Snowder, G. D., Head, W. A., Jr., Glimp, H. A., Stobart, R. H. and Besser, T. 1995. Production by ewes rearing single or twin lambs: effects of dietary crude protein percentage and supplemental zinc methionine. J. Anim. Sci. 73: 1227 1238. Loerch, S. C., McClure, K. E. and Parker, C. F. 1985. Effects of number of lambs suckled and supplemental protein source on lactating ewes performance. J. Anim. Sci. 60: 6 13. PETIT BEET PULP FOR LACTATING EWES 93 McCance, I. 1959. The determination of milk yield in the Merino ewes. Austr. J. Agric. Res. 10: 839 853. Miettinen, H. and Huhtanen, P. 1989. The concentrations of blood metabolites and the relations between blood parameters, fatty acid composition of milk and estimated ME-balance in dairy cows given grass silage ad libitum with five different carbohydrate supplements. Acta Agric. Scand. 39: 321 330. National Research Council. 1985. Nutrient requirements of sheep. 6th. revised ed. National Academy Press, Washington, DC. Petit, H. V. and Tremblay, G. F. 1995. Milk production and intake of lactating cows fed grass silage with protein and energy supplements. J. Dairy Sci. 78: 353 361. Ramsey, W. S., Hatfield, P. G., Wallace, J. D. and Southward, G. M. 1994. Relationships among ewe milk production and ewe and lamb forage intake in Targhee ewes nursing single or twin lambs. J. Anim. Sci. 72: 811 816. Roberts, C. J., Reid, I. M., Rowlands, G. J. and Patterson, A. 1981. A fat mobilisation syndrome in dairy cows in early lactation. Vet. Rec. 108: 7 9. SAS Institute, Inc. 1985. SAS user s guide: statistics, version 5 edition. SAS Institute, Inc., Cary, NC. Seoane, J. R. 1982. Relationships between the physico-chemical characteristics of hays and their nutritive value. J. Anim. Sci. 55: 422 431. Thomas, C. 1987. Factors affecting substitution rates in dairy cows on silage-based rations. Page 205 in W. Haresign and D. J. A. Cole, eds. Recent advances in animal nutrition. Butterworths, London, UK.