Effect of type of forage offered and breed on perform ante of crossbred stickler heifers and their calves Merja Manninen Agricultural Research Centre ofFinland, Animal Production Research, FIN-31600 Jokioinen, Finland, e-mail: merja.manninen@mtt.fi Ilmo Aronen Agricultural Research Centre ofFinland, Animal Production Research. Current address: Rehuraisio Ltd., PO Box 101, FIN-21201 Raisio, Finland Marja-Leena Puntila AgriculturalResearch Centre ofFinland, AnimalProduction Research, FIN-31600 Jokioinen, Finland Reijo Heikkilä Agricultural Research Centre of Finland, Karelia Research Station. Current address: Viikki Experimental Farm, PO Box 27, FIN-00014 University ofHelsinki, Finland Seija Jaakkola Agricultural Research Centre ofFinland, Animal Production Research, FIN-31600 Jokioinen, Finland Thirty Hereford-Ayrshire (HfAy) and 29 Limousine-Ayrshire (LiAy) spring-calving heifers in calf to a Aberdeen Angus (Ab) bull were used to study the effects of cow breed and winter diet on perform- ance. The diets were either primarily based on hay (H, 2 h of dry matter (DM) intake, silage Va) or silage (S, 2 h of DM intake, hay 7a). In addition, animals were offered 1.0 kg milled barley per head daily for two months prior to calving and 1.5 kg/day from calving until grazing commenced. Animals also had free access to barley straw. During the indoor feeding period from 15 December to I June HfAy-heifers consumed slightly but not significantly more feed DM, metabolizable energy and AAT (amino acids absorbed from the small intestine) than LiAy-heifers on both diets. At the start of the experiment LiAy- and HfAy- heifers were 572 and 596 (P<0.05) days ofage, respectively. Corresponding ages at calving were 732 and 729 days. The type of forage feeding did not affect the rate ofpre partum live weight gain (LWG). The calving difficulties observed were minor. Average milk production of HfAy-cows was higher (PcO.OI) than that of LiAy-cows. Calf LWG from birth to weaning was 1058 and 987 g/day for HfAy- and LiAy-progeny, respectively. Corresponding values for the progeny of cows fed S- and H-diets were 1009 and 1036 g/day. All HfAy-cows and 87.1% of LiAy-cows were successfully rebred to Charolais (Ch) sires. Both S- and H-based diets were suitable for crossbred heifers. Although the energy intake was below Finnish recommendations on both diets, particularly pre partum, live weight of 488 kg for HfAy- and 476 kg for LiAy-heifers pre partum proved to be adequate. The incidence of calving diffi- culties was low. Key words', beef heifers, calf performance, calving difficulty, feed requirement, milk production © Agricultural and Food Science in Finland Manuscript received June 1997 367 Vol. 7(1998): 367-380. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Manninen, M. et al. Effect offorage offered and breed on performance ofsuckler heifers ntroduction Most Finnish beef is derived from dairy herds and approximately only six per cent originates from beef suckler herds. Continuous reduction in dairy cow numbers together with a growing consumer demandfor quality beef has increased the need for specialized beef production and therefore, knowledge of feeding suckler heifers and cows. It is known that feeding beef heifers from puberty to weaning of their first calf is a critical period. Under- or over-heifernutrition may have a major influence on calfbirth weight, milk pro- duction, calf survival, and above all, resumption ofoestrus activity (Field 1991). However, infor- mation on crossbred replacement beef heifer management underFinnish conditions, withrel- atively short grazing and long indoor feeding periods, is inadequate. The purpose of the present experiment was to study the effect of forage type (grass silage- vs. hay-based diet) on forage intake, live weight, live weight gain, calving difficulty, milk produc- tion and rebreeding of Hereford x Ayrshire (HfAy) and Limousine x Ayrshire (LiAy) heif- ers and calf performance. An additional aim of the experiment was also to examine the suitabil- ity of direct-cut grass silage in the prevailing cold indoor feeding conditions. Breed types were cho- sen based on calf availability from farms and the popularity of HfAy animals as crossbred suck- ler dams. Furthermore, Limousin was the most popular beef breed used during recent years for beef inseminations on dairy herds. Aberdeen Angus (Ab) was chosen as the maiden heifer sire. Material and methods Animals and experimental design The experiment was carried out at Tohmajärvi research station located in eastern Finland (62° 14’N, 30°21’E). In December, the minimum tem- peratures recorded inside and outside the cow- house were -19°C and -32°C, respectively (Fig- ure 1). Thirty-two HfAy-heifers with an initial live weight (LW) on 14December of436 kg, and 32 LiAy-heifers with an initial LW of 393 kg, both breeds in calf to Ab, were used. The exper- iment commenced 15 December when HfAy- and LiAy-heifers averaged 596 and 572 days old, respectively. At calving both HfAy- and LiAy- heifers averaged 24 months of age, after which they are referred to as cows. Animals were allo- cated to four treatments according to their LW and predicted calving date according to a 2 x 2 factorial design. Factors were breed type (HfAy and LiAy) and diet (hay-based, H and silage- based, S). Animals were group-fed, eight animals per pen, two pens per treatment. The experiment was subdivided in two main parts, the indoor feeding period and the grazing period. During the indoor feeding period animals were housed in a barn with an area of 77 m2/group. Both straw and peat were used as bedding materials. Ani- mals also had access to an outside exercise area of 108 mVgroup. Feeding and feed sampling Animals were fed once a day in the morning. The amount of feed offered and refused was re- corded for each group daily. The quantity of for- age offered daily was restricted. Hay and silage were given to heifers fed S- and H-diets accord- ing to their initial LW and Finnish recommen- dations (Ojala 1987) which are based on feed- ing recommendations for dairy cows and heifers given by Salo et al. (1982). On the H-diet the proportion of total forage dry matter (DM) in- take was designed to be 1h of hay and 1/3 silage. The reverse applied for the S-diet. Pre partum and post partum feeding regimens involved in- creasing the amount of silage two months be- fore the estimated calving date and after calv- ing. Barley straw was fed ad libitumto all groups. Milled barley was offered individually to heif- ers at 1.0 kg/d, two months pre partum and 1.5 368 AGRICULTURAL AND POOD SCIENCE IN FINLAND kg/d from calving to the start of the grazing sea- son by retaining animals in the feed alley. Dur- ing the indoor feeding period 150 g/day of min- eral mixture rich in magnesium (Viher-Terki) and 50 g/week of vitamin mixture (Deb-Karja-Vitan) was given to the heifers. Heifers had free access to water and a salt lick. Meadow fescue-timothy (Festuca pratensis- Phleum pratense) hay was harvested during the first two weeks of July, dried in the swath and baled into small and round bales. Direct-cut grass silage was made using a flail harvester from the same meadow fescue-timothy fields in August and ensiled in three bunker silos using a formic acid based additive (AIV II; 800 g formic acid/ kg, 20 g orthophosphoric acid/kg), applied at 4- 5 1/t of grass. Field-dried barley straw was baled into small bales. Barley was harvested conven- tionally and dried in a hot-air drier. The grazing season commenced on 1 June. Seventeen heifers calving in June were kept in- side and started grazing after calving. The con- tinous grazing area allocated for cows was about 30 hectares. Cows had free access to water and a mineral mixture rich in magnesium. As a re- sult of drought in July, August and September cows on pasture were fed during this period of 8 weeks about 2 kg hay/animal/day. The grazing season ended on 24 August and calves were weaned on either 30 September or 21 October. During the indoor period feed samples for chemical analyses were taken at every feeding and were pooled over a four week period. Cal- culated energy values of hay, grass silage, bar- ley straw and barley are based on determined chemical composition and using average digest- ibility coefficients reported by Tuori et al. (1996). Silage DM content was determined by Fig. 1. Daily temperature (°C) inside and outside the bam during indoor feeding. 369 Vol. 7(1998): 367-380. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Manninen, M. et al. Effect offorage offered and breed on performance ofsuckler heifers oven drying at 105°C for 24 hours and was cor- rected for volatile losses (volatile fatty acids, ammonia, lactic acid) according to Huida et al. (1986). Fresh silage samples were analysed for pH, water soluble carbohydrates according to Somogyi (1945) with modifications of Salo (1965), lactic acid (Barker and Summerson 1941), volatile fatty acids (Huida 1973), ammo- nia nitrogen (N) (McCullough 1967) and solu- ble and total nitrogen N by the Kjeldahl meth- od. Metabolizable energy (ME) values of feeds were calculated according to MAFF (1975, 1984). Amino acids absorbed in the small intes- tine (AAT) and protein balance in the rumen (PBV) were calculated according to Tuori et al. (1996). Live-weight Animals were weighed at the beginning of the experiment, 1-7 days pre partum, within 48 hours after parturition and at the beginning and end of the grazing season. All information from five heifers was omitted from the final data be- cause of deaths and abortions. Calves were weighed immediately after birth, at 100 days of age and at weaning. The results of two calves were omitted from the final data because of re- moval of their dams from the experiment. Calving difficulties All calvings were monitored and assistance was given if calving was prolonged. The character of the calving was recorded using a classifica- tion scale: easy calving with no assistance (1), calving with a slight assistance (2) and difficult calving (3). Milk production Milk production of 16 cows, four cows per treat- ment, was measured using the calf-suckling tech- nique. The cow and her calf were removed from the main group at 1500 hours, and the calf was separated from the dam until 700 hours the fol- lowing morning. In the morning the calf was weighed and then allowed to suckle after which the calf was reweighed. After suckling the calf was separated from the dam. At 1500 hours this procedure was repeated. The sum of both chang- es in calf live weight was used as an estimate of dam milk production. Milk yield was measured on days 10, 50, 95 and 145 of lactation. Data of one HfAy-cow fed the H-diet was deleted due to incomplete pre-calving feed intake records. Rebreeding At pasture an oestrus synchronisation procedure was carried out using PRID (Progesterone Re- leasing Intravaginal Device) on all cows. HfAy- and LiAy-cows were subdivided into three groups according to calving date. After the re- moval of PRID-coils, cows were inseminated using double fixed time artificial insemination (A. 1.) with Charolais-semen. A Charolais-bull ran with the cows from 24 July to 29 September. Statistical analysis The GLM procedure of the Statistical Analysis System (SAS 1989) was used for analysis of variance. Animals were in pens, eight animals per pen, two pens per treatment. Pen was used as an experimental unit (Gill 1989). The mean of the pen was used when interpreting feed in- take data, while for other traits individual cow data was used. Data for heifers was analysed according to the following model y ijki =H+b, + d + bd.. + + e ijk] where y.jk| is the response variable, pis the general mean, b. is the breed, d j is the diet, bd(j is their interaction, p k is a random effect due to the pen within treatmentand e jj|d is the random error term. In the analysis, the pk(bd, j ) term with four 370 AGRICULTURAL AND POOD SCIENCE IN FINLAND Table 1.Duration of feeding periods and age of heifers at calving (days). Breed Hereford xAyrshire Limousin x Ayrshire3 Statistical significance 1 Diet Silage Hay Silage Hay SEM 2 Breed Diet Interaction Number of animals 15 15 13 16 Age at start of experiment 606 586 580 565 7.8 * o NS Experiment start to calving 134 133 160 160 16.4 NS NS NS Age at calving 740 719 740 725 14.7 NS NS NS From calving to the start of grazing 41 35 28 16 (n) 5 (12) (14) (6) (9) 11.64 NS NS NS 1 o PcO.lO; * P<0.05; ** P<0.01; *** P<0.001; NS not significant. 2 SEM = Standard Error of the Mean. 1 Means were based on 13 (LiAy-Silage) or 16(LiAy-Hay) rather than 15 observations. SEM given should be multiplied by 1.08 (LiAy-Silage) or 0.97 (LiAy-Hay) when making comparisions with other mean val- ues. 4 SEM given should be multiplied by 1.10 (HfAy-Silage), 1.32 (LiAy-Hay) or 1.53 (LiAy-Silage) when making comparisions with the mean value of HfAy-Hay. 5 Number calved at the start of grazing. degrees of freedom has been used as an error term. Data for calves was analysed with the same model with the exception that the effect of sex (s ) and interactions between sex and breed, sexv m 7 ’ and diet, and sex, breed and diet were included. In this analysis, the pk(bds,jm ) term with eight degrees of freedom has been used as an error term. Calf birth date was used as a covariate in the analysis of variance when interpreting calf performance data. Standard error of estimate (SEE) was used to interpret calf data due to var- iable number of observations per treatment. Results General results At the start of the experiment LiAy-heifers were younger (Pc0.05) than HfAy-heifers (Table 1). In addition, heifers on the H-diet tended (P<0.10) to be younger than those on the S-diet. One LiAy- heifer was observed to be open during the in- door feeding period and one HfAy-cow was slaughtered as a result of injury at calving. One LiAy-cow died of septicaemia during the graz- ing season and anotherLiAy-heifer aborted. Oth- erwise the health of heifers was good. Chemical composition of feeds and feed intake Average chemical composition and feed values of experimental feeds are given in Table 2. Si- lage was of good fermentation quality with a low pH and low concentration of ammonia N. Average daily intakes of DM, ME, AAT and PBV during the indoor feeding period are sum- marised in Table 3. HfAy-heifers consumed nu- merically more (P>0.10) DM, ME and AAT than LiAy-heifers during the indoor feeding period on both diets. No significant differences were ob- served in DM and AAT intakes between feeding types but ME intake tended (P<0.10) to be low- 371 Vol. 7(1998): 367-380. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Manninen, M. et al. Effect offorage offeredand breed on performance ofstickler heifers Table 2. Chemical composition and feed value of experimental feeds. Silage Hay Barley Barley straw Number of samples 6 6 6 4 Chemical composition (g/kg) Dry matter (DM) 191 860 850 869 In DM, Ash 58 57 48 24 Crude protein 131 102 50 122 Ether extract 55 19 15 23 Crude fibre 314 363 457 54 Nitrogen free extract 442 459 430 777 Feed value, ME, MJ/kgDM 10.6 8.5 6.1 13.3 AAT, g/kg DM 79 75 57 104 PBV, g/kg DM -3 -27 -46 -48 ME, metabolizable energy; ME/11.7 = feed unit, FU. AAT, amino acids absorbed in the small intestine. PBV, protein balance in the rumen. In silage: pH 3.86; in DM (g/kg): lactic acid 53, acetic acid 18, sugar 29. In total nitrogen (g/kg): ammonia N40, soluble N 427. er on the hay-based diet than on the silage-based than on the silage-based diet (-148 g PBV/day diet. Protein balance in the rumen was also sig- vs. -105 g PBV/day). Total ME intakes during nificantly (P<0.01) lower on the hay-based diet the indoor feeding period averaged 72.1 Ml ME/ Table 3. Effect of diet and breed on daily intake of dry matter (DM), energy (metabolizable energy, ME), amino acids absorbed in the small intestine (AAT) and protein balance in the rumen (PBV) during indoor feeding. Breed Hereford x Ayrshire Limousin x Ayrshire Statistical significance 1 Diet Silage Hay Silage Hay SEM 2 Breed Diet Interaction Number of groups 2 2 2 2 Intake DM, kg Silage 4.06 1.90 4.00 1.92 0.016 NS *** o Hay 2.56 4.48 2.49 4,41 0.060 NS **� NS Barley straw 0.03 0.05 0.01 0.03 0.010 o NS NS Barley 0.71 0.70 0.49 0.52 0.133 NS NS NS Total ‘ 7.51 7.27 7.13 7.03 0.179 NS NS NS ME, MJ Total 74,3 67.7 69.9 64.8 2.12 NS o NS AAT, g Total 588 561 552 538 17.4 NS NS NS PBV, g Total -111 -152 -99 -144 6.2 NS ** NS 1 o P<0.10; * P<0.05; ** P<0.01; *** P<0.001; NS not significant. 2 SEM = Standard Error of the Mean. ‘ Including mineral mixture, 150 g/day. 372 AGRICULTURAL AND FOOD SCIENCE IN FINLAND day and 66.2 MJ ME/day on the silage and hay based diets, respectively. During the indoor pe- riod total ME intakes averaged 71.0 MJ ME/day and 67.4 MJ ME/day for HfAy- and LiAy-ani- mals, respectively. Energy intake from barley was higher for HfAy- than LiAy-heifers due to earlier calving of the former and thus, a longer post partum period before the start of the graz- ing season. DM intake of experimental treat- ments during indoor feeding are shown in Fig- ure 2. Also pre partum LW of heifers on the S-diet tend- ed (PcO.lO) to be higher than that of heifers on the H-diet. No interactions between breed and feeding on pre partum LW were observed. At the end of the experimental grazing season LiAy- cows were still significantly (P<0.05) lighter than HfAy-cows. Heifers overwintered on the S-diet continued to be numerically heavier at the end of the grazing season than those overwin- tered on the H-diet. Live weight of heifers The initial LW of LiAy-heifers was lower (PcO.Ol) than that of HfAy-heifers (Table 4). Despite a higher (P<0.01) live weight gain (LWG) pre partum LW of LiAy-heifers tended (P<0.10) to be lower than that of HfAy-heifers. Age of heifers at calving and calving difficulties Mean age at calving of both HfAy- and LiAy- heifers was 24 months. As a consequence of the younger age of LiAy-heifers at the start of the experiment, the period from the start to calving Fig. 2. Average daily intake of dry matter (DM) from experimental feeds on hay (H)- and silage (S)-based diets during indoor feeding. 373 Vol. 7(1998): 367-380. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Manninen, M. et al. Effect offorage offered and breedon performance ofsuckler heifers Table 4. Live weight (LW) and live weight gain (LWG) during indoor feeding and grazing. Breed Hereford x Ayrshire Limousin xAyrshire' Statistical significance 1 Diet Silage Hay Silage Hay SEM 2 Breed Diet Interaction Number ofanimals 15 15 13 16 LW, kg Initial, 15 December 449 423 390 396 7.1 ** NS o Pre partum 498 478 478 473 4.6 o o NS Postpartum 458 445 443 419 8.1 o o NS At the beginning of grazing, 1 June 438 420 434 408 8.8 NS o NS At the end of experimental grazing, 24 August 449 426 419 420 4.6 * o o LWG, g/day From start to calving 357 407 554 480 25.8 ** NS o From calving to start of grazing -584 -763 -434 -390 321.6 NS NS NS During grazing 160 74 -220 165 71.3 NS NS * 1 o PcO.10; * P<0.05; ** P<0.01; *** P<0.001; NS not significant. 2 SEM = Standard Error of the Mean. ' Means based on 13 (LiAy-Silage) or 16 (LiAy-Hay) rather than 15 observations. SEM given should be multiplied by 1.08 (LiAy-Silage) or 0,97 (LiAy-Hay) when making comparisions with other mean values. was longer (P>0.10) for Li Ay-heifers than for HfAy-heifers (Table 1). The calving period was 104 days. Eight calves (13%) were born in March, 15 (24%) in April, 22 (35%) in May and 18 (28%) in June. Two of the calves were dead at parturition, one died immediately after birth and one died accidentally. A significant interaction (P<0.01) between breed and sex was observed for calving difficul- ty (Table 5). HfAy-heifers had more calving dif- ficulties with male than female calves (1.50 vs. 1.06) while no differences were observed be- tween sexes born to LiAy (1.34 vs. 1.32).Also a significant (PcO.001) interaction between diet and calf sex on calving difficulty was observed. Heifers on the S-diet had more calving difficul- ties when they had male than female calves (1.78 vs. 1.21) while heifers on the H-diet producing female calves had slightly more calving difficul- ties than those producing male calves (1.18 vs. 1.06). Live weight of calves There was no effect of breed on calf birth weight but diet and sex of calves tended (P<0.10) to have an effect on calf birth weight (Table 5). At 100 days of age, male calves were heavier (P<0.01) than females (150 kg vs. 137 kg). At weaning Ab X HfAy calves were numerically heavier (197 kg vs. 188 kg) but older (P<0.05) than Ab x LiAy calves (163 days vs. 141 days).The rate ofLWG from birth to weaning of Ab x HfAy calves was numerically higher than thatof Ab xLiAy calves (1058 g/day vs. 987 g/day). The rate of LWG from birth to weaning of male calves was higher (P<0.05) than that of female calves (1078 g/day vs. 968 g/day).The average weaning weight, (i.e. 151-day weight), was higher (P<0.05) for male than female calves (198 kg vs. 179 kg). No in- teractions between breed, type offeeding and sex on calf weight, age or rate of LWG were ob- served. 374 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Table 5. Effect of type of feeding, breed and sex on calving difficulty and calf performance. Breed Diet Aberdeen Angus x HfAy Aberdeen Angus x LiAy Silage Hay Silage Hay Statistical significance 1 Sex Male Female Male Female Male Female Male Female SEE 2 Breed Diet Sex Number of animals 12' 4 8 7 9‘ 5 7 9’ Calving difficulty 34 2.00 1.00 1.00 1.13 1.55 1.42 1.13 1.23 0.186 NS *** ** Live weight, kg At birth 40.8 37.7 36.4 34.3 36.8 36.5 38.1 34.6 3.98 NS o o 100-day 153 143 151 138 143 136 152 132 12.9 NS NS ** At weaning 205 194 198 192 188 181 199 184 22.3 NS NS NS 151-day 5 201 189 202 185 189 167 199 175 26.4 NS NS * Weaning age (days) 156 173 154 169 140 138 138 147 30.9 * NS NS Live weight gain from birth to weaning (g/day) 1093 1021 1110 1010 1025 899 1083 944 152.0 NS NS * 1 o PcO.10; * P<0,05; ** P<0.01; ***P<0.001; NS not significant. 2 SEE = Standard Error of the Estimate. 3 1; Easy, no assistance, 2; Slight assistance, 3; Difficult calving. 4 A significant interaction between breed and sex (p<0.01), diet and sex (pcO.001) and breed, diet and sex (p<0.01). 5 151-day weight; average calf weaning age. ' n = 12 for calving difficulty and birth weight then n = 11 n = 9 for calving difficulty and birth weight then n = 8. Milk production There was no effect of diet on milk production (Table 6). Daily milk production of HfAy-cows was marginally higher at day 10 and day 95 of lactation and much higher (P<0.05) at day 50 and day 145 of lactation than thatofLiAy-cows. Overall milk production of HfAy-cows was high- er (P<0.01) than that of LiAy-cows (7.7 kg/day vs. 5.8 kg/day). Conception rate All HfAy-cows starting the grazing period were successfully bred while only 87.1% of LiAy- cows were recorded to be in calf during preg- nancy testing conducted in the autumn. Type of feeding during the indoor period did not affect conception rate since 93.3% of cows on the S- diet and 93.5% of cows on the H-diet were preg- nant. Overall, 50.8% ofcows were in calf to A. 1., Table 6. Effect of type of feeding and breed on milk production (kg/day) of crossbred suckler cows. Breed Hereford x Ayrshire Limousin x Ayrshire Statistical significance 1 Diet Silage Hay° Silage Hay SEM 2 Breed Diet Interaction Number of animals 4 3 4 4 Day of lactation 10 7.0 7.4 5.5 6.0 0.58 o NS NS 50 8.8 7.6 5.8 6.5 0.59 * NS NS 95 9.8 9.2 7.3 6.4 1.13 o NS NS 145 6.6 5.5 5.0 3.7 0.56 * NS NS Mean 8.1 7.4 5.9 5.6 0.28 ** NS NS 1 o PcO.10; * P<0.05; ** P<0.01; *** P<0.001; NS not significant. 2 SEM = Standard Error of the Mean, for ° multiply by 1.22. 375 Vol. 7(1998): 367-380. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Manninen, M. et al. Effect offorage offeredand breed on performance ofsuckler heifers 42.6% to natural service and 6.6% failed to be- come pregnant. Discussion Feed intake Feed values of hay and silage were satisfactory. In a cold environment the intake of unwilted grass silage may be depressed due to freezing. In the present study feed intakes were good and there were no refusals of silage, hay or barley. Barley straw was available ad libitum, but in- take was minimal. On the coldest days of win- ter, freezing ofunwilted grass silage caused some minor problems when weighing and apportion- ing feed for treatment groups. On the S-diet both breeds received more en- ergy (ME MI) than heifers on the H-diet during the experiment except from the start of the ex- periment to the beginning of pre partum feed- ing. At the onset of the experiment, DM intake was 1.50 kg/100 kg live weight for HfAy-heif- ers and 1.59 kg/100 kg live weight for LiAy-heif- ers. In Finland there are no official feeding stand- ards for replacement beefheifers, but recommen- dations based on feeding standards of dairy heif- ers and cows are available (Salo et al. 1982,Tuori et al. 1996). The calculated AAT intake before calving exceeded recommendations, but DM and energy intake were below Finnish recommenda- tions, particularly for the H-diet just before and after calving. Although indoor energy intake in this experiment was below recommendations (5- 15%) particularlypost partum, it appeared to be sufficient since conception rates were good. DM intakes were also considerably lower than mini- mum limits recommended by Macartney and Moon (1974) and Field (1991). However, feed- ing levels on the S-diet were in good agreement with the recommendations reported by Drennan (1988). Nutrition, especially energy intake, is the most critical factor influencing the interval from calving to first oestrus. Dunn et al. (1969) ob- served that the level of energy intake can mark- edly change reproductive performance in two- year-old heifers as the pregnancy rate 120 days after calving was directly related to post-calv- ing energy intake. Nicol (1977) also reported that a low level of nutrition for 40 days post calving for two- and three-year-old Aberdeen Angus and Aberdeen Angus crosses resulted in a delay of seven days to first oestrus compared to animals on a higher feeding level. Intervals from calving to first oestrus were not recorded due to the syn- chronisation programme during the mating pe- riod and thus, the effect of diet, energy level and breed on the interval to first oestrus can not be clearly identified. However, conception rate was good for all cows. Live weight of cows The higher LWG ofLiAy-heifers may result from their younger age, larger size and later maturity which is typical for larger beef breeds such as the Limousin and Charolais. LWG ofheifers pre partum was 382 g/day for HfAy-heifers and 517 g/day for LiAy-heifers and was thus, satisfacto- ry when compared with recommendations given by Byers et al. (1987). The results observed in this experiment have to be compared with those observed with other Hereford- or Limousin- crosses because comparable to that used crosses in this experiment are not common elsewhere. The LW of heifers before calving was also satis- factory if compared to the results reported by Drennan (1987) with crossbred heifers although in contrast to the present study Limousin x Frie- sian-heifers were heavier than Hereford x Frie- sians before calving. In another experiment More O’Ferrall and Drennan (1989) reported that Her- eford x Friesian first-calf heifers reached an av- erage of 393 kg and Simmental x Friesian first- calf heifers reached an average of 422 kg at 32 months of age in autumn. However, in the present experiment HfAy- and LiAy-heifers reached 80 376 AGRICULTURAL AND FOOD SCIENCE IN FINLAND to 85% of expected mature LW at calving as rec- ommended by Rittenhouse and Roath (1989). Both the hay- and silage-based feeding sys- tems were suitable for Hereford- and Limousin crosses in the current circumstances. During the grazing season LWG was quite poor for HfAy- cows previously on the H-diet in winter and for LiAy-cows offered the S-diet. The latter, in fact, lost LW. Negative LWG may reflect insufficient energy intake from grass due to drought during the grazing season. Additional feeding of hay appeared to be inadequate. On the other hand, the good conception rate of all cows reflects suf- ficient energy intake and condition from calv- ing to the start of insemination and mating. Calving difficulties Generally, few severe calving difficulties were observed in this experiment although 29.5% of all calvings were assisted. Ease of calving prob- ably reflects the sire genotype as was suggested by Roux et al. (1987), who used eitherAberdeen Angus or Aubrac sires on Friesian or Charolais xFriesian heifers and by Harte (1987), who used Hereford x Friesian heifers and Aberdeen An- gus bulls. Puntila et al. (1985) reported that HfAy-heifers had marginally greater calving dif- ficulties than LiAy-heifers calving to a Limou- sin sire. Male calves in the present experiment were heavier at birth than female calves (38.0 kg vs. 35.9 kg). It can be assumed that LW at calving was optimum for both HfAy- and LiAy- heifers to avoid dystocia which is in agreement with the findings by Bellows et al. (1971). Sin- clair and Lowman (1990) observed that feeding level pre partum affected the birth weight of calves as Hereford-Friesian heifers in calf to a Simmental bull given only 50 MJ ME/day in the last 12 weeks of pregnancy gave birth to calves which were significantly (p<0.05) lighter than those from heifers receiving 75 MJ ME/day. Keane et al. (1991) did not observe any effect of different feeding levels pre partum (41 days be- fore calving cows were fed straw ad libitumplus 0.5 kg or 2.0 kg concentrates per head daily) on calf birth weight or calving difficulties of cross- bred beef heifers. Live weight of calves The amount of milk is the most important factor affecting calf growth rate during the first three or four months, particularly for spring-born calves (Allen and Kilkenny 1984). In the present experiment the calf performance was affected only by sex. Although there was no difference in the calving age of heifers, Li Ay-heifers calved significantly later in spring than HfAy-heifers. Lesmeister et al. (1973) observed that earlier born calves grew significantly faster from birth to weaning than calves born in later groups. Calves from LiAy-heifers were younger at the start of the grazing season which probably also affected their LWG. Pre-weaning gains (male calves 1078 g/day vs. female calves 968 g/day) measured in this experiment were, however, sat- isfactory when compared to pre-weaning gains of calves from Hereford x Friesian, Simmental xFriesian and Limousin x Friesian two-year-old dams reported by More O’Ferrall and Drennan (1989). Milk production The first lactation is probably the most impor- tant period in the life of a beef cow. Nutrient requirements of a heifer is greatest during this period because she has to maintain her body, nurse a calf, recover from calving, come into heat, rebreed, and continue to grow (Macartney and Moon 1974). In the present experiment the type of feeding during the indoor period did not affect milk pro- duction, but there was a significant breed affect. It may be possible that the lower milk produc- tion which was measured for LiAy-heifers result- ed from their later average birth date and, the later maturing of Limousin-crosses. However, milk production for both types of cows was sat- isfactory as judged from LWG of their calves. 377 Vol. 7(1998): 367-380. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Manninen, M. et al. Effect offorage offered and breed on performance ofsuckler heifers The effect of breed on milk production is in agreement with the results observed by Jenkins and Ferrell (1992) and Jeffery et al. (1971). In contrast to the observations of Puntila et al. (1985) HfAy-heifers produced more milk than LiAy-heifers. However, milk production of HfAy-heifers was in good agreement with those reported by Chigaru and Topps (1981) with Her- eford x British Friesian heifers. In the present experiment the peak milk yield was observed 95 days after parturition. Somerville and Lowman (1980) observed a peak milk yield of 7.7 kg, 31 days post partum using the calf-suckling tech- nique with Hereford x British Friesian heifers and 7.6 kg, 26 days post partum using the ma- chine-milking technique with the same heifer type. Milk production observed in this experiment with crossbred beef cows seems to be quite sat- isfactory when compared to milk production fig- ures achieved with purebred Hereford-heifers (Johnsson and Obst 1984, Fleck et al. 1980) and other purebred adult beef cows reported by An- dersen (1990). The main reason for good milk production was undoubtedly the effect of the Ayrshire breed although it can be assumed that Ayrshire dairy cows inseminated with beef se- men would have a low production potential and are most likely to be the lowest producing ani- mals in a dairy herd. Conception rate It can be assumed, in spite of the negative LWG from calving to the start of the grazing season, that cows were at least in moderate conditionat the start of the grazing season. The lower con- ception rate of LiAy heifers may reflect their slightly younger age and later maturity. Deut- scher and Whiteman (1971) reported that under range conditions only 13% of Angus-Holstein crossbreds nursing heifers rebred compared to 63% of purebreds nursing Angus-heifers. This would indicate that nutritional requirements of better milking crossbreds are higher in order to ensure good reproductive performance. Van Niekerk et al. (1990) observed that winter and summer levels of nutrition only slightly affect- ed conception rate of Simmental heifers. Conclusions Both H- and S-based diets used in this experi- ment seemed to be suitable for crossbred beef heifers during indoor feeding in a cold environ- ment. Calculated ME and AAT intakes were low- er on the H-diet than the S-diet but this did not cause any major performance differences. DM intake was below minimum recommendations on both diets. On the coldest days of the indoor feed- ing period, freezing of fresh grass silage caused minor technical problems. This may be avoided by using wilted grass silage, hay-based diets or increasing the amount of forages of lower nutri- tive value but higher DM content. Calving difficulties observed in this experi- ment were minor which reflects the size ofheif- ers being adequate at calving and suitable feed- ing level pre partum. In addition, use of an easy calving breed sire probably contributed to the low incidence of calving difficulties. Milk pro- ductionof both crossbred heifer types was satis- factory as indicated by the growth rate of their calves. 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SELOSTUS Karkearehuruokinnan vaikutus risteytyshiehojen ja niiden vasikoiden kehitykseen sisäruokinta- ja laidunkaudella Merja Manninen, Ilmo Aronen, Marja-Leena Puntila, Reijo Heikkilä ja Seija Jaakkola Maatalouden tutkimuskeskus ja Helsingin yliopisto Tutkimuksessa selvitettiin heinävaltaisen (noin 2/s kuiva-aineen syönnistä heinää) ja säilörehuvaltaisen (noin 1h kuiva-aineen syönnistä säilörehua) ruokin- nan vaikutuksia Hereford- Ayrshire- (HfAy) ja Li- mousine-Ayrshire- (LiAy) risteytyshiehojen elopai- non kehitykseen, poikimiseen, maidontuotantoon ja tiinehtymiseen. Lisäksi selvitettiin risteytyshiehojen Aberdeen Angus- (Ab) sonneista syntyneiden vasikoi- den kehitystä syntymästä vieroitukseen. Säilörehuruokinnalla olleet HfAy-hiehot saivat sisäruokintakaudella keskimäärin 74,3 MJ ME/pv ja LiAy-hiehot 69,9 MJ ME/pv ja heinävaltaisella ruo- kinnalla olleet vastaavasti 67,7 MJ ME/pv ja 64,8 MJ ME/pv. HfAy-hiehojen suurempaan kuiva-aineen syöntiin ja siten suurempaan energian saantin lienee osittain vaikuttanut niiden LiAy-hiehoja hieman suu- rempi koko, aikaisempi täysikokoisuuden saavuttami- nen ja siten ruuansulatuskanavan suurempi tilavuus. Poikiessa HfAy- ja LiAy-hiehot olivat keskimää- rin 24 kuukauden ikäisiä. Poikimiset onnistuivat hy- vin, muutamia vaikeita poikimisia esiintyi ja 29,5%:55a poikimisista tarvittiin hieman avustusta. Kokeen alkaessa LiAy-hiehot olivat HfAy-hieho- ja kevyempiä. LiAy-hiehojen elopaino lisääntyi poi- kimiseen mennessä enemmän kuin HfAy-hiehojen, mutta laidunkauden päättyessä LiAy-eläimet olivat edelleen kevyempiä kuin HfAy-eläimet. Ruokinta ei vaikuttanut hiehojen elopainon kehitykseen. Emän rotu tai ruokinta ei vaikuttanut vasikoiden kehitykseen. Syntymästä vieroitukseen Ab x HfAy- sonnivasikat kasvoivat keskimäärin 1101 g/pv ja Ab x LiAy-sonnivasikat 1054 g/pv, lehmävasikat vastaa- vasti 1015 ja 921 g/pv. Ab x LiAy-vasikoiden hieman heikompaan kasvuun vaikutti ilmeisesti LiAy-emojen HfAy-emoja hieman myöhäisempi poikimisajankoh- ta. Vasikoiden keskimääräinen vieroitusikä oli 151 vuorokautta. Sisäkauden ruokinta ei vaikuttanut emojen mai- dontuotantoon eikä tiinehtymiseen laidunkaudella. HfAy-emojen maidontuotanto oli keskimäärin LiAy- emojen maidontuotantoa parempi. Laidunkaudella kaikki HfAy-emot ja 87,1% LiAy-emoista tiinehtyi- vät. Tutkimuksen perusteella heinä-ja säilörehuvaltai- nen ruokinta soveltuu risteytyshiehojen sisäruokinta- kaudelle. Suositusten alle jäänyttä kuiva-aineen syön- tiä voidaan lisätä lisäämällä dieettiin heinää tai ol- kea, Tämän kokeen perusteella Aberdeen Angusta voidaan suositella risteytyshiehojen ensimmäiseen poikimiseen. 380 AGRICULTURAL AND FOOD SCIENCE IN FINLAND