BCS = body condition score, BL = body length, E = enhanced diet (115% requirements), EN = diet sequence E followed by N

Growth of Heifers Fed 100 or 115% of National Research Council Requirements to 1 Year of Age and Then Changed to Another Treatment12 ABSTRACT Eighty-nine Holstein heifers were used from 3 mo of age until 21 d before their estimated calving date to determine the effect of two feeding programs on growth and onset of puberty. From 3 to 12 mo of age, heifers were fed either 100 or 115% of 1989 NRC nutrient requirements for heifers gaining.7 kg/d. At 12 mo, the treatments were switched (100 to 115% and 115 to 100%) until 21 d before calving. When the 115% diet was fed from 3 to 12 mo of age, rate of BW gain, BW at 12 mo, body condition score, and heart girth increased. Heifers fed the 115% diet from 3 to 12 mo of age were 22 d younger at onset of puberty than those fed the 100% diet, but BW at onset of puberty was similar (281 vs. 278 kg, respectively). When diets were switched at 12 mo of age, the rates of BW gain and growth for the heifers switched from 115 to 100% decreased, but rate of BW gain and growth increased for the other group. At 24 mo of age, BW and body size did not differ between treatments. Neither feeding program resulted in a clear advantage for any trait measured, but the results provide further evidence that extra nutrients fed beyond the NRC requirement for.7 Received March 22, 1993. Accepted August 16, 1993. Contribution Number 92-468-J. Kansas Agricultural Experiment Station, Manhattan. This research was conducted as a part of regional research project NC-119, Dairy Herd Management Strategies for Improved Decision Making and Profitability. 1994 J Dairy Sci 77:270-277 270 E. J. BORTONE, J. L. MORRILL, and J. S. STEVENSON Department of Animal Sciences and Industry A M. FEYERHERM Department of Statistics Kansas State University Manhattan 66506-1600 kg/d of BW gain enhance various growth traits in Holstein heifers. wey words: puberty, diet, growth, nutrient) Abbreviation key: ADG = average daily gain, BCS = body condition score, BL = body length, E = enhanced diet (115% requirements), EN = diet sequence E followed by N beginning at 12 mo of age, HG = heart girth, ME = metabolizable energy, N = normal diet (100% requirements), NE = diet sequence N followed by E beginning at 12 mo of age, WH = wither height. INTRODUCTION Heifers calving at an average of 22.9 mo of age produced more milk by 61 mo of age than those calving at 26.5 mo (14). Gill and Allaire (11). using profit functions, found that optimal age for Holstein heifers at first calving for total lifetime performance was between 22.5 and 23.5 mo. Recommendations for dairy heifers often include gaining at least.7 kg/d from 3 to 24 mo of age, freshening at 24 mo of age, and weighing between 550 to 600 kg. Others (9, 12) have shown that dairy heifers fed high energy diets to achieve higher average daily gain (ADG) grew faster, reached puberty sooner, became excessively heavy but required more AI per conception, and produced less milk than controls fed to attain lower ADG. High energy diets fed during the allometric phase of mammary development (17, 21, 22) produced heifers with mammary glands containing less secretory tissue and more adipose tissue than those fed at lower rates of BW gain (7, 21, 23). Daccarett et al. (3) reported that heifers fed >100% of NRC (16) nutrient re-

NUTRIENT INTAKE AND HEIFER GROWTH 27 1 TABLE 1. Examples of diets fed to Holstein heifers at various BW.I Ingredient 90 kg 140 kg 180 kg 230 kg 270 kg 320 kg 360 kg 410 kg 450 kg 500 kg (kg M) Alfalfa hay 1.80 2.10 3.00 3.30 3.40 4.20 5.00 5.50 8.00 7.00 Rairie hay I..,.. 1.60 3.00 3.00 4.30 6.00 6.00 6.60 6.40 Bromegrass hay....52........................ Sorghum grain 1.90 2.00 2.90 2.40 1.60 1.60 1.60 1.60 1.60 1.60 soybean meal.30.52........................ Trace-mineralized salt2.01.02.02.02.03.03.oq.02.03.03 Dicalcium phosphate.01.01.02.02.02.03.02.04.05.02 Limestone.01....01..................... Vitamins, IUkg A 593 755 834 873 892 890 897 886 868 845 D 92 122 131 136 139 140 139 138 136 131 E 28 28 28 28 28 28 28 28 28 28 1Amounts shown were fomulated for least cost to provide 1009b of NRC (16) requirements and then multiplied by 1.15 to obtain 115% of NRC requirements. ZNaCl 295.5% S98.59b and 1,.007%; Mn,.2409b; Fe, 240%; Mg,.OS%; Cu,.032%; Co,.011%; and Zn,.032%. BW quirements were heavier, had larger heart girth, were longer, were not excessively fat at calving, and calved at younger ages (22.6 vs. 23.8 mo) than did heifers fed 100% of NRC (16) requirements. First lactation milk production for these heifers was unaffexted by previous diets (5). Holstein heifers fed 115% of NRC (16) nutrient requirements from 3 mo of age until 21 d before estimated calving date may achieve desired BW and body size at 24 mo of age without negative effect on subsequent milk production. However, the effects on growth and onset of puberty when heifers are fed 115% of NRC (16) requirements from 3 to 12 mo of age or from 12 mo to 21 d before estimated calving are unclear. Therefore, our objective was to compare performance of Holstein heifers fed either 100 or 115% of NRC (16) requirements for metabolizable energy ME), CP, Ca, P, and vitamins A and D from 3 to 12 mo of age and then switched to the opposite diet until 21 d before estimated calving date. MATERIALS AND METHODS Eighty-nine Holstein heifers from the Kansas State University Dairy Teaching and Research Center were housed together according to age and size in free-stall sheds with concrete floors bedded with straw from 3 to 4 mo of age, in dirt lots with sheds from 4 to 6 mo of age, and in free stalls from 6 mo of age until 21 d before calving. The number of heifers per pen was small enough that adequate feeder space always was available. At 3 mo of age, heifers were assigned randomly to two diets consisting of 100% (normal; N) or 115% (enhanced; E) of NRC (16) requirements for ME, CP, Ca, P, and vitamins A and D for large dairy heifers gaining.7 kg/d. At 12 mo of age, the treatments were reversed [lo0 to 115% of NRC requirements (NE) and 115 to 100% of NRC requirements (EN)] until 21 d before expected freshening. Weekly BW were recorded, and diets were formulated for least cost, based on the average BW of the heifers in the group. The diet fed fiom 3 to 6 mo of age contained alfalfa hay and a concentrate composed of rolled sorghum grain, tracemineralized salt, Ca and P supplements, and a vitamin E supplement. From 6 mo of age until 21 d before calving, heifers were fed a TMR once daily, which contained alfalfa hay, prairie or bromegrass hay, sorghum grain, tracemineralized salt, Ca and P supplements, and supplemental vitamins A, D, and E. Examples of diets formulated at different BW are in Table 1. Water was provided for ad libitum intake at all times. When heifers were 3 mo of age and then at 3-mo intervals, wither height (WH), body Joutnal of Dairy Science Vol. 77, No. 1, 1994

272 BORTONE ET AL. length (BL), and heart girth (HG) were recorded. When heifers were 6 mo of age and then at 3-mo intervals, body condition scores (BCS) were recorded using a five-point scale (1 = thin to 5 = obese) with increments of.5 (6). When heifers were 12 mo of age and then at 3-mo intervals, pelvic area and distance between pin bones were measured using a Rice pelvimeter (Lane Manufacturing Co., Denver, CO). Heifers received AI at the first detected estrus after reaching a minimal BW of 350 kg. At 6 mo of age, 20 heifers on each of the diets were selected randomly, and blood samples were collected via coccygeal venipuncture biweekly until heifers were 14 mo of age. Serum was harvested, stored at 20'C, and later analyzed for progesterone by radioimmunoassay according to the method of Skaggs et al. (20) to estimate the first rise in serum progesterone after pubertal ovulation. Samples were analyzed in four assays; the intraassay coefficient of variation was 6.3%, and the interassay coefficient of variation was 18.7%. Statistical Analysis Heifers in a pen represent the experimental unit. Each heifer was the observational unit when individual BW, body measurements, and body condition scores were taken every 3 mo. Data were analyzed using the general linear models procedure of SAS (19). When changes in BW, body size, and BCS of heifers at indicated ages were compared, the model specified changes in the measure over a time interval as a function of treatments and a covariate (measure at the beginning of the period). When reproductive performances were compared, the responses were expressed as functions of the treatments only. Significance was declared at P.05 unless noted otherwise. RESULTS During the experiment, some heifers were removed because of respiratory problems, injury, and failure to conceive after the fourth AI; therefore, 49 heifers were available for observations. The reasons for removal were independent of treatment. Also, heifers were not available for observation after freshening. The diets fed were consumed readily, and, by design, heifers fed E or NE consumed 15% Journal of Dairy Science Vol. 77, No. 1, 1994 more DM than did contemporary heifers fed N or EN. Body Growth from 3 to 12 Mo of Age A summary of data for BW, body size, and BCS from 3 to 12 mo of age is shown in Table 2. At 6, 9, and 12 mo of age, heifers fed E were heavier than those fed N. At 9 and 12 mo of age, heifers fed E had larger (P e.001) HG and higher BCS than heifers fed N. When heifers were 3 to 12 mo of age, BW changes were greater for heifers fed E than for heifers fed N. Changes in WH and BL from 6 to 9 and 9 to 12 mo of age were similar among treatments; however, during those same intervals, heifers fed E had greater changes in HG (P.001) and BCS than heifers fed N. When heifers were 3 to 12 mo of age, ADG was greater (P.OOl) for heifers fed E than for heifers fed N. In addition, heifers fed E had greater (P.01) changes in HG than heifers fed N. Changes in WH and BL did not differ. Body Growth from 12 to 24 Mo of Age A summary of the results from 15 to 24 mo of age is given in Table 3. When heifers were 15 mo of age, or 3 mo after the diets were switched, no differences were significant in any trait measured. At 18 mo of age, heifers fed NE were longer and had higher BCS (P <.01) than heifers fed EN. All other traits measured at 18 mo of age were similar. At 21 and 24 mo of age, heifers fed NE and heifers fed EN both had similar BW, but heifers fed NE had larger HG and higher (P.01) BCS than heifers fed EN. Between 12 and 15 and between 18 and 21 mo of age, heifers fed NE had a greater (P c.001) increase in BW than heifers fed EN. From 15 to 21 mo of age, heifers fed EN had greater changes in BL and greater (P e.01). increases in BCS than heifers fed NE. Heifers fed NE had greater (P <.001) increases in WH and HG only between 12 and 15 mo of age. Changes between 12 and 24 mo of age indicated that heifers fed NE had greater (P e.01) changes in BW, HG, and BCS and greater rates of BW gain than heifers fed EN. Pelvic Measurements Measurements between 12 and 24 mo indicated that heifers fed NE had greater changes

TABLE 2. Measurements of body size and BW from 3 to 12 mo of age for heifers fed either 100 or 115% of NRC (16) nutrient requirements.i Age J o d of Dairy Science Vol. 77, No. 1, 1994 e P 9 9: 3 mo 6mo 9 mo 12 mo E m N E N E N E N E Item (n =44) (n =45) (n =41) (n =43) (n =41) (n =43) (n =40) (n =42) 8 2 9 29 II h 9 E \o 6 w II 9 X X SE X X SE X X SE X X SE BW, kg 88.9 88.2 1.7 155.3 b 165.6 2.5 206.5 c 228.8 3.2 270.4 C 292.0 3.6 Wither height, em 85.0 84.2.4 IOU 101.2.5 109.6 1l0.6.6 115.0 117.0.8 Heart girth, em 104.2 104.1.9 124.4 126.1 1.0 137.lc 142.1.8 151.OC 163.5.8 Body length, em 92.3 91.4.9 109.9 1l1.9.9 123.1" 126.1.9 135.4 136.5.8 Body condition score 2.9 2.9.02 2.9-3.0.01 2.91' 3.1.03 "Differs (f> <.05) between diets within age. bdiffers (f> <.01) between diets within age. cdiffers (f> <.001) between diets within age. ISupplied 100% (N) or 115% (E) of NRC (16) requirements for energy, CP, Ca, P, and vitamins A and D for large dairy heifers gaining.7 kg/d. TABLE 3. Measurements of body size and BW from 15 to 24 mo of age for heifers fed either 100 or 115% of NRC (16) nutrient requirements. Age 15 mo 18 mo 21 mo 24 mo 8 i; NEI EN2 NE EN NE EN NE EN Item (n =40) (n = 42) (n = 40) (n = 42) (n = 35) (n = 40) (n = 27) (n = 32) X X SE X X SE X X SE X X SE BW, kg 350.0 346.3 40 413.2 407.2 4.7 490 477 5.0 548 535 7.0 Wither height, em 122.3 12U.7 126.2 125.2.5 130.0 129.4.5 133.1 132.3.5 Heart girth, em 166.7 165.6.8 176.8 175.2 1.0 188.2" 185.4.8 197.1" 192.4 1.2 Body length, em 147.6 146.7.8 156.5" 154.1.7 161.2 161.0.7 166.1 161.6 2.0 Body condition score 3.0 3.0.02 3.2 b 3.0.03 3.4 c 3.2.03 3.6b 3.5.05 "Differs (f> <.05) between diets within age. bdiffers (f> <.0I) between diets within age. cdiffers (f> <.001) between diets within age. ISupplied 100% of NRC (16) requirements for energy, CP, Ca, P, and vitamins A and D until 12 mo of age and then 115% of those requirements. 2Supplied 115% of NRC (16) requirements until 12 mo of age and then 100% of those requirements. NUTRIENT INTAKE AND HEIFER GROWTH

274 BORTONE ET AL. in pelvic area (P <.Ol).01) and distance between pin bones than heifers fed EN. Only at 18 mo rna of age did heifers fed NE have greater pelvic area than heifers fed EN (Table 4). Reproductive Traltr Traits Measurements of 20 heifers (randomly selected from each of the groups at 6 mo rna of age to determine pubertal age) at 12 mo rna of age indicated that WH, BL, pelvic area, and dis- distance between pin bones were similar for heif- heifers fed N and for heifers fed E. However, when diets were switched at 12 mo rna of age, heifers fed E were 22 kg heavier (P <.Ol),.01), had higher BCS, BeS, and had higher ram rates of BW gain than heifers fed N (Table 2). Measures of reproductive traits are summarized for those heifers in Table 5. Heifers fed EN were 23 d younger at onset of puberty than heifers fed NE. However, BW at puberty was similar for heifers fed EN and heifers fed NE (281 vs. 278 kg, respectively). The heifers fed EN had higher ADG from 3 rna mo of age until onset of puberty than heifers fed NE. However, age at ftrst first AI, BW at ftrst first AI, age at conception, BW at conception, and AI per conception were similar for both groups. Heifers fed NE had a higher (P < c.01) ADO ADG from onset of puberty to conception than heifers fed EN. Body Development DISCUSSION Data from our experiment indicated that, at 12 rna mo of age, heifers fed E and heifers fed N had BW and size comparable with that of heifers fed similar diets by Daccarett et al. (3). As expected, after the diets were switched at 12 rna mo of age, heifers fed NE gained more BW and increased more in WH and HG than heifers fed EN. These greater increases in BW and body size allowed heifers fed NE to overcome the advantage that heifers fed E had attained from 3 to 12 rna mo of age. The greater increases in BW, HG, BL, pelvic area, and distance between pin bones after the diets were switched likely were possible because dairy cattle have the genetic potential to grow to a large BW and size. This genetic potential can be expressed if the heifers are fed the neces neces- heifsary nutrients to meet their requirements for Journal of of Dairy Science Vol. 77, No.1, 1, 1994 'c; II. < 3 00 e,g.. 1.2 'c; j.[ J i :a i ị ;e -i i j til fil M I,gl 1>< II I "!,g 1>< M '" II I til fil N I II _,g I N 1;1 I (::I :8 '" ti I 1>< N,g 1>< til "1 fil N 00 1>< N I II.. "'!,g 1>< I II Vl -,g til fil N M 1>< '" 2: II I "'!,g 1>< (::II QI i::..s 0 11><! _ II I C!,g 1>< f.[ e II Vl co \0 t '" t '" ($, t o M J 8. 51 _tile etis'" j l 'c; til< - i ' o. [ ;l..s < 'c; '1 00 co- '> c i "'" ;l 6 ej"o. [on l:l - <) - '::1 I -... :I :I OC!I [[ :!: ' ' c "-' "-' B u u J '- ' '" 0 0 C! til< v 8 ii :.= :.:: IS: IS: is.. _ N

NUTRIENT INTAKE AND HEIFER GROWTH 275 TABLE 5. Body weight, age at puberty. and reproductive traits of heifers from each group for which treatments were switched at 12 mo of age. Tnatment Item NE' EN2 - - n3 X n X SE BW at Puberty, kg 18 278 17 281 7 Age at puberty,4 d 18 36or 17 337 7 ADG,5 kg/d 18.7DL 17.79.03 BW at Fit AI, kg 19 381 18 369 9 Age at first AI, d 19 484 18 469 15 BW at Conception. kg 19 3% 18 369 10 Age at conception, d 19 506 18 495 17 ADG.6 kgld 19.89b 18.68.05 'Differs (P <.a) between diets. bdiffers (P <.01) between diets. lsupplied 100% of NRC (16) requirements for energy, CP, Ca, P, and vitamins A and D until 12 mo of age and then 115% of those requirements. 2Supplied 115% of NRC (16) requirements for energy, CP. Ca, P. and vitamins A and D until 12 mo of age and then 100% of those requirements. 3Less than 20 because of sickness (not related to experimental tfeatmtnt) of one heifer and missing samples. 4Determimd by rise in serum progesterone 5Average daily gain from 3 mo of age until onset of puberty. 6Frorn puberty to conception. maintenance and growth. Although the data reported by Daccarett et al. (3) indicated that heifers fed >100% of NRC nutrient requirements were heavier and had more body size and development than their counterparts fed 100%. when >115% of NRC (16) requirements are fed, heifers may have had even more BW and size. Therefore, more research is needed to determine the amount of nutrients needed to permit full expression of the genetic potential for growth and development of heifers (without overconditioning) that has been achieved as a result of intensive selection through many generations. In contrast, the results showed that both groups grew to similar WH, in agreement with other reports (3, 13). Similar growth 0 by the heifers in our study and in a previous study (3) suggest an inherited maximal limit to which the heifers could grow or that the heifers had higher nutrient requirements for achieving their genetic potential for height than those provided by the 115% diet. At 24 mo of age, neither heifers fed NE nor heifers fed EN reached the same BW, WH, HG, and BL reported earlier (3) for heifers fed nutrients at 115% of NRC (16) requirements. This finding suggests that switching diets at 12 mo of age was not as desirable as maintaining the heifers on E from 3 mo of age until shortly before calving. Occurrence of dystocia in primiparous cows is primarily a function of pelvic area and size of the calf (1, 18). Larger pelvic area and greater distance between pin bones for heifers fed 115% of NRC requirements than for heifers fed 100% of NRC requirements were reported by Daccarett et al. (3). In addition, those heifers were heavier at 24 mo of age than heifers fed either NE or EN in our study. In contrast, heifers fed NE and heifers fed EN had similar BW, pelvic area, and distance between pin bones at 24 mo of age, which agrees with results of another study (9). in which internal and external measurements of body size at equal BW did not differ, even though growth rates were different among groups. Although rapid growth rates are desirable to produce heifers with adequate BW and size to accommodate breeding, conception, and calving at a young age, effects of high rates of BW gain may be negative when high energy diets are fed during the prepubertal period. Various studies (2, 7, 9, 21, 22) demonstrated that Journal of Drury Science Vol. 77, No. 1, 1994

276 BORTONE ET AL. fattening of dairy heifers during prepubertal growth and development decreased their future milk-producing ability.?his impairment in milk production was the result of fatty mammary glands with decreased milk secretory tissue (7). Our study agrees with results presented by Daccarett et al. (3) that heifers fed E from 3 to 12 mo of age (prepubertal) were in good condition, but not excessively fat (Table 2). When heifers were 24 mo of age (Table 3), BCS was higher for heifers fed NE than for heifers fed EN and similar to the recommended BCS of 3.5 (8). In contrast, Daccarett et al. (3) reported a BCS of 3.47 at 24 mo of age for the heifers fed diets at >lo02 of NRC (16) requirements from 3 mo age until shortly before freshening. Overconditioned heifers are not desirable at calving, because cows can have poor appetite (lo), greater BW losses during lactation (4), lower milk production (10). dystocia (1, 18). and metabolic disorders, such as fat cow syndrome (15). Reproductive Performance Daccarett et al. (3) reported that heifers fed diets at >loo% of NRC (16) requirements were 7 wk younger at first AI than heifers fed 100% of NRC requirements (58 vs. 65 wk, respectively). In contrast in our study, age at first AI occurred at 67 and 69 wk of age for heifers fed NE and heifers fed EN, respectively, and age at conception was similar (71 and 72 wk of age) for heifers fed NE and heifers fed EN, respectively. The negative effect of switching diets at 12 mo of age also was evident for age at first AI and age at first conception and was more detrimental to the heifers fed E than heifers fed N. If heifers fed E had been maintained on the same diet throughout the experiment, as they were in the previous study (3h they should have reached the target breeding BW of 350 kg at about 14 mo of age, thus allowing them to conceive at an earlier age. The number of AI per conception was similar for heifers fed NE and heifers fed EN (1.40 vs. 1.55, respectively) and agree with the results of Daccarett et al. (3). CONCLUSIONS Neither of the two programs used in this study showed any advantage in BW, body size, Journal of Dairy Science Vol. 77, No. 1, 1994 or age at conception of heifers compared with those used in the study by Daccarett et al. (3). Therefore, we recommend that program (3) for feeding Holstein replacement dairy heifers. REFERENCES 1 Bellows, R. A,, D. C. Anderson, and R. E. Short. 1971. Recalving body size and pelvic area relationships associated with calving difficulty. J. Anim. Sci. 33:455. 2 Brannang, E.. and G. Lindkvist. 1978. Rearing intensity, calving age and milk yield. A series of twin studies. Rep. No. 24. Swedish Univ. Agric. Sci.. Dep. Anim. Breed. Genet., Uppsala, Sweden. 3Daccaretf M. G., E. I. Bortone. D. E. Isbell, J. L. Mod. and A. M. Feyerherm. 1993. Performance of Holstein heifers fed 100% or more of National Research Council requirements. J. Dairy Sci. 76:606. 4Davenport, D. G.. and A. H. Rakes. 1969. Effects of prepartum feeding level and body condition on the postpartum performance of dairy cows. J. Dairy Sci. 52:1037. 5Dutrow. N. A.. C. R. Siemens, A. J. Gallegos, M. G. Daccarett, E. J. Bortone, J. E. Shirley, and J. L. Momll. 1991. Fvst lactation performance of Holstein heifers fed 1005% or 115% of NRC requirements from 3 months of age to calving. J. Dairy Sci. 7qSuppl. 1): 213.(Abstr.) 6Edmonson. A. J.. 1. J. Lean, L. D. Weaver, T. Farver, and G. Webster. 1989. A body condition scoring chad for Holstein dairy cows. J. Dairy Sci. 72:68. 7Foldager. J., and K. Sejrsen. 1987. Mammary gland development and milk production in dairy cows in relation to feediig and hormone manipulation during rearing. Page 102 in Cattle Production. Danish Status and Perspectives. Lanhusholdningsselskabets Forlag. Copenhagen, Denmark. 8Fmrr1, M. J., and D. Croxton. 1978. The use of condition scoring in dairy cows and its relationship with milk yield and live weight. Ani. Prod. 273285. 9 Gardner, R. W., J. D. Schuh, and L. G. Vargus. 1977. Accelerated growth and early breeding of Holstein heifers. J. Dairy Sci. 601941. logarnsworthy, P. C., and J. H. Topps. 1982. The effect of body condition of dauy cows at calving on their food intake and performance when given complete diets. Anim. Rod. 35:113. 11 Gill, G. S., and F. R. Allah. 1976. Relationship of age at first calving, days open, days dry and herd life to a pmfit function for dairy de. J. Daily Sci. 59: 1131. 12Hanison, R. D., J. P. Reynolds, and W. Little. 1983. A quantitative analysis of v. glands of dairy heifers Itand at different rates of hve weight gain. J. Dairy Res. 50405. 13Kem A. F.. L. R. Rewitt, and 1. M. Balla. 1987. Increased weight gain and effects on growth parameters of Holstein heifer calves from 3 to 12 mo of age. J. Dairy Sci. 701612. 14Lin, C. Y., A. J. McAUistcr, T. R. Baa A. J. Lee, G. L. Roy, J. A. Vesely. J. M. Wauthy, and K. A. Winter. 1986. Production and reproduction of early and late

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