EFFECTS OF DIETARY CALCIUM LEVELS ON GROWTH-PERFORMANCE AND DIGESTIVE FUNCTION IN CATTLE FED A HIGH-FAT FINISHING DIET

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1 EFFECTS OF DIETARY CALCIUM LEVELS ON GROWTH-PERFORMANCE AND DIGESTIVE FUNCTION IN CATTLE FED A HIGH-FAT FINISHING DIET R. A. Zinn, Y. Shen, R. Brjs, M. Montño, E. Alvrez, nd E. Rmirez Desert Reserh nd Extension Center, University of Cliforni, El Centro ABSTRACT: Sixty medium-frmed rossred yerling steers (395 kg) were used in 90-d feeding tril to evlute the effets of.5,.7, nd.9% C in high-ft (6%) finishing diet on growth-performne. Inresing dietry C level enhned ADG (liner effet, P <.10) nd feed effiieny (liner effet, P <.05). In oth ses, the ulk of the improvement ourred when C level ws inresed from.7 to.9%. There were liner (P <.05) nd qudrti (P <.10) omponents to C level effets on diet NE. As with ADG nd feed effiieny, responses to.5 nd.7% dietry C were similr. Inresing C level to.9% inresed diet NE nd m NE g y 6.5 nd 8.0%, respetively. There lso, were positive liner omponents (P <.10) to C level effets on dressing perentge nd rieye re. Ten Holstein steers (348 kg) with were used in rossover sign experiment to evlute the influene of.7 nd.9% dietry C on digestive funtion. Inresing C level resed ruminl digestion of OM (5%, P <.05), ADF (37%, P <.10), nd feed N (18%, P <.05), nd inresed ruminl miroil effiieny (12%, P <.10) nd ruminl N effiieny (14%, P <.01). Inresing C level enhned postruminl digestiility of OM (4%, P <.05) nd N (4%, P <.01). There were no tretment effets (P >.10) on totl trt digestion of OM, ADF, strh or N. The net effet of inresing C level ws greter postruminl sorption of OM (12%, P <.01), N (19%, P <.01) nd lipid (10%, P <.10). Inresing C level did not ffet (P >.10) either ruminl ph or solule C. Ruminl solule C (C mm) ws 2 losely ssoited with ruminl ph (R =.93). It is onlud tht dietry C levels greter thn.7% re neessry to hieve optiml performne of feedlot steers fed high-ft finishing diet. Introdution Numerous metolism trils hve indited tht when C is inresed in ft supplemented diets digestiility (usully fier) lso inreses (Gringer et l., 1961; Dvison nd Woods, 1963; Glrith et l., 1971; Glrith nd Miller, 1973; Jenkins nd Plmquist, 1982; Drkley et l., 1985). Unfortuntely, very little work hs een reported whih evlutes the influene of dietry C level on performne responses of feedlot ttle when fed high-ft finishing diets. Hth et l (1972) ompred intkes of 11, 22, 32, nd 52 g/d C in steers fed high-moisture orn-sed finishing diet ontining 0, 3 or 6% tllow. No intertions were oserved etween C level nd supplementl ft. Surprisingly, there were no tretment effets (C level or supplementl ft) on ADG or feed effiieny. Bok et l. (1991) ompred C intkes of 58 vs 87 g/d (.6 vs.9% C) in steers fed 90% onentrte (whet-sed) finishing diet ontining 3.5% tllow or soyen oil sopstok. An intertion ws oserved etween ft soure nd C level. With soyen oil sopstok, inresing C level inresed ADG (5%), with little differene in feed onversion. In ontrst, with supplementl tllow, inresing C level resed ADG (9%) nd feed effiieny (6%). Zinn nd Shen (1996) ompred.45 vs.90% C in rley-sed finishing diet ontining 0 vs 5% yellow grese. There ws no intertion etween dietry C nd the feeding vlue of supplementl ft. However, totl lipid intke in tht tril ws not extreme (6.8% of diet DM) The ojetive of this study ws to further evlute the influene of C levels in high-ft (11.1% of diet DM) finishing diet on growth-performne nd digestive funtion of feedlot steers. Experimentl Proedure Tril 1. Sixty medium-frmed rossred yerling steers (pproximtely 25% Brhmn reeding with the reminr represented y Hereford, Angus, Shorthorn, s

2 nd Chrolis reeds in vrious proportions) with n verge initil weight of 395 kg were used in 90-d feeding tril. The tril ws initited Otoer 15, Steers were loked y weight nd rndomly llotted to 15 pens equipped with utomti wterers nd fene-line feed unks. Tretments onsisted of three levels of dietry C;.5,.7, nd.9% of diet DM. Composition of experimentl diets re shown in Tle 1. Steers were implnted with Synovex-S (Syntex, Des Moines, IA). Diets were prepred t weekly intervls nd stored in plywood oxes loted in front of eh pen. Steers were llowed d liitum ess to dietry tretments. Fresh feed ws provid twie dily. Hot rss weights were otined from ll steers t time of slughter. After the rsses were hilled for 48 h the following mesurements were otined: 1) rieye musle re, tken y diret grid reding of the musle t the 12th ri; 2) suutneous ft over the rieye musle t the 12th ri tken t lotion 3/4 the lterl length from the hine one end; 3) kidney, pelvi nd hert ft (KPH) s perentge of rss weight nd 4) mrling sore (USDA, 1965). Energy retention (ER, meglories) ws rived from mesures of live weight (LW, kilogrms) nd ADG (kilogrms/dy) ording to the following eqution: Steers EG = (.0493LW )ADG (NRC, 1984). Net energy ontent of the diet for mintenne nd gin were lulted ssuming onstnt fsting het prodution (MQ) of lw Ml/d (Lofgreen nd Grrett, 1968). From estimtes of ER nd MQ, the NE m nd NE g vlues of the diets were otined y proess of itertion (Zinn, 1987) to fit the reltionship: NE = (.877NEm) -.41 (NRC, 1984). This tril ws g nlyzed s rndomized omplete lok sign experiment (Cohrn nd Cox, 1950). Tretment effets were tested for liner nd qudrti omponents y mens of orthogonl polynomils. Tril 2. Ten Holstein steers (348 kg) with "T" nnuls in the rumen nd proximl duonum (6 m from the pylori sphinter) were used in rossover sign experiment to evlute the influene of.7 nd.9% dietry C (tretments 2 nd 3 of Tril 1) on digestive funtion. A sl diet ws prepred whih ws the sme s tretment 1 (Tle 1), exept tht.5% hromi oxi ws dd s digest mrker. All steers reeived the sme sl diet in omintion with either.63 or 1.25% limestone (DM sis). The limestone ws hnd-mixed into the sl diet t the time of feeding. Steers were llowed d liitum ess to experimentl diets, with feed provid twie dily (0800 nd 2000). Orts were mixed with susequent feed llotments nd refed. Following 10-d tretment djustment period, duonl nd fel smples were tken from respetive steers twie dily over period of four suessive dys. The protool for smple olletion nd nlysis ws the sme s outlined y Zinn nd Shen (1996). Miroil orgni mtter (MOM) nd N (MN) leving the omsum were lulted using purines s miroil mrker (Zinn nd Owens, 1986). Orgni mtter fermented in the rumen (OMF) ws onsired equl to OM intke minus the differene etween the mount of totl OM rehing the duonum nd MOM rehing the duonum. Feed N espe to the smll intestine ws onsired equl to totl N leving the omsum minus mmoni N nd MN nd, thus, inlus ny endogenous ontriutions. Methne prodution ws lulted sed on the theoretil fermenttion lne for oserved molr distriution of VFA nd OM fermented in the rumen (Wolin, 1960). Endogenous urinry energy loss ws estimted s.63w kg.50 (rived from Brouwer, 1965 nd NRC, 1984). This tril ws nlyzed s rossover sign experiment s follows: Y = µ + A + P + T + E, where Y is ijk i j k ijk the response vrile, A is niml, P is period, T is tretment, nd E is residul error (Cohrn nd Cox, 1950). Implitions It is onlud tht dietry C levels greter thn.7% re neessry to hieve optiml performne of feedlot steers fed high-ft finishing diet.

3 Tle 1. Composition of diets (Trils 1 nd 2). Dietry lium, % Item Ingredient omposition, % of DM Alflf hy Sudngrss hy Stem-flked orn Soyen mel Light grese Cne molsses Limestone Dilium phosphte Ure Tre minerl slt Nutrient omposition, DM sis Ne m, Ml/kg NE g, Ml/kg CP, % Lipid, %

4 C, % P, % In Tril 2,.5% hromi oxi ws dd to the diets s digest mrker. Tre minerl slt ontined: CoSO 4,.068%; CuSO 4, 1.04%; FeSO 4, 3.57%; ZnO, 1.24%; MnSO 4, 1.07%; KI,.052%; nd NCl, 92.96%. Bsed on tulr vlues (NRC, 1984), exept for light grese (Zinn, 1988).. Tle 2. Influene of lium level on performne of steers fed high-ft finishing diet (Tril 1) Dietry lium, % Item SD Pens replites Dys on test Weight, kg Initil Finl ADG, kg DMI, kg/d d DM onversion Diet NE, Ml/kg Mintenne Gin Oserved/expeted diet NE Mintenne Gin Initil nd finl live weights redued 4% to ount for fill. Crss djusted finl weight. Liner effet, P <.10. d Liner effet, P <.05. e Qudrti effet, P <.10.

5 Tle 3. Influene of lium level on rss trits of steers fed high-ft finishing diet (Tril 1) Dietry lium, % Item SD Crss weight, kg Dressing perentge Rieye re Ft thikness, m KPH, % Mrling sore Retil yield, % Liver sess, % Liner effet, P <.10. Kidney, pelvi nd hert ft s perentge of rss weight. Cod: Minimum slight = 3, minimum smll = 4, et. Tle 7. Influene of dietry lium on ruminl VFA, molr proportions nd estimted methne prodution 4 h fter feeding (Tril 2) Dietry lium, % Item SD Ruminl VFA, mol/100 mol Aette Propionte Butyrte Methne prodution Methne, mol/mol gluose equivlent fermented.

6 Tle 4. Influene of lium level on hrteristis of OM, strh, ADF, N, nd lipid digestion (Tril 2) Dietry lium, % Item SD Steer replites Intke, g/d DM 6,819 6, OM 6,450 6, Strh 2,930 2, ADF N Lipid Ruminl digestion, % intke OM Strh ADF Feed N Miroil effiieny N effiieny Postruminl digestion, % leving omsum OM Strh ADF d N Lipid Totl trt digestion, % intke OM Strh ADF N

7 Tretments differ, P <.10. Tretments differ, P <.05. Miroil N, g/kg OM fermented. d Tretments differ, P <.01. e Duonl non-mmoni N/N intke. Tle 5. Influene of lium level on hrteristis of lium digestion (Tril 2) Dietry lium, % Item SD Clium, g/d Intke Leving omsum Fel exretion Apprent lium sorption, g/d Ruminl Postruminl Totl trt Tretments differ, P <.01. Tretments differ, P <.05. Tretments differ, P <.10. Tle 6. Influene of dietry lium level on ruminl ph nd solule lium onentrtion (Tril 2) Dietry lium, % Item SD Ruminl ph

8 2 h fter feeding h fter feeding h fter feeding Ionized lium, mm 2 h fter feeding h fter feeding h fter feeding