Growth Of Steers Research Articles

Effects of different levels of fertilizer application to veld on growth of steers and chemical composition of the herbage

Effects of different levels of fertilizer application to veld on growth of steers and chemical composition of the herbage

Performance of Feedlot Steers Supplemented with Natural Protein or Urea During the Early Finishing Phase

Fifty-nine steers were used in a randomized block design to examine the effects of supplemental protein source on finishing steer growth performance and carcass characteristics. The four supplemental N treatments were: 1) urea (urea control), 2) solvent-extracted soybean meal (SBM), 3) expeller-processed soybean meal (SoyPLUS®; SP), and 4) dried brewers grains (DBG). The diets were isonitrogenous (13% CP dry matter basis) and fed for 84 d. From d 85 to 194, all steers were fed the urea-supplemented diet. Steers supplemented with natural protein compared to urea consumed 13% more feed (P<0.01) and gained 11% faster but the effect was not significant (P=0.20). Feed efficiency was not altered by treatment (P>0.10). There were no differences (P>0.10) in steer performance among natural protein sources. Previous supplemental N source did not affect (P>0.10) growth performance of steers after 84 d. Feed cost of gain for the DBG-supplemented diet was the highest (P<0.05). Steers fed supplemental true protein had heavier carcasses, but the difference was not detected statistically (P>0.10). The combination of competitive cost of gain and heavier carcasses for steers supplemented with SBM and SP resulted in average returns per head $9.23 and $15.79 higher than for steers supplemented with urea.

Effects of Compudose® and Rumensin®, alone or in combination, on the growth, and carcass and meat quality of steers finished on pasture

Rumensin® (monensin sodium) and Compudose® (oestradiol‐176) can both promote liveweight gain of pasture‐fed cattle. Limited information exists about their effects on carcass and meat quality characteristics or their combined effects on beef cattle performance. This study examined the effects of Rumensin (R) and Compudose (C), alone and in combination, on the growth, carcass characteristics, and meat quality of steers finished at pasture. Seventy‐two yearling steers (290 ± 4 kg) received either no treatment, R, C, or R+C for the 266‐day experimental period. C led to increased liveweight gain (P < 0.001) but R had no effect and the R x C interaction was not significant. Weight‐corrected height was lower (P < 0.05) in Compudose‐treated cattle. R had no significant effect on any carcass or meat quality traits and no interactions with C were found. Compudose treatment increased carcass weight (P < 0.001) and dressing‐out percentage (P < 0.05), and decreased kidney + pelvic fat weight (P < 0.005) and side length (P < 0.01). Compudose decreased M. longissimus ultimate pH (P < 0.001) and increased meat brightness L* (P < 0.05), but Warner‐Bratzler peak shear values were higher (P < 0.05) in meat of the C group. It is concluded that R has little effect on growth, or carcass or meat characteristics of steers at pasture, and that it has no influence on the way C affects these characteristics.

The effect of immunization against somatostatin and β-agonist administration alone and in combination on growth and carcass composition in young steers

AbstractThe effect of active immunization against somatostatin and β-agonist administration alone and in combination on growth, carcass composition and endocrine responses was investigated in young steers given a pelleted diet of dried grass and barley (0·7: 0·3) ad libitum for 16 weeks. Immunization alone increased growth rate by proportionately 0·10 but had no effect on plasma growth hormone (GH) or insulin-like growth factor-1 (IGF-1) concentrations (P &gt; 0·10). Carcass protein content was unchanged but fat content tended to be increased. This was possibly associated with increased (P &lt; 0·10) plasma insulin concentrations observed in these animals. Cimaterol administration significantly increased growth rate (P &lt; 0·05) and carcass weight (P &lt; 0·01). Carcass protein content was significantly (P &lt; 0·01) increased and carcass fat was significantly (P &lt; 0·001) reduced. Administration of cimaterol to immunized animals resulted in an enhancement of the repartitioning effect of the pagonist although growth rates were intermediate between the separate treatments. The mechanism by which this was achieved is unclear. Plasma IGF-1 concentrations tended (P &lt; 0·10) to be lower in these animals compared with controls. Plasma insulin concentrations were also reduced (P &lt; 0·05) in these animals. Both immunized animals and those given cimaterol alone showed an increased GH response to a single intravenous injection of growth hormone releasing factor (GRF) (P &lt; 0·05). Animals given the combined treatment however showed a reduced response suggesting that the effects were not mediated through direct changes in GH secretion. The improved lean:fat ratio in the carcass was observed to be mediated through an enhancement of the lipolytic response to the /J-agonist with only small effects on protein accretion. It is suggested that immunoneutralization of somatostatin may increase the sensitivity of adipose tissue to lipolytic stimuli. This could occur through changes in the secretion of gastrointestinal or pancreatic hormones as a result of neutralization of the inhibitory influences of somatostatin. Further work is required to clarify these effects.

Inhibiting methane production in Brahman cattle by dietary supplementation with a novel compound and the effects on growth

Three experiments were conducted to determine the effects of dietary supplementation with a novel antimethanogenic compound (AM) on methane production and growth in Brahman (Bos indicus) steers. The compound was a chemical complex of bromochloromethane (BCM) and α-cyclodextrin, which is chemically stable when added to feed, thus overcoming the highly volatile nature of BCM. In these experiments the AM compound was administered to steers as a mixture with different feed supplements. In Expt 1 the effect on in vivo methane production of feeding steers the AM compound was determined using a confinement-type respiration chamber. Methane production of AM-treated steers (0 ± 2·4 mL/min) was lower (P &lt; 0·001) than that of control steers (205 ± 5·2 mL/min) over 28 days. In Expt 2 we determined the effect of AM treatment over 12 weeks on growth of steers fed on a low quality roughage diet. The most marked effect of AM treatment was reduced (P &lt; 0·01) voluntary roughage dry matter intake (DMI), and reduced (P &lt; 0·01) acetate : propionate molar ratio (A : P) in rumen fluid. Average daily liveweight gain (ADG) (0·22 ± 0·01 kg/day) and feed : gain ratio (F : G) (20·7 ± 1·46 kg DMI/kg liveweight) were not significantly affected by AM treatment. In Expt 3 we determined the effect of AM treatment over 10 weeks on growth of steers fed on a medium quality roughage diet, in steers that were either treated or not treated with a hormonal growth promotant (HGP; oestadiol 17β). AM treatment reduced (P &lt; 0·05) DMI below that of steers not treated with AM, whereas DMI was not significantly affected by HGP treatment. Both AM (P &lt; 0· 1) and HGP (P &lt; 0·05) treatments separately reduced A : P ratio in rumen fluid. AM treatment had no significant effect on ADG, whereas ADG of HGP-treated steers was higher (P &lt; 0·05) than that of steers not treated with HGP (0·76 ± 0·27 v. 0·60 ± 0·027 kg/day). F : G was reduced (P &lt; 0·01) by HGP treatment. F : G of both HGP-treated steers and those steers not treated with HGP was reduced (P &lt; 0·05) by AM treatment. We conclude that feeding steers with this novel AM compound enables the potent antimethanogenic properties of BCM to be realised under commercial conditions, and that prolonged use over 10–12 weeks is associated with an improved feed conversion efficiency in steers fed on better quality roughage diets.

Interrelationships of Forage and Steer Growth Dynamics on Wheat Pasture

Little information is available comparing animal performance or stocking stability for different wheat (Triticum aestivum L.) cultivars. Wheat is annually planted on 10 million ha in the Southern Great Plains. Our objective was to determine the effects of wheat cultivars with different forage production potentials on the seasonal and total productivity of steers. 'Lancota' and 'NK Pro 812'(NK 812) were planted in September 1987 and October 1988 at the W.T. Waggoner Ranch in north Texas. Hereford steers (Bos taurus L.), 220 to 233 kg. were grazed from November 1987 to May 1988 and December 1988 to April 1989. Seasonal and total forage production and disappearance were affected (p<0.05) by season and year. Cultivar did not affect forage production and disappearance. Steer average daily gain (ADG), gain head-1, and gain ha-1 were significantly affected by year, season, year X season, and cultivar X season interactions. Steer gain ha-1 was lower (p<0.10) in year 2 than year 1 for both cultivars. Both gain head-1 and gain ha-1 were lower (p<0.10) on NK 812 than Lancota in year 2. Season long gain ha-1 followed similar trends to gain head-1. A season X year interaction (p<0.05) occurred because NK 812 matured earlier and was less winter hardy than Lancota. Across years steer ADG increased with herbage allowance up to 27.3 kg 100 kg BW-1 Day-1 and further increases in herbage allowance had limited effect on steer ADG. Yearly variation in environmental conditions had greater effects on steer performance and forage production than cultivar.

How land condition alters plant-animal relationships in Australia's tropical rangelands

Changes in vegetation composition and land condition that occur in response to grazing in natural grassland systems may alter plant and animal production, but the relationships are poorly understood. This study examined the effect of a change in land condition on herbage and animal production in two tropical tallgrass regions of northern Australia. The contrasting land condition classes, selected along fence-lines separating paddocks with different grazing histories, were defined as: State I. Dominated by palatable tussock perennial grasses; State II. Less palatable tussock perennial grasses, annual grasses and forbs as the major species. State II produced considerably less herbage than State I. Cattle grazed the two land condition classes to achieve comparable utilisation rates over the range 5–60% utilisation in a number of 8 week seasonal grazing periods over 2 years. At both Charters Towers and Katherine, steer growth was greater in State II than in State I, most rapid in the early wet season and least in the late dry season, and greatest at low utilisation rates. Differences in liveweight gain due to land condition class were greatest at the lightest levels of utilisation. Owing to the differences in pasture productivity between land condition classes, comparable levels of utilisation were achieved by imposing contrasting stocking rates. Steer growth was higher from State II land at low stocking rates while at high stocking rates State I produced better liveweight gains. The greater liveweight gain by steers grazing State II at low stocking rates can be explained by better diet quality which was reflected in higher levels of faecal nitrogen. The proportion of C 3 species (forbs, native legumes, shrubs, eucalypt leaves) in the diet of animals grazing State II vegetation was about twice that of steers in State I. These C 3 species were considerably higher in nitrogen than the C 4 grasses at the end of the wet season. At high stocking rates, animals in the State II treatment had less available feed on offer, resulting in lower liveweight gains compared with State I. The likelihood of further deleterious changes to land condition and productivity occurring should management attempt to maximise production from State II land are high.

The effect of plane of nutrition and slaughter weight on growth and food efficiency in bulls, steers and heifers of three breed crosses

The effects of plane of nutrition and slaughter weight on the growth rate and food efficiency of cattle with a range of growth potentials and which had been reared on high-forage diets were examined using 236 Friesian, Limousin × Friesian and Belgian Blue × Friesian bulls, steers and heifers. They were reared under uniform management until 12 to 13 months of age and were then given a complete diet consisting of grass silage and concentrates (2:1 on DM basis) either ad libitum or at 80% of ad libitum intake. Bulls, steers and heifers were initially 394, 362 and 360 kg live weight. Representative groups were slaughtered initially and serially, bulls at 560, 610 and 660 kg live weight, steers at 510, 560 and 610 kg and heifers at 460, 510 and 560 kg. Reducing food intake reduced live-weight, carcass, lean and fat gains by 28, 27, 22 and 37%, respectively, the effect on lean gain being significantly greater in bulls than in steers or heifers. Responses in lean gain to increasing food intake were 5.1, 3.1 and 2.1 g/MJ metabolizable energy for bulls, steers and heifers, respectively. It is concluded that for animals reared on high-forage diets which sustained moderate growth rates during the growth phase and which were slaughtered at moderate levels of fatness, restricting dry matter intake during the finishing stage tended to reduce the efficiency of carcass gain and did not affect the efficiency of lean gain. There were significant interactions between plane of nutrition and the sex of the animals for rate and efficiency of lean gain, but there were no significant interactions between plane of nutrition and either slaughter weight or breed.

Compensatory growth and carcass quality in growth-restricted and refed beef steers.

Beef steers were fed in two phases 1) to determine the relative importance of changes in DMI, gastrointestinal tract fill, energy expenditures, and composition of gain in the compensatory growth phenomenon, 2) to compare the effects of growth restriction due to ad libitum consumption of a low-energy (low-concentrate) diet to those of limited intake of a high-energy (high-concentrate) feed, and 3) to examine changes in carcass composition and quality resulting from different types of growth restriction. During the growing phase (237 to 327 kg), steers were fed either a high- (C) of low- (F) concentrate diet. Diet F was available for ad libitum consumption (FA) and diet C was available either for ad libitum consumption (CA) or on a limited basis (CL) to match the live weight gains by the FA group. During the finishing phase (327 to 481 kg), all steers received diet C, either for ad libitum consumption (CA) or restricted (CL) to 70% of the intake by the corresponding CA steers. Backfat thickness was markedly reduced (P < .001) by final feed restriction (7.4 and 6.9 mm for CL-CL and FA-CL respectively), compared with CA-CA (12.6 mm). Backfat also was lower in CL-CA (11.6 mm, P < .10) and FA-CA (9.9 mm, P < .05) than in CA-CA steers. Conversely, marbling scores were similar among groups, except for the FA-CL steers, which had lower marbling scores than FA-CA and CL-CA steers (P < .05). Higher DMI following growth restriction were accompanied by increased rates of live weight (+54 and +27%) and empty body weight (EBW; +57 and +43%) gain for CL-CA and FA-CA steers, respectively, compared with CA-CA steers. Gain:feed (EBW basis) were improved in some restricted/refed groups (+30, +13, and +10%, for Cl-CA, CL-CM respectively CA-CA. Increased DMI played a major role in the compensatory gain response in both CL-CA and FA-CA groups. Maintenance requirement was reduced (-17%) in CL-CA and increased in the FA-CA group (+21%); both changes affected the magnitude of compensatory gain in those animals. In contrast, composition of gain had little or no effect on the compensatory gain response. Programmed feeding can be used to manipulate carcass quality, but low-concentrate feeding during the growing phase may impair overall feedlot performance.

The effect of nitrogen and protein supplementation on feed intake, growth and digestive function of steers with different Bos indicus, Bos taurus genotypes when fed a low quality grass hay

Two studies were undertaken at Grafton, NSW, to determine the effects of supplementing a subtropical hay diet with a mixture of non-protein nitrogen (urea) and protein (protected casein), on the feed intake and growth of 20 steers of four genotypes (Study I), and on the digestive and metabolic functions of 16 of the steers that were fistulated in the rumen (Study 2). All steers were reared in the one subtropical environment. They consisted of backcross Hereford (H) (H x BH), backcross F1 (BH x BH) and backcross Brahman (B x BH), all of 50% heterosis, and a first-cross F1 of 100% heterosis (BxH). Steers in both studies were confined in pens and offered a basal diet of chaffed pasture hay (digestibility 52f 1.4% and nitrogen [N] content of 6.1 � 0.2 g/kg dry matter [DM]) supplemented with minerals only (low N diet; 8 steers) or with urea or formaldehyde-treated casein and cottonseed meal (high N diet; 12 steers) for 49 days. There were eight steers, for each of the two diets in Study 2, which were fed for 30 days. There was a diet x genotype interaction (P &lt; 0-05) in the daily DM intake (DMI) of hay by steers in Study 1. The mixed N supplement increased ( P &lt; 0.05) DM1 (per kg liveweight) by 14% in HxBH and by 13% in BxBH steers, but there was no significant effect of the supplement on the DM1 of BxH and BHxBH steers. Daily liveweight change was increased (P &lt; 0.05) by the supplement from -30 to 250 (s.e.d � 40) g/steer and there was no significant difference between genotypes. N supplementation increased ( P &lt; 0.05) rumen volume (63 to 87 � 7.6 L) and fluid residence time (491 to 822 � 76.9 min) (P &lt; 0.05) in BHxBH steers, but the increases in other genotypes were not significant. Rumen ammonia concentration (30 to 61 � 3 7 mg N/L) and plasma urea concentration (56 to 94 � 6-0 g N/L) were increased (P &lt; 0.05) by supplementation. Total protozoa density in rumen fluid was greater (P &lt; 0.05) in BxBH than HxBH steers but did not differ significantly between supplemented and unsupplemented steers. The HxBH steers had the lowest density of small entodiniomorph protozoa when N-supplemented, which was less (P &lt; 0.05) than that in BxBH steers which had the greatest density. Supplementation increased (P &lt; 0.05) N retention but only B x BH steers had a positive N balance. These experiments indicated that there are some physiological differences between genotypes. The BxH genotype with the high hybrid vigour had a high DM1 on the low digestibility hay diet without the N supplements and it transferred more urea from the plasma pool to the gut. The backcross steers (HxBH and BxBH) had low DM1 which increased when supplemented. The high content B. indicus steers (BxBH) had positive net retentions of N, but the results indicated that rumen protected proteins may be more usefully fed to steers with a lower B. indicus content.

Fibrolytic enzymes improve growth of steers fed forage-based diets

Fibrolytic enzymes improve growth of steers fed forage-based diets

Growth-related hormones in plasma of bulls, steers and heifers given food with two different energy levels

AbstractConcentrations of growth hormone (GH), insulin-like growth factor (IGF-1), insulin and glucagon were determined in the plasma of growing bulls, steers and heifers (no. = 138 in total, German Simmental breed). The animals were offered either a high level or a low level of energy resulting in relatively high and low average daily gain. Trials were subdivided into two experimental series and started at approximately 3 months of age at an average live weight of 110 kg. The animals were slaughtered at different body weights from 200 to 510 kg (heifers) or 660 kg (bulls, steers). Blood samples (needle puncture) were collected at biweekly intervals. Frequent samples time-course analysis of GH were taken by catheter from nine animals in total. Concentrations of GH declined during growth in steers and heifers as well as in bulls in blood samples collected by means of a catheter. IGF-1 and insulin concentrations increased from the start of the trial onwards up to different ages among the groups. Concentrations of glucagon constantly decreased from the start of the trial until slaughter. Significant differences (P &lt; 0·05) in concentrations ofGH, IGF-1 and insulin could be observed between sexes and levels of nutrition, with the highest GH and IGF-1 levels in bulls followed by steers and heifers. In contrast insulin values were highest in heifers followed by steers and bulls. A high level of nutrition increased concentrations of IGF-1 and insulin in all sexes.

Growth and carcass characteristics of beef steers fed silage and different levels of energy with or without protein supplementation1

Fifty-six large-framed crossbred steers averaging 227 kg were used in an experiment including a growing period (24 wk) and a finishing period ending when the steers had approximately 4 to 10 mm of fat thickness (Canadian grade A1). Steers were individually fed and assigned to a completely randomized design with seven treatments for the growing period. From the end of the growing period until slaughter, all steers received the same basal diet. Half of the steers from each treatment used in the growing period received a supplement containing protein and the other half a supplement containing protein and fat. Treatments during the growing phase consisted of 1) timothy silage alone or mixed (on a DM basis) with 2) 7.5% molasses, 3) 15% molasses, 4) 7.5% canola meal, 5) 5.5% canola meal and 7.5% molasses, 6) 3.6% canola meal and 15% molasses, or 7) 15% canola meal. The total N intake from supplements 2, 5, or 6 was similar. Compared with silage fed alone, canola meal supplementation increased (P < .05) ADG, whereas molasses had no effect. Combining molasses and canola meal did not improve ADG compared with feeding only canola meal on an isonitrogenous basis. Canola meal supplementation compared with feeding only silage during the growing phase reduced (P < .05) days on feed, and molasses tended (P = .059) to reduce it. Carcass data were generally similar among treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of live-yeast culture and lasalocid supplementation on performance of growing–finishing steers fed alfalfa-silage, corn-silage and high-grain diets sequentially

Trials were conducted to determine the effect of supplementing feedlot diets with live-yeast culture (YC), lasalocid (LAS) or YC + LAS on intake, growth and carcass characteristics of steers. Dietary additives in either 96% corn-silage or 75% dry-rolled barley-based diets increased (P &lt; 0.05) final weights and carcass weights of steers. Key words: Yeast, lasalocid, steers, carcass quality, growth

Influence of carboxylic salts on silage conservation, and voluntary intake and growth of steers given lucerne silage

AbstractThree wilted silages (dry matter concentration of approximately 300 g/kg) were prepared from early-bloom lucerne which received no additive (MG-0), or was treated with a mixture of carboxylic salts (Maxgrass) at either 4 (MG-4) or 8 (MG-8) l/t fresh crop. Silages were stored in tower silos. Resulting silages were offeredad libitumto growing Holstein steers without supplementation. Untreated silage (MG-0) exhibited an extensive, predominantly lactic acid fermentation. The nitrogen (N) fraction was highly soluble, relative to the crop at ensiling. Silage fermentation and protein solublization were restricted by Maxgrass application. Maxgrass application reduced aerobic stability of silage removed from the upper third of silos but not of silage from the lower portion of silos. Apparent digestibility showed a quadratic response to level of Maxgrass application (P&lt; 0·05). Voluntary intake was not affected by Maxgrass addition (P&gt; 0·005) but intake of all silages was high (30 g/kg live weight (LW)). There was a positive linear response (P&lt; 0·05) in LW gain to Maxgrass application with gains of 0·74, 0·86 and 0·87 kg/day being achieved in steers given MG-0, MG-4 and MG-8 silages, respectively. Degradability of silage N determined in nylon bags in situ was unaffected by Maxgrass application. However, the immediately degradable N fraction was reduced by Maxgrass application (linear effect,P&lt; 0·001; quadratic effect,P&lt; 0·05). Benefits in animal performance due to Maxgrass application were attributed to improved N composition while restricted carbohydrate fermentation during ensiling was considered to be of secondary importance.

Effect of the addition of live yeast (Saccharomyces cerevisiae) on growth and carcass quality of steers fed high-forage or high-grain diets and on feed digestibility and in situ degradability.

The effects of adding yeast culture (Saccharomyces cerevisiae, 5 x 10(9) live organisms/g of growth medium) at 10 g/steer daily to three diets consisting of 75% alfalfa silage and 25% barley, 96% corn silage and 4.0% soybean meal, or 75% dry-rolled barley and 25% alfalfa hay on performance of growing and finishing steers and carcass characteristics, feed digestibility, and degradability in the rumen were determined. In separate trials over 2 yr, the performance of steers fed the three diets with no supplementary live yeast (control; C) or with live yeast (Y) was determined using 72 Hereford steer calves in eight pens each year in a randomized complete block design. The diets were fed sequentially and the steers were randomized before diets were switched. Each year at the end of the high-grain feeding segment of the trial, the steers were slaughtered when ultrasound backfat was such that the carcass would grade A1 or A2 (Canadian grades). The digestibility of feed DM, CP, and NDF of the three diets was determined sequentially using six and eight mature, ruminally cannulated steers in 2 yr, respectively. The degradation characteristics of the three diets in the rumen were determined using the nylon bag technique in two steers for each additive treatment. In the 1st yr, the feed efficiency of the corn silage diet was lower (P < .05) for C than for Y steers (5.9 vs 6.8). Differences (P < .05) were not observed between C and Y steers for any of the performance or carcass characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of growth and feed efficiency of steers fed barley and triticale diets

Steers fed triticale adapted to the diet more slowly than those fed barley, resulting in reduced overall feed intake (9.4 vs. 10.5 kg d−1, P = 0.08) and average daily gain (ADG) (1.3 vs. 1.5 kg d−1, P = 0.08). No difference was detected in feed:gain ratio (7.1 vs. 6.8, P = 0.65). The reduced ADG in the triticale-fed steers may be due to reduced feed intake and the longer time required to adapt. Key words: Barley, triticale, steers, intake, performance, growth

Effects of anabolic steroids on nitrogen metabolism and growth of steers fed corn silage and corn-based diets supplemented with urea or combinations of soybean meal and feathermeal2

The objectives of these experiments were to examine whether N retention and feedlot performance by steers administered estradiol 17-beta (E2) alone (metabolism study) or in combination with trenbolone acetate (TAB; feedlot study) could be enhanced by increasing dietary ruminal escape protein. For the metabolism study, 16 Angus steers (average weight = 308 +/- 5 kg) were used in a randomized block design experiment having a 2 x 4 factorial arrangement of treatments. Main factors were E2 administration and supplemental CP source. Steers were fed diets based on corn silage and corn (60:30 DM basis) and were supplemented with urea or three combinations of soybean meal (SBM) and feathermeal (Fth). Combinations and SBM and Fth (SBM:Fth) provided 75:25, 50:50, and 25:75 of supplemental CP on a N basis. Estradiol 17-beta increased (P < .05) N retention and decreased (P < .05) plasma urea N concentrations. Total tract N digestion decreased linearly (P < .05) as the proportion of Fth in the diet increased. However, N retention increased linearly (P < .05) with increased Fth. A CP source x E2 interaction (P < .05) was observed for N retention because retention increased linearly with increasing dietary Fth in cattle receiving E2 but was unaffected (P > .05) in control steers. A growth study was conducted using 128 crossbred steers (400 +/- 19 kg) that received no implant or a combination of E2 (Synovex) and TBA (Finaplix-S). Steers were fed diets containing 75% high-moisture corn, 15% corn silage, and 10% supplement (DM basis) for 84 d (heavy replicate) or 124 d (light replicate).(ABSTRACT TRUNCATED AT 250 WORDS)

The growth of phosphorus kinetics of steers grazing a subtropical pasture

The growth and nutrient balances of steers grazing predominantly buffel (Cenchrus ciliaris) grass pastures fertilized with phosphorus (P) at annual rates of 0, 2.5, 5 and 15 kg P ha-1 were studied in three different seasons. There were two additional treatments in which steers grazing the 0 and 2.5 kg P ha-1 treatments were supplied daily with phosphorus supplement at 5 g head-1 throughout the study. Liveweight gain was increased by P fertilization but not P supplementation. Over a period of 15 months, the steers grazing the 15 kg P ha-1 pastures gained 80 kg more than those on the unfertilized pastures. This was associated with a small increase in dry matter intake and larger increases in P and nitrogen (N) intakes. Generally, the apparent absorptions of N, P and calcium by the steers were positive. In each season, the P intake, dietary faecal P and endogenous faecal P were all higher in cattle grazing fertilized pastures. After making allowance for an underestimation of pasture intake, our estimates of P intake were considerably less than published requirements to sustain the liveweight gains recorded. Endogenous faecal P values (13-19 mg kg-1 liveweight) were lower and the efficiency of absorption (mean 76%) was significantly higher so that the P requirements of cattle grazing tropical pastures appear to be much lower than recently published values.

Evaluation of Bos indicus and Bos taurus straightbreds and crosses. I. Post-weaning growth of steers in different environments

Post-weaning growth of 186 steers comprizing straightbred Hereford (H x H) and Brahman (B x B), first-cross (B x H) and back-cross (H x BH and B x BH) was evaluated. The steers had been raised to weaning (8 months of age) by dams which grazed either high, medium or low quality pasture (pre-weaning pasture system) at Grafton, N.S.W. The steers were grown on pasture from time of weaning in one of three locations in New South Wales representing subtropical, temperate-good, and temperate-good to poor environments, and slaughtered when the average fat cover of the back-cross steers in each environment was 4-10 mm at the 12113th rib. Pre-weaning pasture system had a significant effect on post-weaning growth, with mean post-weaning (8-48 months of age) average daily gain (ADG) of steers from low (327� 8 g/day) being higher than that of steers from medium (304�6 g/day), which in turn, was higher than that of steers from high (276�9 g/day) quality pre-weaning pasture, indicating that steers from low and medium quality pastures exhibited compensatory growth. From 8 to 24 months of age, first-cross BxH steers had the highest ADG in all environments. The ranking of the other genotypes differed across environments. In the environment where growth rate was lowest (178 g/day for B x H), B x B and B x BH steers grew faster than H x H and H x BH steers; where growth rate was highest (584 g/day for B x H), the order was reversed; and where growth rate was intermediate (323 g/day for B x H), there were no significant differences in ADG among H x H, H x BH, B x BH and B x B steers. Steers from only two environments were retained after 24 months of age. Mean ADG from 8 to 36 or 48 months of age was not significantly different among straightbred and back-cross steers, but was lower than that for the first-cross steers. Genotype x environment interaction for liveweight at slaughter was not significant. First-cross B x H steers were 56 kg (11%) heavier (P &lt; 0.05) than back-cross steers, which in turn, were 37 kg (8%) heavier (P &lt; 0.05) than straightbred steers at slaughter.