Feedlot Growth Research Articles

Consequences of prenatal and preweaning growth for feedlot growth, intake and efficiency of Piedmontese- and Wagyu-sired cattle

Consequences of low (mean 28.0 kg, n = 77) and high (mean 38.4 kg, n = 77) birthweight followed by slow (mean 548 g/day, n = 75) or rapid (mean 859 g/day, n = 79) growth to weaning for feedlot growth, intake and efficiency from 26 to 30 months of age were determined in Wagyu × Hereford (n = 81) and Piedmontese × Hereford (n = 73) cattle. Cattle were selected for study based on birthweight and preweaning growth rate, from multi-modal distributions achieved by imposition of low or high maternal nutrition during pregnancy and lactation, with the objective of achieving as close as possible to a 30% difference in birthweight and a 2-fold difference in preweaning growth rate between progeny groups. High birthweight cattle entered the intake test 57 kg heavier, grew 100 g/day more rapidly, and ate 1.0 kg dry matter /day more than the low birthweight cattle. The high birthweight cattle tended to have a higher feed conversion ratio than low birthweight cattle, but net feed intake did not differ due to birthweight group. Cattle grown rapidly to weaning entered the intake test 29 kg heavier, grew at an equivalent rate, and ate 0.7 kg dry matter/day more than the cattle grown slowly to weaning. No differences in feed conversion ratio or net feed intake were observed between the preweaning groups. When assessed at the same liveweight, differences in dry matter intake and/or feed conversion ratio due to birthweight or preweaning growth were no longer apparent. Interactions between prenatal and preweaning growth, or between sire genotype and early-life growth, were not evident for feedlot growth, intake or efficiency. It is concluded that severely restricted growth during prenatal life or from birth to weaning results in cattle that are smaller and consume less feed at the same age as their well grown counterparts; however, long-term effects of growth during early life on efficiency of utilisation of feed are not evident.

Mississippi Cattle Producers Gain Insight into Temperament Effects on Feedlot Performance and Subsequent Meat Quality

The Mississippi Farm to Feedlot program has supplied producers with information about feedlot cattle performance since 1993. To add to this information, the effects of temperament score on feedlot growth performance and subsequent carcass value were evaluated. Steers consigned to the Farm to Feedlot program in 2004 were evaluated for temperament in a cattle restraint chute [chute scores (CS) ranged from 1 = calm and no movement to 5 = rearing, twisting, or struggling] and for pen temperament [pen score (PS) ranged from 1 = nonaggressive, docile, not excited by humans or facilities to 5 = very aggressive, excitable, runs into fences and toward humans]. Analyses were conducted to determine the effects of feed group and farm of origin and correlations of exit velocity (EV) and chute and pen temperament with feedlot performance. Exit velocity and PS were positively correlated (r = 0.70; P < 0.0001). Farm of origin had a direct effect on PS, CS, and EV. Sire breed had an effect on CS, PS, EV, pay and final weight, total gain, ADG, hot carcass weight, and USDA QG and YG. Medicine costs, days treated, and net profits were influenced by PS and EV. As EV increased, final BW, total gain, and ADG decreased (P < 0.05). As EV increased, there was a tendency for net returns to decrease and the number of days treated to increase (P < 0.07). These results indicate the importance of educating beef cattle producers on cattle temperament and its relationship to cattle feeding production and economic measures.

Effects of calcium magnesium carbonate and roughage level on feedlot performance, ruminal metabolism, and site and extent of digestion in steers fed high-grain diets1,2

A feedlot growth performance experiment and 2 metabolism experiments were conducted to evaluate dietary roughage concentration and calcium magnesium carbonate in steers fed a high-grain diet. In Exp. 1, one hundred ninety-two crossbred yearling steers (320 +/- 10 kg of initial BW) were fed diets based on steam-flaked corn with 0, 0.75, or 1.5% CaMg(CO(3))(2). There were no effects (P > or = 0.13) on ADG, DMI, G:F, or total water intake due to CaMg(CO(3))(2). In Exp. 2, five ruminally and duodenally fistulated steers (263 +/- 9 kg of initial BW) were used in a 5 x 5 Latin square design, with 5 dietary treatments arranged in a 2 x 2 + 1 factorial: 1) 3.8% dietary roughage and no CaMg(CO(3))(2); 2) 7.6% dietary roughage and no CaMg(CO(3))(2); 3) 11.4% dietary roughage and no CaMg(CO(3))(2); 4) 3.8% dietary roughage and 1.5% CaMg(CO(3))(2); and 5) 7.6% dietary roughage and 1.5% CaMg(CO(3))(2). Water consumption was less (quadratic, P = 0.003) when 7.6% dietary roughage was fed compared with 3.8 or 11.4% dietary roughage. Intake of DM was not affected (P > or = 0.16) by dietary roughage or by CaMg(CO(3))(2). Poststomach and total tract starch digestion decreased (linear, P < 0.01) as dietary roughage increased. Ruminal pH tended (P = 0.08) to increase as dietary roughage increased but was not affected (P = 0.60) by CaMg(CO(3))(2). In Exp. 3, DMI and ruminal pH were continuously monitored in a 6 x 6 Latin square design using 6 ruminally and duodenally fistulated Holstein steers (229 +/- 10 kg of initial BW). A 3 x 2 factorial treatment structure was utilized, with factors consisting of dietary roughage concentration (4.5, 9.0, or 13.5%) and CaMg(CO(3))(2) inclusion (0 or 1.0%) to replace MgO and partially replace lime-stone. A dietary roughage x CaMg(CO(3))(2) interaction (P = 0.01) occurred as steers consuming 13.5% roughage, 1.0% CaMg(CO(3))(2) had greater DMI per meal than those consuming 4.5% dietary roughage, no CaMg(CO(3))(2) and 9.0% dietary roughage, 1.0% CaMg(CO(3))(2). Steers consuming 13.5% dietary roughage, 1.0% CaMg(CO(3))(2) and 9.0% dietary roughage, no CaMg(CO(3))(2) had greater meal length (min/meal; P = 0.01) than steers consuming 4.5% dietary roughage, no CaMg(CO(3))(2). Total tract OM digestibility decreased linearly (P = 0.01), and ruminal pH increased linearly (P = 0.01) with increasing dietary roughage concentration. Inclusion of CaMg(CO(3))(2) can replace limestone and MgO but did not produce ruminal pH responses similar to those observed by increasing dietary roughage in high-concentrate diets.

Primary genome scan to identify putative quantitative trait loci for feedlot growth rate, feed intake, and feed efficiency of beef cattle1

Feed intake and feed efficiency of beef cattle are economically relevant traits. The study was conducted to identify QTL for feed intake and feed efficiency of beef cattle by using genotype information from 100 microsatellite markers and 355 SNP genotyped across 400 progeny of 20 Angus, Charolais, or Alberta Hybrid bulls. Traits analyzed include feedlot ADG, daily DMI, feed-to-gain ratio [F:G, which is the reciprocal of the efficiency of gain (G:F)], and residual feed intake (RFI). A mixed model with sire as random and QTL effects as fixed was used to generate an F-statistic profile across and within families for each trait along each chromosome, followed by empirical permutation tests to determine significance thresholds for QTL detection. Putative QTL for ADG (chromosome-wise P < 0.05) were detected across families on chromosomes 5 (130 cM), 6 (42 cM), 7 (84 cM), 11 (20 cM), 14 (74 cM), 16 (22 cM), 17 (9 cM), 18 (46 cM), 19 (53 cM), and 28 (23 cM). For DMI, putative QTL that exceeded the chromosome-wise P < 0.05 threshold were detected on chromosomes 1 (93 cM), 3 (123 cM), 15 (31 cM), 17 (81 cM), 18 (49 cM), 20 (56 cM), and 26 (69 cM) in the across-family analyses. Putative across-family QTL influencing F:G that exceeded the chromosome-wise P < 0.05 threshold were detected on chromosomes 3 (62 cM), 5 (129 cM), 7 (27 cM), 11 (16 cM), 16 (30 cM), 17 (81 cM), 22 (72 cM), 24 (55 cM), and 28 (24 cM). Putative QTL influencing RFI that exceeded the chromosome-wise P < 0.05 threshold were detected on chromosomes 1 (90 cM), 5 (129 cM), 7 (22 cM), 8 (80 cM), 12 (89 cM), 16 (41 cM), 17 (19 cM), and 26 (48 cM) in the across-family analyses. In addition, a total of 4, 6, 1, and 8 chromosomes showed suggestive evidence (chromosome-wise, P < 0.10) for putative ADG, DMI, F:G, and RFI QTL, respectively. Most of the QTL detected across families were also detected within families, although the locations across families were not necessarily the locations within families, which is likely because of differences among families in marker informativeness for the different linkage groups. The locations and direction of some of the QTL effects reported in this study suggest potentially favorable pleiotropic effects for the underlying genes. Further studies will be required to confirm these QTL in other populations so that they can be fine-mapped for potential applications in marker-assisted selection and management of beef cattle.

Association of Implanting Abnormalities with Growth Performance of Feedlot Steers

<h2>Abstract</h2> Crossbred steers (n = 1, 183, mean initial BW=320 ± 33 kg) were used in an observational study to determine associations between implanting abnormalities and feedlot growth performance. Initial implant status (determined by palpation) was recorded during administration of a terminal implant. Status of the terminal implant was recorded 21 d after reimplant, post-mortem in a packing plant, and post-mortem in a laboratory. At each of the four examinations, implants were classified by palpation as either: 1) normal, 2) abscessed, 3) bunched pellets, 4) separated pellets, 5) partial retention, 6) total failed retention, 7) placed in the cartilage, 8) placed in the inner 1/3 of the ear, or 9) fluid-filled. Least square means for ADG were determined for both the initial period (d 0 to 59) and the terminal period (d 60 to harvest) using initial BW, reimplant BW, pen, health status, liver status, lung status, and implant status as covariates. Average daily gain for the initial period did not differ (P>0.40) across implant status. In the overall model, there was a trend (P<0.10) for d 60 to harvest ADG to be affected by implant status. In pair-wise least square means comparisons of implant defects, only missing implants, compared with normal implants or abscessed implants, showed less gain (P<0.05) in both laboratory and packing plant palpation models.

Interaction of protein nutrition and laidlomycin on feedlot growth performance and digestive function in Holstein steers.

Two isonitrogenous diets (12.5% CP) containing 20 (20% NPN) or 40% (40% NPN) of the N as nonprotein N were evaluated with 0 or 10 mg laidlomycin propionate (LP)/kg in a 2 x 2 factorial arrangement. Changes in dietary NPN:N ratio were developed by partial substitution of urea N for fish meal N. In Trial 1, four Holstein steers (349 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on digestive function. Total tract OM digestion was slightly greater (1.2%, P < .10) for diets containing 20% of N as NPN, due to greater (3.4%, P < .05) postruminal OM digestion. Supplemental LP decreased passage of microbial N to the small intestine (7.4%, P < .10) and ruminal degradation of dietary CP (DIP, 8.1%, P < .10). Decreasing the NPN:N ratio decreased microbial N flow to the small intestine (7.5%, P < .10) and DIP (15%, P < .01) and increased (6%; P < .05) the flow of indispensable amino acids to the small intestine. Supplemental LP increased (P < .10) ruminal pH. There were no treatment effects (P > .10) on ruminal molar proportions of acetate or propionate. In Trial 2, 120 Holstein steers (122 kg) were used to evaluate treatment effects on growth performance. Decreasing the NPN:N ratio increased ADG (P < .01) by 36, 40, and 16%, respectively, for the initial three 56-d periods of the trial. Overall, ADG was 17% greater (P < .01) for cattle consuming diets containing 20 vs 40% NPN. Decreasing the NPN:N ratio increased (P < .01) gain efficiency by 17 and 14%, respectively, for the initial two 56-d periods. Overall, gain efficiency was 6% greater (P < .01) for diets containing 20% NPN. Dietary NPN:N ratio did not influence (P > .10) the NE value of diets. Supplemental LP did not affect DMI (P > .10) but increased ADG (6%, P < .01) and gain efficiency (5%, P < .05) and decreased (11%, P < .05) the maintenance energy requirements. Protein nutrition limited growth performance of calves receiving the 20% NPN diets during the initial 112 d of the trial. With the 40% NPN diets, protein nutrition limited growth performance throughout most of the trial (d 1 to d 224). We conclude that LP will enhance daily weight gain and gain efficiency of calf-fed Holstein steers. Conventional urea-based diets will not diminish response to LP, although they may not meet the metabolizable amino acid requirements of calf-fed Holsteins during the first three-quarters of the feeding period.

Effects of feeding two microbial additives in sequence on growth performance and carcass characteristics of finishing heifers (2000)

Four hundred fifty heifers (846 lb) were used in a 126-day experiment to investigate the effects of feeding two microbial additives, Lactobacillus acidophilus BG2FO4 (MicroCell) and Propionibacterium freudenreichii P-63 (MicroCell PB), alone or in sequence, on feedlot growth performance and carcass characteristics. A 21-day step-up period preceded heifers being placed on a final finishing diet containing 10% corn silage, 42% steam-flaked corn, 42% high-moisture corn, 3% soybean meal, and 3% mineral supplement. Premeasured amounts of microbial additive were mixed with water before being mixed directly with the total ration. Treatments consisted of 1) no microbial additive; 2) MicroCell for the entire period; 3) MicroCell PB for the entire period; 4) MicroCell for 28 days then MicroCell PB for the remainder of the period; and 5) MicroCell PB for 28 days then MicroCell for the remainder of the period. Feeding MicroCell for 28 days and then MicroCell PB for the remainder of the feeding period resulted in significant improvements (P<.10) in daily gain and feed efficiency.

Interaction of dietary calcium and supplemental fat on digestive function and growth performance in feedlot steers.

Four Holstein steers (261 +/- 2 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square experiment to evaluate the interaction of dietary Ca (.45 vs. 90%) and supplemental fat (0 vs 5% yellow grease) on characteristics of digestion. There were no treatment interactions (P > .10). Supplemental Ca did not influence (P > .10) digestibility of OM, NDF, starch, N, and fatty acids. Supplemental fat decreased ruminal (21%, P < .05) and total tract (3%, P < .01) digestibility of OM and ruminal (25%, P < .10) and total tract (20%, P < .01) digestibility of NDF. Supplemental fat increased (P < .10) ruminal microbial efficiency. Ruminal free Ca was not affected (P > .10) by Ca intake but was closely associated with ruminal pH and fatty acid intake (R2 = .84). Apparent ruminal Ca absorption was generally negative, being increased (P < .05) by Ca supplementation and decreased (P < .10) by fat supplementation. Postruminal (P < .05) and total tract (P < .01) apparent Ca absorption was increased by Ca supplementation. Supplemental fat did not influence (P > .10) postruminal or total tract Ca absorption. One hundred forty-four medium-frame crossbred steers were used to evaluate treatment effects on feedlot growth performance. There were no treatment interactions (P > .10). Increasing dietary Ca did not influence (P > .10) steer performance. Supplemental fat decreased (P < .01) DMI and increased NE value of the diet (P < .01). It is concluded that increasing dietary Ca from .45 to .9% in high-grain finishing diets will not affect the feeding value of supplemental fat and that high levels (5%) of supplemental fat will not have a detrimental effect on Ca absorption.

Effect of prenatal androgenization on performance, lactation, carcass, and sensory traits of heifers in a single-calf heifer system.

Twenty-four prenatally androgenized (PA) heifers, born to testosterone propionate-implanted cows, and 27 control (C) heifers, born to nonimplanted cows, were bred, calved, and placed in drylot pens, with calf at side, to assess the effects of PA on feedlot growth and lactational performance of heifers used in a single-calf heifer (SCH) system. Lactating heifers were fed an 85% concentrate diet, calves weaned at 117 d postpartum, and heifers slaughtered at a constant compositional end point of 1.1 cm of s.c. fat. Preweaning, PA heifers gained 22.5% faster (P < .01) and were 17.3% more efficient (P < .01) than controls. Prenatal androgenization of the heifer, however, did not affect calf growth performance. All calves gained more than 1.4 kg/d and had an average weaning weight of 159 kg at 117 d of age. Combining heifer-calf weights, PA and C pairs gained 2.88 and 2.53 kg/d, respectively. Correcting for DMI of calves, PA improved (P < .01) efficiency of beef production 10.8%. Four percent fat-corrected milk yield of PA and C heifers averaged 7.96 and 7.60 kg/d, respectively, and the percentage of milk protein and fat did not differ. Accounting for average BW, milk production, and DMI, PA and C lactating heifers should have gained 1.27 kg/d; however, gains were 137 and 127% of those predicted, respectively. Overall, pre- and postweaning, PA heifers required 10 fewer (P < .04) days on feed, gained 23% faster (P < .01), and were 16% more efficient (P < .02) than C heifers. At slaughter, PA and C heifers averaged 853 and 865 d of age, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Excessive Supplemental Fat on Feedlot Cattle Growth Performance and Digestive Function

Ninety medium-framed crossbred steers (245kg) were used in a 205-d feeding trial to evaluate the influence of 4, 8, and 12% supplemental fat (tallow soap stock) on feedlot growth performance. Increasing level of fat supplementation depressed ADG (P<.01), DM conversion (P<.01), and dietary NE (P<.05). Depressions in DM conversion and dietary NE were more marked at the 12% level of fat supplementation. There was a quadratic effect (P<.01) of level of fat supplementation on DM intake, with intake being higher for 12% supplemental fat than for 8% supplemental fat. Observed:expected diet NEm was 1.00 with 4% supplemental fat and declined (P<.01) to .86 with 12% supplemental fat. The NEm of tallow soap stock declined in a near rectilinear fashion from 5.65 Mcal/kg at the 4% level of supplementation to 2.85 Mcal/kg at the 12% level of supplementation. Six Holstein steers (296kg) with T cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on digestive function. Ruminal digestion of OM (P<.01), feed N (P<.01), and ADF (P<.05) decreased linearly with increasing level of fat supplementation. Most (55%) of the decline in ruminal OM digestion could be directly attributed to ruminal indigestibility of dietary fat. Increasing level of fat supplementation did not influence (P>.10) postruminal digestion of OM, ADF, starch, and N. Postruminal digestion of lipid decreased (P<.01) with increasing level of fat supplementation. Total lipid intake was a better predictor of postruminal lipid digestibility than percentage supplemental fat. True digestibility of supplemental tallow soap stock at the 8 and 12% levels of supplementation averaged 63 and 40%, respectively. Total tract OM digestion declined linearly (P<.01) with increasing level of supplemental fat. This decline was due to differences in lipid digestion. There were no associative effects of supplemental fat on total tract digestion of ADF, starch, and N. It is concluded that optimal growth performance response to supplemental fat will be obtained when levels of total lipid intake are less than 1.6g/kg body weight. Detrimental effects of excessive supplemental fat are primarily associated with depressed intestinal lipid digestibility.

Influence of Levels of Supplemental Urea on Characteristics of Digestion and Growth Performance of Feedlot Steers Fed a Fat-Supplemented High-Energy Finishing Diet

Four Holstein steers (382kg) with cannulas in the rumen and proximal duodenum were used in a 4×4 Latin square experiment. Treatments consisted of 90% concentrate (steam-flaked cornbased) diet supplemented with either 5.5% soybean meal (SBM) or .8, 1.2, or 1.6% urea (dry matter basis). All diets contained 4% tallow. There were no treatment effects (P>.10) on ruminal pH and ammonia concentrations. Ruminal digestion of organic matter, acid detergent fiber, and starch tended to increase with supplemental urea level. There was a quadratic component (P<.10) to urea level effects on total tract dry matter and organic matter digestibility, being maximal with 1.2% supplemental urea. Total tract acid detergent fiber and starch digestion increased (P<.05) with urea level. Passage of nonammonia nitrogen, microbial nitrogen, and feed nitrogen were similar (P>.10) across treatments. Nonammonia nitrogen entering the small intestine/nitrogen intake decreased linearly (P<.05) with increasing level of urea supplementation. Thirty-two Holstein steers were used in a 4×4 Latin square experiment to evaluate treatment effects on feedlot growth performance. Experimental periods were 35 d in duration. There were no treatment effects (P>.10) on daily weight gain, dry matter intake, and diet net energy. Observed:expected net energy increased (P<.10) with increasing urea level. Urea can be efficiently utilized as the sole source of supplemental nitrogen in fat-supplemented highenergy finishing diets for feedlot cattle. Furthermore, feedlot cattle growth performance may be enhanced by supplementing diets with urea at levels beyond that necessary for maximal microbial growth.

Influence of processing on the feeding value of oats for feedlot cattle.

Ninety-six crossbred steers (312 kg) were used in a 118-d feedlot growth performance trial to determine the relative effects of degree of steam processing on the feeding value of oats in a 90% concentrate finishing diet. Treatments were 1) steam-flaked corn (SFC, density = .28 kg/L); 2) dry-rolled oats (DRO, density = .36 kg/L); 3) steam-rolled oats, coarse flake (SRO-C, density = .33 kg/L); and 4) steam-rolled oats, thin flake (SRO-T density = .17 kg/L). Feed intake was similar (P > .10) across oats treatments. However, ADG was lower (13.2%, P < .01) and feed/gain was higher (11.1%, P < .05) for SRO-T than for SRO-C diets. Diet NEm was 7.2% lower (P < .10) for SRO-T than for SRO-C diets. Daily weight gain was greater (9.3%, P < .01) and feed intake and feed/gain were lower (13.1 and 20.8%, respectively; P < .01) for SFC than for oats treatments. Diet NEm and NEg were higher (20.0 and 26.5%, respectively; P < .01) for SFC than for oats treatments. Dressing percentage was 2.5% lower (P < .01) in steers fed the oats diets than in those fed the SFC diet. Four Holstein steers (232 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square experiment to evaluate treatment effects on characteristics of digestion. Ruminal digestibility of OM, starch, and ADF were similar (P > .10) for oats treatments, averaging 58.2, 93.5, and 9.6%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of sodium bicarbonate and monensin on utilization of a fat-supplemented, high-energy growing-finishing diet by feedlot steers.

Two feedlot growth performance trials and a metabolism trial were conducted to evaluate the relationship between monensin (MON) and sodium bicarbonate (BICARB) supplementation on utilization of a high-energy diet by finishing steers. Two levels of MON (0 and 33 mg/kg of diet) and two levels of BICARB (0 and .75% DM) were compared in a 2 x 2 factorial arrangement of treatments. The basal diet contained 75% steam-flaked corn, 4% yellow grease, and 12% forage (DM basis). There were no interactions between supplemental BICARB and MON on feedlot growth performance or characteristics of ruminal and total tract digestion. With either crossbred or Holstein steers there were no treatment effects (P > .10) on ADG, DM intake, feed efficiency, or NE value of the diet. The BICARB did not influence (P > .10) ruminal or total tract digestion of OM, ADF, starch, and N, ruminal pH, or ruminal VFA molar proportions. Monensin decreased (6.6%, P < .10) ruminal OM digestion. However, differences in ruminal digestion were compensated for by increased (3.2%, P < .05) postruminal OM digestion. Effects of MON on total tract digestion of OM, ADF, N, starch and GE were small (P > .10). Monensin decreased ruminal molar proportions of acetate (5.3%, P > .10) and butyrate (29.4%, P < .05) and increased molar proportions of propionate (16.3%, P < .10). Coupled with reduced ruminal OM fermentation, the increase in molar proportions of propionate caused a decrease in ruminal methane energy loss and increased diet ME (2.7%, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of processing on the comparative feeding value of barley for feedlot cattle.

Ninety-six crossbred steers were used in a 172-d feedlot growth performance trial to determine the effects of type processing on the comparative feeding value of barley in a 90% concentrate finishing diet. Treatments were: 1) steam-flaked corn (SFC; density = .31 kg/L); 2) dry-rolled barley (DRB; density = .39 kg/L); 3) steam-rolled barley, coarse roll (SRB-C, density = .39 kg/L); and 4) SRB, thin roll (SRB-T, density = .19 kg/L). The ADG was similar (P > .10) across barley treatments, averaging 1.29 kg/d. Feed intake (P < .05) was lower for SRB than for DRB. Diet NE was greater (P < .05) for SRB than for DRB. Feed intake was lower (P < .05) for SFC than for barley diets. The influence of grain processing on characteristics of digestion was evaluated using four Holstein steers (average BW = 230 kg) with cannulas in the rumen and proximal duodenum. Ruminal and total tract digestibility of OM and starch were lower (P < .05) for DRB than for SRB. Ruminal and total tract digestibility of OM and starch were similar (P > .10) for SRB-C and SRB-T. However, passage of nonammonia N was markedly increased (26.9%, P < .01) with SRB-T compared with SRB-C. This increase in ruminal N efficiency was due partly to reduced ruminal degradation of feed N (23.4%, P < .01) and partly to increased microbial N synthesis (13.3%, P > .10). The comparative feeding value of DRB, SRB-C, and SRB-T in this study was 90, 92, and 96% the value of SFC, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Maternal breed of sire effects on postweaning performance of heifer and steer progeny: postweaning growth and carcass characteristics

Heifer and steer progeny of 2-yr-old first-cross (F1) heifers and 3- to 6-yr-old F1 cows, from Hereford dams and five sire breeds, were evaluated for postweaning feedlot growth and carcass composition. Breeds of sire of dam were Angus (A), Red Poll (RP), Tarentaise (T), Simmental (Sm), and Pinzgauer (P). Calves from 2-yr-old heifers were sired by Shorthorn, and calves from 3- to 6-yr-old dams were sired by Charolais. Breed of sire of dam was significant (P less than .05 to P less than .01) for total gain and final weight for female progeny from 2-yr-old dams. At all weights, Sm, P, and T ranked above A and RP. Progeny of A, P, Sm, and T F1 2-yr-old dams were not significantly different but were higher (P less than .05) than RP heifers in total feedlot gain. Breed of sire of dam was significant (P less than .05) for carcass weight and longissimus muscle area; T ranked highest and RP lowest. Breed was not significant for any growth traits of steer progeny of 2-yr-old dams. Breed was significant for marbling score; A ranked highest and exceeded (P less than .01) both RP and Sm steers. Breed was significant (P less than .05) for most growth traits in the heifer progeny of the 3- to 6-yr-old dams bred to Charolais sires. Heifer calves of the Sm group were heavier (P less than .05) than all other groups for most weights and total gain. For total gain, P and T were intermediate and A and RP lowest. For heifer carcass traits from 3- to 6-yr-old dams, breed was significant (P less than .05 to P less than .01) for carcass weight, longissimus muscle area, percentage of cutability, and estimated kidney, heart, and pelvic fat. Heifers from Sm-sired dams were heavier (P less than .05) than those from all other groups but ranked second to heifers from P for percentage of cutability. Marbling scores of RP heifer carcasses ranked highest of all groups. Breed was not significant (P greater than .05) for any of the weights or gains in steer progeny of 3- to 6-yr-old dams; however, the Sm and P groups ranked above A and RP for all feedlot test weights.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of ovariectomy and ovariectomy with ovarian autotransplantation on feedlot performance and carcass characteristics of heifers.

Feedlot growth performance and carcass characteristics were examined in 96 crossbred heifers of continental breeding. Heifers were assigned to four treatment groups: intact control, sham ovariectomized, ovariectomized, and ovarian autografted. Ovarian autografted heifers were bilaterally ovariectomized via a left flank incision and one ovary was bisected sagittally and implanted in the musculature of the flank. Animals were fed a diet based on corn silage and were slaughtered at a weight of about 450 kg. There was no effect of treatment on feedlot performance or objectively measured carcass traits. However, carcasses of ovariectomized and ovarian autografted heifers had lower maturity scores than carcasses of the intact and sham-ovariectomy heifers. Blood samples were collected monthly throughout the study. Progesterone concentrations in these samples indicated that approximately 20% of the ovarian autografted heifers exhibited ovarian cyclicity. Examination of the transplanted ovaries at slaughter indicated that approximately 20% of the transplanted ovaries were resorbed. Cavitated, fluid-filled, thick-walled structures that were considered to be luteinized follicles were the most prominent structures found on the transplanted ovary; these were found in one-third of the ovarian autografted heifers. These results indicate that an ovary transplanted to the musculature can remain viable; however, its physiological function is disrupted and it does not affect rate or efficiency of gain or carcass composition compared to ovariectomized heifers.

Epididymal sperm reserves in 12-month-old Angus and Hereford bulls: Effects of bull strain plus dietary energy

Bull calves ( n = 103) were obtained from two strains of Angus and two strains of Hereford cattle developed by selecting replacements on the basis of superior feedlot growth performance within breed on either high- or medium-energy diets. From weaning to slaughter at 12 months of age at the end of a 168-day growth performance test, bulls of one strain of each breed were fed the high-energy diet (80% grain +20% forage; 13.064 MJ/kg) and bulls of the second strain were fed the medium-energy diet (100% forage; 9.110 MJ/kg). At one year of age, Angus bulls had heavier ( P < 0.01) testes than Hereford bulls (409 vs. 330 g). Level of dietary energy did not affect paired testicular or paired epididymal weight. Compared with Hereford bulls, Angus had greater ( P = 0.06) cauda epididymal sperm reserves (4.9 × 10 9 vs. 3.6 × 10 9 spermatozoa). Bulls fed the medium-energy diet during the 168-day growth performance test and slaughtered at 12 months of age had 41% greater ( P < 0.05) caput-corpus epididymal sperm reserves (4.8 × 10 9 vs. 3.4 × 10 9 spermatozoa), 58% greater ( P < 0.01) cauda epididymal sperm reserves (5.2 × 10 9 vs. 3.3 × 10 9 spermatozoa), and 52% greater ( P = 0.01) total epididymal sperm reserves (9.9 × 10 9 vs. 6.5 × 10 9 spermatozoa) than bulls in the high-energy diet group. Thus, the sperm reserves of yearling Angus and Hereford bulls appear to be greater if bulls are selected and managed on a medium-energy rather than a high-energy diet.

THE GROWTH AND ECONOMIC PERFORMANCE OF PRECONDITIONED CALVES AND THEIR DAMS ON THE FARM AND OF CALVES IN THE FEEDLOT

A study was conducted to evaluate the effects of preconditioning beef calves. In 1982, each of two producers allocated 100 cow-calf pairs to the study while in 1983, 130 cow-calf pairs were included on Farm 1 and 151 on Farm 2. In 1982, approximately even numbers of cow-calf pairs were randomly assigned to either a preconditioning (PC) or a regular (RG) program. These same groups were maintained in 1983. The length of the period from early weaning to shipment (preconditioning period) was 30 d (PC30) in 1982 and either 30 or 42 d (PC42) in 1983. At the end of the preconditioning period, calves from both farms were shipped to the same feedlot for 68- and 95-d tests in 1982 and 1983, respectively. PC calves gained faster than RG calves during the preconditioning period in five of the six farms by year by treatment situations. Preconditioning calves for 42 d rather than 30 d had no effect on either preconditioning gain or farm to feedlot weight loss. The cost of preconditioning ranged from $29.65 to $38.77 head−1 for PC30 calves and from $41.95 to $49.08 head−1 for PC42 calves. The price differential required by the cow-calf producer to break-even on PC calves ranged from + 5.0C kg−1 for PC30 calves to + 11.0C kg−1 for PC42 calves. Weaning treatment had no effect on either pregnancy rate the following year or on calving interval. In 1982 RG calves gained 0.13 kg d− more in the feedlot than PC30 calves. In 1983 PC30, PC42 and RG calves gained similarly. Treatment for illness of PC30 calves during the feedlot phase was 13.7% lower than RG calves in 1982. In 1983, treatment rate was reduced 42.0% for PC30 calves and 60.6% for PC42 calves. Preconditioning for 42 d rather than 30 d had no effect on feedlot growth or health performance. Cost of gain was 5.0C kg−1 less for PC calves than for RG calves in both 1982 and 1983. Key words: Calves (beef), weaning (early), preconditioning, farm, feedlot

Testicular development, daily sperm production and epididymal sperm reserves in 15-mo-old Angus and Hereford bulls: effects of bull strain plus dietary energy.

Bull calves (n = 143) were obtained from two strains of Angus and two strains of Hereford cattle for which replacements were selected on the basis of superior feedlot growth performance on either high- or medium-energy diets. From weaning to slaughter at 15 mo of age, bulls were fed either the high-energy (80% grain + 20% forage) or medium-energy diet (100% forage) corresponding to their strain. Bulls in high-energy diet groups had a greater (P less than .05) scrotal circumference at 12 mo, but not 15 mo of age, than bulls in medium-energy diet groups. Compared with Hereford bulls, Angus had greater (P less than .01) scrotal circumference (36.1 vs 33.9 cm) and greater (P less than .05) paired testes weight (570 vs 464 g) at 15 mo of age. Daily sperm production per gram testicular parenchyma (DSP/g) was affected by strain-diet (P less than .01) but not by breed. Bulls in medium-energy diet groups had 12% greater DSP/g than did high-energy diet bulls (17.4 X 10(6) vs 15.5 X 10(6)). Daily sperm production (DSP) was 9% and 30% greater (P less than .01) for medium-energy diet bulls in 1980 (8.2 X 10(9) vs 7.5 X 10(9)) and 1981 (8.0 X 10(9) vs 6.2 X 10(9)), respectively, compared with high-energy diet bulls. The effect (P less than .01) of breed on DSP was attributed to breed differences in paired testes weight.(ABSTRACT TRUNCATED AT 250 WORDS)