Effects of growth-promoting agents and season on yearling feedlot heifer performance

Angus x crossbred heifers (270 per trial) were used in an experiment conducted over one 105-d summer and one 104-d winter feeding period. Treatments were identical for each trial and included: 1) control, 2) estrogenic implant (E), 3) trenbolone acetate implant (TBA), 4) E + TBA (ET), 5) melengestrol acetate (MGA) in the feed, and 6) ET + MGA (ETM). Each treatment was replicated in five pens, with nine heifers per pen in each season. Initial weights (mean = 384 kg, SE = 57) were the same for each season. There were no treatment x season interactions for final BW, ADG, G:F, water intake, or carcass characteristics. Heifers receiving a growth-promoting agent were 11.6 kg (SE = 4.08) heavier and gained 0.108 kg/d (SE = 0.04) more (P < 0.05) than control heifers. Heifers receiving ET gained 0.09 kg/d (SE = 0.032) more (P = 0.05) than heifers not receiving ET. Heifers receiving ET (with and without MGA) had greater G:F (P < 0.05) than control, E, and TBA heifers. Carcass weights of ET-treated heifers were greater (P < 0.05) than carcass weights for unimplanted heifers, those fed MGA only, and heifers receiving either E or TBA implants. Marbling scores were increased (P < 0.05) by feeding MGA to ET-treated heifers. Water intake was greater (P < 0.01) in the summer (31 L/d) than in the winter (18 L/ d), with no difference among implant treatments. Heifers fed in the winter had heavier carcasses, less 12th-rib fat, greater marbling scores, larger LM area, and a greater incidence of liver abscesses than heifers finished in the summer (P < 0.01). A treatment x season interaction (P = 0.07) was evident for DMI during the 35-d coldest and hottest portions of the year. Heifers fed MGA and implanted with ET tended (P = 0.07) to have greater DMI in the summer but lesser DMI in the winter. In general, differences among growth-promotant programs were relatively similar over the entire summer and in winter.     

Conception rate in Bos taurus and Bos indicus crossbred heifers after postweaning energy manipulation and synchronization of estrus with melengestrol acetate and fenprostalene

Conception rate in heifers after synchronization of estrus with melengestrol acetate (MGA) and fenprostalene (a prostaglandin F2 alpha analogue; PGF) was determined in pubertal Bos taurus and Bos indicus crossbred yearling heifers. Angus x Hereford (AH, n = 137) and Brahman x Hereford (BH, n = 97) heifers were sorted by body weight after weaning into light (LW) and heavy (HW) weight blocks. Heifers were assigned by age to diets to reach a target weight of 55% (LE) or 65% (HE) of their projected mature weight by the start of breeding. Heifers that exhibited estrus and had serum progesterone greater than or equal to 1 ng/ml (0 or 10 d before estrous synchronization treatment) were assigned randomly within breed and nutritional groups to either an estrous synchronization (S) or control (C) group. Heifers in the S group were fed .5 mg of MGA for 7 d and injected s.c. with 2 mg PGF on d 7 of MGA. All heifers were inseminated 12 h after first detected estrus. A greater proportion of AH (P less than .01) than of BH heifers were in estrus within 6 d after PGF, and more S heifers than C heifers (P less than .01) were in estrus. Conception rate at first service was proportionately higher (P less than .001) in AH than in BH heifers and lower (P less than .02) in S than in C heifers. There was a breed x energy level interaction (P less than .01) for conception rate at first service. Stage of the estrous cycle at the time treatment with MGA was initiated influenced (P less than .05) conception rate at first service in the S, AH heifers, with lower conception rates among heifers beginning treatment late in their estrous cycles (greater than or equal to d 12). Pregnancy rates after 21 d were higher (P less than .01) in AH than in BH heifers and higher (P less than .01) in HW than in LW heifers. More HE than LE heifers (P less than .02), and more AH than BH heifers were pregnant after 45 d. Pregnancy rates at the end of 21 d were higher among HE, BH heifers than among LE contemporaries. A higher (P less than .02) percentage of HE, HW, BH heifers were pregnant at the end of 45 d compared with other BH groups. Results indicated that a 7-d MGA-PGF treatment reduced conception rates at first service in pubertal yearling heifers. Pregnancy rate was affected by prebreeding nutrition in BH yearling heifers at the end of 45 d.     

Effects of source of supplemental zinc on performance and humoral immunity in beef heifers

Two experiments were conducted to evaluate receiving-period performance, morbidity, and humoral immune response, as well as finishing performance and carcass characteristics of heifers fed different sources of supplemental Zn. In Exp. 1, 97 crossbred beef heifers (initial BW = 223.4 kg) were fed a 65% concentrate diet with no supplemental Zn (control) or 75 mg of supplemental Zn/kg of DM from Zn sulfate, Zn methionine, or Zn propionate. During a 35-d receiving period, heifers were monitored daily for signs of bovine respiratory disease. Serum samples were collected for Zn analysis on d 0, 14, and 28. After the receiving period, heifers were adapted to and fed a high-concentrate diet with no supplemental Zn for 42 d. Heifers were then assigned to finishing diet treatments, with the same concentrations and sources of supplemental Zn as during the receiving period and fed for an average of 168 d. Serum samples also were obtained on d 0 and 56 of the finishing period and at the end of the study. During the receiving period, control heifers had a greater (P < or = 0.05) BW and G:F on d 35 than heifers in the other treatments, but no differences were observed among treatments for morbidity or serum Zn concentrations (P > or = 0.50). For the finishing period, DMI and ADG did not differ among treatments; however, overall G:F tended (P = 0.06) to be less for control heifers than for heifers in the 3 supplemental Zn treatments. On d 56 of the finishing period, control heifers tended (P = 0.06) to have a lower serum Zn concentration than heifers in the 3 supplemental Zn treatments. In Exp. 2, 24 crossbred beef heifers (initial BW = 291.1 kg) were fed the same 4 treatments as in Exp. 1 for a 21-d period. The humoral immune response to treatments was determined by measuring specific antibody titers after s.c. injection of ovalbumin on d 0 and 14. Body weights and blood samples for serum Zn concentration and ovalbumin IgG titers were collected on d 0, 7, 14, and 21. Serum Zn concentration and specific ovalbumin IgG titers did not differ (P > 0.10) among the 4 treatments on any sampling day. Results from these 2 studies showed no major differences among the sources of supplemental Zn for receiving period morbidity, ADG, DMI, and humoral immune response of beef heifers; however, a lack of supplemental Zn during an extended finishing period tended to negatively affect G:F.     

Extending Interval from Seventeen to Nineteen Days in the Melengestrol Acetate - Prostaglandin Estrous Synchronization Program for Heifers

Two experiments were conducted to determine whether extending the interval between removal of melengestrol acetate (MGA) from feed and injection of prostaglandin F_2α (PGF) from 17 to 19 d would affect synchronization of estrus, conception, and pregnancy rates of beef heifers. In both experiments, heifers were fed MGA for 14 d, and PGF was given at either 17 or 19 d after cessation of MGA feeding. Heifers were observed for estrus and artificially inseminated for 5 d after PGF injection. In Exp. 1, 240 yearling heifers were randomly assigned to either a 17- or a 19-d treatment group according to estrous status and day of the estrous cycle. In Exp. 2, 1409 yearling heifers on a cooperating ranch were randomly assigned to the same two treatment groups without knowledge of estrous status. The PGF injection at 19 d (Exp. 1) caused a higher (P<0.05) percentage of heifers to exhibit estrus by 72 h after the injection compared with heifers receiving the injection at 17 d. A greater percentage (P<0.01) of heifers in the 19-d group were in the late luteal phase of the estrous cycle at the time of PGF injection compared with the heifers in the 17-d group, and pregnancy rates were higher for the heifers in the late luteal phase. In Exp. 2, heifers injected with PGF at 19 d after MGA had a greater (P<0.05) percentage in estrus (10%) during the 5-d breeding period, and had higher (P<0.05) pregnancy rates in 5 d (7.6%) and 50 d of breeding (5.5%), compared with heifers injected with PGF 17 d after withdrawal of MGA. These results indicate that the PGF injection given at 19 d after removal of MGA from the diet increases synchronized estrous response and results in higher pregnancy rates in heifers compared with the 17-d injection treatment.     

Feedlot performance and pregnancy inhibition of heifers treated with depot-formulated melengestrol acetate

In dose titration trials beef heifers received depot-formulated melengestrol acetate (DEPO-MGA) in single s.c. ear injections to determine effects on performance and pregnancy inhibition. In a 112-d feedlot trial, 105 heifers were assigned to light, medium and heavy weight blocks on five treatments: dietary MGA (.5 mg.hd-1.d-1), control (no MGA) or DEPO-MGA on d 1 at .5, 1.0 or 1.5 ml/hd (30, 60 or 90 mg MGA/hd, respectively). A high-energy cracked corn diet was fed to all heifers ad libitum. At d 56 and d 112, ADG and feed/gain were not affected (P greater than .05) by dietary MGA or DEPO-MGA treatments, although dietary MGA tended to increase 112-d ADG (1.67 vs 1.58 kg) compared with controls. In a pasture trial, 100 beef heifers were assigned by weight to five treatments: control (no MGA) or DEPO-MGA injected on d 1 at .5, 1.0, 1.5 or 2.0 ml/hd (30, 60, 90 or 120 mg MGA/hd, respectively). Heifers were pastured as a single herd and were exposed to fertile bulls from d 7 to d 181. Weights and pregnancy data were recorded at d 62, 90, 134, 181 and 225. Heifer ADG was not affected (P greater than .05) by DEPO-MGA treatment at any weighing date. By d 90, 90% of control heifers were pregnant, and 100% were pregnant by d 134. Pregnancy inhibition rates of 90% to 100% for each DEPO-MGA treatment at d 62, 90 and 134 were higher (P less than .01) than those in control heifers. Pregnancy was inhibited in 90% of heifers on 60-mg and 90-mg DEPO-MGA treatments through d 181, and in 95% of heifers on the 120 mg DEPO-MGA treatment through d 225.     

Effect of testosterone propionate on performance and carcass characteristics of heifers and cows

Two experiments were conducted to evaluate the effect of testosterone on growth and composition of cattle. In the first experiment, crossbred yearling heifers (n = 48) were assigned to four treatments: 1) control (no implant), 2) Synovex-H implants on d 1 and 84, 3) one testosterone propionate implant administered on d 1 and a second on d 84 and 4) two testosterone propionate implants administered on d 1. Heifers were fed a high-energy diet for the 157-d study. Implanting with the high-testosterone treatment improved (P less than .05) daily gain and feed efficiency compared with the other treatments. Marbling score was reduced (P less than .05) with the high-testosterone treatment. In Exp. 2, mature cows (n = 36) were assigned to one of three feeding periods (0, 42, or 84 d) with the cows fed 42 or 84 d subdivided into two groups (implanted with testosterone propionate or nonimplanted control). Cows were fed a high-energy diet and slaughtered at the end of each feeding period. Testosterone did not influence (P greater than .05) feedlot performance. Increased time on feed reduced (P less than .01) daily gain (live weight basis) and feed efficiency but did not influence feed intake. Testosterone treatment had little influence on the fat and moisture contents of the carcass soft tissue or on the palatability characteristics of loin steaks. Time on feed increased lean muscle mass and carcass fat (P less than .05). Sensory traits were improved at 42 d on feed (P less than .05), but no further sensory improvement was observed at 84 d.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synchronization of estrus with melengestrol acetate and prostaglandin F2 alpha in beef and dairy heifers

Beef (n = 783) and dairy (n = 209) heifers at 14 locations were used to evaluate the efficacy of feeding melengestrol acetate (MGA; .5 mg/d) for 7 d followed by an i.m. injection of 25 mg prostaglandin F2 alpha (PGF) on the last day of MGA feeding (MGA + PGF) to synchronize estrus. Untreated heifers (C) and heifers injected once i.m. with PGF served as contemporary controls. Heifers were observed for estrual behavior for a minimum of 38 d starting on the 2nd d of MGA feeding. Heifers in estrus from d 1 through d 60 after PGF injection were artificially inseminated (AI) or bred to bulls (d 30 to 60 post PGF only). During the 7-d MGA feeding period fewer (P less than .01) MGA + PGF (1.5%) than C (20.6%) or PGF (18.1%) heifers were observed in estrus. Percent of heifers in estrus d 1 to 6 post PGF was different among groups (P less than .05; 30.5, 52.8, 72.3 for C, PGF and MGA + PGF, respectively). More (P less than .01) MGA-fed (92%) than non-MGA-fed (C and PGF combined) heifers (85.4%) were observed in estrus during d 1 to 24. Conception rate (CR) during d 1 to d 6 was not different (P = .19) between C (58.9%) and MGA + PGF (51.2%) heifers; CR was lower (P = .01) for MGA + PGF than for PGF (68.3%) heifers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Feedlot performance of hysterectomized and ovariectomized heifers

Seventy-five crossbred heifers (mean weight 304 kg) were stratified by weight and source and placed in eight pens. Four duplicate treatments were randomly assigned to pens as follows: (1) intact-control (n = 19), (2) intact + melengestrol acetate (MGA, n = 20), (3) hysterectomy (n = 17) and (4) ovariectomy (OVX, n = 19). All heifers were preconditioned for 2 mo before beginning the finishing study. Surgery was performed through a high lumbar incision approximately 3 wk before the finishing study began. Group 2 heifers were fed .4 mg X head-1 X d-1 MGA. Blood samples were collected at 28-d intervals throughout the 112-d finishing phase. Ovaries were collected at slaughter and carcass data were obtained 24 h after slaughter. On d 112, progesterone was higher (P less than .05) in hysterectomized heifers than in other treatment groups. Serum progesterone concentration was nondetectable (less than .35 ng/ml) in OVX and MGA heifers. There were no differences (P greater than .05) in feed efficiency or carcass characteristics among the four treatments. Hysterectomized and MGA heifers had similar (P greater than .05) average daily gains, which were higher (P less than .15) than control and OVX heifers. These data suggest that the elevated levels of progesterone from the maintained corpora lutea and the subsequent absence of estrous activity in the hysterectomized heifers are advantageous for promoting growth in feedlot heifers.     

Performance and digestibilities of beef cattle fed diets supplemented with either soybean meal or roasted soybeans and implanted with Synovex.

Two 160-d feedlot experiments, each consisting of 20 Angus-Hereford steers (216 +/- 5 kg BW, Exp. 1; 258 +/- 5 kg BW, Exp. 2) and 20 Angus-Hereford heifers (208 +/- 5 kg BW, Exp. 1; 236 +/- 5 kg BW, Exp. 2), were used to investigate the effects of supplementing diets with either roasted soybeans (RSB, roasted at 127 degrees C for 10 min) or soybean meal (SBM) and implanting or not implanting with an estrogenic growth promoter (SYN; Synovex-S, 20 mg of estradiol benzoate plus 200 mg of progesterone or Synovex-H, 20 mg of estradiol benzoate plus 200 mg of testosterone) on performance. The cattle were fed a basal diet of 15% orchardgrass silage, 15% corn silage, and 70% corn-based concentrate. Treatments were 1) no SYN and fed a SBM-supplemented diet, 2) no SYN and fed a RSB-supplemented diet, 3) SYN and SBM, and 4) SYN and RSB. Cattle in the SYN groups were reimplanted at 80 d. Four additional Angus-Hereford steers were used in a digestion and nitrogen balance experiment conducted during the first half of Exp. 1. For the total 160-d feedlot experiments, DMI for RSB compared with SBM was lower (P < .01; 8.5 vs 9.2 kg/d, SEM = .07) and ADG/DMI tended to be higher (P < .10; 165 vs 157 g/kg, SEM = 1.3). Final BW of steers fed RSB was similar (P > .10) to that of steers fed SBM (473 vs 478 kg, SEM = 5.6), as was ADG (1.39 vs 1.43 kg/d, SEM = .02). Dry matter intake for SYN-implanted steers was higher (P < .01) than for steers not implanted (9.2 vs 8.5 kg/d). Likewise, final BW (491 vs 460 kg) and ADG (1.49 vs 1.33 kg/d) were higher (P < .01), and ADG/DMI (166 vs 157 g/kg) tended to be higher (P < .10), for SYN-implanted steers than for steers not implanted. During the more rapid muscle growth period (0 to 80 d), DMI for RSB compared with SBM was lower (P < .01; 7.8 vs 8.6 kg/d, SEM = .07) and ADG/DMI was similar (P > .10; 181 vs 172 g/kg, SEM = 1.8). Dry matter intake for SYN-implanted steers was higher (P < .05) than for steers not implanted (8.4 vs 8.0 kg/d), as was ADG/DMI (P < .01, 182 vs 171 g/kg). During this more rapid growth period, the supplement x implant interaction for ADG was significant (P < .05; 1.35, 1.36, 1.59, and 1.44 kg/d for Treatments 1, 2, 3, and 4, respectively, SEM = .04). There were no differences in digestibilities or N balance. The results suggest that there is no improvement in performance under feedlot conditions when RSB replaces SBM in the diet of beef cattle, and, in young cattle, RSB may reduce the response expected by an estrogenic growth promoter.     

Effects of restricted versus conventional dietary adaptation on feedlot performance,carcass characteristics,site and extent of digestion,digesta kinetics,and ruminal metabolism

Three experiments were conducted to determine effects of restricting intake of the final finishing diet as a means of dietary adaptation compared with diets increasing in grain over a period of 20 to 22 d on overall cattle performance, carcass characteristics, digestibility, digesta kinetics, and ruminal metabolism. In Exp. 1, 84 Angus x Hereford yearling steers (initial BW = 418 +/- 29.0 kg) were fed for 70 d. Restricting intake during adaptation had no effect (P > 0.10) on overall ADG:DMI, but decreased (P < 0.05) DMI compared with ad libitum access to adaptation diets, which resulted from differences during the initial 28 d of the experiment. In Exp. 2, 150 mixed crossbred steer calves (initial BW = 289 +/- 22.9 kg) were fed for an average of 173 d. Restricting intake decreased (P < 0.01) overall daily gain (1.51 vs 1.65 kg/d) and DMI (8.68 vs 9.15 kg/d) compared with ad libitum fed steers; however, ADG:DMI was not influenced (P > 0.10) by adaptation method. Experiment three used eight ruminally and duodenally fistulated steers (initial BW = 336 +/- 20 kg) in a completely random design. Total tract digestibility, digesta kinetics and ruminal metabolism were determined. Restricting intake reduced (P < 0.10) daily DMI variation from d 1 through 7, 8 through 14, and 22 through 28 compared with ad libitum feeding of three adaptation diets. Restricted steers had reduced (adaptation method x period interaction, P < 0.05) intakes and fecal excretions of ADF and greater OM digestibilities on d 4 through 7, 11 through 14, and 18 through 21. Digesta kinetics and ruminal metabolism were generally not affected (P > 0.10) by adaptation method. Our results suggest that restricted-feeding of the final diet as a means of dietary adaptation can be used in finishing cattle with few problems from acidosis or related intake variation. In light-weight steers (Exp. 2), disruptions in intake during the adaptation period might have resulted in restriction for an extended period, which decreased (P < 0.01) hot carcass weight compared with calves fed ad libitum. Effects of limit feeding during the initial 28 d of the feeding period on site and extent of digestion, digesta kinetics, and ruminal metabolism were minimal, supporting few differences in performance across the finishing period for yearling cattle.     

The effects of ractopamine-hydrogen chloride (Optaflexx) on performance, carcass characteristics, and meat quality of finishing feedlot heifers

Two experiments were conducted at the Kansas State University Beef Cattle Research Center to determine the effects of ractopamine-HCl (Optaflexx) on growth performance, carcass characteristics, and meat quality of finishing feedlot heifers. In Exp. 1, heifers implanted with Revalor-H (n = 302, initial BW = 479 kg) were fed steam-flaked corn diets with 0 (control) or 200 mg of ractopamine-HCl (OPT) per heifer daily for 28 d before slaughter. Average daily gain and DMI were not different between treatments (P > 0.17); however, OPT cattle tended to have a greater G:F (P = 0.06). Treatments did not differ with respect to final BW, HCW, dressing percentage, USDA yield grade, USDA quality grade, marbling score, LM area, KPH, Warner-Bratzler shear force, weight loss during cooking, or L*, a*, or b* colorimetric values during a 7-d retail display or purge loss from loin steaks during retail display (P > 0.19). In Exp. 2, nonimplanted crossbred heifers (n = 281, BW = 451 +/- 2 kg) were fed finishing diets based on steam-flaked corn. A control diet (no ractopamine) was compared with diets providing 200 mg of OPT per heifer daily for periods of 28 or 42 d (200 x 28 and 200 x 42, respectively), 300 mg/d for 28 d (300 x 28), and a step-up regimen consisting of 14 d at 100 mg, followed by 14 d at 200 mg, and the final 14 d at 300 mg of OPT (step-up). Feeding OPT had no effect on carcass weight gain among treatments (P = 0.18). The efficiency of carcass gain was 34 and 35% greater (P = 0.06) for the 200 x 42 and step-up groups compared with control, respectively. Feeding OPT at 300 mg for 28 d reduced DMI compared with the control, 200 x 28, and 200 x 42 (P < 0.05) groups. Administration of OPT had no effect on marbling score, yield grade, LM area, KPH, or percentages of carcasses grading USDA Choice (P > 0.10). Feeding ractopamine-HCl (Optaflexx) to finishing heifers generally improved the efficiency of carcass gain with minimal effect on carcass characteristics. These effects were most pronounced in heifers fed ractopamine for 42 d.     

Effects of a dietary Aspergillus oryzae extract containing alpha-amylase activity on performance and carcass characteristics of finishing beef cattle

Three experiments were conducted to examine the effects of an Aspergillus oryzae extract containing alpha-amylase activity on performance and carcass characteristics of finishing beef cattle. In Exp. 1, 120 crossbred steers were used in a randomized complete block design to evaluate the effects of roughage source (alfalfa hay vs. cottonseed hulls) and supplemental alpha-amylase at 950 dextrinizing units (DU)/kg of DM. Significant roughage source x alpha-amylase interactions (P < 0.05) were observed for performance. In steers fed cottonseed hulls, supplemental alpha-amylase increased ADG through d 28 and 112 and tended (P < 0.15) to increase ADG in all other periods. The increases in ADG were related to increased DMI and efficiency of gain during the initial 28-d period but were primarily related to increased DMI as the feeding period progressed. Supplemental alpha-amylase increased (P = 0.02) the LM area across both roughage sources. In Exp. 2, 96 crossbred heifers were used in a randomized complete block design with a 2 x 3 factorial arrangement of treatments to evaluate the effects of corn processing (dry cracked vs. high moisture) and supplemental alpha-amylase concentration (0, 580, or 1,160 DU/kg of DM). Alpha-amylase supplementation increased DMI (P = 0.05) and ADG (P = 0.03) during the initial 28 d on feed and carcass-adjusted ADG (P = 0.04) across corn processing methods. Longissimus muscle area was greatest (quadratic effect, P = 0.04), and yield grade was least (quadratic effect, P = 0.02) in heifers fed 580 DU of alpha-amylase/kg of DM across corn processing methods. In Exp. 3, 56 crossbred steers were used in a randomized complete block design to evaluate the effects of supplemental alpha-amylase (930 DU/kg of DM) on performance when DMI was restricted to yield a programmed ADG. Alpha-amylase supplementation did not affect performance when DMI was restricted. We conclude that dietary alpha-amylase supplementation of finishing beef diets may result in increased ADG through increased DMI under certain dietary conditions and that further research is warranted to explain its mode of action and interactions with dietary ingredients.     

The effect of forage source and particle size on finishing yearling steer performance and ruminal metabolism.

Two finishing trials and a metabolism trial were conducted to evaluate the effect of forage source and particle size in dry-rolled corn finishing diets. In Exp. 1, 224 crossbred yearling steers (BW = 342+/-11 kg) were used in a randomized complete block design consisting of seven treatments. Treatments were an all-concentrate diet or diets containing equal NDF levels provided by alfalfa hay or wheat straw (three treatments each) with each forage source ground to pass through a .95-, 7.6-, or 12.7-cm screen. Steers fed diets containing forage had greater (P < .05) DMI than steers fed an all-concentrate diet. Steers fed alfalfa diets gained faster (P < .05) with a greater (P < .05) concentrate efficiency than steers fed either all-concentrate or straw diets. In Exp. 2, 120 crossbred yearling steers (BW = 307+/-2 kg) were used in a completely randomized design and fed dry-rolled corn diets containing 10% alfalfa ground to pass through either a .95- or 7.6-cm screen. Alfalfa particle size had no effect on performance or carcass measurements. In Exp. 3, six ruminally fistulated steers (BW = 508+/-34 kg) were used in a 6 x 6 Latin square design and fed an all-concentrate diet or diets containing equal NDF levels provided by alfalfa hay, wheat straw, or ground corncobs with alfalfa and straw ground to pass through either a 2.54- or 12.7-cm screen. Steers fed straw diets spent more time (P < .10) chewing than those receiving the other diets. In conclusion, forage particle size had no effect on finishing cattle performance or ruminal metabolism data. However, cattle consuming different forage sources in dry-rolled corn finishing diets may not respond similarly in animal performance.     

The effects of feeding flaxseed during the receiving period on morbidity, mortality, performance, and carcass characteristics of heifers

Two experiments were conducted at the Kansas State University Beef Cattle Research Center to determine the effects of feeding ground flaxseed (flax) during the receiving period on the growth, health, and subsequent finishing performance of heifers. Crossbred heifers (Exp. 1: n = 363, 214 +/- 1 kg of initial BW; Exp. 2: n = 377, 222 +/- 1 kg of initial BW) were purchased during January and April of 2006. Heifers were fed receiving rations based on steam-flaked corn with 0, 2, 4, or 6% ground flax (DM basis) for 56 d. Following the receiving period, cattle in Exp. 1 and 2 were fed steam-flaked corn-based diets for 150 and 147 d, respectively, and then slaughtered. Heifers were implanted 91 and 109 d before slaughter for Exp. 1 and 2, respectively. In Exp. 1, DMI during the receiving period tended to increase linearly (P = 0.09) with increasing flax in the diet. Average daily gain was 1.46, 1.56, 1.58, and 1.61 kg for heifers fed 0, 2, 4, and 6% flax, respectively (linear, P = 0.03). Final BW in Exp. 1 after the finishing period was increased (linear, P = 0.04) with increasing inclusion of flax in the receiving diets. In Exp. 2, growth performance and mortality during the receiving period were not different among treatments (P > 0.12). During the receiving period in Exp. 2, incidence of the first respiratory treatment tended to be greatest (P = 0.09) for heifers fed 4% flax. During the finishing period, DMI were 8.4, 8.4, 8.0, and 8.1 kg/d for 0, 2, 4, and 6% flax, respectively (linear, P = 0.05). In Exp. 2, LM areas were greatest (quadratic, P = 0.04) for cattle fed 2% flax at receiving. In general, feeding flax during the receiving period may have the potential to improve growth performance; however, performance between experiments was variable, and many factors excluding flax feeding may have contributed to this response.     

Effect of fat type and forage level on performance of finishing cattle.

Four trials were conducted to determine the effects of adding various levels and types of fat to dry-rolled corn (DRC) finishing diets containing 0 or 7.5% forage. In Trial 1, 88 yearling steers (mean BW = 352 +/- 38 kg) and 176 heifers (mean BW 316 +/- 15 kg) were blocked by sex and weight into four replications. Treatments were 0, 2, 4, or 6% (DM basis) bleachable fancy tallow (BT) fed with 0 or 7.5% (DM basis) forage. Addition of BT to the 7.5% forage diet had no effect on ADG or gain/feed (G/F). However, adding BT to the all-concentrate diet decreased ADG (linear, P < .01) and G/F (linear, P = .08). In Trial 2, 184 yearling steers (mean BW = 347 +/- 21 kg) and 144 heifers (mean BW 322 +/- 8 kg) were blocked by sex and weight into six replications. Fat treatments were 0% fat, 4% BT, or 4% animal-vegetable oil blend (A-V); each fat treatment was fed with 0 or 7.5% forage. Across forage levels, the addition of fat increased (P < .01) ADG and G/F for cattle fed DRC. In Trial 3, 18 crossbred wether lambs (mean BW = 44.4 +/- 2.5 kg) were fed DRC and 7.5% forage and allotted randomly to the same fat treatments fed in Trial 2. Apparent total tract fat digestibility increased (P < .01) with the addition of BT or A-V. In Trial 4, 40 crossbred wethers (mean BW = 25 +/- 4.1 kg) and 16 ewes (mean BW = 23 +/- 2.7 kg) were individually fed 7.5% forage diets containing 0, 1, 2, or 4% BT. Addition of BT increased (linear, P = .10) G/F. In summary, fat addition to DRC finishing diets fed to yearling cattle did not consistently affect gain/feed, feed intake, and ADG.     

Effects of feeding whole cottonseed and cottonseed products on performance and carcass characteristics of finishing beef cattle

Three experiments were conducted to determine the effects of whole cottonseed or cottonseed products on performance and carcass characteristics of beef cattle. In Exp. 1, 120 beef steers (initial BW = 381 +/- 31.7 kg) were fed steam-flaked corn-based finishing diets with 10% (DM basis) basal roughage, and whole cottonseed or individual cottonseed components (cottonseed hulls, meal, and oil). Over the entire feeding period, ADG did not differ (P = 0.95), but DMI increased (P = 0.07) and G:F decreased (P = 0.06) for steers fed the cottonseed diets compared with the control diet. Dressing percent (P = 0.02) and marbling scores (P = 0.02) of carcasses from steers fed the cottonseed diets were less than for steers fed the control diet. In Exp. 2, 150 beef steers (initial BW = 364 +/- 9.9 kg) were used to determine the effects of whole cottonseed or pelleted cottonseed (PCS) on performance and carcass characteristics. Cattle were fed steam-flaked corn-based finishing diets in which whole cottonseed or PCS replaced all of the dietary roughage, supplemental fat, and supplemental natural protein of the control diet. Over the entire feeding period, steers fed the cottonseed diets had lower (P = 0.04) DMI and greater (P < 0.01) G:F than steers fed the control diet. Carcass characteristics did not differ (P = 0.16 to 0.96) among dietary treatments. In Exp. 3, 150 beef heifers (initial BW = 331 +/- 17.1 kg) were used to determine the effects of PCS or delinted, whole cottonseed (DLCS) on performance and carcass characteristics. Heifers were fed rolled corn-based finishing diets in which cottonseed replaced the dietary roughage, supplemental fat, and all or part of the supplemental natural protein of the control diet. Over the entire feeding period, ADG, DMI, and G:F of heifers fed the control diet did not differ (P = 0.19 to 0.80) from those of the cottonseed diets; however, heifers fed the diets containing PCS had greater ADG (P = 0.03) and G:F (P = 0.09) than heifers fed diets containing DLCS. Carcass characteristics of heifers fed the control diet did not differ (P > or = 0.28) from those fed the cottonseed diets. Heifers fed the diets containing PCS had greater (P < or = 0.03) HCW, dressing percent, and LM area than those fed DLCS. Based on our results, whole cottonseed, or products derived from processing whole cottonseed, can replace feedstuffs commonly used in beef cattle finishing diets with no adverse effects on animal performance or carcass characteristics.     

Effects of tribasic copper chloride versus copper sulfate provided in corn-and molasses-based supplements on forage intake and copper status of beef heifers

The objective of this study was to investigate the effect of supplemental tribasic copper chloride (Cu(2)(OH(3))Cl; TBCC) vs. Cu sulfate (CuSO(4)) on Cu status and voluntary forage DMI in growing heifers. Two 90-d experiments were conducted using 48 non-pregnant, crossbred heifers (24 heifers/experiment; 355 +/- 10.7 and 309 +/- 9.9 kg for Exp. 1 and 2, respectively). In each experiment, 3 supplemental Cu treatments were randomly allocated to heifers in individual pens consisting of (1) 100 mg of Cu/d from CuSO(4), (2) 100 mg of Cu/d from TBCC, or (3) 0 mg of Cu/d. The 2 experiments differed by the form of supplement used to deliver the Cu treatments (corn- vs. molasses-based supplements for Exp. 1 and 2, respectively). Supplements were formulated and fed to provide equivalent amounts of CP and TDN daily but differed in their concentration of the Cu antagonists, Mo (0.70 vs. 1.44 mg/kg), Fe (113 vs. 189 mg/kg), and S (0.18 vs. 0.37%) for corn- and molasses-based supplements, respectively. All heifers were provided free-choice access to ground stargrass (Cynodon spp.) hay. Jugular blood and liver biopsy samples were collected on d 0, 30, 60, and 90 of each experiment. Heifer BW was collected on d 0 and 90. Heifer ADG was not affected by Cu treatment (average = 0.22 +/- 0.11 and 0.44 +/- 0.05 kg for Exp. 1 and 2, respectively; P > 0.20). In Exp. 1, heifers provided supplemental Cu, independent of source, had greater (P < 0.05) liver Cu concentrations on d 60 and 90 compared with heifers provided no supplemental Cu. In Exp. 2, average liver Cu concentrations were greater (P = 0.04) for heifers receiving supplemental Cu compared with heifers receiving no Cu; however, all treatments experienced a decrease in liver Cu concentration over the 90-d treatment period. Plasma ceruloplasmin concentrations did not differ in Exp. 1 (P = 0.83) but were greater (P = 0.04) in Exp. 2 for heifers receiving supplemental Cu compared with heifers receiving no Cu. In Exp. 1, voluntary forage DMI was greater (P < 0.05) for heifers provided supplemental Cu, independent of source, compared with heifers provided no Cu. In contrast, voluntary forage DMI was not affected (P > 0.10) by Cu supplementation in Exp. 2. These data imply that CuSO(4) and TBCC are of similar availability when offered to growing beef heifers in both corn- and molasses-based supplements. However, corn- and molasses-based supplements appear to affect Cu metabolism differently. These impacts may affect voluntary forage DMI in growing beef heifers.     

Reproductive response of yearling beef heifers to a melengestrol acetate-prostaglandin F2 alpha estrus synchronization system.

A study was designed to evaluate estrus response and fertility after treatment with melengestrol acetate (MGA) and prostaglandin F2 alpha (PGF2 alpha) in yearling beef heifers. Three hundred four heifers at three locations were allotted to one of two treatments: Treatment 1 served as a nonsynchronized control (CON); and heifers in Treatment 2 received .5 mg of MGA.animal-1.d-1 for 14 d and 25 mg of prostaglandin F2 alpha (PGF2 alpha) 17 d after MGA (MGA-PGF). Heifers in CON and MGA-PGF groups were artificially inseminated 12 h after observed estrus for 21 and 6 d after PGF2 alpha, respectively. Blood samples were collected from each heifer 10 d before and on the day MGA feeding began and 10 d before and on the day PGF2 alpha was administered. Heifers with concentrations of serum progesterone greater than 1 ng/mL on either date before administration of MGA or PGF2 alpha were considered pubertal. More (P = .02) prepubertal heifers that received MGA attained puberty by initiation of breeding than did CON heifers (72 vs 45%, respectively). The proportion of heifers that displayed estrus within 6 d after PGF2 alpha was greater (P less than .001) for MGA-PGF than for CON heifers (77 vs 25%, respectively) but was also influenced by location (P = .03). Conception rate at first service for MGA-PGF heifers that attained puberty during MGA feeding and before PGF2 alpha was not different (P = .50) from that of CON that attained puberty during the same period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Value of sunflower seed in finishing diets of feedlot cattle

The value of sunflower seed (SS) in finishing diets was assessed in two feeding trials. In Exp. 1, 60 yearling steers (479 +/- 45 kg) were fed five diets (n = 12). A basal diet (DM basis) of 84.5% steam-rolled barley, 9% barley silage, and 6.5% supplement was fed as is (control), with all the silage replaced (DM basis) with rolled SS, or with grain:silage mix replaced with 9% whole SS, 14% whole SS, or 14% rolled SS. Liver, diaphragm, and brisket samples were obtained from each carcass. In Exp. 2, 120 yearling steers (354 +/- 25 kg) were fed corn- or barley-based diets containing no SS, high-linoleic acid SS, or high-oleic acid SS (a 2 x 3 factorial arrangement, n = 20). Whole SS was included at 10.8% in the corn-based and 14% in the barley-based diets (DM basis). In Exp. 1, feeding whole SS linearly increased DMI (P = 0.02), ADG (P = 0.01), and G:F (P = 0.01). Regression of ME against level of whole SS indicated that SS contained 4.4 to 5.9 Mcal ME/kg. Substituting whole for rolled SS did not significantly alter DMI, ADG, or G:F (8.55 vs. 8.30 kg/d; 1.36 vs. 1.31 kg; and 0.157 vs. 0.158, respectively). Replacing the silage with rolled SS had no effect on DMI (P = 0.91) but marginally enhanced ADG (P = 0.10) and improved G:F (P = 0.01). Dressing percent increased linearly (P = 0.08) with level of SS in the diet. Feeding SS decreased (P < 0.05) levels of 16:0 and 18:3 in both diaphragm and subcutaneous fats, and increased (P = 0.05) the prevalence of 18:1, 18:2, cis-9,trans-11-CLA and trans-10,cis-12-CLA in subcutaneous fat. In Exp. 2, barley diets supplemented with high-linoleic SS decreased DMI (P = 0.02) and ADG (P = 0.007) by steers throughout the trial, whereas no decrease was noted with corn (interaction P = 0.06 for DMI and P = 0.01 for ADG). With barley, high-linoleic SS decreased final live weight (554 vs. 592 kg; P = 0.01), carcass weight (329 vs. 346 kg; P = 0.06), and dressing percent (58.5 vs. 59.4%; P = 0.04). Steers fed high-linoleic SS plus barley had less (P < 0.05) backfat than those fed other SS diets. No adverse effects of SS on liver abscess incidence or meat quality were detected. Although they provide protein and fiber useful in formulating finishing diets for cattle, and did improve performance in Exp. 1, no benefit from substituting SS for grain and roughage was detected in Exp. 2. Because of unexplained inconsistencies between the two experiments, additional research is warranted to confirm the feeding value of SS in diets for feedlot cattle.     

Intake, digestion, and digestive characteristics of Neotyphodium coenophialum-infected and uninfected fescue by heifers offered hay diets supplemented with Aspergillus oryzae fermentation extract or laidlomycin propionate

Tarentaise heifers fitted with a rumen cannula (539 +/- 7.5 and 487 +/- 15.7 kg avg initial BW in Exp. 1 and 2, respectively) were used in two Latin square metabolism experiments having 2 x 2 factorial treatment arrangements to determine the effects of supplementation with Aspergillus oryzae fermentation extract (AO) or laidlomycin propionate (LP) on intake, digestion, and digestive characteristics of Neotyphodium coenophialum-infected (IF) or uninfected (FF) tall fescue (Festuca arundinacea) hay diets consumed ad libitum. Heifers were housed in individual stanchions in a metabolism facility with ambient temperatures controlled to range between 26.7 and 32.2 degrees C daily. Total feces and urine were collected for 5 d following a 21-d dietary adaptation period. In situ DM and NDF disappearance and ruminal fermentation characteristics were also determined. In Exp. 1, DMI was 24% greater (P < 0.01) by heifers offered FF than by those offered IF (6.7 vs 5.4 kg/d). Heifers fed 2 g/d AO tended (P = 0.09) to consume 4% more DM than those fed a diet without AO. Degradable DM and NDF fractions of IF were greater (P < 0.01) than those of FF, but AO supplementation did not affect situ disappearance (P > or = 0.42). In Exp. 2, DMI was 18.9% greater (P < 0.01) by heifers offered FF than by those offered IF (6.6 vs 5.5 kg/d). Heifers fed LP (50 mg/d) consumed 10.6% less (P < 0.05) DM than those not fed LP (5.7 vs 6/5 kg/d). Digestibility of NDF tended to be greater (P = 0.08) and digestibility of ADF was greater (P < 0.05) from FF than from IF. Conversely, apparent N absorption (%) was greater (P < 0.05) from IF than from FF. Heifers fed LP had lower (P < 0.05) ADF digestibility than those not fed LP. In situ degradable DM and NDF fractions were greater (P < 0.01) from IF than from FF. Diets supplemented with LP had higher (P < 0.01) indigestible DM and NDF fractions than those without LP. Propionic acid and total VFA concentrations were greater (P < 0.05) from heifers offered FF than from those offered IF and from heifers fed LP than from those not fed LP. Therefore, it appears the major effect of N. coenophialum was a reduction in forage intake and total-tract fiber digestibility in certain situations. Response to the feed additives was similar whether heifers were offered IF or FF and no evidence was apparent that either additive would improve performance substantially by animals consuming low-quality fescue hay diets.