Use of radio-frequency identification technology to assess the frequency of cattle visits to mineral feeders

Three experiments were conducted to evaluate the frequency of visits to a mineral feeder equipped with radio-frequency identification (RFID). In Exp. 1, twelve heifers (Braford, Brahman, and White Angus; n = 4/breed) were fitted with RFID ear tags and placed into a pasture with access to a RFID-equipped mineral feeder. Number of visits were greater (P ≤ 0.05) during daytime than the night period. Brahman and Braford heifers favored (P ≤ 0.05) daytime than night period. White Angus heifers did not display a specific period preference (P = 0.32). In Exp. 2, Black Angus and Brahman cows (n = 15 and 19, respectively) were placed into a pasture with access to a RFID-equipped mineral feeder. Brahman cows made more (P < 0.01) visits to the mineral feeder than Black Angus cows. There were no breed differences on the number of visits during the morning (P = 0.25) and night (P ≤ 0.25) periods, but Brahman cows made more (P ≤ 0.05) visits to the mineral feeder in the afternoon period than Black Angus cows. In Exp. 3, the location of the mineral feeder was tested using 3 groups of Bos indicus-influenced heifers (n = 12/group). The mineral feeder was moved weekly within pasture. The number of visits to the mineral feeder differed for each location (P < 0.001) with visits being greatest when mineral feeder was placed near supplement and water, followed by center of the pasture, and lastly in the shade.

Effect of rumen-protected methionine supplementation to beef cows during the periconception period on performance of cows, calves, and subsequent offspring

Maternal nutrition affects the development of the fetus and postnatal performance of the calf. Methionine may play a critical role in developmental programming and is likely deficient in beef cows fed low-quality forage. The objective of this study was to determine the effect of metabolizable methionine supply to lactating beef cows during the periconception period on performance of cows, calves, and subsequent offspring. This project involved two consecutive production cycles commencing at calving in which dietary treatments were fed to cows during the periconception period along with measurements on cows and initial calves in Production Cycle 1, and measurements on subsequent calves in Production Cycle 2. Brangus-Angus crossbred lactating beef cows (N = 108; age = 6.4 (2.8) year) were stratified by previous calving date and assigned to one of three supplements: (1) control, molasses plus urea at 2.72 kg/day as fed, (2) fishmeal, 2.27 kg/day molasses plus urea plus 0.33 kg/day as fed of fishmeal, and (3) methionine, 2.72 kg/day of molasses plus urea plus 9.5 g/day of 2-hydroxy-4-(methylthio)-butanoic acid. Cows were fed supplements and low-quality limpograss (Hemarthria altissima) hay while grazing dormant bahiagrass (Paspalum notatum Flüggé) pastures during the 115-day periconception period from December 2014 to April 2015 in Production Cycle 1 only. Body weight change and milk yield of cows were measured during the periconception period in Production Cycle 1. Body weight of calves was measured at birth and weaning in both production cycles. Following weaning in Production Cycle 2, eight subsequent steer calves per treatment were individually housed for a 42-day metabolism experiment. Treatment did not affect (P > 0.10) BW change of cows, but cows fed methionine tended (P = 0.09) to produce more energy-corrected milk than control and fishmeal. Treatment did not affect (P > 0.10) 205-day adjusted weaning weight of calves in either production cycle. During the metabolism experiment, subsequent calves from dams fed fishmeal and methionine gained faster (P < 0.05) and had greater (P < 0.05) gain:feed than control calves. Methionine calves tended (P = 0.06) to have greater apparent total tract NDF and ADF digestibility and lesser (P < 0.05) blood glucose concentration than control and fishmeal calves. These data indicate that maternal methionine supply during the periconception period plays an important role in programming future performance of the offspring.

Preweaning injections of bovine ST enhanced reproductive performance of Bos indicus-influenced replacement beef heifers

A 3 yr study evaluated the effects of three preweaning injections of bovine ST, administered 14 d apart, on growth and reproductive performance of Bos indicus-influenced beef heifers. On d 0 of each year, suckling Angus × Brangus heifers (n = 15 heifers/treatment/yr) were stratified by BW (147 ± 20 kg) and age (134 ± 11 d) and randomly assigned to receive an s.c. injection of saline (SAL; 5 mL; 0.9% NaCl) or 250 mg of sometribove zinc (BST; Posilac, Elanco, Greenfield, IN) on d 0, 14, and 28. Heifers and respective dams were managed as a single group on bahiagrass (Paspalum notatum) pastures from d 0 until weaning (d 127). From d 127 to 346, heifers were grouped by treatment, allocated to bahiagrass pastures (1 pasture/treatment/yr) and fed a molasses-based supplement (2.9 kg/heifer daily; DM basis) until d 346. Blood samples were collected on d 0, 14, 28, 42, and then every 9-10 d from d 179 to 346. In yr 3, liver biopsy samples were collected on d 0, 42, and 263. Heifers were exposed to mature Angus bulls from d 263 to 346. Growth performance and physiological parameters were analyzed using the MIXED procedure, whereas reproductive variables were analyzed using the GLIMMIX procedure of SAS. Effects of treatment × year and treatment × year × time were not detected for any variable measured in this study (P ≥ 0.14), except for calving percentage (P = 0.03). Heifers assigned to BST injections had greater overall plasma concentrations of IGF-1 and ADG from d 0 to 42 (P ≤ 0.05), less ADG from d 42 to 127 (P = 0.04), but had similar BW at weaning and postweaning ADG (P ≥ 0.25) compared to SAL heifers. Heifers assigned to BST tended to achieve puberty 26 d earlier (P = 0.10), had greater percentage of pubertal heifers on d 244, 263, 284, and 296 (P ≤ 0.04), tended to have greater overall pregnancy percentage (P = 0.10), and had greater (P ≤ 0.05) calving percentages in yr 1 and 2 (but not yr 3; P = 0.68) compared to SAL heifers. Liver mRNA expression of GHR-1B and IGF-1 on d 0 and 42 did not differ between treatments (P ≥ 0.15), but was greater for BST vs. SAL heifers on d 263 (P ≤ 0.02). Hence, administering three injections containing 250 mg of sometribove zinc at 14 d intervals before weaning (between 135 and 163 d of age) induced long-term impacts on liver gene expression and may be a feasible management practice to enhance puberty and pregnancy attainment in B. indicus-influenced replacement beef heifers.

Effects of post-weaning growth rate and puberty induction protocol on reproductive performance of Bos indicus-influenced beef heifers

A 3-yr study evaluated the effectiveness of puberty induction using exogenous reproductive hormones in beef heifers undergoing different post-weaning growth rates. On d 0 of each year, grazing Angus × Brahman heifers (60 heifers/yr) were stratified by initial BW and age (BW = 253 ± 30 kg; age = 310 ± 18 d), and randomly assigned, in a 3 × 2 factorial design, to achieve a low (LOW; 0.45 kg/d), medium (MED; 0.73 kg/d), or high (HIGH; 1.00 kg/d) growth rate from d 0 to 168 (5 heifers/pasture; 4 pastures/growth rate/yr). Dietary supplements were offered 3 times weekly (Mondays, Wednesdays, and Fridays) at 0800 h to provide 1.8, 2.9, and 4.4 kg of supplement DM per heifer daily from d 0 to 168. On d 0 of each year, 2 pastures/growth rate treatment were randomly assigned to receive (SYNC) or not (NOSYNC) a puberty induction protocol, which consisted of intravaginal controlled internal drug release (CIDR) insertion on d 65, CIDR removal on d 72, followed by 100-µg i.m. injection of GnRH on d 74, and 25-mg i.m. injection of PGF on d 84. Immediately after the puberty induction protocol, all heifers were grouped by growth rate treatment (1 group/growth rate/yr) into a single pasture and exposed to yearling Angus × Brahman bulls from d 84 to 168 (1 bull/group/yr). Interactions among growth rate and puberty induction protocol were not detected for any variable ( ≥ 0.26). Overall heifer ADG achieved only 51 to 56% of targeted ADG, and percentage of mature BW on d 84 did not differ between MED and HIGH heifers ( = 0.30), but both were heavier than LOW heifers ( < 0.01). Percentage of pubertal heifers on d 84 was greater for MED and HIGH vs. LOW heifers ( ≤ 0.05), whereas puberty induction protocol increased puberty attainment on d 84 ( < 0.01). Overall pregnancy and calving percentages after first breeding season were not affected by growth rate or puberty induction protocol ( ≥ 0.25). However, heifers calved 11 d earlier when enrolled in the puberty induction protocol ( = 0.02). In summary, puberty induction and HIGH and MED growth rates resulted in earlier attainment of puberty and pregnancy in -influenced beef heifers. However, neither growth rate or puberty induction impacted overall heifer pregnancy and calving rates on their first breeding season.

Effects of hydroxychloride sources of copper, zinc, and manganese on measures of supplement intake, mineral status, and pre- and postweaning performance of beef calves

Our objective was to evaluate the effect of Cu, Zn, and Mn source on measures of 1) preferential intake of mineral-concentrated supplements and 2) mineral status and pre- and postweaning performance of beef calves. In Exp. 1, 4 trials were conducted to assess the effect of source of Cu (750 mg/kg; Trial 1), Zn (2,000 mg/kg; Trial 2), Mn (3,000 mg/kg; Trial 3), and all 3 elements (Trial 4) on preferential intake of mineral-concentrated supplements. Supplements differed only by source of Cu, Zn, and Mn, which included hydroxychloride (hydroxy), sulfate, and organic options. In each trial, the 3 supplements were simultaneously offered to 8 pens of early-weaned calves (2 calves/pen; 126 ± 8.0 kg average BW) for a 4-h period and preferential intake was determined. When offered the opportunity to select among 3 supplement options, calves consumed more ( < 0.001) supplement containing hydroxy vs. organic or sulfate sources of Cu (Trial 1), Zn (Trial 2), and Mn (Trial 3). In Trial 4, when all 3 elements were combined within a single supplement, calves almost exclusively selected ( < 0.001) the hydroxy vs. organic or sulfate sources (82.9, 10.4, and 6.7% of total supplement intake, respectively [SEM 3.16]). In Exp. 2, calves were supplemented at a rate of 114 g/calf daily for 84 d before weaning (2 calves/pasture; 10 and 12 pastures in yr 1 and 2, respectively). Supplements were formulated to contain no supplemental minerals (control); hydroxy Cu, Zn, and Mn; or copper sulfate, zinc sulfate, and manganese oxide (sulfate/oxide). Total supplement intake was greater ( = 0.01) for calves consuming the hydroxy vs. the sulfate/oxide sources of Cu, Zn, and Mn (9.0 vs. 7.2 kg [SEM 0.45]). Preweaning calf BW gain did not differ ( ≥ 0.15) among treatments; however, calves provided mineral-fortified supplements had greater ( = 0.003) liver concentrations of Co and Se and tended ( = 0.07) to have greater liver concentrations of Cu at weaning compared with the controls. Calves provided mineral-fortified vs. control supplements had greater ( ≤ 0.05) peak concentrations of ceruloplasmin and haptoglobin and less BW gain during in the 16-d postweaning period. These data demonstrate greater voluntary intake of mineral-concentrated supplements among calves offered hydroxy vs. sulfate or organic sources of Cu, Zn, and Mn. Preweaning mineral-fortified supplementation increased calf mineral status, heightened inflammatory responsiveness, and decreased BW gain during the immediate postweaning period.

Effects of selenium biofortification of hayfields on measures of selenium status in cows and calves consuming these forages

Two experiments were conducted to evaluate the Se status of weaned calves (Exp. 1) and pregnant cows and newborn calves (Exp. 2) consuming bermudagrass [ (L.) Pers.] fertilized with Se. Sodium selenate was dissolved into water (8.8 g/L) and sprayed onto hayfields. Selenium-fertilized forage had greater ( ≤ 0.001) Se concentration compared with the control forage without Se fertilization (7.7 ± 1.81 vs. 0.1 ± 0.04 mg Se/kg DM and 10.8 vs. 0.1 mg Se/kg DM for Exp. 1 and Exp. 2, respectively). In Exp. 1, beef calves ( = 32; 176 ± 8.7 kg initial BW) were stratified by BW and randomly assigned to pens (16 pens; 2 calves/pen). Treatments were randomly assigned to pens, including control (no supplemental Se), Se hay, or sodium selenite ( = 2, 7, and 7 pens, respectively). A 42-d pair-feeding design was used, wherein each pen receiving Se hay was paired to a pen receiving sodium selenite. Blood and liver samples were collected on d 0, 21, and 42. Liver Se concentrations were greatest ( ≤ 0.005) on d 42 for calves provided Se hay compared with calves provided sodium selenite or control. This difference was attributed only to paired-feeding groups consuming <3 mg Se daily. In Exp. 2, mature, late-pregnancy cows were randomly assigned to 3 treatments: Se hay ( = 12), sodium selenite ( = 9), or control (no supplemental Se; = 6). Cows assigned to the sodium selenite and Se hay treatments were provided 2.5 mg of supplemental Se daily. Upon enrollment, cows were moved into individual feeding areas at an estimated 30 d prior to calving. Following calving, cotyledon and colostrum samples were collected from cows. Four days later, liver and blood samples were collected from both cows and calves. Selenium-supplemented cows had greater ( ≤ 0.001) liver, cotyledon, plasma, and whole blood Se concentrations compared with cows not receiving supplemental Se. Furthermore, cows provided Se hay tended ( = 0.11) to have greater liver Se concentrations compared with cows provided sodium selenite. Calves born to Se-supplemented cows had greater ( = 0.001) plasma Se concentrations than calves born to cows receiving no supplemental Se. Furthermore, calves born to cows provided Se hay tended ( = 0.06) to have greater plasma Se concentrations compared with calves born to cows provided sodium selenite. These data imply that Se biofortification of hayfields is an effective method to increase Se concentration of forage. Consumption of these forages result in increased Se status of weaned calves, periparturient cows, and their calves.

Performance of beef cows and calves fed different sources of rumen-degradable protein when grazing stockpiled limpograss pastures

Two experiments evaluated the effects of different sources of RDP on forage characteristics, animal performance, and ruminal and blood parameters of beef cattle grazing stockpiled limpograss (Hemarthria altissima) from January to May 2011 and 2012. In Exp. 1, 24 mature lactating beef cows and their respective calves were allocated to 8 stockpiled limpograss pastures (3 pairs/pasture). Treatments were 2 different sources of RDP, urea or cottonseed (Gossypium spp.) meal (CSM), distributed in a completely randomized design with 4 replicates. Feather meal and corn (Zea mays) meal were added to the urea treatments to balance RUP and energy. Treatments were mixed in sugarcane (Saccharum officinarum) molasses, which resulted in 3 kg DM/cow per day of supplement. There were no differences (P > 0.10) in herbage mass (HM; 3,200 ± 400 kg DM/ha), herbage allowance (HA; 1.9 ± 0.2 kg DM/kg of BW), CP (5.2 ± 0.2%), and in vitro digestible organic matter (IVDOM; 47 ± 0.5%) concentrations. There was a decrease (P < 0.10) in HM (from 4,100 to 2,600 kg/ha), IVDOM (from 46 to 39.9%), and HA (from 2.5 to 1.4 kg DM/kg BW) from January to March. Cow ADG (0.23 ± 0.08 kg/d), BCS (4.6 ± 0.2), milk yield (7.0 ± 0.4 kg/d), and plasma urea nitrogen (PUN; 16.1 ± 0.8 mg/dL) and calf ADG (0.71 ± 0.05 kg/d) were similar (P > 0.10) among treatments. Sixteen cow-calf pairs were moved to 8 drylot pens after Exp. 1, maintained on the same treatment, and evaluated for forage and total DMI. There was no difference in forage (P = 0.16; 2.1 ± 0.1% BW) and total DMI (P = 0.12; 2.5 ± 0.1% BW) between treatments. In Exp. 2, 2 rumen-cannulated steers were used in a 2 × 2 Latin square design, replicated in 2011 and 2012, to test the effects of the same treatments on rumen fluid and blood parameters. There was no difference (P > 0.10) in ruminal NH3-N (12.9 ± 0.3 mg/dL), pH (6.5 ± 0.1), propionic acid (25 ± 2.2 mol/100 mol), acetic acid (69.2 ± 2.9 mol/100 mol), and butyric acid (4.5 ± 0.5 mol/100 mol) as well as branched-chain VFA (1.3 ± 2.2 mol/100 mol) concentrations in the rumen. In addition, there was no difference (P = 0.91) in PUN (7.9 ± 0.3 mg/dL) concentration between treatments. Therefore, urea can be as effective as CSM as the main source of RDP in the molasses-based supplement offered to mature lactating beef cows grazing stockpiled limpograss pastures.

Effects of trace mineral injections on measures of performance and trace mineral status of pre- and postweaned beef calves

Three experiments were conducted to examine the effects of injectable trace minerals (ITM) on measures of trace mineral status and performance in pre- and postweaned Brangus-crossbred beef calves. In Exp. 1, calves were assigned to treatments in alternating birth order (n = 150; 75/treatment), consisting of a 1-mL subcutaneous injection of ITM (MultiMin 90; MultiMin USA, Inc., Fort Collins, CO) or sterile saline. The ITM formulation consisted of 60, 10, 15, and 5 mg/mL of Zn, Mn, Cu, and Se. Treatments were readministered at 100 and 200 d of age. Calf BW was recorded at birth and on d 100, 150, 200, and 250 (weaning). Trace mineral status was assessed in liver biopsy samples (n = 12/treatment) collected on d 150, 200, and 250. Administration of ITM had no impact on BW gain (P ≥ 0.55) but did result in greater (P ≤ 0.02) concentrations of liver Cu and Se and lesser (P = 0.05) liver Fe concentrations compared to saline-injected calves. In Exp. 2, 24 heifers were selected from the weaned calves of Exp. 1 (n = 12/treatment) and transported 1,600 km. Remaining on their original treatments, heifers were administered 5 mL of ITM or saline following transport (d 0). Blood samples, for acute phase protein (APP) analysis, were collected on d 0, 1, 3, 6, 9, and 13 and liver biopsy samples for assessment of trace mineral status on d 13. Plasma APP concentrations increased in all calves following weaning and transport but concentrations were greatest (P < 0.05) in ITM- vs. saline-injected heifers on d 6 and 9. Liver concentrations of Cu, Se, and Zn were greater (P ≤ 0.04) but ADG lesser (P = 0.05) for heifers receiving ITM vs. saline. In Exp. 3, 34 heifers, without previous exposure to ITM, were enrolled in a 177-d development study (n = 17/treatment). Treatments consisted of 2.5-mL injections of ITM or sterile saline on d 0, 51, and 127. Humoral immune response to an injection of porcine red blood cells (PRBC) was evaluated on d 51. Trace mineral status was evaluated in liver biopsy samples collected on d 177. Overall heifer ADG, PRBC antibody titers, and liver Se concentrations were greatest (P ≤ 0.06) for ITM vs. control heifers. Collectively, these studies demonstrate an increased trace mineral status, a greater humoral response to novel antigen, and a heightened APP response to weaning and transport stress in pre- and postweaned beef calves administered ITM.

Effects of anti-phospholipase A(2) antibody supplementation on dry matter intake feed efficiency, acute phase response, and blood differentials of steers fed forage- and grain-based diets

To determine whether supplementation of anti-phospholipase A antibody (aPLA) would alter voluntary DMI, feed efficiency (FE), acute-phase protein concentration, and blood differentials (BD) due to a change in diet from a forage-based to a grain-based diet, individual daily DMI was measured on 80 cross-bred steers during a 141-d period. On d 0, steers were blocked by BW and randomly assigned to receive a growing forage diet containing 1) no additive (CON; = 20), 2) inclusion of 30 mg of monensin and 8.8 mg of tylosin per kg of diet DM (MT; = 20), 3) inclusion of an aPLA supplement at 0.4% of the diet DM (0.4% aPLA; = 20), and 4) inclusion of an aPLA supplement at 0.2% of the diet DM (0.2% aPLA; = 20). On d 60, steers were transitioned into a grain-based diet (90% concentrate) over a 21-d "step-up" period while continuing to receive their supplement treatments and were maintained on the high-grain diet until the end of the trial on d 141. On d 0, 60, 81, and 141, individual shrunk BW was recorded. Blood samples were collected on d 60, 63, 65, 67, 70, 72, 74, 77, 79, 81, and 84 for determination of concentration of plasma ceruloplasmin, haptoglobin, and BD. During the growing forage-diet period, steers from the 0.2% aPLA and 0.4% aPLA treatments had lower ( < 0.05) residual feed intake (RFI; -0.12 ± 0.13 and -0.22 ± 0.13 kg/d, respectively) than steers from the CON treatment (0.31 ± 0.13 kg/d). During the grain-based diet period, the 0.2% aPLA (-0.12 ± 0.10 kg/d), 0.4% aPLA (0.36 ± 0.10 kg/d), and MT (0.10 ± 0.10 kg/d) steers had greater ( = 0.04) RFI than CON steers (-0.37 ± 0.10 kg/d). During the transition phase, white blood cell counts were greater ( = 0.04) for the 0.2% aPLA treatment (13.61 × 10 ± 0.42 × 10 cells/μL) than the 0.4% aPLA and MT treatments (12.16 × 10 ± 0.42 × 10 and 12.37 × 10 ± 0.42 × 10 cells/μL, respectively) and concentrations of lymphocytes also were greater ( = 0.01) for the 0.2% aPLA treatment (7.66 × 10 ± 0.28 × 10 cells/μL) than the 0.4% aPLA and MT treatments (6.71 × 10 ± 0.28 × 10 and 6.70 × 10 ± 0.28 × 10 cells/μL, respectively). Concentrations of plasma ceruloplasmin and haptoglobin were reduced ( < 0.05) for CON compared to aPLA steers (22.2 ± 0.83 vs. 24.4 ± 0.83 mg/dL and 0.18 ± 0.05 vs. 0.26 ± 0.05 mg/mL, respectively). Supplementation of aPLA improved FE of steers fed a forage-based growing diet but not when feeding grain-based diets. The 0.4% aPLA and MT treatments had decreased white blood cell counts and concentration of lymphocytes during the transition period compared to the 0.2% aPLA treatment, and CON steers had reduced concentrations of plasma ceruloplasmin and haptoglobin during the diet transition phase.

Inclusion of anti-phospholipase A2 antibody to backgrounding diets on performance, feed efficiency, in vitro fermentation, and the acute-phase response of growing beef calves

In Exp. 1, individual performance and daily DMI was measured on 70 crossbred weaned calves during a 70-d period using a GrowSafe system (GrowSafe Systems Ltd., Airdrie, AB, Canada) at the University of Florida North Florida Research and Education Center Feed Efficiency Facility (FEF). Calves were fed a low-concentrate (LC) growing diet, blocked by weight and sex, and then randomly assigned to pens to receive either no additional supplement (CON; n = 35) or receive a supplement of anti-phospholipase A2 antibody (aPLA2) at an inclusion rate of 0.6% of the diet DM (n = 35). After the 70-d feed efficiency (FE) trial (Phase 1), calves were loaded into a commercial livestock trailer and were driven for approximately 1,600 km during 24 h. Upon return to the FEF (Phase 2), calves were relocated to the same pens and groups and received the same diets and treatments for 28 d. Blood samples from each calf were collected on d 0, 1, 3, 5, 7, 14, 21, and 28 relative to initiation of transportation and were analyzed for determination of concentrations of plasma ceruloplasmin and haptoglobin. In Phase 1, initial BW (242.0 ± 3.7 kg; P = 0.92), BW at d 70 (313.0 ± 4.1 kg; P = 0.79), and ADG (1.01 ± 0.02 kg; P = 0.95) were similar between treatments. However, daily DMI was greater (P = 0.01) for CON (9.18 ± 0.15 kg) than aPLA2 (8.53 ± 0.15 kg). In addition, residual feed intake was greater (P = 0.002) for CON (0.389 ± 0.110 kg/d) than aPLA2 calves (-0.272 ± 0.110 kg/d). In Phase 2, after transportation, there were no differences between treatments on BW loss due to transportation shrink (26.0 ± 0.6 kg; P = 0.86), BW at d 28 (339.0 ± 4.1 kg; P = 0.72), ADG (1.28 ± 0.03 kg/d; P = 0.72), G:F (0.164 ± 0.004; P = 0.83), and concentrations of plasma haptoglobin (0.08 ± 0.02 mg/mL; P = 0.41). However, concentrations of plasma ceruloplasmin were greater (P < 0.001) for CON calves (14.3 ± 0.3 mg/dL) compared to aPLA2 calves (13.0 ± 0.3 mg/dL). In Exp. 2, the effects of aPLA2 inclusion on LC and high-concentrate (HC) substrates on in vitro fermentation parameters were assessed. Addition of aPLA2 had no effects on in vitro fermentation parameters of LC and HC substrates. In conclusion, supplementation of aPLA2 improved FE of growing beef calves when fed LC diets in Phase 1 and addition of aPLA2 had no effect on fermentation parameters of LC and HC substrates. In addition, calves supplemented with aPLA2 had reduced concentrations of plasma ceruloplasmin after 24 h of transportation.

Effects of calf weaning age and subsequent management systems on growth performance and carcass characteristics of beef steers

Brahman × British crossbred steers (n = 40 and 38 in yr 1 and 2, respectively) were used to evaluate the effects of calf management systems following early weaning (EW) on growth performance, muscle gene expression, and carcass characteristics. On the day of EW (d 0), steers were stratified by BW and age (95 ± 14 kg; 74 ± 14 d) and randomly assigned to a control treatment that was normally weaned (NW) on d 180 (n = 10 steers/yr) or to 1 of 3 EW treatments: 1) EW and limit fed a high-concentrate diet at 3.5% of BW (as-fed basis) in drylot until d 180 (EW180; n = 10 steers/yr), 2) EW and limit fed a high-concentrate diet at 3.5% of BW (as-fed basis) in drylot until d 90 and then grazed on bahiagrass pastures until d 180 (EW90; n = 10 steers/yr), or 3) EW and grazed on annual ryegrass pastures until d 60 (yr 1; n = 10 steers) or 90 (yr 2; n = 8 steers) and then on bahiagrass pastures until d 180 (EWRG). Early-weaned steers on ryegrass and bahiagrass pastures were supplemented with high-concentrate diet at 1.0% of BW (as-fed basis) until d 180. From d 180 to 270 (yr 1), all EW steers remained in their respective treatments, whereas NW steers were provided high-concentrate diet at 1.0% of BW (as-fed basis) on bahiagrass pastures. In yr 1, feedlot finishing period began on d 270. In yr 2, the study was terminated on d 180. In both years, EW180 steers were heaviest (P < 0.0001) on d 180. On d 180 of yr 1, EWRG steers were lightest (P < 0.0001) and EW90 steers were heavier (P = 0.05) than NW steers, whereas EW90, EWRG, and NW steers had similar BW on d 180 of yr 2 (P ≥ 0.14). On d 90, muscle PPARγ mRNA expression tended (P = 0.07) to be greater for EW180 steers and was greater (P = 0.008) for EW90 vs. EWRG steers but similar (P = 0.25) between EW180 and NW steers. On d 180, PPARγ mRNA was greater (P ≤ 0.06) for EW180 vs. NW, EW90, and EWRG steers. From d 274 to 302, EW180 steers had the least ADG (P ≤ 0.09), whereas EW90 steers had similar (P = 0.19) ADG compared with EWRG steers but greater (P = 0.03) ADG than NW steers. At slaughter, carcass characteristics did not differ (P ≥ 0.22) among treatments. In summary, EW steers provided a high-concentrate diet in drylot for at least 90 d were heavier at the time of normal weaning than NW steers and EW steers grazed on ryegrass pastures for 60 to 90 d and supplemented with concentrate at 1.0% of BW. Feeding a high-concentrate diet immediately after EW enhanced the muscle PPARγ expression but did not enhance marbling at slaughter.

Effects of calf weaning age and subsequent management system on growth and reproductive performance of beef heifers

Brahman × British crossbred heifers (n = 40 and 38 heifers in yr 1 and 2, respectively) were used to evaluate the effects of calf weaning age and subsequent management system on growth and reproductive performance. On d 0, heifers were ranked by BW (89 ± 16 kg) and age (72 ± 13 d) and randomly assigned to a conventional management group that was normally weaned on d 180 (NW; n = 10 heifers annually) or early weaned (EW) on d 0 and 1) limit fed a high-concentrate diet at 3.5% of BW (as fed) in drylot until d 180 (EW180; n = 10 heifers annually), 2) limit fed a high-concentrate diet at 3.5% of BW (as fed) in drylot until d 90, then grazed on Bahiagrass pastures until d 180 (EW90; n = 10 heifers annually), or 3) grazed on annual ryegrass pastures until d 60 (yr 1; n = 10 heifers) or 90 (yr 2; n = 8 heifers), then on Bahiagrass pastures until d 180 (EWRG). On d 180, all heifers were grouped by treatment and rotated on Bahiagrass pastures until d 390. Grazing heifers were supplemented at 1.0% BW until d 180 and at 1.5% BW from d 180 to 390. From d 0 to 90, EW180 and EW90 heifers were heavier (P ≤ 0.02) than NW and EWRG heifers, whereas NW heifers tended (P = 0.09) to be heavier on d 90 than EWRG heifers. In yr 1 and 2, EW180 heifers were heaviest (P < 0.0001) on d 180. In yr 1, EWRG heifers were lightest (P < 0.0001), whereas EW90 and NW heifers had similar BW (P = 0.58). Conversely, EW90, EWRG, and NW heifers achieved similar BW on d 180 of yr 2 (P ≥ 0.18). Positive correlations were detected (P ≤ 0.05) between liver IGF-1 mRNA abundance on d 90 and ADG from d 0 to 90 and between liver IGF-1 mRNA abundance on d 180 and ADG from d 90 to 180. The EW180 heifers were youngest (P ≤ 0.01) at puberty. From d 260 to 340, the percentage of pubertal heifers was greater (P ≤ 0.03) for EW90 vs. NW heifers but did not differ (P ≥ 0.15) between EWRG and NW heifers. The ADG from d 0 to 90 and the plasma IGF-1 on d 90 and 180 explained approximately 34% of the variability in age at puberty. In summary, the EW90 and EW180 heifer management systems evaluated in this study altered the BW at the time of NW and were good alternatives for anticipating puberty achievement compared to NW heifers.

Metabolizable protein supply modulated the acute-phase response following vaccination of beef steers

Our objective was to evaluate the effects of MP supply, through RUP supplementation, on the acute-phase response of beef steers following vaccination. On d 0, Brangus-crossbred steers (n = 24; 173 ± 31 kg; 175 ± 16 d of age) were randomly assigned to receive 1 of 3 isocaloric diets formulated to provide 85, 100, and 115% of the daily MP requirements of a beef steer gaining 0.66 kg of BW daily. Diets were limit-fed at 1.8% of BW (DM basis) and individually provided to steers once daily (0800 h) from d 0 to 29. Steers were weighed on d 0 and 29, following a 12-h period of feed and water withdrawal. On d 7, steers were vaccinated against Mannheimia haemolytica (OneShot, Pfizer), and blood samples were collected on d 0, 7, 8, 10, 14, 21, and 30. Plasma metabolites were analyzed as repeated measures using the MIXED procedure of SAS. Final BW and ADG were similar (P ≥ 0.50) among treatments (mean = 184 ± 9 kg and 0.5 ± 0.08 kg/d, respectively). Effects of time were detected (P < 0.01) for plasma concentrations of all acute-phase proteins, which peaked between d 7 to 14, returning to baseline concentrations by d 29. Treatment effects were not detected (P ≥ 0.19) for plasma concentrations of acid-soluble protein, albumin, fibrinogen, IGF-1 and serum amyloid-A. Plasma concentrations of total protein (TP) and plasma urea nitrogen (PUN) increased (P ≤ 0.05) with increasing supply of MP (87.1, 89.6, and 90.1 ± 1.09 mg TP/mL and 6.1, 8.3, and 10.3 ± 0.41 mg PUN/dL for 85, 100, and 115% MP steers, respectively). From d 10 to 29, steers provided 115% MP had less (P < 0.001) plasma concentrations of ceruloplasmin than steers fed 85 and 100% MP, which had similar plasma ceruloplasmin concentrations. On d 14, plasma concentrations of haptoglobin were greatest (P ≤ 0.06) for steers fed 115% MP, intermediate for 100% MP, and least for 85% MP (0.98, 0.71 and 0.44 ± 0.099 mg/mL, respectively). On d 10, plasma concentrations of creatinine were greater (P = 0.01) for steers fed 115 vs. 85% MP, and intermediate for steers fed 100% MP (1.63, 1.28, and 1.50 ± 0.099 mg/dL, respectively). Thus, steers provided increasing metabolizable protein had greater plasma concentrations of haptoglobin, creatinine, total protein and PUN following vaccination against M. haemolytica.

Effects of rubber flooring during the first 2 lactations on production, locomotion, hoof health, immune functions, and stress

Some housing systems on dairy farms can result in long-term chronic pain. The effects of acute pain on immunity have been explored, but chronic pain's influence on immune responses is still poorly understood. Therefore, the objective of this research was to determine chronic effects of flooring on immune responses and production in freestall housing for dairy cows. Thirty heifers were studied from before calving as first-calf heifers until d 180 of their second lactation. Treatments were rubber (Kraiburg; Agromatic Inc., Fond du Lac, WI) flooring or concrete with diamond grooves in a freestall barn, each in 2 quadrants of the barn. Heifers entered the treatments after calving, so the system was dynamic and each cow was considered an experimental unit. At the end of the first lactation, cows were housed in a bedded pack barn with pasture access until calving was imminent. At that time, they returned to their assigned treatment, but not necessarily into the same quadrant. Production, reproduction, cortisol, acute-phase proteins, and health data were recorded throughout lactation 1, locomotion was scored weekly, and hoof scoring and care was conducted on d 60 and 180 of lactations 1 and 2, and quantitative real-time-PCR of blood leukocytes was analyzed in mid lactation of lactation 1. Mature-equivalent milk fat, milk protein, and protein percentages during the first lactation were greater for cows on the rubber flooring. Hoof and leg therapy treatments per cow were fewer for rubber floor-housed cows. Locomotion scores were less for cows housed on rubber during the second lactation. White blood cell counts were less for cows housed on rubber, and caused by greater lymphocyte counts for cows housed on concrete. The possibility of chronic inflammation was substantiated by less IL-1β and more IL-1 receptor antagonists for cows housed on rubber at d 150 in the second lactation. Cortisol and acute-phase proteins did not differ between the treatments. Interferon-γ, IL-12, the modulator of tissue reconstruction (B-cell-transforming growth factor 1), and pain-modulating neurokinin (tachykinin 1) were not different at d 105. These data show indicators of chronic inflammation for cows housed on the concrete flooring compared with those housed on rubber. Implications for the use of rubber flooring in freestall barns are broader than just lameness and may affect many aspects of cow physiology and production.

Effects of vaccination on the acute-phase protein response and measures of performance in growing beef calves

Two experiments were conducted to evaluate the influence of vaccination on the acute-phase protein (APP) reaction (Exp. 1 and 2) and measures of performance (Exp. 2) in growing beef calves. In Exp. 1, the APP reaction was assessed in newly weaned steers administered 1 of 3 treatments (n = 8 steers/treatment), consisting of 1) Mannheimia haemolytica vaccine (One Shot; Pfizer Inc., New York, NY), 2) Clostridium vaccine (UltraBac 7; Pfizer, Inc.), or 3) saline-injected control. Blood samples for the evaluation of APP concentrations were collected on d 0, 1, 3, 5, 7, 10, and 14 and steer BW measured on d 0 and 21 relative to treatment administration. Plasma concentrations of haptoglobin (Hp) increased (P < 0.05) in vaccinated but not control calves and reached a peak on d 3 and 5 for steers receiving Mannheimia haemolytica and Clostridium vaccine, respectively. Plasma concentrations of ceruloplasmin (Cp) and fibrinogen (Fb) increased (P < 0.05) in all calves after treatment administration and Fb concentrations were greatest (P < 0.01) in calves receiving Mannheimia haemolytica vaccine on d 3 and 5 compared with the other treatments. There were no treatment effects (P = 0.44) on 21-d steer ADG (0.43 kg/d; SEM = 0.082). In Exp. 2, 23 heifers were randomly assigned to 2 treatments: 1) vaccinated (Mannheimia haemolytica vaccine (One Shot; n = 12) and 2) saline control (n = 11). After vaccination, blood samples were collected for determination of APP concentrations on d 0, 3, 6, 9, 12, and 15. During this period, individual heifer DMI was measured using an automated feed intake measuring system (Model 4000E; GrowSafe Systems Ltd., Airdrie, Alberta, Canada). Initial and final shrunk BW did not differ (P > 0.36) among treatments. On d 1, plasma Cp concentrations increased (P < 0.01) sharply in vaccinated heifers but not control heifers and were greater (P < 0.05) in vaccinated vs. control heifers on d 3, 6, 9, and 12 relative to injection. Daily DMI did not differ (P = 0.66) among treatments (average = 9.1 kg/d; SEM = 0.34); however, ADG and G:F were greater (P ≤ 0.05) for control vs. vaccinated heifers (1.14 vs. 0.87 kg/d and 0.13 and 0.10 kg, respectively; SEM = 0.064 and 0.011). These data indicate that within a 2 wk period after vaccination, beef calves experience an acute-phase protein response, which may result in reduced ADG and feed efficiency.

Concentrations of haptoglobin in bovine plasma determined by ELISA or a colorimetric method based on peroxidase activity

The objective was to compare different procedures for determination of haptoglobin in bovine plasma. Nine Angus steers were vaccinated against Mannheimia haemolytica to stimulate an acute-phase response. Blood samples were collected immediately prior to vaccination (day 0), and on days 1, 3, 5, 7 and 10. Plasma samples were frozen in duplicates at -80 °C. One set of the duplicates was analysed for haptoglobin concentrations using a commercial ELISA kit. A day effect was detected (p < 0.01) because haptoglobin peaked on day 3 and returned to baseline on day 7 relative to vaccination. The second duplicate was analysed using a procedure that measures haptoglobin-haemoglobin complexing by estimating differences in peroxidase activity (CPPA) with results expressed as optical density. Further, based on the ELISA results, the plasma sample with the greatest haptoglobin concentration was also serially diluted into a plasma sample with negligible haptoglobin concentration from the same steer (1:1 through 1:1024 dilution). These dilutions were used within the CPPA method to generate a standard curve and estimate plasma haptoglobin concentrations (CPPA + STD). A linear standard curve was generated (r(2)  = 0.99). A day effect similar to the ELISA method was detected for the CPPA and CPPA + STD methods (p < 0.01). Results obtained from CPPA and ELISA methods were positively correlated (r = 0.97; p < 0.01). The values generated by the CPPA + STD procedure were similar (p = 0.38) compared to the values generated by the ELISA method. In conclusion, assessing concentrations of haptoglobin in bovine plasma using the CPPA and CPPA + STD methods generate highly correlated or similar results, respectively, compared to ELISA. Therefore, the CPPA + STD and CPPA methods can be used as a less expensive alternative to ELISA to determine concentrations or monitor changes in plasma haptoglobin in bovine samples.

Differential acute phase immune responses by Angus and Romosinuano steers following an endotoxin challenge

Our primary objective of this experiment was to evaluate potential genetic differences between two diverse Bos taurus breeds [Angus (AG) and Romosinuano (RO)] in response to an endotoxin challenge. Eighteen steers (n = 9 steers/breed; 299.4 ± 5.2 kg BW) were acclimated to environmentally controlled chambers maintained at thermoneutrality (19.7 °C) and then fitted with indwelling jugular catheters and rectal temperature (RT) recording devices 1 d before the endotoxin challenge. The next day, blood samples were collected at 30-min intervals from -2 to 8 h, and RT was measured continuously at 1-min intervals throughout the study. At time 0, all steers received an intravenous bolus injection of lipopolysaccharide (LPS; 2.5 μg/kg BW). Serum samples were stored at -80 °C until analyzed for cortisol, proinflammatory cytokines [tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and interferon gamma (IFN-γ)], and acute phase proteins (serum amyloid A, acid soluble protein, ceruloplasmin, and α-acid glycoprotein). Rectal temperatures increased in both breeds within 1 h after LPS, with RO producing a greater increase in RT than AG steers (P < 0.001). Serum cortisol and TNF-α increased (P < 0.01) in both breeds within 1 h after the LPS challenge. For cortisol, an overall breed effect (P < 0.02) was detected, such that AG steers had a higher cortisol response than RO steers. A breed × time interaction (P < 0.01) was observed for TNF-α, such that the response was delayed and extended in the RO steers compared with the AG steers. At 2 and 2.5 h after LPS, TNF-α concentrations were greater (P < 0.03) in RO steers than in AG steers. For IL-1β, a breed × time interaction (P < 0.04) was also observed. At 3 h after LPS, IL-1β concentrations were greater (P < 0.01) in RO steers than in AG steers. Serum IL-6 and IFN-γ increased (P < 0.01) in a similar manner in both groups after the LPS challenge. These data show differences in the innate immune response between two diverse Bos taurus breeds which may provide insight about differences observed in productivity, heat tolerance, disease resistance, and longevity among cattle breeds.

Evaluation of 2 sources of Angus cattle under South Florida subtropical conditions

The objective of this study was to compare performance and aspects of adaptability attributes of cattle from a Florida Angus bloodline (local source from a mostly closed herd for over 50 yr) to cattle that are representative of modern Angus bloodlines (outside source) in US subtropical conditions. Embryos from both sources were transferred to Brahman-crossbred cows in South Florida, and calves (n=82) were born in 3 yr. Before weaning, summer tympanic temperatures were recorded hourly for 3 d in each year. Heifers were placed with fertile bulls until diagnosed pregnant. Traits relative to sexual maturation of bulls were recorded at 1- or 2-mo intervals until approximately 17 mo of age. Calves from outside sources had greater hip height at weaning than calves from the local source (P<0.001; 108.8 ± 0.62 and 104.7 ± 0.68 cm, respectively). Local-source calves (n=37) had greater (P=0.03) exit velocity (2.7 ± 0.3 m/s) than outside-source (n=45) calves (2.0 ± 0.29 m/s), which may be indicative of more nervous or temperamental disposition. However, no source differences were detected for other assessments of disposition (chute or pen score, P>0.8). Few source differences for minimum, maximum, or range of daily tympanic (inner ear) temperatures were detected. At 17 mo of age, outside-source heifers were heavier (P = 0.05) and had greater (P<0.001) hip height than Angus heifers from the local source. Heifers from the outside source were younger (P<0.001) at the time of their first conception (454 ± 17.5 d) than heifers from the local source (550 ± 16.9 d). Outside-source heifers also had greater (P<0.02) pregnancy and calving rates (0.7 ± 0.119 and 0.62 ± 0.125, respectively) from exposure to bulls within a year from weaning than the heifers from the local source (0.29 ± 0.089 and 0.19 ± 0.077, respectively). Bulls from the outside source were heavier (P=0.05) at 320 d of age than local-source bulls. From 14 through 17 mo of age, outside-source bulls had greater (P≤0.05) scrotal circumference and tended (P≤0.15) to be heavier than local-source bulls. There appeared to be no performance or adaptation advantages for the local-source Angus through 17 mo of age. The large source difference for age at first conception in heifers merits additional attention and comparison with cow lifetime production performance for the 2 sources.

Effects of rumen-protected polyunsaturated fatty acid supplementation on performance and physiological responses of growing cattle after transportation and feedlot entry

Two experiments were conducted to evaluate the effects of rumen-protected PUFA supplementation on performance and inflammation measures in beef calves after truck transportation and feedyard entry. In Exp. 1, 30 weaned Braford steers (BW = 218 ± 4.3 kg) were transported for 1,600 km over a 24-h period in a commercial trailer and delivered to a feedlot (d 0). Upon arrival (d 1), steers were stratified by BW and allocated to receive 1 of 3 treatments (10 steers/treatment), which consisted of grain-based concentrates without supplemental fat (NF), or with the inclusion of a rumen-protected SFA (SF; 2.1% as-fed basis) or PUFA source (PF; 2.5% as-fed basis). Shrunk BW was determined on d 1 and 30 for ADG calculation. Individual DMI was recorded from d 2 to 28. Blood samples were collected on d 0, 1, 4, 8, 15, 22, and 29 for determination of acute-phase protein concentrations. Steers fed PF had decreased (P = 0.04) mean DMI and tended to have reduced ADG (P = 0.07) compared with NF-fed steers (2.32 vs. 2.72% of BW, and 0.78 vs. 1.07 kg/d, respectively). No other treatment effects were detected. In Exp. 2, 48 weaned Brahman-crossbred heifers (BW = 276 ± 4.6 kg) were stratified by initial BW and randomly allocated to 6 pastures (8 heifers/pasture) before transportation (d -30 to 0). Pastures were randomly assigned (3 pastures/treatment) to receive (DM basis) 3.0 kg/heifer daily of NF, or 2.5 kg/heifer daily of a concentrate containing 5.7% (as-fed basis) of a rumen-protected PUFA source (PF). On d 0, heifers were transported as in Exp. 1. Upon arrival (d 1), 24 heifers were randomly selected (12 heifers/treatment), placed into individual feeding pens, and assigned the same pretransport treatment. Shrunk BW was recorded on d -30, 1, and 30 to determine ADG. Individual DMI was recorded daily from d 2 to 28. Blood samples were collected on d 0, 1, 4, 8, 15, 22, and 29 for determination of acute-phase protein concentrations. A treatment × day interaction was detected for haptoglobin (P < 0.01) because PF-fed heifers had decreased haptoglobin concentrations compared with NF-fed heifers on d 1, 4, and 8. No other treatment effects were detected. Data from this study indicate that PUFA reduces haptoglobin concentrations in beef calves after transport and feedlot entry when supplemented before and after transportation. Further, PUFA supplementation during the feedyard only appears to negatively affect cattle performance by decreasing ADG and DMI.

Early weaning alters the acute-phase reaction to an endotoxin challenge in beef calves

Previous research indicates that early weaning before shipment can reduce transportation-induced increases in acute-phase proteins (APP) and can increase feedlot performance in beef calves. These data suggest that the combination of weaning and transport stress may compromise the immune system of calves, thus hindering subsequent performance and health. Therefore, our objective was to determine if the innate immune response of early weaned calves (EW; 80 d of age) differed from normal-weaned calves (NW; 250 d of age) in response to an endotoxin challenge. Eighteen Brahman x Angus calves (8 and 10 EW and NW, respectively; 233 +/- 5 kg of BW) were used. Calves were maintained on pasture with supplement and then moved into individual pens for 1 wk of acclimation before the start of the study. Calves were fitted with an indwelling jugular catheter 1 d before LPS challenge (0 h; 1.0 microg/kg of BW, intravenously). Blood samples were collected at 30-min intervals from -2 to 8 h. Serum samples were stored at -80 degrees C until analyzed for cortisol, tumor necrosis factor-alpha (TNF), IL-1 beta, IL-6, interferon-gamma (IFN), ceruloplasmin, and haptoglobin. Whereas LPS increased serum cortisol (P <or= 0.001), no weaning age effect (P >or= 0.15) was observed. A weaning age x time interaction (P <or= 0.04) was observed for TNF, IL-1, IL-6, and ceruloplasmin such that concentrations of these indices were greater in the NW compared with EW calves. For haptoglobin, a weaning age effect (P <or= 0.03) was observed with NW calves having greater average haptoglobin concentrations compared with EW calves. Interestingly, the weaning age x time interaction (P <or= 0.001) for IFN revealed greater IFN in EW compared with NW calves. Based upon these data, the innate immune system of EW calves appears to be more competent in responding to immune challenge compared with that of NW calves. Additionally, the differential IFN response indicates that the immune system of EW calves may be more effective at recognizing and eliminating endotoxin. These data suggest that an altered innate immune system may be one of the factors responsible for the improved feedlot performance previously reported in EW calves.

Technical note: copper chaperone for copper, zinc superoxide dismutase: a potential biomarker for copper status in cattle

Copper chaperone for Cu, Zn superoxide dismutase (CCS) has been shown to be reflective of Cu status in mice and rats. The objective of this study was to evaluate liver and erythrocyte CCS as an indicator of Cu status in beef cattle (Exp. 1), and to test the acute-phase properties of CCS under conditions of inflammation (Exp. 2). In Exp. 1, samples of whole blood and liver were collected at slaughter (492 d of age) from 15 Cu-deficient and 6 Cu-adequate Angus calves. At the time of tissue collection, severe Cu deficiency had been achieved and differences (P < 0.0001) in plasma and liver Cu among Cu-adequate and Cu-deficient calves were extreme (1.26 vs. 0.19 mg/L and 208.4 vs. 6.3 mg/kg for plasma and liver Cu, respectively). Protein levels of CCS were greater in liver (40%; P = 0.02) and erythrocytes (65%; P < 0.0001) of Cu-deficient vs. Cu-adequate calves. In Exp. 2, inflammatory responses were elicited in beef heifers by administration of a Mannheimia hemolytica vaccine. Four days after vaccination, plasma concentrations of the Cu-dependent protein ceruloplasmin and the Cu-independent protein haptoglobin were increased (P < 0.001) by 71 and 83%, respectively. In contrast, detection of CCS protein in samples of liver and erythrocytes did not differ (P >or= 0.45) between baseline (d 0) and d 4 after vaccination. These data demonstrate that bovine erythrocyte and liver CCS protein levels increase in Cu-deficient cattle. Furthermore, levels of CCS protein do not change after a vaccine-induced inflammatory response, suggesting that unlike ceruloplasmin, CCS may be a reliable indicator of Cu status in cattle.

Effects of acclimation to human interaction on performance, temperament, physiological responses, and pregnancy rates of Brahman-crossbred cows

The objective of this study was to evaluate, over 2 consecutive years, the effects of acclimation to human interaction on performance, temperament, plasma concentrations of hormones and metabolites, and pregnancy rates of Brahman-crossbred cows. A total of 160 Braford and 235 Brahman x British cows were assigned to the 2-yr study. Approximately 45 d after weaning (August 2006) in yr 1, cows were evaluated for BW, BCS, and temperament (chute score, pen score, and exit velocity), stratified by these measurements in addition to breed and age, and randomly allocated to 14 groups (Braford = 8; Brahman x British = 6). Groups were randomly assigned to the control or acclimation treatment. In yr 2, cows were reevaluated within 45 d after weaning (August 2007) for BW, BCS, and temperament, stratified, and divided into 14 groups similarly as in yr 1, but in such a way that cows received the same treatment assigned in yr 1. Cows were acclimated to human interaction from August to January, and the acclimation process consisted of the same person visiting groups twice weekly and offering approximately 0.05 kg of range cubes per cow (as-fed basis). In January of both years, cow temperament, BW, and BCS were reassessed and cows were exposed to a 90-d breeding season. Blood samples were collected at the beginning of the acclimation period (August) and breeding season (January) for determination of plasma cortisol, IGF-I, and acute phase proteins. A treatment x breed interaction was detected during yr 1 (P < 0.01) for pregnancy analysis because acclimated Braford cows conceived earlier and at a greater percentage (P < 0.01) compared with control cows. According to values obtained at the beginning of breeding and pooled across treatments and breeds, IGF-I concentrations and BCS affected quadratically (P < 0.05), and concentrations of ceruloplasmin and haptoglobin decreased linearly (P < 0.05), the probability of pregnancy during both years. Temperament and cortisol concentrations decreased the probability of pregnancy linearly (P < 0.05) during yr 1 (only Braford cows for cortisol analysis) and affected the probability of pregnancy quadratically (P < 0.05) during yr 2. Results from this study indicate that acclimation did not affect cow temperament and physiological responses but did increase pregnancy rates of Braford cows during yr 1. Further, measurements and physiological responses associated with temperament influenced the probability of cows becoming pregnant during the breeding season.

Effects of acclimation to handling on performance, reproductive, and physiological responses of Brahman-crossbred heifers

The objective of this study was to evaluate the effects of acclimation to handling on growth, plasma concentrations of progesterone (P4) and cortisol, temperament, and reproductive performance of Brahman-crossbred heifers. Over 2 consecutive years, 37 Braford and 43 Brahman x Angus heifers were initially evaluated, within 30 d after weaning, for BW and puberty status via transrectal ultrasonography and plasma P4 concentrations (d 0 and 10), and for temperament by measurements of chute score, pen score, and exit velocity (d 10 only). On d 11, heifers were stratified by breed, puberty status, temperament score, BW, and age and randomly assigned to receive or not (control) the acclimation treatment. Acclimated heifers were exposed to a handling process 3 times weekly (Mondays, Wednesdays, and Fridays) for 4 wk (d 11 to 39 of the experiment). The acclimation treatment was applied individually to heifers by processing them through a handling facility, whereas control heifers remained undisturbed on pasture. Heifer puberty status, evaluated via plasma P4 concentrations and transrectal ultrasonography, and BW were assessed again on d 40 and 50, d 80 and 90, and d 120 and 130. Blood samples collected before (d 10) and at the end of the acclimation period (d 40) were also analyzed for plasma concentrations of cortisol. Heifer temperament was assessed again on d 40 of the study. No interactions containing the effects of treatment, breed, and year were detected. Acclimated heifers had reduced (P < 0.01) ADG compared with control heifers (0.50 vs. 0.58 kg/d, respectively). Attainment of puberty and pregnancy, however, was hastened (P = 0.02 and 0.04, respectively) in acclimated heifers compared with control. Acclimated heifers had reduced chute score (P < 0.01) and concentrations of cortisol (P < 0.01) and P4 (P = 0.03; prepubertal heifers only) compared with control heifers after the acclimation period (1.37 vs. 1.84 for chute score; 37.8 vs. 50.5 ng/mL of cortisol; 0.52 vs. 0.78 ng/mL of P4). Results from this study indicated that, although acclimation to handling decreased ADG, it resulted in decreased chute score, reduced plasma concentrations of cortisol and prepubertal P4, and enhanced reproductive performance of Brahman-crossbred heifers.

Effects of preshipping management on measures of stress and performance of beef steers during feedlot receiving

Over 2 yr, a total of 96 steers (approximately 7 mo of age) were allocated to 1 of 4 weaning management strategies: 1) control: weaned on the day of shipping; 2) creep-fed: allowed free-choice access to concentrate before weaning and shipping; 3) preweaned: weaned and provided supplemental concentrate on pasture before shipping; and 4) early-weaned: weaned at 70 to 90 d of age and kept on pasture. On the day of shipping, steers were loaded together onto a commercial livestock trailer and transported 1,600 km over 24 h before being received into the feedlot. At the feedlot, steers were penned by treatment (4 pens/treatment) and provided access to free-choice hay and concentrate in separate feeding spaces. Samples of blood were collected on d 0, 1, 4, 8, 15, 22, and 29 relative to shipping. Steer performance was assessed over the receiving period, including DMI of hay and concentrate, ADG, and G:F. Predetermined contrasts included control vs. early-weaned, creep-fed vs. preweaned, and control vs. creep-fed and preweaned. Overall ADG was greater (P < 0.01) for early-weaned vs. control steers (1.39 vs. 0.88 kg). In wk 1, early-weaned steers consumed more concentrate and less hay compared with control steers (P < 0.03), and preweaned steers consumed more concentrate (P < 0.01) but a similar amount of hay (P = 0.75) compared with creep-fed steers. Average DMI was greater for preweaned compared with creep-fed steers (2.84 vs. 2.50% of BW; P = 0.01) and tended to be greater for early-weaned compared with control steers (2.76 vs. 2.50% of BW; P = 0.06). Feed efficiency of early-weaned steers was greater than that of control steers (G:F = 0.17 vs. 0.12; P < 0.01) but similar for preweaned compared with creep-fed steers (P = 0.72). Plasma ceruloplasmin concentrations were less (P < 0.05) in control vs. early-weaned steers on d 0, but increased sharply after shipping and were greater in control vs. early-weaned steers on d 15 and 22 (P < 0.05). Creep-fed steers also experienced greater (P < 0.05) plasma ceruloplasmin concentrations than preweaned steers on d 29. These data suggest that early-weaned steers have improved performance in the feedlot compared with steers weaned directly before transport and feedlot entry. Differences in preshipping management appear to significantly affect measures of the acute phase protein response in steers.

Influence of a CIDR prior to bull breeding on pregnancy rates and subsequent calving distribution

We determined whether insertion of a CIDR for 7 days prior to the breeding season enhanced pregnancy rates and altered the date of conception in suckled beef cows mated naturally. Suckled beef cows (n=2033) from 15 locations were randomly assigned to one of two treatments: (1) cows received a CIDR 7 days prior to the breeding season for 7 days (CIDR; n=999); (2) cows received no treatment (Control; n=1034). On the first day of the breeding season bulls were introduced to herds at a rate of 15-25 cows per yearling bull or 20-30 cows per mature bull. Pregnancy status and the date of conception were determined via transrectal ultrasonography at 56 and 120 days after initiation of the breeding season. Overall pregnancy rates ranged from 59.3 to 98.9% among the 15 locations. The percentage of cows becoming pregnant during the first 30 days of the breeding season was similar between CIDR (68.2%) and Control (66.7%) cows, and overall pregnancy rates were similar between CIDR (88.9%) and Control (88.6%) cows. The average day of conception after initiation of the breeding season was shorter (P<0.01) for CIDR (20.1+/-0.8 days) compared to Control cows (23.2+/-0.8 days). Of cows conceiving during the breeding season, more (P<0.05) CIDR cows (35.9%) conceived during the first 10 days of the breeding season than Control cows (30.8%). Neither body condition score and nor parity affected pregnancy rates or days to conception, whereas pregnancy rates and days to conception were affected (P<0.01) by location and days postpartum. Days to conception were greater for cows that calved within 40 days (31.6+/-1.2 days) of initiation of the breeding season compared to cows calving between 40 and 50 days (25.3+/-1.2 days) prior to initiation of the breeding season, which were greater than those cows calving between 50-60 days (20.0+/-0.8 days) and 60-70 days (21.3+/-1.0 days) prior to initiation of the breeding season. Cows calving greater than 70 days (17.3+/-1.5 days) from initiation of the breeding season had the shortest interval to conception. We concluded that insertion of a CIDR prior to the breeding season failed to increase overall pregnancy rates, but did influence the average day of conception.

Optimizing nitrogen utilization in growing steers fed forage diets supplemented with dried citrus pulp

Our objectives were to compare the effects of sources of supplemental N on ruminal fermentation of dried citrus pulp (DCP) and performance of growing steers fed DCP and bahiagrass (Paspalum notatum) hay. In Exp. 1, fermentation of DCP alone was compared with that of isonitrogenous mixtures of DCP and solvent soybean meal (SBM), expeller soybean meal (SoyPLUS; SP), or urea (UR). Ground (1 mm) substrates were incubated in buffered rumen fluid for 24 h, and IVDMD and fermentation gas production kinetics and products were measured. Nitrogen supplementation increased (P < 0.10) ruminally fermentable fractions, IVDMD, pH, and concentrations of NH3 and total VFA, but reduced the rate of gas production (P < 0.10) and the lag phase (P < 0.01). Supplementation with UR vs. the soy-based supplements increased ruminally fermentable fractions (P < 0.05) and concentrations of total VFA (P < 0.10) and NH3 (P < 0.01), but these measures were similar (P > 0.10) between SBM and SP. In Exp. 2, 4 steers (254 kg) were fed bahiagrass hay plus DCP, or hay plus DCP supplemented with CP predominantly from UR, SBM, or SP in a 4 x 4 Latin square design, with four 21-d periods, each with 7 d for DMI and fecal output measurement. Nitrogen-supplemented diets were formulated to be isonitrogenous (11.9% CP), and all diets were formulated to be isocaloric (66% TDN). Intake and digestibility of DM, N, and ADF were improved (P < 0.05) by N supplementation. Compared with UR, the soy-based supplements led to greater (P < 0.05) DM and N intakes and apparent N and ADF digestibilities. Plasma glucose and urea concentrations increased (P < 0.10) with N supplementation and were greater (P < 0.01) for the soy-based supplements than for UR. Intake, digestibility, and plasma metabolite concentrations were similar (P > 0.1) for SBM and SP. In Exp. 3, 24 steers (261 kg) were individually fed bahiagrass hay plus DCP (control), or hay plus DCP supplemented with CP predominantly from UR or SBM. Over 56 d, DMI and ADG were greatest (P < 0.05) in steers fed SBM. Nitrogen supplementation increased (P < 0.05) DMI, ADG, and G:F. However, SBM supplementation produced greater (P < 0.05) DMI and ADG and similar (P > 0.05) G:F compared with UR supplementation. We conclude that supplemental N is important to optimize ruminal function and performance of growing steers fed forage diets supplemented with DCP. Diets with supplemental N mainly from SBM improved diet digestibility and animal performance beyond that achieved by UR.