Effect of live weight gain of steers during winter grazing: III. Blood metabolites and hormones during feedlot finishing12

Enzymic Activity, Metabolites, and Hematological Responses in High-Risk Newly Received Calves for "Clinical Health" Reference Intervals

Enzymic activity, metabolites, and hematological responses for reference intervals (RIs) establish ranges of physiological normality, which are useful for diagnosing diseases and physiological alterations. Within the same species, RIs vary according to age, gender, productive and physiological states, and environmental factors including health management and nutrition. RIs have been extensively studied in dairy calves during a critical stage of life (from birth up to first 90 days of age). A critical stage for feedlot calves is their arrival at the feedlot, but no reports determine RIs for different enzymic activity, metabolites, and hematological responses during their initial period at the feedlot. Consequently, a total of 461 high-risk crossbreed beef calves, received on three different dates, were examined upon arrival at the feedlot. Of these, 320 calves (148.3 ± 1.3 kg body weight) whose "clinical health" was evaluated were included in the study. Blood samples were taken upon arrival and on days 14, 28, 42, and 56 to determine the following parameters: enzymic activity, metabolites, electrolytes, white blood cells, platelets, and red blood cells. Enzymic activity, metabolites, and complete blood count were determined by automated analyzers. The freeware Reference Value Advisor Software was used to calculate the non-parametric values of RIs. This study is the first to establish RIs for different enzymic activity, metabolites, and hematological responses in high-risk newly received calves during their initial period at the feedlot. This information will be useful for veterinary clinical practice and research related to the health and welfare of high-risk newly received calves during their initial period at the feedlot.

Effects of Supplemental Calcium Propionate and Concentrate Level: Growth Performance, Body Fat Reserves, and Health of High-Risk Beef Calves

The aim of this study was to examine the impact of daily calcium propionate (CaPr) supplementation (0 or 20 g/calf) on growth performance, dietary energetics, body fat reserves, serum metabolites, and hematological responses in high-risk beef calves fed diets with varying (50, 60, or 70%) concentrate (CON) levels. In addition, a cost/income analysis of CaPr supplementation was carried out. Forty-eight crossbred bull calves (152.8 ± 1.56 kg body weight and 5.5 months of age) were involved in a fully randomized experimental design employing a 2 × 3 factorial arrangement of treatments. Calves were allocated (n = 8 per treatment) to individual pens (3.14 × 5.25 m) and were subjected to one of the following treatments during 42 d: No CaPr supplementation in diets containing 50, 60, or 70% CON (NoCaPr + 50, NoCaPr + 60, NoCaPr + 70, respectively) or daily CaPr supplementation dosed at 20 g/calf in diets containing 50, 60, or 70% CON (20CaPr + 50, 20CaPr + 60, 20CaPr + 70, respectively). Non-supplemented calves exhibited decreased dry matter intake (DMI) with increasing CON levels in their diets, while CaPr-supplemented calves displayed the opposite effect (interaction, p = 0.04). In calves fed a lower-CON diet (50%), those supplemented with CaPr showed greater average daily gain (ADG, 20.2%, p = 0.05) and lower DMI (2.2%, p = 0.03), resulting in improved ADG/DMI ratio, dietary energy, and energy retention (24.6, 14.4, and 18%, p < 0.05). These effects diminished when calves received diets with 60 or 70% CON but led to a 14.2% increase in rump fat thickness (p = 0.04). Only in non-supplemented CaPr calves, increasing the level of CON from 50 to 70% in the diet increased ADG (21.2%), decreased DMI (2.2%), and improved the ADG/DMI ratio (22.7%), with no impact on dietary net energy utilization. Non-supplemented calves exhibited an increase in lymphocytes as CON levels rose in their diets, whereas CaPr-supplemented calves showed the opposite effect (interaction, p = 0.05). Supplementation of CaPr decreased total protein (TP, p = 0.03) and albumin (ALB, p < 0.01) serum concentrations, with lower concentrations observed in 20CaPr + 50. CaPr supplementation reduced (p = 0.01) total cholesterol (TCHO) levels. An interaction between CaPr and CON level (p = 0.02) was observed since TCHO levels remained consistently low at higher CON levels. Glucose was decreased with increasing levels of CON (p = 0.02) but not (p = 0.85) for CaPr-supplemented calves. NoCaPr + 50 and NoCaPr + 70 increased (p = 0.05) ALB concentration. Gamma glutamyltransferase levels increased (p = 0.05) with increasing CON levels irrespective of CaPr supplementation. Comparing the profit within the same CON level in the diet, CaPr treatments yielded higher income, with the largest difference in profit observed when CaPr was supplemented at 50% CON level (USD 29 more/calf). In conclusion, CaPr supplementation proves to be an effective strategy for enhancing growth performance and dietary energy among high-risk beef calves, resulting in greater economic returns. The groups that received CaPr demonstrated superior profitability, particularly in calves fed diets with lower CON levels. Under the conditions in which this experiment was carried out, the optimal response occurred when the low-CON diet (50%) was supplemented with CaPr.

Supplementing a Bacillus-based probiotic to high-risk stocker cattle

This experiment evaluated the performance, health, and physiological responses of high-risk steers receiving a Bacillus-based probiotic during a 90-d grazing period. A total of 240 Angus-influenced steers were used in this experiment that was replicated over 2 yr (120 steers/year). Each year, steers were obtained from an auction yard and transported to the experimental facility (120 km). Steer body weight (BW) was recorded at arrival (day -1), and this value was averaged with BW recorded on day 0 to represent the initial BW (236.6 ± 1.5 kg). On day 0, steers were ranked by BW and allocated to 1 of 12 pastures with stockpiled native grass (4-ha pastures; 10 steers/pasture). Pastures were randomly assigned to receive daily supplementation with dried distillers' grains at 1% of BW containing either: 1) Bacillus subtilis + B. licheniformis probiotic (BOV; 2 g/steer daily of Bovacillus; Novonesis, Horsholm, Denmark) or 2) no feed additive (CON). Cattle received treatments from days 0 to 90, in addition to free-choice access to water and mineral + vitamin mix without ionophore. Steers were assessed for bovine respiratory disease (BRD) signs daily. Blood samples were collected and full BW was recorded on days 0, 14, 28, 56, and 90. Shrunk BW was recorded on day 91 after 16 h of feed and water restriction, and a 4% pencil shrink was used to calculate the final BW. Average daily gain (ADG) was calculated based on initial and final BW. No treatment effects were detected (P ≥ 0.73) for steer final BW and ADG. A treatment × day interaction was detected (P ≤ 0.05) for plasma haptoglobin concentration, which was greater for CON steers on days 14 and 28 (P ≤ 0.02). Incidence of BRD signs did not differ (P = 0.97) between treatments (51.7% and 51.3% for BOV and CON, respectively; SEM = 7.70). However, steer mortality + removals for health complications were greater (P = 0.01) in CON compared to BOV (0.00% vs. 5.04%, respectively; SEM = 1.41). Supplementing BOV improved (P ≤ 0.04) total pasture-based liveweight change (643 vs. 502 kg/pasture, respectively; SEM = 45) and final pasture-based total liveweight (3,007 vs. 2,869 kg/pasture, respectively; SEM = 46). Collectively, supplementation with a probiotic based on B. subtilis and B. licheniformis to high-risk stocker cattle did not alleviate the incidence of BRD signs nor improved ADG, but decreased acute-phase protein response, reduced steer mortality + removal, and increased pasture-based productivity during a 90-d grazing period.

Supplementing pre- and probiotic ingredients to feedlot steers: effects on health, growth performance, and physiological responses

Feedlot diets are often enriched with additives to mitigate health disorders and promote cattle performance, including the feed-grade antimicrobials monensin and tylosin. However, alternative feeding strategies are warranted given the increasing regulations regarding the use of antimicrobials in feedlot diets. This study evaluated the performance, physiological, and health responses of feedlot cattle offered a synbiotic supplement (yeast-derived prebiotic + Bacillus subtilis probiotic), which replaced or was fed in conjunction with monensin and tylosin. Angus-influenced steers (n = 192) from four different cowherds were weaned on day -1 and transported (800 km) to the feedlot. Steers were allocated to 1 of 24 pens (eight steers/pen) upon arrival on day 0. Pens were assigned to receive (n = 8/treatment) a total-mixed ration (TMR) containing: (1) monensin and tylosin (RT; 360 mg/steer daily from Rumensin and 90 mg/steer daily from Tylan; Elanco Animal Health, Greenfield, IN, USA), (2) yeast-derived ingredient and B. subtilis probiotic (CC; 18 g/steer daily of Celmanax and 28 g/steer daily of Certillus; Church and Dwight Co., Inc., Princeton, NJ, USA), or (3) a combination of RT and CC (RTCC). Steers were slaughtered according to BW in four groups balanced by treatment and pens and received treatments for 252 ± 4 days. No treatment effects were detected (P ≥ 0.17) for steer BW gain and morbidity responses. Mean TMR intake was greater and gain:feed ratio was less (P ≤ 0.01) in CC compared with RT and RTCC steers. Mean plasma leptin concentration was greater (P ≤ 0.05) in CC compared with RT and RTCC steers. Steers receiving CC had greater (P ≤ 0.04) concentrations of plasma cortisol, haptoglobin, glucose, and beta-hydroxybutyrate, and less (P ≤ 0.05) concentration of non-esterified fatty acids compared with RT and RTCC steers on day 14 of the experiment. Carcass marbling was greater (P = 0.01) in CC compared with RT steers and tended to be greater (P = 0.07) in RTCC compared with RT steers. Proportion of carcasses that graded Choice or better and Longissimus muscle area were greater (P ≤ 0.05) in CC and RTCC compared with RT steers. Incidence of liver abscesses was less (P = 0.01) in RTCC compared with CC steers and tended to be less (P = 0.09) in RT compared with CC steers. Results from this experiment indicate that the synbiotic supplement may replace monensin and tylosin without reducing steer BW gain, with potential improvements to carcass quality traits.

Inclusion of Yucca schidigera extract into finishing diets: impacts on ruminal, physiological, and productive responses of feedlot cattle

This experiment compared ruminal, physiological, and productive responses of feedlot cattle receiving Yucca schidigera extract to replace or fed in conjunction with monensin + tylosin. Angus-influenced steers (n = 120) were ranked by body weight (BW; 315 ± 3 kg) and allocated to 4 groups of 30 steers each. Groups were housed in 1 of 4 drylot pens (30 × 12 m) equipped with GrowSafe feeding systems (4 bunks/pen) during the experiment (day -14 to slaughter). On day 0, groups were randomly assigned to receive a diet containing (2 × 2 factorial): 1) no inclusion or inclusion of monensin + tylosin (360 mg and 90 mg/steer daily, respectively) and 2) no inclusion or inclusion of Y. schidigera extract (4 g/steer daily). Steers were slaughtered in 3 groups balanced by treatment combination (36 steers on day 114, 36 steers on day 142, and 48 steers on day 169). Blood was sampled on days 0, 28, 56, and 84, and the day before shipping to slaughter. On day 41, eight rumen-cannulated heifers (BW = 590 ± 15 kg) were housed with steers (1 pair/pen). Pairs rotated among groups every 21 d, resulting in a replicated 4 × 4 Latin square (n = 8/treatment combination) with 14-d washout intervals. Heifers were sampled for blood and rumen fluid at the beginning and end of each 21-d period. Monensin + tylosin inclusion decreased (P < 0.01) feed intake and improved (P = 0.02) feed efficiency of steers, but did not alter (P ≥ 0.17) steer BW gain or carcass merit traits. Inclusion of Y. schidigera extract did not impact (P ≥ 0.30) steer performance and carcass characteristics. Plasma glucose, insulin, insulin-like growth factor-I, and urea-N concentrations were not affected (P ≥ 0.16) by monensin + tylosin, nor by Y. schidigera extract inclusion in steers and heifers. Ruminal pH in heifers was increased (P = 0.04) by monensin + tylosin, and also by (P = 0.03) Y. schidigera extract inclusion. Rumen fluid viscosity was reduced (P = 0.04) by Y. schidigera extract, and rumen protozoa count was increased (P < 0.01) by monensin + tylosin inclusion. The proportion of propionate in the ruminal fluid was increased (P = 0.04) by monensin + tylosin, and tended (P = 0.07) to be increased by Y. schidigera extract inclusion. Hence, Y. schidigera extract yielded similar improvements in rumen fermentation compared with monensin + tylosin, but without increasing performance and carcass quality of finishing cattle. No complimentary effects were observed when combining all these additives into the finishing diet.

Growth Performance and Plasma Metabolites of Grazing Beef Cattle Backgrounded on Buffel or Buffel-Desmanthus Mixed Pastures

Simple Summary

Pasture quality and digestibility decline during the dry season resulting in weight loss or marginal weight gains of grazing cattle in the seasonally dry subtropics of northern Australia. Oversowing grass with legume pastures has shown potential to improve pasture quality and cattle weight gain. This study aimed to evaluate the change in steers’ weight gain and plasma metabolites in response to grazing buffel grass pastures oversown with Desmanthus spp. (Desmanthus), a tropical legume adapted to cracking clay soils, compared to buffel-grass-only pastures. Results showed that Desmanthus at a low botanical composition had no effect on weight gain and plasma metabolites, although pasture yield and stocking rate were 443 kg/ha and 9.5% higher, respectively. Since the productivity of grazing systems depends on cattle annual weight gain and stocking rate, the practical implication of this study is that Desmanthus may improve the profitability of beef production in the dry tropics of northern Australia by improving pasture-carrying capacity with no adverse effect on cattle health status and growth performance.

Abstract

Dietary crude protein and dry matter digestibility are among the major factors limiting feed intake and weight gain of cattle grazing native and improved pastures in the subtropics of Northern Australia during the dry season. Incorporating a suitable legume into grasses improves pasture quality and cattle weight gain, but only a limited number of legume pastures can establish and persist in cracking clay soils. This study aimed to evaluate the effect of Desmanthus inclusion in buffel grass (Cenchrus ciliaris) pastures on the plasma metabolite profile and growth performance of grazing beef cattle during the dry season. We hypothesised that backgrounding steers on buffel grass-Desmanthus mixed pastures would elicit significant changes in plasma glucose, bilirubin, creatinine, non-esterified fatty acids and β-hydroxybutyrate, resulting in higher liveweight gains than in steers on buffel grass only pastures. Four hundred tropical composite steers were assigned to buffel grass only (n = 200) or buffel grass oversown with Desmanthus (11.5% initial sward dry matter) pastures (n = 200) and grazed for 147 days during the dry season. Desmanthus accounted for 6.2% sward dry matter at the end of grazing period. Plasma metabolites results showed that changes in β-hydroxybutyrate, creatinine, bilirubin, glucose and non-esterified fatty acids were within the expected normal range for all the steers, indicating that with or without Desmanthus inclusion in the diet of grazing steers, animal health status was not compromised. It was also evident that Desmanthus inclusion in buffel grass pastures had no impact on the plasma metabolite profile, liveweight and daily weight gain of grazing steers. Therefore, our tested hypothesis of higher changes in plasma metabolite profile and higher liveweight gains due to backgrounding on low-level buffel grass-Desmanthus mixed pastures does not hold.

Performance, health, and physiological responses of newly received feedlot cattle supplemented with pre- and probiotic ingredients

Nutritional strategies that optimize immunity of feedlot cattle are warranted due to increasing regulations with the use of feed-grade antimicrobials. This study evaluated physiological, health, and performance responses of cattle receiving a synbiotic supplement (yeast-derived prebiotic + Bacillus subtilis probiotic), which replaced feed-grade antimicrobials or were fed in conjunction with monensin during the initial 45 days in the feedlot. Angus-influenced steers (n = 256) were acquired from an auction facility on day -2, and transported (800 km) to the feedlot. Shrunk BW was recorded upon arrival (day -1). Steers were allocated to 1 of 18 pens (day 0), and pens were assigned to receive (n = 6/treatment) a free-choice diet containing: (1) monensin and tylosin (RT; 360 mg/steer daily from Rumensin and 90 mg/steer daily from Tylan; Elanco Animal Health, Greenfield, IN, USA), (2) yeast-derived ingredient and B. subtilis probiotic (CC; 18 g/steer daily of Celmanax and 28 g/steer daily of Certillus; Church and Dwight Co., Inc., Princeton, NJ, USA), or (3) monensin in addition to yeast-derived and B. subtilis ingredients (RCC) as in RT and CC. Steers were assessed for bovine respiratory disease (BRD) and DMI daily. Steer BW was recorded on days 45 and 46, and averaged for final BW. Blood samples were collected on days 0, 7, 17, 31, and 45. Feed intake was greater (P ≤ 0.05) in CC vs. RCC and RT during the initial 3 weeks upon feedlot arrival. No treatment differences were noted (P ≥ 0.41) for average daily gain, BW, and feed efficiency. Incidence of BRD did not differ (P = 0.77) between treatments (average 80.1%). A greater proportion (P ≤ 0.03) of RT steers diagnosed with BRD required a second antimicrobial treatment compared with CC and RCC (57.3, 37.3, and 38.6%, respectively). Removal of steers from the trial due to severe morbidity + mortality was greater (P = 0.02) in RT vs. CC (22.4 and 7.0%), and did not differ (P ≥ 0.16) among RCC (12.9%) vs. RT and CC. Plasma glucose concentrations were greater (P ≤ 0.02) in CC vs. RCC and RT on day 7. Plasma concentrations of nonesterified fatty acids were greater (P ≤ 0.02) in RT and RCC vs. CC on day 7, and in RT vs. CC on day 17. Steers receiving the synbiotic supplement had improved response to BRD treatment, suggesting heightened immunocompetence from partially enhanced metabolism and the nutraceutical effects of B. subtilis and yeast compounds.

Administering an appeasing substance to optimize performance and health responses in feedlot receiving cattle

This experiment evaluated the impacts of administering a bovine appeasing substance (BAS) at feedlot entry to receiving cattle. Angus-influenced steers (n = 342) from 16 sources were purchased from an auction yard on day -1, and transported (12 hr; 4 trucks) to the feedlot. Upon arrival on day 0, shrunk body weight (BW; 240 ± 1 kg) was recorded and steers were ranked by load, shrunk BW, and source and assigned to receive BAS (IRSEA Group, Quartier Salignan, France; n = 171) or placebo (diethylene glycol monoethyl ether; CON; n = 171). The BAS is a mixture of fatty acids that replicate the composition of the bovine appeasing pheromone. Treatments (5 mL) were topically applied to each individual steer on their nuchal skin area. Steers were allocated to 1 of 24 drylot pens (12 pens/treatment) and received a free-choice diet until day 46. Steers were assessed daily for bovine respiratory disease (BRD) signs, and feed intake was recorded from each pen daily. Steer unshrunk BW was recorded on days 7, 17, 31, 45, and 46. Shrunk BW on day 0 was added an 8% shrink to represent initial BW, and final BW was calculated by averaging BW from days 45 and 46. Blood samples were collected from 5 steers/pen on days 0, 7, 11, 31, and 45. Pen was considered the experimental unit. Steer BW gain was greater (P = 0.04) in BAS vs. CON (1.01 vs. 0.86 kg/d, SEM = 0.05). Feed intake did not differ (P = 0.95) between treatments, resulting in greater (P = 0.05) feed efficiency in BAS vs. CON (171 vs. 142 g/kg, SEM = 10). Plasma cortisol concentration was greater (P = 0.05) and plasma glucose concentration was less in CON vs. BAS on day 7 (treatment × day; P = 0.07 and <0.01, respectively). Mean plasma β-hydroxybutyrate concentration was greater (P < 0.01) in BAS vs. CON (3.23 and 2.75 mg/mL; SEM = 0.12). Incidence of BRD was greater (P ≤ 0.05) in BAS vs. CON from days 6 to 10 and days 19 to 23 (treatment × day; P < 0.01), although overall BRD incidence did not differ (P = 0.20) between treatments (82.4% vs. 76.6%, respectively; SEM = 3.2). A greater proportion (P = 0.04) of BAS steers diagnosed with BRD required one antimicrobial treatment to regain health compared with CON (59.3% vs. 47.6%, SEM = 4.2). Hence, BAS administration to steers upon feedlot arrival improved BW gain during a 45-d receiving period by enhancing feed efficiency. Moreover, results suggest that BAS improved steer performance by facilitating early detection of BRD signs, lessening the disease recurrence upon first antimicrobial treatment.

Thyroid Hormones, Insulin, Body Fat, and Blood Biochemistry Indices in Dairy Cows During the Reproduction/Production Cycle

This study investigated the changes in: thyroid hormones, amount of subcutaneous fat, and selected indices of blood biochemistry in dairy cows in relation to the reproduction/production cycle. The blood samples were collected both ante- and post-partum every two weeks. When evaluating the mean values of the investigated indices, the major changes were recorded in dairy cows 3 to 14 days after calving. During this period, we observed a significant decrease in the mean serum levels of T3 (P < 0.05), T4 (P < 0.01), and triglycerides (P < 0.01). An opposite trend was observed with a significant increase after calving in the: mean serum levels of β-hydroxybutyrate (P < 0.05), urea (P < 0.01), and mean AST activities (P < 0.05). A significant increase over the normal range was recorded in the average levels of non-esterified fatty acids (P < 0.01) and total bilirubin (P < 0.01). From the next sampling (28 days after calving) onwards we recorded a significant increase in the blood serum levels of cholesterol (P < 0.01), total lipids (P < 0.01), total protein (P < 0.01), as well as a significant decrease in the insulin levels (P < 0.05) and a reduced layer of subcutaneous fat (P < 0.01). The blood serum iodine concentration showed only slight significant changes (P < 0.05) during the observation. Blood serum levels of glucose did not show any significant changes during the whole observation period. Within the whole observation period we found a negative correlation between T3 levels and the layer of subcutaneous fat (r = −0.2606; P < 0.05). This correlation was much more marked in cows 3 to 14 days after calving (r = −0.5077; P < 0.05), which may indicate a possible relationships between the thyroid status, body condition, and post partum negative energy balance.

Biochemical profiles and physicochemical parameters of beef from cattle raised under contrasting feeding systems and pre-slaughter management

Diet and pre-slaughter stress are key factors that may affect the biochemical processes during conversion of muscle into meat. The aim of the present study was to evaluate the effect of two different pre-slaughter stress managements (PSM) at a slaughterhouse in Angus steers raised and finished in two contrasting feeding systems (FS grain and pasture systems), on the peri mortem muscle metabolism, and its relation to of meat quality. Results obtained showed that a higher level of pre-slaughter stress increased (P < 0.05) glucose, lactate and proteins blood levels and decreased (P < 0.05) the redness (a* parameter) of adipose tissue. Regarding feeding strategy, pasture-fed animals displayed increased (P < 0.05) levels of haematocrit and insulin concentrations, and higher (P < 0.05) muscle pH decrease during the first 3 h post mortem. Despite final pH (pH 24 h) of M. longissimus dorsi (LD) was not significantly modified, LD hardness was significantly affected by an interaction effect of FS and PSM. Lower pre-slaughter stress level led to a decrease (P < 0.05) of LD hardness in grain-fed animals. In general terms, results showed an impact of PSM and FS on meat quality through pH-independent mechanisms.

Supplementation based on protein or energy ingredients to beef cattle consuming low-quality cool-season forages: I. Forage disappearance parameters in rumen-fistulated steers and physiological responses in pregnant heifers

Two experiments evaluated the influence of supplement composition on ruminal forage disappearance, performance, and physiological responses of Angus × Hereford cattle consuming a low-quality cool-season forage (8.7% CP and 57% TDN). In Exp. 1, 6 rumen-fistulated steers housed in individual pens were assigned to an incomplete 3 × 2 Latin square design containing 2 periods of 11 d each and the following treatments: 1) supplementation with soybean meal (PROT), 2) supplementation with a mixture of cracked corn, soybean meal, and urea (68:22:10 ratio, DM basis; ENER), or 3) no supplementation (CON). Steers were offered meadow foxtail (Alopecurus pratensis L.) hay for ad libitum consumption. Treatments were provided daily at 0.50 and 0.54% of shrunk BW/steer for PROT and ENER, respectively, to ensure that PROT and ENER intakes were isocaloric and isonitrogenous. No treatment effects were detected on rumen disappearance parameters of forage DM (P ≥ 0.33) and NDF (P ≥ 0.66). In Exp. 2, 35 pregnant heifers were ranked by initial BW on d -7 of the study, allocated into 12 feedlot pens (4 pens/treatment), and assigned to the same treatments and forage intake regimen as in Exp. 1 for 19 d. Treatments were fed once daily at 1.77 and 1.92 kg of DM/heifer for PROT and ENER, respectively, to achieve the same treatment intake as percent of initial BW used in Exp. 1 (0.50 and 0.54% for PROT and ENER, respectively). No treatment effects (P = 0.17) were detected on forage DMI. Total DMI was greater (P < 0.01) for PROT and ENER compared with CON and similar between PROT and ENER (P = 0.36). Accordingly, ADG was greater (P = 0.01) for PROT compared with CON, tended to be greater for ENER compared with CON (P = 0.08), and was similar between ENER and PROT (P = 0.28). Heifers receiving PROT and ENER had greater mean concentrations of plasma glucose (P = 0.03), insulin (P ≤ 0.09), IGF-I (P ≤ 0.04), and progesterone (P = 0.01) compared to CON, whereas ENER and PROT had similar concentrations of these variables (P ≥ 0.15). A treatment × hour interaction was detected (P < 0.01) for plasma urea N (PUN), given that PUN concentrations increased after supplementation for ENER and PROT (time effect, P < 0.01) but did not change for CON (time effect, P = 0.62). In conclusion, beef cattle consuming low-quality cool-season forages had similar ruminal forage disappearance and intake, performance, and physiological status if offered supplements based on soybean meal or corn at 0.5% of BW.

Supplementation based on protein or energy ingredients to beef cattle consuming low-quality cool-season forages: II. Performance, reproductive, and metabolic responses of replacement heifers

This experiment evaluated the influence of supplement composition on performance, reproductive, and metabolic responses of Angus × Hereford heifers consuming a low-quality cool-season forage (8.7% CP and 57% TDN). Sixty heifers (initial age = 226 ± 3 d) were allocated into 15 drylot pens (4 heifers/pen and 5 pens/treatment) and assigned to 1) supplementation with soybean meal (PROT), 2) supplementation with a mixture of cracked corn, soybean meal, and urea (68:22:10 ratio, DM basis; ENER), or 3) no supplementation (CON). Heifers were offered meadow foxtail (Alopecurus pratensis L.) hay for ad libitum consumption during the experiment (d -10 to 160). Beginning on d 0, PROT and ENER were provided daily at a rate of 1.30 and 1.40 kg of DM/heifer to ensure that PROT and ENER intakes were isocaloric and isonitrogenous. Hay and total DMI were recorded for 5 consecutive days during each month of the experiment. Blood was collected every 10 d for analysis of plasma progesterone to evaluate puberty attainment. Blood samples collected on d -10, 60, 120, and 150 were also analyzed for plasma concentrations of plasma urea N (PUN), glucose, insulin, IGF-I, NEFA, and leptin. Liver samples were collected on d 100 from 2 heifers/pen and analyzed for mRNA expression of genes associated with nutritional metabolism. No treatment effect was detected (P = 0.33) on forage DMI. Total DMI, ADG, and mean concentrations of glucose, insulin, and IGF-I as well as hepatic mRNA expression of IGF-I and IGFBP-3 were greater (P ≤ 0.02) for PROT and ENER compared with CON and similar between PROT and ENER (P ≥ 0.13). Mean PUN concentrations were also greater (P < 0.01) for PROT and ENER compared with CON, whereas PROT heifers had greater (P < 0.01) PUN compared with ENER. Plasma leptin concentrations were similar between ENER and PROT (P ≥ 0.19) and greater (P ≤ 0.03) for ENER and PROT compared with CON on d 120 and 150 (treatment × day interaction, P = 0.03). Hepatic mRNA expression of mitochondrial phosphoenolpyruvate carboxykinase was greater (P = 0.05) in PROT compared with CON and ENER and similar between CON and ENER (P = 0.98). The proportion of heifers pubertal on d 160 was greater (P < 0.01) in ENER compared with PROT and CON and similar between PROT and CON (P = 0.38). In conclusion, beef heifers consuming a low-quality cool-season forage had a similar increase in DMI, growth, and overall metabolic status if offered supplements based on soybean meal or corn at 0.5% of BW.

Potential nutritional strategies for the amelioration or prevention of high rigor temperature in cattle – a review

Environmental conditions influence animal production from an animal performance perspective and at the carcass level post-slaughter. High rigor temperature occurs when the animal is hyperthermic pre-slaughter, and this leads to tougher meat. Hyperthermia can result from increased environmental temperature, exercise, stress or a combination of these factors. Consumer satisfaction with beef meat is influenced by the visual and sensory traits of the product when raw and cooked, with beef consumers commonly selecting tenderness of the product as the most important quality trait. High rigor temperature leads to a reduction in carcass and eating quality. This review examines some possible metabolic causes of hyperthermia, with focus on the importance of adipose tissue metabolism and the roles of insulin and leptin. Potential strategies for the amelioration or prevention of high rigor temperature are offered, including the use of dietary supplements such as betaine and chromium, anti-diabetic agents such as thiazolidinediones, vitamin D, and magnesium (Mg) to provide stress relief.

Effects of increasing dosages of zeranol implants on lamb growth, carcass characteristics, blood hormones, and nitrogen metabolism

The objective of this research was to compare the growth performance, incidence of prolapse and mortality, carcass characteristics, blood hormone concentration, and N balance of lambs implanted with increasing dosages of zeranol. One hundred forty-four crossbred lambs (29.6 ± 4.9 kg) were used in a completely random design and placed into 16 feedlot pens (4 pens/treatment) for a 116 d finishing study. Lambs were fed an 84.7% corn and 15.3% market lamb pellet (DM basis) diet ad libitum. Treatments were 0, 12, 24, and 36 mg zeranol (Ralgro; Schering-Plough), and lambs were implanted in the ear according to treatment on d 0. Lambs were weighed. Thirty lambs (67.6 ± 3.4 kg) and 96 lambs (65.8 ± 5.1 kg) were harvested on d 84 and d 118, respectively. Carcass data were collected 24 h after chill. Blood samples were collected on d 0, 28, 56, 70, 82, 99, and 116 from 64 lambs (29.6 ± 2.1 kg) in the feedlot study (subsample of 4 lambs per pen) and analyzed for thyroxine, triiodothyronine, and IGF-I. A second study was conducted to compare effects of 0, 12, 24, or 36 mg zeranol on N balance in 16 crossbred lambs (34.8 ± 2.1 kg). There were no differences among treatments for BW, ADG, DMI, and G:F (P > 0.05) in the feedlot study. However, there was a linear increase for incidence of prolapse (P = 0.006; 2.78, 5.55, 24.98, and 27.75%, respectively) and mortality (P = 0.005; 0.00, 5.55, 11.10, and 13.88%, respectively) as zeranol dosage increased. Carcass characteristics, blood hormone concentrations, and N balance were not affected by treatment (P > 0.05). These results indicate zeranol increases incidence of prolapse and mortality without increasing growth performance.

Prepartum dietary energy source fed to beef cows: II. Effects on progeny postnatal growth, glucose tolerance, and carcass composition

Mature Angus-cross beef cows (n = 228) were used to evaluate effects of prepartum dietary energy source on postnatal growth and carcass composition of progeny in a 2-yr study. Starting at approximately 160 d of gestation, cows were fed diets consisting of 1 of 3 primary energy sources: grass hay (HY), corn (CN), or dried corn distillers grains with solubles (DG). The CN and DG diets were limit-fed to achieve similar energy intakes as cows fed HY. Following parturition, cows were fed a common diet and managed as a single group. Calves were weaned at an average of 185 ± 6 d of age and backgrounded for 28 d. A subset of progeny (n = 134) was individually fed a common finishing diet until slaughter, when each calf reached 1.2 ± 0.05 cm of backfat. A glucose tolerance test (GTT) was conducted in year 2 on 4 calves/treatment after 41 and 111 d on the finishing diet (DOF). Calf birth weights were greater (P = 0.002) in calves from cows fed CN and DG than calves from cows fed HY, and weaning BW (P = 0.08) was less for calves from cows fed HY vs. CN. Receiving BW, final BW, and HCW did not differ (P ≥ 0.16) among treatments. No difference (P ≥ 0.28) in ADG, morbidity, and mortality from birth to slaughter was observed among treatments. In response to a GTT, increased DOF resulted in greater (P ≤ 0.005) fasting insulin, faster glucose disappearance rate, and greater insulin:glucose area under the curve ratio. Glucose disappearance rate was greater (P = 0.01) in calves from cows fed CN than in calves from cows fed HY or DG. A greater initial insulin response (P = 0.005) was observed in calves from cows fed CN or DG than in calves from cows fed HY. Carcass traits used to measure yield grade did not differ (P ≥ 0.19) among treatments. Calves from dams fed CN had the lowest marbling score (P = 0.03) and intramuscular fat content (P = 0.07). These results indicate that prepartum maternal dietary energy source can alter fetal adipose tissue development and insulin sensitivity resulting in long-term effects on progeny's intramuscular fat deposition. Moreover, present findings suggest that increasing the number of days on a corn-based finishing diet increases insulin resistance in beef cattle.

Camelina meal and crude glycerin as feed supplements for developing replacement beef heifers

Angus × Gelbvieh rotationally crossbred yearling heifers (n = 99, yr 1; n = 105, yr 2) were used in a 2-yr randomized complete block design experiment with repeated measures to determine the effect of feeding camelina biodiesel coproducts (meal and crude glycerin) on serum concentrations of triiodothyronine, thyroxine, insulin, β-hydroxybutyrate, and glucose, as well as on growth and reproductive performance. Heifers were assigned to 1 of 15 pens, and pens were assigned initially to receive 7.03 k·•heifer(-1)·d(-1) of bromegrass hay plus 0.95 kg·heifer(-1)·d(-1) of 1 of 3 supplements for 60 d before breeding: 1) control (50% ground corn and 50% soybean meal, as-fed basis); 2) mechanically extracted camelina meal; or 3) crude glycerin (50% soybean meal, 33% ground corn, 15% crude glycerin, 2% corn gluten meal; as-fed basis). Preprandial blood samples were collected via the jugular vein on d 0, 30, and 60 of the feeding period. A 2-injection PGF(2α) protocol (d 60 and 70 of the study) was used to synchronize estrus. Heifers were artificially inseminated 12 h after estrus was first detected. Heifers not detected in estrus within 66 h received a GnRH injection and were artificially inseminated. Dietary treatment × sampling period interactions were not detected (P = 0.17 to 0.87). Dietary treatment did not affect BW (P = 0.44 to 0.59) or serum concentrations of thyroxine (P = 0.96), β-hydroxybutyrate (P = 0.46), glucose (P = 0.59), or insulin (P = 0.44). Serum concentrations of triiodothyronine were greater (P = 0.05) in heifers fed camelina meal. Additionally, dietary treatment did not affect the percentage of heifers detected in estrus before timed AI (P = 0.83), first-service pregnancy rates of those heifers detected in estrus (P = 0.97), or overall first-service pregnancy rates (P = 0.58). Heifers fed camelina meal, however, had greater (P = 0.05) first-service pregnancy rates to timed AI than did heifers fed the control and crude glycerin supplements. The cost per pregnancy was similar for heifers fed the crude glycerin or the control supplement, whereas the cost per pregnancy was the least for heifers fed camelina meal. We conclude that camelina coproducts can replace conventional corn-soybean meal supplements in the diets of developing replacement beef heifers.

Artificial cooling as an alternative to increase productivity and welfare of steers under heat stress

The effects of a cooling system on productive efficiency and welfare of Holstein steers were evaluated during the summer. Sixty steers in the finishing phase were randomly allotted to one of two treatment-groups. Animals of control group were only provided with shade (non-cooled group) and a group of animals under a cooling system were installed in the shaded area (cooled group), which were operated daily from 09am to 6pm during the 69d of the study. The averages of environmental temperature and relative humidity were 35.4°C and 35.3%, respectively, with a temperature-humidity index average of 81.4 during the study. Individual body weight was recorded every two weeks, while body surface temperature and respiratory frequency were recorded three times per week. Blood samples were biweekly taken from coccygeal vein for determination of T3 and T4. The average daily gain in the cooled group gain (1.46kg/d) was similar (P=0.21) to non-cooled group (1.37kg/d). Body surface temperature (35.9ºC vs 38.7ºC) and respiratory frequency per minute (77 vs 104) were lower (P<0.01) in the cooled group than in non-cooled group, respectively. Triiodotironine levels were similar (P=0.30) in cooled (0.80ng/mL) and non-cooled (0.87ng/mL) groups, while, tiroxine level was lower (P<0.01) in cooled group (44.0ng/mL) compared to non-cooled group (56.6ng/mL). The cooling system did not improve productive parameters but the welfare in the cooled group was increased.

Serum progesterone concentration and conception rate of beef cows supplemented with ground corn after a fixed-time artificial insemination protocol

The effects of different levels of finely ground corn (FC) supplementation to grazing beef cows after fixed-time AI (TAI) on serum progesterone (P4) concentrations on day 7 and conception rates on day 28 after TAI were investigated. Three hundred and sixty-four lactating multiparous Brangus cows had follicular and luteal activity synchronized by treatment with estradiol benzoate (Estrogin; 2.0mg IM) and insertion of intra-vaginal P4 releasing device (CIDR) on day -11, followed by treatment with PGF2α (Lutalyse; 25mg IM) on day -4, CIDR and calf removal on day -2, and treatment with GnRH (Fertagyl; 100µg IM) TAI and calf return on day 0. On day 0, cows were randomly allotted in one of the following FC supplement treatments: G1 - 2kg/day from day 0 to 21; G2 - 2kg/day from day 0 to 7, and 6kg/day from day 8 to 21; G3 -6kg/day from day 0 to 7, and 2kg/day from day 8 to 21; and G4 -6kg/day from day 0 to 21. Blood samples were collected on day 7, and pregnancy was determined by ultrasonography indicating the presence of a fetus on day 28. Cows supplemented with 2kg/d of FC had higher serum concentration of P4 on day 7 than cows supplemented with 6kg/d (1.58 vs. 1.28ng/mL; P<0.01; SEM = 0.08). Cows from G4 had higher conception rates compared to G1 cows (58.4 vs. 41.9%, respectively; P<0.05). The level of supplemental energy intake after TAI is negatively associated with following serum P4 concentrations, but positively associated with conception rates of grazing beef cows.

Effects of supplement type on performance, reproductive, and physiological responses of Brahman-crossbred females

Two experiments were conducted to compare the performance and physiological responses of forage-fed beef females supplemented with either a molasses-based (ML) or a citrus pulp-based (CT) supplement. In Exp. 1, BW gain, reproductive performance, and concentrations of blood urea N (BUN), plasma glucose, insulin, IGF-I, and progesterone (P4) were assessed in 60 Brahman x Angus heifers supplemented 3 times weekly with either ML or CT. Supplement intakes were formulated to be isocaloric and isonitrogenous. Reproductive performance was not affected by treatments, but mean BW gain was greater (P < 0.01) for heifers fed CT than for those fed ML (0.40 vs. 0.30 kg/d). Mean plasma concentrations of glucose, insulin, and IGF-I were greater (P < 0.05) for heifers fed CT, whereas BUN was greater (P < 0.05) for heifers fed ML. Mean plasma P4 concentration did not differ between treatments, but both groups had lower plasma P4 concentrations during days that supplements were offered (P < 0.01). In Exp. 2, forage DMI and concentrations of BUN, plasma glucose, insulin, IGF-I, and P4 were assessed in 24 Brahman x British mature cows supplemented with the same treatments described in Exp. 1. Overall forage DMI did not differ between treatments, but a day effect and a treatment x day interaction were detected (P < 0.05). Both groups consumed less forage during the days on which the supplements were offered (P < 0.01), and forage DMI for cows fed CT was less (P < 0.05) than for cows fed ML during those days. No differences were detected in any blood or plasma measurement. In addition, no differences in concentrations of P4 were detected between CT- and ML-fed cows. We concluded that CT-supplemented heifers had greater BW gain compared with ML-supplemented heifers, but no differences in reproductive performance were observed. We also observed that CT-supplemented cows had a greater variability in forage DMI compared with ML-supplemented cows.

Effects of growth-promoting agents and season on blood metabolites and body temperature in heifers1,2

To assess the efficacy of growth-promoting agents among seasons, triiodothyronine (T3), thyroxine (T4), plasma urea nitrogen (PUN), IGF-I, and tympanic temperature (TT) were measured in summer and winter studies. Heifers (n = 9/pen) were allotted to 12 pens in both December and June. Pens were assigned to 1 of 6 growth promotant treatments: control (no growth promotant), estrogenic implant (E), trenbolone acetate implant (TBA), E + TBA (ET), melengestrol acetate (MGA), and ET + MGA (ETM). Blood samples were collected from 4 heifers per pen per study on d 0, 28, 56, and 84 via jugular puncture. Near the midpoint of both studies, TT were obtained from the heifers. There was a season by sample day interaction for all blood metabolites (P < 0.05). During the winter, IGF-I levels peaked on d 28, whereas T3, T4, and PUN peaked on d 56. In the summer, IGF-I levels increased from d 0 to 28 and remained elevated throughout the study. Season by growth promotant interactions (P < 0.05) indicated that in the winter ET increased T3, whereas TBA alone decreased both T3 and T4, compared with control, or ET, and ETM treatment groups. Across seasons, treatments ET and ETM increased (P < 0.05) IGF-I and decreased (P < 0.05) PUN. However, E, TBA, and MGA alone had no effect on IGF-I or PUN concentrations. The maximum TT was greater (P < 0.01) in the summer than in the winter, whereas the minimum TT was lower (P < 0.01) in the summer. Mean TT did not differ among growth-promoting treatments. However, in the summer and over both seasons, the maximum TT was lower (P < 0.05) in E-, MGA-, and ETM-treated heifers. Although limited growth promotant by season interactions existed, changes in blood metabolite levels resulting from the use of growth promotants do not appear to influence seasonal changes in body temperature as measured by TT.

The relationship between mitochondrial function and residual feed intake in Angus steers1

The objective of this study was to examine the relationship between mitochondrial function and residual feed intake in Angus steers. Individual feed intakes were recorded for a contemporary group of 40 steers via the GrowSafe feed intake system. Intakes were then used to calculate residual feed intake (RFI), a measure of efficiency. Based on these calculations, 9 low (RFI = -0.83) and 8 high (RFI = 0.78) RFI animals were selected for further study. Blood samples were collected via jugular venipuncture 1 wk before slaughter for the determination of plasma glucose and insulin concentrations. Tissue samples were taken from the LM from both the high and low RFI animals and mitochondria were isolated for measurement of oxygen consumption and hydrogen peroxide production. Average daily gain and carcass composition were not different between the high and low RFI steers; however, ADFI by the high RFI animals was 1.54 kg/d greater (P < 0.001) than for the low RFI animals. Low RFI steers exhibited a greater (P < 0.05) rate of state 2 and 3 respiration, respiratory control ratio, and hydrogen peroxide production than high RFI steers when provided with glutamate or succinate as a respiratory substrate. The acceptor control and adenosine diphosphate:oxygen ratios were not different between the 2 groups for either substrate. When hydrogen peroxide production was expressed as a ratio to respiration rate there was no difference between groups, signifying that electron leak was similar for both groups. Plasma glucose concentration was greater (P < 0.05) in the high RFI steers than in the low RFI steers; however, plasma insulin concentration was not different (P = 0.22) between the 2 groups. The ratio between plasma glucose and insulin concentration was similar (P = 0.88) between the 2 groups indicating no difference in glucose metabolism. The increased plasma glucose concentration observed in the high RFI steers was presumed to be the result of a greater feed intake by these animals. It seems that mitochondrial function is not different between the high and low RFI groups but rather the rate of mitochondrial respiration is increased in low RFI steers compared with high RFI steers.