The objective of this experiment was to determine the association of glucocorticoids and markers for immune status in finishing beef steers and heifers with DMI, growth, and efficiency. Steers (n = ...127) and heifers (n = 109) were individually fed a finishing ration for 84 d with BW measured every 21 d. Blood samples were collected via jugular venipuncture for metabolite (glucose and lactate) and cortisol analysis and rectal grab samples of feces were collected for corticosterone analysis on d 83 of the experiment. Plasma cortisol was not correlated to DMI (r = -0.08, P > 0.05) or fractional DMI (g DMI/kg BW; r = -0.03; P > 0.05), but was negatively correlated with ADG (r = -0.17, P < 0.01) and G:F (r = -0.20; P < 0.01) and positively correlated to residual feed intake (RFI; r = 0.14, P < 0.05). Fecal corticosterone was positively correlated to fractional DMI (r = 0.15, P < 0.05) and RFI (r = 0.23, P < 0.01) and negatively correlated to G:F (r = -0.18; P < 0.01). Using a mixed model analysis, none of the metabolites or hormones were associated with DMI (P > 0.05), but fecal corticosterone was positively associated with BW-adjusted DMI in heifers only (P = 0.04). Plasma lactate (P < 0.01) was and plasma cortisol (P < 0.10) tended to be negatively associated with ADG. Plasma cortisol (P < 0.05) and fecal corticosterone tended (P < 0.10) to be negatively associated with G:F. Fecal corticosterone was positively associated with RFI in heifers (P < 0.04). In a mixed model analysis, total leukocyte count was positively associated with ADG (P < 0.04) and tended to be positively associated with G:F (P < 0.06). Amongst leukocyte subtypes, neutrophil count was positively associated with ADG in steers (P < 0.02) and monocytes were positively associated with ADG in heifers (P < 0.03). Lymphocyte counts (LY) in steers were negatively associated with DMI (P = 0.03) and fractional DMI (P < 0.03). In heifers, LY tended to be positively associated with DMI (P < 0.09) and BW-adjusted DMI (P < 0.06). Lymphocyte count was also positively associated with ADG (P < 0.01) and G:F (P = 0.05) in heifers. The association of production traits with immune status seems to be different between steers and heifers. There was a stronger relationship of cortisol than fecal corticosterone to feed efficiency measures, suggesting that an cortisol concentrations could be a better marker for feed efficiency traits than fecal corticosterone concentrations.
The use of wet distillers grains with solubles (WDGS) in feedlot diets has increased in the Southern Great Plains as a result of the growing ethanol industry. Nutrient balance and respiration ...calorimetry research evaluating the use of steam-flaked corn (SFC)-based diets in conjunction with WDGS is limited. Therefore, the effects of increasing concentrations of WDGS in a SFC-based diet on energy metabolism, C, and N balance, and enteric methane (CH4) production was evaluated in Jersey steers fed at 2 times maintenance, using respiration calorimetry chambers. Four treatments were used in two 4 × 4 Latin square designs, using 8 steers. Treatments consisted of: 1) SFC-based diet with 0% WDGS (SFC-0); 2) SFC-based diet with 15% WDGS (SFC-15); 3) SFC-based diet with 30% WDGS (SFC-30); and 4) SFC-based diet with 45% WDGS (SFC-45). Diets were balanced for degradable intake protein (DIP) by adding cottonseed meal to the SFC-0 diet. As a proportion of GE, fecal, urinary, and CH4 energy increased linearly (P < 0.03) as WDGS concentration increased in the diet. In contrast, DE, ME, and retained energy decreased linearly (P < 0.01) as a proportion of GE as WDGS concentration increased. Increasing concentration of WDGS in the diet did not affect (P > 0.78) heat production as a proportion of GE. As a result of greater N intake, total N excretion increased linearly (P < 0.01) with increasing WDGS inclusion in the diet. Fecal C loss and CH4-C respired increased linearly (P < 0.01) when WDGS concentration increased in the diet whereas CO2-C respired decreased (linear, P = 0.05) as WDGS concentration increased. We conclude that CH4 production as a proportion of GE increases linearly (P < 0.01) when WDGS concentration in the diet is increased; however, dietary inclusion of WDGS at up to 45% seems to have no effect (P > 0.78) on heat production as a proportion of GE. The reason for a linear decrease in retained energy as WDGS increased was likely because of increased fecal energy loss associated with feeding WDGS. Total N excretion, fecal C loss, and CH4-C respired increased linearly with increasing concentration of WDGS in the diet. We determined NEg values for WDGS to be 2.02, 1.61, and 1.38 Mcal/kg when included at 15%, 30%, and 45%, respectively, in a SFC-based diet. From these results we conclude that the energy value (NEg) of WDGS in a finishing cattle diet based on SFC must be decreased as the inclusion increases.
Methane (CH) loss from finishing cattle is important as it represents an energy loss that could be used for maintenance and growth, and CH is a greenhouse gas with a global warming potential 21 to 25 ...times that of CO. Our objectives were to determine hourly CH production from growing cattle fed diets differing in corn processing method (dry rolling or steam flaking) and wet distillers grains with solubles (WDGS) inclusion rate. Eight steers (195 kg ± 2.3 in Exp. 1 and 322 kg ± 3.7 in Exp. 2) were fed the following diets: 1) steam-flaked corn (SFC)-based diet with 0% WDGS (SFC-0); 2) SFC-based diet with 15% WDGS (SFC-15); 3) SFC-based diet with 30% WDGS (SFC-30); 4) SFC-based diet with 45% WDGS (SFC-45); 5) Dry-rolled corn DRC)-based diet with 0% WDGS (DRC-0); and 6) DRC-based diet with 30% WDGS (DRC-30). All hourly CH data were analyzed using the MIXED procedure of SAS. Individual animal was the experimental unit. The model included the fixed effect of h, diet, and the h × diet interaction. Hourly differences in CH were analyzed using repeated measures. There were numerous h × diet interactions and thus simple-effect means are presented. In steers fed DRC-0 or DRC-30 at 2-times maintenance, the greatest hourly CH emissions occur 6 h after feeding ( < 0.01) with a secondary peak between 10 and 11 h after feeding ( < 0.01). For cattle fed SFC-0, SFC-15, SFC-30, and SFC-45 at 2-times maintenance, all diets had peak CH emissions 5 and 6 h after feeding ( < 0.01), with a secondary CH peak for SFC-45 nine to 11 h after feeding ( < 0.01). Cattle fed all diets at a maintenance level of intake exhibited 1 peak in hourly CH production between 3 and 6 h after feeding ( < 0.01). All steers fed SFC-30 and SFC-45 had sustained CH production over several hours, irrespective of intake level. Steers fed SFC-45 produced more CH beginning 4 h after feeding ( < 0.01) and produced a greater amount of CH than any other treatment ( < 0.01). Methane production generally peaked 6 h after feeding irrespective of intake level or diet type. Additionally, when fed above a maintenance level of intake, a secondary peak in CH production was observed 9 to 11 h after feeding, and steers fed at a maintenance level of intake had only 1 peak in CH production in a 23-h period.
Feeding fat to lactating dairy cows may reduce methane production. Relative to cellulose, fermentation of hemicellulose is believed to result in less methane; however, these factors have not been ...studied simultaneously. Eight multiparous, lactating Jersey cows averaging (±SD) 98 ± 30.8 d in milk and body weight of 439.3 ± 56.7 kg were used in a twice-replicated 4 × 4 Latin square to determine the effects of fat and hemicellulose on energy utilization and methane production using a headbox-type indirect calorimetry method. To manipulate the concentration of fat, porcine tallow was included at either 0 or 2% of the diet dry matter. The concentration of hemicellulose was adjusted by manipulating the inclusion rate of corn silage, alfalfa hay, and soybean hulls resulting in either 11.3 or 12.7% hemicellulose (dry matter basis). The resulting factorial arrangement of treatments were low fat low hemicellulose (LFLH), low fat high hemicellulose (LFHH), high fat low hemicellulose (HFLH), and high fat high hemicellulose (HFHH). Neither fat nor hemicellulose affected dry matter intake, averaging 16.2 ± 1.18 kg/d across treatments. Likewise, treatments did not affect milk production, averaging 23.0 ± 1.72 kg/d, or energy-corrected milk, averaging 30.1 ± 2.41 kg/d. The inclusion of fat tended to reduce methane produced per kilogram of dry matter intake from 24.9 to 23.1 ± 1.59 L/kg, whereas hemicellulose had no effect. Increasing hemicellulose increased neutral detergent fiber (NDF) digestibility from 43.0 to 51.1 ± 2.35%. Similarly, increasing hemicellulose concentration increased total intake of digestible NDF from 6.62 to 8.42 ± 0.89 kg/d, whereas fat had no effect. Methane per unit of digested NDF tended to decrease from 64.8 to 49.2 ± 9.60 L/kg with increasing hemicellulose, whereas fat had no effect. An interaction between hemicellulose and fat content on net energy balance (milk plus tissue energy) was observed. Specifically, increasing hemicellulose in low-fat diets tended to increase net energy balance, but this was not observed in high-fat diets. These results confirm that methane production may be reduced with the inclusion of fat, whereas energy utilization of lactating dairy cows is improved by increasing hemicellulose in low-fat diets.
The addition of fat and calcium sulfate to diets fed to ruminants has resulted in a reduction in methane production, but the effects on energy balance have not been studied. A study using indirect ...calorimetry and 16 multiparous (8 Holstein and 8 Jersey; 78 ± 15 d in milk; mean ± standard deviation) lactating dairy cows was conducted to determine how mitigating methane production by adding corn oil or calcium sulfate to diets containing reduced-fat distillers grains affects energy and nitrogen balance. A replicated 4 × 4 Latin square design with 35-d periods (28 d of adaption and 4 d of collections) was used to compare 4 different dietary treatments. Treatments were composed of a control (CON) diet, which did not contain reduced-fat distillers grain and solubles (DDGS), and treatment diets containing 20% (dry matter basis) DDGS (DG), 20% DDGS with 1.38% (dry matter basis) added corn oil (CO), and 20% DDGS with 0.93% (dry matter basis) added calcium sulfate (CaS). Compared with CON, dry matter intake was not affected by treatment, averaging 29.6 ± 0.67 kg/d. Milk production was increased for diets containing DDGS compared with CON (26.3 vs. 27.8 ± 0.47 kg/d for CON vs. DDGS, respectively), likely supported by increased energy intake. Compared with CON, energy-corrected milk was greater in DG and CO (30.1 vs. 31.4, 31.7, and 31.0 ± 0.67 kg/d for CON, DG, CO, and CaS, respectively). Compared with CON, the addition of calcium sulfate and corn oil to diets containing DDGS reduced methane production per kg of dry matter intake (22.3, 19.9, and 19.6 ± 0.75 L/kg per d for CON, CO, and CaS, respectively). Similarly, methane production per kilogram of energy-corrected milk was reduced with the addition of calcium sulfate and corn oil to diets containing DDGS (14.2, 12.5, and 12.4 ± 0.50 L/kg per d for CON, CO, and CaS, respectively). Compared with CON and CaS, the intake of digestible energy was greater for DG and CO treatments (57.7, 62.1, 62.0, and 59.0 ± 1.38 Mcal/d for CON, DG, CO, and CaS, respectively). Intake of metabolizable energy was greater in all treatments containing DDGS compared with CON (50.5 vs. 54.0 ± 1.08 Mcal/d for CON vs. DDGS, respectively). Net balance (milk plus tissue energy) per unit of dry matter was greater in CO (containing DDGS and oil) than CON (1.55 vs. 1.35 ± 0.06 Mcal/kg for CO vs. CON, respectively). Tissue energy was greater in DG and CO compared with CON (6.08, 7.04, and 3.16 ± 0.99 Mcal/d for DG, CO, and CON, respectively. Results of this study suggest that the addition of oil and calcium sulfate to diets containing DDGS may be a viable option to reduce methane production and in the case of oil also improve net energy balance in lactating dairy cows.
Methane (CH4) production of ruminants typically increases with increased dry matter intake (DMI). However, few studies have observed the effects of feeding multiple times a day and its effects on ...diurnal variation in CH4 production and energy balance in late-lactation dairy cattle. A study using headbox-style indirect calorimetry and 12 multiparous (225 ± 16.2 d in milk; mean ± SD) lactating Jersey cows was conducted to determine the effects of feeding twice daily on diurnal variation in CH4 production and total energy balance. A crossover design with 14-d periods (10 d of adaption and 4 d of collection) was used to compare 2 treatments. Treatments consisted of either once a day feeding (1×; 100% of feed given at 1000 h) or twice a day feeding (2×; 50% of feed given at 1000 h and the final 50% at 2000 h) with a common diet fed in both treatments. Dry matter intake was not different between treatments, with a mean of 16.9 ± 0.88 kg/d. Once a day feeding tended to have greater milk yield compared with twice a day feeding (21.2 vs. 20.4 ± 1.59 kg/d, respectively). Milk fat and milk protein percentage were not different, with means of 6.18 ± 0.20% and 3.98 ± 0.08%, respectively. Total CH4 production did not differ between treatments, with a mean of 402.1 ± 20.8 L/d. Similarly, CH4 per unit of milk yield and DMI was not different between treatments, with means of 20.5 ± 1.81 and 23.8 ± 1.21 L/kg, respectively. Feeding frequency did not affect diurnal variation of hourly CH4 production, with a mean of 17.1 ± 0.74 L/h. A trend was observed for a treatment × hour interaction. Methane production per hour increased after the second feeding for cattle fed twice versus once daily. Gross energy, digestible energy, metabolizable energy, and balance (milk plus tissue) per kilogram of DMI did not differ by feeding frequency, with means of 4.41 ± 0.01, 3.05 ± 0.03, 2.63 ± 0.03, and 1.32 ± 0.08 Mcal/kg of DM, respectively. Metabolizable energy for maintenance was 146 kcal/kg of metabolic body weight, with an efficiency of converting metabolizable energy to net energy balance (milk plus tissue) of 76%. Nitrogen balance did not differ among treatments, with a mean balance of 17.3 ± 13.0 g/d. Therefore, total CH4 production and energy maintenance were not affected by feeding frequency. However, CH4 was variable throughout the day, and caution should be exercised when collecting CH4 samples at a limited number of time points because this may under- or overestimate total production.
The use of an added lipid is common in high-concentrate finishing diets. The objective of our experiment was to determine if feeding increasing concentrations of added dietary corn oil would decrease ...enteric methane production, increase the ME:DE ratio, and improve recovered energy (RE) in finishing beef steers. Four treatments were used in a replicated 4 × 4 Latin square ( = 8; initial BW = 397 kg ± 3.8). Data were analyzed using a Mixed model with the fixed effects of period and dietary treatment and random effects of square and steer within square. Treatments consisted of: (1) 0% added corn oil (Fat-0); (2) 2% added corn oil (Fat-2); (3) 4% added corn oil (Fat-4); (4) 6% added corn oil (Fat-6). Dry matter intake or GE intake did not differ across diets ( ≥ 0.39). As a proportion of GE intake, fecal energy loss, DE, and urinary energy loss did not differ by treatment ( ≥ 0.27). Additionally, methane energy produced decreased linearly as corn oil increased in the diet ( < 0.01). No differences were detected in ME loss as a proportion of GE intake ( ≥ 0.98). However, the ME:DE ratio increased linearly ( < 0.01; 93.06, 94.10, 94.64, and 95.20 for Fat-0, Fat-2, Fat-4, and Fat-6, respectively) as corn oil inclusion increased in the diet. No differences in RE or heat production as a proportion of GE intake were noted ( ≥ 0.59) and dry matter digestibility did not differ across diets ( ≥ 0.36). Digestibility of NDF as a proportion of intake responded quadratically increasing from 0% corn to 4% corn oil and decreasing thereafter ( = 0.02). Furthermore, ether extract digestibility as a proportion of intake responded quadratically, increasing from 0% to 4% corn oil inclusion before reaching a plateau ( < 0.01). As a proportion of GE intake, RE as protein decreased linearly as corn oil was increased in the diet ( < 0.01). As a proportion of total energy retained, RE as protein decreased when corn oil increased from 0% to 6% of diet DM ( < 0.01). Similarly, RE as fat and carbohydrate as a proportion of GE intake increased linearly as corn oil increased in the diet ( = 0.05). From these data, we interpret that adding dietary fat decreases enteric methane production and increases the ME:DE ratio, in addition to increasing the amount of energy retained as fat and carbohydrate.
The objective of this experiment was to determine the association of circulating plasma leptin concentrations with production and body composition measures of finishing beef steers and heifers and to ...determine if multiple sampling time points improve the associations of plasma leptin concentrations with production and body composition traits. Individual dry matter intake (DMI) and ADG were determined for 84 d using steers and heifers (n = 127 steers and n = 109 heifers). Blood was collected on day 0, day 42, and day 83 for determination of plasma leptin concentrations. Leptin concentrations were greater in heifers than those in steers on day 0 (P < 0.001 for sex by day interaction), and leptin concentrations increased in both sexes but were not different from each other on day 83. Leptin concentrations at all 3 time points and the mean were shown to be positively associated with DMI (P ≤ 0.006), whereas the mean leptin concentration explaining 8.3% of the variance of DMI. Concentrations of leptin at day 42, day 83, and the mean of all 3 time points were positively associated with ADG (P ≤ 0.011). Mean leptin concentration was negatively associated with gain:feed ratio and positively associated with residual feed intake (RFI), indicating that more efficient cattle had lower leptin concentrations. However, leptin concentrations explained very little of the variation in residual feed intake (≤3.2% of the variance). Leptin concentrations were positively associated with body fat measured by ultrasonography at the 12th rib and over the rump (P < 0.001), with the mean leptin concentration explaining 21.9% and 12.7% of the variance in 12th rib and rump fat thickness, respectively. The same trend was observed with carcass composition where leptin concentrations were positively associated with 12th rib fat thickness, USDA–calculated yield grade (YG), and marbling score (P ≤ 0.006) and mean leptin concentration explained 16.8, 18.2, and 4.6% of the variance for 12th rib fat thickness, yield grade, and marbling score, respectively. Given these and previous results, it appears that leptin physiology could be a candidate for mechanisms that contribute to feed intake and feed efficiency variation in beef cattle.
•Plasma leptin association with production traits of beef cattle was examined.•Plasma leptin was positively associated with feed intake and average daily gain.•More efficient cattle tended to have lower plasma leptin.•Plasma leptin concentrations were positively associated with body fatness measures.•Leptin physiology could be a mechanism that contributes to production variation.
Although the inclusion of fat has reduced methane production in ruminants, relatively little research has been conducted comparing the effects of source and profile of fatty acids on methane ...production in lactating dairy cows. A study using 8 multiparous (325 ± 17 DIM; mean ± SD) lactating Jersey cows was conducted to determine effects of feeding canola meal and lard versus extruded byproduct containing flaxseed as a high-C18:3 fat source on methane production and diet digestibility in late-lactation dairy cows. A crossover design with 32-d periods (28-d adaptation and 4-d collections) was used to compare 2 different fat sources. Diets contained approximately 50% forage mixture of corn silage, alfalfa hay, and brome hay; the concentrate mixture changed between diets to include either (1) a conventional diet of corn, soybean meal, and canola meal with lard (control) or (2) a conventional diet of corn and soybean meal with an extruded byproduct containing flaxseed (EXF) as the fat source. Diets were balanced to decrease corn, lard, and canola meal and replace them with soybean mean and EXF to increase the concentration of C18:3 (0.14 vs. 1.20% of DM). Methane production was measured using headbox-style indirect calorimeters. Cattle were restricted to 95% ad libitum feed intake during collections. Milk production (17.4 ± 1.04 kg/d) and dry matter intake (15.4 ± 0.71 kg/d) were similar among treatments. Milk fat (5.88 ± 0.25%) and protein (4.08 ± 0.14%) were not affected by treatment. For methane production, no difference was observed for total production (352.0 vs. 349.8 ± 16.43 L/d for control vs. EXF, respectively). Methane production per unit of dry matter intake was not affected and averaged 23.1 ± 0.57 L/kg. Similarly, methane production per unit of energy-corrected milk was not affected by fat source and averaged 15.5 ± 0.68 L/kg. Heat production was similar, averaging 21.1 ± 1.02 Mcal/d. Digestibility of organic matter, neutral detergent fiber, and crude protein was not affected by diet and averaged 69.9, 53.6, and 73.3%, respectively. Results indicated that increasing C18:3 may not affect methane production or digestibility of the diet in lactating dairy cows.
Ghrelin is a gut peptide that when acylated is thought to stimulate appetite. Circulating ghrelin concentrations could potentially be used as a predictor of DMI in cattle. The objective of this ...experiment was to determine the association of circulating ghrelin concentrations with DMI and other production traits. Steers and heifers were fed a finishing diet and individual intake was recorded for 84 d. Blood samples were collected via jugular venipuncture following the DMI and ADG measurement period. Plasma active ghrelin and total ghrelin were quantified using commercial RIA. Active ghrelin was not correlated to DMI (P = 0.36), but when DMI was modeled using a multivariate analysis including plasma metabolites and sex, active ghrelin was shown to be positively associated with DMI (P < 0.01) and contributed for 6.2% of the variation accounted for by the regression model (R2 = 0.33). Total ghrelin was negatively correlated to DMI (P < 0.01), but was not significant in a multivariate regression analysis (P = 0.13). The ratio of active:total ghrelin was positively associated with DMI (P < 0.01), and accounted for 10.2% of the variation in the model (R2 = 0.35). Active ghrelin was positively associated with ADG (P < 0.05), while total ghrelin was negatively associated with ADG (P < 0.01), and the ratio of active:total ghrelin was positively associated with ADG (P < 0.01). Active ghrelin was not associated with G:F (P = 0.88), but total ghrelin concentrations were negatively associated with G:F (P < 0.01) and accounted for 10.24% of the variation (R2 = 0.25). Heifers consumed less feed than steers (P < 0.01), tended to have greater active ghrelin concentrations (P = 0.06), and had greater total ghrelin concentrations than steers (P = 0.04). Total ghrelin concentrations were not different between sire breeds (P = 0.80), but active ghrelin concentrations and the ratio of active:total ghrelin differed between breeds (P < 0.01), indicating that genetics have an effect on the amount and form of circulating ghrelin. Total ghrelin concentrations tended (P = 0.08) to be correlated with HCW, but no other carcass characteristics were correlated with active or total ghrelin concentrations (P > 0.10). Results indicated that ghrelin concentrations are associated with DMI in beef cattle and that there is genetic variation that leads to differences in the amount and form of circulating ghrelin which could contribute to variation observed in DMI of beef cattle.
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