Effects of feeding corn silage from short-season hybrids and extending the backgrounding period on production performance and carcass traits of beef cattle

Corn silage (CS) acreage in western Canada continues to expand with CS being used increasingly in feedlot cattle diets where barley silage (BS) previously was the main forage fed. Our study evaluated the effects of increasing the amounts of CS in backgrounding (BKGN) diets on performance of cattle by 1) replacing BS with early-maturing CS, 2) increasing the proportion of CS in the diet, and 3) extending the BKGN duration. A total of 160 steers (mean BW ± SD; 272 ± 22.4 kg) were used in a completely randomized design. Steers were assigned to 16 pens and fed BKGN diets (4 pens per diet) that contained 60% BS (DM basis; CON), 60% CS (60CS), 75% CS (75CS), or 90% CS (90CS) until reaching a mean pen BW of either 380 (SBKGN) or 430 ± 15 kg (LBKGN) with 2 pens per treatment. All steers were finished (FIN diet; 9% CS, 86% barley grain, and 5% supplement) to an equal-BW end point (700 ± 15 kg LW). During BKGN and FIN phases, DMI, ADG, and G:F were measured for all pens. Carcass data also were collected. No BKGN diet × duration interactions were statistically significant (P ≥ 0.412) for most production measures. As dietary CS content was increased during BKGN, DMI and ADG decreased (quadratic; P ≤ 0.003). There also was a tendency (P = 0.078) for a decrease in G:F at the highest level of CS. As expected, LBKGN steers took longer (105 vs. 71 d; P = 0.001) than SBKGN steers to reach the BKGN target end weight. In addition, as a result of their heavier weight at the beginning of FIN, LBKGN steers also had a higher DMI (11.6 vs. 11.0 kg/d; P = 0.045) than SBKGN steers. However, no carryover effects (P ≥ 0.354) of BKGN diet on DMI, ADG, and G:F were significant during the FIN phase. Similarly, the BKGN diet and duration had no effect (P ≥ 0.219) on carcass traits including HCW, dressing percentage, and quality grade. However, we detected an interaction between BKGN diet and duration on backfat thickness (P = 0.009); SBKGN steers that were fed 75CS during BKGN accumulated more backfat during FIN than LBKGN steers that were fed 75CS during BKGN, and because they were lighter at the beginning of FIN they took longer to reach 700 kg BW, their end point. In conclusion, dietary inclusion of CS (up to 90% of diet DM) in place of BS and extending the BKGN period had marginal effects on FIN performance or carcass traits in our study. Therefore, beef producers can make extensive use of early-maturing CS in growing cattle diets without compromising animal performance or carcass quality.

Effect of rate of weight gain of steers during the stocker phase. III. Gene expression of adipose tissues and skeletal muscle in growing-finishing beef cattle

The objective of this study was to determine the impact of stocker production systems differing in growth rate on differential adipogenic and lipogenic gene expression of intramuscular (IM), subcutaneous (SC), and perirenal (PR) adipose tissues. Angus steers were assigned to 4 stocker cattle production systems in 2 consecutive years: 1) cottonseed meal-based supplement while grazing dormant native range (CON), 2) ground corn/soybean meal-based supplement while grazing dormant native range (CORN), 3) grazing wheat pasture at a high stocking rate for a low rate of BW gain (LGWP), and 4) grazing wheat pasture at a low stocking rate for a high rate of BW gain (HGWP). Steers were harvested during the stocker phase at similar age (different carcass weight) in Exp. 1 (3 steers/treatment) or at similar carcass weight in Exp. 2 (4 steers/treatment). Adipose tissues were analyzed for mRNA expression of adipogenic (peroxisome proliferator activated receptor γ [PPARγ], sterol regulatory element binding factor 1 [SREBF1], CAATT/enhancer binding protein β, and delta-like homolog 1) and lipogenic (glycerol-3-phosphate dehydrogenase [GPDH], fatty acid synthase [FASN], and diacylglycerol acyltransferase 2 [DGAT2]) genes. Multivariate analysis was used to evaluate the expression of adipogenic or lipogenic genes collectively. There was not a treatment × adipose tissue interaction (F-test, P > 0.15) when steers were harvested at similar age, but a treatment × adipose tissue interaction (F-test, P < 0.05) was evident when steers were harvested at similar carcass weight. At similar carcass weight, treatment had no effect (P > 0.10) on the canonical variate of adipogenic or lipogenic mRNA expression in IM adipose tissue, but faster rates of gain of LGWP and HGWP steers increased (P < 0.10) the canonical variate of adipogenic and lipogenic mRNA expression in SC and PR adipose tissue compared with CON and CORN steers. Strong positive correlations (P < 0.05) of PPARγ, SREBF1, GPDH, FASN, and DGAT2 mRNA expression with the canonical variate indicate that these genes strongly influenced differences between treatments and adipose tissues. These results suggest that contrary to our hypothesis rate of gain has little influence on differentiation and lipid synthesis of IM adipose tissue at similar carcass weight but faster rates of gain increase differentiation and lipid synthesis of SC and PR adipose tissue even at similar carcass weight.

Effects of calf- and yearling-fed beef production systems and growth promotants on production and profitability

López-Campos, Ó., Aalhus, J. L., Okine, E. K., Baron, V. S. and Basarab, J. A. 2013. Effects of calf- and yearling-fed beef production systems and growth promotants on production and profitability. Can. J. Anim. Sci. 93: 171–184. In each of 2 yr, 112 spring-born steers were used to evaluate the effect of calf-fed vs. yearling-fed with and without growth implant and β-adrenergic agonist on production parameters and economic potential. Steers were grouped into: (1) non-implanted feeders harvested at 11–14 mo of age, (2) growth implanted feeders harvested at 11–14 mo of age, (3) non-implanted feeders harvested at 19–23 mo of age, and (4) growth implanted feeders harvested at 19–23 mo of age. Production data were collected and economic evaluation was performed. Calf-fed steers grew slower (1.21 vs. 1.99±0.07 kg d−1) and had a poorer feed conversion ratio [5.32 vs. 4.99±0.34 kg dry matter intake (DMI) kg−1 gain] during the feedlot dietary adjustment period than yearling-fed. Calf-fed steers were more efficient than yearling-fed during the first 76–83 d (5.16 vs. 7.33±0.11 kg DMI kg−1 gain) and latter 48–79 d (5.69 vs. 14.28±1.50 kg DMI kg−1 gain) of the finishing period. Implanted steers were more efficient than non-implanted during the dietary feedlot adjustment period (4.80 vs. 5.52±0.15 kg DMI kg−1 gain), and during the first 76–83 d (6.05 vs. 6.44±0.11 kg DMI kg−1 gain) and latter 48–79 d of the finishing period (9.29 vs. 10.69±1.50 kg DMI kg−1 gain). Implanted steers grew 11.4–19.6% faster than non-implanted throughout the finishing period, while yearling-fed grew 11.1–12.9% faster during the first 76–83 d, but 49.1–64.4% slower during the last 48–79 d of the finishing period compared with calf-fed. Quality grade was improved for non-implanted steers, with 43.6% of yearling-fed and 35.7% calf-fed steers grading AAA. Adjusted net return was best for calf-fed implanted ($17.52 head−1), followed by calf-fed non-implanted ($−41.92 head−1), yearling-fed implanted ($−73.77 head−1), and yearling-fed non-implanted ($−99.65 head−1) production strategies. The results of the present study suggest that reducing age at slaughter combined with growth implant can increase profit and reduce risk, but growth implants can negatively affect the carcass quality.

Southern Section Interdisciplinary Beef Cattle Symposium: Carryover effects of stocker cattle systems on feedlot performance and carcass characteristics

Stocker cattle production practices may affect subsequent performance of cattle in economically meaningful ways. Literature was reviewed to summarize possible carryover effects of stocker cattle management on finishing performance and carcass traits. The most consistent effects of stocker phase practices on finishing-phase and carcass performance of cattle appear to be explained by changes in placement weight of feeder cattle. Increasing placement weight typically is confounded with age at placement, ADG during stocker period, and duration of the stocker period. It may also be confounded with other factors, such as season of grazing and/or finishing. Data from studies comparing calf-fed to yearling-fed cattle indicate that as age or BW at feedlot entry increased, finishing ADG, DMI, and HCW increased (P<0.01) whereas G:F and days on feed decreased (P<0.01). As age and BW at feedlot entry increased, marbling score decreased (P<0.01) whereas Warner-Bratzler shear force increased (P<0.01). Studies with yearling cattle entering the feedyard after a forage-based backgrounding phase indicate that as backgrounding ADG increased, finishing ADG, DMI, and days on feed decreased (P<0.01) yet HCW and ribeye area increased (P<0.01) with no effect (P=0.45) on marbling. Stocker cattle systems are complex, integrated systems in which producers typically seek to maximize their own economic return with little regard for subsequent performance. If cattle are owned across both stocker and finishing phases of production, then management decisions should focus on maximizing return over the entire ownership period and not just within one segment of ownership. Of the traits of feeder cattle that can be affected by stocker cattle systems, BW is the primary determinate of their value when they are placed into commercial feedyards.

An evaluation of production and economic efficiency of two beef systems from calving to slaughter

A 3-yr experiment was conducted with cows and their calves to evaluate resource inputs, animal performance, and carcass characteristics of two production systems. In the control system, cows (CON; n = 99/yr) grazed pasture and were fed hay during the winter, and CON steer calves were finished in the feedlot for 211 d after weaning. In the treatment system (TRT; n = 100/yr), cows grazed pasture and crop residue during the winter and were fed hay. Treatment steer calves grazed crop residue after weaning, grazed pasture in the spring and summer, and were finished in the feedlot for 90 d. Body condition scores after TRT cows returned from crop residue grazing were greater (P < 0.01) for CON than for TRT cows. Calving rates were similar for both groups (CON = 91%; TRT = 93%). In the feedlot, CON steers had lower (P < 0.05) ADG and DMI, but were more efficient (P < 0.01) than TRT steers. Treatment steers had greater (P < 0.05) final weight, hot carcass weight and longissimus muscle area, and decreased marbling score. The cost per weaned calf and weaning breakeven were greater (P = 0.07) for the CON system than for the TRT system (CON = 455.12 dollars, 0.91 dollar/0.45 kg; TRT = 421.43 dollars, 0.84 dollar/0.45 kg). When steers were priced into the postweaning phase on an economic basis, slaughter breakeven was lower (P = 0.01), and profit potential tended (P = 0.14) to be greater for TRT steers when they were sold on a live basis. When steers were priced into the postweaning phase on a financial basis, slaughter breakeven was lower (P = 0.03) and profit potential from the sale of steers on a live basis was greater (P = 0.07) for TRT than for CON steers. Economic evaluation of the total system resulted in greater (P = 0.06) profit potential for the TRT system when steers were priced into the system on either an economic or a financial basis and when steers were sold on a live basis, but no differences were observed when steers were sold on a grid basis. Despite differences in cow weight and body condition, calving rates did not differ between systems. Although calves were herdmates, feedlot performance and carcass characteristics differed between systems. The TRT system had lower weaning and slaughter breakeven, lower cost per weaned calf, and greater profit potential when finished steers were sold on a live basis.

Effect of field pea replacement level on intake and digestion in beef steers fed by-product-based medium-concentrate diets

Four ruminally and duodenally cannulated steers (703.4 +/- 41 kg initial BW) were used in a 4 x 4 Latin square to evaluate the effects of field pea inclusion level on intake and site of digestion in beef steers fed medium-concentrate diets. Steers were offered feed ad libitum at 0700 and 1900 daily and were allowed free access to water. Diets consisted of 45% grass hay and 55% by-products based concentrate mixture and were formulated to contain a minimum of 12% CP (DM basis). Treatments consisted of (DM basis) 1) control, no pea; 2) 15% pea; 3) 30% pea; and 4) 45% pea in the total diet, with pea replacing wheat middlings, soybean hulls, and barley malt sprouts in the concentrate mixture. Experimental periods consisted of a 9-d dietary adjustment period followed by a 5-d collection period. Grass hay was incubated in situ, beginning on d 10, for 0, 2, 5, 9, 14, 24, 36, 72, and 98 h; and field pea and soybean hulls for 0, 2, 5, 9, 14, 24, 36, 48, and 72 h. Total DMI (15.0, 13.5, 14.1, 13.5 +/- 0.65 kg/d) and OM intake (13.4, 12.0, 12.6, 12.0 +/- 0.58 kg/d) decreased linearly (P = 0.10) with field pea inclusion. Apparent ruminal (17.5, 12.0, 0.6, 6.5 +/- 4.31%) and true ruminal CP digestibility (53.5, 48.7, 37.8, 46.2 +/- 3.83) decreased linearly (P < 0.10) with increasing field pea. Neutral detergent fiber intake (8.9, 7.9, 7.8, 7.0 +/- 0.3 kg/d) and fecal NDF output (3.1, 2.9, 2.6, 2.3 +/- 0.2 k/d) decreased linearly (P < 0.03) with increasing field pea. No effects were observed for microbial efficiency or total-tract digestibility of OM, CP, NDF, and ADF (P > or = 0.16). In situ DM and NDF disappearance rates of grass hay and soybean hulls decreased linearly (P < 0.05) with increasing field pea. Field pea in situ DM disappearance rate responded quadratically (P < 0.01; 5.9, 8.4, 5.5, and 4.9 +/- 0.52%/h, for 0, 15, 30, and 45% field pea level, respectively). Rate of in situ CP disappearance of grass hay decreased linearly (P < 0.01) with increasing field pea level. Field pea is a suitable ingredient for beef cattle consuming medium-concentrate diets, and the inclusion of up to 45% pea in by-products-based medium-concentrate growing diets decreased DMI, increased dietary UIP, and did not alter OM, NDF, or ADF digestibility.

Effect of the live weight gain of steers during winter grazing on digestibility, acid-base balance, blood flow, and oxygen consumption by splanchnic tissues during adaptation and subsequent feeding of a high-grain diet1,2

Ten multicatherized steers were used in a completely random design to determine the effect of previous BW gain on blood flow, acid-base balance, and oxygen consumption across portal-drained viscera and liver of growing beef steers fed a high-grain diet. Treatments were high (1.31 +/- 0.09 kg/d) or low (0.68 +/- 0.07 kg/d) daily BW gain during an 82-d winter wheat pasture grazing period and a subsequent 37-d transition period. Blood flow, blood gas measurements, and oxygen consumption were determined on d 0, 14, 28, 42, and 64 of a high-grain finishing period. Compensatory growth was evident in low-gain steers; ADG (1.50 vs. 1.11 kg/d, P < 0.05) and gain efficiency (0.221 vs. 0.109 kg/kg, P < 0.01) were greater from d 14 through 28 than for high-gain steers. Arterial base tended (P < 0.12) to be greater in low-gain than in high-gain steers, whereas calculated HCO3- (mmol/L; P < 0.20) did not differ between treatments. Arterial O2 concentration was not different (P < 0.97) between treatments but increased (P < 0.001) with increasing days on feed. Portal blood flow increased with days on feed (P < 0.001) but did not differ (P < 0.34) between treatments. Hepatic blood flow scaled to metabolic BW was 19.7% greater (P < 0.02) in low-gain than in high-gain steers. Across the feeding period, O2 consumption and CO2 flux by PDV, liver, and total splanchnic tissue (TST) did not differ (P < 0.33) between treatments. However, TST O2 consumption (mmol/[h x kg BW(0.75)]) tended (P < 0.12) to be greater in low- than in high-gain steers. Compensating steers' arterial blood acid-base measurements did not change with days on feed, indicating that they were not more susceptible to metabolic acidosis than high-gain steers. However, steers that had lower BW gain before high-grain feeding exhibited increased hepatic blood flow and TST O2 consumption (metabolic BW basis) during the finishing period compared with high-gain steers. Greater hepatic blood flow and energy expenditure by TST of previously restricted steers might have facilitated compensatory growth.