Sean P. Montgomery

Plasma metabolites of receiving heifers and the relationship between apparent bovine respiratory disease, body weight gain, and carcass characteristics.

Six hundred sixty-five crossbred beef heifers initially weighing 225 kg were used in a completely randomized design to measure plasma glucose, lactate, and urea N concentrations at time of initial processing, determine the incidence of apparent bovine respiratory disease (BRD) in receiving cattle, and evaluate the effect of apparent BRD on subsequent cattle growth and carcass characteristics. Heifers were processed within 24 h of arrival, and processing included vaccination against common viral and clostridial diseases, recording rectal temperature, and sampling whole blood for subsequent measurement of plasma glucose, lactate, and urea concentrations. Heifers were monitored for clinical signs of apparent BRD, including depression, lethargy, anorexia, coughing, rapid breathing, and nasal or ocular discharge. Heifers exhibiting signs of apparent BRD received antibiotic therapy, and the number of times a heifer was treated for apparent BRD was recorded. Following the 36-d receiving period, heifers were transported to native grass pastures and allowed to graze for 136 d. At the end of the grazing season, heifers were transported to a commercial feedlot where they were adapted to a common finishing diet offered for ad libitum consumption. Following the 124-d finishing period, heifers were slaughtered and carcass data were collected. Heifers treated for apparent BRD had decreased plasma glucose (linear, P < 0.01), lactate (linear, P < 0.01), and urea N concentrations (linear, P < 0.06) measured at time of initial processing. Rectal temperature measured at time of initial processing tended to be greater (linear, P < 0.11) for heifers treated for apparent BRD. Heifers treated for apparent BRD during the receiving period had decreased overall ADG (linear, P < 0.10), final BW (linear, P < 0.01), HCW (linear, P < 0.01), fat thickness (linear, P < 0.01), and marbling score (linear, P < 0.03). These data suggest that initial plasma glucose and lactate concentrations might be affected by the health status of receiving cattle and that increased incidence of apparent BRD in cattle decreases ADG and carcass quality.

Dakota Gold®-brand dried distiller’s grainswith solubles: effects on finishingperformance and carcass characteristics

A 153-day trial was conducted using 345 heifers to determine optimal level of Dakota Gold dried distiller’s grains with solubles (DDGS) in finishing diets based on steam-flaked corn. Diets contained six levels of DDGS: 0%, 15%, 30%, 45%, 60%, and 75%. DDGS affected average daily gain, final weight and hot carcass weight, all of which increased with 15% DDGS and then decreased as additional DDGS was added. Growth performance of heifers fed 30% DDGS was similar to those fed no DDGS. In general, heifers were overfinished, with 61% being Yield Grade 3 or greater and 83% grading Choice or Prime. Backfat tended to decrease with addition of DDGS, and kidney, pelvic, and heart fat and marbling scores tended to be greatest for intermediate levels of DDGS. Percentage of carcasses grading Choice or Prime tended to be lower for heifers fed 60 or 75% DDGS.

Effects of corn processing and dietary wet corn gluten feed inclusion on performance and digestion of newly received growing cattle

Effects of corn processing and of dietary inclusion of wet corn gluten feed (WCGF) on growth performance and digestibility were analyzed in 2 experiments. Dietary treatments were arranged as a 2 × 2 factorial. Diets contained corn as either whole-shelled corn (WSC) or as dry-rolled corn (DRC), and they contained either 47% corn with no WCGF or 29% corn with 30% WCGF. In Exp. 1, 279 crossbred calves (230 kg) were allocated to treatments in a complete block design and were used to measure performance and digestion during a 60-d receiving period. Corn processing did not affect (P ≥ 0.31) growth performance. Inclusion of WCGF in the diet increased final BW and ADG (P = 0.03) but did not affect gain efficiency (P = 0.45). Digestibility of DM was increased (P < 0.01) by dietary inclusion of WCGF, and this response was greater in diets containing DRC than in those containing WSC (interaction P = 0.02). For Exp. 2, a digestibility trial used 5 ruminally cannulated Holstein heifers (248 ± 13 kg BW) in a 4 × 4 Latin square with the additional animal administered the same treatment sequence as another heifer. A tendency (P = 0.09) was observed for heifers fed DRC to have greater DMI than those fed WSC. Dietary WCGF inclusion increased (P ≤ 0.01) DMI. Similar to observations in Exp. 1, DM digestibility was improved by addition of 30% WCGF to diets containing DRC but not diets containing WSC (interaction P = 0.02). Ruminal pH was not affected by corn processing (P = 0.90), but it tended (P = 0.09) to be increased by dietary WCGF additions. Ruminal VFA concentrations were not different between WSC and DRC, but dietary inclusion of 30% WCGF decreased (P < 0.01) acetate concentrations and increased (P = 0.05) butyrate concentrations. Liquid passage rate from the rumen and ruminal liquid volume were not affected by corn processing or dietary WCGF inclusion (P ≥ 0.66). In summary, processing corn had no effect on steer performance, but including WCGF in the diet at 30% of DM increased gains of steers over the 60-d receiving period. Diet digestibility did not follow the same pattern observed for gains and efficiencies.

Alfalfa hay and wet corn gluten feed levelsin steam-flaked corn finishing diets

A 153-day finishing experiment was conducted using 631 heifers to determine optimum alfalfa hay and wet corn gluten feed (WCGF) combinations in steam-flaked, corn-based diets. Diets contained either 2 or 6% alfalfa hay and 25, 35, or 45% WCGF (dry basis). Performance was similar (P>0.16) for cattle fed 2 or 6% alfalfa hay. Gain efficiencies (P<0.05) and fat thickness (P<0.10) declined linearly with increasing amounts of WCGF. For heifers fed 2% alfalfa hay, ribeye area increased with increasing dietary WCGF. However for heifers fed 6% alfalfa hay, ribeye area decreased with increasing dietary WCGF. Liver abscesses were lowest for heifers fed 35% WCGF. Alfalfa hay fed at 2% of diet dry matter is sufficient for steam-flaked corn diets containing 25, 35 or 45% WCGF.

Effect of Corn Containing the Cry1F Protein on Performance of Beef Heifers Fed a Finishing Diet Based on Steam-Flaked Corn12

Abstract Corn (maize; Zea mays) lines with the Herculex I trait have been modified to express both the Cry1F protein from Bacillus thuringiensis subsp. aizawai and the phosphinothricin-N-acetyltransferase (PAT) protein from Streptomyces viridochromogenes. Hybrids containing event TC1507 express the Cry1F protein that controls European corn borer and certain other lepidopteran pests. Event TC1507 also expresses the PAT protein that confers tolerance to glufosinate-ammonium herbicides. The current study was conducted to evaluate the nutritional value of grain containing the TC1507 event by comparing the growth performance and carcass traits of beef heifers fed diets containing grain from a hybrid containing the TC1507 event to that of grain obtained from the near-isoline (control) as well as 2 nontransgenic commercial corn grain controls (Pioneer hybrids 33J56 and 33R77). Diets composed of steamflaked corn were individually fed to 80 beef heifers (360 kg) for 118 d. Dry matter intake, ADG, and G:F were not different (P > 0.05) between groups of heifers fed diets containing different sources of corn grain. Carcass traits, incidence of liver abscesses, and yield grade and quality grade were not affected by dietary treatment. In summary, growth performance and carcass characteristics of beef heifers were not significantly altered by feeding diets containing TC1507 corn grain vs. grain from its near-isoline or 2 other nontransgenic commercial corn grain hybrids.

Effects of MGA in receiving diets on health, performance, and carcass characteristics

A trial was conducted using 723 crossbred heifers (468 lb initially) to evaluate the effects of including melengestrol acetate (MGA) in receiving diets on growth performance, morbidity, mortality, and carcass characteristics. Treatments were: 1) MGA included in the receiving diet at a rate of 0.5 mg per heifer daily or 2) no MGA in the receiving diet. Diets were fed once daily and contained 42% steamflaked corn, 45% alfalfa hay, 6% steep liquor, and 2% tallow; monensin and tylosin were included. Receiving diets were fed for 35 days. After 35 days MGA was fed to all heifers, and cattle were stepped up to common finishing diets. Cattle exhibiting clinical signs of bovine respiratory disease (BRD) were treated with Excenel (1 ml/100 lb body weight) for 3 days. Animals requiring followup treatment received the same therapy. Cattle pulled a third time received oxytetracycline (4.5 ml/100 lb body weight) and Predef (5 ml/heifer). Initial respiratory pulls (73.9% for MGA and 77.3% for no MGA), re-treatments, and death loss were not different (P>0.40) during the first 35 days. The number of heifers requiring a third antibiotic treatment tended (P=0.09) to be higher for heifers not receiving MGA. Average daily gain (deads out) for the first 35 days tended to be higher for heifers fed MGA (P=0.06), but dry matter intake and feed efficiency were not different between treatments (P>0.17). Gain throughout the 220-day feeding period was 2.6% higher for cattle fed MGA during the receiving phase (P=0.05). Overall, feed intake and feed efficiency were not different (P>0.50) between treatments, but heifers fed MGA during the initial receiving period tended to have heavier carcass weights (P=0.13). No differences were detected in quality grade, yield grade, or marbling (P>0.23). Feeding MGA during the initial 35 days after arrival may improve gain and carcass weights.

Using a mixture of cottonseed hulls andcottonseed meal to replace alfalfa hay indiets for stressed feeder calves

One 28-day receiving experiment was conducted using 625 exotic x British cross heifers to evaluate growth performance and morbidity on receiving diets that contained either alfalfa hay or a pellet composed of 65% cottonseed hulls and 35% cottonseed meal as the roughage source. Heifers fed the cotton byproduct pellet consumed more feed (P<0.01) but tended to be less efficient than those fed alfalfa hay. Daily gain was comparable between diets (P>0.05), and the percentages of heifers diagnosed, treated, or retreated for respiratory disease were similar.

Refractive index: a rapid method for determination of starch availability in grains

Steam-flaked corn samples were used in a series of experiments to determine if refractive index could be used as a rapid, inexpensive method to predict starch availability. Results were best when samples were incubated for 15 min with 500 to 600 active units of enzyme/gm of grain prior to measuring on a hand-held refractometer. Correlations to starch availability determined from gas production by a commercial lab were R=.64 for whole flakes and R=.79 when samples were ground. Samples of corn flaked to different densities produced estimates of solubility similar to an in situ dry matter disappearance assay (R = .84, P < .01). Furthermore, refractive index yielded estimates of starch solubility that were well related to a commercial lab’s measures of glucose release for samples of flaked corn that were stored for 0 to 48 hours subsequent to flaking.

Combinations of wet corn gluten feed and steam flaked corn in finishing cattle diets

A 152-day experiment was conducted using 615 crossbred steers to evaluate cattle performance when steam-flaked corn in finishing diets was replaced partially with wet corn gluten feed (CGF). Finishing diets contained no wet CGF (0CGF) or 30 and 60% CGF on a dry matter basis (30CGF and 60CGF). Ruminal and fecal pH increased linearly (P<.01) as the proportion of wet corn gluten feed increased. Cattle fed 60CGF gained less than those fed 30CGF (P<.01) and were less efficient than cattle fed 0CGF or 30CGF (P<.05). Dressing percentage was lower (P<.03) for cattle fed 60CGF compared to cattle fed 30CGF. Incidence of liver abscesses increased linearly (P<.01) as the level of CGF increased. Replacing steamflaked corn with wet CGF at 30% of the diet did not alter performance.

Effect of corn endosperm type and corn containing the Cry1F protein on performance of beef heifers fed finishing diets basedon steam-flaked corn

Eighty beef heifers (initial body weight = 795 ± 18 lb) were individually fed finishing diets based on steam-flaked corn for 118 days. Dietary treatments consisted of corn hybrids containing vitreous (HARD), opaque (SOFT), or intermediate (INT) types of corn endosperm. Within the HARD endosperm type, a transgenic hybrid (HARD-GMO) containing the Herculex I Cry1F protein was compared with its nontransgenic, conventional (HARDCONV) counterpart. Dry matter intake, average daily gain, and gain efficiencies were similar among treatments. Likewise, hot carcass weight, dressing percentage, and ribeye area were unaffected by dietary treatment. Heifers fed HARD-CONV were fatter than heifers fed HARD-GMO, having fewer (P<0.01) USDA Yield Grade 1 and 2 carcasses. In this experiment, feeding flaked corn finishing diets that contained different endosperm types did not alter performance or carcass characteristics. Feeding heifers HARD-GMO compared with HARD-CONV corn resulted in similar performance, although heifers fed HARD-CONV had higher USDA Yield Grades, perhaps because of greater starch availability of HARD-CONV flaked corn than HARD-GMO corn.