Applied Animal Science最新文献

Purpose

Our objective was to discuss sources of variation in nutrient composition of feeds and diets, how nutritionists should use that information, methods to reduce nutrient variation, and how nutrient variation may affect dairy cows.

Sources

We reviewed peer-reviewed journals and large nutrient composition databases.

Synthesis

Nutrient composition of feeds varies for multiple reasons including growing, harvesting, and storage conditions and manufacturing processes. These sources are referred to as “true variation” or variation experienced by the cow. The other source of variation is “observer variation,” which includes analytical and sampling variation. Dietary true variation can be reduced by using a TMR and limiting the inclusion of variable feeds. Sampling variation can be reduced by taking duplicate, independent samples. True variation can cause nutrient composition of diets to vary between days. However, current data do not show any substantial negative effects when diets vary day to day if when averaged over a few days, nutrient composition meets diet specifications. Arguably, observer variation can be the greater problem. Observer variation may cause a nutritionist to change a diet when feed composition has not changed, or a diet might be formulated using feed data that are not representative, resulting in a poor diet.

Conclusions and Applications

Typical amounts of true variation in feedstuffs when included in a well-made TMR may not cause significant problems with cows when the variation is centered around the correct mean. Sampling error can lead to poorly balanced diets. To reduce that risk, diet formulation should use the mean of at least 2 duplicate independent samples of the ingredients.

Objective

The objective of this experiment was to evaluate the relationship between 2 measures of daily individual animal variation in DMI with measures of overall DMI, ADG, carcass traits, and feed efficiency of finishing beef cattle.

Materials and Methods

Daily DMI data were collated from 3 previously published experiments within which beef cattle were individually fed using a Calan gate system (American Calan, Northwood, NH) or an Insentec Roughage Intake Control system (Hokofarm Group, Emmeloord, the Netherlands). The day-to-day CV for DMI of each animal was calculated. Next, the average Euclidian distance (ED) was calculated. The Pearson’s (rp) and Spearman’s (rs) correlations between CV and ED methods and production traits and efficiency indexes were calculated.

Results and Discussion

The CV was inversely correlated with DMI (rp = −0.65; rs = −0.59), ADG (rp = −0.52; rs = −0.52), and residual feed intake (rp = −0.41; rs = −0.35) and positively correlated with residual intake and gain (rp = 0.29; rs = 0.25). The CV was negatively correlated with hot carcass weight (HCW; rp = −0.46; rs = −0.45), back fat thickness (rp = −0.25; rs = −0.31), yield grade (rp = −0.29; rs = −0.31), and calculated empty body fat (rp = −0.30; rs = −0.32). The ED was negatively correlated with ADG (rp = −0.55; rs = −0.61), G:F (rp = −0.49; rs = −0.50), residual ADG (rp = −0.57; rs = −0.56), and HCW (rp = −0.33; rs = −0.39).

Implications and Applications

The 2 measures of DMI variation appear to divergently explain variation in DMI and the relationship with production traits and feed efficiency. However, cattle with more improved production outcomes were associated with less day-to-day variation in DMI.

Objective

The objective of this study was to quantify the sustainability of representative dairy-beef farms in Ireland (AVE) and to compare these with dairy-beef farms participating in a farm improvement program (IMP) and research (RES) systems. The study aimed to determine the differences in technical performance and key sustainability indicators among these farm categories.

Material and Methods

Within each farm category, dairy-beef systems differing in sire breed (early maturing, late maturing, and Holstein-Friesian), animal sex (steer and heifer), finishing age (ranging from 18 to 30 mo of age), and production system (finishing from grazing or indoor-based systems) were modeled using the Grange Dairy-Beef Systems Model.

Results and Discussion

The average finishing age was 25.4, 23.8, and 20.6 mo on AVE, IMP, and RES, respectively. Results highlighted a wide range in net margins (from €185 to €806 per hectare; €1 = $1.05) for the systems modeled. Sex had the largest effect on profitability (steer greater than heifer), followed by finishing system (finishing from grazing systems greater than indoor systems) and breed type (late maturing greatest and Holstein-Friesian least). Greenhouse gas emissions of the 3 farm categories ranged from 10.8 to 16.6 kg of carbon dioxide equivalents (CO₂eq) per kilogram of carcass weight produced. All farm categories were, on average, net producers of human-edible protein, and all farms were net consumers of human-edible energy.

Implications and Applications

Key sustainability performance indicators identified in this study include carcass output per hectare, reduced age at slaughter, high individual animal performance, and increasing of the proportion of grazed pasture in the animal’s diet. There is a temporal dimension to ranking farm categories from an economic, environment, labor, feed-food competition, and land-use perspective because none of the 3 farm categories investigated were without fault from a sustainable dairy- beef production perspective.

Objective

The objective of this study was to determine the effects of degree of steam flaking of corn (SFC) on energy metabolism of finishing cattle fed diets containing wet distillers grains with solubles (WDGS).

Materials and Methods

Crossbred steers (n = 4; initial BW = 308 ± 7.0 kg) were randomly assigned to 4 diets containing 0% or 20% WDGS and corn steam flaked to either 321 or 270 g/L bulk density (26 or 22 lb/bu, respectively) in a 2 × 2 factorial arrangement. Energy metabolism was measured in respiration chambers with a 4 × 4 Latin square design.

Results and Discussion

There were no interactions between WDGS concentration and SFC bulk density for nutrient digestion, nitrogen metabolism, or energy metabolism values. Digestibility of OM, NDF, and ether extract were not influenced by the degree of steam flaking of corn. Decreasing bulk density of SFC increased starch digestion, tended to increase the ratio of DE to digestible OM, and numerically decreased the plasma urea-N concentration, but did not significantly affect ME concentration or the DE:TDN ratio. Replacing SFC with 20% WDGS decreased fat digestion but did not affect digestion of other nutrients or dietary energy values.

Implications and Applications

Results suggest that increasing the degree of steam flaking of corn to less than 321 g/L does not improve diet digestibility or energy metabolism of cattle fed diets containing 0% or 20% WDGS.

Objective

Dual-purpose wheat (Triticum aestivum L.) systems are commonly used in the Great Plains of the United States but are not often used in the Southeast. This study aimed to evaluate the viability of dual-purpose wheat management in the Southeast.

Materials and Methods

Wheat varieties evaluated were generic feed type (unknown variety blend, Feed), seed type GA Gore (Seed), and 2 forage types, AGS 2024 (AGS) and Pioneer 26R41 (Pioneer). The experiment was a randomized complete block design (n = 4) conducted during the winters of 2021 and 2022. Three grazing frequencies were used: an ungrazed control (NG) and low-frequency (LF) or high-frequency (HF) grazing. Low- frequency plots received monthly grazing in January and February, whereas HF treatments received a third grazing in March. Destructive forage sampling occurred at monthly intervals. Data were analyzed using PROC GLIMMIX of SAS (v. 9.4, SAS Institute Inc., Cary, NC), with differences declared at P < 0.05. Ad hoc economic evaluation was performed for establishment costs and potential net returns.

Results and Discussion

Before grazing, AGS herbage mass (2,660 kg/ha) was greater than all other varieties. Compared with all other varieties, AGS had greater ADF (24.9%) and least TDN (72.5%). Across grazing frequencies, Pioneer had greater final grain yield (3,620 kg DM/ ha), with Seed having the least (1,270 kg DM/ha). Dual- purpose returns above costs were greatest for Pioneer.

Implications and Applications

Results indicate that common southeastern wheat varieties can be successfully used in a dual-purpose management system.

Objective

Livestock disease management is crucial for producers. To control and eradicate disease, the US gov- ernment has a duty to depopulate infected or potentially infected animals, and current indemnity policy dictates that producers must receive fair market compensation for depopulated animals. This study surveys producers’ pref- erences regarding livestock indemnity policy to better un- derstand ordered preferences for any changes in the future.

Materials and Methods

Through a ranked-ordered probit model, we analyzed producers’ rankings of 4 dif- ferent types of indemnity from an online producer survey.

Results and Discussion

Based on the responding producers, the most preferred method of livestock indem- nity is fair market value for the animal, and the second most preferred indemnity policy is government-subsidized livestock insurance.

Implications and Applications

The results indicate heterogeneity in preference rankings across producers and by producer characteristics. Our findings provide policy- makers with information on producers’ opinions for com- pensation after a disease outbreak. These insights allow legislators to consider producers’ preferences when updat- ing or creating new policies regarding livestock disease management in the future.

Objectives

The objective of this study was to evaluate the accuracy of Brix in predicting sugar concentrations in fresh alfalfa (ALF; Medicago sativa L.) and orchardgrass (OG; Dactylis glomerata L.) forages to be used as an inexpensive and rapid field-level assessment of relative energy in forages.

Materials and Methods

In a 2-yr study, fresh forages samples from ALF and OG monoculture pastures in central Pennsylvania, USA, were collected once monthly from May to September. Samples were immediately evaluated for Brix values with a hand-held digital refractometer, and the remaining biomass was frozen immediately with liquid N to halt cellular respiration. Samples were lyophilized and analyzed for individual sugars and wet chemistry nutritive analyses.

Results and Discussion

Brix was positively correlated with total and individual sugars in ALF during late spring and late summer (0.53–0.93), but correlations were nonexistent or negative in mid-summer. However, Brix values did not correlate with any notable sugar parameters in OG beyond the first sampling date. These findings were attributed to greater fibrous fraction contamination, lower sugar concentrations found in grasses and legumes compared with horticultural crops, and changes in seasonal growth of ALF and OG.

Implications and Applications

Brix values did not consistently predict sugar concentrations in fresh ALF and OG forages. Because Brix measures dissolved solids in solution (not just sugars), Brix readings collected from crushed ALF or OG samples may be confounded by fibrous fractions found in the solution. Brix accuracy may also be dependent on seasonal temperature patterns, plant growth stage, and daily weather patterns. Other solutions should be investigated that rapidly assess sugar profiles and nutritive values of fresh forages.