Paul J. Kononoff

Summary:This study explores the preference of individual feedstuffs by dairy cattle. Cows were presented with the choices of ground corn, dried corn distillers grains with solubles (DDGS), a corn fermented protein product of the dry corn milling industry, and pelleted corn distillers grains. Of these options, cows largely preferred the pelleted distillers grains. Although previous research has shown that dried corn distillers grains are highly palatable to cows, altering the form to add bulk density to the feed can allow cows to consume the feed more readily.

Two experiments were conducted to evaluate enteric methane, manure composition, and digestor methane potential in lactating cows fed diets differing in substitution of dried distillers grains and solubles (DDGS). The objectives of experiment 1 were to examine the effects of feeding DDGS by reducing dietary starch, NDF, and forage NDF (fNDF) on enteric methane production, feed intake, energy and N utilization, manure output, and milk production in lactating Jersey cows. Twelve multiparous Jersey cows (98 ± 6.5 DIM and weighing 441 ± 26.9 kg) were arranged in a triplicated 4 × 4 Latin square design consisting of 4 periods of 28 d. Cows were randomly assigned to 1 of 4 treatment diets: control (CON; 0% DDGS); reduced fiber (RF; based upon 13% DDGS and lower in NDF and fNDF than CON); reduced starch (RS; based upon 13% DDGS and lower in starch than CON); and intermediate (INT; 6.5% DDGS but compared with RF and RS, intermediate in fiber and starch). Diets were balanced to be isonitrogenous (16.6% ± 0.15% CP). Diet amylase-treated NDF on an OM basis (aNDFom) was 28.6%, 26.9%, 31.9%, and 29.2% and starch was 28.2%, 29.7%, 22.8%, and 27.2% DM for CON, RF, RS, and INT, respectively. Compared with CON, DMI increased when cows consumed RF (18.2 vs. 19.4 ± 0.60 kg/d for CON and RF, respectively), but intake for cows consuming RS or INT (average 18.6 ± 0.60 kg/d) did not differ compared with CON. Energy-corrected milk yield increased with RF (37.4 vs. 39.7 ± 1.07 kg/d for CON and RF, respectively), but RS or INT (average 37.5 ± 1.07 kg/d) did not differ from CON. No differences were observed for the ratio of ECM to DMI (average 2.04 ± 0.045 kg/d). Treatments did not affect methane production (average 413.2 ± 20.85 L/d). Compared with CON, manure output (sum of feces and urine output) increased when cows consumed RS (59.1 vs. 63.2 ± 1.89 kg/d for CON and RS, respectively), but no difference was seen for RF or INT (average 60.2 ± 1.89 kg/d). Manure volatile solids (VS) output increased when feeding RF (5.35 vs. 5.70 ± 0.169 kg/d for CON and RF, respectively), but no difference was seen when feeding RS or INT (average 5.46 ± 0.169 kg/d). The objectives of experiment 2 were to test how differences in diet composition can affect the chemical composition of manure and resulting methane production in an anerobic digestor. Manure samples were collected from cows in experiment 1, and a biochemical methane potential test was conducted over 2 runs averaging 32 d. Manure substrate aNDFom was higher when cows consumed RS or CON and lower when cows consumed RF or INT (43.5%, 42.9%, 40.4%, and 39.2% TS for RS, CON, RF, and INT, respectively). Treatment did not affect manure methane (average 279.7 ± 10.76 mL/g VS) or biogas production (average 444.2 ± 19.96 mL/g VS). Total manure methane potential increased when cows consumed RF or RS (1,464.4, 1,642.0, and 1,571.7 ± 48.11 L/d for CON, RF, and RS, respectively), but no difference was observed for INT (1,466.1 ± 48.11 L/d). Results of these experiments indicate that feeding DDGS in place of dietary starch, NDF, and fNDF does not affect enteric methane production, but that intake and milk production may be increased by replacing dietary NDF and fNDF. Furthermore, feeding DDGS in place of other dietary ingredients has no effect on manure methane production in an anaerobic digestor, but it may influence manure VS output and thus total manure methane potential.

Most studies employ indirect calorimetry to study ruminant energetics and indirectly measure heat production (HP) using an equation published by Ede Brouwer in 1965. Initially estimates of HP used measured oxygen (O₂) consumption and carbon dioxide (CO₂) production, and this was based on the relationship developed by Antoine Lavoisier between the 2 respiratory gases and metabolic HP. These gases were subsequently integrated into the first indirect calorimetry equation by Nathan Zuntz in the late 1800s. However, based on incomplete oxidation of methane (CH₄) and HP associated with urinary N (UN) excretion, inputs into this equation now include O₂ consumption, CO₂ and CH₄ production, and UN losses. In most cases, little to no hydrogen (H₂) is eructated by cattle but this may increase when cattle consume some feed supplements and compounds that reduce ruminal CH₄ production and as a result, H₂ may be considered when HP is indirectly estimated.

Summary: This experiment evaluated the effect of 2-bromoethanesulfonate in combination with monensin or calcium propionate on in vitro gaseous CH₄ and H₂ production. Gas pressure and composition data were collected at 0, 4, 8, 18, 24, and 48 hours of fermentation. Results suggest all treatments containing 2-bromoethanesulfonate reduced CH₄ production, but monensin may further reduce CH₄ compared with 18 hours of 2-bromoethanesulfonate alone. The addition of monensin and calcium also reduced H₂, and this observation serves as evidence that the compounds may serve as a short-term strategy to reduce gaseous H₂ production when CH₄ mitigators such as 2-bromoethanesulfonate are used to reduce enteric CH₄ production.

An accurate estimation of ME content is critical for optimizing dairy cattle nutrition and improving feed efficiency. This meta-analysis used data from studies conducted in Wageningen (the Netherlands) using Holstein cows and in Nebraska using Jersey cows to refine predictive models of dietary ME content (kJ/kg DM) based on total-tract digestible nutrients. In the Wageningen studies (except for one study), apparent total-tract digestibility of nutrients was estimated using chromium oxide as an external marker included in the concentrate. In contrast, the Nebraska studies determined digestibility by difference, based on measured nutrient intake and total fecal output. Importantly, the digestibility values for nutrients used in the models' development were directly measured from total-tract digestibility data, rather than estimated values. Models varied from a simple model including a single total-tract digestible organic matter (dOM) fraction as explanatory variable to complex models in which dOM was fractionated into total-tract digestible crude protein (dCP), fat (ether extract or fatty acids; dFAT), starch (dSTA), neutral detergent fiber (dNDF), sugars (SUG), and a residual fraction (dOM - dFAT - dCP - dNDF - dSTA - 0.97 × SUG). Compared with the simplest model, which predicted ME content based on dOM (with a corrected Akaike information criterion [AICc] of 9,570, R² of 0.859, and root mean square prediction error [RMSPE] of 3.69% of the observed mean). The complex model with the various digestible components improved model fit by reducing the AICc by 102 units to 9,468, increasing R² to 0.878, and lowering the RMSPE to 3.43% of observed mean, thereby achieving an improvement of ∼7% in estimation accuracy. Including feeding level (FL; calculated as ME intake [kJ/d/kg BW⁰·⁷⁵] divided by 562, assuming the ME requirement for maintenance is 562 kJ/d/kg BW⁰·⁷⁵) further improved model performance, with ME content increasing by ∼412 kJ/kg DM per unit rise in FL, underscoring the impact of intake levels on dietary energy estimates. Correcting dFAT and dCP for basal endogenous losses did not further improve model performance. Additionally, location had a significant effect on ME estimation, likely reflecting differences in breed (Holstein vs. Jersey), diet composition, and methodological approaches (e.g., respiration chambers vs. head boxes, marker vs. total collection). Findings from this study provide insight into within-study relationships between observed digestible nutrient fractions and dietary ME content, which may be used for improving energy evaluation systems for dairy cattle.

Summary: During feed metabolism, ruminants consume O₂ and produce CO₂ and CH₄; thus, accurate analyses of these gases after capture are not only integral to quantifying environmental impact, but also describing nutrient utilization. This article recounts 2 experiments evaluating the ability of gas bags made of polyvinyl fluoride (PF) and multilayer fabrication with aluminum (NAP) to retain gas concentrations over a 72-hour period compared with a polyethylene terephthalate (PET) control. The results from the experiment determined that the PF bags initially contained similar gas concentrations relative to the PET, but the PF bag did not retain similar concentrations of O₂ and CO₂ over the 72-hour period, leading to significant treatment by time interactions for experiment 1. In experiment 2, the NAP bag and the PET control bag initially contained and maintained similar concentrations of O₂, CO₂, and CH₄. This resulted in no significant interactions in regard to the NAP in comparison to the PET over time. These results suggest PF does not maintain respiratory gas composition over time and that the NAP bag is a comparable gas bag to the PET gas bag.

Maintenance energy requirements for growing dairy heifers have not been experimentally studied in great depth since the mid-1980s, and to our knowledge, no direct measurements of maintenance have ever been conducted on growing Jersey heifers. The maintenance energy requirement of growing animals is first fulfilled before energy use for gain. As a result, current estimates of maintenance are needed to effectively model gain. Therefore, the objectives of this study were first to use indirect calorimetry to estimate maintenance energy requirements and fasting heat production (FHP) of growing Jersey heifers and second to compare NEM via indirect methods of regression from the data associated with metabolizable energy for maintenance (MEmaint) versus that estimated using direct measures of FHP. Eight nonpregnant growing Jersey heifers (9.53 ± 0.114 mo, 239 ± 14.5 kg) were enrolled in the study and fed at maintenance estimated based on NASEM guidelines (NEM, Mcal/d = 0.10 × BW^0.75, where BW^0.75 represents metabolic body weight) for 24 d. Subsequently, energetic measures were made for 4 d, including indirect calorimetry, intake, and total feces and urine excretion. Heifers were then fasted for 96 h with measures once again taken over the final 2 h. Heat production for growing heifers at NASEM model-calculated maintenance intake averaged 9.55 ± 0.608 Mcal/d, and FHP was observed to be 6.56 ± 0.444 Mcal/d. This resulted in the following representation of maintenance energy requirements: MEmaint (Mcal/BW^0.75 ± SD) = 0.157 ± 0.0056 and NEM (Mcal/BW^0.75 ± SD) = 0.108 ± 0.0051 × BW^0.75. The efficiency of conversion of energy for maintenance averaged 0.684 ± 0.0410. Thus, these estimates of maintenance support those of NASEM (2021), although they are slightly higher.

Methane (CH₄) is an anthropogenic GHG produced by ruminant animals in their conversion of feed to milk or meat. Alga Bio 3.0 (ALB) is a proprietary feed additive (Alga Biosciences Inc.) containing stabilized, synthetic bromoform, which is known to reduce CH₄ emission in the rumen of cattle. The objective was to evaluate the effects of feeding increasing inclusion of an algae feed additive containing bromoform on DMI, energy and N utilization, total gas production with headbox-style indirect calorimetry, and milk production in lactating Jersey cows. Twelve mid lactation multiparous Jersey cows were used in a quadruplicated 3 × 3 Latin square design consisting of 3 periods of 28 d each. Treatments were randomly assigned so that cows consumed increasing concentrations (DM basis) of ALB: 0% of diet DM (0CTRL), 0.46% of diet DM (0.46LOW), and 0.93% of diet DM (0.93HIGH). Increasing ALB inclusion linearly reduced CH₄ production by 19.7% in L/d and 18.4% in L/kg DMI (430, 392, 345 ± 22.02 L/d and 22.8, 20.6, 18.6 ± 1.04 L/kg DMI), and linearly increased hydrogen gas production (none detected, 15.6, 62.4 ± 22.21 L/d). No differences were observed in DMI, milk yield, or ECM averaging 18.9 ± 0.56, 28.4 ± 0.69, and 35.1 ± 0.84 kg, respectively. Milk fat percentage linearly decreased with increasing ALB inclusion (5.22%, 5.04%, 4.92% ± 0.136%), but no difference was observed in milk fat yield (average 1.42 ± 0.048 kg/d). No difference was observed in DM, NDF on an OM basis, CP, starch, and crude fat digestibility averaging 65.6% ± 0.50%, 43.4% ± 0.99%, 67.1% ± 0.64%, 94.3% ± 0.34%, and 73.9% ± 1.88%, respectively. Increasing inclusion of ALB linearly increased the concentration of ME of the diet (2.49, 2.50, 2.55 ± 0.022 Mcal/kg). The efficiency of converting digestible energy (DE) to ME linearly increased (0.88, 0.89, and 0.89 ± 0.003 Mcal/Mcal). Milk samples were analyzed for presence of bromoform residues, and the concentrations were below the limit of detection. Results suggest that ALB can reduce CH₄ production by up to 19.6% in lactating dairy cows, leading to increased efficiency of converting DE to ME.