A meta-analysis was conducted to quantify production responses to chromium (Cr) supplementation and better understand variables that affect this response. Multivariate random and mixed effects models were used to develop and fit all models. The response variable was described by the mean difference of milk yield, ECM, DMI, and milk fat and protein yields between cows that received Cr supplementation and cows in the control group. Treatment means from 28 studies were used to assemble a database of studies designed specifically to investigate the effects of supplementing Cr on dairy cows. Of the 93 treatment means, 38 means fed the Cr starting in the dry period. Overall, Cr supplementation increased production, and the mean difference is affected by stage of lactation (characterized by DIM in our analysis), Cr source (Cr-methionine, Cr-propionate, Cr-chelate, Cr-picolinate, Cr-yeast), and dose (0-19 mg/d). The models for milk yield, milk fat, and milk protein suggest the greatest response for Cr supplementation between a 6 to 7 mg/d supplementation rate. However, the greatest response for DMI was predicted to be at a supplementation rate of 9 mg/d. The models suggest peak mean differences in yields of milk, ECM, fat, and protein at approximately 100 DIM with supplementation of Cr starting at pre- or postcalving. Although the production of ECM maximizes at approximately 100 DIM there is still a benefit in production to feeding Cr up to 168 to 186 DIM, depending on the Cr source.

Ruminal bacteria can either synthesize branched-chain amino acids (BCAA) from central metabolites or from reductive carboxylation and transamination of the branched-chain volatile fatty acids (BCVFA). There is bidirectional mixing within a metabolic pair (i.e., isoleucine/2-methylbutyrate, leucine/isovalerate, and valine/isobutyrate). The keto acid of valine is the intermediate in its synthesis but also branches off in the leucine synthesis pathway. Therefore, we hypothesized that interconversion of 13C-isobutyrate with its keto acid could label both valine and, to a lesser extent, leucine, especially if increased leucine concentration inhibited its de novo synthesis from pyruvate. In Experiment 1, treatments with inadequate (8.5% formulated using NASEM, 2021) RDP and 1.72 mmol per day of each of the 3 BCVFA without or with supplemental leucine (5.16 mmol/d) were arranged in a truncated 6 × 6 Latin square design using a dual flow continuous culture system that allowed measurement of BCVFA production and recovery of isotope. Each of 3 periods consisted of 7 d adaptation that were followed by a 7-d sampling period that included 2 pulse doses of individually 13C-labeled BCVFA or BCAA with 4 d of washout between each dose of isotope within a respective metabolic pair. Supplemental leucine did not change degradation of nutrients or flows of bacterial N, but supplemental leucine did increase isovalerate, valerate, and caproate production. More 13C was recovered in bacterial protein when the isotope was dosed as a labeled BCAA than as BCVFA. Negligible 13C was recovered in amino acids other than BCAA, suggesting minimal metabolism beyond BCVFA. Recovery of 13C into branched-chain fatty acids documented the importance of branched-chain vinyl ethers in plasmalogens, which was especially important for 2-methylbutyrate. In a second experiment using starch (from potato) or cellulose (from corn) grown in 13CO2, low RDP increased de novo synthesis of most amino acids from cellulose, whereas de novo synthesis of leucine increased from starch more than from cellulose. Results are discussed to further document the relative sinks of BCAA and BCVFA in bacterial cell constituents, documenting their importance in the rumen.

Background Claw lesions are a major contributor to lameness, significantly affecting sow welfare, yet the relationship between farrowing performance and lesion severity is underexplored. This study used a multivariate approach to examine the link between farrowing performance—total piglets born (TB), piglets born alive (BA), and stillbirth rate (SBR)—and various claw lesions. Results The sows were clustered into two groups (C1 and C2) using k-means clustering based on claw lesions and farrowing performance. Clusters differed notably in heel overgrowth and erosion (HOE), white line (WL), lesion index (L-Index), and stillbirth rate (SBR), which decreased from C1 to C2, while BA increased (P < 0.05). Linear (LR) and quadratic (QR) models were applied to assess relationships among claw lesions, farrowing performance, and parity order (PO). Additionally, linear mixed models evaluated the effects of claw lesion severity on farrowing performance and vice versa. Parity order progression increased the severity of HOE and L-Index and decreased the severity of WL in C1 (P < 0.05). Parity order had a concave quadratic effect on TB and BA and a convex quadratic effect on SBR across clusters (P < 0.05). Sows scored 3 for HOE had the highest SBR, while those scored 0 and 1 had the lowest, independent of cluster (P < 0.05). Farrowing performance did not influence lesion severity (P > 0.05). Conclusions These findings suggest that Brazilian sows with severe claw lesions, especially WL and HOE, have poorer farrowing outcomes, as indicated by increased SBR, regardless of PO.

Effects of isobutyrate and 2-methylbutyrate (IB-2MB) supplementation and its interaction with 2 levels of dietary RDP were investigated in a replicated 4 × 4 Latin square design with 2 × 2 factorial arrangement: 9% or 11% RDP (% of dietary DM) with or without IB-2MB supplementation (0.09% IB and 0.06% 2MB in dietary DM). The level of dietary RDP was mainly adjusted with soybean meal products, and the concentration of RUP was constant (6% of dietary DM) based on National Academies of Sciences, Engineering, and Medicine 2021 requirements. Eight ruminally cannulated Holstein cows in the second lactation (192 DIM ± 41.3 SD; milk yield, 42.6 kg/d ± 4.67 SD) were fed the treatment diets for 4 wk in each period. The triple marker system and reticular sampling technique were used to determine ruminal digestibility of nutrients and microbial protein synthesis. Total collection of feces and urine were collected for 3 d in the last week of each period. Data were analyzed using the PROC MIXED of SAS with treatment and period as fixed effects, and square and cow within square as random effects. The model for rumen fermentation data included time (repeated measure) and its interaction with RDP and IB-2MB as fixed effects (0, 3, 6 h after feeding). Milk yield and DMI were not affected by treatments. The high RDP treatments increased ruminal ammonia, plasma urea concentration, and increased urinary N and urea excretion compared with low RDP. Ruminal digestibility of NDF was lower (23.4% vs. 27.3%) for high RDP compared with low RDP. Milk fat yield was increased for IB-2MB when high RDP was supplied (1.20 kg/d vs. 1.43 kg/d) and was not affected under low RDP. The IB-2MB supplementation increased ruminal concentration of IB and did not affect 2MB concentration. An interaction between RDP and IB-2MB supplementation was observed in which milk fat yield and ECM were greater for IB-2MB supplementation under high RDP, whereas no difference was detected under low RDP. Similar interactions were observed for the concentrations of 18:1 trans-10 and UFA in milk fatty acids, which was decreased for IB-2MB supplementation under high RDP. The IB-2MB supplementation decreased ruminal true digestibility of nonammonia N and ruminal apparent digestibility of NDF and tended to decrease ruminal true digestibility of DM, and OM, although the efficiency of microbial protein synthesis (nonammonia bacterial N per unit of OM digested; efficiency of microbial protein synthesis [EMPS]) increased for IB-2MB supplementation. No effect of RDP levels, IB-2MB supplementation, or their interaction on total-tract DM, OM, NDF, N, and starch digestibility was observed. In conclusion, the IB-2MB supplementation increased milk fat yield only when RDP was sufficient and was likely due to changes in ruminal fatty acid metabolism. Although EMPS was increased, IB-2MB supplementation decreased ruminal apparent NDF digestibility in this experimental condition without affecting total-tract digestibility of NDF.

Folates are required in one-carbon metabolism and DNA methylation. During the transition period, these roles are particularly important for the final stages of fetal development and the onset of lactation. The objective of this retrospective study was to assess plasma folate concentration when a portion of dietary inorganic chloride trace minerals (ITM) and cobalt (Co) carbonate was replaced by AA complexes of trace minerals (AATM) and Co glucoheptonate during the transition period. Relationships between serum folate concentration and health biomarkers were also evaluated. With dietary trace mineral concentrations being the same between treatments, a total of 36 Holstein multiparous cows were randomly assigned based on their parity number and previous 305-d mature equivalent milk production to either (1) an ITM blend consisting of zinc (75 mg/kg DM), manganese (65 mg/kg), and copper (10 mg/kg) as hydroxychlorides, and cobalt (1 mg/kg) as carbonate (ITM) or (2) partial replacement of ITM with AATM of Zn (40 mg/kg), Mn (20 mg/kg), Cu (3.5 mg/kg), and Co glucoheptonate (1 mg/kg; AATM, Availa-Dairy, Zinpro Corp.) from 1 wk after dry-off through 8 wk of lactation. Milk yields were recorded at each milking. Blood samples were taken at wk-8 (before treatment administration), -1, 1, 2, and 8 relative to parturition for serum folate analysis. Serum folate concentration from wk-1 to 8 relative to parturition averaged 8.39 (SE: 0.44) ng/mL and was not affected by treatments. Regardless of treatments, serum folate concentration significantly decreased from wk-8 to-1, plateaued from wk-1 to 2 relative to parturition, and then significantly increased through wk 8 of lactation. Milk yield, DMI, serum alanine aminotransferase, and alkaline phosphatase concentrations were positively correlated with serum folate concentration, whereas serum BHB concentration tended to be negatively correlated with serum folate concentration. In conclusion, in the current study, the source of the trace mineral supplement fed during the dry period and early lactation did not have an impact on serum folate concentrations.

Data are limited on how cow hooves develop early in life and how this will affect susceptibility to lameness and claw disorders later in life. The aim of this study was to characterize individual claw growth and wear in dairy calves. A total of 90 male Holstein calves <1 wk old were enrolled in this completely randomized design experiment and monitored until wk 20 of age. Evaluation of hoof development was conducted by visual inspection, and individual claw measurements were taken with a graduated ruler. Claws were numbered from 1 to 8 to maintain consistent data collection, where front claws were numbered 1 to 4 (left to right) and rear claws were 5 to 8. Lateral claws were numbered 1, 4, 5, and 8, and medial claws were 2, 3, 6, and 7. Measurements included length from the coronary band to the end of the hoof wall and from the coronary band to the groove line, resulting in the variables claw length (CL) and groove length (GL), respectively. Hoof development was evaluated at wk 0, 5, 10, 15, and 20. All evaluations were performed by the same person throughout the study to eliminate variation between observers. Hoof growth and wear were derived from CL and GL measurements and analyzed from wk 0 to 20. Claw length at wk 0 was different across claw positions, and maximal claw length was observed in claws in positions 6 and 7 (i.e., rear medial claws). A similar growth pattern in claw length was observed when evaluated from wk 0 to 20, where a greater claw length was observed in claws 6 and 7 compared with other claws. In contrast to claw length, claw wear at wk 20 was lower in claws 6 and 7 compared with other claws. Compared with rear claws, front claws had greater wear at wk 20, and compared with medial claws, lateral claws had greater wear at wk 20. Factors associated with claw length differences at wk 0 remain to be elucidated, but the fact that this uneven claw length difference was maintained 20 wk after birth is puzzling. The complementary claw length to wear described greater wear in claws 1 and 4 (i.e., front lateral) in young calves, which is translated into lower claw length in the same claws by wk 20 after birth. Future research in postnatal hoof growth should strive to understand the potential biological significance of this effect on lameness resistance and longevity of dairy cows.

Our objective was to determine the effects of isoacids (ISO) on the lactation performance, digestibility, and milk fatty acids (FA) profile of Holstein cows fed 2 forage NDF levels (FL). The study lasted 10 wk (including 2 wk for covariate) using a randomized complete block design. Sixty-four mid-lactating Holstein cows (662 ± 71 kg BW, 119 ± 51 DIM, 2 ± 0.9 parity [±SD]) were blocked by parity, DIM, and prior milk yield (MY) for multiparous cows or genetic merit for primiparous cows, and randomly assigned to 1 of the 4 diets (n = 16). Diets were arranged as a 2 × 2 factorial, with 2 FL containing 21% forage (HF) and 17% forage NDF (LF) without (WIA) or with ISO supplementation (IA; 7.85 mmol/kg of DM and 3.44 mmol/kg of DM for isobutyrate and 2-methylbutyrate, respectively). Diets were balanced for similar NEL (1.58 Mcal/kg of DM), CP (16.0%), and total NDF (27.2%). Feed intake and MY were recorded daily. Nutrient digestibility for each cow was determined using indigestible NDF as a marker, and fecal samples were collected at 8-time points (4-h intervals between samples). Individual cow milk samples composited over a 10-wk period were analyzed using GC for FA profile. The statistical model included FL, ISO, and FL × ISO as fixed effects and block as a random effect (lme4 in R). The ISO did not affect DMI, and LF cows had greater DMI than HF cows (27.8 vs. 26.0 kg/d). However, ISO increased MY (34.7 vs. 37.2 kg/d) and ECM (41.9 vs. 39.0 kg/d) by 7% in cows fed the HF but not in those fed the LF diet, suggesting a FL × ISO interaction. Interestingly, ISO increased ADG (0.4 kg/d) but decreased MUN by 9% only in LF diet as indicated by the FL × ISO interaction. Additionally, ISO increased DM, OM, NDF, and CP digestibility by 10% to 24% in HF, but not in LF (FL × ISO). As expected, ISO increased milk odd-chain FA profiles in the IA groups irrespective of FL; for example, the IA had greater C15:0 (1.87 vs. 1.54 g/100g FA) and a tendency to be greater C17:0 levels (0.86 vs. 0.76 g/100g FA) compared with WIA groups. Overall, ISO improved MY and nutrient digestibility in cows fed the HF diets, whereas it increased ADG and decreased MUN in cows fed the LF diet. Additionally, ISO increased milk odd-chain FA (C15:0 and C17:0) regardless of FL.

Introduction Claw lesions significantly contribute to lameness, greatly affecting sow welfare. This study investigated different factors that would impact the severity of claw lesions in the sows of Brazilian commercial herds.Methods A total of 129 herds (n = 12,364 sows) were included in the study. Herds were in the Midwest, Southeast, or South regions of Brazil. Inventory sizes were stratified into 250-810 sows, 811-1,300 sows, 1,301-3,000 sows, and 3,001-10,000 sows. Herds belonged to Cooperative (Coop), Integrator, or Independent structures. The herd management was conducted either maintaining breeds from stock on-site (internal), or through purchase of commercially available genetics (external). Herds adopted either individual crates or group housing during gestation. Within each farm, one randomly selected group of sows was scored by the same evaluator (two independent experts evaluated a total of 129 herds) from 0 (none) to 3 (severe) for heel overgrowth and erosion (HOE), heel-sole crack (HSC), separation along the white line (WL), horizontal (CHW) and vertical (CVW) wall cracks, and overgrown toes (T), or dewclaws (DC) in the hind legs after parturition. The study assessed differences and similarities between herds using Principal Component Analysis (PCA) and Hierarchical Agglomerative Clustering (HAC) analysis. The effects of factors (i.e., production structure, management, housing during gestation, and region) were assessed using the partial least squares method (PLS).Results and discussion Heel overgrowth and erosion had the highest prevalence, followed by WL and CHW, while the lowest scores were observed for T, DC, and CVW. Herds were grouped in three clusters (i.e., C1, C2, and C3). Heel overgrowth and erosion, HSC, WL, CHW, CVW, and T were decreased by 17, 25, 11, 25, 21, and 17%, respectively, in C3 compared to C1 and 2 combined. Independent structure increased the L-Index in all three clusters. Furthermore, individual housing increased the L-Index regardless of the cluster. The results suggest that shifting toward larger, more technologically advanced herds could potentially benefit claw health. Additionally, adopting group gestation housing appears to mitigate the adverse effects on claw health, although further validation is necessary, as Brazil has only recently transitioned from individual housing practices.

Some cellulolytic bacteria require 1 or more branched-chain volatile fatty acids (BCVFA) for the synthesis of branched-chain AA and branched-chain long-chain fatty acids because they are not able to uptake branched-chain AA or lack 1 or more enzymes to synthesize branched-chain AA de novo. Supplemental BCVFA and valerate were included previously as a feed additive that was later removed from the market; these older studies and more current studies have noted improvements in neutral detergent fiber digestibility and milk efficiency. However, most studies provided a single BCVFA or else isobutyrate (IB), 2-methylbutyrate (MB), isovalerate, and valerate altogether without exploring optimal combinations. Our objective was to determine a combination of isoacids that is optimal for milk production. Sixty (28 primiparous and 32 multiparous) lactating Jersey cows (106 ± 54 days in milk) were blocked and assigned randomly to either a control (CON) treatment without any isoacids, MB [12.3 mmol/kg dry matter (DM)], MB + IB (7.7 and 12.6 mmol/kg DM of MB and IB, respectively), or all 4 isoacids (6.2, 7.3, 4.2, and 5.1 mmol/kg DM of MB, IB, isovalerate, and valerate, respectively). Cattle were fed the CON treatment for a 2-wk period, then were assigned randomly within a block to treatments for 8 wk (n = 15). There was a trend for an interaction of supplement and parity for milk components. There were no differences in components for primiparous cows, whereas MB + IB tended to increase protein concentration by 0.04 and 0.08 percentage units in multiparous cows compared with the CON and MB treatments, respectively. Feeding MB + IB increased fat concentration by 0.23 to 0.31 percentage units compared with all other treatments in multiparous cows. Milk yield and dry matter intake (DMI) did not change with treatment. Treatment interacted with week for milk net energy for lactation/DMI; MB + IB tended to increase milk net energy of lactation/DMI by 0.10 Mcal/kg compared with MB and approached a trend for CON, mainly during the early weeks of the treatment period, whereas differences decreased during the last 2 wk of the treatment period. Cows fed MB had the highest 15:0 anteiso fatty acids in the total milk fatty acid profile, which was greater than that for CON or MB + IB cows, but not cows supplemented with isoacids. Cows fed MB alone had the numerically lowest milk net energy for lactation/DMI. The combination of MB + IB appeared optimal for increasing feed efficiency in our study and was not at the expense of average daily gain. Further research is needed for evaluating how potential changes in supplemental isoacid dosage should vary under differing dietary conditions.

To maintain membrane homeostasis, ruminal bacteria synthesize branched-chain fatty acids (BCFA) or their derivatives (vinyl ethers) that are recovered during methylation procedures as branched-chain aldehydes (BCALD). Many strains of cellulolytic bacteria require 1 or more branched-chain volatile fatty acid (BCVFA). Therefore, the objective of this study was to investigate BCVFA incorporation into bacterial lipids under different dietary conditions. The study was an incomplete block design with 8 continuous culture fermenters used in 4 periods with treatments (n = 4) arranged as a 2 × 2 × 2 factorial. The factors were high (HF) or low forage (LF, 67 or 33% forage, 33:67 alfalfa:orchardgrass), without or with supplemental corn oil (CO; 3% dry matter, 1.5% linoleic fatty acid), and without or with 2.15 mmol/d (5 mg/d 13C each of isovalerate, isobutyrate, and 2-methylbutyrate). After methylation of bacterial pellets collected from each fermenter's effluent, fatty acids and fatty aldehydes were separated before analysis by gas chromatography and isotope ratio mass spectrometry. Supplementation of BCVFA did not influence biohydrogenation extent. Label was only recovered in branched-chain lipids. Lower forage inclusion decreased BCFA in bacterial fatty acid profile from 9.45% with HF to 7.06% with LF and decreased BCALD in bacterial aldehyde profile from 55.4% with HF to 51.4% with LF. Supplemental CO tended to decrease iso even-chain BCFA and decreased iso even-chain BCALD in their bacterial lipid profiles. The main 18:1 isomer was cis-9 18:1, which increased (P < 0.01) by 25% from CO (data not shown). Dose recovery in bacterial lipids was 43.3% lower with LF than HF. Supplemental CO decreased recovery in the HF diet but increased recovery with LF (diet × CO interaction). Recovery from anteiso odd-chain BCFA and BCALD was the greatest; therefore, 2-methylbutyrate was the BCVFA primer most used for branched-chain lipid synthesis. Recovery in iso odd-chain fatty acids (isovalerate as primer) was greater than label recovery in iso even-chain fatty acids (isobutyrate as primer). Fatty aldehydes were less than 6% of total bacterial lipids, but 26.0% of 13C recovered in lipids were recovered in BCALD because greater than 50% of aldehydes were branched-chain. Because BCFA and BCALD are important in the function and growth of bacteria, especially cellulolytics, BCVFA supplementation can support the rumen microbial consortium, increasing fiber degradation and efficiency of microbial protein synthesis.

Some cellulolytic bacteria cannot transport branched-chain AA (BCAA) and do not express complete synthesis pathways, thus depending on cross-feeding for branched-chain volatile fatty acid (BCVFA) precursors for membrane lipids or for reductive carboxylation to BCAA. Our objective was to assess BCVFA uptake for BCAA synthesis in continuous cultures administered high forage (HF) and low forage (LF) diets without or with corn oil (CO). We hypothesized that BCVFA would be used for BCAA synthesis more in the HF than in LF diets. To help overcome bacterial inhibition by polyunsaturated fatty acids in CO, BCVFA usage for bacterial BCAA synthesis was hypothesized to decrease when CO was added to HF diets. The study was an incomplete block design with 8 dual-flow fermenters used in 4 periods with 8 treatments (n = 4) arranged as a 2 × 2 × 2 factorial. The factors were: HF or LF (67 or 33% forage, 33:67 alfalfa:orchardgrass pellets), without or with supplemental CO (3% of dry matter), and without or with 2.15 mmol/d (5 mg/d 13C) each of isovalerate, isobutyrate, and 2-methylbutyrate for one combined BCVFA treatment. The flow of bacterial BCAA increased by 10.7% by supplementing BCVFA and 9.14% with LF versus HF; similarly, dosing BCVFA versus without BCVFA increased BCAA by 1.98% in total bacterial AA, whereas LF increased BCAA by 1.92% versus HF. Additionally, BCVFA supplementation increased bacterial AA flow by 16.6% when supplemented in HF - CO and 12.4% in LF + CO diets, but not in the HF + CO (-1.5%) or LF - CO (+6.7%) diets (Diet × CO × BCVFA interaction). The recovery of 13C in bacterial AA flow was 31% lower with LF than with HF. Of the total 13C recovered in bacteria, 13.8, 17.3, and 30.2% were recovered in Val, Ile, and Leu, respectively; negligible 13C was recovered in other AA. When fermenters were dosed with BCVFA, nonbacterial and total effluent flows of AA, particularly of alanine and proline, suggest decreased peptidolysis. Increased ruminal outflow of bacterial AA, especially BCAA, but also nonbacterial AA could potentially support postabsorptive responses from BCVFA supplementation to dairy cattle.

Branched-chain amino acids are deaminated by amylolytic bacteria to branched-chain volatile fatty acids (BCVFA), which are growth factors for cellulolytic bacteria. Our objective was to determine the dietary conditions that would increase the uptake of BCVFA by rumen bacteria. We hypothesized that increased forage would increase cellulolytic bacterial abundance and incorporation of BCVFA into their structure. Supplemental polyunsaturated fatty acids, supplied via corn oil (CO), should inhibit cellulolytic bacteria growth, but we hypothesized that additional BCVFA would alleviate that inhibition. Further, supplemental BCVFA should increase neutral detergent fiber degradation and efficiency of bacterial protein synthesis more with the high forage and low polyunsaturated fatty acid dietary combination. The study was an incomplete block design with 8 dual-flow continuous cultures used in 4 periods with 8 treatments (n = 4 per treatment) arranged as a 2 × 2 × 2 factorial. The factors were: high forage (HF) or low forage (LF; 67 or 33%), without or with supplemental CO (3% dry matter), and without or with 2.15 mmol/d (which included 5 mg/d of 13C each of BCVFA isovalerate, isobutyrate, and 2-methylbutyrate). The isonitrogenous diets consisted of 33:67 alfalfa:orchardgrass pellet, and was replaced with a concentrate pellet that mainly consisted of ground corn, soybean meal, and soybean hulls for the LF diet. The main effect of supplementing BCVFA increased neutral detergent fiber (NDF) degradability by 7.6%, and CO increased NDF degradability only in LF diets. Supplemental BCVFA increased bacterial N by 1.5 g/kg organic matter truly degraded (6.6%) and 0.05 g/g truly degraded N (6.5%). The relative sequence abundance decreased with LF for Fibrobacter succinogenes, Ruminococcus flavefaciens, and genus Butyrivibrio compared with HF. Recovery of the total 13C dose in bacterial pellets decreased from 144 µg/ mg with HF to 98.9 µg/ mg with LF. Although isotope recovery in bacteria was greater with HF, BCVFA supplementation increased NDF degradability and efficiency of microbial protein synthesis under all dietary conditions. Therefore, supplemental BCVFA has potential to improve feed efficiency in dairy cows even with dietary conditions that might otherwise inhibit cellulolytic bacteria.

Abstract Three experiments were conducted with growing wethers to evaluate apparent excretion and retention of Zn from various sources. In experiments 1 and 2, Zn-ethylene diamine (ZE), Zn hydroxychloride (ZHYD), Zn-lysine/glutamate (ZAA), and Zn-glycinate (ZG) were used and ZnSO4 (ZS), ZHYD, ZAA, and ZG were used in experiment 3. In experiment 1, eight wethers were used in a replicated 4 × 4 Latin square design. In experiments 2 and 3, 40 wethers were used in a randomized block design. In experiment 1, each period (total four periods) consisted of 14-d diet adaptation and 4 d of total collection of feces and urine. In experiments 2 and 3, wethers received a basal diet for 14 d and received experimental diets for 9 d (diet adaptation), followed by 4 d of total collection of feces and urine. Total collection was conducted in wooden metabolic cages. All data were analyzed using the MIXED procedure of SAS as a Latin square design for experiment 1 and a completed randomized block design for experiments 2 and 3. In all experiments, dry matter intake did not differ among treatments except that it tended to be different in experiment 2. In experiment 1, no difference in Zn excretion (88%) and retention (11%) as proportion of Zn intake was observed among Zn sources. In experiment 2, total tract digestibility of crude protein was greater (P < 0.01) for ZAA than ZE and ZG (82.0% vs. 79.1% and 77.8%, respectively) and greater (P < 0.01) for ZHYD than ZG (80.2% vs. 77.8%). However, total tract digestibility of neutral detergent fiber was low (on average 16%) for all treatments with no difference among treatments in experiment 2. Apparent excretion and retention of Zn as proportion of Zn intake did not differ among treatments, and Zn retention (~1.4% of Zn intake) was very low for all treatments. In experiment 3, ZHYD and ZAA had greater retention of Zn (17.8% vs. 1.5%; P = 0.01) than ZG. Fecal Zn excretion was greater (97.3% vs. 81.2%; P = 0.01) for ZG vs. ZHYD and ZAA, and Zn retention for ZG was only 1.5% of Zn intake. In conclusion, potential increases in Zn absorption and retention were observed for ZHYD and ZAA compared with ZS and ZG in experiment 3 and these differences were not found in experiments 1 and 2. Experiment 1 used a Latin square design and experiment 2 used a diet containing largely undigestible fiber. These experimental conditions may have affected Zn metabolism in wethers. Inconsistent results on Zn balance for ZG among the experiments warrant further studies regarding its bioavailability.

Three experiments assessed branched-chain volatile fatty acid (BCVFA) stimulation of neutral detergent fiber (NDF) disappearance after 24 h of incubation in batch cultures derived from ruminal fluid inocula that were enriched with particulate-phase bacteria. In experiment 1, a control was compared with 3 treatments with isomolar doses of all 3 BCVFA (plus valerate), all 3 branched-chain AA (BCAA), or half of each BCVFA and BCAA mix with either alfalfa or grass hays (50%) and ground corn grain (50%). A portion of the BCAA and BCVFA doses were enriched with 13C, and valerate (also enriched with 13C) was added with BCVFA. Although BCAA yielded a similar production of BCVFA compared with dosing BCVFA, equimolar substitution of BCVFA for BCAA decreased the percentage of N in bacterial pellets when alfalfa hay was fed but increased N when grass hay was fed. Substituting BCVFA for BCAA increased total fatty acid (FA) concentration with alfalfa hay. Dosing of BCAA or BCVFA did not affect total branched-chain FA, iso-FA, or anteiso-FA percentages in bacterial total FA, whereas numerous individual FA isomers and their 13C enrichments were affected by these treatments. Increasing recovery of the 13C dose from respective labeled BCVFA primers indicated facilitated BCVFA uptake and incorporation into FA compared with BCAA, whereas increased recovery of 13C from labeled BCAA in the bacteria pellet but not in the FA fraction suggested direct assimilation into bacterial protein. The BCVFA and valerate were dosed in varying combinations that either summed to 4 mM (experiment 2) or had only 1 mM no matter what combination (experiment 3). In general, grass hay was more responsive to stimulation in NDF digestibility by BCVFA than was alfalfa hay, which was attributed to the higher degradable protein in the latter. The net production of the BCVFA (after subtracting dose) was affected by source and combination of BCVFA. Isovalerate dosing tended to increase its own net production; in contrast, isobutyrate seemed to be used more when it was added alone, but 2-methylbutyrate seemed to be preferred over isobutyrate when 2-methylbutyrate was added. Results supported potential interactions, including potential feedback in production from feed BCAA or increased concentration-dependent competition for dosed BCVFA into cellular products. Under our conditions, the BCVFA appear to be more readily available than BCAA, probably because of regulated BCAA transport and metabolism. Valerate consistently provided no benefit. Using nonparametric ranking, all 3 BCVFA or either isovalerate or isobutyrate (both yielding iso-FA) should be combined with 2-methylbutyrate (yielding anteiso-FA) as a potential opportunity to improve NDF digestibility when rumen-degraded BCAA are limited in diets to decrease environmental impact from N in waste.

Calves born to multiparous Holstein cows fed during the last 30 d of pregnancy 2 different cobalt sources [cobalt glucoheptonate (CoPro) or cobalt pectin (CoPectin)], folic acid (FOA), and rumen-protected methionine (RPM) were used to study neonatal immune responses after ex vivo lipopolysaccharide (LPS) challenge. Groups were (n = 12 calves/group) CoPro, FOA+CoPro, FOA+CoPectin, and FOA+CoPectin+RPM. Calves were weighed at birth and blood collected at birth (before colostrum), 21 d of age, and 42 d of age (at weaning). Growth performance was recorded once a week during the first 6 wk of age. Energy metabolism, inflammation, and antioxidant status were assessed at birth through various plasma biomarkers. Whole blood was challenged with 3 µg/mL of LPS or used for phagocytosis and oxidative burst assays. Target genes evaluated by real-time quantitative PCR in whole blood samples were associated with immune response, antioxidant function, and 1-carbon metabolism. The response in mRNA abundance in LPS challenged versus nonchallenged samples was assessed via Δ = LPS challenged − LPS nonchallenged samples. Phagocytosis capacity and oxidative burst activity were measured in neutrophils and monocytes, with data reported as ratio (percentage) of CD14 to CH138A-positive cells. Data including all time points were subjected to ANOVA using PROC MIXED in SAS 9.4 (SAS Institute Inc.), with Treatment, Sex, Age, and Treatment × Age as fixed effects. A 1-way ANOVA was used to determine differences at birth, with Treatment and Sex as fixed effects. Calf birth body weight and other growth parameters did not differ between groups. At birth, plasma haptoglobin concentration was lower in FOA+CoPro compared with CoPro calves. We detected no effect for other plasma biomarkers or immune function due to maternal treatments at birth. Compared with CoPro, in response to LPS challenge, whole blood from FOA+CoPectin and FOA+CoPectin+RPM calves had greater mRNA abundance of intercellular adhesion molecule 1 (ICAM1). No effect for other genes was detectable. Regardless of maternal treatments, sex-specific responses were observed due to greater plasma concentrations of haptoglobin, paraoxonase, total reactive oxygen metabolites, nitrite, and β-carotene in female versus male calves at birth. In contrast, whole blood from male calves had greater mRNA abundance of IRAK1, CADM1, and ITGAM in response to LPS challenge at birth. The longitudinal analysis of d 0, 21, and 42 data revealed greater bactericidal permeability-increasing protein (BPI) mRNA abundance in whole blood from FOA+CoPectin versus FOA+CoPro calves, coupled with greater abundance in FOA+CoPro compared with CoPro calves. Regardless of maternal treatments, most genes related to cytokines and cytokine receptors (IL1B, IL10, TNF, IRAK1, CXCR1), toll-like receptor pathway (TLR4, NFKB1), adhesion and migration (ICAM1, ITGAM), antimicrobial function (MPO), and antioxidant function (GPX1) were downregulated over time. Phagocytosis capacity and oxidative burst activity in both neutrophils and monocytes did not differ due to maternal treatment. Regardless of maternal treatments, we observed an increase in the percentage of neutrophils capable of phagocytosis and oxidative burst activity over time. Overall, these preliminary assessments suggested that maternal supplementation with FOA and Co combined with RPM had effects on a few plasma biomarkers of inflammation at birth and molecular responses associated with inflammatory mechanisms during the neonatal period.

The objectives of this experiment were to determine the effects of increased diet fermentability and polyunsaturated fatty acids (FA) with or without supplemental 2-hydroxy-4-(methylthio)-butanoic acid (HMTBa), isoacids (IA; isobutyrate, 2-methylbutyrate, isovalerate, and valerate) or the combination of these on milk fat depression (MFD). Ten Holstein cows (194 ± 58 DIM, 691 ± 69 kg BW, 28 ± 5 kg milk yield) were used in a replicated 5 × 5 Latin square design. Treatments included a high-forage control diet (HF-C), a low-forage control diet (LF-C) causing MFD by increasing starch and decreasing neutral detergent fiber (NDF), the LF-C diet supplemented with HMTBa at 0.11% (28 g/d), the LF-C diet supplemented with IA at 0.24% of dietary dry matter (60 g/d), and the LF-C diet supplemented with HMTBa and IA. Preplanned contrasts were used to compare HF-C versus LF-C and to examine the main effects of HMTBa or IA and their interactions within the LF diets. Dry matter intake was greater for LF-C versus HF-C, but milk yield remained unchanged. The LF-C diet decreased milk fat yield (0.87 vs. 0.98 kg/d) but increased protein yield compared with HF-C. As a result, energy-corrected milk was lower (28.5 vs. 29.6 kg/d) for LF-C versus HF-C. Although the concentration of total de novo synthesized FA in milk fat was not affected, some short- and medium-chain FA were lower for LF-C versus HF-C, but the concentrations of C18 trans-10 isomers were not different. Total-tract NDF apparent digestibility was numerically lower (42.4 vs. 45.6%) for LF-C versus HF-C. As the main effects, the decrease in milk fat yield observed in LF-C was alleviated by supplementation of HMTBa through increasing milk yield without altering milk fat content and by IA through increasing milk fat content without altering milk yield so that HMTBa or IA, as the main effects, increased milk fat yield within the LF diets. However, interactions for milk fat yield and ECM were observed between HMTBa and IA, suggesting no additive effect when used in combination. Minimal changes were found on milk FA profile when HMTBa was provided. However, de novo synthesized FA increased for IA supplementation. We detected no main effect of HMTBa, IA, and interaction between those on total-tract NDF digestibility. In conclusion, the addition of HMTBa and IA to a low-forage and high-starch diet alleviated moderate MFD. Although the mechanism by which MFD was alleviated was different between HMTBa and IA, no additive effects of the combination were observed on milk fat yield and ECM.