Increasing production efficiency of dairy cows through improved health is not possible without adequate nutrition. Hippocrates (460–370 BC), the father of modern medicine, apparently claimed that all diseases begin in the gut, and this might be appropriately applied to dairy cows. The transition period, defined as 3 wk before and 3 wk after parturition, is characterized by extensive metabolic and physiologic changes mediated by homeostatic and homeorhetic processes ( Figure 1; Bauman and Currie, 1980), and the use of nutritional and management strategies during this period can provide long-lasting effects for dairy cows. For instance, failing to manage the calcium status of the animal during the transition period can be detrimental to milk production in the subsequent lactation. Multiparous cows with delayed or persistent hypocalcemia measured at days 1 and 4 postpartum produced less milk (up to 7.2 kg/d in the first 6 wk of lactation) than cows with transient or no hypocalcemia ( Seely et al., 2021).

Botanical extracts have a potential to modify ruminal fermentation while enhancing metabolism and immunity in dairy cows. The objective of this study was to investigate the effects of a combination of Capsicum oleoresin and clove essential oil (botanicals; BTC) on lactational performance, nutrient utilization, enteric methane (CH₄) emissions, and blood parameters in dairy cows. Twenty Holstein cows (12 multiparous and 8 primiparous) averaging (±SD) 77 ± 28 d in milk in the beginning of the study were used in a replicated 4 × 4 Latin square design experiment with 4 periods of 28 d each. Cows were grouped into squares based on parity, milk yield and days in milk, and assigned to 1 of 4 treatments: control (CON), 150, 300, or 600 mg/cow per day of BTC. Cows received the same basal diet and BTC were top-dressed on the total mixed ration once daily. Dry matter intake, milk production, and milk composition were not affected by BTC supplementation, except for milk fat content that tended to be increased in BTC, compared with CON. Daily CH₄ emission (measured using the GreenFeed system) was linearly decreased by up to 7.5% with increasing doses of BTC. Treatment decreased CH₄ yield (kg of CH₄ ÷ kg of DMI) and tended to decrease CH₄ intensity (kg of CH₄ ÷ kg of milk or energy-corrected milk yields) by 5% in BTC, compared with CON. Supplementation of BTC resulted in a quadratic decrease of serum β-hydroxybutyrate in all cows, and a linear decrease of serum insulin concentration in primiparous but not in multiparous cows. Nutrient utilization and other blood parameters (e.g., blood cells count) were not affected by BTC in the current study. The reduction of enteric CH₄ emission demonstrates a moderate mitigation effect on carbon footprint of milk by BTC supplementation. These results must be further investigated and confirmed in longer-term experiments.

A meta-regression was conducted to determine the production effects of 3-nitrooxypropanol (3-NOP) and investigate their associations with dose, dietary nutrient composition, and supplementation length in dairy cows. Forty treatment and control mean comparisons extracted from 21 studies conducted or published between 2014 to 2024 were used in the meta-regression. Response variables were DMI, milk yield (MY), ECM yield, ECM feed efficiency, BW, BW change, and concentrations of milk fat, true protein, lactose, and MUN. Treatment and control mean differences (MD) as well as standardized MD were calculated and used for data presentation and statistical analysis, respectively. Dose (± SD; 77.0 ± 33.17 mg 3-NOP/kg DMI), forage-to-concentrate ratio (FC; 58.9 ± 8.83%, expressed as average ± SD% of forage in the diet), dietary concentrations of CP, ether extract, NDF, and starch (16.3 ± 1.84%, 4.3 ± 1.03%, 33.7 ± 4.40%, and 20.9 ± 3.97%, as average ± SD% of DM, respectively), supplementation length (days), and DIM and BW of the cows at the beginning of the study were used as continuous explanatory variables. Mixed-effects models were fitted using the robust variance estimation method. Full models containing uncorrelated explanatory variables (Pearson correlation <0.50) were fitted, and variables were removed from the final model if nonsignificant using the stepwise selection approach. Compared with control, supplementation of 3-NOP decreased DMI and MY by 0.80 ± 0.149 and 0.98 ± 0.250 kg/d, respectively, but only numerically decreased ECM by 0.50 ± 0.298 kg/d. Consequently, feed efficiency was increased by 0.05 ± 0.012 kg ECM/kg DMI with 3-NOP supplementation. Body weight and BW change were not affected by 3-NOP supplementation. Milk fat, true protein, and MUN concentrations were increased by 0.09 ± 0.028%, 0.02 ± 0.006%, and 0.59 ± 0.106 mg/dL, respectively. Increasing 3-NOP dose further decreased DMI and increased milk fat and MUN concentrations. Increasing dietary NDF and FC lessened the negative effect of 3-NOP on DMI and MY, respectively, and decreased its effect on milk fat and MUN (dietary NDF concentration effect only). Similarly, increasing dietary CP lessened the negative effect of 3-NOP on DMI and decreased its effect on MUN. To explain some of the production effects herein observed, ruminal fermentation data from 6 published studies were included in the meta-regression. Supplementation of 3-NOP tended to increase rumen pH and decreased NH₃ concentration. Concentrations of total VFA, acetate, and the acetate-to-propionate ratio were decreased, whereas the concentration of propionate was increased, and that of butyrate was numerically increased by 3-NOP supplementation. Overall, 3-NOP supplementation of dairy cow diets decreased DMI and MY but did not affect ECM because of increased milk fat and true protein contents. Increased milk fat and MUN responses can be explained by shifted ruminal fermentation, and the increased milk true protein response may be explained by increased rumen propionate molar proportion by 3-NOP supplementation.

Yeast culture and phytonutrients are dietary supplements with distinct modes of action, and they may have additive effects on the performance of dairy cattle. The objective of this study was to investigate the effects of a preparation of phytonutrients and a yeast culture from Saccharomyces cerevisiae on lactational performance, total-tract digestibility of nutrients, urinary nitrogen losses, energy metabolism markers, and blood cells in dairy cows. Thirty-six mid-lactation Holstein cows (10 primiparous and 26 multiparous) were used in an 8-wk randomized complete block design experiment with a 2-wk covariate period, 2 wk for adaptation to the diets, and a 4-wk experimental period for data and samples collection. Following a 2-wk covariate period, cows were blocked by days in milk, parity, and milk yield and randomly assigned to 1 of 3 treatments (12 cows per treatment): basal diet supplemented with 14 g/cow per day yeast culture (YC; S. cerevisiae), basal diet supplemented with 1.0 g/cow per day phytonutrients (PN; 5.5% cinnamaldehyde, 9.5% eugenol, and 3.5% capsicum oleoresin), or basal diet supplemented with a combination of YC and PN (YCPN). Treatments were top-dressed once daily on the total mixed ration at time of feeding. Dry matter intake, milk yield, and feed efficiency were not affected by treatments. Milk composition and energy-corrected milk yield were also not affected by supplementation of YC, PN, and YCPN. There were no differences in intake or total-tract digestibility of dietary nutrients among treatments. Compared with YC, the PN and YCPN treatments tended to decrease the proportion of short-chain fatty acids in milk fat. There was an additive effect of YC and PN supplementation on urinary urea nitrogen (UUN) excretion relative to total nitrogen intake. Cows fed a diet supplemented with YCPN had lower UUN excretion than cows in YC and tended to have lower UUN excretion compared with PN. Blood monocytes count and percentage were decreased in cows fed PN and YCPN diets compared with YC. Treatments did not affect concentrations of blood β-hydroxybutyrate and total fatty acids. Overall, lactational performance, digestibility of nutrients, energy metabolism markers, and blood cells were not affected by YC, PN, or YCPN supplementation. A combination of PN and YC had an additive effect on nitrogen excretion in dairy cows.

The objective of this study was to investigate the effects of an exogenous enzyme preparation from As-pergillus oryzae and Aspergillus niger on lactational performance of dairy cows. Forty-eight Holstein cows (32 primiparous and 16 multiparous) averaging (+/- SD) 36.3 +/- 8.7 kg/d milk yield and 141 +/- 52 d in milk were enrolled in a 10-wk randomized complete block design experiment (total of 24 blocks) and assigned to 1 of 2 treatments: basal diet, no enzyme supplementation (CON) or the basal diet supplemented with 4.2 g/kg dry matter intake (DMI) of an exogenous enzyme prep-aration containing amylolytic and fibrolytic activities (ENZ). After a 2-wk covariate period, premixes with the enzyme preparation or control were top-dressed daily by mixing with approximately 500 g of total mixed ra-tion. Production data were collected daily and averaged by week. Milk samples were collected every other week, and milk composition was averaged by week. Blood, fe-cal, and urine samples were collected over 2 consecutive days at 0, 4, 8, 12, and 36 h after feeding during the last week of the experiment. Compared with CON, cows fed ENZ tended to increase DMI and had increased milk concentrations of true protein, lactose, and other solids. Milk fat content tended to be higher in CON cows. A treatment x parity interaction was found for some of the production variables. Primiparous cows receiv-ing ENZ had greater yields of milk, energy-corrected milk, milk true protein, and lactose compared with CON primiparous cows; these production variables did not differ between treatments for multiparous cows. Intake and total-tract digestibility of nutrients did not differ between treatments. Concentrations of blood glucose and total fatty acids were not affected by ENZ supplementation, but 0-hydroxybutyrate concentration tended to be greater in ENZ cows. Overall, the exog-enous enzyme preparation used in this study increased milk protein and lactose concentrations in all cows, and milk production in primiparous but not multiparous cows. The differential production response between pri-miparous and multiparous cows was likely a result of a greater increase in DMI with ENZ supplementation in the younger animals.

RESUMO Avaliou-se o valor nutricional do capim-elefante verde colhido aos 56, 84 e 112 dias de idade, por meio do consumo e da digestibilidade em ovinos, da degradabilidade in situ e da cinética da fermentação ruminal. O capim-elefante colhido aos 56 dias proporcionou maiores valores de consumo da MS (1204,81g/dia), da EB (4910,41kcal/dia), da ED (3436,21kcal/dia) e da PB (130,90g/dia). Para o capim-elefante colhido aos 56 dias, ainda foram observados os maiores valores de digestibilidade da MS (70,64%), da EB (70,11%), da PB (68,96%), da FDN (71,4%) e do conteúdo ED (2,86Mcal/kg MS). Com o avanço da idade de corte, houve redução da degradabilidade potencial da MS (77,99% x 68,33%), da PB (84,80% x 56,52%) e da FDN (72,18% x 64,33%), para as idades de corte de 56 e 112 dias, respectivamente. O capim cortado aos 56 dias apresentou maior valor de produção cumulativa de gases (210,50mL/g de MS) e de degradabilidade da matéria seca (63,9%) após 96 horas de fermentação. O capim-elefante verde deve ser colhido aos 56 dias de rebrota em razão das características nutricionais apresentadas.