Dairy cow diets can be categorized into three types: the formulated diet, the farm-prepared diet, and the diet consumed by cows. Aligning these diets requires monitoring the quality of the total mixed ration (TMR) to ensure consistency. However, limited information exists on nutritional markers to assess TMR homogeneity. We hypothesized that nutritional markers could monitor TMR mixing quality in ruminant diets. Therefore, this study aimed to validate a methodology, determine an appropriate coefficient of variation (CV), and identify the optimal marker to assess TMR mixing quality. TMR was sampled for five consecutive days on a commercial dairy farm, evaluating three diets (high-producing cows, mid-lactation cows, and dry cows). For each diet, three daily feedings were assessed, and in each feeding ten incremental samples were collected along the feed bunk immediately after feed delivery and before animal access. Ten equidistant sampling points were established. The marker was defined as the nutrient showing the highest residual variance among sampling points, with diet as a fixed effect and day and feeding as random effects. Residual variance proportions were: Potassium (99.1%), Crude protein (CP; 96.0%), Ether extract (95.7%), Zinc (94.3%), Phosphorus (93.0%), Neutral Detergent Fiber (NDF; 92.8%), Magnesium (91.3%), Manganese (81.9%), Iron (79.3%), Calcium (77.9%), and Sodium (77.4%). Magnesium was the most consistent marker (CV = 9.5%), while NDF and CP (CV = 9.04% and 9.27%) were also effective indicators of TMR mixing quality. These markers provide a practical approach to monitor TMR mixing quality and improve feed consistency in dairy production systems.

Our objective was to evaluate the influence of substrate dispersion method and particle size on in vitro digestibility, gas production kinetics and composition, and fermentation characteristics of different feed types. Alfalfa hay, tall fescue hay, ground corn, soybean meal, and a total mixed ration (TMR) were used as substrates. Treatments were designed according to a 2 × 2 × 5 factorial arrangement: two substrate dispersion methods (loose substrate and in filter bags), two particle sizes (1 mm and 2 mm), and five feeds. Filter bags decreased (P ≤ 0.001) digestibility and gas production compared with loose samples. Filter bags decreased digestibility and total gas production to a greater extent for forages, whereas the effects on concentrate feeds were less pronounced. Using filter bags decreased (P ≤ 0.015) both methane production and methane concentration in headspace gas across all feeds. Substrates incubated in filter bags showed a lower molar proportion of acetate and a greater molar proportion of propionate than loose substrates (P< 0.001). In general, energy-rich feeds incubated using filter bags had a decreased (P ≤ 0.036) acetate-to-propionate ratio, while substrate dispersion method did not influence (P ≥ 0.16) the VFA profile of protein-rich feeds. Incubating substrates in filter bags alters in vitro digestibility, gas production, and fermentation characteristics regardless of particle size. However, the magnitude of responses is greater for forage-based feeds than concentrate feeds.

The objective of this study was to evaluate the interaction between dried distillers grains (DDG) inclusion and forage NDF (fNDF) concentration on nutrient intake, apparent partial and total-tract digestibility, feed sorting, milk yield (MY) and composition, nitrogen utilization, ruminal pH, and blood metabolites in lactating dairy cows. Twelve primiparous Holstein dairy cows, 6 of which were rumen-cannulated, with a mean (±SD) BW of 552 ± 27.9 kg, initial MY of 32.5 ± 1.36 kg/d, and DIM of 99 ± 24.5, were blocked by MY and DIM. They were randomly assigned to a replicated 6 × 6 incomplete Latin square design in a 3 × 2 factorial arrangement. Diets contained 0, 20, or 40% DDG (DM basis) combined with low fNDF (21%) or high fNDF (31%) levels. Significant DDG × fNDF interactions were observed for CP and NFC intake, NDF total-tract digestibility, ECM, 3.5% fat-corrected milk, feed efficiency, milk protein concentration, nonfat solids concentration, and nitrogen retention. At 21% fNDF, increasing DDG inclusion reduced CP and NFC intake, milk protein concentration, and nitrogen retention, whereas at 31% fNDF, increasing DDG inclusion reduced NDF total-tract digestibility, ECM, 3.5% fat-corrected milk, and feed efficiency. Inclusion of 40% DDG consistently reduced DM, OM, NDF, and uNDF intakes, as well as total-tract digestibility of DM, OM, and CP, regardless of fNDF levels. In contrast, inclusion of up to 20% DDG maintained intake, digestibility, and MY across fNDF levels. These results demonstrate that the negative effects of high DDG inclusion are exacerbated under high fNDF conditions, highlighting the importance of considering forage fiber concentration when formulating diets with DDG for lactating dairy cows.

Indigestible neutral detergent fiber (iNDF) is a relevant nutritional fraction related to fiber digestion in ruminants and is widely used in intake modeling. However, its estimation still depends on long time in situ incubations, which involve labor, high costs, and ethical constraints. We evaluated the predictive performance of iNDF in tropical grasses using portable near-infrared (NIR) spectroscopy alone or combined with laboratory composition and in vitro NDF digestibility (IVNDFD). A total of 275 samples of Urochloa and Megathyrsus spp. were collected from three regions and analyzed for dry matter (DM), organic matter (OM), nitrogen (N), neutral detergent fiber (NDF), IVNDFD, and iNDF. Spectra were acquired from dried and ground samples using a portable reflectance NIR spectrometer operating from 900 to 1700 nm. Five predictor sets were evaluated: spectra only, spectra plus laboratory composition (DM, OM, N, and NDF), spectra plus IVNDFD, spectra plus laboratory composition and IVNDFD, and a non-spectral model with IVNDFD and laboratory analyses (DL). The dataset was divided into train (80%) and test (20%) subsets using the Kennard-Stone algorithm, stratified by genus. Forty-nine spectral preprocessing combinations were tested, and partial least squares regression models were fitted in the train set. In external validation, spectra plus IVNDFD, and spectra plus laboratory composition and IVNDFD showed the best performance, with RMSEv values of 26.8 and 27.1 g kg-1 DM, R2v values of 0.888 and 0.889, and RPDv values of 2.96 and 2.97, respectively, whereas spectra only and spectra plus laboratory composition remained below an RPDv of 2.0. Bootstrap comparisons supported the superior and more stable performance of spectra plus IVNDFD, and spectra plus laboratory composition and IVNDFD. Integrating portable NIR spectra with IVNDFD improved iNDF prediction and offers a promising alternative to routine reliance on long in situ procedures.

The supply of metabolizable nutrients to suckling beef calves on pasture can improve their performance, increasing weaning weight and productivity in cow–calf systems. The objective was to evaluate the effects of dried distillers grains (DDG) inclusion on intake, digestibility, metabolism, and performance of suckling beef calves grazing tropical pastures. Forty-eight Nellore calves, 120 ± 35 days of age and 135 ± 23.4 kg of body weight (BW), were used. During 117 days, calves received one of the following treatments under a creep-feeding strategy: mineral mixture only, provided ad libitum (CONTROL); or concentrate supplementation (SUP, 6 g/kg BW, containing 225 g/kg crude protein) with 0

This study evaluated whether partial dehydration methods alter the chemical composition of high-moisture forages. Two experiments were conducted. In Experiment 1, 20 maize silage samples were subjected to freeze-drying, forced-air oven drying, forced-air oven drying preceded by a microwave preheating step, or microwave drying. In Experiment 2, 28 forages (silages, fresh grasses, and fresh legumes) were evaluated using freeze-drying, forced-air oven drying, microwave drying, or air-fryer drying. Method effects were assessed based on water removal efficiency, nitrogenous and fibrous compound profiles, in vitro digestibility, indigestible fibre, and colorimetric properties. Microwave and air-fryer drying removed less water than freeze-drying and resulted in greater differences in nitrogenous compound concentrations and profiles, including apparent N volatilisation and greater concentrations of detergent-insoluble nitrogen. Heat application inconsistently affected fibrous components but consistently reduced in vitro dry matter digestibility without altering in vitro fibre digestibility, likely reflecting starch retrogradation and production of heat-derived artefacts soluble in neutral detergent. These modifications were most pronounced in fresh forages, indicating an interaction with their chemical matrix. Among heat-based methods, forced-air oven drying produced the least chemical alteration. Overall, heat application during partial dehydration modifies the chemical characteristics of high-moisture forages, and when freeze-drying is not feasible, forced-air oven drying best preserves the original sample composition.

This study evaluated the direct and carry-over effects of nutritional strategies during the suckling and backgrounding phases on performance, blood metabolites, and gene expression related to lipid metabolism in grazing F1 Red Angus x Nellore heifers. Thirty-four female calves were assigned in a 2 x 2 factorial design: with or without creep feeding during the suckling phase and low or high level of supplementation during backgrounding. All animals were finished on intensive grazing in a common nutritional treatment. Performance traits, blood parameters, muscle ether extract content, and the expression of adipogenic and lipogenic genes (ZFP423, PPAR gamma, ACC, CPT1 beta, PGC1 alpha) were assessed. Creep feeding increased weight (P = 0.073) and average daily gain (ADG) (P = 0.079) at weaning, and altered lipid and nitrogen metabolism markers, including reductions in cholesterol (P = 0.007), HDL (P = 0.004), and creatinine (P = 0.03), and increase the serum urea nitrogen (P < 0.10). During backgrounding, high level supplementation improved body weight (P = 0.04), ADG (P = 0.02), and increased concentrations of glucose (P = 0.07) cholesterol (P = 0.01), triglycerides (P = 0.001), albumin (P = 0.01), and IGF1 (P = 0.01). No interactive effects between phases were observed (P > 0.10). In the finishing phase, slaughter body weight was affected (P = 0.04) being higher in animals previously fed high level. No effects of supplementation strategy were detected on carcass traits, muscle ether extract, or gene expression. These results indicate that early-life supplementation improves intermediate performance and metabolic status, but does not alter carcass composition or intramuscular fat gene markers at slaughter.

During the period preceding the first ovulation in heifers (prepubertal period), several physiological and metabolic changes occur which may impact reproductive efficiency. Body weight (BW) and metabolic markers such as insulin-like growth factor 1 (IGF-1) and glucose, play a crucial role in these processes. For Bos indicus heifers, it is recommended to achieve at least 60% of mature BW before initiating reproductive protocols. Nutritional strategies that optimize BW and metabolic responses may enhance reproductive efficiency. This study aimed to evaluate the effects of different yeast types in an energy-protein supplementation regime on the performance and metabolic profile of Bos indicus beef heifers under grazing regime during the prepubertal period. Thirty-six Nelore heifers (initial BW of 263.6 ± 2.7 kg; 12 ± 0.09 months old) were randomly assigned to one of three dietary treatments: T1 - soluble fermentation solids (yeast cell wall), T2 - Saccharomyces cerevisiae, and T3 - Saccharomyces boulardii. Heifers were supplemented with an energy-protein supplement mix (6 g/kg BW) containing 20% crude protein, 69.12% corn, 18.58% soybean meal, and 12.30% commercial mineral premix. The trial lasted 120 days, consisting of 60 days of performance and 60 days of reproductive efficiency evaluations. Performance data, including BW and average daily gain (ADG), were collected on days 60 and 120. Carcass ultrasonography assessed at the Longissimus dorsi rib-eye area (REA), subcutaneous fat thickness at the 9th-12 th rib (SFTrib) and at the rump (SFTrump). Blood samples were collected on days 60 and 120 were analyzed for glucose, blood urea nitrogen (BUN), and IGF-1concentrations. Data were analyzed using the MIXED procedure of SAS, and statistical significance was declared at P ≤ 0.05. A significant treatment x time interaction was observed for BW (P = 0.018), while ADG was higher during the reproductive period (P = 0.02). No treatment effects were detected for REA (P > 0.05), whereas SFTrib and SFTrump increased over time (P < 0.01). Glucose and BUN levels increased (P = 0.02 and 0.04) whereas IGF-1 concentrations declined (P < 0.05) throughout the trial. In conclusion, yeast supplementation did not significantly influence performance or metabolic markers in grazing Bos indicus beef heifers during the prepubertal period. The observed effects likely reflect the overall availability of nutrients in the provided nutritional plane rather than the direct effect of yeast supplementation. Further research is needed to determine potential long-term reproductive implications of these metabolic shifts.

This study aimed to evaluate the effects of sequential supplementation with different crude protein levels and periods on performance, nutritional and metabolic characteristics, and efficiency of nitrogenous compounds use in grazing male Nellore calves at pre-weaning. Fifty male Nellore calves during pre-weaning were distributed in a completely randomized design in a 2 × 2 factorial arrangement. The strategies were as follows: Supplementation period in the initial pre-weaning was 1–78th experimental day and in the final pre-weaning was 79–156th experimental day. The Low and high protein levels in the supplement were 150 g CP/kg) and 300 g CP/kg, respectively. All animals received 6 g/kg BW of supplement. Protein levels in the supplement did not affect intake of forage DM, and neutral detergent fiber in the animals. However, a higher CP intake and the CP to DOM ratio (p-value < 0.05) was evidence for the high calves compared with low calves. Supplementation strategies did not affect the blood concentrations of IGF-1, glucose, and total protein. Likewise, protein levels in the supplement did not affect the ADG and number and diameter of muscle fibers. In conclusion, the decrease in protein levels in the supplement from 300 to 150 g CP/kg DM does not detrimentally affect performance and nutritional and metabolic characteristics in male beef calves under a grazing system at pre-weaning.

We aimed to evaluate the esophageal leakage, ruminal fermentation characteristics, passage rate, and microbial crude protein (MCP) synthesis and its flow in the immature rumen of preweaning animals fed different amounts of liquid diet. Sixty newborn male kids, not castrated, from Saanen and Swiss Alpine breeds, with BW of 3.834 ± 0.61 kg (mean ± SD), were distributed in a randomized block design in a 2 × 6 factorial scheme composed of 2 nutritional plans (either 1 L or 2 L of milk replacer [MR] per kid per day), and 6 time points of slaughter after feeding. Breeds were the blocking factor in the model (random effect). All kids were slaughtered at 45 d of life. Esophageal leakage was not affected by the nutritional plan. Esophageal leakage into the rumen averaged 56.0%, whereas 42.0% leaked directly into the abomasum. Furthermore, a low proportion (2.0%) of the MR escaped immediately into the small intestine. Passage rates were also not affected by the nutritional plan (P > 0.050). Milk replacer passage rates were 0.290 h-1, 0.307 h-1, and 0.369 h-1, and their respective mean retention times were 3.44 h, 3.22 h, and 6.06 h in the kids' rumen, abomasum, and small intestine, respectively. Microbial crude protein synthesis was not affected by the nutritional plan, averaging 1.95 (g/day) for the kids. Lastly, most ruminal fermentation characteristics were affected by the nutritional plans and slaughter time after feeding, such as ammonia, soluble protein, and VFA. In conclusion, a high MR allowance influences performance and rumen parameters without affecting esophageal leakage, passage rates, and MCP synthesis in preweaning dairy kids.

The objectives of the study were to evaluate the effects of substituting dried distillers grains with solubles (DDGS) with soybean meal (SBM) on nutrient and amino acid (AA) intake, flow, and digestibility. Red Angus steers (n = 4; BW = 360 ± 9 kg) with ruminal, duodenal, and ileal cannulas were used in a 4 × 4 Latin square. Diets consisted of (DM basis) dry-rolled corn (70%), grass hay (10%), liquid supplement (5%), and test ingredients (15%). Treatments were: 1) 15.0% DDGS (CON); 2) SBM in replacement of 50% of DDGS (SBM50); 3) SBM in replacement of 75% of DDGS (SBM75), and 4) SBM in replacement of 100% of DDGS (SBM100). Each period lasted 18-d, consisting of a 10-d diet adaptation followed by an 8-d collection period. Data were analyzed using the MIXED procedure of SAS, with treatment included as a fixed effect and period and steer as random effects. Linear, quadratic, and cubic contrasts were applied to assess the response patterns to varying levels of DDGS and SBM. Nitrogen intake (P = 0.038, quadratic) decreased from CON to the intermediate SBM inclusion levels (i.e., SBM50 and SBM75), and then increased to SBM100. The duodenal flow of non-fiber carbohydrates linearly decreased (P = 0.050) as SBM inclusion increased. The total tract digestibility of neutral detergent fiber exhibited a cubic pattern (P = 0.033), with the greatest value observed for CON, the lowest value for SBM50, and intermediate values for SBM75 and SBM100. The amount of essential (EAA) and non-essential (NEAA) AA reaching the small and large intestines were not affected by treatment (P ≥ 0.12). When DDGS was exclusively fed, most AA exhibited AA utilization indexes greater than 1.0, indicating a net ruminal gain. Conversely, AA utilization indexes were near 1.0 when SBM was the sole protein source, suggesting minimal net ruminal change for most AAs. Total tract digestibility of lysine tended to increase linearly (P = 0.058) with the inclusion of SBM, while tryptophan (P = 0.063) and arginine (P = 0.088) displayed a quadratic tendency, increasing from CON to SBM50 and SBM75 and then decreasing to SBM100. True intestinal digestibility of individual EAA varied from 79.5% for histidine to 89.1% for lysine, while for NEAA it varied from 70.4% for cysteine to 89.7% for tyrosine. This study demonstrated that the extent of absorption in the small intestine varied among AA, with lysine and arginine exhibiting greater small intestinal availability in finishing cattle. Ultimately, DDGS and SBM deliver similar metabolizable amino acids in beef cattle finishing diets. This allows producers to prioritize cost-effectiveness and regional availability when selecting a protein source.

Context In the tropics, there is a substantial demand for a broader understanding of the impact of supplementation strategies on animal growth.Aims The aim of this study was to evaluate the effects of different concantrate supplementation strategies during the dry, rainy, or both seasons on intake, digestibility, performance, and carcass weight of young Nellore bulls.Methods Twenty-eight young Nellore bulls with an initial average liveweight (LW) of 327 +/- 4.2 kg of were used. Animals had ad libitum access to a Urochloa brizantha pasture and a mineral mixture sequentially in dry and rainy seasons. Treatments consisted of the following four concentrate supplementation strategies: (1) no concentrate supplementation (-/-); (2) 8 g/kg LW in rainy season (-/+); (3) 8 g/kg LW in dry season (+/-); and (4) 8 g/kg LW in both dry and rainy seasons (+/+).Key results Forage intake was lesser (P < 0.05) in cattle fed +/+ when contrasted against all other supplementation strategies. In the dry season, concentrate supplementation increased (P < 0.04) LW gain from 0.40 to 0.74 kg/animal.day. Considering performance in both the dry and rainy seasons, all supplementation strategies increased (P < 0.05) total LW gain, hot carcass weight, carcass fat and muscle when compared with the negative control treatment -/-. Bulls receiving +/+ had greater (P < 0.05) total LW gains and hot carcass weights than did -/+ and +/- treatments. Directly contrasting -/+ and +/-, supplementation in the rainy season tended (P < 0.10) to increase total LW gain and hot carcass weights.Conclusions Under the conditions of this experiment, concentrate supplementation decreased forage intake but increased LW gain, hot carcass weight and carcass quality. Concentrate supplementation in both the dry and rainy seasons provided greater LW gain and hot carcass weights than did concentrate supplementation during only the dry or rainy seasons. Concentrate supplementation only during the rainy season produced greater hot carcass weights and LW gains than did concentrate supplementation only during the dry season.Implications To achieve maximum LW gains and hot carcass weights, concentrate supplementation should be provided during both dry and rainy seasons. If supplementation costs are a limiting factor, concentrate supplementation during the rainy season is likely to provide greater LW gains and carcass weights than does concentrate supplementation only during the dry season. However, pasture nutritive value, carcass prices and supplement costs must be evaluated before selecting a supplementation strategy.

We aimed to evaluate how the amount and frequency of nitrogen (N) supplementation impact nutritional performance and metabolism in cattle fed medium-quality tropical forage. Five young Nellore × Holstein bulls (262 ± 20 kg) were used in a 5 × 5 Latin square design. The basal diet consisted of medium-quality signal grass hay, with the following treatments: (1) control, without supplementation; (2) daily supplementation with 30

To ensure an accurate homogeneity test, animal feed manufacturers should apply standardised techniques and procedures, which aim to guarantee the product quality. Our objective was to propose a new protocol for performing concentrate ration homogeneity tests in commercial feed mills, based on three main points: the suitability of different minerals as markers; establishing a simplified and reliable sampling protocol; and developing a simplified statistical approach for evaluating marker dispersion among increments. Four horizontal commercially available mixers were used. Increments were collected sequentially during the mixer-emptying time over five consecutive days, totalling 200 increments, in which nine potential mineral markers were evaluated. The minerals potassium (K) and magnesium (Mg) were considered suitable, as they simultaneously exhibited low variability among batches, among mixers, and among increments. Based on the variation patterns of K and Mg, the new protocol for homogeneity testing in feed mill concentrate rations is based on the following additional key points: two increments must be collected per ration batch, taken during the mixer-emptying operation—specifically at the second and eight tenths of the mixer-emptying time, and a concentrate ration mixture is considered homogeneous when the ratio between the highest and lowest marker contents in the increments is lower than 1.26.

Genetic selection and nutritional management have advanced puberty onset in Zebu cattle, enabling first calving at two years. To achieve this, heifers must reach 55–60% of their adult body weight (BW) in the peri-pubertal period. Nutrition influences weight gain rate and through neuroendocrine modulation. Achieving the target weight is essential; however, in grazing systems, the weight gain rate can vary. This study evaluated supplementation levels during the dry season on the performance and body composition of Nellore heifers. A total of 44 heifers (298 days average age) were evaluated over seven months: a four-month of growing phase, a one-month follicular evaluation to assess corpus luteum presence, and a two-month of reproductive phase, during which heifers underwent fixed-time artificial insemination (FTAI). During the growing phase, heifers received one of four treatments: a control group (ad libitum mineral mix) or supplementation at 3, 6, or 9 g/kg BW (330 g crude protein (CP)/kg dry matter). The 6 g/kg level met 100% of CP requirements to growth, while the 3 and 9 g/kg levels provided 50% and 150%, respectively. After this phase, all heifers received the same nutritional management. BW and carcass traits, including Longissimus dorsi rib-eye area (REA) and subcutaneous fat thickness at the rib (SFTrib) and rump (SFTrump), were measured at the end of the growing, follicular evaluation, and reproductive phases. Data were analyzed using a completely randomized design with the GLIMMIX procedure of SAS (version 9.4), adopting a 5% significance level. A linear effect (P = 0.01) was observed for BW, average daily gain (ADG), REA, SFTrib, and SFTrump. At the end of the growing phase, heifers supplemented at 6 and 9 g/kg BW had greater BW (P = 0.001). All groups reached the target BW before the reproductive phase, with greater weight in the 6 and 9 g/kg groups (P < 0.001). By the end of the reproductive period, heifers supplemented at 3, 6, and 9 g/kg exhibited similar BW (P = 0.007). A significant interaction (P < 0.001) between supplementation and ADG showed that heifers receiving 9 g/kg BW had the highest ADG during the growing (P < 0.001) and follicular (P = 0.001) phases but the lowest at the end of the reproductive phase (P < 0.001). No corpus luteum was detected during the follicular evaluation. Final pregnancy rates were 17%, 53%, 81%, and 50% for the control, 3, 6, and 9 g/kg BW groups, respectively. Despite all groups reaching the target BW before reproduction, differences in conception rates and fetal losses suggest that a steady weight gain, with corresponding body composition modifications, enhances productive and reproductive performance.

The objective of this study was to evaluate how parity (primiparous vs. multiparous) influences metabolic profile, performance, and offspring growth in grazing Nellore cows, and to explore potential associations among key metabolic traits, milk yield, and performance indicators. Thirty-four pregnant Nellore cows at approximately 230 ± 20 days of gestation were sorted by parity group and randomly allocated into one of six Uruchloa decumbens pastures, totaling 17 multiparous cows (597.8 ± 39 kg; age = 4 to 6 yrs) and 17 primiparous cows (407 ± 33 kg, age = 2 to 3 yrs). Considering calving day as day 0, cow full BW and BCS were collected on days −63, −21, −7, 0, 7, 21, 63, 91, 140 and 203. Cow blood samples were collected on days −21, −14, −7, 0, 7, 14, 21, 42, 63, 91, 140 and 203. Milk yield was measured in the following day after all blood collections. Primiparous cows had higher glucose on days −7 and 0 (p = 0.04), greater NEFA concentration from −14 to 63 days (p < 0.001), and lower IGF-1 concentration from days 7 to 42 but higher on days 140 and 203 (p < 0.001). They also exhibited lower total proteins, albumin, and globulins, but higher serum urea N concentration (p < 0.001). Primiparous cows also had lower milk yield (p = 0.02), calf birth (p = 0.02) and weaning weights (p = 0.01) compared with multiparous cows. Pearson correlation analysis revealed distinct metabolic and physiological interrelationships across gestational and lactational stages in multiparous and primiparous cows. Overall, multiparous cows showed a less catabolic metabolic profile during the periparturient period to lactation. Primiparous cows experienced a more intense mobilization of body reserves during the early lactation period, but a more positive nutritional status towards late lactation, evidenced by recovery of IGF-1 levels and body weight gain.

Maternal nutrient availability and body condition (BCS) during the peripartum period can influence the postpartum performance of beef cows and the growth and metabolism of their progeny. Maternal parity may also impact these responses, yet the mechanisms remain unclear. Furthermore, the effect of calf supplementation on maternal performance according to parity shows conflicting results, particularly in primiparous cows. This study aimed to evaluate the interaction between maternal parity and creep feeding supplementation on the productive performance and metabolism of grazing Nellore cow-calf pairs. A total of 54 pregnant Nellore cows (24 primiparous and 30 multiparous, average gestational age 230 days) were monitored from 60 days into prepartum until 240 days postpartum. At 100 days old, calves were divided into two groups: Control (n=25) receiving ad libitum mineral mix, and Supplemented (n=27) receiving a daily protein-energy supplement (6 g/kg of body weight (BW); 270 g of crude protein/kg dry matter). Cow BW was recorded every 30 days, and BCS was assessed at -60, -30, 1, 30, 60, and 240 days relative to calving. Milk production was measured at 30, 100, and 240 days, while colostrum Brix value was assessed 12-24 hours postpartum. Cow blood samples were taken at -20, 1, 20, 40, and 240 days relative to calving to analyze glucose, blood urea nitrogen (BUN), total proteins, and protein fractions. Calves were weighed every 30 days, and blood samples were collected at 1, 8, 20, 100, and 240 days of age to assess glucose, total proteins and fractions, and ceruloplasmin concentrations. Data were analyzed using a completely randomized design with the GLIMMIX procedure of SAS (version 9.4), with statistical significance declared at (P < 0.05). Multiparous cows had greater BW (P < 0.05) throughout and greater BCS at weaning (P < 0.05). Primiparous cows had higher BCS at 60 days prepartum (P < 0.05). A significant interaction (P < 0.05) was observed between parity and milk collection day, with multiparous cows producing more milk (P < 0.05) at 100 days. Parity and collection day affected albumin and BUN levels (P < 0.05), but not for other metabolites (P > 0.05). Colostrum Brix values did not differ by parity (P > 0.05). Calf supplementation improved BW (P < 0.05) from 150 to 240 days of age, regardless of parity (P > 0.05). Supplemented calves also had greater BUN levels (P < 0.05). However, supplementation had no effect on serum glucose, total proteins, albumin, globulins, and ceruloplasmin (P > 0.05). Maternal parity influenced cow BCS, BW, and milk yield, with multiparous advantages over primiparous cows. Creep feeding supplementation improved calf growth but had minimal metabolic effects. The findings highlight the importance of managing nutritional strategies in cow-calf systems to optimize productive efficiency.

Context. To mitigate the influence of gastrointestinal tract and urinary system contents on the quantification of average daily gain (ADG), a fasting period prior to the weighing procedure has been recommended. Nonetheless, fasting prior to weighing may increase animal stress, thereby potentially compromising welfare. Aims. We investigated whether there are differences in the estimates of ADG, as well as whether there is a decrease in the random variability of experiments with solids fasting in cattle prior to the weighing procedures. Methods. A database was compiled from eight experiments conducted with growing and finishing animals, totalling 214 animals. Analyses of variances were performed within each experiment to evaluate the effects of the fasting period on residual variances. Subsequently, the data were analysed according to a meta-analytical approach to assess the relationships between ADG with and without fasting, and body weight (BW) variation caused by the fasting period as a function of animals' BW. Key results. Residual variances for ADG within experiments were not affected (P >= 0.29) by a fasting period prior to weighing. Moreover, estimates of ADG did not differ (P >= 0.05) when estimated with or without a fasting period. The relationship between absolute BW loss after fasting and animals' BW was constant (P < 0.05). However, the relative values of weight loss (%BW) after fasting presented a decreasing exponential pattern as the animals' BW increased (P < 0.05).Conclusions. Fasting in cattle under experimental conditions prior to weighing does not influence ADG estimates, nor does it affect experimental random variability. Implications. Fasting animals prior to weighing is an unnecessary practice, as it neither affects ADG estimates nor alters experimental precision. Moreover, omitting fasting promotes better animal welfare, as it avoids infringing animal rights.

This study evaluated the effects of propionic acid inclusion (PAI; 0, 0.25, and 0.50% of fresh matter) and ensiling time (ENT; 30, 60, 90, 120, 150, and 180 d) on the chemical composition, fermentation profile, DM losses, and in situ ruminal starch degradability of high-moisture flint corn grain silage (HMC). Rolled corn grain with 45% moisture and 80% vitreousness was ensiled in 10-L mini silos at a packing density of 1,300 kg/m3. The experimental design followed a 3 × 6 factorial arrangement with 3 replicates per treatment, totaling 54 silos. Samples were analyzed for chemical composition, ammonia-N, pH, organic acids, and ruminal starch degradability. Ruminal degradability was assessed using a nylon bag technique incubated in 3 rumen-cannulated Holstein cows, and a nonlinear modeling approach was applied to estimate starch degradation kinetics. For mycotoxin analysis and ruminal starch degradability, the 0-d (non-ensiled) sample was also included. Data analysis employed the NLMIXED procedure of SAS, with the Newton-Raphson optimization algorithm and adaptive Gaussian quadrature for likelihood integration. Contrasts were conducted to compare PAI versus control treatment (0% PAI) and between the PAI levels. An interaction between PAI and ENT was observed for DM losses, with the greatest losses (>6%) occurring in silages treated with 0.50% PAI at 60 d ENT. Silages treated with PAI had lower final pH values than the control, although PAI did not improve fermentation profile. Crude protein decreased, and ammonia-N increased with longer ENT. Ruminal starch degradability improved with ENT, but PAI reduced both the degradation rate and the maximum extent of starch degradation. At 180 d, estimated degradation rates were 100%/h for the control treatment, 80%/h for 0.25% PAI, and 70%/h for 0.50% PAI. In conclusion, under the conditions of this study, PAI did not improve silage fermentation profile and negatively affected starch degradability in the rumen. Conversely, prolonged ENT improved starch availability. Therefore, long-term ENT (180 d) is recommended to optimize the nutritional value of HMC, particularly in flint-type corn grain.

Forty multiparous Nellore cows, with an average body weight, body condition score, and gestation days of 533 ± 32 kg, 5.7 ± 0.4 points, and 198 days, respectively, were managed under continuous grazing on a Urochloa decumbens pasture and either received or did not receive 1 kg/day of supplement varying in the levels of inclusion of dried distillers grains (DDG) (Control, 0% DDG, 42% DDG, or 84% DDG) during the last trimester of gestation. The objective was to evaluate the effects of prepartum DDG supplementation on performance, reproduction, fetal development, and calf performance. A quadratic effect of supplementation on BW variation pre- and postpartum was observed (p < 0.05), with cows treated with 42% DDG showing higher BW gain prepartum and low BW loss postpartum. Cows supplemented with 42% DDG had lower levels of non-esterified fatty acids and β-hydroxybutyrate prepartum (p < 0.05). However, body weight-related metrics, such as condition score, carcass traits, and metabolic indicators, varied only by measurement day (p < 0.05). No effect of supplementation was observed on fetal development, calf metabolic profile, milk yield, or postnatal calf performance (p > 0.05). It is recommended to include up to 42% DDG in supplements for beef cows during late gestation grazing on low-quality tropical forage conditions.