Ruminants, Volume 5, Issue 3 (September 2025) – 8 articles

Due to the feeding system (high-concentrate diet) during the early lactation stage, ruminal pH in dairy cows follows a diurnal pattern and can remain below the critical level of 5.5 for extended periods of the day. This study aimed to evaluate the effect of low ruminal pH on blood concentrations of certain macrominerals, trace minerals, and fat-soluble vitamins and on the oxidative status of dairy cows during the first half of lactation. Fifty-three randomly selected lactating Holstein cows were used; blood and ruminal fluid samples were collected from all cows on days 30, 90 and 150 of lactation. Blood samples were obtained via coccygeal venipuncture, while the ruminal fluid was obtained by rumenocentesis and the pH was measured immediately after collection. Using a threshold pH of 5.5, samples were classified as normal (pH > 5.5) or low pH (pH ≤ 5.5). Serum concentrations of Ca, Mg, K, Cr, Mn, Zn, Se, and vitamins A, D3, E, and K were not significantly affected by ruminal pH, either by days in milk or by their interaction (p > 0.05). Plasma malondialdehyde and reduced glutathione followed the same trend (p > 0.05). Copper concentration was significantly higher (p < 0.05), and Fe concentration tended to be higher in cows with low pH compared to those with normal pH (p = 0.052). On day 150 of lactation, Cu, Fe, and Co concentrations were significantly higher in low-pH cows compared to normal-pH cows (p < 0.05). Low ruminal pH is associated with significant changes in serum concentrations of copper, iron, and cobalt but has no significant effect on the oxidative status of the animals or on the serum concentrations of the macro elements and fat-soluble vitamins studied. Full article

The objective of this analysis was to compare the greenhouse gas (GHG) emissions from contemporary grazing cattle production with bison grazing, both modern and historical. The data sets used in this analysis were derived from existing research and conservation properties located outside of Manhattan, KS (USA), which are home to stocker cattle, cow–calf production (CCS), and grazing bison. For stocker cattle, 10 years of animal production data (2007–2016) from season-long stocking (SLS, grazing 156 d) and intensive early stocking systems (IES; 76 grazing d and 2× stocking density) were used for GHG calculations. Enteric CH₄, manure CH₄, and direct nitrous oxide emissions were estimated using the IPCC tier 2 methodology. Historic bison (HGB) enteric CH₄ estimates were calculated using a stocking density of 0.15 ha/animal and assuming that only 13% of grassland was used by bison each year. Within contemporary systems, IES had the lowest emissions (463.3 kg CO₂-eq./ha/yr), while SLS, CCS, and MGB had the highest estimates (494.7, 493.9, and 595.9 kg CO₂-eq./ha/yr, respectively). HGB had the lowest estimated annual emissions at 295.7 kg CO₂-eq./ha/yr. These results imply that the historic grazing baseline of this grassland system is lower but similar to that of contemporary grazing cattle in the Great Plains region. Full article

Geometric morphometrics is performed on different species in different contexts. Here, the aim was to investigate morphological differences in the head of the Sanmartinero Creole bovine to examine head shape variations between sexes using geometric morphometric methods. A sample of cranial pictures of 43 animals (13 males and 30 females) was obtained, and form (size + shape) was studied by means of geometric morphometric techniques using a set of 14 landmarks. This approach eliminated potential dietary effects, ensuring that the observed shape variations were primarily due to intrinsic morphological differences. Sexual dimorphism was found in form (for both size and shape) of the head of the Sanmartinero Creole bovine breed. Males had significantly larger heads based on centroid size (U = 714, p = 0.0004), confirming true sexual size differences, and Principal Component Analysis revealed overlapping head shapes with sexual dimorphism concentrated at midline sagittal landmarks (between the most rostral and caudal orbit points) and paired lateral points, indicating that males have broader and longer heads. The two evaluated characters (head size and shape) are of special interest for the conservation of the breed, especially in those cases whose objectives are to maintain the uniqueness, distinctiveness, and uniformity of the populations. This study analyzed animals subjected to the same feeding program, ensuring the elimination of additional variables. Full article

The aims of the current study were to characterize the natural compounds of Salsola tragus via GC-MS and determine its effects as a forage source on lamb growth, in vitro rumen fermentation kinetics, carcass quality, cellular damage, and metabolomic meat interaction. Twenty-one Rambouillet lambs were randomly assigned to one of three experimental diets (seven lambs per treatment): (1) a control diet (W/o-Salsola) containing 300 g/Kg dry matter (DM) of sorghum stover; (2) a diet with a medium inclusion of Salsola tragus (15-Salsola), which contained 150 g/Kg DM of Salsola tragus and 150 g/Kg DM of sorghum stover; and (3) a diet comprising 300 g/Kg of Salsola tragus (30-Salsola). The results showed there were no differences (p > 0.05) in lamb growth performance during the fattening phase. The in vitro gas analysis demonstrated that the 30-Salsola treatment increased lag time h⁻¹ (p < 0.05) and reduced gas production (p = 0.03). The metabolomic analysis findings suggest that the treatments that included Salsola tragus significantly positively affect the metabolomic composition of meat (p < 0.05). The use of 15-Salsola as a source of forage is promising for feeding lambs during the fattening phase. Full article

A key factor in calculating dairy cows’ nitrogen (N) excretion is knowing the amount of daily excreted urine. The present study aimed to investigate two methods to calculate the daily urine volume (UV) excreted using spot urine samples. Data were obtained from nine balance experiments involving 47 lactating and seven non-lactating German Holstein cows, with an average body weight (BW) of 620 ± 95 kg and an average age of 5.6 ± 1.4 years. Daily urinary creatinine (Cr) and UVs were known for all animals. The first method was developed by linearly regressing the daily excreted amount of Cr in urine against BW (p < 0.001; R² = 0.51; RSE: 2.8). The slope of the regression was used to calculate UV. The second method includes a non-linear regression of UV on Cr concentration in urine, allowing direct estimation of UV without knowledge of BW (p < 0.001; RSE: 8.13). Both estimation methods were compared to the standard method to determine UV from balance trials using Lin’s concordance correlation coefficient (CCC) and Bland–Altman plots. The first method had a CCC of 0.81, and the second method had a CCC of 0.85. Both methods can confidently be applied to calculate UV. Therefore, the second method is usable if BW is unavailable. Full article

Overmilking occurs when the teat cups remain attached to the udder during milking, even though there is little or no milk flow. This puts pressure on the teat tissue and reduces milk production due to longer milking times, meaning fewer cows are milked per hour. Therefore, the correct removal of the teat cup at the end of mechanical milking is crucial for the milking process. The aim of this study was to describe the factors influencing automatic teat cup removal (ATCR) at the end of mechanical milking and to demonstrate its importance for udder health, milk production and milk quality. There are considerable differences between milking system suppliers and countries regarding the minimum removal of the teat cup at the end of the milking process. However, to ensure good milk quality, prevent teat damage and reduce the risk of mastitis, it is important to shorten the working time of the milking machine on the udder in both automatic and conventional milking systems. For this reason, several studies have shown that increasing the milk flow switch point effectively reduces milking time, especially in automatic milking systems where dairy cows are milked more than twice a day. However, when the ATCR setting was increased above 0.5 kg·min⁻¹, milk production decreased, and the number of somatic cells in the milk produced increased. Therefore, the use of ATCR at a milk flow rate of 0.2 kg·min⁻¹ significantly increased milk production, improved milk quality and maintained udder health when a low vacuum level (34–36 kPa) was used in milking machines such as MultiLactor and StimuLactor (Siliconform, Germany). In conclusion, ATCR at a milk flow of 0.2–0.3 kg·min⁻¹ is a useful level to achieve various goals on dairy farms when a low vacuum of 34–36 is used in the milking machine. If the milking machine uses a higher vacuum, it is possible to program a higher ATCR at a milk flow of up to 0.5 kg·min⁻¹. Full article

The 8th revised edition of the Nutrient Requirements of Beef Cattle was released in 2016, with the recommendations provided in the publication being used extensively in both research and production settings. In the context of research needs identified in that publication, our objective was to review research on beef cattle nutrient requirements published since 2016 and identify knowledge gaps that should be addressed. Relative to energy requirements, the effects of environmental temperature and grazing activity, along with stress and disease, on maintenance requirements are inadequately characterized or defined. In addition, relationships between retained energy and protein should be more fully elucidated, and additional guidance on body weight at a target compositional endpoint is needed. Areas of continuing concern include accurately and precisely predicting microbial protein supply, predicting N recycling, and the metabolizable protein requirements for maintenance. Mineral and vitamin requirements are often challenging because of a lack of consistency in models used to determine requirements and potential effects of unique production settings on requirements. Based on recent research with feedlot cattle, zinc and chromium requirements should be examined more closely. Because predictions of dry matter intake are critical to supplying nutrients, additional development of prediction equations is needed, especially for beef cows and grazing beef cattle in general. Given considerable research in prediction of greenhouse gases, reevaluation of 2016 recommendations is warranted, along with a need for the updating of equations to predict excretions of N and P. Composition of feeds, particularly byproducts from ethanol production or other industrial streams, represents a knowledge gap, with obtaining reliable energy values of these feeds being a notable challenge. Nutritional models provide the means to integrate nutrient requirement recommendations into practice, and moving towards mechanistic models that take advantage of artificial intelligence and precision livestock farming technologies will be critical to developing future modeling systems. Full article

This study aimed to evaluate the microbiological quality of colostrum on three dairy farms with different colostrum management hygiene practices and to compare it with the current colostrum quality guidelines. On farm A, colostrum was fed raw, while on farms B and C it was heat treated. On farms A and B, the feeding equipment was cleaned manually, while on farm C, an automated cleaning system was used. Samples were collected from the calf-feeding equipment and submitted for microbial culture: total plate count (TPC); total coliform count (TCC); and E. coli, enterobacteria (ENTB), staphylococci (STAP), and lactic acid bacteria counts. In addition, pH, water activity (a_W), and Brix were analyzed. Colostrum quality was defined as follows: good quality (GQ)—TPC < 100,000, TCC < 10,000, STAP < 50,000 cfu/mL, and Brix ≥ 22%; excellent quality (EQ)—TPC < 20,000, TCC < 100, STAP < 5000 cfu/mL, and Brix ≥ 25%. Mean concentrations were as follows: TPC was 3.99 × 10⁵ cfu/mL (min: 40.00, max: 1.32 × 10⁷ cfu/mL); TCC was 1.17 × 10⁴ cfu/mL (min: <detection limit, max: 6.37 × 10⁵ cfu/mL); and STAP was 1.77 × 10⁴ cfu/mL (min: <detection limit, max: 3.50 × 10⁵ cfu/mL). Approximately 54% (GQ) and 32% (EQ) of samples met the defined criteria. Farm C consistently showed lower microbial counts across all culture types. Colostrum from farm B had lower TCC, LAB, and E. coli counts than farm A but not TPC, STAP, and ENTB. These results showed that a considerable proportion of calves were fed colostrum with suboptimal quality, especially when less rigorous hygiene practices were implemented. Full article