The importance of fiber particle size in ruminal health is well known, but there are fewer studies to assess the requirements of physically effective NDF (peNDF) in beef cattle than in dairy cattle. The objective of this study was to establish the optimal peNDF proportion in high-concentrate diets fed to beef cattle, to reduce the risk of subacute ruminal acidosis. The experimental design was a replicated Latin Square 4 × 4, with four periods of 21 d. Treatments consisted of four diets with different peNDF proportions: 6.4%, 10.4%, 13.6%, and 15.4%, offered ad libitum as total mixed ration, and containing 15% barley straw and 85% concentrate. Diets, which differed in proportions of straw > 4 mm (considered peNDF) and straw < 4 mm, were manually mixed with concentrate. This concentrate was the same for all diets. A ruminal bolus was orally administered to each heifer for pH measurement. Intake, water consumption, intake by particle size, feed sorting, feeding behavior, behavioral activities, and rumen pH were recorded. Chemical composition and particle sizes of diets offered were assessed in the last week of each period. Data were analyzed using the MIXED procedure of SAS. Orthogonal contrasts determined the linear and quadratic effects of increasing peNDF proportion. T-test procedure determined whether heifers carried out sorting behavior. Particles >4 mm linearly increased (P = 0.001), and particles 4 mm linearly increased, whereas intake of particles < 4 mm linearly decreased (P = 0.001) as peNDF increased. Diet 6.4% performed sorting for particles > 4 mm (P < 0.01), and diets 13.6% and 15.4% against particles > 4 mm (P < 0.01). Diet 10.4% tended to sort against particles > 4 mm (P < 0.10). Time spent ruminating linearly increased (P = 0.001) as peNDF increased. Diets did not differ in mean and minimum rumen pH, but time under rumen pH thresholds (5.8, 5.7, 5.6, and 5.5) linearly decreased as peNDF increased (P < 0.05). The results suggested that the diet that best met the requirements of not compromising intake, limiting sorting behavior, and promoting time spent ruminating to reduce the number of hours under rumen pH thresholds, was the 10.4% diet.

To ascertain the agronomic value of the material resulting from the compost-bedded pack (CBP) in dairy barns, a cross-over experiment was designed with eight dry non-pregnant Holstein cows. The study was performed in two 11-week periods. Bedding materials used were: (1) CBP with sawdust (S) and (2) CBP with forest biomass (FB). Samples were taken from the raw bedding materials and from the CBP across the experiment. We conducted an additional study preparing two piles, one of each CBP material, to accomplish a composting process of 3 months, where samples were also taken. Granulometry and some chemical composition characteristics of FB made it a suitable bedding material to be used as CBP, but its high moisture content limited the ability to absorb liquid manure. Both the degree of stability of the organic matter and the temperature evolution of CBP suggest that a real composting process did not occur. Finally, the composting process of the piles did not lead to any relevant change in CBP materials. From the agronomic point of view, S and FB present potentially valuable characteristics as regards organic amendment in the soil, thanks to their high organic matter content and low nutrient content.

The present study aimed to evaluate the potential hazardous effects of NO₃⁻ concentration in drinking water on health, feed intake, rumen fermentation and microbiota, and nitrogen excretion of Holstein heifers fed a high-concentrate diet for a sustainable water use. Twenty-four Holstein heifers were individually allocated and assigned to one of four treatments with increasing drinking water NO₃⁻ concentration: CTR, without NO₃⁻; LOW, with 44 mg NO₃⁻/L; MOD, with 110 mg NO₃⁻/L; and HIGH, with 220 mg NO₃⁻/L. The entire study lasted 168 days. Fortnightly water NO₃⁻ concentration and daily feed and water intake were recorded. Blood parameters, rumen pH, volatile fatty acids, NO₃⁻ and NO₂⁻ concentration, microbiota, and apparent total tract digestibility were determined at the beginning and at the end of the study. Most of the analyzed parameters were similar among treatments. Denitrifying bacteria population, estimated as nosZ gene copies, were greater in HIGH animals than in CTR animals at the end of the study. In conclusion, drinking water NO₃⁻ concentration up to 220 mg/L has no detrimental effect on health, feed intake, rumen fermentation, nor N excretion in dairy beef cattle for periods up to 168 days; moreover, denitrifying bacteria population increased, which are related with the neutralization of the greenhouse gas N₂O.