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<p><strong>Background: </strong>Nitrogen (N) plays an important role in dairy systems, both in production costs and as an indicator of environmental impact. <strong>Objective: </strong>The objective was to investigate the effects on milk production and nitrogen excretion by dairy cows fed cut pastures either of perennial ryegrass-red clover (PRG-RCL) or annual ryegrass-white clover (ARG-WCL), complemented with ground maize straw and of commercial concentrate. <strong>Methodology: </strong>Six dairy cows were used in a double cross-over on-farm experiment with 14-day experimental periods. Milk yield and composition, live weight, body condition score, chemical composition of feeds and N content in f<del cite="mailto:HP%20%200455648" datetime="2021-03-18T11:36">a</del>eces, urine, milk and blood were recorded over the last four days of each experimental period. <strong>Results: </strong>No differences were found (<em>P </em>&gt; 0.05) for milk yield nor composition. Cows on ARG-WCL had a higher N intake and N balance than those on PRG-RCL (<em>P </em>&lt; 0.05); also, there were higher levels of blood urea nitrogen (BUN) and urine urea nitrogen (UUN) when cows were fed ARG-WCL than PRG-RCL (<em>P</em> &lt; 0.05). <strong>Implications:</strong> This work allows us to know the amount of nitrogen excreted in milk production in small-scale dairy systems.<strong> Conclusions: </strong>It is concluded that PRG-RCL may be a feeding strategy to reduce N excretion and achieve higher efficiency in N use for small-scale dairy systems.</p>

A survey was conducted in a sample of galician dairy farms from 1991 to 2002 with teh objective of studying the relationships between the ensiling techniques and herbage silage quality, being analysed about 2,600 silage samples of first and second cuts from which information about herbage types, practise of wilting and additive use, presence of rain during ensiling operations, harvester and type of silo was obtained at farm. Samples were anlysed by refemce methods for dry matter (MS), organic matter (MO), crude protein (PBt, expressed as total nitrogen x 6.25) and acid detergent fiber (FAD) contents by reference methods until 1996. Organic matter digestibility was estimated by regression using an equation based on PBt and FAD. From 1997 onwards, PBt, FAD and DM0 were estimated by NIRS. Preservation quality was estimated comparing the pH as measured on the sample and the reference pH for a good fermentation based on the equation of Haigh (1987), which relates pH to MS concentration. Valúes are not corrected for volatile losses during oven drying. The average valúes of the sample were: MS (%) 26.5±9.4, MO (%MS) 89.5±1.9, PBt 13.4±2.3, DM0 (%) 66.8±5.2 and pH 4.6±0.42. The average frequency of poor fermentation quality (42%) almost doubles that of low energy or protein content indicating that the improvement of fermentation quality of herbage silages in galician dairy farms is one of the critical points to be focused by farmers, extensionists and researchers. Year, harvest date and cut number were the known factors that explained a higher proportion of the variance of silage protein content and digestibility. Year, location, harvester type and wilting were the factors which most contributed to explain fermentation quality variability. A trend was observed towards an improvement of energy valué and preservation quality of silages from 1991 to 2002, which is positively correlated with earlier VII Summary cutting, an increase in the silage dry matter content (19.8% and 33.7 % in 1991 and 2002, respectively) and the frequency of wilting practise (40.2% of the samples in 1991 and 85.4% in 2002). It was nevertheless observed a marked dependence of silage quality on weather conditions, indicating a deficiency in wilting programming operations. It was observed that, in practice, increasing herbage dry matter content by wilting to MS levéis of 30% and higher is a most powerftil tool than additive use for a correct fermentation quality. Although, on average, one out of three silages were additive-treated, the effectiveness of its use was low, with the exception of wilted silages treated with inoculants. The lack of effect of additive use (from which formic acid was the most popular) is related, basically, to the low dosing of the product and poor homogenisation in the forage mass, since applicators were no used for the liquid additives distribution. Farm silage harvesting systems tended clearly to shorter-chop and higher performance machinery. The frequency of silage samples harvested with long-chop forage wagón (5-11 knives)...