Silage making can be conveniently divided into field, ensiling, storage, and feed-out phases. In all of these stages, controllable and uncontrollable components can affect silage quality. For instance, silages produced in hot or cold regions are strongly influenced by uncontrollable climate-related factors. In hot regions, crops for silage are influenced by (1) high temperatures negatively affecting corn yield (whole-crop and grain) and nutritive value, (2) butyric and alcoholic fermentations in warm-season grasses (Panicum, Brachiaria, and Pennisetum genera) and sugarcane, respectively, and (3) accelerated aerobic deterioration of silages. Ensiling expertise and economic factors that limit mechanization also impair silage production and utilization in hot environments. In cold regions, a short and cool growing season often limits the use of crops sensitive to cool temperature, such as corn. The fermentation triggered by epiphytic and inoculated microorganisms can also be functionally impaired at lower temperature. Although the use of silage inoculants has increased in Northern Europe, acid-based additives are still a good option in difficult weather conditions to ensure good fermentation quality, nutritive value, and high intake potential of silages. Acid-based additives have enhanced the quality of round bale silage, which has become a common method of forage preservation in Northern Europe. Although all abiotic factors can affect silage quality, the ambient temperature is a factor that influences all stages of silage making from production in the field to utilization at the feed bunk. This review identifies challenges and obstacles to producing silages under hot and cold conditions and discusses strategies for addressing these challenges.

This manuscript brings an overview of the current challenges, advances and opportunities for silage production and utilization in tropical areas, with particular reference to Brazil and South America. Tropical crops have a high production potential during the rainy season; therefore, silage has a central role in feed preservation in the tropics. Use of silage all‐year round is expanding, since a significant number of dairy farmers are moving from grazing to housed systems, and the number of beef cattle finished in feedlots is increasing. Whole‐plant maize silage has been by far the main conserved forage in both dairy and beef operations, whereas the use of grain silages (maize and sorghum) is increasing. Recently, there has been great interest in snaplage (mainly comprised of maize kernels, cob and husk) due to the logistic benefits. Although pull‐type forage harvesters are still common in Brazilian dairies, the majority of beef feedlots use self‐propelled foragers by hiring custom services. Hence, the number of contractors with self‐propelled harvesters has significantly increased. The convenience of a secondary high‐quality forage in diets of dairy cows as well as the opportunity of including forage sources alternative to maize silage in rations for beef cattle warrants the resumption of research on tropical grass silages. Conservation of wet by‐products, environmental aspects of silage making and, especially, silage pathogenicity and food safety are also fields of research opportunity.

Dairy farmers across Brazil were invited to participate in a study on silage production and utilization practices. Two hundred sixty farmers filled out a questionnaire, which was made available on a website. The questionnaire consisted of 14 questions, including information about the characteristics of the herd (n=3), the crop(s) used in the ensiling process, the use of additives, the harvest (n=3), the type of silo (n=1), aspects related to sealing (n=2), and management practices applied during feed-out (n=3). Farmers were also asked a final question about the main barriers they faced when producing and using silage. The main dairy-producing regions of Brazil had a strong influence on the number of participants. The profiles of farmers were heterogeneous and divided into 5 groups, which was considered a positive attribute of the study, allowing better analysis and assessment of current circumstances. Corn was the most widely grown crop for silage. Sorghum, tropical grasses, and sugarcane were the other species most cited. Additives were used by a small number of farmers (27.7%). Approximately 40% of farmers still depended on loaned equipment or outsourced services. The pull-type forage harvester was the main piece of equipment used on dairy farms (90.4%). Only 54.6% of respondents answered that they sharpen their harvester knives daily. Horizontal silos (bunker and stack) were the structures most commonly used to store silage. Most farmers sealed silos with double-sided plastic film (black-on-white) and with soil. However, almost one-fifth of all farmers still use black plastic. Manual removal of silage from the silos was practiced at most farms (i.e., the lack of equipment was also reflected in the stage of silage utilization). Disposal of spoiled silage before inclusion in the livestock feed was not a common practice on the farms. The main barriers encountered on the farms were lack of equipment, lack of manpower, and climatic variations. The results of this research may guide researchers, industries, extension workers, and governments to seek efficiency in milk production on farms using silage in the diet of livestock throughout the year or during part of the year in Brazil.

um dos aditivos. Os dados foram analisados em esquema fatorial 4 × 3 com três repetições para cada tratamento. Foram determinadas as perdas ocorridas durante o processo fermentativo nas formas de gases e de efluentes e a recuperação da MS. Durante a exposição aeróbia, determinaram-se a recuperação da MS e a estabilidade aeróbia medida pela variação da temperatura. A associação de L. buchneri e NaOH reduziu as perdas por gases e efluentes e elevou a recuperação da MS. No período após abertura, destacou-se a atuação do benzoato de sódio em manter o pH com variação de apenas 0,1 unidade em cinco dias de exposição aeróbia e dos inoculantes L. buchneri e P. acidipropionici + L. plantarum em prolongar o tempo para elevação da temperatura de 34 horas nas silagens controle para 54 e 50 horas, respectivamente.A ensilagem de cana-de-açúcar requer a inclusão de algum aditivo eficiente no controle das perdas quantitativas durante a fermentação e a exposição aeróbia.Palavras-chave: estabilidade aeróbia, fermentação, inoculantes, silagem, valor nutritivo Losses evaluation of the sugar cane silage treated with chemical and microbial additives ABSTRACT -The experiment was carried out to evaluate sugar cane silage treated with chemical additive: urea 1.5%, sodium benzoate 0.1%, and sodium hydroxide 1.0% on the wet basis, associated with Propionibacterium acidipropionici + Lactobacillus plantarum and Lactobacillus buchneri, plus control silage in a factorial scheme 4 x 3, with three replications.The gas and effluents losses during the fermentation phase, and dry matter recovery were determined. During the aerobic phase were determined the dry matter recovery and aerobic stability through the temperature variation. The Lactobacillus buchneri and NaOH association reduced gas and effluent losses and increased the dry matter recovery. At the aerobic phase, the sodium benzoate maintained the pH values, with changes of 0.1 unit during five days. The time to temperature elevation increased from 34 hours on the control silage to 54.0 and 50.0 hours, respectively on the silage inoculated with Propionibacterium acidipropionici + Lactobacillus plantarum or Lactobacillus buchneri. The sugar cane silage production required an efficient additive inclusion which can control the quantitative losses during the fermentation and aerobic phases.

Aims:  The effect of the inoculation of maize and sorghum silages with Lactobacillus plantarum (LP) and Lactobacillus buchneri (LB) on the clostridia spore formation during aerobic deterioration has been studied. Methods and results:  The crops were ensiled in 30 l jars, without a lactic acid bacteria inoculant (C), and with an LP or LB inocula (theoretical rate of 1 × 106). After 90 days of conservation, the silages were analysed for the chemical and microbiological characteristics and subjected to an aerobic stability test, during which pH, temperature, nitrate, yeast, mould and clostridia spores were measured. Compared to the C and LP silages, yeasts were reduced in the LB silages, resulting in an increased aerobic stability. Clostridia spores, determined by most probable number (MPN) procedure, increased to 6 log10 MPN g−1 in the C and LP maize silages, whereas they reached 3 log10 MPN g−1 in C and LP sorghum silages. Conclusions:  Clostridia spore count only slightly increased in the LB maize silages after 342 h (2·59 log10 MPN g−1), whereas it did not show any increase in the LB sorghum silages for the whole period of air exposure. Significance and impact of the study:  The data indicated that clostridia spore outgrowth can take place during silo feedout in aerobic‐deteriorated silages and that LB inoculation reduces the risk of clostridia outgrowth after silage opening by increasing the aerobic stability.