The current study aimed to test whether organic matter intake by free-ranging ruminants could be estimated from the amount of nitrogen (N) excreted in faeces and to compare this approach to conventional techniques. An equation describing the relationship between excreted N and nutrient intake was developed in indoor digestibility trials conducted with male sheep (n = 36) and cattle (n = 24) housed in metabolism cages and solely fed hay harvested from a local rangeland. Faecal N excretion was linearly related to organic matter (OM) intake without a significant animal species effect. To evaluate the linear equation, data from free-ranging trials conducted with sheep and cattle were used. The faecal N approach was compared with either in situ digestibility plus external marker (n = 123) or n-alkanes (n = 272) to estimate OM intake and digestible OM intake. Estimates obtained through the faecal N approach did not closely fit those obtained with either conventional technique for any variable. Averaging all individual values, the supply of metabolizable energy (ME) estimated through faecal N was similar to the required level, whereas both the in situ and n-alkanes techniques overestimated ME supply. In conclusion, OM intake by free-ranging sheep and cattle can be estimated based on the amount of N excreted in faeces with some advantages over conventional techniques: knowledge about herbage attributes is not required and it accounts for individual variability on selectivity and digestion processes.

Two studies were carried out to assess the effects of seed inoculation by arbuscular mycorrhizal fungi (AMF) coupled to a reduced fertilizer supply on yield, economic benefit and energy balance of maize and sorghum forage cropping. The effect of dietary inclusion of mycorrhizal forages on milk yield was also examined. The control treatments (control maize and control sorghum) were non-mycorrhizal seeds fertilized with recommended doses of nitrogen (N) and phosphorus (P). The inoculated treatments (inoculated maize and inoculated sorghum) were the mycorrhizal seeds fertilized with a half dose of N. For each treatment, two plots, 1.5 ha each, were used. The forages were ensiled and fed to lactating buffaloes (maize) and dairy cows (sorghum). Plant traits and yield parameters were generally found to be higher in inoculated compared to the control plants. Inoculation positively influenced the chemical composition of sorghum silage that resulted in less fibre and more protein and presented higher dry matter degradability. No differences between the control and inoculated maize silages were found. For both inoculated crops, higher profitability (+670 and 732€ for maize and sorghum, respectively), as well as an increment of net energy (+0.24 and 0.60, respectively), and energy use efficiency (+0.53 and 0.85, respectively) were observed. The use of the inoculated silages did not affect milk yield. Results suggest that seed inoculation with mycorrhizal fungi combined with the low rate of fertilizers could be a viable solution to increase the eco-efficiency and profitability in forage production without affecting forage quality and lactating cow productivity.

Forage cactus is an important dry-season feed source for livestock in semi-arid regions, but in north-eastern Brazil, its contribution is limited by susceptibility to the carmine cochineal [Dactylopius opuntiae (Cockerell)] insect. New cactus germplasm shows superior agronomic performance, but the nutritive value of this material has not been adequately described. The objective of the current study was to assess the divergence in chemical composition and rate and extent of in vitro degradation of these genotypes. The treatments were 13 spineless cactus genotypes, eight of which were insect resistant types, two semi-resistant and three susceptible to the carmine cochineal. Treatments were arranged in a randomized complete block design and were replicated three times. Nutritional divergence was assessed using canonical variate analysis and hierarchical agglomerative clustering, using the variables: crude protein, total and non-fibrous carbohydrates, degradation rate and potential dry matter degradation. Five distinct nutritional groups were identified: Group I (OO), Group II (F-13 and F-15), Group III (OEA, OEM, COP, IPA 20 and GG), Group IV (V-16 and F-08) and Group V (Miuda, IS and F-21). Group II (F-13 and F-15; resistant genotypes) showed a chemical composition degradability in vitro suggesting it may have the greatest nutritive value as ruminant feed, while Group I had the least. Spineless cactus genotypes resistant to the carmine cochineal showed nutritional characteristics similar to or better than traditionally used cactus genotypes, such as Gigante and IPA 20, which can expand the range of options for using this forage.

Forage is the primary feed source for livestock in tropical regions and energy is one of the most important nutrients for ruminant nutrition. The effects of harvest management of Marandu palisade grass (Brachiaria brizantha cv. Marandu Syn. Urochloa brizantha cv. Marandu) on non-structural carbohydrate (NSC) concentrations were evaluated. A plot (Experiment 1) and a greenhouse study (Experiment 2) were conducted in 2013–14. In Experiment 1, treatments were the factorial arrangement of two harvest times and two vertical canopy layers (upper and intermediate), distributed in a completely randomized design with five replicates. In Experiment 2, treatments were the factorial arrangement of six harvest times and two morphological fractions (leaf blade and pseudostem). In both experiments, NSC concentration increased during the day. Upper and intermediate canopy layers had greater NSC concentration at 15.00 than 06.00 h during spring and summer. In addition, the magnitude of NSC increase was greater in the upper than intermediate canopy layer and in spring than summer. Marandu palisade grass shows greater digestibility in the afternoon than morning, representing an opportunity to optimize energy concentration through harvest management.

In vivo and in vitro trials were conducted to assess the effects of tributyrin (TB) supplementation on short-chain fatty acid (SFCA) concentrations, fibrolytic enzyme activity, nutrient digestibility and methanogenesis in adult sheep. Nine 12-month-old ruminally cannulated Small Tail ewes (initial body weight 55 ± 5.0 kg) without pregnancy were used for the in vitro trial. In vitro substrate made to offer TB at 0, 2, 4, 6 and 8 g/kg on a dry matter (DM) basis was incubated by ruminal microbes for 72 h at 39°C. Forty-five adult Small Tail ewes used for the in vivo trial were randomly assigned to five treatments with nine animals each for an 18-d period according to body weight (55 ± 5.0 kg). Total mixed ration fed to ewes was also used to offer TB at 0, 2, 4, 6 and 8 g/kg on a DM basis. The in vitro trial showed that TB supplementation linearly increased apparent digestibility of DM, crude protein, neutral detergent fibre and acid detergent fibre, and enhanced gas production and methane emissions. The in vivo trial showed that TB supplementation decreased DM intake, but enhanced ruminal fermentation efficiency. Both in vitro and in vivo trials showed that TB supplementation enhanced total SFCA concentrations and carboxymethyl cellulase activity. The results indicate that TB supplementation might exert advantage effects on rumen microbial metabolism, despite having an enhancing effect on methanogenesis.