Sheep preference for different tanniniferous tree fodders and its relationship with in vitro gas production and digestibility

Effects of condensed tannin-amended cassava silage blend diets on feeding behavior, digestibility, nitrogen balance, milk yield and milk composition in dairy goats

Condensed tannins (CTs) are phenolic compounds derived from secondary plant metabolism that act as part of the plant's chemical defense system against pathogen invasion and herbivorous attack. This study aimed to evaluate the intake, digestibility, nitrogen (N) balance, production and composition of milk from goats fed cassava silage with added levels of CTs. Eight Anglo-Nubian goats with a mean BW of 40 ± 2.0 kg were distributed in a double Latin square design with four levels of CTs (0, 25, 50 and 75 g/kg DM) with four 20-day periods with 15 days of adaptation and five evaluation days for each period. No differences were observed in DM, NDF, CP intake and feed conversion (grams of DM intake (DMI) per gram of milk produced); however, when expressed as percent of BW, DMI showed a quadratic increase to 29.1 g/kg. As the level of supplemented CTs increased in the diet, the CP digestibility (P = 0.023), NDF (P = 0.044), non-fiber carbohydrates (NFC; P = 0.032) and total digestible nutrients (P = 0.033) exhibited a linear decrease. Furthermore, the addition of CTs to cassava silage induced a linear increase in N-fecal excretion (P = 0.014) and a positive quadratic effect on N-retained (P = 0.014) and N-balance (P = 0.024) as well as a positive quadratic trend in N-digested (P = 0.092). Milk urea N (P = 0.023) decreased linearly. The addition of CTs to cassava silage had a positive quadratic effect on ruminating time (P = 0.011). In addition, comparing the use or non-use from the orthogonal contrast test, the inclusion of CTs in goat diet increased water and N-intake, CP and NDF digestibility, spent time eating and ruminating and N-balance and decreased milk production corrected^3.5%, fat milk content, milk urea N and dry defatted extract of milk. Thus, adding CTs to cassava silage at 25 g/kg total DM promoted goats' greater use of the diet without impairing feed conversion and the quality of goat milk produced. Dietary levels of 50 and 75 g/kg total DM are not recommended because under the conditions of this study, they reduced the productive efficiency of dairy goats.

Stocking Rate Has No Confounding Effect on the Use of Internal and Inert Markers to Predict Botanical Composition, Diet Quality, Degradability and Passage Rate Kinetics in Sheep

Simple Summary

Internal markers are components of diets recovered to different degrees in faeces of animals. These feed components maybe helpful in predicting diet selection, nutrient intake and digestibility in animals. The development of sustainable grazing management and practices to prevent the depletion of natural grasslands as a result of overgrazing depends on the knowledge of feed intake, chemical and botanical composition of diets selected and consumed by ruminants. Determination of the botanical composition of diets selected by free ranging ruminants by visual observation is time consuming and tedious, while the use of oesophageal cannulated animals is invasive and impairs animal welfare. Therefore, it is imperative to use non-invasive methods, such as internal markers to predict feed preferences and composition of diets that ruminants consume. However, it is unclear if the accuracy of results obtained using internal markers is confounded by other factors, such as stocking rate, which is expected to determine the availability and botanical composition of pasture, which, in turn, may exert its influence on the diet selected and consumed by grazing animals. The findings of this study, however, showed that stocking rates did not affect diet selection and nutrient intake in sheep, while a combination of internal markers can be used to estimate the quality of diet selected by animals under cafeteria feeding conditions, regardless of the stocking rate used. Thus, the use of modified acid detergent fibre, acid insoluble ash and acid detergent lignin contents in feeds achieved high accuracy and precision in estimating diets selected by sheep. This approach serves as a proof of concept that these markers can be also used in free ranging animals.

Abstract

This study investigated if there is any confounding effect of stocking rate on the use of internal markers to determine and predict the dietary ingredient composition, dry matter intake (DMI) and digestibility of diets consumed by sheep. Fifteen sheep were randomly allocated to stocking rate treatments of one (SR1), two (SR2), four (SR4) and eight (SR8) sheep per pen (space allowance: 31.04 m², 15.52 m², 7.76 m² and 3.88 m² per sheep, respectively) and fed ad libitum maize stover, sorghum stover and veld hay by supplying 110% of previous day’s intake. Sheep were rotated across the treatments in four periods of 10 days. The proportion of feeds selected and total DMI were similar across all stocking rate treatments. However, diets selected by sheep in SR2 had the highest digestibility compared to other treatments. The prediction of the effective degradability of dry matter using acid detergent fibre content achieved an accuracy of 84.6%. A combination of crude protein and neutral detergent fibre contents achieved 63% accuracy in the prediction of the rate of degradation of feeds. The use of acid insoluble ash (AIA) as an internal marker to predict nutrient intake, digestibility, DMI and dietary ingredient intake accounted for 84.3%, 81.2%, 53.0% and 64.1% of the variation, respectively. The predictions of dietary feed proportions and nutrient quality selected obtained with least squares procedure using a combination of modified acid detergent fibre (MADF), acid detergent lignin (ADL) and AIA accounted for 81.0% and 72.4% of the variation, respectively. In conclusion, regardless of the different stocking rate tested in this study, a combination of MADF, ADL and AIA as internal markers can be used to estimate diet and nutrient selection by sheep using the least squares procedure. Hence, these markers can be used to predict ingredient composition of diet, diet and nutrient selection, nutrient intake and digestibility in free ranging animals.

In vitro control of parasitic nematodes of small ruminants using some plant species containing flavonoids

This study determined in vitro anthelmintic efficacy of three plant species: Trema orientalis, Urtica dioica and Zanthozylum capense on nematode larvae of small ruminants. Dried leaf samples (40 g) were extracted in 70% ethanol, in portions of 10 g and concentrated to 100 ml. Half and one quarter of the original crude extract were both made to 100 ml. Rectal faecal material from 10 Merino sheep and 25 Nguni goats was pooled within species and thoroughly hand-mixed. Dung samples, each of 5 g were cultured for 12 days at 27 °C. On day 13, 4 plates were watered and 4 others treated with ethanol to correct for solvent effect on mortality. The design was 2 (animal species) × 3 (plant species) × 3 (extract concentrations). In each of three runs, three plates were treated with each crude extract in three incremental concentrations. Surviving L3 larvae were isolated, counted and mortalities became indices of anthelmintic efficacy. Data from nematode larval mortality were analysed to determine the effect of animal species, plant species, concentration and their interactions. Efficacy was affected by concentration (P = 0.0001), animal species (P = 0.0046), plant species (P = 0.0572), the interactions of animal species and concentration (P = 0.0010), plant species and concentration (P = 0.0123) and concentration × animal × plant species (P = 0.0435).

A tannin-blocking agent does not modify the preference of sheep towards tannin-containing plants

Sheep have been suggested to use their senses to perceive plant properties and associate their intake with consequences after ingestion. However, sheep with browsing experience do not seem to select against tannin-rich browsing materials in cafeteria trials. Thus, the objective of the present study was to evaluate the relationship between the chemical composition, selectivity index (SI), preference and intake rate (IR) of tannin-containing forage trees offered to sheep in cafeteria experiments. Four trees were selected for their condensed tannin content and their varying biological activities. Havardia albicans (high biological activity), Leucaena leucocephala (medium biological activity), Acacia gaumeri (low biological activity) and Brosimum alicastrum (very low biological activity) were used in this study. Ten hair sheep (23.7kg±1.43LW) with eight months of browsing experience in native vegetation were used in this study. Polyethylene glycol (PEG 3600MW) was administered to five sheep during all experiments. In experiment 1, fresh foliage from all trees was offered ad libitum for 4h. In experiment 2, B. alicastrum was withdrawn and the preference was determined again. The forage preference in experiment 1 was A. gaumeri (14.77gDM/kgLW)>B. alicastrum (11.77gDM/kgLW)>H. albicans (3.71gDM/kgLW)=L. leucocephala (1.87gDM/kgLW) (P<0.05). The preference in experiment 2 was A. gaumeri>H. albicans=L. leucocephala. PEG administration had no effect on the preference or IR. The intake rate seemed to have been affected by the plant density. Moreover, fiber compounds were found to be better predictors of DM intake than polyphenolic compounds at levels typically found in the evaluated forages. It was concluded that tannins and PEG did not modify the preferences of sheep in cafeteria trials. Thus, tannins are not involved in the preference regulation of animals with browsing experience.

Use of three fodder trees in the feeding of goats in the subhumid tropics in Mexico

Chemical composition, in vitro gas production with and without polyethyleneglycol (PEG-4000 MW), and in vitro digestibility of dry matter (IVDMD) and organic (IVOMD) foliage from Pithecellobium dulce, Gliricidia sepium and Haematoxylum brasiletto were determined. The preference test was run for 15 days: the first 10 days as adaption period and the 5 days served as evaluation period. It was conducted in ten developing female Creole goats of 6 months old, weighing 14 ± 2.0 kg in order to determine goat preference for any of the three foliages. Productive performance of 35 male creole kids of 6 months old (14 ± 3.0 kg) was also determined by ad libitum feeding of the foliage of the tree: the 30 and 15 % of each of the P. dulce (T1, T2), G. sepium (T3, T4), and H. brasiletto (T5, T6) foliages were added to the experiment diets, while T7 served as control diet that did not contain any foliage. The crude protein (CP), total phenols (TP), condensed tannins (CT), IVDMD, and IVOMD were different among the foliages. The PEG determined the biological activity of the TP and CT of H. brasiletto. Goats preferred to consume the foliage of P. dulce because of its higher content of CP and IVDMD and low content of TP and CT. In the productive response, dry matter intake (DMI) was higher in kids fed T1 diet and was stimulated by higher IVDMD and IVOMD, which resulted in the higher daily weight gain (DWG). The contribution with TP and CT of H. brasiletto to T5 and T6 and the rejection by the animals of G. sepium in T3 and T4 explain the negative effects on the DMI and the DWG. Findings of the study suggested higher kid performance for P. dulce foliage. Possible attributes may include its better CP, low TP and CT, and higher digestibility.

Effect of the consumption of Lysiloma latisiliquum on the larval establishment of gastrointestinal nematodes in goats

The consumption of tannin-rich (TR) forages has been associated with negative effects against gastrointestinal nematodes and with an improved host resilience. It has been hypothesized that tannins affect the capacity of infective larvae to establish in the mucosae of the host. In this study, we aimed at testing this hypothesis using Lysiloma latisiliquum, a tropical TR tree. The objectives were: (i) to evaluate the effect of the consumption of L. latisiliquum on the establishment of nematode third-stage larvae (L3) in goats; (ii) to define the role of tannins in these effects in vivo by using an inhibitor (polyethylene glycol, PEG); and (iii) to examine a possible indirect effect of tannins on the inflammatory response in the digestive mucosa. Eighteen Criollo goats composed three experimental groups. The control group received fresh leaves of Brosimum alicastrum, a plant with a low level of tannins. Two groups received L. latisiliquum leaves either with (L.L.+PEG) or without (L.L.) daily addition of 25 g PEG. After a 7-day adaptation period, each goat was infected with both Haemonchus contortus and Trichostrongylus colubriformis (3000 L3 per species). The goats were slaughtered 5 days after infection and worm counts and histological analyses were performed. No difference in the voluntary feed intake of foliage was observed between the 3 groups. The consumption of L. latisiliquum significantly reduced the larval establishment of both nematode species compared to the control (P<0.01). For both worm species, the effects were totally alleviated with PEG (L.L.+PEG group), suggesting a major role of tannins in the observed effects. Only minor differences in the mucosal cellular response were observed between the 3 groups. These results confirm that the consumption of TR plants reduces the establishment of nematode larvae in the host and that a direct effect is principally involved.