Short communication: Utilisation of n-alkanes to estimate feed intake in horses fed known amounts of a labelled concentrate supplement

The assessment of feed intake in stabled horses is a difficult task to accomplish. Faecal markers, namely n-alkanes, have been used successfully for the estimation of this important nutritional parameter. This usually involves the dosing of synthetic n-alkanes via different matrices, a laborious task that may also influence the animal normal foraging behaviour. An experiment was conducted to evaluate a relative simple methodology to quantify feed intake in horses, based on the provision of measured amounts of a concentrate supplement labelled with beeswax and the utilisation of n-alkanes as faecal markers. Four Lusitano horses were used in three consecutive experimental periods. Animals were fed on cereal straw and different proportions of a previously prepared beeswax-labelled concentrate supplement (BLCS; 0.05, 0.10 and 0.20, DM basis). Beeswax labelling was performed to provide a distinct n-alkane profile for the concentrate feed. Prior to feed intake calculations, proportions of labelled concentrate supplement in the diets were estimated using n-alkanes C₂₅ to C₃₃ by least-square optimisation procedures. Results showed that the beeswax labelling resulted in high n-alkane concentrations in the concentrate feed, especially for the odd-chain n-alkanes. Estimates of diet composition did not differ from the measured values, except for the diet with highest BLCS incorporation, with an underestimation of 10%. DM intake was accurately estimated by the "labelled supplement method" in all diets. However, for the lowest BLCS incorporation, DM intake was underestimated by 16% whereas for the higher levels of BLCS in the diet, measured and estimated DM intake values were almost identical with a slight overestimation of only 0.7 and 0.2% (10 and 20% of BLCS, respectively). Results indicate that both diet composition and feed intake can be accurately estimated in horses using the "labelled supplement method", even when very low levels of the labelled concentrate supplement are included in the animals' diet. This method eliminates the need for daily dosing with external synthetic markers, providing advantages in terms of minimising animal management and interference with their normal foraging behaviour.

Beef production from yearling calves under conventional or organic management

The objective of this research was to compare yearling beef calf production (bodyweight – BW gains and carcass characteristics) under organic and conventional (semi-extensive) management. The study comprised three production cycles (from weaning to slaughter) with a total of 67 calves. For the grazing periods, three replicates (1.6-ha paddocks with Lolium perenne–Trifolium repens pasture) per treatment were established, and 4–5 animals per paddock were managed. Conventional paddocks were fertilised with synthetic NPK, whereas manure was used in the organic ones. During finishing, conventional feeding consisted of concentrate ad libitum with straw (CC). Under organic regulation, pasture grazing (PG), herbage silage (HS) and maize silage (MS), all supplemented with organic concentrate, were tested. Results showed similar individual performances before finishing in both treatments. Daily BW gain per unit area during spring was greater in conventional than in organic system (5.62 vs 4.27 kg/ha; P < 0.01), propitiating greater final production in the former, a result of greater herbage production allowing higher stocking rates managed on conventional pastures. During finishing, CC yearlings had greater (P < 0.001) BW gains (1340 g/day) compared with organic feeding systems, although MS feeding enhanced the gains (1116 g/day) over those achieved in PG or HS (average 709 g/day). There were no differences among feeding systems in carcass weight and conformation, while the rib dissection revealed greater fat contents in CC and MS relative to PG and HS (10.2 vs 7.5%; P < 0.05). Feeding with maize silage during finishing could be a good option to achieve organic beef production levels close to the conventional ones. However, the high price of organic concentrate raised feeding costs during finishing in a way that organic beef fattening was 36% less efficient than the conventional system in terms of product sales (applying the same price per kg carcass weight) minus feeding costs per unit of land area.

Forage intake, digestibility and performance of cattle, horses, sheep and goats grazing together on an improved heathland

A mixed herd of five cows, five mares, 32 ewes and 32 goats was managed with their offspring during two consecutive years in a paddock (22.3 ha) with 76% of heathlands and 24% of improved pasture area, with the aim of studying their differences in ingestive behaviour and performance. Diet composition, dry matter intake (DMI) and digestibility (DMD) were estimated on three occasions using the alkane technique, and all animals were periodically weighed to calculate bodyweight (BW) changes per livestock unit (LU). Goats selected higher proportions of shrubs than the other herbivore species (P < 0.001). Overall, daily DMI was higher (P < 0.001) in equines (218 g/kg BW0.75) than in ruminants (174, 121 and 80 g/kg BW0.75 for cattle, goats and sheep, respectively), whereas DMD was lower (P < 0.001) in equines (569 g/kg DM) compared with ruminants (733–791 g/kg DM). During the first half of the grazing season (from late April to mid-July), dams’ BW changes per LU did not differ between species. However, during late summer–autumn lower (P < 0.001) BW losses per LU were observed in sheep and goats (–89 g/day) than in cattle (–534 g/day), being intermediate in horses (–254 g/day). For the overall grazing season, ewes and goats showed greater (P = 0.056) BW gains per LU (338 g/day) than cows and mares (178 g/day). Regarding the offspring, BW gains per LU were greater (P < 0.001) in lambs (3612 g/day) than in other species. Calves presented greater gains than kids (2647 vs 1909 g/day.LU), whereas foals showed intermediate gains (2385 g/day.LU). Therefore, under these conditions of partially improved heathlands, sheep was the most productive species. However, looking at the diet selection and digestibility, goats could complement sheep or cattle herds by achieving a more efficient utilisation of heathland vegetation, and increasing overall productivity per hectare. By contrast, horses, having high levels of grass intake, compete with cattle and sheep for pasture utilisation.

Comparison of feed intake, digestion and rumen function among domestic ruminant species grazing in upland vegetation communities

This study aimed to compare feed intake, digestion, rumen fermentation parameters and bacterial community of 5 beef cows, 12 crossed ewes and 12 goats grazing together in spring-early summer on heather-gorse vegetation communities with an adjacent area of improved pasture. Organic matter intake (OMI) and digestibility (OMD) were estimated using alkane markers. Ruminal fluid samples were collected for measuring fermentation parameters, and studying the bacterial community using terminal restriction fragment length polymorphism (T-RFLP). Spot samples of urine were taken to determine purine derivative (PD) and creatinine concentrations to estimate microbial protein synthesis in the rumen. Herbaceous species were the main dietary component in all animal species. Cattle had higher (p < 0.05) daily OMI (g/kg LW^0.75 ) and OMD, whereas sheep and goats showed similar values. The highest ammonia concentration was observed in sheep. Total VFA, acetate and butyrate concentrations were not influenced by animal species, while propionate concentrations in goats were 1.8 times lower (p < 0.05) than in sheep. Acetate:propionate ratio was greater (p < 0.05) in goats, whereas cattle excreted more allantoin (p < 0.05). Estimated supply of microbial N was higher in cows (p < 0.01), whereas the efficiency of microbial protein synthesis was lower (p < 0.01) in this animal species. Hierarchical clustering analysis indicated a clear effect of animal species on rumen bacterial structure. Differences among animal species were also observed in the relative frequency of several T-RFs. Certain T-RFs compatible with Lachnospiraceae, Proteobacteria and Clostridiales species were not found in goats, while these animals showed high relative frequencies of some fragments compatible with the Ruminococcaceae family that were not detected in sheep and cattle. Results suggest a close relationship between animals' grazing behaviour and rumen bacterial structure and its function. Goats seem to show a greater specialization of their microbial populations to deal with the greater fibrous and tannin content of their diet.

Anthelmintic effect of heather in goats experimentally infected with Trichostrongylus colubriformis

The effects of heather (composed primarily of Calluna vulgaris with a smaller content of Erica umbellata and Erica cinerea) consumption on the establishment of incoming infective larvae (experiment 1, preventive treatment) and an adult worm population (experiment 2, curative treatment) were investigated in Cashmere goats experimentally infected with Trichostrongylus colubriformis. In experiment 1, 12 castrated male goats were divided into two groups: heather-supplemented vs. non-supplemented animals. After 2 weeks of adaptation to the diet, all goats were experimentally infected per os with 6,000 T. colubriformis third-stage larvae. Three weeks post-infection, the goats were slaughtered, and worm counts as well as female worm fecundity and development were determined. Heather consumption was associated with a close to significant (P=0.092) reduction (mean 14 %) in larvae establishment. No effect on fecundity was observed, but the length of female worms in supplemented goats was greater (P<0.001). In experiment 2, 15 non-lactating does were experimentally infected with 6,000 T. colubriformis third-stage larvae. At 6 weeks post-infection, three groups were established: control, heather-supplemented and heather-supplemented with polyethylene glycol. Individual faecal nematode egg output was measured twice weekly to assess gastrointestinal nematode egg excretion. The goats were slaughtered 5 weeks after heather administration (11 weeks post-infection), and worm counts as well as female worm fecundity and development were subsequently determined. Heather administration was associated with a significant (P<0.001) decrease (between 47 and 66 % compared with control group) in egg excretion from 45 to 76 days post-infection. Although worm counts and female fecundity were lower in supplemented goats, no significant differences were observed. Overall, the results showed a reduction in T. colubriformis larvae establishment and a decrease in nematode egg excretion when heather was administered in experimentally infected goats. The heather plus polyethylene glycol treatment reduced nematode egg excretion levels at the same proportion as heather, thereby suggesting that the threshold of tannins required for an anthelmintic effect is most likely quite low.

In vitro effect of heather (Ericaceae) extracts on different development stages of Teladorsagia circumcincta and Haemonchus contortus

The aim of the present study was to evaluate the in vitro effects of heather (Ericaceae) phenolic extracts on the abomasal nematodes Teladorsagia circumcincta and Haemonchus contortus. Extracts of three heather species (Calluna vulgaris, Erica cinerea, Erica umbellata and a balanced mixture of all three) were tested in vitro on different development stages of T. circumcincta (eggs, infective larvae and adult worms) and H. contortus (eggs and infective larvae) using an egg hatching assay (EHA), a larval exsheathment inhibition assay (LEIA) and an adult motility inhibition assay (AMIA). The egg hatching rate was measured after incubation with heather extracts for 48 h at 25 °C. Ensheathed infective larvae were incubated for 3h at 20 °C with heather extracts. Artificial exsheathment was induced in vitro by adding hypochloride solution to the larval suspension. The progress of exsheathment over time was measured by repeated observations at 10-min (T. circumcincta) and 20-min (H. contortus) intervals for 60 min. Adult T. circumcincta worms were obtained from two donor goats and incubated with the extracts at 37 °C for 3 days in 48-well multiwell plates. Worm motility was measured at 0, 19, 24, 43, 48, 67 and 72 h. The extracts were tested at concentrations of 75, 150, 300, 600 and 1200 μg/mL. Incubation with E. cinerea, E. umbellata and mixed heather extracts had a significant (P<0.01) dose-dependent effect on T. circumcincta egg hatching. H. contortus egg hatching was significantly (P<0.01) inhibited only by the E. cinerea extract. All extracts had a significant (P<0.01) dose-dependent effect on the exsheathment of T. circumcincta and H. contortus infective larvae. The incubation with all heather extracts induced a reduction in adult T. circumcincta motility compared to the control, although significant (P<0.05) differences were only found at the highest concentration (1200 μg/mL). The effect of the mixed extract was significant at all concentrations and significant effects were also observed for C. vulgaris and E. umbellata at 600 μg/mL. These results show anthelmintic properties of heather phenolic extracts against T. circumcincta and H. contort, thus confirming observations from previous in vivo studies.

Effect of breed body size and the muscular hypertrophy gene in the production and carcass traits of concentrate-finished yearling bulls

To examine the extent of the effect of muscular hypertrophy character in beef of northern-Spanish breeds, animal performance and carcass characteristics of 152 finishing steers from 5 genotypes were studied: 32 yearling bulls from a rustic Asturiana de la Montaña (AM) breed, 96 yearling bulls from Asturiana de los Valles (AV) breed, divided in 3 groups depending on the presence of the gene responsible for double-muscling (i.e., 32 AV mh/mh, 32 AV mh/+, 32 AV +/+), and 24 yearling bulls from AM x AV cross were used. Each genotype was composed of 8 animals per year (4 animals per pen) for 4 yr, except for the AM x AV genotype, which was only evaluated in the last 3 yr of the experiment. All animals were fed indoors with concentrate meal and barley straw ad libitum. Average daily gains in AV animals (1.41 kg/d) were greater (P < 0.01) than in AM (1.12 kg/d), whereas AM x AV were intermediate (1.29 kg/d) to these. No significant differences (P = 0.604) in ADG were found among the 3 AV genotypes. Longer fattening periods (P < 0.001) were taken for AM animals to reach acceptable BW at slaughter. Double-muscled animals (AV mh/mh) were found to have the best feed efficiencies when expressed as G:F (P < 0.001). However, residual feed intake calculated on a daily basis showed a greater efficiency in AV mh/mh and AM than in other genotypes. Carcasses from double-muscled animals had greater BW, yield, conformation and compactness index, and less fat cover than the other genotypes (P < 0.001). Carcasses from AM breed were the lightest and had the worst conformation, whereas those from AM x AV generally presented intermediate characteristics between AV and AM. Double-muscled animals had the greatest LM weight and area. The sixth-rib dissection revealed a greater percentage of muscle (84.6%) and decreased percentages of subcutaneous fat (1.1%), intermuscular fat (4.7%), bone (8.5%), and other tissues (1.2%) in AV mh/mh compared with other genotypes. Water-holding capacity was greatest in AM and least in AV mh/mh. In conclusion, double-muscled AV bulls would provide the greatest economic returns at intensive feeding systems because of their greater efficiency, reduced feeding costs, greater carcass weight and conformation, and greater lean yields, though some LM characteristics (reduced fat content and water-holding capacity) could negatively affect the sensory attributes of the meat compared with other genotypes with greater fatness.

Anthelmintic and nutritional effects of heather supplementation on Cashmere goats grazing perennial ryegrass-white clover pastures1

To investigate anthelmintic and nutritional effects of heather supplementation in goats grazing perennial ryegrass-white clover pastures, 40 dry Cashmere goats were randomly assigned to 4 treatments in a 2 x 2 factorial arrangement: 2 grazing management treatments (supplementation with heather vs. nonsupplementation) and 2 anthelmintic treatments (treatment vs. nontreatment). Goats grazed continuously from May to September 2004. At the end of the grazing period, the number of dead goats due to gastrointestinal parasitism was 1 in the group supplemented with heather and dosed with anthelmintic, 4 in the group that received neither supplementation nor anthelmintic, and 0 in the other 2 groups. For goats that did not receive anthelmintic treatment, the percentage of heather in the diet was negatively correlated with fecal egg count in August (r = -0.59, P < 0.05) and September (r = -0.49, P < 0.1) and positively correlated (r = 0.54, P < 0.05) with BW changes during the grazing season. Therefore, the correlation coefficient between BW change and fecal egg count was negative (r = -0.62, P < 0.05). Rumen ammonia concentrations were always lower in supplemented goats (P < 0.05). However, VFA concentrations were greater in goats consuming heather (58.9 vs. 50.9 mmol/L), which suggests that ruminal fermentation was not adversely affected by consumption of tannins. Heather availability in the vegetation might represent a valuable opportunity and sustainable method to control gastrointestinal nematode infections in a goat production system based on grazing perennial ryegrass-white clover pastures.

Application of n-alkanes as diet composition markers in grazing/browsing goats and sheep: effect of using different faecal recovery corrections and plant species grouping approaches

The present study aimed to test the effect of applying different sets of n-alkane faecal recoveries and different plant species grouping approaches on the estimates of the diet selected by goats and sheep when grazing/browsing complex vegetation communities composed of mosaics of heather-gorse vegetation interspersed with patches of perennial ryegrass. The use of different sets of n-alkane faecal recoveries significantly affected the estimated proportions of most vegetation components in both animal species. The diet estimates were also significantly affected by the calculation approach: A1 (using all individual plant species); A2 (grouping plant species with similar n-alkane profile, with equal weighting within the group); and A3 (grouping plant species with similar n-alkane profile, with different weighting according to the botanical composition of the plot). There was a significant interaction between calculation approach (A) and faecal recovery sets (FR) on the resulting estimates of the Ericaceae species in the diet of goats and of all diet components in sheep. When using A1 approach, the estimated proportion of Agrostis capillaris in the diets was high and seemed to be overestimated, compared with its low availability (1.1% of total cover) in the field. However, the application of calculation approaches A2 and A3 gave lower dietary proportions of component D2 (Agrostis capillaris and Ulex gallii) and higher proportions of components D1 (Lolium perenne and Pseudarrhenatherum longifolium), D3 (Erica umbellata, Erica cinerea, Erica australis, Calluna vulgaris) and Erica arborea. These results indicate that the application of the n-alkane technique for estimation of the diet composition in field with complex vegetation conditions is sensitive to the use of faecal recovery corrections and to the grouping of possible dietary components.