Is intensification of reproduction rhythm sustainable in an organic sheep production system? A 4-year interdisciplinary study.

A 4-year interdisciplinary study was performed to compare two organically managed sheep production systems, using 118 ewes and 24 ha each. The systems differed in the ewes' reproduction rhythm: one lambing per ewe per year (1L/1Y), with the aim of balancing feed self-sufficiency and lamb marketing periods v. three lambings over 2 years (3L/2Y), with the aim of maximising ewes' productivity. The sustainability was evaluated through ewes' reproductive performance, lamb growth rate, carcass characteristics and quality, animal health, forage and feed self-sufficiency, soil mineral balance and gross margin. General animal health was assessed by recording ewe and lamb mortality and putative cause of death. Nematode digestive-tract strongyles parasitism was studied using faecal egg counts and necropsies. Carcass quality was assessed by recording carcass weight, conformation and fatness, and colour and firmness of subcutaneous fat. Thirty-three percent of 3L/2Y ewes lambed twice a year against 4% of 1L/1Y. Mean ewe productivity was 161.3% and 151.0% in 3L/2Y and 1L/1Y, respectively, and it was more variable between years in 3L/2Y. Average concentrate feed consumption and the corresponding cost per ewe were higher in 3L/2Y than in 1L/1Y (156 v. 121 kg, and €49.5 v. €39.3, respectively). Finally, average gross margin was lower in 3L/2Y than in 1L/1Y (€59 v. €65 per ewe, respectively). Even in year 2002, when ewe productivity was highest in 3L/2Y (193%), gross margin was not different between systems (€90 v. €86 per ewe in 3L/2Y and 1L/1Y, respectively), because of higher concentrate costs in 3L/2Y. The 3L/2Y animals presented a lower health status, with a higher lamb mortality (P < 0.05) and a higher digestive-tract strongyles and coccidia parasitism level (P < 0.05). Lamb carcass conformation, fatness and fat colour were not different between systems, but carcass weight and subcutaneous dorsal fat firmness were lower in 3L/2Y lambs than in 1L/1Y lambs (P < 0.05 and < 0.001, respectively). Intensification in an organically managed sheep system, through an increased reproduction rhythm, thus did not lead to better economic results and proved riskier, more variable and more difficult to manage, and so less sustainable. The less intensive system (1L/1Y) was both highly efficient from the animal standpoint and highly feed self-sufficient. The technical and economic results of this system were better than those of organic private farms in the same area and matched those of non-organic farms.

Voluntary intake and digestibility in horses: effect of forage quality with emphasis on individual variability.

Food intake is a key biological process in animals, as it determines the energy and nutrients available for the physiological and behavioural processes. In herbivores, the abundance, structure and quality of plant resources are known to influence intake strongly. In ruminants, as the forage quality declines, digestibility and total intake decline. Equids are believed to be adapted to consume high-fibre low-quality forages. As hindgut fermenters, it has been suggested that their response to a reduction in food quality is to increase intake to maintain rates of energy and nutrient absorption. All reviews of horse nutrition show that digestibility declines with forage quality; for intake, however, most studies have found no significant relationship with forage quality, and it has even been suggested that horses may eat less with declining forage quality similarly to ruminants. A weakness of these reviews is to combine data from different studies in meta-analyses without allowing the differences between animals and diets to be controlled for. In this study, we analysed a set of 45 trials where intake and digestibility were measured in 21 saddle horses. The dataset was analysed both at the group (to allow comparisons with the literature) and at the individual levels (to control for individual variability). As expected, dry matter digestibility declined with forage quality in both analyses. Intake declined slightly with increasing fibre contents at the group level, and there were no effects of crude protein or dry matter digestibility on intake. Overall, the analysis for individual horses showed a different pattern: intake increased as digestibility and crude protein declined, and increased with increasing fibre. Our analysis at the group level confirms previous reviews and shows that forage quality explains little of the variance in food intake in horses. For the first time, using mixed models, we show that the variable 'individual' clarifies the picture, as the horses showed different responses to a decrease in forage quality: some compensated for the low nutritional value of the forages by increasing intake, few others responded by decreasing intake with declining forage quality, but not enough to cause any deficit in their energy and protein supplies. On the whole, all the animals managed to meet their maintenance requirements. The individual variability may be a by-product of artificial selection for performance in competition in saddle horses.

Comparative study of forestomach digestion in llamas and sheep.

To compare digestion in the forestomach of llamas and sheep, the animals were fed four different diets: hay alone (H), low in nitrogen; the same hay with soybean meal (HS), with barley (HB) and with both soybean meal and barley (HSB). The sheep intakes were restricted to obtain about the same intake level in the two species. On average, the digestibilities of DM, OM and NDF were significantly higher in llamas: respectively, +2.7, 3.6 and 5.3 for the four diets. Added barley impaired hay digestion in the sheep, but very little in the llamas. The llamas retained nitrogen better than the sheep owing to very low urine losses. For hay alone, the retention time of digesta in the forestomach was higher in the llamas than in the sheep. In contrast, there was no difference between species for the other diets. The pH and ammonia levels were higher in llamas. In contrast, the SCFA levels were lower. In all cases the in-situ rate of digestion was greater in llamas. The low intake of llamas generally observed in the literature does not account for their better digestion. The stability of the two first compartment pH levels and an excellent cellulolytic activity are determining factors in the better digestion efficiency of plant cell walls in the llamas. However, higher NH3 levels were observed in llamas, although the urinary N excretion was lower.

The influence of ammonia, biogenic amines and gamma-aminobutyric acid on grass silage intake in sheep.

We investigated whether biogenic amines alone, or a combination of NH3, amines and gamma-aminobutyric acid (GABA) influenced grass-silage intake, intake behaviour and rumen liquid content in sheep. Three diets were studied: a grass silage preserved with formic acid (4 litres/tonne) (FAS), FAS with 4.9 g amines/kg DM added (FAS+A), and FAS supplemented with a combination of N-components at the following concentrations: 2.7 g amines, 3.0 g NH3 and 5.0 g GABA/kg DM (FAS+C). The diets were offered ad libitum, once daily to six rumen-cannulated Texel wethers in a crossover design. Daily DM intake (DMI; g DM/d) tended to be influenced by diet (P = 0.08). The DMI of FAS+A was similar to that of FAS alone, whereas that of FAS+C tended to be higher. The mean rate of ingestion (g DM/min) over all feeding bouts tended to be the lowest for FAS+A (P = 0.06). No differences were found among the diets concerning intake behaviour during the principal meal. Average intake rate of the small meals tended to be the lowest for FAS+A (P = 0.06). Although rumen NH3 concentration was higher (P < 0.05) after the principal meal, rumen pH, osmolality, rumen pool size and liquid content were not significantly altered by adding amines or the mixture of N-components to FAS. We conclude that biogenic amines or N-containing products of protein fermentation in concentrations normally found in poor-quality silages do not reduce the intake of well-preserved formic acid-treated silage. A direct effect on chemostatic regulation of intake was not observed, but a slight negative effect on silage palatability cannot be excluded.

Control of voluntary intake of precision-chopped silages by ruminants: a review.

The aim of this review is to provide a better understanding of the ways in which ruminants control their voluntary intake of finely-chopped silages. Silages with an excellent conservation quality can be ingested at similar levels to the corresponding fresh or dry forages. Intake levels decrease when conservation quality decreases. The implicated physiological mechanisms for this phenomenon are discussed in this review. Poorly preserved silages may have low palatibility, decreasing the animal's motivation to ingest. At the ruminal level, the physical control of intake is generally not involved. On the other hand the fermentation products present in silage seem to induce a high and rapid level of satiation, out of proportion to their relatively low quantity. At the metabolical level some limiting factors may also exist (eg, a poor balance between amino acids and energy, and high levels of acids to be metabolized). Fermentation products induce most of the observed reactions. For well-preserved silages, high quantities of lactic and acetic acids limit intake. Their effects seem to be additive, which explains the observation that low pH often has a negative action. The negative effect of moisture is generally strengthened by that of the acids. For poorly-preserved silages, products of protein decomposition must be considered in addition to volatile fatty acids. The effect of N-compounds is less clearly explained than that of acids. For example, ammonia alone generally seems to have no direct effect. However it is clear that N-compounds taken together have a negative effect on appetite. It can be concluded that the negative effects of poor quality silages are multifactorial; each fermentation product alone has a low effect, but the sum of all the components must be considered. Moreover, it is apparent that some physiological mechanisms are used to control silage intake, which explains the complexity of the studies on this subject.

The effect of protein degradation products in grass silages on feed intake and intake behaviour in sheep.

The effects of NH3 and amines on grass-silage intake, intake behaviour and rumen characteristics were studied in sheep. From a single sward, two direct-cut grass silages were prepared, either untreated (WAS) or with 4.51 formic acid/tonne (FAS). Four experimental diets: WAS, FAS, FAS with addition of 2.9 g NH3/kg DM (FAS + N) and FAS with 2.8 g amines/kg DM (FAS + A), were offered ad lib. once daily to four rumen-cannulated wethers in a 4 x 4 Latin square design. Daily DM intake (DMI) tended to be influenced by dietary treatment (P = 0.09). Compared with FAS, DMI was lower for WAS. Addition of NH3 did not alter DMI, whereas amine addition slightly lowered daily DMI. Reduced DMI resulted from lower intake rates during both the principal meal and the subsequent small meals. Lower initial intake rate during the principal meal suggested reduced palatability of WAS and FAS + A. Amines and NH3, however, did not influence chewing efficiency. No treatment effects were observed on total rumen pool size, DM and neutral-detergent fibre content. Furthermore, NH3 and amines did not alter rumen pH, NH3 and volatile fatty acid concentrations to the extent that they could act on chemostatic intake regulation. Amine addition, however, lowered osmolality of the rumen liquid. No treatment effects on rumen motility were observed. In conclusion, daily DMI was not reduced by the addition of NH3, suggesting that NH3 per se is not the causal factor in the negative correlations between silage NH3 content and intake observed by other authors. Amines, however, tended to reduce DMI only by their effect at the oro-pharyngeal level of intake control.

Influence of the method of forage conservation on feeding behaviour, intake and characteristics of reticulo-rumen content, in sheep fed ad libitum.

The influence of silage conservation methods on eating behaviour and the characteristics of reticulo-rumen contents was studied in sheep by comparing 3 forages, a silage without additive (WAS), one with additive (FAS) and hay (H), prepared from the same cut green forage. The sheep were rumen fistulated. WAS was very badly and FAS poorly preserved while the hay was dried under favourable conditions. The forages were fed ad libitum and the dry matter (DM) intake was 1,054, 1,241 and 1,469 g/day for WAS, FAS and H respectively. There was a single feeding in the morning. At the main meal, DM intake was 270, 317 and 388 g/day and ingestion rate 4.76, 4.56 and 4.16 g of DM/min for WAS, FAS and H respectively. There was slight recovery in ingestion around 16-19 h with hay and FAS but not with WAS. With hay, rumination lasted much longer than with the silages and began sooner after the end of the main meal. In contrast, overall rumination efficiency was the same for hay and FAS. There were fewer contractions of the reticulo-rumen with both WAS and hay. The amounts of reticulo-rumen contents were comparable for the 2 silages and higher for hay. The amounts of NH3 in the contents were the same with WAS and hay but greater with FAS. With WAS, contents were richer in butyric, valeric and caproic acids. The DM turnover rate of the contents was the same for FAS and hay and lower, but not significantly, for WAS. Accordingly, with silage, satiety seems to be rapidly reached but there was no evidence that organoleptic factors were involved. There were no problems with the digestion rate of silages. However, the factors limiting silage intake persisted throughout the diurnal cycle, and reticulo-rumen fill was affected. The more poorly preserved the silage the more these factors reduced the duration and volume of the meals, or both.

[Effect of feeding rhythm on digestive activities and diurnal variation in rumen content in sheep]. / Influence du rythme de distribution sur les activités alimentaires et l'évolution journalière du contenu ruminal chez le mouton.

Three feeding frequencies of late-cut grass hay (two times per day at 8 h interval, once a day, two times per day at 12 h interval) were compared in sheep fitted or not with a rumen fistula. The following parameters were recorded: daily dry matter intake, ingestive activities, reticulorumen load before and after the large meal following each feeding. The daily dry matter intake was not significantly affected by the treatments although it tended to be lower with one only feeding per day. The animals consumed a larger meal after a single feeding in the morning than after two feedings and they thereafter had more small meals during the day. The total time spent eating and ruminating was similar for the three treatments, always with more time spent ruminating in the night than in the day. Whatever the feeding interval (8 or 12 h), the weight of the reticulorumen content was higher after the evening meal.

[Feeding behavior and reticulo-ruminal repletion status in sheep fed ad libitum on grass hay or alfalfa hay, with continuous or limited access: effects on the physical control of intake]. / Comportement alimentaire et état de réplétion du réticulo-rumen chez le mouton nourri à volonté de foin de prairie ou de luzerne, avec accès continu ou limité: incidences sur le contrôle physique de l'ingestion.

1) The effects of limiting time of access to forage (twice 1 hr 30 min vs continuous access) on feeding behavior and reticulo-ruminal fill were studied with two hays: a late cut grass hay and an early second cut lucerne hay. 2) With continuous access to forage, voluntary intake of lucerne hay was higher (1,693 g dry matter (DM) per day) than that of grass hay (974 g DM per day). Lucerne hay was eaten more rapidly and needed less mastication per g DM. With limited time of access, eating rates were increased, but voluntary intake was maintained only with the grass hay. 3) With continuous access to forage, rumen pool sizes (RPS) of fresh matter, DM, organic matter (OM), and fibre were higher after the evening main meal than after the morning main meal. RPS were always lower with lucerne hay, except after the evening meal. With limited time of access, RPS after the morning meal were higher than those reached by continuous access, but this was not true after evening meal. 4) The net removal of DM and OM, but not of fibre were increased during the main meal, and turnover rates of DM, OM and fibre were higher for lucerne hay. 5) These results confirm that the maximum degree of rumen fill is involved in the control of voluntary intake. However, rumen fill does not seem to control intake during the whole day and other factors may be involved, specially with rapidly digestible hays.

Energy utilization of sodium hydroxide treated or untreated straw supplemented with protein or concentrates by adult sheep. 1. Feed intake, digestibility, metabolizability and net energy value.

NaOH treated (T) or untreated (UT) barley straws were supplemented either with protein (P) or with concentrates based on maize (M) or beet pulp (BP) at rates of 25 or 50% of the diet. Each of the 8 diets was fed to 8 sheep near ad libitum and near maintenance. Energy balances were determined by indirect calorimetry. Straw and feed intakes were doubled by the alkali treatment (P, BP25 and BP50 diets) or increased by 83% (M25 diet) and 63% (M50 diet). Near maintenance, energy digestibility (dE) and metabolizability (q) of the straw were improved by 36% and 40% respectively in the P diet and by 28% and 25% on average in the other diets. Ad libitum feeding reduced energy digestibility of treated straw by 11% and metabolizability by 5% on average in the BP25, BP50 and M25 diets; in the case of the M50 diet dE of the T straw was depressed by 30% and the beneficial effect of the alkali treatment was suppressed. The efficiency of metabolizable energy (ME) of the treated straw diets for maintenance was also raised by 9% (P diet) to 3% (M50 diet) and the corresponding net energy content of the treated straw was increased by 58 to 30%. ME efficiencies of the diets for fattening ranged from 44.0 to 52.8%. Energy retention of sheep was considerably increased by the alkali treatment of straw, whereas their maintenance requirement could not be met by the untreated straw diets supplemented with 25% concentrate.

Energy utilization of sodium hydroxide treated or untreated straw supplemented with protein or concentrates by adult sheep. 2. Rumen digestion.

NaOH treated (T) or untreated (UT) barley straws were supplemented either with protein (P) or with concentrates based on maize (M) or beet pulp (BP), the two last at rates of 25 and 50% of the diet. Each of the 10 diets was fed to two sheep ad libitum. Two diets were also fed at limited intakes. For these 12 diets in sacco cellulolytic activity in the rumen and ruminal fermentation were measured. Cellulolytic activity was measured with the studied straws, so that their digestion rate was also determined. NaOH treatment increased rate of digestion of straw, while high levels of concentrates decreased it. In contrast NaOH treatment and high levels of concentrate decreased cellulolytic activity but neither type of concentrate nor limitation of intake altered it. NaOH treatment only slightly modified pH because a higher level of VFA in rumen balanced NaOH presence. An important negative effect on pH of high levels of concentrate was observed, but there was no effect or type of concentrate or limitation of intake. Fermentation pattern was only slightly influenced by studied factors: +2.2 units of butyric acid and -2.1 units of acetic acid with treated straw; lower level of acetic acid occurred when concentrate was increased, especially for maize. Limitation of intake increased acetic acid molar proportion.

[Food ingestion in ruminants: modalities and associated phenomena]. / L'ingestion alimentaire chez les ruminants: modalités et phénomènes associés.

This paper synthesizes the literature on modalities of food intake in ruminants and their main associated phenomena. Firstly, circadian distribution of feeding and ruminating activities has been examined. Ruminants spend a large part of their time chewing. Their meals have been described in detail; changes in rates of intake, time spent eating, the effect of restricting the amount fed or the period of feed accessibility have been discussed. When food is distributed, the animals have a "long" meal. These meals have been analysed in relation to the type of animal and the feed offered. The other meals ("small" meals) have been briefly described. The paper next examines the phenomena associated with meals, or induced by them, and implied in the control of food intake. Forestomach motricity varies according to ruminant feeding behavior and plays a basic role in digesta transit. Rumen content varies with the meal and its chemical composition due to the arrival in the rumen of food, water and saliva. Rumination may require 600 to 650 min/day and is important in the comminution and sorting of rumen particles. The digestive phenomena associated with meals are related to control of intake. The influence of rumen fill has been thoroughly discussed. Finally, main humoral changes due to intake have been reviewed. The influence of volatile fatty acids (VFA) and metabolites has been discussed as well as the role of glucose, amino acids and fatty acids. Among the hormones, insulin and glucagon seem to play an important role in controlling food intake. The amounts of gastrointestinal hormones increase during intake and may also play an important part. Despite a net improvement in the knowledge of phenomena related to intake, much still remains to be done in setting up models to describe these phenomena in relation to feeding activities and to aid in understanding the mechanisms controlling feed intake in ruminants.