Enteric methane production and greenhouse gases balance of diets differing in concentrate in the fattening phase of a beef production system.

The purposes of this study were 1) to assess the effects of 3 high-concentrate diets on enteric CH(4) production, total tract digestibility, and rumen fermentation of beef cattle, and 2) to evaluate, by life cycle assessment, the potential effects of these feeding systems on the environment. Six bulls (age of 12.4 mo and BW of 417 kg at midexperiment) of the Blond d'Aquitaine breed were assigned to 3 dietary treatments in a replicated 3 × 3 Latin square design. Diets consisted of 1) 49% natural grassland hay, 41% ground corn grain, and 10% soybean meal (hay); 2) 63% corn silage, 21% ground corn grain, and 16% soybean meal (CS); and 3) 70% ground corn grain, 16% soybean meal, and 14% wheat straw (CG). Daily CH(4) emission (g/d), measured using the sulfur hexafluoride tracer technique, was similar for the hay and CS diets and was 56% greater than for the CG diet (P < 0.001). This difference between diets was maintained when CH(4) output was expressed by unit of feed intake (P < 0.001) or digested feed (P < 0.001). Gross energy intake loss as CH(4) averaged 6.9% for the hay and CS diets and 3.2% for the CG diet (P < 0.001). Organic matter intake and GE intake did not differ between diets. Organic matter digestibility was less for the hay diet than for the CS and CG diets (P=0.008). Digestibility of NDF was greatest for the hay diet, intermediate for the CS diet, and least for the CG diet (P=0.02), with ADF digestibility being similar between the hay and CS diets and greater than for the CG diet (P < 0.001). The rumen pH at 5 h postfeeding was less for animals fed the CG diet compared with those fed the other 2 diets (on average, 5.1 vs. 5.9, respectively; P < 0.001). Total CH(4) emission (enteric + manure) was least for the CG diet, whereas N(2)O and CO(2) emissions were greatest for the CG diet. Total greenhouse gas emissions were least for the CG diet when C sequestration by grasslands was not taken into account.

The motivation of cows to walk as thwarted by tethering.

Cows are often housed in tie-sheds for some part of the year (from 20 to 80% of adult cows in European countries). By contrast, regulations aiming at improving animal welfare generally provide for more opportunity to express behavior and so limit tethering (the European directive for sows). To inform current debate on whether cows should be tethered from an animal welfare point of view, 2 experiments were conducted to determine whether cows were motivated to walk (if their walking motivation was thwarted by tethering) and whether this frustration resulted in acute or chronic stress. In Exp. 1, fifteen cows were housed in tie-stalls for 1, 3, 9, or 27 d or loose-housed in a pen equipped with free-stalls for 27 d according to a Latin square design. On d 28, cows were observed in an 80-m(2) arena where they could walk or run for 10 min. In Exp. 2, fifteen cows were either loose-housed or tie-housed with or without 1 h of daily access to an exercise area according to a Latin square design (treatment duration of 27 d). On d 28, cows were observed in the test arena for 10 min as in Exp. 1. In addition, in Exp. 2, milk was sampled twice weekly for cortisol concentrations and cows underwent a chronic stress test (challenge with ACTH, followed by blood samples for cortisol concentrations). When they were tied with no access to exercise, cows displayed a greater locomotor activity in the test arena (time spent walking x 1.4 in Exp. 1, P < 0.05; time spent trotting x 5 in Exp. 2, P < 0.05), whatever the duration of tie-housing. Regular exercise caused locomotor activity in the arena test to revert to levels observed when cows were loose-housed. Basal cortisol concentrations in milk decreased with time whatever the housing condition (P < 0.001). This decrease was more marked when cows were tied than when they were loose-housed (P < 0.05). Cortisol responses to ACTH were similar between treatments. Adult cows are motivated to walk, and tethering thwarts this motivation. However, the frustration produced by tethering does not result in either acute or chronic physiological stress responses. We recommend that cows housed in tie-sheds be given regular access to an exercise area.

Positive attitudes of farmers and pen-group conservation reduce adverse reactions of bulls during transfer for slaughter.

Transfer to slaughter may be very stressful for cattle and negatively affect their ultimate carcass pH. A potential link between farmers' attitudes, farmers' behaviour, responses of animals to handling and carcass pH in beef bull production was questioned. Whether carcass pH depends on experiences in handling and social mixing was analysed. We conducted a survey on commercial farms where we questioned farmers on their work and beliefs about bulls. Farmers' behaviour with bulls during a test and bulls' behaviour during loading in the truck for transport to the slaughterhouse were observed. The ultimate carcass pH was measured. Farmers tended to behave more gently with their bulls when they had positive attitudes towards gentle contacts with bulls (P = 0.07). The loading of bulls in the truck tended to be more difficult when the farmer was more ready to approach his bulls (P = 0.07). Carcass pH was higher for bulls that had not been transferred from a breeding to a finishing unit (P = 0.03). It tended to be higher when the farmer did not display a gentle behaviour (P = 0.09). The link between farmers' attitudes and farmers' behaviour and the lower meat pH resulting from a gentle farmers' behaviour during finishing are consistent with previous findings in pig, veal or dairy productions. However, the present links were weaker than in the other productions, probably due to the low frequency of close contacts between farmers and beef bulls. When loading bulls into a truck, handlers use the tendency of animals to avoid people, hence overly positive behaviour with the animals during finishing may result in more difficulties at loading. In that case, use of alternative driving aids should be recommended. Our results on carcass pH suggest some habituation to transport among bulls transferred between breeding and finishing, even though the two experiences are several months apart. In view of our results, it seems that contacts with bulls, when they are needed, should be gentle.

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.

Effects of the forage-to-concentrate ratio of the diet on feeding behaviour in young Blond d'Aquitaine bulls.

The activities of bulls, their feeding behaviour and their ruminal pH were examined at several stages during the finishing period, according to the forage-to-concentrate ratio of their diet. Twenty-four bulls of the Blond d'Aquitaine breed (initial body weight = 326 ± 21 kg) were assigned to six balanced pens with a space allowance of 9.4 m2 per bull during the finishing period. They were fed three different diets with achieved forage-to-concentrate ratios of (i) 8% straw and 92% concentrate, (ii) 44% hay and 56% concentrate and (iii) 57% maize silage and 43% concentrate. Bulls had ad libitum access to feed dispensed once daily. Offered and refusals were weighed on 5 consecutive days per week. The bulls were slaughtered at the common final live weight of 650 kg and the finishing period lasted 138, 181 and 155 days for straw-concentrate, hay-concentrate and maize silage-concentrate diets, respectively. The time budget was estimated four times by scan sampling with a 10-min interval. Feeding behaviour was appraised using data from electronic feeding gates. Ruminal pH was measured from a ruminal fluid sample collected by rumenocentesis. On average, the bulls spent 78% of the time lying or standing still, and 11% of the time eating. The forage-to-concentrate ratio of the diet influenced only those activities directly linked to feeding, i.e. eating and drinking. Bulls fed a high-concentrate diet spent less time eating than the other bulls (47 min v. >2 h) and took shorter meals (7 min v. 17 min). The bulls fed the straw-concentrate diet spread their meals over the entire day, whereas the others maintained two major peaks of eating activity, the main one in the morning after feed dispensing, the other one at the end of the diurnal period. Intake rate ranged widely between diets, from 58 g/min on average for the diets based on hay or maize silage up to 173 g/min for the high-concentrate diet. The concentrate-diet bulls also had a lower ruminal pH during the first 2 months of the finishing period. The dispersion of meals based on a high-acidosis-risk diet may be a way to limit the decrease in ruminal pH.

Young Salers suckled bull production: effect of diet on performance, carcass and muscle characteristics and meat quality.

The aim of this work was to improve the knowledge on young suckled Salers bull production and to study the effect of forage type and concentrate level on performance, carcass and muscle characteristics as well as on meat quality. Twenty-four Salers male calves of 150 days of age were assigned to six groups: C0 (fed exclusively with hay and dam's milk and slaughtered at approximately 6 months of age), and HH (hay - high concentrate), HL (hay - low concentrate), GH (cut grass - high concentrate), GL (cut grass - low concentrate) and CP (control pasture: pasture - high concentrate) groups differing in feeds received until slaughter and slaughtered unweaned at approximately 10 months of age. Carcass weights averaged 210 kg at 10 months of age at slaughter. Average daily weight gain (ADWG) in HH and GH groups tended to be higher (P = 0.09) than in HL and GL groups (1354 v. 1248 g/day). ADWG in CP group (1542 g/day) was higher (P < 0.05) than in the other groups. Carcass weight in CP group (230 kg) tended to be higher (P < 0.1) than in HL (198 kg) and GL (200 kg) groups. Carcass muscle weight was higher (P < 0.05) in GH (155 kg) and CP groups (165 kg) than in HL (141 kg) and GL (142 kg) groups. Carcass and offal fatty tissue weights and carcass fatness did not differ between groups. Neither forage type nor concentrate level had significant effect on the area of muscle fibres or on muscle metabolic enzyme activities (namely, lactate dehydrogenase - LDH, phosphofructokinase - PFK, isocitrate dehydrogenase - ICDH, citrate synthase - CS and cytochrome-c oxidase - COX). semitendinosus muscle of CP group presented higher CS enzyme activities (8.10 µmol/min per g) than HH (5.30 µmol/min per g) and GL (4.52 µmol/min per g) groups. Neither total nor insoluble collagen content significantly differed between groups. Lipid content in rectus abdominis muscle was relatively low (average 67.5 mg/g dry matter) and was not affected by diet (P > 0.05). The ratio between n-6 and n-3 polyunsaturated fatty acid content was lower (P = 0.01) in the low-concentrate-fed than in the high-concentrate-fed group (3.95 v. 5.37, respectively). Sensory analysis noted that longissimus thoracis muscle from CP animals was more tender and juicy than that from HH and GH animals (P < 0.05).

Variations in meat pH of beef bulls in relation to conditions of transfer to slaughter and previous history of the animals.

Animals are subjected to various events that cause physical exhaustion and psychological stress during transfer to slaughter. This can lead to defective meat quality. Some animals may be better able to withstand the stress of transfer, depending on their previous experience of transport and on their finishing conditions (mixing, farmers' attitudes). The objective of this study was to assess the impact of 1) the conditions of transfer to slaughter (including duration of the journey, waiting time at lairage, etc.); and 2) the bulls' previous history (including experience in transport, mixing during finishing, and the farmers' attitudes) on the reactions of bulls to transfer and on their meat quality. We conducted a survey in commercial conditions. The history of the bulls and the facilities on the farms were noted; farmers were questioned on their attitudes; the bulls' reactions to loading into and unloading from the truck were observed; journey-related data were collected; and cortisol concentration at slaughter and the pH of the LM and the rectus abdominis were measured. Our study confirmed that certain physical factors associated with transport can increase stress and limit the decline of meat pH. These factors include the absence of loading facilities on the farm, transport on a warm day, or a short waiting time at lairage. Social aspects also played a role; the presence of bulls from the same finishing group limited stress and improved the pH decline. Events and management before transfer were also of importance; the farmer awareness of the sensitivity of bulls to humans or to feeding schedules but the absence of a positive attitude toward close contacts with bulls were all likely to limit stress or its consequences on meat pH. Although these results need to be confirmed in controlled experiments, they suggest that good management of beef bulls before and during transfer is essential to meat quality.

Systemic bone growth factors in light breed mares and their foals.

There is a high incidence of bony pathology in race horses. Thus, plasma GH, IGF-1, osteocalcin (OC), calcium (Ca) and inorganic phosphorus (P) concentrations were measured in 12 healthy Selle Français foals and their dams during the first five months after birth. Plasma IGF-1 and OC concentrations were higher in foals than in mares (336 +/- 25 vs 230 +/- 18 ng/ml, P < 0.05; 52.5 +/- 3.2 vs 4.9 +/- 0.1 ng/mg, P < 0.01, respectively). A significant positive linear relationship could be established between these two parameters in foals (IGF-1 = 19 + 0.619 OC; P < 0.05). Another striking evidence was the increase in plasma IGF-1, OC and P concentrations observed during the first week of postnatal life. IGF-1, OC, P and Ca concentrations remained elevated during the experimental period, indicating an intense skeletal growth (confirmed by growth curve) in these animals.

Growth hormone (GH) secretory pattern and GH response to GH-releasing factor (GRF) or thyrotropin-releasing hormone (TRH) in newborn foals.

The present study was undertaken to assess GH secretory profiles in 12 light-breed foals and their dams during forty days after delivery, and the possible influence of GRF and TRH on plasma GH concentrations in these newborn foals. GH secretory pattern was pulsatile in one day- as well as in forty days-old foals. The number of secretory spikes (10 per 24 h) did not vary between days 1 and 40. In the same times, GH secretion did not show any circadian rhythm either in foals or in their dams. Mean daily plasma concentrations (measured through blood samples collected every 20 min for 24 h) were lower in mares (3.4 +/- 0.3 ng/ml) than in their foals (7.4 +/- 0.9 ng/ml; P < 0.05). This difference resulted from both a lower number of GH spikes per 24 h (5 +/- 2 vs 10 +/- 1; P < 0.01) and from a lower pulse amplitude average (8 +/- 5 vs 16 +/- 1; P < 0.05). In three days- and in six days-old foals, synthetic human GRF (0.3 microgram/kg body wt, i.v.) significantly increased plasma GH concentrations. TRH (3 micrograms/kg body wt, i.v.) did not significantly modify plasma GH.