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Repeatability of traits for characterizing feed intake patterns in dairy goats: a basis for phenotyping in the precision farming context
- S. Giger-Reverdin, C. Duvaux-Ponter, D. Sauvant, N. C. Friggens
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In ruminants, feeding behaviour variables are parameters involved in feed efficiency that show variation among individuals. This study aimed to evaluate during the first two production cycles in ruminants the repeatability of feed intake pattern, which is an important aspect of feeding behaviour. Thirty-five dairy goats from Alpine or Saanen breeds were housed in individual pens at four periods (end of first gestation, middle of first and second lactations and middle of second gestation which is also the end of first lactation) and fed a total mixed ration (TMR) ad libitum. Individual cumulative dry matter intake (DMI) was automatically measured every 2 min during the last 4 days of each period. Feed intake pattern was characterized by several measures related to the quantity of feed eaten or to the rate of intake during the 15 h following the afternoon feed delivery. Two main methods were used: modelling cumulative DMI evolution by an exponential model or by a segmentation-clustering method. The goat ability to sort against dietary fibre was also evaluated. There was a very good repeatability of the aggregate measures between days within a period for a given goat estimated by the day effect within breed and goat, tested on the residual variance (P > 0.95). The correlations between periods were the highest between the second and either the third or fourth periods. With increasing age, goats sorted more against the fibrous part of the TMR and increased their initial rate of intake. Alpine goats ate more slowly than Saanen goats but ate during a longer duration. Principal component analysis (PCA) was performed on all the aggregate measures of feed intake patterns. The factor score plots generated by the PCA highlighted the opposition between the different measures of feed intake patterns and the sorting behaviour. The projection of the animals on the scoring plots showed a breed effect and that there was a continuum for the feed intake pattern of goats. In conclusion, this study showed that the feed intake pattern was highly repeatable for an animal in a given period and between periods. This means that phenotyping goats in a younger age might be of interest, either to select them on feeding behaviour and choose preferentially the slow eaters or to adapt the quantity offered and restrict feed delivery to the fast eaters in order to increase feed efficiency and welfare by limiting the occurrence of acidosis, for example.
Effect of concentrate percentage on ruminal pH and time-budget in dairy goats
- M. Desnoyers, C. Duvaux-Ponter, K. Rigalma, S. Roussel, O. Martin, S. Giger-Reverdin
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The aim of this study was to compare rumen pH and time-budget in eight mid-lactation goats receiving two diets in a cross-over design (low-concentrate diet (L): 30% and high-concentrate diet (H): 60% concentrate). Feeding H increased daily intake (4.3 ± 0.08% v. 4.7 ± 0.08% of body weight for L and H, respectively) and daily milk production (3.01 ± 0.130 v. 3.50 ± 0.130 kg/day of 3.5% fat-corrected milk for L and H, respectively). It decreased milk fat and inverted the fat-to-protein ratio (1.07 ± 0.054 v. 0.94 ± 0.054 for L and H, respectively). As suggested by the percentage of time spent with rumen pH below 6.0 (23.4 ± 6.60% v. 39.9 ± 5.88% for L and H, respectively), H was more acidogenic than L. When offered H instead of L, goats spent less time eating (298 ± 17.5 v. 265 ± 17.5 min for L and H, respectively) and ruminating (521 ± 21.0 v. 421 ± 21.0 min for L and H, respectively) but more time resting (352 ± 27.1 v. 459 ± 21.1 min for L and H, respectively) over a 24-h period. They also tended to spend more time drinking (20 ± 2.9 v. 25 ± 2.9 min for L and H, respectively; P = 0.08) when offered H rather than L. These differences in activities were mainly observed during the first hours following feeding. When offered H, goats adapted their feeding behaviour around the feedings, which allowed them to limit the physiological disturbances potentially inducible by H and to increase milk production, without experiencing too much acidosis.
Meta-analysis of 0 to 8 h post-prandial evolution of ruminal pH
- C. Dragomir, D. Sauvant, J.-L. Peyraud, S. Giger-Reverdin, B. Michalet-Doreau
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The objective of this study was to identify relevant descriptors of ruminal pH post-prandial evolution that can replace the mean pH (considered unsatisfactory). These descriptors are to be used in the attempts to predict ruminal pH from dietary characteristics, in order to quantify the potential of a diet to induce subacute ruminal acidosis from its intrinsic characteristics. A total of 219 pH curves, reported as graphics in 48 published articles describing the post-prandial evolution of ruminal pH (first 8 h), were digitized by image analysis then summarized in 15 pH variables. Relationships among pH variables and the principal components (PCs) of pH variability were analyzed in order to identify possible alternatives to mean pH, as the average value of all pH data the curve is composed of. Two groups of pH variables were identified according to their relationship with the most important principal components. A first group, including mean pH, was closely related to PC1, which accounted for 78% of data variability; hence, correlations between variables of this group were generally high. Of these, threshold-related variables were distinct as their within-study correlations with mean pH were rather moderate (0.69 on average). This suggests they might carry supplementary information that could explain the variation in ruminal pH induced by within-study factors, e.g. diet characteristics. However, caution should be taken in their use because of their truncation at 0 h and their non-normal distribution. Variables from the second group were independent of the PC1, and thus of the first group of variables, whereas they were mostly related to PC2 and PC3. This implies they are complementary to mean pH. Of this second group, the rate of pH decreases or the time period when pH reaches its minimum might be useful to better describe the ruminal status, from the point of view of the risk of subacute ruminal acidosis.
In vitro techniques for modelling rumen transformation and syntheses
- D. Sauvant, L. Broudiscou, S. Giger-Reverdin
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- BSAP Occasional Publication / Volume 22 / 1998
- Published online by Cambridge University Press:
- 27 February 2018, p. 157
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- 1998
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There are two major ways to model the microbial activity in the rumen. The first is the material or physical modelling with in vitro systems and the other is mathematical modelling with sets of equations.
The evaluation of the ability of in vitro devices is to mimic in vivo ruminal digestion needs to perform first a typology of the most known and published in vitro procedures. This typology is aimed at clustering them according to their basic function (batch or continuous), to their major targets (studies of food degradation, of microbial proteosynthesis, of volatile fatty acid (VFA) production and profile, of gas production and composition, of outflow influences, of interactions between microbe species … also of prediction of intake of food nutritive value), to their level of time integration (cumulative at a given time or kinetic values), to their actual validity to simulate one or several items of ruminal digestion. Another key of typology of in vitro procedures is also the nature of the active substance, microbes or enzymes.
Rumen mathematical modelling can be variously used in connection with in vitro and in vivo experimentations. At least three main targets can be pursued in this perspective:
To model in vivo ruminal digestion. This aspect already has a long history because the first actual mechanistic model of whole rumen digestion was that of Baldwin et al. (1970). Since this date around a tenth of whole rumen models were proposed. Their current limits are those of the knowledge on rumen digestion: proteosynthesis, VFA production, nutrient absorption, liquid and particle outflows. As far as we are aware, none of these published rumen models was checked against in vitro data. One reason could be that some of them were more or less built from in vitro data.
To model in vitro devices. Surprisingly no such specific model seemed to be published until now. In our opinion it is urgent to develop such models because they could be highly useful: to compare analogies and discrepancies between the various in vitro procedures; to try to build a unique model of in vitro ruminal digestion which could be parameterized according to the type of device; to elucidate intrinsic properties of micro-organisms.
To model both in vitro and in vivo digestion. This way is likely to be the most difficult but it is also potentially the most fruitful. Effectively the use of an intermediate mathematical model of the rumen seems to be a priori the best way to check the major areas of analogy and discrepancy between in vivo and in vitro events. Thus this approach could be an objective mean of validation of in vitro studies.