-In order to estimate the quantity of solubilized nitrogen in the rumen that can contribute to intestinal feed non-ammonia nitrogen, degradation in the rumen was studied both for a control soya bean meal (cSBM) and a treated one (tSBM) to assess simultaneously the kinetics of: 1) protein disappearance from rumen bags and 2) rumen fluid contents in various nitrogen fractions in the rumen fluid: total nitrogen (Nt), ammonia nitrogen (NH 3 -N), non-ammonia nitrogen (NAN), peptides-N and amino acids-N, and true protein (protein-N). Measurements were taken on four sheep fed successively with four diets consisting of hay plus one of the two meals, in the proportion of 40 % and 20 % control meal (cSBM 40 % and cSBM 20 %), 40 % treated meal (tSBM) and a control diet based on hay alone supplemented with starch and urea (HSU). The effective degradability estimated with the nylon bag method was 0.727 and 0.502 for cSBM and tSBM, respectively. Sodium dodecyl sulphate gel electrophoresis (SDS-PAGE) showed that the cSBM conglycinins were degraded at a higher rate in the rumen than glycinins. The same proteins were degraded at a slower rate in the tSBM. Most of the nitrogen degraded in the rumen fluid was in NH 3 -N form, and only 30 % as NAN. For cSBM, NAN comprised protein-N (concentration was low 1 and 2 h after feeding), peptides-N and amino acids-N, while for the treated meal the NAN comprised solely peptides-N and amino acids-N. These results showed that for soya bean meal -a feed in which the dietary proteins are strongly degraded at moderate rates -very little of the solubilized proteins from the bags can escape degradation in the rumen. Whatever the meal studied (treated or untreated), the estimation of feed NAN in rumen fluid able to escape degradation in the rumen compared to the degraded proteins (

The aim of this study was to evaluate the effects of incorporating rice straw and orange leaves into the diets for goats. Ten Murciano-Granadina goats at mid lactation weighing 45 ± 0.3 kg were used in a crossover design. Two isoproteic and isoenergetic diets (180 g/kg DM and 17 MJ/kg DM, respectively) with alfalfa hay as forage source (33% of DM) were fed. A control diet (CON) incorporated barley as energy source and soy hulls as fiber component. The experimental diet (ORG) replaced barley and soy hulls with orange leaves (19% on DM basis), rice straw (12%, on DM basis) and soya oil (2%). Peas and horsebeans were the protein source in both diets. Each goat received the 2 treatments in 2 periods. Goats were fed the experimental diets and after 14 d on their respective treatments moved to individual metabolism cages for another 7 d. Subsequently, feed intake, total fecal and urine output and milk yield were recorded daily over the first 5 d. During the next 2 d ruminal fluid and blood samples were collected, and then individual gas-exchange measurements were recorded by a mobile open-circuit indirect calorimetry system using a head box. No differences in dry matter intake were detected, and apparent total-tract digestibility was greater in CON than ORG. Efficiency of metabolizable energy intake for milk and maintenance also was lower in response to ORG (0.65 vs. 0.63), with energy balance being negative (−12 kJ/kg of BW 0.75 ) due to mobilization of fat (−16 g/animal vs. 68 g/animal for ORG and CON, respectively). Although actual milk yield was lower in goats fed ORG (2.32 vs. 2.06 kg/d, respectively), energy-corrected milk did not differ (2.81 kg/d on average). In terms of milk quality, milk fat content, and concentrations of monounsaturated (18.54 vs. 11.55 g/100 g milk fat) and polyunsaturated fatty acids (5.75 vs. 3.99 g/100 g milk fat) were greater in goats fed ORG. Based on various indices, the milk produced by ORG would be less atherogenic and thrombogenic than CON milk. Compared with CON, enteric CH 4 emission was lower due to feeding ORG (reduction of 38 g CH 4 /kg milk fat). Data suggest that greater fat mobilization in goats fed ORG might have been due to the apparent lack of synchrony between degradable protein and carbohydrate and the lipogenic nutrients associated with the lower cereal content of the ORG diet. Thus, goats fed ORG seemed to rely more on fat depots to help meet energy requirements and reach optimal performance. As such, the lower content of glucogenic nutrients in ORG did not favor body fat deposition and partitioning of ME into body tissue. Overall, responses in terms of CH 4 emissions and milk quality suggest that inclusion of rice straw and orange leaves in diets for small ruminants could be a valuable alternative to reuse, recycle and revalue agricultural by-products.

The main objective of this study was to develop a dynamic energy balance model for dairy goats to describe and quantify energy partitioning between energy used for work (milk) and that lost to the environment. Increasing worldwide concerns regarding livestock contribution to global warming underscore the importance of improving energy efficiency utilization in dairy goats by reducing energy losses in feces, urine and methane (CH 4 ). A dynamic model of CH4 emissions from experimental energy balance data in goats is proposed and parameterized (n = 48 individual animal observations). The model includes DM intake, NDF and lipid content of the diet as explanatory variables for CH4 emissions. An additional data set (n = 122 individual animals) from eight energy balance experiments was used to evaluate the model. The model adequately (root MS prediction error, RMSPE) represented energy in milk (E-milk; RMSPE = 5.6%), heat production (HP; RMSPE = 4.3%) and CH4 emissions (E-CH 4 ; RMSPE = 11.9%). Residual analysis indicated that most of the prediction errors were due to unexplained variations with small mean and slope bias. Some mean bias was detected for HP (1.12%) and E-CH4 (1.27%) but was around zero for E-milk (0.14%). The slope bias was zero for HP (0.01%) and close to zero for E-milk (0.10%) and E-CH4 (0.22%). Random bias was >98% for E-CH4, HP and E-milk, indicating non-systematic errors and that mechanisms in the model are properly represented. As predicted energy increased, the model tended to underpredict E-CH4 and E-milk. The model is a first step toward a mechanistic description of nutrient use by goats and is useful as a research tool for investigating energy partitioning during lactation. The model described in this study could be used as a tool for making enteric CH4 emission inventories for goats.