Ruminal degradation characteristics of neutral detergent fibre (NDF), starch and crude protein (CP) in concentrate ingredients were estimated in dairy cows using nylon bag incubations. Soluble fraction (starch, CP), undegradable fraction (NDF, CP), lag time (NDF) and rate of degradation of the insoluble but degradable fraction (NDF, starch, CP) were measured and showed large variation. Based on measured and partly estimated characteristics ratio's were calculated between total rumen available CP and carbohydrates, between soluble CP and soluble carbohydrates and between insoluble rumen available CP and insoluble rumen available carbohydrates. Ratio's varied largely between feeds and between soluble and insoluble fractions. It is concluded that such ratio's can be used to optimize the composition of concentrates with regard to rumen fermentation. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Many pig growth models assume that there is no effect of energy intake and of body weight on the ratio of lipid to protein deposition rate in pigs below their maximal protein deposition rate. An experiment was performed to check whether an effect of body weight and of amount of energy intake on this partitioning of energy is indeed absent when protein deposition is limited by energy intake. Two constant amounts of energy were given above maintenance requirement (12·6 and 16·3 MJ digestible energy (DE) per day for production, treatment L and H, respectively). A total of 52 entire male pigs were slaughtered at 25,45, 65, 85 or 105 kg live weight. Results showed that, for both levels of intake, the ratio of lipid to protein deposition rate increased with increasing body weight. At the L energy intake, the ratio of lipid to protein deposition rate increased from 0·74 at 25 kg to 0·99 at 105 kg body weight. In animals receiving the H treatment, the ratio of lipid to protein deposition rate increased from 0·82 to 1·35 in that weight range. This change in nutrient partition was also reflected in daily gain. Daily gain declined with increasing live weight, a decrease of 150 g/day over the weight range 25 to 105 kg. The 3·7 MJ DE difference in energy intake between treatment H and L resulted in an average overall difference of 105 g daily gain. A control group fed ad libitum showed that protein deposition capacity was above 200 g/day, thus the pigs at the L and H treatment were below their protein deposition capacity. It was concluded that both live weight and energy intake influence the ratio of lipid to protein deposition rate. The mechanism of partitioning between lipid and protein deposition below maximal protein deposition capacity needs further specification in order to improve the predictions of growth models which use the linear-plateau concept.

The effect of length of the allowed grazing time (Experiment 1), length of starvation time and placement in the rumen of inert bulk material before grazing (Experiment 2) on liquid and particulate rumen pool sizes, composition and fermentability was investigated. In Experiment 1, four lengths of allowed grazing time (1.00, 1.75, 2.50 and 3.25 h) after overnight starvation were compared. The allowed grazing time had no significant effect on total and liquid rumen pool sizes after grazing but did affect (P < 0.05) dry‐matter (DM) and organic matter (OM) rumen pool sizes. The non‐significant diferences between the volatile fatty acid (VFA) rumen pool sizes before and after 1 h of grazing may indicate a delay in the availability of the more rapidly fermentable substrate for the microorganisms. The total VFA remen pool sizes increased significantly (P < 0.01) with the allowed grazing time, which suggests that these fermentation products may be involved in the control of the grazing time in later stages during the day. Experiment 2 consisted of a factorial combination of two lengths of starvation before grazing (16.5 and 2.5 h) and the presence or absence in the rummen of 12.5 kg of a synthetic indigestible material. The duration of starvation before grazing did not affect significantly the particulate, ammonia and VFA rumen pool sizes after grazing except for propionic acid, which was reduced (P < 0.09) by the longer starvation time. The inclusion of inert bulk material in the rumen before grazing significantly reduced (P < 0.05) the total, Liquid DM, OM, and ammonia rumen pool sizes but not the VFA rumen pool sizes after grazing. High levels of ammonia as well as total rumen contents may be involved in the control of the grazing time in this experiment.

Government targets for ammonia emission and for N and P loss per hectare (ha) of agricultural land were used to assess carrying capacity for poultry production in The Netherlands with data from 1990. In addition, the effect of alternative management strategies on carrying capacity was determined. Ammonia emission from poultry production in 1990 [20.5 gigagrams (Gg) N] exceeded the target for 2000 (i.e., 6.9 Gg N). Targets defined for 2000 and 2010 (i.e., 4.6 Gg N) can be achieved, however, without reducing poultry numbers, assuming national introduction of measurements studied. Measures that reduced ammonia emission directly, i.e., introduction of low-emission housing or manure application techniques, were most effective. In 1990, N and P losses equalled 215 kg/ha for N and 31 kg/ha for P. The N loss was slightly lower than the target for 2000 (219 kg N/ha) but exceeded the target for 2010 (144 kg N/ha). Reduction of application of artificial N fertilizer, however, reduced N loss effectively from 215 to 22 kg/ha. National P loss in 1990 exceeded the target for 2000 (15.3 kg P/ha). Reduction of application of artificial P fertilizer reduced P loss most effectively from 31 to 14 kg/ha. To achieve the target for 2010 (8.7 kg P/ha), additional reduction in P excretion by poultry is required. This reduction can be achieved by use of phytase in layer and broiler feed and by use of a coarse Ca source in layer feed. Unlike pig production, carrying capacity for poultry production in The Netherlands is not limited by governmental targets for acidification, eutrophication, or drinking water contamination.

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