Effects of feed restriction and subsequent refeeding on energy utilization in growing pigs

An experiment was carried out to evaluate the metabolic utilization of energy in crossbred barrows during feed restriction and subsequent refeeding. Ten pigs, initially weighing 52 kg, were used in 5 blocks of 2 littermates each. A 7-d adaptation period (P1) was used in which pigs were offered feed at 2.60 MJ of ME.kg of BW(-0.60).d(-1). This adaptation period was followed by a 7-d period (P2), in which 1 pig of each block continued to receive feed at the same level of feeding, whereas for its littermate a 40% reduction in feed intake was imposed (i.e., 1.55 MJ of ME.kg of BW(-0.60).d(-1)). During the subsequent 7-d period (P3), both pigs were offered feed at 2.60 MJ of ME.kg of BW(-0.60).d(-1). After P3, pigs were fasted for 1 d. Heat production (HP) was measured for all pigs during the last 3 d of P1 and on all days for P2 and P3. Heat production was measured using an open-circuit respiration chamber. Energy and N balances were determined for P1, P2, and P3. The HP was partitioned into HP due to physical activity, the short-term thermic effect of feeding, and resting HP. Feed restriction during P2 decreased (P < 0.01) total HP, resting HP, short-term thermic effect of feeding, and retained energy, whereas HP due to physical activity was not affected by feed restriction (P = 0.50). Likewise, fecal and urinary N loss, protein gain, lipid gain, and ADG were reduced during feed restriction (P < 0.01). There were no differences in components of HP and metabolic utilization of energy between the 2 groups during P1 and P3. Nevertheless, urinary N loss was decreased (P < 0.05) and ADG increased (P < 0.01) during P3 for pigs that were restricted in P2. Compensatory growth after a period of feed restriction does not seem to be related to a change in the metabolic utilization of energy for gain but more likely is due to gain in water and gut contents.

Influence of extruded soybeans with or without bicarbonate on milk performance and fatty acid composition of goat milk

The effects of extruded soybeans (ESB) included at 0, 10, or 20% of dry matter (DM) of the diet in combination with sodium bicarbonate (0 vs. 1% bicarbonate added to DM) on rumen fermentation characteristics, production parameters, and fatty acid (FA) profiles of milk fat were examined in 30 midlactation goats and 6 rumen-cannulated goats fed high-concentrate diets (30:70 forage-to-concentrate ratio) ad libitum in a 3 x 2 factorial design. Diets were fed as total mixed rations. The trial lasted 13 wk with the final 9 wk as the test period. Milk yield and composition were recorded each week throughout the trial. Individual samples of milk were taken in wk 4, 7, 10, 11, and 13 to determine FA profile of milk fat. Dry matter intake and intake of net energy for lactation were not affected by dietary treatments. Feeding ESB did not modify ruminal pH or volatile fatty acids concentration in the rumen fluid, but it increased the molar proportion of propionate. Feeding ESB increased fat-corrected milk, milk fat content, and fat yield compared with the control diets. There was no change in milk protein content when ESB were fed. Feeding ESB increased the proportions of oleic, linoleic, and linolenic acids in milk fat at the expense of most of the saturated FA. It also increased the n-6 to n-3 FA ratio of milk. The largest changes in milk yield and milk composition were generally obtained with ESB included at 20% of DM. The addition of sodium bicarbonate tended to increase ruminal pH, VFA concentrations in the rumen fluid, and the molar proportions of acetate. The addition of sodium bicarbonate increased milk fat content and fat yield, with no change in milk FA composition. It is concluded that during midlactation, the inclusion of ESB to 20% of DM prevented low milk fat content for goats fed high-concentrate diets, with no decrease in milk protein content. The addition of sodium bicarbonate may enhance the effects of ESB on milk fat content and fat yield.

Fatty acid composition of mixed-rumen bacteria: effect of concentration and type of forage

The effects of concentration and type of forage in the diet on lipid content and fatty acid (FA) composition of rumen bacteria were studied in 14 goats fitted with duodenal cannulas. The goats were fed a complete maintenance diet containing 40, 70, or 100% chopped forage (dry matter basis) in two equal meals. Forage was either corn stover or alfalfa hay. Microbial cell matter (MCM) was isolated by differential centrifugation of duodenal contents. The FA content of the MCM varied from 5 to 11% of DM and decreased with forage level in the diet. Main FA in MCM were C18:0 and C16:0: together they accounted for 70% of total FA in MCM. The mono-unsaturated FA and branched-chain FA (iso-FA and anteiso-FA) each represented about 10% of FA by weight. The proportion of even-chain saturated FA decreased and those of odd- and branched-chain FA increased with increasing forage. With the corn stover-based diet even-chain saturated FA were lower than with the alfalfa hay-based diet, whereas the unsaturated FA, odd-chain FA, and branched-chain FA were higher. The neutral detergent fiber content of the diet seemed to explain most of the variation associated with even-chain saturated FA, and odd- and branched-chain FA. Our results suggest that, for diets not supplemented with fat, mixed rumen bacteria accumulated energy reserves, by increasing synthesis of either even-chain saturated FA, or saturated odd-chain FA and saturated branched-chain FA.

Modeling homeorhetic and homeostatic controls of pig growth

A dynamic mechanistic model of homeorhetic and homeostatic controls of pig growth was developed. The homeorhetic principles were based on changes in time of fractional rates of anabolism and catabolism of tissues. A minimum number of homeostatic principles integrated current data on plasma kinetics and the partitioning of nutrients between anabolism and catabolism of body tissues, and endogenous losses with integument and into the gut. The major features of the model are two levels of organization (tissue and plasma) and three body tissues (carcass proteins, visceral proteins, and body lipids). The protein tissues and plasma amino acids were subdivided into lysine, methionine and cystine, threonine, tryptophan, other essential AA, and nonessential AA compartments. Plasma glucose and fatty acids were also considered. Adenosine triphosphate and adenosine diphosphate were used to represent energy transformations, although these energy transformations were not included in the homeostatic control of pig growth. The mass variations within each of the 23 basic compartments were described with a specific deterministic, dynamic differential equation. The simulated metabolic rates of the protein and lipid tissues were similar to published data. The principal outputs from the model (protein and lipid gain, body weight, chemical body constituents, plasma parameters) showed that the proposed homeorhetic and homeostatic controls provide a mechanistic approach to modeling growth.

Metaanalysis of input/output kinetics in lactating dairy cows

The kinetics of dry matter intake, raw milk yield, milk fat yield, and body weight of 140 treatment groups of cows reported in 37 articles published between 1959 and 1999 were collected in a database. The majority of these experiments were performed with Holstein-Friesian cows (primiparous: n = 51, multiparous: n = 89). Animals were fed with forages and concentrates, offered separately (n = 98) or as a total mixed ration (n = 42). Empty body weight was calculated assuming that an increase of 1 kg in dry matter intake corresponded to an increase of 4 kg in gastrointestinal tract content. Each kinetic, denoted Y, was fitted with the model proposed by Grossman (1999) for raw milk yield. This model allowed the partitioning of the kinetic into three stages (early, middle, and late stages of lactation), each characterized by its own linear tendency. Kinetics were therefore summarized with parameter estimates of the model: the plateau value of Y in middle stage, the slopes of Y in early and late stages, and the weeks of start and end of the middle stage. The following additional variables were also calculated: the total increase of Y in early stage, the extrapolated value of Y at calving, and the persistency of Y defined as the duration of the middle stage. Variability of these parameters for each kinetic across treatment groups was examined through mixed models including the year of publication as covariate, parity as a fixed between-group factor, and trial as a random factor. Correlations between parameters within a Y-kinetic and between different Y-kinetics were calculated by parity group and feed allocation system. Finally we propose predictive models which emphasized (1) the effect of empty body weight at calving on the depletion of empty body weight in early lactation, (2) the incidence of the kinetic of dry matter intake on the kinetic of raw milk yield in middle and late stages of lactation, and (3) the relationships between the kinetics of raw milk yield and milk fat yield in middle and late stages of lactation.

Lactation response and nitrogen, calcium, and phosphorus utilization of dairy goats differing by the genotype for alpha S1-casein in milk, and fed diets varying in crude protein concentration

Twenty-four dairy goats were used in a preliminary trial to evaluate the effect of the genotype for alpha S1-casein (alpha S1-CN) in milk [homozygous variant A/A (n = 12) or F/F (n = 12)] on milk yield and composition for 2 wk from kidding. After this period, the main trial aimed at determining the effects of the genotype for alpha S1-CN in milk, the dietary crude protein concentration on milk yield and composition, and utilization of N, Ca and P. The goats within each genotype were allocated to a 3 x 3 Latin square for 14 wk with three crude protein concentrations in the total mixed ration (13.2, 16.8, and 19.8% of dry matter) and three periods (wk 3 to 6, wk 8 to 11, and wk 13 to 16 postpartum) as factors. Balances of N, Ca, and P were determined in the last week of each period. Two wk after kidding, the alpha S1-CN A/A goats had higher percentage and yield of protein and lower body weight than the alpha S1-CN F/F goats. During the main trial, yields of protein and fat, as well as percentages of fat and protein in milk were higher for the alpha S1-CN A/A goats than for the alpha S1-CN F/F goats, independent of dietary CP concentration and period. Efficiency of N digestion for milk N was higher for the alpha S1-CN A/A goats than for the alpha S1-CN F/F goats. Urinary N as a percentage of digested N, and total N excretion expressed relative to milk N were lower for the alpha S1-CN A/A goats than for the alpha S1-CN F/F goats. Neither the apparent absorption of calcium or phosphorus was affected by the genotype for alpha S1-CN. Goats fed the low crude protein diet had lower milk yield and lower yields of fat and protein than those fed the other diets. Increasing dietary crude protein concentration increased urinary N, milk N, and N excretion relative to milk N; it also decreased the efficiency of digested N for milk N. In conclusion, selection of goats with a genetically higher yield of casein and fed with diets formulated to reduce N excretion improves the cheese-making properties of goat milk and reduces concerns about N wastes in the environment.

Ruminal phosphorus availability from several feedstuffs measured by the nylon bag technique

The present study was aimed at determining rumen phosphorus availability of some feedstuffs assessed with the nylon bag technique: forage (alfalfa), cereals (control-C wheat, formaldehyde treated-FT wheat, barley, corn), cereal by-products (wheat bran, wheat distillers, corn distillers) and meals (C and FT soya bean meals, rapeseed meals and sunflower meals). Rumen phosphorus availability was not uniform amongst the feedstuffs, varying from 33.1% (FT rapeseed meal) to 84.7% (C wheat). Alfalfa phosphorus release kinetics showed high bacterial phosphorus contamination. Technological treatments affected phosphorus content of by-products by either increasing (wheat bran and distillers) or decreasing (corn distillers) after germ extraction from the seed. Formaldehyde treatment decreasing rumen phosphorus availability (from 77.2% vs. 89.4% for wheat to 33.1% vs. 64.4% for the rapeseed meal) may depreciate the phosphorus nutritional value of FT meals.

Influence of feed intake and source of dietary carbohydrate on the metabolic response to propionate and glucose challenges in lactating goats

The influence of type of nutrients in the diet (rapidly degraded starch plus rapidly degraded N or highly digestible fiber plus slowly degraded N) and amount of feed offered (2.40 +/- 0.10 or 2.00 +/- 0.10 kg of dry matter/d) on plasma constituents after a glucose tolerance test or a propionate challenge test were studied using 12 multiparous dairy goats. Type of diet and interaction between type of diet and amount of feed offered had no effect on the concentrations of any plasma metabolite measured during propionate challenge. During propionate challenge, goats fed at the high dry matter intake (DMI) had a higher clearance of propionate and glucose and a higher ratio of plasma insulin to glucose. During glucose challenges, goats fed diets that were rich in highly digestible fiber tended to have lower peak concentrations of glucose, and goats fed at the high DMI had a higher clearance of glucose. The plasma insulin response to the glucose test was not altered by treatment. The ratio of plasma insulin to glucose was numerically, although nonsignificantly, higher for goats fed at the high rate of DMI. Most of the differences concerning glucose metabolism, insulin response, and tissue responsiveness to insulin appeared to be primarily due to the amount of feed offered and not to the type of diets fed to dairy goats in midlactation.

Influence of feed intake and source of dietary carbohydrate on milk yield and composition, nitrogen balance, and plasma constituents of lactating goats

The influence of diet (synchronized or not synchronized for the degradation rate of the carbohydrate and N fractions) and amount of feed offered [2.40 +/- 0.10 or 2.00 +/- 0.10 kg of dry matter (DM)/d] on milk yield and composition, N balance, and some plasma constituents was studied using 32 multiparous dairy goats (100 +/- 16 d in milk) that were fed a mixed diet for 9 wk. Diets were 40% concentrate with rapidly degraded starch and rapidly degraded N or highly digestible fibers and slowly degraded N. Nitrogen balance was determined at wk 4 and 8. Goats that were fed greater amounts of DM had higher yields of milk, fat-corrected milk, and protein, but lower milk fat concentrations during the whole trial. Raw milk yield was higher at wk 4 and from wk 6 to 7 for goats consuming the rapidly degraded diet than for goats fed the slowly degraded diet at a high feed intake. Concentrations of milk fat tended to be greater for goats fed the rapidly degraded diet at wk 5, 7, and 8. At wk 5 and 6, an interaction between feed intake and diet was observed for milk protein concentration. Nitrogen digestibility, milk N, and N balance were increased for goats fed at high intakes. The output of N in urine and the efficiency of N use for milk output was greater, and N balance was lower, for goats fed the rapidly degraded diet. Plasma concentrations of nonesterified fatty acids, beta-hydroxybutyrate, and urea (wk 2 to 6) were lower, and insulin concentrations were transiently increased, for goats fed at high intakes. Goats fed the rapidly degraded diet compared with goats fed the slowly degraded diet had higher plasma concentrations of urea, which may indicate inefficient use of ruminal N.

Influence of flushing on LH secretion, follicular growth and the response to estrus synchronization treatment in suckled beef cows

The effects of energy supplementation (flushing) on LH and estradiol secretion, follicular growth and the response to estrus synchronization treatment (Norgestomet + PMSG initiated 41.9 +/- 3.4 d after calving) were investigated in 16 suckled beef cows fed either 70% (Group C, n = 8) of energy requirements from calving to 3 wk after AI or fed the same restricted diet until 11 d before synchronization and then were supplemented with 2 kg concentrate until 3 wk after AI (Group S, n = 8). Concentrations of LH and estradiol 17 beta were measured from 3 sampling periods: 25 and 39 d after calving and between 29 and 49 h after implant removal. Ovaries were examined by ultrasonography 11 d before treatment to implant withdrawal (IR). The effects of energy level, day (or hour) of observation and corresponding interactions were tested on repeated measurements by split-plot ANOVA. No positive effect of flushing was observed on characteristics of LH secretion on Day 39. However, the size of the largest follicle and the number of large follicles were higher in Group S than in Group C cows, respectively, 7 and 9 d after the beginning of flushing to 2 d after the start of treatment. After IR, the estradiol secretion tended to be higher in Group S than in Group C cows (9.8 +/- 0.4 pg/mL vs 7.2 +/- 0.2 pg/mL; P = 0.06), but no effect on LH secretion was observed. After implant removal 12 cows ovulated (Group S: 7/8 vs Group C: 5/8; P > 0.05), 7 were pregnant at 21 d after AI (Group S: 6/8 vs Group C: 1/8; P < 0.05) and 4 at 45 d after AI (Group S: 4/8 vs Group C 0/8; P > 0.05). To conclude, flushing had a positive effect on follicular growth, which does not seem to be mediated by LH. In cows fed a restricted diet, flushing enhanced follicular growth, increased the fertilization rate and/or reduced early embryonic death.

Quantitative aspects of protein fractional synthesis rates in ruminants

Protein fractional synthesis rate (FSR) is a key-factor in the characterisation of ruminant metabolism. Published data from the literature were collected and statistically analysed to isolate the factors influencing FSR. FSR varied largely depending on the tissue considered, over a range from 1 to 20. FSR, with the plasma as the precursor pool for protein synthesis, was halved compared to that of the intracellular pool. The method for supplying the amino acid also significantly affects FSR since the flooding dose technique gave higher FSR estimates than the constant infusion technique. The choice of the labelled amino acid infused influenced FSR. There is a ranking order depending on the tissue or organ. The protein and energy levels of the diets significantly increased FSR, which raises the question of the body nitrogen requirements. Moreover, FSR values were dependent on the physiological status of the animals. To conclude, FSR values should be determined simultaneously with other biological parameters in order to obtain a realistic quantitative estimate of the nitrogen turnover rates during intermediary metabolism.

Absence of response to oestrus induction and synchronization treatment is related to lipid mobilization in suckled beef cows

Energy status, follicular growth, oestradiol and LH secretion were investigated in 17 suckled Charolais cows synchronised 59.0 +/- 3.6 days after calving with a 10 day ear implant containing 3 mg of Norgestomet. The cows received 3 mg of Norgestomet and 5 mg of oestradiol valerate by IM injection at implant insertion (day 0) and 600 IU PMSG at implant removal (day 10). They were artificially inseminated (AI) 48 and 72 h after implant removal. Energy status was assessed by measuring weekly plasma concentrations of non-esterified fatty acids (NEFA), beta hydroxy-butyrate (BHB), glucose and insulin 7 weeks before AI. Progesterone plasma concentrations were measured during the same period to assess the presence of a functional corpus luteum. Follicular growth was followed daily by ultrasonography from day -3 to day 13. Oestradiol secretion was measured on day -3, day 6 and day 10 from five hourly samples. Oestradiol and LH plasma concentrations were measured hourly from 29 to 48 h after implant removal for seven cows. Cows were checked for pregnancy by ultrasonography 45 days after AI. Pregnant cows (P) were compared with non-pregnant cows (NP) for energy status, follicular growth, and oestradiol secretion by split-plot ANOVA. Two cows (11.8%) were cyclic before treatment, seven ovulated after treatment (41.2%) and five were found pregnant 45 days after AI (29.4%). There was no difference in body condition score and body weight between P and NP cows on day 0 (2.5 +/- 0.2 and 685 +/- 24 kg vs 2.5 +/- 0.1 and 670 +/- 13 kg; P > 0.05). Mean plasma NEFA concentrations before treatment were significantly lower in P than in NP cows (218 +/- 29 mu eq/L vs 279 +/- 18 mu eq/L; P < 0.05). No significant differences between P and NP cows were found for BHB, glucose and insulin concentrations. P cows presented more medium sized follicles (5 mm < or = diameter < 10 mm) than NP females during the period of observation (2.65 +/- 0.19 vs 2.50 +/- 0.12; P = 0.05). Plasma oestradiol concentrations were not different between P and NP cows on day -3 (8.4 +/- 0.7 pg/mL vs 7.7 +/- 0.4 pg/mL, P > 0.05), day 6 (10.4 +/- 0.6 pg/mL vs 9.8 +/- 0.4 pg/mL, P > 0.05) but were higher in P than in NP cows on day 10 (10.9 +/- 0.6 pg/mL vs 7.8 +/- 0.4 pg/mL; P < 0.05). After implant removal, oestradiol secretion only increased in P cows and a LH peak occurred whereas no increases in oestradiol (11.0 +/- 0.4 pg/mL vs 6.3 +/- 0.3 pg/mL, P < 0.05) and LH (6.0 +/- 0.5 ng/mL vs 1.2 +/- 0.5 ng/mL, P < 0.05) secretion were observed in NP cows. The conclusion was that follicular growth, oestradiol secretion, ovulation and pregnancy rate after oestrus synchronisation treatment are related to mobilization of energy stores before treatment in suckled beef cows in the same body condition score.

Quantitative review of ruminal and total tract digestion of mixed diet organic matter and carbohydrates

The mean response and main factors of variation (level of concentrate, nature of carbohydrate in the concentrate and level of intake) for organic matter, cell wall material, starch digestion and microbial synthesis in the gastrointestinal tract of ruminants were quantitatively reviewed using a data base involving 157 papers. The ruminal digestion (mean +/- SE%) of organic matter, cell wall material, and starch were 45.2 +/- 11.2 (n = 553), 47.7 +/- 17.7 (n = 348), and 74.1 +/- 16.2 (n = 140), respectively and the proportion of each component digested in the rumen in relation to total tract digestibility was 64.7 +/- 12.3, 78.8 +/- 18.5 and 80.5 +/- 16.3, respectively. The efficiency of microbial synthesis (g of microbial protein/kg of organic matter truly fermented in the rumen) and the proportion of microbial nitrogen in the total amount of nitrogen leaving the stomachs (%) were, 23.6 +/- 9.3 (n = 320) and 55.1 +/- 16.5 (n = 289), respectively. The ruminal digestion of organic matter increased by 2 points for every 10 percent increase in concentrate incorporation. The ruminal digestion of cell wall material was maximal when the concentrate incorporation in the diet was 30%. When the ruminal digestion of cell wall decreased, the substitution of ruminal digestion by intestinal digestion was partial (10%). The efficiency of microbial synthesis was optimal when the level of concentrate incorporation was 40%. The nature of the carbohydrates in the concentrates had a significant effect on the efficiency of the microbial synthesis, which was higher (+6.6 g of nitrogen/kg of fermentable organic matter in the rumen) with slowly degradable starch (SS) or digestible fiber (DF) than with rapidly degradable starch (RS). Moreover, the mean depression of cellulolysis in the rumen was higher with RS (-13 points) comparatively to SS (-7 points) or DF (-5 points).