Rumen Fill Research Articles

Comparison of voluntary feed intake, rumen passage and degradation kinetics between crossbred Brahmam cattle (Bos indicus) and swamp buffaloes (Bubalus bubalis) fed a fattening diet based on corn silage

ABSTRACTThree crossbred tropical cattle and three crossbred buffaloes, fitted with rumen cannulas, were used to investigate the differences in feed intake, digestibility and parameters with rumen degradation kinetics between cattle and buffalo fed a fattening diet in the Philippines. The animals were fed a diet consisting of 50% corn silage (CS), 30% brewer's grain (BG) and 20% concentrate mixture (CM) on a dry matter (DM) basis, at a level of 3% bodyweight (BW) as DM. Total DM intake (DMI) and rumen fill were greater (P < 0.05) for buffaloes than for cattle, but significant differences were not detected between the animal species when those were expressed as percentage of BW. The DMI per metabolic body size for BG and CM were greater for buffaloes than for cattle (P < 0.05), whereas that of CS did not differ between the species (P > 0.05). The weight proportion of consumed feedstuffs differed between cattle and buffaloes (P < 0.05), although nutrient intake per total DMI did not differ significantly (P > 0.05) between the animal species. Nutrients digestibility was higher (P < 0.05) for buffaloes than for cattle. Ruminal passage rate constant of feed particles and rumen fluid did not differ (P > 0.05) between the animal species. Higher DM degradation rate constant and effective degradability with CS were prominent for buffaloes than for cattle (P < 0.05). Degradation parameters did not differ (P > 0.05) between cattle and buffaloes, neither with BG nor CM. The results indicate that the greater digestibility with DM and energy for buffaloes are ascribable to greater effective degradability of CS fedad libitumlevel.

Intake Regulation and Grazing Behavior of Dairy Cows Under Continuous Stocking

This experiment aimed at studying the behavioral strategies grazing dairy cows use to satisfy their nutritional needs as the day progresses and the possible role of rumen fill in controlling these behavioral strategies. The day was divided into 3 main periods (0600 to 1200h, 1200 to 1800h, and 1800 to 2400h), where the 3 main grazing bouts (dawn, afternoon, and dusk) of dairy cows usually occur. Four late lactating rumen-cannulated dairy cows were used in a repeated measures design; grazing bout was the within-subjects factor. Cows had access to a 1-ha grass sward under a continuous stocking system. To estimate dry matter intake, bite rate, bite mass (BM), and intake rate at the 3 grazing bouts, cows were rumen-evacuated at 0600, 1200, 1800, and 2330h, and the jaw recorders were fitted to the cows between these time points. Time spent eating by dairy cows at the dusk grazing bout was much longer than that at the other 2 grazing bouts and composed about 40% of the daily total eating time. Total grazing jaw movement (TGJM) rate was constant during the day at around 75/min. Bite rate, BM, and, hence, intake rate increased, but chewing rate decreased as the day progressed. The increase in BM was mainly due to the increase in dry matter content of the grass at dusk rather than increased bite dimensions. Therefore, it could be concluded that the main behavioral strategies dairy cows use to satisfy their nutritional needs under continuous stocking include manipulating their eating time, biting rate, and chewing rate, with little control over TGJM rate and BM. Dairy cows interrupted the first 2 grazing bouts (dawn and afternoon) long before reaching their maximal rumen capacity, indicating that rumen fill is less likely to play a significant role in signaling the termination of these 2 grazing bouts. However, rumen pool sizes were always maximal at the time when the dusk grazing bout ceased, indicating that rumen fill is more likely to play a major role in signaling the termination of the dusk grazing bout.

A study of rumen fill on eating behaviour and voluntary intake in sheep using rumen digesta exchange method

A study of rumen fill on eating behaviour and voluntary intake in sheep using rumen digesta exchange method

Evaluation of Forest Tree Leaves of Semi-hilly Arid Region as Livestock Feed

Samples of 13 species of forest tree leaves fed to livestock in the semi-hilly arid zone of Punjab State in India were collected at 30 d interval for 12 months, in order to assess their nutritional worth for livestock. The ground samples were pooled for 4 different seasons viz. dry hot, hot humid, fall and winter. The chemical composition irrespective of the season revealed that CP content varied between 8.9 (Carrisa) to 22.0% (Leucaena). Globulin was the major protein fraction in most of the leaves. The lowest concentration of cell wall constituents was observed in Morus alba and Grewea. The leaves in general became fiberous and lignified during winter and fall as compared to summer season. The leaves of Grewea, Morus alba, Leucaena, Carrisa and Acacia were rich in Ca, P and most of the trace elements. The total phenolics ranged between 1.88% (Azardirachta) to 15.82% (Acacia). The leaves of Acacia had the highest concentration of hydrolysable tannins (14.6%) whereas that of Carrisa had that of condensed tannins (5.9%). The condensed tannins (more than 3%) were negatively correlated to the digestibility of dry matter (DM), neutral detergent fiber (NDF) and crude protein (CP). The digestion kinetic parameters for DM, NDF and CP revealed that leaves of Morus alba, Zizyphus and Ehretia had highest insoluble but potentially degradable fraction. The minimum rumen fill values also revealed that leaves of Grewea, Azardirachta, Morus, Ehretia and Leucaena had great potential for voluntary DM intake. The leaves of Ougeinia, Malha, Dodenia and Carrisa had significantly higher rumen fill value indicating poor potential for voluntary DM intake. Season did not have any significant impact on digestion kinetic parameters except that most of the leaves had low potentially degradable fraction, which was degraded at slow rate during winter. It was concluded that the leaves of Morus, Ehretia, Grewea and Leucaena had great potential as livestock feed, while feeding of Ougeinia, Malha and Dodonea leaves should be avoided.

Comparison of Grass and Legume Silages for Milk Production. 2. In Vivo and In Sacco Evaluations of Rumen Function

Two experiments were conducted to investigate the basis for higher voluntary intakes and increased α-linolenic acid content in milk from cows offered clover silages. Six cows with rumen and duodenal cannulae were used in a four-period changeover-design experiment. Cows received 8 kg/d of dairy concentrate and had ad libitum access to one of six silage treatments: grass, red clover, white clover, alfalfa, and 50/50 (dry matter basis) mixtures of grass with red clover or white clover. The rumen fermentability of grass, red clover, white clover, and grass/red clover silages was also evaluated in a nylon bag study. Legume silages led to increased dry matter intake and milk production in comparison with grass silage. There was no significant effect of legume silages on rumen pH and volatile fatty acid concentrations, but a significant increase in rumen ammonia concentration with the legume silages, reflecting their higher protein content. The inclusion of white clover or alfalfa silage, but not red clover silage, in diets led to an increase in molar proportions of iso-butyric, iso-valeric, and n-valeric acids in comparison with diets based on grass silage. Rumen fill was significantly lower, and rumen passage rates were significantly higher for cows offered alfalfa or white clover silages. However, the markedly different particle size distribution of rumen contents with these feeds suggests very different mechanisms for the high intake characteristics: high rates of particle breakdown and passage with alfalfa, and high rates of fermentation and passage with white clover. Microbial energetic efficiency (grams microbial N per kilogram organic matter apparently digested in the rumen) was highest for cows offered alfalfa silage, intermediate for clover silage, and lowest for cows offered grass silage. These differences reflect the higher rumen outflow rates for legume silages in comparison with grass silage. However, the effect of these differences on N-use efficiency (feed to milk) was probably quite small in comparison with effects of N intake. Although the biohydrogenation of α-linolenic acid was still high for red clover silage (86.1% compared with 94.3% for grass silage), there was a 240% increase in the proportion of α-linolenic acid passing through the rumen. This explains the increased recovery of α-linolenic acid from feed into milk with diets based on red clover silage.

Rumen function and digestion parameters associated with differences between sheep in methane emissions when fed chaffed lucerne hay

An indoor experiment involving 10 rumen-cannulated Romney sheep was conducted in May and June 1998 at AgResearch Grasslands, Palmerston North, New Zealand, under restricted feeding conditions, in order to test the hypothesis that animal factors, in particular rumen fractional outflow rate (FOR) and rumen volume, have an influence on the between-sheep variation in methane (CH4) emission. Sheep were fed 2-hourly on chaffed lucerne hay. Following an acclimatization period of 21 days, the experiment lasted 16 days. Energy and nitrogen (N) balances were measured on days 1–6. Cr-EDTA marker was continuously infused into the rumen from day 9 to 16, and rumen contents emptied and sampled on days 13 and 16. Particulate and fluid FOR were estimated using feed lignin and Cr-EDTA, respectively. Daily CH4 production was measured by the sulphur hexafluoride tracer technique on days 2, 5, 6, 12 and 15 of the experiment.CH4 production (g/day) was positively correlated with the pool size of organic matter (OM) in the rumen (OM pool, g) (r=0·84, P=0·002), OM intake (OMI, g/day) (r=0·67, P=0·04), and the rumen fill (g, wet digesta) (r=0·76, P=0·01). Multiple regression analysis showed that CH4 production was best predicted (R2=0·88) as a function of OM pool and the molar % of butyrate; however, OM pool alone accounted for a large proportion (R2=0·71) of the variation in CH4 production.CH4 yield (% gross energy intake, % GEI) was negatively correlated with the particulate FOR (%/h) (r=−0·75, P=0·01) and buffering capacity of rumen fluid (mmol HCl) (r=−0·72, P=0·02), but positively correlated with the digestibility of cellulose (r=0·66, P=0·04). Multiple regression analysis showed that CH4 yield was best predicted as a function of particulate FOR, OMI (g/kg liveweight0·75) and the molar % of butyrate (R2=0·88). Particulate FOR alone explained a large proportion (R2=0·57) of the variation in CH4 yield. Particulate FOR was negatively correlated with rumen fill (r=−0·69, P=0·03) and digestibility of cellulose (r=−0·65, P=0·04).These results suggest that sheep with lower rumen particulate FOR (i.e. longer rumen retention times) had larger rumen fills and higher fibre digestibilities and CH4 yields. If rumen particulate FOR is to be used as a tool for CH4 mitigation, the repeatability of its relationship to CH4 emission must be assessed, preferably under grazing conditions.

The addition of external water to fresh grass does not affect dry matter intake, feeding behaviour and rumen characteristics in dairy cows

Fresh grass is often a fodder of high nutritive value for ruminants, but its intake is limited in spite of its high digestibility. The high water content of fresh grass could limit grass DM intake by cows. The effect of external water on intake, feeding behaviour and rumen fill was studied in dairy cows fed indoors with fresh perennial ryegrass offered ad libitum. Three treatments were compared: fresh grass as harvested (C: control); C with water added to the grass (SW: surface water) and C with perfusion of water in the rumen after each distribution (PW: perfused water). Grass was offered to cows at 14:00 h, 19:00 h on each day and 07:00 h the following morning. Free access was given to drinking water. In treatment SW, the DM content of the offered grass was reduced from 161 to 117 g·kg -1 on a fresh basis (P < 0.02) without changing the chemical composition of the grass on a DM basis. Compared to C and PW, the fresh matter intake and its rate of intake increased in SW (+ 36 and 39%, respectively), but the grass DM intake (16.4 kg DM·day -1 ), the rate of DM intake (35.3 g DM·min -1 ), the daily eating time (468 min) and rumination time (515 min) were not modi- fied. Perfusion of water into the rumen did not affect intake or feeding behaviour. The weight of the rumen contents (150 kg) and their DM content (115 g·kg -1 fresh matter), rumen fluid osmolality, as well as proportions of free water and bound water and turnover rate were not modified by the treat- ments. In conclusion, for dairy cows fed on grass, important inputs of external water do not affect feeding behaviour, rumen fill nor grass DM intake. dairy cows / fresh grass / surface water / intake / behaviour / rumen fill

Effect of Parotid Saliva Secretion on Dry Forage Intake in Goats

Research was carried out to clarify whether a suppression of dry forage intake during the early stages of feeding in ruminants is caused by feeding induced hypovolemia which is produced by the accelerated secretion of parotid saliva. Goats with a parotid fistula were fed roughly crushed alfalfa hay cubes, commercial ground concentrate feed and NaHCO 3 twice daily (10:00-12:00, 16:00-18:00). The animals were free access to drinking water all day prior to, during and after experiments. The animals were intraruminally infused every day prior to the morning feeding period with parotid saliva collected from the parotid fistula over a 24 h period. The present experiment consisted of two treatments, non-infusion (RNI) and intraruminal infusion of parotid saliva (RSF). In the RSF treatment, 4-5 kg of parotid saliva (280-290 mOsm/l) collected over a 24 h period was intraruminally infused 1 h prior to the commencement of the morning feeding. During feeding, eating and parotid saliva secretion rates were measured. Blood samples were also periodically collected from the jugular vein. During and after 2 h feeding, water intakes were measured, respectively. These measurements were used to define thirst levels. It is thought that rumen fill in the RSF treatment was higher than the RNI treatment. Plasma osmolality in the RSF treatment increased in the first half of the 2 h feeding period due to the intraruminal infusion of parotid saliva. Therefore, parotid saliva secretion rates in the RSF treatment were lower than the RNI treatment for 30 min period from 30 to 60 min after the commencement of feeding. On the other hand, plasma total protein concentration and hematocrit in the RSF treatment decreased by 3.2 and 3.3% prior to the commencement of feeding due to the intraruminal infusion of parotid saliva. In the first half of the 2 h feeding period, plasma total protein concentration and hematocrit in the RSF treatment showed a tendency to decrease compared to the RNI treatment. Thirst level in the RSF treatment during feeding was approximately 31.3% less than the RNI treatment. Upon the completion of the 2 h feeding period, cumulative feed intake in the RSF treatment was significantly larger (19.7%) than the RNI treatment. The results suggest that a suppression of dry forage intake during the early stages of feeding in goats is partly caused by feeding induced hypovolemia, which is produced by the accelerated secretion of parotid saliva.

Digestive processes of dairy cows fed silages harvested at four stages of grass maturity.

The objective of this experiment was to quantify ruminal digestive processes that could help to identify factors limiting DMI when silages differing in grass maturity were fed to dairy cows. Four silages were harvested at 1-wk intervals from a primary growth of a timothy-meadow fescue sward, resulting in feeds with digestible OM content in DM (D-value) of 739, 730, 707, and 639 g/kg in the order of succeeding harvest date. Four ruminally cannulated dairy cows were given ad libitum access to these silages supplemented with 7 kg concentrate per day in a 4 x 4 Latin square design. Rumen function was clearly affected by decreasing digestibility of silage fed. Passage rate of digestible NDF (DNDF) and indigestible NDF (INDF) increased, but it could not prevent the accumulation of DM, NDF, DNDF, and INDF into the rumen when silages of progressing grass maturity were fed. The greatest proportional increases in rumen pool were found in INDF and in medium particles (separated by wet sieving and measuring 315 to 2,500 microm). The passage of medium INDF particles decreased (P < 0.01) linearly (from 0.0365/h to 0.0281/h) with increasing maturity of grass ensiled, and it was slower than passage of small (80 to 315 microm) particles (on average 0.0524/h). Particle size reduction of large INDF particles to medium INDF particles was slower (P < 0.001) in the early cut silages (0.0216/h to 0.0484/h) but reduction of medium INDF particles to small INDF particles was faster (P < 0.001) in early cut silages (0.0436 to 0.0305). Passage of medium size particles and(or) rate of medium particle breakdown to small particles were potential intake-constraining properties of low digestibility forages, whereas large particle reduction to medium particles seemed not to be limiting. The increased feed intake of the early-cut silages was accompanied by decreased rumen fill, suggesting that rumen fill was not at least solely responsible for feed intake control.

Intake, digestibility, milk production and kinetics of digestion and passage for diets based on maize or grass silage fed to late lactation dairy cows

This experiment compares maize and grass silage in relation to dry matter (DM) intake, milk production and the kinetics of digestion and passage for both forages. Twenty-two multiparous late lactation dairy cows were fed diets based on maize or grass silage (diets MS and GS, respectively) for a period of 7 weeks. Milk production was determined over 4 weeks ( n=11 per treatment) with total diet digestibility, forage DM intake and rumen outflow rate being determined in tie stalls ( n=7 per treatment). Forage degradability characteristics were determined using three fistulated steers. The difference in forage DM intake between treatments was highly significant ( P<0.001) with a higher forage DM intake realised for the MS diet (13.54 vs. 9.49 kg/day). Milk yield did not differ significantly with treatment ( P>0.05). However, cows fed the MS diet had a significantly higher milk fat and milk protein content and milk fat yield ( P<0.01). When rumen fill was estimated using the degradability characteristics for forage NDF and the determined rumen outflow rates (2.45 and 2.02% per hour for the grass and maize silage, respectively), the maize silage NDF caused a higher rumen fill than the grass silage NDF (6.83 vs. 4.83 kg of NDF). These results suggest that rumen fill proceeds to a greater degree for cows fed maize silage and that under the conditions of this experiment, extra production from the increased forage DM intake was realised in milk fat and protein content and milk fat yield.

Effects of Intraruminal Saliva Flow on Feed Intake in Goats Fed on Alfalfa Hay Cubes

Research was carried out to ascertain whether or not the volume of saliva flowing into the rumen regulates dry forage intake in ruminants. Goats with a parotid fistula were fed roughly crushed alfalfa hay cubes, concentrated beef cattle feed and NaHCO3 twice daily (10:00-12:00, 16:00-18:00). Except for the days on which experiments were conducted, the animals were free access to drinking water. The animals were intraruminally infused every day prior to the morning feeding period with parotid saliva collected from the parotid fistula over a 24 h period. The present experiment consisted of three treatments, non-infusion (NI), intraruminal infusion of parotid saliva (RSI), and intraruminal infusion of warm water (RWI). In the RSI treatment, approximately 4-5 kg of parotid saliva (280-290 mOsm/l) collected over a 24 h period was intraruminally infused 1 h prior to the commencement of morning feeding. In the RWI treatment, parotid saliva was substituted for warm water (36°C). After infusions, the animals were fed on roughly crushed alfalfa hay cubes for 2 h. During feeding, eating and saliva secretion rates were measured. Blood samples were also periodically collected from the jugular vein. After 2 h feeding, water intake was measured for 30 min. These measurements were used to define thirst levels. On the day of the experiment, the animals were not access to drinking water during the morning feeding. It is thought that rumen fill in RSI and RWI treatments was higher than the NI treatment. In comparison with the NI treatment however, cumulative feed intake increased by 39.3% with RSI treatment and by 45.9% with RWI treatment after completion of the 2 h feeding period. After 2 h feeding, thirst level in the RSI treatment showed only a 10% decrease compared to the NI treatment, but thirst level in the RWI treatment decreased 49.8%. Despite the significant differences in thirst levels between RSI and RWI treatments, the cumulative feed intake in both treatments was similar. When comparing accumulated saliva secretion volumes 2 h after feeding, volumes in the RSI treatment were significantly 35.9% lower than the NI treatment while volumes in the RWI treatment were unchanged. However, the volumes of saliva and fluid flowing into the rumen were greater in both RSI and RWI treatments when compared to the NI treatment. The results indicate that the amount of saliva flowing into the rumen is a factor regulating feed intake in ruminants fed on dry forage. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 12 : 1738-1746)

In-sacco Degradability of Dietary Combinations Formulated with Naturally Fermented Wheat Straw as Sole Roughage

Twelve dietary combinations were prepared using 70 parts of fermented wheat straw (FWS) as the sole roughage supplemented with 30 parts of either the low protein concentrate mixture (Conc.-I), high protein concentrate mixture (conc.-II), maize grains (M), solvent extracted mustard cake (DMC), deoiled rice bran (DRB), uromol bran mixture (UBM), deep stacked poultry litter (DSPL), dried poultry droppings (DPD), M-DMC mixture (50:50), M-UBM mixture (50:50), M-DPD mixture (50:50) or M-UBM-DPD mixture (50:25:25) and evaluated by in-sacco technique. The above dietary combinations were also evaluated by changing the roughage to concentrate ratio to 60:40. The digestion kinetics for DM and CP revealed that FWS:DPD had the highest, whereas, the FWS:M-DMC had the lowest rapidly soluble fraction. The potentially degradable fraction was found to be maximum in FWS:M and minimum in FWS:DPD dietary combinations. The higher degradation rate of FWS:DRB and FWS:UBM combinations was responsible for their significantly (p<0.05) higher effective degradability as compared to other combinations. The highest undegradable fraction noted in FWS:M-UBM-DPD followed by FWS:DMC was responsible for high rumen fill values. The FWS:DRB, FWS:UBM and FWS:DPD combinations had higher potential for DM intake. The dietary combination with higher concentrate level (60:40) was responsible for higher potentially degradable fraction, which was degraded at a faster rate resulting in significantly higher effective degradability as compared to the corresponding dietary combination with low concentrate level (70:30). The low undegradable fraction in the high concentrate diet was responsible for low rumen fill values, which predicted of high potential for DM intake. Out of 24 dietary combinations, FWS with either of UBM, DRB, DMC, Maize, M-DMC or DPD in 70:30 ratio supplemented with minerals and vitamin A in comparison to conventional feeding practice (roughage and concentrate mixture) could be exploited as complete feed for different categories of ruminants. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 9 : 1307-1311)

Design and evaluation of a non-steady state rumen model

A dynamic simulation model of digestion and absorption of nutrients was modified and evaluated under non-steady state conditions. The results of detailed grazing experiments, including allowed grazing times (Exp. 1), combinations of rumen fill and starvation length before grazing (Exp. 2) and contrasting sward masses and sward heights (Exp. 3) as main treatments were used as reference values. The model was modified to run under a discontinuous feed input of ryegrass. Neutral detergent fibre (NDF) and nitrogen rumen pools were predicted with a relatively low root mean square prediction error (MSPE) of the observed means (11%) in Exps. 1 and 2, but a higher value (18%) was observed in Exp. 3. This significantly higher root MSPE was ascribed to the long period (up to 20.5 hours) of starvation that followed grazing. Prediction was poorer for organic matter rumen pool (root MSPE of 16%) than for NDF and N rumen pools, which requires further validation. Volatile fatty acid (VFA) rumen pool and VFA concentration were predicted with a root MSPE of the observed mean of 32–33%, which was close to the random variation observed in the experiments. Ammonia rumen pool was poorly predicted and the way ammonia is represented in the model must be modified to predict ammonia production and absorption under non-steady state conditions. The model can be used to predict ruminal digestion and absorption of nutrients (except ammonia) of grazing lactating dairy cows under discontinuous feeding regimens provided large periods of starvation are avoided.

Strategies for Increasing Energy Density of Dry Cow Diets

The objective of this trial was to compare the effects of increasing dietary energy density from 1.51 to 1.65 Mcal/kg of dry matter (DM) by replacing forage with concentrate or by further increasing concentrate via the substitution of corn silage and alfalfa silage by a mixture of straw, starch, and soybean meal. Our hypothesis was that the latter diet would be more glucogenic while increasing rumen fill and be potentially desirable for transition cows. Nine far-off dry cows (greater than 3 wk before parturition at the end of the trial) were fed three diets: low energy diet, [LE, 1.51 Mcal/kg of DM, 14.0% crude protein (CP) and 35% nonfiber carbohydrates (NFC)], high energy diet, (HE, 1.65 Mcal/kg of DM, 13.9% CP and 39.5% NFC) and high energy diet, where a portion of alfalfa and corn silage was replaced by straw, soybean meal, and cornstarch (HES, 1.65 Mcal/kg of DM, 13.5% CP and 40.5% NFC). The experiment was a replicated 3 x 3 Latin square design with 21-d periods. Six cows from two squares were used to examine kinetics of DM disappearance from nylon bags suspended in the rumen. Two contrasts of interest were: LE versus HE, HES (effects of energy density) and HE versus HES (method of increasing energy density). Increasing energy density increased the potentially degradable (B) and decreased the undegradable (C) DM fractions of the diets. Because HES had greater B and a faster rate of degradation of fraction B (k), effective rumen degradable DM (ERDDM) was higher in HES compared to HE. Cows fed high energy diets had greater DM intake. No differences in DM intake were observed between HE and HES. Rumen volume or DM pool sizes were not affected by treatment. High energy diets increased total ruminal fluid volatile fatty acid concentration compared with LE. Propionate concentration was higher in cows fed high energy diets compared with cows fed LE. The partial replacement of alfalfa and corn silage by straw, soybean meal, and cornstarch further increased propionate concentration. The greatest increase in serum insulin concentration following feeding was observed in cows fed HE. Cows consuming high energy diets had lower plasma nonesterified fatty acids (NEFA) before and after feeding. The HES diet was less effective in decreasing plasma NEFA concentration after feeding compared to HE. In conclusion, increasing diet energy density of far-off dry cows positively affected DMI, ruminal propionate, serum insulin, and plasma NEFA. Increasing energy density with a blend of feeds that represent extremes in rates of carbohydrate fermentation may be a strategy to provide greater amounts of glucogenic precursors. Applicability of this strategy should be examined in transition cows.

Effects of Forage Source and Amount of Concentrate on Rumen and Intestinal Digestion of Nutrients in Late-Lactation Cows

The objectives of this study were to determine the effects of dietary forage source with two concentrate concentrations on dry matter (DM) intake, rumen fill, ruminal and intestinal digestibility of nutrients, and duodenal N fractions in lactating cows. Four rumen and duodenal cannulated Holstein cows in late lactation were used in 4 × 4 Latin square design experiment with 21-d periods. Diets were 1) 65% first-cut alfalfa silage and 35% concentrate, 2) 50% alfalfa and 50% concentrate, 3) 65% bromegrass silage and 35% concentrate, and 4) 50% bromegrass and 50% concentrate. Dry matter intake was not affected by forage source but tended to be (P = 0.08) higher for cows fed diets with 50% concentrate. Rumen fill was greater (P<0.01) for cows fed bromegrass compared with those fed alfalfa silage. Ruminal and intestinal digestion of DM was not affected by dietary forage source or concentrate level. Total N intake was greater for cows fed alfalfa-based diets, reflecting the higher crude protein content of alfalfa. However, total N flow at the duodenum was not affected by either forage source or concentrate in the diet. Although forage source influenced the site of digestion of some nutrients no significant effects on total tract digestibilities were observed.

Comparison of voluntary food intake, apparent digestibility, digesta kinetics and digestive tract content in Manchega and Lacaune dairy sheep in late pregnancy and early and mid lactation

AbstractTwo experiments were carried out with pregnant (experiment 1) and lactating ewes (experiment 2), to compare dry-matter (DM) intake, and total tract apparent digestibility, digesta kinetics and weight of digestive tract contents of Lacaune and Manchega sheep, with the aim of explaining possible differences between the breeds in voluntary food intake. In experiment 1, 20 3-year-old single-bearing pregnant ewes, 10 Manchega and 10 Lacaune, were permanently housed for the last 10 weeks of pregnancy. The diet used consisted of lucerne hay, offeredad libitum, supplemented with 0·3 kg/day of concentrate. DM and digestible DM intake per kg M0·75were higher (P&lt; 0·01) in Lacaune than in Manchega sheep. Breed did not affect total tract apparent digestibility, fractional rates of passage, transit time, total mean retention time, or weight of digestive tract contents. Changes in body weight and body condition score were similar between breeds. In contrast, Lacaune lambs tended (P= 0·09) to weigh less than Manchega lambs, suggesting genetic differences in the energy utilization between breeds in late pregnancy. Higher DM intake observed in Lacaune sheep may have been related to a higher energy demand for mammary development. In experiment 2, 32 3-year-old lactating multiparous ewes, 16 Manchega and 16 Lacaune, were permanently housed during the first 12 weeks of lactation. The experimental diet used was based on a mixture of maize silage and dehydrated lucerne (10: 1, fresh weight basis), offeredad libitum, and supplemented with 0·8 kg/day of concentrate. Milk, fat and protein yield as well as DM and digestible DM intake in Lacaune ewes was higher (P&lt; 0·01) than in Manchega ewes. DM intake was constant in Lacaune sheep with advancing lactation, while in Manchega sheep DM intake decreased. Throughout this period Lacaune ewes lost 0·5 kg of body weight while Manchega gained 4·4 kg. Breed did not affect either apparent digestibility of DM, organic matter and neutral-detergent fibre, or fractional rates of passage, transit time and total mean retention time. The weight of total tract digestive contents was greater (P&lt; 0·05) in Lacaune than in Manchega sheep, particularly in the reticulo-rumen. Results suggest that the scheme of selection in Lacaune dairy sheep has increased milk yield together with voluntary food intake, the latter being associated with an increase in the rumen fill capacity. The higher milk yield of Lacaune ewes cannot be attributed to the higher DM intake only; other factors, i.e. mobilization of fat reserves, are required to support this higher milk output.

Prediction of Energy Balance in High Yielding Dairy Cows with Test-Day Information

This study used a previously developed model to predict herd mean energy balance of the first 12 wk of lactation from test-day information. The predictions were compared with calculated energy balance based on feed analysis and to changes in body weight. Seven independent feeding trials including 43 diets (519 lactations, 254 cows; 1987 tto 1996) were used. Conventional diets were discriminated from nonconventional diets by significant differences between mean calculated energy balance of subtrial diets versus control diets. The total difference between group means of predicted minus calculated energy balance was positive throughout the observed lactation period. It was lowest (5 to 9 MJ of net energy for lactation) during negative energy balance of the conventional diets in wk 2 to 7 when 18 to 50% of the total difference was due to random variation. Because of this difference, both predicted and calculated energy balances were compared to body weight change as a reference for true energy balance. Body weight change was adjusted for rumen fill. While calculated energy balance tended to be negative at times when cows gained weight, predicted energy balance was positive. Cows fed nonconventional diets gained weight, while calculated energy balance was extremely negative, whereas predicted energy balance based on test-day information was positive. We concluded that the prediction difference was relatively small when standard rations were used, and that nonconventional rations biased predicted energy balance to a lesser extent than calculated energy balance. Estimating energy balance based on test-day information appears feasible.

Plasma oxytocin and cortisol concentrations in dairy cows in relation to feeding duration and rumen fill

The aim of this study was to investigate if the release of oxytocin and cortisol were different depending on levels of oral manipulation with feed or rumen fill in dairy cows. Blood samples and behavior of 12 rumen-fistulated cows were analyzed in 2 consecutive years during morning and afternoon periods when the cows were subjected to either (A) long duration of oral manipulation of feed with low rumen fill or (B) short duration of oral manipulation of feed but with filled rumen. The response areas under the curve for oxytocin in both years were larger in A than in B in the afternoons. There were peaks in oxytocin release at milking in the afternoon in both treatments. In B, the oxytocin concentration was higher after than before feeding, higher in B than in A after the non-oral rumen filling, and higher in B after than before the non-oral rumen filling in Year 1. The level of cortisol was higher in B than in A in the morning, lower in both treatments before than after milking in the afternoon, and there was a tendency for the cortisol level to be higher in A than in B after oral feeding. The B cows spent a shorter time eating and the A cows spent a shorter time ruminating. This study indicates that a long duration of oral manipulation of feed in cows, may, per se be linked to higher oxytocin but lower cortisol levels, compared with shorter oral feeding time and filled rumen.

Effect of feeding duration and rumen fill on behaviour in dairy cows

The aim of the present experiment was to test the hypothesis that oral manipulation of feed is a behavioural need in cattle, irrespective of actual rumen load. Twelve rumen fistulated cows were used and subjected to four different treatments: low rumen content+long duration of eating (A), high rumen content+short duration of eating (B), high rumen content+long duration of eating (=positive control) (C) and low rumen content+short duration of eating (=negative control) (D). To obtain treatment A and B, rumen content was transferred by hand from cow A to B through the rumen fistulaes. Each treatment lasted for 3 days with 2 weeks of recovery between each new treatment. The experiment was repeated twice during two consecutive years. All cows were fed the same mixture of silage, concentrate and hay. The cows were videotaped under normal conditions (24 h), and on the third day of the experiment. From these videotapes, the behaviours (frequency and duration per 24 h) have been analysed. Time spent eating differed between the four treatments ( P<0.001), with shortest eating-times in B and D. The cows with low rumen content (A and D) spent shorter time ruminating ( P<0.001) than the cows with filled rumen (B and C). The B and D cows (short duration of eating) spent longer time ( P<0.001) with behaviours related to feed-searching than the cows with long duration of eating (A and C). The C cows had fewer ( P<0.001) bouts of behaviours related to feed-searching than the A, B and D cows. Time spent with stereotypies (tongue-rolling) was longer ( P<0.01) in D than in the other treatments. There was a difference ( P<0.001) between treatments in eating bouts. The A cows had more ( P<0.05) eating bouts than the cows in B, C and D. The cows with low rumen content (A and D) had fewer ruminating bouts ( P<0.001) than the cows with filled rumens (B and C). The number of bouts with stereotypies differed ( P<0.01), the cows in D having the highest figures compared with all the other treatments. In conclusion, our results support the hypothesis that oral manipulation of feed is a behavioural need in cattle irrespective of rumen load. A low duration of feeding behaviours combined with a low rumen load, which is a common practice in certain categories of growing cattle or dry dairy cows, seriously impairs the welfare in cattle.

Fracionamento dos carboidratos e cinética de degradação in vitro da fibra em detergente neutro da extrusa de bovinos a pasto

Os objetivos do presente trabalho foram a caracterização e a determinação das estimativas dos parâmetros relativos à cinética de degradação ruminal dos carboidratos, em amostras de extrusa de animais mantidos em pastagem natural da Zona da Mata (MG), nas estações chuvosa e seca do ano. Para obtenção de amostras representativas, foram usados quatro animais fistulados no esôfago durante dois períodos experimentais na estação chuvosa, e três destes animais por dois períodos experimentais na estação seca, do ano de 1996. Foi efetuado o fracionamento dos carboidratos de acordo com o sistema Cornell e determinadas as taxas de degradação da fibra em detergente neutro (FDN), a partir dos perfis de degradação in vitro deste componente. Foram determinadas as frações potencialmente degradável (B2) e indegradável (C) da FDN, corrigida para proteína e cinzas, e as taxas de latência dinâmica, degradação e crescimento específico dos microrganismos, a partir da fração B2, além dos coeficientes de degradabilidade e do efeito de repleção ruminal da FDN. Observou-se que os carboidratos não-estruturais compreenderam pequena fração dos carboidratos totais nas amostras do pasto, em ambas as estações. Os carboidratos estruturais foram responsáveis pelo aumento no teor de carboidratos totais da extrusa, com a mudança da estação chuvosa para a estação seca; contudo, por causa do aumento da fração C e da menor taxa de crescimento específico dos microrganismos durante a estação seca, foi possível notar redução da degradabilidade e aumento do efeito de repleção ruminal da FDN da extrusa.