Chewing Activity Research Articles

Apoptosis during the salivary gland enlargement

Aims: A close relationship between cell proliferation and subsequent apoptosis has been established in several organs and tissues. The aim of the present study was to investigate whether there is an increased apoptotic activity in the hypertrophy/hyperplasia of the rat parotid and submandibular glands induced by the β-agonist stimulation (isoproterenol, IPR) and soy feeding. In both experimental models hypertrophy and hyperplasia developed simultaneously. Material and methods: Female Wistar rats weighing 200–250g were used. The level of apoptosis was measured by the activity of caspase-3/7 (effector caspase) from the mitochondria-free supernatants of tissue homogenates using a chemiluminescent assay. Results and conclusion: Marked enlargement of the parotids were detected in both IPR-treated and soya fed animals but the same increase of submandibular gland weights were produced only by IPR. In enlarged glands the elevated level of apoptosis was demonstrated. The soy feeding failed to induce glandular enlargement and increased caspase-3/7 activity on submandibular glands. The mastication plays an important role in maintaining normal morphology and function of the salivary glands whereby increased mastication leads to hypertrophy of glands. The animals fed by raw soybean had to exert a higher chewing activity. To eliminate this effect subsequent experiment we used dry powder or powdered soy mixed with water. The data of this experiment confirmed the effect of mastication on the condition of salivary glands. At the same time our findings demonstrated that by switching off the higher masticatory activity it could not inhibit the effect of soy feeding on the parotid enlargement. In the investigated experimental models enlargement of the salivary glands and the increased level of the apoptosis seem to be coupled processes. Supported by: OTKA T-046511 and ETT-384, Hungary

Evaluation of Whole Cottonseed as Effective Fiber Source in Early Lactating Holstein Cows

Twelve Holstein cows in early lactation were used in balanced changeover design to evaluate the effect of replacing alfalfa Neutral Detergent Fiber (NDF) with NDF from whole cottonseed at different levels (0,7,14,20 %) on dry matter basis. The diets were similar as crude protein and neutral detergent fiber on dry basis. Cows were fed with total mixed ration individually. Dry matter intake and milk yields were higher for cows fed with high whole cottonseed (14.20%) diets than for the alfalfa control diet. High whole cottonseed diet had best efficiency. Milk fat percentage and milk fat yield were highest for high whole cottonseed diets, but no significant difference were found among the another milk composition compounds (protein, lactose and SNF). Milk component yields were significantly different (p<0.05). Rumen pH and fecal pH were not significantly affected by experimental diets. Chewing activity increased linearly when whole cottonseed percentage increased. High percentage of whole cottonseed percentage was associated with increased physically effective fiber. Digestibility results were indicated that control diet and 7 % whole cottonseed diets had highest dry matter digestibility (p<0.05), while organic matter, crude protein and NDF digestibility were not significantly affected among diets. Daily weight gain and body condition score change were affected by diets. Thus, the 14 and 20 % whole cottonseed diets produced the highest daily weight gain and body condition score (p<0.05). Plasma urea nitrogen was higher for 14 and 20 % whole cottonseed in diets.

Effects of alfalfa hay particle size and cottonseed hulls as nonforage fiber source on chewing activity and rumen pH

Ration particle size has been observed to affect DMI, chewing activity, rumen pH, milk fat and nutrient digestibility (Yang et al., 2001; Grant et al., 1990). Nonforage fiber sources (NFFS) possess a large amount of NDF that can be used as a forage substitute based on their price and availability. Cottonseed hulls (CSH), a by-product of cotton processing, contain a large proportion of NDF and associated lignin, and have been considered a useful NFFS. It was suggested that physical characteristics of dietary forage can interact with nonforage fiber sources (Grant, 1997). The objectives of this study were to determine effects of CSH as nonforage fiber sources and to investigate interaction between CSH as NFFS and alfalfa particle size on Chewing Activity and rumen pH.

Effects of lucerne hay and barley grain particle sizes on chewing activity, rumen pH and milk composition of Holstein dairy cows

NRC (2001) recommended 250 g/kg dietary neutral detergent fibre (NDF) with a minimum of 190 g/kg dietary forage NDF to prevent milk fat depression. This recommendation does not account for the differences in forage particle size. The forage particle size requirements of dairy cows fed barley grain-based diets can differ from those fed maize grain-based diets (Yang and Beauchemin, 2006). The objective of this experiment was to evaluate the effects of lucerne hay and barley grain particle sizes on chewing activity, rumen pH, milk yield and milk composition using barley grain-based diets.

Effects of Varying Dietary Forage Particle Size in Two Concentrate Levels on Chewing Activity, Ruminal Mat Characteristics, and Passage in Dairy Cows

The objective of this study was to investigate the effects of varying dietary forage particle size on chewing activity, ruminal mat characteristics, passage, and in situ ruminal and total tract digestion in dairy cows at a low- and high-concentrate inclusion. The experiment was designed as a 4×4 Latin square with a 2×2 factorial arrangement of treatments. Four ruminally cannulated late-lactating dairy cows were restrictively fed (17kg of dry matter/d), in four 23-d periods, 1 of 4 different diets varying in the theoretical particle size (6 and 30mm) of hay (56.6% NDF of dry matter) and in the levels (approximately 20 and 60%, dry matter basis) of a cereal-based concentrate. Ingredients of the ration were offered separately to the cows; dietary hay and low-level concentrate were offered twice daily at 0800 and 1600h, whereas concentrate of the high-level treatment was offered in 4 meals a day at 0800, 1200, 1600, and 1900h. This study showed that altering the forage particle size from 6 to 30mm in a low-concentrate diet significantly increased the rumination time and ruminal mat consistency without affecting ruminal fermentation and passage. Further, particle breakdown and proportion of mat in the rumen increased, and in situ hay dry matter degradability improved, which in turn indicated a higher capacity of ruminal digesta to degrade fiber. On the other hand, increasing the forage particle size in a diet containing a high amount of concentrate increased the proportion of dry matter retained on a 1.18-mm screen from 37.5 to 42.0% and extended the rumination time by 100min/d, as well as increasing the ruminal mat consistency. However, ruminal particle breakdown, short-term ruminal pH, fibrolytic capacity of the digesta, and proportion of mat in the rumen decreased. This was also reflected in a higher bailable liquid pool, increased fractional passage rate of solid digesta from the reticulorumen, and increased retention time in the hindgut, which in turn indicated a shift of fiber digestion from the rumen to the lower digestive tract. This study showed that the response of chewing or ruminating activity alone seemed to be insufficient to assess the dietary physical effectiveness or fiber adequacy in limit-fed dairy cows when high-concentrate diets were fed separately. Based on the results of this study, we concluded that inclusion of coarsely chopped hay in the high-concentrate diet did not appear to further improve rumen conditions and digestion when the rations were formulated to exceed the fiber requirements in limit-fed dairy cows.

Physically effectiveness of beet pulp in dairy cows 2: Intakes, digestibility and chewing activity, and performance of Holstein dairy cows

Many non-forage fibrous sources (NFFS) such as beet pulp (BP) contain more NDF than some forage sources, and have been successfully used in dairy rations to replace a portion of the effective or physical effective fiber (peNDF) that is normally provided by forages. However, BP has limited forage replacement value and effectiveness factor of 0.40 (fraction of NDF) versus 1.0 for forages (Mertens, 1997). In addition, Mertens (1997) suggested that the physically effectiveness factor of ground and pellet were 0.40 and 0.30, respectively. However, the effects of BP when substituted with different feed sources in TMR are variable that depend on chemical composition, types and physical characteristics. The objective of this experiment was to measure the effects of three types of BP on intakes, digestibility, and chewing activity and performance of Holstein dairy cows.

Investigation into the substitution of alfalfa with sugar beet pulp on milk yield and composition of Holstein cows

The non-NDF carbohydrates (NFC) are important sources of energy in the ration of high producing cows. The fibre must be proper quality and particle size to insure maximum DMI, optimal chewing activity, normal ruminal fermentation, and milk fat percentage. The NRC (1989) recommends 25 to 28% NDF in the rations of lactating cows; a minimum of 75% of the NDF should come from forages. These recommendations provide no adjustment for the physical effectiveness of the fibre, interactions among fibre sources and non fibre carbohydrates, or animal characteristics that may influence ration design. Few data are available to document the effect of the substitution of by-product NDF for forage NDF; our objective was to determine the effect of the substitution of alfalfa NDF from sugar beet on DMI, milk yield and composition, chewing activity, faecal and rumen pH, and apparent digestibility of DM.

Feed intake and digestive responses of dairy cow fed lucerne hay varying in particle size

Chemical composition and physical characteristics of diet influences its optimal utilization in dairy cow. Neutral detergent fiber measures the chemical characteristics, but not the physical characteristics of fiber such as particle size and density (Mertens, 1997). Both the amount and physical form of fiber are important in the diet of lactating dairy cow for maintaining normal milk fat content, chewing and digestive activities. A sufficient supply of long particles or NDF must be included in the ration to increase chewing activities, maintaining the rumen pH and providing an optimal rumen environment in order to avoid metabolic disorders. Current NRC guidelines (NRC, 2001) have proven useful information in defining animal requirements and feed composition but do not provide detailed recommendation on physical form of ration. The objective of this experiment was to determine the effect of lucerne particle size on feed intake and digestibility in dairy cow in early lactation period.

Aspectos metodológicos do comportamento ingestivo de cabras lactantes alimentadas com farelo de cacau e torta de dendê

Objetivou-se definir o intervalo de registro do comportamento ingestivo de cabras Saanen lactantes alimentadas com dietas contendo farelo de cacau e torta de dendê em substituição ao concentrado. Ao final de cada período experimental, cinco cabras (41,6 kg de PV) alojadas em baias individuais foram observadas continuamente (24 horas/dia). O concentrado padrão (milho e farelo de soja) foi substituído por 0, 15 e 30% de farelo de cacau ou torta de dendê. O comportamento ingestivo consistiu dos tempos despendidos em alimentação, ruminação e ócio. Foram testados os intervalos de 10, 15 e 20 minutos contra o registro de observação a intervalos de cinco minutos. O farelo de cacau e a torta de dendê não provocaram alterações no comportamento ingestivo em nenhum dos intervalos avaliados. Não houve diferença entre os tempos médios despendidos em alimentação, ruminação e ócio nos diferentes intervalos de tempo avaliados, indicando que os animais podem ser observados a intervalos de até 20 minutos.

Substituição do milho pela casca de café ou de soja em dietas para vacas leiteiras: comportamento ingestivo, concentração de nitrogênio uréico no plasma e no leite, balanço de compostos nitrogenados e produção de proteína microbiana

Objetivou-se avaliar o efeito da substituição do milho pela casca de café ou pela casca de soja em dietas à base de cana-de-açúcar, com 60% de concentrado, sobre o comportamento ingestivo, o pH e a concentração de amônia no líquido ruminal, a excreção de uréia na urina (EU), a concentração de N-uréia no plasma (NUP) e no leite (NUL), o balanço de compostos nitrogenados e a síntese de proteína microbiana em vacas leiteiras, em comparação a uma dieta com silagem de milho. Foram utilizadas 12 vacas holandesas, puras e mestiças, distribuídas em três quadrados latinos 4 x 4. A dieta controle foi composta de silagem de milho e 40% de concentrado (SiMi), com base na MS. Foram utilizadas três dietas contendo cana-de-açúcar e 60% de concentrado, de modo que os percentuais de substituição do milho foram 0% (CMi), 25% com casca de café (CCC) ou 50% com casca de soja (CCS), com base na MS total da dieta. O tempo total de mastigação foi menor para a dieta SiMi e não foi afetado pela inclusão de casca de café ou casca de soja. O pH ruminal não diferiu nos tempos 0 e 3 horas após a alimentação matinal. A dieta CCC resultou, três horas após alimentação, em menor concentração de amônia ruminal em relação às demais, com exceção da dieta CMi. Não foram observadas diferenças na EU e NUL, sendo registrados valores médios de 179,31 mg/kg de PV e 12,59 mg/dL, respectivamente. A substituição do milho pela casca de café ou de soja não promove melhora no ambiente ruminal. A síntese de compostos nitrogenados microbianos e a eficiência microbiana ruminal não são influenciadas pelas dietas e apresentam valores médios de 273 g/dia e 130,08 gPBmic/kg de NDT, respectivamente.

The effect of dry corn gluten feed on chewing activities and rumen parameters in lactating dairy cows

The objectives of this research were to evaluate the effects of increasing levels of dry corn gluten feed (DCGF) on dry matter intake (DMI), chewing activity, and rumen fermentation when used to replace a portion of corn silage in diets for lactating Holstein cows. Eight lactating Holstein primiparous cows averaging 98±20 d in milk and weighing 515±20 kg were randomly assigned in a 4x4 Latin square design with 4 week periods. Dietary treatments were 1) a control diets (C) of 50% forage (corn silage and wheat straw, 35%, 15% DM basis, respectively), 2) a low DCGF diet (L-DCGF) in which 10% of the same corn silage was replaced by DCGF, 3) a medium DCGF diet (M-DCGF) in which 18% of the same corn silage was replaced by DCGF, and 4) a high DCGF diet (H-DCGF) in which 25% of the same corn silage was replaced by DCGF.The proportion of particles retained on the 19.0 mm screen and physical effectiveness factor of the H-DCGF was lower (P<0.05) than in the other groups. Increasing the level of DCGF did not change DMI. Cows fed the C diet spent significantly more time ruminating and chewing per day compared with the M-DCGF and H-DCGF diets (483.88, 435.63, 431.25 min/d, P<0.05; and 818.38, 753.00, 745.75 min/d respectively, P<0.05). Cows fed the C diet had ruminal pH values higher than the cows fed the M-DCGF and H-DCGF diets (6.02, 5.95, and 5.91, P<0.05). The total volatile fatty acid and propionate levels of H-DCGF fed cows were higher than the control (P<0.05). The changes in acetate (A) and propionate (P) concentrations resulted in a decrease in A/P ratio, when corn silage was replaced by DCGF, which led to a reduction in the particle size of the diets (P<0.05). It was concluded that when ratio 18 and 25% DCGF were substituted for corn silage, rumination time, chewing activities and ruminal pH are negatively affected. The optimum level for the addition of DCGF was found to be below 18% of the diet for a healthy rumen and a chewing behaviour in dairy cows.

Effect of different fibrous and nonfiber carbohydrate levels on nutrients digestibility of total mixed ration using in vivo in buffalo

In order to investigate the effect of different levels of NDF on chewing behavior and their relationship with ruminal acidity, 3 ruminally fistulated buffalo steers (average BW = 389.6 ±7.5 Kg) were allotted in a change over design in Agriculture and Natural Resource center of Uremia city of Iran. Two diets with 2 levels of NDF were used as treatments. First and second diets had 52 and 47 % of NDF, respectively. The experiment had two periods and each period’s take 15d for adaptation, 7d for sample collection and determination of nutrient digestibility and for determination of passage rate, 2d for measuring ruminal pH, and 3d for measuring chewing activity. Using Penn Stat Particle Separator (PSPS), distribution, geometric mean, its standard deviation and physically effective factor (pef) of diets were determined. Animals fed ad libitum at 09:00a.m and 21:00p.m. The time that spent for eating and rumination were optically recorded in 24h with 5 minutes intervals and total chewing activity calculated from sum of eating and rumination time. There were no significant differences between chemical composition, particles distribution, geometric mean, its standard deviation and physically effective factor (pef) of diets, dry matter intake (kg/d) and nutrients intake (NDF, ADF, NFC and crude protein) and their digestibility, but digestibility ADF, NDF and NFC decreased as content of fiber increased(P<0.05). Increasing NFC reduced ruminal pH at 0.5, 1.0, 4.5, 6.0 9.0 and 10.0 h post feeding (P<0.05). In addition, there were no significant differences on eating time, rumination time and total chewing activity between diets, but increased as NDF intake and peNDF>1.18 increased (P<0.05). Also, rumination time and total chewing activity over night decreased as NDF intake and peNDF>1.18 increased (P<0.05).

Evaluation of the efficacy of rumen cannulation technique on some rumen metabolic parameters in buffaloes

This experimental study was carried out to determine the efficacy of rumen cannulation technique on some rumen metabolic parameters in buffaloes. Four healthy male River (Azari) buffaloes with no previous history of gastrointestinal dysfunction were chosen. There are several surgical techniques that can be used for rumen cannulation in farm animals, including buffaloes. This procedure was performed in a modified two-stage technique. In the first stage, the dorso – lateral portion of the dorsal sac of the rumen wall was sutured to the skin incision in the left para lumbar fossa region. In the second – stage, after six days left, the exposed rumen wall area was incised and the cannula was inserted and fixed manually in the rumenal opening incision site. In order to evaluate the efficacy of rumen cannulation technique on some rumen metabolic parameters, this study was achieved with different levels of NDF, and chewing behavior and their relationship with ruminal acidity, was measured in a change over design. Two diets with 2 levels of NDF were used as treatments. First and second diets had 52 and 47 % of NDF, respectively. Animals fed ad libitum at 09:00 and 21:00. There were no significant differences between chemical composition, particles distribution, geometric mean, its standard deviation and physically effective factor (pef) of diets, dry matter intake (kg/d) and nutrients intake (NDF, ADF, NFC and crude protein) and their digestibility. Increasing NFC reduced ruminal pH at 0.5, 1.0, 4.5, 6.0 9.0 and 10.0 h post feeding. In addition, there were not significant differences on eating time, rumination time and total chewing activity between diets. All data obtained in this study were in normal range may indicating the efficacy of this cannulation method. More investigation should be done to determine the efficacy and comparison of the other surgical rumen cannulation techniques on Azari buffaloes of Iran.

The effects of restricted feed access and social rank on feeding behavior, ruminating and intake for cows managed in automated milking systems

In the present research the effects on feed intake and chewing activities of dairy cows subjected to three different degrees of controlled cow traffic were examined. The hypothesis tested was that restricted access to the feeding areas provokes effects on chewing activities related to feeding and rumination. The cows were subjected to three different cow traffic routines in a carry-over design with three periods of 3 weeks each. In each period, the cows were subjected to one of the following cow traffic routines: (1) the free cow traffic routine (FR) that implied cows always had access to the feeding areas through the control gates; (2) the selective cow traffic routine (SE) that implied cows had access to the feeding areas through control gates until 5 h after the last milking; (3) the forced cow traffic routine (FO) that implied cows never had access to the feeding areas through the control gates. Despite no difference in feed intake between cows of high and low social rank, the cows of high social rank spent significantly more time chewing while feeding: 214 min/day for cows of high social rank and 175 min/day for cows of low social rank, respectively. The FO enhanced the social effects on chewing activities; cows of high social rank tended to have more chews per kilogram of dry matter intake (512 chews/kg DM) compared to cows of low social rank (382 chews/kg DM). During FR cows had a higher dry matter intake and ruminated for a longer time compared to the other cow traffic routines. It was concluded that forced cow traffic provoked effects that may have negative effects on feed intake and cow welfare.

Silage Chop Length and Hay Supplementation on Milk Yield, Chewing Activity, and Ruminal Digestion by Dairy Cows

The effects of whole-plant corn silage (CS) particle size and long unprocessed grass hay (LH) supplementation on milk yield, chewing activity, and ruminal digestion in dairy cows were evaluated in 2 experiments. In Experiment 1, corn silage harvested at fine (6mm; FCS) or coarse (23mm; CCS) theoretical cut length were fed to 22 lactating Holstein cows. Treatments were 2 total mixed rations containing 58% of dry matter (DM) as FCS or CCS. Diet DM intake tended to be higher in cows fed FCS than those fed CCS (23.4 vs. 22.1kg/d). However, milk yield and composition, body condition score, and plasma metabolite concentrations were not affected by the dietary treatments. In the second experiment, 5 cannulated Holstein cows were used in a 5×5 Latin square design to evaluate the effects of the addition of LH to the diets evaluated in Experiment 1 on chewing activity and ruminal digestion. Treatments were 5 total mixed rations: FCS-based diet plus the addition of 0, 5, or 10% LH (DM basis) and CCS-based diet plus 0 or 5% LH. Long hay addition linearly decreased DM intake in cows fed FCS-based diets (25.0 to 21.7 kg/d), but increased DM intake in those fed CCS-based diets (22.7 to 27.1 kg/d). The intake of neutral detergent fiber (NDF) increased with LH addition in CCS-based diets (7.6 vs. 9.4 kg/d). Rumination time increased (16.8 to 21.0 min/kg of DM intake) when LH was added to FCS-based diets, but it decreased when included in CCS-based diets (18.8 vs. 12.9 min/kg of DM intake). Ruminal pH was higher (5.9 vs. 5.7) and lag-time for in situ NDF disappearance was shorter (3.5 vs. 8.7h) for cows fed CCS compared with cows fed FCS. The rate of NDF disappearance tended to be higher for the CCS-based diet with 5% LH than for the diet with 0% LH (2.0 vs. 4.4%/h), but solids passage rate was not affected by the treatments. These results suggest that addition of LH to FCS-based diets does not affect ruminal environment or digestion, but depressed DM intake. In contrast, addition of LH to CCS-based diets may improve ruminal NDF digestion, increasing DM intake by reducing filling effect and time needed for rumination.

Digestibility, methane production and chewing activity of steers fed whole-crop round bale corn silage preserved at three maturities

The effects of the lengths of growth of round bale whole-crop corn silage on its nutritive value, the methane production, chewing time, and ruminal fermentation were evaluated in three Holstein steers (599.3 ± 31.5 kg). Corn forages were harvested, baled and wrapped on the same day at 129 (D129), 118 (D118) and 107 (D107) days from planting. All steers were fed the three corn silages along with urea at maintenance energy requirements during three 14-day periods in a 3 × 3 Latin square design. A balance trial was conducted to investigate whole tract digestibility by the collection of total feces and urine over a 7-day test period. For 2 days of the test period, a head hood-type respiration chamber was used to measure methane production. Ruminal fluid was collected immediately before and 3 h after, the morning feeding on the last day of the test period. There was no spoilage in any of the silages ( n = 9). The average fresh weight of the bales was 326.4 ± 10.7 kg. The DM content of the corn silage was highest in D118 and lowest in D129 (P<0.01). The pH of all silages was lower than 4.0. The aNDFom content of the corn silage was higher in D129 than in other forages (P<0.05). There were no differences in the metabolizable energy content of the corn silage. The ruminating and chewing times, chewing per unit of DM intake and chewing per unit aNDFom intake were higher (P<0.05) in steers fed D129 than those fed other forages. Before the morning feeding, the acetate proportion of total volatile fatty acid in the steers fed D129 was higher (P<0.01) than that in other steers. The nutrients and energy value of each corn silage in this study ranged from 232 to 305 g/kg of DM, from 87 to 90 g/kg of crude protein, from 426 to 492 g/kg of aNDFom, from 667 to 707 g/kg of TDN and from 11.39 to 11.84 MJ/kg of metabolizable energy on a DM basis. These results show that the DM and aNDFom contents of corn silage and total chewing time of the steers, and the acetate proportion of the total VFA in the rumen before the morning feeding were affected by the lengths of growth of corn forage.

Nocturnal Eating: Sleep-Related Eating Disorder or Night Eating Syndrome? A Videopolysomnographic Study

To describe the clinical and videopolysomnographic characteristics of nocturnal eating episodes in sleep-related eating disorder. Descriptive study of outpatients prospectively enrolled in 2 sleep centers. Videopolysomnographic recordings done in the sleep laboratory. Thirty-five consecutive drug-free patients with nocturnal eating. N/A. Clinical interviews disclosed abnormal compulsory nocturnal eating episodes in all patients associated with a clinical report of sleepwalking (in 1), somniloquy (in 5), restless legs syndrome (in 8), and periodic limb movements during sleep (in 4). Videopolysomnography documented 45 episodes of nocturnal eating in 26 patients. Eating always occurred after complete awakenings from non-rapid eye movement sleep and only in 1 patient from REM sleep and was characterized by electroencephalographic alpha activity with no dissociated features of state-dependent sleep variables. Patients interviewed during the eating episodes were fully conscious and remembered the events the next day. Pathological periodic limb movements during sleep index was recorded in 22 and restless legs syndrome dyskinesias in 5 patients. Recurring chewing and swallowing movements during sleep were a feature in 29 patients, associated in about half of the events with electroencephalographic arousals. In our patients, eating episodes occurred with normal consciousness and recall. Chewing or swallowing movements during sleep occurred frequently, resembling rhythmic masticatory-muscle activity in bruxism patients. The presence of periodic limb movements during sleep and chewing activity, the reported efficacy of dopaminergic medications, and the compulsory food-seeking behavior all argue for a dopaminergic dysfunction underlying the pathogenesis of sleep-related eating disorder.

Physically Effective Fiber: Method of Determination and Effects on Chewing, Ruminal Acidosis, and Digestion by Dairy Cows

A study was conducted to investigate the effects of physically effective neutral detergent fiber (peNDF) content of dairy cow diets containing corn silage as the sole forage on intake, chewing, ruminal pH, microbial protein synthesis, digestibility, and milk production. A second objective was to compare current methods of measuring peNDF to determine the most suitable approach for use in ration formulation. The experiment was designed as a replicated 3×3 Latin square using 6 lactating dairy cows with ruminal cannulas. Diets varied in peNDF content (high, medium, and low) by altering the particle length of corn silage. The physical effectiveness factors (pef) and peNDF contents of the corn silage and diets were determined based on the original (19- and 8-mm sieves) and new Penn State Particle Separator (PSPS; 19-, 8-, and 1.18-mm sieves). A dry-sieving technique that measures the proportion of particles retained on a 1.18-mm sieve was also used. The new PSPS and the 1.18-mm sieve produced similar estimates of pef and peNDF of diets but gave higher values than the original PSPS. There was a much smaller range in pef of corn silage when 3 sieves, rather than 2, were used with the PSPS (range of 0.93 to 0.96 vs. 0.41 to 0.72, respectively). Consequently, increased forage particle length in the diets increased dietary peNDF content and its intake when using the original PSPS; however, the new PSPS and the 1.18-mm sieve failed to detect changes in dietary peNDF and peNDF intake. The peNDF values estimated based on fractional NDF rather than the total NDF content were higher, but the ranking of diets was not changed. Increased intake of peNDF linearly increased digestibility of CP and tended to linearly increase digestibility of fiber in the total tract. As a result, milk yield tended to linearly increase with no effect on milk composition. Ruminal microbial protein synthesis and microbial efficiency were higher with the medium peNDF than with the high or low peNDF diets. Total chewing time and ruminating time were linearly increased with increasing dietary peNDF, whereas influence of dietary peNDF on ruminal pH and fermentation was minimal. This study showed that increasing peNDF content of diets improved fiber digestion. Of the systems used to measure peNDF, the original PSPS provided a good description of dietary particle length and its effects on chewing time and rumen pH, whereas the new PSPS provided a more consistent chewing index, the ratio of total chewing activity to peNDF, across diets varying in chop length of corn silage.

Le contrôle de l’acidose ruminale latente

Le principal critère d’évaluation de l’acidose du rumen est le pH moyen mesuré pendant plusieurs heures après le repas. D’autres critères ont été proposés, cependant ils restent très corrélés au précédent et ne fournissent pas d’information plus pertinente.&#x0D; Différentes mesures peuvent être effectuées sur les aliments, ou les régimes alimentaires, pour évaluer le risque d’acidose ruminale. Au niveau des aliments, il est ainsi possible de mesurer leur pouvoir tampon propre, leur fermentescibilité in vitro, ou la chute de pH induite, et la dégradabilité à court terme (4h) in sacco de leur MS. D’autres critères peuvent être utilisés, il s’agit en particulier de la teneur en amidon dégradable pour les matières premières amylacées. Enfin, le bilan cation-anion peut aussi être évalué au niveau des aliments et être utilisé pour évaluer une facette du pouvoir acidogène des aliments. Au niveau des régimes, la fibrosité représente un facteur essentiel de risque d’acidose ; il y a en fait deux composantes de fibrosité, la fibrosité chimique, quantifiée par la teneur en NDF (NDF/MS &gt; 35 %), la fibrosité physique évaluée par la taille moyenne des particules (TP &gt; 4 mm), ou la proportion de MS retenue à un tamis de 2 mm (P2 &gt; 40 %). Il est possible de chercher à combiner ces deux types de critères. Les critères de fibrosité sont très importants dans la mesure où ils déterminent l’activité masticatoire et, de ce fait, le recyclage des tampons ainsi que le flux liquidien ruminal, critères plus déterminants de l’acidose que ceux qui prédisent la production des AGV. D’autres aspects interviennent de façon non négligeable dans le risque d’acidose, il s’agit en particulier du niveau d’ingestion ainsi que du rôle de certaines populations microbiennes du rumen telles que les protozoaires. Outre les facteurs relatifs aux aliments et aux rations, il est possible d’envisager des supplémentations de substances préventives, c’est en particulier le cas des substances tampons et de certaines substances probiotiques.&#x0D; L’ensemble des équations et recommandations proposées permettent de tenir compte de différents critères pour prévenir le risque d’acidose latente.

Effects of dietary nonstructural carbohydrates and protein sources on feeding behavior of tethered heifers fed high-concentrate diets1

To describe the feeding behavior of growing heifers fed high-concentrate diets with different sources of protein and nonstructural carbohydrates, and to explain the ruminal fermentation pattern, 4 ruminally fistulated Holstein heifers (BW = 132.3 +/- 1.61 kg) were assigned to a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. Two non-structural carbohydrate sources (barley and corn) and 2 protein sources [soybean meal (SBM) and sunflower meal (SFM)] that differ in their rate and extent of ruminal degradation were combined, resulting in a synchronized, rapid fermentation diet (barley-SFM), a synchronized, slow fermentation diet (corn-SBM), and 2 unsynchronized diets consisting of a rapidly and a slowly fermenting component (barley-SBM and corn-SFM). The corn-SFM diet resulted in a lower frequency of feeding (P < or = 0.05), longer meal length (P < or = 0.043), and larger meal size (P < or = 0.037) than the other 3 diets. Dietary treatment had no effect (P > or = 0.09) on the daily percentages of posture and behaviors. In general, heifers spent 9.97 +/- 0.83% of the day eating, 2.11 +/- 0.42% drinking, 25.13 +/- 1.36% ruminating, 16.97 +/- 1.42% in other activities such as social behavior and self-grooming, and the rest of the day (45.82 +/- 2.55%) resting or doing no chewing activities. Eating, drinking, and social behaviors were performed while standing (P < or = 0.01), whereas resting and ruminating occurred mainly while lying (P = 0.001). Eating took place mainly in the first 4 h after feeding (P = 0.001), whereas ruminating occurred mainly at night (P = 0.001). When chewing activities (eating and ruminating) were expressed per kilogram of DM or NDF from roughage intake, more time (P = 0.004) was spent chewing per kilogram of DMI for barley-based diets, and per kilogram of NDF from roughage intake for barley- (P = 0.01) and SFM- (P = 0.002) based diets. Tethered heifers fed the more fermentable and rapidly synchronized diet (barley-SFM) reduced intake and increased chewing time. With these high-concentrate diets, time spent chewing was inversely related to roughage intake.