Effects of monensin on voluntary intake, eating and ruminating behavior and ruminal motility in heifers fed corn silage

Eating and ruminating behavior and associated ruminal motility of six heifers (1/4 Brahman X 1/4 Jersey X 1/2 Angus, 290 kg average weight) given ad libitum access to corn silage with or without 100 mg monensin X head-1 X d-1 were examined according to a two-period crossover design. There was no effect (P greater than .05) of monensin on level of intake, daily and unitary eating, ruminating and masticating times [min X g dry matter-1 X (kg body weight X 75)-1], duration or number of these activity periods, duration of main meals or latency time for onset of rumination following cessation of main eating activities. With the monensin treatment, daily numbers of normal boli and total boli were decreased (P less than .05) and mean duration of one rumination bolus cycle was longer (P less than .05). Analysis of covariance indicated relationships between intake of corn silage and duration of the main morning meal, duration or number of rumination boli and total ruminal contractions were affected (P less than .01) by monensin. Frequency and unitary number of strong cranio-dorsal ruminal contractions were similar for both treatments. During eating, number of contractions per minute was about twice (2.55/min) that during idling and rumination activity (1.43/min and 1.22/min, respectively). The unitary daily number of contractions was negatively (P less than .05) related to level of intake. Total daily ruminal contractions were slightly reduced (-3.96%, P greater than .05) by monensin. Results are interpreted to suggest that monensin indirectly affects rumination through a lowered motility and thereby affects turnover, gut fill and intake.     

Effects of methionine hydroxy analog on voluntary intake, digestibility, nitrogen balance, and chewing behavior in sheep fed grass silage

Voluntary intake, digestibility, N balance, and chewing behavior of six 6-mo-old (young) and six 30-mo-old (mature) Texel wethers (32.6 and 83.1 kg average BW) given ad libitum access to grass silage and 100 g of top-dressed soybean meal with or without 5 g of methionine hydroxy analog (MHA) in the acid form were examined according to a two-period crossover design. Supplementation level of MHA in the acid form corresponded to .32 and .16 g of MHA/kg BW.75, respectively, in young and mature wethers. There was no effect (P greater than .10) of MHA on mean voluntary DMI. Methionine hydroxy analog supplementation increased (P less than .02) digestibility of DM, OM, and CP by young wethers but not (P greater than .18) by mature wethers. The MHA decreased eating time (P less than .03) in both young and mature wethers and intake level (P = .01) in young wethers during the first 1.5 h of access to grass silage. With MHA, both age groups increased (P less than .05) the daily number of meals and decreased (P less than .02) the mean duration of each meal. There was no effect (P greater than .06) of MHA on daily and unitary eating, ruminating, and masticating times; however, mean duration of consecutive rumination bolus cycles was longer (7.2%; P = .01) in young wethers. Young vs mature sheep ate more (53.4 vs 39.3 g of DM/[d.kg BW.75]; P less than .001) and had shorter unitary mastication times (P = .001). Results suggest that, depending on its relative level of supplementation, MHA in the acid form could act through both palatability and effects on ruminal metabolism.     

Site and extent of neutral detergent fiber digestion, efficiency of ruminal digesta flux and fecal output as related to variations in voluntary intake and chewing behavior in heifers

Six heifers (1/4 Brahman x 1/4 Jersey x 1/2 Angus, 290 kg avg wt) with ruminal, duodenal and ileal cannulas were given ad libitum access to a corn silage-based diet with or without 100 mg monensin.hd-1.d-1 in a two-period crossover design. There was no significant effect of monensin on voluntary intake (VI), flow of NDF to the abomasum, fecal output or the efficiency of transfer of NDF to the duodenum (unitary fluxes of NDF through the reticulo-omasal orifice, number.g NDF.(kg BW.75)-1). Monensin increased extent of NDF digestion (NDFD) in the dorsal (P = .07) and ventral (P = .09) ruminal sac. As a fraction of the total tract NDFD, NDFD increased progressively in dorsal rumen (.214), ventral rumen (.548) and duodenal (.818) sites. The VI among individual heifers was negatively related to unitary fluxes of NDF through the reticulo-omasal orifice (P = .001) and to the extent of digestion of potentially digestible NDF (PDNDFD) in the ventral rumen (P = .006) and duodenum (P = .032), but not in the dorsal rumen (P = .720) or in the total tract (P = .785). Fecal output of NDF was negatively related to unitary times of eating (P = .027), ruminating (P = .001), masticating (P = .001) and unitary number of rumination boli (P = .001). These relationships all were influenced (P = .001) by individual heifer.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intake of direct cut or wilted grass silage as related to chewing behavior, ruminal characteristics and site and extent of digestion by heifers

Six nonpregnant Friesian heifers (516 kg avg BW) with ruminal and duodenal cannulas were used to examine intake of direct cut (DC) or wilted (W) grass silage in relation to chewing behavior, ruminal characteristics and site and extent of digestion. Dry matter content of the silages was 20.3% and 40.3%, and feed intake averaged 1.88% and 2.17% of BW (P less than .01), respectively. Mean ruminal osmolality was 291 mosm/liter for the DC and 318 mosm/liter for the W silage (P less than .05), with extreme values exceeding 350 mosm/liter for the W silage at 1 h to 2 h postfeeding. There was a shift from eating to ruminating on W silage associated with a longer duration of the average rumination bolus cycle (P less than .01). Duration of chewing time per kilogram of DM intake was 103.5 min and 91.7 min (P less than .05) for the DC and W silages, respectively. Fecal mean particle length was 2.2 times greater (P less than .01), accompanied by higher spread coefficients (P less than .001), for the W silage. No differences occurred between silages in ruminal digestibility of OM and NDF. In the total digestive tract, apparent digestibilities of OM and NDF were depressed after wilting grass prior to ensiling (P less than .01), but the proportion of digestible OM apparently digested in the rumen was .74 for both silages.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intake and chewing behavior of steers consuming switchgrass preserved as hay or silage

Effect of preservation method on intake and chewing behavior was examined using a first, late vegetative harvest (mid-June) of Kanlow switchgrass (Panicum virgatum L.). For silage (S), forage was harvested with a commercial field chopper (1.5 to 4 cm average chop length) and ensiled directly in silos 1.2 m in diameter and 3.6 m in height. For hay (H), forage was harvested with a flail-chopper (7 to 15 cm average chop length) and cured as hay in a drier at 77 degrees C. Diets of H and S were fed to six Hereford steers (338+/-5 kg) in a single crossover experiment. Chewing behavior was monitored for 4 d with a computerized system. At feeding, H was higher in DM and contained greater concentrations (DM basis) of NDF, CP, and hemicellulose, but lower concentrations of ADF and cellulose, and had lower in vitro DM disappearance values. Steers fed S had higher intakes of DM (P < .02) and NDF (P < .04) and consumed less water from the water supply (P < .01) than animals fed H. However, total amount of water (from water supply and feed) consumed per kilogram of DMI did not differ between diets. Crude protein intake was similar between diets. Preservation method had no effect on eating time, number of boli ruminated, bolus duration, and number of rumination chews per bolus. Steers fed S made fewer eating chews (P < .10) and ruminated for a longer time (P < .05) while making a greater number of rumination chews (P < .04) than steers fed H. Rumination intercycle time was slightly shorter in steers fed H (P < .05) than in steers fed S. When expressed per kilogram of NDF intake, steers fed S spent less time eating (P < .03) and made fewer eating chews (P < .02) than steers fed H; however, rumination time, number of rumination chews, and number of boli ruminated were not affected by preservation method. Steers fed S ingested feed at a greater rate (P < .03), excreted smaller fecal particles (P < .03), had meals of shorter duration (P < .06), spent less time eating during main meals (meals following feed distribution: P < .05), had more rumination periods (P < .01), and a shorter morning (P < .06) latency time (interval between end of main meal and onset of rumination) than steers fed H. These results indicate that preservation method with its concomitant differences in chop length affected forage chemical composition and voluntary intake, and that differences in chewing behavior occurred mostly during eating.     

Quantitative analysis of nycterohemeral eating and ruminating patterns in heifers with different voluntary intakes and effects of monensin

The nycterohemeral pattern of eating and ruminating behavior was examined in six heifers given ad libitum access to a corn silage-based diet with or without 100 mg monensin.hd-1.d-1 in a two-period crossover design. Rhythm components (no. of cycles/24 h) were characterized by the finite Fourier transform of 24-h mastication activities series measured over 7 d. Analysis of variance of the daily mean of hourly activities and rhythm components 1 to 12 showed significant effects of heifer (H), monensin treatment (T), period (P) and T x P x H interactions. A reparameterization of the finite Fourier transform yielded the amplitude and the phase for each rhythm component and allowed the plot of periodograms and phase diagrams, respectively. Rhythm components 1, 2 and 3 contributed primarily in explaining the total dispersion of 24-h eating and ruminating mastication series. The major effect of monensin was to increase the phase at rhythm component 1, delaying by 1 h in the onset of rumination after the morning feeding. Heifer effects were significant and appeared related to variations in daily voluntary intake (VI) of individual heifers. Heifer 5, with the largest VI, had two main eating periods and the highest rate of eating. Heifer 4, with the smallest VI, partitioned mastication activity throughout the day into four main eating and ruminating periods. Differences among animals in their nycterohemeral chewing behavior patterns may be related to differences in forestomach structure associated with a larger VI capacity by animals having mastication rhythm components 1 and 3.     

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

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.     

Effects of feeding frequency on intake, ruminal fermentation, and feeding behavior in heifers fed high-concentrate diets

Four ruminally fistulated Holstein heifers (BW = 385 +/- 6.2 kg) were used in a 4 x 4 Latin square experiment to determine the effect of feeding frequency on intake, water consumption, ruminal fermentation, and feeding and animal behavior. The treatments consisted of different feeding frequencies: a) once daily (T1); b) twice daily (T2); c) 3 times daily (T3); and d) 4 times daily (T4). Heifers were offered ad libitum access to concentrate and barley straw. Feeding frequency did not affect DMI (P >0.10), but water consumption tended to increase linearly as feeding frequency increased (P = 0.08). Average ruminal pH was not affected (P >0.10) by feeding frequency, but at 12 h after feeding ruminal pH was greater for T2 than for the other treatments. Total VFA concentration and VFA proportions were not affected (P >0.10) by feeding frequency, except valerate proportion, which increased linearly (P = 0.05) as feeding frequency increased. The concentration of ammonia-N was affected (P <0.05) cubically as feeding frequency increased (greatest for T3 = 9.3 mg of N/100 mL; lowest for T2 = 7.2 mg of N/100 mL). Feeding frequency had no effect on daily percentages of behavioral activities (P >0.05), except for observational behavior, for which there was a linear decrease as feeding frequency increased (P = 0.02). Heifers spent the same time on chewing activities, independent of feeding frequency. However, meal criteria tended to be affected (P = 0.07) by feeding frequency, with T2 (39.4 min) showing the longest intermeal interval. Total daily meal time, meal frequency, and meal size were not affected by feeding frequency (P >0.10), whereas meal length and eating rate showed cubic tendencies (P = 0.10 and P = 0.06, respectively) as feeding frequency increased. These results suggest that in the present experimental conditions, with heifers fed high-concentrate diets and with noncompetitive feeding, a smaller range of ruminal pH values was observed when feed was offered twice daily. Although heifers spent the same time on chewing activities, more stable ruminal conditions were probably achieved by feeding twice daily due to the rumination pattern, which was more constant during daytime in T2 than in T1. Moreover, when daytime and nighttime ruminating activity were analyzed separately, this activity was different in T1 (17.3 vs. 30.8%, respectively; P <0.05) but not in T2 (21.5 vs. 28.0%, respectively; P >0.05).     

Effects of dietary phosphorus, soil ingestion and dietary intake level on performance, phosphorus utilization and serum and alimentary tract mineral concentrations in lambs

Two experiments were conducted with lambs fed concentrate-based diets to study the effects of dietary P and soil ingestion on performance, P utilization and mineral composition of serum and alimentary tract contents. In Exp. 1, 20 wether lambs were fed diets for 21 d in a 2 X 2 factorial arrangement of treatments with .2 or .3% total dietary P and O or 9% added Florida Ultisol (highly weathered soil with high P-fixation capacity) containing 4,600 and 6,400 mg/kg total Al and Fe, respectively. True P absorption increased (P less than .05) from 30 to 42% and from 37 to 54% when soil was added to the basal and high P diets, respectively. In Exp. 2, 24 wether lambs were assigned randomly to a 2 X 2 X 2 factorial arrangement of treatments. Lambs were fed during a 70-d period using diets described previously on either a restricted or an ad libitum basis. Soil increased Fe concentration in ruminal fluid (P less than .05) and ash percentage (P less than .001) in ruminal solids and feces. Aluminum concentration in ruminal solids and feces and Fe in ruminal solids were increased (P less than .001) by soil addition, whereas concentrations of Ca, Mg, P, Zn, Cu and Mn in ruminal solids and feces were decreased (P less than .01) by soil addition. There were time X P interactions on serum inorganic P (P less than .01) and Mg (P less than .05) concentrations. Although high in P-fixing capacity, soil fed to lambs in these experiments improved P utilization. Lambs appeared to be able to adapt to changes in intake of dietary minerals in soil, possibly through adaptation of ruminal microflora or a redistribution of body mineral pools.     

Comparative digestion, rumen fermentation and kinetics of forage diets by steers and wethers

Four rumen fistulated wether and beef steers were used to evaluate differences in dry matter digestibility (DMD) between cattle and sheep. They were fed either perennial ryegrass or switchgrass hay at an ad libitum or restricted level for four experimental periods. Significant ruminant species X forage and ruminant species X level of intake (P less than .05) interactions were observed for digestible dry matter. The steers digested the switchgrass 7 percentage units greater than the wethers while ryegrass was digested equally. Digestibility differences between the steers and wethers were 6 percentage units at the ad libitum level of intake and 1 unit at the restricted level of intake. Crude protein digestibility tended to be greater (P less than .10) for sheep with a 7 unit difference for switchgrass and a 3 unit difference for ryegrass. The mean ruminal solids retention time of the digesta was approximately (P less than .01) 50% greater (26.0 vs 17.4 h) in cattle, with no difference in ruminal liquid dilution rate (LD) between animal species. Total ruminal volatile fatty acid concentration differed (P less than .01) with level of intake; however, no influence due to intake on the molar proportion of acetate (P greater than .10) or propionate (P greater than .10) was evident in spite of a difference (P less than .01) in LD. Rumen pH (P less than .05) and osmolality (P less than .01) were affected by both level of intake and forage, with the ryegrass and high level of intake decreasing pH and increasing osmolality.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of chewing behavior and ruminal digestion processes on voluntary intake of grass silages by lactating dairy cows

Four primiparous Holstein-Friesian cows (518 kg average BW) with ruminal and duodenal cannulas were used to examine voluntary intake of direct cut (DC) or wilted (W) grass silage in relation to ruminal characteristics and chewing behavior. Dry matter content of the silages was 17.0 and 38.1%, concentrate DM intake was restricted to 5.0 and 5.3 kg/d, and voluntary DM intake from silages averaged 7.4 and 9.5 kg/d (P = .008), respectively. The acetate/propionate ratio in ruminal fluid decreased from 4.0 on DC to 3.3 on W silage (P = .021). The protein content in milk increased from 26.3 to 27.5 g/liter (P = .042) and the protein yield from 469 to 574 g/d (P = .038). The distribution of concentrates (38% of DM intake) with a mean particle size of .04 cm reduced differences in fecal mean particle size between diets. There was a shift from eating to ruminating on W silage with regard to daily duration (min/d) and number of jaw movements (no./d). However, ruminating index (no./kg DM intake) remained unchanged, irrespective of wilting and chop length of the silages or physiological state of the animals. These results are interpreted to indicate that the time lag for functional density of feed particles in the reticulorumen to increase, as affected by ruminating activity, not rate of reduction of the particle size, limits voluntary intake of grass silage by cattle.     

Effects of cottonseed meal supplementation time on ruminal fermentation and forage intake by Holstein steers fed fescue hay.

Four ruminally cannulated Holstein steers (average BW 303 kg) were used in a 4 x 4 Latin square design digestion trial to study the influence of daily cottonseed meal (CSM; 1.6 g of CP/kg of BW) supplementation time on forage intake and ruminal fluid kinetics and fermentation. Steers were housed individually in tie stalls and were fed chopped fescue hay on an ad libitum basis at 0600 and 1400. Treatments were 1) control, grass hay only (CON) and grass hay and CSM fed once daily at 2) 0600 (EAM) 3) 1000 (MAM), or 4) 1400 (PM). Ruminal NH3 N concentrations reflected a time of supplementation x sampling time interaction (P less than .05); CON steers had the lowest (P less than .05) ruminal NH3 N concentrations at all times other than at 0600, 1000, 1200, and 2400, when they did not differ (P greater than .05) from at least one of the supplemented groups. Forage intake, ratio of bacterial purine:N, rate of DM and NDF disappearance, and ruminal fluid kinetics were not influenced (P greater than .05) by supplementation time. Total ruminal VFA differed (P less than .05) between CON and supplemented steers, as well as among supplemented steers (linear and quadratic effects P less than .05). Acetate, propionate, and valerate proportions were influenced (P less than .05) by a sampling time X supplementation time interaction. Under the conditions of this study, greater peak ammonia concentrations with morning supplementation than with afternoon supplementation did not stimulate ruminal fermentation or rate of NDF disappearance.     

The influence of timing and the addition of urea to supplements containing DL-methionine on ruminal fermentation and cow weight change in beef cows.

A study was conducted to determine an optimal time for supplementation of DL-methionine in relation to time of forage intake by mature British breed-type crossbred cows, and two other experiments were conducted to determine whether ruminal ammonia concentration limited changes in disappearance rates in situ and ruminal functions caused by supplements containing DL-methionine. Experiments 1 and 2 used 4 x 4 Latin square designs with four cows in each experiment. Treatments in Exp. 1 were no supplement (CON), DL-methionine at feeding (0800), DL-methionine 4 h after feeding (1200), and DL-methionine 7 h after feeding (1500). Treatments in Exp. 2 were .5 kg of beet pulp (CON), .5 kg of beet pulp plus 16.5 g of DL-methionine (MET), .5 kg of beet pulp plus 16.5 g of DL-methionine and 55 g of urea (METU), and .4 kg of soybean (SOY). Experiment 3 was conducted in a 326-ha pasture with treatments of no supplement (CON), .5 kg of beet pulp plus 12.5 g of DL-methionine and 30 g of urea (METU), and .4 of kg soybean meal (SOY). In Exp. 1, in situ NDF disappearance rates of cows supplemented at 1200 and 1500 were greater (P less than .01) than those of cows supplemented at 0800. In Exp. 2, ruminal ammonia concentration was greatest (P less than .001) for METU (5.2 mg/dl) and least for CON (1.5 mg/dl). Disappearance rates in situ for DM differed (P less than .01) among treatments; METU was similar (P greater than .2) to SOY but faster (P less than .01) than MET. Disappearance rates of NDF were greatest (P less than .001) for METU-supplemented cows. In Exp. 3, DM and NDF disappearance rates were faster (P less than .10) for SOY than for METU. Cow BW change was positive for METU and SOY, and decrease in condition score was least (P less than .10) for METU- and SOY-treated cows. These studies indicate favorable ruminal responses to DL-methionine supplementation; however, the response depended on time of supplementation and ruminal ammonia concentration.     

Evaluation of alfalfa-corn cob associative action. I. Interactions between alfalfa hay and ruminal escape protein on growth of lambs and steers

Three trials evaluated associative action of alfalfa in ammonia (NH3)-treated corn residue diets and(or) potential ruminal degradable protein X escape protein interactions. In trial 1, 128 crossbred steers (250 kg) were fed 0 or 3% NH3-treated residue diets replaced by 0, 15, 30 or 100% of alfalfa hay. Basal diets were formulated to contain adequate metabolizable and crude protein but were nearly devoid of ruminal degradable protein. Ammonia treatment increased (P less than .02) dry matter (DM) intake of residues. Pooled across residue treatment, intake increased linearly (P less than .01) with increased level of alfalfa. A residue treatment X level of alfalfa interaction (P less than .02) for daily gain resulted because the response to level of alfalfa was linear (P less than .01) for nontreated residues and quadratic (P less than .01) for NH3-treated residues. Similar responses (P less than or equal to .07) were found for efficiency of gain, indicating that addition of 15 or 30% alfalfa promoted greater associative action for combinations involving NH3-treated vs nontreated residues. In an in vitro trial (trial 2) with the same corn cob and alfalfa diets used in trial 1, NH3 treatment increased (P less than .01) in vitro DM disappearance and rate of cell wall digestion of corn cobs. Alfalfa had no effect on rate of nontreated cob cell wall digestion, but increased (P less than .01) the rate for NH3-treated cobs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Energy and protein supplementation of ammoniated wheat straw diets for growing steers

Eighty-eight yearling beef steers (308 +/- 1.4 kg) were used in two separate trials to determine the protein-sparing value of the N added to wheat straw during the ammoniation process and to determine the effects of supplementing ammoniated straw diets with energy and ruminal escape protein. In Exp. 1, steers were fed untreated straw (US) with either 0, 150, or 500 g of soybean meal (SBM) for 88 d. The addition of SBM to US diets increased (P less than .01) straw intake and average daily gains (ADG), indicating that N was limiting. When ammoniated straw (AS) was substituted for US, the N in the AS was used as efficiently as 500 g of SBM for growth. In Exp. 2, steers had ad libitum access to AS with three levels of supplemental corn (0, 1.23, or 2.45 kg DM.animal-1.d-1) either with or without .41 kg DM of corn gluten meal (CGM) added. Straw intake decreased (P less than .01) as the amount of corn in the diet was increased, but ADG increased (P less than .01) with the addition of corn. Straw consumption was not altered by the addition of CGM, but ADG was increased (P less than .01) by an average .35 kg by CGM. Rumen and blood N components indicated that the N from AS was contributing to the ruminal N pool and that CGM was compensating for microbial protein deficiencies postruminally.     

Time of daily supplementation for steers grazing dormant intermediate wheatgrass pasture.

To compare the effects of time of daily protein supplementation on grazing behavior, forage intake, digesta kinetics, ruminal fermentation, and serum hormones and metabolites, 12 ruminally cannulated Holstein steers (449 and 378 kg average initial and final BW, respectively) were allotted to three groups. Treatments consisted of CON = no supplement, AM = cottonseed meal (.25% of BW) at 0600, and PM = cottonseed meal (.25% of BW) at 1200. Steers grazed a dormant (1.1% N) intermediate wheatgrass (Thinopyrum intermedium Host) pasture. Sampling trials occurred in December, January, and February. Supplementation altered (P = .01) time spent grazing; CON steers grazed approximately 1.5 h longer than supplemented steers. Supplemented steers lost less (P = .02) BW (-40 kg) than CON steers (-75 kg) did. Supplementation did not alter (P greater than .15) forage OM intake; however, total OM intake was greater (P = .01) for supplemented steers (22.3 g/kg of BW) than for CON (18.4 g/kg of BW) steers. Supplementation did not affect (P greater than .15) digesta kinetics. Extent of in situ NDF (96 h) and rate (%/h) of disappearance for supplemented steers was greater (P = .01) than for CON steers. Across all periods, ruminal NH3 N and total VFA concentrations were lower (P = .01) for CON steers than for supplemented steers. Serum insulin (ng/mL) concentration was lower (P = .03) and concentration of serum growth hormone (ng/mL) was higher (P = .02) for CON steers than for supplemented steers. Cottonseed meal supplementation enhanced utilization of intermediate wheatgrass; however, supplementation time had minimal effects on the variables measured.     

Effects of forage source and particle size on chewing activity,ruminal pH,and saliva secretion in lactating Holstein cows

The present study investigated the effects of dietary forage source (quality) and particle size on chewing activity, saliva secretion, and ruminal pH. Twelve multiparous lactating Holstein cows, four of which were ruminally cannulated, were used in a replicated 4 × 4 Latin square experimental design with a 2 × 2 factorial arrangement of treatments. Cows fed wild‐rye hay diets had longer daily eating times than cows fed oaten hay diets. Treatments had no effect on ruminating time; therefore, resting time varied inversely to eating time. Neither the rate nor the amount of saliva secretion while eating, ruminating, or resting was affected by diet, resulting in similar total daily saliva secretions across treatments (231 L/day). Total volatile fatty acids (VFAs) in the ruminal fluid from animals fed oaten hay diets were higher than those from animals fed wild‐rye hay diets; further, VFAs increased with decreasing forage particle size (FPS). Consistent with elevated VFA concentrations, reducing FPS and including oaten hay in the diet decreased mean ruminal pH and increased the daily time of ruminal pH under 5.8. Results of this study suggest that forage source and particle size affect ruminal pH might be via variations in VFA production rather than increased salivary recycling of buffering substrates.     

Steam-rolled wheat diets for finishing cattle: effects of dietary roughage and feed intake on finishing steer performance and ruminal metabolism

Two experiments were conducted to determine the influence of dietary roughage concentration and feed intake on finishing steer performance and ruminal metabolism. In Exp. 1, 126 steers (334 kg) were used in a completely randomized design and fed (120 d) diets of steam-rolled wheat without roughage or containing 5, 10 or 15% roughage (50% alfalfa hay:50% corn silage). Steers fed 5 or 10% roughage gained faster (quadratic, P less than .05) and were more efficient (quadratic, P less than .05) than steers fed 15% or no roughage. In Exp. 2, six ruminally cannulated steers (447 kg) were used in a 6 x 6 latin square design and fed (twice daily) diets of steam-rolled wheat without roughage or containing 5 or 15% alfalfa hay at twice or three times NE required for maintenance. Increasing dietary roughage increased (linear, P less than .01) ruminal liquid passage 38%, indigestible ADF passage 63%, Yb-labeled wheat passage 75% and fiber fill 31%. The rate of in situ starch digestion tended to increase (linear, P = .16), and ruminal VFA concentration was 40 mM higher (P less than .01) at 4 h after feeding with increased roughage. Increased feed intake increased (P less than .05) ruminal starch fill, fiber fill, liquid fill and liquid passage 23%, Yb-labeled wheat passage 50% and Dry-labeled hay passage 20%. It reduced protozoa five- to sixfold (P less than .01) but doubled total bacterial counts (P less than .01). Ruminal NH3N was lower (P less than .01) and total VFA concentration was 50 mM higher (P less than .01) at 4 h after feeding. The acetate:propionate ratio was reduced from 2.3 to 1.3 (P less than .01) with increased intake. Adding roughage to a steam-rolled wheat diet increased passage and tended to increase rate of starch digestion; increased feed intake with its associated effects on ruminal fill and passage dramatically shifted the microbial population and fermentation end products.     

Effect of faunation on ruminal solubility and liver content of copper in sheep fed low or high copper diets

Naturally fauna-free crossbred rams approximately 5 mo old, 49.3 +/- 1.88 kg live weight, were allotted to four groups. Two groups remained fauna-free, whereas the other two groups were faunated. A diet based on corn silage-soybean meal containing either a low or a high Cu concentration (7 or 15 micrograms/g dry matter) was fed ad libitum to the two groups for 197 d. The rams were killed at the end of the experiment and livers and ruminal contents were analyzed for Cu. Faunated sheep grew faster (P less than .01) and as a group consumed 1.53 kg diet dry matter daily compared with 1.34 for the fauna-free sheep. Faunated sheep had lower final liver Cu concentrations (P less than .01), total liver Cu per unit of Cu intake and ruminal Cu solubilities (P less than .01) when fed both low and high Cu diets. The relative hepatic Cu uptake was higher by rams fed the low Cu than by those fed the high Cu diet. The results are interpreted to show that faunation decreased the availability of Cu in sheep fed a corn silage-soybean meal diet. The magnitude of the effect was independent of the Cu concentration in the diet.     

Influence of cottonseed meal supplementation on voluntary intake, ruminal and cecal fermentation, digesta kinetics and serum insulin and growth hormone in mature ewes fed prairie hay

To determine the influence of protein supplementation on intake and fermentation of low-quality hay, six ruminal- and cecal-cannulated Rambouillet ewes (avg wt 43.6 kg) in a crossover design were given ad libitum access to prairie hay with or without 80 g of cottonseed meal (CSM) X head-1 X d-1. Voluntary hay intake was measured the last 7 d of each 18-d period. Ruminal, cecal and blood samples were collected at 0, 1 (except cecal), 3, 6, 9, 12, 15, 18, 21 and 24 h post-supplementation on d 14 of each period to measure fluid dilution rate, fermentation characteristics and serum concentrations of insulin and growth hormone. An intraruminal dose of Yb-labeled hay, followed by fecal sampling on d 15 through 18, was used to measure particulate passage rate. Voluntary intake of prairie hay was increased (P less than .04) from 23.7 to 28.3 g/kg of body weight by CSM supplementation. Particulate passage rate constants did not differ (P greater than .15) between supplemented (3.76%/h) and control (3.72%/h) ewes, and total mean retention time was not altered (P greater than .15) by CSM supplementation. Ruminal retention time of particulates did not differ (P greater than .15) between treatments; however, intestinal transit time was faster (P less than .03; 18.1 vs 22.6 h) in supplemented than in control ewes. Estimated gastrointestinal dry matter fill was greater (P less than .05; 14.3 vs 12.9 g/kg body weight) in supplemented ewes. Ruminal fluid volume did not differ (P greater than .15) between treatments; however, supplemented ewes tended to have faster fluid dilution rates (P less than .14) and fluid outflow rates (P less than .11) than control ewes. Cecal fluid volume, dilution rate and outflow rate did not differ (P greater than .15) between groups. Ruminal and cecal pH and total volatile fatty acids were similar between treatments. Similarly, cottonseed meal supplementation did not affect (P greater than .15) ruminal or cecal ammonia concentrations. Molar proportions of ruminal and cecal individual fatty acids were not affected (P greater than .15) by CSM supplementation. Feeding cottonseed meal increased (P less than .05) serum insulin, decreased (P less than .07) serum growth hormone and increased (P less than .06) serum free fatty acids, but did not influence (P greater than .15) either serum urea N or glucose concentrations. Cottonseed meal supplementation in ewes fed prairie hay caused increased hay intake but had minimal effects on ruminal and cecal fermentation.