Indigestion in young calves. IV. Lesions of ruminal papillae in young calves fed barley and barley plus hay.

Fiftysix calves, in 2 similar experiments, were given 1 of 4 diets including a high lactose milk replacer: ground barley (GB), ground barley plus coarse hay (GB + GH), coarse hay (CH) and the liquid diet only (NS) ; the 2 last diets were held as controls. The calves were on the experimental diet from 1–2 weeks of age until slaughtered at 7-8 weeks of age. As observed by stereo-microscopy, the ruminai papillae in calves fed on GB were thickened, mostly finger- or club-shaped and sometimes nodular; nodular papillae were always arranged on prominent mucosal folds. Scattered nodular papillae had white coats. For calves fed on GB + CH the papillae were mostly finger- or tongue-shaped. Histologically papillae in calves fed on GB had hyperplasia of secondary papillae and epithelial layers. Microabscesses associated with penetrating hairs were frequent, and some calves had dyskeratosis with infiltration of polymorphonuclear leucocytes at the apex of papillae, identified as the white coats. For calves given GB+CH, abscesses and apical dyskeratosis were absent and the hyperplasia of epithelial layers milder than in the case of the GB diet. An ameliorative effect of hay on papillary changes caused by barley is indicated.     

Effect of diet composition and feed intake level on diet digestibility and ruminal metabolism in growing lambs.

Lambs (29 +/- 2.5 kg) were fed three diets at various intakes to determine whether diet composition or level of intake was reflected in changes in diet digestibility or ruminal fluid characteristics. In Exp. 1, a 90% concentrated, pelleted diet or a whole shelled corn diet with a pelleted protein supplement was fed at three levels of intake: ad libitum and 92.5 and 85% of ad libitum (n = 15). Exp. 2 compared the 90% concentrate diet with diets in which the energy density was diluted to 55 or 72.5% concentrate by including alfalfa hay as a possible method of restricting energy intake (n = 6). Lambs were adapted to diets for 13 d; feces were collected for 6 d and ruminal fluid was collected 0, 3, and 6 h after feeding on the day following fecal collection. Restricting intake in Exp. 1 did not affect DM digestibility or digestibility of CP or starch. Digestibility of ADF was increased (P less than .10) by restricting intake. Ruminal fluid pH, ammonia concentration and VFA concentrations were affected little by either restricted intake level. Digestibility of DM was 4% higher (P less than .001) and starch 5% higher (P less than .001) for the whole shelled corn diet than for the pelleted, high-concentrate diet. Ruminal pH of lambs fed the whole shelled corn diet was higher and fluctuated less than the ruminal pH of lambs fed the high-concentrate, pelleted diet. In Exp. 2, diet digestibility was reduced (P less than .01) and ruminal pH was increased (P less than .002) by addition of hay. Restricted feeding of lambs did not seem to increase diet digestibility or alter ruminal conditions.     

Digestion, feed intake, and live weight gain by cattle consuming bermudagrass hay supplemented with whey.

Three experiments were conducted with cattle consuming bermudagrass hay to determine whether low-level supplements of whey alone, corn alone, or whey plus corn affect feed intake, digestion, and(or) BW gain. Six ruminally and duodenally cannulated beef cows (574 kg), used in a Latin-square trial (Exp. 1), were fed bermudagrass hay without supplementation (control) or with 2.8% whey (low whey, LW), 5.6% whey (high whey, HW), 17.4% ground corn (C), 2.8% whey plus 14.9% corn (C-LW), or 5.6% whey plus 12.4% corn (C-HW). Supplementing with whey and(or) corn increased ruminal butyrate (8.8, 9.4, 10.0, 9.6, 10.5, and 11.0 mol/100 mol of total VFA for control, LW, HW, C, C-LW, and C-HW, respectively; SE = .20). Supplements did not affect microbial N flow at the duodenum. Six Holstein steer calves (158 kg) in a Latin square (Exp. 2) consumed bermudagrass hay ad libitum alone (control) or with .075 or .15% BW whey (LW and HW, respectively), .5% BW ground corn (C), or corn-whey mixes made by substituting whey for corn (C-LW and C-HW). Substituting .15% BW of whey for corn increased (P less than .05) total OM intake slightly (3.99, 3.84, 3.75, 4.11, 4.28, and 4.47 kg for control, LW, HW, C, C-LW, and C-HW, respectively; SE = .10). In an 84-d randomized block experiment (Exp. 3), 96 beef calves (194 kg) consumed (ad libitum) low-quality bermudagrass hay alone or with C, LW, HW, C-LW, or C-HW supplements.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of wet corn gluten feed and intake level on diet digestibility and ruminal passage rate in steers

Twelve ruminally cannulated Jersey steers (BW = 534 kg) were used in an incomplete Latin square design experiment with a 2 x 2 factorial arrangement of treatments to determine the effects of wet corn gluten feed (WCGF) and total DMI level on diet digestibility and ruminal passage rate. Treatments consisted of diets formulated to contain (DM basis) steam-flaked corn, 20% coarsely ground alfalfa hay, and either 0 or 40% WCGF offered once daily for ad libitum consumption or limited to 1.6% of BW (DM basis). Two consecutive 24-d periods were used, each consisting of 18 d for adaptation, 4 d for collection, and a 2-d in situ period. Rumens of all steers were evacuated once daily at 0, 4, 8, and 12 h after feeding. Chromic oxide (10 g/[steer*d]) was fed as a digestibility marker, and steers were pulse-dosed with Yb-labeled alfalfa hay to measure ruminal particulate passage rate. Dacron bags containing 5 g of steam-flaked corn, WCGF, or ground (2-mm screen) alfalfa hay were placed into the rumens of all steers and removed after 3, 6, 12, or 48 h. Wet corn gluten feed increased percent apparent total-tract digestion of OM (P < 0.01), NDF (P < 0.01), and starch (P < 0.03), decreased (P < 0.01) ruminal total VFA concentration, increased (P < 0.01) ruminal NH3 concentration, and increased (P < 0.01) ruminal pH. Wet corn gluten feed also increased (P < 0.01) ruminal passage rate of Yb. Limit feeding decreased (P < 0.01) percent apparent total-tract digestion of both OM and NDF, ruminal total VFA concentration (P < 0.01), and ruminal fill (P < 0.01), but increased (P < 0.01) ruminal NH3 concentration. Apparent total-tract digestion of starch was not affected (P = 0.70) by level of DMI. A DMI level x hour interaction (P < 0.01) occurred for ruminal pH. Limit feeding increased ruminal pH before and 12 h after feeding, but decreased ruminal pH 4 h after feeding compared with diets offered ad libitum. A diet x DMI level interaction (P < 0.02) occurred for in situ degradation of alfalfa hay, with dietary addition of WCGF increasing (P < 0.02) the extent of in situ alfalfa hay degradation in steers fed for ad libitum consumption. This study suggests that WCGF increases OM and NDF digestion, and that limit feeding diets once daily might depress OM and NDF digestion, possibly due to decreased stability of the ruminal environment.     

Effect of intake level and alfalfa substitution for grass hay on ruminal kinetics of fiber digestion and particle passage in beef cattle

Two experiments were conducted to evaluate digestion kinetics of alfalfa (Medicago sativa L.) substitution for grass hay in beef cattle. In Exp. 1, forage combinations evaluated in situ consisted of 0% alfalfa-100% big bluestem (Andropogon gerardi Vitman), 25% alfalfa-75% big bluestem, 50% alfalfa-50% big bluestem, and 100% alfalfa-0% big bluestem. Nonlinear regression was used to determine the immediately soluble fraction A, the potentially degradable fraction B, the undegraded fraction C, and the disappearance rate of DM and NDF. Dry matter fraction A increased linearly (P = 0.03), and DM and NDF fraction B decreased linearly (P = 0.01) with increasing alfalfa substitution. Rate of DM and NDF disappearance increased linearly (P /= 0.23) on total tract apparent digestibility of all nutrients except CP. Steers fed orchardgrass plus alfalfa had 33% greater (P = 0.01) total tract apparent digestibility for CP than those fed orchardgrass alone. Lag time of DM and NDF disappearance was not affected (P >/= 0.20) by alfalfa supplementation or intake level. Rate of DM and NDF disappearance of orchardgrass was faster (P 相似文献   

Ruminal microbial development in conventionally or early-weaned calves

Eight bull calves (four Holsteins and four Ayrshire calves with mean birth weight of 38.8 kg) were ruminally cannulated at 3 d of age and allocated to one of two weaning programs. All calves were fed colostrum for 3 d after birth and milk until weaning. Calves in the conventional-weaning program were fed a starter diet from 3 d of age and weaned at 6 wk of age. In the early-weaning program, calves were fed a highly palatable pre-starter diet from 3 d of age until they consumed 227 g/d, and then fed a mixture of pre-starter (227 g) and starter diet ad libitum. Calves in this group were weaned at 4 wk of age. Ruminal samples were collected at 3 and 7 d, then weekly thereafter through 8 wk and at 10 and 12 wk of age to assess microbial activity. Calves in the early-weaned group had a higher concentration of total ruminal volatile fatty acids at an earlier age than the calves in the conventional-weaning program. This was accompanied by a trend toward higher lactate concentrations and lower ruminal pH in the early-weaned group during their first 4 wk of age. Lactate and ammonia concentrations decreased with calf age. The total anaerobic bacterial counts increased slightly with calf age, whereas Streptococcus bovis and facultative bacterial populations decreased with calf age. Amylolytic, proteolytic, lactobacilli, lactate-utilizers, cellulolytic and methanogenic bacterial populations increased progressively in both groups. Cellulolytic and methanogenic bacteria were present in both groups at 3 d of age. No protozoa were detected in calves of either group. In general, the most significant changes in bacterial populations and metabolic activity in both groups occurred between 4 and 6 wk of age. Although calves in both groups had similar patterns of bacterial development, calves in the early-weaning program tended to have high ruminal microbial activity at an earlier age than the conventionally weaned calves.     

Effects of source and level of dietary neutral detergent fiber on feed intake, ruminal fermentation, ruminal digestion in situ, and total tract digestion in beef cattle fed pelleted concentrates with or without supplemental roughage.

The effects of source and level of dietary NDF on intake, ruminal digestion in situ, ruminal fermentation, and total tract digestion were evaluated in Hereford steers using a replicated 5 x 5 Latin square design. Diets contained 62 to 64% TDN and included 1) 80% control concentrate (contained pelleted ground grains) and 20% timothy hay (traditional diet), 2) 80% control concentrate and 20% alfalfa cubes, 3) 90% control concentrate and 10% cubes, 4) a completely pelleted diet using corn cobs as the primary NDF source, and 5) 80% textured (rolled instead of ground grains) concentrate and 20% hay. Dry matter intake differed (P less than .05) between the traditional and cube diets due to limited acceptance of alfalfa cubes. Increased (P less than .05) ruminal osmolality, total VFA, and NH3 N and lower (P less than .01) ruminal pH in steers fed corn cob and cube diets relative to steers fed the traditional diet were due to preferential consumption of concentrate over supplemental roughage and the resultant rapid fermentation of concentrates. Potentially degradable DM in the traditional diet exceeded (P less than .06) all other diets, resulting in the increased (P less than .10) extent of DM disappearance despite a slower (P less than .05) rate of DM disappearance. Rate of NDF disappearance and all in situ starch disappearance parameters were similar between the traditional, corn cob, and cube diets. All ruminal digestion parameters involving NDF disappearance were similar between hay diets and between cube diets, whereas rate and extent of starch disappearance differed (P less than .05) between hay diets. Although formulation of diets with different sources of dietary NDF did not affect total tract digestion of nutrients, nutrient availability and ruminal fermentation were altered due to dietary differences in sources of dietary NDF and preferential selection of feedstuffs by steers.     

Effects of restricted and ad libitum intake of diets containing wheat middlings on site and extent of digestion in steers

A 5 x 5 Latin square design was used to determine the effects of restricted and ad libitum intake of diets containing wheat middlings on the site and extent of digestion compared to ad libitum intake of a corn-based diet and ad libitum intake of chopped alfalfa hay. Five ruminally and duodenally cannulated Angus steers (519 +/- 41.5 kg BW) were used to compare five dietary treatments. The five treatments were as follows: ad libitum access to a corn-based finishing diet (control), the control diet with 25 percentage units of the corn and soybean meal replaced with wheat middlings offered ad libitum (WM), the WM diet restricted to 75% of predicted ad libitum intake (RWM), the RWM diet with wheat middlings replaced with ammoniated wheat middlings (RNWM), and ad libitum access to a chopped alfalfa hay diet. Although RWM steers were fed to consume 75% of ad libitum intake, RWM steers consumed 15.5% less DM than WM. Steers fed ad libitum hay consumed 28.6, 31.7, and 37.2% less (P < 0.01) DM, OM, and nitrogen than RWM steers. No differences in apparent or true ruminal digestibility were observed among steers fed the control vs WM, WM vs RWM, RWM vs RNWM, or RWM vs hay diets. However, the steers fed the hay diet had 32.5, 33.4, and 36.9% lower (P < 0.01) apparent total tract digestibilities of DM, OM, and N than those fed the RWM diet. Average ruminal pH was lower (P < 0.01) for control steers than those fed the WM diet and for those fed RWM compared to the hay diet. The acetate:propionate ratio was higher for cattle fed hay vs the RWM diet. Microbial DM and OM flow to the small intestine was higher (P < 0.02) for steers fed the RWM diet than those fed the hay diet. In addition, bacterial N flow to the small intestine was higher (P < 0.01) for cattle receiving the RWM diet than the hay diet. Feeding diets containing 25 percentage units of wheat middlings at 75% ad libitum intake had no effect on ruminal digestibility.     

Effect of monensin on rumen fermentation and performance of young calves

The effect of monensin on the growth and rumen metabolism of young calves (30 days old initially) was followed in 70-day experiment. Calves diet consisted of a milk substitute (4 1 per day), a concentrate mixture (13 g per 1 kg of live weight per day) and meadow hay ad libitum. Ten calves were fed 0.65 mg of monensin (SPOFA, Czechoslovakia) per 1 kg of live weight per day. Ten calves served as a control. The non-glucogenic/glucogenic ratio of VFA, mol-% acetate and butyrate were significantly lower and propionate higher in monensin-treated calves. Monensin-fed calves gained non significantly more (+ 7.2%) than control calves. A possible mode of action of monensin in young calves is discussed.     

Effects of receiving and growing diets on compensatory gains of stressed calves

Three hundred seventy-seven male stocker calves were used to study the effects of three receiving diets, two growing-finishing diets and two levels of shipping shrink on compensatory gains during the post-receiving feeding period. Calves received on a 75% concentrate diet gained 19 kg more during the first 42 d than those received on hay plus .91 kg daily of protein supplement (P less than .01). Calves received on hay plus protein supplement gained 11 kg more than the calves received on hay alone during the same period (P less than .01). When calves were fed an 85% concentrate diet throughout finishing, there was no difference in the rate of compensatory gain made by calves fed hay alone or hay plus protein supplement. Neither of the latter two groups completely compensated for the slow rates of gain made during receiving. When calves were fed a 50% concentrate growing diet from the end of the receiving period to a body weight of 272 kg then finished on an 85% concentrate diet, those received on hay alone lacked only 1 kg of compensating fully for the low gains of the receiving period. However, this procedure had no effect on the compensatory gains of those received on hay plus protein supplement. High-shrink calves received on hay alone or hay plus protein never compensated fully for the low gains made in the receiving period. However, with low-shrink calves, those received on hay alone fully compensated for the low gains of the receiving period and those received on hay plus protein lacked only 2 kg of making full compensation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of alfalfa-corn cob associative action. II. Comparative tests of alfalfa hay as a source of ruminal degradable protein

The effect of ruminal degradable protein source in roughage diets on nutrient digestibility and animal growth was evaluated in two trials using lambs. In trial 1, two qualities of alfalfa and smooth brome hays replaced 0, 15, 30 or 100% of an ammonia (NH3)-treated corn cob negative control diet in a digestion trial using 26 mixed breed wethers (31.8 kg). Fifteen or 30% inclusion of hay increased (P less than .01) dry matter (DM) intake, regardless of hay type or quality. Cell wall intake was highest for 100% high quality brome hay. Positive associative action on digestibility of DM and cell walls occurred with 30% of each hay tested when diets were fed ad libitum. Measured at equal intakes, DM and cell wall digestibilities were affected by forage type X level and forage quality X level interactions (P less than .01), which showed that the magnitude of associative action was greater for 30% of high vs low quality and alfalfa vs brome hay, respectively. Magnitude of associative response on cell wall digestibility was more highly correlated to degradable N (r = .88) than cell solubles (r = .64) content of hay. In trial 2, 72 young growing lambs were allotted to three sources of supplemental ruminal degradable N (NH3, casein, corn steep liquor) superimposed upon two levels of alfalfa hay (0 or 30% of diet DM). Diets containing 0% alfalfa were supplemented with ruminal escape protein equivalent to that supplied by 30% alfalfa hay.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of crabgrass (Digitaria ciliaris) hay harvest interval on forage quality and performance of growing calves fed mixed diets

Twelve 0.81-ha crabgrass (Digitaria ciliaris [Retz.] Koel.) hay fields were harvested at 21, 35, and 49 d of regrowth (average phonological growth stage of 30, 51, and 56, respectively). Increased harvest interval exhibited a linear decrease (P < 0.01) in CP (14.1, 13.7, and 10.6% of DM, respectively) and increase (P < 0.01) in NDF (65.3, 70.6, and 70.2% of DM, respectively) and ADF (35.7, 38.9, and 42.7% of DM, respectively). Hays were incorporated into 3 diets that contained 20% (DM basis) crabgrass hay, ground corn (33%), and soybean hulls (32%). Diets contained 14.4, 14.4, and 13.6% CP; 1.83, 1.72, and 1.81 Mcal of NE(m)/kg; and 1.21, 1.10, and 1.17 Mcal of NE(g)/kg; respectively. Diets were fed to beef calves in 12 pens at a rate of 2.3% (DM basis) of BW in 1 experiment (n = 120, initial BW 210 +/- 4.4 kg) and ad libitum in another experiment (n = 60, initial BW 207 +/- 4.4 kg). To measure passage rate of the hay and concentrate portions of the diets, 12 heifer calves (BW = 145 +/- 4.5 kg) were individually fed at 2.3% of BW for 14 d and dosed with Dy-labeled soybean hulls and Yb-labeled hay. In situ DM digestibility of the hays and diets were determined using 3 ruminally cannulated steers (BW = 584 +/- 10.4 kg). Harvest interval did not affect (P > or = 0.11) ADG of limit-fed calves during the diet acclimation or growing phases (average 0.32 and 0.80 kg, respectively) or ADG of calves fed ad libitum (average 1.21 kg). Dry matter intake of calves fed ad libitum averaged 7.9 kg/d (3.28% of BW) and was not affected (P > or = 0.22) by harvest interval. Gain:feed was not affected (P > or = 0.20) by harvest interval (0.13 and 0.15 for limit-fed and ad libitum-fed calves, respectively). Increased harvest interval linearly increased (P < 0.01) ruminal retention time of the hay and tended (P = 0.06) to linearly increase ruminal retention time of the concentrate portions of the diet. Harvest interval linearly decreased (P < or = 0.05) the extent of degradability and effective degradability of DM and NDF of hays, but DM disappearance of the total diet did not differ (P > or = 0.35). In the conditions of this study, increasing harvest interval of crabgrass hay from 21 to 49 d had no deleterious impact on animal performance or efficiency of gain when fed to growing calves in a high-concentrate mixture.     

Effect of diet on preweaning performance of Sahiwal calves

The objective was to study the growth potential of Sahiwal calves given milk or milk replacer with or without concentrates. For this purpose, forty-eight Sahiwal calves were divided into four groups of 12 animals each with equal sex ratio. In each group, the calves were offered either milk or a milk replacer (MR) at a rate of 10% of their body weight adjusted weekly. In addition to this, calves were fed either a starter ration plus Egyptian clover hay (SR + H) or hay only (H) until the end of trial. The milk or MR was withdrawn gradually from day 56 until animals were weaned completely by day 84. Calves offered milk grew faster than those offered MR (357 ± 9 vs. 162 ± 9 g/day; p < 0.05) and displayed higher weaning weights (51.6 ± 0.8 vs. 35.2 ± 0.8 kg; p < 0.05). The calves offered SR + H grew faster (311 ± 9 vs. 208 ± 9 g/day; p < 0.05) and displayed higher weaning weights (48.7 ± 0.8 vs. 38.1 ± 0.8 kg; p < 0.05) than those fed H alone. Calves offered milk plus SR + H showed the highest growth rate and weaning weights (401 ± 13 g/day and 56.3 ± 1 kg, respectively). The lowest growth rate and weaning weights were observed in calves offered MR and H only (115 ± 13 g/day and 30.3 ± 1 kg, respectively). Calves offered the MR had higher number of scour days than those offered milk (13.5 vs. 3.3). The feeding of whole milk in combination with the starter ration and hay resulted in superior growth rates, higher weaning weights, and healthier calves than the other feeding regimens.     

The effect of a preassembly zeranol implant and post-transit diet on the health performance and metabolic profile of feeder calves

A total 262 Angus steer calves averaging 207 kg from none (trial 1) and five farms (trial 2) were identified on the farm of origin and one-half of the calves on each farm was implanted with 36 mg of zeranol before entering the feeder calf assembly and marketing system. Calves were assembled, fasted for 24 h and fed hay for 72 h, then shipped 1,368 km. Upon arrival, the following receiving diets were fed for 4 wk to one-third of the calves from each farm and implant group: 1) control diet, 2) high-potassium diet, 3) escape-protein diet using corn gluten meal, which can escape ruminal degradation as a protein source. Implanted calves gained more weight (P less than .10) than nonimplanted calves while on the farm, but changes in weight during assembly, transit and the 28-d receiving period were not different (P more than .10). Plasma glucose and total protein concentrations were higher (P less than .05), while urea nitrogen concentration was lower (P less than .05) for implanted calves following transit. Increasing the potassium concentration of the receiving diet increased (P less than .05) post-transit weight gains, but had no affect on dry matter consumption. Corn gluten meal replaced soybean meal in the escape-protein diet and resulted in similar weight gains. Plasma urea nitrogen concentrations were higher (P less than .05) at 2 wk post-transit in the escape-protein diet group as compared with the control group. Receiving diet had no effect on the incidence or severity of bovine respiratory disease, but affected (P less than .05) performance during the subsequent 69-d stocker phase of ad libitum access to medium quality hay and 2.27 kg of supplement per day.     

Comparison of D-alanine and diaminopimelic acid as bacterial markers in young calves

D-alanine (DAL) and diaminopimelic acid (DAP) were compared as markers to estimate proportion of bacterial N in total N reaching the abomasum of young calves. Sixteen Holstein bull calves fed complete pelleted starter or unpelleted starter plus hay and weaned at 4 or 8 wk of age were fitted with ruminal and abomasal cannulas and sampled twice weekly from 2 to 11 wk of age. Isolated ruminal bacterial cells contained more DAL than DAP at all weeks and averaged 7.0 and 5.4 mg N/g N, respectively. Weekly mean marker concentrations were highly correlated (.89) in ruminal bacteria, except at 3 wk of age. Concentration of DAL in abomasal digesta was greater than that of DAP at all weeks and averaged 5.2 and 2.4 mg N/g N, respectively. Weekly mean DAL correlated with DAP .61 in abomasal digesta and correlated .57 and .89 with starter intake, respectively. The proportion of bacterial N in total abomasal N was greater at all weeks when estimated by DAL than by DAP and averaged 77% and 46%, respectively. Estimates by DAL exceeded 100% in several cases and reflected large variation in analytical estimates. Estimates by DAL and DAP correlated .33 and .92 with starter intake. D-alanine was not an acceptable bacterial marker in this study.     

Morphological and functional development of the rumen in the calf: influence of the time of weaning. 1. Morphological development of rumen mucosa.

The objective of this study was to determine whether the nutritional regimen of rearing calves would influence the morphometric and histological development of rumen mucosa. Twelve male Holstein calves 7 d of age were assigned to three groups of 4 animals each: milk group (I), early weaned (6 weeks) group (II) and late weaned (9 weeks) group (III). All animals received additional solid feed. Animals of group I were slaughtered after 6 weeks of age, whereas those in groups II and III were slaughtered after 9 weeks of age. At slaughter, the ruminal digesta amounted to 2035 g (milk group), 3092 g (late weaned group) and 5374 g (early weaned group). The differences in the ruminal molar percentage of SCFA were not significant. There was a trend for lower pH and higher SCFA concentrations in the order late weaned, early weaned and milk fed animals (pH: 6.4, 6.6 and 6.7, respectively; SCFA: 96, 87 and 77 mmol/l, respectively). The mean length (1.07 mm in milk group, 1.45 mm in late weaned group and 1.87 mm in early weaned group), width (0.43, 0.58 and 0.71 mm, respectively) and surface of papillae (190, 232 and 241 mm2/cm2 mucosa, respectively) increased with both the age of the animals and the elevated intake of solid feed, whereas the number of papillae (210, 140 and 92 per cm2 mucosa, respectively) decreased. In both milk-fed groups type A and B corneal cells were present in the Stratum corneum, whereas in the earlier weaned calves type C-cells could be also seen. These findings indicate a more advanced stage of development of the rumen epithelium in the earlier weaned calves fed higher amounts of concentrate and hay.     

不同饲喂模式对犊牛小肠及胰腺内消化酶活性的影响

为研究饲喂模式对犊牛肠道及胰腺内消化酶活性的影响。试验选择24头体重和出生日期相近的犊牛,随机分成2组,每组12头,其中Ⅰ组采用传统饲喂模式(干草+粉状开食料),4 d开始补充开食料,10 d开始补充苜蓿干草,干草自由采食。Ⅱ组采用现代饲喂模式(颗粒型开食料)犊牛于4 d开始补充开食料。60 d断奶。各组分别在0、15、30、60 d屠宰3头犊牛。结果表明:Ⅰ组犊牛中性洗涤纤维以及酸性洗涤纤维日均摄入量均显著高于Ⅱ组(P<0.05),粗蛋白、消化能、粗脂肪、钙和磷的日均摄入量差异均不显著(P>0.05)。Ⅱ组犊牛小肠以及胰腺内淀粉酶、糜蛋白酶、胰蛋白酶、脂肪酶均高于Ⅰ组,尤其是胰蛋白酶以及糜蛋白酶在60 d时显著高于Ⅰ组(P<0.05)。结果提示,断奶前饲喂颗粒开食料有利于促进犊牛小肠以及胰腺内消化酶的分泌,利于提高犊牛对饲料的消化利用率。     

Low- and high-quality forage utilization by heifers and mature beef cows.

Eight cows (7 to 9 yr old, 522 kg) and six heifers (10 mo old, 169 kg) were fed either alfalfa hay (18.7% CP) or mature brome hay (5.1% CP) to determine the effect of cattle age on apparent forage utilization. Cattle were fitted with ruminal and duodenal cannulas and were individually fed once daily (ad libitum intake, 1000). The split-plot design consisted of age (whole-plot) and two sampling periods feeding alfalfa or brome hay (subplot). Each period consisted of 28 d: d 1 to 13 for adaptation, d 13 to 20 for feed intake determination, and d 20 to 28 for sampling. Nylon bags containing NDF substrate from alfalfa or brome hay were incubated ruminally for 0, 3, 6, 12, 24, 48, 96, and 192 h to determine the rate and extent of fiber degradation. Ruminal liquid dilution rate and fermentation characteristics were conducted on d 27. Ruminal fill was determined by total evacuation at 0800 on d 28. Cows consumed more feed (BW.75; P<.01) and had greater ruminal OM fill (P = .04) but had similar fluid fill (P = .88) compared with heifers. Ruminal liquid dilution rate was greater in cows than in heifers (P<.01). The rate of in situ NDF degradation was 3 and .5% per hour greater in cows than in heifers when alfalfa and brome hay were fed, respectively (age x hay, P<.01). Ruminal NDF digestibility as a percentage of intake was greater in cows than in heifers (P<.01). Numbers of ruminal cellulolytic bacteria were not affected by treatment (P>.21). These data indicate that mature cows have a smaller ruminal fluid fill that turns over more rapidly, and this may be responsible for a faster rate of ruminal fiber degradation in cows than in young heifers.     

Ostertagia ostertagi in neonatal calves: establishment of infection in ruminating and non-ruminating calves

An experiment was carried out to study the role of the ruminal function in the establishment of Ostertagia ostertagi in neonatal calves. Three groups of calves were fed either milk only (groups A and C), or hay and concentrate in addition to milk (group B) from birth. At the time of infection, ruminal function was negligible in groups A and C, whereas it was well developed in group B. Calves of groups A and B were each given 25,000 normal ensheathed infective larvae of O ostertagi and those of group C were given 25,000 infective larvae exsheathed in vitro. Daily faecal egg output and post mortem worm counts 28 days after infection were higher in calves with well developed ruminal function than those having only negligible ruminal function. In the latter group, exsheathed larvae established at a lower rate than did ensheathed larvae. The results suggest that the degree of development of the ruminal function influences the establishment of O ostertagi.     

Influence of realimentation diet on recovery of rumen activity and feed intake in beef steers

Two trials were conducted to determine the influence of realimentation diet energy, protein, B-vitamin (BV) and Lactobacillus acidophilus (LAC) content on recovery of rumen activity and feed consumption in beef steers. In trial 1, ruminal-fistulated steers were fasted and refed 1) prairie hay, 2) 10% protein (LCP), 3) 12.5% protein (MCP), 4) LCP + BV or 5) LCP + LAC. In trial 2, calves were fasted and refed 1) 60% cottonseed hulls-40% alfalfa dehy (high roughage), 2) LCP, 3) 15% protein (HCP), 4) LCP + BV or 5) LCP + LAC. Rumen fermentative capacity declined 74% (P less than .05) during feed and water deprivation, but returned to control levels by d 7 of realimentation. On d 3 of realimentation, steers fed the LCP and MCP diets had molar proportions of ruminal butyrate in excess of 35%. Steers fed the hay, LAC and BV diets did not have a high butyrate fermentation. In trial 2, calves lost about 15% of their body weight during feed and water deprivation. Calves fed the high roughage diet appeared to return to prefast feed and energy intakes more slowly than steers fed the medium roughage diets. Results of this study indicate that rumen fermentative capacity is a factor limiting feed intake in fasted calves for 7 to 14 after the reintroduction of feed and water.