Benefits of barley straw as a forage for dairy calves before and after weaning

The aim of this study was to assess the potential consequences on calf intake, performance, behavior, ruminal microbiome, and ruminal epithelium development of combining the inclusion of chopped barley straw and alfalfa hay during the pre- and postweaning periods keeping concentrate to forage ratio constant among dietary treatments. Forty-five Holstein calves (44 ± 5.7 kg of body weight [BW] and 3 ± 1.5 d of age) individually penned were blocked by BW and randomly assigned to a common pellet concentrate fed ad libitum along with one of following forage feeding strategies: barley straw before and after weaning (S-S), barley straw before and alfalfa hay after weaning (S-A), or alfalfa hay before and after weaning (A-A). All calves received the same milk replacer regimen. Forage was supplied in a separated bucket at the rate of 7.5% (preweaning) and 15% (postweaning) of total solid feed intake of the previous day. Feed intake and BW were recorded daily and weekly, respectively. Rumen samples were obtained via a stomach tube at 53, 66, and 87 d and were composite in 3 samples of 5 animals each for subsequent rumen microbiome analysis. A rumen epithelium sample was taken by endoscopy at 90 d to assess gene expression of OCLN, CLDN4, SLC9A1, SLC9A3, SLC16A1, SLC16A4, IL6, and TGFB1. Data were analyzed with a mixed-effects model accounting for the fixed effects of block, forage, week of study, and their interaction, and calf as a random effect. The type of forage fed did not affect concentrate feed, forage, or total DM intake before weaning. However, S-A and A-A calves consumed less concentrate feed and S-A calves grew at a lower rate after weaning than S-S calves. Expression of the gene coding for SLC16A1 in the rumen epithelium was greatest in S-S among treatments. Rumen microbiome did not differ among treatments, while the relative abundance of Acidaminococcus and Selenomas genera increased, while Alloprevotella, Bifidobaterium, Olsenella, and Succiclasticum genera decreased with age. In conclusion, feeding barley straw before and after weaning was more effective than feeding alfalfa hay in promoting concentrate feed intake after weaning and fostering an increase in the expression of SLC16A1 in the rumen epithelium.

Whole-plant flint corn silage inclusion in total mixed rations for pre- and postweaning dairy calves

Assuming that acetic acid plays a minor role in the development of ruminal epithelium of preweaning dairy calves, the fiber supply for growing calves has been neglected. More research has been done on including starch and nonfibrous carbohydrates in solid feed for preweaning calves. Accordingly, the fiber requirement of these calves is not well known, as diet recommendations vary greatly. Hence, elucidating the effects of including fiber from long particle sizes in the diet may be essential for helping calves overcome the transition challenge during weaning. Forty-five Holstein calves were used in a randomized block design, considering sex, birth date, and weight at 28 d of age, when the supply of the total mixed ration (TMR) with the inclusion of corn silage started. Three TMR with increasing whole-plant flint corn silage content (0, 10, or 20% on a dry matter basis) were compared: 0CS, 10CS, or 20CS, respectively. During the first 28 d of life, the calves were managed homogeneously and were fed 6 L/d of whole milk, a commercial calf starter pelleted, and water ad libitum. Next, the solid diet was changed to the respective solid feed treatment. Calves were gradually weaned from 52 to 56 d of age but were evaluated for an additional 14 d postweaning. Feed intake was measured daily, while body weight and metabolic indicators of intermediate metabolism were evaluated weekly. Ruminal fluid was collected at 6, 8, and 10 wk of age. Behavioral analysis was conducted on wk 7 (preweaning) and 10 (postweaning). There was a quadratic effect for dry matter intake from wk 7 to 10, with higher intake for the 10CS diet than the 0CS and 20CS diets. Consequently, the 10CS diet also promoted greater average daily gain at wk 8 and 9 compared with the 0CS and 20CS diets. However, the final body weight was not affected by the different solid diets. Silage inclusion in calves' diet positively affected time spent ruminating and chewing pre- and postweaning. Including 10% of whole-plant flint corn silage in the diets of young dairy calves is a strategy to increase total solid intake and decrease acidosis risk by increasing pH and ruminating activity around weaning.

Replacing concentrates with a high-quality hay in the starter feed in dairy calves: I. Effects on nutrient intake, growth performance, and blood metabolic profile

Concentrate-rich starter feeds are commonly fed to dairy calves to stimulate early solid feed intake and growth performance; yet, starter feeds lacking in forage fiber may jeopardize gut development. This research primarily aimed to test a complete or partial replacement of concentrates with hay of different qualities in the starter feed on nutrient intake, growth performance, apparent total-tract digestibility (ATTD) of nutrients, and blood metabolites in dairy calves. Immediately after birth, 40 Holstein Friesian calves were randomly allocated to 1 of 4 starter diets, which differed in hay quality and concentrate inclusion [MQH = 100% medium-quality hay, 9.4 MJ of metabolizable energy (ME), 149 g of crude protein (CP), 522 g of neutral detergent fiber (NDF)/kg of dry matter (DM); HQH = 100% high-quality hay, 11.2 MJ of ME, 210 g of CP, 455 g of NDF/kg of DM; MQH⁺C = 30% medium-quality hay + 70% starter concentrate; HQH⁺C = 30% high-quality hay + 70% starter concentrate]. The concentrate consisted mainly of grains, oilseeds, and mineral supplements (13.5 MJ of ME, 193 g of CP, 204 g of NDF/kg of DM). Calves were used in the experiment from d 1 to 99 of life. During the first 4 wk, all calves were fed acidified whole milk ad libitum, and afterward they were gradually weaned from wk 5 to 12. Calves had ad libitum access to their starter diets and water throughout the experiment. Milk, water, and solid feed intake was recorded daily, live weight was measured once a week, and blood samples were collected on d 1, 3, 7, 21, 49, 77, and 91 and analyzed for selected metabolites. The ATTD was measured in wk 14 of life. Total DM intake and daily weight gain of calves were not affected by the starter feed during the first 8 wk of life. However, from wk 9 to 14, calves fed the MQH diet had lower DM, ME, and CP intake and gained less weight than calves from the other experimental groups. Feeding the HQH diet resulted in similar CP and ME intake and growth performance compared with calves receiving diets containing concentrates. Furthermore, feeding the HQH diet improved the ATTD of NDF, resulting in similar ATTD of organic matter with the HQH⁺C and MQH⁺C groups. Interestingly, calves fed the HQH⁺C diet showed less sorting for concentrate, compared with the MQH⁺C group. Concentration of blood metabolites, including glucose, lactate, insulin, nonesterified fatty acids, triglycerides, and total protein, did not differ after the first week of life. However, serum β-hydroxybutyrate was higher in calves fed the HQH diet starting from wk 11. Both groups fed the hay-only diets maintained higher cholesterol levels after weaning compared with the groups fed hay-concentrate mixtures. In conclusion, feeding high-quality hay can fully replace starter concentrates in the feeding of dairy calves without adverse effects on performance during the rearing period, while increasing forage fiber intake and utilization, which enhanced ruminal ketogenesis and cholesterogenesis around weaning. Further research is needed to evaluate long-term effects of feeding high-quality hay on health and development of dairy calves, especially in terms of the observed improvements in ruminal ketogenesis and cholesterogenesis around weaning.

Increasing grass hay inclusion level on weaned dairy calf growth, intake, digestibility, and ruminal fermentation

The objective was to determine effects of increasing grass hay (GH) inclusion level on weaned dairy calf growth, intake, digestibility, and ruminal fermentation. Holstein calves (n = 45) were randomly assigned to 1 of 3 total mixed rations with increasing GH [10, 17.5, or 25% on a dry matter (DM) basis; LGH, MGH, or HGH, respectively]. Calves were weaned at 6 wk of age, housed individually, and studied from 7 to 16 wk of age. Rations, consisting of texturized calf starter (20% crude protein) and coarsely chopped GH, were offered ad libitum as separate components from 7 to 9 wk of age. After 9 wk, feed was offered as a total mixed ration containing the assigned level of GH and fed according to the clean bunk feeding strategy as a means of limiting refusals. Initial 9-wk body weight was 81.6 ± 9 kg (mean ± standard deviation). Intake and growth were measured weekly. Blood samples were collected at 9, 10, 12, 14, and 16 wk of age for analysis of plasma glucose and β-hydroxybutyrate. Total fecal collection (12 calves; 4 per treatment) was conducted at 11 and 15 wk of age for 4 d consecutively. Rumen samples were collected over the final 24 h of each fecal collection period to evaluate pH and volatile fatty acid profile. Feeds and feces were evaluated for DM, neutral detergent fiber, acid detergent fiber, and starch to estimate total-tract digestibility. Intake and weight gain were analyzed from 7 to 9 wk and 9 to 16 wk, representing pretreatment and treatment periods. No differences were observed between treatments from 7 to 9 wk. However, differences were found from 9 to 16 wk. Final body weight, average daily gain, DM intake, and metabolizable energy intake all decreased with increased GH. However, skeletal frame measurements did not vary between treatments. Plasma β-hydroxybutyrate tended to decrease with increased GH. No differences were observed in DM or starch digestibility, but neutral detergent fiber and acid detergent fiber digestibility increased with increased GH. Mean rumen pH and total volatile fatty acid did not change with increasing GH inclusion; however, there was an interaction with time indicating that ruminal fermentation patterns throughout the day were different for calves offered MGH and HGH versus those offered LGH. These results indicate that feeding levels of GH >10% reduce growth and intake before 16 wk and alter ruminal fermentation patterns.

Feeding various forages and live yeast culture on weaned dairy calf intake, growth, nutrient digestibility, and ruminal fermentation

The objective of this study was to determine effects of various forages and live yeast culture on intake, growth, nutrient digestibility, and ruminal fermentation of weaned dairy calves. Holstein calves (n = 45) were randomly assigned to 2 × 3 factorial treatments: live yeast culture or no yeast and alfalfa haylage (AH), corn silage (CS), or grass hay (GH). Calves were weaned at 6 wk of age, housed individually, and studied from 7 to 16 wk of age. Rations, consisting of an 18% crude protein texturized grower (yeast or no yeast) and assigned forage, were offered as separate components until 9 wk of age. After 9 wk, diets were offered as a total mixed ration (TMR). Concentrate intake was capped at 2.25 kg of dry matter (DM)/d, and forage was offered ad libitum. The TMR contained equal forage neutral detergent fiber (8 ± 0.5%) on a DM basis for each basal diet. Calves were fed TMR to limit concentrate intake, and additional forage was offered ad libitum after 8 h if the entire TMR allotment was consumed. Total fecal collection (12 calves) was conducted for 4 d at 11 and 15 wk of age. Feeds and feces were evaluated for DM, neutral detergent fiber, acid detergent fiber, and starch to calculate digestibility. On the last day of fecal collection, rumen samples were collected to evaluate pH and volatile fatty acid (VFA) profile. Metabolizable energy and DM intake was least for calves consuming GH compared with other forages. Forage intake (% of DM intake) increased as calves aged (AH = 20 to 44.4%, CS = 24.5 to 37.6%, GH = 11.3 to 32.3% at 10 and 16 wk of age, respectively). Calves on CS had the greatest average daily gain and empty body weight gain, and calves on GH had the least. Calves on GH tended to have the lowest final body weight. There were no differences in structural growth. Digestibility of DM decreased with age. Fiber digestibility was least for calves on CS, and starch digestibility was least for calves on AH. Mean and minimum rumen pH increased with age. Forage offered changed VFA profile and there was an interaction between yeast and forage on VFA profile. These results indicated that recently weaned calves perform well on AH, CS, or GH and have minimal benefit from yeast supplementation. Feeding GH reduced weight gain, but all calves achieved a level of gain to meet growth goals for breeding and freshening. Furthermore, the ability to consume large portions of the ration as forage allows for more economical diets to be fed.

Effect of converting weaned dairy calves from a component-fed diet to a total mixed ration on growth and nutrient digestibility

The objective was to determine the effects of converting calves from a component-fed ration to a total mixed ration (TMR) at 8, 10, or 12 wk of age on intake, growth, and nutrient digestibility. Holstein calves (n = 40) were randomly assigned to 1 of 4 groups (no TMR, TMR conversion at 8, 10 or 12 wk; T0, T8, T10, and T12, respectively). Calves were weaned at 6 wk of age, housed individually, and studied from 7 to 14 wk of age. Rations, consisting of a 20% crude protein texturized starter and grass hay, were offered ad libitum as separate components or as a TMR with 85% starter and 15% grass hay on a dry matter (DM) basis. Intakes and body weights (BW) were measured weekly. Component intake for TMR was calculated from the proportion of grass hay and starter contained in the TMR. Fecal grab samples were collected every 9 h over 3 d for a total of 8 samples that formed a composite at 9, 11, and 13 wk of age from the same 4 calves per group. Rumen fluid samples were collected via esophageal tube at -1, 0, 3, and 7 d relative to conversion from component to TMR. Feed and feces were evaluated for DM, neutral detergent fiber, acid detergent fiber, and acid detergent lignin (internal flow marker) to estimate digestibility. Average daily gain and final BW tended to be least for T8. Empty BW gain was significantly less for T8 than for T0 but not different from T10 or T12 (T0 = 1.07, T8 = 0.93, T10 = 1.02, T12 = 1.04 kg/d). Hip growth tended to be least for T8 and resulted in lower final hip width (T0 = 25.9, T8 = 25.2, T10 = 25.6, T12 = 25.8 cm). Intake tended to be reduced for calves converted to TMR earlier. Throughout the study, calves fed TMR ate more hay and less starter than component-fed calves. Metabolizable energy intake was less for T8 versus T0 but not different from T10 or T12 (T0 = 8.46, T8 = 7.55, T10 = 8.01, T12 = 8.23 Mcal/d). We observed no differences in feed efficiency for the duration of the study. Differences in DM digestibility were not observed, but fiber digestibility was greater for calves fed TMR at 9, 11, and 13 wk of age. Conversion to TMR increased rumen pH. These results indicate that TMR conversion increased hay consumption and subsequently decreased starter and total DM intake. This led to reduced weight and structural growth; however, calves that were converted to TMR as early as 8 wk still achieved adequate growth. The increase in rumen pH and subsequent increase in fiber digestibility allowed for calves to be converted to a 15% grass hay TMR as early as 8 wk and still achieve desirable growth goals.

Effect of starter form, starch concentration, and amount of forage fed on Holstein calf growth from 2 to 4 months of age

Young, weaned calves are commonly offered ad libitum forage with limited amounts of starter, in contrast to the suggested amount of approximately 5% forage in the diet due to the limited capacity of the rumen, as well as limited ability to digest high fiber feeds. The objective of this research was to compare 2 types of starters (low starch, pelleted vs. high starch, textured), both fed either ad libitum with 5% chopped hay, or fed at restricted rates with ad libitum long grass hay to calves between 2 and 4 mo of age. In trial 1, 48 calves were housed in group pens (68.4 ± 3.37 kg of initial body weight ± standard deviation; 3 pens of 4 calves/pen) and randomly assigned to 1 of 4 diets: (1) low starch pelleted starter (8% starch) blended with 5% chopped hay fed free choice; (2) high starch textured starter (45% starch) blended with 5% chopped hay fed free choice; (3) low starch pelleted starter (8% starch) fed at a rate up to 2.3 kg of dry matter (DM)/d, with free-choice long grass hay; or (4) high starch textured starter (45% starch) fed at a rate up to 2.3 kg of DM/d, with free-choice long grass hay. Trial 1 was analyzed as a completely randomized design using a 2 × 2 arrangement of treatments. Repeated measures were used as appropriate. Pen was the experimental unit. In trial 2, 48 calves (76.4 ± 1.55 kg of initial body weight; 6 pens of 4 calves/pen) were randomly assigned to 1 of 2 diets: (1) ad libitum access to a blend of 95% high starch textured starter (42% starch) and 5% chopped grass hay; or (2) high starch textured starter fed up to 2.7 kg of DM/d with free-choice long grass hay. Trial 2 was analyzed as for trial 1, without factorial arrangement. Trials were 56 d long. In trial 1, feed efficiency, average daily gain (ADG), and change in hip width were greater for calves fed high versus low starch diet. Final hip width, ADG, DM intake, and change in hip width were greater for calves fed limited chopped versus free-choice long hay diets. In trial 2, intake, feed efficiency, and all growth measurements were greater in calves fed the ad libitum mixed diet compared with those limit-fed starter up to 2.7 kg as fed with ad libitum hay. Ad libitum hay intake was highly variable among pens and differed up to 2.5-fold by the last week of the trials. In both trials, restricted feeding of starter with ad libitum long grass hay reduced total DM intake by 13 to 17%, ADG by 20%, and hip width change by 10 to 23% compared with a blend of 95% starter and 5% chopped grass hay fed ad libitum.

Effect of milk replacer program on digestion of nutrients in dairy calves

There are concerns with feeding young dairy calves amounts of milk solids approaching 0.9kg of dry matter (DM) or more because of slumps in average daily gain (ADG) at weaning and low starter intakes. Additionally, programs feeding more than 0.6kg of DM have not been thoroughly tested for success at different weaning ages. Four milk replacer (MR) programs were compared in trial 1. Program A was 0.44kg of DM of a 21% crude protein (CP), 21% fat MR powder fed daily for 42 d. Program B was 0.66kg of DM of a 27% CP, 17% fat MR powder fed daily for 42 d. Program C was 0.66kg of DM of a 27% CP, 17% fat MR powder daily fed for 28 d. Program D was up to 1.09kg of DM of a 29% CP, 21% fat MR daily fed for 49 d. Digestibility estimates were made and blood was sampled for serum constituents on d 53 to 56, and performance was measured for 84 d. Three programs feeding a 27% CP, 17% fat MR powder were compared in trial 2 over 56 d. Calves on program A were fed 0.66kg of DM powder daily and weaned at 28 d. Calves on program B were fed 0.66kg of DM powder daily and weaned at 42 d. Calves on program C were fed up to 1.09kg of DM powder daily and weaned at 42 d. Digestibility estimates were made and blood was sampled for serum constituents d 21 to 24, d 36 to 39, and d 53 to 56. In trial 1, calves fed program A had the least overall ADG. Calves fed program D had the greatest ADG from 0 to 56 d, the least ADG from d 56 to 84, the least digestibility estimates, and the least concentrations of serum amylase. At 84 d, there were no differences in body weights of calves fed programs B, C, and D. In trial 2, calves fed program A had the greatest starter intake and greatest concentrations of serum amylase. Calves fed program C had the least estimates of digestibility from d 53 to 56 and the least serum concentrations of amylase. Calves fed up to 1.09 kg/d of 27 to 29% MR powders and weaned at 42 or 49 d had lower starter intakes, concentrations of serum amylase, and digestion of starter postweaning compared with calves fed conventional 21% CP, 21% fat MR powders fed at 0.44 kg/d. Calves fed 0.66 kg/d of a 27% CP, 17% fat MR powder and weaned at 28 or 42 d of age had no reductions in intake or digestion compared with calves fed conventional MR and gained as much total body weight from 0 to 84 d as calves stepped up to 1.09kg of MR.

Influence of undergradability of protein in the diet on intake, daily gain, feed efficiency, and body composition of Holstein heifers

Thirty-two Holstein heifers with body weights (BW) between 213 and 231 kg were randomly assigned to one of four treatments for the 50-d trial. Treatments consisted of four percentages of rumen-undegradable protein (RUP) (31, 43, 50, and 55% of total N) at 100% of National Research Council recommendations for total digestible nutrients and crude protein. Total mixed diets composed of corn silage, ground barley straw, soybean meal, blood meal, urea, and minerals were formulated for a mean daily BW gain of 0.60 kg. Ration RUP percentage was varied by shifting protein sources. Mean dry matter intake (grams per kilogram of BW0.75) was 97.6, 84.4, 77.8, and 73.5 for 31% RUP (soybean meal), 43% RUP (blood and soybean meal), 50% RUP (blood meal with urea), and 55% RUP (blood meal) treatments, respectively. Daily gain was 0.84, 0.89, 0.91, and 0.96 kg/d, respectively. Intake of digestible energy (megacalories per kilogram of BW0.75 per day) was 0.28, 0.24, 0.22, and 0.21, respectively, and feed efficiency (megacalories of digestible energy per kilogram of BW gain) was 20.6, 16.1, 15.2, and 13.3, respectively. Dry matter intake (grams per kilogram of BW0.75), digestible energy intake, feed efficiency, daily BW gain, and hip height differed with respect to treatment. There were no differences in growth, wither height, or heart girth because of treatments. Changes in percentage of empty body fat as estimated by urea space procedures was 6.73, 4.67, 6.67, and 7.32, respectively, and did not differ with respect to treatments. These results indicate that increasing the RUP percentage in the diets of growing heifers improves feed efficiency and increases BW gain.

Effect of varying levels of neutral detergent fiber and total digestible nutrients on intake and growth of Holstein heifers

Intake, growth, DM intake, BW, and wither height were recorded from 108 Holstein heifers weighing between 100 and 400 kg. Heifers were divided into two blocks based on beginning BW (mean = 182 kg, light and mean = 270 kg, heavy). Heifers within blocks were assigned randomly to one of five treatments for the 35-d trial to examine effects of dietary NDF and TDN on growth. Light heifer treatments were 35, 45, or 50% of NDF at 100% of NRC TDN recommendation and 85 and 115% of NRC TDN at 45% NDF. Heavy heifer treatments were 40, 50, or 60% of NDF at 100% NRC TDN and 85 and 115% of TDN at 50% NDF. Total mixed rations formulated for .68 kg/d of BW gain were fed. Rations contained corn silage, alfalfa haylage, ground orchardgrass hay, soybean meal, high moisture corn, and a mineral mix. Mean DM intake (kilograms per day) and BW (kg) were 5.9, 217 and 7.28, 311, respectively, for the light and heavy blocks. Mean BW gain (kilograms per day) and growth in wither height (centimeters per day) were 1.07, .122 and .96, .076, respectively, for light and heavy blocks. Maximal DM intake per kilogram of BW.75 occurred at 41% NDF, below which NDF and ADF correlations with DM intake per kilogram BW.75 were -.16 and -.42. Above 41% NDF, correlations were -.28 and -.21. Ration NDF content had more influence than TDN on intake and growth of heifers with less than 200 kg BW. Above 200 kg BW, heifer performance more closely reflected the changes in ration energy content (TDN); NDF had less effect.

Increased weight gain and effects on growth parameters of Holstein heifer calves from 3 to 12 months of age

Two trials involving 280 Holstein heifer calves were to determine effects of increasing nutrient intake on growth (weight, height, and heart girth), dry matter intake, and water intake. In trial 1, 80 calves were fed from 60 to 172 d of age. More calf grower fed increased daily gain from .87 to .92 kg. Gain was further increased to .97 kg with higher energy content and to .99 kg with higher energy and higher protein content of calf growers. Alfalfa hay intake decreased as calf grower intake increased. Wither height and heart girth increased proportionally to body weight. Water intake was variable but proportional to dry matter intake. In trial 2, 114 heifers were fed alfalfa hay with either control or higher protein and higher energy heifer (accelerated program) growers from 187 to 369 d of age. Grass hay was fed to 86 heifers from 230 to 369 d of age with the same grower rations. Daily gain increased from .83 to .93 kg with the accelerated program. Hay intake decreased with higher grower intake on the accelerated program. When fed ad libitum on both programs, grass hay intake was about 5% lower than alfalfa hay. Heart girth at 369 d of age was increased on the accelerated program but there was no effect on wither height. Growth of Holstein heifers can be accelerated up to 1 kg daily gain from 3 to 12 mo of age without excessive fattening.

Effect of protein on growth of Holstein heifer calves from 2 to 10 months

Two trials involving 44 weaned Holstein heifer calves were to determine effects of protein on growth in weight and wither height, dry matter intake, and digestibility. In trial 1, 24 calves were fed according to requirements from 85 to 182 d of age, then at 80, 100, or 120% of recommended amounts for dietary protein content until 295 d. Weight at 295 d increased linearly with protein (280, 287, 298 kg), but wither height and dry matter intake were unaffected. In trial 2, 20 calves were fed 80, 100, or 120% of recommended protein from 71 to 182 d. Weight and wither height at 182 d responded quadratically to protein with highest values from the medium protein diet. From 183 to 295 d, trial 2 calves were rerandomized to diets of medium or high protein. Weight at 295 d was increased by high protein. An interaction between treatments for wither height indicated responses to high protein after 182 d for calves on low or medium protein before that time and a decrease for calves on high protein throughout. In male calves of similar age, elevated protein increased apparent protein digestibility but had inconsistent effects on digestibility of dry matter. Current protein recommendations appear adequate for calves to 6 mo of age but thereafter may be too generous.

Protein sources evaluated for ruminating Holstein calves

Fifty calves were fed a basal diet of 11.6% crude protein or one of four diets (15.5% crude protein) containing added soybean meal, corn gluten meal, cottonseed meal, or fish meal. Diets were calculated 75% total digestible nutrients. Body weight gain increased an average of 17% with added protein. Fish meal and soybean meal generated highest rates of gain. Ruminal ammonia-nitrogen was higher for soybean meal and cottonseed meal than other diets, indicating greater rates of degradability. Molar proportions of rumen volatile fatty acids were not different among diets, but concentration was lower for fish meal. Serum urea nitrogen was lowest for the basal and fish meal diets. Microbial nitrogen in the abomasum was 33.6% of total nitrogen for corn gluten meal and 42.8% for soybean meal. Apparent dry matter and nitrogen digestibilities were greater for corn gluten meal and fish meal diets than for soybean meal or cottonseed meal diets. Rumen degradability of feedstuffs, as determined by dacron bag technique, ranged from 38.1% for corn gluten meal to 71.3% for soybean meal. Degradability of mixed diets reflected those of the protein supplement present in each diet except for diet containing cottonseed meal. Fish meal and soybean meal were better protein sources for growth of ruminating calves than were corn gluten meal or cottonseed meal.

Effect of sodium bicarbonate and disodium phosphate on animal performance, ruminal metabolism, digestion, and rate of passage in ruminating calves

With a five-point radial response design, a control group, and several single factor points, effects of dietary sodium bicarbonate (0 to 4.5%) and disodium phosphate (0 to 2.0%) on calf growth, ruminal fermentation, ration digestibility, and rate of passage of liquid and particulate digesta were studied. Growth and intake data were collected age 7 to 14 wk. Rumen and blood were sampled three times. Digestion and rate of passage trials were during age 16 wk. Gains were not affected significantly but were maximized between 1 and 2% sodium bicarbonate and 0% disodium phosphate. Dry matter intake, feed efficiency, dry matter digestibility, volatile fatty acid ratio, ruminal pH, and buffering capacity were not altered by buffers. Ruminal osmolality and concentration of volatile fatty acids were increased by buffers. Digestibility of acid detergent fiber and neutral detergent fiber tended to be higher for rations containing buffers. Dilution rate of ruminal liquid increased by 40% with 2.0% sodium bicarbonate and .75% disodium phosphate, and ruminal volume was decreased. Passage rate of particulate digesta was increased by a similar amount.