Effects of feeding frequency and feeding level on nutrient utilization in heavy preruminant calves

The objective of this study was to determine the effects of feeding frequency (FF) and feeding level (FL) on protein and energy metabolism in adapted, heavy preruminant calves. It was hypothesized that an increased FF would increase protein utilization by an improved synchrony between the supply of and requirements for protein during the day when a quickly hydrolyzable protein source was used. Eighteen Holstein Friesian calves of 136 ± 3 kg of body weight were assigned to FF (1, 2, or 4 meals daily) at 2 FL (1.5 or 2.5 times the metabolizable energy requirements for maintenance), except for calves fed once daily (only at a low FL). Calves were individually housed in respiration chambers during 2 experimental periods of 10 d. Whey protein was the only protein source in the diet. Neither FL nor FF affected apparent fecal nutrient digestibility. Increasing FF increased the efficiency with which digestible protein was utilized in calves. The increase was greater at a high FL (+11% from 2 to 4 meals/d) than at a low FL (+5% from 2 to 4 meals/d), but no significant interaction occurred between FL and FF. An increased FF and a higher FL enhanced fat deposition. Heat production was not affected by FF, but its circadian rhythm differed considerably between FF. Activity-related heat production was not affected by FF or FL. Thus, increasing FF improved the efficiency with which protein and energy were utilized in heavy preruminant calves when a quickly hydrolyzable protein source was used.     

Effects of propionibacteria and yeast culture fed to steers on nutrient intake and site and extent of digestion

The effects of feeding Propionibacterium strain P169 (P169), yeast culture (XPY), and their combination on nutrient intake, site and extent of digestion, and ruminal kinetics were evaluated in a completely randomized experimental design. Ruminally and duodenally cannulated Angus × Hereford steers (n = 12) were assigned to 1 of 4 treatments in each of 2 periods: 1) control, fed a sorghum silage-based total mixed ration; 2) P169, fed the control plus P169 (6 × 10¹¹ cfu/steer per d); 3) XPY, fed the control plus XPY (56 g/steer per d); and 4) P169 + XPY, fed the control plus P169 and XPY (at 6 × 10¹¹ cfu/steer per d and 56 g/steer per d, respectively). Each period lasted 21 d; d 1 to 15 were used for diet adaptation and d 16 to 21 were used for fecal, duodenal, ruminal, and blood sample collection. Steers were individually housed and fed. Feeding XPY tended to decrease intake of organic matter, acid detergent fiber, and N, and decreased intake of neutral detergent fiber. However, feeding XPY alone tended to increase total tract digestibility of organic matter, N, neutral detergent fiber, and acid detergent fiber. Ruminal digestibility, duodenal flow, microbial N synthesis, microbial efficiency, and fluid and particulate passage rates were not affected by dietary treatments. Feeding P169 tended to decrease molar proportion of acetate, increased molar proportion of propionate (by 9.7%), and tended to decrease acetate:propionate ratio compared with control steers. No other effects of XPY or P169 on ruminal fermentation were observed. Plasma glucose and insulin concentrations were not affected by dietary treatment. Our results suggest that feeding P169 alters ruminal metabolism toward increased propionate without affecting feed intake or ruminal kinetics, whereas feeding XPY alone tended to increase total tract digestibilities of nutrients.     

Composition of ruminal bacteria harvested from steers as influenced by dietary energy level, feeding frequency, and isolation techniques

The effects of isolation techniques and time of sampling on composition of ruminal bacteria were examined in four steers fed two energy levels (2.24 or 2.92 Mcal metabolizable energy/kg DM) at two feeding frequencies. Diets were alfalfa hay and corn silage or ground corn/corn silage and were fed twice or 12 times daily. Whole ruminal contents were collected at four time intervals over a 4-d period. Fluid- and particle-associated bacteria were isolated. Energy level, feeding frequency, and preisolation freezing had little effect on composition of bacteria. Sampling time did not affect composition of bacteria harvested from steers fed frequently but had linear and quadratic effects on concentrations of cell components of bacteria harvested from steers fed twice daily. Differences were observed in the composition of bacteria harvested from the fluid phase compared with particle-associated or mixed populations of ruminal bacteria. These differences translated into different estimates of bacterial N supplied to the small intestine depending on N:purine ratio used. Composition of bacteria may be affected by fraction of contents sample and by time of sampling for animals fed infrequently. Freezing of samples before isolation of mixed bacteria does not appear to affect composition or estimates of bacterial N flows to the small intestine.     

Effect of source of carbohydrate and frequency of feeding on rumen parameters in dairy steers

Four rumen-fistulated, Holstein steers (358 kg) were fed two diets at two frequencies (2 and 8 times/d) in a 4 X 4 Latin square design with 28-d periods. The two diets consisted of corn silage and a concentrate mixture in a ratio of 40:60 on a dry matter basis. The two concentrate mixtures (control and dried whole whey) contained, as a percentage: ground shelled corn, 87.85, 19.05; soybean meal, 9.4, 5.9; dicalcium phosphate, 1.7, 0; trace mineralized salt, 1.0, 1.0; vitamin A and D premix, .05, .05; and dried whole whey, 0, 74.0, respectively. Rumen fluid samples were taken at hourly intervals for 24 h and analyzed for pH, volatile fatty acids, lactate, ammonia nitrogen, and protozoal numbers. Total concentration of volatile fatty acids in the rumen were not affected by treatments. Feeding the control diet resulted in significantly higher ruminal acetate and isovalerate but lower butyrate and valerate expressed as a molar percentage. Increasing the feeding frequency from 2 to 8 times/d resulted in an increase in the molar percentage of acetate and a decrease in the concentration of lactate in ruminal fluid. Numbers of protozoa varied considerably with time after feeding and tended to be higher on the whey diet.     

Effects of feed intake and protein degradability on ruminal characteristics and site of digestion in steers

Four multiple-fistulated Hereford steers were used in a 4 X 4 Latin square design with a 2 X 2 factorial arrangement of treatments [two intakes (9.1 and 6.1 kg dry matter/d) and two protein sources differing in ruminal degradability (dry distillers grains and dry corn gluten feed)]. Steers fed at the high intake had faster fluid dilution rates (7.63 versus 6.52%/h), higher ruminal fluid outflows (120.2 versus 91.7 L/d), lower apparent ruminal digestibilities of organic matter (41.3 versus 44.3%) and neutral detergent fiber (56.0 versus 60.2%), and lower total tract digestibilities of neutral detergent fiber (64.3 versus 68.7%) than when they were fed at the low intake. Steers fed dry corn gluten feed had higher apparent ruminal digestibilities of organic matter (45.5 versus 40.1%) and neutral detergent fiber (60.2 versus 56.0%) and lower duodenal flows of nonammonia-nonbacterial N (40.1 versus 52.2% of N intake) than when they were fed dry distillers grains. Efficiency of ruminal bacterial growth was higher when steers were fed at the high versus low intakes. Efficiency of ruminal bacterial growth and site and extent of fiber digestion, especially hemicellulose, but not ruminal escape of protein, can be readily altered by manipulation of feed intake of moderately high forage diets.     

Effect of feeding according to energy balance on performance,nutrient excretion,and feeding behavior of early lactation dairy cows

The objectives of this study were to evaluate 2 feeding strategies for early lactation cows on performance and efficiency of nutrient utilization. Fifty-eight Holsteins cows were blocked by parity and production during the pretreatment period and then randomly assigned at 21 d postpartum to a control diet [n = 29; 16.2% crude protein, 1.64 Mcal of net energy for lactation (NE_L), 22% starch, and 19% forage neutral detergent fiber (NDF)] or a diet with caloric density manipulated weekly (precision diet; n = 29; 16.2% crude protein; 1.59 to 1.68 NE_L; 18 to 26% starch; and 16 to 22% forage NDF) to promote a calculated positive energy balance of 5 Mcal/day. Diets were fed as total mixed rations and precision cows had their diets adjusted individually once a week, by feeding additional grain supplementation from 0 to 25% of daily dry matter (DM) offered, according to the energy balance of the preceding week. Energy balance was calculated daily and then averaged weekly. The study lasted from wk 3 to 19 postpartum, and nutrient digestibility, rumen fluid composition, urinary output, estimates of microbial protein synthesis, and feeding behavior were evaluated between wk 9 and 13 postpartum. Compared with controls, precision cows had similar DM intake (24.3 kg/d), but NE_L intake tended to be greater primarily between wk 4 and 8 postpartum. Yields of milk (45.2 vs. 41.9 kg/d), milk components, 3.5% fat-corrected milk (44.0 vs. 40.8 kg/d), and energy-corrected milk (43.4 vs. 40.2) were all greater for precision than control cows, resulting in greater energy-corrected milk production per kilogram of diet DM consumed (1.79 vs. 1.72). Precision cows produced more milk calories per kilogram of metabolic weight (0.227 vs. 0.213 Mcal of NE_L/kg), although the amount of consumed calories partitioned into milk (82.3%) and measures of energy status did not differ between treatments throughout the study. Glucose concentrations were greater throughout the day in precision cows compared with controls at 6 wk, but not 13 wk postpartum. Apparent digestibility of nutrients, composition of rumen fluid, mean and low rumen pH, and estimated rumen microbial N synthesis remained mostly unaltered by treatments. Although precision cows produced more milk true protein, measures of efficiency of dietary N use were not influenced by treatment. On wk 13 postpartum, precision cows consumed a diet with longer NDF particles, which resulted in a tendency for greater intake of NDF >8 mm because of less sorting against the long particles than control cows. Meal pattern differed with treatment, and precision cows consumed feed more sparsely throughout the day, spent more time ruminating lying, and had similar meal duration (mean of 36.3 min/meal) compared with control cows, but smaller meal size (3.33 vs. 3.64 kg/meal). Results from the current study indicate that allocating dietary resources according to the individual needs of cows based on energy balance improves lactation performance compared with feeding a single total mixed ration, despite similar average nutrient intake between treatments. Improvements in performance are likely related to allocation of calories based on the needs of the cow and on shifts of feeding behavior that might favor intake of smaller meals.     

Effects of limestone on starch digestion in Holstein steers

Eight calcitic and three dolomitic limestones were examined for particle size and reactivity with hydrochloric acid at pH 3.5 and 5.5. Reactivity was higher in calcitic than dolomitic limestone. Within calcitic limestones, reactivity was highly related to particle size. A highly reactive limestone was selected for use in two digestion trials with Holstein steers. In Trial 1, 4 steers (approximately 300 kg) were fed diets consisting of 40% corn silage and 60% concentrate (DM basis) with .62 or 2.34% limestone in a single reversal trial with 3-wk experimental periods. Added limestone affected only starch digestibility, which increased from 91.3 to 93.2%. Fecal pH increased from 5.7 to 6.4 by limestone addition. In trial 2, four rumen and duodenally cannulated steers (approximately 475 kg) were fed the same diets in the same design. Limestone addition increased fecal pH from 5.7 to 6.5. There were no effects of limestone on rumen or total tract digestion of starch or other nutrients. Limestone addition had no effect on rumen pH, buffering capacity, or VFA concentrations. Addition of a highly reactive limestone to diets containing high amounts of starch had little effect on starch digestion in either the rumen or lower gastrointestinal tract.     

Effects of grain source and enzyme additive on site and extent of nutrient digestion in dairy cows

Four lactating, cannulated Holstein cows were used in a 4 x 4 Latin square design to investigate the effects of grain source and fibrolytic enzyme supplementation on ruminal fermentation, nutrient digestion in the rumen and in the intestine, and milk production. A 2 x 2 factorial arrangement was used; two grains (barley and hull-less barley) were combined with and without enzyme. The enzyme supplement (Pro-Mote; Biovance Technologies Inc., Omaha, NE) contained primarily cellulase and xylanase activities and was applied daily to the total mixed diet. Dry matter intake was not affected by diet, but starch intake was greatest when hull-less barley was fed. Starch from hull-less barley was more digestible in the rumen and in the total tract than was starch from barley, but opposite results occurred for fiber digestion, indicating that hull-less barley depressed fiber digestion. As a result, cows fed the hull-less barley diets tended to produce more milk with a higher milk lactose content than did cows fed the barley diets. Enzyme supplementation had minimal effects on ruminal digestion but increased nutrient digestibility in the total tract and the proportion of microbial N in nonammonia N. Consequently, cows fed diets supplemented with enzyme had a higher milk protein content and tended to produce more 4% fat-corrected milk than did control cows. These results indicate that the use of hull-less barley rather than barley increased the digestible energy intake of dairy cows, resulting in higher milk production. The use of a fibrolytic enzyme mixture enhanced feed digestibility and milk production.     

Effect of protein on nutrient digestion and milk production by Holstein cows

Four multiparious Holstein cows fitted with ruminal and duodenal cannulae were in a 4 X 4 Latin square experiment to assess effects of increasing dietary protein on ruminal blood and duodenal traits, milk production, and nutrient digestion. Protein percents of 13, 15, 17, and 19 dry matter were achieved by rolled barley replaced with 0, 12, 24, and 36% rapeseed (canola) meal in pelleted concentrate mixtures. Increasing dietary protein concentration increased ruminal ammonia nitrogen, urea nitrogen in blood serum, and concentration of duodenal total, nonammonia, and feed nitrogen. Highest microbial nitrogen concentration was in cows fed the 15% protein diet; ruminal ammonia nitrogen was 6 mg/100 ml at this percent of protein. Cows fed 13% protein lost body weight (.43 kg/day), whereas those at 15, 17, and 19% protein gained .59, .38, and .59 kg/day. Efficiency of conversion of feed protein to milk protein declined, but digestibility of dry matter, organic matter, and nitrogen was improved with increasing dietary protein. From the traits measured, 15% crude protein appeared to be optimum for cows producing an average of 28 kg milk per day.     

The impact of somatotropin, milking frequency, and photoperiod on dairy farm nutrient flows

Three technologies that increase milk production per cow and that are available to dairy producers are bovine somatotropin, three times daily milking, and extended daily photoperiod. Dairy herds fed according to National Research Council requirements were simulated to predict the impact of these technologies on N losses to manure and to water resources. Because Dairy Herd Improvement Association total lactation records (n = 93,080) revealed a positive linear relationship between 305-d milk production and calving interval, calving intervals were predicted to increase with the use of technologies and to result in a change in the ratio of lactating cows to growing heifers in a herd. Compared with a herd using no technologies, the use of bovine somatotropin, three times daily milking, or extended photoperiod were predicted to reduce herd N excretion per unit of milk by 7.8, 7.0, and 3.6%, respectively. When the use of all three technologies was simulated, N losses to manure were decreased by 15.7% when assuming calving interval increases from the technologies or 15.4% without accounting for calving interval increases. Reductions in feed N requirements and manure N losses with these three technologies were predicted to reduce environmental N loading by up to 16%.     

Passage of inert particles varying in length and specific gravity through the postruminal digestive tract of steers

Postruminal passage of inert particles varying in specific gravity, length, and time of administration in relation to feeding, as well as interactions among these factors, were studied in four ruminally cannulated steers. Animals were allowed access to a 40% grain mix, 60% long alfalfa hay diet for 6 h daily. Eleven combinations of particle specific gravity (.9, 1.17, 1.41, or 1.77) and length (1, 5, or 10 mm) were used. Two hundred particles of each combination were placed in the abomasum at the beginning of the meal, the end of the meal, or 6 or 12 h after the end of the meal. Recovery of particles in feces within 24 or 48 h of administration and times of first appearance and maximal concentration were examined. Particle recovery 24 h after dosing as a percentage of 48-h recovery and time of maximal concentration in feces best described postruminal passage of inert particles. Passage was affected by specific gravity, but not length, of particles. Those having a specific gravity of 1.17 passed most quickly. Time at which particles were placed in the abomasum in relation to feeding affected the passage of particles varying in specific gravity. This interaction may be important in studies of ruminal passage that depend on marker appearance in feces.     

Effect of milking frequency and feeding level before and after dry off on dairy cattle behavior and udder characteristics

The effects of 2 common dry-off management procedures, feed restriction [8 vs. 16 kg of dry matter (DM)/d] and reduced milking frequency (once, 1× vs. twice, 2×/d), on the behavior and udder characteristics of dairy cattle were assessed in late lactation and the early dry period. Milking cows 1× instead of 2× in the week before dry off reduced milk yield (7.0 vs. 8.9 ± 0.95 kg/d for 1× and 2×, respectively), but had little effect on behavior before or after cessation of milking. In comparison, feed restriction reduced milk yield (6.9 vs. 9.1 ± 0.95 kg/d for 8 and 16 kg of DM/d, respectively), udder firmness after dry off (7.3 vs. 8.0 ± 0.24 g force for 8 and 16 kg of DM/d, respectively), milk leakage (2 d after dry off, 14% of cows offered 8 kg of DM/d were leaking milk compared with 42% cows offered 16 kg of DM/d), and the likelihood of Streptococcus uberis intramammary infection (nonclinical mastitis; 12.5 vs. 62.5% of groups with at least 1 cow with a new intramammary infection for 8 and 16 kg of DM/d, respectively). Despite these benefits, cows offered only 8 kg of DM/d spent less time eating (7.3 vs. 8.3 ± 0.28 h/d for 8 and 16 kg DM/d, respectively), more time lying (8.8 vs. 7.3 ± 0.24 h/d), and vocalized more before dry off than cows offered 16 kg of DM/d (0.8 vs. 0.2 ± 0.15 calls/min for 8 and 16 kg of DM/d, respectively). These behavioral changes indicate that this level of feed restriction may cause hunger. Information is needed about alternative dry-off procedures that maintain the health benefits and comfort associated with lower milk yield before dry off but prevent hunger, such as feeding low quality diets ad libitum.     

Effects of feeding level and milking frequency on behavior of dairy cows before dry-off

Drying-off may challenge the welfare of especially high-yielding dairy cows. In this study, 119 loose-housed Holstein cows yielding ≥20 kg milk/d were enrolled in a 2 × 2 factorial design aiming to investigate effects of changes in diet energy density and daily milking frequency on behavior. The last 7 d before the dry-off day, cows were milked either twice or once daily, and were fed either a lactation diet or the same diet diluted with 30% barley straw, both offered in individual bins for ad libitum intake. All cows were fitted with sensors to record lying time and activity, and data from 109 of these cows were used together with behavioral observations obtained from video recordings of 52 of the cows. Data from activity sensors and video recordings were obtained during 24 h on d −6, −3, and −1 relative to the dry-off day (i.e., the day of the last milking). Across all days of observation, cows milked once daily spent more time feeding (149 vs. 130 min/d) than cows milked twice daily. Cows on the reduced diet and milked twice daily had a shorter lying time compared with cows on the normal diet and milked twice (759 vs. 837 min/d), whereas lying times of cows on the remaining 2 treatments were intermediate. Among cows on the lactation diet, reduced milking frequency increased time spent perching (from 11.1 to 28.7 min/d). Cows fed the energy-reduced diet spent more time feeding (154 vs. 124 min/d), showed more attempts to feed from unassigned feed bins (31.7 vs. 15.4 attempts daily), and spent less time using a mechanical brush (6.5 vs. 9.2 min/d) than cows fed the lactation diet. These results show that several aspects of cows' behavior, including main activities such as lying and feeding, but also behaviors of low resilience such as brush use, and to some extent more subtle and complex behaviors such as perching and attempts to feed from unassigned feed bins, are sensitive to management changes typically applied during the days before dry-off. The behavioral effects of the reduced feed energy level support earlier findings suggesting that qualitative feed restriction renders cows hungry. The effects of the reduced milking frequency on behavior were generally less pronounced, but 2 noteworthy interactions between milking frequency and diet were seen. First, cows milked twice daily and fed the energy-reduced diet spent less time lying, which is possibly related to increased energy demand and hunger. Second, cows milked once daily and fed the lactation diet spent more time perching, which may be related to udder discomfort. However, these more complex findings warrant further study. Taken together, the results of this study show that a dry-off procedure involving reduced energy supply induces behavioral changes indicating a higher degree of compromised welfare compared with reduced milking frequency.     

Effects of feeding polyphenols from pomegranate extract on health, growth, nutrient digestion, and immunocompetence of calves

Objectives were to determine effects of feeding pomegranate extract (POMx) rich in polyphenols on performance, health, nutrient digestion, and immunocompetence of calves in the first 70 d of age. Holstein calves (n = 67), at 2 ± 1 d of age (d 0 = birth day) were randomly assigned to 0 (control), 5 (POMx5), or 10 g/d (POMx10) of pomegranate extract containing 16.9% gallic acid equivalent (GAE) to result in intakes of 0, 850 and 1,700 mg of GAE/d or an average of approximately 0, 15, and 30 mg of GAE/kg of body weight (BW) per day. All calves received colostrum during the first 24 h, pasteurized milk thereafter until 61 d of age, and grain was fed ad libitum for the first 70 d of age. Calves were housed in individual hutches, and grain intake, attitude and fecal scores, incidence and duration of health disorders, and treatments for health problems were evaluated daily. Body weight was measured on 2 consecutive days at 2, 30, and 70 d of age and averaged for each measurement. Concentrations of glucose and 3-hydroxybutyrate were measured in plasma. Nutrient digestion was measured using total fecal collection during a 3-d period. Neutrophil phagocytic and killing activities and antibody response to immunization with ovalbumin were measured. Peripheral blood mononuclear cells were cultured and cytokine production measured. Feeding POMx had no effect on intake or BW gain in the first 30 d of age, but after 30 d of age, both grain dry matter intake and BW gain decreased with increasing addition of POMx, which resulted in calves that were 1.8 and 4.3 kg lighter at 70 d of age for POMx5 and POMx10, respectively, compared with controls. Feeding POMx did not influence dry matter, organic matter, or starch digestibility, but it reduced crude protein and fat digestion. Plasma concentrations of glucose and 3-hydroxybutyrate were similar among treatments throughout the first 70 d of age. Measures of calf health such as fecal and attitude scores, risk of fever, and rectal temperature were not altered by treatments. Similarly, neutrophil phagocytic and killing activities did not differ among treatments. On the contrary, feeding POMx increased synthesis of interferon-γ and interleukin-4 by peripheral blood mononuclear cells and improved total immunoglobulin G responses to ovalbumin vaccination. These results suggest that feeding POMx top-dressed onto the grain suppresses intake of grain and digestibility of fat and protein, likely because of the high tannin content. Nevertheless, polyphenols from POMx enhanced mitogen-induced cytokine production and response to vaccination, which might benefit immune competence of calves and potentially health. Additional studies are warranted to minimize the effect of POMx on intake and digestibility and to better understand the mechanisms by which polyphenols improve immune response of calves.     

Effects of intake of a mixed dairy steers on digestion events

Ruminally cannulated steers were in a 4 X 4 Latin square to determine the effect of amount of feed ingested on fiber digestion and other digestion events. Alfalfa haylage, corn silage, and a corn-soybean meal mix were incorporated in a ratio 45:20:35 (dry matter) and fed at either 100, 85, 70, or 55% of ad libitum intake. Acid-insoluble ash, lanthanum, and chromium-ethylenediaminetetraacetic acid were digestion, particulate, and liquid markers. Apparent digestibility of dry matter, neutral detergent fiber, and cell solubles decreased linearly as feed intake increased. The fiber fraction digested was a larger percentage of the dry matter digested at low than at high intakes of feed. A more rapid rate of cellulose disappearance and a slow rate of passage of particulate matter through the rumen and total digestive tract with decreasing feed intake were key factors responsible for bringing about changes of digestion coefficients. A consistently lower rumen pH of steers at high intakes of feed was thought to account for the slower rate of ruminal fiber disappearance. The lower tract accounted for 11 to 17% of dry matter disappearance, and tended to play a greater role during periods of high feed intake. Rumen and fecal sampling techniques provided similar ruminal rates of solids passage.     

Starch and stage of maturity of grass silage: site of digestion and intestinal nutrient supply in dairy cows

The interaction between the quality of grass silage and starch supplementation on ruminal digestion was studied in an experiment with a 2 x 2 factorial design using four dairy cows. Treatment factors were grass silage harvested after either 21 or 37 d of regrowth and two concentrations of steam-flaked corn starch (0 or 4 kg/d). Ruminal volume and flow of duodenal digesta were estimated. When forage was harvested at a more mature stage, only minor effects were noted for silage composition and, consequently, ruminal and intestinal digestion. The addition of starch to the diet tended to reduce ruminal digestion of neutral detergent fiber. The reduction in ruminal digestion was not compensated by increased digestion in the large intestine. Starch increased duodenal nonammonia N flow because of an increase in bacterial N flow. The increase in bacterial N was accompanied by a reduction in the escape of feed N from the rumen. Results from this study indicate that the addition of ruminally available starch to diets based on grass silage reduced ruminally degradable neutral detergent fiber and increased the duodenal supply of protein. These effects have to be taken into account to predict production responses to extra starch.     

Effects of feeding forage soybean silage on milk production, nutrient digestion, and ruminal fermentation of lactating dairy cows

The objective of this study was to determine the feeding value of forage soybean silage (SS) for dairy cows relative to a fourth-cut alfalfa silage (AS). Forage soybean was harvested at full pod stage. Two isonitrogenous diets were formulated with a 48:52 forage:concentrate ratio. Soybean silage and AS constituted 72% of the forage in each diet, with corn silage constituting the remaining 28%. Twenty Holsteins cows in early lactation were used in a switchback design. Four lactating Holsteins cows fitted with ruminal cannulas were used to determine the effects of dietary treatments on ruminal fermentation parameters and in vivo total tract nutrient utilization. Relative to AS, SS contained 15, 28, and 25% more neutral detergent fiber, acid detergent fiber, and crude protein, respectively. Dry matter intake (23.5 vs. 25.1 kg/d) and milk yield (35.5 vs. 37.2 kg/d) were lower for cows fed SS than for those fed AS. However, energy-corrected milk and milk efficiency were similar for both dietary treatments. Milk protein, lactose, and total solids concentrations were not influenced by dietary treatments (average 3.0, 4.7, and 12.6%, respectively). However, cows fed SS produced milk with greater milk fat (3.8 vs. 3.6%) and milk urea nitrogen concentrations (15.6 vs. 14.3 mg/dL) compared with cows fed AS. Ruminal pH was lower, whereas ruminal NH₃-N concentration was greater in cows fed SS than in cows fed AS. Total tract digestibilities of dry matter, crude protein, and neutral detergent fiber were not influenced by silage type. We concluded that forage SS, when compared with AS, had a negative impact on feed intake and milk yield, whereas energy-corrected milk, milk efficiency, and total tract nutrient digestion were similar.     

Effects of milk replacer feeding rate and fat content on Jersey calf nutrient digestion and performance to 4 months of age

This study evaluated effects of milk replacer (MR) feeding rate and fat concentration in MR on total-tract digestion (TTD) and growth performance in Jersey calves. Jersey heifer calves (n = 100, 2 blocks of 50; initially 30 ± 3.0 kg of body weight; 4–11 d of age) were randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement of MR feeding rate [454 g for 42 d, and 227 g for 7 d (MOD); or 454 g for 7 d, 681 g for 35 d, and 341 g for 7 d (HI), as-fed basis] and MR fat content (17 or 24% fat as-fed basis). Milk replacers (24% crude protein as-fed basis) were reconstituted to 14% solids and fed in 2 equal feedings for 42 d, and then mornings only for 7 d. Textured calf starter (21% crude protein, 40% starch, dry matter basis) and water were offered for ad libitum consumption. From d 57 to 112, calf starter was mixed with 5% chopped grass hay. Calves were housed individually to d 56 and housed in groups (4–5 calves/pen) from d 57 to 112. Estimates of TTD were measured in 5 calves/treatment (block 1) at wk 3 of the study using acid-insoluble ash as an indigestible marker. From 0 to 56 d, calf starter intake (CSI) was greater for MOD vs. HI and 17 versus 24% fat; average daily gain was greater for HI versus MOD; and hip width change was greater for 17 versus 24% fat. Estimates of organic matter TTD were greater for HI versus MOD, but neutral detergent fiber TTD was greater for MOD versus HI and for 17 versus 24% fat. From 57 to 112 d, hip height change was greater for MOD versus HI, and hip width change was greater for 17 versus 24% fat. In this study, feeding Jersey calves more MR improved preweaning average daily gain, but had a negative effect on CSI and likely rumen development, as neutral detergent fiber TTD was reduced at 3 wk and frame growth was reduced from d 57 to 112. This resulted in similar final calf body weights between MR feeding rates at the end of the study. No benefits were observed for feeding more fat in MR as CSI or for NDF digestibility, and frame growth was reduced.     

Effect of genetic potential and level of feeding on milk protein composition

Two groups of 15 multiparous cows in mid-lactation were used in a Latin square design experiment with 4-week experimental periods. The genetic milk protein concentration level was high in the first group and low in the second. Each group of cows was given in a random order three feeding levels that covered 85, 100 and 115% of energy requirements and 90, 110 and 125% of nitrogen requirements, respeetively. In both groups, increasing level of feeding induced a significant increase in milk yield (+ 2.4 kg/d between lowest and highest levels) and in protein concentration (+ 1.7 g/kg). The proportion of paracasein in total proteins was not altered by either genetics or nutrition. The proportion of casein in total proteins was slightly increased by 0.5 percentage points (P < 0.05) with the intermediate level of feeding. Plasmin and plasminogen activities were not significantly modified by the genetic milk concentration level. Plasmin activity significantly increased with nutrient supplementation, but only in animals of low genetic potential (+ 21% between low and high levels, P < 0.01). Casein composition was not significantly altered by the genetics or level of nutrition. Over the whole range of individual measurements taken (n = 90), the relationships between casein or paracasein and total protein concentrations were linear and very narrow (R2 = 0.92 and 0.95, respectively). The proportion of casein or paracasein in total proteins significantly decreased as plasmin activity increased.     

Effect of corn particle size on site and extent of starch digestion in lactating dairy cows

Two experiments were conducted to determine the effects of corn particle size (CPS) on site and extent of starch digestion in lactating dairy cows. Animals were fitted with ruminal, duodenal, and ileal cannulas. Dry corn grain accounted for 36% of dry matter intake. In experiment 1, 6 cows were used in a duplicate 3 x 3 Latin square design. Semiflint corn was used. Corn processing methods were grinding, medium rolling, and coarse rolling. The mean particle size of the processed corn was 730, 1807, and 3668 microm, respectively. Rumen digestibility of starch linearly decreased from 59% with ground corn to 36% with coarsely rolled corn. Similarly, small intestine digestibility linearly decreased with increased CPS, and consequently, the amount of starch digested in the small intestine was not affected by corn processing. In experiment 2, 4 cows were used in a 2 x 2 crossover design. Dent corn was used. Corn processing methods were grinding and coarse rolling. The mean particle size of the processed corn was 568 and 3458 microm, respectively. Rumen digestibility of starch decreased from 70% with ground corn to 54% with coarsely rolled corn. Small intestine digestibility of starch was not significantly affected by CPS, and the amount of starch digested in the small intestine tended to be greater for rolled than for ground corn. In both experiments, starch total tract digestibility decreased with increased CPS. In conclusion, CPS is an efficient tool to manipulate rumen degradability of cornstarch. In midlactation cows, the decrease in the amount of starch digested in the rumen between grinding and coarse rolling is partly compensated for by an increase in the amount of starch digested in the small intestine with dent genotype, but with semiflint genotype postruminal digestion is not increased and rumen escape starch is not utilized by the animal.