Effects of feed processing and frequency of feeding on ruminal fermentation, milk production, and milk composition

Frequency of diet delivery to dairy cows: Effect on nutrient digestion, rumen fermentation, methane production, nitrogen utilization, and milk production

The objective of this study was to examine the effect of frequency of diet delivery to dairy cows on nutrient digestion, rumen fermentation, milk production, nitrogen utilization, enteric methane emission, and manure methane production potential. Twelve lactating cows were used in a replicated 3 × 3 Latin square design (35-d period) and offered a TMR ad libitum [56:44 ratio of forage to concentrate, dry matter (DM) basis] once (0930 h), twice (0930 and 2130 h), or 4 times daily (0930, 1300, 1630, and 2130 h). Frequency of diet delivery did not affect intake or apparent total-tract digestibility of DM and nutrients. Likewise, milk production, milk composition (fat, protein, and lactose), and milk production efficiency (kg of milk/kg of DM intake or g of milk N/g of N intake) were not changed by frequency of diet delivery. Although diurnal variation of ruminal pH, total VFA, and acetate molar proportion were influenced by frequency of diet delivery, daily average ruminal pH, total VFA, and acetate and propionate molar proportions were not affected by frequency of diet delivery. Daily enteric CH₄ emission averaged 534 g/d and was not changed by frequency of diet delivery. Methane energy losses (on gross energy intake basis) were lower when cows received the diet once daily (5.8%) versus twice or 4 times daily (6.1%). Urinary N excretion was higher for cows receiving the diet 4 times daily compared with cows receiving the diet once or twice daily (36 vs. 34% of N intake). Frequency of diet delivery had no influence on manure volatile solids excretion or maximal CH₄ production potential. Results from this study show that delivering the diet once daily reduces enteric CH₄ energy losses compared with twice or 4 times daily, whereas urinary N losses increased by delivering the diet 4 times daily compared with once or twice daily. However, milk production and maximal manure CH₄ emission potential were not affected by frequency of diet delivery.

Effects of 2 colostrum and subsequent milk replacer feeding intensities on methane production, rumen development, and performance in young calves

A growing need exists for the development of practical feeding strategies to mitigate methane (CH₄) emissions from cattle. Therefore, the objective of this study was to evaluate the influence of milk replacer feeding intensity (MFI) in calves on CH₄ emission, rumen development, and performance. Twenty-eight female newborn Holstein calves were randomly assigned to 2 feeding groups, offered daily either 10% of the body weight (BW) in colostrum and subsequently 10% of the BW in milk replacer (MR; 10%-MR), or 12% of the BW in colostrum followed by 20% of the BW in MR (20%-MR). In wk 3, half of each feeding group was equipped with a permanent rumen cannula. Both groups were weaned at the end of wk 12. Hay and calf starter (mixture of pelleted grains) were offered from d 1 until wk 14 and 16, respectively. A total mixed ration was offered from wk 11 onward. Feed intake was measured daily and BW, anatomical measures, and rumen size weekly. Methane production and gastrointestinal passage rate were measured pre-weaning in wk 6 and 9 and post-weaning in wk 14 and 22, with additional estimation of organic matter digestibility. Rumen fluid, collected in wk 1, 2, 3, 6, 9, 14, 18, and 22, was analyzed for volatile fatty acid concentrations. Although the experimental period ended in wk 23, rumen volume of 17 calves was determined after slaughter in wk 34. Data was analyzed using ANOVA for the effects of feeding group, cannulation, and time, if applicable. Dry matter intake (DMI) of solid feed (SF) in 20%-MR animals was lower pre-weaning in wk 6 to 10 but mostly higher post-weaning. From wk 6 onward, anatomical measures and BW were greater in 20%-MR animals, and only the differences in body condition score gradually ceased post-weaning. Following the amount of SF intake, 10%-MR calves emitted more CH₄ pre-weaning in wk 9, whereas post-weaning the 20%-MR group tended to have higher levels. Methane emission intensity (CH₄/BW) was lower pre-weaning in 20%-MR animals but was comparable to the 10%-MR group post-weaning. Methane yield (CH₄/DMI of SF) and estimated post-weaning organic matter digestibility were not affected by MFI. Rumen size normalized to heart girth was greater in 10%-MR calves from wk 5 to 10, but differences did not persist thereafter. In wk 34, rumen volume was higher in 20%-MR calves, but normalization to BW revealed no difference between feeding groups. In conclusion, high MFI reduces CH₄ emission from calves pre-weaning, although this effect ceases post-weaning.

Milk yield and quality in Guernsey cows fed cottonseed cake-based diets partially substituted with baobab (Adansonia digitata L.) seed cake

The objective of this study was to determine the effects of partially substituting cottonseed cake with graded levels of baobab (Adansonia digitata L.) seed cake (BSC) on milk yield and quality in Guernsey cows. Sixteen cows in mid-lactation and in their third parity were allocated to diets containing 0% (control), 5%, 10%, and 15% BSC in a completely randomized design. Each cow was given a daily feed ration of 6 kg and a basal diet of soya bean stover ad libitum. There were no differences in daily feed intake (P > 0.05), but basal intake differed among all treatment groups with cows on the control diet having the highest intake (30 ± 0.34 kg/day). Mean daily milk yield differed (P < 0.05) among all treatment groups. However, the control had higher milk yield of 12.1 ± 0.73 kg/day, and the 15% BSC had the least yield of 7.46 ± 0.73 kg/day. Cows on the control diet had higher milk butterfat content (6.12%; P < 0.05) than those on the BSC-based diets. Protein content differed (P < 0.05) across all treatment groups with cows on 15% BSC producing the highest protein content (3.43%) while the control had the least (2.6%). The concentration of milk total solids for cows fed on 15% BSC was higher (P < 0.05) than that from cows on other diets. Lactose content was not affected by the diets (P > 0.05). These results indicate that BSC can substitute soya bean cake in dairy diets, but milk production and butterfat content are compromised.

Effects of feeding frequency on intake, ruminal fermentation, and feeding behavior in heifers fed high-concentrate diets1

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

Initial pH as a Determinant of Cellulose Digestion Rate by Mixed Ruminal Microorganisms In Vitro

In vitro fermentations of pure cellulose by mixed ruminal microorganisms were conducted under conditions in which pH declined within ranges similar to those observed in the rumen. At low cellulose concentrations (12.5 g/L), the first-order rate constants (k) of cellulose disappearance were successively lower at initial pH values of 6.86, 6.56, and 6.02, but in each case the value of k was maintained over a pH range of 0.3 to 1.2 units, as the fermentation progressed. Plots of k versus initial pH were linear, and k displayed a relative decrease of approximately 7% per 0.1 unit decrease in pH. At high cellulose concentration (50 g/L) and an initial pH of 6.8, cellulose digestion was initially zero order, the absolute rate of digestion declined with pH and digestion essentially ceased at pH 5.3 after only 30% of the added cellulose was digested. Further incubation resulted in a loss of bound N and P, suggesting that at low pH cells lysed or detached from the undigested fibers. Pure cultures of ruminal cellulolytic bacteria also were able to ferment cellulose to a minimum pH of 5.1 to 5.3, but the extent of fermentation was increased by coculture with noncellulolytic bacteria. A model is proposed in which the first-order rate constant of cellulose digestion is determined by the pH at which the fermentation is initiated, and end product ratios reflect greater activity of the noncellulolytic population as pH declines.

[Effect of hay particle size at different concentrations and feeding levels on digestive processes and feed intake in ruminants. 1. Chewing activity and fermentation in the rumen]

In order to study the main effects of particle size three ruminally fistulated cows were fed a hay rich in fibre in long (28.7 mm), chopped (9.2 mm) and ground (2.9 mm) form in a 3 x 3 Latin square design. In another three factorial experiment with 8 wethers (4 animals were ruminally fistulated) the main effects and interactions of the above mentioned hay particle size at two concentrate levels (10.4 to 13.3 and 29.5 to 40.1% in the ration) and at two feeding levels (restricted and ad libitum) were investigated. There was no effect of chopped hay (9.2 mm) on chewing activity, whereas ground hay (2.9 mm) reduced rumination time (52% in sheep and 36% in dairy cows) and chewing expense (time/unit of DM or NDF intake). These effects were more pronounced at high concentrate intake. Sheep increased feed intake more through reduction of rumination expense than through the extension of rumination time. pH-value, concentration of bicarbonate and C2:C3-ratio indicate favourable fermentation conditions in long (28.7 mm) and chopped hay (9.2 mm), whereas a negative influence of ground hay (2.9 mm) or ruminal fermentation could be observed.

Effects of extrusion of grain and feeding frequency on rumen fermentation, nutrient digestibility, and milk yield and composition in dairy cows

The effect of corn extrusion and feeding frequency on ruminal and postruminal digestibility and milk yield was studied in cows fed a high concentrate diet. Four Israeli Holstein cows fitted with rumen and abomasal cannulas were used. The experiment was arranged as a 2 x 2 factorial design, with two diets and two feeding frequencies (two or four meals per day). One diet contained 40% ground corn. In the second diet, half of the ground corn was replaced with extruded corn. Feeding cows the extruded versus ground corn diet decreased ruminal ammonia N and plasma urea N concentrations, increased postruminal digestibility of nonstructural carbohydrates, reduced dry matter intake, decreased yield of milk and milk components, and increased efficiency of milk energy and milk protein synthesis. The inclusion of extruded corn in the diet did not affect ruminal volatile fatty acid. Increasing the feeding frequency reduced the diurnal variation in ruminal pH, ruminal ammonia, and plasma urea, and increased dry matter intake--considerably more in the cows fed ground versus extruded corn--and improved postruminal organic matter, nonstructural carbohydrate, and crude protein digestibility. Total tract digestibility of organic matter and crude protein and milk yield and composition were also increased when cows were fed four versus two meals. Concurrent with the feeding frequency and grain processing effect, an increase in rumen-undegradable protein flow was related to increased digestion of nonstructural carbohydrate postruminally (r = 0.54). We concluded that for cows fed high-starch diets more frequent meals are useful for improving postruminal digestibility and milk yield and composition.

Measuring the effectiveness of fiber by animal response trials

Chemical analysis of neutral detergent fiber (NDF) provides a useful description of forages and other feeds. However, use of NDF as the sole measure of the fiber contribution of a feed has proved problematic for two classes of feeds: forages processed into differing physical forms and high fiber by-products. By-products and physically fine forages contribute to the fiber value of dairy rations, but contribute less than long forages do. Therefore, some discount factors must be assigned to these feeds if fiber requirements are to be used in balancing the carbohydrate portion of dairy diets. The effectiveness factors applied to NDF from these feeds provide an improved measure of fiber value. The assumptions and trial designs used to measure the effectiveness of NDF based on any single animal response variable are discussed, and improved approaches are suggested. The use of different response variables to measure physical and overall fiber effectiveness is discussed. Measured effectiveness of a high fiber feed differs when estimated by chewing, by the ratio of acetate to propionate, or by milk fat concentration. In all cases, inclusion of negative control treatments is necessary to measure the effect of removing fiber without introducing a substitute fiber source.

Relationship between fermentation acid production in the rumen and the requirement for physically effective fiber

The content of ruminally fermented OM in the diet affects the fiber requirement of dairy cattle. Physically effective fiber is the fraction of feed that stimulates chewing activity. Chewing, in turn, stimulates saliva secretion. Bicarbonate and phosphate buffers in saliva neutralize acids produced by fermentation of OM in the rumen. The balance between the production of fermentation acid and buffer secretion is a major determinant of ruminal pH. Low ruminal pH may decrease DMI, fiber digestibility, and microbial yield and thus decrease milk production and increase feed costs. Diets should be formulated to maintain adequate mean ruminal pH, and variation in ruminal pH should be minimized by feeding management. The fraction of OM that is fermented in the rumen varies greatly among diets. This variation affects the amount of fermentation acids produced and directly affects the amount of physically effective fiber that is required to maintain adequate ruminal pH. Acid production in the rumen is due primarily to fermentation of carbohydrates, which represent over 65% of the DM in diets of dairy cows and have the most variable ruminal degradation across diets. The non-fiber carbohydrate content of the diet is often used as a proxy for ruminal fermentability, but this measure is inadequate. Ruminal fermentation of both nonfiber carbohydrate and fiber is extremely variable, and this variability is not related to the nonfiber carbohydrate content of the diet. The interaction of ruminally fermented carbohydrate and physically effective fiber must be considered when diets for dairy cattle are evaluated and formulated.

Chewing activities and milk production of dairy cows fed alfalfa as hay, silage, or dried cubes of hay or silage

The objective of this research was to compare the effects of dried cubed hay or silage and long hay or silage on chewing activities and milk production of dairy cows. Second-cutting alfalfa was preserved as hay or wilted silage, and a portion of each forage was dried (hay at 80 degrees C; silage at 175 degrees C) and cubed (5 x 3 x 3 cm). The crude protein effective degradability of forages measured in sacco was (dry matter basis) hay, 69%; hay cubes, 70%; silage, 87%; and silage cubes, 82%. Forages were fed in a replicated 4 x 4 Latin square to eight lactating Holstein cows. The diets, consisting of 45% forage (dry matter basis), were fed in a 2 x 2 factorial arrangement; hay or silage was unprocessed or cubed. The dry matter intake were about 2.6 kg/d lower for cows fed silage than for cows fed hay, but the method of preservation did not affect production or fat content of milk or chewing times. Cubing decreased dry matter intakes of both forages by about 1.5 kg/d (2.90%), resulting in a 3.5 to 4.3% reduction in milk production and a 52 to 62% reduction in rumination time. The milk fat content was unexpectedly low for cows fed long hay (2.90%); therefore, cubing only decreased the milk fat content of cows fed silage (silage, 3.34%; silage cubes, 2.86%). Silage offers a viable alternative to hay for cubing. However, for dairy cows receiving high concentrate diets, cubed hay or silage as the sole source of forage might lower intake and reduce milk production compared with effects of uncubed hay or silage.

Compressed baled alfalfa hay for primiparous and multiparous dairy cows

Compressed baled alfalfa hay was fed to cows, and the effects on productivity, chewing activities, and digestion were measured using a replicated 4 x 4 Latin square design. Cows received second-cutting alfalfa hay (20% CP; 40% NDF) from either compressed or standard small rectangular bales at two forage to concentrate ratios (35:65 and 65:35, DM basis). Compressed hay did not affect milk yield, although milk fat content was higher (2.90 vs. 2.68%). Higher concentrate diets increased milk yield (32.2 vs. 28.3 kg/d), lowered milk fat (2.66 vs. 2.91%), and increased milk protein (3.16 vs. 2.99%) and lactose (5.06 vs. 4.99%) with no interaction between concentrate proportion and hay type. Cows fed compressed bales spent less time eating per kilogram of DM and NDF consumed than cows fed standard bales, but rumination time was unaffected by forage processing. For cows fed both types of hay, digestibilities of DM, ADF, and NDF were similar; ruminal liquid outflow rates also were similar, but rate of particulate passage from the reticulo-rumen was greater for cows receiving compressed hay. Compressing alfalfa hay did not adversely affect forage quality but increased the ease of shipping and handling and minimized storage space requirements. This process may be beneficial when higher milk fat content is desirable or when cows have limited time to consume forage.