Effects of maize grain and lucerne particle size on ruminal fermentation, digestibility and performance of cows in midlactation

This study evaluated the effects of, and interactions between, maize grain particle size (MPS) and lucerne particle size (LPS) on dry matter intake, milk production, milk composition, ruminal fermentation, microbial yield, chewing activity and nutrient digestibility in midlactation cows. Four multiparous Holstein cows with ruminal cannulas were assigned randomly to a 4 x 4 Latin square design, averaged 595 kg (SD = 52) of body weight and 121 days in milk (SD = 21) at the start of the experiment. Experimental periods were 21 days in length (14 days of treatment adaptation and 7 days of data collection). All diets were fed as total mixed ration and were formulated to meet or exceed the requirements of a 600 kg multiparous cow producing 20 kg milk/day with 4.0% fat. The ratio of concentrate to forage was 39:61 (dry matter basis). Treatments were arranged in a 2 x 2 factorial design; two levels of LPS (2.54 and 6.22 mm) were combined with concentrates based on either ground maize grain (711 mum) or cracked maize grain (1755 mum). Maize grain and LPS did not affect milk production and milk fat percentage. Milk protein percentage increased when MPS was decreased (p = 0.04). Milk urea nitrogen was lower for cows fed ground maize grain compared with cracked maize grain (118-134 mg/l, p = 0.05). Estimated microbial N supply increased 41.9 g/day for ground maize grain compared with cracked maize grain. Cows fed long lucerne (LL) hay spent more time ruminating compared with cows fed short lucerne (SL) hay ranging from 293 to 336 min/day (p < 0.001). Total time spent chewing by cows increased from 505 to 574 min/day (p = 0.002) for SL and LL respectively. Based on the results from this study, midlactation cows can be fed diets that contain ground maize grain and SL hay without leading to negative effects on ruminal pH and nutrient digestibility.     

Effects of inclusion of graded amounts of soya bean hulls on feed intake,chewing activity and nutrient digestibility in dairy cows

Twelve multiparous Holstein dairy cows were used in a replicated 4 × 4 Latin square changeover design to evaluate the effects of graded inclusion of soya bean hulls (SHs) in replacement of diet forages at 0%, 10%, 20% and 30% of dietary dry matter (DM) basis on peNDF > 8 and peNDF > 1.18 contents of diets and their resulting effects on chewing activity, nutrient digestibility and milk production of dairy cattle. The control diet contained 50% forage, 50% concentrate and no SH. In the other three diets, SH was substituted for alfalfa hay, corn silage and wheat bran to supply 10%, 20% and 30% of the dietary DM. Increasing SH concentration in the diets resulted in decreasing concentrations of forage neutral detergent fibre (NDF), physically effective NDF (peNDF) and mean particle size (p < 0.01). Chewing activity per kilogram of daily dry matter intake (DMI) was not affected by the different diets tested. However, chewing activity significantly decreased for kilogram intake of NDF, but increased for peNDF > 1.18 when SH was included in the diets (p < 0.01). Total tract apparent digestibility of nutrients significantly increased for DM, organic matter (p < 0.05) and NDF (p < 0.01) but decreased for crude protein (p < 0.05) as the proportion of SH was increased in the diets. Rumen pH value of cattle was not influenced by the diets. Including medium and high amounts of SH in the diets decreased DMI of the animals (p < 0.05) without any significant effect on their daily milk or 4% fat‐corrected milk production. In conclusion, the results of this study showed that the NDF from a non‐forage fibre source like SH had a lower potential for stimulating chewing activity than did forage NDF. Despite this, the small size of dietary particles increased not only the chewing activity per kilogram of peNDF intake but also saliva secretion as well as the potential for rumen to neutralize acids. The findings of this study demonstrate the greater differences in peNDF > 8 among the diets and that these differences are better reflected in terms of DMI, chewing activity and nutrient digestibility, but not in rumen pH.     

Effects of feeding ratio of beet pulp to alfalfa hay or grass hay on ruminal mat characteristics and chewing activity in Holstein dry cows

The influence of the feeding ratio of a non‐forage fiber source and hay on ruminal mat characteristics and chewing activity was evaluated in dairy dry cows. Cows were fed four different diets: the ratios of alfalfa hay (AH) to beet pulp (BP) were 8:2 (dry matter basis, A8B2) and 2:8 (A2B8), and those of grass hay (GH) to BP were 8:2 (G8B2) and 2:8 (G2B8). Total eating time was decreased with increasing BP content (P < 0.01). Total rumination time for AH was shorter than that for GH (P < 0.01), and it decreased with increasing BP content (P < 0.01). The ruminal mat was detected by using a penetration resistance test of the rumen digesta. Penetration resistance value (PRV) of ruminal mat was highest with the G8B2 diet and PRV decreased with increasing BP content (P < 0.05) and feeding AH (P < 0.05). Thickness of the ruminal mat was greater for increasing BP content (P < 0.05). Simple linear regression of ruminal mat PRV on total rumination time resulted in a high positive correlation (r = 0.744; P < 0.001; n = 16). The results demonstrated that increasing the PRV of the ruminal mat stimulated rumination activity and a ruminal mat could be formed, although it was soft even when cows were offered a large quantity of BP.     

Effects of substituting kraft pulp with corn silage on dry matter intake,ruminal mat formation,rumen fermentation,and rumination activity in non‐lactating cows

The present study examined the effects of substituting kraft pulp (KP) with corn silage (CS) on dry matter intake (DMI), ruminal mat and rumen fermentation characteristics, and rumination. Four non‐lactating, rumen‐cannulated Holstein cows were fed a CS diet comprising 36% grass silage (GS) and 64% CS or a KP diet comprising 36% GS, 57% KP, and 7% soybean meal. DMI was significantly lower in cows fed the KP diet than in those fed the CS diet (p < 0.05), whereas rumination time did not significantly differ between the treatments. Dry matter content in the rumen immediately before and 3 h after feeding was significantly higher in cows fed the KP diet than in those fed the CS diet (p < 0.05). The consistency and thickness of the ruminal mat did not significantly differ between the treatments. The ruminal mean retention time of feed particles tended to be longer in cows fed the KP diet than in those fed the CS diet (p < 0.10). The ruminal digestion rate of KP was comparable to that of GS and CS. Because ruminal mat was formed and rumination was stimulated, KP was considered to have the equivalent physical effectiveness as CS.     

Effects of inclusion levels of pelleted silvergrass (Miscanthus sinensis Andress.) in the diet on digestibility,chewing activity,ruminal fermentation and blood metabolites in breeding Japanese Black cows

To examine the effects of inclusion levels of pelleted silvergrass (PS) in the diet on digestibility, ruminal fermentation and nutrient status of breeding Japanese Black cows, four cows were allotted to a 4 × 4 Latin square design experiment. Treatments were control fed a diet consisting of 89.4% Sudangrass hay and 10.6% soybean meal on a dry matter (DM) basis, and PS18, PS27 and PS45 fed the diet replaced with 18%, 27% and 45% of control with PS, respectively. The total digestible nutrients (TDN) content of PS was 45.6% on a DM basis. The TDN intakes were significantly decreased by increasing PS level in the diet (P < 0.05), but were higher than the TDN requirement of maintenance cows in all treatments. The total chewing time was decreased significantly by increasing PS level in the diets (P < 0.05). However, the pH and concentration of volatile fatty acid in the ruminal fluid and serum metabolite concentrations were not significantly different among the treatments. The results suggested that including PS up to 45% in the diet did not have adverse effects on the ruminal fermentation and nutrient status in breeding Japanese Black cows at the maintenance stage.     

Effects of different forage combinations in total mixed rations on in vitro gas production kinetics,ruminal and milk fatty acid profiles of lactating cows

This study aimed to determine the effects of different forage combinations on in vitro gas production (GP) kinetics, ruminal and milk fatty acid profiles. Forty‐five lactating cows were randomly arranged into three groups and fed three total mixed rations (TMRs) with different forage combinations: TMR1, 23% alfalfa hay, 7% Chinese wild ryegrass hay and 15% whole corn silage; TMR2, 30% corn stover plus 15% whole corn silage; TMR3, 30% rice straw plus 15% whole corn silage. In vitro dry matter disappearance ranked: TMR1 > TMR2 > TMR3, and highest cumulative GP and asymptotic GP occurred in TMR1 while no difference occurred between TMR2 and TMR3. The average GP rate ranked: TMR1 > TMR2 > TMR3. TMR1 in comparison with TMR2 and TMR3 presented lower rumen contents of acetate and butyrate and greater rumen contents of propionate, valerate, C13:0, C14:0, C15:0, C18:1cis‐9, C18:2n‐6, C18:3n‐3, C20:0 and C22:0 as well as milk C18:2n‐6 and C18:3n‐3 proportions. Transfer efficiencies of C18:2n‐6 and C18:3n‐3 from diet to milk ranked: TMR1 > TMR2 > TMR3. The findings suggest TMRs containing alfalfa hay and Chinese wild ryegrass hay in comparison with corn stover or rice straw improve rumen fermentation and transfer efficiency of C18:2n‐6 and C18:3n‐3.     

Effect of a non‐forage fiber of red bean hulls on ruminal mat characteristics,chewing activity and milk production in dairy cows

The evaluation of red bean hulls (RBH) as a non‐forage fiber source on ruminal mat formation, chewing activity and milk production was determined using two experiments. In experiment 1, four non‐lactating, rumen‐cannulated Holstein cows were offered a control diet of 60.1% forage, and an RBH diet of 51.6% forage and 9.4% RBH. Although the neutral detergent fiber (NDF) intake was higher with the RBH diet than the control diet, the physically effective NDF (peNDF) intake was lower. The rumination period tended to be longer with the RBH diet than with the control diet and the ruminal mat was formed even when the RBH diet was consumed. Ruminal fermentation parameters were not affected by treatment. In experiment 2, 40 lactating cows were fed a control diet of 53.4% forage or an RBH diet of 50.3% forage and 8.1% RBH. Dry matter intake, chewing activity and milk production were not affected by diet. Cows sorted against NDF in the control diet, but not in the RBH diet. It is concluded that normal ruminal function can be maintained because the ruminal mat was stratified and rumination activity was not reduced even when a low peNDF diet that contained RBH was given to dairy cows.     

粗饲料颗粒长度对山羊咀嚼活动和瘤胃发酵的影响

试验旨在研究粗饲料颗粒长度对山羊咀嚼活动和瘤胃发酵的影响。以4只体重为(40.0±2.2)kg安装瘤胃和十二指肠瘘管的成年山羊为试验动物,采用4×4拉丁方设计,饲喂4种不同粗饲料长度的日粮。结果表明:随粗饲料颗粒长度的增加,反刍和咀嚼时间分别线性增加175和156min/d,进而提高了瘤胃平均pH值;增加粗饲料颗粒长度,趋向于线性提高丙酸(P=0.08)和降低(P=0.09)丁酸的摩尔比例,但不影响总VFA浓度和乙酸丙酸比。结果证实,增加粗饲料颗粒长度,刺激了动物的咀嚼活动,改善了瘤胃pH值。     

Effects of grain source and marginal change in lucerne hay particle size on feed sorting,eating behaviour,chewing activity,and milk production in mid‐lactation Holstein dairy cows

This study investigated the effects of grain source and lucerne hay (LH) particle length on eating behaviour, chewing activity, and milk production of lactating dairy cows. Eight Holstein dairy cows (175 ± 21 days in milk) were used in a replicated 4 × 4 Latin square design with four 21‐days periods. The experiment was a 2 × 2 factorial arrangement of treatments with barley grain alone or equal blend of barley and maize grains combined with short (15 mm) and long (30 mm) LH. Diets were fed ad libitum as total mixed ration with a concentrate to forage ratio of 60:40. Interactions between grain source and LH particle length on feed particle distributions, sorting index, chewing activity, and milk production were minimal. Partially replacing barley grain with maize in the diet overall did not change diurnal distributions of particles retained on the sieves of Penn State Particle Separator but reduced the proportion of particles on 1.18‐sieve and increased that of particles on pan (p < 0.05). Grain source did not affect sorting index and chewing activity. However, feeding long LH increased (p < 0.01) intakes of long particles retained on 19‐ and 8‐mm of sieve, prolonged (p < 0.05) eating time, and lowered eating rate (p < 0.05). Interestingly, cows fed with long LH ate more coarse particle during critical‐early time post feeding (i. e. 1.5 h), where eating time increased and eating rate decreased (p < 0.05). Increasing particle length of dietary LH tended to increase milk fat‐to‐protein ratio (p = 0.08). The results suggested that the increased eating time and decreased eating rate as a result of marginally increasing LH particle length would be beneficial to alleviate reduction of ruminal pH and milk fat percentage following the ingestion of highly fermentable diets.     

Effects of physically effective fiber in diets based on rice straw and cassava pulp on chewing activity,ruminal fermentation,milk production,and digestibility in dairy cows

The objective of this study was to evaluate the effects of physically effective neutral detergent fiber (peNDF) in rice straw and cassava pulp diets on the chewing activity, ruminal fermentation, milk production, and digestibility in low‐producing dairy cows. Eight lactating Holstein crossbred cows were randomly divided into two groups in a crossover design with two dietary treatments over two 21‐day periods. The difference in peNDF contents was achieved by balancing the ratio of rice straw, cassava pulp, and concentrate. The high cassava pulp diet had 15.5% peNDF and the low cassava pulp diet had 20.2% peNDF. The results showed that feeding the low cassava pulp diet increased the concentrations of milk protein, milk fat, solids‐not‐fat, and total solids in the milk. In contrast, the dry matter intake, milk yield, lactose content, chewing activity, nutrient digestibility, ruminal fermentation, and pH were not affected by treatments.     

Effect of wood kraft pulp feed on digestibility,ruminal characteristics,and milk production performance in lactating dairy cows

The effect of wood kraft pulp (KP) feed on dietary digestibility, ruminal fluid pH, rumen fermentation characteristics, and milk production performance in lactating dairy cows was examined. Four lactating dairy cows were used for the feeding experiment by the cross‐over design. The control group and KP group were set up as treatments. The control group was fed total mixed ration (TMR) (40% roughage and 60% concentrate) and the KP group was fed TMR containing 12% KP that replaced half of the rolled corn in the control diet. The dry matter intake, digestibility of the feed components, and milk yield were not significantly different between control group and KP group. The number of times that the ruminal fluid pH was below 6.1 tended to decrease in the KP group compared to the control group (p < 0.10). The acetic acid ratio in the ruminal fluid of the KP group increased compared to the control group (p < 0.05) and the propionic acid ratio in the ruminal fluid of the KP group decreased compared to the control group (p < 0.05). The acetate:propionate acid ratio was increased in the KP group compared with the control group (p < 0.05). Lipopolysaccharide levels in the ruminal fluid of the KP group tended to decrease compared to the control group (p < 0.10). Based on these results, it was indicated that the use of KP feed for lactating dairy cows induced the same rumen fermentation characteristics as those in cows given a large amount of roughage without depressing milk productivity. Therefore, KP could be a valuable feed resource substitute for grains, which would also reduce the risk for subacute rumen acidosis.     

Dietary forage concentration and particle size affect sorting,feeding behaviour,intake and growth of Chinese holstein male calves

The objective of study was to evaluate the effect of forage concentration (F:C) and forage particle length (FPL) on sorting, feeding behaviour, intake, growth and body measurements of growing calves. Twenty‐eight weaned calves of body weight 156.79 ± 33.44 (mean ± SD) were used in 2 × 2 factorial arrangements with the factors FPL of hay grass (full and short) and hay grass concentrations (low, 50% and high, 65%). The treatments were as follows: full length (FL) with low F:C (50:50), FL with high F:C(65:35), short length (SL) with low F:C (50:50) and SL with high F:C (65:35). Increasing F:C and decreasing FPL enhanced sorting for short and fine particle and sorting against long particle (p < 0.05). Dry matter intake (DMI) was decreased by decreasing the FPL (p < 0.05). Increasing F:C (65:35) increased the DMI (p < 0.05). A positive interaction between FPL and F:C was found for (daily weight gain) DWG, weight gain (WG) and feed conversation ratio (FCR) (p < 0.05). In case of feeding behaviour, interaction for eating time and eating time per kilogram DM was present. Increasing the F:C increased the eating time in both FL and SL (p < 0.05). Chopping of hay had decreased the chewing time (p < 0.05). Increasing F:C increased chewing time per kilogram DMI. High F:C decreased the lying time (p < 0.05) in FL and SL treatments (p < 0.05). Increasing F:C reduced the overall abnormal behaviour (p < 0.05). These results suggested that animals performed better at higher F:C at SL diet. Intensity of sorting for short and fine particle and against long particle increased at higher F:C and SL diets. Eating time and eating time per kilogram DMI increased by increasing F:C level in both FL and SL treatments. Chewing time increased by increasing the FPL, while increasing the F:C enhanced the chewing time per kilogram DMI and reduced animal's abnormal behaviour.     

Effect of feeding fine maize particles on the reticular pH,milk yield and composition of dairy cows

The particle size of cereal grains has been found to modulate the rate of passage from the rumen and the digestibility of starch and neutral detergent fibre (NDF), but few studies have examined its impact on reticular pH. The study aimed to evaluate the effect of feeding finely ground maize on the risk of ruminal acidosis, milk yield and composition. Twelve Holstein‐Friesian cows were assigned to one of two experimental groups and fed according to a cross‐over design. Diets were isoenergetic and isonitrogenous and were characterised by the same NDF and ADF, differing only in maize particle size. In the control diet (Ct), the maize meal was ground to 1.0 mm, whereas in the experimental diet, it was finely ground (Fg) to 0.5 mm. The pH and temperature of the reticulum were continuously measured in eight cows throughout the trial using indwelling sensors. Dry matter intake was higher in cows offered Fg diet than in Ct (19.0 vs. 20.3 kg/day; p = 0.067). However, milk yield (p = 0.855) and the 3.5% fat‐corrected milk (FCM) (p = 0.724) did not show any differences between the diets. Casein (2.48 vs. 2.57%; p = 0.035) and crude protein (CP) (3.18 vs. 3.31%; p = 0.021) resulted higher in Fg. Similarly, starch digestibility increased in animals offered Fg diet versus Ct (0.94 vs. 0.98; p = 0.078). Among the reticular parameters, the Fg‐fed cows spent a significantly higher time below the 5.5 pH threshold (15 vs. 61 min/day; p = 0.047) and had an average daily variation in reticular pH characterised by a lower nadir pH (5.95 vs. 5.72; p < 0.001) and a higher pH range (0.79 vs. 0.94; p = 0.003). In this study, grain particle size affected the risk of the onset of ruminal acidosis. Therefore, it should be carefully considered when formulating rations.     

产酶益生素对西门塔尔牛瘤胃液pH及氨态氮浓度的影响

试验选用4头体重(500±20)kg,年龄3.5岁,装有永久性瘤胃瘘管的西门塔尔牛阉牛,采用4×4拉丁方设计,以混合精料和风干玉米秸秆为基础日粮,研究日粮中添加产酶益生素(0、10、20 g/d和30 g/d)对瘤胃液pH及氨态氮浓度的影响。结果表明:日粮添加产酶益生素后,瘤胃pH在采食后3、6 h以及平均值随着添加量的增加有提高的趋势,但差异不显著(P>0.05);20 g/d组和30 g/d组瘤胃液氨态氮浓度显著低于对照组(P<0.05)。以上结果表明,产酶益生素的适宜添加水平为20 g/d。     

Effects of soybean meal supplementation on ruminal kinetics of feed particle size reduction and passage in dairy cows fed rice straw

Six ruminal-cannulated nonlactating Holstein Friesian cows (mean body weight:660 ± 42.9 kg) were used to investigate the effect of soybean meal (SBM) supplementation on voluntary rice straw (RS) intake, feed particle size reduction, and passage kinetics in the rumen. They were allocated to two dietary treatments: RS alone or RS supplemented with SBM. Voluntary dry matter intake of RS and total tract fiber digestibility was increased by SBM supplementation (p < 0.05). Supplementation with SBM decreased rumination time per dietary dry matter (DM) and neutral detergent fiber (NDFom) intake (p < 0.01). Particle size distribution in the rumen and total ruminal NDFom digesta weights were not affected by SBM supplementation. However, the disappearance rates of total digesta and large and small particles from the rumen were increased by SBM supplementation (p < 0.01). Moreover, SBM supplementation increased the rate of size reduction in ruminal particles (p < 0.05). In situ disappearance of DM and NDFom of RS in the rumen was greater in SBM-supplemented cows than in nonsupplemented cows (p < 0.05). This study clearly showed that increased ruminal RS particle size reduction, passage, and fermentation due to SBM supplementation accelerated the RS particle clearance from the rumen and resulted in increased voluntary RS intake of dairy cows.     

Effect of supplemental zinc source and corn particle size on 40-day broiler performance

Zinc (Zn) supplementation source and particle size of feed ingredients are two factors that can affect poultry performance and should be considered for proper feeding of poultry. The objective of the current study was to assess the effects of Zn supplementation source and corn particle size on broiler performance, breast yield, and tibia Zn concentration. Treatments were arranged in a 5 × 2 factorial randomized complete block design with the main effects Zn treatment and corn particle size (550 micron vs. 1,050 micron). Zinc treatments included a basal diet (no added Zn), 80 mg/kg Zn sulfate, and 3 diets with 40 mg/kg Zn sulfate + 40 mg/kg of either Zn-glycine amino acid (AA) chelate (Zn-gly), Zn-AA complex (Zn-AA), or Zn bis(-2-hydroxy-4-methylthio)butanoic acid (Zn-HMTBA). A total of 8 replications per treatment were fed to 23 broilers per pen from d one to 40. A Zn treatment x corn particle size interaction was observed for ending bird weight (EBW; P < 0.05) demonstrating that feeding small particle corn produced larger broilers except when supplemental Zn was not included. Broilers fed small particle corn or diets supplemented with Zn consumed the most feed (P < 0.05); however, FCR was decreased (P < 0.05) by 1.9 points for broilers fed large particle corn diets. Tibia Zn concentration was higher (P < 0.0001) for Zn supplemented diets, but no other treatment effects were observed. In conclusion, Zn supplement source had little effect on broiler performance; however, Zn supplementation per se optimized performance.     

Technical note: development and testing of a radio transmission pH measurement system for continuous monitoring of ruminal pH in cows

An indwelling ruminal pH system has been used for the continuous recording of ruminal pH to evaluate subacute ruminal acidosis (SARA) in dairy cows. However this system does not allow the field application. The objective of this study was to develop a new radio transmission pH measurement system, and to assess its performance and usefulness in a continuous evaluation of ruminal pH for use on commercial dairy farms. The radio transmission pH measurement system consists of a wireless pH sensor, a data measurement receiver, a relay unit, and a personal computer installed special software. The pH sensor is housed in a bullet shaped bolus, which also encloses a pH amplifier circuit, a central processing unit (CPU) circuit, a radio frequency (RF) circuit, and a battery. The mean variations of the measurements by the glass pH electrode were +0.20 (n = 10) after 2 months of continuous recording, compared to the values confirmed by standard pH solutions for pH 4 and pH 7 at the start of the recording. The mean lifetime of the internal battery was 2.5 months (n = 10) when measurements were continuously transmitted every 10 min. Ruminal pH recorded by our new system was compared to that of the spot sampling of ruminal fluid. The mean pH for spot sampling was 6.36 ± 0.55 (n = 96), and the mean pH of continuous recording was 6.22 ± 0.54 (n = 96). There was a good correlation between continuous recording and spot sampling (r = 0.986, P < 0.01). We also examined whether our new pH system was able to detect experimentally induced ruminal acidosis in cows and to record long-term changes in ruminal pH. In the cows fed acidosis-inducing diets, the ruminal pH dropped markedly during the first 2 h following the morning feeding, and decreased moreover following the evening feeding, with many pulse-like pH changes. The pH of the cows showed the lowest values of 5.3-5.2 in the midnight time period and it recovered to the normal value by the next morning feeding. In one healthy periparturient cow, the circadian changes in ruminal pH were observed as a constant pattern in the pre-parturient period, however that pattern became variable in the post-partum period. The frequency of the ruminal pH lower than 5.5 increased markedly 3 and 4 days after parturition. We demonstrated the possible application of a radio transmission pH measurement system for the assessment and monitoring of the ruminal pH of cows. Our new system might contribute to accurate assessment and prevention of SARA.     

Interactive effect of corn particle size and insoluble fiber source on performance,nutrient utilization and intestine morphology in broilers fed pelleted diets

The effects of corn particle size and dietary fibre on the performance, coefficient of apparent ileal digestibility (CAID) and intestinal characteristics in broiler starters fed pelleted diets were studied. The experiment included 10 treatments arranged as a 2 × 5 factorial with two corn particle sizes (GMD of 1071 [CGC] vs. 534 [FGC]) and five diets that consisted in a low-fibre diet and four extra diets resulting from the inclusion of insoluble fibre sources (10 g/kg of lignocellulose (LC), and 30 g/kg of oat hulls; OH, rice hulls; RH, and sunflower hulls; SFH). In coarse grinding, all-fibre sources improved body weight gain and feed intake compared to the control diet (p < 0.01). Feed conversion ratio (FCR) improved with fibre supplementation (p < 0.01) and fine grinding of corn (FGC) (p < 0.01). Coarse grinding of corn (CGC) and inclusion of RH, SFH and OH reduced gizzard pH (p < 0.01). Fibre inclusion increased ileal fat and Ca digestibility (p < 0.01), gizzard weight (p < 0.01), digesta transit time (p < 0.01) and length of duodenum and small intestine (p < 0.01). The CAID of phosphorus increased in CGC fed birds and inclusion of RH, SFH and OH (p < 0.05). The weight of gizzard, proventriculus and pancreas (p < 0.01) was greater in CGC fed birds. Feeding SFH, RH and OH (p < 0.01), and CGC (p < 0.01) increased the villus height (VH) of the duodenum. The OH, RH and SFH supplementation increased the caecal population of Lactobacillus spp. and total anaerobic bacteria (p < 0.01) only in FGC fed birds. Overall, birds fed pelleted diets containing RH, OH and SFH (3%) exhibited improved performance, and increased nutrient digestibility, which may be caused by developed gizzards and intestine. Furthermore, coarse grinding of corn is beneficial to gizzard development.     

Reduced energy density of close‐up diets decrease ruminal pH and increase concentration of volatile fatty acids postpartum in Holstein cows

The objective of this study was to determine the effect of reduced energy density of close‐up diets on ruminal fermentation parameters in transition cows. Fourteen Holstein dry cows were blocked and assigned randomly to three groups fed a high energy density diet (HD, 1.62 Mcal of net energy for lactation (NE_L)/kg dry matter (DM)), or a middle energy density diet (MD, 1.47 Mcal NE_L/kg DM), or a low energy density diet (LD, 1.30 Mcal NE_L/kg DM) prepartum, and were fed the same diet postpartum. The reduced energy density diets decreased the average dry matter intake (DMI) prepartum and tended to increase the DMI postpartum. The ruminal pH of the LD group was significantly higher prepartum and lower during the first week of lactation compared with the other two groups. The reduced energy density diet depressed the average ruminal concentration of propionate and butyrate prepartum, and increased the average concentration of total volatile fatty acids (VFA) postpartum. The LD group had higher populations of Butyrivibrio fibrisolvens and Ruminococcus flavefaciens relative to HD and MD groups on 7 days in milk. In conclusion, the cows fed reduced energy density diet prepartum had higher VFA concentration, but were more susceptible to subacute ruminal acidosis postpartum.