Grain source and marginal changes in forage particle size modulate digestive processes and nutrient intake of dairy cows

This study investigated the effects of, and interactions between, dietary grain source and marginal changes in alfalfa hay (AH) particle size (PS) on digestive processes of dairy cows. A total of eight Holstein dairy cows (175 days in milk) were allocated in a replicated 4 × 4 Latin square design with four 21-day periods. The experiment was a 2 × 2 factorial arrangement with two levels of theoretical PS of AH (fine = 15 mm or long = 30 mm) each combined with two different sources of cereal grains (barley grain alone or barley plus corn grain in a 50 : 50 ratio). Results showed that cows consuming diets supplemented with corn had greater dry matter and nutrient intakes (P < 0.01), independent of forage PS. In addition, the apparent digestibility of fiber fractions was greater for diets supplemented with corn (P = 0.01). The feeding of barley grain-based diets was associated with greater apparent digestibility of non-fiber carbohydrates, and this variable was even greater when long AH was fed (P = 0.04). Moreover, the feeding of long AH resulted in longer time spent eating (P = 0.03) and higher pH (P < 0.01), as well as a tendency for higher acetate-to-propionate ratio in the rumen fluid (P = 0.06) at 3 h post feeding. In conclusion, the results indicated that the marginal increase of PS of AH may prolong eating time and improve rumen fermentation, particularly in diets based on barley grain. Partial substitution of barley grain by corn can improve feed intake and fiber digestibility in mid-lactation dairy cows.     

Intake,digestibility and rumen characteristics in cattle offered whole-crop wheat or barley silages of contrasting grain to straw ratios

The effects of varying the grain (G) to straw (S) ratio (G:S) of whole-crop wheat and barley silages on intake and digestibility and whole-crop barley silage on rumen fermentation characteristics were examined in two parallel studies. For the intake and digestibility study, eight Aberdeen Angus cross-bred steers (mean bodyweight 407 kg (S.D. 24.2)) were used in two (barley and wheat) 4 × 4 Latin Square designed experiments. The dietary treatments were four G:S ratios: 0:100, 30:70, 60:40 and 90:10. Intake of grain linearly increased (P<0.001) while that of straw decreased (P<0.001) as the ratio of G:S increased for both cereals. No effect (P>0.05) was observed in total dry matter (DM) intake (DMI) or in DMI per kg liveweight. There was a positive linear (P<0.001) effect on the digestibility of the DM and organic matter (OM) and a negative linear effect on neutral detergent fibre (aNDFom) digestibility (P<0.01) as the G:S ratio increased for both cereals. Both a positive linear (P<0.05) and quadratic (P<0.01) effect were observed for the G:S ratio on nitrogen (N) digestibility of barley and a corresponding positive linear increase (P<0.01) for wheat. A negative linear effect was found for digestibility of starch (P<0.01) and a positive linear effect for faecal grain content (P<0.01) with increasing G:S ratio. Four Holstein–Friesian steers (mean bodyweight 659 kg (S.D. 56.9)) fitted with rumen cannulae were used in the rumen study. A negative linear effect of G:S ratio was found on rumen pH (P<0.001) while a positive linear effect was found on rumen ammonia (P<0.001) and total volatile fatty acid (VFA) concentration (P<0.01) with increasing G:S ratio. A negative linear effect (P<0.01) was found on the molar proportion of acetic acid. However, this decrease was offset by linear increases in the molar proportions of iso- and n-butyric acid, iso- (P<0.01) and n- (P<0.05) valeric acid, and to a lesser extent in propionic acid (P<0.01). No effect of treatment was found on rumen pool sizes of DM or its constituents. A positive linear effect (P<0.01) was found on the effective degradability (ED) of the DM, OM, N and starch while it was found to be negative in aNDFom (P<0.05). No effect (P>0.05) was found on the fractional clearance rates of DM, OM, aNDFom or starch or on liquid passage rate. It is concluded that increasing the G:S ratio in whole-crop wheat or barley silage linearly increased the intake of digestible nutrients for both wheat and barley and increasing the G:S ratio for whole-crop barley increased the concentration of fermentation products (total VFA, ammonia and the molar proportions of the VFAs, except acetic acid) in the rumen.     

Effects of isobutyrate supplementation in pre- and post-weaned dairy calves diet on growth performance,rumen development,blood metabolites and hormone secretion

Isobutyrate supplements could improve rumen development by increasing ruminal fermentation products, especially butyrate, and then promote the growth performance of calves. The objective of this study was to evaluate the effects of isobutyrate supplementation on growth performance, rumen development, blood metabolites and hormone secretion in pre- and post-weaned dairy calves. In total, 56 Chinese Holstein male calves with 30 days of age and 72.9±1.43 kg of BW, blocked by days of age and BW, were assigned to four groups in a randomized block design. The treatments were as follows: control, low-isobutyrate, moderate-isobutyrate and high-isobutyrate with 0, 0.03, 0.06 and 0.09 g isobutyrate/kg BW per calf per day, respectively. Supplemental isobutyrate was hand-mixed into milk of pre-weaned calves and the concentrate portion of post-weaned calves. The study consisted of 10 days of an adaptation period and a 50-day sampling period. Calves were weaned at 60 days of age. Seven calves were chosen from each treatment at random and slaughtered at 45 and 90 days of age. BW, dry matter (DM) intake and stomach weight were measured, samples of ruminal tissues and blood were determined. For pre- and post-weaned calves, DM intake and average daily gain increased linearly (P<0.05), but feed conversion ratio decreased linearly (P<0.05) with increasing isobutyrate supplementation. Total stomach weight and the ratio of rumen weight to total stomach weight tended to increase (P=0.073) for pre-weaned calves and increased linearly (P=0.021) for post-weaned calves, whereas the ratio of abomasum weight to total stomach weight was not affected for pre-weaned calves and decreased linearly (P<0.05) for post-weaned calves with increasing isobutyrate supplementation. Both length and width of rumen papillae tended to increase linearly for pre-weaned calves, but increased linearly (P<0.05) for post-weaned calves with increasing isobutyrate supplementation. The relative expression of messenger RNA for growth hormone (GH) receptor and 3-hydroxy-3-methylglutaryl-CoA synthase 1 in rumen mucosa increased linearly (P<0.05) for pre- and post-weaned calves with increasing isobutyrate supplementation. Blood concentrations of glucose, acetoacetate, β-hydroxybutyrate, GH and IGF-1 increased linearly (P<0.05) for pre- and post-weaned calves, whereas blood concentration of insulin decreased linearly with increasing isobutyrate supplementation. The present results indicated that isobutyrate promoted growth of calves by improving rumen development and its ketogenesis in a dose-dependent manner.     

Beet pulp substituted for corn silage and barley grain in diets fed to dairy cows in the summer months: feed intake,total-tract digestibility,and milk production

The responses of dairy cows to the substitution of beet pulp (BP) for grain or forage are not consistent, and heat stress may affect the response of dairy cows to this substitution. The effects of substituted BP for corn silage and barley grain on feed intake, performance, and ruminal parameters were evaluated using eight multiparous Holstein cows in a duplicated 4 × 4 Latin square design with 21-day periods. Cows were in mid-lactation (45.4 ± 3.6 kg/day milk production and 116 ± 10 days in milk) with an average BW of 664 ± 41.2 kg. Dietary treatments were as follows: 1) 0% BP (0BP, control, 38.5% barley grain, and 20.3% corn silage); 2) 12% BP (12BP, 32.5% barley grain, and 14.3% corn silage); 3) 18% BP (18BP, 29.5% barley grain, and 11.3% corn silage); and 4) 24% BP (24BP, 26.5% barley grain, and 8.3% corn silage). Cows were under mild heat stress and the average temperature–humidity index was 70.5; increasing BP caused a linear decrease in respiration rate (P < 0.01). Higher BP in the diet caused a linear increase in DM intake (P = 0.01) and NDF digestibility (P = 0.03). Dry and organic matter (OM) digestibilities tended to increase linearly with higher BP (P < 0.10). Milk yield, energy-corrected milk, protein, lactose, and fat production and content were not affected by the treatments. Increasing BP in the diet caused a linear decrease in feed efficiency and rumen ammonia (P < 0.05) and a tendency to a linear decrease in milk urea nitrogen (P < 0.10). Rumen pH and acetate to propionate ratio were not affected by the replacement. Total volatile fatty acid concentration in the rumen increased linearly with increasing the BP inclusion (P = 0.04). Acetate and butyrate (P = 0.07) proportion tended to increase, whereas propionate (P = 0.06) and isovalerate (P = 0.08) proportion tended to decrease linearly as BP was substituted for corn silage and barley grain. The results indicated that under mild heat stress condition, BP can be successfully substituted for barley grain and corn silage up to 24% of the diet without any negative effect on production and ruminal pH.     

Indigestion in Young Calves. II. The Influence Of Ground Barley,Coarse and Fine Hay

Four experiments comprising 86 calves have been carried out in order to examine the influence of ground barley, coarse and fine hay, when raising young calves on a high lactose milk replacer causing diarrhoea. The frequency of diarrhoea decreased when feeding barley (P < 0.01) or fine hay (P < 0.001), but increased when feeding coarse hay (P<0.01). Barley increased (P < 0.01) live weight gain and carcass weight, reduced (P < 0.001) rumen pH, favoured gram-positive cocci and rods in the rumen, caused hyperkeratosis and gave increased (P < 0.01) empty reticulo-rumen weights, the latter being supposed to be enhanced by hyperkeratosis. The calves ate more (P < 0.001) fine than coarse hay, fine hay being superior (P < 0.01) in promoting growth of the rumen. All hay maintained a predominantly gram-negative rumen flora, but somewhat different from that on the milk replacer, and counteracted (P < 0.01) low pH in the rumen and apparently also hyperkeratosis due to barley. The results with barley indicated no relationship between diarrhoea and hyperkeratosis.     

Feeding dried distillers grains with solubles to lactating beef cows: impact of excess protein and fat on cow performance,milk production and pre-weaning progeny growth

Multiparous Angus×Simmental cows (n=54, 5.22±2.51 years) with male progeny were fed one of two diets supplemented with either dried distillers grains with solubles (DDGS) or soybean meal (CON), from calving until day 129 postpartum (PP) to determine effects of excess protein and fat on cow performance, milk composition and calf growth. Diets were formulated to be isocaloric and consisted of rye hay and DDGS (19.4% CP; 8.76% fat), or corn silage, rye hay and soybean meal (11.7% CP; 2.06% fat). Cow–calf pairs were allotted by cow and calf age, BW and breed. Cow BW and body condition score (BCS; P⩾0.13) were similar throughout the experiment. A weigh-suckle-weigh was performed on day 64 and day 110±10 PP to determine milk production. Milk was collected on day 68 and day 116±10 PP for analysis of milk components. Milk production was unaffected (P⩾0.75) by dietary treatments. Milk urea nitrogen was increased at both time points in DDGS compared with CON cows (P<0.01). Protein was decreased (P=0.01) and fat was increased (P=0.01) in milk from DDGS compared with CON cows on day 68 PP. Compared to CON, DDGS decreased medium chain FA (P<0.01) and increased long chain FA (P<0.01) at both time points. Saturated FA content of milk was decreased (P<0.01) at both time-points in DDGS compared with CON cows, which resulted in an increase (P<0.01) in monounsaturated and polyunsaturated FA, including cis-9, trans-11 conjugated linoleic acid. Daily gain of the DDGS calves was increased (P=0.01) compared with CON calves, resulting in heavier BW on day 129 (P=0.01). Heavier BW of DDGS calves was maintained through weaning (P=0.01). Timed-artificial insemination (TAI) rates were greater for cows fed DDGS compared with cows fed CON (P<0.02), but dietary treatment had no effect on overall pregnancy rates (P=0.64). In summary, feeding DDGS to lactating beef cows did not change cow BW or BCS, but did improve TAI rates and altered milk composition compared with CON. As a result, male progeny from cows fed DDGS during lactation had greater average daily gain and were heavier at day 129 and at weaning compared with male progeny from cows fed a control diet.     

Grass maturity effects on cattle fed silage-based diets. 1. Organic matter digestion,rumen fermentation and nitrogen utilization

Four silages were harvested at approximately one-week intervals from the same timothymeadow fescue sward. Advanced maturity of the herbage was evidenced by increased neutral detergent fibre [409, 497, 579 and 623 g in 1 kg dry matter (DM)] and decreased nitrogen (N; 29.9, using four ruminally and duodenally cannulated young cattle in a 4 × 4 Latin square experiment. On DM basis (g kg⁻¹), the diet comprised grass silage (700), rolled barley (240) and rapeseed meal (60) and it was given at a rate of 70 g DM (kg live weight)^−0.75 per day.Organic matter digestibility decreased in a curvilinear manner (P_{LINEAR (L)} < 0.001, P_{CUBIC (C)} < 0.01) the values being 0.821, 0.816, 0.758 and 0.747 for the diets based on the four silages in the order of harvest date. Rumen pH increased linearly (P_L < 0.05) and ammonia N concentration decreased curvilinearly (P_L < 0.01, P_C < 0.05) as the grass matured. The molar proportion of acetate in the rumen VFA increased (P_L < 0.001) and the proportion of butyrate decreased (P_L < 0.001) with increased grass maturity. The silage harvest date did not affect the proportion of propionate. The changes in rumen fermentation pattern were associated with a decrease (P_L < 0.05) in rumen protozoal number with increasing maturity of grass.N intake decreased significantly (P_L < 0.001, P_C < 0.01) with the maturity of grass from 167.5 to 118.0 g per day, but duodenal non-ammonia N decreased only from 111.3 to 97.3 g per day indicating greater N losses from the rumen with early-cut silages. The efficiency of microbial protein synthesis in the rumen was not affected by the maturity of grass ensiled. Apparent digestibility of N decreased (P_L < 0.001, P_C < 0.01) and the degradability of N in the rumen decreased (P_L < 0.05) as the grass matured.     

Impact of subacute ruminal acidosis on the diversity of liquid and solid-associated bacteria in the rumen of goats

This study was aimed to investigate the impact of subacute ruminal acidosis (SARA) on the diversity of liquid (LAB) and solid-associated bacteria (SAB) following high-grain feeding. Six ruminally cannulated goats were divided into two groups: one group was fed a hay diet (COD), and the other group was fed a high grain diet (SAID). Rumen liquids and rumen solids were sampled after 2 weeks adaption. SARA was diagnosed with a pH below 5.8 for 8 h. SAID decreased ruminal pH (P < 0.001) and increased the acetate (P = 0.017), propionate (P = 0.001), butyrate (P < 0.001) and total volatile fatty acid (P < 0.001) concentration in rumen compared with the COD. Denaturing gradient gel electrophoresis fingerprints analysis revealed a clear separation between both the diet and the fraction of rumen digesta in bacterial communities. Pyrosequencing analysis showed that the proportion of phylum Bacteroidetes in the SAID-LAB and SAID-SAB communities was less than in the COD group, whereas the SAID group had a greater percentage of Firmicutes in both the LAB and SAB libraries. UniFrac analyses and a Venn diagram revealed a large difference between the two diets in the diversity of rumen bacterial communities. Overall, our findings revealed that SARA feeding did alter the community structure of rumen liquids and rumen solids. Thus, manipulation of dietary factors, such as ratio of forage to concentrate may have the potential to alter the microbial composition of rumen liquid and rumen solid.     

High-grain diet feeding altered the composition and functions of the rumen bacterial community and caused the damage to the laminar tissues of goats

In the current intensive production system, ruminants are often fed high-grain (HG) diets. However, this feeding pattern often causes rumen metabolic disorders and may further trigger laminitis, the exact mechanism is not clear. This study investigated the effect of HG diet feeding on fermentative and microbial changes in the rumen and on the expression of pro-inflammatory cytokines and matrix metalloproteinases (MMPs) in the lamellar tissue. In all, 12 male goats were fed a hay diet (0% grain; n=6) or an HG diet (56.5% grain; n=6). On day 50 of treatment, samples of blood, rumen content, and lamellar tissue of hooves of goats were collected. The data showed that compared with the hay group, HG-fed goats had lower (P<0.05) rumen pH but higher (P<0.05) total volatile fatty acids and lactate in the rumen and higher (P<0.05) lipopolysaccharide (LPS) levels in the rumen and blood. HG diet feeding altered the composition of rumen bacterial community, and correspondingly, the results suggested that their functions in the HG group were also altered. HG diet feeding increased (P<0.05) the expression of interleukin-1β, interleukin-6, tumour necrosis factor-α and MMP-2 mRNA in the lamellar tissues compared with the hay group. Correlation analysis indicated that the expression of pro-inflammatory cytokines were positively correlated with MMP-2 expression in lamellar tissues. Overall, these results revealed that HG feeding altered the patterns of rumen fermentation and the composition and functions of rumen bacterial community, and lead to higher levels of LPS in the peripheral blood, and further activated the inflammatory response in lamellar tissues, which may progress to the level of laminar damage.     

Different endosperm structures in wheat and corn affected in vitro rumen fermentation and nitrogen utilization of rice straw-based diet

Starchy grain is usually supplemented to diets containing low-quality forage to provide sufficient energy for ruminant animals. Ruminal degradation of grain starch mainly depends on the hydrolysis of the endosperm, which may be variable among grain sources. This study was conducted to investigate the influence of endosperm structure of wheat and corn on in vitro rumen fermentation and nitrogen (N) utilization of rice straw. The 3×4 factorial design included three ratios of concentrate to forage (35:65, 50:50 and 65:35) and four ratios of wheat to corn starch (20:80, 40:60, 60:40 and 80:20). The endosperm structure was detected by scanning electronic microscopy and a confocal laser scanning microscopic. An in vitro gas test was performed to evaluate the rumen fermentation characteristics and N utilization. Starch granules were embedded in the starch–protein matrix in corn, but more granules were separated from the matrix in the wheat endosperm. With the increasing ratio of wheat, rate and extent of gas production, total volatile fatty acids, and ammonia N increased linearly (P<0.01), but microbial protein concentration decreased (quadratic, P<0.01), with the maximum value at a ratio of 40% wheat. The efficiency of N utilization decreased linearly (P<0.01). Rumen fermentation and N utilization were significantly affected by the concentrate-to-forage ratio (P<0.01). Significant interactions between the concentrate-to-forage ratio and the wheat-to-corn ratio were detected in total volatile fatty acids and the efficiency of N utilization (P<0.01). In summary, the starch–protein matrix and starch granules in the wheat and corn endosperm mixture play an important role in the regulation of rumen fermentation and N utilization under low-quality forage.     

The effect of immunocastration and a diet based on granulated barley on growth performance and carcass,meat and fat quality in heavy gilts

A total of 48 Duroc×(Landrace×Large White) gilts of 33.2 kg BW were used to investigate the influence of immunocastration and diet on growth performance and carcass, meat and fat quality. Four treatments were arranged factorially (2×2) with two sexes (immunocastrated gilts: IG v. entire gilts: EG) and two dietary treatments (a commercial feedstuff as control v. granulated barley as a single major ingredient) provided during the finishing period (from 103 to 126 kg BW). There were four replicates of three pigs per treatment. At the end of the trial, the IGs grew faster (P<0.05) and ate more feed (P<0.05) than the EGs. Carcasses from the IGs had thicker backfat depth than those from the EGs (P<0.01) and carried out a lower percentage of rejected carcasses (P<0.05) at slaughterhouse owing to lack of fat. Meat from the IGs tended to have higher intramuscular fat (IMF) content in the Longissimus thoracis (LT) muscle than that from the EGs (P=0.09). In addition, immunocastration increased the total saturated fatty-acid proportion in subcutaneous fat and IMF (P<0.001) and decreased the total monounsaturated fatty acid (MUFA) and total polyunsaturated fatty acid (PUFA) percentages in subcutaneous backfat (P<0.05 and P<0.001, respectively) and in IMF (P<0.01 and P=0.06, respectively). The use of a diet based on granulated barley during the finishing period had no effect on growth performance but tended to increase IMF content in the LT muscle (P<0.06), and increased MUFA (P<0.05) and decreased PUFA (P<0.01) proportions in omental fat. It is concluded that immunocastration of gilts intended for dry-cured ham industry improved some aspects of growth performance and carcass and meat quality, whereas granulated barley had scarce effect on productive traits and fatty-acid profile but tended to improve IMF content.     

Total mixed ration pellets for light fattening lambs: effects on animal health

Fifty male Merino lambs (6 to 8 weeks, 14.1 kg; n=10 per group) were used to study the effect of feeding system: barley straw in long form and concentrate pellets in separate troughs (Control), ad libitum alfalfa supplemented with concentrate in separate troughs (Alfalfa) or including various levels of ground barley straw in concentrate pellets (B05, B15 and B25 for 50, 150 and 250 g barley straw/kg), on rumen characteristics, acid-base status, blood cell counts and lymphocyte stimulation. Alfalfa lambs had the heaviest digestive tract contents, highest rumen pH values, lowest volatile fatty acid concentration, highest papillae counts and best mucosa colour and the greatest blood pCO₂ values, lowest sodium and chloride and highest potassium concentrations (P<0.05). Including ground barley straw in the concentrate pellet or providing straw in long form separately from the concentrate reduces rumen pH and darkens ruminal mucosa as compared with alfalfa-fed lambs, thus affecting acid-base status.     

Use of Pyrosequencing to Characterize the Microbiota in the Ileum of Goats Fed with Increasing Proportion of Dietary Grain

This study evaluated the effects of an increasing proportion of dietary grain on changes in bacterial populations in the goat ileum. Nine ruminally fistulated, castrated male goats were assigned to three diets in a completely randomized design. Goats were fed three different dietary treatments containing different proportions of corn grain (0, 25, and 50 %). The pH of the ileal contents and rumen fluid (P = 0.015) linearly decreased (P < 0.001), and the acetate, propionate, butyrate, and total volatile fatty acid in ileal contents increased (P < 0.05) with increases in dietary corn, and similar results were also observed in rumen fluid. The barcoded DNA pyrosequencing method was used to reveal 8 phyla, 70 genera, and 1,693 16S operational taxonomic units (OTUs). At the genus level, the proportions of Acetitomaculum, Enterococcus, Atopobium, unclassified Coriobacteriaceae, and unclassified Planctomycetaceae were linearly decreased (P < 0.05) with increases in corn grain. At the species level, high grain feeding linearly decreased the percentage of OTU8686 (unclassified Bacteria) (P = 0.004). To the best of our knowledge, this is the first study using barcoded DNA pyrosequencing method to survey the ileal microbiome of goats and the results suggest that increasing levels of dietary corn change the composition of the ileal bacterial community. These findings provide previously unknown information about the ileal microbiota of goats and a new understanding of the ileal microbial ecology, which may be useful in modulating the gut microbiome.     

Effect of flaxseed on the fatty acid profile of egg yolk and antioxidant status of their neonatal offspring in Huoyan geese

The aim of this study was to evaluate the effects of geese’s maternal diet supplemented with flaxseed on the fatty acid profiles of egg yolks and the antioxidant status of their offspring. A total of 288 female Huoyan geese (42 weeks old) were randomly allotted to four experimental groups in this 56-day experiment and fed on diets containing flaxseed at 0% (control), 5%, 10% and 15%, respectively. There were nine replicate pens per treatment, with eight geese per replicate pen. The concentration of α-linolenic acid (linear, P<0.01), EPA (20:5n-3; linear, P<0.01), DHA (22:6n-3; quadratic, P=0.03) and n-3 polyunsaturated fatty acid (PUFA) (linear, P<0.01) levels in the yolk lipids increased with increasing dietary flaxseed levels. Yolk palmitic acid (16:0, linear, P=0.05), saturated fatty acid (linear, P=0.04) level and total n-6/n-3 ratio (P<0.01) decreased in a linear fashion as dietary flaxseed levels increased. Increasing dietary flaxseed levels linearly decreased (P=0.01) the total cholesterol in egg yolks. After hatching, three 1-day-old gosling were selected randomly from each replicate to determine blood characteristics and liver antioxidant status. Aspartate aminotransferase activity (linear, P=0.03), total triglycerides (linear, P=0.02) and total cholesterol (linear, P=0.05) contents in blood linearly decreased as the levels of flaxseed increased. A linear dose response to maternal dietary flaxseed was detected for the activities of the goslings’ liver enzymes catalase (linear, P=0.01), superoxide dismutase (linear, P<0.01) and glutathione peroxidase (linear, P<0.01). The malondialdehyde (quadratic, P=0.03) and alkaline phosphatase content in the livers of goslings decreased as flaxseed supplementation levels increased. In conclusion, the dietary addition of flaxseed up to 15%, in the maternal diet resulted in increased n-3 PUFA levels in egg yolks and improved the antioxidant status of offspring in a dose-dependent manner.     

Effects of resistant starch on behaviour,satiety-related hormones and metabolites in growing pigs

Resistant starch (RS) has been suggested to prolong satiety in adult pigs. The present study investigated RS-induced changes in behaviour, satiety-related hormones and metabolites in catheterized growing pigs to explore possible underlying mechanisms for RS-induced satiety. In a cross-over design with two 14-day periods, 10 pigs (initial BW: 58 kg) were assigned to two treatments comprising diets containing either 35% pregelatinized starch (PS) or 34% retrograded starch (RS). Diets were isoenergetic on gross energy. Pigs were fed at 2.8× maintenance. Postprandial plasma response of satiety-related hormones and metabolites was measured at the end of each period using frequent blood sampling. Faecal and urinary energy losses were measured at the end of each period. Behaviour was scored 24 h from video recordings using scan sampling. Energy digestibility and metabolizability were ~6% lower in RS compared with PS diet (P<0.001), and metabolizable energy (ME) intake was ~3% lower in RS-fed than in PS-fed pigs (P<0.001). RS-fed pigs showed less feeder-directed (P=0.001) and drinking (P=0.10) behaviours than PS-fed pigs throughout the day. Postprandial peripheral short-chain fatty acid (SCFA) levels were higher in RS-fed than in PS-fed pigs (P<0.001). Postprandial glucose and insulin responses were lower in RS-fed than in PS-fed pigs (P<0.001). Triglyceride levels were higher in RS-fed than in PS-fed pigs (P<0.01), and non-esterified fatty acid levels did not differ between diets (P=0.90). Glucagon-like peptide-1 (GLP-1) levels were lower in RS-fed than in PS-fed pigs (P<0.001), and peptide tyrosine tyrosine (PYY) levels did not differ between diets (P=0.90). Blood serotonin levels were lower (P<0.001), whereas monoamine oxidase activity (P<0.05) and tryptophan (P<0.01) levels were higher in RS-fed than in PS-fed pigs. Despite a lower ME intake, RS seemed to prolong satiety, based on behavioural observations. Possible underlying mechanisms for RS-induced satiety include increased 24 h plasma SCFA levels, and decreased postprandial glucose and insulin responses. GLP-1 and PYY seemed not to play a role in RS-induced satiety. Low blood serotonin levels in RS-fed pigs suggested a difference in intestinal serotonin release between treatments. Increased postprandial plasma triglyceride levels corresponded with increased SCFA levels, but it is unclear whether triglycerides may have signalled satiety in RS-fed pigs.     

Effect of harvest time and physical form of alfalfa silage on chewing time and particle size distribution in boli,rumen content and faeces

The study examined the effects of physical form and harvest time of alfalfa silage on eating and ruminating activity and particle size distribution in feed boli, rumen content and faeces in dry cows. The alfalfa crop was harvested at two stages of growth (early: NDF 37%, late: NDF 44% in dry matter (DM)), and from each harvest, a chopped (theoretical cutting length: 19 mm) and an unchopped crop was ensiled in bales. The silages were fed restrictively to four rumen cannulated non-lactating Jersey cows (391 ± 26 kg) in a 4 × 4 Latin square design. The cows were fed restrictively 80% of their ad libitum intake twice daily. Chewing activity was recorded for 96 h continuously. Swallowed boli, rumen content, rumen fluid and faeces samples were collected, washed in nylon bags (0.01 mm pore size) and freeze-dried before dry sieving through 4.750, 2.360, 1.000, 0.500 and 0.212 mm pore sizes into six fractions. The length (PL) and width (PW) of particles within each fraction was measured by the use of image analysis. The eating activity (min/kg dry matter intake (P < 0.01) and min/kg NDF (P < 0.05)) was affected by harvest time. The mean ruminating time (min/kg DM) was affected by harvest time (P < 0.01), physical form (P < 0.05) and NDF intake per kg BW (P < 0.01). The proportion of washed particle DM of total DM in boli, rumen content, rumen fluid and faeces was affected by harvest time (P < 0.01) and highest by feeding late-harvested alfalfa silage. Two peaks on the probability density distribution function (PDF) of PW and PL values of boli, rumen content and faeces were identified. Chopping of the silage decreased the mean PL and PW, the most frequent PL (mode) and 95% percentile PL and PW values in boli. In the rumen content, chopping increased the mean PW (P < 0.05). The dimension sizes of faeces particles were not significantly affected by chopping. The mode PW value was lower in rumen content and faeces than in boli (P < 0.001), and the mode PL value was higher in boli and lower in faeces compared with rumen contents (P < 0.001). In conclusion, the mean total chewing activity per kg NDF decreased due to chopping and early harvest time. The mean PL and PW in boli decreased due to chopping and late harvest. The two peak values on the PDF (PL) and PDF (PW) of boli, rumen content and faeces particles are most likely related to the leaf and the stem residues.     

Effects of protozoa on Methane production in rumen and hindgut of calves around time of weaning

Effects of the presence or absence of ciliate protozoa on methanogenesis in the rumen and hindgut were investigated in young calves during a 7-week period. Ten Holstein calves, aged 7 days, were divided in two groups (n = 5) and fed an increasing amount of a commercial milk replacer and small amounts of a calves starter. One group was inoculated with ciliate fauna on two occasions, week 5 and 6, while the second remained ciliate-free. The absence of protozoa in the rumen decreased rumen empty weight ( ? 23%, P < 0.01), and rumen pool size of N ( ? 36%, P < 0.01) and crude fat ( ? 37%, P < 0.05). Rumen bacteria of non-faunated calves contained a higher proportion of total amino acid-N per 16 g N ( + 3%, P < 0.01) and D-alanine-N per 16 g N ( + 13%, P < 0.05) compared to faunated calves. Further results contain a reference for a higher bacterial mass in the ciliate-free rumen with an increased number of bacteria adherent to rumen mucosa. The CH₄ production in the rumen increased exponentially with the increase in protozoa population size (R² = 0.68). In presence of 46 · 10⁴ protozoa per ml rumen fluid, the in vitro CH₄ production of rumen fluid per mol total VFA was about 34% higher in faunated than in non-faunated calves (P < 0.001). Hydrogen (2H) recovery of rumen fermentation was positively correlated (R² = 0.55) to the CH₄ production rate. Methanogens were attached on rumen mucosa. Methanogenesis, induced by rumen mucosa attached bacteria, was stimulated by ruminal protozoa. In the absence of protozoa in the rumen, the acetate - propionate ratio and butyrate proportion of VFA were reduced. In vivo in the absence of protozoa not only the whole animal CH₄ production ( ? 30%, P < 0.05) but also the digestibility of carbohydrates ( ? 4%, P < 0.05) was reduced. Thereby no difference was observed in the intake of ME per kg DM between the groups. In conclusion, the methanogenesis in the rumen, but not in hindgut, is associated with the development of the ruminal protozoa population. The level of methanogenesis (mol/mol VFA) in the hindgut amounts to 20% of the ruminal methanogenesis.     

Chemical composition and rumen degradability of three corn hybrids treated with insecticides against the European corn borer (Ostrinia nubilalis)

This experiment determined the chemical composition, rumen degradability (aNDF in stalks and starch in kernels) and in vitro gas production of kernels from three corn hybrids treated (TT) or not treated (control, CTR) with insecticides against the European corn borer (ECB, Ostrinia nubilalis). Two whole-plant silage hybrids belonging to the FAO rating 600 and 700 maturity class (S600 and S700, respectively) and one selected for grain production (G600, FAO rating 600, Dekalb-Monsanto Agricoltura S.p.A., Lodi, Italy) were sown in two main plots (TT and CTR) of an experimental field. Two subsequent treatments of pyrethroids (25 and 1.2 g/ha of cyfluthrin and deltamethrin, respectively) were applied to the TT plots. The insecticide treatment reduced the number of damaged plants (4.5 broken plants/plot versus 0.3 broken plants/plot, P<0.01) and increased the total grain yield by 11% (13.8 t/ha versus 12.4 t/ha), while hybrids did not differ. ECB larvae which bored into the stalk tunnels modified the chemical composition of stalks and kernels. In stalks, total sugars content (i.e. glucose, fructose, sucrose) was about twice that in TT versus CTR plants (123 g/kg versus 60 g/kg DM, P<0.01), while aNDF content was higher in CTR stalks (765 versus 702 g/kg DM, P<0.01). DM degradability after 48 h of incubation of stalks was higher in TT than in CTR, both in vitro (0.360 versus 0.298, P<0.01) and in situ (0.370 versus 0.298, P<0.05), while there were no differences in aNDF degradability. Kernels from TT plots contained less DM (615 g/kg versus 651 g/kg, P<0.01) and more CP (84 g/kg and 78 g/kg DM, P<0.05) than those from CTR plots, while in situ rumen starch disappearance and in vitro gas production were similar. Corn hybrid selected for yield of grain (G600) differed from S600 and S700 due to a higher (P<0.01) content of aNDF, ADF and lignin(sa) in the stalks, and a higher starch content (696 g/kg versus 674 and 671 g/kg DM, P<0.01) and CP (87 g/kg versus 77 and 76 g/kg DM, P<0.05) in grain. The G600 hybrid produced stalks with a lower (P<0.01) aNDF rumen degradability than the S600 and S700.     

Effect of milk replacer and concentrate intake on growth rate,feeding behaviour and systemic metabolite concentrations of pre-weaned bull calves of two dairy breeds

Early-life nutrition affects calf development and thus subsequent performance. The aim of this study was to examine the effect plane of nutrition on growth, feeding behaviour and systemic metabolite concentrations of artificially reared dairy bull calves. Holstein-Friesian (F; n=42) and Jersey (J; n=25) bull calves with a mean±SD age (14±4.7 v. 27±7.2 days) and BW (47±5.5 v. 33±4.7 kg) were offered a high, medium or low plane of nutrition for 8 weeks using an electronic feeding system which recorded a range of feed-related events. Calves were weighed weekly and plasma samples were collected via jugular venipuncture on weeks 1, 4 and 7 relative to the start of the trial period. The calves offered a high plane of nutrition had the greatest growth rate. However, the increased consumption of milk replacer led to a reduction in feed efficiency. Holstein-Friesian calves offered a low plane of nutrition had the greatest number of daily unrewarded visits to the feeder (P<0.001). β-hydroxybutyrate (BHB) concentrations were greater in F calves on a low plane of nutrition (P<0.001). Although there was no effect of plane of nutrition, BHB concentrations in F calves increased before weaning, concomitant with an increase in concentrate consumption. Urea concentrations were unaffected by plane of nutrition within either breed. Jersey calves on a low plane of nutrition tended to have lower triglycerides than those on a high plane (P=0.08), but greater than those on a medium plane (P=0.08). Holstein-Friesian calves offered a high plane of nutrition tended to have greater triglyceride concentrations than those on a medium plane (P=0.08). Triglycerides increased from the start to the end of the feeding period (P<0.05), across both breeds. A medium plane of nutrition resulted in a growth, feeding behaviour and metabolic response comparable with a high plane of nutrition in pre-weaned bull calves of both F and J breeds.     

Effects of an artificial hay aroma and compound feed formulation on feed intake pattern,rumen function and milk production in lactating dairy cows

The Kempen system is a dairy feeding system in which diet is provided in the form of a compound feed (CF) and hay offered ad libitum. Ad libitum access to CF and hay allows cows in this system to achieve a high DM intake (DMI). Out of physiological concerns, the voluntary hay intake could be increased and the consumption pattern of CF could be manipulated to maintain proper rumen functioning and health. This study investigated the effects of an artificial hay aroma and CF formulation on feed intake pattern, rumen function and milk production in mid- to late-lactating dairy cows. Twenty Holstein–Friesian cows were assigned to four treatments in a 4 × 4 Latin square design. Diet consisted of CF and grass hay (GH), fed separately, and both offered ad libitum, although CF supply was restricted in maximum meal size and speed of supply by an electronic system. Treatments were the combination of two CF formulations – high in starch (CHS) and fibre (CHF); and two GH – untreated (UGH) and the same hay treated with an artificial aroma (TGH). Meal criteria were determined using three-population Gaussian–Gaussian–Weibull density functions. No GH × CF interaction effects on feed intake pattern characteristics were found. Total DMI and CF intake, but not GH intake, were greater (P < 0.01) in TGH treatment, and feed intake was not affected by type of CF. Total visits to feeders per day, visits to the GH feeder, visits to the CF feeder and CF eating time (all P < 0.01) were significantly greater in cows fed with TGH. Meal frequency, meal size and meal duration were unaffected by treatments. Cows fed CHF had a greater milk fat (P = 0.02), milk urea content (P < 0.01) and a greater milk fat yield (P < 0.01). Cows fed TGH had a greater milk lactose content and lactose yield (P < 0.05), and milk urea content (P < 0.01). Cows fed TGH had smaller molar proportions of acetic acid and greater molar proportions of propionic acid compared with UGH. In conclusion, treatment of GH with an artificial aroma increased CF intake and total DMI, but did not affect hay intake. Additionally, GH treatment increased the frequency of visits to both feeders, and affected rumen volatile fatty acid profile. Type of CF did not affect meal patterns, ruminal pH, nor fermentation profiles.