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.     

Safflower seeds in corn silage and alfalfa hay based early lactation diets: A practice within an optimum forage choice

Safflower seed (SS), Carthamus tinctorius L., has the highest concentration of linoleic acid among 80 oilseeds. It was hypothesized that an Iranian variety of SS can be effectively fed with cottonseeds (CS) to maintain feed intake, energy metabolism and productivity of early lactation cows under negative energy balance. Our objective was to determine effects of feeding diets containing 100 g whole CS with (1) no SS (SS0), (2) 75 g CS + 25 g SS (SS25), or (3) 50 g CS + 50 g SS (SS50), per kg of dietary DM, on feed intake, rumen fermentation, blood metabolites and milk production of early lactation cows fed diets based on a uniform mixtures of alfalfa hay and corn silage. Nine multiparous early lactation Holstein cows (46 ± 7 d in milk) were used in a replicated 3 × 3 Latin square design study with three 21-d periods. Each period had 14 d of adaptation and 7 d of data collection. Dietary inclusion of SS did not affect (P>0.10) DM intake, rumen pH and concentrations of ammonia and VFA, blood concentrations of insulin, non-esterified fatty acids, urea and triglycerides, and milk production. Adding SS linearly reduced blood glucose (P=0.05) and beta-hydroxybutyric acid (P<0.05), and increased blood total cholesterol (P<0.01) and low-density lipoproteins (P<0.05) concentrations. Results demonstrated that SS as an economical and rich source of essential fatty acids can be included up to 50 g/kg of dietary DM alongside CS for early lactation cows without affecting feed intake while maintaining rumen fermentation, peripheral energy supply and milk production.     

Effects of feeding cows in early lactation with soy hulls as partial forage replacement on heat production,retained energy and performance

This study measured the effects of replacing corn silage and vetch hay by soy hulls in total mixed rations (TMRs) fed to 25 pairs of cows through 90 d in milk, on dry matter (DM) intake, in vivo digestibility, milk yield and composition, onset of normal estrous activity, body condition score (BCS), health and the energy balance of lactating cows. The partitioning of metabolizable energy (ME) intake between heat production (HP) and retained energy (RE) in milk and body change of each cow was measured. The two TMRs differed in the content of forage and forage aNDFom [235 g/kg versus 350 g/kg; and 128 g/kg versus 187 g/kg DM, in the experimental (EXP) and control (CON) diets, respectively]. This was reflected by an increase in voluntary DM intake by 7.2% (P=0.02) in the EXP group as compared with the CON. In vivo DM and aNDFom digestibility were 4.9% (P=0.03) and 22.7% higher (P=0.01), respectively, in the EXP group than in the CON. The higher DM intake and digestibility of the EXP TMR were reflected by a concomitant increase of 7.4% in milk yield and 10.8% in RE (P=0.01) of the EXP cows as compared with the CON. The two dietary groups expressed similar somatic cell counts, and metabolic disorders (i.e., ketosis and/or lameness), as well as pedometer activity (steps/h) suggesting similar udder health, behavior and animal welfare. A trend to an earlier return to normal ovarian activity occurred in the EXP cows as reflected by fewer days to 1st ovulation and advanced outset of estrous cycle. Despite the higher RE of the EXP cows, the HP of both groups was maintained at an upper level of 141–136 MJ/cow/d during the 90 d of the experiment.     

Chemical composition, intake by sheep, and in situ disappearance in cannulated cows of bermudagrass hayed at two moisture concentrations and treated with a non-viable Lactobacillus-lactic acid preservative

Bermudagrass [Cynodon dactylon (L.) Pers.] is commonly used for grazing and haying in the southern USA, but hay curing can be challenging due to frequent rainfall events during spring and early summer. An existing stand of ‘Greenfield’ bermudagrass was divided into 12 plots using a randomized complete block design with a 2×2 factorial treatment arrangement to evaluate the influence of a non-viable Lactobacillus-lactic acid preservative and moisture concentration at baling on chemical composition, intake by sheep, and in situ disappearance in cattle. At time of mowing, half of the plots in each block were either spray-treated (T) or not treated (U) with 81 mL/t forage dry matter (DM) of the preservative solution. Hay was then baled at target moisture concentrations of either 174 g/kg DM (L) or 267 g/kg DM (H). Maximum temperature and heating degree days were greater (P<0.05) from H compared with L during the 42-d storage period. An interaction between spray and moisture treatments tended (P<0.10) to affect recovery of DM; recoveries for LT (0.992) differed (P<0.10) from HT (0.913), but LU and HU were intermediate between the spray-treated hays, and did not differ from either (P>0.10). Post-storage nutritive value was largely influenced by moisture treatments only. Intake and digestibility, and in situ DM disappearance of these same hays were determined using 16 wether lambs (43 ± 3.7 kg initial BW), or six ruminally cannulated cows (617 ± 3.5 kg initial BW), respectively. Dry matter intake by sheep was not affected by either treatment factor (P>0.05), but DM digestibility and digestible DM intake were greater (P<0.05) from U compared with T. The in situ immediately soluble DM portion was greater from (P<0.05) L compared with H, but the reverse was true for the potentially degradable DM fraction. The lag time tended (P<0.10) to be greater from H compared with L. Treating bermudagrass with a non-viable Lactobacillus acidophilus-lactic acid spray product at time of baling may not offset the negative effects on forage quality and digestibility of baling bermudagrass hay at excessive moisture concentrations.     

Effect of grain type and processing method on rumen fermentation and milk rumenic acid production

It was hypothesized that differences in starch degradability account for observed differences in rumen vaccenic acid (t11-18:1) and milk rumenic acid (RA) concentrations. To test this hypothesis, starch degradability was varied through grain source and by processing. Eight Holstein cows in mid-lactation were assigned to two 4 × 4 Latin squares with four 21-day periods and four diets: dry rolled barley, ground barley, dry rolled corn and ground corn. Diets contained similar starch content and were supplemented with whole sunflower seed to provide similar total polyunsaturated fatty acid (PUFA) (18:2n-6 + 18:3n-3) contents. Forage/concentrate ratios of all diets were 42 : 58. Rumen, plasma and milk samples were collected in the third week of each period. In situ degradation rates (%/h) for rolled corn, ground corn, rolled barley and ground barley were 5.4, 8.9, 17.0 and 19.4, respectively, for dry matter (DM) and 6.3, 10.8, 25.3 and 43.8, respectively, for starch. DM intakes were greater for corn-based diets (CBD) than for barley-based diets (BBD) with no difference between rolled and ground diets. Daily minimum rumen pH was less (5.2 v. 5.5) and pH duration <5.8 (h/d) was greater (7.4 v. 4.3) for BBD than for CBD. Milk fat content and yield were less for BBD than for CBD with greater values observed for rolling compared with grinding. Variability in milk fat yield was strongly related (R2 = 0.55; P < 0.01) to total starch intake (45%) and milk c9t11-CLA (10%) and none of the t-18:1 isomers or CLA isomers that are typically associated with milk fat depression entered the model. The concentrations (%) of t10-18:1 and t11-18:1 were greater for BBD than for CBD in rumen contents (t10-18:1, 3.5 v. 1.3; t11-18:1, 3.2 v. 1.9), plasma (t10-18:1, 1.2 v. 0.2; t11-18:1, 0.97 v. 0.58) and milk (t10-18:1, 3.8 v. 1.0; t11-18:1, 2.6 v. 1.7) despite greater total PUFA intakes for CBD. Milk RA concentration was greater for BBD than for CBD (1.46 v. 0.89) but was not influenced by the method of grain processing. This study clearly demonstrated that the milk content and profile of t-18:1 and CLA isomers were more strongly influenced by the source of grain starch (barley > corn) than by the method of grain processing indicating that factors inherent in the source of starch were responsible for the observed differences and these factors could not be modified by the processing methods used in this study.     

Long-term influence of feeding barley treated with lactic acid and heat on performance and energy balance in dairy cows

The study evaluated the long-term influence of feeding ground barley treated with lactic acid (LA) alone or with LA and heat on performance, energy and protein balance in dairy cows. Thirty cows were fed three diets differing in the treatment of barley grain, either unprocessed ground barley (Control), ground barley steeped in 1% LA at room temperature (LA-treated barley) or ground barley steeped in 1% LA with an additional heating at 55°C (LAH-treated barley). Cows were studied from week 3 to 17 post-partum. Dry matter intake (DMI), milk yield and composition and body weight (BW) were measured daily. Estimated energy and protein balances were calculated and blood samples were collected three times during the experiment and analysed for common metabolites of energy and lipid metabolism. Digestibility of different treated barley and other dietary ingredients was investigated in vivo using four wethers. The treatment of barley with LA and LAH increased the digestibility of organic matter (OM) by approximately 5% and the content of metabolisable energy by 0.5–0.6 MJ/kg DM. Data showed no effect of feeding diets containing LA- or LAH-treated barley at 39% of DM on overall DMI, BW, BW change, milk production and composition and on the blood variables studied. Diet influenced the estimated balances of net energy of lactation (p < 0.01) and the content of utilisable protein at the duodenum (p = 0.07) with cows fed the diet with LA-treated barley showing improved balances. In conclusion, feeding diets containing LA- or LAH-treated barley had no influence on performance, milk composition and blood metabolites, but LA treatment without heat seems to improve the energy balance of cows.     

Effects of lowering crude protein supply alone or in a combination with essential oils on productivity,rumen function and nutrient utilization in dairy cows

Lowering dietary protein concentration is known to decrease urinary nitrogen (N) losses and increase milk N efficiency in dairy cows, but it may negatively affect animal productivity. Plant-derived essential oils (EO) may alleviate these negative effects by improving the efficiency of rumen fermentation in cows fed reduced feed protein diets. The experiment was conducted to investigate the effects of lowering crude protein (CP) supply alone or in a combination with an EO product on feed intake, milk production and composition, rumen fermentation, total tract digestibility and N utilization in dairy cows. Twenty-one Holstein cows were used in a replicated 3 × 3 Latin square design experiment. Each period consisted of 14 days for adaptation and 14 days for data collection and sampling. Cows were randomly assigned to one of three experimental diets: a 165 g/kg CP diet (control), a 155 g/kg CP diet (LCP) and LCP supplemented with 35 g/day per cow EO (LCPEO). The dry matter (DM) intake was decreased by LCP and LCPEO compared with the control; there was no effect of EO on DM intake. Milk yield and composition and feed efficiency were similar among treatments. Ruminal pH, lactate, ammonia and volatile fatty acids concentrations were not affected by treatment, except increased valerate concentration by LCPEO compared with LCP. The supplementation of EO tended to decrease protozoal counts. The LCP and LCPEO increased total tract digestibility of DM and organic matter and decreased CP digestibility compared with the control. Supplementation with EO did not affect total tract digestibility of dietary nutrients compared with the control or LCP. The LCP and LCPEO decreased urinary and fecal N excretions and increased milk N efficiency; nitrogen losses were not affected by EO. In this study, lowering dietary CP by 10 g/kg decreased urinary and fecal N excretion without affecting productivity. The supplementation of EO to LCP had only minor effects on rumen fermentation and did not affect productivity, digestibility and N excretion in lactating dairy cows.     

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.     

Fenugreek (Trigonella foenum-graecum L.) as an alternative forage for dairy cows

Fenugreek is a novel forage crop in Canada that is generating interest as an alternative to alfalfa for dairy cows. To evaluate the value of fenugreek haylage relative to alfalfa haylage, six, second lactation Holstein cows (56 ± 8 days in milk), which were fitted with rumen cannulas (10 cm i.d., Bar Diamond Inc., Parma, ID, USA) were used in a replicated three × three Latin square design with 18-day periods. Diets consisting of 400 g/kg haylage, 100 g/kg barley silage and 500 g/kg concentrate on a dry matter (DM) basis were fed once daily for ad libitum intake. The haylage component constituted the dietary treatments: (i) Agriculture and Agri-Food Canada F70 fenugreek (F70), (ii) Crop Development Center Quatro fenugreek (QUAT) and (iii) alfalfa (ALF). DM intake (DMI), milk yield and milk protein and lactose yields were higher (P < 0.001) for cows fed ALF than fenugreek (FEN, average of F70 and QUAT). Milk fat of cows fed FEN contained lower concentrations of saturated, medium-chain and hypercholestrolemic fatty acids (FAs; P < 0.05) than that of cows fed ALF. Apparent total tract digestibility of DM and nutrients was not affected by treatments. Similarly, individual ruminal volatile FA concentrations and rumen pH (5.9) were not affected by treatments. Rumen ammonia-N concentration was higher for FEN than ALF (P < 0.001). Estimates of neutral detergent fiber (NDF) passage rate (P < 0.05) and NDF turnover rate (P < 0.001) in the rumen were higher for ALF than FEN. Our results suggest that although the digestibility of the FEN diets was not different from that of the ALF diet, fenugreek haylage has a lower feeding value than ALF for lactating dairy cows due in part to lower DMI and subsequently lower milk yield.     

Effect of feeding yeast culture (Yea-sacc1026) on rumen fermentation in vitro and production performance in crossbred dairy cows

The effect of supplementing diet with yeast culture (Yea-sacc¹⁰²⁶) on dairy cattle was studied by rumen in vitro studies and a feeding trial. Using rumen inoculum from a cow, yeast adapted (YA) and yeast unadapted (YU), incubations were carried out with finger millet (Eleusine coracana) straw (FMS) and a commercial cattle feed (CCF). The 24 h cumulative gas production and digestibility of neutral detergent fibre and acid detergent fibre were not different with YU and YA rumen inoculum for both FMS and CCF. Microbial nitrogen synthesis (mg N ml⁻¹ gas produced) with rumen inoculum from YA feeding regime was higher (P < 0.01) than YU with starch (0.1068 vs. 0.1008) and cellulose (0.0900 vs. 0.0859).A feeding trial was conducted using twelve multiparous cows in midlactation in a switch over design. The cows were divided into two groups of six cows in each group. The duration of the trial was fourteen weeks, each period lasting for 7 weeks. There were no differences in dry matter intake, body weight gain and milk yield. Milk composition for the two groups were also similar.     

Milk production is unaffected by replacing barley or sodium hydroxide wheat with maize cob silage in rations for dairy cows

Starch is an important energy-providing nutrient for dairy cows that is most commonly provided from cereal grains. However, ruminal fermentation of large amounts of easily degradable starch leads to excessive production and accumulation of volatile fatty acids (VFA). VFA not only play a vital role in the energy metabolism of dairy cows but are also the main cause of ruminal acidosis and depressed feed intake. The aim of the present study was to compare maize cob silage (MCS) as an energy supplement in rations for dairy cows with highly rumen-digestible rolled barley and with sodium hydroxide wheat (SHW), which has a higher proportion of by-pass starch than barley. Two studies were carried out: (1) a production study on 45 Danish Holstein cows and (2) an intensive study to determine digestibilities, rumen fermentation patterns and methane emission using three rumen-cannulated Danish Holstein cows. Both studies were organised as a 3×3 Latin square with three experimental periods and three different mixed rations. The rations consisted of grass-clover silage and maize silage (~60% of dry matter (DM)), rapeseed cake, soybean meal, sugar beet pulp and one of three different cereals as a major energy supplement: MCS, SHW or rolled barley (~25% of DM). When MCS replaced barley or SHW as an energy supplement in the mixed rations, it resulted in a lower dry matter intake; however, the apparent total tract digestibilities of DM, organic matter, NDF, starch and protein were not different between treatments. The energy-corrected milk yield was unaffected by treatment. The fat content of the milk on the MCS ration was not different from the SHW ration, whereas it was higher on the barley ration. The protein content of the milk decreased when MCS was used in the ration compared with barley and SHW. From ruminal VFA patterns and pH measures, it appeared that MCS possessed roughage qualities with respect to rumen environment, while at the same time being sufficiently energy rich to replace barley and SHW as a major energy supplement for milk production. The environmental impact, expressed as methane emissions, was not different when comparing MCS, SHW and barley.     

Effects of pressed beet pulp silage inclusion in maize-based rations on performance of high-yielding dairy cows and parameters of rumen fermentation

Beet pulp contains high amounts of pectins that can reduce the risk of rumen disorders compared to using feedstuffs high in starch. The objective was to study the effects of inclusion of ensiled pressed beet pulp in total mixed rations (TMR) for high-yielding dairy cows. Two TMR containing no or about 20% (on dry matter (DM) basis) beet pulp silage were used. The beet pulp silage mainly replaced maize silage and corn cob silage. The TMR were intentionally equal in the concentrations of energy and utilisable crude protein (CP) at the duodenum. TMR were fed to 39 and 40 dairy cows, respectively, for 118 days. The average daily milk yield was about 43 kg/day. No significant differences in milk yield and milk fat or milk protein content were detected. DM intake of cows was significantly reduced by the inclusion of beet pulp silage (23.0 v. 24.5 kg/day). However, a digestibility study, separately conducted with sheep, showed a significantly higher organic matter digestibility and metabolisable energy concentration for the TMR that contained beet pulp silage. In vitro gas production kinetics indicated that the intensity of fermentation was lower in the TMR that contained beet pulp silage. In vitro production of short-chain fatty acids, studied using a Rusitec, did not differ between the TMR. However, the inclusion of beet pulp silage in the ration caused a significant reduction in the efficiency of microbial CP synthesis in vitro. The amino acid profile of microbial protein remained unchanged. It was concluded that beet pulp silage has specific effects on ruminal fermentation that may depress feed intake of cows but improve digestibility. An inclusion of beet pulp silage of up to 20% of DM in rations for high-yielding dairy cows is possible without significant effects on milk yield and milk protein or milk fat.     

Influence of barley grain particle size and treatment with citric acid on digestibility,ruminal fermentation and microbial protein synthesis in Holstein calves

Chemical and physical treatments of barley grain increase ruminally resistant starch and can improve the rumen fermentation pattern. The objective of the present study was to evaluate the effects of chemical (addition of citric acid, CA) and physical (grinding to two different particle sizes, PS) treatment of barley grain on performance, rumen fermentation, microbial protein yield in the rumen and selected blood metabolites in growing calves. In all, 28 male Holstein calves (172±5.1 kg initial BW) were used in a complete randomised design with a factorial arrangement of 2 barley grain particle sizes×2 levels of citric acid. The diets were as follows: (i) small PS (average 1200 µm) barley grain soaked in water (no CA addition); (ii) small PS barley grain soaked in a CA solution (adding 20 g CA/kg barley); (iii) large PS (average 2400 µm) barley grain soaked in water (no citric acid addition) and (iv) large PS barley grain soaked in a citric acid solution (adding 20 g CA/kg barley). Barley grain was then incorporated at 35% in a total mixed ration and fed to the calves for 11 weeks. Feeding small PS barley decreased feed intake (P=0.02) and average daily weight gain (P=0.01). The addition of CA to barley grain did not affect intake but increased weight gain (P<0.01) and improved feed to gain ratio (P=0.03). Digestibility of organic matter and NDF tended (P<0.10) to increase, whereas faecal scoring was improved (P=0.03) and the presence of undigested grain particles in faeces was reduced (P<0.01) with CA-treated barley grain. Glucose and urea concentrations were increased (P<0.01) in the blood of calves fed the CA-treated barley grain. Ruminal pH tended (P=0.08) to be decreased with more finely ground barley and was increased when barley grain was treated with CA. Total volatile fatty acid concentrations in the rumen did not differ among treatments (P>0.05). However, the molar proportion of propionate was increased (P=0.03) when barley was more finely ground, and that of acetate was increased (P=0.04) when CA was added to barley grain. The ruminal concentration of ammonia nitrogen was increased (P<0.01) and microbial nitrogen synthesis in the rumen tended to decrease by adding CA to barley. Treating barley grain with citric acid increased fibre digestibility of total mixed rations, attenuated the decrease in ruminal pH, and improved weight gain and feed efficiency in male Holstein growing calves fed a high-cereal diet (550 g cereal grain/kg diet).     

Effects of Agave salmiana Otto Ex Salm-Dyck silage as forage on ruminal fermentation and growth in goats

Ensiling of Agave salmiana Otto Ex Salm-Dyck, a widespread plant in Mexico, as a viable preservation method to create a potential animal feed resource for ruminants was investigated. Fresh A. salmiana with 205 g dry matter (DM)/kg and wilted alfalfa with 602 g DM/kg were ensiled in combinations (DM:DM) of 1000:0, 500:500 and 350:650, to evaluate feeding value of agave:alfalfa silages on ruminal fermentation and growth of goats. Chemical composition and in situ ruminal disappearance of three total mixed rations (TMRs), which included 240 g/kg DM of each silage (1000:0, 500:500 and 350:650) were determined. The TMR were used to assess ruminal fermentation and growth of 15 goats (20 ± 2.2 kg body weight (BW)). Silage pH (≤4), lactate (>25 g/kg DM) and ammonia (<50 g/kg total N) concentrations indicate that silage quality was good. Lactic acid was the main acid in all silages, acetic acid concentrations were relatively low, and butyrate was only detected in only the 1000:0 agave:alfalfa silage. Potential DM disappearance of the TMR increased quadratically as the amount of alfalfa included in the silage mixture increased. The BW gain and feed efficiency were not changed by treatment, even though DM intake decreased and aNDF intake increased linearly as the amount of alfalfa included in the silage mixture increased. Ruminal pH and butyrate increased, and ammonia N, lactate and propionate decreased linearly as alfalfa proportion of alfalfa in the silage mixture was increased. The TMR ingredient selectivity by the goats may have limited goat performance when alfalfa was included in agave silage mixtures. Because the agave:alfalfa blend improved nutritional quality, ruminal digestibility and intake of agave silage, alfalfa inclusion may improve nutritional characteristics of agave plants silages for ruminants.     

Effect of feeding long or short wheat hay v. wheat silage in the ration of lactating cows on intake,milk production and digestibility

The objective of this study was to evaluate in lactating cows the effect of either chopping or ensiling of wheat roughage on: intake, digestibility, lactation performance and animal behavior. Three groups of 14 lactating cows each, were fed total mixed rations (TMRs) based on either long wheat hay (HL), short wheat hay (HS) or wheat silage (SI), as the sole roughage source (30% of TMR dry matter (DM)). Parameters examined: sorting behavior, DM intake, milk yield and composition, rumination, recumbence, average daily rumen pH, digesta passage rate, and in-vivo digestibility. Performance data was summarized by day and analyzed using a proc-mixed model. The content of physically effective neutral detergent fiber (peNDF) was similar in the HL and SI and lower in the HS, resulting in similar differences among the three corresponding TMRs. In vitro DM digestibility of wheat silage was higher than that of the two hays (65.6% v. 62.8%) resulting in higher in vitro DM digestibility of the SI-TMR compared with the hay-based TMRs (79.3 v. 77.0%). HS-TMR was better than HL- or SI-TMRs at preventing feed sorting by cows after 12 or 24 h eating of the diets. Cows fed HS-TMR consumed more DM and NDF but less peNDF than the other two groups. Average daily rumen pH was similar in the three groups, but daily rumination time was highest in the cows fed HS-TMR. Rumen retention time was longest in cows fed HL-TMR. DM digestibility in cows fed SI-TMR was higher than that of HS and HL groups (65.2%, 61.8% and 62.4%, respectively), but NDF digestibility was similar in the three treatments. The highest intake of digestible DM was observed in cows fed SI-TMR, HS cows were intermediate and HL cows were the lowest. Consequently, cows fed SI-TMR had higher yields of milk, 4% fat corrected milk and energy-corrected milk (47.1, 42.9 and 43.2 kg/day, respectively) than cows fed HS-TMR (45.7, 41.0 and 41.0 kg/day, respectively) or HL-TMR (44.1, 40.3 and 40.3 kg/day, respectively). Net energy production (NE_L+M+gain) per kg DM intake was highest in the SI-TMR, lowest in the HS-TMR and intermediate in the HL-TMR (1.52, 1.40 and 1.45, respectively). Animal welfare, as expressed in daily recumbence time and BW gain was similar in the SI and HS groups and higher than the HL cows.     

Grass silage pulp as a dietary component for high-yielding dairy cows

Green biorefineries provide novel opportunities to use the green biomass efficiently and utilize the ecosystem services provided by grasslands more widely. The effects of the inclusion of fractionated grass silage solid fraction (pulp) on feed intake, rumen fermentation, diet digestion and milk production in dairy cows were investigated. Pulp was separated from grass silage using a screw press simulating a green biorefinery. Partial removal of liquid from forage increased DM concentration from 220 to 432 g/kg and NDF from 589 to 709 g/kg DM while CP decreased from 144 to 107 g/kg DM. A feeding trial using an incomplete changeover design with 24 Nordic Red cows and two 3-week periods was conducted. The pulp replaced grass silage in the diet at 0 (P0), 25 (P25) and 50 (P50) percentage of total forage, which was fed ad libitum with 13 kg of concentrate for all treatments. The forage DM intake was highest on P25 (14.1 kg/day) while P0 and P50 did not differ from each other (13.2 and 13.0 kg/day, respectively). There were no differences between the treatments in rumen pH or ammonia N, but the proportion of acetate increased with increasing pulp inclusion. The digestibility was measured using acid insoluble ash and indigestible NDF (iNDF) as internal markers. Neither of the markers detected differences in NDF digestibility, but according to iNDF, apparent total tract organic matter digestibility decreased with increasing pulp inclusion. The cows maintained milk production at P25, but it showed some decline at P50 (energy-corrected milk at P0 and P25 was 39.8 kg/day while for P50, it was 38.5 kg/day, P = 0.056) and the milk protein yield significantly declined with higher pulp inclusion. Simultaneously, the nitrogen use efficiency in milk production increased. It seems that the fibrous grass-based fraction from a biorefinery process has potential to be used as a feed for ruminants.     

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.     

Effects of hybrid and maturity on performance and nutritive characteristics of forage maize at high latitudes, estimated using the gas production technique

We evaluated effects of hybrid and advancing plant maturity on performance, chemical composition, and nutritional characteristics of whole plant forage maize as well as the relative contributions of its plant fractions at high latitudes. Three maize hybrids, Avenir (FAO 180), Isberi (FAO 190) and Burli (FAO 210), were grown in southern Sweden in a field experiment with a replicated complete randomized block design. Plants were harvested four times during maturation, and dry matter (DM) yield and DM as a proportion of fresh weight were recorded. Whole plants were separated into four morphological fractions representing stems, leaves, kernels and cobs and the contribution of each fraction to the DM of the whole plant was estimated. Plant material was subjected to chemical analysis followed by measurement of in vitro gas production (GP) in buffered rumen fluid and finally, by calculation of in vitro true digestibility of organic matter (OM) and neutral detergent fibre (aNDFom). The GP profiles were fitted to a first order kinetic model with a discrete lag. Parameters describing the GP profiles were used in a recently developed mechanistic two compartment rumen degradation model to estimate in vivo OM digestibility (OMD) and first order rate of degradation in the rumen. Hybrids were compared and effects of maturity were assessed by analysis of variance using DM concentration as covariate. There were differences (P<0.05) among the hybrids in DM yield and relative contributions of the plant fractions. Differences (P<0.05) in modelled in vivo digestibility of OM and rates of degradation also occurred among hybrids. Increased maturity caused a reduction in in vitro digestibility of aNDFom in all plant fractions (P<0.05), but increased the rate of rumen degradation of OM in the whole plant as evaluated from GP results. The DM yield had a quadratic relationship with increasing maturity, with maximum yield at a DM concentration of about 370 g/kg. In vitro GP can describe the nutritive characteristics of forage maize in relation to advancing maturity and increased maturity affected agronomic performance and plant composition as well as the nutritive characteristics of hybrids.     

Nutritional characterization of Mucuna pruiriens: 2. In vitro ruminal fluid fermentability of Mucuna pruriens,Mucunal-dopa and soybean meal incubated with or without l-dopa

Three in vitro experiments were conducted to determine the rumen fermentability of Mucuna (M) pruriens (24 g 3,4-dihydroxy-l-phenylalanine (l-dopa)/kg dry matter (DM) and soybean meal treated with (SBD) or without (SB) 138 g l-dopa/kg DM). Additional objectives were to determine if l-dopa inhibits rumen fermentation, and if ruminal microbes can adapt to l-dopa or M. In Experiment 1, ground (1 mm) substrates were incubated in triplicate at 38 °C in 9 ml nutrient media and 1 ml rumen fluid in a series of six, 48 h, consecutive batch cultures. The first culture was inoculated with rumen fluid from two donor cows. Subsequent cultures were inoculated with fluid (1 ml) from the previous culture. The DM digestibility (DMD, 616 g/kg vs. 540 g/kg; P<0.01) and gas production (51.7 ml/g vs. 44.2 ml/g DM; P<0.05) were higher from fermentation of M versus SB but similar for SB and SBD (540 g/kg vs. 554 g/kg and 44.2 ml/g DM vs. 43.5 ml/g DM, respectively). The slopes of the relationships between DMD (g/kg) or gas production (ml/g DM) and fermentation period were not reduced by fermenting M (−0.014 DMD slope; 2.28 gas production slope) or SBD (−0.014 DMD slope; 0.459 gas production slope), instead of SB (−0.002 DMD slope; 1.039 gas production slope), indicating microbial adaptation to M and SBD. Total volatile fatty acid concentration (VFA; 53.7, 54.9 and 54.9 mmol/l) and molar proportions of VFA were similar among substrates. Gas production kinetics of M versus SB (Experiment 2), and SB versus SBD (Experiment 3) were also measured after substrates were incubated in triplicate in buffered rumen fluid for 24 h using a non-linear exponential model to fit the data. Residual l-dopa was measured after separate fermentation of substrates in triplicate for 0, 4, 8, 16 and 24 h. Fermentation of M versus SB produced more (P<0.05) gas (250 ml/g vs. 100 ml/g DM) and total VFA (203 mmol/l vs. 180 mmol/l) and a lower (P<0.05) acetate:propionate ratio (1.35 vs. 1.87; P<0.05). Adding l-dopa to SB increased (P<0.01) gas production (92 ml/g DM vs. 200 ml/g DM), and total VFA concentration (132 mmol/l vs. 188 mmol/l), but reduced (P<0.05) gas production rate (0.08 ml/h vs. 0.05 ml/h). The concentration of l-dopa in fermented M and SBD decreased by 53 and 47%, respectively during fermentation. In conclusion, M was more fermented than SB and degradation of l-dopa during ruminal fermentation and microbial adaptation to l-dopa were confirmed. Adding l-dopa to SB did not impair ruminal fermentation.     

Effects of medium-chain fatty acid supplementation on performance and rumen fermentation of lactating Holstein dairy cows

Medium-chain fatty acids (MCFAs) have antimicrobial properties and cause negative or positive effects on animal performance depending on its dosage. We hypothesized that MCFA supplementation at a lower dose (i.e., 0.05–0.2% of dietary DM) would increase rumen pH and milk production without decreasing nutrient digestibility which is typically observed with the higher inclusion rates (i.e., >1% of dietary DM). The objective of this study was to evaluate the effects of MCFA supplementation at a lower dose on productivity, plasma energy metabolite concentrations, apparent total tract nutrient digestibility, rumen fermentation, and rumen microbial profile of lactating dairy cows. Thirty (n = 8 primiparous, n = 22 multiparous) Holstein cows in mid-lactation (637 ± 68.5 kg of initial BW, 98.5 ± 27.4 d in milk; mean ± standard deviation) were used in a crossover design with two 28-d periods. The MCFA supplement, consisted of 25% MCFA (containing 32% C8:0, 21% C10:0, 47% C12:0 on DM basis) and 75% carrier ingredients, was fed at 0.25% of dietary DM replacing dry ground corn in control (CON). Total inclusion of MCFA was 0.063% of dietary DM. No differences were observed in DM intake, apparent total tract nutrient digestibility and BW change between MCFA and CON. Milk and milk component yields did not differ between treatment groups. The MCFA supplementation tended to have higher minimum rumen pH (5.66 vs. 5.54), and decreased daily fluctuation range of rumen pH (1.17 vs. 1.40) compared to CON. However, the duration of acidosis (pH < 5.8, min/d) did not differ between treatment groups and ruminal total volatile fatty acid concentration and its profile did not differ between treatment groups. For rumen microbiota, the Chao1 index of bacterial community tended to be lower (10.9 vs. 11.6) whereas the Shannon index did not differ (0.91 vs. 0.93) in MCFA compared to CON, and both indices did not differ for archaeal and protozoan communities between treatment groups. The relative abundance of Methanobrevibacter gottschalkii increased when supplemented with MCFA (5.14 vs. 4.92%). These results suggest that supplementation of MCFA at 0.063% dietary DM may not affect overall animal performance or total tract nutrient digestibility, but decrease the daily range of pH and the bacterial richness in the rumen.