Alfalfa cut at sundown and harvested as baleage improves milk yield of late-lactation dairy cows

A meta-analysis of the relationship between milk protein production and absorbed amino acids and digested energy in dairy cattle

Milk protein production is the largest draw on AA supplies for lactating dairy cattle. Prior NRC predictions of milk protein production have been absorbed protein (MP)-based and used a first-limiting nutrient concept to integrate the effects of energy and protein, which yielded poor accuracy and precision (root mean squared error [RMSE] >21%). Using a meta-data set gathered, various alternative equation forms considering MP, absorbed total EAA, absorbed individual EAA, and digested energy (DE) supplies as additive drivers of production were evaluated, and all were found to be superior in statistical performance to the first limitation approach (RMSE = 14%-15%). Inclusion of DE intake and a quadratic term for MP or absorbed EAA supplies were found to be necessary to achieve intercept estimates (nonproductive protein use) that were similar to the factorial estimates of the National Academies of Sciences, Engineering, and Medicine (2021). The partial linear slope for MP was found to be 0.409, which is consistent with the observed slope bias of -0.34 g/g when a slope of 0.67 was used for MP efficiency in a first-limiting nutrient system. Replacement of MP with the supplies of individual absorbed EAA expressed in grams per day and a common quadratic across the EAA resulted in unbiased predictions with improved statistical performance as compared with MP-based models. Based on Akaike's information criterion and biological consistency, the best equations included absorbed His, Ile, Lys, Met, Thr, the NEAA, and individual DE intakes from fatty acids, NDF, residual OM, and starch. Several also contained a term for absorbed Leu. These equations generally had RMSE of 14.3% and a concordance correlation of 0.76. Based on the common quadratic and individual linear terms, milk protein response plateaus were predicted at approximately 320 g/d of absorbed His, Ile, and Lys; 395 g/d of absorbed Thr; 550 g/d of absorbed Met; and 70 g/d of absorbed Leu. Therefore, responses to each except Leu are almost linear throughout the normal in vivo range. De-aggregation of the quadratic term and parsing to individual absorbed EAA resulted in nonbiological estimates for several EAA indicating over-parameterization. Expression of the EAA as g/100 g total absorbed EAA or as ratios of DE intake and using linear and quadratic terms for each EAA resulted in similar statistical performance, but the solutions had identifiability problems and several nonbiological parameter estimates. The use of ratios also introduced nonlinearity in the independent variables which violates linear regression assumptions. Further screening of the global model using absorbed EAA expressed as grams per day with a common quadratic using an all-models approach, and exhaustive cross-evaluation indicated the parameter estimates for BW, all 4 DE terms, His, Ile, Lys, Met, and the common quadratic term were stable, whereas estimates for Leu and Thr were known with less certainty. Use of independent and additive terms and a quadratic expression in the equation results in variable efficiencies of conversion. The additivity also provides partial substitution among the nutrients. Both of these prevent establishment of fixed nutrient requirements in support of milk protein production.

Invited review: Advances in nutrition and feed additives to mitigate enteric methane emissions

Methane, both enteric and from manure management, is the most important greenhouse gas from ruminant livestock, and its mitigation can deliver substantial decreases in the carbon footprint of animal products and potentially contribute to climate change mitigation. Although choices may be limited, certain feeding-related practices can substantially decrease livestock enteric CH4 emission. These practices can be generally classified into 2 categories: diet manipulation and feed additives. Within the first category, selection of forages and increasing forage digestibility are likely to decrease enteric CH4 emission, but the size of the effect, relative to current forage practices in the United States dairy industry, is likely to be minimal to moderate. An opportunity also exists to decrease enteric CH4 emissions by increasing dietary starch concentration, but interventions have to be weighed against potential decreases in milk fat yield and farm profitability. A similar conclusion can be made about dietary lipids and oilseeds, which are proven to decrease CH4 emission but can also have a negative effect on rumen fermentation, feed intake, and milk production and composition. Sufficient and robust scientific evidence indicates that some feed additives, specifically the CH4 inhibitor 3-nitrooxypropanol, can substantially reduce CH4 emissions from dairy and beef cattle. However, the long-term effects and external factors affecting the efficacy of the inhibitor need to be further studied. The practicality of mass-application of other mitigation practices with proven short-term efficacy (i.e., macroalgae) is currently unknown. One area that needs more research is how nutritional mitigation practices (both diet manipulation and feed additives) interact with each other and whether there is synergism among feed additives with different mode of action. Further, effects of diet on manure composition and greenhouse gas emissions during storage (e.g., emission trade-offs) have not been adequately studied. Overall, if currently available mitigation practices prove to deliver consistent results and novel, potent, and safe strategies are discovered and are practical, nutrition alone can deliver up to 60% reduction in enteric CH4 emissions from dairy farms in the United States.

Effects of graded levels of dietary pomegranate peel on methane and nitrogen losses, and metabolic and health indicators in dairy cows

This study aimed to quantify the effects of dietary inclusion of tannin-rich pomegranate peel (PP) on intake, methane and nitrogen (N) losses, and metabolic and health indicators in dairy cows. Four multiparous, late-lactating Brown Swiss dairy cows (796 kg body weight; 29 kg/d of energy corrected milk yield) were randomly allocated to 3 treatments in a randomized cyclic change-over design with 3 periods, each comprising 14 d of adaptation, 7 d of milk, urine, and feces collection, and 2 d of methane measurements. Treatments were formulated using PP that replaced on a dry matter (DM) basis 0% (control), 5%, and 10% of the basal mixed ration (BMR) consisting of corn and grass silage, alfalfa, and concentrate. Gaseous exchange of the cows was determined in open-circuit respiration chambers. Blood samples were collected on d 15 of each period. Individual feed intake as well as feces and urine excretion were quantified, and representative samples were collected for analyses of nutrients and phenol composition. Milk was analyzed for concentrations of fat, protein, lactose, milk urea N, and fatty acids. Total phenols and antioxidant capacity in milk and plasma were determined. In serum, the concentrations of urea and bilirubin as well as the activities of alanine aminotransferase (ALT), aspartate aminotransferase, glutamate dehydrogenase, alkaline phosphatase, and γ-glutamyl transferase were measured. The data were subjected to ANOVA with the Mixed procedure of SAS, with treatment and period as fixed and animal as random effects. The PP and BMR contained 218 and 3.5 g of total extractable tannins per kg DM, respectively, and thereof 203 and 3.3 g of hydrolyzable tannins. Total DM intake, energy corrected milk, and methane emission (total, yield, and intensity) were not affected by PP supplementation. The proportions of C18:2n-6 and C18:3n-3 in milk increased linearly as the amount of PP was increased in the diet. Milk urea N, blood urea N, and urinary N excretion decreased linearly with the increase in dietary PP content. Total phenols and antioxidant capacity in milk and plasma were not affected by the inclusion of PP. The activity of ALT increased in a linear manner with the inclusion of PP. In conclusion, replacing up to 10% of BMR with PP improved milk fatty acid composition and alleviated metabolic and environmental N load. However, the elevated serum ALT activity indicates an onset of liver stress even at 5% PP, requiring the development of adaptation protocols for safe inclusion of PP in ruminant diets.

Changing the grazing session from morning to afternoon or including tannins in the diet was effective in decreasing the urinary nitrogen of dairy cows fed a total mixed ration and herbage

Our aim was to evaluate whether increasing soluble carbohydrates in the herbage by changing the time of the grazing session or including Acacia mearnsii tannin in the diet would affect intake, digestion, N partitioning, and productive performance of dairy cows fed a diet combining ryegrass herbage with partial total mixed ration (PMR). We hypothesized that both strategies could reduce the concentration of NH₃-N in the rumen, reducing urinary N excretion. Nine Holstein cows were used in a triplicate 3 × 3 Latin square experiment with 3 experimental periods of 22 d. The cows were fed a fixed amount of PMR [60% of the predicted individual dry matter intake (DMI)], and an unrestricted amount of herbage in 1 grazing session of 5 h/d. The treatments were (1) morning grazing session and afternoon PMR meal (AM); (2) morning PMR meal and afternoon grazing session (PM); and (3) morning grazing session and afternoon PMR meal supplemented with 15.0 g of tannins/kg of PMR dry matter (TAN). Milk production was not affected by treatments. Although the protein concentration was lower for TAN than for PM, no differences were detected for the yield of any component between treatments. The concentration of individual or grouped fatty acids in milk fat was not affected by treatments, except for 16:1 cis-9 and Δ⁹-desaturase ratios 14:1/14:0 and 16:1/16:0, which were lower for TAN. Treatments did not affect total DMI, but PM tended to increase herbage DMI and reduce dry matter and crude protein digestibilities. Treatments did not affect cow eating and ruminating behavior except for the proportion of time spent eating PMR, which was higher for PM and TAN. Although no relevant effects of treatments on ruminal fermentation, purine derivatives excretion in urine, or N excretion in milk were detected, both PM and TAN decreased the total N excreted in urine by an average of 8% compared with AM. In conclusion, changing the grazing session from the morning to the afternoon and including tannins in the diet were effective in decreasing the excretion of urinary N but did not change the productive performance of dairy cows fed PMR and ryegrass herbage.

A review on the potentials of using feeds rich in water-soluble carbohydrates to enhance rumen health and sustainability of dairy cattle production

Cows are adapted to degrade structural plant carbohydrates (SC), such as cellulose and hemicelluloses, prevailing in grasses. Yet, the need for energy-dense diets in many intensive dairy production systems has shifted the dairy cattle's diet from SC-rich to high levels of starch. Feeding of starch-rich diets increases the risk of ruminal acidosis in cows, and feeding starch in the form of grains intensifies the competition over cereal grains and arable land among different livestock species, as well as between livestock and humans. Besides cellulose and hemicelluloses, grasses are also often rich in water-soluble carbohydrates (WSC), which comprise mono-, di-, oligo- and polysaccharides (fructans). Although the ruminal fermentation profile of mono- and disaccharides resembles that of starch, the degradation of oligo- and polysaccharides is slower, and their fermentation elicits a rather protecting effect on ruminal pH. When harvested in an early phase (i.e. ear emergence), grass hay and silages can reach WSC levels up to 150-200 g kg^-1 dry matter and energy levels close to starch-rich diets, allowing a significantly reduced inclusion of concentrate supplements. By doing so, this will enhance both rumen health and the sustainability of milk production. However, because the WSC are chemically very heterogeneous, the patterns and extent of their ruminal fermentation are difficult to predict without a clear analytical characterization. This review article aims to summarize both the benefits and potentials, as well as the challenges, with respect to using WSC-rich feedstuffs in the nutrition of dairy cattle and their effects on ruminal fermentation characteristics and milk production. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Omasal flow of nonstructural carbohydrates and nitrogenous compounds in lactating dairy cows fed diets containing timothy cut in the afternoon or morning

Shifting the cutting of grass from morning to afternoon has been shown to increase the concentration of nonstructural carbohydrates (NSC) in forages. We compared the effects of diets (66:34, forage:concentrate ratio) containing a mix (% of the diet dry matter) of baleages (46.5%) and silages (19.3%) harvested from timothy cut in the afternoon (p.m.-cut TIM diet) or morning (a.m.-cut TIM diet) on omasal flows of NSC and nitrogenous fractions, ruminal and total-tract digestibilities of nutrients, plasma concentration of AA, and milk yield and composition. Eight ruminally cannulated Holstein cows averaging (mean ± standard deviation) 31.4 ± 6.13 kg/d of milk, 136 ± 17.0 d in milk, and 611 ± 66.4 kg of body weight in the beginning of the experiment were used in a crossover design with 21-d periods (14 d for diet adaptation and 7 d for data and sample collection). Intake of total ethanol-soluble carbohydrates (TESC; +150 g/d), starch (+129 g/d), and total NSC (TESC plus starch = +278 g/d) was greater with feeding the p.m.- than the a.m.-cut TIM diet. Likewise, the apparent ruminal digestibilities of TESC (+149 g/d), starch (+167 g/d), and total NSC (+316 g/d) increased in the p.m.-cut TIM diet. Diets, however, had no effect on the omasal flows and apparent ruminal and total-tract digestibilities of dry matter and organic matter. Intake of N increased in cows fed the p.m.- versus the a.m.-cut TIM diet (562 and 528 g/d, respectively) despite no effect of diets on dry matter intake. Diets did not affect the omasal flows of total nonammonia N, total bacterial nonammonia N, nonammonia and nonbacterial N, and individual AA, and the efficiency of microbial protein synthesis in the rumen. Contrarily, supply of rumen-degradable protein increased (+9.2%) in cows fed the p.m.-cut TIM diet, with this response driven by the 6.4% increase in N intake. Plasma concentrations of essential and nonessential AA followed the omasal flow of AA and were not changed by diets. Feeding the p.m.- versus the a.m.-cut diet significantly increased yields of 4% fat-corrected milk and milk fat, and tended to increase energy-corrected milk, milk true protein, and milk lactose yields. Overall, feeding the p.m.-cut TIM diet to mid-lactation dairy cows did not improve microbial protein synthesis and omasal flow of AA, and these responses were in line with the lack of a treatment effect on dry matter intake.

Non-fiber Carbohydrates in Forages and Their Influence on Beef Production Systems

Forages can provide a complete diet for ruminant animals, increasing the sustainability of beef production systems worldwide while reducing competition with humans for agricultural land or grain crops. Much of the emphasis on the nutritional characteristics of forages has been on the fiber, sugars, starch, and protein they supply to the rumen, despite the fact that other less-explored constituents, i.e., neutral detergent soluble fiber (NDSF) and other non-structural or non-fiber carbohydrates (NFC) also play a key role in the nutrition of ruminants. This paper explores the less investigated potential of temperate legumes to accumulate levels of NFC comparable to corn silage or beet pulp in cool, dry environments under irrigation, and its implications for forage-based beef production systems. We conclude that genetic or managerial interventions (i.e., breeding programs, defoliation frequency) or ecological conditions (i.e., climate, elevation) that increase concentrations of NFC in legumes can enhance beef production, meat quality, and the efficiency of nitrogen utilization by ruminants while reducing environmental impacts.

Effects of cutting time and maceration on preference and nitrogen balance in beef steers fed mixed birdsfoot trefoil-timothy grass hay cut at sunrise or sundown

Forages cut at sundown usually contain a greater concentration of nonstructural carbohydrates (NSC) than those cut at sunrise. Maceration can speed up the rate of moisture loss of cut forage during field drying and reduce NSC utilization by plant cells. We aimed to evaluate the effects of cutting time and forage maceration on feed preference, apparent total tract digestibility of nutrients, and N balance in growing steers. A mixed sward of birdsfoot trefoil and timothy grass was divided into two halves, with the first half cut at sundown (1800 h) after a sunny day and the second half at sunrise (0600 h) the next day. Approximately 50% of the sundown- and sunrise-cut herbage were macerated. Forages were harvested as hay resulting in four treatments: 1) sunrise-cut hay (AM); 2) AM plus maceration (AM-M); 3) sundown-cut hay (PM); and 4) PM plus maceration (PM-M). Hays were offered as the sole feed source to four crossbred steers (296.1 ± 7.25 kg) according to a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Each period lasted 21 d with 14 d for diet adaptation and 7 d for collection. Hays cut at sundown had 15% greater NSC than those cut at sunrise. A cutting time by maceration interaction was found (P < 0.05) for intake and apparent digestibility of crude protein (CP), indicating that these two variables decreased more when maceration was applied to sundown- versus sunrise-cut hays. Similarly, interaction effects were observed (P < 0.05) for total digestible nutrients and digestible energy, showing that maceration decreased the energetic value of sundown-cut hays but did not change that of sunrise-cut hays. Steers fed hays cut at sundown had decreased urinary N excretion and improved retained N (P < 0.05), whereas N retention was reduced by maceration (P < 0.05). In addition, six crossbred steers were used to assess feed preference, 2 wk before (period 1) and 1 wk after (period 2) the digestibility trial. Animals were randomly assigned to receive a sequence of the four hays combined in pairs. The intake rate was greater for sundown- than sunrise-cut hays, and it was decreased by maceration. Steers showed the greatest preference for PM hay, while AM-M was the most rejected. In conclusion, shifting forage cutting from sunrise to sundown increased hay NSC concentration, which resulted in improved N utilization and preference. Forage maceration during field drying decreased CP concentration and N retention in beef steers under the conditions of our study.

Potential effects of a high CO2 future on leguminous species

Legumes provide an important source of food and feed due to their high protein levels and many health benefits, and also impart environmental and agronomic advantages as a consequence of their ability to fix nitrogen through their symbiotic relationship with rhizobia. As a result of our growing population, the demand for products derived from legumes will likely expand considerably in coming years. Since there is little scope for increasing production area, improving the productivity of such crops in the face of climate change will be essential. While a growing number of studies have assessed the effects of climate change on legume yield, there is a paucity of information regarding the direct impact of elevated CO₂ concentration (e[CO₂]) itself, which is a main driver of climate change and has a substantial physiological effect on plants. In this review, we discuss current knowledge regarding the influence of e[CO₂] on the photosynthetic process, as well as biomass production, seed yield, quality, and stress tolerance in legumes, and examine how these responses differ from those observed in non-nodulating plants. Although these relationships are proving to be extremely complex, mounting evidence suggests that under limiting conditions, overall declines in many of these parameters could ensue. While further research will be required to unravel precise mechanisms underlying e[CO₂] responses of legumes, it is clear that integrating such knowledge into legume breeding programs will be indispensable for achieving yield gains by harnessing the potential positive effects, and minimizing the detrimental impacts, of CO₂ in the future.

Assessment of cutting time on nutrient values, in vitro fermentation and methane production among three ryegrass cultivars

OBJECTIVE

The 3×3 factorial arrangement was used to investigate if either high watersoluble carbohydrates (WSC) cultivars or suitable time of day that the grass cut could improve nutrient values and in vitro fermentation characteristics.

METHODS

The 3 cultivars were mowed at 3 diurnal time points and included a benchmark WSC ryegrass cultivar 'Premium', and 2 high WSC cultivars AberAvon and AberMagic, which contained, on average, 157, 173, and 193 g/kg dry matter (DM) of WSC, and 36.0, 36.5, and 34.1 g/kg DM of N during 7th regrowth stage, respectively. The fermentation jars were run at 39°C with gas production recorded and sampled at 2, 5, 8, 11, 14, 17, 22, 28, 36, and 48 h. The rumen liquid was collected from 3 rumen fistulated cows grazing on ryegrass pasture.

RESULTS

High WSC cultivars had significantly greater WSC content, in vitro DM digestibility (IVDMD) and total gas production (TGP), and lower lag time than Premium cultivar. Methane production for AberMagic cultivar containing lower N concentration was marginally lower than that for AberAvon and Premium cultivars. Grass cut at Noon or PM contained greater WSC concentration, IVDMD and TGP, and lower N and neutral detergent fiber (NDF) contents, but CH4 production was also increased, compared to grass cut in AM. Meanwhile, the effects of diurnal cutting time were influenced by cultivars, such as in vitro CH4 production for AberMagic was not affected by cutting time. The IVDMD and gas production per unit of DM incubated were positively related to WSC concentration, WSC/N and WSC/NDF, respectively, and negatively related to N and NDF concentrations.

CONCLUSION

These results imply either grass cut in Noon or PM or high WSC cultivars could improve nutrient values, IVDMD and in vitro TGP, and that AberMagic cultivar has a slightly lower CH4 production compared to AberAvon and Premium. Further study is necessary to determine whether the increase of CH4 production response incurred by shifting from AM cutting to Noon and/or PM cutting could be compensated for by high daily gain from increased WSC concentration and DM digestibility.

Tall fescue as an alternative to timothy fed with or without alfalfa to dairy cows

Tall fescue might be an alternative to timothy in northeastern North America because of its tolerance of recurring drought periods and its good summer regrowth, but is not always considered as an option in dairy rations because of its possible lack of palatability. The objective of this study was to evaluate the effects on the performance of lactating dairy cows of (1) replacing timothy silage by tall fescue silage, offered as sole forage in the diet or in combination with alfalfa silage, and (2) feeding tall fescue as silage (35% dry matter, DM) or haylage (55% DM). Experimental diets with a forage-to-concentrate ratio of 70:30 were (1) 100% timothy silage (TS); (2) 100% tall fescue silage (TFS); (3) 55:45 timothy:alfalfa silages (TS + AS); (4) 55:45 tall fescue:alfalfa silages (TFS + AS); and (5) 100% tall fescue haylage (TFH). Fifteen Holstein cows in mid-lactation (5 fitted with a rumen fistula) were randomly assigned to treatments in a triple 5 × 5 Latin square design with treatment periods of 21 d. Preplanned contrasts were timothy versus tall fescue silages, sole grass species versus grass-alfalfa, interaction between sole grass species and grass-alfalfa, and TFS versus TFH. Grass species did not affect dry matter intake (DMI) or milk yield and fat concentration. Milk protein concentration was not affected by grass species when offered in combination with alfalfa, but it was higher with the TS diet than the TFS diet when offered as sole forages. Adding alfalfa to either tall fescue or timothy silage resulted in greater DMI and milk yield, but lower milk fat concentration, than when the grass silages were the sole forage in the diet. The molar proportion of propionate in the rumen was greater when cows were fed diets with tall fescue silage compared with timothy silage, which resulted in a lower acetate-to-propionate ratio. Milk fat concentrations of fatty acids from microbial origin, namely branched-chain fatty acids, were greater when grass silage, and especially timothy silage, were fed as sole forages rather than with alfalfa silage. Feeding TFH rather than TFS caused a decrease in DMI and tended to lower milk protein concentration, but did not affect milk yield. A more fibrolytic fermentation profile was observed in rumen of cows fed TFH compared with TFS, as indicated by the increase in the molar proportion of acetate and the higher acetate-to-propionate ratio in rumen fluid, and a concomitant increase in branched-chain fatty acid concentration in milk fat. Tall fescue as silage or haylage is a valuable alternative to timothy silage for lactating dairy cows.

Urine volume and nitrogen excretion are altered by feeding birdsfoot trefoil compared with alfalfa in lactating dairy cows1

Legumes that contain condensed tannins may have lower ruminal protein degradation than alfalfa. The present study investigated the effects of feeding birdsfoot trefoil (Lotus corniculatus L.) hay on lactational performance and N utilization and excretion. Eight multiparous Holstein cows in midlactation (150 ± 22.3 d-in-milk) were randomly assigned to 2 treatments [alfalfa hay-based total mixed ration (AHT) or birdsfoot trefoil hay-based total mixed ration (BHT)] in a crossover design with 2 experimental periods. Each experimental period lasted 17 d (14 d of adaptation and 3 d of sampling and total collection). Hays comprised approximately 50% of DM in experimental diets. There were no treatment effects on dry matter intake (DMI; 21.4 vs. 20.7 kg/d), milk yield (29.4 vs. 28.1 kg/d), milk fat concentration (3.20% vs. 3.21%), and milk protein concentration (3.20% vs. 3.16%) for AHT and BHT, respectively. In addition, dietary treatments did not affect milk yield/DMI or energy-corrected milk yield/DMI. In contrast, apparent crude protein digestion decreased in cows fed BHT compared with those fed AHT (60.7% vs. 69.1%). Concentration of milk urea-N decreased by feeding BHT compared with AHT (11.9 vs. 13.3 mg/100 mL), whereas total N excretion did not differ between AHT and BHT diets. However, cows fed BHT excreted more N in feces (194 vs. 168 g/d), whereas urinary N excretion was lower compared with cows fed AHT. The shift of N to feces resulted in a decrease in urinary N:fecal N ratio in cows fed BHT relative to those fed AHT. Overall results in the current study suggest that feeding birdsfoot trefoil in dairy diets shifts routes of N from urine to feces compared with feeding alfalfa hay, with little effect on lactational performance. Reduction in urinary N and any impact on environment may be attributed to functional effect of condensed tannins in birdsfoot trefoil hay.

Lamb Fattening Under Intensive Pasture-Based Systems: A Review

The benefits of pasture-based systems on the fatty acid composition of sheep meat appear to be achievable despite variability in the quality of the pastures. Lambs fed high levels of temperate pastures have an excess of N-ammonia derived from protein degradation. Furthermore, animal performance is highly variable depending on the quality of the pasture at the time of grazing, and high animal performance in these systems appears to be linked to the use of high-quality pastures with high availability, and is possibly added to by the inclusion of concentrates that allow increasing energy intake and a better use of the N in the pasture. The combination of high-quality pastures and total mixed ration offers a good alternative to the inclusion of concentrates in the diet, improving the use of N, and avoiding acidosis problems. However, information to determine the effect of a number of nutritional strategies on meat quality, and the minimum level of pasture intake necessary to achieve the benefits of pastoral systems is still lacking.

Symposium review: Comparisons of feed and milk nitrogen efficiency and carbon emissions in organic versus conventional dairy production systems

Evaluation of feed efficiency (FE; calculated as energy-corrected milk yield/dry matter intake) and milk nitrogen efficiency (MNE; calculated as milk N yield/N intake) is needed to help farmers make decisions regarding the economic and environmental sustainability of dairy farms. Our primary objective was to compare FE and MNE data obtained from studies conducted with organic versus conventional dairy cows. Specifically, 3 data sets were constructed to meet this goal: (1) the organic Jersey data set (ORG-JE) built with studies (n = 11) done at the University of New Hampshire Burley-Demeritt Organic Dairy Research Farm (Lee, NH), (2) the conventional Jersey data set (CON-JE) constructed using 19 experiments reported in the literature, and (3) the organic non-Jersey-breed (mostly Holstein, Swedish Red, and Norwegian Red) data set (ORG-NJE) created with 11 published studies. Comparisons were made between ORG-JE and CON-JE and between ORG-JE and ORG-NJE. A second objective was to compare the enteric methane (CH₄) emission data set from studies using organic Jerseys (n = 5) with those using conventional Jerseys (n = 4). Cows used in the ORG-JE data set had lower FE (-16%) and MNE (-15.5%) than cows used in the CON-JE counterpart, possibly because dry matter intake increased by an average of 10.4% in organic cows. Feed efficiency and MNE computed from cows belonging to the ORG-NJE data set were intermediate between ORG-JE and CON-JE. Measured CH₄ intensity (g/kg of energy-corrected milk) from cows in the ORG-JE CH₄ data set increased by 71% compared with that from cows in the CON-JE CH₄ data set. Estimated FE and enteric CH₄ emissions revealed that Wisconsin organic dairies with the heaviest reliance on forage sources and longest grazing time during the summer were the least feed efficient and emitted the greatest amount of CH₄ per kilogram of energy-corrected milk at the animal and whole-farm levels. Overall, the comparisons of FE, MNE, and enteric CH₄ emissions between organic and conventional dairies and within organic systems made in this symposium review should be interpreted cautiously because they are based on study means and small data sets. Research is needed to better characterize the performance, efficiency, profitability, and carbon emissions of forage-based organic dairies in the United States, including the fast-growing "grass-fed" segment, which relies exclusively on forage diets. The effect of large organic dairies on the economic and social sustainability of small and mid-size organic dairy operations nationwide also deserves further investigation.

Criollo goats limit their grass intake in the early morning suggesting a prophylactic self-medication behaviour in a heterogeneous vegetation

The present study compared the feeding behaviour of goats in the early morning (EM = 7:00-8:30 a.m.) and late morning (LM = 9:30-11:00 a.m.) in response to their natural gastrointestinal nematode (GIN) infection status. Twelve female adult goats (37 ± 7.7 kg live weight (LW); 5 ± 1 years) with browsing experience in the tropical deciduous forest were divided into two groups (n = 6): INF group, with natural GIN infection, and non-infected (NI) group, dewormed with moxidectin (0.4 mg/kg LW subcutaneous). Feeding behaviour (dry matter intake (DMI)) of two resource types (grasses vs. shrubs + herbs) was estimated by direct observation for 4 weeks on two grazing moments (EM vs. LM). Environmental temperature and relative humidity at pasture level were measured twice weekly. The GIN egg counts and goats' LW were measured on days 0, 14 and 28. Temperature (mean ± standard deviation) at EM (26.2 ± 1.5 °C) was lower than at LM (38.7 ± 1 °C; P < 0.01). Humidity was higher on the EM (85.1 ± 2.6%) compared to LM (60.4 ± 5.6%; P < 0.01). Irrespective of the infection status, goats consumed similar amounts of grass and shrubs + herbs during EM (P > 0.05). On the other hand, the experimental groups consumed more grass than shrubs + herbs during LM (P < 0.05). The latter suggested prophylactic behaviours strategies to (a) avoid GIN infective larvae, (b) balance the protein:energy ratio of the diet and (c) avoid saturation of detoxification pathways for the secondary compounds consumed from shrubs + herbs. The constant consumption of shrubs + herbs during the study may have reduced the GIN egg count of the INF group.

Symposium review: Technologies for improving fiber utilization

The forage lignocellulosic complex is one of the greatest limitations to utilization of the nutrients and energy in fiber. Consequently, several technologies have been developed to increase forage fiber utilization by dairy cows. Physical or mechanical processing techniques reduce forage particle size and gut fill and thereby increase intake. Such techniques increase the surface area for microbial colonization and may increase fiber utilization. Genetic technologies such as brown midrib mutants (BMR) with less lignin have been among the most repeatable and practical strategies to increase fiber utilization. Newer BMR corn hybrids are better yielding than the early hybrids and recent brachytic dwarf BMR sorghum hybrids avoid lodging problems of early hybrids. Several alkalis have been effective at increasing fiber digestibility. Among these, ammoniation has the added benefit of increasing the nitrogen concentration of the forage. However, few of these have been widely adopted due to the cost and the caustic nature of the chemicals. Urea treatment is more benign but requires sufficient urease and moisture for efficacy. Ammonia-fiber expansion technology uses high temperature, moisture, and pressure to degrade lignocellulose to a greater extent than ammoniation alone, but it occurs in reactors and is therefore not currently usable on farms. Biological technologies for increasing fiber utilization such as application of exogenous fibrolytic enzymes, live yeasts, and yeast culture have had equivocal effects on forage fiber digestion in individual studies, but recent meta-analyses indicate that their overall effects are positive. Nonhydrolytic expansin-like proteins act in synergy with fibrolytic enzymes to increase fiber digestion beyond that achieved by the enzyme alone due to their ability to expand cellulose microfibrils allowing greater enzyme penetration of the cell wall matrix. White-rot fungi are perhaps the biological agents with the greatest potential for lignocellulose deconstruction, but they require aerobic conditions and several strains degrade easily digestible carbohydrates. Less ruminant nutrition research has been conducted on brown rot fungi that deconstruct lignocellulose by generating highly destructive hydroxyl radicals via the Fenton reaction. More research is needed to increase the repeatability, efficacy, cost effectiveness, and on-farm applicability of technologies for increasing fiber utilization.

Milk production and composition, nitrogen utilization, and grazing behavior of late-lactation dairy cows as affected by time of allocation of a fresh strip of pasture

Eighty late-lactation dairy cows were used to examine the effects of allocating a new pasture strip of a sward based on ryegrass (Lolium perenne L.) in the morning (a.m.; ∼0730 h) or in the afternoon (p.m.; ∼1530 h) on milk production and composition, nitrogen (N) utilization, and grazing behavior. Cows grazed the same pasture strips for 24 h and were offered the same daily herbage allowance. Herbage composition differed among treatments; p.m. herbage had greater dry matter (DM; 22.7 vs. 19.9%), organic matter (OM; 89.5 vs. 88.9%), and water-soluble carbohydrate (10.9 vs. 7.6%) concentrations and lesser crude protein (20.5 vs. 22.2%) and neutral detergent fiber (48.8 vs. 50.4%) concentrations compared with a.m. herbage. Total fatty acids (FA), α-linolenic acid, and polyunsaturated FA (PUFA) were greater in a.m. herbage, whereas monounsaturated FA were greater in p.m. herbage. Estimates of herbage DM intake did not differ among treatments. Daily milk yields and milk fat and milk protein concentrations were similar among treatments, whereas milk fat (684 vs. 627 g/cow), milk protein (545 vs. 505 g/cow), and milk solids (milk fat + milk protein) yields (1,228 vs. 1,132 g/cow) tended to be greater for cows on p.m. herbage. Rumenic acid and total PUFA in milk were greater for cows on a.m. herbage, whereas oleic acid was greater for cows on p.m. herbage. Estimates of urinary N excretion (g/d) did not differ among treatments, but urinary N concentrations were greater for cows on a.m. herbage (5.85 vs. 5.36 g/L). Initial herbage mass (HM) available (kg of DM/ha) and instantaneous HM disappearance rates (kg of DM/ha and kg of DM/h) did not differ, but fractional disappearance rates (0.56 vs. 0.74 per hour for a.m. vs. p.m., respectively) differed. Under the current conditions, timing of pasture strip allocation altered the herbage nutrient supply to cows; allocating a fresh strip of pasture later in the day resulted in moderate increases in milk and milk solids yields in late-lactation dairy cows. Conversely, a greater concentration of precursor FA in a.m. herbage resulted in a greater concentration of beneficial FA in milk, compared with cows on p.m. herbage.

Milk production and composition of dairy cows grazing two perennial ryegrass cultivars allocated in the morning and afternoon

The objective of the study was to evaluate the effect of perennial ryegrass cultivar and timing of herbage allocation on herbage nutritive value and milk production of mid-lactation dairy cows. An autumn grazing trial using 48 Friesian × Jersey spring-calving cows was conducted over 10 days. Twelve groups of four cows were allocated to three replicates of four treatments, namely, two perennial ryegrass cultivars (AberMagic or Prospect) offered either after milking in the morning (0830 hours) or afternoon (1630 hours). Cows were offered a daily herbage allowance of 30 kg DM/cow above ground level. There were no significant differences in sward structure and morphological characteristics between cultivars, except for Prospect having a lower average tiller mass (43.1 mg) than AberMagic (48.4 mg). The concentration of water-soluble carbohydrates (WSC) and organic matter digestibility in DM (DOMD) was greater in AberMagic (180 g/kg, 74.2%) than in Prospect (153 g/kg, 71.4%). Herbage DM percentage, WSC concentration and DOMD were lower in the morning than in the afternoon (18.8% vs 22.3% DM; 154 vs 179 g/kg WSC; 72.1% vs 73.5% DOMD). Herbage DM intake (12.0 kg/cow.day), milk yield (17.2 kg/cow.day) and milksolids yield (1.60 kg/cow.day) did not differ significantly among treatments. Cultivar choice and timing of allocation influenced herbage WSC concentration and digestibility, but did not alter milksolids production.

Performance and nitrogen use efficiency in mid-lactation dairy cows fed timothy cut in the afternoon or morning

Shifting cutting from morning to afternoon has been shown to increase the concentration of nonstructural carbohydrates in forages. We hypothesized that, compared with a total mixed ration containing timothy baleage and silage cut in the morning (a.m.-cut TIM), a total mixed ration containing timothy baleage and silage cut in the afternoon (p.m.-cut TIM) would improve animal performance and N use efficiency in mid-lactation Holstein cows due to enhanced supply of ruminal fermentable energy. The objective of this study was to compare the effects of p.m.- versus a.m.-cut TIM on milk yield, concentrations and yields of milk components, ruminal metabolism, and plasma concentrations of AA in mid-lactation Holstein cows. Ten (6 ruminally cannulated) primiparous cows averaging 139±13 d in milk and 550±56 kg of body weight, and 6 (2 ruminally cannulated) multiparous cows averaging 128±11 d in milk and 632±57 kg of body weight at the beginning of the experiment, were used in a crossover design. Each period lasted 21 d with 14 d for diet adaptation and 7 d for data and sample collection. The concentration of nonstructural carbohydrates (water-soluble carbohydrates plus starch) was numerically greater in the p.m.- versus the a.m.-cut TIM and averaged 13.2±1.06% and 12.2±1.13%, respectively. Treatment × parity effects were observed for milk urea N, feed efficiency, and milk N efficiency, whereas parity effects were observed for nutrient intake, milk yield, and plasma concentration of several essential and nonessential AA. Intakes of dry matter (19.3 versus 18.6 kg/d) and nonstructural carbohydrates (2.56 versus 2.31 kg/d), and yields of 4% fat-corrected milk (23.1 versus 22.2 kg/d), energy-corrected milk (25.0 versus 24.1 kg/d), milk fat (0.91 versus 0.88 kg/d), and milk protein (0.77 versus 0.73 kg/d) were all greatest with feeding p.m.-cut TIM. Milk yield (23.5 versus 22.7 kg/d) tended to increase in cows fed p.m.-cut TIM. The ruminal fermentation profiles and plasma concentrations of AA were mostly unaffected by treatments. However, ruminal valerate (1.01 versus 1.17 mol/100 mol) and plasma Gly (172 versus 188 µM) were lowest with feeding p.m.-cut TIM. Overall, feeding mid-lactation dairy cows a total mixed ration that consisted of p.m.-cut timothy baleage and silage significantly increased dry matter intake and yields of milk, milk fat, and milk protein.

Effect of glycerol in combination with alfalfa on in vitro gas production and microbial protein synthesis

Alfonso-Ávila, Á. R., Charbonneau, E., Lafrenière, C. and Berthiaume, R. 2015. Effect of glycerol in combination with alfalfa on in vitro gas production and microbial protein synthesis. Can. J. Anim. Sci. 95: 577–588. This study sought to determine the effect of added glycerol on microbial protein synthesis, ruminal degradation and utilization of alfalfa at different concentrations of nonstructural carbohydrates (NSC), using in vitro gas production. The 2×3 factorial plus one treatment consisted of oven-dried alfalfa with two NSC levels [high: 17.9 (HNSC) or low: 7.4% dry matter (DM) (LNSC)] and three glycerol treatments [control without glycerol, 15% crude glycerol (CG) and 15% pure glycerol (PG)], the additional treatment was LNSC+exogenous sugars (LNSC+ES: LNSC with 5% sucrose+5% starch). Five pre-planned contrasts were evaluated from the seven treatments: (1) HNSC vs. LNSC alfalfa; (2) with glycerol vs. without; (3) interaction of alfalfa and glycerol; (4) CG vs. PG, and; (5) LNSC+ES vs. HNSC. Gas production over 24 h was higher for HNSC than LNSC (202 vs. 179 mL g−1 DM) and with glycerol than without glycerol (202.2 vs. 168 mL g−1 DM). A decrease in the acetate:propionate ratio was observed for HNSC compared with LNSC (2.87 vs. 3.27) and for the addition of glycerol vs. no glycerol (2.78 vs. 3.65). Reduced microbial mass (185.5 vs. 240.5 mg g−1 DM) was observed for CG compared with PG. The LNSC+ES treatment had lower microbial protein synthesis and propionic acid production in relation to HNSC. No significant interaction was observed between the effect of NSC content of alfalfa and glycerol utilization. When effects were studied separately, results indicate that increasing NSC in alfalfa stimulates the synthesis of microbial protein. Also, the addition of glycerol promotes the synthesis of glucose precursors. Finally, the type of glycerol has an impact on results obtained suggesting caution when extrapolating results for PG to CG.

Short communication: Feeding red clover cut in the afternoon or morning to late-lactation dairy cows

Forages cut in the afternoon (p.m.) generally yield a higher concentration of nonstructural carbohydrates (NSC) than those cut in the morning (a.m.). We aimed to compare the effects of p.m.-cut red clover baleage (p.m.-RC) versus a.m.-cut RC baleage (a.m.-RC) on milk yield, concentrations and yields of milk components, and apparent total-tract digestibility of nutrients in late-lactation Holstein cows. Twelve multiparous and 2 primiparous Holstein cows received a total mixed ration containing, on a dry matter (DM) basis, 65% p.m.-RC or a.m.-RC plus 35% concentrate in a crossover design with 14 d for diet adaptation and 7 d for data and sample collection. One RC field was split in 2 with the first half cut in the afternoon (1600 h) and the second half in the following morning (0600 h). The p.m.-RC and a.m.-RC contained (% of DM): 12.6 versus 9.43% NSC in samples collected before the beginning of the experiment and 7.49 versus 7.79% NSC in samples collected during the sampling periods (i.e., d 14 to 21). The total mixed rations averaged 18.2 and 17.5% NSC for the p.m.-RC and a.m.-RC, respectively. Feeding p.m.-RC or a.m.-RC did not improve feed intake or milk yield and composition in late-lactation dairy cows. However, milk urea N and plasma urea N were both lowest in cows offered p.m.-RC. With the exception of the apparent total-tract digestibility of DM, which was highest in cows fed p.m.-RC, no other changes in nutrient digestibility were observed. Similarly, no treatment effect was observed for the urinary excretion of N and purine derivatives. Further research is needed to better understand NSC losses during storage and the associated effects on baleage quality and animal performance.

Effects of dietary total non-structural carbohydrates and folic acid and vitamin B12 supplement on growth and meat quality of yearling steers in a forage-based beef production system

Mercier, J., Cinq-Mars, D., Berthiaume, R., Faucitano, L. and Girard, C. L. 2015. Effects of dietary total non-structural carbohydrates and folic acid and vitamin B12 supplement on growth and meat quality of yearling steers in a forage-based beef production system. Can. J. Anim. Sci. 95: 281–291. Thirty-two spring calving cows [760±91 kg body weight (BW)] and calves (44±4.5 kg BW) were assigned to eight blocks of four cows and their calves each according to parity and calving date. Within each block, two cows were fed a low total non-structural carbohydrate (TNC) diet, while the two others were fed a high TNC diet. Within each diet, cows were administered either no vitamins or weekly intramuscular injections of 160 mg of folic acid plus 10 mg of vitamin B12. Calves were slaughtered at 305±9 d. Neither TNC concentration nor vitamin supplementation affected (P>0.10) milk yield but the vitamin supplementation increased (P=0.002) milk concentrations of vitamin B12. There was no treatment effect on calf performance, or carcass and meat characteristics (P>0.10) except for collagen concentrations and shear force measurements in the longissimus lumborum muscle, which had a tendency to be decreased (P≤0.06) by the vitamin supplement. In the present study, differences in forage TNC concentrations did not influence cow and calf performance. Moreover, folic acid and vitamin B12 supplements were shown to have little impact in this study on growth of beef cattle.

Potential of legume-based grassland-livestock systems in Europe: a review

European grassland-based livestock production systems face the challenge of producing more meat and milk to meet increasing world demands and to achieve this using fewer resources. Legumes offer great potential for achieving these objectives. They have numerous features that can act together at different stages in the soil-plant-animal-atmosphere system, and these are most effective in mixed swards with a legume proportion of 30-50%. The resulting benefits include reduced dependence on fossil energy and industrial N-fertilizer, lower quantities of harmful emissions to the environment (greenhouse gases and nitrate), lower production costs, higher productivity and increased protein self-sufficiency. Some legume species offer opportunities for improving animal health with less medication, due to the presence of bioactive secondary metabolites. In addition, legumes may offer an adaptation option to rising atmospheric CO₂ concentrations and climate change. Legumes generate these benefits at the level of the managed land-area unit and also at the level of the final product unit. However, legumes suffer from some limitations, and suggestions are made for future research to exploit more fully the opportunities that legumes can offer. In conclusion, the development of legume-based grassland-livestock systems undoubtedly constitutes one of the pillars for more sustainable and competitive ruminant production systems, and it can be expected that forage legumes will become more important in the future.

Special topics--Mitigation of methane and nitrous oxide emissions from animal operations: I. A review of enteric methane mitigation options

The goal of this review was to analyze published data related to mitigation of enteric methane (CH4) emissions from ruminant animals to document the most effective and sustainable strategies. Increasing forage digestibility and digestible forage intake was one of the major recommended CH4 mitigation practices. Although responses vary, CH4 emissions can be reduced when corn silage replaces grass silage in the diet. Feeding legume silages could also lower CH4 emissions compared to grass silage due to their lower fiber concentration. Dietary lipids can be effective in reducing CH4 emissions, but their applicability will depend on effects on feed intake, fiber digestibility, production, and milk composition. Inclusion of concentrate feeds in the diet of ruminants will likely decrease CH4 emission intensity (Ei; CH4 per unit animal product), particularly when inclusion is above 40% of dietary dry matter and rumen function is not impaired. Supplementation of diets containing medium to poor quality forages with small amounts of concentrate feed will typically decrease CH4 Ei. Nitrates show promise as CH4 mitigation agents, but more studies are needed to fully understand their impact on whole-farm greenhouse gas emissions, animal productivity, and animal health. Through their effect on feed efficiency and rumen stoichiometry, ionophores are likely to have a moderate CH4 mitigating effect in ruminants fed high-grain or mixed grain-forage diets. Tannins may also reduce CH4 emissions although in some situations intake and milk production may be compromised. Some direct-fed microbials, such as yeast-based products, might have a moderate CH4-mitigating effect through increasing animal productivity and feed efficiency, but the effect is likely to be inconsistent. Vaccines against rumen archaea may offer mitigation opportunities in the future although the extent of CH4 reduction is likely to be small and adaptation by ruminal microbes and persistence of the effect is unknown. Overall, improving forage quality and the overall efficiency of dietary nutrient use is an effective way of decreasing CH4 Ei. Several feed supplements have a potential to reduce CH4 emission from ruminants although their long-term effect has not been well established and some are toxic or may not be economically feasible.

Effect of time of cutting and maceration on nutrient flow, microbial protein synthesis, and digestibility in dual-flow continuous culture

Maceration and evening-cutting are 2 forage management techniques that have independently improved forage quality and nutrient utilization in ruminants, but have not been evaluated in combination. Using a dual-flow continuous culture fermenter system, this preliminary study was designed to evaluate the individual and combined effects of time of cutting and maceration on in vitro ruminal digestion, nutrient flows, and microbial protein synthesis. Forages were harvested as hay from a timothy (Phleum pratense L.)-birdsfoot trefoil (Lotus corniculatus L.) stand in the morning (AM) or evening (PM). Half of each morning- and evening-cut treatment was macerated (AM-M, PM-M). The chemical composition (DM, OM, CP, NDF, ADF), including nonstructural carbohydrates (NSC) and water-soluble carbohydrates (WSC), was determined for each of the 4 treatments (AM, AM-M, PM, PM-M). Forages were ground to 2 mm and allocated to separate fermenters at 60 g of DM/d in a 4 × 4 Latin square design. Fermenters were operated over four 10-d periods with the first 7 d for adaptation followed by 3 d of sampling. Evening-cutting enhanced the apparent digestibility of NDF (P = 0.02) and ADF (P = 0.006), with a tendency (P < 0.10) for improved true DM digestibility and microbial protein synthesis. Molar proportions of individual VFA were not affected (P > 0.10) by time of cutting, though evening-cutting increased (P = 0.02) total concentration of VFA. Maceration had no effect (P > 0.10) on true nutrient digestibility or microbial protein synthesis. An interaction of time of cutting and maceration (P < 0.05) was observed whereby maceration decreased true DM and OM digestibilities in evening-cut treatments, but had no effect in morning-cut treatments. Similarly, maceration reduced total N supply (P < 0.001) and molar proportions of acetate (P = 0.04) and increased molar proportions of propionate (P = 0.01) in evening-cut treatments with no effect on morning-cut treatments. These results indicate that independent use of evening cutting increased fiber digestibility and total VFA concentration, and independent use of maceration shifted molar proportions of VFA toward glucogenic fermentation. The combined use of these management techniques afforded no improvement for in vitro digestibility or metabolism when applied to morning-cut hay, and decreased nutrient digestibility when applied to evening-cut hay. Due to inherent limitations of in vitro systems, the results of this study should be interpreted with caution. Further in vivo studies are needed to support our conclusions.

Morning versus afternoon cutting time of Berseem clover (Trifolium alexandrinum L.) affects feed intake, milk yield and composition in Girgentana goats

Twenty lactating Girgentana goats were used to evaluate the effect of morning v. afternoon cutting time of Berseem clover (Trifolium alexandrinum L.) on feed intake, milk yield and milk composition. Goats were randomly divided into two groups of ten animals, receiving 10 kg of fresh Berseem clover cut at 9.00 (AM group) or 16.00 (PM group), respectively; 500 g of concentrate was given individually to goats before offering forage. Feed intake increased (P<0·01) in the PM group (30·5 v. 25·3 g dry matter/kg body weight), associated with the different nutrient content of diets: lower crude protein but higher dry matter, neutral detergent fibre, water soluble carbohydrates (WSC) and total fatty acids in the PM-harvested forage. Milk production, protein and casein content were higher (P<0·05) in the PM group (1415 g/d, 3·25% and 2·42% v. 1277 g/d, 3·15% and 2·33%, respectively), whereas no differences between groups were detected for milk fat, lactose or urea content. Body weight slowly decreased from the start to the end of the experiment, without differences between groups. This study showed an important milk yield responses in Girgentana goats offered afternoon-cut compared with morning-cut Berseem clover, due to a marked increase in WSC in the afternoon-cut forage.

Metabolism of grazed vs. zero-grazed dairy cows throughout the vegetation period: hepatic and blood plasma parameters

Grass may have a differential impact on the metabolism of the dairy cow, depending on the grazing system applied. In this study, the hypothesis was tested that metabolism of grazed vs. zero-grazed dairy cows is differently regulated throughout the vegetation period. The study included three experimental periods (p1, p2 and p3) of 14 days each, and two treatments [grazing from pasture, PASTURE, n = 9; or zero-grazing in a free-stall barn (BARN, n = 9)]. Blood and liver samples were collected at the end of each period when the cows were on average 64, 120 and 197 DIM. Concentrations of metabolites and hormones, and activities of various enzymes were determined in plasma. Liver samples were measured for mRNA abundance of genes encoding enzymes and nuclear receptors involved in metabolic pathways. PASTURE cows had higher plasma concentrations of T(3), BHB, and total protein than BARN cows across periods (p < 0.05). BARN cows had higher concentrations of NEFA (in p1) and urea (in p1 and p2) in relation PASTURE cows (p < 0.05), and had higher mRNA abundance of liver-X-receptor-α and glycerol-3-phosphate-acyltransferase across periods (p < 0.05). The results confirm the hypothesis that metabolism is different between BARN and PASTURE cows throughout the vegetation period, and show that the observed differences are mainly reflected in parameters of lipid metabolism.

Review: Effects of feeding sugars on productivity of lactating dairy cows

Oba, M. 2011. Review: Effects of feeding sugars on productivity of lactating dairy cows. Can. J. Anim. Sci. 91: 37–46. Sugars are water-soluble carbohydrates that are readily available in the rumen. Although sugars ferment faster than starch or fibre in the rumen, the rates of disaccharide hydrolysis and monosaccharide fermentation vary greatly depending on the type of sugar and rumen environment. Despite rapid fermentation in the rumen and their potential to provide greater fermentable energy to enhance microbial protein production, feeding sugars in place of dietary starch sources may not decrease rumen pH or improve N utilization efficiency and milk protein production in dairy cows. However, feeding high-sugar diets often increases dry matter intake, butyrate concentration in the rumen, and milk fat yield. These nutritional characteristics of sugars may allow us to use high-sugar feedstuffs as an alternative energy source for lactating dairy cows to increase dietary energy density with reduced risk of rumen acidosis, but there is little evidence in the literature to indicate that the synchrony of rumen fermentation would be enhanced by feeding high-sugar diets with high soluble protein. Greater butyrate production from feeding high-sugar diets is expected to enhance proliferation of gut tissues, but its physiological mechanisms and effects of butyrate metabolism on overall productivity of dairy cows warrant further investigations.