K.J. Soder

Effects of rumen fill on short-term ingestive behavior and circulating concentrations of ghrelin, insulin, and glucose of dairy cows foraging vegetative micro-swards

The objective of this study was to investigate changes in foraging behavior, hunger-related hormones, and metabolites of dairy cows in response to short-term variations in rumen fill (RF). The effect of RF on intake rate, jaw movements, bite rate and dimensions, and concentrations of plasma ghrelin, and serum insulin and glucose were measured in 4 rumen-cannulated lactating dairy cows (612 +/- 68 kg, empty live weight; 237 +/- 29 d in milk) foraging micro-swards of vegetative orchardgrass (Dactylis glomerata L.). The treatments compared were the removal of different proportions of total rumen contents: 1.00 (RF0), 0.66 (RF33), 0.33 (RF66), or 0 (RF100). Treatments were randomly applied 2 h before foraging sessions in a 4 x 4 Latin square design. Micro-swards were weighed before and after foraging sessions. Cows were allowed to take a maximum of 15 bites with no time restriction. Eating time, intake rate, total jaw movements, and bite mass, depth, area, and rate were determined. Plasma was analyzed for ghrelin and serum for insulin and glucose immediately before and 2 h after the treatments were applied. Intake rate, bite mass, and bite area increased, whereas bite depth decreased as RF decreased. The RF did not affect bite rate or total jaw movements. Decreasing RF resulted in increased plasma concentrations of ghrelin and tended to increase serum insulin, with reduced concentrations of serum glucose. Incremental variation in plasma ghrelin and serum insulin correlated with bite depth and mass, whereas changes in serum glucose correlated with intake rate, bite area, depth and mass, as well as with herbage intake per jaw movement. The present study elucidates some of the underlying endocrine physiology of cattle with short-term temporal variations of RF and their effects on some components of foraging behavior.

REVIEW: The Interaction of Diurnal Grazing Pattern, Ruminal Metabolism, Nutrient Supply, and Management in Cattle

ABSTRACT Daily herbage intake depends on factors governing the initiation and cessation of successive grazing bouts. Ruminal fill is one such factor, regulating grazing bout-eating behavior. Under grazing conditions, nutrient supply varies among grazing bouts, not only in amount, but also in balance. Also, there is evidence suggesting differential energy expenditures in herbage harvesting and ingestive mastication among grazing bouts. The animal internal state plays an important role in shaping grazing pattern, although demands of ruminal microflora may be at times more important. It may well be that perception of ruminal conditions most likely dominates the short-term intake rate during a complete grazing bout, whereas on a larger spatiotemporal scale, the animal may operate within a framework of daily level of energy demand. Simultaneously, cattle might be dealing with pasture progressive defoliation as the grazing event progresses. This leads to selective behaviors and herbage intake rate reductions. From this work emerges that integrating different ingestive and digestive behaviors across foraging spatio-temporal scales would provide greater comprehension of factors driving the diurnal grazing patterns of cattle, helping in the design of better grazing methods.

Grazing Can Reduce the Environmental Impact of Dairy Production Systems

Incorporating managed rotational grazing into a dairy farm can result in an array of environmental consequences. A comprehensive assessment of the environmental impacts of four management scenarios was conducted by simulating a 250-acre dairy farm typical of Pennsylvania with: (i) a confinement fed herd producing 22,000 lbs of milk per cow per year; (ii) a confinement fed herd producing 18,500 lbs; (iii) a confinement fed herd with summer grazing producing 18,500 lbs; and (iv) a seasonal herd maintained outdoors producing 13,000 lbs. Converting 75 acres of cropland to perennial grassland reduced erosion 24% and sediment-bound and soluble P runoff by 23 and 11%, respectively. Conversion to all perennial grassland reduced erosion 87% with sediment-bound and soluble P losses reduced 80 and 23%. Ammonia volatilization was reduced about 30% through grazing, but nitrate leaching loss increased up to 65%. Grazing systems reduced the net greenhouse gas emission by 8 to 14% and the C footprint by 9 to 20%. Including C sequestration further reduced the C footprint of an all grassland farm up to 80% during the transition from cropland. The environmental benefits of grass-based dairy production should be used to encourage greater adoption of managed rotational grazing in regions where this technology is well adapted.

Dietary Selection by Domestic Grazing Ruminants in Temperate Pastures: Current State of Knowledge, Methodologies, and Future Direction

Abstract Ruminants grazing mixed-species pastures face many choices, including when and where to graze and how much herbage to consume. These choices affect not only the nutritional status of the animal, but also sward composition and nutritive value through selective defoliation. Limited research has been conducted in the area of dietary selection and preference, most of which has been limited to simple model systems often involving a choice between only two herbage species. Although these studies have provided a vital tool to allow understanding of the fundamental principles of foraging behavior, in reality, grazing ruminants are faced with more complex situations. Understanding and managing animal preferences in mixed swards and thereby altering dietary selection can result in greater primary (plant) and secondary (animal) productivity. Key issues to improve this understanding include a better linking of behavioral and nutritional studies, a better understanding of the genetic factors influencing diet selection, and the development of more explicit spatial models of foraging behavior that incorporate multiple scales of decision making. This article, as part of a set of synthesis articles, reviews the current state of knowledge and research methodologies related to diet selection of grazing domestic ruminants with particular reference to improved temperate grazing environments, including how well we understand each part of the complex decision-making process a grazing ruminant faces, the links with primary and secondary productivity, and developments in methodologies. Finally, we identify key areas where knowledge is lacking and further research is urgently required.

Short communication: Use of a portable, automated, open-circuit gas quantification system and the sulfur hexafluoride tracer technique for measuring enteric methane emissions in Holstein cows fed ad libitum or restricted

The objective of this study was to measure enteric CH4 emissions using a new portable automated open-circuit gas quantification system (GQS) and the sulfur hexafluoride tracer technique (SF6) in midlactation Holstein cows housed in a tiestall barn. Sixteen cows averaging 176 ± 34 d in milk, 40.7 ± 6.1 kg of milk yield, and 685 ± 49 kg of body weight were randomly assigned to 1 out of 2 treatments according to a crossover design. Treatments were (1) ad libitum (adjusted daily to yield 10% orts) and (2) restricted feed intake [set to restrict feed by 10% of baseline dry matter intake (DMI)]. Each experimental period lasted 22d, with 14 d for treatment adaptation and 8d for data and sample collection. A common diet was fed to the cows as a total mixed ration and contained 40.4% corn silage, 11.2% grass-legume haylage, and 48.4% concentrate on a dry matter basis. Spot 5-min measurements using the GQS were taken twice daily with a 12-h interval between sampling and sampling times advanced 2h daily to account for diurnal variation in CH4 emissions. Canisters for the SF6 method were sampled twice daily before milking with 4 local background gas canisters inside the barn analyzed for background gas concentrations. Enteric CH4 emissions were not affected by treatments and averaged 472 and 458 g/d (standard error of the mean = 18 g/d) for ad libitum and restricted intake treatments, respectively (data not shown). The GQS appears to be a reliable method because of the relatively low coefficients of variation (ranging from 14.1 to 22.4%) for CH4 emissions and a moderate relationship (coefficient of determination = 0.42) between CH4 emissions and DMI. The SF6 resulted in large coefficients of variation (ranging from 16.0 to 111%) for CH4 emissions and a poor relationship (coefficient of determination = 0.17) between CH4 emissions and DMI, likely because of limited barn ventilation and high background gas concentration. Research with improved barn ventilation systems or outdoors is warranted to further assess the GQS and SF6 methodologies.

Effects of timing of corn silage supplementation on digestion, fermentation pattern, and nutrient flow during continuous culture fermentation of a short and intensive orchardgrass meal

Using a dual-flow continuous culture fermenter system, this study evaluated the effect of timing of corn silage supplementation on ruminal digestion and nutrient flows following a short and intensive orchardgrass herbage meal. Treatments included 28 g dry matter (DM) of corn silage added either 9h (9BH; 0700 h) or 1h (1BH; 1500 h) before adding 42 g DM orchardgrass herbage or no corn silage (control; 70 g DM herbage). Herbage was fed as follows: 66% of the total herbage meal at 1600 h, 22% at 1720 h, and the remaining 12% at 1840 h. Effluent was analyzed for organic matter (OM), crude protein (CP), and neutral detergent fiber (NDF). Purine concentrations in effluent and bacterial isolates were used to estimate the partition of effluent N flow into bacterial and nonbacterial fractions, and to calculate true OM digestibility. Fermenters were sampled for pH, volatile fatty acids (VFA), and NH(3)-N at 0730, 1100, 1530, 1600, 1720, 1840, and 2000 h on d 10. Data were analyzed as a 3 x 4 Latin square experimental design. True digestibilities for OM (average of 78.5%) and CP (average of 84.6%), and apparent NDF digestibility (average of 82.7%) were not affected by treatment. Mean ruminal pH was lower for 9BH than for 1BH, averaging 5.6 and 6.5, respectively. Molar proportions of acetate were not affected by treatment. Propionate concentration was greater for 9BH than for 1BH, averaging 20.5 and 18.1mM, respectively. Diurnal patterns of pH, NH(3)-N, and acetate:propionate ratio were affected by treatment: 9BH had the lowest values for all measurements as the day progressed. The NH(3)-N concentration and effluent NH(3)-N flow were higher for 1BH (11.4 mg/100mL and 0.26 g/d, respectively) than for 9BH (8.8 mg/100mL and 0.20 g/d, respectively). Effluent NH(3)-N flow (as a % of total N flow) was the lowest for 9BH. Bacterial efficiency was not affected by treatments, with a mean of 10.5 g of N/kg of OM truly digested. Under the same resource allocation (pasture plus supplement), a simple change in timing of corn silage feeding (9 rather than 1h before an orchardgrass herbage meal) may alter ruminal fermentation pattern. These changes could increase the glucogenic nutrient supply and improve N utilization by reducing ammonia N losses.

Incremental amounts of Ascophyllum nodosum meal do not improve animal performance but do increase milk iodine output in early lactation dairy cows fed high-forage diets.

The objective of this study was to investigate the effects of incremental amounts of Ascophyllum nodosum meal (ANOD) on milk production, milk composition including fatty acids and I, blood metabolites, and nutrient intake and digestibility in early lactation dairy cows fed high-forage diets. Twelve multiparous Jersey cows averaging (mean±standard deviation) 40±21 d in milk and 464±35 kg of body weight and 4 primiparous Jersey cows averaging 75±37 d in milk and 384±17kg of body weight were randomly assigned to treatment sequences in a replicated 4×4 Latin square design. Each period lasted 21 d with 14 d for diet adaptation and 7 d for data and sample collection. Cows were fed a total mixed ration (64:36 forage-to-concentrate ratio) supplemented (as fed) with 0, 57, 113, or 170 g/d of ANOD. Milk yield as well as concentrations and yields of milk components (fat, protein, lactose, milk urea N) were not affected by increasing dietary amounts of ANOD. Concentration (from 178 to 1,370 µg/L) and yield (from 2.8 to 20.6 mg/d) of milk I increased linearly in cows fed incremental amounts of ANOD as a result of the high concentration of I (820 mg/kg of dry matter) in ANOD. Overall, only minor changes were observed in the proportion of milk fatty acids with ANOD supplementation. Quadratic trends were observed for dry matter intake and total-tract digestibilities of organic matter and neutral detergent fiber, whereas negative linear trends were observed for serum concentration of cortisol and crude protein digestibility with ANOD supplementation. Serum concentrations of triiodothyronine and thyroxine were not affected by ANOD supplementation and averaged 1.1 and 48.4 ng/mL, respectively. However, feeding increasing amounts of ANOD linearly reduced the plasma concentration of nonesterified fatty acids (from 164 to 132 mEq/L). Quadratic effects were found for the total-tract digestibility of ADF and urinary output of purine derivatives, suggesting that ANOD supplementation may stimulate growth of ruminal cellulolytic bacteria in a dose-dependent fashion. In general, feeding incremental amounts of ANOD to early lactation dairy cows dramatically increased milk I concentration and output with no effect on animal performance.

Interactions of corn meal or molasses with a soybean-sunflower meal mix or flaxseed meal on production, milk fatty acid composition, and nutrient utilization in dairy cows fed grass hay-based diets1

We investigated the interactions of corn meal or molasses [nonstructural carbohydrate (NSC) supplements] with a soybean-sunflower meal mix or flaxseed meal [rumen-degradable protein (RDP) supplements] on animal production, milk fatty acids profile, and nutrient utilization in dairy cows fed grass hay diets. Eight multiparous and 8 primiparous Jersey cows averaging 135±49d in milk and 386±61kg of body weight in the beginning of the study were randomly assigned to 4 replicated 4×4 Latin squares with a 2×2 factorial arrangement of treatments. Each period lasted 19d with 14d for diet adaptation and 5d for data and sample collection. Cows were fed diets composed of mixed-mostly grass hay plus 1 of the following 4 concentrate blends: (1) corn meal plus a protein mix containing soybean meal and sunflower meal; (2) corn meal plus flaxseed meal; (3) liquid molasses plus a protein mix containing soybean meal and sunflower meal; or (4) liquid molasses plus flaxseed meal. Data were analyzed for main effects of NSC and RDP supplements, and the NSC × RDP supplement interactions. Significant NSC × RDP supplement interactions were observed for milk urea N, milk N efficiency, and the sums of milk saturated, monounsaturated, and polyunsaturated fatty acids. No effect of NSC supplements was observed for nutrient intake and milk yield. However, 4% fat-corrected milk (-0.70kg/d) and energy-corrected milk (-0.60kg/d) were significantly reduced in cows fed liquid molasses due to a trend to decreased concentration of milk fat (-0.17%). Diets with liquid molasses resulted in increased (+35%) concentration and yield of milk enterolactone, indicating that this mammalian lignan can be modulated by supplements with different NSC profiles. Overall, NSC and RDP supplements profoundly changed the milk fatty acid profile, likely because of differences in fatty acids intake, Δ(9)-desaturase indices, and ruminal biohydrogenation pathways. Feeding liquid molasses significantly reduced plasma urea N (-1.2mg/dL), urinary N excretion (-20g/d), and N digestibility (-3.2 percentage units). Flaxseed meal significantly reduced yields of milk (-1.3kg/d), milk fat (-90g/d), and milk lactose (-60g/d), but significantly increased the concentration and yield of milk enterolactone. Further research is needed to elucidate the negative responses of flaxseed meal on yields of milk and milk components.

Incremental amounts of ground flaxseed decrease milk yield but increase n-3 fatty acids and conjugated linoleic acids in dairy cows fed high-forage diets1

The objective of this study was to investigate the effect of incremental amounts of ground flaxseed (GFX) on milk yield and concentrations and yields of milk components, milk fatty acids (FA) profile, ruminal metabolism, and nutrient digestibility in dairy cows fed high-forage diets. Twelve multiparous Jersey cows averaging (mean ± SD) 112±68d in milk and 441±21kg of body weight and 8 primiparous Jersey cows averaging 98±43d in milk and 401±43kg of body weight were randomly assigned to treatment sequences in a replicated 4×4 Latin square design. Each period lasted 21d with 14d for diet adaptation and 7d for data and sample collection. Treatments were fed as a total mixed ration (63:37 forage-to-concentrate ratio) with corn meal and soybean meal replaced by incremental levels (i.e., 0, 5, 10, or 15% diet dry matter) of GFX. The ruminal molar proportions of acetate and butyrate decreased linearly with GFX supplementation, whereas the ruminal molar proportion of propionate increased linearly resulting in decreased acetate-to-propionate ratio. Apparent total-tract digestibilities of nutrients either decreased (dry matter) or tended to decrease (organic matter, neutral detergent fiber, acid detergent fiber) linearly in cows fed GFX. Milk yield decreased linearly in cows fed increasing amounts of GFX, which is explained by the linear reduction in dry matter intake. Except for the concentrations of milk protein and urea N, which decreased linearly with GFX supplementation, no other changes in the concentration of milk components were observed. However, yields of milk protein and fat decreased linearly with GFX supplementation. The linear decrease in the yields of milk fat and protein are explained by reduced milk yield, whereas that in milk urea N is explained by decreased crude protein intake. No treatment effects were observed for plasma urea N and nonesterified fatty acids, serum cortisol, and body weight change. Milk odd- and branched-chain FA and saturated FA decreased linearly with GFX supplementation. Milk trans-11 18:1, α-linolenic acid, cis-9,trans-11 18:2, and the sum of n-3 FA all increased linearly and quadratically, whereas the milk ratio of n-6 to n-3 decreased linearly in cows fed GFX. Overall, compared with the control diet (0% GFX), the diet with 15% GFX supplementation resulted in the lowest milk yield but highest milk proportions and yields (data not shown) of cis-9,trans-11 18:2 and n-3 FA.

A Snapshot in Time of Fatty Acids Composition of Grass Herbage as Affected by Time of Day

Polyunsaturated fatty acid contents in the products of pasture-fed ruminants depend on the amount and composition of fatty acid ingested and rumen biohydrogenation. The total nonstructural carbohydrates (TNC) and DM concentrations of herbage increase during the day; however, it is not known if fatty acids follow the same pattern. This study aimed to quantify the diurnal variation of herbage fatty acid concentrations. Vegetative micro-swards of orchardgrass (Dactylis glomerata L.) and meadow fescue (Festuca pratensis Hud.) were sampled in July and September, respectively, over 2 consecutive days. Sampling occurred 4 times/d: sunrise (0537 or 0650 h), morning (1037 or 1110 h), afternoon (1537 or 1530 h), and sunset (2037 or 1930 h) for orchardgrass and meadow fescue, respectively. Cut herbage was analyzed for DM, CP, TNC, NDF, ADF, and palmitic, oleic, linoleic and α-linolenic acids. Diurnal variation of temperature, relative humidity, and photosynthetic radiation were recorded every 5 min. Time of day affected (P 0.01) concentrations of palmitic, linoleic, and α-linolenic acids of herbage. Oleic acid increased (P 0.01) time of day effect on total fatty acids. Concentrations of PUFA in grass herbage remain stable during the day, whereas structural and nonstructural carbohydrates, as well as CP, do not.