Feed Efficiency In Dairy Cows Research Articles

Can greenhouse gases in breath be used to genetically improve feed efficiency of dairy cows?

There is considerable interest in improving feed utilization of dairy cattle while limiting losses to the environment (i.e., greenhouse gases, GHG). To breed for feed-efficient or climate-friendly cattle, it is first necessary to obtain accurate estimates of genetic parameters and correlations of feed intake, greenhouse gases, and production traits. Reducing dry matter take (DMI) requirements while maintaining production has high economic value to farmers, but DMI is costly to record and thus limited to small research or nucleus herds. Conversely, enteric methane (CH4) currently has no economic value, is also costly to record, and is limited to small experimental trials. However, breath gas concentrations of methane (CH4c) and carbon dioxide (CO2c) are relatively cheap to measure at high throughput under commercial conditions by installing sniffers in automated milking stations. The objective of this study was to assess the genetic correlations between DMI, body weight (BW), fat- and protein-corrected milk yield (FPCM), and GHG-related traits: CH4c and CO2c from Denmark (DNK) and the Netherlands (NLD). A second objective was to assess the genetic potential for improving feed efficiency and the added benefits of using CH4c and CO2c as indicators. Feed intake data were available on 703 primiparous cows in DNK and 524 in NLD; CH4c and CO2c records were available on 434 primiparous cows in DNK and 656 in NLD. The GHG-related traits were heritable (e.g., CH4c h2: DNK = 0.26, NLD = 0.15) but were differentially genetically correlated with DMI and feed efficiency in both magnitude and sign, depending on the population and the definition of feed efficiency. Across feed efficiency traits and DMI, having bulls with 100 daughters with FPCM, BW, and GHG traits resulted in sufficiently high accuracy to almost negate the need for DMI records. Despite differences in genetic correlation structure, the relatively cheap GHG-related traits showed considerable potential for improving the accuracy of breeding values of highly valuable feed intake and feed efficiency traits.

Effects of replacing wheat starch with glycerol on methane emissions, milk production, and feed efficiency in dairy cows fed grass silage-based diets

To lower the effect of climate change from cattle production, we should aim at decreasing their enteric methane emissions per kilogram of milk or meat. Glycerol may be absorbed through the rumen epithelium and would consequently be less available to microbes in the rumen. Glycerol could thus supply dairy cows with energy for milk production without contributing much to methane production. This study evaluated the effect of replacing wheat starch with glycerol on milk production, feed intake, and methane emissions. Twenty-two Swedish Red cows in mid lactation were used in a switch-back, change-over experiment with 3 periods of 21 d. The 2 dietary treatments consisted of a total mixed ration based on (g/kg of dry matter) grass silage (605), rapeseed meal (120), and barley (70) and either wheat starch or refined glycerol (200) fed ad libitum. The glycerol diet resulted in higher dry matter intake (21.6 vs. 20.1 kg/d) and methane emissions (482 vs. 423 g/d) compared with the diet containing wheat starch, whereas no difference was found in energy-corrected milk yield (28.4 vs. 29.7 kg/d). These results indicate that when glycerol is mixed with the feed, it is available to rumen microbes to a larger extent than initially assumed. Compared with wheat starch, adding refined glycerol (200 g/kg of dry matter) to the feed of dairy cows does not seem to have the potential to decrease enteric methane emissions.

Methane production, rumen fermentation, and diet digestibility of Holstein and Jersey dairy cows being divergent in residual feed intake and fed at 2 forage-to-concentrate ratios

Improving feed efficiency of dairy cows through breeding is expected to reduce enteric methane production per unit of milk produced. This study examined the effect of 2 forage-to-concentrate ratios on methane production, rumen fermentation, and nutrient digestibility in Holstein and Jersey dairy cows divergent in residual feed intake (RFI). Before experimental onset, RFI was estimated using a random regression model on phenotypic herd data. Ten lactating Holstein and 10 lactating Jersey cows were extracted from the herd and allocated to a high or low pre-experimental RFI group of 5 animals each within breed. Cows were fed ad libitum with total mixed rations either low (LC) or high (HC) in concentrates during 3 periods in a crossover design with a back-cross and staggered approach. Forage-to-concentrate ratio was 68:32 for LC and 39:61 for HC. Cows adapted to the diets in 12 to 24 d and feces were subsequently collected on 2 d. Afterward, gas exchange was measured in respiration chambers and rumen liquid was collected once after cows exited the chambers. Pre-experimental RFI was included in the statistical analysis as a class (low and high RFI) or continuous variable. Methane per kilogram of dry matter intake (DMI) was lower for Holsteins than Jerseys and the response to increased concentrate level was more pronounced for Holsteins than Jerseys (27.2 vs.13.8%); a similar pattern was found for the acetate:propionate ratio. However, methane production per kilogram of energy-corrected milk (ECM) was unaffected by breed. Further, total-tract digestibility of neutral detergent fiber was higher for Jerseys than Holsteins. For RFI as a class variable, DMI, methane production regardless of the expression, and digestibility were unaffected by RFI. For RFI as a continuous variable, DMI was lower and methane per kilogram of DMI was higher for cows with negative (efficient) than positive (inefficient) RFI values, and neutral detergent fiber digestibility was higher for Holsteins with negative than positive RFI values, but not for Jerseys. Daily methane production and methane per kilogram of ECM were unaffected by RFI. In conclusion, methane per kilogram of DMI of Jerseys was lowered to a smaller extent in response to the HC diet than of Holsteins. When pre-experimental RFI was used as a continuous variable, higher methane per kilogram of DMI was found for cows with negative RFI than positive RFI values, but not for methane per kilogram of ECM. These findings call for validation in larger studies.

Association of residual feed intake with abundance of ruminal bacteria and biopolymer hydrolyzing enzyme activities during the peripartal period and early lactation in Holstein dairy cows

BackgroundResidual feed intake (RFI) in dairy cattle typically calculated at peak lactation is a measure of feed efficiency independent of milk production level. The objective of this study was to evaluate differences in ruminal bacteria, biopolymer hydrolyzing enzyme activities, and overall performance between the most- and the least-efficient dairy cows during the peripartal period. Twenty multiparous Holstein dairy cows with daily ad libitum access to a total mixed ration from d − 10 to d 60 relative to the calving date were used. Cows were classified into most-efficient (i.e. with low RFI, n = 10) and least-efficient (i.e. with high RFI, n = 10) based on a linear regression model involving dry matter intake (DMI), fat-corrected milk (FCM), changes in body weight (BW), and metabolic BW.ResultsThe most-efficient cows had ~ 2.6 kg/d lower DMI at wk 4, 6, 7, and 8 compared with the least-efficient cows. In addition, the most-efficient cows had greater relative abundance of total ruminal bacterial community during the peripartal period. Compared with the least-efficient cows, the most-efficient cows had 4-fold greater relative abundance of Succinivibrio dextrinosolvens at d − 10 and d 10 around parturition and tended to have greater abundance of Fibrobacter succinogenes and Megaspheara elsdenii. In contrast, the relative abundance of Butyrivibrio proteoclasticus and Streptococcus bovis was lower and Succinimonas amylolytica and Prevotella bryantii tended to be lower in the most-efficient cows around calving. During the peripartal period, the most-efficient cows had lower enzymatic activities of cellulase, amylase, and protease compared with the least-efficient cows.ConclusionsThe results suggest that shifts in ruminal bacteria and digestive enzyme activities during the peripartal period could, at least in part, be part of the mechanism associated with better feed efficiency in dairy cows.

Yeast culture increased plasma niacin concentration, evaporative heat loss, and feed efficiency of dairy cows in a hot environment

The supplementation of dairy cows with yeast culture may increase diet digestibility, plasma niacin concentration, heat dissipation, and lactation performance. Our objective was to evaluate the response of Holstein cows in late lactation (234 ± 131 d in milk) to dead yeast culture (YC, 15 g/d, Factor SC, GRASP, Saccharomyces cerevisiae) during Brazilian summer (temperature-humidity index >68 for 92.2% of the time). Thirty-two cows were individually fed a standard total mixed ration for 14 d and control (CTL) or YC treatments for 35 d, in a covariate adjusted complete randomized block design. Response was evaluated in wk 5 or as repeated measures over time. Cows were milked 3 times per day and treatments (YC or placebo) were orally dosed to each cow before each milking. Plasma niacin was 1.50 for CTL and 1.66 µg/mL for YC. The YC reduced rectal temperature, respiration rate, and skin temperature, whereas it tended to increase sweating rate. The proportion of cows with rectal temperature ≥39.2°C on CTL and YC was, respectively, 8 and 0% at 0730 h, 52 and 25% at 1500 h, and 35 and 26% at 2200 h. Plasma glucose was increased by YC. The total-tract apparent digestibility of nutrients, plasma urea N concentration, molar proportion of ruminal VFA, and urinary allantoin excretion were not affected by YC. Cows fed YC were less selective against feed particles >19 mm in the morning, in the afternoon were more selective against long feed particles and in favor of particles <8 mm, and refused short particles at night. Milk yield was not different (30.5 kg/d for CTL and 30.2 kg/d for YC). Feeding YC reduced dry matter intake (20.3 vs. 19.4 kg/d) and the digestible organic matter intake (15.6 vs. 13.9 kg/d). The inclusion of YC increased the ratios of milk to dry matter intake (1.50 vs. 1.64) and energy-corrected milk to dry matter intake (1.81 vs. 1.98). The covariate adjusted body weight (648 kg) and body condition score (3.0) did not differ. Milk solids yields and concentrations, linear somatic cell count, and milk urea N were also similar. The supplementation of YC increased plasma niacin concentration, body heat loss, and feed efficiency of late lactation dairy cows by reducing intake at similar milk yield.

Dose- and type-dependent effects of long-chain fatty acids on adipogenesis and lipogenesis of bovine adipocytes

Differentiation and lipid metabolism of adipocytes have a great influence on milk performance, health, and feed efficiency of dairy cows. The effects of dietary long-chain fatty acids (FA) on adipogenesis and lipogenesis of dairy cows are often confounded by other nutritional and physiological factors in vivo. Therefore, this study used an in vitro approach to study the effect of dose and type of long-chain FA on adipogenesis and lipogenesis of bovine adipocytes. Stromal vascular cells were isolated from adipose tissue of dairy cows and induced into mature adipocytes in the presence of various long-chain FA including myristic, palmitic, stearic, oleic, or linoleic acid. When concentrations of myristic, palmitic, and oleic acids in adipogenic mediums were 150 and 200 μM, the induced mature adipocytes had greater lipid content compared with other concentrations of FA. In addition, mature adipocytes induced at 100 μM stearic acid and 300 μM linoleic acid had the greatest content of lipid than at other concentrations. High concentrations of saturated FA were more toxic for cells than the same concentration of unsaturated FA during the induction. When commitment stage was solely treated with FA, the number of differentiated mature adipocytes was greater for oleic and linoleic acids than other FA. When the maturation stage was treated with FA, the number of mature adipocytes was not affected, but the lipid content in adipocytes was affected and ranked oleic > linoleic > myristic > stearic > palmitic. In summary, this study showed that adipogenesis and lipogenesis of bovine adipocytes were differentially affected by long-chain FA, with unsaturated FA more effective than saturated FA.

656 Effects of two sources of malate on milk performance and feed efficiency of dairy cows

656 Effects of two sources of malate on milk performance and feed efficiency of dairy cows

Effects of rumen-protected Capsicum oleoresin on productivity and responses to a glucose tolerance test in lactating dairy cows

The objective of this experiment was to investigate the effects of rumen-protected Capsicum oleoresin (RPC) supplementation on feed intake, milk yield and composition, nutrient utilization, fecal microbial ecology, and responses to a glucose tolerance test in lactating dairy cows. Nine multiparous Holstein cows were used in a replicated 3 × 3 Latin square design balanced for residual effects with three 28-d periods. Each period consisted of 14 d for adaptation and 14 d for data collection and sampling. Treatments were 0 (control), 100, and 200 mg of RPC/cow per day. They were mixed with a small portion of the total mixed ration and top-dressed. Glucose tolerance test was conducted once during each experimental period by intravenous administration of glucose at a rate of 0.3 g/kg of body weight. Dry matter intake was not affected by RPC. Milk yield tended to increase for RPC treatments compared to the control. Feed efficiency was linearly increased by RPC supplementation. Concentrations of fat, true protein, and lactose in milk were not affected by RPC. Apparent total-tract digestibility of dry matter, organic matter, and crude protein was linearly increased, and fecal nitrogen excretion was linearly decreased by RPC supplementation. Rumen-protected Capsicum oleoresin did not affect the composition of fecal bacteria. Glucose concentration in serum was not affected by RPC supplementation post glucose challenge. However, compared to the control, RPC decreased serum insulin concentration at 5, 10, and 40 min post glucose challenge. The area under the insulin concentration curve was also decreased 25% by RPC. Concentration of nonesterified fatty acids and β-hydroxybutyrate in serum were not affected by RPC following glucose administration. In this study, RPC tended to increase milk production and increased feed efficiency in dairy cows. In addition, RPC decreased serum insulin concentration during the glucose tolerance test, but glucose concentration was not affected by treatment.

Disentangling the relative roles of resource acquisition and allocation on animal feed efficiency: insights from a dairy cow model.

BackgroundFeed efficiency of farm animals has greatly improved through genetic selection for production. Today, we are faced with the limits of our ability to predict the effect of selection on feed efficiency, partly because the relative importance of the components of this complex phenotype changes across environments. Thus, we developed a dairy cow model that incorporates the dynamic interplay between life functions and evaluated its behaviour with a global sensitivity analysis on two definitions of feed efficiency. A key model feature is to consider feed efficiency as the result of two processes, acquisition and allocation of resources. Acquisition encapsulates intake and digestion, and allocation encapsulates partitioning rules between physiological functions. The model generates genetically-driven trajectories of energy acquisition and allocation, with four genetic-scaling parameters controlling these processes. Model sensitivity to these parameters was assessed with a complete factorial design.ResultsAcquisition and allocation had contrasting effects on feed efficiency (ratio between energy in milk and energy acquired from the environment). When measured over a lactation period, feed efficiency was increased by increasing allocation to lactation. However, at the lifetime level, efficiency was increased by decreasing allocation to growth and increasing lactation acquisition. While there is a strong linear increase in feed efficiency with more allocation to lactation within a lactation cycle, our results suggest that there is an optimal level of allocation to lactation beyond which increasing allocation to lactation negatively affects lifetime feed efficiency.ConclusionsWe developed a model to predict lactation and lifetime feed efficiency and show that breaking-down feed conversion into acquisition and allocation, and introducing genetically-driven trajectories that control these mechanisms, permitted quantification of their relative roles on feed efficiency. The life stage at which feed efficiency is evaluated appears to be a key aspect for selection. In this model, body reserves are also a key component in the prediction of lifetime feed efficiency since they integrate the feedback of acquisition and allocation on survival and reproduction. This modelling approach provided new insights into the processes that underpin lifetime feed efficiency in dairy cows.Electronic supplementary materialThe online version of this article (doi:10.1186/s12711-016-0251-8) contains supplementary material, which is available to authorized users.

Hot topic: Definition and implementation of a breeding value for feed efficiency in dairy cows

A new breeding value that combines the amount of feed saved through improved metabolic efficiency with predicted maintenance requirements is described. The breeding value includes a genomic component for residual feed intake (RFI) combined with maintenance requirements calculated from either a genomic or pedigree estimated breeding value (EBV) for body weight (BW) predicted using conformation traits. Residual feed intake is only available for genotyped Holsteins; however, BW is available for all breeds. The RFI component of the “feed saved” EBV has 2 parts: Australian calf RFI and Australian lactating cow RFI. Genomic breeding values for RFI were estimated from a reference population of 2,036 individuals in a multi-trait analysis including Australian calf RFI (n=843), Australian lactating cow RFI (n=234), and UK and Dutch lactating cow RFI (n=958). In all cases, the RFI phenotypes were deviations from a mean of 0, calculated by correcting dry matter intake for BW, growth, and milk yield (in the case of lactating cows). Single nucleotide polymorphism effects were calculated from the output of genomic BLUP and used to predict breeding values of 4,106 Holstein sires that were genotyped but did not have RFI phenotypes themselves. These bulls already had BW breeding values calculated from type traits, from which maintenance requirements in kilograms of feed per year were inferred. Finally, RFI and the feed required for maintenance (through BW) were used to calculate a feed saved breeding value and expressed as the predicted amount of feed saved per year. Animals that were 1 standard deviation above the mean were predicted to eat 66 kg dry matter less per year at the same level of milk production. In a data set of genotyped Holstein sires, the mean reliability of the feed saved breeding value was 0.37. For Holsteins that are not genotyped and for breeds other than Holsteins, feed saved is calculated using BW only. From April 2015, feed saved has been included as part of the Australian national selection index, the Balanced Performance Index (BPI). Selection on the BPI is expected to lead to modest gains in feed efficiency.

Dose–response to eugenol supplementation to dairy cow diets: Methane production, N excretion, ruminal fermentation, nutrient digestibility, milk production, and milk fatty acid profile

The objective of this study was to evaluate the effects of increasing dietary concentrations of eugenol on enteric CH4 production, N excretion, ruminal fermentation characteristics, nutrient digestibility, milk production, and milk fatty acid (FA) composition. For this purpose, eight ruminally cannulated multiparous lactating cows were used in a replicated 4×4 Latin square design (28-d periods). Cows were fed a total mixed ration without (0mg/kg dry matter [DM]) or with (25, 50, 75mg/kg DM) eugenol supplementation. Enteric methane production was measured using the sulfur hexafluoride (SF6) tracer gas technique. Dry matter intake, N excretion, and apparent total-tract digestibility of DM, organic matter, acid detergent fiber, neutral detergent fiber, and gross energy (GE) were not changed by increasing dietary doses of eugenol. Likewise, total volatile fatty acid (VFA) concentration was unaffected while of the individual VFA, only the molar proportion of branched-chain VFA decreased linearly with increasing eugenol levels. Diet supplementation with increasing doses of eugenol had no effect on ruminal ammonia concentration, but tended (P=0.08) to increase linearly total protozoa number. Milk production and milk concentrations of protein, lactose, and urea nitrogen were unchanged, whereas milk fat yield was quadratically affected by increasing dietary levels of eugenol (1.38, 1.32, 1.31, and 1.33kg/d for 0, 25, 50 and 75mg/kg eugenol, respectively). Diet supplementation with eugenol had minor effects on milk FA profile. Enteric CH4 emissions (g/d) and CH4 energy losses (as a proportion of GE intake) were not changed by including incremental levels of eugenol in the diet. Results from this study show no effects of supplementing dairy cow diets with eugenol (up to 75mg/kg) on enteric CH4 emissions, N excretion, and milk performance. We concluded that at the dosage levels assessed in the current study (up to 75mg/kg), eugenol cannot be promoted as an effective dietary approach to mitigate enteric CH4 emissions, decrease N excretion, and enhance feed efficiency in dairy cows.

Feeding protein supplements in alfalfa hay-based lactation diets improves nutrient utilization, lactational performance, and feed efficiency of dairy cows

Due to the increasing cost of soybean meal and concerns of excess N being excreted into the environment, new protein supplements have been developed. Two products that have shown potential in increasing N utilization efficiency are slow-release urea (SRU; Optigen; Alltech Inc., Nicholasville, KY) and ruminal-escape protein derived from yeast (YMP; DEMP; Alltech Inc.). The objective of this study was to assess the effects of feeding these 2 supplements in alfalfa hay-based [45.7% of forage dietary dry matter (DM)] dairy diets on nutrient utilization, feed efficiency, and lactational performance of dairy cows. Twelve multiparous dairy cows were used in a triple 4 × 4 Latin square design with one square consisting of ruminally cannulated cows. Treatments included (1) control, (2) SRU-supplemented total mixed ration (SRUT), (3) YMP-supplemented total mixed ration (YMPT), and (4) SRU- and YMP-supplemented total mixed ration (SYT). The control consisted only of a mixture of soybean meal and canola meal in a 50:50 ratio. The SRU and the YMP were supplemented at 0.49 and 1.15% DM, respectively. The experiment consisted of 4 periods lasting 28 d each (21 d of adaptation and 7 d of sampling). Cows fed YMPT and SYT had decreased intake of DM, and all supplemented treatments had lower crude protein intake compared with those fed the control. Milk yield tended to have the greatest increase in YMPT compared with the control (41.1 vs. 39.7kg/d) as well as a tendency for increased milk fat and protein yields. Feed efficiencies based on yields of milk, 3.5% fat-corrected milk, and energy-corrected milk increased at 10 to 16% due to protein supplementation. Cows fed protein supplements partitioned less energy toward body weight gain, but tended to partition more energy toward milk production. Efficiency of use of feed N to milk N increased by feeding SRUT and YMPT, and milk N-to-manure N ratio increased with YMPT. Overall results from this experiment indicate that replacing the mixture of soybean meal and canola meal with SRU and YMP in alfalfa hay-based dairy diets can be a good approach to improve nutrient utilization efficiencies in lactating dairy cows.

English

Recombinant bovine somatotropins (rbST) have been synthesized and manufactured using recombinant DNA (rDNA) techniques. The rbST has increased milk production in dairy animals, including cow, sheep and goats. There are management factors including dosage of rbST, injection interval, genetic potential and environmental conditions which affect the magnitude of the animal-response to rbST. For dairy cows, the optimal dose of rbST treatment is between 25 and 50 mg/day. Daily injection of rbST may produce better response, but sustained-release formulations of rbST are more practical. The magnitude of milk production response to rbST range from 10 to 35% in dairy cows. The rbST has no or little effects on the milk composition, processing properties and taste. The rbST did not affect digestion of feeds or the efficiency of utilizing absorbed nutrients for milk synthesis, and it has no or little effect on rumen fermentation, flow of nutrients to the small intestine and total tract digestibility, but it improves the feed efficiency in dairy cows. The rbST induced significant increase in serum bST. It has a galactopoietic effect, since it increase the metabolic activity of mammary cells or slow their involution, thereby allowing more secretory cells to persist over time and contribute to increasing milk synthesis and yield. It has a great impact on mammary gland development and subsequently milk-producing capacity in dairy heifers. The rbST increase the hypothyroid status of lactating cows and maintain euthyroid condition in the mammry gland, thus enhancing its metabloic priority. The rbST did not adversely affect reproduction, and the observed decreases in reproductive performance in rbST-treated cows may be attributed more to the increases in milk yield than to direct effect of rbST. The increased production responses to rbST in heat-stressed dairy cows is less than that under more moderate conditions. The incidence of mastitis in rbST-treated cows is due more to increased milk yield than to any direct effects of rbST. The rbST was efficacious in increasing milk yields in sheep and goats without adverse effects. &nbsp; Key words: Recombinant bovine somatotropin, dairy animals, physiological responses.&nbsp

Compared with stearic acid, palmitic acid increased the yield of milk fat and improved feed efficiency across production level of cows

The effects of dietary palmitic and stearic acids on feed intake, yields of milk and milk components, and feed efficiency of dairy cows were evaluated in an experiment with a crossover arrangement of treatments with a covariate period. Cows with a wide range of milk production (38 to 65kg/d) were used to determine if response to fat supplementation varied according to production level. Thirty-two Holstein cows (143±61d in milk) were assigned randomly to a treatment sequence within level of milk production. Treatments were diets supplemented (2% of diet dry matter) with palmitic acid (PA; 97.9% C16:0) or stearic acid (SA; 97.4% C18:0). Treatment periods were 21d and cows were fed a nonfat supplemented diet for 14d immediately before the first treatment period. The final 4d of each period were used for sample and data collection. Milk production measured during the covariate period (preliminary milk yield) was used as the covariate. No interactions were detected between treatment and preliminary milk yield for the production response variables measured. Compared with SA, the PA treatment increased milk fat concentration (3.66 vs. 3.55%) and yield (1.68 vs. 1.59kg/d), and 3.5% fat-corrected milk yield (47.5 vs. 45.6kg/d). Treatment did not affect dry matter intake, milk yield, milk protein yield, body weight, or body condition score. Milk protein concentration was lower for PA compared with SA treatment (3.24 vs. 3.29%). The PA treatment increased feed efficiency (3.5% fat-corrected milk yield/dry matter intake) compared with SA (1.48 vs. 1.40). The increase in milk fat yield by PA was entirely accounted for by a 24% increase in 16-carbon fatty acid output into milk. Yields of de novo (3.2%) and preformed fatty acids (2.9%) were only slightly decreased by PA relative to SA. The PA treatment increased plasma concentration of nonesterified fatty acids (96.3 vs. 88.2μEq/L) and glucose (56.6 vs. 55.7mg/dL) compared with SA, but insulin and β-hydroxybutyrate were not altered by the treatments. Results demonstrate that palmitic acid is more effective than stearic acid in improving milk fat concentration and yield as well as efficiency of feed conversion to milk. Responses were independent of production level and without changes in body condition score or body weight. Further studies are required to test the consistency of these responses across different types of diets.

Dietary ratios of maize silage to lucerne hay affect feed intake, chewing activity and milk production of dairy cows

The present study investigated the effects of substitution of chopped lucerne hay (LH) for maize silage on feed intake, rumen pH and fermentation, digestibility, milk production and feed efficiency of dairy cows. Fifteen Holstein dairy cows in early lactation (37 ± 10 days in milk) were randomly assigned to three dietary treatments in a completely randomised design. The experiment lasted for 80 days, with 10 days of adaptation and 70 days of data collection. Treatment diets consisted of 60% concentrate and 40% forage, comprising 30 : 10 (MS30), 20 : 20 (MS20) or 10 : 30 (MS10) of maize silage (MS) to LH ratio (MS : LH). Cows were fed ad libitum as total mixed ration. Water was added daily to adjust the moisture content of the feed to be similar across diets. Decreasing the ratio of MS : LH resulted in linear and quadratic decreases of DM intake and physically effective neutral detergent fibre, without affecting apparent digestibility in the total digestive tract. Decreasing MS : LH also linearly reduced total chewing time and tended to reduced chewing index (min/kg DM intake), but had limited effects on rumen pH and fermentation characteristics. Increasing the substitution of LH for MS decreased milk production (33.1, 31.7, and 29.8 kg/day for MS30, MS20, and MS10, respectively), and tended (P = 0.06) to decrease 4% fat-corrected milk and fat yield. However, milk content of protein (2.70%, 2.77% and 2.77%) and fat improved, and tended to improve by decreasing the MS : LH ratio, respectively. The efficiency of milk production, expressed as either milk yield/kg DM intake or 4% fat-corrected milk/kg DM intake, was not affected by the treatments. Results indicated that under the current feeding conditions, decreasing the ratio of MS : LH was not recommended to maintain milk production and DM intake.

Genetic factors controlling feed efficiency in dairy cows

The direct control of feed efficiency is feasible only in test stations and experimental farms. Here coefficients of heritability were found below those for milk yield. Between milk yield and feed efficiency there exist strong genetic correlations, while the correlations between feed intake and feed efficiency are smaller. In spite of these favourable correlations, breeding for higher milk yield entails a serious energy deficit during the first part of lactation. The feed intake reaches its maximum not earlier than 10 to 12 weeks post partum, but peak daily milk yield has already been reached by two to four weeks post partum. Due to energy deficiency the feed efficiency during the first part of lactation seems to be very high, but in fact the feed intake at this time does not cover the energy demand of the high yielding dairy cow. In future more research on genetic factors controlling the feed intake during the first 10 weeks of lactation is required. As potential single factors the capacity of the digestive tract, the production of saliva, the ruminal fermentation, the rate of passage and the overall physiological status of the animal should be investigated. To estimate the real feed efficiency one should observe not only the direct production in milk, milk fat, protein and lactose but also the metabolism of depot fat, growth, nutrition of the foetus, maintenance requirements and a genetically affected resistance against metabolic disorders. Higher feed intake at beginning of lactation can reduce the feed costs, increase the protein content in milk and improve the conception rate in dairy cows. For breeding purposes we need indirect parameters for feed intake under field conditions, e.g. changes in body measurements, urea content in milk, oleic acid proportion in milk fat or content of ketone bodies.

Plasma and blood volume in the cow using the T-1824 hematocrit method.

ArticlePlasma and Blood Volume in the Cow Using the T-1824 Hematocrit MethodMonica ReynoldsMonica ReynoldsFrom the Department of Physiology and Pharmacology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PennsylvniaPublished Online:01 Jun 1953https://doi.org/10.1152/ajplegacy.1953.173.3.421MoreSectionsPDF (1010 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByWhy mass allocation with representative allocation factor is preferential in LCA when using residual livestock products as organic fertilizersJournal of Environmental Management, Vol. 297Highly Scalable Conversion of Blood Protoporphyrin to Efficient Electrocatalyst for CO 2 ‐to‐CO Conversion16 May 2021 | Advanced Materials Interfaces, Vol. 8, No. 12Cardiac function and feed efficiency: Increased right-heart workload in feed inefficient beef cattleLivestock Science, Vol. 229Yeast culture increased plasma niacin concentration, evaporative heat loss, and feed efficiency of dairy cows in a hot environmentJournal of Dairy Science, Vol. 101, No. 7A dynamic model to simulate potassium balance in dairy cowsJournal of Dairy Science, Vol. 100, No. 12Fetal sex alters maternal anti-Mullerian hormone during pregnancy in cattleAnimal Reproduction Science, Vol. 186Applying Least Absolute Shrinkage Selection Operator and Akaike Information Criterion Analysis to Find the Best Multiple Linear Regression Models between Climate Indices and Components of Cow’s Milk23 July 2016 | Foods, Vol. 5, No. 4Mammary immunoglobulin transfer rates following prepartum milkingJournal of Dairy Science, Vol. 99, No. 11Lactation driven dynamics of adiponectin supply from different fat depots to circulation in cowsDomestic Animal Endocrinology, Vol. 47Effect of sitagliptin treatment on metabolism and cardiac function in genetic diabetic miceEuropean Journal of Pharmacology, Vol. 723Does rosiglitazone affect adiposity and cardiac function in genetic diabetic mice?European Journal of Pharmacology, Vol. 700, No. 1-3Effects of dehydration on cardiovascular development in the embryonic American alligator (Alligator mississipiensis)Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Vol. 162, No. 3Dynamics of red and white blood picture in dairy cows during the periparturient periodComparative Haematology International, Vol. 9, No. 3Kinetics of Niacin Supplements in Lactating Dairy CowsJournal of Dairy Science, Vol. 77, No. 2Endogenous labeling of bovine milk with the stable isotope 44Ca1,2Nutrition Research, Vol. 8, No. 10Water Dynamics of Dairy Cattle as Affected by Initiation of Lactation and Feed IntakeJournal of Dairy Science, Vol. 67, No. 10Scaling of blood parameters in mammalsComparative Biochemistry and Physiology Part A: Physiology, Vol. 67, No. 4Influence of season and body condition on plasma volume levels of white‐tailed deer, Odocoileus virginianus30 September 2008 | Journal of Interdisciplinary Cycle Research, Vol. 9, No. 3Plasma kinetics of exogenous bovine parathyroid hormone in calvesPflügers Archiv European Journal of Physiology, Vol. 371, No. 3Pharmacokinetics of sulphadimethoxine in cattleResearch in Veterinary Science, Vol. 23, No. 1Plasma, Blood and Extracellular Fluid Volumes in Grazing Hereford CattleResearch in Veterinary Science, Vol. 8, No. 1Das Blutvolumen der Ziege in Abhängigkeit von Alter und Gewicht113 May 2010 | Zentralblatt für Veterinärmedizin Reihe A, Vol. 13, No. 3OBSERVATIONS ON EQUINE AND BOVINE HAEMATOCRIT DETERMINATIONSAustralian Veterinary Journal, Vol. 41, No. 12Section A. 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