Total Digestible Organic Matter Intake Research Articles

401 Effect of protein and starch supplementation level on intake and digestibility by steers consuming low-quality forage: I. Bos taurus

Abstract A deficiency of ruminally available N (RAN) caused by a basal diet of low-quality forage depresses forage utilization. Supplemental protein improves forage utilization by increasing RAN, resulting in increased intake and potentially improving digestion. Addition of starch to a supplement can increase total digestible organic matter (OM) intake (TDOMI); however, too much starch decreases RAN and pH potentially decreasing forage utilization. Our objective was to determine the effect of starch supplementation on intake and digestion in Bos taurus indicus steers. Accordingly, five ruminally cannulated Brahman steers [body weight (BW) = 420 ± 55 kg) were used in a 4 × 4 Latin square to evaluate the effect of decreasing supplemental starch when consuming King Ranch Bluestem hay (3.5% CP, 73% NDF). Steers received four isonitrogenous (130 mg N/ kg BW) supplements providing increasing levels of starch (2% starch = 100% soybean meal; 20% starch = 26.3% corn, 73% soybean meal, 0.7% urea; 38% starch = 51.6% corn, 47% soybean meal, 1.4% urea; 56% starch = 78.6% corn, 19% soybean meal, 2.4% urea). Five 14-d periods were conducted, consisting of 9 d adaptation and 4 d to measure intake and digestion, and 1 d for ruminal fermentation. As designed, supplement OM intake (SOMI) increased linearly (P < 0.01) as starch level increased. Other measures of intake, including forage OM intake (FOMI), total OM intake (TOMI), and total neutral detergent fiber intake (TNDFI) decreased in a cubic manner in response to increasing starch (P ≤ 0.04). Forage OMI also responded with a cubic decrease (72.2, 68.9, and 69.5 g/kg BW0.75) when the protein supplement contained 2, 20, and 38% starch, respectively, but decreased to 61.2 g/kg BW0.75 when the 56% starch supplement was provided. Similarly, TOMI decreased 5.3% when starch inclusion increased from 38 to 56%. Total tract OM digestion and NDF digestion were not significantly affected (P ≥ 0.86) by starch level in the supplement; therefore, despite TOMI and TNDFI decreasing, there was no effect on total digestible OM intake and (TDOMI) and total digestible NDF intake (TDNDFI). In conclusion, providing supplemental starch over 38% decreased forage utilization. Decreases in FOMI with starch inclusion may be attributed to competition for RAN between fiber fermenting and starch fermenting bacteria.

91 Mealworm and black soldier fly larvae as protein supplements for beef steers consuming forage

Abstract The global population is projected to increase, indicating there will be greater demand for animal protein to meet the associated food needs. This demand will place additional pressure on livestock systems to increase output while also minimizing natural resource inputs. Insect protein has emerged as a potential environmentally sustainable alternative to conventional protein feeds, such as soybean meal. Further, insect protein does not compete in the human food market as the products of conventional oil crops often do. Mealworm larvae (MWL) has been studied in poultry and swine as an alternative protein feed; however, there is not currently research evaluating MWL for cattle. Black soldier fly larvae (BSFL) has also received attention for its potential use in livestock feed due to its scalability and nutritional value, but research in cattle is limited. The objective of this study was to evaluate the effects of whole dried MWL and defatted BSFL as protein supplements for cattle consuming forage. These procedures were approved by IACUC at Texas State University (#7726). Five ruminally cannulated steers were utilized in a 5×5 Latin square experiment to determine how MWL and BSFL supplementation affect forage utilization. Steers consuming low-quality forage (4.2% crude protein) were provided one of five treatments each period: 1) control with no supplement (CON), 2) soybean meal (CONV), 3) BSFL, 4) MWL, and a 5) 50% BSFL and 50% MWL by-weight (MIX). Supplements were provided at 100 mg N/kg BW. Periods included 8-d for treatment adaptation, 5-d for intake and digestion measurements, and 1-d for ruminal fermentation measures. Dry matter (DM), organic matter (OM), CP, neutral detergent fiber (NDF), and acid detergent fiber (ADF) were determined for diet, ort, and feces. Protein supplementation stimulated forage OM intake (P ≤ 0.01) relative to CON. There was a significant difference in FOMI (P ≤ 0.01) between BSFL and CONV. Steers receiving CONV treatment consumed 4.71 kg FOMI/d, which was significantly greater (P ≤ 0.01) than those receiving BSFL (4.30 kg/d). There were not differences in FOMI between other treatment groups. Total digestible OM intake (TDOMI) was stimulated by protein supplementation (P ≤ 0.01) from 1.94 kg/d for CON to an average of 3.24 kg/d across protein supplements. Organic matter digestibility (OMD) and neutral detergent fiber digestibility (NDFD) were not affected by treatment (P ≥ 0.37), for an average OMD of 66.5% and NDFD of 62.7%. There was also not a treatment effect (P = 0.96) on total volatile fatty acid (VFA) concentrations, although there were some shifts in molar proportions of individual VFAs across treatments. These data indicate that MWL may be more efficacious than BSFL in stimulating forage utilization in beef cattle, but both are viable protein supplements.

Acceptance and forage utilization responses of steers consuming low-quality forage and supplemented black soldier fly larvae as a novel feed.

As the insect-rearing industry scales in the United States and other developed nations, it has the potential to create multiple product streams (e.g., oil and protein-rich biomass) for existing markets. Black soldier fly larvae (BSFL; Hermetia illucens) has been identified as a potential livestock feed because it is not expected to compete in the human food sector and its production has a lesser environmental footprint than that of conventional feeds. Existing research on BSFL as feed focuses on full-fat BSFL for poultry and aquaculture. Therefore, the objective of our experiment was to evaluate the viability of defatted BSFL as an alternative protein source for beef cattle consuming forage. Procedures were approved by Texas State University IACUC (#7726). Two experiments were conducted using ruminally cannulated beef steers fed low-quality forage in 5 × 5 Latin squares. Experiment 1 assessed consumption of BSFL as a protein supplement and included five 5-d periods with 3-d for washout and 2-d for measurement of supplement intake and preference. There were five treatments delivered in addition to the basal forage: 100% soybean meal (SBM); 75% SBM/25% BSFL; 50% SBM/50% BSFL; 25% SBM/75% BSFL; and 100% BSFL. Supplement and forage intake did not differ between treatments (P ≥ 0.45) nor was there a treatment × day interaction (P ≥ 0.45). Experiment 2 evaluated the effect of BSFL supplementation on forage (5.3% crude protein) intake and digestion and included five 14-d periods with 8-d for treatment adaptation, 5-d for measurement of intake and digestion, and 1-d for determination of ruminal fermentation. There were four treatments of supplemental BSFL provided at graded N levels: 0, 50, 100, or 150mg N/kg BW and one level of SBM at 100mg N/kg BW. Increasing provision of BSFL linearly increased forage organic matter (OM) intake (P = 0.04), total OM intake (P < 0.01), total digestible OM intake (P < 0.01), dry matter digestibility (P = 0.01), and OM digestibility (P = 0.02). There were no significant differences (P ≥ 0.17) in intake or digestibility between levels of BSFL and SBM. Ultimately, defatted BSFL has potential to replace conventional feeds as a protein supplement without sacrificing forage utilization.

83 Effect of a Saccharomyces cerevisiae fermentation product on intake and digestion in young horses undergoing exercise training

Young growing horses subjected to exercise have greater dietary requirements than horses at maintenance necessitating the delivery of a more nutrient dense diet. Inclusion of a grain concentrate in the total daily ration achieves this goal but also may put the young horse at risk of digestive disorders and reduced forage utilization. As such, the objective of this study was to determine if a dietary S. cerevisiae fermentation product (SCFP; TruEquine C, Diamond V) could influence nutrient utilization in young horses being introduced to grain concentrate feed and if the response was dose dependent. Thirty Quarter horse yearlings (561 ± 15.8 d of age and 371 ± 24.4 kg BW) were adapted to a 14% CP grain concentrate feed (Nutrena SafeChoice Original formulated without microbial ingredients), fed at 1% of BW as fed to meet or slightly exceed nutrient requirements for yearling horses undergoing light to moderate work and allowed ad-libitum access to Coastal bermudagrass (Cynodon dactylon) hay (67.8% NDF) and fresh water. Horses were stratified by age, BW, and sex and randomly assigned to one of 3 levels of SCFP: 0, 46, or 92 mg/kg BW divided evenly and top-dressed onto the grain concentrate meal at 12 h intervals. After 14 d of adaptation, intake and total fecal production were measured overa 4-d period. Horses were housed in individual 3.7 × 3.7 m stalls and allowed 1 h of exercise in individual 3.7 × 7.4 m runs daily during the collection period. All statistical analyses were performed in SAS 9.4 using PROC MIXED with the model containing treatment and horse included as the random variable. There was no significant treatment difference for any measure of intake (P ≥ 0.33); forage DM intake averaged 6.14 kg/d, total DM intake averaged 9.60 kg/d, and total digestible organic matter intake averaged 4.97 kg/d. There was a tendency for improved DM digestibility (P = 0.09) with supplementation (56.3 and 56.8% for 46 and 92 mg/kg BW, respectively) compared with no supplementation (54.2%). Supplementation of SCFP resulted in no significant differences (P ≥ 0.15) in organic matter (OM) or NDF digestibility. There were no differences in any indicator of nutrient digestibility between the low and high level of SCFP supplementation. An observed tendency for improved DM digestibility with SCFP supplementation suggests further research is warranted.

Evaluation of Black Soldier Fly larvae (Hermetia illucens) as a protein supplement for beef steers consuming low-quality forage.

Black Soldier Fly larvae (BSFL; Hermetia illucens) has been the focus of recent feeding trials in poultry, swine, and fish; however, in vivo research has not yet been conducted in cattle. Accordingly, a study was conducted to evaluate the effects of BSFL as a protein supplement in beef steers. Six steers (603 ± 20 kg of BW, n = 3 and 404 ± 17 kg of BW, n = 3) consuming King Ranch bluestem hay (6.55% dry matter [DM] crude protein [CP]) ad libitum were used in two simultaneous 3 × 3 Latin squares. Steers were provided one of three treatments each period: 1) a control with no supplement (CON), 2) a supplement comprised of conventional feed ingredients with whole cottonseed and soybean meal as the main protein sources (CONV), and 3) a supplement with BSFL as the main protein source (BSFL). Three 14-d periods were conducted with 8 d to adapt to treatments, 5 d to measure intake and digestion, and 1 d to complete a ruminal fermentation profile. DM, organic matter (OM), CP, neutral detergent fiber (NDF), and acid detergent insoluble ash were determined in forage, supplement, ort, and fecal samples. Protein supplementation as CONV or BSFL stimulated forage OM intake (P ≤ 0.01) relative to CON with a trend for a difference (P = 0.08) between the supplements such that CONV steers consumed more FOMI than BSFL steers. Treatment affected total digestible OM intake (TDOMI; P ≤ 0.01); TDOMI for CON steers was 47.5 g/kg metabolic body weight (MBW) which was significantly less (P ≤ 0.01) than that of CONV or BSFL steers. Steers supplemented with CONV consumed significantly more TDOMI than BSFL steers (P = 0.05; 62.2 vs. 60.1 g/kg MBW, respectively). Treatment did not significantly affect digestibility of DM, OM, or NDF (P > 0.32). There was also not a significant effect (P ≥ 0.17) of treatment on ruminal ammonia-N, total volatile fatty acids, or ruminal pH. Overall, these data indicate that BSFL may be an effective protein supplement for beef cattle consuming low-quality forage.

PSXIV-1 Effects of passage rate on forage intake and digestion in beef cattle

Abstract The objective was to evaluate treatments designed to increase passage rate on forage intake and digestion. Eight ruminally-cannulated steers were assigned to a replicated 4 × 4 Latin square design. All steers were fed an ad libitum diet of prairie grass hay (10.4% CP) with the following treatments designed to increase passage rate: no treatment (control; CON), pelleted (PEL), 7% Ca(OH)2 treated (CAOH), and six 2 kg weights inserted into the rumen (WTS). Molasses (3% of diet DM) was added to all treatments. Feed, orts, and total feces was collected on d 12–17 to determine total tract digestibility. On d 17–20, ruminal pH was recorded every 8 hr. Data were analyzed using the MIXED procedure of SAS 9.4 with treatment and period as fixed effects and steer as a random effect. A treatment effect (P &amp;lt; 0.01) was observed for ruminal pH; steers fed CAOH had the highest pH (6.97) with WTS and CON intermediate and PEL being the lowest (6.34). Organic matter intake (OMI) was affected (P &amp;lt; 0.01) by treatment with PEL steers consuming the most (7.86 kg). While steers consuming CON had greater OMI than CAOH (P = 0.04), WTS was not different from CON (P = 0.50). Organic matter digestibility (OMD) was also affected (P &amp;lt; 0.01) by treatment as WTS and CON were the greatest (62.8% and 61.7%, respectively) and CAOH (58.7%) tended (P = 0.08) to be greater than PEL (55.9%). Total digestible organic matter intake (TDOMI) was affected (P &amp;lt; 0.01) by treatment; PEL had the greatest TDOMI with CON being intermediate, and CAOH and WTS being the least. Treatments designed to increase passage rate did affect forage intake and digestion with the greatest effect resulting from pelleting grass hay due to the severe reduction in particle size.

Effect of supplemental carbohydrate source on the utilization of low-quality tallgrass-prairie hay by beef steers (1998)

Twenty ruminally fistulated steers were used in different two experiments to evaluate the effects of supplemental carbohydrate source (starch, glucose, fructose, or sucrose) fed at .3% BW/day on the utilization of low-quality tallgrass-prairie hay. In Experiment 1, all supplemental carbohydrates were fed with a low level of supplemental degradable intake protein. In Experiment 2, the level of supplemental degradable intake protein was high. Intake of the tallgrass-prairie hay was not affected significantly by supplementation in either experiment, but as a result of the added carbohydrate, total intake was increased. When supplemental protein intake was inadequate, supplemental carbohydrates depressed digestion, but when supplemental protein was higher, fiber digestion was not depressed. Because of increased total intake (forage plus supplement) and increased digestion in Experiment 2, total digestible organic matter intake was greater in the supplemented animals, with little difference among carbohydrate sources.

Promising tropical grasses and legumes as feed resources in Central Tanzania V. Effect of supplementing Cenchrus ciliaris hay with leaves from four legumes on intake and digestibility by growing Mpwapwa bulls

In Trial 1, six growing Mpwapwa bulls (mean age 1.5 years, mean body weight 158 kg) were used in a 6 × 6 Latin square design to study the effect on intake and digestion of supplementing Cenchrus ciliaris cv. Kongwa hay with four different legume leaf proteins. Hay alone and fish meal (FM) treatments were included as negative and positive control treatments, respectively. The grass hay was fed allowing above 40% refusal to maximize selectivity and contained 5.1% crude protein (CP), 76.1% neutral detergent fibre (NDF), 9.9% lignin and 3.1% silica. The protein sources were dried leaves of Macroptilium atropurpureum cv. Siratro (MAS), Macrotyloma axillare (MAA), Neonotonia wightii cv. Mpwapwa (NWM), Stylosanthes scabra cv. Seca (SSS) and FM. The protein sources were fed aiming at supplying approximately 150 g CP/day. The legume CP contents varied from 18.6–20.6% and the FM contained 54.7%. In Trial 2 in a completely randomised block design, 8 bulls were used to measure the digestibility of the legumes alone. Selective feeding resulted in consumption of hay containing 6.2% CP. The apparent digestibility of organic matter (OM) and NDF were 58.3 and 62.5%, respectively. Supplementing the hay resulted in intake of a diet with CP ranging from 8.0–8.5%. Despite the increased CP intake, neither the digestibility of OM nor NDF increased significantly, implying that the protein was not a first limiting factor for fibre digestion. The grass hay OM intakes varied between 21.0 and 22.2 g/kg body weight (BW) per day (77.3–86.0 g/kg BW 0.75/d) and were not improved by protein supplementation. Significant improvements ( P < 0.001) in daily intakes of total OM and CP were observed by supplementation, although total NDF was not improved. All protein supplements except MAS improved ( P < 0.05) digestible OM intakes compared to the unsupplemented hay. Calculated digestible and metabolizable energy values for the diets were not improved by supplementation. However, an improvement in total energy and protein intake may be obtained as a result of supplementation. It is concluded that it is beneficial to use MAA, NWM, SSS and also FM in C. ciliaris-based diets to improve total intake of CP by growing bulls. Total intake of OM and digestible OM may also be improved, but the levels are only on the order of 10%. The use of legume supplements and allowing ample feed refusals may result in an estimated daily BW gain of 200–400 g.

Effects of various supplemental starch and protein levels on ruminal fermentation and liquid passage of beef steers fed tallgrass-prairie hay (1997)

The effect of supplements containing various proportions of degradable intake protein (DIP) and starch on ruminal digestion characteristics of forage-fed beef steers was evaluated. Fluid passage rates, ruminal ammonia (N H), 3 and total volatile fatty acid (VFA) concentrations increased as the amount of supplemental DIP increased. Starch infused at .3% of BW increased molar proportion s of propionate and butyrate and decreased acetate, compared to feeding DIP alone. However, proportions of branched-chain VFA increased with DIP at all levels of starch infusion. Total digestible organic matter intake (TDOMI) was increased with each addition of DIP; however, infusing starch within a DIP level decreased TDOMI. Providing supplemental DIP is more important for improving the use of low-quality, tallgrass-prairie hay than is ruminally available starch.

Effect of ammonia treatment and carbohydrate supplementation on the intake and digestibility of barley straw diets by sheep

The changes in straw voluntary intake and apparent digestibility caused by the ammoniation of straw and energy supplementation in diets fed to adult, non-productive sheep were studied in two experiments. In Experiment 1, untreated (US) or ammonia treated (TS) barley straw were given as the only feed to four ewes in a cross-over design. Ammoniation increased straw dry matter (DM) intake from 30.2 to 50.6 g kg −1 LW 0.75, organic matter digestibility (OMD) from 0.438 to 0.519 and digestible organic matter intake (DOMI) from 12.5 to 24.7 g kg −1 LW 0.75, allowing energy maintenance requirements to be met. In Experiment 2, three groups of four ewes received US, with another three groups of four receiving TS, both supplemented with meadow grass hay (H), rolled barley (B) or sugar-beet pulp (P) in a 2 × 3 factorial design. Each supplement was given in amounts of 150, 300, 450 and 600 g day −1, in a Latin-square design. The type of supplement did not significantly affect straw intake at any level of inclusion. The level of supplementation scarcely affected US intake, whereas DM intake of TS diminished linearly. Substitution rates were 0.49 ± 0.088, 0.61 ± 0.085 and 0.55 ± 0.131 for TS-H, TS-B and TS-P diets, respectively ( P > 0.05). Apparent digestibility of straw was not significantly affected by supplementation. Increases in total DOMI when the level of supplementation was augmented were lower in TS than in US diets, and with H than with B or P as supplements. To reach the DOMI obtained with TS as the only feed, US has to be supplemented with 420, 272 or 269 g DM of H, B or P, respectively.

The effects of cereal supplementation of grass and maize silages

AbstractGrass and maize silages were fed alone and with two levels of a barley supplement to Friesian steers of about 300 kg liveweight. The organic matter (OM) intakes of grass and maize silage were similar although the OM digestibilities of the silages were 0·722 and 0·649 respectively. For both silages, barley supplementation increased total OM intake and total digestible OM intake by 0·46·0·08 and 0·37·0·06 g per g OM of supplement respectively. Liveweight gains on grass and maize silage diets were 1·38 and 1·20 kg d‐1 respectively, but the differences were not significant (P&gt; 0·05).

The effects of forage digestibility and concentrate supplementation on the nutritive value of the diet and performance of finishing cattle

ABSTRACTHays varying from 58 to 75% organic matter digestibility (OMD) were offered ad libitum to steers weighing approximately 400 kg, together with concentrates at rates varying from 0·0 to 8·5 g organic matter (OM)/kg live weight per day. Total digestible OM intake (DOMI) increased linearly by 0·75 g/g concentrate OM intake (OMI) for a hay of 58% OMD, but by only 0·26 to 0·36 g/g concentrate OMI for hays above 70% OMD. With hays above 70% OMD, supplementary feeding had little effect on the overall OMD of the diet but significantly depressed the cellulose digestibility of the diet. With the hays of lower digestibility, supplementary feeding increased the OMD of the diet by an average of 0·90% units/unit concentrate OMI, and had no significant effect on the cellulose digestibility of the diet. Live-weight gain increased with increasing digestibility of the hay and with increasing level of supplement.In multiple regression equations, variations in hay digestibility and concentrate intake accounted for from 77 to 91% of the variation in hay intake, diet digestibility and total DOM intake.

Response of beef cattle to infused supplements of urea and of urea-molasses when offered a low quality grass hay

Eight Hereford steers, fistulated at the rumen and offered a low quality grass hay (Axonopus affinus comprised 75 per cent of the pasture) were studied in pens for 100 days to evaluate urea and urea-molasses supplements in terms of their effect on hay intake, rumen fermentation and liveweight changes. The hay contained 0.58 per cent nitrogen and had an apparent digestibility of 49.8 per cent. Supplements were made up in a liquid form and infused directly and continuously into the rumen so that on a daily basis 56 g urea with and without 500 g molasses, or 112 g urea with 500 g or 1000 g molasses was delivered. When urea alone was infused, rumen ammonia and plasma urea concentrations were increased (P &lt; 0.05) but the urea had no significant effect on liveweight change, on digestible organic matter intake (DOMI) or on the pattern of rumen fermentation. When infusions of urea and molasses were given, total DOMI was increased (P &lt; 0.08) and the pattern of rumen fermentation changed: total rumen volatile fatty acid (VFA) concentrations were increased (P &lt; 0.05), with an increased (P &lt; 0.05) molar proportion of propionate in one of the treatments. Neither urea nor urea and molasses infusions significantly increased the animal's intake of hay. Liveweight change was related (r= 0.60) to DOMI and it was estimated that steers in the experiment required 41 g DOM kg.-0.75 day-1 for maintenance of liveweight. This level of intake occurred only when supplements containing molasses were given. Overall, the results indicated that little improvement in growth of cattle or of their utilization of low quality pastures could be obtained from a urea supplement. However, there may be potential for molasses as a concentrate supplement for cattle grazing native pastures.

Some relationships between wool production, nitrogen intake and digestible organic matter intake

Two experiments are described in which the wool production of Merino wethers receiving roughage rations of varying quantity and average crude protein content was examined. The results support a hypothesis that wool growth response to supplementation of low quality roughage is more closely related to the total digestible organic matter intake than to the total nitrogen intake. The second experiment demonstrates that in the short term the efficiency with which dietary nutrients are used for wool production depends upon the direction of liveweight change of the sheep.

The effect on food intake and milk production of adding concentrates to the ration of pasture-fed cows

Abstract Nine lactating Jersey cows were each fed pasture to appetite indoors, and the effects of addition of 2.7 kg and 4.0 kg of a concentrate mixture/cow/day on voluntary intake and on milk yield and composition were determined in a 3 × 3 Latin square design. A further 4 Jersey cows with rumen flstulae were used to provide information on the effects of supplementing pasture with 2.7 kg of the concentrate mixture on rumen pH and volatile fatty acid proportions. Supplementation with the concentrates decreased the voluntary intake of pasture dry matter by 0.63 and 0.66 kg/kg concentrate dry matter fed at the lower and higher levels respectively. The total digestible organic matter intake of cows receiving concentrates was significantly higher (P < 0.01) than that of cows receiving pasture alone. Only minor changes occurred in rumen pH and volatile fatty acid proportions with the addition of 2.7 kg concentrate/cow/day to the pasture. The supplementary feeding had little effect on milk yield, and the small changes that occurred in milk composition with concentrate feeding were not statistically significant. Live-weight gain averaged 0.5 kg/day/cow throughout the experiment, but no significant differences in live-weight gain were detected between treatments.

The feed intake of milk cows I. Intake of winter rations during pregnancy and lactation and the influence of change to pasture

SUMMARY1. For 4 weeks before calving in December or January a group of 7 Ayrshire cows each received daily 6 lb. hay and silage to appetite, whilst a second group of 9 received the same roughages and 6–10 lb. concentrates. After calving, cows from both of the pre-calving treatments were placed in each of two post-calving groups of 8 cows. A High treatment received approximately 8 lb./day more concentrates at the same milk yield than the Low treatment. Both groups continued to receive 6 lb. hay/cow/day and silage to appetite. The cows were allowed to graze by day from 21 February and by day and night from 13 April. Hay, at 5 lb./cow/day and reducing rates of concentrates were offered until 8 May.2. Individual feed intakes were estimated from faecal output and digestibility. Direct measures of the intakes of different treatment groups on indoor feeding agreed fairly closely with the mean individual estimates.3. The digestible organic matter intake (DOMI) of 1,300 lb. cows in the last stages of pregnancy was increased from 10 up to 14–16 lb./day by giving 8–10 lb./day concentrates. Immediately after calving, the increases in DOMI compared with pre-calving levels were about 2.5 lb./day for cows which received concentrates before calving and 8.5 lb./day for cows which received no concentrates before calving.4. When all cows had calved and were in full milk production there were no significant differences in DOMI, milk yield or rate of live-weight gain attributable to pre-calving treatment. Mean DOMI on the High and Low post-calving treatments were 23.8 and 19.4 lb./day, mean fat-corrected milk yields 44.5 and 38.8 lb./day and mean rates of live-weight gain 05 and nil lb./day, respectively.5. DOMI increased by 0.7 and 4.9 lb./day for High and Low post-calving treatments when cows were turned out to night as well as day grazing, and milk yields increased by 1.0 and 2.2 lb./day respectively.6. Regression equations relating animal production and feed intake, and substitution rates of concentrate usage were calculated. Faecal output and DOMI were closely related to milk yield. When additional concentrates were given the resulting increase in total DOMI was greater when the bulk feed was of low digestibility than when it was of high digestibility.

The feed intake of milk cows II. The effect of roughage quality during late pregnancy and lactation

SUMMARY1. An experiment is described in which the individual feed intakes of 16 cows under winter housing conditions in yards, during the transition to spring grazing and on. summer grazing, were determined by faecal indexdigestibility methods. The influence of quality of feed before calving on intake and subsequent performance and the influence of pasture quality and availability on feed intake were included in the study.2. The provision of a diet of 67% organic matter digestibility, either as high quality hay or as low quality hay with concentrates, increased feed intake before calving when compared with a diet of low quality hay (digestibility 62%) alone. Compared with previous lactation yields the better diets were associated with the maintenance of milk yield, while the low quality hay diet before calving was associated with a 10%, but non-significant, reduction in milk yield.3. There was a marked rise in faecal output and digestible organic matter (DOM) intake after calving. During lactation, and especially on pasture, faecal output and DOM intake were both correlated with milk yield and metabolic live-weight. Total DOM intake was lower when the availability of feed was restricted and increased when feed was readily available; this increase was associated with a high maintenance requirement.4. When herbage with OM digestibility of 74–82% was consumed, faecal output rose with decreasing digestibility, but DOM intakes were relatively constant. Provided that efficient utilisation can be achieved, total utilisation per acre might be increased if herbage were grazed at the lower end of this range of digestibility.