Preferences for foods varying in macronutrients and tannins by lambs supplemented with polyethylene glycol

Supplemental polyethylene glycol (PEG) increases intake when animals eat foods high in tannins, but little is known about how PEG affects preference for foods that vary in concentrations of macronutrients and tannin. We investigated how varying macronutrients and tannins (commercially available extracts from quebracho trees) affected food intake, and we assessed the degree to which PEG (MW 3350) affected intake of tannin-rich foods by sheep. From 0715 to 1800 daily, lambs were offered diets that varied in concentrations of macronutrients: high energy/low protein (75% barley/25% alfalfa), medium energy/medium protein (35% barley/65% alfalfa), and low energy/high protein (100% alfalfa). Preference for these diets was determined in the absence of tannin, and then, in Trials 1 to 3, tannin was added in increasing concentrations (from 5 to 20%) to the diets with high and medium levels of energy. In Trial 4, tannin (10%) also was added to the low-energy diet. Lambs were supplemented with either 50 g of PEG mixed with 50 g of ground barley or 50 g of ground barley alone from 0700 to 1715 daily; lambs always consumed all of these supplements. In the absence of added tannins, all lambs preferred high energy/low protein > medium energy/medium protein > low energy/high protein. As tannin levels increased, preference for the high- and medium-energy foods decreased, and all lambs preferred foods that were lower in tannins and higher in protein. Lambs supplemented with PEG ate more macronutrients and tannins than unsupplemented lambs, and the effect became increasingly apparent as tannin levels increased from Trials 1 to 4. We conclude that the effectiveness of supplemental PEG may be low if alternative forages are equal or superior in nutritional quality and contain fewer metabolites with adverse effects. In such cases, animals would likely prefer alternatives to high-tannin foods.     

Intake of lambs offered ad libitum access to one of three iso-caloric and iso-nitrogenous mixed rations or a choice of all three foods

Modern practices for finishing livestock typically involve offering a single uniform food to large groups of presumably similar animals in an attempt to increase efficiency. Nevertheless, differences in physiology and behavior still cause variations in performance that may precipitate biological inefficiencies by not appreciating the importance of differences among individuals, the capacity of animals to select foods that meet ever-changing individual needs, and the dynamic nature of a nutrient's value to an animal. We examined intakes of groups of lambs offered a single food or three foods differing only in their proportions of cereal grains: High, 70%; Medium, 50%; Low, 40%. Foods consisted of the same ingredients (barley, corn, sugar beet pulp, alfalfa, soybean meal, grape pomace, feather meal, wheat straw), had similar levels of metabolizable energy (ME) and crude protein (CP), and met NRC requirements. We hypothesized that intake and performance would be greater when animals had a choice of foods because high grain concentrations would not limit intake of individuals unable to process high amounts of energy from grain. In general, lambs offered a Choice of the three foods ate more, converted food more efficiently, and cost less per unit gain than lambs fed the High food (P < 0.05). Animals fed the Low or Medium foods were intermediate in their responses between these two extremes. Within Choice, preference for High, Medium, and Low shifted from the beginning (21 d) to the finishing (21 d) periods of the trial. Though lambs in the Choice treatment preferred Low > Medium and High in the beginning stage of the trial, their preferences became pronounced as we increased the amount of grain in each food during the finishing period (P < 0.05). Collectively, our findings suggest improved intake, rate of gain, and feed efficiency can result when animals are allowed to select their diets from biochemically complementary foods, possibly enabling them to realize greater benefits than typically thought from inexpensive forages. In addition, offering animals choices is an alternative to feeding uniform diets of rapidly fermented energy, a major cause of illness in feedlots.     

Learned appetites for calcium, phosphorus, and sodium in sheep

If supplemental minerals are needed to promote optimal animal performance, what is the best way of providing them: free choice or in the diet? We hypothesized that herbivores discriminate among feeds containing Na, P, and Ca and modify their choices as a function of need. One group of lambs was fed a basal diet low in P and high in Ca (low P-high Ca), whereas another group was fed a basal diet high in P and low in Ca (high P-low Ca). After 73 d of exposure to the unbalanced diets, the lambs were conditioned by offering flavored grape pomace containing NaCl, CaCO(3), or NaH(2)PO(4). Preference for pomace + minerals was determined when all lambs were fed a basal diet of alfalfa pellets and barley grain (initial preference) and during 4 phases. Phases 1 and 2 occurred after 40 and 67 d of feeding the unbalanced basal diets, phase 3 occurred after conditioning with NaCl, CaCO(3), or NaH(2)PO(4), and phase 4 occurred 22 d after the groups were moved to 2 new (separate) locations so the animals in the different groups could not eat dirt, urine, or feces from the other pen. Preference for pomace did not differ between the groups during the initial preference tests (P = 0.62); both groups preferred NaCl > CaCO(3) = NaH(2)PO(4) (P < 0.001). As the study progressed, and lambs fed low P-high Ca had lower P and greater Ca concentrations in serum than lambs fed high P-low Ca (P < 0.001), the preference between groups diverged. In phase 2, lambs in high P-low Ca continued to prefer NaCl (P < 0.001), but lambs in low P-high Ca preferred NaH(2)PO(4) (P < 0.05). After conditioning, both groups preferred NaCl = NaH(2)PO(4) > CaCO(3) (P < 0.01 to 0.11). After the groups were moved to different locations, lambs fed low P-high Ca showed the lowest concentration (3.7 mg/dL) of inorganic P in serum for all phases (P < 0.001), and they preferred NaH(2)PO(4) > NaCl = CaCO(3) (P < 0.001). In contrast, lambs in high P-low Ca avoided NaH(2)PO(4) (P < 0.05). Lambs offered high P-low Ca showed a greater preference for CaCO(3) (P = 0.12) and NaCl (P < 0.05) and a lower preference for NaH(2)PO(4) compared with lambs fed low P-high Ca (P < 0.001). In summary, lambs discriminated among different flavored feeds containing NaCl, CaCO(3), and NaH(2)PO(4) and displayed preferences as a function of the mineral imbalance in their basal diets. Thus, it may be possible to feed Ca and P supplements free choice, such that individual animals within a group can manifest preferences based on their specific needs.     

Nutrient-specific preferences by lambs conditioned with intraruminal infusions of starch, casein, and water

We hypothesized that lambs discriminate between postingestive effects of energy and protein and associate those effects with a food's flavor to modify food choices. Based on this hypothesis, we predicted that 1) lambs would acquire a preference for a poorly nutritious food (grape pomace) eaten during intraruminal infusions of energy (starch) or protein (casein) and that 2) shortly after an intraruminal infusion of energy or protein (preload), lambs would decrease their preferences for foods previously conditioned with starch or casein, respectively. Thirty lambs were allotted to three groups and conditioned as follows. On d 1, lambs in each group received grape pomace containing a different flavor and water was infused into their rumens as they ate the pomace. On d 2, the flavors were switched so each group received a new flavor and a suspension of starch (10% of the DE required per day) replaced the water infusion. On d 3, the flavors were switched again, and a suspension of casein (2.7 to 5.4% of the CP required per day) replaced the starch infusion. Conditioning was repeated during four consecutive trials. Lambs in Trial 1 had a basal diet of alfalfa pellets (e.g., free access from 1200 to 1700) and 400 g of rolled barley. Lambs in Trials 2, 3, and 4 received a restricted amount of alfalfa pellets (990 g/d) as their basal diet. After conditioning, all animals received an infusion of water, and, 30 min later, they were offered a choice of the three flavors previously paired with water, starch, or casein. On the ensuing days, the choice was repeated, but starch, casein, and barley replaced the water preload. The nutrient density of the infused preloads was increased during consecutive trials. Lambs preferred the flavors paired with starch > water > casein during Trial 1 (P < .05) and the flavors paired with starch > casein > water during Trials 2 (P < .05), 3 (P < .001), and 4 (P < .001). Preloads of casein decreased preferences for flavors previously paired with casein (P < .10 [Trial 2]; P < .001 [Trial 3], and increased preferences for flavors paired with starch (P < .05 [Trial 2]; P < .001 [Trial 3]). Preloads of energy (barley) had the opposite effect (P < .05 [Trial 3]). These results indicate that lambs discriminated between the postingestive effects of starch and casein and associated the effects with specific external cues (i.e., added flavors) to regulate macronutrient ingestion.     

Energy source and ionophore supplementation effects on lamb growth, carcass characteristics, visceral organ mass, diet digestibility, and nitrogen metabolism.

In Exp. 1, 72 Targhee lambs (initial BW 22.1+/-.3 kg) were used to determine the effects of energy source (alfalfa pasture vs limit-fed, all-concentrate) and ionophore addition on performance, visceral organ mass, and carcass characteristics. There were no differences (P > . 10) in ADG or gain/ feed due to ionophore supplementation. Lambs that grazed alfalfa had greater (P < .05) liver, omasum, abomasum, small intestine, cecum, and large intestine weights than did lambs fed the concentrate diet. Lambs fed the concentrate diet had greater (P < .01) hot carcass weights, larger (P < .01) loin eye areas, and greater (P < .001) dressing percentages than lambs that grazed alfalfa. In Exp. 2, lambs offered the concentrate diet had greater (P < .001) DM and OM digestibilities than lambs offered alfalfa (89.5 and 91.1 vs 72.4 and 74.2%, respectively). Apparent and true N digestibilities were greater (P < .001) for the concentrate diet than for alfalfa (90.9 and 101.7 vs 77.7 and 91.9%, respectively). Likewise, grams of N retained per day were twice as great (P < .001) with the concentrate diet than with alfalfa (14.9 vs 6.0 g/ d). The greater visceral organ mass and resulting increases in energy and protein requirements in lambs that grazed alfalfa were probably responsible for the lesser hot carcass weight and dressing percentage compared with lambs fed 100% concentrate.     

Changes in preferences of gestating heifers fed untreated or ammoniated straw in different flavors.

We determined how a food's flavor and digestibility, along with an animal's recent experiences, influenced food preference and intake. In three experiments, pregnant heifers were fed a basal ration (7.75 kg/animal) of alfalfa, barley, corn silage, and a vitamin/mineral supplement from 1500 to 2200. Exp. 1 determined the influence of recent exposure to flavored straw. Animals were divided into two groups (n = 16/group) and fed either untreated or ammoniated straw with digestibilities of 43 and 58%, respectively. Within each group, half of the heifers were fed maple-flavored straw and the other half were fed coconut-flavored straw from 1100 one day to 0900 the next day, with no base ration. We then offered straw in both flavors from 1000 to 1200 for the next 5 d. Animals fed maple-flavored straw for 1 d generally preferred coconut- over maple-flavored straw for the next 5 d, whereas animals previously fed coconut-flavored straw preferred maple-flavored straw (P < 0.001). The change in preference was stronger when animals were fed untreated compared with ammoniated straw. Experiments 2 and 3 determined the influence of offering straw in different flavors, either in sequence (Exp. 2) or simultaneously (Exp. 3). In Exp. 2, we offered heifers (n = 16) straw in three flavors (maple from 0900 to 1100, coconut from 1100 to 1300, and unflavored from 1300 to 1500) and compared their intake with that of heifers (n = 16) offered unflavored straw throughout the day. In Exp. 3, we compared intake of heifers (n = 16) simultaneously offered straw in three flavors (coconut, maple, and unflavored) with that of heifers (n = 16) offered only unflavored straw from 1000 to 1500. In both experiments, straw intake and preference differed between heifers offered straw in a variety of flavors as opposed to only unflavored straw (P < 0.05), but animals fed a variety of flavors did not consistently eat more than those fed only one flavor. During a post-trial preference test, heifers previously restricted to straw in one flavor for 5 d preferred straw in alternative flavors, whereas heifers fed straw in all three flavors preferred unflavored straw. Changes in preference were stronger for heifers fed untreated compared with ammoniated straw. Collectively, our results suggest that palatability, as evidenced by changes in preference and intake, is dynamic and depends on a food's flavor and nutritional quality and an animal's recent experiences with the food.     

Influence of free-choice vs mixed-ration diets on food intake and performance of fattening calves.

Research findings and management recommendations typically emphasize responses of the "average" individual, yet more than half of the animals in a group may differ significantly from the mean regarding food preference and intake. The productivity of a herd may be adversely affected if animals differing from the mean are fed a uniform diet formulated to meet the needs of the "average" individual. We compared the intake and performance of beef calves offered a choice or no choice among foods. Diets consisted of ad libitum access to either a chopped, mixed ration of rolled barley (31.3%), rolled corn (31.3%), corn silage (15.5%), and alfalfa hay (18.9%) (n = 16 calves) or a choice among those foods offered individually (n = 15 calves). Averaged across the 63-d trial, the two groups did not differ in ratios of protein to energy ingested (43 vs 43 g CP/Mcal ME; P = 0.50), but preference for foods high in energy or protein varied markedly for animals fed free-choice: on d 21 they had protein:energy ratios higher than those of animals fed the mixed ration, on d 2 the ratios were equal, and on d 40 they had protein:energy ratios lower than those of animals fed the mixed ration. Throughout the trial, no two animals consistently chose the same ingredients, and none selected a diet similar to the nutritionally balanced mixed ration, yet each animal ate a diet adequate to meet its needs. Animals offered the mixed ration tended to eat more than animals offered a choice (109 vs 102 g/kg MBW/d; P = 0.10), but they did not gain at a faster rate (0.89 vs 0.92 kg/d; P = 0.65). Gain/unit of food consumed also was similar for both groups (0.09 vs 0.10 kg/kg; P = 0.38). However, food cost/day was higher for animals fed the mixed ration than for those offered a choice ($1.58 vs $1.36; P = 0.03). Consequently, cost/kilograms of gain was higher for the mixed ration than for the choice group ($1.84 vs $1.49/kg; P = 0.045). These findings suggest that 1) animals can more efficiently meet their individual needs for macronutrients when offered a choice among dietary ingredients than when constrained to a single diet, even if it is nutritionally balanced; 2) transient food aversions compound the inefficiency of a single mixed diet by depressing intake even among animals suited to that nutritional profile; and 3) alternative feeding practices may allow producers to efficiently capitalize on the agency of animals, thus reducing illness and improving performance.     

Digestibility and dry matter intake of diets containing alfalfa and kenaf

Two experiments were conducted to determine the dietary value of pellets containing kenaf (Hibiscus cannabinus cv. 'Everglade 41') hay. Averaged across both experiments, kenaf pellets contained 82.6% kenaf hay, 16.6% liquid molasses, and 0.8% mineral oil. The chemical composition of the kenaf pellet was 12.6% crude protein (CP), 41.2% neutral detergent fiber (NDF), and 14.4% acid detergent fiber (ADF). In Exp. 1 (digestion and N balance trial), 18 lambs (body weight [BW] = 36.4 kg) were blocked by BW. Lambs were randomly assigned within a block to Diet 1 (59.5% corn and 40.5% alfalfa pellet), Diet 2 (59.7% corn, 28.4% alfalfa pellets, and 11.9% kenaf pellets), or Diet 3 (59.6% corn, 16.5% alfalfa pellets, and 23.9% kenaf pellets). Diets were formulated so that CP was the first-limiting nutrient. Each diet was limit-fed at 2.4% of BW. Replacing alfalfa pellets with kenaf pellets tended to decrease (P = 0.10) CP and ADF intakes, but increased (P = 0.01) DM digestibility. Diet had no effect (P = 0.33) on N balance. In Exp. 2 (dry matter [DM] intake trial), 32 lambs (BW = 30.4 kg) were blocked by gender and BW. Within a block, lambs were randomly assigned to one of four diets in a 2 x 2 factorial arrangement. Main effects were hay (bermudagrass or fescue) and supplemental protein source (kenaf or alfalfa pellets). Lambs were housed in individual pens with ad libitum access to the assigned hay. Supplemental protein was fed (185 g of DM) once daily. Hay intake was measured weekly for 8 wk. Lambs consumed more (P = 0.002) fescue than bermudagrass hay (743 vs 621 g/ d). Lambs fed fescue hay gained weight more rapidly (P = 0.001) than lambs fed bermudagrass hay (120 vs 72 g/d). Hay intake and ADG were similar (P = 0.90) for lambs fed alfalfa or kenaf pellets. Kenaf hay mixed with molasses and mineral oil can be formed into a pellet. In the diets used in this experiments, kenaf pellets can replace alfalfa pellets in diets fed to lambs without altering forage intake, gain, or N retention.     

Effects of dietary protein level and clinoptilolite on the weight gain and liver mineral response of growing lambs to copper supplementation

Growing male Synthetic I (1/2 Finnish Landrace x 1/4 Dorset x 1/4 Rambouillet) lambs were used in two experiments (64 lambs in Exp. 1 and 63 in Exp. 2) to test the hypothesis that dietary CP level (9 or 14% of diet as fed) and(or) clinoptilolite (clino; 0 or 2% of diet) affects growth and tissue mineral concentrations of growing lambs fed supplemental Cu. Lambs were individually fed their respective diets ad libitum and killed after 12 wk (Exp. 1) or 16 wk (Exp. 2) to obtain carcass measurements, organ weights and liver mineral concentrations. In Exp. 1, 20 ppm added Cu (as CuSO4.5H2O) increased mortality and depressed BW gain (P less than .01) and daily feed intake (P less than .05) in the presence or absence of clino and at both levels of CP. Liver Cu concentration was greater (P less than .01) in lambs fed added Cu than in those not fed Cu (408 ppm vs 110 ppm, respectively). Neither CP nor clino affected liver Cu concentration. Clinoptilolite increased daily gain of lambs fed high CP but not low CP (P less than .01). In Exp. 2, clino in the diet had no effect on daily gain or daily feed, but 20 ppm Cu addition depressed daily gain (P less than .01) and gain/feed (P less than .07). Organ weights and levels of trace elements other than Cu in the liver generally were not affected by diet in either experiment. It is concluded that high dietary CP or 2% dietary clino did not protect against toxic signs of Cu when Cu was added to the basal diet (10 ppm Cu) at 10 or 20 ppm.     

Roles of novelty, generalization, and postingestive feedback in the recognition of foods by lambs

Ruminants select foods higher in nutrients and lower in toxins than the average of what is available whether fed in confinement or foraging on pastures or wild lands. Our objective was to better understand how sheep learn to select the most nutritious foods when they concurrently ingest different foods. We hypothesized that novelty and generalization are two ways sheep discriminate among foods. The first experiment determined whether lambs offered two foods in a meal (one a novel-flavored food and the other a familiar food) acquired a preference for the novel-flavored food following an infusion of energy (starch) into the rumen. Lambs did not increase preference for the novel-flavored food when the amount of starch infused (150 g) was held constant (P > 0.05). However, when the amount of starch infused was made directly proportional to the amount of novel-flavored food ingested, lambs quickly formed a preference for the novel-flavored food (P < 0.001). The second experiment determined whether lambs generalized preferences from familiar to novel foods. Lambs fed coconut-flavored milo grain for 51 d subsequently preferred coconut-flavored straw to plain straw (P < 0.001). Conversely, lambs that were not fed coconut-flavored milo grain preferred plain to coconut-flavored straw (P < 0.001). Lambs infused with a source of energy (starch, 100 g/[lamb x d]) consumed more coconut-flavored straw and less plain straw than lambs that had no infusions or lambs infused with a toxin (LiCl, 100 mg/kg BW; P < 0.05). Lambs infused once with LiCl had the lowest preference for coconut-flavored straw (P < 0.05). Lambs conditioned with starch had the highest intakes of coconut-flavored straw, even after starch infusions were suspended (P < 0.1). When straw was replaced by an energy-dense food (wheat grain), all lambs equally preferred coconut-flavored grain to plain grain (P < 0.001). Collectively, our results suggest that lambs learned to prefer a novel-flavored food when the amount of energy reward was contingent on the amount of novel-flavored food ingested, and that they generalized from familiar to unfamiliar foods based on common flavor cues. Once generalization occurred, postingestive feedback from nutrients and toxins calibrated preference according to the food's utility.     

Effects of dietary lipid type on muscle fatty acid composition, carcass leanness, and meat toughness in lambs

Isonitrogenous amounts of two protein sources differing in rumen degradation rate and in lipid composition were fed to sheep with or without a rapidly fermentable cereal grain. The effects on intake, carcass leanness, and muscle fatty acid (FA) composition were examined. Thirty-eight crossbred wether lambs (9 mo, 35 to 48 kg) were allocated by stratified randomization to six treatment groups: 1) basal diet of alfalfa hay:oat hay (20:80) ad libitum = basal; 2) basal + lupin (358 g DM/d) = lupin; 3) basal + fish meal (168 g DM/d) = fish meal; 4) basal + barley (358 g DM/d) = barley; 5) basal + barley + lupin (179 + 179 g DM/d) = barley/lupin; or 6) basal + barley + fish meal (179 + 84 g DM/d) = barley/ fish meal. Lambs were fed individually. Dietary treatments were imposed for 8 wk, and the supplements were offered at 2-d intervals. Daily feed intake and weekly BW of lambs were recorded. At the end of the feeding period lambs were slaughtered after an overnight fast. Hot carcass weight (HCW) and fat depth (GR; total fat and muscle tissue depth at 12th rib, 110 mm from midline) were recorded. At 24 h postmortem samples of longissimus thoracis (LT) and longissimus lumborum (LL) muscles were taken from chilled (4 degrees C) carcasses for the assessment of FA composition and meat tenderness, respectively. Lambs fed lupin or fish meal with or without barley had heavier slaughter weights (P < 0.004) and HCW (P < 0.001) than lambs fed basal or barley when initial BW was included as a covariate. The lupin diet also resulted in heavier carcasses (P < 0.05) than the fish meal or barley/fish meal diets. With GR as an indicator, fish meal and barley/ fish meal diets produced leaner carcasses (P < 0.01) than lupin and barley/lupin lambs. Long-chain n-3 FA content [20:5n-3 (P < 0.001), 22:5n-3 (P < 0.003), and 22:6n-3 (P < 0.001)] in the LT muscle were substantially higher with the fish meal and barley/fish meal diets, whereas muscle total n-6 FA was increased (P < 0.003) by lupin and barley/lupin compared with all other diets. Thus, increased muscle long-chain n-3 FA content occurred without an increase in fatness measured as GR, whereas increased muscle n-6 FA content was associated with an increase in carcass fatness. Under these circumstances, a reduction in carcass fatness had no effect on meat tenderness measured as Warner-Bratzler shear force.     

Interactions between mild nutrient imbalance and taste preferences in young ruminants

Thirty-two crossbred lambs (BW = 31.2 ± 4.7 kg; 16 females, 16 males) housed in individual pens were used to investigate the relationship between nutrient supply and taste preferences in ruminants. Experiment 1 determined whether an imbalanced CP supply would alter preferences for feeds containing flavors designed to elicit either umami (U) or a mixture (1/3:1/3:1/3) of umami, sweet, and bitter (M) tastes. Lambs were randomly allocated to either a low (LP; 10.9% CP) or a high (HP; 20.4% CP) CP diet for 21 d. Afterward, lambs were presented during 21 d with a choice of the same LP or HP diet unflavored (LPC or HPC, respectively) or flavored (0.1% as fed) with U (LPU or HPU, respectively) or M (LPM or HPM). Experiment 2 determined the influence of CP status on preference for dietary CP, bitter taste, and sweet taste elicited by sucrose or a noncaloric sweetener. In test 1, sixteen lambs previously fed LP or HP for 42 d in Exp. 1 could choose between the HP and LP diets. In test 2, the remaining 16 lambs from Exp. 1 were offered a choice between unflavored LP or HP diets or the same diets flavored (0.066% as fed) with a bitter flavor. In test 3, the 16 lambs from test 1 were offered a choice between an unflavored diet (LP or HP) and the same diet flavored with sucrose (0.2%) or a noncaloric sweetener (0.066%). In Exp. 1, when offered a choice, all lambs showed a preference (P < 0.05) for the unflavored diet except for LP lambs, who clearly preferred (P < 0.05) LPU (72% of total DMI) over LPC. However, preference for LPU progressively decreased (P < 0.05) as time of exposure to the choice increased. In Exp. 2 (test 1), lambs previously fed LP progressively increased (P < 0.05) total DMI when presented with LP and HP, whereas consumption was constant for lambs previously fed HP and offered a choice of LP and HP diets. At the onset of test 2, lambs fed LP progressively reduced (P < 0.05) preference for the bitter flavor from 53 to 34%. In test 3, lambs previously fed LP diets consumed less (P < 0.05) sweetener- than sucrose-supplemented diet, whereas lambs previously offered HP diets consumed more sweetener- than sucrose-supplemented diet. In summary, protein-restricted lambs were able to differentiate and increase consumption of U-flavored feeds. However, this increase disappeared over time. These results indicate that lambs are able to sense dietary CP content and modulate short-term consumption of flavored feeds based on their nutrient requirements.     

Growth performance, diet apparent digestibility, and plasma metabolite concentrations of barrows fed corn-soybean meal diets or low-protein, amino acid-supplemented diets at different feeding level

Two experiments, each with 36 barrows with high-lean-gain potential, were conducted to evaluate apparent nutrient digestibilities and performance and plasma metabolites of pigs fed corn-soybean meal diets (CONTROL) and low-protein diets. The low-protein diets were supplemented with crystalline lysine, threonine, tryptophan, and methionine either on an ideal protein basis (IDEAL) or in a pattern similar to that of the control diet (AACON). Amino acids were added on a true ileally digestible basis. The initial and final BW were, respectively, 31.5 and 82.3 kg in Exp. 1 and 32.7 and 57.1 kg in Exp. 2. In Exp. 1, the CONTROL and IDEAL diets were offered on an ad libitum basis or by feeding 90 or 80% of ad libitum intake. Pigs were fed for 55 d. In Exp. 2, the CONTROL, IDEAL, and AACON diets were offered on an ad libitum basis or by feeding 80% of the ad libitum intake. Pigs were fed for 27 d. Pigs fed the CONTROL diet had greater (P < 0.05) ADG and feed efficiency (G/F) than pigs fed the IDEAL (Exp. 1 and 2) and AACON diets (Exp. 2). As the level of feed intake decreased, ADG decreased (P < 0.05), but G/F tended to improve (P < 0.10) for pigs fed 90% of ad libitum in Exp. 1 and for pigs fed 80% of ad libitum in Exp. 2. In Exp. 1, the apparent total tract digestibilities of DM and energy were greater (P < 0.01) for pigs fed the IDEAL diet than for pigs fed the CONTROL diet. In Exp. 2, the apparent total tract digestibility of protein was greatest in pigs fed the CONTROL diet (P < 0.05) and was greater (P < 0.05) in pigs fed the AACON diet than in pigs fed the IDEAL diet. Plasma urea concentrations were lower in pigs fed the IDEAL diet than in pigs fed the CONTROL diet, regardless of feeding level. For pigs fed the CONTROL diet, plasma urea concentrations were lower when feed intake was 80% of ad libitum (diet level, P < 0.01). In summary, pigs fed the IDEAL and the AACON diets gained less and had lower plasma urea concentrations than pigs fed the CONTROL diet. Based on these data, it seems that the growth potential of pigs fed the IDEAL and AACON diets may have been limited by a deficiency of lysine, threonine, and(or) tryptophan and that the amino acid pattern(s) used was not ideal for these pigs.     

Effect of diets containing n-3 fatty acids on muscle long-chain n-3 fatty acid content in lambs fed low- and medium-quality roughage diets

In two experiments, each with 32 cross-bred ([Merino x Border Leicester] x Poll Dorset) wether lambs (26 to 33 kg weight range), animals were randomly assigned to one of four treatments. A mixture of lucerne chaff:oaten chaff was used as a basal diet, offered in different ratios. Animals were allowed to consume on a free-access basis in Exp. 1 or 90% of ad libitum intake in Exp. 2 in order to provide a low- (6.5 MJ ME/d) and medium- (9.5 MJ ME/d) quality basal diet, respectively. Isoenergetic amounts of lipid supplements, fish meal (80 g DM), canola meal (84 g DM), and soy meal (75 g DM) were tested in Exp. 1. In Exp. 2, fish meal (9% DM), unprotected rapeseed (7% DM), and protected canola seed (6% DM) were fed as supplements. At the end of 53-d (Exp. 1) or 46-d (Exp. 2) experimental periods, lambs were slaughtered at a commercial abattoir and at 24 h postmortem longissimus thoracis (LT) muscle was collected for the analysis of fatty acid (FA) composition of structural phospholipid and storage triglyceride fractions. Fish meal diet increased LT muscle long-chain n-3 FA content by 27% (P < 0.02) in Exp. 1 and 30% (P < 0.001) in Exp. 2 compared with lambs fed the basal diet, but fish meal decreased (P < 0.01) the n-6 FA content only in Exp. 1. Soy meal and protected canola seed diets increased (P < 0.01) LT muscle n-6 FA content but did not affect long-chain n-3 FA content. Longissimus thoracis muscle long-chain n-3 FA were mainly deposited in structural phospholipid, rather than in storage triglyceride. In both Exp. 1 and Exp. 2, the ratio of n-6:n-3 FA in LT muscle was lowest (P < 0.01) in lambs fed fish meal supplement compared with all other treatments. Protected canola seed diet increased the ratio of n-6:n-3 FA (P < 0.01) and PUFA:saturated fatty acid (P < 0.03) content from those animals fed the basal, fish meal, and unprotected rapeseed diets in Exp. 2. This was due to an increase in muscle n-6 FA content, mainly linoleic acid, of both phospholipid (P < 0.001) and triglyceride (P < 0.01) fractions and not to an increase in muscle n-3 FA content. The results indicate that by feeding fish meal supplement, the essential n-3 FA can be increased while lowering the ratio of n-6:n-3 content in lamb meat to an extent that could affect nutritional value, attractiveness, and the economic value of meat.     

Effects of supplementing with calcium salts of palm oil fatty acids or hydrogenated tallow on ewe milk production and twin lamb growth

Two experiments were conducted with Polypay ewes nursing twin lambs to evaluate the effects of supplementing fat (calcium salts of palm oil fatty acids or hydrogenated tallow) on ewe lactation. In Exp. 1, ewes were fed a 52% concentrate:48% hay-based diet (as-fed basis) consisting of alfalfa hay (n = 4), endophyte-free fescue hay (n = 4), or fescue hay with 3.7% fatty acids (n = 4) from d 4 to 56 of lactation. In Exp. 2, ewes were fed similar diets that had endophyte-free fescue hay (n = 6), fescue hay with 3.7% fatty acids (n = 5), or fescue hay with 3.1% tallow (n = 6) from d 14 before lambing until d 57 of lactation. Diet formulations with supplemental fat were more nutrient dense, and treatments were fed to meet ewe nutrient requirements; this caused diets with added fat to be offered at 10 and 17% lower rates than unsupplemented diets in Exp. 1 and 2, respectively. Lambs were maintained to consume only ewe milk. Ewe milk production and composition were determined using a portable milking machine following a 3-h separation from lambs. In Exp. 1, milk fat content was increased (P < 0.01) when ewes consumed fescue hay with fatty acids vs. the fescue hay diet (11.4 vs. 8.3%). Ewes fed fescue hay with fatty acids lost the most (P < 0.05) weight over lactation (-8.6 kg) compared with ewes fed the alfalfa hay (-2.4 kg) and fescue hay (-3.8 kg) diets. Other milk measures, lamb gain, and production efficiencies were not changed. In Exp. 2, ewes supplemented with fatty acids produced more (P < 0.05) milk fat than those fed tallow (290 vs. 210 g/d). The proportion of synthesized milk fat 14:0 was decreased (P < 0.01), but the percentage of incorporated 16:0 increased (P < 0.05) when fatty acids were fed. Dietary fat digestibility by ewes was increased (P < 0.01) by fatty acid supplementation but decreased (P < 0.01) when tallow was added. Although ewe weight measures were not changed in Exp. 2, twin lamb gain per ewe organic matter intake was most efficient (P < 0.05) when ewes were supplemented with fatty acids. Results suggest that feeding hydrogenated tallow decreased nutrient availability for ewe milk fat production. A complete diet based on endophyte-free fescue hay can replace a traditional alfalfa hay diet, whereas supplementing with the calcium salts of palm oil fatty acids may be more feasible when energy is limiting during ewe lactation.     

Effect of dietary cation-anion difference on urinary pH, feedlot performance, nitrogen mass balance, and manure pH in open feedlot pens

Six experiments were conducted to evaluate dietary cation-anion difference (DCAD) in concentrate diets on urinary pH, feedlot performance, and N mass balance. In Exp. 1, 15 wether lambs (33.5 ± 3.0 kg) in five 3 × 3 Latin squares were fed a basal diet of 82.5% dry-rolled corn (DRC), 7.5% alfalfa hay, 5% molasses, and 5% supplement with different proportions of anionic and cationic salts. The DCAD was -45, -24, -16, -8, 0, +8, +16, +24, +32, and +40 mEq per 100 g of DM with the control basal diet (DCAD = +8) included in each square. Urinary pH increased (cubic, P < 0.01) as DCAD increased and DMI increased linearly (P < 0.01) with increasing DCAD. In Exp. 2 and 3, 8 Holstein steers (312 ± 24 kg) were used in 2 consecutive 4 × 4 Latin squares. Steers were fed either the same basal diet as Exp. 1 or a basal diet with 20% wet distillers grains (WDGS) replacing DRC. In Exp. 2, DCAD was adjusted to -2, -12, and -22 mEq per 100 g of DM from the basal diet (DCAD = +8) and DCAD was adjusted in Exp. 3 to -12, -22, and -32 mEq per 100 g of DM from the basal WDGS diet (DCAD = -2). Urinary pH decreased linearly as DCAD decreased (P < 0.01) in both experiments, whereas DMI decreased linearly in Exp. 2 (P = 0.02) but not Exp. 3 (P = 0.96). In Exp. 4, 6 crossbred steers (373 ± 37 kg) were used in a 2-period crossover design. Steers were fed the same basal diet as Exp. 3 with DCAD of -16 (NEG) and +20 (POS) mEq per 100 g of DM. Urinary pH and DMI (P < 0.05) were less for cattle fed the NEG diet compared with POS. In 2 experiments, steers (n = 96 each) were fed NEG or POS as calves (260 ± 22 kg of BW) for 196 d from November to May (Exp. 5) or as yearlings (339 ± 32 kg of BW) for 145 d from June to October (Exp. 6). Final BW, DMI, ADG, and HCW were not different (P > 0.11) among treatments in either experiment. Efficiency of BW gain was increased (P = 0.05) for steers fed NEG compared with POS in Exp. 5 but was not different (P = 0.11) in Exp. 6. Amount of N intake, retention, excretion, and manure N (kg/steer) were not different (P > 0.11) among treatments in either experiment. Manure pH (soil, feces, and urine) was decreased (P < 0.01) in pens fed NEG compared with POS in both experiments. Amount of N lost (kg/steer) was not different (P = 0.44) in Exp. 5, but tended (P = 0.09) to be 10.6% greater for POS compared with NEG in Exp. 6. Urinary pH was decreased by reducing DCAD, but this had minimal effect on N losses in open feedlot pens in these experiments.     

Effect of level of intake and supplemental barley on marker estimates of fecal output using an intraruminal continuous-release chromic oxide bolus

Sixty wethers (average BW = 45 kg) fitted with fecal collection bags were used in four experiments to evaluate the ability of a intraruminal continuous-release chromic oxide bolus to predict fecal DM output. In Exp. 1, 18 wethers housed in metabolism crates were fed barley at either 0, 100, or 200g/d and allowed ad libitum consumption of alfalfa pellets. In Exp. 2, 18 wethers were housed in metabolism crates and fed alfalfa pellets at either 70, 85, or 125% of pre-study ad libitum consumption. In Exp. 3, 12 wethers grazed a sagebrush-bunchgrass range and were individually fed barley at 0 or 200 g/d. In Exp. 4, 12 wethers grazed either an ungrazed (383 kg/ha herbaceous biomass) or a heavily grazed (175 kg/ha herbaceous biomass) sagebrush-bunchgrass range. Experiments 1 and 2 were balanced 3 x 3 Latin squares, and Exp. 3 and 4 were crossover designs. Chromium content was determined in rectal grab samples. Treatment effects were compared using marker-estimated fecal output divided by total fecal collection, multiplied by 100, as the dependent variable. Accuracy of the estimate was verified by comparing marker-estimated fecal output with total fecal collection using a paired t-test. In Exp. 1 and 2, treatments were different (P less than .05). No differences (P greater than .50) were detected in Exp. 3 and 4. In Exp. 1, 2, and 3 accuracy was different (P less than .02) among wethers within study and treatment. Only in Study 4 were minor or no differences (P greater than .09) in accuracy found.(ABSTRACT TRUNCATED AT 250 WORDS)     

Terpenes and carbohydrate source influence rumen fermentation, digestibility, intake, and preference in sheep

We hypothesized that toxins and nutrients in foods interact to influence foraging behavior by herbivores. Based on this hypothesis we predicted that 1) terpenes in big sagebrush (Artemisia tridentata) influence intake and preference in sheep for diets varying in sources of nonstructural (barley grain) and structural (sugar beet pulp) carbohydrates, and 2) these effects are due to the differential effects of terpenes on fermentation products and apparent digestibility of each class of carbohydrates. Lambs were fed 2 isoenergetic and isonitrogenous diets with varying proportions of the same ingredients (beet pulp- and barley grain-based diet) or offered a choice between the 2 diets; all feeds were fed without and with terpenes, in consecutive periods. We also compared intake and preference of the beet pulp-and barley-based diets before and after the lambs ate a meal of sagebrush. Finally, we assessed the effect of terpenes on ruminal variables and in vivo digestibility. Lambs ate less when fed beet pulp or when they were offered a choice of diets with terpenes (P < 0.001), and intake of the beet pulp-based diet was the most affected (P < 0.05). Lambs preferred the beet pulp-to the grain-based diet with terpenes, but their preference reversed when terpenes were removed from the diets (P < 0.05). When lambs were offered both diets, intake and preference did not differ (P > 0.20) before eating sagebrush, but they preferred the beet pulp-based diet after eating sagebrush (P < 0.05). Intake of sagebrush did not differ among groups consuming the test diets (P = 0.21). Addition of terpenes to both diets increased the digestibility of DM, NDF, and ADF and decreased concentrations of total VFA and acetate (P < 0.05). Terpenes also depressed butyrate concentration in the barley-based diet (P < 0.05). Propionate concentrations were not affected by terpenes in either feed (P = 0.63). In summary, the predominant type of feed ingredient (beet pulp, grain) ingested with terpenes influenced fermentation products, intake, and preference in lambs. The source of energy from supplements, or other plants in the diet, is likely to influence intake and preference for sagebrush in sheep foraging on rangelands. Moreover, ingesting terpenes from sagebrush may also influence intake and preference for other plant species or supplements.     

Body composition and tissue accretion rates of barrows fed corn-soybean meal diets or low-protein, amino acid-supplemented diets at different feeding levels

Two experiments, each with 39 high-lean-gain potential barrows, were conducted to evaluate the organ weights, body chemical composition, and tissue accretion rates of pigs fed corn-soybean meal diets (CONTROL) and low-protein diets supplemented with crystalline lysine, threonine, tryptophan, and methionine either on an ideal protein basis (IDEAL) or in a pattern similar to that of the control diet (AACON). Amino acids were added on a true ileally digestible basis. The initial and final BW were, respectively, 31.5 and 82.3 kg in Exp. 1 and 32.7 and 57.1 kg in Exp. 2, and pigs were fed for 55 and 27 d in Exp. 1 and 2, respectively. In Exp. 1, the CONTROL and IDEAL diets were offered on an ad libitum basis, or by feeding 90 or 80% of ad libitum intake. In Exp. 2, the CONTROL, IDEAL, and AACON diets were offered on an ad libitum basis, or by feeding 80% of the ad libitum intake. Three pigs were killed at the start of the experiments and three from each treatment were killed at the end of each experiment to determine body chemical composition. In both trials, the whole-body protein concentration (g/kg) and the accretion rates of protein (g/d) were greater (P < 0.05) for pigs fed the CONTROL than for pigs fed the IDEAL and AACON diets. In Exp. 1, pigs fed the CONTROL diet had a trend (P < 0.10) for greater water and lower lipid concentration and had greater (P < 0.05) water and ash accretion rates. Whole-body protein concentration was greatest (P < 0.05) in pigs fed at 80% of ad libitum, but protein, water, and ash accretion rates were greatest (P < 0.05) in pigs allowed ad libitum access to feed. In summary, pigs fed the IDEAL and the AACON diets had less protein in the body and lower protein accretion rates than pigs fed the CONTROL diet. It seems that reductions in protein deposition in pigs fed the IDEAL and AACON diets may have been due to a deficiency of one or more essential amino acids or possibly to increases in the NE for metabolic processes leading to increases in adipose tissue deposition.     

Influence of two levels of enzyme preparation on ruminal fermentation, particulate and fluid passage and cell wall digestion in wether lambs consuming either a 10% or 25% grain diet

Effects of a fungal enzyme preparation on ruminal fermentation, digesta kinetics and cell wall digestion were studied. Either 0, 22 or 25 g/d of enzyme preparation was offered to nine ruminally cannulated Rambouillet or Columbia wether lambs (avg wt 28.6 kg) in two randomized complete block experiments. An alfalfa hay-corn mixture at 2.1% of body weight (10% corn) was used in Exp. 1. In Exp. 2, 2.7% of body weight (25% corn; Exp. 2) was fed. Ruminal samples were collected at 0, 4, 8, 12 and 24 h postfeeding on d 17 of each 22-d period to measure fluid dilution rate and fermentation characteristics. An intraruminal dose of Yb-labeled hay followed by fecal sampling on d 19 through 22 was used to estimate particulate passage and fecal output. Ruminal pH, NH3 concentrations, total volatile fatty acid and proportion of individual acids were not influenced (P greater than .10) by the addition of either level of enzyme preparation in either Exp. 1 or 2. Dry matter digestibility also showed no effect (P greater than .10) of enzyme preparation added to either diet. In Exp. 1, wethers receiving 35 g/d of the enzyme preparation had greater cell wall digestion (49.8%; P less than .05) than wethers receiving either 22 g/d or no enzyme preparation (45.7 and 42.9%, respectively). In Exp. 2, with a 25% corn diet, no influence (P greater than .10) of enzyme preparation was noted on cell wall digestibility. Particulate and ruminal fluid passage rate parameters remained unchanged (P greater than .10) by the addition of either level of enzyme preparation, regardless of the diet fed.(ABSTRACT TRUNCATED AT 250 WORDS)