Dietary effects on body weight, feed intake and diurnal feeding behavior of genetically obese rats.
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Animals↗
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The voluntary feed intake of pigs given feeds based on wheat bran, dried citrus pulp and grass meal, in relation to measurements of feed bulk.
Two experiments were carried out to investigate the capacities of pigs for bulky feeds. In Expt 1 fifteen pigs were offered, from 12 to 25 kg live weight, ad lib. access to one of five feeds which were made by progressively diluting a high-quality feed with wheat bran. Intake initially increased, and then declined, as the proportion of wheat bran was increased. The pigs became better able to accommodate to the more bulky feeds over time. In Expt 2 thirty-six pigs, initially of 12 kg live weight, were used. The feeds were the same high-quality basal feed as in Expt 1 and three others made almost entirely of either wheat bran, dried grass or dried citrus pulp, respectively. The equal-parts mixtures of each of these three bulky feeds with the basal feed were also made to give three series of feeds each comprising the basal, the mixture and the bulky feed. The three feeds in each series were given ad lib. to twelve pigs in a design of two replicated Latin squares with three time-periods. Within each series, and across periods, the intakes of the feeds that were limiting intake were directly proportional to live weight and so a scaled intake, expressed as g/kg live weight per d, was calculated. Across the six limiting feeds, scaled intakes in the final 5 d of each period, when the pigs were in equilibrium with their feeds, were directly proportional to the reciprocal of the water-holding capacities (WHC) of the feeds, as measured by a centrifugation method. There were large effects of feed changes on intake, in the short term, with previous experience of a bulky feed leading to higher intakes of another bulky feed. The intake of the basal feed was not affected by the feed given previously. It was concluded that: (a) the time of adaptation to bulky feeds needs to be considered when attempting to measure, or predict, the rates of intake on different bulky feeds and, (b) the WHC of the feeds could be an appropriate measurement of 'bulk' responsible for limiting their intake, and could be used to predict the maximum feed intake capacity of pigs on different bulky feeds.
Adaptation, Physiological↗
Short-term changes in eating patterns explain the effects of condensed tannins on feed intake in heifers.
Ingestion of condensed tannins decreases feed intake in ruminants. Polyethylene glycol (PEG) forms high-affinity complexes with tannins. In two experiments carried out on Holstein heifers, quebracho (Q) from the Aspidosperma quebracho served as source of condensed tannins. The aims of the study were (i) to quantify the effect of Q on feed intake and eating behaviour in cattle fed complete mixed diets (CMDs); (ii) to clarify if changes induced in ingestive behaviour and feed intake by Q in cattle can be reversed by feeding PEG; and (iii) to clarify if the decrease in feed intake is associated with short-term (astringency, post-ingestive malaise) or longer-term effects. In experiment 1, 500 g/day of Q was found to be the minimal dose that decreased feed intake in heifers. A ratio of PEG:Q equal to 1:12.5 did not fully restore feed intake. In experiment 2, four heifers received a random sequence of four rations in a Latin-square design with feeding cycles of ca. 7 days: CMD containing no supplements (C), or supplemented with 625 g/day of Q without PEG (Q), with 625 g/day of Q and 250 g/day of PEG (Q-PEG), or with 250 g/day of PEG without Q (PEG). Individual rations were continuously weighed in the trough and the behaviour of heifers was observed for 180 min after distribution of CMD. Overall, feeding Q was associated with lowered feed intake and shorter duration of eating bouts, mainly of the first eating bout, immediately after distribution of the diet. A larger portion of the diet was consumed subsequent to 180 min after distribution in Q-fed heifers. Eating rate and the water to food ratio were not affected by Q. The effects of Q on feed intake were attenuated by feeding PEG. Heifers adapted effectively to condensed tannins by increasing the number of eating bouts and the portion of diet consumed subsequent to 180 min after distribution, so that no differences in feed intake were noted on the last day of each feeding cycle. Data are interpreted to show that: (i) negative effects of Q on feed intake derive from astringency of CT and short-term post-ingestive malaise; (ii) the increased number of eating bouts and their wider partition throughout the day are means to preserve the ruminal environment in Q-fed heifers; (iii) PEG has the potential to neutralize negative effects of condensed tannins in cattle.
Journal Article↗
Short-term number of pecks and feed intake levels: a link with the physical characteristics of feed in four-week-old turkeys.
Short-term reactions of young turkeys to changes in the physical characteristics of their feed sometimes give rise to problems of adaptation in the field. Specific feeders were designed for this study to automatically count the number of pecks given at feed by 4-wk-old male turkeys during 95-min sessions. The lighting program was intermittent (0140L:0100D). In experiment 1, 4 series of 12 birds were tested 4 times/day from 28 to 31 d of age. Four control turkeys were consistently tested with 1 feed, and 8 experimental turkeys ate 1 of 32 commercial feeds (30 as pellets and 2 as crumbs) with a distinct feed for each test (16 replicates/experimental feed). Feed intake, total number of pecks, and pecking efficiency (mg/peck) were recorded for each test and normalized for each turkey. The effects of series, day, and test were not significant for controls. The number of pecks and pecking efficiency differed among feeds (P < 0.001) but not feed intake. Hierarchical Cluster Analysis for these variables distinguished 3 groups of feed: group 3 (6 crumb and small pellets) resulted in high pecking and low efficiency. However, group 1 (10 feeds) were pecked at less but more efficiently than group 2 (16 feeds) for similar feed intake, although the average sizes of the pellets were similar (6.23 and 6.16 mm, respectively), as were the average bulk density, hardness, resistance to abrasion, and color characteristics of the pellets for both groups. Two feeds of each of these 2 groups were compared in a second experiment for 12 turkeys receiving the 4 feeds successively each day over 4 d in varying order. The turkeys consistently pecked the feeds of group 1 less and less efficiently compared with group 2. The automated measurement of pecking, combined with a more detailed image analysis of feed particles, might enhance the evaluation of the effects of feed technology on the behavior of turkeys and thus become a useful tool for the feed industry.
Adaptation, Physiological↗
Water dynamics of dairy cattle as affected by initiation of lactation and feed intake.
Effects of lactation and feed intake on sizes and half-lives of body water pools were investigated in four Holstein cows in a thermoneutral environment. Various markers were administered, on average, 24 days prepartum (Period 1, feed intake fixed to average of consumption after offered at a rate ensuring 10% refusal), 24 days postpartum (Period 2, restricted to intake in Period 1), and 42 days postpartum (Period 3, feed again offered at a rate ensuring 10% refusal). Total body water decreased from period 1 to 2; however, it did not change as a percent of body weight. Estimated body water half-lives and fluxes for the three periods were 7.5, 3.7, and 2.9 days; and 42, 66, and 87 liters/day. Increased water intake during lactation closely matched water secreted in milk. Empty body water, estimated by a two-compartment, four-parameter model, as a percent of body weight did not change across periods. Lactation and increased feed intake decreased half-life of body water. Plasma volume increased as a percent of body weight because of loss of body weight in early lactation; however, extracellular volume tended to decrease with body weight. Initiation of lactation and feed intake during lactation affect water dynamics of the dairy cow.
Animals↗
Individually measured feed intake characteristics and growth performance of group-housed weanling pigs: effects of sex, initial body weight, and body weight distribution within groups.
Feed intake characteristics of 192, 27-d-old weanling pigs housed in groups and given ad libitum access to feed and water were measured individually with the use of computerized feeding stations. The groups were either homogeneous or heterogeneous as to BW distribution; pigs of three defined initial BW classes were used (mean BW of 6.7, 7.9, or 9.3 kg). The effects of BW distribution, BW class, and sex were studied with regard to average performance traits, latency time (interval between weaning and first feed intake), initial feed intake (intake during the first 24 h following first feed intake), and daily increase in feed intake during the interval between first feed intake and the day on which energy intake met or exceeded 1.5 times the maintenance requirement. Homogeneous and heterogeneous groups had similar latency times, initial feed intakes, and daily increases in feed intake. For the period 0 to 34 d after weaning, ADFI and ADG were also similar for homogeneous and heterogeneous groups, but gain:feed ratio was greater (P < 0.05) in the homogeneous groups. Gilts had higher (P < 0.05) initial feed intakes than barrows and also had greater (P < 0.05) ADFI and ADG during the period 0 to 13 d after weaning. Pigs with average BW of 6.7 kg had higher (P < 0.05) initial feed intakes than their counterparts with average BW of 7.9 kg and 9.3 kg, but the daily increase in feed intake was similar for the three groups. The lighter pigs had more daily visits and a lower feed intake per visit and tended to have a shorter postweaning latency to the onset of feeding than the heavier pigs. This study indicates that the high variability in early feeding behavior among group-housed weanling pigs may be related to BW and sex.
Animal Feed↗
Effect of creep feed consumption on individual feed intake characteristics and performance of group-housed weanling pigs.
To assess the effects of creep feed consumption on individual feed intake characteristics and performance of group-housed weaned pigs, 16 litters (149 piglets) were fed a commercial creep feed (3,040 kcal NE/kg, 15.2 g lysine/kg) supplemented with 1% chromic oxide. Another five litters (48 piglets) were not given access to creep feed (no-feed). Piglets were weaned at 28 d after birth. On d 18, 22, and 27 of age, fecal samples from all the piglets were taken using fecal loops. A green color of the feces indicated that the piglet had eaten creep feed. Piglets that had green-colored feces three times were considered as eaters. Piglets that never showed green-colored feces were considered as non-eaters. At weaning 22 piglets of each type (no-feed, non-eaters, and eaters) were selected based on BW, litter origin, and sex. These 66 pigs were assigned to six pens equipped with computerized feeding stations. Eaters, non-eaters, and no-feed pigs were equally divided over all six pens. After weaning a prestarter (d 0 to 13) and a starter diet (d 14 to 34) were offered for ad libitum consumption. The individual feed intake characteristics of latency time (interval between weaning and first feed intake) and initial feed intake (intake during the first 24 h following first feed intake) and performance traits were determined for all piglets. The pigs that were designated as eaters needed less time between weaning and first feed intake than the pigs that were designated as non-eaters and no-feed pigs (P = 0.04 and P = 0.06, respectively). Initial feed intake was not affected (P > 0.1) by feed intake prior to weaning. However, during d 0 to 8 the eaters had more visits per day during which feed was consumed than both the non-eaters and no-feed pigs. Averaged over the first 8 d after weaning, the ADFI and ADG of the eaters were higher than that of the non-eaters and no-feed pigs (P < 0.05). Averaged over the total 34-d period the effect of creep feed intake on postweaning ADFI was much less pronounced (P = 0.20), whereas ADG of the eaters was the highest (P < 0.05). Creep feed intake during the sucking period stimulates early postweaning feed intake as well as postweaning performance.
Animal Feed↗
[Feed intake and performance of dairy cows during feeding of fodder beets supplementing grass silage].
In a feeding experiment 3 x 12 dairy cows (German Simmental x Red Holstein Friesian) were used to investigate the influence of different amounts of fodder beets on feed intake, milk yield and milk composition. The fodder beets (variety Kyros) were fed in exchange for concentrate. The amounts of fodder beets were either 22 kg cow-1 d-1 or 44 kg cow-1 d-1 or zero (control group). All groups received 4 kg hay cow-1 d-1, grass silage ad libitum, and concentrate corresponding to the milk yield. In order to balance the rations the concentrate was either rich in protein or rich in energy. Feeding 22 kg or 44 kg fodder beets increased forage intake (including fodder beets) significantly. However, the total feed intake diminished on average from 18.3 kg DM cow-1 d-1 (control group) to 17.2 kg DM cow-1 d-1 (fodder beet groups). In each treatment the intake of hay was 3.3 kg DM cow-1 d-1. However, the intake of grass silage offered ad libitum was significantly suppressed by the fodder beets. Considering the different amounts of concentrate the quantity of suppression of grass silage by feeding fodder beets was calculated at -0.8 kg DM of grass silage per kg DM of fodder beet intake. The milk yield decreased linearly with increasing fodder beets on average up to 4 kg cow-1 d-1. However, the milk composition was scarcely influenced. The fat content increased a little, the mean alterations of the protein and lactose content were below 0.1 percentage points. Therefore, the change in daily excretion of milk fat, protein or lactose were similar to the change in milk yield. In conclusion, feeding fodder beets in combination to grass silage causes a positive effect on forage intake (including fodder beets). However, the amount of concentrate should not be reduced equivalently to the energy contents of the added fodder beets.
Animal Feed↗
Divergent selection for growth in Japanese quail under split and complete nutritional environments. 5. Feed intake and efficiency patterns following nineteen generations of selection.
High (H) and low (L) quail lines divergently selected for 4-wk BW under complete-diet (CD) and split-diet (SD) environments were evaluated to examine changes in feed intake and feed efficiency before and after the age at selection. Progeny from the four quail lines (H-SD, L-SD, H-CD, L-CD) were fed the CD in Generation 17 and the SD in Generation 19. The BW of H-line quail were highest under their respective selection environments, and the BW of quail in the L lines were highest under reciprocal environments. However, the BW of the two H lines were similar as were those of the two L lines. Relative growth rates of H-line quail were superior to those of L-line quail for the first 2 wk posthatch but L-line rates were superior after Week 4. However, the BW of H-line birds were always higher than for the L-line birds. Adjusted feed intake (grams of feed per 100 g of BW) values for the H lines were similar but lower than values for the L lines. Differences in adjusted feed intake between the H and L lines from 1 to 10 wk remained constant, although adjusted feed intake declined with age in all lines. Feed efficiencies (grams of gain divided by grams of feed) were superior in the H lines for Weeks 1 through 3 and superior in the L lines for Weeks 5 through 9. The same relative shifts between lines were observed in relative growth rates. Therefore, feed efficiency, in addition to feed intake, appears to play an important role in the divergence of BW in the H- and L-quail lines.
Abdomen↗
Long-term feed intake regulation in sheep is mediated by opioid receptors.
These experiments were conducted to determine if 1) syndyphalin-33 (SD33), a mu-opioid receptor ligand, affects feed intake; 2) SD33 effects on feed intake are mediated by actions on opioid receptors; and 3) its activity can counteract the reduction in feed intake associated with administration of bacterial endotoxin. In Exp. 1, 5 mixed-breed, castrate male sheep were housed indoors in individual pens. Animals had ad libitum access to water and concentrate feed. Saline (SAL; 0.9% NaCl) or SD33 (0.05 or 0.1 micromol/kg of BW) was injected i.v., and feed intake was determined at 2, 4, 6, 8, 24, and 48 h after the i.v. injections. Both doses of SD33 increased (at least P < 0.01) feed intake at 48 h relative to saline. In Exp. 2, SAL + SAL, SAL + SD33 (0.1 micromol/kg of BW), naloxone (NAL; 1 mg/kg of BW) + SAL, and NAL + SD33 were injected i.v. Food intake was determined as in Exp. 1. The SAL + SD33 treatment increased (P = 0.022) feed intake at 48 h relative to SAL + SAL. The NAL + SAL treatment reduced (at least P < 0.01) feed intake at 4, 6, 8, 24, and 48 h, whereas the combination of NAL and SD33 did not reduce feed intake at 24 (P = 0.969) or 48 h (P = 0.076) relative to the saline-treated sheep. In Exp. 3, sheep received 1 of 4 treatments: SAL + SAL, SAL + 0.1 micromol of SD33/kg of BW, 0.1 microg of lipopolysaccharide (LPS)/kg of BW + SAL, or LPS + SD33, and feed intake was monitored as in Exp. 1. Lipopolysaccharide suppressed cumulative feed intake for 48 h (P < 0.01) relative to saline control, but SD33 failed to reverse the reduction in feed intake during this period. These data indicate that SD33 increases feed intake in sheep after i.v. injection, and its effects are mediated via opioid receptors. However, the LPS-induced suppression in feed intake cannot be overcome by the opioid receptor ligand, SD33.
Animals↗
Adipose tissue lipogenesis in growing steers adapted to different levels of feed intake.
The association between feed intake and lipogenic activity in adipose tissue was investigated in growing cattle. Twenty-five 300-kg steers were allotted by BW to one of five levels of intake of a single high-energy corn-corn silage-based diet. Steers were adapted to diets over 4 wk and intakes were adjusted weekly to achieve steady but varying rates of growth. Daily intakes (% of BW) averaged .92, 1.15, 1.64, 2.28 and 2.69 and resulted in growth rates over the final 3 wk of -.28, .07, .71, 1.67 and 1.69 kg/d, respectively. Lipogenic activities in biopsied tissue and circulating concentrations of glucose and insulin were lowest at maintenance feeding and below but increased linearly (P less than .01 for lipogenesis; P less than .1 for glucose and insulin) as intake increased above maintenance. Mean minimal and maximal rates (mumoles.-min(-1).10(6) cells(-1)) or concentrations were fatty acids synthesis ([14C]acetate---fatty acid)), .065 and .723; fatty acid synthetase (NADPH oxidized), .266 and 2.97; lipoprotein lipase (fatty acid released), .048 and .359; glucose (mg/dl), 60.4 and 70.7 and insulin (ng/ml), .70 and 1.66. In a preliminary study with the same 25 steers fed ad libitum, nearly 25% of the variability in adipose tissue lipogenesis was accounted for by variation in feed intake. Results indicate that activities of lipogenic enzymes and lipogenic capacity in growing steers coordinately adapt to the level of feed consumed and that nutrient availability and(or) insulin concentrations may participate in this adaptation.
Adipose Tissue↗
Recording strategies and selection potential of feed intake measured using the X-ray method in rainbow trout.
This study examines the way long-term feed intake should be recorded accurately for selective breeding purposes, and estimates selection potential in feed intake using the X-ray method to record individual daily feed intake in rainbow trout (Oncorhynchus mykiss). The analysis showed that the point estimates of daily feed intake displayed low repeatabilities (r = 0.09-0.32). This indicates that a minimum of three repeated records were needed to accurately record average feed intake at a fixed age. To effectively breed for feed intake over the whole growing period, it is necessary to determine average feed intake at different ages, since there were only moderate phenotypic and genetic correlations between average daily feed intake recorded at 140 g, 750 g and 2000 g wet mass. Heritability for average daily feed intake was low (average h(2) = 0.10), indicating that modest genetic changes can be obtained in response to selection. It was concluded that selection to genetically change long-term feed intake can be successful, yet repeated observations at several life stages are needed to ensure the accuracy of feed intake estimates and the efficiency of selection.
Animal Feed↗
Effects of feed intake and dietary level of wet corn gluten feed on feedlot performance, digestibility of nutrients, and carcass characteristics of growing-finishing beef heifers.
The objective was to compare the relative energy value of wet corn gluten feed (WCGF) to that of corn in a feedlot situation when diets were initially offered ad libitum (AL) or at restricted feed intake (RFI; 80% of AL). In a completely randomized block (pen location) design experiment, 144 beef heifers (204.1 +/- 18.2 kg) were used (six treatments; three pens of eight heifers/treatment). Treatments were levels of WCGF (on DM basis) in corn silage-based diets (AL; 25 or 50% WCGF) or high-moisture corn-based diets (RFI; 0, 25, 50, or 75% WCGF) during the growing phase (127 d). During finishing (84 d), all diets were offered AL and contained 5% corn silage by replacing corn silage with high-moisture corn in diets that were offered AL. Heifers that were initially at AL had similar (P > .1) feedlot performance (during growing and during the whole trial), digestibility of nutrients (OM, NDF, CP, and GE), and carcass characteristics. During finishing, however, these heifers had better (P = .06) ADG and gain:feed when 25% WCGF was fed. Heifers that were initially at RFI showed a linear decrease (P < .01) in ADG and gain:feed during growing with increasing dietary level of WCGF. However, increasing dietary level of WCGF resulted in a quadratic (P = .02) response in ADG and gain:feed during finishing and also in a quadratic (P = .07) response in ADG and a linear (P = .005) decrease in gain:feed during the whole trial. These quadratic responses indicated that the best performance was achieved at the 25 and 50% levels of WCGF. The decrease in cumulative gain:feed was only 3.5% at the 25 and 50% levels of WCGF but it was 11.4% at the 75% level. Increasing the level of WCGF in diets of heifers that were initially at restricted feed intake did not affect (P > .1) digestibility of nutrients but it improved some carcass characteristics linearly, decreasing fat thickness (P = .04), liver abscess (P = .02), and yield grade (P = .13). Results suggest that WCGF can substitute up to 25 or 50% of dietary DM without negative effects on feedlot performance, digestibility of nutrients, or carcass characteristics. In addition, restricting feeding during growing may be strategy that improves the utilization of WCGF at these levels.
Animal Feed↗
Feed intake pattern during lactation and subsequent reproductive performance of sows.
Daily feed intake during lactation was recorded for 20,296 lactating sows on 30 commercial farms in the United States. Each lactation feed record was categorized into one of six patterns: RAPID, rapid increase in feed intake; MAJOR, major drop; MINOR, minor drop; LLL, low feed intake throughout lactation; LHH, low intake during the 1st wk then an increase in feed intake for the remainder of lactation; and GRADUAL, gradual increase. A database containing 24,340 farrowing records and 19,015 subsequent litter records were abstracted from the PigCHAMP data files of the farms enrolled in the study. Multiple regression analyses revealed that ADFI during lactation had nonlinear or linear associations with weaning-to-first service interval (WSI), weaning-to-conception interval (WCI), litter weight at weaning (WWT), and subsequent litter size (SLS). Sows having LLL and LHH had longer (P < .01) WSI and WCI than the other patterns. Sows with MAJOR had a longer WCI (P < .05) than females with RAPID. Further, sows having MAJOR had lighter (P < .01) WWT than those with RAPID, MINOR, and GRADUAL. Sows having MAJOR had a higher (P < .01) proportion of females culled for anestrus relative to RAPID. Furthermore, sows exhibiting a drop in feed intake in either wk 1 or 2 were more likely to be culled for anestrus than sows having no drop. These results suggest that both the amount and pattern of feed intake during lactation influence subsequent reproductive performance.
Anestrus↗
Cyclic variation in cattle feed intake data: characterization and implications for experimental design.
Feed intake data were collected every 6 h in a 140-d feeding trial involving two pens of 15 bull calves, each using one Pinpointer single-animal feeding stall per pen. Spectral analysis of these data revealed strong cyclic patterns of feed intake. These patterns were unique to each animal and consisted of two or more cycle lengths, some up to 28 d, for each animal. Feed intake behavior is an important factor in many forms of animal experimentation. Animal researchers frequently use row-column designs, where columns represent animals and rows represent periods. Latin squares and crossover designs are common examples. Standard analysis of variance procedures are appropriate for these experiments only if certain assumptions are met; one is that if cyclic variation is present, it is identical for all animals, i.e., there is no row X column interaction. If this assumption is not satisfied, standard analysis of variance procedures will result in upward bias of the mean square error and may result in serious distortion of treatment effect estimates. This occurred using the data from the feeding trial reported in this paper. Time-series analysis of covariance greatly improved the accuracy and efficiency of estimates of treatment effects. Consideration of variations in cyclic behavior should be part of the design process in experiments using feed intake data. Guidelines for the design of experiments to take advantage of time-series methodology are given.
Animals↗
Characterization of feed intake patterns during lactation in commercial swine herds.
This study created and used a data-base containing 25,719 farrowing and 19,393 subsequent litter records abstracted from the PigCHAMP records of 30 commercial farms and daily feed intake records of 25,040 of these lactating sows. Each lactation feed record was categorized into one of six patterns: RAPID, rapid increase in feed intake following farrowing; MAJOR, major drop in feed intake during lactation; MINOR, minor drop; LLL, low feed intake throughout lactation; LHH, low feed intake during the first week then increasing for the remainder of lactation; and GRADUAL, gradual increase in feed intake throughout lactation. At the herd level, patterns RAPID, MAJOR, MINOR, LLL, LHH, and GRADUAL were observed in 22.8%, 32.9%, 27.8%, 1.0%, 8%, and 14.7% of sows, respectively. On a sow basis, across all feed intake records of all farms, patterns RAPID, MAJOR, MINOR, LLL, LHH, and GRADUAL were observed at frequencies of 17.8%, 38.3%, 25.8%, 1.2%, 1.5%, and 15.4%, respectively. Using logistic regression, the risk factors affecting the occurrence of MAJOR and MINOR patterns were lower parity, thicker backfat, higher room temperature, and greater feed intake during early lactation. Average daily feed intake and the day of peak intake were 5.2 (1.4 SD) kg/sow and 12.6 (4.6 SD) d after farrowing. Regression coefficients of factors affecting ADFI derived from multiple regression analyses were 247 g for parity, 9 g for weaning litter weight (kg), -13 g for room temperature (degree C), 62 g for lactation length (d), and -.4 g for energy density (kcal/kg). This study demonstrated substantial individual sow and farm variation in overall feed intake and pattern of feed intake during lactation. It also identified key risk factors (i.e., parity, lactation length, room temperature, weaning litter weights, energy density) for ADFI and pattern of feed intake on commercial farms.
Animal Husbandry↗
Plasma cholecystokinin-8 in pigs with divergent genetic potential for feed intake and growth.
Plasma cholecystokinin-8 (CCK-8) was studied in pigs with divergent genetic potential for feed intake. Differences in feed intake resulted from selection for either fast (line F) or slow (line S) postweaning gain. The hypothesis was that the relatively lesser feed intake in S versus F may be attributable, in part, to greater circulating concentrations of the putative satiety hormone CCK-8. In Experiment I, barrows from F (n = 23) and S (n = 19) were used to determine changes in CCK-8 associated with ad libitum feed consumption. Blood samples were collected after overnight feed deprivation, then periodically during a 2-hr feeding period. Averaged across sampling times, concentration of CCK-8 tended to be greater (P = 0.07) in S (6.70 pmol/l) than in F (5.06 pmol/l). Concentration of CCK-8 per unit of feed consumed (CCK-8/cumulative feed intake) was greater (P < 0.01) in S than in F during the first 30 min of the feeding period. In Experiment 2, plasma concentrations were determined for nine pairs (F, S) of the same barrows allowed an amount of feed equal to the previous ad libitum intake of the S barrow in the pair. Averaged across times, the difference between CCK-8 concentrations of S (11.65 pmol/l) and F (7.94 pmol/l) barrows was not significant (P = 0.18). A greater concentration of CCK-8 per unit of feed consumed in S than in F supports the hypothesis that satiety effects of CCK-8 may play a role in genetic differences between the lines for feed intake.
Animals↗
High fat diets increase plasma cholecystokinin and pancreatic polypeptide, and decrease plasma insulin and feed intake in lactating cows.
High fat diets often decrease feed intake in dairy cows; however, mechanisms underlying fat-induced depression of feed intake are yet to be established. The postulate that high fat diets decrease feed intake by increasing concentrations of lipid metabolites or satiety hormones in blood was tested by using eight multiparous Holstein cows in a simultaneously replicated 4 x 4 Latin-square design. Treatments were control diet with 1) no fat added, 2) 30 g/kg calcium salts of long-chain fatty acids, 3) 60 g/kg calcium salts of long-chain fatty acids, and 4) 90 g/kg calcium salts of long-chain fatty acids. Cows were fed once daily a diet of concentrate, corn silage, alfalfa haylage and alfalfa hay (50:25:14:11 on a dry matter basis). Dry matter and energy intakes were decreased by inclusion of calcium salts of long-chain fatty acids >30 g/kg of total diet dry matter (P = 0.0001). Plasma nonesterified fatty acids and triglyceride concentrations were increased linearly by feeding increasing amounts of fat (P < 0.003 and P = 0.0001, respectively), whereas plasma beta-hydroxybutyrate and glucose concentrations were not influenced by supplemental fat. Fat supplementation increased postfeeding plasma cholecystokinin concentrations and linearly increased plasma pancreatic polypeptide concentrations. Highest concentrations of plasma cholecystokinin (P < 0.001) and pancreatic polypeptide (P < 0.05) were observed in cows fed the 90 g/kg fat supplement. Plasma insulin was lowered linearly by feeding fat (P = 0.0001). Increased concentrations of cholecystokinin and pancreatic polypeptide were associated with decreased intakes of feed and energy, whereas insulin may not be involved in the control of feed intake in cows fed fat.
Animals↗