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PubMed1987

Thyroid activity in relation to feed intake, growth rate and feed conversion in growing heifers.

Phenotypic and genetic parameters for thyroid activity (T4 serum level, T4 apparent distribution volume, T4 fractional turnover rate and T4 degradation), and for certain production traits (roughage dry matter intake, daily weight gain and roughage dry matter/kg weight gain), were investigated in cattle. In the experiment, 480 growing heifers were studied, daughters of 20 AI sires previously tested for thyroid activity. Repeatabilities for thyroid traits 2-3 months apart varied, with an average 0.3-0.6 for the different traits. Heritability estimates based on sire components were 0.1-0.4 for the thyroid traits, 0.16 +/- .10 for roughage intake and 0.18 +/- .11 for daily gain. The sire component for feed efficiency (roughage dry matter/kg weight gain) was 0, and genetic correlations between thyroid traits and the production traits in growing heifers were low with large standard errors.

Animal Nutritional Physiological Phenomena↗
PubMed2001

The IVOG feeding station: a tool for monitoring the individual feed intake of group-housed weanling pigs.

Three batches of weanling pigs (total n=310 pigs) were used in a 34-day experiment to validate the use of an IVOG feeding station as a tool for monitoring individual feed intake of group-housed weanling pigs. An IVOG feeding station for weanling pigs consists of a single-space dry feeder placed on a load cell in combination with electronic identification. Data of 192 weanling pigs (18 pens) fed by IVOG feeding stations were used to develop a protocol for the screening of IVOG data. To assess the quality of the IVOG data, the feed intake per pen computed from the screened IVOG data was compared with the feed intake calculated from feed weighing. To assess the suitability of the use of IVOG feeding stations under practical pig husbandry conditions, performance of 96 weanling pigs fed by the IVOG feeding stations was compared with that of 118 weanling pigs that were fed using commercial single-space dry feeders (11 pens). Feed intake per pen computed from the IVOG data was similar to the feed intake calculated from feed weighing (average recovery 101.1%) for all test periods (p > 0.1). Furthermore, feed recovery did not differ among feeding stations (p > 0.1). During the first 13 days after weaning, the average daily feed intake (ADFI) of weanling pigs fed by the single-space dry feeders was higher (p < 0.05) than that of weanling pigs fed by the feeding stations. Average daily gain and gain to feed ratios did not differ (p > 0.1) between both feeding systems. During the remaining 21 days and averaged over the entire experimental period, performance did not differ between the feeding systems (p > 0.1). It can be concluded that IVOG feeding stations for weanling pigs are a suitable tool to monitor individual feed intake of group-housed weanling pigs.

Animal Feed↗
PubMed1986

The effect of meal intervals and weaning on feed intake of early weaned pigs.

Feed intake was investigated in early weaned pigs housed in two environments. In the first experiment, pigs in an unfamiliar environment (removed from the sow and placed in nursery pens) were offered a dry diet either ad libitum or at different meal intervals (2, 4 and 6 h). Regardless of meal interval (ad libitum or hourly intervals), early weaned (21 d) pigs failed to consume sufficient feed for maintenance during the first 3 d postweaning. Pigs provided feed ad libitum consumed more (P less than .001) feed (142 vs 84 g/d) and gained more (P less than .05) weight (57 vs 3 g/d) than meal-fed pigs over the 7-d period. Pigs fed at 2-h intervals consumed more (P less than .001) feed than pigs fed at 4-h or 6-h intervals. Compared with preweaning levels (307 mu eq/liter), plasma free fatty acid (FFA) levels increased approximately fourfold by d 1 postweaning (1,372 mu eq/liter), then decreased through d 7 to levels below preweaning (142 mu eq/liter). The FFA levels were not affected (P greater than .1) by meal interval. In a second experiment, feed intake was investigated in weaned pigs that were allowed to consume food by a familiar method and in a familiar environment (suckling the sow). When allowed to nurse following a 24-h weaning period, weaned pigs consumed (24.3 +/- 2.8 g/suckling) the same amount (P greater than .1) as non-weaned littermates (28.7 +/- 1.8 g/suckling).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

The effect of nutrients on feed intake in ruminants.

The purpose of the present review is to examine the role played by nutrients in controlling feed intake in ruminants, in light of their particular anatomical, physiological, nutritional and behavioural characteristics. The ration is first digested in the rumen for several hours by microbial fermentation. Volatile fatty acids, which constitute 50-75% of a ruminant's energy supply, considerably depress feed intake when administered by short-term infusion into the rumen. However, this effect seems to be largely due to osmolarity problems. Only propionate seems to have a specific action, unrelated to osmolarity, in the mesenteric or portal veins. Nitrogenous nutrients have little short-term effect on feed intake, except when there is excess NH3 in the rumen. Metabolic cues from intestinal digestion, particularly of glucose and starch, have very little short- or long-term influence in controlling feed intake, in comparison with rumen digestion cues. However, the short-term responses in feeding behaviour do not always reflect longer-term effects on feed intake control. The effects of volatile fatty acid infusion on feed intake are much less significant over the long term, except in the case of propionate. The nutrients required for good microbial activity (proteins in the rumen) generally promote feed intake, whereas nutrients that disrupt rumen functioning (lipids) reduce feed intake. After a learning period, preferences are always governed by a tendency toward optimum rumen functioning, rather than by animal nutritional requirements, although the two factors are not independent. Ruminants, due to their particular anatomical and nutritional characteristics, have, in the course of their evolution, developed specific feed intake control mechanisms based on nutritional cues.

Animal Nutritional Physiological Phenomena↗
PubMed2006

The relationship between mitochondrial function and residual feed intake in Angus steers.

The objective of this study was to examine the relationship between mitochondrial function and residual feed intake in Angus steers. Individual feed intakes were recorded for a contemporary group of 40 steers via the GrowSafe feed intake system. Intakes were then used to calculate residual feed intake (RFI), a measure of efficiency. Based on these calculations, 9 low (RFI = -0.83) and 8 high (RFI = 0.78) RFI animals were selected for further study. Blood samples were collected via jugular venipuncture 1 wk before slaughter for the determination of plasma glucose and insulin concentrations. Tissue samples were taken from the LM from both the high and low RFI animals and mitochondria were isolated for measurement of oxygen consumption and hydrogen peroxide production. Average daily gain and carcass composition were not different between the high and low RFI steers; however, ADFI by the high RFI animals was 1.54 kg/d greater (P < 0.001) than for the low RFI animals. Low RFI steers exhibited a greater (P < 0.05) rate of state 2 and 3 respiration, respiratory control ratio, and hydrogen peroxide production than high RFI steers when provided with glutamate or succinate as a respiratory substrate. The acceptor control and adenosine diphosphate:oxygen ratios were not different between the 2 groups for either substrate. When hydrogen peroxide production was expressed as a ratio to respiration rate there was no difference between groups, signifying that electron leak was similar for both groups. Plasma glucose concentration was greater (P < 0.05) in the high RFI steers than in the low RFI steers; however, plasma insulin concentration was not different (P = 0.22) between the 2 groups. The ratio between plasma glucose and insulin concentration was similar (P = 0.88) between the 2 groups indicating no difference in glucose metabolism. The increased plasma glucose concentration observed in the high RFI steers was presumed to be the result of a greater feed intake by these animals. It seems that mitochondrial function is not different between the high and low RFI groups but rather the rate of mitochondrial respiration is increased in low RFI steers compared with high RFI steers.

Animal Nutritional Physiological Phenomena↗
PubMed2000

Composition of bacteria harvested from the liquid and solid fractions of the rumen of sheep as influenced by feed intake.

A study was conducted to determine the effect of the feed intake on the chemical composition of bacteria associated with the solid (solid-associated bacteria; SAB) and liquid (liquid-associated bacteria; LAB) fractions of rumen digesta, the digestive passage kinetics and their relationships. Whole rumen contents were sampled after a period of continuous infusion of 15NH3 from four ruminally-cannulated wethers provided successively with a hay-concentrate diet (2 : 1 w/w on a DM basis) at two rates of feed intake: 40 and 80 g DM/kg body weight 0.75. SAB had a higher content of organic matter and total lipids (P < 0.001) and a similar N content as compared with LAB. The concentration of purines and 15N was lower (P = 0.011 and P < 0.001 respectively) in SAB than LAB, whereas the opposite was observed for the concentration of amino acids (mg/g DM; P = 0.031). An increase in feed intake produced an increase in the N (P = 0.034) and purine (P = 0.066) concentrations in bacteria and a decrease (P = 0.033) in their amino acid concentrations. Significant increases of rumen outflow rates of liquid and particles were also observed with increased feed intake. Rates of rumen outflow showed positive and negative linear relationships (P < 0.001) with the purine : N ratio and the proportion of amino acid on total N of bacteria respectively. SAB contained significantly higher proportions of leucine, isoleucine, lysine and phenylalanine and lower proportions of alanine, methionine and valine than LAB. The increase in feed intake also induced significant changes in the amino acid profile of bacteria, increasing arginine and methionine and decreasing alanine and glycine proportions. Results show that the outflow rate of rumen contents is a major factor in determining the proportion of nucleic acids and protein in rumen bacteria and explains some of the differences observed between LAB and SAB.

Amino Acids↗
PubMed1998

Relationship of gestation protein and feed intake level over a five-parity period using a high-producing sow genotype.

High-producing Landrace-Large White crossbred gilts (n = 50) involving 198 farrowings were used to evaluate dietary gestation protein (13 vs 16% CP) and gestation feed intakes (Control vs High), and their interaction, over a five-parity period on sow reproductive performance. Gestation feed intake for Control was 1.81 kg/d during parity 1, increasing by .09 kg for each successive parity. The daily feed intake for High was greater by .13 kg or approximately 450 kcal ME at each respective parity. The experiment was a 2 x 2 in a randomized complete block design conducted in two replicates with parity nested within sow groups. Sow weights and backfat thickness were determined at various intervals. A lactation diet containing .90% lysine in parity 1 and .80% lysine during parities 2 to 5 was fed to all sows from farrowing to weaning (21 d). Sow and pig weights, feed intakes, and colostrum and 21-d milk samples were collected during each lactation. The High feed intake and the 13% protein diet resulted in greater (P < .01) backfat thicknesses, and the effects were additive. Backfat thickness declined quadratically (P < .01) by parity and from late gestation to the rebreeding period of the following parity. The High feed intake resulted in a larger litter size (P < .01), whereas dietary gestation protein concentration had no effect on parturition performance. Sows in each parity consumed more (P < .01) feed from 0 to 7 d postpartum and for the overall 21-d lactation period (P < .01) for parity 1 when the 16% gestation protein had been fed. Gestation feed intake regimens did not affect lactation feed intake. Neither gestation variable affected colostrum or 21-d milk fat, but concentrations declined (P < .01) in all groups after parity 2. Parity 1 litters were heavier at 14 and 21 d, with larger litter gains from 0 to 14 and 0 to 21 d when gestating sows had been fed the 16% protein and the High feed intake combination compared to the other sow treatment groups. From parity 2 to 5, litter weights and gains were similar for all treatment groups. This resulted in a three-way interaction response (P < .05) for these variables. These results suggest that primiparous sows required a greater gestation protein concentration and greater feed intake than generally recommended, but the 13% CP diet at the High feed intake was effective in older sows.

Adipose Tissue↗
PubMed1997

Amino acid and energy interrelationships in growing beef steers: I. The effect of level of feed intake on ruminal characteristics and intestinal amino acid flows.

Five cannulated Holstein steers (538 +/- 35 kg) were used in a 4 x 4 Latin square design experiment with extra observations to examine the influence of level of feed intake on postruminal flow and intestinal disappearance of N and amino acids (AA). Treatments consisted of a single diet fed at four levels of energy intake (1.5, 2.0, 2.5, and 3.0 times NEm requirement). The diet was formulated on a DM basis to contain 13.25% CP using cracked corn (56.1%), soybean hulls (18%), cottonseed hulls (15%), soybean oil (4.25%), and corn gluten meal (5.6%). Increasing feed intake linearly increased (P < .0001) the quantity of OM truly digested in the stomach but tended to decrease (P = .11) OM digestion as a percentage of intake. Level of feed intake had no effect (P > .10) on ruminal pH, NH3 N, or peptide concentration or on particulate and fluid passage rates. However, total VFA concentration increased linearly (P < .0001) and the acetate: propionate ratio decreased linearly (P < .0001) as feed intake increased. Flows of microbial and nonmicrobial N at the duodenum linearly increased (P < .002) with increasing intake but did not differ (P > .10) as a percentage of intake. Level of feed intake did not affect (P > .10) microbial efficiency, N disappearance from the small intestine, or total tract N digestibility. With the exception of tryptophan, flows of all individual AA increased linearly (P < .01) with increasing intake. As a percentage of duodenal flow, AA digestion in the small intestine did not differ (P > .10), leading to a linear increase (P < .10) in the net quantity of individual (with the exception of tryptophan) and total AA disappearing from the small intestine as feed intake increased. Likewise, the profile of AA (except tryptophan) disappearing from the small intestine was unaffected (P > .10) by level of feed intake. When compared with predicted requirements for a 227-kg growing beef steer, Arg, Met, His, and Lys were suggested to be the most limiting AA for growth when this diet is fed. We conclude that altering energy intake by restricting intake of a single diet has only minor effects on the profile of digestible AA or other nutrients presented to the animal.

Amino Acids↗
PubMed1993

[Effect of bovine growth hormone on performance criteria of dairy cows during summer feeding with grass. 1. Feed intake and protein and energy supply].

The influence of long-term administration of bovine growth hormone (bGH) with prolonged release (Somidibove from Lilly Germany GmbH, section Elanco, 640 mg/28 d) in six consecutive injection periods on feed intake under summer feeding conditions with grass feeding ad libitum was investigated. After a pretreatment period of 22 days 30 dairy cows were divided into 15 blocks with two cows each in consideration of milk yield, days postpartum and number of calving. In each block the bGH-treated animal received the same concentrate supply as the corresponding control animal which was supplemented in order to requirement. In a 42 day posttreatment period without bGH-injection possible effects of bGH-treatment on feed intake (grass silage and maize silage) was investigated. The first injection was administrated 75 days postpartum, respectively. During all six injection periods feed intake corrected to the pretreatment period was increased by 0.63 kg DM/animal.d resulting from a higher grass intake in the bGH-treated dairy cows compared to the control group. This difference in feed intake raises from 0.40 kg DM/animal.d in the first injection period up to 0.84 kg DM/animal.d in injection period six and continued in the posttreatment period without bGH-injection (+0.89 kg DM/animal.d). The higher feed intake of grass in the injection periods by the bGH-treated dairy cows resulted in an increased energy intake sufficient on average for the production of 1.2 kg milk/animal.d. Possibilities and limits of a sufficient nutrient supply in bGH-treated dairy cows by an increasing intake of grass are discussed.

Animals↗
PubMed2005

A QTL affecting daily feed intake maps to Chromosome 2 in pigs.

Our understanding of the molecular genetic basis of several key performance traits in pigs has been significantly advanced through the quantitative trait loci (QTL) mapping approach. However, in contrast to growth and fatness traits, the genetic basis of feed intake traits has rarely been investigated through QTL mapping. Since feed intake is an important component of efficient pig production, the identification of QTL affecting feed intake may lead to the identification of genetic markers that can be used in selection programs. In this study a QTL analysis for feed intake, feeding behavior, and growth traits was performed in an F2 population derived from a cross between Chinese Meishan and European Large White pigs. A QTL with a significant effect on daily feed intake (DFI) was identified on Sus scrofa Chromosome 2 (SSC2). A number of suggestive QTL with effects on daily gain, feed conversion, and feeding behavior traits were also located. The significant QTL lies close to a previously identified mutation in the insulin-like growth factor 2 gene (IGF2) that affects carcass composition traits, although the IGF2 mutation is not segregating in the populations analyzed in the current study. Therefore, a distinct causal variant may exist on the P arm of SSC2 with an effect on feed intake.

Animals↗
PubMedDate not supplied

Digestive capacity of the rabbit during the post-weaning period, according to the milk/solid feed intake pattern before weaning.

The milk/solid feed intake pattern and digestive capacity were compared in two groups of young rabbits reared between 16 and 32 days in litters of four (L4 group, n = 18 litters) or ten pups (L10, n = 20) in order to modulate milk availability. Compared to the L4 group, rabbits in the L10 group presented a lower milk intake (22.3 versus 28.8 g x day(-1)) and a higher solid feed intake (12.9 versus 8.0 g x day(-1)) between 16 and 32 days of age. Live weight and weight gain were significantly lower in the L10 (-15%) than in the L4 group from 22 until 42 days. No significant difference was observed among the two groups for post-weaning digestibility and for the intraluminal specific or total activities of amylase and maltase. The total intraluminal activity (pool of enzyme) of amylase and maltase doubled between weaning (32 days) and 42 days. At weaning, the specific activity of amylase was similar in the jejunal and ileal segments (8.5 AU x g(-1)). From 32 to 42 days, the specific amylase activity doubled in the jejunum, while it remained steady in the ileum. The intraluminal specific maltase activity did not significantly change between 32 and 42 days, while it was twice as high in the jejunum compared to the ileum (3.5 versus 1.8 micromoles hydrolysed maltose x g(-1), respectively).

Amylases↗
PubMed1986

Effect of serum magnesium and feed intake on serum growth hormone concentrations.

Concentration of serum growth hormone was increased and feed intake was reduced in lactating dairy cows fed an 84% concentrate diet supplemented with either 100.8 g MgO or 121.2 g of Mg(OH)2. Analysis of serum growth hormone, feed intake, and serum Mg showed an interaction of serum Mg and feed intake, which suggests low concentrations of serum Mg lessen the increase of concentration of serum growth hormone caused by reduced feed intake. Also, compared with control, treatments with Mg supplementation and reduced feed intake increased growth hormone concentration 12 d into the subsequent treatment.

Animal Feed↗
PubMed1999

The correlation between feed-intake cycle and nutritional zinc-deficient status in rats.

The characteristic cyclic variation in feed intake of rats fed a Zn-deficient diet (Mills et al, Am J Clin Nutr 22: 1240-1249 (1969)) followed a Cosinor curve, as determined by computer analysis (Tamaki et al, Br J Nutr 73: 711-722 (1995)). The values of amplitude for the feed-intake cycle had a positive correlation to their own day-to-day variations and to the correlation value of their own simulated cycles (r2 = 0.764, df = 50, p < 0.001 and r2 = 0.682, df = 50, p < 0.001, respectively). The cyclic variation in feed intake was accompanied by a cyclic variation in body-weight change in rats fed the Zn-deficient diet, and cyclic variation in body-weight change occurred similarly in pair-fed control rats. There were no differences in the mesors of body-weight change cycles of Zn-deficient rats and pair-fed control rats (Zn-deficient rats: 2.5 +/- 1.0 g/d, pair-fed rats: 2.8 +/- 1.0 g/d, mean +/- SD, df = 18, t = -0.674, ND). Rats fed the Zn-deficient diet were given different amounts of Zn supplementation by daily subcutaneous injection. The amplitude of the feed-intake cycle was decreased with increasing Zn supplementation (r2 = 0.919, df = 5, p < 0.001). The concentration of Zn for the appearance of the feed-intake cycle was estimated to be 71.6 +/- 6.6 micrograms/d per rat. The Zn level in the serum showed a significant decrease in the Zn-deficient diet groups, but the supplement of Zn did not vary in the Zn-deficient rats injected with up to 47.3 micrograms/d per rat. From these results, an analysis of the feed-intake cycle allowed us to estimate the quantitative Zn-deficient status of rats.

Animals↗
PubMed1999

Genetic parameters for production traits and measures of residual feed intake in large white swine.

The purpose of this study was to estimate genetic parameters for ADG, backfat thickness and loin eye area (LEA), and measures of feed intake and efficiency for purebred Large White boars born from 1990 to 1997. Boars from 60% of the litters were culled at weaning based on a maternal breeding value (index) of the dam, and remaining boars (n = 26,706) were grown to 100 d of age. Selection of boars for individual pen testing was based on a combination of growth and maternal indices. Boars were fed a corn-soybean meal diet that was 1.14% lysine, 19% protein, and 3,344 kcal/kg ME for approximately 77 d. Boars were weighed at the beginning and end of the test, and feed intake was recorded. Daily feed intake (DFI), ADG, and feed:gain ratio (FG) were computed. Four measures of residual feed intake (RFI) were estimated as the difference between actual feed intake and that predicted from models that included 1) initial test age and weight and test ADG (RFI1); 2) initial test age and weight, test ADG, and backfat (RFI2); 3) initial test age and weight, test ADG, and LEA (RFI3); and 4) initial test age and weight, test ADG, backfat, and LEA (RFI4). Genetic parameters were estimated using an animal model and single- or multiple-trait DFREML procedures. Models included fixed effects of contemporary groups and initial test age as a covariate and random animal and litter effects. Heritability estimates for test ADG, DFI, FG, backfat, LEA, RFI1, RFI2, RFI3, and RFI4 were .24, .23, .16, .36, .24, .17, .11, .15, and .10, respectively. Genetic correlations between ADG and backfat, ADG and LEA, ADG and DFI, and ADG and FG were .37, .36, .82, and -.32, respectively. Genetic correlations between ADG and measures of residual feed intake ranged from .11 to .18. Genetic correlations of backfat with LEA, DFI, and FG were -.27, .64, and .40, respectively. Genetic correlations of backfat with RFI measures were higher when backfat was not included in the estimation of RFI. Genetic correlations for LEA with DFI and FG were 0 and -.52, respectively. Genetic correlations for LEA with RFI measures were all negative and ranged from -.31 to -.51. Genetic correlations indicate that selection for reduced RFI could be made without adversely affecting ADG. Backfat should also decrease, and LEA should increase. The amount of change in backfat or LEA would depend on the measure of RFI used.

Animal Feed↗
PubMed1982

Effects of dietary excess tyrosine and level of feed intake on nitrogen and energy utilization in chicks.

The present study using 8-day-old White Leghorn male chicks, was made to determine whether retarded growth of chicks fed a tyrosine excess (Tx) diet ad lib was due to the depression in feed intake or the reduced efficiency of feed utilization. A Tx diet was prepared by supplementing a 20% crude protein basal diet with 5% L-tyrosine. The levels of feed intake prepared for 10 days were as follows: 160 (corresponding to the amounts of the basal diet the chick would consume ad lib), 140, 120 (corresponding to the amounts of the Tx diet the chick would consume ad lib), 100, and 80 g per bird. Body weight gain, gain:feed ratio, and energy retention rate of chicks fed the basal or Tx diet decreased proportionally as the level of feed intake was decreased. The addition of Tx to the basal diet significantly reduced the body weight gain, gain:feed ratio, metabolizable energy (ME) value, and nitrogen and energy retention rates at all levels of feed intake. Body composition was not significantly affected by the addition of Tx to the basal diet at all levels of feed intake. The plasma free tyrosine concentration was markedly increased by the addition of Tx to the basal diet and also with increments in feed intake. Dietary Tx per se had a decreasing effect on body weight gain, efficiencies of dietary nitrogen, energy utilization, and ME value. The growth retardation of chicks fed a Tx diet ad lib was due to the combined effects of the depression in feed intake and the reduced efficiency of feed utilization.

Amino Acids↗
PubMed1984

Control of feed intake in sheep.

The control of feed intake is highly complex, involving many peripheral, as well as central nervous system (CNS) factors. The various signals involved in the control of feeding behavior are integrated in the hypothalamus and appropriate responses, i.e., feeding or cessation of feeding, are generated. The actual neurochemical events subserving this function are not well understood, although specific roles for each of the neurotransmitter systems have been proposed. More recently, certain neuropeptides have been shown to affect feeding behavior in sheep, as well as many other species. Most of the evidence points to the involvement of two families of neuropeptides in the control of feed intake in sheep: the opioid peptides, which include enkephalins, endorphins and dynorphins, and cholecystokinin (CCK) peptides, of which CCK-8 is the primary brain form. Certain opioid peptides, such as met-enkephalins, beta-endorphin and dynorphin A peptides, have been shown to stimulate feeding after CNS administration in sheep, while CCK peptides suppress feeding. Thus it has been proposed that opioid peptides are involved in the initiation of feeding, or hunger, and CCK peptides, in the inhibition of feeding, or satiety. Although much more is known about the effects of CCK peptides than opioid peptides on feeding behavior of sheep, evidence is accumulating for direct interaction between CCK- and opioid-containing neurons that could lead to better understanding of hunger and satiety in sheep.

Adipose Tissue↗
PubMed2001

Central infusion of leptin into well-fed and undernourished ewe lambs: effects on feed intake and serum concentrations of growth hormone and luteinizing hormone.

Leptin has been implicated in the regulation of feed intake, growth, and reproduction. The objective of this study was to determine if centrally administered leptin would affect feed intake and the secretion of growth hormone (GH) and luteinizing hormone (LH) in ewe lambs. Eighteen ewe lambs were ovariectomized and fitted with intracerebroventricular (i.c.v.) cannulae. Lambs were randomly assigned to receive either a maintenance diet (fed), or a diet that provided 38% of maintenance requirements (diet-restricted) for 14 weeks. Subsequently, recombinant ovine leptin or vehicle was continuously infused, via i.c.v. cannulae, in a linearly increasing dose for 8 days, reaching a maximum of 1.25 microg/kg per h. Feed intake was recorded on days -1 to 7. Blood was collected via jugular cannulae every 10 min for 4 h on days 0, 2, 4, 6 and 8 for the determination of serum leptin, insulin, LH and GH. Leptin suppressed feed intake in fed lambs on days 4 to 7 (P<0.001), but had no effect on feed intake in diet-restricted lambs (P>0.25). Fed lambs had greater serum concentrations of leptin than diet-restricted lambs (P=0.007). Also, although not different on day 0 (pretreatment), on day 8 serum leptin concentrations were greater in leptin-treated lambs than in saline-treated lambs (P=0.003). Insulin was lower in diet-restricted than in fed lambs (P=0.003), but was not affected by leptin treatment (P=0.82). LH pulse frequencies were lower in diet-restricted lambs than in fed lambs (P=0.038), but were not affected by leptin treatment (P=0.85). Mean serum GH was greater in diet-restricted than in fed lambs (P<0.01). In diet-restricted lambs treated with leptin or saline, mean GH did not differ on day 0, but increased in response to leptin treatment (P<0.006). Treatment of fed lambs with leptin did not affect serum GH (P>0.32). From this work, we propose that leptin represents an important functional link between adipose stores and hypothalamic function in ruminants. We demonstrate that leptin concentrations change in response to reduced nutritional status, and that leptin has the ability to regulate multiple physiological processes in lambs, including both feed intake and secretion of GH.

Animal Nutritional Physiological Phenomena↗
PubMed1999

Effect of missing data on the estimate of average daily feed intake of growing pigs.

The effect of missing records for feed intake per day (FID) on the estimate of average daily feed intake (DFI) during the test period of individual pigs was studied. Data from 192 growing pigs tested with single-space computerized feeding stations during an average of 93 d were used. True DFI was computed by averaging FID records per pig, individually. A first- and third-degree polynomial and a nonlinear function were fit to FID records per pig to estimate DFI by averaging estimated FID records per pig, individually. The three functions showed small differences for goodness of fit. Missing FID records were simulated by random as well as period-wise deletions of FID records. The effect of missing FID records was judged on the Pearson correlation between true and estimated DFI. Deleting randomly up to 70% of FID records per pig before fitting each function reduced this correlation only from 1.00 to .96 for each function. Deleting 25 successive FID records (approximately 27% of records) before fitting reduced the correlation to values ranging from .92 to .96 and from .59 to .96 for the first- and third-order degree polynomial function, respectively, and from .80 to .97 for the nonlinear function. Using iteratively reweighted least squares regression methods to exclude undesirable effects of outlier values gave similar results for the effect of missing FID records on estimated DFI. Results imply that considering incorrect FID records as missing is a good alternative for adjusting incorrect data in combination with using functions to estimate DFI of growing pigs. Use of a first-degree polynomial function is recommended. Moreover, use of functions enables a more efficient use of feeding stations by recording feed intake data during only parts of the test period.

Algorithms↗