Effect of feeding a milk replacer to early-weaned pigs on growth, body composition, and small intestinal morphology, compared with suckled littermates

Feeding of milk replacer to early-weaned pigs was evaluated in two experiments. In Exp. 1, 18 litters of pigs were either weaned conventionally (d 21), split-weaned and fed milk replacer plus starter diet (d 14 and 21), or weaned and fed milk replacer plus starter diet (d 21). Split weaning combined with feeding a milk replacer increased ADG 22% from d 14 and d 28 compared to conventional weaning (P < .05). Feeding a milk replacer plus starter diet after weaning increased ADG 30% between d 21 and 28 compared to conventional weaning (P < .01). In Experiment 2, four litters of 12 pigs each were divided at d 18 into six heavy and six light pigs and randomized across sow-suckled, milk replacer, or starter diet groups. After 1 wk, pigs fed milk replacer weighed 20% more (P < .001), contained 10% more protein (P < .01) and 17% more fat (P < .05), and had 74% longer villi in the proximal small intestine (P < .001) than suckled pigs. In contrast, pigs fed starter diet weighed 19% less (P < .001), contained 20% less protein and fat (P < .001), and had 28% shorter villi in the proximal small intestine (P < .05) than suckled pigs. Therefore, milk replacer feeding the 1st wk after weaning stimulates pig development, both locally in the small intestine and on a whole-body basis, most likely by an increased energy and nutrient intake. Suckling beyond 18 d postnatally inhibits pigs to reach maximal potential weight gain. In conclusion, milk replacer feeding might be beneficial to reach maximal pig weight gain at weaning.     

An investigation of responding on schedules of electrical brain-stimulation reinforcement.

In Exp I, the leverpressing responses of rats (8 male hooded Long-Evans) were maintained by reinforcement consisting of single trains of electrical stimulation of the brain (ESB) presented on random-interval (RI) schedules ranging in value from RI 3-min to RI 10-min. Both the cumulative response patterns and the relationship of response rates to reinforcement density were similar to those observed for Ss reinforced conventionally. In Exp II with 19 male hooded Long-Evans rats, leverpressing was reinforced with single trains of signalled ESB, unsignalled response-contiguous ESB, or sweetened condensed milk presented on random-ratio schedules. Most of the ESB-reinforced Ss and half of the milk-reinforced Ss stopped responding at ratio values exceeding 50:1, while the remaining Ss responded at higher ratios. Response rates were higher at lower ratio values for the ESB groups than for the milk group, but as ratio values increased, all groups showed similar decreases in rate. All Ss were observed to initiate responding faster than inexperienced controls, and priming was not required. (French summary) (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rats (Rattus norvegicus) do not prefer salted solid food.

Conducted 3 studies to evaluate the ingestive responses of Sprague-Dawley rats to salt in foods and to determine whether prior exposure to salted foods influenced their intake. In Exp I, 16 Ss were given 1-hr access to salted and unsalted foods (e.g., potato chips, peanuts, soup) commonly consumed by humans in the salted form. In each choice situation, rats consumed more of the unsalted variety of solid food. In Exp II, the concentration of salt in a wider variety of foods was varied. 15 Ss were allowed a choice of a given salt concentration or the unsalted food. In no case was the salted solid food eaten in excess of the unsalted solid food, and in general, more of the unsalted solid food was eaten. In Exp III, 2 groups of 8 Ss were given exposure from weaning to either salted or unsalted potato chips for 3 mo. Exposure did not alter the Ss' relative intake of salted chips. When given a choice, more unsalted chips were consumed by both groups. Results indicate that sodium-replete Sprague-Dawley rats generally prefer unsalted solid foods to salted ones. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ACTH and ACTH4–20 modification of neophobia and taste aversion responses in the rat.

A series of 6 experiments assessed the effects of ACTH and the ACTH analog ACTH4–20 on drinking in conditioned taste aversion and neophobic situations using a total of 168 male Sprague-Dawley rats as Ss. Both substances delayed the extinction of a conditioned taste aversion established by a single pairing of lithium chloride with milk (Exp I). However, in this situation, the ACTH parent peptide was more potent behaviorally. ACTH supressed milk consumption in Ss with no toxicosis experience (Exp II). This effect was apparently not due to the conditioning of a taste aversion (Exp III) with ACTH serving as a weak aversive UCS. Exogenous ACTH (Exp IV) or ACTH4–20 (Exp V) did not enhance neophobia; however, repeated injections of ACTH suppressed drinking. This ACTH suppression was related to the familiarity/novelty of the substance being consumed. The neophobic response to milk was not accompanied by pituitary-adrenal activation (Exp VI). Both neophobic and conditioned taste aversion situations appear to be useful for assessing peptide effects on consummatory behavior. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of photoperiod and social environment on sexual maturation in female deer mice (Peromyscus maniculatus bairdii).

Tested the reproductive response of young female deer mice to either a long or short photoperiod combined with the presence of adult males, adult females, or social isolation. 266 Ss were reared on either a long photoperiod (15 hrs light, 9 hrs dark) or on short days (8 hrs light, 16 hrs dark) from birth. Beginning at weaning, females were housed with an adult male, with an adult female, or in social isolation. In Exp I, vaginas opened more slowly in Ss on short days than in those on long days. Vaginal introitus was also retarded in Ss reared with an adult female in comparison with Ss reared in isolation. When examined at 37 days of age, Ss reared with an adult male had larger uteri than those reared alone; uteri were also larger in long-day than in short-day Ss. In Exp II, Ss were killed at 30 days of age; again, uterine growth was stimulated by exposure to either long days or an adult male. As was previously demonstrated for male deer mice, sexual maturation in females is regulated by photoperiod and social cues. Heterospecific social stimuli accelerate maturation in individuals that otherwise would be inhibited by having been reared on a short photoperiod. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ventral scent marking in Meriones unguiculatus may contribute to thermoregulation.

Conducted 3 experiments with adult male gerbils to demonstrate that ventral scent marking can act to transfer body heat to the object marked. Exp I, with 16 Ss, showed that surgical removal of the ventral gland pad in 8 Ss reduced the amount of heat transferred by 50%, even though intact and glandless Ss did not differ in the average frequency of scent marking. Exp II, with the same 16 Ss used in Exp I, demonstrated that the difference in heat transfer due to the presence or absence of the scent pad was not due to differential pressure applied to the substrate during marking. Exp III, with 14 Ss, showed that the pattern of ventral hair spread that occurred as an S moved over an object was different between intact and glandless Ss but that this difference did not account for the difference in heat transfer. It is suggested that heat transfer to the environment with ventral scent marking may increase thermoregulatory competence and also may function to volatilize sebum used in chemocommunication. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of neonatal dopamine depletion on spatial ability during ontogeny.

Investigated the effects of neonatal dopamine (DA) depletion on spatial discrimination tasks. Ss were lesioned at 3 and 6 days of age with intraventricular 6-hydroxydopamine preceded by Desipramine. In Exp 1, Ss were tested before weaning for the ability to spontaneously alternate in a T maze both in the presence of their home cage shavings and with a screen covering the shavings. Lesioned Ss were significantly impaired in their ability to spontaneously alternate. Control and lesioned Ss both showed a decrease in performance when the screen prevented full access to the shavings and the magnitude of the impairment was significantly greater for the lesioned animals. In Exp 2, Ss were tested after weaning in an appetitively motivated task in T maze. The task required both a functional working and reference memory. Lesioned Ss were impaired on both the working and the reference components of the task; however, the magnitude of the impairment was greater in the working memory task. Results suggest that early lesions of general DA systems produce deficits in tasks requiring spatial alternation behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ontogeny of thermal and olfactory determinants of huddling in the rat.

In Exp I, in standardized tests of huddling behavior, 64 5-, 10-, 15-, and 20-day-old Sprague-Dawley rat pups spent substantial and equivalent amounts of time with an immobile rat or a heated, fur-covered tube, which suggests that the conspecific and inanimate stimuli were equally attractive to the pups. In Exp II, with 32 Ss, 2-choice preference tests showed developmental differences in attraction. Younger Ss preferred to huddle with the warmer, inanimate target, whereas older Ss preferred the conspecific. The emergent conspecific preference appears mediated by attraction to species odors. In Exp III (64 Ss), the 5- and 10-day-olds huddled equally with an immobile rat and an immobile gerbil (stimuli with similar thermal and tactile properties), but older Ss preferred the conspecific. In Exp IV, with 16 15-day-old and 16 20-day-old Ss, intranasal zinc sulfate treatment eliminated preference for the conspecific but did not disrupt huddling per se. Results from all experiments show that thermal cues were sufficient to elicit huddling at all ages, but olfactory cues became a more salient influence before weaning. An ontogenetic transition from "physiological" to "filial" huddling is discussed in terms of changes in sensory control of early behavior. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sham feeding in rats after ventromedial hypothalamic lesions and vagotomy.

Two studies examined sham feeding in female Sprague-Dawley rats with ventromedial hypothalamic (VMH) lesions with or without abdominal vagotomy. In Exp I, intact Ss consumed more than twice as much sweet milk during 1-hr tests of sham feeding as they did when feeding normally. Ss with VMH lesions showed exaggerated sham feeding, which was elevated almost four-fold over their already high normal feeding baseline. In Exp II, vagotomy substantially reduced sham feeding in Ss with VMH lesions. After vagotomy, VMH Ss sham fed half as much as nonvagotomized VMH Ss. Vagotomy did not, however, reduce sham feeding to control levels. Results are consistent with the hypothesis that VMH hyperphagia arise from exaggeration of orosensory responsiveness, which is, in part, a consequence of perturbed vagal function. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial memory in pigeons on the radial maze.

A series of 7 experiments with 10 pigeons showed, contrary to recent suggestions that pigeons show little or no spatial memory on the radial maze, highly accurate performance by Ss on an 8-arm radial maze. In Exp I, Ss were trained on successive phases that raised the number of alleys to be remembered from 1 to 4. In Exp II, Ss were allowed to search the maze for food with all 8 arms open. Measures of spatial memory showed that Ss performed at a level equivalent to that found with rats in previous research by A. B. Bond et al (see record 1982-25052-001). In Exp III, testing with massed trials revealed proactive interference. Ss were able to form reference memory for subsets of baited and unbaited alleys in Exp VI. In Exp VII, Ss learned about quantities of food associated with 4 different alleys and ordered their alley choices from the largest to the smallest reward. Contrary to the previous findings with rats, Ss in Exp IV showed forgetting over retention intervals of 0–360 sec between forced and free choices. It is concluded that spatial memory in pigeons generally shows the same properties as that in rats. (49 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Tolerance to amphetamine anorexia: Role of learning versus body weight settling point.

Conducted 3 experiments with male Sprague-Dawley rats to study the development of tolerance to amphetamine (AM) anorexia. In Exp I, 19 Ss that had become tolerant to the suppressant effect of AM on milk intake were anorexic when offered other foods or water. These results appear to support a conditioning interpretation. In Exps II (38 Ss) and III (24 Ss), Ss made tolerant with milk as the diet showed prolonged anorexia when switched to Purina pellets or slightly bitter milk; but when switched from pellets or adulterated milk to milk, tolerant Ss were anorexic only 1 day and then ingested significantly more of the new diet. Results are inconsistent with a conditioning interpretation. Tolerant Ss maintained their weight below the level of saline controls despite the recovery of food intake, and the level at which they maintained their weight varied with the palatability of the diet. These results suggest that AM lowers the settling point for body weight and that tolerance to this effect does not develop. Thus, the reinstatement of prolonged anorexia when apparently tolerant Ss were switched to a less palatable diet can be understood as an attempt to attain a lower weight level. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Monitoring eye movements under conditions of associative matching, response production, and stimulus and response production.

Monitored eye movements in each of 3 studies with 20, 19, and 18 undergraduates, respectively, while Ss were given 8 study trials on a 7-item paired-associate list. Ss were then subjected to a single test trial of associative matching (Exp. I), response production (Exp. III) or stimulus and response production (Exp. IV). A 4th study with 42 Ss, (Exp. II), without eye movement monitoring, involved 3 groups of Ss given either 2, 4, or 6 study trials followed by a single test trial of associative matching. Results, with the exception of Exp. I, were generally consistent with a 2-stage notion of verbal paired-associate learning. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of feeding in rats: III. Thermal determinants of early ingestive responding.

High ambient temperatures (38°C) stimulated high spontaneous levels of activity and high frequencies of behaviors normally associated with ingestion (mouthing and probing), particularly in young, 3- and 6-day-old Charles River CD rat pups (Exp I). The level of spontaneous behavior was highly correlated with body temperature and also depended on deprivation condition. Temperature played an important role in determining responses to food stimuli as well. When Ss were fed by oral infusion (Exp II) or by placing milk on the floor beneath them (Exp III), warm ambient temperatures were required for active ingestion. In Exp IV, body temperature and ambient temperature were manipulated independently to assess their relative importance for Ss' feeding behavior. Ss with a low (29°C) or normal (34°C) core temperature at the start of testing were fed in either a 24°C or a 34°C ambience. Regardless of body temperature, Ss' levels of intake, activity, mouthing, and probing were higher in a warm than in a cool ambience. Therefore, the suppressed ingestive behavior of Ss fed at cool temperatures occurred not simply because Ss became hypothermic and inactive. Perceived warmth appears to be a significant contextual cue that regulates pups' responses to food stimuli. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patterned (single) alternation in infant rats after combined or separate lesions of hippocampus and amygdala.

The role of the developing hippocampus and the amygdala on patterned (single) alternation (PA) in the infant rat was investigated in 4 experiments. In Exps 1 and 2, Ss were given 2 bilateral electrolytic hippocampal lesions or sham surgeries at 10 or 11 days of age and were trained 6 days later in a straight runway. In Exp 1, there were 120 trials in 1 day, with an 8-, a 15-, or a 30-s intertrial interval (ITI). PA learning occurred in lesion and sham Ss at the 8- and 15-s ITIs. In Exp 2, training was extended to 240 trials over 2 days, with a 30- or 60-s ITI. Sham and lesion Ss showed PA at the 30-s ITI, but the emergence of PA was delayed in the lesion pups at the 60-s ITI. In Exp 3, amygdaloid lesions had no effect on PA learning at the 8-s ITI. However, when Ss with hippocampal and amygdaloid lesions were trained at the 8-s ITI, the emergence of PA was delayed, and its size was reduced (Exp 4). Results argue for a role of the hippocampus in PA learning at long ITIs and suggest that, even in 16-day-old Ss exposed to an 8-s ITI, the combined hippocampal and amygdaloid lesion produces a deficit greater than either the hippocampal or the amygdaloid lesion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of performance attributions on others' perceptions of the attributor.

Two studies investigated the effects that performers' attributions actually have on others' impressions. 441 undergraduates served as Ss. "Self-serving" internal attributions for success and external attributions for failure produced slightly higher ability evaluations than did the opposite pattern in 1 of the 2 experiments. However, in both experiments, these self-serving attributions produced lower ratings on a modesty dimension. External attributions were also perceived as relatively dishonest for all Ss in Exp I and for unsuccessful Ss in Exp II. Publicity (Exp I) and task variables (Exp II) did not affect ability, modesty, or honesty judgments made from performance attributions but did strongly affect the influence these dimensions had on overall likability evaluations. In general, Ss who made internal attributions tended to be better liked than those who made external attributions. The implications and limitations of these results are discussed relative to self-presentational considerations. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of out-group cues in determining social identity.

Examined the role of out-group cues in determining social identity and guiding behavior in 2 experiments with 131 undergraduates. In Exp I, Ss were exposed to a cue either of an in-group (Ss' college), a relevant out-group (a rival college), or an irrelevant out-group (a baseball team). Ss examined a list of words and were later asked to recognize those they had seen from a larger list in which words related to the 3 groups were embedded. Results indicate that Ss made more false recognitions of in-group related words when a relevant out-group was salient than when an irrelevant out-group was salient. Exp II tested a behavioral implication of Exp I: Out-group salience increases adherence to an in-group norm. In the 1st phase of Exp II, Ss were divided into 2 groups and deliberated 2 civil suits. Ss' in-group favored the plaintiffs for both cases. Ss were divided into new groups for the 2nd phase, and the same procedure was followed. This time, however, the in-group favored the defendants. In the 3rd phase, Ss were exposed to a cue either of the out-group in Phase 1 or Phase 2. Ss' judgments for 2 new cases were biased in the direction of the norm of the in-group that was associated with the salient out-group. Ss favored the plaintiff (or defendant) when the 1st (or 2nd) out-group was salient. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age of first appearance of simultaneous and successive negative contrast in infant rats.

Simultaneous (SimNC) and successive (SNC) negative contrast, 2 paradoxical effects that are related to shifts in reward magnitude, were studied in 148 rat pups. In Exps I and II, 11-, 14-, and 17-day-old Ss were able to discriminate between the large (milk suckling) and small (dry suckling) reward odor cues as measured by attachment latencies, but only the 14- and 17-day-olds showed SimNC. At none of the 3 ages was a discrimination formed to the differential odor cues in the alley in terms of runway speeds. In Exp III, Ss were placed directly on the dam's ventrum to facilitate attachment. As in the earlier experiment, the 11-day-olds discriminated between the odors signaling the 2 reward conditions but did not show the SimNC effect. In Exp IV, SNC was shown at 17 days but not at 14 days in the attachment latency measure and at neither age in the run measure. These 4 experiments extend earlier findings that the paradoxical effects that emerge out of intermittent schedules of reward magnitude occur earlier than those associated with single abrupt shifts in reward magnitude. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Caloric regulation of food intake in man.

Investigated caloric regulation in normal 18-36 yr old human Ss on a liquid diet. In Exp I, 8 Ss failed to compensate for changes in the caloric density of a preload (.25-1.8 kcal/ml) by adjusting meal size within 1 meal or from 1 meal to the next. In Exp II, 15 Ss were required to ingest nothing but the liquid diet for 10-21 days. They were given adlib access to a standard liquid diet (1.0 kcal/ml) for 4-9 days followed by 4-14 days on a diluted diet (.5 kcal/ml). 9 Ss failed to regulate their caloric intake in the time allowed. 6 Ss failed to regulate their caloric intake in the time allowed. 6 Ss compensated dramatically for the caloric dilution by increasing both meal size and meal frequency. Regulation was slow to occur (2-5 days) and usually was not perfect (mean level of 87%). Results are discussed in the light of work with animals and man on the mechanisms controlling regulation of food intake. (30 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of potato proteins on the growth performance of early-weaned pigs

We conducted five experiments to evaluate conventional and low-glycoalkaloid potato protein (CPP and LGPP, respectively) in diets for early-weaned pigs. In Exp. 1, 150 weanling pigs (initially 4.4 +/- .9 kg and 15.5 +/- 2 d of age) were fed either a control diet containing 3% spray-dried animal plasma (SDAP) or diets with additional SDAP (2.5 or 5% added; 5.5 or 8% total) or CPP (2.6% or 5.1%) substituted on a total lysine basis. From d 0 to 14 after weaning, increasing SDAP increased (linear, P < .05) ADG and ADFI, whereas increasing CCP had no effect on growth performance. In Exp. 2, 180 weanling pigs (initially 5.9 +/- 1.2 kg and 20 +/- 2 d of age) were fed diets containing a LGPP replacing 25, 50, 75, or 100% of the 7% dietary SDAP on a digestible lysine basis. From d 0 to 7 after weaning, increasing LGPP increased and then returned to control levels ADG and ADFI (quadratic, P < .01) and gain:feed ratio (quadratic, P < .05). In Exp. 3, 175 weanling pigs (initially 5.5 +/- 1.1 kg and 20 +/- 3 d of age) were fed either a control diet containing 20% dried whey, 17.5% dried skim milk, and 4% select menhaden fish meal (SMFM) or diets consisting of lactose and either 3.5 and 7.0% SDAP or 4.0 and 8.0% LGPP added at the expense of dried skim milk on a digestible lysine basis. From d 0 to 7 after weaning, ADG and ADFI increased (linear, P < .05) with increasing SDAP. With increasing LGPP, ADG and ADFI increased and then decreased (quadratic, P < .10 and P < .05, respectively). Gain:feed ratio (G/F) was not affected by SDAP and was improved (linear, P < .05) for pigs fed increasing LGPP. In Exp. 4, 270 weanling pigs (initially 6.2 +/- 1.6 kg and 20 +/- 3 d of age) were used to compare three diets that contained either 2.5% spray-dried blood meal (SDBM), 4.8% SMFM, or 3.92% CPP; test feedstuffs were substituted on a total lysine basis and diets were fed from d 7 to 28 after weaning. Pigs fed CPP had decreased (P < .05) ADG and G/F compared with those fed the other protein sources. In Exp. 5, 255 weanling pigs (initially 5.3 +/- 1.2 kg and 17 +/- 2 d of age), were used to compare five diets that contained either 2.5% SDBM, 5.51% SMFM, 4.17% CPP, 4.17% LGPP or 8.34% LGPP; feedstuffs were substituted on a digestible lysine basis and diets were fed from d 7 to 28 after weaning. No differences (P > .10) were observed in growth performance among pigs fed any of the protein sources within the experiment. However, pigs fed the LGPP had numerically greater ADG and better G/F than those fed CPP. In conclusion, these results suggest that LGPP can be an effective replacement for a portion of the SDAP in diets for weanling pigs.     

Memory for pictures: Does an age-related decline exist?

Examined the effects of varying detail on memory. In Exp I, pictorial embellishment was varied by presenting 27 Ss aged 60+ yrs and 30 undergraduates with normal photographs, high-contrast photographs, or line drawings, and testing their memory immediately and 4 wks later. All of the Ss did best with the most elaborate pictures (normal photographs), and old Ss remembered as well as young at the immediate but not at the delayed interval. In Exp II, with 21 old Ss and 21 18–36 yr olds, detail was varied by adding background to line drawings of a central object. Ss of both ages profited from enhanced background detail, and there were no differences in memory as a function of age. Exp III replicated Exp II, except that Ss (10 elderly and 17 college students) studied the pictures under divided attention conditions. Again, Ss of both ages recognized elaborate pictures best, and no significant age differences emerged. Results suggest that old and young adults profit from visual embellishment and that memory for meaningful pictures remains relatively intact with age. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)