Food preferences in farm animals: why don't they always choose wisely?
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Animal Nutritional Physiological Phenomena↗
Biomedical subjects
I Kyriazakis
Publications and source records attributed to I Kyriazakis.
The effect of subclinical intestinal nematode infection on the diet selection of growing sheep.
To test the hypothesis that subclinical gastrointestinal parasitism, associated with an impairment in N digestion and metabolism and a reduction in the voluntary feed intake (VFI), could affect the diet selection of sheep given a choice between two feeds that differed in their crude protein (CP) content, twenty-four Texel x Scottish Blackface ewe lambs growing from 28 to 48 kg live weight (LWT) were given a daily dose of 2500 larvae of the intestinal nematode Trichostrongylus colubriformis; twenty-four similar lambs were used as uninfected controls. Six infected and six control lambs were given a free choice between two pelleted feeds (10.4 MJ metabolizable energy/kg), with different CP contents (90 (L) and 214 (H) g CP/kg fresh feed respectively). In addition, eighteen parasitized and eighteen control sheep were given access ad lib. to either feed L, or feed H, or their mixture M (164 g CP/kg; twelve per feed), in order to quantify the effects of the feeds when offered alone, and to test for any interactions between feed CP content and parasitism on the performance of the lambs. Intestinal parasitism reduced significantly (P < 0.001) both the rates of LWT gain (by 30%) and VFI (by 10%). The adult and developing parasitic forms took 4 weeks to establish and develop to a significant adult worm population (as judged by the faecal egg counts and blood variables) and until then there was no effect of parasitism on the performance of the lambs. The diet selection of the lambs given a choice between two feeds was similar between the two groups in the first 4 weeks of the experiment, but differed significantly (P < 0.05) in the second part of the experiment (4th week to the end). Thus, while parasitized lambs had a reduced rate of feed intake, by changing their diet selection they achieved a daily rate of CP intake similar to the control ones. However, since the parasitized lambs had a reduced rate of LWT gain, they also consumed a higher total amount of CP to reach the same LWT. It is concluded that sheep infected daily with a small number of larvae of T. colubriformis and given a choice between two feeds that differ in their protein contents are able to modify their diet selection in order to meet the increased protein requirements resulting from such an infection.
Animals↗
The effect of breed on the relationship between feed composition and the efficiency of protein utilization in pigs.
The objective of the present experiment was to test whether the relationship between feed composition and the efficiency of protein utilization in pigs was different between two very different breeds. Forty-eight entire male pigs, half Large White x Landrace (LW x) and half Chinese Meishan (CM), were assigned at 13 kg live weight either to an initial slaughter group or to one of six feeding treatments for 6 weeks. The two feeds used were starch, with 12.52 MJ metabolizable energy (ME) and 0 kg digestible crude protein (DCP)/kg, and a high-protein feed, with 11.95 MJ ME and 0.362 kg DCP/kg. In the first week the LW x pigs were given 400 g high-protein feed/d with 0, 100, 200 or 300 g starch/d, or 200 g high-protein feed/d with 400 or 500 g starch/d. The six diets had ME:DCP ratios of between 33 and 119 MJ/kg. The diet compositions were held constant within each of the six treatments but the allowances were increased weekly on time-based linear scales to be 2.25 as great in week six as in week one. The allowances for the CM pigs were 0.75 of those for the LW x. The calculated efficiency of protein utilization, ep, was found to be directly proportional, up to a maximum value, to the ME:DCP ratio of the diet for both breeds, as found previously for LW x male and female pigs. The overall constant of proportionality was ep = 0.0108 (SE 0.00024) ME:DCP, the value of which did not differ significantly between the two breeds. The maximum observed ep values were 0.710 (SE 0.014) and 0.824 (SE 0.016) for the LW x and CM pigs respectively. It is likely that the lower maximum value for the LW x pigs was an experimental artefact due to increased feed spillage by these pigs on the two highest starch allowances used. In previous experiments the maximum value of ep was found to be 0.813 for LW x pigs, a value similar to that found here for the CM pigs. The results are consistent with the view that the two very different pig breeds have the same net efficiency in using protein and use the same rules for partitioning a scarce resource such as energy.
Amino Acids↗
The effect of protein source on the diets selected by pigs given a choice between a low and high protein food.
To test the effect of the protein source on the diet selection of growing pigs, four foods of high protein concentration were made. Each food was based on a different protein meal: fish, soya bean, and two types of rape seed (with low and high glucosinolate contents), and was offered to growing pigs together with a food of low protein concentration (L), as a choice. Pigs given a choice between the fish or the soya bean meal-based food and L, selected a diet that met their protein requirements, as judged by their growth rates and food efficiency: the protein content of the selected diet declined systematically with pig weight. Pigs given a choice between the rape seed meal-based foods and L selected diets with a high proportion of L and, consequently, failed to meet their protein requirements. Given that the preference for L was more marked when the animals were given access to the rape seed meal higher in glucosinolates, it is suggested that their diet selection on these foodpairs was a tradeoff between minimising glucosinolate intake, which has potentially goitrogenic properties, and achieving a protein intake sufficient for maximum performance. This suggestion is supported by the fact that the fish meal-based food was preferred over the ones containing rape seed meal, and that the rape seed meal lower in glucosinolate content was preferred over the other when pigs were given a choice between them.
Aging↗
Diet selection in sheep: the ability of growing lambs to select a diet that meets their crude protein (nitrogen x 6.25) requirements.
To test the proposition that sheep are able to select a diet that meets their crude protein (N x 6.25; CP) requirements, feeds L, A, B, C and H with the same energy content (11 MJ metabolizable energy/kg feed) but different CP contents (78, 109, 141, 172 and 235 g CP/kg fresh feed respectively) were formulated. In addition, feed U, which was feed L plus 21.4 g urea/kg (CP content 132 g/kg), was also made. The feeds were offered ad lib. either singly (n 4 per treatment) or as a choice between feed H and another feed (pairs LH, AH, BH, CH and UH; n 9 per feed pair) to individually penned Suffolk x Scottish mule wether lambs, over the live-weight range 25-45 kg. On the single feeds the rates of live-weight gain were 273, 326, 412, 418, 396 and 407 g/day (SE of difference (SED) 34; P < 0.01) and protein (excluding wool) gain were 27, 32, 44, 45, 41 and 39 g/d (SED 4; P < 0.001) for feeds L, A, B, C, H and U respectively. When sheep were given a choice between a feed below (L or A) and a feed above their CP requirements (H; as judged by the single-feeding treatments) the CP concentration selected was not different between the two pairs: 131 (SE 4) v. 133 (SE 4) g CP/kg feed for pairs LH and AH respectively. On the choices BH and CH (a choice between two feeds above requirements) the feed lower in CP was constantly preferred (874 (SE 33) and 910 (SE 33) g feed B and C respectively per kg total feed intake; CP selected was 157 and 178 g CP/kg respectively). However, this was not the case with the UH choice on which sheep consumed only 599 (SE 61) g feed U/kg total feed intake, resulting in a selection of a higher CP in their diet (173 g CP/kg). The live-weight gains of the animals given a choice between two feeds were 416, 387, 415, 410 and 383 g/d (SED 37) and protein gains were 45, 40, 46, 50 and 43 (SE 7) for pairs LH, AH, BH, CH and UH respectively, which were comparable with the best performance achieved on a single feed. The results suggest that sheep were able to select a diet that meets their CP requirements and avoid, at least to a certain extent, excess of protein intake.(ABSTRACT TRUNCATED AT 400 WORDS)
Animal Feed↗
The behavioural effects of undernutrition in confined farm animals.
Results suggest that where the animal is unable to engage in functional feeding to reduce nutrient deficit, it may still continue to engage in feeding by directing its feeding behaviour to other alternative stimuli. If feeding is to be maintained where there are constraints on further intake, the alternative stimuli to food must be of sufficient incentive to prevent feeding being inhibited by other tendencies. Alternatives to food then are likely to be chosen on the basis of their sensory (incentive) qualities, and the precise form of feeding behaviour will depend on the interaction between the feeding tendency and the choice of available stimuli. Growing pigs offered single diets ad lib. and experiencing relatively mild deficits of specific-nutrients, may direct this behaviour towards pen-mates as alternative foraging stimuli, with blood resulting from this foraging activity acting as a further incentive to sustain the behaviour. If specific-nutrient deficits in growing pigs are generally mild then feeding may only be sustained in the presence of high incentives such as pen-mates. However, it is not always clear why stimuli such as pen-mates continue to attract foraging activity when they provide little of the deficient nutrients underlying the behaviour. Where the nutrient deficit is more extreme, such as in food-restricted sows and broiler breeders even stimuli with low incentive (e.g. chains, bars or walls) may be sufficient to maintain feeding tendency. The environment, by only allowing simple and non-complex behaviour to be performed, channels the expression of feeding behaviour into simple and repetitive stereotypic behaviours. Other behavioural processes such as arousal and sensitization may facilitate the marked persistence of stereotypies.
Animal Welfare↗
The growth of mammals following a period of nutritional limitation.
A theory of predicting the growth of an animal following a period of nutritional limitation is proposed here. The theory consists of the following three propositions. Proposition 1: there is a scale of size, such that the growth rate following a period of nutritional limitation is that of normal animals at the same size. Proposition 2: any abnormalities in body composition at the end of the period of limitation will be corrected over time. Proposition 3: the rates at which abnormalities in body composition at the end of the period of limiting conditions are corrected, are always set by the conditions of rehabilitation. The propositions are connected with three other problems viz normal growth, growth under some limitation and the conditions needed by an animal to perform at its potential. These problems are dealt here by: (i) using a simple description of normal growth, (ii) considering the limitation by its effects rather by attempting to predict the effects of a given limitation, and (iii) using simple assumptions about protein and energy scales and requirements. The predictions of the theory are compared with experimental data, and a good qualitative agreement is found. Important conclusions from the theory are: (a) that it is essential to measure as fully as may be the state of the animal at the end of the period of limitation and to compare it with the state of normal animals and (b) that careful attention needs to be given to the choice and the description of the treatment, or preferably treatments, during the rehabilitation period.
Animals↗
Selection of a diet by growing pigs given choices between foods differing in contents of protein and rapeseed meal.
The objective of the experiment was to test whether the rules that appear to underlie diet selection by pigs given choices between two foods of different crude protein (CP) content, persist when a rapeseed meal with possible goitrogenic effects is included in one or both foods. Forty-four pigs were given access to one food, or to two foods as a choice, from 12-30 kg liveweight. The foods were the combinations of two levels of CP (140 and 300 g CP/kg food) and two levels of inclusion (0 and 180 g/kg food) of a rapeseed meal, which resulted in foods L, H, LR, HR; in addition the equal parts mixture of foods L and H was also made (food M). The treatments were: access to a pair of foods as a choice, pairs LH, LR, H, LHR and LRHR (n = 6 per treatment) or access to a single food L, LR, M, H and HR (n = 4 per treatment). The inclusion of the rapeseed meal did not significantly affect the rates of food intake and liveweight gain of the pigs given access to one food. Pigs given a choice between a rapeseed-based food and another one (pairs LRH and LHR), showed a significant preference for the food without it. The rejection of the foods with rapeseed meal was such that it overpowered the physiological need of the pig to select a diet that would meet its CP requirement. When the two foods differed only in CP content (pairs LH and LRHR) pigs were able to select a diet whose composition changed systematically as they grew, and supported rapid growth. The diet selection of the choice-fed pigs is consistent with the idea that pigs, given a choice between a potentially harmful food and a non-harmful one, will favour the latter irrespective of its nutritional properties, only if it is assumed that the inclusion of rapeseed meal had a detrimental effect on the single fed pigs, which could not be seen in their performance as measured by the rates of food intake and liveweight gain.
Animals↗
The effects of varying protein and energy intakes on the growth and body composition of pigs. 1. The effects of energy intake at constant, high protein intake.
The objective of the present experiment was to define the form of the relationship between varying levels of energy intake at constant, high protein intake and the performance of young pigs. By doing so it was expected that we could distinguish between four models that predict the pig's responses to its diet as rates of protein and lipid retention. Forty young pigs were assigned at 12 kg live weight either to an initial slaughter group (n 8) or to one of four allowances of starch intake at a constant intake of a high-protein feed (with 345 g crude protein (nitrogen x 6.25)/kg food). Half the pigs were killed after 4 weeks and half after 8 weeks on the treatments; at each slaughter point on each treatment half the pigs were entire males and half were females. Increasing the intake of starch (energy) resulted in significant increases in the rates of live weight, empty-body, protein and lipid gains of pigs slaughtered at both stages. There was no minimum positive lipid:protein ratio in the gain of the pigs. Male pigs deposited more protein and less lipid than females but this effect of sex on protein and lipid retention was seen only on the two highest allowances of starch intake. The calculated efficiency of protein utilization increased with increasing starch intake up to a maximum of 0.81, when probably the energy:protein in the diet became non-limiting. The results led to the rejection of two of the models that predict the rates of protein and lipid retention as responses to protein and energy intake, but the two remaining models could not be rejected, at least qualitatively.
Animals↗
The effects of varying protein and energy intakes on the growth and body composition of pigs. 2. The effects of varying both energy and protein intake.
The objective of the experiment was to define the form of the relationship between varying levels of protein and energy intake and the performance of young pigs. Forty-four young-pigs were assigned at 12 kg live weight for 6 weeks either to an initial slaughter group (n 8) or to one of the nine feeding treatments (n 4); three allowances of a high-protein food with 355 g crude protein (nitrogen x 6.25; CP)/kg (P1, P2, P3) at three levels of feeding (L, M and H). Each feeding level was met by supplementing the allowance of feed P with the appropriate amount of starch and each treatment had two males and two females. The rate of protein deposition was not affected by feeding level at the two lowest allowances of basal feed P (P1 and P2), but it increased with increasing the feeding level for the pigs on treatment P3. Males deposited more protein than females, but this effect was more pronounced with treatment P3. The rate of lipid deposition increased with each increase in the level of feeding and decreased with increasing the allowance of feed P. The calculated efficiency of protein utilization (ep) was expressed as a function of the energy:protein ratio in the feed (MJ metabolizable energy/kg digestible CP). The best model to describe the relationship was a linear-plateau model, with the maximum value for ep of 0.814 at 73 MJ/kg. This relationship provided the basis of a model that could predict the response of a growing pig to its diet as rates of protein and lipid retention.
Animals↗
The ability of pigs to control their protein intake when fed in three different ways.
The ability of pigs to control their protein intake was tested in three different ways. When pigs were offered access to single feeds of different protein contents, at a constant liveweight of 20 kg, they increased their daily feed intake as the protein content of their feed was decreased (long-term protein intake regulation). When the protein content of their feed was altered daily, pigs consumed consistently higher amounts of feed when they had access to a low protein feed rather than to a high protein one (short-term protein intake regulation). When, finally, they were given a choice between two feeds of different protein contents, pigs selected a diet that met their protein requirements (as judged by their growth rates and feed efficiencies) and avoided excess of protein intake, but only if they had had previous experience of both feeds. It is suggested that pigs first need to learn about the feeds that are subsequently offered as a choice, before they can make correct dietary choices.
Animal Feed↗
Diet selection of pigs and poultry.
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Animal Nutritional Physiological Phenomena↗
The immediate effects of abrupt diet composition changes in young pigs.
Forty pigs (twenty males and twenty females) were weaned at 4 weeks of age into individual cages, and their weights and feed intakes measured daily. From weaning to 16 kg live weight they were given free access to a feed with either 134 (L) or 278 (H) g crude protein (nitrogen x 6.25)/kg fresh weight. During this period pigs on feed L grew at a slower rate and converted feed less efficiently than pigs on feed H. At 16 kg live weight they were introduced to a 6 d period of feeding when, on successive days, they were given feeds L, H, L, H, L and H (if previously fed on L) or feeds H, L, H, L, H and L (if previously fed on H). For pigs previously given access to feed L the live-weight gain was 1061 v. 575 g/d on the days when H or L was given; the feed intake was 1078 v. 1027 g/d respectively. For pigs previously given access to feed H, the live-weight gain was 655 v. 610 g/d and the feed intake 844 v. 1071 g/d on the days when H or L were given. The interactions between the feed given previously and the feed given for the 3 d of the subsequent 6 d period were highly significant for both live-weight and feed intake. These rapid changes in feed intake and growth rate suggest that the metabolism of young pigs is extremely flexible, with a rapid rate of response to a change in the protein content of their feed.
Animal Feed↗
The way in which the data are combined affects the interpretation of short-term feeding behavior.
Short-term feeding behavior of pigs has been analyzed using random process models and log-normal models. Both were successful despite very different underlying assumptions relating to the theory of control. Feeder visits of growing pigs, housed individually from 17 to 52 kg live weight, were recorded electronically over a continuous period of 35 days. For the combined data, intervals between visits to the feeder greater than 30 min could be described well by the negative exponential model. The starting probability of a visit was constant at around 0.3, suggesting randomness. Disaggregating the data for individual pigs or for individual weeks did not change this conclusion. Intervals in the day were of a different nature to those at night, and disaggregation of the data into these two periods revealed that the negative exponential model was not satisfactory for either period. The starting probability for both periods increased with time since the last visit. This is consistent with the idea of satiety. Therefore, the apparent randomness in the data pooled across the day and night is an artefact caused by pooling itself, and is not in conflict with the satiety concept. The implications of data handling are discussed with reference to studies of the physiological control of food intake.
Animals↗