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Metabolizable protein (MP) supplementation can reduce faecal egg count (FEC) in periparturient ewes, thus reducing pasture contamination for their lambs (Houdijk et al. 2006). In addition, lambs grazing on bioactive forage (chicory) had lower FEC than lambs grazing grass/clover (Athanasiadou et al. 2007). Both periparturient MP nutrition and grazing on chicory increase lamb performance but these approaches have been developed and investigated independently. The objective of this experiment was to assess their interactive effects on lamb parasitic status and performance. It was hypothesised that, although beneficial effects of maternal nutrition will be augmented with subsequent grazing on bioactive forage, the magnitude of the latter effect will be higher for lambs from unsupplemented ewes.
Nematode egg excretion by periparturient ewes is the main source of infection for their immunologically naïve lambs. It has been shown that periparturient metabolizable protein (MP) supplementation can reduce nematode egg excretion (Houdijk et al, 2003). The latter experiment used a single moderate level of infection, but effects of MP supply on periparturient parasitism may depend on the level of infection. The objective of this study was to investigate the effects of MP supplementation on parasite control, ewe and lamb performance in ewes trickle infected with the abomasal nematode Teladorsagia circumcincta at three different infection levels. We hypothesised that the magnitude of beneficial effects of MP supplementation will be higher at the highest level of infection due to the expected nutrient drain on the host.
The breakdown of acquired immunity during the periparturient period in the ewe can be reduced by metabolizable protein (MP) supplementation (Houdijk et al 2001). Recent evidence suggests that the development of immune response results in reduced food intake (anorexia) in many disease models (Materase et al, 2005). However, it is not known whether an immune response following the periparturient relaxation of immunity is associated with a reduction in food intake and whether this is affected by protein supplementation in parasitized ewes. In addition, differences in nutrient partitioning between sheep breeds that differ in production potential may affect the ability of the hosts to express immunity and this may be reflected by differences in their magnitude and/or duration of anorexia. The aim of the present study was to test the hypotheses that: a) nematode infection during the periparturient period results in anorexia and protein supplementation can effect the degree of anorexia in ewes, and b) ewes of a high production potential breed show higher breakdown of acquired immunity than ewes of a low production potential breed, and exhibit higher degree of anorexia.
A primary infection of a parasite naïve animal has detrimental effects on intake (anorexia), which in turn results in impaired animal productivity. Recent studies have indicated that anorexia in nematode infected lambs is a direct consequence of the acquisition of immunity (Greer et al., 2005). In many models of disease, immune system activation results in elevated leptin levels and these have been associated with anorexia. However, whether the expression of acquired immunity following a secondary nematode infection results in elevated leptin levels and/or anorexia in growing lambs it is not known. In addition, it is not known whether the expression of acquired immunity differs between breeds that differ in production potential. The aim of the present study was to test the hypotheses a) that a secondary nematode infection results in increased leptin levels and anorexia in growing lambs and b) that lambs of a high production potential breed exhibit a higher degree of anorexia than lambs of a low production potential.
We need to improve our understanding of the factors that are important for the control of food intake on high bulk foods. The study of short term feeding behaviour (STFB) may help to do this. The objective of this experiment was to study the effects of giving foods differing in bulk content on the STFB of growing pigs. It was expected that the foods would result in different levels of daily intake and that this would be reflected as differences in STFB between the foods. Two hypotheses were developed based on ideas about the way in which a physical constraint to intake could arise. H1; there would be less diurnal variation in feeding on high bulk foods that limit intake. H2; feeding patterns on bulky foods would be less flexible than those on a control food when feeding time is limited by reducing time of access to the feeder.
It is frequently assumed that energy intakes from mixed foods with a high proportion of silage (HS) are lower than those from mixed foods with a high proportion of concentrate (HC), because of short-term constraints, i.e. gut fill, that physically limit the amount of food a cow can consume. It was the aim of the present study to analyse how different proportions of concentrate in mixed foods affect short-term feeding behaviour. We hypothesised that cows offered HS are likely to have more meals that are more spread out during the day and vary less in size than cows offered HC. Alternatively, we expected higher correlations between meal size and the length of intervals before (pre-prandial) or after (post-prandial) meals for cows offered HS than for cows offered HC. We tested the hypotheses with a data set of 21195 meals.
The objective of this experiment was to provide a severe test of the two frameworks currently available for understanding and predicting voluntary food intake. Framework 1 predicts that an animal will eat at a level that will allow potential performance to be achieved subject to its capacity to deal with a constraint, such as the bulk content of the food, not being exceeded. In framework 2 intake is seen as that which will allow some biological efficiency, such as the ratio of net energy intake per litre of oxygen consumed, to be maximised (Tolkamp and Ketelaars, 1992). The frameworks differ in their prediction of the effect that a period of prior feeding on a high bulk food (severely limiting) will have upon the subsequent intake of foods of differing bulk content. Framework 1 predicts that the intake of a low bulk food, that is non limiting, but not that of a moderate bulk food, that is limiting, will be increased under such circumstances. Framework 2 predicts that intake will be increased regardless of the type of food being fed as long as the Metabolisable Energy of that food is utilised more efficiently.
An experiment was carried out on pigs to provide a test of two current conceptual frameworks available for the understanding and prediction of food intake. Framework 1 assumes that food intake will be that which allows potential (genetic) performance to be achieved. If this is not achieved then it is because intake is being constrained. Framework 2 sees food intake as being a consequence of a process of optimization such that biological efficiency (the ratio of net energy ingested to oxygen consumed) is maximized. Both frameworks predict that a reduction in temperature will increase the intake of a high quality food. For a food of low quality framework 2 predicts that intake will also be increased when temperature is decreased while framework 1 predicts that it will not. This difference between the predictions of the two frameworks allows them to be tested by means of an experiment in which foods of different quality were given to animals at different environmental temperatures.
Forty pigs were randomly allocated to a control (C) food based on micronized wheat with 13·1 MJ digestible energy (DE) and 232 g crude protein (CP) per kg fresh food, or one of two high bulk foods. The high bulk foods contained either 650 g/kg of unmolassed sugar-beet pulp (SBP) or 650 g/kg of wheat bran (WB). Half the pigs were maintained at a thermoneutral temperature of 22ºC for 14 days followed by a cold temperature of 12ºC for 14 days. The other half were maintained at 12ºC for a period of 14 days followed by a temperature of 22ºC for 14 days. Food intake was recorded daily and live weight twice weekly.
There was a highly significant food ✕ temperature interaction ( P < 0·001) for food intake. A reduction in temperature resulted in an increase in food intake on C and WB but had no effect on the intake of SBP. There was a highly significant effect of both temperature and food on intake ( P < 0·001). A reduction in temperature resulted in a significant increase in food intake, intake on WB was higher than that of either C or SBP. There was no overall effect of temperature on live-weight gain although a reduction in temperature resulted in a non-significant increase in the gain of C and reduction in the gain of WB and SBP. There was a highly significant effect of food ( P < 0·001) on live-weight gain, as gain on C was higher than that on either WB or SBP.
The results of the experiment were in agreement with the predictions set forward by the first framework that growing pigs are eating to achieve maximum performance subject to constraints.
The effect of a period of feeding on a high bulk food, upon the subsequent intake of foods of differing bulk content, was investigated in two experiments of the same design. The intention was to provide a severe test of the two current conceptual frameworks available for the prediction and understanding of food intake. In each experiment 40 male Manor Meishan pigs were randomly allocated to one of four treatment groups at weaning. Each experiment was split into two periods, P1 (12 to 18 kg) and P2 (18 to 32 kg). The treatments, all with ad libitum feeding, were: a control food (C) given throughout (treatment CC); a medium bulk food (M) given throughout (treatment MM); a high bulk food (H) given in P1 and then C in P2 (treatment HC); H given in P1 and M in P2 (treatment HM). C was based on micronized wheat with 13·4 MJ digestible energy and 243 g crude protein per kg fresh food. In experiment 1 M contained 350 g/kg and H 560 g/kg of unmolassed sugar-beet pulp and in experiment 2 M contained 500 g/kg and H 700 g/kg of unmolassed sugar-beet pulp. Framework 1 predicted that food intake on the medium bulk food (M) would not be increased, whereas framework 2 predicted that intake on M would be increased after a period of feeding on H, compared with when M was offered continuously.
In P1, both food intake (P < 0·01) and growth (P < 0·001) were severely limited on H compared with C. In experiment 1 growth was limited on M compared with C during the first 7 days of P1 (P < 0·01) only. In experiment 2 intake (P < 0·001) and growth (P < 0·001) on M were limited throughout P1, compared with C but not thereafter. Therefore, in neither experiment did M cause a lower growth rate than C from 18 to 32 kg. In experiment 1 there was full adaptation to M after about 10 days from 12 kg. In experiment 2 adaptation was complete by the end of the first 7 days from 18 kg.
In P2, food intake (P < 0·001) and live-weight gain (P < 0·05 and P < 0·001 in experiments 1 and 2, respectively) were increased on HC compared with CC. By the last 7 days of P2 intake was still higher (P < 0·01) but growth rate was no longer different to CC. Intake and gain were increased in P2 on HM compared with MM but, in general, these differences were small and not significant. In the first 7 days of P2, in experiment 1 pigs on HM had higher intakes (P < 0·001) and gains (P < 0·05) than those on MM, but in experiment 2 only intake was higher (P < 0·01) with no difference in gain. By the last 7 days of P2 there was no difference in either intake or gain between these two groups in either experiment. Pigs on HC increased intake by more than those on HM. There was, therefore, a significant interaction for food intake (P < 0·05, in experiment 1 and P < 0·001, in experiment 2) between prior and present food.
The unexpected failure of either M food to limit growth throughout the experimental period meant that the results of these experiments could not be used as a strong test to reject either one of the frameworks. However, the ability of the pigs to compensate on M was less than that on C. The data provide some evidence that under conditions of compensation foods such as M may be limiting. This is in closer agreement with the framework that predicted that consumption of a limiting food will not increase after a period of feeding on a high bulk food (framework 1).
Currently there are two theoretical frameworks for the prediction of feed intake of animals. The first considers feed intake to be a consequence of the animal eating to achieve its genetic potential (Kyriazakis and Emmans, 1999). When potential performance is not achieved it is because feed intake is being constrained, for example through the bulkiness of the feed or the hotness of the environment. The second framework considers feed intake to be an outcome of some process of optimisation so that intake is that which allows the maximisation of biological efficiency (Tolkamp and Ketelaars, 1992). The two frameworks differ in their predictions of the effect of temperature on the intake of bulky feeds. In the first, feed intake on bulky feeds is seen as a function of the type of feed; in the second, feed intake is a function of both the type of feed and the environment. The first framework predicts that in the cold the intake of low, but not high, bulk feeds will increase. The second framework predicts that in the cold intake will be increased regardless of the type of feed offered. This experiment was designed to provide a severe test of the two feed intake theories.
Study of short-term feeding behaviour (STFB) could improve the understanding of variation in daily intake in dairy cows. STFB is generally measured in short bouts (e.g. visits to feeders) that are clustered in larger bouts (or meals). The value of bout analysis depends strongly on the choice of an appropriate bout. Before bouts can be grouped into meals, a meal criterion (MC, that is: the longest non-feeding interval accepted as part of a meal) must be estimated. Tolkamp and Kyriazakis (1999) criticised existing methods and recently developed a new technique to estimate meal criteria. These log-normal models were developed on basis of the idea that eating bouts end when animals are satiated (i.e., in a state of low feeding motivation) (Tolkamp and Kyriazakis, 1999). This implies that feed consumption during the relevant eating bout will result in a gradual increase in satiety. This will be associated with an increase in the probability of cows ending a bout. In this study we will analyse whether meals are a more biologically relevant unit of STFB than the short feeding bouts (i.e. visits) that are routinely recorded.
Short-term feeding behaviour (STFB) has been used to elucidate the physiological mechanisms which control eating. It has been proposed as a means by which to predict voluntary food intake, and could be used to quantify behavioural characteristics of the cow. The first step in assessing the usefulness of STFB for these purposes is to identify the major factors which influence STFB. The aim of the study reported here was to evaluate, in dairy cows, the differences in STFB resulting from two different foods, the effect of stage of lactation on STFB, and the effect on STFB of changing from one food to another.
An experiment was carried out to determine the ability of lactating cows to select a diet from two similar feeds differing in the ratio of metabolisable protein to energy (MP/ME) content and to investigate the effect of training through previous access to feeds separately on diet choice.
Holstein-Friesian cows (n=36), 1-5 months in lactation, yielding 37 (s.d.=5) kg of milk were housed in a cubicle shed equipped with 28 computer linked Hokofarm feeders which can be programmed to give or deny specific animals access and record intake, meal size and meal duration. All feeds were mixtures of grass silage and pelleted concentrates. Approximately 75 % of daily offer was given in the morning and topping up occurred during afternoon milking. After adapting to feeders and feed for at least two weeks, intake was recorded in week 1 when all feeders contained a standard mixed feed calculated to contain 8.3 g MP/MJ ME. In weeks 2-7 a low protein (lp) and a high protein (hp) feed were offered in 14 feeders each (in the order 7 lp, 7 hp, 7 lp, 7 hp).
Recently, we have proposed a new theory of feed intake regulation in ruminants (Ketelaars and Tolkamp, 1992a,b; Tolkamp and Ketelaars, 1992). This theory attributes great significance to the efficiency of metabolizable energy (ME) utilization for feed intake regulation. In brief, we assume that feed intake behaviour of ruminants aims at maximizing the ratio of net energy intake (representing the benefits of feeding) relative to oxygen consumption (representing the metabolic costs of feeding). Starting from this assumption, we have shown that knowledge of the efficiency of ME utilization obtained under conditions of restricted feeding can be used successfully to predict voluntary intake (Tolkamp and Ketelaars, 1992).
If, indeed, voluntary feed intake and the efficiency of ME utilization are so intimately related, the question comes up what the effect of ad lib feeding is on the overall efficiency of ME utilization (total net energy intake, NEI, as a fraction of ME intake, MEI). This paper investigates this question by means of model calculations for growing and lactating cattle according to the UK energy evaluation system.
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