A survey on the feeding of eventing horses during competition

This study aims at the comparison of the actual feeding of horses with the recommendations from the literature, and it studies the effects of feeding and exercise on several blood metabolic parameters before and after exercise. Blood samples were collected from 25 horses during one-star eventing competitions and evaluated for blood glucose, insulin, lactate, free fatty acids and triglyceride levels. Questionnaires on the feeding practices of the horses were evaluated. The questionnaires revealed that during training, and on tournament days, horses received on average 4.3 kg of concentrate per day (min. 1.54 kg, max. 8 kg). The statistical analysis showed no significant effect of the amount of concentrate fed before exercise on the measured blood values. Oil was supplied as a supplementary energy source to 30% of the horses, but most of them only received very small quantities (0.02–0.4 l/day). Five horses (20%) had no access to salt supplements at all, and eleven horses (45%) had no access to salt on tournament days. Fifteen horses (60%) were supplied with mineral feed. Twenty-one horses (84%) had daily access to pasture during the training period. During competition, 55% of the horses received roughage ad libitum, compared with 37% during training. The majority of the horses received less roughage on days before the cross-country competition. It could not be ascertained whether feeding a large amounts of roughage had a beneficial effect on performance, because only a few horses in this study were fed with very restrictive roughage. Feeding of most of the horses was in agreement with the recommendations from the literature, except the need for sodium and chloride. The sodium and chloride need for sport horses may be overestimated in literature and needs to be re-evaluated.

Parental influence on sibling rivalry in great tit, Parus major, nests

Sibling and parente-offspring conflicts arise mainly over the amount and distribution of parental care, especially food. In altricial bird species where the young depend on parents for obtaining food, parents may control sibling competition by the choice of their respective provisioning locations. In great tits, the parents use fixed provisioning positions on the nest rim that are determined early in the breeding cycle and maintained until. edging. The two parents may choose positions that are close to each other, or far apart, and thereby increase or relax the pressure for optimal feeding positioning among nestlings. As an inspiration to this study we previously found that the two parents provide food from closer positions if the nest is infested by ectoparasites. Here, we tested the hypothesis that the parental choice of relative provisioning locations could be strategically used to control nestling competition. We forced parents to feed from either one or two provisioning locations and assessed the induced change in nestling movement, weight gain, and food distribution among siblings. We show that the angular distance between male and female locations influences the level of behavioural competition and affects nestling weight gain and food distribution. It is the first evidence for hole-nesting birds, where it was assumed that the nestling closest to the entrance hole was fed first, that the apparent choice of feeding positions by parents could be a way of controlling sibling competition and thereby also taking partial control over the outcome of parente-offspring conflict. (c) 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Intermediate Kinematics Produce Inferior Feeding Performance in a Classic Case of Natural Hybridization

Selection on naturally occurring hybrid individuals is a key component of speciation theory, but few studies examine the functional basis of hybrid performance. We examine the functional consequences of hybridization in nature, using the freshwater sunfishes (Centrarchidae), where natural hybrids have been studied for more than a century and a half. We examined bluegill (Lepomis macrochirus), green sunfish (Lepomis cyanellus), and their naturally occurring hybrid, using prey-capture kinematics and morphology to parameterize suction-feeding simulations on divergent parental resources. Hybrid individuals exhibited kinematics intermediate between those of the two parental species. However, performance assays indicated that hybrids display performance most similar to the worse-performing species for a given parental resource. Our results show that intermediate hybrid phenotypes can be impaired by a less-than-intermediate performance and hence suffer a larger loss in fitness than could be inferred from morphology alone.