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No abstract

W ith ex tra-p air p atern ity now known to be com m on am ong m any species of birds, it is not surprising th at males of most species exhibit behaviour th at minimizes the risk of losing paternity. T h e most com m on form of p atern ity assurance is m ate guarding w hereby the m ale closely follows his m ate during her fertile period and attem p ts to prevent other males from copulating w ith her. Even in com m unal or cooperative breeding species w here two or m ore males collaborate in defending a breeding territory, m ate guarding by the alp h a m ale still occurs. H ere we report th a t w ithin com m unally breeding groups of pukeko (.Porphyrioporphyrio) d o m in an t males do not guard their m ates and rarely in terru p t the copulations of unrelated rival males. This population of pukeko meets the conditions of a m odel th at predicts th at unrelated individuals who form breeding coalitions should interact in an egalitarian m anner. DNA fingerprinting revealed a tendency for alpha males to father the m ajority of offspring in a brood, but frequent, u n in terru p ted copulations by subordinate birds assured th at most males w ithin the group had at least some p atern ity . Because the tim ing of ovulation is difficult to predict in female pukeko, individual males m ay be unable to estim ate the proportion of eggs th at they have fertilized, which could explain why most males p articip ate m ore or less equally in p aren tal care.

This chapter presents information obtained from experiments involving male Ross 308 broiler chickens on the effects of a standardised combination of plant extracts (PE) including carvacrol, cinnamaldehyde and capsicum oleoresin, on bird performance, hepatic antioxidant concentration and immunomodulation. Birds were reared under industryrecognised environments and were fed one of four diets. There were two control diets based on either wheat or maize, formulated to be iso-energetic and iso-nitrogenic. The other two diets were the control diets supplemented with 100 g per tonne of PE, respectively. Feeding PE improved dietary feed efficiency, dietary net energy and hepatic antioxidant contents of the birds, but did not change dietary metabolisable energy (ME). Overall, feeding PE reduced the mRNA transcript levels of three cytokines (IL-12B, IFN-G, and IL-6) and the marker CD 40 LG in caecal tonsils. Dietary PE may maximise the nutritional value of feed through improving gut health by reducing intestinal inflammation. Their mode of action is associated with improved dietary energy availability, immune status and hepatic antioxidant contents of the birds. However, studies that have focused solely on the effect of PE on ME alone may not have detected their full benefit to improve the efficiency of broiler meat production.