title: Effect of heat intensity and persistency on prolificacy and preweaning kit growth at different stages of the rabbit production cycle.
abstract: The aim of this research was to assess the effect of temperature intensity and variation both throughout the day and between days within different periods of the reproductive cycle and the lactation of the rabbit. This information would help in establishing optimal patterns of environmental temperature control in rabbitries. The traits analyzed were total number of kits born (TB), number of kits alive at weaning (NW), and average individual weight at weaning (AvgWW). For each trait, several mixed models were fitted to the data, differing only in the number and type of temperature descriptors included in the vector of fixed effects. Those descriptors were the average daily mean, maximum, and range of temperatures (AvgTmean, AvgTmax, and AvgRg, respectively) and the CV of daily mean temperature (CVTmean). All were calculated for periods in which important physiological processes related to the studied traits occur. High environmental temperature was found to have a detrimental effect on prolificacy and preweaning growth of the kits. When the average daily mean reached 20°C, it produced a linear decay of TB of around 0.1 kit/°C. The most sensitive period for TB could cover from spermatogenesis to embryo implantation. However, the high correlation between descriptors calculated for different periods makes it difficult to assign an effect to each specific period and therefore to the specific physiological process occurring in that period. The effect on NW was smaller and quadratic, with an optimum value between 18°C and 21°C. Weaning weight was the most strongly affected trait similar to NW. It also showed a quadratic response to AvgTmean, with an optimum value in the same temperature interval as NW and a strong decline in weaning weight with temperatures higher than 21°C (-14 g/°C). There were no differences on the effect of heat at different stages of lactation on NW and AvgWW. The impact of high environmental temperatures on prolificacy is alleviated if a drop in temperature is produced during the day. Thus, the effect of AvgRg was relevant and positive for TB and NW. However, it had a quadratic negative effect for AvgWW at late lactation. The temperature variation between days within a period has a positive effect on TB and AvgWW but a negative effect on NW when it is produced at middle lactation, whereas there is no effect at other stages of lactation.
authors.affiliation: Unitat de Cunicultura, Institut de Recerca i Tecnologia Agroalimentàries, Torre Marimon s/n, 08140, Caldes de Montbui, Barcelona, Spain. miriam.piles@irta.es
authors.forename: M
authors.initials: M
authors.lastname: Piles
authors.forename: L
authors.initials: L
authors.lastname: Tusell
authors.forename: O
authors.initials: O
authors.lastname: Rafel
authors.forename: J
authors.initials: J
authors.lastname: Ramon
authors.forename: J P
authors.initials: JP
authors.lastname: Sánchez
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D000833:Animals, Suckling; D002940:Circadian Rhythm; D005260:Female; D006358:Hot Temperature; D008297:Male; D008954:Models, Biological; D011817:Rabbits / Q000254:growth & development* / Q000502:physiology*; D013312:Stress, Physiological; D016019:Survival Analysis; D013997:Time Factors