Effects of water restriction on dairy goats under temperate or semi-arid environments

Water scarcity is a widespread problem in arid and semi-arid regions affecting goat production. This project aimed to study the effects of water restriction on goats from semi- arid and temperate regions. A first step consisted in reviewing the literature on the subject leading to two review manuscripts. In addition, research articles specifically addressing the topic of water restriction in sheep and goat were retained for the compilation of a large database that was used for a preliminary quantitative review (meta-analysis) with the aim of visualizing the effects of water restriction on different physiological and production parameters as reported in literature. The qualitative and quantitative reviews covered sheep and goat as species of interest. The subject of water stress was also addressed experimentally through two experiments on lactating and gestating Shami goats, respectively, raised under semi-arid environment and one experiment on lactating Saanen and alpine goats raised under temperate conditions. An intermittent watering regime of once every four days was imposed on the Shami goats for a period of around 1 month while the Saanen and alpine goats were subjected to a 15-hour overnight water restriction for two consecutive days. The effect of heat stress was also studied during a short episode of rise in ambient temperature from 19oC to 28oC in Saanen and alpine goats. Physiological data, key blood parameters and milk production and composition were recorded and analyzed.Lactating Shami goats subjected to intermittent watering showed increased serum osmolarity, urea, protein and albumin concentrations, denoting dehydration. Milk composition and production, and body weight were not affected by the treatment. However, in the gestating shami goats osmolarity was higher while insulin was lower indicating a possible state of negative energy balance. The kids born to the restricted goats had lower body weight at birth and at one month of age which warrants further research.Similarly, alpine and Saanen lactating goats, although subjected to a milder water restriction regime showed signs of dehydration reflected by the increase in albumin, urea, osmolarity and Na+. The goats were able to maintain body weight and milk production although milk urea and lactose increased under water restriction thus keeping milk isotonic with the blood.Heat stress had no effect on feed intake or on feed and water intake patterns in lactating Saanen and alpine goats. However, there was a 40% increase in water intake. Blood pCO2 decreased because the animals hyperventilated to reduce their body temperature, whereas rectal temperature increased. Milk production was not modified, but milk fat content decreased. Alpine goats drank more water per kg of dry matter intake than the Saanen. This could be explained either by their higher level of feed intake or by the effect of coat colour.The qualitative and quantitative reviews as well as the experimental part helped in determining the most prominent physiological effects of water restriction in small ruminants that are consistently reported namely: decrease in feed intake and milk production and weight loss, increase in osmolarity, urea, sodium, cholesterol and fatty acids and of milk components such as lactose and protein content. At the same time, understudied areas in relation to the effects of water restriction were identified such as water stress in interaction with other environmental factors, the comparison between breeds, the impact of individual variability, methods of water stress alleviation and impact on animal welfare, etc.As a conclusion, this project helped in condensing the relevant information on the effects of water stress on goats thus serving as an accessible resource for guiding future research and possibly goat producers, in facing water scarcity.