No abstract

The changes in the environmental factors like ambient temperature, relative humidity, wind speed and solar radiation causes stresses in lactating cattle. Heat stress is a condition in which the animal body has problems dissipating excess heat. Results of inadequate heat dissipation range from general discomfort to symptoms of heat rash, heat syncope, heat cramps, heat exhaustion and heat stroke. Heat stress assessment methods were carried out using some equations presented temperature-humidity index (THI) or heat stress index (HSI) or using different heat index charts. Temperature Humidity Index is calculated based on the relationship between environmental temperature and relative humidity. The heat stress index is a simple combination of temperature and humidity and has been designed as a measure of animal comfort. Heat Index Chart is a chart used by dairy producers to estimate the severity of heat stress of a dairy cow. This chart utilizes ambient temperature and relative humidity, which are readily available to the dairy producer on a daily basis and indicate from slight to severe heat stress of dairy cattle from some equations

The present work was planned to study the effects of different lighting regimes in both mild and hot periods of the year on New Zealand White doe rabbit traits. The light regimes used were natural daylight as control, 16 h light and 8 h darkness, 12 h light and 12 h darkness, and 8 h light and 16 h darkness. The traits studied were thermoregulatory parameters (respiration rate and temperatures of ear, rectum and skin), type of mating necessary, conception rate, gestation period, fur plucking, behavioural indicators of stress, litter size, litter weight, kit body weight, kit daily gain in weight, milk yield, kit milk intake, efficiency of conversion of milk into live-weight gain and kit mortality, at weekly intervals between birth and weaning at 35 days. Estimation of temperature-humidity index indicated that the doe rabbits were exposed to very severe heat stress, during the hot period of the year. Period of the year (heat stress) affected adversely many of the doe traits studied. The effects were significant (P < 0·001, 0·01 or 0·05) on thermoregulatory parameters (respiration rate and temperatures of ear, rectum and skin), litter weight at days 21 and 28 of age, kit body weight at birth, milk yield of the doe at day 7 of suckling and milk intake per kit at 7 and 14 days of age. Exposure of doe rabbits to a long daylight regime affected adversely many of the traits studied, while the contrary occurred with short daylight. The effects were significant (P < 0·001, 0·01 or 0·05) on litter size at all ages except at birth, litter weight at 14, 21 and 28 days of age, milk yield on all days studied, efficiency of conversion of milk into live-weight gain at days 7, 21 and 28 and mortality at birth and pre-weaning. There was no significant interaction between period of the year and light regime on any of the traits examined. Therefore, only the main factors are reported.

Twenty Zaraibi goat bucks were used in this experiment which lasted 3 months during summer season of Egypt. The animals were divided randomly into two equal groups. The first group was kept without treatment as control while in the second group, rumen-protected choline (RPC) at the level of 20 g/buck/day was added to the concentrate feed mixture at the morning feeding. RPC additives to diet of Zaraibi goat bucks during the period of hot summer season increased (P < 0.01) total gain and average daily gain compared to the control group. RPC increased (P < 0.05) dry matter intake and feed conversion while water intake was not affected by RPC additives. RPC increased (P < 0.05) red and white blood cell (RBC × 10, WBC × 10) counts and hemoglobin concentration and hematocrit percentage. RPC increased total protein (P < 0.05), globulin, and γ-globulin (P < 0.01). On the other hand, total lipids, total cholesterol, and triglyceride concentrations decreased (P < 0.05 and P < 0.05) while phospholipids, glucose, and choline concentrations increased (P < 0.01) due to RPC supplementation. RPC increased (P < 0.01) thyroxin and triiodothyronine, increased (P < 0.05) testosterone levels, and decreased (P < 0.01) cortisol level compared with control bucks. It is concluded that dietary RPC at the rate of 20 g daily is required for growing male goats, especially, under heat stress conditions of summer season in Egypt and showed the best results concerning the growth, feed conversion, blood metabolites, and economic efficiency.

Ninety of each of New Zealand White (NZW) and Californian (Cal) male weaned rabbits at 5 weeks of age with nearly similar average live weights were used during two periods of the year (mild and hot, each of 9 weeks), in a trial to evaluate their adaptability as meat animals to the subtropical conditions of Egypt. The results showed that NZW surpassed Cal, in most of the traits studied. The increase was significant in final live weight, daily weight gain, final body solids, daily body solids gain, body water concentration (ml per 100 g body solids) and pre-slaughter weight. Meanwhile, Cal significantly surpassed NZW in daily water consumption. The temperature-humidity index (THI) values indicated absence of heat stress in the first period and exposure to moderate (but very close to severe) heat stress in the second. The hot conditions induced significant decline in final live weight, daily weight gain, food intake, final body solids, daily body solids gain, plasma tri-iodothyronine (T3) hormone, total proteins, albumin, globulin, total lipids, glucose, electrolytes (Na, K, Ca, Mg and P), pre-slaughter weight and kidneys with fat weight. In contrast, the hot conditions were accompanied by significant increases in water intake, body water concentration, plasma urea-N, creatinine and physiological body reactions (respiration rate and temperatures of rectum, skin and ear). Drinking water containing high levels of salt (3000 p. p. m. and more) caused significant decreases in final live weight, daily live-weight gain, final body solids, daily body solids gain, plasma T3 hormone, total proteins, albumin, total lipids, glucose, pre-slaughter weight and kidneys with fat weight. At the same time, significant increases occurred in water consumption, body water concentration, plasma urea-N, creatinine, electrolytes (Na, K, Ca and P), respiration rate and rectal and skin temperatures. Estimations of adaptability to the subtropical environment of Egypt and tolerance to drinking saline water under the same conditions were found to be proportionately 0·844 and 0·876 and 0·821 and 0·803, in NZW and Cal, respectively.