الفهرس 
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Abstract
This experment was carried out at the Animal Production Experimental Farm, Faculty of Agriculture, New Valley University. The study was started from June, 2022 to May, 2023 in the New Valley Governorate.
A total number of fifteen healthy Boer does about 4-5 years of age and an average body weight of 41.12 ± 0.93 kg were used in this study. The animals were divided randomly into three equal groups, viz, control group and two levels of Chlorella vulgaris (CV) supplemented group, with five goats in each group. All goats were fed on basal diet. The basal diet consists of 60% concentrate feed mixture and 40% fresh berseem, and wheat straw. Does of the control group did not received any supplementation. While, the first supplemented group received CV (7.5 g/h/d) and the second supplemented group received CV (15 g/h/d) for the entire period of the study in addition to the regular maintenance diet. The objectives of the present study were to evaluate the ability of CV microalgae to overcome the harmful effects of HS. Furthermore, to determine its impact on thermoregulatory responses, blood characteristics, antioxidant status, reproductive performance, and milk production of Boer goats and the growth performance of their newborn kids under New Valley hot climatic conditions.
The obtained results could be summarized as the following
1. Climatic conditions during experimental period
• The average ambient temperature during the experimental period ranged from 24.2oC to 27.3o C at 08:00 am and 37.4 o C to 42.5oC at 02:00 pm. While, the respective RH ranged from 11% to 22%.
• The average values of temperature-humidity index THI were between 71.6 to 74.78 at 08:00 am and 76.93 to 83.33 at 02:00 pm during the experimental period.
2-Digestibility coefficients
Digestibility coefficients of dry matter (DM), organic matter (OM), crude protein (CP), fat, crude fiber (CF) and nitrogen free extract (NFE) were increased for CV groups than control. Goats received CV-7.5 recorded the highest digestibility of DM, OM, CP and CF, followed by CV-15 group, whereas, control group had the lowest values.
3- Thermoregulatory responses
Supplementation of CV decreased rectal temperature (RT), respiration rate (RR), heart rate (HR), hair temperature (HT), skin temperature (ST) and ear temperature (ET) at 08:00 am, but the differences were not significant. While, caused a significant decrease in RT, RR and PR at 02:00 pm in CV treated goats.
4- Hematological parameters
The number of red blood cell (RBC) count, hemoglobin concentration (Hb), hematocrit (Ht),in the CV-7.5 group goats were statistically higher (P<0.05) than control. Whereas there was no difference observed between treatments on mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), white blood cell (WBC) and platelets (PLT). Dietary CV at level of 15g/d/h had no statistically significant differences on hematological parameters vs. control group.
5- Blood biochemical parameters
• Serum concentrations of total protein (TP), glucose (Glu), serum cholesterol (TC), did not differ significantly among treatment. Moreover, Urea-N (BUN), creatinine (Cr), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) was significantly higher (P< 0.05) in control group than CV groups.
• The highest (P< 0.05) TAC was recorded for goats treated with CV-7.5 followed by those goats treated with CV-15, and to lesser extent of control group.
• Serum concentration of triiodothyronine (T3) and thyroxine (T4) hormones was significantly (P<0.05) higher in CV groups than control group.
5- Reproductive performance
• Response to Synchronization
The present study illustrated that all goats exhibited no difference in their response to synchronization due to treatments. As all the animals taken in each treatment were cyclic, thus all the goats showed normal estrus. So, all the animals in these groups were inseminated at the appropriate time of estrus as per the observations of the signs of estrus.
• Conception rate
The higher conception rate (100%) was recorded for goats treated with CV. While, lower conception rate (80%) was extent in control group.
• Kidding performance
Supplementation (CV) significantly improve kidding rates, number of kids born, number of viable kids at weaning and shortened the gestation length.
• Estrogen and progesterone hormone
The highest levels of estrogen and progesterone hormone were recorded in CV-7.5 group followed by CV-15 compared with control.
6. Milk yield and compositions
The current study showed an increase of the milk yield in the CV groups compared to that of the control group. At the same time, total solids, fat percentage, protein, lactose, ash and calorific value (Kcal/100g) in milk were significantly increased (P<0.05) by CV microalgae supplementation. While, fat percentage, milk protein, lactose and ash in colostrum didn’t show significant differences.
7. Growth performance of the newborn kids
The average birth weight of kids was 3.300 kg, 2.883kg, and 3.200 kg, in control, CV-7.5 and CV-15 groups, respectively. Supplementation of CV microalgae at level of 7.5 g / d revealed increase in live body weight at 30, 45, 60, 75 and 90 days of age in comparison with the other groups.
Conclucion
It was concluded that CV microalgae have an ameliorative effect on the physiological responses of Boer goats including thermoregulatory responses and improved the productive and reproductive performance, without any harmful effect on animal health, blood hematology and serum biochemical indices under heat stress of New Valley conditions