Factors affecting Growth | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Introduction

Understanding how a baby grows in the mother's womb involves considering various factors. From the influence of hormones and genetics to the impact of maternal size, nutrition, and even the ambient temperature, these elements play a crucial role in shaping the growth and development of the fetus. Let's explore these factors in simpler terms to grasp their significance in the journey of prenatal growth.

Hormones

• The baby inside the mother's womb grows with the help of hormones from glands like the pituitary, thyroid, and adrenal.
• Growth hormone and thyroid hormone are crucial for normal development.

Genetics

• The baby's size at birth and overall development are mainly determined by its genetic makeup.
• Differences in species and breeds contribute to variations in size.

Maternal Size and Age

• The mother's size directly influences the baby's growth.
• Even with a genetic predisposition for a larger size, if the mother is small, the baby may not reach its full potential.
• Older mothers tend to have larger babies due to better maternal body size.

Maternal Nutrition

• The baby continues to grow even if the mother is underfed, but at a slower rate.
• Inadequate nutrition during pregnancy can lead to reduced growth and lower birth weight.
• Proper nutrition is essential for the baby's development, especially during the later stages of pregnancy.

Litter Size

• In animals that give birth to one offspring (monotocous), having more than one baby (twinning) can decrease each baby's birth weight.
• This effect is influenced by both nutritional factors and the number of fetuses in the uterus.

Placental Size

• The growth of the baby is directly linked to the size of the placenta.
• A smaller placenta can lead to slower fetal growth.

Sex of the Fetus

• Male fetuses generally grow faster and have better birth weights than female fetuses.
• This difference is observed in various species, such as mules having a higher birth weight than female foals.

Ambient Temperature

• High temperatures during pregnancy can directly affect fetal growth.
• It's not just about the mother's food intake but also the temperature's direct impact on the baby.

In simpler terms, a baby's growth is influenced by hormones, genetics, the size and age of the mother, maternal nutrition, litter size, placental size, the baby's gender, and the ambient temperature during pregnancy. Each factor plays a role in ensuring the baby develops properly before birth.

Effects of Heat on Pregnant Ewes and Animal Growth

Heat Stress and Fetal Growth

• Exposure to high temperatures during pregnancy reduces the growth of lamb fetuses.
• The longer the exposure, the greater the reduction in fetal growth.
• Dwarfing of lamb fetuses is specifically caused by higher temperatures, not by reduced food intake.

Consequences of Undersized Birth

• Animals born undersized are like premature babies and face higher risks of neonatal mortality.
• They struggle with poor ability to regulate body temperature and handle stress in a new environment.

Impact of Temperature on Fetal Growth

• Lower environmental temperatures also affect fetal growth but in different ratios based on genetic makeup.
• Two types of growth are observed: isometric (same rate as the body) and allometric (different rate).
• Different organs follow both growth rates during prenatal and postnatal periods.

Sequence of Organ Growth

• In prenatal life, the central nervous system (CNS) grows first, followed by the circulatory system, bones, muscles, and adipose tissue.
• Postnatal growth follows a sequence: loins, pelvis, thorax, head, neck, and finally legs.

Factors Affecting Animal Growth

• Genetics, nutrition, disease, hormones, environmental factors, and more impact animal growth.
• Chemical compounds, even those naturally in animals, influence growth when deficient.

Nutrition's Role

• Proper nutrition with calories, amino acids, vitamins, minerals, and water supports energy and raw materials for growth.
• Both prenatal and postnatal environments significantly affect physical development and long-term animal performance.

Postnatal Growth Factors

• Genetics, nutrition, sex, hormones, vitamins, climate, antibiotics, feed additives, growth factors, litter size, maternal milk, nervous system, and social environment control animal growth.

Genetic Influence

• Heredity or genetic makeup determines an animal's growth potential.
• Outbred and crossbred animals generally have higher growth rates compared to inbred ones.

Nutrition's Economic Impact

• Nutrition plays a crucial role in the economics of meat and milk production.
• Different nutrition levels at various ages affect carcass composition, with high nutrition leading to early marketable weight.

Effects of Poor Nutrition

• Poor nutrition early in life results in permanent growth retardation.
• The impact of low nutrition depends on the growth stage, emphasizing the need for adequate nutrition throughout an animal's life.

Sex and Growth

• The sex of the animal, both genetically and hormonally, affects growth.
• Outbred and crossbred animals generally show higher growth rates compared to inbred ones.

Animal Growth Influencers Explained

Gender Differences in Growth

• Generally, male animals grow faster and reach better weights than females, even with identical nutrition.
• In cattle and swine, males outgrow females. Horses show no birth weight difference, but males surge in growth after 17 months due to androgens.

Hormones and Growth

• Four hormone types affect growth: sex hormones, thyroid hormones, adrenal corticoids, and pituitary hormones.
• Androgens (sex hormones) promote growth, especially in females. Estrogens slow skeletal growth.
• Thyroid hormones, when balanced, maintain growth. Mild imbalances may impact carcass quality.
• Lack of adrenal corticoids (cortin) leads to growth retardation. Pituitary hormones directly and indirectly influence growth.

Vitamins' Role

• Vitamins, especially B-complex, A, and C, are essential for normal growth.
• Vitamin B12 is crucial in poultry and swine for optimal growth.

Climate's Impact

• Climate affects growth by influencing fodder availability and the animal itself.
• In hot climates, reduced food intake slows growth. In cold climates, increased food intake compensates for energy expenditure and promotes growth.
• Animals adapt differently to varied climates, influencing their growth rates.

Antibiotics and Feed Additives

• Antibiotics like penicillin enhance growth by removing infections and improving nutrient absorption.
• Feed additives, like synthetic hormones or anthelmintics, can positively impact growth but may have adverse effects later.

Tranquilizers and Growth Factors

• Tranquilizers reduce animal activity, improve appetite, and promote growth.
• Growth factors like epidermal and nerve growth factors influence skin and nervous system development.

Litter Size and Milk Impact

• Animals from singles grow better than twins, and twins grow better than triplets.
• Milk supplied by the mother promotes rapid growth in young animals.

Nervous System's Role

• The nervous system directly controls growth by regulating feed intake through hunger and satiety centers.
• Indirectly, it regulates hormone release crucial for optimal growth.

Social Environment's Influence

• Social organization and relationships among animals impact growth.
• Dominant animals in group feeding have higher priority and tend to exhibit better growth.