DSCI 230 - E3

Bull reproductive organs: Scrotum

Main Form: Oval sac outside the body that houses the testes

Main Function: Regulate the temperature of the testes to support sperm production, while also providing protection and support.

• Temperarure vs sperm viability

• Testes cooler by 1-4°C than body temp

• Cryptorchid

Bull reproductive organs: Testes

Main Form: Oval-shaped (ellipsoid) organs; vertical in scrotum

Main Function: Sperm production & Testosterone production (responsible for development of secondary sex characteristics)

• Primary organs of reproduction

• Maintains normal function of accessory sex glands

Bull reproductive organs: Epididymis

Main Form: Long, tightly coiled duct leading out of the testes

→ 3 main parts: Head (Caput), Body (Corpus), Tail (Cauda)

Main Function: Absorption and Reduction of fluid volume; Storage of sperm

• Secretions - thought to maintain sperm viability

• Essential for fertility - improper function leads to immature or non-motile sperm

• Indictator of reproductive health - in breeding soundness exams, the size and tone of the epididymis and testicles are evaluated.

Bull reproductive organs: Vas Deferens

Main Form: Thick, muscular tube extending from the epididymus to the urethra; includes the ampulla in bulls

→ Duct connecting epididymis and ampulla

Main Function: Transports and helps store sperm; contracts during ejaculation to move sperm into the urethra

Bull reproductive organs: Ampulla

Main Form: Enlarged, glandular end portion of the vas deferens in bulls

Main Function: Stores and concentrates sperm, adds seminal fluid, and helps propel sperm during ejaculation

• Passageway for sperm

• Adds some fluid

Bull reproductive organs: Accessory Sex Glands (Seminal vesicles, prostate, and cowper’s gland)

Seminal Vesicles

• Form: Large, paired, lobulated

• Function: Adds volume, fructose, and nutrients to semen

Prostate

• Form: Small, unpaired, near bladder/urethra

• Function: Adds fluid for sperm mobility and urethral cleaning

Cowper’s Glands

• Form: Small, paired, oval-shaped

• Function: Secrete mucus to lubricate and cleanse the urethra

Bull reproductive organs: Penis

Form: Fibroelastic, S-shaped (sigmoid flexure), with a twisted glans

Function: mating organ that becomes erect by extending the sigmoid flexure and ejaculates semen into the cow’s reproductive tract (vaginal insertion)

Bull reproductive organs: Sheath

Form: Skin-covered, tubular structure with muscular and mucosal lining

Function: Protects the penis, helps with erection and retraction, and keeps the area clean and lubricated

• Protective covering for penis during relaxed state

What is a cryptorchid and how does that affect repro (fertility and hormone production)?

When one teste is not descended and the bull only produces ½ as much sperm

Age of Bull at Puberty

6-12 months

Age When Bull is First Used for Semen Collection

18-20 months

Female reproductive organs: Ovary

Form: Paired, oval reproductive organs with a cortex (functional) and medulla (supportive)

Function: Produce ova and secrete reproductive hormones to control the estrous cycle and supoort reproduction

• Produce eggs and female hormones (progesterone and estrogen)

Female reproductive organs: Oviduct

Form: Coiled tube with three regions - infundibulum, ampulla, and isthmus

Function: Transport egg and sperm, site of fertilization, and delivers the embryo to the uterus.

• Transport egg to uterus; Site of fertilization

Female reproductive organs: Cervix

Form: Thick, muscular canal with 3-5 interlocking folds (annular rings)

Function: Protects teh uterus, regulates sperm entry, supports pregnancy, and opens during birth

• Physical separation between vagina and uterus

Female reproductive organs: Uterine Horns

Form: Long, curved paired structures branching from the uterus

Function: Primary site of embryo implantation and fetal development

• Supports sperm transportation to the oviducts

• The site for fetal growth and development during pregnancy

What is a follicle?

A follicle is a small fluid-filled sac in the ovary that contains an immature egg. It helps the egg grow and mature before ovulation.

What is ovulation?

Ovulation is when a mature egg is released from a follicle in the ovary, ready to be fertilized

What hormone is needed to maintain pregnancy and where is it produced?

• Progesterone is needed to maintain pregnancy

• Produced by the corpus luteum

Differences between polyestrous, seasonal polyestrous, and monoestrous

• Polyestrous: year round, cyclic estrous periods (cow)

• Seasonal polyestrous: ovulation on a regular cycle for portion of the year

• Monoestrous: one fertile period/year

Difference between estrous and estrus

Estrous: the entire cycle in days/months

Estrus: very short window known as standing heat (when the animal is receptive to breeding)

What is estrus and how long is estrus?

• Period of sexual receptivity

• 12-18 hours

Signs of Estrus

• Mucus secretion

• Mounting and riding other cows

• Standing to be mounted; Chin resting on others behind

• Off feed

• Decreased milk production

• Nervous, excitable

Methods of heat detection- pros/cons

1. Visual Observation (Mounting, restlessness, or mucas discharge)

   • Pros: Low-cost, no equipment needed; Immediate, real-time detection

   • Cons: Time-consuming; Easy to miss silent or nighttime heats; Observer experience matters

2. Heat Detection Aids (Patches, tail paint, etc)

   • Pros: Good for large herds; Helps confirm visual signs; Inexpensive

   • Cons: Can give false positives; Requires regular checking and maintenance

3. Activity Monitors (neck or leg-mounted sensors, rumenation collar)

   • Pros: Automated, continuous monitoring; Useful for detecting nighttime heat; Data can be synced with herd management software

   • Cons: Expensive to install and maintain; Requires technical setup and training

Methods of Heat Detection

• Tailhead chalk

• Ink patches (explode when mounted)

• Scratch patches (scratch off when mounted)

• Thermal readings

• Monitoring activity levels and rumination levels based on collar

Trends of use of Artificial Insemination in the US: Beef vs Dairy

• Fewer, larger bull studs

• Majority of dairy heifers and cows bred with AI

• Much fewer beef heifers and coes bred AI

• As of 2014 - 80% of dairy but only 4% of beef

Overview of Semen Collection Methods

• Copulation (have sex)

• Massage: Massage seminal vesicles and ampulla from rectum; Used frequently under conditions where AV or electroejaculation cannot be used

• Electroejaculation: Mild current applied across accessory sex glands

• Artificial vagina: Preparation and procedure try to imitate natural conditions

What characteristics should be evaluated when collecting semen?

• Measure volume

• Evaluate concentration, motility, and morphology

• Check color: creamy yellow, granular, slightly viscous

How should semen be stored and why?

• Package in straws and freeze in liquid nitrogen (-300 F)

• Can be stored for long periods of time

• Average collection contains enough sperm to breed 300 cows

In the lab, what semen characteristics should be evaluated?

• Concentration

  → Hemocytometer - red blood cell counter

  → Photoelectric colorimeter - measure optical density

  → Electronic particle counter - Coulter counter

• Motility: ability to move effectively

• Viability: live/dead

  → Methylene, Trypan Blue

  → Live = clear, Dead = blue

  → 70-80% live is typical

Semen morphology: What would you look for?

• Around 15% abnormal expected

• In 25% of collections, fertility is significantly affected by morphologic problems

Advantages and Disadvantages of AI (Artificial Insemination)

Advantages:

• Wider use of superior sires

• Higher quality product (semen)

• Cost – heavier fencing and feed costs

• Disease control

• Permits use of injured bulls

• Bull proving

• Danger- working around bulls

Disadvantages:

• Observe heats

• Semen care and handling

• Record keeping- heats, semen inventory

• Time

• Training

What is estrus synchronization and when is it useful?

• Controlling or manipulating the estrous cycle so females express estrus at approximately the same time

• Useful when doing AI

• Useful if doing embryo transfer

Three main "hormones" you can inject

• PGF2α

• GnRH

• Progestin

What does PGF2α do and when would you want to inject it?

• PGF2α will cause the regression of the corpus luteum

• Cow will exhibit estrus 2-5 days after PGF2α present

What does GnRH do and when would you want to inject it?

• GnRH controls follicular phase of estrous cycle (FSH); If dominant follicle is present, injection will cause LH surge and ovulation; Overrides progesterone

  → GnRH: Triggers ovulation by stimulating LH and FSH.

  → Use it: For timed AI, cyst treatment, and estrus synchronization.

  → Doesn’t work: If the cow has no active follicle, isn’t cycling, or is mistimed.

What does Progestin do and when would you want to inject it?

• Acts like progesterone to prolong luteal phase and stop ovulation

• Once progestin is removed, progesterone is low so cow will exhibit estrus and ovulate

What does follicle stimulating hormone (FSH) do?

FSH stimulates the follicle to mature and release estrogen

What does luteinizing hormone (LH) do?

LH causes ovulation and helps form the corpus luteum, which is essential for maintaining progesterone and supporting pregnancy.

Which hormones increase at ovulation?

• Estrogen

• LH

• PGF2α

What does progesterone do?

Maintains pregnancy and lining of uterus

Age of Puberty for Heifers

6-9 months

Length of Gestation

285 days (9 months)

Average Weight of Jersey and Holstein Calves

Holsteins: 80-120 lbs
Jerseys: 45-80 lbs

Signs of Approaching Parturition

• Swelling of the vulva

• Relaxation of tissue at the tail head

• Nervousness, separation from other animals, & muscular exertion

What is navel ill?

Navel infection of newborn calves

• Characterized by a loss of appetite, swelling & soreness of joints, umbilical swelling & discharge.

Why do we dip navels at birth?

• To prevent the entrance of infectious organisms

Common Navel Dips Used

• Iodine

• Navel guard

• Nisin

• Chlorohexidine

What are downsides to allowing calf to stay with cow and suckle?

~40% of calves get FPT (Failure of Passive Transfer)

• FPT means a calf didn’t get enough protective antibodies from colostrum, leaving it vulnerable to disease. Failure to absorb colostrol immunoglobulins

Teats are dirty

What is esophageal feeder? Pros and cons?

An esophageal feeder is a tool to give fluids directly to a calf that can’t drink on its own. It’s very helpful but must be used carefully.

• Pros: Ensures colostrum intake; Fast and reliable; Life-saving; Useful in emergencies

• Cons: Requires skill; Can be stressful for calf; Not a long-term feeding method; Risk of esophageal injury

Why does esophageal groove close when calves feed?

The esophageal groove closes during suckling so that milk goes straight to the abomasum, not the rumen- helping the calf digest it properly and stay healthy.

Basics about vaccinating calves

Best Practices:

• Use clean, sterile needles

• Follow label directions and timing

• Store vaccines at proper temp (usually refrigerated)

• Record what was given and when

• Use a booster if required

• Don’t vaccinate stressed or sick calves- wait until healthy

Vaccinating calves protects them from deadly diseases. Start around 2–4 months, follow a schedule, and give boosters as needed. Healthy calves = better growth and lower risk of illness.

Give oral vaccines with colostrum?

Yes and often recommened

• Oral scours vaccines are often given within the first few hours after birth, before or with colostrum.

• These vaccines stimulate local gut immunity (IgA), which works alongside maternal antibodies from colostrum.

• Giving them before the gut closes (within 12-24 hrs) is important for best absorption.

Give intranasal vaccine?

Can be given very early - even at birth

• Intranasal vaccines protect against respiratory diseases like:

  → IBR (infectious bovine rhinotracheitis)

  → PI3 (parainfluenza virus)

  → BRSV (bovine respiratory syncytial virus)

• THese vaccines bypass the gut and stimulate local immunity in the nasal passages/lungs

• Often used in young calves, including those with maternal antibodies, because they don’t interfere with intranasal immunity.

When to give subcutaneous or intramuscular vaccines?

• Subcutaneous (SubQ): Given under the skin. Preferred for young calves (less tissue damage). Often used for clostridial vaccines and many respiratory vaccines.

• Intramuscular (IM): Into the muscle. Used when specifically required by vaccine label. May cause more tissue reaction. Avoid in meat-producing animals unless necessary.

Most injectable vaccines are given at 6-8 weeks of age or older, after maternal antibodies decline, so the calf can mount its own immune response.

What vaccines are recommended at birth? Why?

• Rotavirus and Coronavirus, to prevent scours

• Later on (3-6 months): Bovine rhinotracheitis, Bovine Virus Diarrhea, Parainfluenza-3, and Bovine Respiratory Syncytial Virus

What is scours? What can cause it?

Diarrhea caused by bacteria, viruses, and protozoa

Basics of colostrum composition: What is higher in colostrum than milk?

• Colostrum is rich in immunoglobins, carotenoids, fat soluble vitamins, minerals, and protein

• Low in lactose

When do we want to feed colostrum?

1st hour of calf life and then 12 hours later

What do we look for regarding colostrum quality?

• Free of blood, debris and mastitis (E. coli scours)

• Healthy, vaccinated cow

• Bacteria count: <100,00 CFU/mL; >50 g/L IgG

How much to feed a calf based on body weight?

Feed about 10% of body weight as high quality

How can we measure colostrum quality?

• Colostrometer: a simple tool used to measure the quality of colostrum based on its specific gravity. Looks like a float inside a cylinder or test tube

  → Green zone

• Refractometer: measures colostrum quality, but by checking Brix %, which reflects sugar and protein content (a proxy for IgG). Only a few drops of colostrum are needed.

  → >22% Brix

What concentration of IgG is considered good quality?

• IgG > 50 mg/ml

What Brix value?

• Brix > 22%

How does colostrum quality affect calves?

• Clean colostrum will provide better long-term benefits to the calf

How do we store and thaw colostrum? Why?

• Colostrum stored at room temp for any period of time results in bacterial growth

• Frozen colostrum should be thawed in warm water or at room temperature, but not hot water

How does pasteurization affect colostrum?

• Lowers bacteria

• Temperatures above 60C (140F) may denature whey proteins (Ig)

• Temperatures above 65C (149F) may cause a degrease in IgG levels

How does heat treating colostrum affect quality and passive transfer rates?

• Lowers bacteria concentration

• Higher serum total protein and IgG

How does Scourguard work to protect calves?

Given to pregnant cows to prevent scours in calf

Methods of identifying calves: Most common?

• Ear tags (most common)

• Tattoos

• Branding

• Photos and drawings

• Registration certificate

Why do we dehorn?

• For the safety of other cows and people

Methods of dehorning: Most common?

• Electric hot iron (most common)

• Chemical pastes

• Barnes dehorner

• Tube scoop

Basics of cleaning calf feeding utensils

• Warm water rinse

• Soap and hot water

• Chlorine and/or acid water wash with cold water

What should calf starter mainly be composed of? Roughage or concentrate? Why?

• Rolled corn (36%), rolled oats (25%), Molasses (5%); More platable

Calf starter should mainly be concentrate, not roughages, because it supports rumen development, growth, and early weaning. Add roughage later, in small amounts.

When can we start thinking about weaning? Considerations?

• Weaning at 5 to 6 weeks of age, calf should be eating > 1.5 lb/day

• Weaning at 8 to 12 weeks of age, intake is not an issue

What are the main goals of heifer replacement program?

• Low mortality rate of calves from birth to weaning - less than 5%

• Normal growth rate to allow for early breeding

• Heifers of high genetic potential for the economically important traits

Basics of Senate Bill 1383

The state has set methane emission targets, with the goal of reducing statewide emissions by 40% below 2013 levels by 2030, as well as reducing emissions in the dairy and cattle sectors by 2030.

SB 1383 is a statewide mandate to:

1. Reduce organics to landfills by 75%,

2. Divert edible food for donation (20% increase),

3. Standardize collection programs across households, businesses, and facilities,

4. Build composting/digestion infrastructure, and

5. Enforce compliance with penalties starting in 2022–2024.

Advantages/disadvantages of feeding milk, fermented colostrum/milk, or milk replacer?

Whole milk:

• Pros: Natural, nutritious, digestible

• Cons: Disease risk, variable quality, expensive

Fermented Colostrum:

• Pros: Preserves feed, may aid gut health

• Cons: Spoliage risk, variable taste and quality

Milk Replacer:

• Pros: Consistent, convenient, lower disease risk

• Cons: Depends on quality, can cause scours if mixed poorly