Why have a breeding season n To know

Why have a breeding season? ? n To know what is going on n Produce a more uniform, calf crop n Make money

As calving season length increases 1 day: cost of producing each hundredweight of calf weaned increases $0. 047. Reducing calving season from year-round (365 days to 75 days associated with $13+ less cost per cwt. Key Factors Contributing to Cow-calf Costs, Profits, And Production Ruslyn Parker, Damona Doye, Clement Ward, Derrell Peel James Mc. Grann, Larry Falconer and Stan Bevers Southern Association of Agric. Scientists, Tulsa, Okla. 2004

“What we use is about 2 acres per bull with a 5 -strand High Tensile fence with wires at 10/10/10 which is 50 inches tall and a GOOD Charger. One that will keep 5 -7000 volts on the fence. Hot wires are (from ground up) 2, 3 & 5 with 1 & 4 being well grounded… I have seen 3 bulls in a fight in a 5 - acre+- trap like this and they would actually quit fighting when they got close to the fence. ”

May want to electrify bottom wire and also use the pen for calf weaning.

Growing Phases of Young Bulls • Pre-puberty -- Pre-weaning milk capacity and nutrition of the mother • Do NOT implant

Growing Phases of Young Bulls • Pre-puberty -- After-weaning Growing programs aimed at 2. 0 to 2. 5 pounds per day • Diet that is 40% to 60% concentrate:

Growing Phases of Young Bulls • Complete diet should be 12 to 13% Crude Protein. • If hay is 10% CP: Grain mix is 16% CP (4 parts corn: 1 part SBM).

Mineral Programs for Bulls • Simple but still effective 1/2 Dical: 1/2 Salt • Complicated if concerned about trace minerals:

Mineral Program (including TM) • Salt • Dical • CSM • Zinc Sulfate • Se 600 • Cu Sulfate • Mineral oil 6. 61 0. 59 • Ca: 9. 4% P : 8. 3% 44. 10 2. 20 0. 18 2. 20 100

Growing Phases of Young Bulls • Gain tested bulls are often fed at higher percent concentrate. • Rate of gain often exceeds 4 lb/d. • KSU data shows bulls have normal fertility if allowed to reduce condition gradually.

Effects of Sudden Decline of Nutrition on Cycling Of Heifers Treatments 1. 2 M Day 0 Day 14 9 # Heifers 9 711 Weight 704 100 % cycle 100 0. 4 M Day 0 Day 14 10 10 691 658 100 30

Step Down Procedure for Young Bulls on High Concentrate Diets Week Type % of Body wt. lb. for 1000 lb. bull lb. for 1500 lb. bull 1 st bull ration hay 1. 5 1. 0 15 10 23 15 2 nd bull ration hay 1. 0 1. 5 10 15 15 23 3 rd bull ration hay 1. 0 1. 5 10 15 15 23 4 th bull ration hay . 75 1. 75 7. 5 11 27

Consider the Protein Content of the Ration as Step-down Add a pound of soybean meal pellets as concentrate is reduced. 2 nd Choice—Substitute 20% range cubes for high concentrate.

Growing Phases of Young Bulls • Conditioning prior to breeding. • 30 to 60 days before breeding. • Bulls should be gaining 2 lb/day. • Young bulls should be BCS=6.

Before the Breeding Season • Put bulls together to establish social order. • Check feet and legs; trim feet early. • Breeding Soundness Exam.

Normal neck 72% Satisfactory Scrotal Shapes Study - 958 bulls Wedged 1% Satisfactory Straight sided 27% Satisfactory Scrotal Circumference

Percent Satisfactory Bulls Effect of Scrotal Circumference on Semen Quality Scrotal Circumference

Recommended Scrotal Circumference Age < 15 months 15 - 18 months 18 - 21 months 21 - 24 months > 24 months Min SC (cm) Good 30 31 32 33 34 >36 >37 >38 >39

Heat Stress Can Cause Reduced Fertility n Very hot ambient temperatures n High body heat due to fever disease infection n Excessive fatness

Sperm Cells Take 60 Days from Initial Development to Maturation and Ejaculation

Bull Rotation During Breeding • Use mature bulls FIRST, young (yearling bulls) last 1/3. • If ALL young bulls, consider rotating in and out in 2 weeks. • Bulls may lose 100 - 200 lbs.

Growing Phases of Young Bulls • Nutrition during breeding • Limited opportunity; Prior nutrition is key • Monitor young bulls closely

Cow to Bull Ratio Bull age in months 12 -15 15 -18 18 - 24 More than 24 Number of females 10 - 12 12 - 18 18 - 25 25 - 35

Percentage Pregnant by Each Bull in Single-sire Mating of Estrus Synchronized Females. 10 0 90 Percent 80 70 60 50 40 30 20 10 0 0 5 10 15 20 25 30 35 40 Number of Females Exhibiting Estrus per Bull 45 50

Mature Bulls

Management after Breeding Season • Nutrition after breeding • Mature bulls may need to regain lost condition • Gradually increase grain to 1% • Bulls in good condition need protein and forage