effect of breed type and post-weaning plane of nutrition

Effect of breed type and post-weaning plane of nutrition on age at puberty and pregnancy rate in beef heifers

J. Heslin 1,2, D.A. Kenny 1, A.K. Kelly 2 and M. McGee 1 1Teagasc, AGRIC, Grange, Dunsany, Co. Meath, Ireland; 2School of Agriculture and Food Science,

University College Dublin, Belfield, Dublin 4, Ireland.

Introduction Approx. 1 m suckler cows in Ireland

• 85% spring-calving

Currently late-maturing (LM) continental breeds dominate breeding within suckler herd Source of replacement heifers ~25% dairy herd, ~75% suckler herd

• Within-herd generation of replacements “Replacement Index”

• Dairy expansion – opportunity for sourcing

2

Introduction Reproductive efficiency is essential for

profitability • Calve at 24 months

• Seasonal calving herds e.g. spring/autumn

» Central to this is age at puberty – available for breeding

Modelling analysis from Grange: Delaying age at first calving from 24 to 36 months decreased net margin per ha by 50%

Teagasc Presentation Footer 3

Calving at 24 months of age Current reproductive performance of

beef heifers in Ireland • Average age @ first calving is 31.5 months

• 20% calve for first time between 22-26 months

• Top 15% of herds: 50% of heifers 1st calve at 24 months

Challenging but can be done i.e. The Derrypatrick, Newford and Maternal Herds


Objectives 1. Establish age at puberty for contrasting

replacement heifer breed types

2. Study the effect of overwinter plane of nutrition on age at puberty and pregnancy rate in beef heifers

3. Identify growth rates and develop nutritional regimes to reach target weights to maximise reproductive performance


Experiment details Duration 2 years (2015, 2016)

Animals 320 heifers (160 annually) Spring-born Early – (Angus; EM) OR late – maturing

(Limousin; LM) sire breeds Born to either suckler beef (B) OR dairy

(D) cows Sourced via ICBF – known parentage


Animal management Indoor “winter” period

Housing Housed slatted-floor shed; pens of 5 141 (2015) and 150 (2016) days until

turnout to pasture (Nov-Apr)

Diet Grass silage (69% DMD) to appetite +

1.5kg barley-based concentrate/head/d (MOD) Grass silage (69% DMD) and concentrate

to appetite (HI)



Animal management Outdoor “grazing” period

Turnout to pasture April 7 (2015), April 15 (2016) 6 groups Diet Rotationally grazed perennial ryegrass

dominant swards Breeding Late April – Late July in both year

simulate spring – calving system A.I. – single sire – AM:PM rule

Animal measurements Dry matter intake Silage + conc (pen basis)

Bodyweight Indoor period – weekly Outdoor period – fortnightly until “in-calf”

Blood sampling Twice weekly – [Progesterone] to determine

age at puberty

Scanning Pregnancy confirmation



Results

Feed (DM) intake of heifers during indoor period


No difference in daily silage, concentrate or total DM intake between D and B heifers EM heifers had a higher DM intake of concentrate and GS than LM heifers By design, heifers on HI diet had a higher DM intake of concentrates and total DM

intake than heifers on MOD diet, while MOD heifers had a higher total DM intake of silage

0

1

2

3

4

5

6

7

D B

Dam Breed (DB)

kg D

MI/h

d/d

ConcentrateGrass silageTotal

0

1

2

3

4

5

6

7

EM LM

Sire Breed (SB)

kg D

MI/h

d/d


0

1

2

3

4

5

6

7

8

MOD HI

Nutrition (N)

kg D

MI/h

d/d


***


0.84

0.70 0.78 0.76

0.51

1.03

D B EM LM MOD HI

Dam breed (DB) Sire breed (SB) Nutrition (N)

ADG Indoor Period (kg) *** ***


05

101520253035404550556065707580859095

100

D B

Dam breed

%

6 w sub6 w preg12 w preg

05

101520253035404550556065707580859095

100

EM LM

Sire breed

%


05

101520253035404550556065707580859095

100

MOD HI

Nutrition

%


Heifer reproductive performance

Compared to B heifers, D heifers had a: Greater 6 week submission rate Higher 6 and 12 week pregnancy rate

Compared to LM heifers, EM heifers:

Were younger at puberty Had a higher 6 week pregnancy rate However, there was no difference in 12 week pregnancy rate

Compared to MOD heifers, HI heifers were: Younger at puberty However, there was no difference in 6- or 12- week pregnancy rate

Conclusion Heifers from dairy dams had a higher

pregnancy rate at 6 and 12 weeks Early maturing sired heifers had a

higher 6 week pregnancy rate than late maturing heifers. No difference in 12 week pregnancy rate No difference in pregnancy rate

between MOD and HI heifers


Implications at farm level


Target weight at breeding and required performance

EM Dairy LM Dairy EM Beef LM Beef Target WT @ breeding, kg 360 380 420 450

Housing WT, kg 200 210 290 300

Winter ADG required, kg 0.87 0.95 0.65 0.80


1 135 d winter

2 6 weeks turnout and breeding assuming ADG 1kg

3 Breeding 1st May

Target weight – Breed type LM Dairy

Housing WT 210kg Target WT @ breeding 380kg 120 d winter (Nov-Mar) ADG required 0.82kg ADG (Mar – May) 1.20kg 150 d winter (Nov-Apr) ADG required 0.89kg ADG (Apr-May) 1.20kg


Target weight @ breeding: 380kg

Target weight – Breed type EM Suckler




Target weight – Breed type LM Suckler






EM D LM D

Age at puberty, d 420 438

6 week preg % 72 56

8 week preg % 83 71

10 week preg % 91 78


Key weights (kg) Time EM D LM D

Housing 220 213 Yearling 314 308 Turnout 338 336 Puberty 341 353

Breeding 332 328 1st AI 354 358

Conception 362 369



EM B LM B

Age at puberty, d 426 437

6 week preg % 58 54

8 week preg % 70 69



Key weights (kg) Time EM B LM B

Housing 280 311 Yearling 360 384 Turnout 385 403 Puberty 390 415

Breeding 377 397 1st AI 403 420

Conception 415 429



ADG Indoor Period EM D 1 EM D 2 0.59 kg 1.07 kg

Pregnancy rate EM D 1 EM D 2

6 week 70 % 74 %

8 week 78 % 89 %

10 week 90 % 92 %

12 week 95 % 92 %

Time EM D MOD EM D HI

Housing 219 kg 221kg


Turnout 304 kg 372 kg


Breeding 305 kg 358 kg



Time LM D MOD LM D HI

Housing 213kg 214kg

Time LM D MOD LM D HI Turnout 299kg 373kg

Time LM D MOD LM D HI Breeding 301kg 356kg

ADG Indoor Period LM D 1 LM D 2 0.59kg 1.13kg

Pregnancy rate LM D 1 LM D 2

6 week 61% 54%

8 week 74% 72%

10 week 74% 85%

12 week 92% 92%



Time EM B MOD EM B HI Housing 281kg 279kg

Time EM B MOD EM B HI Turnout 350kg 421kg Time EM B MOD EM B HI

Breeding 348kg 406kg

ADG Indoor Period EM B MOD EM B HI

0.46kg 1.02kg

Pregnancy rate EM B MOD EM B HI

6 week 57% 60%

8 week 70% 70%

10 week 73% 78%

12 week 78% 85%



Time LM B MOD LM B HI Housing 310kg 312kg

Time LM B MOD LM B HI Turnout 372kg 435kg

Time LM B MOD LM B HI Breeding 373kg 421kg

ADG Indoor Period LM B MOD LM B HI

0.43kg 0.89kg

Pregnancy rate LM B MOD LM B HI

6 week 55% 54%

8 week 75% 62%

10 week 85% 72%

12 week 90% 74%

Results - Breed type


Time EM D LM D EM B LM B Housing 220 213 280 311*** Yearling 314 308 360 384* Turnout 338 336 385 403 Puberty 341 353 390 415*

Breeding 332 328 377 397 1st AI 354 358 403 420

Conception 362 369 415 429

Weight (kg) - Breed type


Time EM D LM D Housing 220 213 Yearling 314 308 Turnout 338 336 Puberty 341 353

Breeding 332 328 1st AI 354 358

Conception 362 369

Time EM B LM B Housing 280 311 Yearling 360 384 Turnout 385 403 Puberty 390 415

Breeding 377 397 1st AI 403 420

Conception 415 429


200

250

300

350

400

450

(kg)

Time-point

Bodyweight gain from housing to conception

AA D LM D AA S LM S

Turn-out to pasture


050100150200250300350400450

410

415

420

425

430

435

440

AA D LM D AA B LM B

(kg)

(day

s)

Age at puberty Weight at puberty

Age and bodyweight at puberty – Breed type


0102030405060708090

100

6 week preg 8 week preg 10 week preg 12 week preg

%

Pregnancy rate - Breed type

AA D LM D AA B LM B


0102030405060708090

100

0 w 3 w 6 w 8 w 10 w 12 w

% P

uber

tal

Week of breeding

Timing of puberty – Breed type

AA D LM D AA S LM S

6 weeks of breeding

effect of breed type and post-weaning plane of nutrition

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