Evidence of improved fertility arising from genetic selection: weightings and timescale required

Transcription

1 Department of Animal and Aquacultural Sciences Evidence of improved fertility arising from genetic selection: weightings and timescale required Torstein Steine Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, Ås, Norway Fertility Seminar Cork April 11,

2 Department of Animal and Aquacultural Sciences Fertility as a trait Complex Low heritability Large variation When: Days from calving to first insemination Days from first to last insemination Result: Pregnant or not Calving interval 2

3 Department of Animal and Aquacultural Sciences Fertility as a trait Low heritability Large progeny groups needed ( daughters per sire) Low or moderate genetic correlation among fertility traits Different aspects of fertility Unfavourable genetic correlations to milk production Postive genetic correlations between mastitis and some fertiltiy traits 3

4 Experience of fertility situation Genetic change, fertility: Progress Farmer s situation today: High fertility breed Low fertility breed Years

5 Department of Animal and Aquacultural Sciences Experiences with Norwegian Red 5

6 Norwegian Red Population size: cows in the recording system (96%) dairy herds 95 % of the cows in Norway are Norwegian Red 90 % of calves have an A.I. sire Selected for a broad breeding objective with emphasis on functional traits like health and fertility over the last 40 years

7 Breeding for improved fertility in Norwegian Red Cow fertility included in the breeding program for Norwegian Red since 1971 Relative weight in total merit index increased from 8% to 18 % 7

8 Relative weight on traits included in the total merit index used for selection of Norwegian Red sires Trait groups Relative weight Milk production 28 Mastitis 21 Fertility 18 Udder conformation 15 Leg conformation 6 Growth rate 6 Temperament 2 Diseases other than mastitis 2 Milking speed 1 Calving difficulty 0,5 Stillbirth 0,5 8

9 Relative weight on traits included in the total merit index used for selection of Norwegian Red sires

10 Fertility traits Non-return rate within 56 days (NR56) Scored as 1 or 0 based on whether or not the cow had a second insemination (other than double inseminations, i.e. a new insemination 0 5 days after a first one) within 56 days after the first insemination 3 traits: Heifers 1 st lactation cows 2 nd and 3 rd lactation cows Interval from calving to first insemination (CFI) Number of days from calving to first insemination 2 traits: 1 st lactation cows Calving interval (CI) 2 nd and 3 rd lactation cows Number of days between 1 st and 2 nd calving.

11 Fertility indexes NR56 heifers (since 1971) NR56 heifers + NR56 cows (since 2002) NR56 heifers + NR56 cows + CFI (since 2008) Current fertility index = (1/3 NR56 heifers) + (1/3 NR56 cows) + (1/3 CFI) where NR56 cows = (2/3 NR56 1.lact) + (1/3 NR56 2-3lact) CFI = (2/3 CFI 1.lact) + (1/3 CFI 2.-3.lakt) Multi-trait animal models for genetic evaluation 11

12 Phenotypic trend NR56 12

13 Phenotypic trend CFI 13

14 Genetic trend for NR56 14

15 Genetic trend for CFI 15

16 Genetic trend for calving interval 16

17 Correlated Selection Responses in Fertility after Selection for Increased Protein Yield or Against Mastitis in a Selection Experiment with Norwegian Red cows (Heringstad and Larsgard, JDS 2010) 17

18 Genetic relationships Antagonistic genetic relationship between milk production and female fertility Selection for increased milk yield genetic deterioration of fertility Positive genetic correlations between health and fertility Selection against mastitis some genetic improvement of fertility as correlated responses

19 Selection experiment with Norwegian Red Started in 1989 Collaboration between Geno, Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences and 8 herds (agricultural schools) 2 selection groups: HPY = High Protein Yield LCM = Low Clinical Mastitis In each herd approx same no cows in the 2 groups 19

20 Proven sires from Norwegian Red breeding program used as sires HPY: The 2-4 highest ranking sires for protein yield each year LCM: The 2 4 highest ranking sires for mastitis resistance Proven sires from the active breeding program single trait selection (milk or mastitis) of sires pre-selected for Norwegian Red s breeding objective

21 Selection experiment Previous studies has shown Large genetic differences in mastitis resistance Correlated selection responses for resistance to other diseases Ketosis, retained placenta Correlated selection responses for SCC Genetic difference between HPY and LCM after 5 cow generations 10 %-units clinical mastitis 25 kg 305-day protein yield 21

22 Genetic trends for NR56 Mean EBV for NR56 in (a) heifers, (b) first lactation cows and (c) 2nd and 3rd lactation cows per cowgeneration for HPY and LCM cows (a) (b) (c) 22

23 Genetic trends for calving interval Genetic difference after 6 cow-generations = 4 days 23

24 Conclusions from selection experiment Correlated selection responses for female fertility detected LCM cows genetically better for fertility than HPY cows Higher NR56 for heifers and cows Shorter calving interval Shorter CFI in 1st lactation No significant differences in CFI for older cows Genetic difference between HPY and LCM cows after 6 cow generations: 2.5 %-units NR56 in heifers 2 %-units NR56 in cows, 4 days calving interval

25 Summary - Breeding for improved female fertility in Norwegian Red Fertility included in total merit index since 1971 Genetic improvement of fertility and milk production simuntanously Despite unfavourable genetic correlations to milk production low heritability of fertility traits Because Large daughter groups reliable EBV Weight on fertility in total merit index used for selection of NRF elite sires 25

26 Department of Animal and Aquacultural Sciences Weight of traits in TMI Weight on milk yield is the important point This is valid in a TMI like the Norwegian with health and fertility included, per progeny group: Weigth on milk yield: Below 26 % - room for genetic improvement in both health and fertility % - stable situation for health and fertility, enough selection to avoid reduction Above 32 % - the breeding program is mainly for improving milk yield. Negative genetic change in health and fertility traits 26

27 Department of Animal and Aquacultural Sciences Future Genomic selection: Reference population Large Reliable breeding values Regular check of parameters 27

28 Department of Animal and Aquacultural Sciences Summing up: Data Data Data.. Progeny Selection = weight Genomic selection: Data Data Weight 28

29 Thank you 29