Ability of dairy cows to be inseminated according to breed and genetic merit for production traits under contrasting pasture-based feeding systems

Abstract

Strong genetic selection on production traits is considered to be responsible for the declined ability of dairy cows to ensure reproduction. The present study aimed to quantify the effect of genetic characteristics (breeds and genetic merit for production traits) and feeding systems (FS) on the ability of dairy cows to be inseminated. An experiment was conducted during 9 years on Normande and Holstein cows assigned to contrasted pasture-based FS. Diets were based on maize silage in winter and grazing plus concentrate in spring in the High FS; and on grass silage in winter and grazing with no concentrate during spring in the low FS. Within breed, cows were classified into two genetic groups with similar estimated breeding values (EBV) for milk solids: cows with high EBV for milk yield were included in a Milk-Group and those with high EBV for fat and protein contents were included in a Content-Group. Holstein produced more milk throughout lactation than Normande cows (+2294 kg in the High FS and +1280 kg in the Low FS, P<0.001) and lost more body condition to nadir (-1.00 point in the High FS and -0.80 kg in the Low FS, P<0.001). They also showed a poorer ability to be inseminated because of both a delayed commencement of luteal activity (CLA) and delayed first service (more days from start of the breeding season to first service, DAI1). Cows in the Milk-Group produced more milk than cows in the Content-Group, but milk solids production was similar. Cows in the Content-Group had earlier CLA than cows in the Milk-Group (P<0.01). Genetic group neither affected ovulation detection rate nor DAI1. Within breed and FS, cows with high genetic merit for milk yield had later CLA and DAI1. Cows in the High FS produced more milk and lost less condition to nadir than cows in the Low FS. FS did not affect dairy cows' ability to be inseminated. However, cows with higher milk protein content, and presumably better energy balance, had earlier CLA (P<0.01) and DAI1 (P<0.10). In addition, higher milk yield was associated with poorer ovulation detection rate and oestrus intensity (P<0.05). The study showed that at similar EBV level for milk solids, selection for increased milk fat and protein content resulted in improved cyclicity and similar oestrous expression and submission rates compared with selection for increased milk yield.

Ability of dairy cows to ensure pregnancy according to breed and genetic merit for production traits under contrasted pasture-based systems

“…Holstein cows in the content group and under the low FS showed the lowest conception rate (38% at 42 d and 66% by the end of the breeding season). This is not consistent with their submission rate (63% at 21 d; Bedere et al, 2016b), and the present study showed they had a higher proportion of NF/EEM than other groups (47% at first and second services the range was from 19 to 29% for other groups). Holstein cows had the lowest BCS at calving, at nadir, at first and second service, and at the end of lactation.…”

“…Other results also showed that Holstein cows in the milk group had the lowest submission in both FS (Bedere et al, 2016b). Their ability to be pregnant at second service balanced this result so that their recalving rate (56%) is not different from Holstein cows in the milk group under the low FS (54%) and Holstein cows in the content group under high FS (53%).…”

Review: New considerations to refine breeding objectives of dairy cows for increasing robustness and sustainability of grass-based milk production systems

“…Much of those protestations 'fell on deaf ears' because it was largely regarded that breeding for or against fertility traits was not possible due to its low heritability (Berry et al, 2014). Numerous experiments were undertaken in New Zealand (Kolver et al, 2002;Roche et al, 2006a;Macdonald et al, 2008b), Australia (Fulkerson et al, 2001 and2008), France (Bedere et al, 2015(Bedere et al, , 2016(Bedere et al, , 2017a(Bedere et al, and 2017b and Ireland (Buckley et al, 2000;Kennedy et al, 2002;Horan et al, 2005a) to determine if different genetic strains performed differently under different feeding systems, in a holistic or overall economic sense. Although there was evidence that feeding regimen influenced the marginal milk production response to non-pasture feed and the ability of the dairy cow to exhibit her genetic potential, compared with her peers (Kennedy et al, 2002;Fulkerson et al, 2008), the greatest differences between the strains were in the extent of their negative energy balance in early lactation (Buckley et al, 2000;Roche et al, 2006a;McCarthy et al, 2007) and in their pregnancy rates in a seasonal calving system (Horan et al, 2005c;Macdonald et al, 2008b;Bedere et al, 2017a).…”

Characteristics of robust animals for grass-based production systems

“…The dairy cow situation is more complicated as a consequence of the high nutrient demand for lactation in this period (Friggens et al, 2010) and impacts on a range of fertility characteristics. To obtain good reproductive performance, luteal activity has to be restored and regular, oestrus and heats should be well expressed and easy to detect, and after artificial insemination (AI), fertilisation should be effective and the embryo implantation successful to re-calve (Bedere et al, 2017a(Bedere et al, , 2017b. Although evidence of genotype × environment interaction is scarce (Washburn & Mullen, 2014), evidence by O' Sullivan et al, (2019aSullivan et al, ( , 2019b and Horan et al (2004) suggests that sustainable genetic improvement is contingent on compatibility with the system in which the genetics is expected to perform.…”