Relationship between cow parity and maternal parity on dairy cow lactation performance

The effect of dam parity on the subsequent performance of her female progeny is of interest when exploring the cost-benefit of alternative herd-level breeding strategies. This is especially true with the growing adoption of sexed semen where proportionally more of the heifers and younger cows in a herd may be selected as candidate dams of the next generation. There is a paucity of information on the effect of, or association between, dam parity and subsequent progeny lactation productivity in dairy cows. The objective of the cross-sectional analysis of 1,833,875 cow lactation records in the present study was to quantify the association between dam parity (1 to 10+) and subsequent progeny lactation yield, milk fat and protein concentration, and SCC. Also of interest were model cow parity effects for these traits so as to inform cost-benefit analyses of improving cow lifespan. All associations were estimated using linear mixed models with cow included as a random effect while also facilitating heterogeneous dam and cow parity variance components. Mean yield increased with cow parity up to parity 5 (30% to 33% higher than yields from first parity cows) after which it declined; parity 10+ cows still produced, on average, 19% to 21% more milk than first parity cows although mean lactation SCC increased with advancing parity in multiparous cows. The mean 305-d lactation milk yield of cows increased as the parity number of their dams increased, peaking at parity 7 (19.8 kg more milk than progeny from first lactation dams) before declining. In contrast, peak fat and protein yields occurred at younger dam parities. Although the mean SCS of cows was greatest in progeny from parity 2 dams, mean lactation SCS declined thereafter as dam parity number increased. In conclusion, although dam parity was associated with progeny lactation performance, the biological extent of this association was almost negligible.