Hot topic: Definition and implementation of a breeding value for feed efficiency in dairy cows

Abstract

A new breeding value that combines the amount of feed saved through improved metabolic efficiency with predicted maintenance requirements is described. The breeding value includes a genomic component for residual feed intake (RFI) combined with maintenance requirements calculated from either a genomic or pedigree estimated breeding value (EBV) for body weight (BW) predicted using conformation traits. Residual feed intake is only available for genotyped Holsteins; however, BW is available for all breeds. The RFI component of the "feed saved" EBV has 2 parts: Australian calf RFI and Australian lactating cow RFI. Genomic breeding values for RFI were estimated from a reference population of 2,036 individuals in a multi-trait analysis including Australian calf RFI (n=843), Australian lactating cow RFI (n=234), and UK and Dutch lactating cow RFI (n=958). In all cases, the RFI phenotypes were deviations from a mean of 0, calculated by correcting dry matter intake for BW, growth, and milk yield (in the case of lactating cows). Single nucleotide polymorphism effects were calculated from the output of genomic BLUP and used to predict breeding values of 4,106 Holstein sires that were genotyped but did not have RFI phenotypes themselves. These bulls already had BW breeding values calculated from type traits, from which maintenance requirements in kilograms of feed per year were inferred. Finally, RFI and the feed required for maintenance (through BW) were used to calculate a feed saved breeding value and expressed as the predicted amount of feed saved per year. Animals that were 1 standard deviation above the mean were predicted to eat 66 kg dry matter less per year at the same level of milk production. In a data set of genotyped Holstein sires, the mean reliability of the feed saved breeding value was 0.37. For Holsteins that are not genotyped and for breeds other than Holsteins, feed saved is calculated using BW only. From April 2015, feed saved has been included as part of the Australian national selection index, the Balanced Performance Index (BPI). Selection on the BPI is expected to lead to modest gains in feed efficiency.

Residual feed intake divergence during the preweaning period is associated with unique hindgut microbiome and metabolome profiles in neonatal Holstein heifer calves

“…Previous studies with dairy heifers revealed that RFI divergence between postweaned growing heifers (i.e., M-eff vs. L-eff heifers) is maintained during the first lactation [6,23]. Thus, understanding the biologic differences between M-eff and L-eff heifer calves during the preweaning period is warranted.…”

Reliability of breeding values for feed intake and feed efficiency traits in dairy cattle: When dry matter intake recordings are sparse under different scenarios

“…However, including feed efficiency (FE) as a selection criterion is constrained by the fact that many definitions of FE traits such as residual feed intake (RFI; Koch et al, 1963), gross FE (Korver, 1988;Van Arendonk et al, 1991;Spurlock et al, 2012), and feed saved (Pryce et al, 2015) require in their calculations recordings on the DMI of cows. Such measurements on individual animals and particularly on a large scale in commercial farms are costly and logistically demanding.…”

Predicting feed intake and feed efficiency in lactating dairy cows using digesta marker techniques

“…This is mainly due to the increased pressure facing the dairy industry to maintain profitability in an era of increasing feed costs and to reduce greenhouse gas production and nutrient losses to the environment. Feed efficiency has become a more common standard for monitoring the economic viability of milk production and it is already a primary marker for genetic improvement in dairy cattle breeding programs (Vallimont et al, 2011;Pryce et al, 2015;Tempelman et al, 2015). There are numerous definitions of FE, among which the most relevant definition for dairy production systems is still unclear (see review by Connor, 2015).…”