The Effect of Calf Gender on Milk Production in Seasonal Calving Cows and Its Impact on Genetic Evaluations

Abstract

Gender of the calf whose birth initiates lactation could influence whole lactation milk yield of the dam due to hormonal influences on mammary gland development, or through calf gender effects on gestation length. Fetal gender could influence late lactation yields because cows become pregnant at peak lactation. The effects of calf gender sequences in parities 1–3 were assessed by separately fitting animal models to datasets from New Zealand comprising 274 000 Holstein Friesian and 85 000 Jersey cows, decreasing to 12 000 and 4 000 cows by parity 3. The lactation initiated by the birth of a female rather than a male calf was associated with a 0.33–1.1% (p≤0.05) higher milk yield. Female calf gender had carryover effects associated with higher milk yield in second lactations for Holstein Friesians (0.24%; p = 0.01) and third lactations for Jerseys (1.1%; p = 0.01). Cows giving birth to bull calves have 2 day longer gestations, which reduces lactation length in seasonal calving herds. Adding a covariate for lactation length to the animal model eroded some of these calf gender effects, such that calving a female led to higher milk yield only for second lactation Holstein Friesians (1.6%; p = 0.002). The interval centering method generates lower estimates of whole lactation yield when Wood’s lactation curves are shifted to the right by 2 days for male calves and this explained the higher yield in female calves when differences in lactation length were considered. Correlations of estimated breeding values between models including or excluding calf gender sequence were 1.00 for bulls or cows. Calf gender primarily influences milk yield through increased gestation length of male calves, and bias associated with the interval centering method used to estimate whole lactation milk yields. Including information on calf gender is unlikely to have an effect on selection response in New Zealand dairy cattle.

Ewes giving birth to female lambs produce more milk than ewes giving birth to male lambs

“…This relationship between prolificacy and placental lactogen concentrations might explain, at least in part, the high milk production by ewes that bear multiple offspring. It seems that female and male foetuses differ in the expression of the hormones that affect secretion milk synthesis, as has been demonstrated in cows presenting sex-biased milk yields (Hess et al 2016). Moreover, the bovine foetus secretes INSL3, which is the first sex-specific foetal hormone identified with potential to influence placental and maternal physiology (Anand-Ivell et al 2011).…”

“…In dairy cattle, an effect of offspring sex on milk production has been reported. Thus, milk production in Holstein dairy cows in the USA present a sex-biased milk production in favour of female calves (Hinde et al 2014) and, in New Zealand, the birth of a female rather than a male calf was associated with a 0.33-1.1% higher milk yield (p < .05) (Hess et al 2016). In sheep, references in the literature on the effect of the number of lambs and their gender on milk production of their dams are scarce.…”

Effect of Calf Gender on Milk Yield and Fatty Acid Content in Holstein Dairy Cows

“…[9–11] In any case, reported effects are always marginal- the 2.7% advantage for two heifer calves born in the first two lactations found by Hinde et al6 is the largest reported by far. Other factors that affect milk yield such as mastitis[37] and lameness[38] are likely to be more important in a herd overall than calf gender.…”

“…For example, Hess[9] used total lactational yield, calculated using the test interval method. Hinde[6] and Barbat[10] used the test day model[39] rather than predicting 305 day milk yields.…”

“…Canadian data agreed, but demonstrated a much smaller effect of less than 0.5%,[7] and Iranian data[8] also showed higher milk production in dams giving birth to heifers for up to four parities. The yield advantage conferred by heifer calves was only seen in the second lactation in New Zealand Holstein-Friesians,[9] and only in the first lactation in French Holstein-Friesians. [10] In contrast, Graesboll et al[11] found that bull calves conferred a milk yield advantage in a dataset from 578 Danish Holstein herds.…”