Effect of ewe milk production on profitability of dryland lamb production systems

Abstract

<jats:p>A farmlet study was carried out over 2 years to examine the role of milk production in dryland lamb production systems. Poll Dorset ewes (high milk producers) were mated with Romney rams and Romney ewes (average milk producers) were mated with Poll Dorset rams to produce lambs of a similar genotype. As well as two levels of milk production, two fecundity treatments were used and farmlets were replicated. Farmlets were 2.9 ha and stocked at a rate of 15 ewes/ha. Farmlets were managed to ensure similar pasture covers at the start of winter and at lambing. Poll Dorset ewes produced more milk and in both years their twin lambs had a small but significant advantage in lamb growth rate. This resulted in earlier drafting of lambs and the ability to obtain early season premiums. In the low fecundity farmlets, net financial returns for Romney and Poll Dorset ewes were $605/ha and $676/ha (+ 12%) in Year 1 and $709/ ha and $762/ha (+ 7%) in Year 2. For the high fecundity farmlets, financial returns for Romney and Poll Dorset ewes were $637/ha and $818/ha (+ 28%) in Year 1 and $866/ha and $921/ha (+ 6%) in Year 2. The greatest financial benefits to increased milk production were achieved in high fecundity ewes in Year 1 when feeding during lactation was less than optimal and this resulted in a significant effect on the rate at which twin lambs were drafted to achieve early season premiums. Lambs failing to reach minimum drafting weights were also penalised because of the prevailing drought conditions and low market prices for lighter lambs. Keywords: breed, dryland, ewes, farming systems, fecundity, milk production, pre-weaning growth, profitability, sheep</jats:p>

Maximising lamb growth rates

“…Whilst it is tempting to associate the increased lamb growth with the increased milk production of EFxR ewes, there is evidence that increased lamb growth rates may be also due to lamb genotype (i.e., mature size effect) and to hybrid vigour (Muir, unpublished data) for ewe milk production. Moreover, the half-East Friesian ewes in the present study produced similar daily milk yields to pure Poll Dorset ewes (Muir et al 1998). Although the Poll Dorset ewes were milked in a different season, feeding conditions were very similar and lambs reared by Poll Dorset ewes grew only slightly faster than lambs reared by Romney ewes.…”

“…In recent years, there has been considerable interest in sheep genotypes with improved milking ability for improving lamb productivity. The milk production of New Zealand's traditional breeds has been quantified (Geenty 1979) and the benefits of the increased ewe milking ability of Poll Dorsets compared to Romneys has been demonstrated by Muir et al(1998). However, there is little information about the influence of recently introduced breeds such as the Finnish Landrace and the East Friesian, on ewe milking ability and lamb growth rate.…”

Can lambs compensate for less milk by grazing more often?

“…However as the lamb grows, the necessity for milk decreases and this is reflected in the increase of herbage intake by the lamb (Wallace 1948;Treacher 1983). While high milk production is generally assumed to produce high lamb growth rates, in some circumstances the relationship between milk volume and lamb growth rate is unclear (Muir et al 1998). Factors such as the time lambs spend grazing and the interaction between the ewe and lamb in the effort to obtain milk, may be particularly important.…”

The effect of weaning weight on subsequent lamb growth rates

“…The question of when to wean lambs, and whether to wean only part of a flock, is a complex one. On the one hand, a "good" mother may buffer its lamb from the effects of fluctuations in quantity or quality of the pasture on offer by an increase in milk production (Muir et al 1999). Also, high pasture-quality can influence lamb liveweight gains when ewe milk production is limiting (Muir et al 1999).…”

“…On the one hand, a "good" mother may buffer its lamb from the effects of fluctuations in quantity or quality of the pasture on offer by an increase in milk production (Muir et al 1999). Also, high pasture-quality can influence lamb liveweight gains when ewe milk production is limiting (Muir et al 1999). On the other hand, if the lambs are weaned, they can be given first choice of the pasture in the rotation, with the ewes following behind to clean up low-quality forage and prepare pastures for subsequent grazings.…”