Milk production and body composition of single-bearing East Friesian × Romney and Border Leicester × Merino ewes
Introduction
East Friesian (EF) sheep, introduced into Australia in 1996, still play only a minor role in the Australian prime lamb and milking sheep industries. While there is a move toward incorporating new breeds into the traditional prime lamb breeding program in Australia, the productivity of the EF is largely unknown under Australian conditions. Research in New Zealand (Newman and Stieffel, 1999) concluded that introducing EF genetics into commercial milking herds would improve milk yield. Another New Zealand study found that introducing EF genetics resulted in improvements in growth, fleece weights and reduced dagginess (Jopson et al., 2000). EF cross lambs have been shown to have excellent carcass traits (Allison, 1995, Jopson et al., 2000). As a common prime lamb dam in Australia, the Border Leicester × Merino (BLM) serves as a good comparison with new breeds such as the EF. There is also little information in the literature on the milk production of the BLM.
Ewes are generally in a state of negative energy balance during early and into mid lactation (Geenty and Sykes, 1986). Depending on the demand for milk by lambs, they may not be able to consume sufficient energy to counter the energy output in milk. In the face of these demands, body reserves may be mobilised to supplement energy intake. The extent of mobilisation and the homeorhetic adjustments that underlie it are variable, depending on genotype and past nutritional history (Cowan et al., 1980, Geenty and Sykes, 1986). To evaluate animals on the basis of efficiency of energy use for lactation therefore requires measurement of changes in body composition during lactation. While some studies have undertaken serial slaughter to examine this (Cowan et al., 1981), terminal trials are not always feasible. Researchers have also used ultrasound and dilution techniques to measure body composition of lactating ewes (Cowan et al., 1979, Foot et al., 1979, Brown et al., 1987) and goats (Dunshea and Bell, 1989, Dunshea et al., 1990). While correlations developed between body composition of lactating ruminants by dilution techniques and chemical composition were reported to have R-values ranging from 0.63 to 0.99 (Foot et al., 1979), these dilution techniques give information on fat tissue mass only.
Accurate measurement of changes in body composition would provide very useful information on lactational performance and tissue mobilization of different breeds of sheep. While dual energy X-ray absorptiometry (DXA) has not previously been used for lactating ewes, body composition measurements using DXA were shown to correlate strongly with chemical composition of wethers and non-lactating ewes (Hunter et al., 2011). The aim of this experiment was to measure the milk production (in terms of yield and composition), feed intake, liveweight changes and longitudinal changes in body composition of East Friesian × Romney (EFR) and BLM ewes over the first nine weeks of lactation.
Section snippets
Experimental animals, housing and diet
Eight second parity single-bearing EFR ewes and eight second parity single-bearing BLM ewes were selected from a flock located in Western Victoria. All ewes had been mated to a purebred EF ram and therefore the lambs produced were ¾ EF from the EFR ewes and ½ EF from the BLM ewes. For simplicity, the lambs from the EFR ewes will be referred to as EFR lambs and those from the BLM ewes will be BLM lambs.
Two to six weeks before lambing the lambs were housed in individual pens (1.40 × 1.35 m)
Results
Potential milk production over the entire lactation was higher in EFR than BLM ewes (2.57 vs. 1.92 kg/d, P = 0.028) and declined (P = 0.005) as lactation advanced (Fig. 1a). Milk fat content tended to be higher in EFR than BLM (4.88 vs. 4.26%, P = 0.094) and declined (P < 0.001) as lactation progressed (Table 1). Consequently, potential milk fat yield was higher in EFR than BLM ewes (131 vs. 83.7 g/d, P = 0.015) and declined (P < 0.001) as lactation advanced (Fig. 1b). Milk protein content was not different
Discussion
The major finding from this study was that EFR ewes have greater potential milk yield than BLM ewes. The EFR ewes ate more than BLM ewes during lactation and mobilized less fat than BLM ewes to maintain similar nursing lamb growth. Also, DXA was able to predict body tissue mobilization and accretion in lactating ewes and these changes in body composition, although underestimated, were related to estimated energy balance.
In both breeds, potential milk and milk component yield peaked in the first
Conclusions
The introduction of EF genetics into commercial sheep milking herds has the potential to improve milk yield and offer a robust dam for meat lamb production systems. The major finding from this study was that EFR ewes have greater potential milk yield than BLM ewes. The EFR ewes ate more than BLM ewes during lactation and mobilized less fat than BLM ewes to maintain similar nursing lamb growth. However, a greater milking demand of twins or triplets or via increased machine milking may allow the
Conflict of interest
None of the authors have any actual or potential conflict of interest including any financial, personal or other relationships with other people or organizations within three years of beginning the submitted work that could inappropriately influence, or be perceived to influence, their work.
References (38)
- et al.
Quantitative and compositional variations of Massese sheep milk by parity and stage of lactation
Small Ruminant Res.
(1989) - et al.
Lamb and milk production of Awassi and East-Friesian sheep and their crosses under Mediterranean environment
Small Ruminant Res.
(1996) - et al.
Dual energy X-ray absorptiometry (DXA) can be used to predict live animal and whole carcass composition of sheep
Small Ruminant Res.
(2011) - et al.
Reproduction rate, milk and wool production of Corriedale and East Friesian × Corriedale F1 ewes grazing on natural pastures
Small Ruminant Res.
(2010) - et al.
Predicting milk yield in sheep used for dairying in Australia
J. Dairy Sci.
(2007) - et al.
Use of wood's model to analyze the effects of milking methods on lactation curve in sheep
Small Ruminant Res.
(2013) - et al.
Comparison between native and ‘synthetic' sheep breeds for milk production in Sardinia
Livest. Prod. Sci.
(2001) - et al.
Recent advances in exploiting goat's milk: quality, safety and production aspects
Small Ruminant Res.
(2010) - et al.
Prediction of the energy value of cow's milk
J. Dairy Sci.
(1965) - et al.
Impact of high-yielding foreign breeds on the Spanish dairy sheep industry
Livest. Prod. Sci.
(2001)