Elsevier

Small Ruminant Research

Volume 131, October 2015, Pages 123-129
Small Ruminant Research

Milk production and body composition of single-bearing East Friesian × Romney and Border Leicester × Merino ewes

https://doi.org/10.1016/j.smallrumres.2015.08.006Get rights and content

Highlights

  • Lactational performance of EF × Romney (EFR) and Border Leicester × Merino (BLM) ewes were measured.

  • Potential milk production and component yield was higher in EFR than BLM ewes and declined as lactation advanced.

  • Changes in tissue energy estimated using dual energy X-ray absorptiometry scans were highly correlated to average estimated energy balance.

  • EFR ewes have greater potential milk yield than BLM ewes but this was not realized as increased daily gain of single lambs possibly because of insufficient difference in milking pressure.

Abstract

The introduction of East Friesian (EF) genetics into commercial sheep milking herds has the potential to improve milk yield and offer a robust dam for meat lamb production systems. This study was conducted to measure the milk production, feed intake and longitudinal changes in body composition of EF × Romney (EFR) and Border Leicester × Merino (BLM) ewes over the first nine weeks of lactation. Sixteen seconds parity single-bearing EFR (n = 8) and BLM (n = 8) ewes that had been mated to a purebred EF ram were housed in individual pens from 2 weeks prior to, and until 9 weeks after, lambing and fed a commercial pelleted diet with additional chaff. Milk yield was measured twice a week using the four-hour milking interval technique after injection of oxytocin and body composition was determined by dual energy X-ray absorptiometry (DXA) at 1, 3, 5 and 9 weeks of lactation. Potential milk production was higher in EFR than BLM ewes (2.57 vs. 1.92 kg/d, P = 0.028) and declined as lactation advanced. Similarly, the yields of milk fat (P = 0.015), protein (P = 0.018) and lactose (P = 0.062) were all higher in EFR than BLM ewes and declined as lactation advanced. Energy intake increased over the first 4 weeks of the study, before reaching a plateau for the remaining 5 weeks of the study. However, there was no significant difference in energy intake or energy balance between EFR and BLM ewes. Changes in tissue energy between DXA scans were highly correlated (R2 = 0.51, P < 0.001) to average estimated energy balance over the same periods. There was no effect of breed on birth weight of lambs nor was there any effect of dam breed on average daily gain of lambs. In conclusion, EFR ewes have greater potential milk yield than BLM ewes but this was not realized as an increased average daily gain in the single lambs possibly due to insufficient milking pressure failing to produce a difference in actual milk yield. It is likely that this difference would be expressed in response to a greater milking demand (i.e. from a milking machine or twin/triplet lambs). 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 may allow the greater potential milk yield of EFR to be expressed. Alternatively, machine milking EFR would most likely allow the expression of their full milking potential. Finally, DXA was able to predict body tissue mobilization and accretion in lactating ewes and these changes in body composition were related to estimated energy balance indicating that DXA can be used to serially determine body composition in lactating sheep.

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.

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