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Hogget Mating and Lambing – A Discussion Paper

Lew Willoughby and Richard Gavigan, MWI, June 2001

Introduction

Lifetime ewe productivity is a major factor governing the profitability of sheep production. Increasing ovulation rate, lamb survival and subsequent weaning rate can increase reproductive efficiency in adult ewes. Mating and lambing ewe hoggets may provide another means of increasing lifetime productivity.

While the attitude of farmers toward mating and lambing hoggets varies considerably, the practice is increasing throughout New Zealand. Key factors in this trend include:

an improved knowledge and application of feed management techniques;
the widespread use of ultrasound scanning for pregnancy diagnosis;
the increasing availability of high fertility breeds and strains of sheep; and,
an overriding need to improve farm income.

Claimed advantages and disadvantages of hogget lambing

Advantages

Provides extra lambs and higher net profit.
Improves lifetime performance.
Results in a higher fertility flock through selection for hogget lambing.
Lambed hoggets are superior mothers as two-year-olds.
Provides an opportunity to better utilise less expensive spring feed from October to December.
A focus on hogget growth during pregnancy and lactation results in better fed and subsequently higher performing two-tooth ewes.

Disadvantages

Increases the risk of creating lighter, lower performing two-tooth ewes.
Pregnant ewe hoggets require more expensive winter feed from July to October.
Increases the workload with extended lambing and increased animal health requirements.
Ewe lambs require priority feeding from their own weaning through to the weaning of their own lambs.
Non-pregnant hoggets require separate management.
Hogget lambing performance can vary greatly from season to season.
Increases the death rate in ewe hoggets.
Pregnant/lambing hoggets produce less wool at hogget and two-tooth shearings.
Lambing hoggets compete with other stock for spring feed.
Hogget lambs are smaller, slower growing and less marketable.
Hogget mating requires extra teaser and entire rams.

Suggested hogget mating and lambing best practice

Points that are discussed further are identified with a link to a note further down the page.

1. Pre-mating management

Manage ewe lambs to achieve average live weight of 40kg plus by hogget joining.
Time tupping to match lambing date to the onset of spring feed flush.
Run teaser rams with hoggets for at least 21 days prior to tupping date.*
Vaccinate for Toxoplasmosis and Campylobacter and administer 5 in 1 vaccine.*
If second shearing, shear no later than 2 weeks before tupping.

2. Mating management

Only mate hoggets that are 35kg or heavier. *
Run harnessed teaser rams with light hoggets to identify those cycling. *
Select rams for ease of lambing. *
Use a minimum of 2% mature rams with harnesses.
Mate hoggets in smaller, easier contoured paddocks or use more rams.
Mate for 21 – 35 days. *

3. Winter and pre-lambing management

Scan hoggets mated identifying twin-bearing, single-bearing and dry hoggets.
Differentially feed in-lamb hoggets on covers no less than 1000kgDM/ha. *
Ensure that hoggets lamb at condition score 3 or better to cope with lactation.
If pre-lamb shearing, shear no later than 2 weeks prior to lambing date.
Treat with a long acting anthelmintic injection or capsule before lambing. *

4. Lambing and lactation management

Lamb onto feed with covers of no less than 1300kgDM/ha.
Leave lambing hoggets alone. *
Ensure that feed covers rise to 1500kgDM/ha by peak lactation 3 weeks after lambing.
Do not allow feed covers to drop below 1300kgDM/ha.
Adjust paddock stocking rate to ensure that pasture quality is maintained.
Monitor hogget live weight against your live weight targets.
Don’t forget about the dry hoggets. *

5. Weaning management

Wean hoggets no later than 10 weeks of age. *
If feeding levels cannot be maintained weaning should take place. *
Lamb weight is a better weaning criterion than age. *

Discussion points from suggested best practice

1. Run teaser rams with hoggets for at least 21 days prior to tupping date?

There is no need to use teasers – use entire rams as very few hoggets are cycling and the only risk is a few early hogget lambs?

Just leave ewe hoggets in paddocks alongside ewes and rams to get a “ram effect”?

2. Vaccinate for Toxoplasmosis and Campylobacter and administer 5 in 1 vaccine?

Do Toxoplasmosis and Campylobacter vaccines work in young sheep?

3. Only mate hoggets that are 35kg or heavier?

Don’t draft to weight, let the rams do the selection for you?

35kg is too light. Hoggets that are mated around 35kg will never catch up?

Draft to a minimum of 40kg live weight to ensure that two-tooths achieve their potential?

4. Run harnessed teaser rams with light hoggets to identify those cycling?

Oestrous should be used as a flock replacement selection criterion?

5. Select rams for ease of lambing?

Southdown and Cheviot rams have narrow shoulders and their progeny have easier births?

Black-faced rams should be used to enable easier identification of hogget lambs?

Hogget lambs sired by black-faced rams have better survival, grow faster and are more marketable?

Flock rams should be used so that good hogget lambs can be retained as replacements?

6. Mate for 21 – 35 days?

35 days is too long as it extends lambing and complicates weaning decisions?

21 days is enough as the timing, not the length of mating, is the critical issue, particularly in traditional breeds?

7. Differentially feed in-lamb hoggets on covers no less than 1000kgDM/ha?

In-lamb hoggets will lose weight grazing to 1000kgDM/ha. Aim for residuals of 1200kgDM/ha?

8. Treat with a long acting anthelmintic injection or capsule prior to lambing?

Better to simply give lambing hoggets a docking drench?

9. Leave lambing hoggets alone?

Too many good hoggets will die due to lambing difficulties if left un-shepherded?

Don’t forget about the dry hoggets?

Empty hoggets are a useful “buffer” and are used as such in most commercial flocks?

11. Wean hoggets no later than 10 weeks of age?

10-week-old hogget lambs will be too small to do well off their mothers?

Is the focus the lambs or the ewe hoggets?

12. If feeding levels cannot be maintained weaning should take place?

Better to wean early ewes first and continue to feed lambing hoggets?

Once again, is the focus the lambs or the ewe hoggets?

13. Lamb weight is a better weaning criterion than age?

What is the recommended weaning weight?

Longer mating makes weaning to weight more difficult?

A snapshot of the last 20 years of research

The following links will take you to pages that summarise some of the research done over the past 20 years that this advice is based on.

The effect of hogget lambing on subsequent two-tooth and lifetime performance.
The effect of hogget feeding around mating and during pregnancy on conception rate, placental development, lamb birth weight, lamb survival and colostrum production.
The effect of sheep breed on the efficiency of hogget mating and lambing.
The effect of mating management on the efficiency of hogget mating and lambing.

The effect of hogget lambing on subsequent two-tooth and lifetime performance.

Baker et al (1981) mated 504 Romney hoggets to Romney rams between 1971 and 1976. They reported:

75% of ewe hoggets cycled at least once (pre-tup live weight was not stated but hogget yearling weight was 41.8kg).
30% of hoggets mated lambed. The average lambing rate for those that lambed was 109%, and 72% of lambs born survived to weaning. This resulted in an average weaning rate (lambs weaned/hoggets mated) of 24%.
Two-tooth ewes that had lambed as hoggets were 3kg lighter (47.7kg v. 50.7kg) and cut 0.2kg less wool than control ewes. There was little difference between experimental groups in live weight and fleece weight by the four-tooth and six-tooth stage.
Ewes which had lambed as hoggets exceeded ewes first mated as two-tooths by 10% in weaning rate, 12% in average lamb weaning weight and 22% in weight of lamb weaned (average result per lambing).

McCall and Hight (1981) analysed the records of 15731 ewe hoggets and 8157 2-year-old ewes born in the Waihora Romney Breeding Scheme from 1972 to 1976. They reported:

Two-year-old lambing performance was highest in ewes that reared lambs as hoggets (+6%). The level of barrenness decreased in ewes with increasing hogget lambing status and lamb survival was significantly greater in the progeny of ewes that had previously reared lambs.
Hogget December fleece weight was depressed by up to 0.16kg due to the effects of pregnancy and lactation. This effect did not appear to persist in subsequent years when body weights equalised.

McMillan and McDonald (1983) mated 134 Romney or Romney x Border Leicester ewe hoggets to Southdown ram hoggets. They reported:

The mean joining live weight of ewe hoggets was 36kg. The overall weaning rate (lambs weaned/hoggets joined) was 58%. The average lamb birth weight was 4.0kg and 78% of lambs born survived to weaning.
Two-tooth ewes that lambed as hoggets were 6kg lighter (49kg v. 55kg) than ewes that had not lambed. However, two-year-old ewes that had lambed previously weaned 15% more lambs than control ewes lambing for the first time.
Lambs born to two-year-old ewes lambing for a second time had higher survival rates than lambs born to control ewes. There was a tendency for fewer ewes lambed as hoggets to require assistance at second lambing.
There was little difference in November fleece weight between different hogget groups. However previously unmated ewes produced February fleeces that were 0.4kg heavier than ewes lambed as hoggets.

Moore et al (1983) mated a total of 529 Romney, Coopworth and Perendale hoggets to Southdown rams in 1979 and 1980. They reported:

Hoggets that lambed were 2 – 4kg lighter at weaning in mid-December than hoggets that did not lamb. However, there was no difference in two-tooth pre-mating weight, reflecting the preferential treatment given to lambing hoggets in this study.
Hoggets that lambed produced up to 0.14kg less wool at shearing in February but had higher lambing and weaning rates as two-year-olds than hoggets that did not lamb.

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The effect of hogget feeding around mating and during pregnancy on conception rate, placental development, lamb birth weight, lamb survival and colostrum production.

Wallace et al (1996, 1997, 2000) fed a total of 48 embryo recipient Suffolk or Dorset Horn x Greyface (Border Leicester x Scottish Blackface) ewe hoggets feed concentrates indoors to achieve either “rapid” or “normal” maternal weight gain during the first 95 days of pregnancy. They reported:

High intake hoggets were fed ad libitum and grew at around 263g/day (excluding the weight of conceptus) to day 95 of pregnancy. Normal intake hoggets grew at around 50g/day during this period. The 95-day weight of foetus, placenta, fluids etc was 2.9kg and 3.5kg for high intake and normal intake hoggets respectively.
The proportion of ewe hoggets initially conceiving after embryo transfer was significantly lower in the rapid growth group (57%) than in the normal growth group (85%).
The incidence of non-infectious spontaneous abortion was higher in the rapid growth group (33%) than in the normal growth group (8%).
Rapid maternal growth rates were associated with a significant reduction in both foetal and total placental weights at day 95 of pregnancy. Placental mass is highly correlated with lamb birth weight.
High maternal feed intakes were associated with reduced gestation length and a higher incidence of newborn lamb deaths.
Rapid maternal growth during pregnancy resulted in a highly significant reduction in lamb birth weight (2.74kg v. 4.34kg).
Colostrum production was significantly lower in the rapidly growing compared with the normally growing hoggets.
The hormone progesterone plays a major role in controlling maternal secretions of substances required for successful embryo growth and development. High feeding levels were associated with lower progesterone concentrations during early pregnancy, which may have been limiting the growth of the conceptus.
Reduced placental size may have been limiting the production of prolactin and growth hormones required for development and function of the udder.
Wallace (pers. comm.) has no estimate of the safety margin involved in pregnant hogget growth but suggested that the 130 – 140g/day growth or ad libitum feeding considered appropriate by some NZ farmers is too high for optimal foetal growth and lactation performance.

Palmer et al (1998) conducted a similar experiment to Wallace et al (1996 and 1997) feeding recipient ewe hoggets at moderate and high levels. They reported:

High intake hoggets were fed ad libitum and gained 327g/ to day 104 of pregnancy. Normal intake hoggets gained 62g/day during this period.
Foetuses from the high intake hoggets were smaller than those from mothers fed at a lower intake.

Stevens (2001) collected information on the effect of feeding level and subsequent ewe hogget growth rates on the success of hogget lambing in a survey of nine Otago/Southland farmers. He reported:

While there was a trend towards increased live weight gain around mating resulting in reduced conception success, it appeared to be less significant than reported by Wallace et al (1996). The survey results suggested that the effect may differ between breeds, with Romney and Coopworth ewe hoggets demonstrating a greater reduction in conception rate with increasing weight gain around mating than Finn and East Friesian crosses.
Live weight at mating appeared to have the most significant effect on conception success, with approximately 2% more ewe hoggets lambing for every 1kg increase in live weight at mating. This may also provide the basis for the positive effect on lambing percentage of pre-joining shearing of hoggets (McMillan and Wilson, 1984).
Lamb losses from scanning onwards reduced significantly as winter (tupping to day 126 of pregnancy) live weight gain increased. However, there appeared to be some increase in lamb losses as winter weight gain (including weight of conceptus) increased above 12kg (actual maternal growth of around 70g/day). Average hogget growth rate in the survey appeared to be around 20g/day.

The effect of sheep breed on the efficiency of hogget mating and lambing.

Meyer and French (1979) mated nine sire breeds (Oxford Down, Poll Dorset, Border Leicester, German White Headed Marsh, Finnish Landrace (Finn), Finn x Romney, Cheviot, Booroola and Romney to Romney ewes for 4 years. They weighed the progeny monthly and ran them with vasectomised rams from April through July each year. Oestrous activity was monitored for 2735 hoggets. They reported:

Within breeds, hogget body weight was positively correlated with number of hogget oestruses. Both hogget live weight and oestrous activity varied between years but the rank among breeds for both traits remained fairly constant.
The proportion of hoggets cycling over the 4 years ranged from 88 – 97% for 29.3kg half Finn hoggets to 12 – 38% for 24.2kg Romneys. The performance of other hoggets was very similar.
Only Finn and Booroola cross hoggets had appreciable numbers of twin ovulations.

McMillan et al (1988) mated Texel, Oxford Down, Finn, Border Leicester, Suffolk, Coopworth and Perendale purebred and crossbred hoggets over three years. They reported:

Purebred Finn hoggets produced the most lambs with 1.3 lambs born per hogget joined. Finn x Coopworth hoggets also excelled in early reproduction with 1.0 lambs born per hogget joined.

Newman and Stieffel (1999) measured the daily milk yield and milk composition of East Friesian x Poll Dorset and purebred Poll Dorset hoggets throughout their lactation. They reported:

The live weight of Poll Dorset and East Friesian cross hoggets was similar throughout the trial. Hoggets gained weight from 51.5kg to 61.8kg over the 102 day trial period, reflecting the high plane of nutrition on which the animals were run (pre and post grazing ryegrass - white clover pasture levels of at least 2000 and 1400kgDm/ha respectively).
Mean daily milk yields of the East Friesian cross hoggets were significantly higher than for the Poll Dorset hoggets. Total milk production of the East Friesian cross hoggets was 30% higher in milk volume but had a lower milk solids content resulting in a 25% higher yield of milk solids than Poll Dorset hoggets.
There was no difference in milk yield between the East Friesian cross and Poll Dorset hoggets for the first 3 weeks of lactation. However, East Friesian cross production continued to increase to a peak 6 weeks after the start of lactation while Poll Dorset were consistent for the first 7 weeks then gradually declined.
Between breed differences in fat, protein, total milk solids and lactose concentrations in milk were small and of little practical importance.

Muir (2001) monitored the onset of oestrous and ovarian activity in a total of 280 Finn x Romney, East Friesian x Romney, Poll Dorset x Romney and purebred Romney ewe hoggets. He reported:

All Finn cross and East Friesian cross hoggets showed oestrous and were marked by teaser rams over a 5-month period. 90% of Poll Dorset and 76% of Romney hoggets showed oestrous.
Finn cross and East Friesian cross hoggets averaged 5 cycles between March and September (began earlier and finished later). Poll Dorset cross and Romney hoggets averaged 3.1 and 2.3 cycles respectively. This suggests that the timing of hogget mating is more important for Romney hoggets than for Finn cross and East Friesian cross hoggets and that the latter breeds offer more flexibility in terms of mating/lambing date.
Finn cross, East Friesian cross, Poll Dorset cross and Romney hoggets scanned 115%, 92%, 73% and 69% per ewe hogget mated respectively.

Stevens (2001) collected information on the effect of different breeds on the success of hogget lambing in a survey of nine Otago/Southland farmers. He reported:

Ewe hogget conception success varied widely in Romney and Coopworth flocks with some highly successful results.
The inclusion of 1/8th East Friesian or Finn genetics appeared to provide little change from the average of traditional breeds.
The inclusion of 1/4 East Friesian or Finn genetics appeared to improve conception success. This effect appeared to peak at 3/8th with no further change with 1/2 East Friesian or Finn.

The effect of mating management on the efficiency of hogget mating and lambing.

Allison et al (1975) conducted four experiments in which Romney, Cheviot x Romney, Coopworth, Perendale and Border Leicester x Romney ewe hoggets were mated to Southdown rams. They reported:

The mean live weight of hoggets marked by harnessed rams was higher than those not marked. This is in agreement with a number of reports emphasising the importance of live weight as a factor affecting the percentage of ewe hoggets exhibiting oestrous (reviewed by Drymundsson, 1973).
There was an advantage in increasing ram ratio from 1 ram per 100 ewe hoggets (1%) to 2 rams per 100 hoggets (2%) in that more hoggets were mated at an earlier stage of the joining period. This would result in earlier lambing and subsequent weaning thus providing more time to achieve optimal two tooth mating weight/condition. There appeared to be no benefit in increasing ram ratio above 2%.