Enhancing the productivity of ewe lambs through the use of reproductive management

Enhancing the productivity of ewe lambs through the use of reproductive management

Summary

Replacement ewe lambs comprise 30% of the breeding flock but their productivity is 30-40% lower than that of adult ewes resulting in significant loss in revenue. Delaying breeding of females until they are 15-18 months increases cost of production and does not consistently improve performance. At the end of the first full-year of our studies we demonstrated that increasing the plane of nutrition and the use of progesterone pre-treatment can increase lambing rates and in so doing increase profitability of producers. We also demonstrated that the age at first breeding can be reduced to 9 months without negatively impacting fertility and in so doing reduce the cost of raising replacement females. Further, we showed that progesterone pre-treatment and gonadotropin stimulation can be used to successfully breed fall-born ewe lambs during the anestrous period, facilitating the implementation of out-of-season breeding programs and the receipt of higher prices for lambs born from such breeding programs. The use of AMH as a marker of fertility in replacement females is currently been examined. Findings of our studies have been presented to approximately 75 producers in PA and WV.

Objectives/Performance Targets

The objective of the research component of the project is to assess and demonstrate the efficacy of various replacement ewe lamb management strategies. We will use ewe lambs that are 7-15 months at breeding to test the following hypotheses: 1. the fertility and prolificacy increases with weight at breeding independent of age 2. Fertility of ewe lambs increases with progesterone pre-treatment independent of age 3. Fertility in ewe lambs is positively correlated with serum concentrations of anti-mullerian hormone. The project also includes a comprehensive educational program and on-farm trials on approaches to enhance the productivity of ewe lambs.

 On conclusion we project that sixty (60) sheep producers will adopt reproductive and other management practices (selection, nutrition) to enhance productivity of 3000 ewe lambs costing an additional of $8-10/ animal treated, and will increase lambing rate by 30-40%, producing 900 more lambs valued at ~$220,000 each year.

Accomplishments/Milestones

Research Component
1. 817 replacement females ranging in age from 6.5-16 months have been used to evaluate the effects of age, progesterone, nutrition supplementation and gonadotropin stimulation on fertility of ewe lambs. Our preliminary findings suggest the following:
a. Progesterone pre-treatment improves fertility, in particular fertility to the first service period in replacement females bred during and outside the normal breeding season by 22-35%.
b. Gonadotropin-stimulation improves fertility of fall-born ewe lambs bred during the anestrous period, but does not improve fertility over progesterone pre-treatment only in yearling females bred during anestrous or in ewe lambs bred during the normal breeding season
c. Increasing the plane of nutrition 2 months prior to breeding of ewe lambs increases prolificacy and lambing rates to the first service period and overall by 36, 65 and 55 % respectively.
d. Age at breeding (beyond 6.5 months) did not influence fertility of replacement females bred during the normal breeding season
e. 1 manuscript have been prepared and published
2. Blood samples from 437 replacement females have been analyzed to determine circulating concentrations of anti-Mullerian hormone (AMH). We are in the process of analyzing the relationship between concentration of AMH and fertility

Educational Component
1. Three educational meetings (1 in PA and 2 in WV) was conducted where the benefits of improving the fertility of replacement females were discussed and initial findings were presented to a total of 75 producers.
2. A manual on raising replacement females is being prepared
3. Six educational meetings are planned for spring 2015.
4. one (1) article was published in popular press:  Knights, M., D. Singh-Knights (2015). Lifetime Productivity of the Ewe Flock Starts With the Ewe Lamb. The West Virginia Small Farm Advocate, Summer 2015 Edition, pg. 16 & 

• Ewe lamb summary findings
• Effect of gonadotropin stimulation
• Article on ewe lambs

Impacts and Contributions/Outcomes

We have demonstrated that manipulating the nutrition of replacment ewelambs during the last 2 months prior to breeding can increase the number of lambs born per 100 ewe lambs bred by as much as 55. Assuming the additional feed cost is $9/ewe lamb (60 lbs feed @ $0.15/lb) and a lamb is valued at $50.00 this represents additional profits of more than $2200/100 ewe lambs.

We also demonstrated that the fertility of ewe lambs bred for the first time at 9 months was similar to  those bred at 12 or 17-18 months. Implementation of early breeding of ewe lambs will reduce the cost of rasing replacements by 33-50%.

Collaborators: