8th World Congress on Genetics Applied to Livestock Production, August 13-18, 2006, Belo Horizonte, MG, Brasil

ECONOMIC VALUES FOR PRODUCTION TRAITS IN SANTA INÊS SHEEP

O.R. Morais1 and F.E. Madalena1

1UFMG, School of Veterinary Science, Department of Animal Science, Cx.P. 567, 30123-970 Belo Horizonte, MG, Brazil.

INTRODUCTION During the last 10 years meat sheep production has been increasing in Central West and South East Brazil. Santa Inês, a Brazilian breed of hair sheep, is the major contributor for this development because it is easy to obtain and cheap to acquire, breeds all year round and complies with the farmers’ shearing aversion. Most farms in those regions sell lambs on a live weight basis, with prices and standards set by slaughter firms. In 2003 a cooperative was created in Minas Gerais state whereupon the lamb marketing basis changed to carcass weight. Despite the Santa Inês breed being used for meat production, selection is based mostly on type only, and breeding programmes are often discontinued (Morais, 2000). Although estimates of genetic parameters are available for some traits, a formal definition of breeding objectives based in economic values of traits is lacking. According to James (1982), an efficient selection for the wrong objective may be worse than no selection at all. Ponzoni and Newman (1989) stressed that the derivation of the economic value of each trait influencing income and inputs is a crucial step in the development of breeding objective. The aim of this study is to contribute to develop breeding objectives for Santa Inês sheep in the Central West and South East regions of Brazil. MATERIAL AND METHODS Simulated economic and production data for a typical 1000-ewe flock associated with the Lamb Production Cooperative in Minas Gerais state were used. Four 45-day mating seasons per year were assumed. The system was pasture-oriented but the flock was gathered at night. The numbers of animals per category and the numbers sold annually are in table 1. Table 2 shows the productive and reproductive flock performance assumed, mainly based on actual data of one farm where detailed records were available (Morais, 2005 ) Table 1. Flock composition and numbers of animals sold annually Animal category Age (days) Number of animals 1 Sold per year Lambs (females) 1 to 150 294 0 Lambs (males) 1 to 150 294 665.4 Ewe lambs 151 to 360 187 436.8 Replacement ewe lambs 151 to 485 87 0 Ewes 485 to culling 1018 163.7 Rams 730 to 2190 8.33 1.6 1 Average number of animals over 12 months.

8th World Congress on Genetics Applied to Livestock Production, August 13-18, 2006, Belo Horizonte, MG, Brasil

Table 2. Assumed flock productive and reproductive performance1

Trait Mean Ewe weight, kg 45.0 Fertility (ewes lambed /ewes exposed to ram) 0.85 Lambing interval, days 243 Prolificacy (number of lambs per birth) 1.23 Birth weight ( singles, doubles, triplets), kg 3.80; 3.20; 2.80 Male pre-weaning daily weight gain (singles, doubles, triplets), g 175; 150; 132 Lamb survival (singles, doubles, triplets) 0.91; 0.78; 0.71 Age at death of non-survivor lambs (singles, doubles, triplets), d 47.5; 38.3; 27.7 Lamb slaughter age , d 150 Lamb slaughter weight (singles, doubles, triplets), kg 30.0; 25.6; 22.7 Lamb carcass yield (kg of carcass/kg of live weight) 0.40 1 Based on data from one farm with detailed performance recording Incomes and expenses Income sources were lambs sold for slaughter (on a carcass weight basis), ewe lambs sold (on a per animal basis) and cull for age ewes sold (per kg live weight). Expenses were: roughages and pastures costs, including fencing maintenance; concentrates and minerals; shed repairs; health costs (vaccination, dipping, drugs, labour and veterinary costs); reproductive costs (costs related to rams); electricity, fuel and machinery maintenance and repairs. The total farm expenditure on concentrates, roughages and pastures was apportioned to each animal category according to its proportional energy requirements (NRC, 1985); health costs were apportioned on a per animal or per weight basis, as appropriate, shed maintenance on a per live weight2/3 basis and labour on the basis of direct observations in some farms (Morais, 2005). Current market prices were used for income and expenses items. All prices were expressed in equivalent kilograms of lamb (ekl), i.e., the current price for one kilogram of live lamb. Some calculated or observed values involved in expenses or income are presented in table 3. Table 3 – Prices of some expense or income items, in equivalent kg of live lamb (ekl)1. Item Unit price (ekl)1

Live lamb (male), kg 1.00 Carcass, kg 2.50 Live ewe, kg 0.67 Live ewe lamb, animal 43.33 Roughage, Mcal 0.01 Concentrate, Mcal 0.05 Labour, per man/year 2216 1An equivalent kg of lamb (ekl) = current price of a kg of live lamb = US$ 1.09 Calculation of economic values Economic values were calculated for lamb daily weight gain (Lwg), replacement ewe lamb daily weight gain (Erg), ewe lamb daily weight gain (Elg), average ewe weight (Ew), ewe/ram ratio (Err), fertility (Fe), prolificacy (Prl), lambing interval (Lin), lamb survival (Lsv) and carcass yield (Cy). The economic value of each trait was obtained by two methods: 1) Vi = P’ – P, where P and P’ are the profits before improvement and after improving the trait in 1%, keeping all other traits at their mean value (Ponzoni, 1988).

8th World Congress on Genetics Applied to Livestock Production, August 13-18, 2006, Belo Horizonte, MG, Brasil

2) vi = (Φ’- Φ)C, where Φ and Φ’ are the farm income/expense ratios before improvement and after improving the trait in 1%, keeping all other traits at their mean value (emulating Smith et al, 1986), and C is the total farm cost (before the improvement). The economic values were expressed per ewe per year. RESULTS AND DISCUSSION The economic values of traits are shown in table 4, both as the value derived from a 1% increase in each trait and as a ratio of the value of each trait to the value of lamb daily gain. Table 4 – Economic values of traits, per ewe per year, in equivalent kg of lamb (ekl)1

Income – Expense (vi = P’ – P) Income / Expense (vi = (Φ’- Φ)C) Trait2 1% trait increase Ratio vi /v(Lwg) 1% trait increase Ratio vi /v(Lwg) Lwg , g 0.148 1.000 0.138 1.000 Cy, % 0.190 1.284 0.190 1.377 Elg, g -0.003 -0.020 -0.005 -0.036 Erg, g -0.002 -0.014 -0.003 -0.022 Ew, kg -0.029 -0.196 -0.068 -0.493 Prl , % 0.255 1.723 0.218 1.580 Fe, % 0.308 2.081 0.213 1.543 Lin, days -0.303 -2.047 -0.213 -1.543 Err, units 0.011 0.074 0.016 0.116 Lsv, % 0.400 2.703 0.355 2.572 1An equivalent kg of lamb (ekl) = current price of a kg of live lamb = U$ 1.09 2 Lwg =lamb daily weight gain, Cy= carcass yield, Elg = ewe lamb daily weight gain, Erg = replacement ewe lamb daily weight gain, Ew = ewe weight, Prl= prolificacy, Fe = fertility, Lin = lambing interval, Err = ewe/ram ratio and Lsv = lamb survival. Traits related to reproduction had high economic values. The similarity in the values of these traits (Table 4) arose from their multiplicative effect, i.e., Prl, Fe and Lin determine the number of lambs born. Dickerson (1970) stated that an opportunity for major improvement in sheep meat production efficiency is given by an increase in reproduction rate from 1 to 3 or 4 lambs per ewe per year. However, lambing 3 times in a 2-year period is already quite feasible in the Santa Inês, so there would seem to be more room for improvement of prolificacy or fertility. Prolificacy differs from the other reproductive traits because it is negatively related with lamb survival, which was considered here by the different mortalities of singles, doubles and triplets, although the distribution of frequencies in those classes was assumed constant, which should be checked against actual results. Lamb survival was the most import trait, which may be explained by the wastage of resources involved in rearing lambs that die, given the relatively high age at death (Table 2). Costs, of course, are greater at older death ages, and for this reason lamb survival may be more important in our production circumstances than in temperate climates, where most lamb deaths occur due to freezing few hours after birth (Slee, 1985). However, lamb survival was not an important trait in a study in Kenya (Kosgey et al., 2004), where lamb production cost was very low. Carcass yield was an important trait, especially because, in the present circumstances, this trait influenced only for income, but not expenses. For the cooperative system, as in other industries, greater carcass yield represents less money spend in transport and slaughter, that are considered as fixed costs per animal. In a cooperative, as farmers are the owners of the packing plant, greater carcass yield is a trait of interest, while farms selling their lambs on a live weight basis would have no interest in improving carcass yield.

8th World Congress on Genetics Applied to Livestock Production, August 13-18, 2006, Belo Horizonte, MG, Brasil

REFERENCES Dickerson, G. (1970) J.Anim. Sci.30: 849-859 James, J.W. (1982) Proc. 2nd WCGALP. 5 : 130-139. Kinghorn, B.P. The genetics of sheep (1997) Editors: Piper, L. & Ruvinsky, A. CAB

International Kosgey I.S., Van Arendonk, J.A.M, Baker, R.L. (2004) Liv. Prod. Sci .88: 143-160. Morais, O.R. (2000) In: 3rd Simpósio Nacional De Melhoramento Animal. Anais...Soc. Bras.

Melh. Animal- Belo Horizonte: FEPMVZ 266-272 Morais, O.R. (2005) PhD Thesis. Federal University of Minas Gerais Ponzoni, R.W. (1988) J. Anim. Breed. Genet. 105 : 143-153 Ponzoni, R.W., Newman, S. (1989) Anim. Prod. 49: 35-47 Slee, J. (1985) In: A seminar in the CEC programme of coordination of agricultural research

Brussels, 22 and 23 January 1985, p.21-34 Smith, C., James, J. W., Brascamp, E. W (1986) Anim. Prod.43: 545-551