Chios Sheep Research Articles

Determination of BMP-15, BMPR-1B and GDF-9 Gene Mutations of the Indigenous Sheep Breeds in Turkey

Summary The high ovulation rate and fertility are very important production traits in sheep production. The aim of the study was to determine the BMP-15, BMPR-1B and GDF-9 gene mutations which are related with the high ovulation with high ovulation rate in Chios, Kivircik, Awassi and Imrose sheep breeds. Fifty sheep from each breed were provided for this study. Blood samples for all the animals were collected in sterile-2 ml tubes containing EDTA. Genomic DNAs were isolated using a standard salt-out method. Thereafter target sites were amplified with polymerase chain reaction (PCR). FecX I , FecX H , FecX G , FecX B mutations in BMP-15 gene, FecB mutation in BMPR-IB gene and FecGH mutation in GDF-9 gene were determined by restriction fragment length polymorphism (RFLP) method. All individuals were non-carriers for these mutations, except FecX G mutation in BMP-15 gene. The animals analyzed in this study were found to be heterozygous carriers for FecX G mutation. There may be other genes affecting fertility in Anatolian breeds. For the genetically explanation of multiple lambing, especially in Chios sheep, it was concluded that different genes should be investigated in the further studies.

Polymorphism in Melatonin Receptor 1A (MTRN1A) Gene in Chios, White Karaman and Awassi Sheep Breeds

Polymorphism in Melatonin Receptor 1A (MTRN1A) Gene in Chios, White Karaman and Awassi Sheep Breeds

Analysis of PrP genotypes in relation to reproductive and production traits in Chios sheep

The study describes the changes with time in gene and genotype frequencies of a closed Chios herd. Genomic DNA was isolated and purified from peripheral blood leucocytes using standard procedures. The identification of the allelic variants present in the DNA samples, was performed in a simple multiplex PCR reaction and melting curve analysis of the PrP gene. Only ARR/ARR female genotypes were kept for breeding, and only males of the same genotype were used following year 2 of the study. As a result of planned individual matings and selection, the susceptible ARQ/ARQ genotype was eliminated from the flock in 4 years. The gene frequency of the R allele from a low 0.056 at year 1 reached a high 0.911 at year 6 of the study. Data from first lactation ewes of known genotypes were used to examine possible associations between PrP genotypes and ewe reproductive (litter size at birth and at weaning) and production traits (litter weight at birth and at weaning and 60-day milk yield after weaning). No effects of the sire genotype (ARR/ARR and ARR/ARQ) were found for any of the traits studied. The ewe genotype was associated with performance for reproductive traits but not with total weight of lamb output at birth or at weaning. ARR/ARR ewes had a higher litter size at birth (2.09) compared to ARQ/ARQ ewes (1.79) and higher litter size at weaning (1.84) compared to ARR/ARQ ewes (1.59). 60-day milk yield after weaning was not influenced by genotype (114.8, 105.8 and 114.8 kg for ARR/ARR, ARR/ARQ and ARQ/ARQ genotypes, respectively). Birth weight and 98-day weight were not influenced by the lamb genotype. ARQ/ARQ lambs were slightly heavier ( P < 0.05) than ARR/ARR lambs at weaning as a result of faster pre-weaning growth. Post weaning growth was similar for the homozygous genotypes.

Effects of Age and Reproductive Stage on Certain Serum Biochemical Parameters of Chios Sheep Under Greek Rearing Conditions

The aim of the present study was to determine the normal ranges of the most commonly used serum biochemical parameters of sheep reared under Greek breeding conditions, as well as to test for the effects of the age and reproductive status of the animals on the normal values of these parameters. In total, 200 clinically healthy Chios sheep from 10 farms were used in the experiment. For the determination of the effect of age 150 sheep were assigned in three groups. Group A consisting of 50 lambs aged 2-6 months (mean +/- SD: 4.15 +/- 1.08), group B of 50 non-pregnant ewes into lactation aged 1-3 years (mean +/- SD: 2.12 +/- 0.86) and group C of 50 non-pregnant ewes into lactation aged more than 3 years (mean +/- SD: 5.98 +/- 1.66). For evaluating the effect of reproductive status 50 pregnant ewes in dry period were used, 15-30 days before the expected day of lambing (group D), along with the 100 non-pregnant ewes into lactation of groups B and C (group E). Blood sampling was performed once, in dry ewes from December to January, and in lambs and lactating ewes from March to May. The results showed that of the 14 biochemical parameters determined in serum, six were significantly affected by the age and eight by the reproductive stage of the animals.

Relationship between spontaneous, out-of-season ovulatory activity and other reproductive characteristics of Chios sheep

Spontaneous, out-of-season ovulatory activity (SOA) may contribute to the improvement of the reproductive capacity and management of sheep. The relationship between SOA and other important traits becomes an issue in the development of a breeding goal. In this article, the relationship of SOA with fertility, measured as success at conception, prolificacy, measured as number of lambs born, and stillbirth, measured as number of lambs born dead, was assessed. Data included 662 reproductive records of 391 Chios ewes kept at the Agricultural Research Station, Chalkidiki, Greece. These ewes were daughters of 140 rams. Blood progesterone levels were used to determine SOA status. Measurements took place prior to the onset of the breeding season, which is marked by the introduction of rams to the flock. Data were collected over two consecutive years. The frequency of SOA was 29.9%, the average success rate at conception was 81.7% and the mean litter size was 2.14 lambs, while 0.24 lambs, on average, were born dead. Linear and non-linear mixed models were used for the statistical analysis of these data. Both ewes that did and did not exhibit SOA had similar success at conceiving in the subsequent mating season. However, ewes that had exhibited SOA gave birth to 0.22±0.08 fewer lambs than ewes from the other group. This estimate was adjusted for the effects of season of lambing, year, age and status of the ewe, and sire of the ewe, and was significant ( P<0.05). The effect of SOA on stillbirths was not significant. Additive genetic and residual correlation estimates of SOA with fertility and stillbirth were not different from zero. The additive genetic correlation between SOA and prolificacy was not different from zero. A residual correlation estimate of −0.15±0.05 was found between these two traits, associating the presence of SOA with smaller litter size. This residual correlation is due to environmental and non-additive, non-heritable genetic factors. The results of this study imply that development of a breeding program including SOA would not be expected to affect fertility, litter size and stillbirth rate in the Chios breed.

Sources of variation and genetic profile of spontaneous, out-of-season ovulatory activity in the Chios sheep

Organising the breeding plan of a seasonally breeding species, such as sheep, presents a challenge to farmers and the industry as a whole, since both economical and biological considerations need to be carefully balanced. Understanding the breeding activity of individual animals becomes a prerequisite for a successful breeding program. This study set out to investigate the sources of variation and the genetic profile of the spontaneous, out-of-season ovulatory activity of ewes of the Chios dairy sheep breed in Greece. The definition of the trait was based on blood progesterone levels, measured before exposing the ewes to rams, which marks the onset of the usual breeding season. Data were 707 records, taken over two consecutive years, of 435 ewes kept at the Agricultural Research Station of Chalkidiki in northern Greece. When all available pedigree was included, the total number of animals involved was 1068. On average, 29% of all ewes exhibited spontaneous, out-of-season ovulatory activity, with no substantial variation between the years. Significant sources of systematic variation were the ewe age and live weight, and the month of previous lambing. Older, heavier ewes, that had lambed early the previous autumn, exhibited more frequent activity. Heritability estimates were 0.216 (± 0.084) with a linear and 0.291 with a threshold model. The latter better accounts for the categorical nature of the trait. The linear model repeatability was 0.230 (± 0.095). The results obtained in this study support the notion that spontaneous out-of-season ovulatory activity can be considered in the development of a breeding plan for the Chios sheep breed.

Genetic and phenotypic relationships between milk production and body weight in Chios sheep and Damascus goats

Data on 2087 lactations from 737 Chios ewes collected between 1978 and 1989, and 1611 lactations from 486 Damascus goats collected from 1982 to 1998 at the experimental station of the Agricultural Research Institute were utilized. The ewes were the progeny of 101 sires (mean sire family size 7.3) and the goats of 101 sires (mean sire family size 4.8). A mixed linear model that accounted for the year and season of lambing/kidding and parity of ewes or goats (fixed effects) and sires within years (random effects) was used. Phenotypic and genetic variance and covariance estimates were obtained from paternal halp sib correlations. The study was conducted to investigate genetic and phenotypic relationships between milk production (90-day and total milk) and live weight at mating. Year effects were significant ( P<0.01) for all traits studied, while season of parturition significantly affected ( P<0.01) only milk production (part and total). Parity had a significant quadratic effect ( P<0.01) on all traits examined; the highest response in milk production was reached in the third parity and the highest body weight at mating in the fifth parity. Heritability estimates for 90-day (0.44±0.08 and 0.45±0.11) and total milk yield (0.54±0.09 and 0.49±0.11) for sheep and goats, respectively, were high, indicating that genetic progress from direct selection on either trait would be effective. Heritability of body weight at mating, unadjusted or adjusted to mature equivalent, was high in both species (sheep: 0.79±0.09 and 0.76±0.09, respectively; goats: 0.79±0.11 and 0.80±0.11, respectively). Genetic and phenotypic correlations between part and total lactation yield were both high and positive, justifying selection on early measures of milk production. The genetic associations between production traits and body weight at mating were very low in both species. It was positive in sheep and negative in goats, but no or extremely small correlated responses could be expected in body weight from selection on milk production. Increased body size, when expressed, should be the consequence of better feeding and improved management practices during periods of stress.

Estimation of genetic parameters for production traits of Chios sheep using a multitrait animal model

Genetic parameters for commercial milk yield, litter size at birth and mean litter weight at weaning of Chios sheep were estimated. The data originated from the Agricultural Research Station of Chalkidiki and included 5343 lactations of 2315 ewes with lambings from 1977 until 1996. Variance components were estimated using restricted maximum likelihood, fitting a multitrait animal model. The random effects included in the model were the additive genetic effect of the animal, the effect of the permanent environment of the animal and the residuals. Heritability estimates were 0.23±0.015, 0.16±0.011 and 0.16±0.010, for commercial milk yield, litter size at birth and mean litter weight at weaning, respectively. In the same sequence the repeatabilities of the traits were 0.38, 0.18 and 0.16. Genetic correlations were 0.03±0.040 between milk yield and litter size, −0.77±0.036 between litter size at birth and mean litter weight at weaning and −0.06±0.037 between milk yield and mean litter weight at weaning.

Seasonal effects on puberty and reproductive characteristics of female Chios sheep and Damascus goats born in autumn or in February

Ten Chios ewe lambs and 10 Damascus she-kids born in October–November and similar numbers born in February along with eight multiparous females from each species, were used to examine pubertal events and reproductive seasonality. Reproductive activity was monitored by determining serum progesterone concentrations once a week for 12 months. The mean date of onset of ovulation (puberty) in autumn-born Chios females (7 August) was earlier ( p<0.05) than in February-born ones (11 September) though the onset of regular cyclicity was not significantly different between the two groups (30 August and 19 September, respectively). The age and live weight at puberty in autumn-born females was higher ( p<0.01) than in February-born ones, the respective values being 43.3 weeks and 50.1 kg, versus 29.9 weeks and 42.0 kg. All animals, irrespective of time of birth, started ovulating after the summer equinox. Multiparous Chios ewes had reproductive cycles covering most time of the year with acyclic periods during spring and summer. In ewe lambs, about half of the animals ceased cycling during the second half of winter and in spring, while the rest continued cycling. The total number of cycles detected over the experimental period was lower ( p<0.05) for February-born ( n=9.4) compared with autumn-born females ( n=13.7) and adult ewes ( n=17.1). In Damascus she-kids born in autumn or in February, onset of puberty was at the same time in the following autumn, the respective mean date for the two groups being 1 November and 27 October. For autumn-born animals, age (48.4 weeks) and live weight (53.8 kg) at puberty were higher ( p<0.01) than for those born in February (37.3 weeks, 42.9 kg). Reproductive cycles in adult goats started in the second half of September and continued until the end of March. Most young goats (75%) had their last seasonal cycle in February and the rest in March. The total number of cycles was higher ( p<0.01) in adult ( n=8.1) than in young goats born either in autumn ( n=6.3) or in February ( n=5.7). It is concluded that reproductive development and puberty in Chios female sheep are mostly under seasonal influences though age and body weight are also contributing factors. This breed has a long reproductive season with some animals cycling throughout the year. The Damascus female goat is strictly seasonal with distinct periods of reproductive cyclicity and inactivity. Puberty attainment of Damascus females born in autumn or in February is at the same time the following autumn.

Improvement of Ossimi Productive Traits Through Crossing With Chios Sheep. II- Livability and Twinning Percentage

Improvement of Ossimi Productive Traits Through Crossing With Chios Sheep. II- Livability and Twinning Percentage

Alterations in follicular maturation associated with within-breed variation in ovulation rate in Chios sheep.

Within-breed comparisons may be helpful to identify, in a given genetic background (Chios sheep), ovarian strategies and control mechanisms associated with altered ovulation rate. High and low ewes were identified from two large groups (n = 27 and n = 33 in Exp. 1 and Exp. 2 respectively) of Chios ewes submitted to repeated laparoscopies (24 times in Exp. 1 and six times in Exp. 2). High ovulatory ewes (n = 6 and n = 7 in Exp. 1 and Exp. 2 respectively) had mean ovulation rates of 4.3 (Exp. 1) and 4.2 (Exp. 2) while low ovulatory ewes (n = 6 and n = 7 in Exp. 1 and Exp. 2 respectively) had mean ovulation rates of 2.5 (Exp. 1) and 1.9 (Exp. 2). In Exp. 1, follicular function was compared in these two groups of ewes using follicles obtained at 30 h following luteolysis in the same ewes before and after unilateral ovariectomy (ULO). In Exp. 2, circulating follicle stimulating hormone (FSH) concentrations were measured from the end of the luteal phase up to the preovulatory surge in high and low ewes. Thereafter, to demonstrate a causal link between high FSH and high ovulation rate, pituitary downregulation was achieved by a 17-day gonadotrophin releasing hormone (GnRH) agonist treatment and the ovarian response to similar amounts of exogenous gonadotrophins compared between high and low ewes. Numbers of oestrogenic (in vitro oestradiol > 250 pg ml-1 h-1) follicles on the first ovary removed (Exp. 1) were 2.16 +/- 0.5 vs. 1.33 +/- 0.17 in high and low ewes (P = 0.1). Following ULO, these numbers were 3.33 +/- 0.33 and 2.5 +/- 0.18 (P < 0.05 between high and low ewes). There were no significant differences between the first and second ovaries for any of the parameters studied. Follicles from high ovulatory ewes (n = 33) differed from those of low ovulatory ewes (n = 23) by a smaller size (P < 0.01), a reduced number of granulosa cells (P < 0.01) together with decreased oestradiol (P < 0.05) and testosterone (P < 0.01) production in vitro. However, steroid production per cell (oestradiol per granulosa cell, testosterone per thecal cell) was similar in the two groups of sheep. FSH concentrations (Exp. 2) in high ovulatory ewes were significantly higher than those of low ovulatory ewes during the late luteal phase, and the decrease in FSH concentrations was steeper (1.4 ng) during the early follicular phase for high ovulatory ewes than low ovulatory ewes. Chemical hypophysectomy achieved by a 17-day treatment with a GnRH agonist demonstrated that these high FSH concentrations may be important to generate the high ovulation rate of the 'high' ewes as ovulation rate of high and low ewes was similar following chemical hypophysectomy followed by administration of similar amounts of exogenous gonadotropins to both groups of ewes. It is concluded that, despite different genetic control of their high ovulation rate (Chios-polygenic; Booroola-major gene), alterations in follicular function and its control are very similar in high ovulatory Chios and in FecB carriers.

Feedlot Performance and Carcass Characteristics of Local and Cross-bred (Local X Chios) F1sheep fed on By-products-based Diet

Abstract El, Hag, M.G. and Al-Shargi, K.M. 1995. Feedlot performance and carcass characteristics of local and cross-bred (local X Chios) sheep fed on by products-based diet. J. Appl. Anim. Res: 8: 197–202. Feedlot performance and carcass characteristics of growing local and cross-bred (local X Chios) sheep were studied using a by product based (BP) diet and a commercial concentrate diet (General ruminant, 14% CP), produced by Oman Flow Mill. The BP diet was based on 33% Date leaves + Rachis: 15% Date syrup by-product (DSBP) and 12% fish sardine (60% local by-products). BP diet was more fibrous (17.5% CF) than the concentrate diet (7.8% CF). In general feed intake as well as feed efficiency from both BP and concentrate diets were similar. Cross-bred sheep gained significantly (P 0.05) between diets for daily gain. Dressing percent of empty body weight and longissimus dorsi area was unaffected by both diets or breeds. BP diet was che...

A comparative study on the haemoglobin polymorphism of domestic sheep of the islands of Chios, Cyprus and Sardinia

Different alleles at the two linked α-globin loci are present in sheep: I α 113Leu and II α 113Leu, I α 8Ala,113Leu, I α 15Asp,113Leu, and II α 113His. Triplicated α-gene haplotypes are also common. Six different β-globins (A, B, E, G, H, and I) contribute to the Hb polymorphism. A comparative study on the biochemical polymorphism of α- and β-globins in pure sheep breeds of the Mediterranean islands of Chios, Cyprus, and Sardinia is described. Cyprus and Sardinia breeds have the lower frequency of α-globin variants. Chios sheep possess the high 0.40 frequency of the I α 8Ala,113Leu- II α 113His arrangement. No α-gene triplications were observed amongst Chios and Cyprus breeds. None showed the I α 15Asp,113Leu variant. The β B allele largely predominates; the frequency of the β A was lower ( f = 0.03) amongst Sarda sheep that also possess the β I variant. A novel β B-globin variant was observed in the Chios breed. Both natural and artificial selection may be the cause for these differences.

Superovulatory response of Chios sheep to PMSG during spring and autumn

To study the superovulatory response of Chios sheep to pregnant mares' serum gonadotrophin (PMSG), two experiments were carried out; one in spring and one in autumn. Four doses of PMSG (1500 IU, Group 1; 1000 IU, Group 2; 750 IU, Group 3; 500 IU, Group 4; controls, Group 5) were tested on 46 ewes. Oestrus was synchronised by means of MAP intravaginal sponges and PMSG was injected i.m. at the time of sponge withdrawal. When in oestrus, ewes were naturally mated. On Day 7 after sponge removal, mid-ventral laparotomy was performed and the uterine horns and/or oviducts were flushed with 20–40 ml Dulbecco's phosphate-buffered saline supplemented with 15% foetal bovine serum (FBS). The embryos were examined under a dissecting microscope and were evaluated according to morphological criteria. The interval from sponge removal to the onset of oestrus was significantly (P < 0.001) shorter in autumn than in spring in all groups. No significant differences regarding superovulatory response, collection and fertilisation rate or numbers of ova and embryos collected were found between spring and autumn. The clinical signs of oestrus started earlier (P < 0.001) in all PMSG treated animals than in the controls, both in spring and in autumn. The highest ovulation rate was recorded in Group 2 (5.9 ± 1.0), followed by Groups 1 (5.0±0.9), 3 (3.9±0.5), 4 (26±0.4) and 5 (1.3±0.1). The increase observed in total ovarian response (corpora lutea + large anovulated follicles) parallelled the increase of PMSG dose (10.7 ± 1.6, 7.7 ± 0.9, 4.5 ± 0.6, 3.4 ± 0.5 and 1.8 ± 0.2 for Groups 1, 2, 3, 4 and 5, respectively). The highest mean number of ova was collected from Group 3 (3.4±0.5), followed by Groups 2 (2.6 ± 0.4), 4 (2.2 ± 0.3), 1 (1.6 ± 0.5) and 5 (1.1 ± 0.1). The higher doses of PMSG (1500 and 1000 IU) significantly increased the mean number of anovulated follicles and significantly decreased recovery rate. Mean number of high viability embryos collected per ewe treated (0.9 ± 0.6, 1.5 ± 0.4, 2.2 ± 0.5, 1.5 ± 0.4, 0.9 ± 0.1 for Groups 1, 2, 3, 4 and 5, respectively) was not improved by PMSG dose. It is concluded that Chios sheep can be superovulated in autumn and in spring with similar results. Clinical signs of oestrus are initiated earlier in autumn than in spring. PMSG treatment shortens the interval from sponge removal to the onset of oestrus. Although PMSG does not seem to be the most suitable hormone for the induction of superovulation in Chios sheep, a dose of 750–1000 IU PMSG gives satisfactory results; higher doses are associated with side effects in a significant number of animals (many anovulated follicles, low recovery rate).

Ovulation rate and reproductive performance of Ossimi, Awassi, Chios sheep and their crosses

Ovulation rate and reproductive performance of Ossimi, Awassi, Chios sheep and their crosses

Relationships between pre-weaning growth, post-weaning growth and mature body size in Chios sheep

ABSTRACTThe study examined early measures of growth and their relationships with mature body size. Data on 792 purebred females of the Chios breed, born and reared on two experimental farms between 1978 and 1986, were analysed. Pedigree information and records on live weight at birth, at weaning, 105 days of age and at first and subsequent matings was recorded. There were flock-year differences for all traits studied (P &lt; 0·01) and birth type was important for all traits except post-weaning growth rate. Dam lactation number had no significant effect on birth weight and pre-weaning growth rate, but it significantly affected all subsequent weights and post-weaning growth rate. Estimated heritabilities increased with age and ranged from 0·13 (s.e. 0·14) (birth weight) to 0·30 (s.e. 0·15) (mature weight). Genetic correlations were generally positive between weights and growth traits. Phenotypic correlations were positive and followed the pattern of the genetic correlations. The results suggest that selection for 105-day weight will result in increased mature weight.

The effect of cereal processing on the lactation performance of Chios sheep and Damascus goats and the pre-weaning growth of their offspring

Three trials with ewes and three with goats were conducted to study the effect of cereal processing (mash, pelleted and whole grains) on their milk yield and milk composition. In all trials, concentrates and roughages (long form) were offered from separate feed containers. Within trials, the roughage to concentrate ratios and the source and form of roughages were identical for the control and the treatment (whole grains) diets. In Trial 1 with ewes, milk yield and weight changes of ewes were similar for both the pelleted and whole grain diets during the pre-weaning period. During the post-weaning period ewes on the whole-grain diet produced milk of significantly higher fat content; fat yield was also higher. In the other two trials, a comparison between whole-grain and mash diets was made during the post-weaning period. Ewes on both diets produced similar milk yields, but the fat content of milk, the fat yield and the energy secreted in milk were significantly higher in ewes on the whole-grain diet. In the three trials with goats, milk yield and weight changes of goats were similar for both the whole-grain and the pelleted diet during the pre-weaning period. Results in the post-weaning period were similar to those before weaning except for fat content, which was higher in goats on the whole-grain diet.

Fractional outflow of soyabean meal from the rumen of Chios lambs and Damascus kids

In earlier studies, results from incubation experiments were combined with measurements of outflow rates of small particles from the rumen to predict the extent of degradation of dietary protein in vivo (Orskov &amp; McDonald 1979). The degradability of a protein supplement was shown to decrease when fractional outflow rate increased (Orskov 1982). In a series of experiments, the factors affecting the fractional rates of outflow of dietary protein supplements from the rumen of sheep and lactating dairy cows were investigated (Agricultural Research Council 1984). In addition, outflow rate of soyabean meal from the rumen of dry and lactating Chios sheep and Damascus goats offered high concentrate diets was determined in recent studies (Hadjipanayiotou et al. 1988). Chromium-treated protein supplements were used to measure their outflow from the rumen using the marker concentration in faeces (Ørskov 1982). This paper reports outflow from the rumen of growing Chios lambs and Damascus kids offered concentrates ad libitum.

Characteristics and experiences of Chios breed

Discussed are the reproductive and productive characteristics of the dairy and prolific Chios sheep breed, originating from the homonymous Greek island. Besides the island, the breed is also raised in the Greek mainland, the westcoast of Turkey and in Cyprus. It is early maturing, with long reproductive reason and lambing period, extending from October to March. Inspite its high ovulation rate, repeatability estimates do not suggest the presence of fecundity genes. The average prolificacy ratio ranges between 1.80 and 2.0, with triplets and quadruplets not uncommon. The average exploitable milk yield varies between 180 and 200 kg, with occasionally reported productions of up to 400 and 500 kg. Repeatabilities of prolificacy and milk production based on island data were found 0.15 and 0.40, respectively. Heritability of milk yield from the island was 0.31 and 0.40, respectively, for second and third lactations. Recent estimates from Cyprus report values of 0.30 and 0.39 for 90-day milk and total milk yield, respectively. Other parameters and information on udder (mechanical milking), growth, and carcass characteristics as well as on crossbreeding trials are also reported. Some considerations are given with regard to potential and valorization of this highly productive sheep breed.

Estimation of the energy value of milk and prediction of fat-corrected milk yield in sheep and goats

The milk production and its composition (fat and total solids) of Chios sheep and Damascus goats were used to estimate the energy value of sheep ( n=604) and goat milk ( n=529). The energy values of sheep and goat milk, estimated from energy in fat alone, were E s=453+91.17 f and E g=292+104.74 f, respectively. Equations for the prediction of milk production, adjusted for fat content (fat-corrected milk yield), were developed using the relationships between fat and gross energy value of milk. These prediction equations express milk production in terms of 6% fat-corrected milk for sheep, FCM s= M (0.453+0.0912 f) and 4% for goats, FFCM g= M(0.411+0.147 f). Fat-corrected milk yield is a much better criterion for comparisons among individuals with regard to their genetic and/or phenotypic merit.