Influence of Season on Milk Yield and Milk Composition of Red Sokoto Goats in Mubi Area of Adamawa State, Nigeria

MATERIALS AND METHODS

Location of the Study
Mubi area (Mubi north and Mubi south local government areas) lie within Northern Guinea Savannah zone of Nigeria and located at latitude10°00 North, longitude 13°30 East and about 305 m above sea level, with an area of 961.39 km². The dry season in this area commences early October and last up to April. The wet season begins from May and attains its peak between July and August and declines in September; the mean annual rainfall is 1050 mm. The relative humidity is extremely low 20-30% between January and March and start increasing as from April and reaches a peak of about 80% in August and September, the relative humidity starts to decline from October following the cessation of rains. The maximum temperature can reach 40°C particularly in April while minimum temperature is about 18°C between December and January. The varieties of livestock include cattle, sheep, goats and pigs. The dwarf goats are the most common breeds (Adebayo and Tukur, 1999).

Mubi area consisting of twenty-one political wards, eleven wards in Mubi North and ten wards in Mubi South, with a population of about 151,072 in Mubi North and 128,937 in Mubi South local government areas (National Population Commission, 2006). Mubi is bounded to the South by Maiha local government area to the West by Hong local government area and to the North by Michika local government area and to the East by Cameroun republic. The people are predominantly farmers. Most households keep various livestock species.

Goats Management
The goats are allowed to range freely in the dry season and confined as soon as the crops are sown in the wet season. They are released as soon as the crops are harvested; they are mostly released out to grazing fields in the morning. In the evening, they are brought back and enclosed in huts made for the goats, no concentrates was given.

Sampling Techniques
Purposeful, multistage and random sampling techniques were used, to select 40 lactating Red Sokoto does, 20 in the dry season (January-April, 2008) and 20 in the wet season (June-September, 2008), was selected within Mubi area to determine the milk yield and its composition.

Collection of Milk Samples and Analysis
Forty Goat milk samples were collected from the two local government areas, in the dry and wet seasons, during the year 2008. During milk collection, the udder and teats of each doe were washed with lukewarm water and cleaned with cotton wool soaked in disinfectant and then they were hand-milked into previously sterilized containers and measured. Milk yield was measured for 12 weeks from each doe after kidding except for the first 3 days postpartum. The entire content was then evaluated for the following; total solid, solid non fat, fat, cholesterol, calcium, phosphorus and magnesium levels, these were determined according to the standard procedures described by AOAC (1990), Pearson’s chemical analysis of food, Harold and Kirk (1981) and Bohac et al. (1984). The minerals (Phosphorus, Calcium and Magnesium) were determined by Atomic Absorption Spectrophotometer (AAS), (Perkin-Elmer, 1976). Data generated were subjected to analysis of variance using GenStat Release 7.2 (2007).

RESULTS

The results in Table 1 shows that effect of parity was not significant on calcium, cholesterol, milk yield, magnesium, phosphorus and solid non fat, but there was significant effect of parity on fat (p<0.001) and total solid (p<0.005). Table 2 showed parity had significant effect on fat (p<0.001), solid non fat (p<0.01) and total solid (p<0.001), while there was no significant difference on phosphorus, magnesium, milk yield, cholesterol and calcium. In comparison between wet and dry season, there was significant effect of season on calcium (p<0.01), which shows that the result obtained for calcium was lower in the dry season (Table 2), milk yield was higher in the wet season with significant difference at (p<0.001) as affected by season. Table 3 and 4 show the statistical result of the effect of parity on the milk components in wet season and dry season respectively.

Table 1:	Milk yield and composition (Red Sokoto goat milk) in the wet season (n = 20)

Table 2:	Milk yield and composition (Red Sokoto goat milk) in the dry season (n = 20)

Table 3:	Mean effect of parity on milk composition (Wet season) (n = 20)
P: Parity, SED: Standard error of difference

Table 4:	Mean effect of parity on milk composition (Dry season) (n = 20)
P: Parity, SED: Standard error of difference

DISCUSSION

Milk Yield
Generally the result was better, with higher values obtained during the wet season; this is in line with the findings of El-Hassan et al. (2009) that productivity in goats is better during this period. The values obtained in the study were 3.38 and 2.08 kg per week in wet and dry season respectively. It was observed that the milk yield is higher in the wet season, there was a significant difference (p<0.001), this may be due to the availability of forages in the wet season, which was lower in the dry season, the result of Table 3 and 4 show that the effect of parity were not significant in both seasons. This values are comparable to the previously reported values of 3.8 litres per week (Ehoche and Buvanendran, 1983) 3.3 litres per week (Adu et al., 1979) 3.3 litres per week (Akinsoyinu et al., 1981) and lower than 3.7 kg per week (Alawa and Oji, 2008), but higher than 1.6 kg per week obtained by Sankey (1991) from does of the same breed (Red Sokoto goats). The milk yield is low compared to the values reported for European breeds of 1.9 kg per day (Morand-Fehr and Sauvant, 2006) this might be due to breed differences.

Milk Fat
The milk fat obtained in this study were 5.01 and 4.84% in wet and dry season respectively, the difference was not significant. Fat showed significant difference (p<0.001) with parity effect in both seasons, as shown in Table 3 and 4. The values obtained were similar to the values 5.04 and 4.94 (Zarhraddeen et al., 2007), 5.7 (Alawa and Oji, 2008), 5.32 (Mba et al., 1975), 4.30 (Sankey, 1991) 4.60 (Akinsoyinu et al., 1981) and 4.75 (Ehoche and Buvanendran, 1983) reported for the Red sokoto goat these similarities might be due to similarities in breeds. In comparison to the values for, WAD goat 4.74, Sahel goat 5.16 (Zahraddeen et al., 2007), WAD 7.78, Saanen 5.48 (Mba et al., 1975), Previous studies have shown that the WAD goat has high milk fat than the Red Sokoto goat, but the values obtained in this study can be compared to the value obtained for Sahel goat in previous studies. The study (Table 1, 2) have shown that, the mean value of fat was lower in the dry season and higher in the wet season, this might be in relation with nutritional status of the animals during wet season, where feeds are available and richer in minerals and vitamins, the fat content tends to increases as parity increases this might be due to increase in age.

Total Solid and Solid Non Fat (SNF)
The values of solids-non-fat and total solids in this study, were 11.79 and 16.58%, wet season, 13.42 and 17.86% dry season, respectively, the effect of season is significant (p<0.05) and significant at (p<0.01) with effect of parity in the dry season, these values are similar to the values obtained, 11.4 and 17.1%, respectively (Alawa and Oji, 2008), but also higher than the previously reported lower values of 10.53 and 15.83% by Mba et al. (1975), 13.63 and 0.73% by Sankey (1991) The values were higher in the dry season, the effect of parity was significant on total solid (p<0.001).

The Mineral Content
There were no significant differences in the values of the minerals obtained in this study with parity. The values of calcium found in this study was 0.22 and 0.29% in dry and raining season, respectively, there was a significant difference in calcium at (p<0.001) caused by seasonal effects might not be unrelated to the nutritional level in the raining season. These values are comparable to the value 0.20% obtained by Alawa and Oji (2008). Magnesium values were 0.14 and 0.15% in dry and wet season respectively, which are also comparable to 0.14% (Alawa and Oji, 2008). The values obtained for phosphorus were 0.13 and 0.14% in the dry and wet season, the influence of season and parity was not significant, 0.13%, (Alawa and Oji, 2008) obtained for same breed in the dry season (Red Sokoto goat ) was in agreement with the value obtained in this study in the dry season.

Cholesterol Level
Cholesterol values obtained in this study were 0.17 and 0.18% in the dry and wet season respectively; research on Red Sokoto goat milk cholesterol level seems unavailable, an average of 0.14% for European goats breed. But in comparison with cow milk the cholesterol level in Red Sokoto goat milk obtained in this study was slightly higher than the average value 0.15% for European breeds of cattle (Chicama, 2009). An average cholesterol level in human milk 0.20% is higher than the values for both goat and cow milk. Low-cholesterol means the food contains 20 mg cholesterol or less per 100 g. The American Heart Association recommended in 2009 that, average daily cholesterol intake of less than 300mg, if you have heart disease, up to 400 mg for healthy persons.

CONCLUSION

There is need to improve milk production potentials of the local breed through breeding, nutrition, improved management systems as well as creating awareness on nutritional value of goat milk.