India is predominantly an agricultural country and livestock sector is an important allied sector of the agriculture contributing to about 25.6% of total agricultural GDP. The major contribution in livestock sector is from dairy farming. India has a livestock population of about 535.78 million which includes 192.49 millions of cattle and 109.85 millions of buffaloes (20
th Livestock Census of India). India rank at the top in the milk production with total milk production of 209.96 million tons in 2020-21. However, the average milk production per animal is still lower as compared to global average. The milk yield variation is attributed to considerable variability in lactation length which is greatly affected by non genetic factors, which includes direct climate effect, managemental and nutritional aspects, age of animal, year and season of calving
etc. Studies have been conducted to understand the impact of various genetic and non-genetic factors on lactation length. The selection program can be made effective over time by segregating the factors like period, season and parity and their effect on lactation length. It will enable the design of appropriate breeding strategies to maximize the genetic gain and suggest modification, if required, in the managemental standards. The targeted improvement towards these non genetic factors may be helpful substantially to increase the performance of dairy cattle in terms of milk yield traits within the standard duration of lactation. Similarly, the genetically determined variations can be useful for improvement of characteristics and to study the associations existing between the characters. Thus, considering the above fact, an attempt is made to quantify the effect of various non-genetic factors and sire on lactation length in Frieswal cattle.
The data for the present study were collected on Frieswal cattle maintained at Military Dairy Farm, Pimpri, Pune (India) for the period of 1983 to 2018. A total of 9094 lactation records belonging to 3425 Frieswal cows born to 239 sires were recorded. The further analysis was carried out using SAS 9.13 version. The data collected from 1983-2018 was classified into four periods P1 (1983-2003), P2 (2004-2008), P3 (2009-2013), P4 (2014-2018),and three seasons winter (October to January), Summer (Feb- May) and Rainy (June to September). The first period was prolonged from 1983 to 2003 because very few records were available in that period. The total parities were numbered from first to the last parity. The cows which were affected with disease or debilited or died before completion of first three lactations and the sires with less than five progenies were omitted from the study. Further, the data were standardized by removing the records for the cows having age at first calving above 1250 days, lactation length below 100 days and above 365 days, lactation milk yield below 1000 kg and inter-calving period below 250 days. Normalized data were utilized to find out the effect of non genetic factors on lactation length using
PROC GLM procedure of SAS. The means of different levels within a class factor were compared using DMRT. All non genetic effects were considered fixed effects.
The effect of non genetic factors on lactation length were analyzed by adopting the following model.
Y
ijkl = µ + b (AFC
ijkl - AFC) + S
i + P
j+ A
k + e
ijkl
Where,
Y
ijkl = Observation on the lth individual in ith season/month,
j
th period and kth parity.
µ = Overall population mean.
b (AFC
ijkl - AFC) = The regression of the trait on age at first calving.
S
i = Effect of i
th season where i =1,2 and 3.
P
j = Effect of j
th period where j = 1, 2, … 4.
A
k = Effect of k
th parity k = 1,2…..11.
e
ijkl = Random error, NID (0, 𝛔2e).
The sire effect on lactation length was estimated using PROC GLM procedures of SAS by fitting the linear regression model to the data using lactation length as dependent variable and sire as independent variable.
The effect of period of calving was found to be highly significant (p<0.001) on lactation length (Table 1). The average lactation length during the second (302.30±1.22) and third (304.46±0.89) periods did not differed significantly from one another; however, they were significantly different from the mean lactation length of the first period. The lowest mean lactation length was observed in period one (292.52±1.31 days) while the highest was in the third period (304.460.89± days) as shown in Table 2. The variation in lactation length observed during different periods might be due to the level of management practices introduced from one year to another and the variations caused due to the environmental factors like fluctuations in temperature and humidity and also due to some genetic factors like herd genetic levels, changes in the age of the animals etc. The significant effect of the period of calving on lactation length was found by
Chopade et al., (2002) in crossbred cattle,
Das et al., (2011) in crossbred dairy cows and
Beneberu et al., (2020) in pure Jersey cattle in Central Highland Ethiopia. Highly significant effect of period of calving on first lactation length was observed by
Eid (2012) in Friesian cattle,
Hussain et al., (2015) in Tharparkar cattle. However,
Kumar et al., (2016) in Ongole cattle and
Dongre et al., (2017) in Deoni cattle reported the non significant effect of period of calving on lactation length.
The least squares means of lactation length of rainy, summer and winter seasons was found to be 301.66±1.00, 300.68±0.86 and 299.44±0.77 days, respectively (Table 2). The season of calving had a significant effect on lactation length. The lactation length of winter season differed significantly from lactation length of rainy and summer season. Cows calved during the rainy season had the highest lactation length (301.66 ±1.00 days) and that of the cows calved during the winter season had the lowest lactation length (299.44±0.77 days). The season-wise differences in lactation length may be attributed to a different production setup and variation in managemental conditions during these seasons.
Singh et al., (2015) reported the significant effect of season on the lactation length in crossbred cattle.
Choudhary et al., (2019) reported a significant effect of calving seasons on lactation length in Tharparkar cattle. However, the contradictory result of a season of calving was reported by
Lakshmi et al., (2010) in Frieswal cattle,
Wondifraw et al., (2013) in Holstein Friesian × Deoni crossbred cows and
Rokade et al., (2021) in Phule Triveni cattle.
The parity had a highly significant (P<0.001) effect on the lactation length (Table 1). The DMRT showed that the lactation length from second (305.77±1.20) to sixth (305.48±2.14) parity did not differ significantly from each other. Similarly, parity numbers eight (304.02±3.25), nine (305.32±4.29) and eleven (304.81±1.30) were also showing non-significant differences between them. However, the lactation length in first (288.19±0.86) and tenth (308.40±5.42) parities differ from all other lactation lengths, as shown in Table 2. The minimum lactation length was observed during the first parity and the maximum lactation length was observed during the tenth parity. The short lactation length during the first parity may be due to the fact that the reproductive organs and mammary glands were not fully developed during this period. The non-significant difference in lactation length from the second to sixth parities indicates the stability of lactations and milk yield (Table 2).Similar results were also obtained by
Kumar et al., (2016) in Ongole cattle,
Alex et al., (2017) in Frieswal cows in the northern zone of India and
Beneberu et al., (2020) in pure Jersey cattle. Whereas, the non- significant effect of parity was reported by
Dongre et al., (2017) in Deoni cattle of Marathwada region and
Rokade et al., (2021) in Phule Triveni cattle.
The least squares mean for age at first calving was found to be 961.06±1.51 days (Table 2). Age at first calving had highly significant effect on lactation length in Frieswal cattle.
Heravi et al., (2008) reported the significant effect of age at first calving on lactation length however,
Gatchearle et al., (2009) and
Naceur et al., (2012) found the non-significant effect of age at first calving on lactation length in Holstein Friesian × Deoni (HF × D) and Tunisian Holstein cows, respectively.
The genetic factor considered for the present study was the effect of sire. It was observed that the sire effect was found to be highly significant (p<0.001) on lactation length (Table 1). Thus, the proper selection of sire may bring about an improvement in lactation length.
Mishra (2016) and
Choudhary et al., (2019) reported the highly significant effect of sire on lactation length in Tharparkar cattle. The significant effect of sire on lactation length was also reported by
Abbas et al., (2010), Kumar et al., (2016), Jadhav et al., (2019) and
Kuchekar et al., (2021) in Sahiwal cattle, Ongole cattle, HF × Gir Cattle and Phule Triveni cattle, respectively. However,
Kharat et al., (2008) reported the non significant effect of sire lactation length in Holstein Friesian crossbred cows.
