Factors affecting milk yield, lactation length and milk composition of dual-purpose cattle in Ashanti region of Ghana

Abstract

The objective of this study was to determine factors affecting milk yield, lactation length and milk composition of smallholders’ dual-purpose cattle in the Ashanti Region. Specifically it was intended to assess the effect of breed and non-genetic factors on (1) average value of milk yield, (2) lactation length of cows and (3) percentage milk components of various breeds of local cows. The study was conducted in four Districts of the Ashanti Region from 2012 to 2014. The cattle used for the study comprised 328 dual purpose cows. Longitudinal survey was used with purposive sampling techniques. The cows were kept under farmers own practices and care with or without feed supplementation. Fresh milk samples from various breeds of cows were analysed for percentage composition of protein, fat, lactose, cholesterol, solid-non-fat and total solids. Lactation lengths were assessed by monitoring the date of calving to the date of weaning. All data were analysed using Generalized Linear Model Type III procedure of SAS. Results on average milk yield indicated that breed, parity, season of lactation, teat size, feed supplementation and body condition score (BCS) influenced (p<0.01) average milk yield, whereas udder size had little effect. Average daily milk yield per cow across breeds was 2.0 litres. Average daily milk yield per cow for West African Shorthorn (WASH), N’dama, Sanga, White Fulani, Sanga-Gudali crossbred and Sokoto Gudali were 1.5, 1.5, 1.9, 2.0, 2.8 and 3.5 litres (p<0.01), respectively. Milk yield increased (p<0.01) with increasing parity and dropped after the sixth parity. Small, medium and large teat sizes had daily milk yield of 2.0, 2.5, and 2.7 litres (p<0.01), respectively. Average daily milk yield per cow receiving regular and occasional feed supplementation, and no feed supplementation were 2.8, 2.2, and 1.9 litres (p<0.01), respectively. Lower BCS (≤ 2) and extremely high BCS led to reduced milk yield. Study on lactation length (LL) revealed that breed, feed supplementation and BCS influenced (p<0.01) LL whilst farm location, season of lactation, parity of cow and sex of calf had little (p>0.05) effect. Average LL across breeds was 246.4 days with minimum and maximum being 155 and 303 days, respectively. Mean LL for Sokoto Gudali, White Fulani, Sanga-Gudali cross, Sanga, West African Shorthorn (WASH) and N’dama were 278.1, 255.7, 262.5, 260.7, 214.5, and 261.2 days, respectively. West African Shorthorn had the least (p<0.01) LL whilst similar (p>0.05) LL were recorded for all the other breeds. The shortest mean LL was observed in cows provided with no supplementation whilst regular and occasional supplemented cows had similar (p>0.05) LL. Lactation length of 270.7, 257.6 and 237.9 days (p<0.01) were recorded for BCS 4, 3, and 2, respectively. Thus, LL significantly increased (p<0.01) as body condition score increased up to BCS 4. Percentage milk components of various dual purpose cows were significantly (p<0.01) influenced by breed and season. Parity and stage of lactation had little (p>0.05) effects on percentage components of fresh milk, however, the latter influenced (p<0.01) cholesterol levels. Gudali, and Sanga-Gudali crossbred had similar (p>0.05) percentage protein and fat whereas other breeds differed (p<0.01). Protein and solids-non-fat components were low (p<0.01) in major rains whilst lactose and total solids increased (p<0.01) with increasing intensity of rains. There were important interaction effects between breed, stage of lactation and season on percentage protein, fat, lactose and solid-non-fat components. It was concluded that given optimum environmental conditions, the dual-purpose cows in good body condition could provide relatively improved productive performances.