Effects of calf sex, breed and parity on the lactation performance of dairy cows in Trinidad and Tobago

Dairy farming is important for food and nutrition security and livelihood protection in most tropical countries. However, productivity of dairy cows is affected by many factors and is usually low on smallholder farms in tropical environments. Therefore, the aim of this study was to investigate the effects of calf sex, cattle breed and parity on milk yield and lactation length and to determine the relationship between early lactation milk yield and total lactation milk yield of a small-scale dairy herd at the Centeno Livestock Station (CLS), Trinidad and Tobago. Productivity data for the period 2014 to 2019 were retrieved from the record system at CLS. The data were analyzed by analysis of variance (ANOVA) using SPSS (version 27) with calf sex, breed, parity and breed × parity interaction as fixed effects. The relationship between early lactation milk yield and total milk yield was established by regression analysis. Calf sex, breed and the interaction of breed × parity did not affect milk yield and the length of lactation ( p > 0.05). However, early lactation milk yield of cows in fourth to sixth parities (849 ± 66 kg) and those in more than sixth parity (1005 ± 116 kg) were not significantly different, but both groups produced higher milk yield in early lactation compared to cows in the first to third parity group (673 ± 41 kg). Similarly, daily milk yield (5.6 ± 0.33 kg) was lowest in cows in the first to third parities. Early lactation milk yield accounted for 73% of the variability of total lactation milk yield. Therefore, optimizing the productivity of smallholder dairy farms such as the CLS requires improved management to reduce heat stress and improve nutrition and reproductive efficiency of cows, especially those in the fourth and later parities as well as those cows in early lactation is critical because milk production is maximized at these physiological stages.