Year Of Calving Research Articles

Genetic and Non-Genetic Factors Affecting Test Day Milk Yield and Milk Composition Traits in Crossbred Dairy Cattle in Ethiopia

This study evaluated the effects of genotype, parity, days in milk (DIM), calving season (CS), and calving year (CY) on the milk yield and composition traits of four hundred twenty lactating crossbred dairy cows in 13 districts in Ethiopia. Test day milk yield (TMY), protein (P), fat (F), lactose (L), solid not fat (SNF), density (D), total solids (TS), total protein (TP), casein (CN), whey (W), salts (S), and freezing point (FP) were determined using standard procedures. The data were analyzed using generalized linear models (GLM) using R software. Cows in the genetic group ≥ 87.5%, at 101–200 days, calved in the rainy season, in 2022, and at second parity all had the highest value of TMY. F, SNF, and TS were significantly (P<0.05) influenced by genotype, DIM, CS, CY, and parity. F was higher in cows with ≤ 50% genetic group, in early and late lactation, in the dry season, in 2020, in primiparous and above parity three cows than their counterparts. Proteins (P, TP, CN, and W) were affected by genotype, DIM, and CY but not by CS and parity (P<0.05). All milk proteins had a higher value in cows with ≤ 50% genetic group, and in early lactation. In this study, milk yield and composition were affected by genetic and non-genetic factors, providing an opportunity for crossbreeding programs to balance the quality and quantity of milk by manipulating the level of the exotic gene found in cows, choosing the best agro-climatic conditions, and improving the level of management.

Determining the Factors Affecting 305-Day Milk Yield of Dairy Cows with Regression Tree

The purpose of this study was to determine the factors affecting the 305-day milk yield of dairy cattle by using Regression Tree Analysis (RTA). The data set of this study consisted of 8 different cattle breeds grown in Turkey. Breed (B), Province (P), Lactation Length (LL), Service Period (SP), Dry Period (DP), Parity (PR), Calving Year (CY), Calving Age (CA) and Calving Month (CM) were used to predict the 305-day milk yield. Results of RTM showed that the usage of this method might be appropriate for determining the important factors that would be able to affect the 305-day milk yield (R2=71.3%). It was seen that the most important factors affecting the 305-day milk yield were the Breed, Lactation Length, Province, and Parity. Therefore, those selected factors were more efficient than the others in predicting the 305-day milk yield. RTA results also indicated that the lowest milk yield was estimated for Jersey, Jersey Crossbred, and Yerli Kara. Among the highest 305-day milk yield cows, the milk yield estimates of the cows in the second, third, fourth, fifth, and the sixth parities were found significantly higher than that of the cows in the first and seventh parities.

Genetic analysis of a purebred herd of Kundhi buffaloes in Pakistan

Kundhi is amongst the best dairy buffalo breeds of the world and main source of milk production in Sindh province of Pakistan. A Research and Development Kundhi Buffalo Farm was established at Rohri, Sukkur. Time series production performance data of 237 buffaloes, along with their pedigree, from 1976 through 2004 was collected and analyzed using Harvey Model-1 for fixed effects and DFREML for GLS solutions and genetic / phenotypic variances. The traits of economic importance studied were age at first calving (AFC), milk yield (MY), lactation length (LL), calving interval (CI) and dry period (DP). The fixed effects included year of birth (YOB), year of calving (YOC) season of calving (SOC) and lactation number (L No.). The data analyses revealed that among the fixed effect only YOC had significant effect (p < 0.05) on milk yield and all other traits. The average MY was 1356.48 ± 453.27 kg with mean lactation length 218.72 ± 122.97 days. The heritability of MY, CI, LL and DP was 0.209, 0.018, 0.009 and 0.024, respectively. Among the 5 sires used during this period, one sire contributed positively to milk production of the daughters. One hundred and three Kundhi buffaloes had positive and 134 negative breeding values for milk production. The genetic and phenotypic variance for milk yield was 35427.67 and 168521.94, respectively. The progeny testing program for Kundhi buffalos was initiated in August 2005. Under this program, more than 700 buffaloes are registered and ear tagged. The production and reproduction performance data recording at farmers doorstep has been initiated which will be used to identify bull mothers.

Causas de variação da produção de leite em um rebanho da raça Holandesa em São Carlos, SP

O objetivo deste trabalho foi avaliar a importância dos efeitos de ano de parto (AP), estação de parto (EP), grupo genético (GG), sexo do bezerro (SB), causa de secagem (CS), idade da vaca ao parto (IP, em meses) e duração do período de lactação (DL, em dias) e de touro (PAI), na produção de leite (PL), em um rebanho da raça Holandesa. Um total de 684 observações, provenientes de 267 vacas criadas em um modelo físico de sistema de produção de leite mantido na Embrapa - Centro de Pesquisa de Pecuária do Sudeste, São Carlos, SP foi incluído nas análises. Os dados foram coletados no período de outubro de 1984 a dezembro de 1993 e analisados pelo método dos quadrados mínimos por meio de um modelo incluindo os efeitos fixos de AP, EP, GG, SB e CS, os efeitos linear e quadrático de IP e DL como covariáveis e o efeito aleatório de PAI. Houve efeitos de AP, EP, CS, IP (linear e quadrático), DL (linear e quadrático) e PAI sobre a PL. As variáveis GG e SB não influenciaram a PL. No período estudado, houve aumento linear da PL de 347,6±22,02 kg de leite/lactação·ano. As vacas com lactações iniciadas no verão (janeiro-março) foram menos produtivas (4.325±82 kg) que as com lactações iniciadas nas demais estações do ano (4795±49 kg). As vacas com lactações encerradas por motivo de pré-parto apresentaram maior PL (4903±78 kg) que as com lactações encerradas por baixa produção/outras causas (4452±61 kg). A PL foi influenciada pelos efeitos linear (18,86±2,39 kg/mês) e quadrático (-0,2934±0,0456 kg/mês²) da idade da vaca ao parto. Houve efeitos linear (15,83±0,41 kg/dia) e quadrático (-0,0057±0,0023 kg/dia²) da duração do período de lactação sobre a PL.