Risk factors associated with reproductive performance in small-scale dairy farms in Mexico.

Several studies suggest that reproductive performance in small-scale dairy farms is low reducing the farms' profitability. Therefore, identifying risk factors associated with low reproductive performance is a key step to implement an improved reproductive management program. Accordingly, the aim of the present study was to identify the main risk factors affecting the reproductive performance of cows in small-scale dairy farms. Ninety-six dairy farms were incorporated into this study, and data from 1263 lactations were collected with different events as potential risk factors. Logistic regression models were used to assess the association (odds ratio, OR) and impact (population attributable fraction, PAF) between the potential risk factors and the reproductive variables. The main risk factors associated with assisted calving were male calf and primiparous cows (OR = 1.7, PAF = 0.315 and OR = 1.5, PAF = 0.131, respectively), while for retained fetal membranes (RFM) were assisted calving and abortion (OR = 4.5, PAF = 0.440 and OR = 8.1, PAF = 0.239, respectively). The main risk factors for days to first service over 70 days in milk were low body condition score at calving (BCS ≤ 2.5) and primiparous cows (OR = 2.2, PAF = 0.285 and OR = 1.4; PAF = 0.096, respectively), while for days open over 110 days in milk were low BCS at calving (BCS ≤ 2.5) and primiparous cows (OR = 1.7, PAF = 0.213 and OR = 1.4; PAF = 0.096, respectively) The main risk factor for non-pregnant cows at first service was RFM (OR = 1.7; PAF = 0.059). In conclusion, assisted calving, male calf, BCS ≤ 2.5 and RFM were the main risk factors associated with reduced reproductive performance in small-scale dairy farms in tropical and subtropical regions of Mexico.

Morphostructural Characterization of the Black Creole Goat Raised in Central Mexico, a Currently Threatened Zoogenetic Resource.

In order to evaluate the morphostructural variability of the Black Creole goat (BCG), the present study was carried out in a population of 226 animals from eight localities and 14 morphometric variables were taken. Descriptive statistics for the variables were obtained and 10 of these presented variation coefficients of less than 10%. The degree of harmony in the morphology of the population was determined by the number of positive correlations with significant differences (p < 0.05), including a correlation test using Spearman's method. In order to reduce the matrix of variables, a principal components analysis was performed, and it was evaluated based on Kaiser's criteria (eigenvalue > 1). Finally, a hierarchical analysis of conglomerates using Ward's method was performed using the Euclidean distance to evaluate the distances among localities. Morphometric variables were also included to visualize the relationship among the localities and their average per variable. The results showed that the animals evaluated presented a certain degree of homogeneity and maintained a highly harmonic model. The BCG population showed a high aptitude for milk production, which confirmed the zootechnical purpose of the breed. The BCG populations evaluated maintain similar morphostructural profiles specific to them that can distinguish this population from other animal breeds.

Body Condition Score and Milk Production on Conception Rate of Cows under a Small-Scale Dairy System.

Management and production characteristics impact conception rate to first service (CR1S) in small-scale dairy farms, but the impact of body condition score (BCS) and milk production levels on cows' fertility is unknown. Our objective is to determine the effect of BCS and milk production on CR1S in small-scale dairy farms of western Mexico. Logistic regression models are used to determine the effect of BCS (at calving and first service), 60-d and 305-d milk production, protein and fat production, lactation number, and days at first service on CR1S. BCS at calving does not affect CR1S in cows with three or more lactations (39.5%; p > 0.1). However, first-lactation cows with BCS < 3.0 at calving and second lactation cows with BCS ≤ 2.5 at calving have higher CR1S (63.2 and 67.9%, respectively; p < 0.1). This result is perhaps due to reduced milk production, which leads to lower metabolic stress. BCS ≤ 2.5 at calving is associated (p < 0.05) with a reduced milk yield, explaining partially the observed higher CR1S in these groups. Cows with BCS ≤ 2.5 at first service in the higher quartile of 60-d milk production (≥ 28kg/day) show lower CR1S (23.9 and 51.1%, respectively; p < 0.01). In conclusion, BCS at calving and at first service, 60-d milk production, and lactation number are factors associated with CR1S.