Effects of an injectable mineral supplement on physiological responses and milk production of heat-stressed Holstein cows

Summer heat stress in northwest Mexico compromises the physiological thermoregulation capacity and productive performance of lactating Holstein cows, and supplementation of minerals appears to reduce the adverse impact of heat stress in cattle. The objective herein was to evaluate the effects of an injectable mineral supplement containing phosphorus, selenium, potassium, magnesium, and copper on physiological responses, milk production, and milk composition of Holstein cows exposed to heat stress. Sixteen cows were blocked by parity and assigned to one of two treatments (n = 8) using a randomized complete block design: 1) control cows and 2) mineral-treated cows. All cows were exposed to environmental heat stress conditions (i.e., temperature-humidity index = 79.4 ± 4.3 units). No study variable was affected (P ≥ 0.20) by the treatment x sampling day interaction. While the mineral supplement did not affect any physiological variable in the afternoon, this treatment decreased breaths per min (P = 0.01) and most body surface temperatures (P ≤ 0.06; head, shoulder, leg, right-flank, and udder) in the morning. There was no effect (P = 0.37) of the mineral supplementation on milk yield but increased (P ≤ 0.03) the percentages of solids non-fat, protein, lactose, and density in the milk. In conclusion, Holstein cows' physiological thermoregulation and milk composition experiencing summer heat stress were improved by applying an injectable mineral supplement.(AU)

Effect of the supplementation of biocomplexed minerals in diets for free-range chickens on performance and carcass characteristics

We intended to evaluate the influence of supplementation with biocomplexed minerals on the performance and carcass characteristics of Label Rouge broilers of both sexes, as well as on the feed efficiency and feed costs. The experimental design was completely randomized arranged in factorial scheme (3×2) ­ three experimental diets (control, 0.50 ppm of selenium, and 0.40 ppm of chromium) and two sexes (male and female). Each treatment was composted of three plots, each one represented by 21 birds. The average weight (g/bird), weight gain (g/bird), feed intake (g/bird), and feed conversion in periods of 1 to 7, 1 to 21, 1 to 35, 1 to 49, 1 to 63, and 1 to 90 days were calculated. Weight and yield of carcass and cuts were determined. Both average feed cost (AFC, R$/bird) and cost per kg of weight gain (CWG, R$/kg weight gain) as well as economic efficiency index (EEI) were estimated. There was no influence of the diet on performance, carcass characteristics, and feed costs of the birds. The males presented higher means of average weight (3819.2 g/bird), weight gain (3780.9 g/bird), feed intake (11030.2 g/bird), and better feed conversion index (2.9) in the period of 1 to 90 days, besides presenting higher values of live weight at slaughter (3740.2 g), carcass weight (3117.5 g) and carcass yield (83.4%), breast weight (832.4 g), thigh weight (432.5 g), and thigh yield (13.9%); the females presented higher breast yield values (28.1%). The males presented higher AFC and lower CWG. The addition of minerals in the diet does not change performance, carcass characteristics and feed costs. The males present better performance and better carcass characteristics, in addition to being economically more viable.(AU)