Effects of dry period length on milk yield and content and metabolic status of high-producing dairy cows under heat stress.

The objective of the present study was to investigate the effects of shortening dry period (DP) on milk yield, milk composition, and blood parameters in cows under heat stress. For this purpose, three DP groups were considered (30, 45, and 60 days), and 14 heat-stressed high-producing dairy cows (7 primiparous and 7 multiparous) were assigned to each DP group. The results showed that shortening the DP (from 60 to 30 days) decreased a 305-day milk yield in subsequent lactation. The difference in milk yield between 30- and 60-day DP groups was significant in the second 100 days of lactation. Accounting for additional milk yield before calving completely compensate for the loss of milk production resulting from shortening the DP. Milk protein, lactose, and solids non-fat percentages were significantly lower for cows with a 60-day DP compared to cows with a 45- or 30-day DP. Serum BHBA and urea concentrations were significantly higher, and serum glucose concentration was significantly lower for cows with a 60-day DP compared to cows with a 30-day DP. In conclusion, results showed that shortening the DP improved the metabolic status of heat-stressed transition dairy cows without decreasing total milk yield.

Influence of spray-dried rumen fluid supplementation on performance, blood metabolites and cytokines in suckling Holstein calves.

Rumen fluid from slaughtered animals is one of the wastes of slaughterhouses released to the environment that, due to its high nitrogen and phosphorus contents, can lead to soil and groundwater pollution. Meanwhile, it contains ruminal microbes and some bioactive compounds such as enzymes, minerals, vitamins and organic acids. This study was designed to examine the potential of rumen fluid as a feed additive. Therefore, the effects of spray-dried rumen fluid (SDR) with 1% maltodextrin on the performance, blood metabolites and some cytokines of sucking dairy calves during the pre-weaning phase were investigated. Forty male Holstein calves, with a mean weight of 39.4 ± 3.7 kg and 7 ± 1 days old, were randomly assigned to four groups (n = 10 calves per group) in a completely randomized design. Experimental treatments were: control diet with no additive (CON); control diet with 0.5 g/day of SDR (SDR0.5); control diet with 1 g/day of SDR (SDR1); and control diet with 1.5 g/day of SDR (SDR1.5). Daily feed intake and average daily gain of calves were not affected by feeding SDR as a feed additive. Cholesterol concentration was significantly affected by the 20th and 40th days of the experiment and decreased linearly by increasing SDR feeding level. Levels of liver enzymes, including aspartate aminotransferase and alanine aminotransferase, in the blood decreased by feeding SDR at day 40 of the experiment. Serum concentration of interleukin-6 at day 20 was not affected by dried rumen fluid feeding, whereas at day 40, a significant effect was observed among experimental treatments. The lowest value was recorded for SDR1.5 v. control calves. At day 20, the serum concentration of interferon-γ was influenced by supplementing SDR, and the highest value was recorded for SDR1.5 calves. The inclusion of SDR with 1% maltodextrin in suckling dairy calves had beneficial effects on the stimulation of calves' immune system.

Effects of a locally produced blood meal on performance, carcass traits and nitrogen retention of broiler chickens.

The study was designed as a 2 x 5 factorial arrangement with main effects of feeding blood meal as a replacement of 0, 25, 50, 75 or 100% of dietary fish meal and the duration of this substitution at 1-42 or 21-42 days of age. One thousand 1 day old male Cobb 500 broiler chicks assigned randomly to each of 40 floor pens (25 birds/pen) and were fed five isonitrogenous and isocaloric feeds formulated to contain 20.38 and 17% crude protein and 2900 and 3000 kcal kg(-1) metabolizable for starter and grower periods, respectively. Duration of dietary manipulation didn't affect the measured parameters. More than 25% blood meal/fish meal substitution ratios significantly increased chickens daily weight gain and decreased the cost of producing a unit of meat. Other traits didn't affect by dietary fish meal/blood meal replacement ratio. Spleen and proventriculus percents and small intestine length affected by level of replacement but didn't follow a distinct pattern. These results indicate that this locally produced blood meal is a suitable substitute for dietary fish meal and a full replacement didn't cause any adverse effect on performance, carcass important traits and dietary nitrogen retention of broiler chickens.